HIV Glossary of Terms




AACTG:  See: Adult AIDS Clinical Trials Group

Acquired Immunity:  The body's ability to fight or prevent aspecific infection. This ability can be acquired either actively (byhaving and recovering from an infection or by being vaccinated againstan infection) or passively (by receiving antibodies from an outsidesource, such as breast milk or donated blood components).  See Also: Active Immunity, Passive Immunity

Acquired Immunodeficiency Syndrome (AIDS):  A disease of thebody's immune system caused by the human immunodeficiency virus (HIV).AIDS is characterized by the death of CD4 cells (an important part ofthe body's immune system), which leaves the body vulnerable tolife-threatening conditions, such as infections and cancers. See Also: AIDS-Defining Condition, AIDS-Related Cancer, Human Immunodeficiency Virus (HIV), Opportunistic Infection (OI)

Acquired Resistance:  See: Primary Resistance

ACTG:  See: AIDS Clinical Trials Group

Active Immunity: Protection from a specific infection thatdevelops after having and recovering from the infection or after beingvaccinated against the infection. See Also: Acquired Immunity

Acute HIV Infection:  Also known as primary HIV infection oracute retroviral syndrome (ARS). The period of rapid HIV replicationthat occurs 2 to 4 weeks after infection by HIV. Acute HIV infection ischaracterized by a drop in CD4 cell counts and an increase in HIVlevels in the blood. Some, but not all, individuals experience flu-likesymptoms during this period of infection. These symptoms, collectivelyknown as AIDS-related complex, can include fever, inflamed lymph nodes,sore throat, and rash. These symptoms may last from a few days to 4weeks and then go away. See Also: AIDS-Related Complex (ARC)

Acute HIV Infection and Early Diseases Research Program (AIEDRP):  Aprogram funded by the National Institute of Allergy and InfectiousDiseases (NIAID) to conduct research with people who have been recentlyinfected with HIV. This research is aimed at understanding how HIVinfects humans and how the disease progresses to AIDS. Scientistsbelieve that events that occur during acute and early infection maydetermine the ultimate course of the disease.

Acute Retroviral Syndrome (ARS):  See: Acute HIV Infection

ADAPs:  See: AIDS Drug Assistance Programs

ADC:  See: AIDS Dementia Complex

Adenopathy:  See: Lymphadenopathy Syndrome (LAS)

Adenovirus:  A type of virus that commonly causes respiratorytract and eye infections. Adenovirus-based vaccines are being studiedas a potential way of introducing viral particles that may stimulate animmune response against HIV, thereby preventing or treating HIVinfection.  See Also: Retrovirus, Preventive HIV Vaccine

Adherence:  Closely following (adhering to) a prescribedtreatment regimen. Requires a patient to take the correct dose of adrug at the correct time, exactly as prescribed. Failure to adhere toan anti-HIV treatment regimen can lead to virologic failure and drugresistance.  See Also: Virologic Failure, Drug Resistance

Adjuvant:  Substance added to a drug that enhances or modifiesthe original drug. Also refers to a substance added to a vaccine toimprove the body's immune response to that vaccine.

ADR:  See: Adverse Drug Reaction

Adult AIDS Clinical Trials Group (AACTG):  A large clinicaltrial organization that conducts clinical research to test treatmentand prevention strategies for adult HIV infection and AIDS. The AACTGis funded by the National Institute of Allergy and Infectious Diseases(NIAID).  See Also: Clinical Trial

Adverse Drug Reaction (ADR):  Any drug effect that is unwanted,unpleasant, or potentially harmful. These effects may be mild and maydisappear when the drug is stopped or may subside as the body adjuststo the drug. Other ADRs, such as skin rashes, anemia, or organ damage,are more serious. ADRs may be assigned grades of 1 (mild) to 4(serious) to describe the strength of the reaction.  See Also: Side Effect

Adverse Effect:  See: Adverse Event

Adverse Event (AE):  Any unfavorable and unintended sign (i.e.,an abnormal laboratory finding), symptom, or disease associated usuallyin relation to timing, with the use of a drug or other intervention,whether or not the event is considered related to this product.  See Also: Adverse Drug Reaction (ADR)

AETCs:  See: AIDS Education and Training Centers

Agammaglobulinemia:  Absence or low levels of antibodies in the blood. This condition leaves a person vulnerable to infections. See Also: Antibody

Agency for Healthcare Research and Quality (AHRQ):  An agency ofthe U.S. Department of Health and Human Services (HHS) that sponsorsand conducts research on health care results, quality, cost, use, andaccess.

AHRQ:  See: Agency for Healthcare Research and Quality

AIDS:  See: Acquired Immunodeficiency Syndrome

AIDS Case Definition:  See: AIDS-Defining Condition

AIDS Clinical Trials Group (ACTG):  A clinical trials networkthat evaluates treatments and new therapeutic approaches for thetreatment of HIV infection and opportunistic diseases related toHIV/AIDS in adults.

AIDS-Defining Condition:  Any of a list of illnesses that, whenoccurring in an HIV-infected person, leads to a diagnosis of AIDS, themost serious stage of HIV infection. AIDS is also diagnosed if anHIV-infected person has a CD4 count less than 200 cells/mm3, whether ornot that person has an AIDS-defining condition. The Centers for DiseaseControl and Prevention (CDC) published a list of AIDS-definingconditions in 1993. The 26 conditions include candidiasis,cytomegalovirus disease, Kaposi's sarcoma, Mycobacterium avium complex, Pneumocystis jiroveci  neumonia,recurrent pneumonia, progressive multifocal leukoencephalopathy,pulmonary tuberculosis, invasive cervical cancer, and wastingsyndrome.  See Also: Acquired Immunodeficiency Syndrome (AIDS)

AIDS Dementia Complex (ADC):  Also called HIV-associateddementia. A progressive mental disorder with different nervous systemeffects and mental symptoms. Mental symptoms may include memory loss;speech problems; inability to concentrate; poor judgment; or moodchanges, such as depression. Nervous system effects may includebehavior changes, such as not being able to perform daily tasks, andmotor difficulties, such as loss of control of the legs or movingslowly or stiffly. ADC is considered an AIDS-defining condition inpeople with HIV.

AIDS Drug Assistance Programs (ADAPs):  Programs authorizedunder Title II of the Ryan White Comprehensive AIDS Resources Emergency(CARE) Act that operate in all 50 states, the District of Columbia,Guam, Northern Mariana Islands, Puerto Rico, and the Virgin Islands.These programs provide HIV-related prescription drugs to underinsuredand uninsured individuals living with HIV/AIDS.

AIDS Education and Training Centers (AETCs):  A network of 15regional centers that conduct targeted, multidisciplinary HIV educationand training programs for health care providers. The mission of thesecenters is to increase the number of health care providers who areeducated and motivated to counsel, diagnose, treat, and manageindividuals with HIV infection and to assist in the prevention ofhigh-risk behaviors that may lead to infection. AETCs are administeredby the Health Resources and Services Administration (HRSA).

AIDS Encephalopathy:  Malfunction of the brain as a result ofHIV infection. Can occur as part of acute HIV infection or can resultfrom chronic HIV infection.

AIDSinfo:  A U.S. Department of Health and HumanServices (HHS) project that offers the latest federally approvedinformation on HIV/AIDS clinical research, treatment and prevention,and medical practice guidelines for people living with HIV/AIDS, theirfamilies and friends, health care providers, scientists, andresearchers. The service includes a Web site with "Live Help," atoll-free hotline (1-800-448-0440); responses to e-mail inquiries; anda variety of publications that include treatment guidelines, drug factsheets, and fact sheets based on the guidelines.

AIDS-Related Cancer:  A cancer that is more common or moreaggressive in people with HIV. These cancers include certain types ofimmune system cancers (lymphomas), Kaposi's sarcoma (KS), cancers thataffect the anus and the cervix, and others. Having HIV appears to playa role in the development and progression of these cancers, althoughpeople without HIV can also have them.

AIDS-Related Complex (ARC):  A group of complications thatcommonly occur in the early stage of HIV infection. These may includerecurrent fever, unexplained weight loss, swollen lymph nodes,diarrhea, herpes, or fungal infection of the mouth and throat.  See Also: Acute HIV Infection

AIDS Service Organization (ASO):  A health association, support agency, or other service actively involved in the prevention and treatment of HIV/AIDS.

AIEDRP:  See: Acute HIV Infection and Early Diseases Research Program

Alanine Transaminase (ALT):  See: Liver Function Tests

Alkaline Phosphatase:  An enzyme normally present in certaincells within the liver, bone, kidney, intestine, and placenta. Whencells are destroyed in those tissues, the enzyme leaks into the blood,and levels rise in proportion to the severity of the condition.Measurement of this enzyme is one way to evaluate the health of theliver.

ALT:  See: Alanine Transaminase

Amino Acid:  A building block the body uses to make proteins. See Also: Protein

Anaphylaxis:  Also called anaphylactic shock. A rare butlife-threatening, whole-body allergic reaction. Symptoms may appearquickly and include difficulty breathing, swelling of the throat orother parts of the body, rapid drop in blood pressure, dizziness, orunconsciousness. Anaphylaxis can be triggered by foods, drugs, insectstings, or exertion, depending on an individual's sensitivity.

Anemia:  A lower than normal number of red blood cells. Symptoms may include fatigue, chest pain, or shortness of breath.

Anorexia:  Lack or loss of appetite.

Antagonism:  See: Drug Antagonism

Antenatal:  See: Prenatal

Antepartum:  The time period before childbirth (refers to the mother).

Antibiotic:  A natural or man-made substance that can kill orstop the growth of micro-organisms, such as bacteria or fungi, that cancause infections.

Antibody:  Also known as immunoglobulin. A protein produced bythe body's immune system to recognize and fight infectious organismsand other foreign substances that enter the body. Each antibody isspecific to a particular piece of an infectious organism or otherforeign substance. Antibodies develop after the first exposure to asubstance.  See Also: Antigen

Antifungal:  A natural or man-made substance that can kill or stop the growth of a fungus.

Antigen:  Any substance considered foreign to the body that canstimulate the body to produce antibodies against it. Antigens includebacteria, viruses, and allergens such as pollen.  See Also: Antibody

Antigen-Presenting Cell (APC):  A type of cell that collectsforeign materials (antigens), digests them into small pieces, anddisplays or presents the pieces on its surface. Other cells of theimmune system recognize these pieces and become activated to fight theforeign invader. APCs include Blymphocytes, macrophages, and dendriticcells.  See Also: Antigen, B Lymphocytes, Dendritic Cell, Macrophage

Antineoplastic:  A natural or man-made substance that can kill or stop the growth or spread of cancer cells.

Antiprotozoal:  A natural or man-made substance that can kill or stop the growth of single-celled micro-organisms called protozoa.

Antiretroviral (ARV):  A drug that interferes with the ability of a retrovirus, such as HIV, to make more copies of itself.  See Also: Antiretroviral Therapy (ART), Highly Active Antiretroviral Therapy (HAART) Retrovirus

Antiretroviral Pregnancy Registry:  An ongoing project tocollect observational, nonexperimental information about the use ofantiretrovirals during pregnancy. Information from the registry is usedto help health care providers and patients weigh the potential risksand benefits of treatment during pregnancy. The registry does not usepatient names, and registry staff obtain information from the patients'physicians.

Antiretroviral Therapy (ART):  Treatment with drugs that inhibitthe ability of retroviruses, such as HIV, to multiply in the body. Theantiretroviral therapy recommended for HIV infection is referred to ashighly active antiretroviral therapy (HAART), which uses a combinationof drugs to attack HIV at different points in its life cycle. See Also: Highly Active Antiretroviral Therapy (HAART), Retrovirus

Antisense Drug:  A man-made segment of DNA or RNA that can lockonto a strand of DNA or RNA from a virus or other micro-organism. Thismarks the organism's genetic instructions for destruction and preventsthe organism from making more copies of itself.  See Also: Deoxyribonucleic Acid (DNA), Ribonucleic Acid (RNA)

Antiviral:  A natural or man-made substance that can kill or stop the growth of a virus.

APC:  See: Antigen-Presenting Cell

Aphthous Ulcer:  A painful shallow sore in the mouth. The soreis usually oval shaped, with a yell ow-white center surrounded by anarrow red ring. Aphthous ulcers are 1/8- to 1/4-inch across and haveno blisters.  They occur on the soft surfaces of the mouth, such as theinner cheeks, inner lips, soft areas of the roof and floor of themouth, tongue, gums, and throat.

Apoptosis:  The deliberate, programmed death of a cell.Apoptosis occurs as a normal part of life and helps the body stayhealthy. If cells are damaged (for example, cancerous cells or cellsinfected with HIV), the body orders those cells to die in order tocontain the disease.

Approved Drug:  In the United States, the Food and DrugAdministration (FDA) must approve a drug before it can be marketed andsold to the public.  The approval process involves several steps,including laboratory and animal studies, clinical trials for safety andefficacy, filing of a New Drug Application (NDA) by the manufacturer ofthe drug, FDA review of the application, and FDA approval/rejection ofthe application.  See Also: New Drug Application (NDA)

ARC:  See: AIDS-Related Complex

Area Under the Curve (AUC):  A measure of how much drug reachesa person's bloodstream in a given period of time (usually the timebetween each dose or within 24 hours of a dose). The AUC is calculatedby plotting the drug's blood levels on a graph at different timesduring the set period to form a curve. The area under this curvereflects the total drug exposure in the set time period.

Arm:  Any of the treatment groups in a clinical trial. Mostclinical trials have two arms, but some have three or even more. Eacharm receives a different treatment or placebo.  See Also: Clinical Trial, Placebo

ARS:  See: Acute Retroviral Syndrome

ART:  See: Antiretroviral Therapy

Arthralgia:  Joint pain with additional symptoms such as heat, redness, tenderness to touch, loss of motion, or swelling.

ARV:  See: Antiretroviral

ASO:  See: AIDS Service Organization

Aspartate Aminotransferase (AST):  See: Liver Function Tests

Aspergillosis:  An infection of the lungs caused by the fungus Aspergillus.The infection may also spread through the blood to other organs.Symptoms include fever, chills, difficulty in breathing, and coughingup blood. If the infection reaches the brain, it may cause dementia.

ASTL  See: Aspartate Aminotransferase

Asymptomatic:  Having no obvious signs or symptoms of disease.

Ataxia:  Partial or complete loss of coordination of voluntarymuscular movements. This can interfere with a person's ability to walk,talk, eat, and perform other tasks of daily living.

Atherosclerosis:  A condition that results from the gradualbuildup of fatty substances, including cholesterol, on artery walls.Use of PIs may increase cholesterol levels, which increases the risk ofdeveloping atherosclerosis. However, a recent study has shown thatlong-term HAART may actually decrease the risk of therosclerosis.  See Also: Cholesterol

Attachment Inhibitor:  Class of anti-HIV drugs that prevents the virus from attaching to anew, healthy host cell, thus preventing cell infection.  See Also: Entry Inhibitor

Attenuated:  A term used to describe a bacterium or virus thathas been changed in the laboratory so that it is not harmful to people.Attenuated viruses are often used as vaccines, because they can nolonger cause disease but can still stimulate a strong immune response.Examples include the vaccines against polio (Sabin oral vaccine),measles, mumps, and rubella.

AUC:  See: Area Under the Curve

Autoantibody:  An antibody directed against the body's own tissue.  See Also: Antibody

Avascular Necrosis (AVN):  Death of bone (also known asosteonecrosis) caused by a loss of blood supply to the bone tissue. AVNhas occurred in the hip bones of some people with HIV, but it is notclear if bone death occurs because of HIV infection itself or as a sideeffect of anti-HIV drugs. Symptoms include pain in the affected area ofthe body, limited range of motion, joint stiffness, limping, and musclespasms. If untreated, AVN can cause progressive bone damage that leadsto bone collapse.  See Also: Osteonecrosis

AVN:  See: Avascular Necrosis






B2M:  See: Beta-2 Microglobulin

Bactericide:  A natural or man-made substance that kills bacteria.

Bacteriostatic:  A natural or man-made substance that can prevent bacteria from reproducing but cannot actually kill existing bacteria.

Bacterium:  A microscopic organism consisting of one simplecell. Bacteria occur naturally almost everywhere on earth, including insoil, on skin, in the human gastrointestinal tract, and in many foods.Some bacteria can cause disease in humans.

Baseline:  An initial measurement (for example, CD4 count orviral load) made before starting treatment or therapy for a disease orcondition. In people infected with HIV, the baseline measurement isused as a reference point to monitor HIV infection.

Basophil:  An infection-fighting white blood cell that causes inflammation in response to a micro-organism or other foreign invader.

B Cell:  See: B Lymphocyte

B-Cell Lymphoma:  A type of cancer of the lymphatic tissue.People with HIV are more prone to non-Hodgkin's and other B-celllymphomas, some of which are considered AIDS-defining conditions inpeople with HIV. See Also: Lymphoma, Non-Hodgkin's Lymphoma (NHL)

bDNA Assay:  See: Branched-Chain DNA Assay

Beta-2 Microglobulin (B2M):  A protein found on the surface ofwhite blood cells. Increased production or destruction of white bloodcells causes B2M levels in the blood to increase. This increase is seenin people with cancers involving white blood cells and in people withadvanced HIV disease.

b.i.d.:  Twice-a-day dosing instructions.

Bilirubin:  A yellowish substance excreted by the liver. Itsmeasurement can be used as an indication of the health of the liver.Large quantities of bilirubin may cause the skin to take on a yellowtint (jaundice), and very high levels may cause brain damage.  See Also: Jaundice

Bioavailability:  Rate and extent to which a drug is absorbed and available in the tissues of the body.

Biological Response Modifier (BRM):  A natural or man-made substance that can boost, direct, or restore immune system function.

Biopsy:  The surgical removal and examination of an organ or tissue to aid in diagnosis and treatment of a health condition.

Black Box Warning:  Information found at the beginning of adrug's prescribing information, manufacturer labeling, and promotionalmaterial. This information highlights important safety information,such as serious side effects, drug interactions, or use restrictions.The black box warning is one of the strongest warnings issued by theFood and Drug Administration (FDA) and is reserved for drugs withsignificant risks or monitoring requirements. See Also: Package Insert

Blip:  A temporary increase in viral load in someone whopreviously had undetectable virus and who later returns to havingundetectable virus. The viral load during a blip is usually low (50 to500 copies/mL). See Also: Undetectable Viral Load (UDVL)

Blood-Brain Barrier: A selective obstacle between circulatingblood and brain tissues that prevents damaging substances from reachingthe brain. Certain substances easily cross the blood-brain barrier;others are completely blocked.

B Lymphocyte:  Also known as a B cell. Infection-fighting whiteblood cell that develops in the bone marrow and spleen. B lymphocytesproduce antibodies. In people with HIV, the ability of B lymphocytes todo their job may be damaged.  See Also: Antibody

Body Habitus Changes:  Abnormal changes in the body's physical characteristics.  See Also: Wasting Syndrome, Lipoatrophy, Lipohypertrophy

Bone Marrow Suppression:  See: Myelosuppression

Booster:  An additional dose or doses of a vaccine given afterthe initial dose to enhance the immune response to the vaccine. Alsoused as a term to describe a medicine given to enhance anothermedicine, such as using ritonavir (RTV) as a booster with other PIs.

Branched-Chain DNA (bDNA) Assay:  A test that measures aperson's viral load (level of HIV RNA in the blood) to identify HIVinfection and to monitor disease progression and treatmenteffectiveness. Results are reported as the number of HIV RNA copies permilliliter of blood. bDNA assay is an alternative to measuring viralload by reverse transcriptase-polymerase chain reaction (RT-PCR). See Also: Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR), Viral Load (VL)

BRM:  See: Biological Response Modifier

Bronchoscopy:  Visual examination of the bronchial passages ofthe lungs using an endoscope (a curved, flexible tube containing fibersthat carry light down the tube and project an enlarged image of thebronchial passages onto a viewing screen). Can also be used forextraction of material from the lungs.

Budding:  The final step in the HIV life cycle, in which anindividual virus pushes out (or "buds") from the host cell, steals partof the cell's outer envelope, and frees itself to attach to and infectanother host cell.

Buffalo Hump: See: Dorsocervical Fat Pad, See Also: Body Habitus Changes

Burkitt's Lymphoma:  Also known as small, noncleaved-celllymphoma. A type of non-Hodgkin's lymphoma. There are three types ofBurkitt's lymphoma, one type occurs in people with weakened immunesystems, such as those with AIDS.  See Also: Non-Hodgkin's Lymphoma (NHL)






Cachexia:  Loss of weight, muscle wasting, fatigue, weakness,and decrease of appetite in someone who is not actively trying to loseweight.  Usually associated with serious disease.

CAM:  See: Complementary and Alternative Medicine

Candidiasis:  Infection caused by a species of the yeast-like fungus Candida, usually C. albicans.Candidiasis can affect the skin; nails; and mucous membranes throughoutthe body, including the mouth (thrush), esophagus, vagina, intestines,and lungs. The infection appears as white patches when in the mouth orany other mucous membrane. Candidiasis is considered an AIDS-definingcondition in people with HIV.

Cardiomyopathy:  A condition that weakens the heart muscle orcauses a change in heart muscle structure. Cardiomyopathy is associatedwith inadequate heart pumping or other heart function abnormalities.Cardiomyopathy may occur in HIV-infected people with advanced disease.Irregular heartbeat, abnormal heart and breath sounds, decreased heartfunction, or heart enlargement may indicate cardiomyopathy.

CARE Act:  See: Ryan White CARE Act

CBC: See: Complete Blood Count

CBO:  See: Community-Based Organization

CCR5:  Chemokine receptor 5 (CCR5) is a protein on the surfaceof some immune system cells. It is one of two co-receptors that HIV canuse along with the CD4 receptor to bind to and enter host cells. (Theother co-receptor is CXCR4.) See Also: Co-receptor CXCR4, CD4 Receptor, CCR5 Receptor Blocker

CCR5 Receptor Blocker:  Class of anti-HIV drug that stops HIVfrom binding to the CCR5 coreceptor, a receptor that most strains ofHIV need to enter cells.  Without the ability to bind to CCR5, HIVentry is halted.  See Also: CCR5 Co-receptor

CD4 Cell:  Also known as helper T cell or CD4 lymphocyte. A typeof infection fighting white blood cell that carries the CD4 receptor onits surface.  CD4 cells coordinate the immune response, which signalsother cells in the immune system to perform their special functions.The number of CD4 cells in a sample of blood is an indicator of thehealth of the immune system. HIV infects and kills CD4 cells, whichleads to a weakened immune system. See Also: CD4 Cell Count, CD4 Receptor

CD4 Cell Count:  A measurement of the number of CD4 cells in asample of blood.  The CD4 count is one of the most useful indicators ofthe health of the immune system and the progression of HIV/AIDS. A CD4cell count is used by health care providers to determine when to begin,interrupt, or halt anti-HIV therapy; when to give preventive treatmentfor opportunistic infections; and to measure response to treatment.  Anormal CD4 cell count is between 500 and 1,400 cells/mm3 of blood, butan individual's CD4 count can vary. In HIV-infected individuals, a CD4count at or below 200 cells/mm3 is considered an AIDS-definingcondition.  See Also: CD4 Cell

CD4 Percentage:  The percent of lymphocytes (white blood cells)that are CD4 cells.  This measurement is less likely to vary in betweenblood tests than CD4 count, but CD4 count remains a more reliablemeasure of immune function than CD4 percentage for most people. See Also: CD4 Cell Count, CD4 Cell

CD4 Receptor:  A specific molecule present on the surface of aCD4 cell. HIV recognizes and binds to a CD4 receptor and a co-receptorto gain entry into a host cell.  See Also: CD4 Cell Co-receptor

CD8 Cell:  Also called a cytotoxic T lymphocyte (CTL), killer Tcell, or suppressor T cell. A type of white blood cell that is able toidentify and kill cells infected with bacteria, viruses, or otherforeign invaders.

CDC:  See: Centers for Disease Control and Prevention

CDCINFO:  A service sponsored by the Centers for Disease Controland Prevention (CDC) to provide referrals, education, and informationabout topics including HIV/AIDS, other sexually transmitted diseases(STDs), immunizations, and disease outbreaks. The CDCINFO hotlinenumber is 1-800-CDCINFO (232-4636).

Cell-Mediated Immunity:  Immune protection provided by thedirect action of immune cells.  With this type of immune protection,the response to infectious micro-organisms is performed by specificcells-such as CD8 cells, macrophages, and other white bloodcells-rather than by antibodies. The main role of cell-mediatedimmunity is to fight viral infections.  See Also: Macrophage, Antibody, Immune Response

Cellular Immunity:  See: Cell-Mediated Immunity

Centers for Disease Control and Prevention (CDC):  An agency ofthe U.S. Department of Health and Human Services (HHS) that is chargedwith protecting the health and safety of citizens at home and abroad.The CDC serves as the national focus for developing and applyingdisease prevention and control, environmental health, and healthpromotion and education activities designed to improve the health ofthe people of the United States.

Centers for Medicare and Medicaid Services (CMS):  Previouslyknown as the Health Care Financing  Administration (HCFA). An agency ofthe U.S. Department of Health and Human Services (HHS) responsible foradministering Medicare, Medicaid, State Children's Health InsuranceProgram (SCHIP), Health Insurance Portability and Accountability Act(HIPAA), Clinical Laboratory Improvement Amendments (CLIA), and otherhealth related programs.

Central Nervous System (CNS):  The part of the nervous systemmade up of the brain, spinal cord, and spinal nerves. These serve asthe main processing center for the whole nervous system and togethercontrol all the workings of the body. HIV can infect and damage partsof the central nervous system.

Cerebrospinal Fluid (CSF):  A clear, colorless fluid that fillsthe spaces in the brain and the central canal of the spinal cord aswell as the spaces between nerve cells.

Cervical Cancer:  A condition in which a cancerous growth (also called a malignancy) develops on the lower portion of the uterus (cervix). See Also: Cervical Dysplasia, Pap Smear, Human Papillomavirus (HPV).

Cervical Dysplasia:  The abnormal growth of cervical cells,usually with no symptoms. It can be detected by a Pap smear, andtreatment can prevent it from progressing to cervical cancer. See Also: Cervical Cancer, Pap Smear, Human Papillomavirus (HPV)

Cervical Intraepithelial Neoplasia (CIN):  A general term forthe growth of abnormal cells on the surface of the cervix. Numbers from1 to 3 may be used to describe how much of the cervix contains abnormalcells. See Also: Cervical Dysplasia

Cervix:  The lower, narrow end of the uterus that forms a canal between the uterus and vagina.

Chancroid:  A sexually transmitted disease (STD) caused by a bacterium called Hemophilus ducreyi.Often causes swollen lymph nodes and painful sores on the penis,vagina, or anus. The lesions appear after an incubation period of 3 to5 days and may facilitate HIV transmission.

Chemical Barrier:  A mechanism that uses chemicals to try toprevent sexually transmitted infections (STIs), including HIVinfection. Microbicides are currently being studied as chemicalbarriers to prevent the transmission of STIs. See Also: Microbicide

Chemokines:  Proteins that serve as chemical messengers tocontrol the activities of the immune system. Chemokines are involved ina wide variety of processes, including the control of infectiousdiseases, cancers, and inflammation. Chemokines include interferons,interleukins, and many other small proteins.

Chemoprevention:  Also known as chemoprophylaxis. The use ofnatural or man-made agents to help reduce the risk of or delay thedevelopment or recurrence of a disease, such as cancer.

Chemoprophylaxis:  See: Chemoprevention

Chemotherapy:  Treatment with anticancer drugs that kill orprevent the growth and division of cells. The drugs enter thebloodstream and travel through the body killing mostly cancer cells,but some healthy cells may be killed as well.

Chlamydia: A sexually transmitted disease (STD) caused by a bacterium called Chlamydia trachomatis.The bacteria infect the genital tract and, if left untreated, can causedamage to the female and male reproductive systems, resulting ininfertility.

Cholesterol: A fat-like substance used as a building block forcells. Cholesterol is both made by the liver and absorbed from food andis carried in the blood. When blood cholesterol levels are too high(hyperlipidemia), some of the cholesterol is deposited on the walls ofthe blood vessels, increasing the risk of heart disease andatherosclerosis. Use of PIs may also increase cholesterol levels.  See Also: Hyperlipidemia

Chronic Idiopathic Demyelinating Polyneuropathy (CIPD):  Chronic,spontaneous loss or destruction of myelin, a white fatty material thatprotects and insulates nerve cells. People with CIPD show progressive,usually symmetrical weakness in the arms and legs. CIPD can be one ofthe symptoms of lactic acidosis or progressive multifocalleukoencephalopathy.  See Also: Lactic Acidosis, Progressive Multifocal Leukoencephalopathy (PML).

CIN:  See: Cervical Intraepithelial Neoplasia

CIPD:  See: Chronic Idiopathic Demyelinating Polyneuropathy

CIPRA:  See: Comprehensive International Program of Research on AIDS

Clade:  A group of organisms that are genetically similar anddescended from a single parent organism. With HIV, the term claderefers to a group of specific HIV-1 strains within an HIV subtype. Forexample, HIV-1 subtype M contains clades A through H, J, and K. CladesB and C account for the majority of HIV infections around the world. See Also: Subtype

Class-Sparing Regimen:  An anti-HIV drug regimen thatpurposefully does not include one or more classes of anti-HIV drugs. Aclass-sparing regimen may be prescribed to save certain classes ofdrugs for later use or to avoid side effects specific to a class. Forexample, a PI-sparing regimen would not include any PIs. Because somePIs may cause an increase in cholesterol in the blood, a PI-sparingregimen might be prescribed for an HIV-infected person who already hashigh cholesterol levels.

Clinical Alert:  The National Institutes of Health (NIH)publishes these electronic bulletins containing urgent early results ofclinical trials. The data in these bulletins warn about possiblemorbidity (sickness rates) and mortality (death rates) in participantsinvolved in the clinical trials.

Clinical Endpoint:  A measurement used in clinical trials toevaluate the effect of the treatment being tested. Examples of clinicalendpoints for HIV disease include death, serious drug toxicity, ordevelopment of an AIDS-defining illness. Because these endpoints may bedifficult to measure without long-term follow-up, surrogate(substitute) short-term endpoints, such as a change in viral load orCD4 count, may also be used as clinical endpoints.  See Also: Clinical Trial

Clinical Failure:  The occurrence or recurrence of HIV-relatedinfections or a decline in physical health despite taking an HIVtreatment regimen for a minimum of 3 months. Clinical failure may occuras a result of virologic or immunologic failure. See Also: Virologic Failure, Immunologic Failure

Clinical Practice Guidelines:  Recommendations by panels ofexpert health care practitioners designed to assist clinicians andpatients in making decisions about appropriate health care for specificdiseases and conditions.

Clinical Progression:  A term for the overall progression of adisease as measured by deterioration of clinical outcomes. In anHIV-infected person, clinical progression may be defined as theoccurrence or recurrence of HIV related events (after at least 3 monthson an antiretroviral regimen), excluding immune reconstitutionsyndromes. HIV-infected patients who have a CD4 T-cell count less than100 cells/mm3 are considered to have a high likelihood of clinicalprogression.

Clinical Trial:  A research study that uses human volunteers toanswer specific health questions. Carefully conducted clinical trialsare regarded as the fastest and safest way to find effective treatmentsfor diseases and conditions as well as other ways to improve health.Interventional trials use controlled conditions to determine whetherexperimental treatments or new ways of using known treatments are safeand effective. Observational trials gather information about healthissues from groups of people in their natural settings. Clinical trialsmay be prospective (studying data from a time point forward) orretrospective (studying data from collected records in the past).  An online, searchable database ofinformation about clinical trials sponsored by governments,pharmaceutical companies, and other organizations. This database ismanaged by the National Institutes of Health (NIH) through its NationalLibrary of Medicine (NLM). See Also: Clinical Trial

CMAX:  Also called maximum concentration. The maximum (peak) amount of drug measurable in the blood after a dose is administered. See Also: CMIN

CMIN:  Also called minimum concentration. The lowest (trough) amount of drug measurable in the blood after a dose is administered. See Also: CMAX

CMS:  See: Centers for Medicare and Medicaid Services

CMV:  See: Cytomegalovirus

CMV Retinitis:  See: Cytomegalovirus Retinitis

CNS:  See: Central Nervous System

Coccidioidomycosis:  Also called desert fever, San JoaquinValley fever, or valley fever.  An infectious disease caused by theinhalation of spores of Coccidioides immitis. The disease isespecially common in hot, dry regions of the Southwestern United Statesand Central and South America. It is an AIDS-defining condition inpeople with HIV.  See Also: AIDS-Defining Condition

Cognitive Impairment:  Loss of the ability to process, learn,and remember information. The progression of HIV disease may lead tocognitive impairment. See Also: AIDS Dementia Complex

Cohort:  A group of individuals who are alike in some way. Forexample, the people in a cohort of HIV-infected individuals are allinfected with HIV.

Coinfection:  Infection with more than one virus, bacterium, orother microorganism at a given time. For example, an HIV-infectedindividual may be coinfected with hepatitis C virus (HCV) ortuberculosis (TB).

Colitis:  Inflammation of the colon (large intestine). This maylead to intestinal bleeding, ulcers, or perforations (holes) in thecolon.

Combination Therapy:  Two or more drugs used together to achieveoptimal results in controlling HIV infection. Combination therapy hasproven more effective in decreasing viral load than monotherapy(single-drug therapy), which is no longer recommended for the treatmentof HIV. An example of combination therapy is the use of two NRTIs plusa PI or an NNRTI.

Community-Based Organization (CBO):  A service organization thatprovides social services to local clients.  CBOs include nonprofitorganizations and free clinics targeted at helping people with HIV.

Community Programs for Clinical Research on AIDS (CPCRA):  Alsoknown as the Terry Beirn Community Programs for Clinical Research onAIDS. A network of clinical research units composed of community-basedhealth care providers. CPCRA's aim is to serve populationsunder-represented in previous clinical trials.  CPCRA is funded by theNational Institute of Allergy and Infectious Diseases (NIAID).

Comorbid Condition:  Any disease or condition that occurs at thesame time as another disease or condition. The second disease mayworsen or be worsened by the initial disease. For example, tuberculosis(TB) may occur as a co-morbid condition in an individual infected withHIV, and the HIV infection may worsen the TB.

Compassionate Use:  General term used to describe any programthat provides an experimental therapy outside of clinical trials topatients who do not have any FDA-approved treatment options (forexample, HIV-infected individuals who have extensive drug resistance toapproved anti-HIV drugs). To enroll in compassionate use programs, anindividual has to meet strict medical criteria.  See Also: Expanded Access Investigational Drug

Complementary and Alternative Medicine (CAM):  Health carepractices not currently considered part of conventional medicine. Atherapy is called complementary when it is used in addition toconventional treatments. It is called alternative when it is usedinstead of conventional treatment. CAM includes a broad range ofhealing therapies, approaches, and systems. Some examples of CAM areacupuncture, herbs, homeopathy, chiropractic, hypnosis, and traditionalChinese medicine.

Complete Blood Count (CBC):  A general blood test that measuresthe levels of white and red blood cells, platelets, hematocrit, andhemoglobin in a sample of blood. Changes in the amounts of each ofthese may indicate infection, anemia, or other health problems.

Comprehensive International Program of Research on AIDS (CIPRA):  Aprogram administered by the National Institute of Allergy andInfectious Diseases (NIAID) to support research and development ofpractical, affordable, and acceptable methods to prevent and treatHIV/AIDS in resource-poor countries.

Concentration:  The relative amount of a substance, such as anadministered drug or a circulating enzyme, found in a particularlocation, such as the blood or a specific organ. For example, drugconcentrations are often reported as the amount of drug in a measuredsample of blood. See Also: CMIN, CMAX

Condyloma Acuminatum:  See: Genital Warts

Contagious:  Easily passable between people through normalday-to-day contact. For example, chicken pox is both an infectious(causing infection) and a contagious disease. In contrast, HIV is anexample of an infectious disease that is not a contagious disease(i.e., it cannot be passed from person to person through casualcontact).

Contraindication:  A specific situation in which a particulartreatment should NOT be used, because it may be harmful to the patient.For example, some anti-HIV drugs are primarily broken down by the liverand should not be given to people who have liver damage.

Controlled Trial:  A control is a standard against whichexperimental treatments may be compared and evaluated for safety andeffectiveness. In clinical trials, one group of patients may be givenan experimental drug, while another group (the control group) is giveneither a standard treatment for the disease or a placebo. See Also: Placebo

Core:  The inner protective coat of protein that surrounds thegenetic material of most viruses. In HIV, the core is mostly made up ofthe p24 protein, which surrounds two copies of HIV's genetic material.

Coreceptor:  A protein on the surface of a cell that serves as asecond binding site for a virus or other molecule. Although the CD4protein is HIV's primary receptor, the virus must also bind to eitherthe CCR5 or CXCR4 coreceptor to get into a host cell.  See Also: CCR5, CXCR4, CD4 Receptor

CPCRA:  See: Community Programs for Clinical Research on AIDS

Creatinine:  A protein found in muscles and blood and excretedby the kidneys into the urine. The level of creatinine in the blood orurine provides a measure of kidney function. Increased levels ofcreatinine indicate abnormal or impaired kidney function.

Cross Resistance:  Cross resistance occurs when a micro-organismhas changed, or mutated, in such a way that it loses its susceptibilityto multiple drugs simultaneously. For example, HIV resistance to oneNNRTI drug usually produces resistance to the entire NNRTI drug class. See Also: Drug Resistance, Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI), Mutation

Cross Sensitivity:  A drug reaction that may occur again withthe use of a different, but related, drug. Cross sensitivity can occurwithin a drug class, such as when a person reacts to all NNRTIssimilarly after treatment with just one. Cross sensitivity can alsooccur among chemically similar drug classes. For example, a person whohas a negative side effect to a sulfa-based antibiotic is at risk forthe same negative side effect if he or she takes any other sulfa-baseddrug.

Cryotherapy:  The use of liquid nitrogen to freeze and destroy alesion or growth to prevent further spread of the growth. In peoplewith HIV, it is used to treat lesions caused by Kaposi's sarcoma (KS)and condyloma acuminatum (genital warts).  See Also: Genital Warts, Kaposi's Sarcoma (KS)

Cryptococcal Meningitis:  A life-threatening infection of the membranes surrounding the brain and the spinal cord caused by the fungus Cryptococcus neoformans.Symptoms include headache, dizziness, stiff neck, and-if untreated-comaand death. Immunocompromised individuals, such as those with HIV, aremore susceptible to this infection. It is considered an AIDS-definingcondition in people with HIV.

Cryptococcosis:  An infection caused by the fungus Cryptococcusneoformans.  This fungus typically enters the body through the lungsand usually spreads to the brain, causing cryptococcal meningitis. Insome cases, it can also affect the skin, skeletal system, and urinarytract.  It is considered an AIDS defining condition in people withHIV.  See Also: Cryptococcal Meningitis

Cryptosporidiosis:  A diarrheal disease caused by the protozoa Cryptosporidium. Symptoms include abdominal cramps and severe chronic diarrhea.  It isconsidered an AIDS-defining condition in people with HIV.  See Also: Cryptosporidium

Cryptosporidium:  The protozoan that causescryptosporidiosis. It is found in the intestines of animals and may betransmitted to humans by direct contact with an infected animal, byeating contaminated food, or by drinking contaminated water. See Also: Cryptosporidiosis

CSF: See: Cerebrospinal Fluid

CTL:  See: Cytotoxic T Lymphocyte

Cutaneous:  Of, relating to, or affecting the skin.

CXCR4:  Chemokine receptor 4 (CXCR4, also known as fusin) is aprotein on the surface of some immune system cells. It is one of twoco-receptors that HIV can use along with the CD4 receptor to bind toand enter host cells. (The other co-receptor is CCR5.)  See Also: Co-receptor, CD4 Receptor, CCR5

CYP450:  See: Cytochrome P450

Cytochrome P450 (CYP450):  A system of enzymes, locatedprimarily in the liver, that participates in the breakdown of drugs.Many drugs inhibit or enhance the activity of these enzymes. Any changein CYP450 enzyme activity may cause an increase or decrease in bloodlevels of drugs that are broken down through this system.  See Also: Drug Interaction

Cytokine: A protein produced by white blood cells that acts as achemical messenger between cells. Cytokines can stimulate or inhibitgrowth or activity of immune cells and are essential for a coordinatedimmune response. Cytokines include the interleukins and theinterferons.  See Also: Interleukin (IL-2, IL- 7), Interferon (IFN)

Cytomegalovirus (CMV):  A herpesvirus that can cause infections,including pneumonia (infection of the lungs), gastroenteritis(infection of the gastrointestinal tract), encephalitis (inflammationof the brain), or retinitis (infection of the eye), in immunosuppressedpeople.  Although CMV can infect most organs of the body, HIV-infectedpeople are most susceptible to CMV retinitis.  See Also: Cytomegalovirus Retinitis, Herpesviruses

Cytomegalovirus Retinitis:  An infectious eye disease caused bycytomegalovirus (CMV). People with CMV retinitis can lose their vision,and CMV retinitis is the most common cause of blindness among peopleinfected with HIV.  See Also: Cytomegalovirus (CMV)

Cytopenia:  A condition in which the production of one or morekind of blood cells is greatly reduced or stops completely. Some drugsused to treat HIV or cancer may cause cytopenia.

Cytotoxic:  Toxic or destructive to cells. For example, cancerchemotherapy is cytotoxic, because it destroys both cancerous andnon-cancerous cells.

Cytotoxic T Lymphocyte (CTL):  See: CD8 Cell





DAART:  See: Directly Administered Antiretroviral Therapy

DAIDS:  See: Division of Acquired Immunodeficiency Syndrome

Data and Safety Monitoring Board (DSMB):  An independentcommittee of community representatives and clinical research expertswho review data while a clinical trial is in progress to ensure thatparticipants are not exposed to undue risk. A DSMB may recommend that atrial be stopped if there are safety concerns or if the trialobjectives have been achieved, or the DSMB can require changes to thestudy design to ensure safety of participants.

Dementia:  See: AIDS Dementia Complex (ADC)

Dendritic Cell:  A type of antigen-presenting cell that picks upforeign substances from the bloodstream and presents them to otherparts of the immune system, which activates an immune response againstthe

foreign invader.  See Also: Antigen-Presenting Cell (APC), Antigen

Dendritic Cell Vaccine:  Vaccine made of antigens and dendriticantigen-presenting cells.  Dendritic cell vaccines are being studied aspossible therapeutic HIV vaccines to treat HIV-infected people.  See Also: Therapeutic HIV Vaccine, Dendritic Cell

Deoxyribonucleic Acid (DNA):  Chemical structure that containsthe genetic instructions for reproduction and protein synthesis for allcells and for many viruses.

Department of Health and Human Services (HHS):  The U.S.government's principal agency for protecting the health of allAmericans and for providing essential human services. HHS includes morethan 300 programs that cover a wide spectrum of activities. More than300 programs are administered by 11 operating divisions, including theCenters for Disease Control and Prevention (CDC), the Food and DrugAdministration (FDA), and the National Institutes of Health (NIH). HHSworks closely with state and local governments, and many HHS-funded services are provided at thelocal level by state or county agencies or through private-sectorgrantees.

Desensitization:  A gradual increase in the dose of a medicineto avoid severe side effects. Desensitization procedures are sometimesused when administering some anti-HIV drugs and antibiotics.

DEXA:  See: Dual Energy X-Ray Absorptiometry Scan

Diabetes:  Also known as diabetes mellitus. A diseasecharacterized by high levels of sugar in the blood (hyperglycemia). Itcan be caused by too little insulin (a hormone produced by the pancreasto regulate blood sugar), resistance to insulin, or both. Some anti-HIVdrugs may cause or worsen diabetes.

See Also: Hyperglycemia, Insulin Resistance

Diarrhea:  Uncontrolled, loose, watery, and frequent bowelmovements caused by diet, infection, drug, or irritation orinflammation of the intestine.  Severe or long-lasting diarrhea canlead to weight loss and

malnutrition. The most common infectious organisms that cause HIV-related diarrhea include cytomegalovirus (CMV); the parasites Cryptosporidium, Microsporidia, and Giardia; and the bacteria

Mycobacterium avium and Mycobacterium intracellulare.Bacteria and parasites that cause diarrheal symptoms in otherwisehealthy people may cause more severe, prolonged, or recurrent diarrhea in people with HIV or AIDS.

Directly Administered Antiretroviral Therapy (DAART):  Method ofensuring that a person takes anti-HIV drugs as prescribed. DAARTrequires that a caregiver directly observe the patient ingest theanti-HIV drugs to increase adherence to the treatment plan.  See Also: Adherence,  Directly Observed Therapy (DOT)

Directly Observed Therapy (DOT):  A treatment strategy to ensureadherence, in which a health care provider or other observer watches apatient take each dose of a drug. This strategy is used with diseaseslike tuberculosis (TB) and HIV infection, in which adherence isimportant for effective treatment and to prevent emergence of drug resistance.  See Also: Adherence

Discordant Couple:  A pair of long-term sexual partners in whichone person is infected with a sexually transmitted infection (such asHIV) and the other is not.

Disseminated:  Widely dispersed across the entire body. Inimmune-compromised people, such as those with AIDS, coinfections (e.g.,cryptococcosis, histoplasmosis, Mycobacterium avium complex,etc.) may become disseminated and spread through the bloodstream toinfect lymph nodes, bone marrow, liver, spleen, spinal fluid, lungs,and the intestinal tract.

Division of Acquired Immunodeficiency Syndrome (DAIDS):  Adivision of the National Institutes of Health's (NIH's) NationalInstitute of Allergy and Infectious Diseases (NIAID). DAIDS was formedin 1986 to address the national research needs created by the HIV/AIDSepidemic; to increase basic knowledge of the pathogenesis, naturalhistory, and transmission of HIV disease; and to support research topromote HIV detection, treatment, and prevention.  See Also: National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH)

DNA:  See: Deoxyribonucleic Acid

Dorsocervical Fat Pad:  A type of lipodystrophy (a problem inthe way the body produces, uses, and distributes fat) in which fattytissue builds up on the upper back and neck. It most often occurs inHIV-infected people as a result of PI or NRTI drug treatment. This fatbuildup, also known as buffalo hump, may be associated with othermetabolic side effects, such as high insulin levels.  See Also: Lipodystrophy, Body Habitus Changes

Dosage:  The scheduled administration of individual drug doses,usually expressed as a quantity per unit of time. For example, aprescribed drug dosage may be 200 mg per day (but the individual dosecould be 100 mg in the morning and 100 mg in the evening).

Dose:  The measured amount of a therapeutic agent that is takenat one time, or the total amount taken during one time period. Forexample, a single dose of 100 mg may be taken at one time, or a totaldose of 1,000 mg may be taken during one 5-day treatment period.  See Also: Dosage

Dose-Ranging Study:  Clinical trial in which different doses ofa drug are tested to determine which is the safest and most effective.Before drugs are approved by the FDA, they must go through Phase I andII doseranging studies. See Also: Clinical Trial, Phase I Trial, Phase II Trial

Dose-Response Relationship:  The relationship between the doseof a drug and its corresponding effect on the body. If a drug exhibitsa dose-response effect, it means that as the dose increases, so doesthe effect.

DOT:  See: Directly Observed Therapy

Double-Blind Study:  A clinical trial design in which neitherthe participants nor the study staff know which individuals arereceiving the experimental treatment and which are receiving a placebo(or another control therapy). Double-blind trials produce moreobjective results, because the expectations of the study staff and theparticipants do not affect the outcome.  See Also: Controlled Trial

DRESS:  See: Drug Rash with Eosinophilia and Systemic Symptoms

Drug Antagonism:  An interaction between two or more drugs in which one drug blocks or reverses the effect of another drug.

Drug Class:  A group of drugs that share common properties, such as mechanisms of action.

Drug Concentration:  See: Concentration

Drug-Drug Interaction:  A change in the way a drug works when itis taken along with another drug. The effect may be an increase or adecrease in the action of either drug, or it may be a side effect thatdoes not normally occur with either drug alone.  See Also: Drug Interaction

Drug Formulation:  See: Formulation

Drug Holiday:  See: Structured Treatment Interruption (STI)

Drug Interaction:  An effect that can occur when one drug istaken with another drug or when a drug is taken with particular foods.Possible effect

Drug Rash with Eosinophilia and Systemic Symptoms (DRESS): A rare but life-threatening allergic drug reaction that sometimes occurs in people taking certain NNRTIs. Symptoms include severe trash along with fever, blood abnormalities, and organ inflammation. 

Drug Resistance: The ability of some micro-organisms, such as bacteria, viruses, and parasites, to adapt so that they can multiply even in the presence of drugs that would normally kill them. 

Drug Toxicity: See: Toxicity

DSMB: See: Data and Safety Monitoring Board

Dual Energy X-Ray Absorptiometry (DEXA) Scan: A painless test that uses low energy x-rays to measure the mineral content of bones. DEXA scans are commonly used to test for osteopenia or osteoporosis and are also used to evaluate lipodystropy. See Also: Osteopenia, Osteoporosis, Lipodystrophy

Dyslipidemia: Abnormal levels of fat in the blood, usually referring to abnormally high levels. Dyslipidemia may occur as a result of HIV infection or as a side effect of some anti-HIV drugs. See Also: Hyperlipidemia

Dyspnea: Difficult or labored breathing.



EBV: See: Epstein-Barr Virus

EF: See: Eosinophilic Folliculitis

Effectiveness: The measure of the success of a treatment for a particular disease or condition.

Efficacy: The ability of a treatment to produce the desired effect on the disease or condition being treated.

ELISA: See: Enzyme-Linked Immunosorbent Assay

Encephalitis: Inflammation of the brain, which can be caused by a virus infection. The brain tissue swells, which may lead to the destruction of nerve cells, bleeding within the brain, and brain damage.

Endemic: A term that refers to diseases associated with particular geographic regions or populations. For example, malaria is endemic in tropical regions of the world where mosquitoes carry the parasite that causes malaria.

Endpoint: General term for a measurement used to analyze results of a clinical trial. Common endpoints of a clinical trial are dose-limiting toxicity of a study drug and progression of the disease or condition being studied. See Also: Surrogate Endpoint, Clinical Endpoint

End-Stage Disease: The final period or phase in the course of a disease that leads to a person's death. An example of this is end-stage renal disease (ESRD), in which a person's kidneys have deteriorated to the point that the damage is life threatening and likely fatal.

Enteric: Of or relating to the intestines. This term also refers to a coating used on some drugs to prevent the breakdown of the drug by the stomach before it has a chance to be absorbed by the intestines.

Enteritis: Inflammation of the small intestine caused by bacterial or viral infection. Often causes diarrhea and dehydration and may also involve the stomach and large intestine. See Also: Colitis

Entry Inhibitor: A class of anti-HIV drugs designed to disrupt the ability of HIV to enter a host cell through the cell's surface. This class includes receptor inhibitors (CD4, CCR5, or CXCR4) and fusion inhibitors. See Also: Fusion Inhibitor

Envelope: The outer protective membrane of HIV that is composed of two layers of fat-like molecules called lipids. HIV uses specific proteins embedded in the envelope to attach to and enter host cells.

Enzyme: A protein that helps a chemical reaction happen by decreasing the energy needed for the reaction to occur.

Enzyme-Linked Immunosorbent Assay (ELISA): A highly sensitive laboratory test used to determine the presence of antibodies to HIV in the blood or saliva. Positive ELISA test results indicate that a person is HIV infected, but these results should be confirmed with a highly specific laboratory test called a Western blot. See Also: Western Blot, Antibody

Eosinophilia: A condition in which the number of eosinophils (a type of white blood cell) in the blood is higher than normal. Eosinophilia is often a response to infection or allergens (substances that cause an allergic reaction).

Eosinophilic Folliculitis (EF): A type of folliculitis (inflammation of hair follicles) characterized by recurring patches of inflamed, pus-filled sores that occur primarily on the face and sometimes on the back or upper arms. The sores usually spread, may itch intensely, and often leave areas of darkerthan-
normal skin (hyperpigmentation) when they heal. HIV associated EF most commonly occurs in people with low CD4 counts.

Epidemic: A disease that has spread rapidly through a segment of the human population in a given geographic area.

Epidemiology: The branch of medical science that studies the occurrence, distribution, and control of a disease in populations.

Epithelium: The protective covering of the internal and external organs of the body, including the lining of blood vessels, body cavities, glands, and organs. In addition to its protective properties, the epithelium also provides a surface to absorb and secrete chemicals needed by the body.

Epitope: A particular segment of an antigen that the body's antibodies can recognize and bind to. See Also: Antibody, Antigen

Epstein-Barr Virus (EBV): A human herpesvirus that causes infectious mononucleosis (mono), a contagious disease. Symptoms of infectious mononucleosis are fever, sore throat, and swollen lymph nodes. EBV infection can also lead to oral hairy leukoplakia, Burkitt's lymphoma, and nasopharyngeal carcinoma, especially in immune-compromised people, such as those with HIV. See Also: Burkitt's Lymphoma, Human Herpesviruses, Oral Hairy Leukoplakia (OHL)

Eradication: In terms of an infectious disease, the complete removal of a pathogen (such as HIV). Although eradication of HIV is currently not possible, antiretroviral treatment can control the disease through the suppression of viral load. See Also: Viral Load (VL)

Erythema: Abnormal redness of the skin caused by a buildup of red blood cells in the capillaries.

Erythema Multiforme: A type of rash that can occur in response to drugs, illness, or infections, such as herpes simplex or mycoplasma infections. Severe forms of this condition include Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). These may also be serious side effects of some anti-HIV drugs. See Also: Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN)

Erythrocyte: Red blood cell. The primary function of erythrocytes is to carry oxygen throughout the body.

Etiology: The branch of medical science that studies causes of disease. Such causes are called etiologic agents. For example, HIV is the etiologic agent of AIDS.

Exclusion/Inclusion Criteria: See: Inclusion/Exclusion Criteria

Expanded Access: Refers to any of the Food and Drug Administration (FDA) procedures that allow distribution of experimental drugs to people who are failing currently available treatments and are unable to participate in ongoing clinical trials. These procedures include compassionate, treatment, or emergency use. See Also: Compassionate Use

Experimental Drug: See: Investigational Drug

Extensively Drug-Resistant Tuberculosis (XDR-TB): A relatively rare type of tuberculosis that is resistant to almost all anti-tuberculosis drugs, including the two best first-line drugs and the best second-line drugs. XDR-TB is of special concern for people infected with HIV or other conditions that can weaken the immune system.




False Negative: A test or procedure result that incorrectly indicates a negative or normal result when an abnormal condition is actually present.

False Positive: A test or procedure result that incorrectly indicates a positive or abnormal result when no abnormal condition is actually present.

Fanconi Syndrome: A disorder of the kidney in which certain substances that are normally absorbed into the bloodstream by the kidneys are released into the urine instead. Fanconi syndrome can be caused by faulty genes, or it may result later in life as a result of kidney damage. It isa relatively uncommon adverse effect of some antiretroviral drugs.

Fat Maldistribution/Redistribution: See: Lipodystrophy

FDA: See: Food and Drug Administration

FDC: See: Follicular Dendritic Cell

First-Line Regimen: The recommended treatment plan and drugs used when treating a person for the first time.

Fixed-Dose Combination: A capsule or tablet that contains two or more drugs. This type of drug formulation allows a patient to take multiple drugs at one time to decrease pill burden and increase adherence. See Also: Pill Burden Formulation

Follicular Dendritic Cell (FDC): A specific type of dendritic cell found in lymphoid tissues, such as the thymus and lymph nodes. See Also: Dendritic Cell

Food and Drug Administration (FDA): The U.S. Department of Health and Human Services (HHS) agency responsible for ensuring the safety and effectiveness of drugs, biologics, vaccines, and medical devices. The FDA also works with the blood banking industry to safeguard the nation's blood supply.

Formulation: The physical form in which a drug is administered. Examplesinclude tablets, capsules, liquids, topical creams and ointments, and injectable solutions. A single drug may be available in multiple formulations.

Fungus: A group of primitive organisms that includes mushrooms, yeasts, rusts, and molds, some of which can infect humans and cause disease. For example, mouth thrush is caused by the fungus Candida.

Fusin: See: CXCR4

Fusion Inhibitor: A class of anti-HIV drugs that inhibits the fusing of HIV's outer envelope with the host cell membrane, which prevents infection
of the cell. See Also: Envelope



Gamma Globulin: The part of blood that contains antibodies. It is also available as an injectable treatment that can provide temporary protection from certain infections. See Also: Antibody Passive Immunotherapy

GART: See: Genotypic Assay

Gastrointestinal (GI): Of or relating to the stomach or intestines.

G-CSF: See: Granulocyte-Colony Stimulating Factor

Gene: A short segment of DNA or RNA that acts as a blueprint forbuilding a specific protein. See Also: Deoxyribonucleic Acid (DNA) Ribonucleic Acid (RNA)

Generic: A generic drug is one that has the same active ingredient(s) asa brand-name drug in dosage, safety, strength, how it is taken, quality, performance, and intended use.

Gene Therapy: An experimental technique that uses genes to treat or prevent disease. This technique may eventually allow doctors to treat a disorder by
inserting a gene into a patient's cells instead of using drugs or surgery.

Genetic Engineering: Artificially changing an organism's genetic material (DNA or RNA) to change particular characteristics of that organism. This laboratory
technique can produce proteins for use as drugs and vaccines.For example, a virus such as canarypox virus (which does not cause disease in humans) can be genetically engineered so that it produces specific HIV proteins. The modified canarypox virus can then be tested as an experimental HIV vaccine.

Genital Ulcer Disease: Sores on the genitals, usually caused by a sexually transmitted disease (STD), such as herpes, syphilis, or chancroid. The presence of genital ulcers may increase the risk of becoming infected with HIV through sexual intercourse.

Genital Warts: Also known as condyloma acuminatum and venereal warts. Growths or bumps that appear in and around the vagina, anus, or cervix in females or on the penis, scrotum, groin, or thigh in males. They can be raised or flat, single or multiple, small or large. Some cluster together to form a cauliflower-like shape. They are caused by the human papillomavirus (HPV) and are usually flesh-colored and painless. See Also: Human Papillomavirus (HPV)

Genitourinary Tract: Also called genitourinary system, urogenital system, or urogenital tract. The organs involved in the production and excretion of urine and in reproduction.

Genome: The complete set of genes for a particular organism. See Also: Gene

Genotypic Antiretroviral Resistance Test (GART): See: Genotypic Assay

Genotypic Assay: Also known as Genotypic Antiretroviral Resistance Test (GART). A test that determines if HIV is resistant to particular anti-HIV drugs. The test analyzes a sample of the virus from an individual's blood to identify any genetic mutations that are associated with resistance to specific drugs. See Also: Drug Resistance Mutation

GI: See: Gastrointestinal

Glycoprotein: A substance composed of both a protein and a carbohydrate (a sugar molecule) joined together by a chemical linkage.

GM-CSF: See: Granulocyte Macrophage-Colony Stimulating Factor

Gonorrhea: A sexually transmitted disease (STD) caused by the bacterium Neisseria gonorrhoeae. Many people with gonorrhea have no
symptoms. If symptoms do occur, they may include burning on urination, frequent urination, yellow or green discharge from the genitals, redness or swelling of the genitals, or a burning or itching sensation of the genitals. Active gonorrhea infection may increase the risk of becoming infected with HIV through sexual intercourse.

gp120: Glycoprotein 120. One of the proteins embedded in the outer envelope of HIV. gp120 projects from the surface of HIV and binds to the CD4 receptor on CD4 cells, which initiates the process by which HIV enters and infects a host cell. See Also: Envelope

gp160: Glycoprotein 160. A precursor of HIV envelope proteins gp41 and gp120. gp160 is cut by HIV protease to form gp120 and gp41. See Also: gp120 gp41 Protease

gp41: Glycoprotein 41. One of the proteins embedded in the outer envelope of HIV. gp41 plays a key role in HIV's infection of CD4 cells by fusing HIV's envelope with the host cell membrane, which allows the virus to enter the cell. See Also: Envelope Fusion Inhibitor

Granulocyte: A type of white blood cell particularly important in fighting bacterial infections.

Granulocyte-Colony Stimulating Factor (G-CSF): A protein that stimulates the production of infection-fighting white blood cells. A laboratory-made version of G-CSF, called filgrastim, is used to treat low white blood cell levels, which may occur after chemotherapy or as a result of certain diseases.

Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF): A protein that stimulates the production of infection-fighting white blood cells. A laboratory-made version of GM-CSF, called sargramostim, is used to treat low white blood cell levels, which may occur after chemotherapy or as a result of certain diseases.

Granulocytopenia: A lower than normal number of specific white blood cells called granulocytes.

Guillain-Barré Syndrome: A rare disorder that causes the immune system to attack the peripheral nervous system (PNS). The PNS connects the brain
and spinal cord with the rest of the body. Damage to these nerves makes it hard for them to transmit signals. As a result, muscles have trouble responding to the brain.



HAART: See: Highly Active Antiretroviral Therapy

Half-Life: The time period in which the concentration of a drug falls to half its original concentration.

HBV: See: Hepatitis B Virus

HCFA: See: Health Care Financing Administration

HCV: See: Hepatitis C Virus

Health Care Financing Administration (HCFA): See: Centers for Medicare and Medicaid Services (CMS)

Health Resources and Services Administration (HRSA): A U.S. Department of Health and Human Services (HHS) agency that directs national health programs aimed at improving the health of Americans by assuring quality health care to underserved, vulnerable, and special-needs populations. Among other functions, HRSA administers the Ryan White Comprehensive AIDS Resources Emergency (CARE) Act and the AIDS Education and Training Centers (AETCs) to provide treatment and services for those affected by HIV/AIDS. See Also: AIDS Education and Training Centers (AETCs), Ryan White CARE Act

HELLP Syndrome: A term that stands for Hemolysis, Elevated Liver enzyme levels, and a Low Platelet count. This is a rare but serious complication that can develop in the third trimester of pregnancy. Symptoms may include liver, blood pressure, and bleeding problems that can harm both the mother and the baby. Pregnant women taking NRTIs for HIV infection are at an increased risk for developing HELLP syndrome.

Helper T Cell: See: CD4 Cell

Hematocrit: A laboratory measurement that determines the percentage of red blood cells in a sample of blood. In women, red blood cells are normally 37% to 47% of the blood. In men, red blood cells are normally 40% to 54% of the blood.

Hematotoxic: Toxic or destructive to the blood or bone marrow.

Hemoglobin: A protein in  red blood cells that transports oxygen from the lungs to the tissues of the body.

Hemolysis: Rupture of red blood cell membranes, which causes a release of hemoglobin. See Also: Hemoglobin

Hemophilia: A hereditary blood defect that occurs almost exclusively in males and is characterized by delayed clotting of the blood. This leads to difficulty in controlling bleeding, even after minor injuries.

Hepatic: Pertaining to the liver.

Hepatic Necrosis: Death of liver cells. See Also: Hepatotoxicity

Hepatic Steatosis: Accumulation of too much fat inside liver cells. Also known as fatty liver. See Also: Lactic Acidosis

Hepatitis: Inflammation of the liver. This condition can lead to liver damage and liver cancer. See Also: Hepatitis B Virus (HBV) Hepatitis C Virus (HCV) Coinfection

Hepatitis B Virus (HBV): The virus that causes hepatitis B, an inflammation of the liver that can lead to liver damage and liver cancer. HBV is spread through contact with the blood of an infected person, through sexual intercourse, or from mother to child during childbirth. A vaccine is available to prevent infection with this virus, and hepatitis B can be treated with several drugs.

Hepatitis C Virus (HCV): The virus that causes hepatitis C, an inflammation of the liver that can lead to liver damage and liver cancer. HCV is primarily spread through contact with the blood of an infected person. There is no vaccine for HCV, and the only current treatment for hepatitis C is  combination of the drugs peginterferon and ribavirin.

Hepatomegaly: Enlargement of the liver.

Hepatotoxicity: A general term for liver damage. Often caused by drugs, including those used to treat HIV infection. Symptoms of hepatotoxicity include nausea, vomiting, abdominal pain, loss of appetite, diarrhea, unusual tiredness or weakness, jaundice (yellowing of the skin and eyes), and unusual swelling or weight gain. Laboratory testing may show increased levels of liver enzymes in the blood. See Also: Liver Function Tests

Herpes Simplex Virus 1 (HSV-1): A virus that causes cold sores or fever blisters on the mouth or around the eyes and that can be transmitted to the genital region. The virus can become latent (inactive), and symptoms disappear. Stress, trauma, other infections, or suppression of the immune system can reactivate the latent virus, and symptoms can return. See Also: Herpesviruses

Herpes Simplex Virus 2 (HSV-2): A virus that causes painful sores around the anus or genitals. The virus can become latent (inactive), and symptoms then disappear until the virus is reactivated. HSV-2 may be transmitted either sexually or from an infected mother to her infant during birth.

Herpesviruses: A family of viruses that includes several individual members, including herpes simplex viruses 1 and 2 (HSV-1 and -2), cytomegalovirus (CMV), varicella zoster virus (VZV), Epstein-Barr virus (EBV), and Kaposi's sarcoma herpesvirus (KSHV or HHV-8). Each of these viruses can cause disease in humans.

Herpes Zoster: See: Varicella Zoster Virus (VZV)

HGH: See: Human Growth Hormone

HHS: See: Department of Health and Human Services

Highly Active Antiretroviral Therapy (HAART): The name given to treatment regimens that aggressively suppress HIV replication and progression of HIV disease. The usual HAART regimen combines three or more anti-HIV drugs from at least two different classes.

Histoplasmosis: A lung disease caused by the fungus Histoplasma capsulatum. Symptoms are similar to those of influenza. People with severely damaged immune systems, such as those with AIDS, are vulnerable to a very serious form of the disease called progressive disseminated histoplasmosis. This form of histoplasmosis typically lasts a long time and involves organs other than the lungs. Histoplasmosis is considered an AIDS-defining condition in people with HIV.

HIV: See: Human Immunodeficiency Virus

HIV-1: The HIV type responsible for the majority of HIV infections worldwide. See Also: Human Immunodeficiency Virus (HIV), HIV-2

HIV-2: A virus that is closely related to HIV-1 and that also causes immune suppression and AIDS. Although the two viruses are very similar, immunodeficiency seems to develop more slowly and to be milder in people infected with HIV-2. The majority of HIV-2 cases have been found in West Africa. Not all drugs used to treat HIV-1 infection are effective against HIV-2. See Also: Human Immunodeficiency Virus (HIV), HIV-1

HIV-Associated Adult-Onset Nemaline Myopathy: See: Nemaline Rod Myopathy (NM)

HIV Decay: See: Viral Decay

HIV Prevention Trials Network (HPTN): A worldwide clinical trials network established by the National Institutes of Health (NIH) to develop and evaluate the safety and efficacy of nonvaccine HIV interventions designed to prevent the transmission of HIV.

HIV RNA: See: Viral Load (VL)

HIV Vaccine Trials Network (HVTN): An international group of scientists and educators that was formed in 1999 by the Division of AIDS (DAIDS) of the National Institute of Allergy and Infectious Diseases (NIAID). The main goal of HVTN is to find a safe and effective preventive HIV vaccine. HVTN staff and
volunteers around the world are also involved in helping community members understand the general science of HIV/AIDS vaccines, research methods, and clinical trials processes. See Also: Preventive HIV Vaccine

HLA-B*5701: See: Human Leukocyte Antigen

HLA-B Testing: See: Human Leukocyte Antigen

Hodgkin's Lymphoma: A type of cancer that affects certain white blood cells. Symptoms include enlarged lymph nodes, fever, night sweats, weight loss, and itching. This type of cancer most commonly affects people ages 15 to 40, people older than 55, and people who are HIV infected. It is also known as Hodgkin's disease. See Also: Lymphoma, Non-Hodgkin's Lymphoma (NHL)

Horizontal Transmission: A term used to describe transmission of a disease from one individual to another, except from parent to offspring. For example, HIV can be spread horizontally through sexual contact or exposure to infected blood. In contrast, spread of disease from parent to offspring is called vertical transmission. See Also: Vertical Transmission

Hormone: A chemical produced in one part of the body and passed through the blood to another part of the body to regulate its structure or function. HIV infection and AIDS can affect the production of hormones and cause imbalances in hormones, such as estrogen and testosterone.

HPTN: See: HIV Prevention Trials Network

HPV: See: Human Papillomavirus

HRSA: See: Health Resources and Services Administration

HSV-1: See: Herpes Simplex Virus 1

HSV-2: See: Herpes Simplex Virus 2

HTLV-I: See: Human T-Cell Lymphotropic Virus Type I

Human Growth Hormone (HGH): A protein produced in the pituitary gland that stimulates the liver to
produce somatomedins (substances that stimulate growth of bone and muscle). A laboratory-made version of HGH, called serostim, has been approved by the Food and Drug Administration (FDA) as a treatment for AIDS wasting syndrome. See Also: Wasting Syndrome

Human Herpesviruses: See: Herpesviruses

Human Immunodeficiency Virus (HIV): The virus that causes Acquired Immunodeficiency Syndrome (AIDS). HIV is in the retrovirus family, and two types have been identified: HIV-1 and HIV-2. HIV-1 is responsible for most HIV infections throughout the world, whereas HIV-2 is found primarily in West Africa. See Also: Acquired Immunodeficiency Syndrome (AIDS), Retrovirus

Human Leukocyte Antigen (HLA): Also known as major histocompatibility complex (MHC). Found on the surface of almost every cell in the body, HLAs are proteins that play an important role in controlling the immune system by identifying substances as foreign to the body. The type of HLA proteins a person inherits from his or her parents is important in identifying good matches for tissue grafts and organ transplants. Variants of an HLA protein may be expressed in some individuals, and these variations may increase the risk of developing certain diseases or experiencing certain drug reactions. For example, some HLA types are associated with either a faster or slower progression of HIV disease. In addition, expression of the HLA-B*5701 variant is associated with hypersensitivity to abacavir, an anti-HIV drug.

Human Papillomavirus (HPV): A virus that causes various warts, including plantar and genital warts. Some strains of HPV can also cause cervical cancer. See Also: Cervical Cancer, Genital Warts

Human T-Cell Lymphotropic Virus Type I (HTLV-I): A virus in the same family (retrovirus) as HIV. In rare cases, HTLV-1 can cause adult T-cell leukemia/lymphoma, a rare and aggressive cancer of the blood. People infected with HTLV-1 may also develop myelopathy, a disease of the spinal cord. See Also: Retrovirus

Humoral Immune Response: See: Humoral Immunit See Also: Cell-Mediated Immunity

Humoral Immunity: Term used to describe the body's antibody-based immune response, as opposed to its cell-based immune response (cell-mediated immunity). Immune cells called B cells produce antibodies against foreign invaders. See Also: Antibody Cell-Mediated Immunity B Lymphocyte

HVTN: See: HIV Vaccine, Trials Network

Hyperadiposity: See: Lipohypertrophy

Hypergammaglobulinemia: Higher than normal amounts of gamma globulins (antibodies) in the blood. See Also: Antibody

Hyperglycemia: Higher than normal glucose (sugar) levels in the blood. See Also: Diabetes

Hyperlipidemia: Elevated concentration of lipids (cholesterol, triglycerides, or both) in the blood. Hyperlipidemia increases the risk of serious heart diseases. In HIV-infected individuals, hyperlipidemia may occur as a side effect of PI treatment.

Hyperplasia: An abnormal increase in the number of cells in a tissue or an organ.

Hypersensitivity: An exaggerated or excessive response to a specific agent (such as a drug or antigen) that can sometimes be life-threatening or cause death.

Hypersensitivity Reaction: See: Hypersensitivity

Hypertension: Also known as high blood pressure. Hypertension is a condition in which the force of blood being pumped through blood vessels exerts too much pressure on the walls of blood vessels. When pressure increases and stays too high, it can cause damage to blood vessels (e.g., hardening of the arteries or atherosclerosis), the heart, the brain, the eyes, and other vital organs.

Hypertriglyceridemia: Elevated levels of triglycerides in the blood. Hypertriglyceridemia can increase the risk of serious heart disease. This condition may occur as a side effect of protease inhibitor treatment. See also: Triglycerides, Hyperlipidemia

Hypogammaglobulinemia: A deficiency of gamma globulins (antibodies) in the blood. This condition may occur in late stages of HIV disease, when
the immune system has been severely damaged. See Also: Antibody

Hypogonadism: Inadequate activity of the ovaries or testes. This can result in abnormally low levels of gonadal hormones (androgens and estrogens) and problems with sperm or egg production. Hypogonadism may occur in men and women with HIV.

Hypoxia: A condition in which not enough oxygen reaches the tissues of the body.



Idiopathic: Without a known cause.

Idiopathic Thrombocytopenia Purpura (ITP): A rare autoimmune disorder characterized by a shortage of platelets in the blood, which results in bruising and spontaneous bleeding. See Also: Platelet

IDU: See: Injection Drug User

IFN: See: Interferon

IG: See: Immunoglobulin

IHS: See: Indian Health Service

IL-2: See: Interleukin-2

IL-7: See: Interleukin-7

IM: See: Intramuscular

IMPAACT: See: International Maternal Pediatric Adolescent AIDS Clinical Trials Network

Immune Complex: Term used to describe an antibody bound to an antigen. See Also: Antibody Antigen

Immune Reconstitution Syndrome (IRS): Also known as immune restoration disease (IRD) or immune reconstitution inflammatory syndrome (IRIS). An inflammatory reaction that can occur when an immunocompromised person's immune system improves, such as when a person with HIV disease begins anti-HIV treatment and experiences an increase in CD4 cell count. Fever, along with swelling, redness, or discharge at the site of an injury or infection, may signal that an infection that was previously unnoticed by a weak immune system is now a target of a stronger immune system. Although IRS indicates that a person's immune system has grown healthier, it can be a serious, sometimes fatal condition and must be treated aggressively.

Immune Response: The body's defensive reaction to a foreign invader, such as a virus, bacterium, or fungus. The immune response includes both humoral (antibody-based) and cell-mediated immunity. See Also: Cell-Mediated Immunity Humoral Immunity

Immune System: The collection of cells and organs whose role is to protect the body from foreign invaders. Includes the thymus, spleen, lymph nodes, B and T cells, and antigen-presenting cells.

Immunity: Protection against or resistance to disease.

Immunization: See: Vaccination

Immunocompetent: Able to mount a normal immune response.

Immunocompromised: Unable to mount a normal immune response because of an impaired immune system.

Immunodeficiency: Inability to produce normal amounts of antibodies, immune cells, or both.

Immunogenicity: The ability of an antigen or vaccine to stimulate an immune response. See Also: Antigen Vaccine

Immunoglobulin (IG): See: Antibody

Immunologic: Related to the immune system, which defends the body against infection and disease.

Immunologic Failure: Occurs when an HIV-infected individual's CD4 count decreases below the baseline count or does not increase above the baseline count within the first year of anti-HIV treatment. People who experience virologic failure but do not switch to an effective drug regimen usually progress to immunologic failure within about 3 years. Immunologic failure may be followed by clinical failure. See Also: Baseline Virologic Failure Clinical Failure

Immunomodulator: A natural or man-made substance that can modify the functioning of the immune system.

Immunomodulatory Therapy: See: Immunomodulator

Immunosuppression: Inability of the immune system to function normally. May be caused by drugs (for example, chemotherapy) or result from certain
diseases (for example, HIV infection).

Immunotherapy: Treatment to stimulate or restore the body's immune system to fight disease.

Incidence: The rate of occurrence of new cases of a particular disease in a given population. Often reported as the number of cases per 100,000 people.

Inclusion/Exclusion Criteria: A specific set of selection rules that determine whether a person is eligible to enroll in a particular clinical trial. For example, some trials may not accept people with chronic liver disease or with certain drug allergies. Others may exclude men or women or only include people with a certain CD4 count or viral load. See Also: Clinical Trial

Incubation Period: The period between infection with a micro-organism and the development of symptoms. See Also: Window Period

IND: See: Investigational New Drug (IND) Application

Indian Health Service (IHS): The agency within the U.S. Department of Health and Human Services (HHS) responsible for providing Federal health services to
American Indians and Alaska Natives.

Infection: Establishment of an infectious micro-organism in a suitable host. The term is also used to refer to disease caused by an infectious micro-organism.

Infectious: Capable of causing infection.

Informed Consent: A person's agreement to participate in a clinical trial after understanding all aspects of the trial, including potential risks and benefits. See Also: Clinical Trial

infoSIDA: The Spanish-language companion Web site to AIDSinfo, which offers information on HIV/AIDS treatment and clinical trials.

Infusion: Administration of a solution (such as a glucose, salt, or drug solution), usually into a vein.

Injection Drug Use: The abuse of drugs by injecting them into a vein. Sharing of syringes transmits blood-borne viruses (such as HIV, hepatitis), which can spread rapidly through populations of injection drug users (IDUs). The sharing of needles and supplies (e.g., syringes, water, mixing spoon) is thought to be three times more likely to transmit HIV than sexual intercourse.

Injection Drug User (IDU): See: Injection Drug Use

Injection Site Reaction: An adverse effect, such as a rash, on the skin where an injection or shot was given.

Inoculation: See: Vaccine

INSIGHT: See: International Network for Strategic Initiatives in Global HIV Trials

Institutional Review Board (IRB): A committee of experts who review and monitor clinical trials to ensure that they are ethical and that the rights of study participants are protected. Federal regulations dictate that any institution that conducts or supports clinical trials must have an IRB.

Insulin: A hormone produced by the pancreas to regulate blood sugar. Because of this regulatory activity, insulin plays a role in the development and control of diabetes mellitus and other conditions that affect blood sugar levels. See Also: Diabetes

Insulin Resistance: An abnormal body response to insulin, a hormone that regulates glucose (sugar) levels. People with insulin resistance have abnormally high blood levels of insulin, which may lead to heart and cholesterol problems and obesity. Insulin resistance may occur in HIV-infected individuals taking certain PIs.

Insulin Sensitivity: The body's ability to respond to insulin's signal to take up glucose from the blood. Normal insulin sensitivity encompasses a wide range; people who have low insulin sensitivity may also be considered insulin resistant, which would result in an increase of insulin secretion.

Integrase: An HIV protein that plays an important role in the virus's life cycle. Integrase inserts HIV's genetic information into the infected cell's own DNA. See Also: Integration

Integrase Inhibitor: A class of anti-HIV drugs that prevents the HIV integrase protein from inserting HIV's genetic information into an infected cell's own DNA See Also: Integrase

Integration: The process by which HIV integrase inserts HIV's genetic material into an infected cell's own DNA. This crucial step in HIV's life cycle is targeted by the class of anti-HIV drugs called integrase inhibitors. See Also: Integrase Integrase Inhibitor

Intensification: Adding additional anti-HIV drugs to an existing treatment regimen, usually because that regimen failed to adequately control HIV replication.

Interaction: See: Drug Interaction

Interferon (IFN): A cytokine (protein that regulates immune system activity) that the body produces to fight viruses. Laboratory-made versions of IFN are used in the treatment of some viral infections and cancers. There are three main types of interferon: alpha, beta, and gamma. IFN alpha is used to treat hepatitis C virus (HCV) infection and many cancers, including Kaposi's sarcoma (KS). See Also: Cytokine, Hepatitis C Virus (HCV), Kaposi's Sarcoma (KS): Interleukin-2 (IL-2) A cytokine (protein that regulates immune system activity) that can increase the production of certain disease-fighting white blood cells. During HIV infection, IL-2 levels gradually decline. A laboratorymade version of IL-2 is used to treat some cancers and has been studied as a way to increase the number of CD4 cells and other immune system cells in people with HIV. See Also: Cytokine

Interleukin-7 (IL-7): A cytokine (protein that regulates immune system activity) produced in small amounts in bone marrow cells that increases the body's
production of certain disease-fighting white blood cells. Laboratoryproduced IL-7 is a drug product that appears to induce HIV replication in latent, or resting, infected cells. Activation of HIV in resting cells allows antiretroviral drugs to target HIV in those cells. See Also: Cytokine

International Maternal Pediatric Adolescent AIDS Clinical Trials(IMPAACT) Network: A clinical trials network that evaluates treatments for HIV-infected children and adolescents and also develops new therapeutic approaches for preventing mother-to-child transmission (MTCT) of HIV.

International Network for Strategic Initiatives in Global HIVTrials (INSIGHT): A clinical trials network that evaluates strategies for optimizing treatment by doing large simple trials in HIV-infected individuals.

Interstitial Nephritis: A kidney disorder caused by inflammation of the small spaces between parts of the kidney. The condition is a potential side effect of certain anti-HIV drugs.

Intervention: In medicine, a treatment or action taken to prevent or treat a disease or to improve health in other ways.

Intramuscular (IM): Relating to the area within a muscle. Intramuscular also refers to an injection made directly into a muscle.

Intrapartum: The time period spanning labor and delivery.

Intravaginal: Within the vagina.

Intravenous (IV): Inside a vein. Intravenous also refers to an injection made directly into a vein.

Intravenous Immunoglobulin (IVIG): A solution of antibodies taken from healthy donors and injected into the veins of people with low or abnormal antibody production to help protect them from infections. See Also: Antibody

In Utero: The time period when an unborn baby is in its mother's uterus.

Investigational Drug: Also known as experimental drug. A drug that has not been approved by the Food and Drug Administration (FDA) to treat a particular disease or condition. The safety and effectiveness of an investigational drug must be tested in clinical trials before the manufacturer can request FDA approval for a specific use of the drug. See Also: Clinical Trial Investigational New Drug (IND) Application

Investigational New Drug (IND) Application: The process through which data about an experimental drug is submitted to and reviewed by the Food and Drug Administration (FDA) before the drug is allowed to be tested in clinical trials. See Also: Clinical Trial New Drug Application (NDA) Investigational Drug

In Vitro: Latin for "in glass." Indicates that a research study was conducted in an artificial environment created outside a living organism (for example, in a test tube or petri dish). In Vivo Latin for "in life." Indicates that a research study was conducted in a living organism (animal or human).

IRB: See: Institutional Review Board

IRIS: See: Immune Reconstitution Syndrome

IRS: See: Immune Reconstitution Syndrome

Isosporiasis: An infection caused by the protozoan Isospora belli, which enters the body through contaminated food or water. Symptoms include diarrhea, fever, headache, abdominal pain, vomiting, and weight loss. Isosporiasis is considered an AIDS-defining condition in people with HIV.

ITP: See: Idiopathic Thrombocytopenia Purpura

IVIG: See: Intravenous Immunoglobulin



Jaundice: Yellowing of the skin, mucous membranes, whites of the eyes, and body fluids. Jaundice is caused by increased levels of bilirubin, and it is associated with liver and gallbladder disease. See Also: Bilirubin



Kaposi's Sarcoma (KS): A type of cancer caused by anovergrowth of blood vessels,which causes pink or purple spots or small bumps on the skin. The condition can also occur inside the body, especially inside the intestines, lymph nodes, and lung. When inside the body, KS can be life threatening. In people infected with HIV, KS is considered an AIDS-defining condition. A virus called Kaposi's sarcoma herpesvirus (KSHV) or human herpesvirus 8 (HHV-8) is associated with Kaposi's sarcoma. See Also: Kaposi's Sarcoma Herpesvirus (KSHV)

Kaposi's Sarcoma Herpesvirus (KSHV): Also known as Human Herpesvirus 8 (HHV-8). The virus associated with Kaposi's sarcoma (KS), a type of cancer that is considered an AIDS-defining condition in people with HIV. See Also: Herpesviruses, Kaposi's Sarcoma (KS)

Karnofsky Score: A score between 0 and 100 assigned by a health professional after watching a patient perform common tasks. A score of 100 means that the patient has normal physical abilities with no signs of disease. Decreasing numbers mean that the patient has less ability to perform activities of daily living.

Killer T Cell: See: CD8 Cell

KS: See: Kaposi's Sarcoma

KSHV: See: Kaposi's Sarcoma Herpesvirus



Lactic Acidosis: A condition caused by a buildup of lactate, a cellular waste product, in the blood. Symptoms, if any, may include stomach and breathing problems and general weakness. Severe, untreated lactic acidosis can be life threatening. Increased lactate levels, often combined with hepatic steatosis, may occur in HIV-infected individuals taking NRTIs. See Also: Hepatic Steatosis

LAS: See: Lymphadenopathy Syndrome

Latency: The time period when an infectious organism is in the body but is not producing any noticeable symptoms. In HIV disease, latency usually occurs in the early years of infection. Also refers to the period when HIV has integrated its genome into a cell's DNA but has not yet begun to replicate.

Latent HIV Reservoir: A collection of resting cells (such as T cells) in the body that are infected with HIV. The virus is spread within the body when these host cells become active. See Also: Latency

Latent Period: See: Latency

Lentivirus: A subgroup of the retrovirus family that includes HIV. Lentiviruses are characterized by a long time period between infection and the onset of symptoms (long latent period). See Also: Retrovirus Incubation Period

Lesion: An area of the body where tissue is abnormal, such as an infected patch or sore on the skin.

Leukocyte: See: White Blood Cell

Leukocytosis: An abnormally high number of white blood cells in the blood. This condition usually occurs during infection or inflammation. See Also: White Blood Cell

Leukopenia: A lower than normal number of total white blood cells. A white blood cell count less than 4,000 cells/mL is considered leukopenia.

Leukoplakia: See: Oral Hairy Leukoplakia (OHL)

LGV: See: Lymphogranuloma Venereum

Life Cycle: A sequence of developmental phases that cells or organisms undergo. For example, a cell's life cycle ends with division; a virus's life cycle includes replication within a host cell.

Linear Gingival Erythema: Inflammation of the gums that usually appears as a red band around the gums in the back of the mouth. Also known as HIV gingivitis or red-band gingivitis.

LIP: See: Lymphoid Interstitial Pneumonitis

Lipid: Any member of a chemical group of fats or fat-like substances.

Lipid Profile: A group of blood tests that are often ordered together to evaluate an individual's risk for heart disease or stroke. These tests include measurements of total cholesterol, HDL cholesterol ("good" cholesterol), LDL cholesterol ("bad" cholesterol), and triglycerides. See Also: Cholesterol Triglycerides Hyperlipidemia

Lipoatrophy: Loss of body fat from particular areas of the body, especially the arms, legs, face, and buttocks. Lipoatrophy is a potential side effect of some NRTIs.

Lipodystrophy: A problem with the way the body produces, uses, and distributes fat. Lipodystrophy is associated with certain anti-HIV drugs. HIVrelated lipodystrophy includes the body changes known as buffalo hump and protease paunch. See Also: Body Habitus Changes, Lipohypertrophy

Lipohypertrophy: Also known as hyperadiposity. Abnormal buildup of fat, particularly in the breasts, on the back of the neck and upper shoulders (buffalo hump), deep within the abdomen (protease paunch), or in fatty growths known as lipomas. Lipohypertrophy may occur with the use of some PIs and NRTIs. See Also: Body Habitus Changes, Lipodystrophy

Liver Function Tests: Blood tests that measure the levels of liver enzymes (proteins made and used by the liver) to determine if the liver is working properly. The liver enzymes that are routinely measured as part of liver function tests are aspartate aminotransferase (AST) - also called serum glutamic oxaloacetic transaminase (SGOT), alanine aminotransferase (ALT) - also called serum glutamic pyruvic transaminase (SGPT), and gamma-glutamyltransferase (GGT). Increased levels of these enzymes indicate that the liver has been damaged. See Also: Hepatotoxicity

Localized: A term used to describe a disease or treatment that affects only a specific or limited part of the body rather than the entire body. See Also: Systemic

Log: This mathematical term represents a change in value of what is being measured by a factor of 10. Changes in viral load (the amount of HIV in the blood) are often reported as logarithmic or log changes. For example, if the viral load is 20,000 copies mL, then a 1-log increase equals a 10-fold (10 times) increase, or 200,000 copies/mL. A 2-log increase equals a 100-fold increase, or 2,000,000 copies/mL.

Long-Term Nonprogressors: People who have been infected with HIV for a number of years (usually at least 7) but who have had stable CD4 cell counts of 600 cells/mL or more, no HIV-related diseases, and no need for anti-HIV therapy.

Lumbar Puncture: See: Spinal Tap

Lymph: A clear, slightly yellow fluid that carries disease-fighting white blood cells from the blood to and from body tissues.

Lymphadenopathy Syndrome (LAS): Swollen, firm, and possibly tender lymph nodes. The causes range from infection, such as HIV, the flu, or mononucleosis, to lymphoma (cancer of the lymphoid tissue). See Also: Lymph Nodes

Lymph Nodes: Very small organs of the immune system that are located throughout the body. Lymph fluid that bathes body tissues is filtered through lymph nodes as it carries white blood cells to and from the blood. See Also: Lymph, Lymphadenopathy Syndrome (LAS)

Lymphocyte: A type of infection-fighting white blood cell found in the blood, lymph, and lymphoid tissue.

Lymphocyte Proliferation Assay: A laboratory test that measures the ability of lymphocytes (infection-fighting white blood cells) to recognize an antigen and to make more copies of themselves (proliferate) in response to the antigen encountered. See Also: Antigen

Lymphogranuloma Venereum (LGV): A sexually transmitted disease (STD) caused by a species of the Chlamydia bacterium. It is characterized by genital lesions and swelling of lymph nodes in the groin. See Also: Chlamydia

Lymphoid Interstitial Pneumonitis (LIP): A lung disorder that causes hardening of the parts of the lung that aid in oxygen absorption. The cause of LIP is unknown, and there is no clear treatment. LIP is an AIDS-defining condition in HIV-infected children.

Lymphokine: A cytokine (chemical messenger that affects the immune response) secreted by white blood cells. See Also: Cytokine

Lymphoma: Cancer of the lymphoid tissues. Some types of lymphomas, such as non-Hodgkin's lymphoma and Hodgkin's disease, are associated with HIV infection.

Lymphopenia: A lower than normal number of lymphocytes, a specific type of white blood cell.

Lymphoproliferative Response: An immune system response that results in a rapid increase in the number of white blood cells.

Lysis: The destructive breaking apart of a cell.



MAC: See: Mycobacterium Avium Complex

Macrophage: A type of disease-fighting white blood cell that destroys foreign invaders and stimulates other immune system cells to fight infection.

MACS: See: Multicenter AIDS Cohort Study

Magnetic Resonance Imaging (MRI): A noninvasive technique that uses magnetic fields and radio waves instead of x-rays to produce three-dimensional computerized images of the body's internal tissues and organs.

Maintenance Therapy: Also known as secondary prophylaxis. A treatment to prevent an infection from coming back after it has been brought under control.

Major Histocompatibility Complex (MHC): See: Human Leukocyte Antigen (HLA)

Malabsorption Syndrome: A condition that occurs when the intestines have problems absorbing nutrients. Malabsorption syndrome is associated with HIV infection and can cause loss of appetite, muscle pain, and weight loss. See Also: Wasting Syndrome

Malaise: A general feeling of discomfort or not feeling well.

Malaria: A disease, more common in areas with warm climates (e.g., South America, Africa), that is caused by a parasite and transmitted by the bite of an infected female mosquito. People infected with malaria have flu-like symptoms, most commonly chills and fever. More severe symptoms, such as seizures and coma, may also develop. Malaria is harder to prevent and treat in people with weakened immune systems, such as those infected with HIV.

Malignant: Referring to uncontrolled cell growth that may spread to other tissues, such as in cancer.

Mast Cell: A type of leukocyte. See Also: Leukocyte

Maternal-Child Transmission: See: Mother-to-Child Transmission (MTCT)

MDR-TB: See: Multiple Drug-Resistant Tuberculosis

Medication Event Monitoring System (MEMS): A method of measuring drug adherence that uses a computer chip embedded in a pill bottle lid to record the date and time each dose is taken. Current obstacles to its use include its large size, the possibility of malfunction when refrigerated, and inaccurate reporting when pillboxes are used in place of the original bottle. See Also: Adherence Directly Observed Therapy (DOT)

MedlinePlus: A database of health information developed by the National Library of Medicine (NLM). MedlinePlus has information on several hundred diseases and conditions as well as other health information. http://

Memory T Cell: A specific type of infection-fighting T cell that can recognize foreign invaders that were encountered during a prior infection or vaccination. At a second encounter with the invader, memory T cells.

MEMS: See: Medication Event Monitoring System

Meningitis: Inflammation of the membranes that surround the brain or spinal cord. Meningitis can be caused by a bacterium, fungus, or virus, such as HIV.

Messenger RNA (mRNA): A molecule that carries genetic instructions for building a particular protein from the cell's DNA to the place in a cell where proteins are assembled. There, the messenger RNA serves as a blueprint for the construction of a specific protein. See Also: Translation, Transcription

Metabolic: Related to the processes of metabolism, or the chemical changes in living things by which substances are built up or broken down.

Metabolic Syndrome: Also known as Syndrome X. A cluster of disorders that affect the body's metabolism, including high blood pressure, high insulin levels, excess body weight, and abnormal cholesterol levels. Some anti-HIV drugs may cause or worsen these metabolic disorders.

Metabolism: The physical and chemical reactions that produce energy for the body. Metabolism also refers to the breakdown of drugs or other substances within the body, which may occur during digestion or elimination.

MHC: See: Major Histocompatibility Complex

Microbe: A living organism that can be seen only through a microscope, such as bacteria, protozoa, viruses, and fungi.

Microbicide: A natural or man-made substance that kills microbes. Researchers are studying the use of microbicides to prevent the transmission of sexually transmitted diseases (STDs), including HIV infection. See Also: Microbe

Microbicide Trials Network (MTN): A clinical trials network that evaluates the development of microbicides to reduce the transmission of HIV. See Also: Microbicide

Microsporidiosis: An infection of the intestines caused by a parasite. The infection can cause diarrhea and wasting (loss of weight and strength) in people with HIV.

Mitochondria: Rod-like structures that produce energy for a cell.

Mitochondrial Toxicity: A condition in which mitochondria are damaged. This condition is a potential side effect of NRTIs and can cause problems in the heart, nerves, muscles, pancreas, kidneys, and liver. See Also: Mitochondria

Molluscum Contagiosum: A disease of the skin and mucous membranes caused by a virus. The condition causes pearly white or flesh-colored bumps on the face, neck, underarms, hands, and genital region. In people with8 HIV, molluscum contagiosum can get worse with time and often becomes resistant to treatment.

Monotherapy: The use of only one drug to treat a disease. For HIV, combination therapy with three or more active anti-HIV drugs has proven to be more effective than monotherapy. Combination therapy, also known as highly active antiretroviral therapy or HAART, is now the gold standard for HIV treatment. See Also: Highly Active Antiretroviral Therapy (HAART)

Morbidity: The rate of sickness or disease within a certain population.

Mortality: The death rate, measured as the number of deaths within a certain population. The measure can apply to death from a particular disease or condition.

Mother-to-Child Transmission (MTCT): The passage of HIV from an HIV-infected mother to her infant. The infant may become infected while in the womb, during labor and delivery, or through breastfeeding. See Also: Vertical Transmission

MRI: See: Magnetic Resonance Imaging

mRNA: See: Messenger RNA

MSM: Abbreviation for men who have sex with men.

MTCT: See: Mother-to-Child Transmission

MTN: See: Microbicide Trials Network

M-Tropic Virus: See: R5-Tropic Virus See Also: CCR5

Mucocutaneous: Relating to mucous membranes and the skin. Examples of mucocutaneous areas include the mouth, lips, eyes, vagina, and anal area.

Multicenter AIDS Cohort Study (MACS): An ongoing study of HIV infection in homosexual and bisexual men. The study is cofunded by the National Institute of Allergy and Infectious Diseases (NIAID); the National Cancer Institute (NCI); and the National Heart, Lung, and Blood Institute (NHLBI) and is conducted at four clinical centers. Information about the natural history of HIV disease, the impact of treatment on disease progression, the role of genetic factors, and other long-term therapy issues are continually reported from study evaluations.

Multi-Class Antiretroviral Therapy: See: Highly Active Antiretroviral Therapy (HAART)

Multiple Drug-Resistant Tuberculosis (MDR-TB): A tuberculosis (TB) infection that does not respond to two or more standard anti-TB drugs. MDR-TB usually occurs when inadequate or improper treatment allows the bacteria that cause TB to continue multiplying and become drug resistant. See Also: Tuberculosis (TB)

Mutation: A change or adaptation, such as in a virus, that can be passed down to future generations of virus. Mutations can occur only when a virus is actively replicating, and not when anti-HIV drugs have suppressed the viral load to an undetectable level. If HIV replication is not well controlled, an individual's original HIV strain can adapt to infect different cell types or resist different anti-HIV drugs. See Also: Drug Resistance

Myalgia: Muscle pain or tenderness that spreads throughout the body and is usually accompanied by a general feeling of discomfort or weakness.

Mycobacterium Avium Complex (MAC): An infection caused by two bacteria, Mycobacterium avium and M. intracellulare, found in soil and dust particles. The infection can be limited to a specific area or can spread throughout the body. This life-threatening disease is extremely rare in people who are
not infected with HIV, and MAC is considered an AIDS-defining condition in HIV-infected people.

Mycobacterium Avium-Intracellulare (MAI): An infection caused by Mycobacterium intracellulare, which is found in soil and dust particles. The infection can be limited to a specific area or can spread throughout the body. This life threatening disease is extremely rare in people who are not infected with HIV, and MAI is considered an AIDS-defining condition in HIV-infected people. See Also: AIDS-Defining Condition Mycobacterium Avium Complex (MAC)

Mycobacterium tuberculosis: The bacterium that causes tuberculosis (TB). See Also: Tuberculosis (TB)

Mycosis: Any disease caused by a fungus.

Myeloablation: Severe myelosuppression. See Also: Myelosuppression

Myelosuppression: Decreased bone marrow function that results in reduced production of red blood cells, white blood cells, or platelets. Myelosuppression is a side effect of certain anti-HIV drugs.

Myopathy: A disease of muscle tissue. Myopathy may be caused by certain anti-HIV drugs or may be a consequence of HIV infection itself.



Nadir: The lowest level to which viral load (the amount of HIV in the blood) falls after a person starts anti-HIV treatment. Also refers to the lowest CD4 count a person reaches during HIV infection.

National Cancer Institute (NCI): An institute of the National Institutes of Health (NIH) and the U.S. government's principal agency for cancer research and training. This institute provides health information and supports programs focusing on the causes, diagnosis, prevention, and treatment of cancer; rehabilitation from cancer; and the continuing care of cancer patients and the families of cancer patients.

National Institute of Allergy and Infectious Diseases (NIAID): An institute of the National Institutes of Health (NIH) that conducts and funds research to better understand, treat, and prevent infectious, immunologic, and allergic diseases.

National Institutes of Health (NIH): A multi-institute agency of the U.S. Department of Health and Human Services (HHS). NIH conducts research in its own laboratories and funds research in universities, medical schools, hospitals, and other research institutions throughout the United States and abroad.

National Library of Medicine (NLM): An institute of the National Institutes of Health (NIH) and the world's largest medical library. NLM collects materials in all areas of biomedicine and health care and is involved in biomedical aspects of other fields, such as technology and the social sciences.

National Prevention Information Network (NPIN): A national reference, referral, and distribution service for information on HIV/AIDS, other sexually transmitted diseases (STDs), and tuberculosis (TB), sponsored by the Centers for Disease Control and Prevention (CDC).

Natural History Study: A study designed to investigate the natural development of a disease or condition over time.

Natural Killer (NK) Cell: A type of white blood cell that is able to kill tumor cells and cells infected with viruses or other foreign invaders.

NCI: See: National Cancer Institute

NDA: See: New Drug Application

Nemaline Rod Myopathy (NM): A rare disorder in which thread-like rods grow inside muscle cells and can lead to debilitating muscle weakness. It can develop as a result of a genetic defect or as a complication of HIV.

Neonatal: The time period from birth through the first 4 weeks after birth.

Neoplasm: Also called a tumor. Any new, abnormal growth of tissue. Neoplasms may be benign (not cancerous) or malignant (cancerous).

Nephritis: Inflammation of the kidney that can occur as a side effect of some anti-HIV drugs.

Nephrotoxic: Toxic or destructive to the kidneys.

Neuralgia: Sharp, shooting pain along a nerve pathway.

Neuropathy: A disorder that occurs when nerve cells are damaged. Symptoms range from a tingling sensation or numbness in the toes and fingers to paralysis. Neuropathy can occur as a result of HIV infection or as a side effect of certain anti-HIV drugs. See Also: Peripheral Neuropathy

Neutropenia: A lower than normal number of neutrophils (a type of white blood cell) in the blood. Moderate to severe neutropenia can increase the chance of developing bacterial infections. Neutropenia may occur as a result of HIV infection or as a side effect of some anti-HIV drugs. See Also: Neutrophil

Neutrophil: A type of white blood cell that can engulf and kill foreign invaders, such as bacteria.

New Drug Application (NDA): An application submitted by a drug manufacturer to the Food and Drug Administration (FDA) for a license to market and sell a particular drug in the United States. The drug manufacturer files an NDA after information from clinical trials is available for FDA review. See Also: Investigational New Drug (IND) Application

NHL: See: Non-Hodgkin's Lymphoma

NIAID: See: National Institute of Allergy and Infectious Diseases

NIH: See: National Institutes of Health

NK Cell: See: Natural Killer Cell

NLM: See: National Library of Medicine

NNRTI: See: Non-Nucleoside Reverse Transcriptase Inhibitor

NNRTI-Sparing Regimen: Drug combination that omits the use of any NNRTIs so that the drug class can be saved for use in future treatment. See Also: Class-Sparing Regimen

Non-Hodgkin's Lymphoma (NHL): A cancer of the lymphoid tissue that can affect the lymph nodes, spleen, bone marrow, and other organs of the immune system. This type of cancer typically develops in people with weakened immune systems, including organ transplant recipients and people with HIV
or AIDS. See Also: Hodgkin's Lymphoma Lymphoma

Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI): A class of anti-HIV drugs that bind to and disable HIV-1's reverse transcriptase enzyme, a protein that HIV needs to make more copies of itself. Without functional reverse transcriptase, HIV replication is halted. Current NNRTI drugs are only effective against HIV-1 and not against HIV-2. See Also: Reverse Transcriptase (RT)

Non-Steroidal Anti-Inflammatory Drug (NSAID): A class of drugs that can reduce inflammation, swelling, stiffness, and joint pain. They are used to treat arthritis and mild to moderate pain. Some common NSAIDs are aspirin and ibuprofen.

NPIN: See: National Prevention Information Network

NRTI: See: Nucleoside Reverse Transcriptase Inhibitor

NRTI-Sparing Regimen: Drug combination that omits the use of any NRTIs so that the drug class can be saved for use in future treatment. See Also: Class-Sparing Regimen

NSAID: See: Non-Steroidal Anti-Inflammatory Drug

Nucleic Acid: Chemical structure that stores genetic information. There are two types of nucleic acid, DNA and RNA. Human genetic information is stored as DNA, whereas HIV's genetic information can be stored as both DNA and RNA. See Also: Deoxyribonucleic Acid (DNA) Ribonucleic Acid (RNA)

Nucleic Acid Test: A laboratory test that can detect very small amounts of specific genetic material in blood, plasma, or other tissue. This test can detect several types of viruses and is used to screen blood from blood donors.

Nucleoside: A precursor to a building block of DNA or RNA. Nucleosides must be chemically changed into nucleotides before they can be used to make DNA or RNA. See Also: Deoxyribonucleic Acid (DNA), Ribonucleic Acid (RNA), Nucleotide

Nucleoside Analogue Reverse Transcriptase Inhibitor (NRTI): A class of anti-HIV drug. Nucleoside analogues are faulty versions of the building blocks necessary for HIV reproduction. When HIV's reverse transcriptase enzyme uses a nucleoside analogue instead of a normal nucleoside, reproduction of the virus's genetic material is halted. Also called nucleoside analogues or nukes. See Also: Nucleoside Reverse Transcriptase (RT)

Nucleoside-Associated Resistance Mutation (NAM): A viral mutation that increases HIV resistance to treatment by NRTI drugs. See Also: Thymidine Analogue Mutation (TAM)

Nucleotide: A building block of DNA or RNA, the chemical structures that store genetic information. See Also: Deoxyribonucleic Acid (DNA) Ribonucleic Acid (RNA)

Nucleotide Analogue Reverse Transcriptase Inhibitor (NtRTI): A class of anti-HIV drug. Nucleotide analogues are faulty versions of the building blocks necessary for HIV reproduction. When HIV's reverse transcriptase enzyme uses a nucleotide analogue instead of a normal nucleotide, reproduction of the virus's genetic material is halted. Although technically different from nucleoside analogues, nucleotide analogues work in the same way. Also called nucleotide analogues or nukes. See Also: Nucleotide, Reverse Transcriptase (RT)

Nucleus: The part of a cell that contains the organism's genetic information.

Nuke: Slang term for nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). See Also: Nucleoside Analogue Reverse Transcriptase Inhibitor (NRTI) Nucleotide Analogue Reverse Transcriptase Inhibitor (NtRTI)



OAR: See: Office of AIDS Research

Observational Study: See: Clinical Trial

OBT: See: Optimized Background Therapy

Occupational Exposure: Exposure to potentially infectious material, such as blood, tissue, body fluids, medical equipment, or supplies, while at work. The exposure could occur through a needlestick, a cut with an object, contact with the mucous membrane, or contact with skin that has a break in it.

Office of AIDS Research (OAR): The office within the National Institutes of Health's (NIH's) National Institute of Allergy and Infectious Diseases (NIAID) responsible for the scientific, budgetary, legislative, and policy elements of the NIH HIV/AIDS research program.

Off-Label Use: Prescribed use of a drug for a condition other than one approved by the Food and Drug Administration (FDA) or for a patient population or at a dosage not approved by the FDA.

OHL: See: Oral Hairy Leukoplakia

OI: See: Opportunistic Infection

Open-Label Trial: A clinical trial in which both the researchers and the participants know who is getting which drug or vaccine. See Also: Double-Blind Study

Opportunistic Infection (OI): An illness caused by any one of various organisms that occur in people with weakened immune systems, including people with HIV/AIDS. OIs that are common in people with AIDS include Pneumocystis jiroveci pneumonia (PCP); cryptosporidiosis; histoplasmosis; toxoplasmosis; other parasitic, viral, and fungal infections; and some types of cancers.

Optimized Background Therapy (OBT): The anti-HIV drugs in a treatment regimen that are chosen for an individual on the basis of resistance testing and treatment history. In clinical trials, patients often receive either the drug being tested or a placebo (sugar pill for comparison) in addition to OBT, so that they do not receive monotherapy or no treatment.

Oral Hairy Leukoplakia (OHL): A white-colored, hairy, or ribbed patch that appears on the side of the tongue and inside the cheeks. It develops mainly in people with weakened immune systems, including people with HIV. It is caused by Epstein-Barr virus (EBV), a member of the herpesvirus family. See Also: Epstein-Barr Virus (EBV)

Osteonecrosis: Also referred to as avascular necrosis. A medical condition in which bone tissue dies. Osteonecrosis affects some people with HIV, but it is unclear if it develops as a complication of HIV infection or as a side effect of anti-HIV drugs. See Also: Avascular Necrosis (AVN)

Osteopenia: A medical condition in which bones lose their minerals and become less dense, making them weaker and easier to break.

Osteoporosis: Severe loss of bone mass, density, and strength. Although usually an age-related disorder, osteoporosis may also occur as a result of HIV infection or as a side effect of anti-HIV drugs.




p24: An HIV protein that makes up the virus core that surrounds HIV's genetic material. See Also: Core

Package Insert: Also known as prescribing information or product label. A document prepared by the manufacturer of a drug and approved by the Food and Drug Administration (FDA) to describe a drug's approved uses, dosages, contraindications, potential side effects, and other relevant information. This information is inserted inside each manufactured drug bottle and attached to any promotional or labeling materials.

PACTG: See Also: Pediatric AIDS Clinical Trials Group

Palliative Care: Medical care that helps to alleviate symptoms of chronic illnesses without offering a cure. Palliative care offers therapies to comfort and support patients with terminal illnesses.

Pancreas: A gland located near the stomach that secretes digestive fluids that help to break down fats, proteins, and carbohydrates. The pancreas also secretes the hormones insulin and glucagon, which help to stabilize blood sugar.

Pancreatitis: Inflammation of the pancreas that can cause severe pain. Laboratory tests that indicate pancreatitis include increased blood levels of triglycerides and the pancreatic enzyme amylase. See Also: Pancreas

Pancytopenia: A lower than normal number of all types of blood cells, including red and white blood cells and platelets. Pandemic: An outbreak of an infectious disease, such as HIV, that affects people or animals over an extensive geographic area. Also known as a global epidemic See Also: Epidemic

Papilloma: A tumor that grows on the skin, such as a wart or polyp. Human papillomavirus (HPV) is the virus that causes papillomas, including genital warts. See Also: Human Papillomavirus (HPV) Genital Warts

Pap Smear: A method for the early detection of cancer and other abnormalities of the female genital tract. A Pap smear is done by placing a speculum in the vagina, locating the cervix, and then scraping a thin layer of cells from the cervix. The cells are placed on a slide, sent to a laboratory, and analyzed for abnormalities. HIV-infected women often have abnormal results of Pap smear tests, usually as a result of human papillomavirus (HPV) infection. See Also: Human Papillomavirus (HPV) Cervical Cancer

Parasite: An organism that lives and feeds on or within another living organism and causes some degree of harm. Immunocompromised people, such as those infected with HIV, are more likely to develop parasitic infections, such as Pneumocystis jiroveci pneumonia (PCP) and toxoplasmosis.

Parenteral: Any route of administration, such as for a drug, into the body other than through the digestive system. For example, through the veins (intravenous), into the muscles (intramuscular), or through
the skin (subcutaneous).

Paresthesia: Abnormal sensations, such as burning, tingling, or a "pins-andneedles" feeling, that occur without external stimulation. Paresthesia can occur as a symptom of peripheral neuropathy or as a side effect of certain anti-HIV drugs. See Also: Peripheral Neuropathy

Passive Immunity: The body's ability to prevent or fight a specific infection after receiving antibodies from another person. The most common example of passive immunity is when an infant receives the mother's antibodies by consuming her breast milk. See Also: Antibody

Passive Immunotherapy: The transfer of antibodies from one person to another to help the recipient fight infection. An example of passive immunotherapy is the use of plasma donated by healthy HIV-infected people who have high CD4 counts and high levels of anti-HIV antibodies. The plasma is administered to people with AIDS who have lost CD4 cells and can no longer make their own antibodies. Passive immunotherapy has been used with limited success in treating advanced HIV disease in adults, but it is still sometimes used in HIV-infected children. See Also: Passive Immunity

Pathogen: General term for any disease-causing organism.

Pathogenesis: General term for the origin and development of disease.

PBMC: See: Peripheral Blood Mononuclear Cell

PCP: See: Pneumocystis jiroveci Pneumonia

PCR: See: Polymerase Chain Reaction

Peak Concentration: See: CMAX

Pediatric AIDS Clinical Trials Group (PACTG): Now known as the International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Network. A large clinical trials network that evaluates treatments for HIV-infected children and adolescents and that develops new therapeutic approaches for preventing mother to- child transmission (MTCT) of HIV. See Also: International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Network

Pelvic Inflammatory Disease (PID): An infection of the upper female genital tract affecting the uterus, fallopian tubes, and ovaries. It is usually caused by the bacteria responsible for two common sexually transmitted diseases (STDs), gonorrhea and chlamydia. If left untreated, PID can cause severe pain, tubal pregnancy, and infertility. Severe cases may even spread to the liver and kidneys, causing dangerous internal bleeding and death.

People Living with AIDS (PLWA): Infants, children, adolescents, and adults infected with HIV/AIDS.

PEP: See: Post-Exposure Prophylaxis

PEPFAR: See: President's Emergency Plan for AIDS Relief

Peptide: A short chain of amino acids that are chemically linked to one another. Longer chains of amino acids are referred to as polypeptides. See Also: Polypeptide Amino Acid

Perianal: Around the anus.

Perinatal: The time period spanning shortly before and after birth.

Perinatal Transmission: See: Mother-to-Child Transmission

Peripheral Blood Mononuclear Cell (PBMC): A general term for white blood cells that contain one nucleus, particularly lymphocytes and macrophages. See Also: Lymphocyte Macrophage

Peripheral Neuropathy: Condition characterized by sensory loss; pain; muscle weakness; and wasting of muscle in the hands, legs, or feet. It may start with burning or tingling sensations or numbness in the toes and fingers. In severe cases, paralysis may occur. Peripheral neuropathy may result from HIV infection itself or may be a side effect of certain anti- HIV drugs, particularly NRTIs. See Also: Neuropathy

Persistent Generalized Lymphadenopathy (PGL): Chronic and persistent swollen lymph nodes in at least two areas of the body for at least 3 months. PGL occurs in people with persistent bacterial, viral, or fungal infections and in individuals with weakened immune systems, including people with HIV.

PGL: See: Persistent Generalized Lymphadenopathy

Pharmacokinetics: The interaction of a drug with the body over a period of time. General pharmacokinetic processes are absorption, distribution, metabolism, and excretion. These processes are usually measured through blood and urine samples.

Pharmacology: The branch of medical science that studies the chemistry, effects, and uses of drugs. Pharmacology includes the study of a drug's therapeutic value, toxicology, and interaction with the body (pharmacokinetics). See Also: Pharmacokinetics

Phase I Trial: An initial clinical study of new drugs or other therapies in small groups of healthy volunteers, usually 20 to 80 people. This phase of clinical trial determines initial drug safety and side effects.

Phase II Trial: An early clinical study that evaluates the safety and effectiveness of new drugs or other therapies. Phase II trials also help determine short-term side effects and risks associated with new drugs. This trial phase usually recruits no more than 100 people affected with the disease or condition under study.

Phase III Trial: A clinical study that compares the effectiveness of new drugs to standard therapies for the disease or condition in question. This trial phase recruits a large population of people with the disease or condition being studied, ranging from several hundred to several thousand volunteers. The results of these trials are used to evaluate the overall risks and benefits of the drug and to provide the information needed for the Food and Drug Administration (FDA) to consider the drug for approval.

Phase IV Trial: A clinical study that occurs after a drug has been approved by the Food and Drug Administration (FDA) to determine long-term safety and effectiveness. Sometimes referred to as a post marketing study. This trial phase recruits the largest population of patients to gain additional information about the drug's risks, benefits, and optimal use.

Phenotypic Assay: A laboratory test that determines by direct experiment whether a particular strain of HIV is resistant to anti-HIV drugs. This is different from a genotypic assay, which uses an indirect method to find out if a particular strain of HIV has specific genetic mutations that are associated with drug resistance. See Also: Resistance Testing Genotypic Assay

Photosensitivity: Increased sensitivity of skin to sunlight or ultraviolet light. Photosensitivity commonly causes reddening and blistering of the skin and in time increases a person's risk of skin cancer. Photosensitivity may occur as a side effect of some drugs or as a result of HIV infection.

PHS: See: Public Health Service

PI: See: Protease Inhibitor

PID: See: Pelvic Inflammatory Disease

Pill Burden: The number and schedule of pills taken each day in a particular anti-HIV drug regimen. A high pill burden may lead to decreased treatment adherence because of the difficulty of taking a large number of pills properly. See Also: Adherence

PI-Sparing Regimen: An anti-HIV drug regimen that does not include a PI. See Also: Protease Inhibitor (PI) Class-Sparing Regimen

Placebo: Sometimes called a sugar pill. A pill or other treatment that looks like the treatment being tested in a clinical trial but does not actually contain the active ingredient. Placebos are used in some clinical trials to control for what is called the "placebo effect": an effect that is caused by the power of suggestion alone. The effects of the placebo are then compared with the effects of the active ingredient to determine if the ingredient is truly effective. See Also: Placebo Effect

Placebo-Controlled Study: A study that identifies the true effect of a treatment by comparing results in patients taking the actual treatment to those in patients taking an inactive look-alike, or placebo, treatment. See Also: Placebo Effect

Placebo Effect: A positive or negative response to an inactive treatment (placebo) caused by a patient's or researcher's expectations that a particular treatment will have an effect. See Also: Placebo, Placebo-Controlled Study

Plasma: The clear, liquid part of the blood in which red blood cells, white blood cells, and platelets are suspended. Plasma contains nutrients, wastes, salts, gases, and proteins.

Platelet: A type of cell in the blood responsible for clotting. When blood vessels are damaged, platelets help to form a plug that prevents the loss of blood.

PLWA: See: People Living With AIDS

PML: See: Progressive Multifocal Leukoencephalopathy

PMTCT: See: Prevention of Mother-To-Child Transmission

Pneumocystis jiroveci: A type of fungus that can cause severe pneumonia in humans, particularly in people with weakened immune systems, and especially in people with AIDS. P. jiroveci is related to P. carinii, the species for which PCP (originally, P. carinii pneumonia) is named. See Also: Pneumocystis jiroveci Pneumonia (PCP)

Pneumocystis jiroveci Pneumonia (PCP): A lung infection caused by Pneumocystis jiroveci, a fungus related to P. carinii (the species for which PCP was originally named). PCP occurs in people with weakened immune systems, such as people with HIV. It is considered an AIDS-defining condition in HIV-infected individuals. The first signs of infection are difficulty breathing, high fever, and dry cough. See Also: Pneumocystis jiroveci

Polymerase Chain Reaction (PCR): A laboratory technique that rapidly replicates tiny amounts of DNA so that it can be detected and measured. See Also: Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) Polyneuritis: Inflammation of several nerves at the same time.

Polypeptide: A long chain of amino acids that are chemically linked to one another. Shorter chains of amino acids are referred to as peptides. See Also: Amino Acid Peptide

Polyvalent Vaccine: A vaccine that combines multiple antigens. This type of vaccine may produce a stronger immune response or may provide protection from multiple strains of an infectious organism. See Also: Antigen Vaccine

Post-Exposure Prophylaxis (PEP): Administration of anti-HIV drugs within 72 hours of a high-risk exposure, including unprotected sex, needle sharing, or occupational needle stick injury, to help prevent development of HIV infection. See Also: Prophylaxis Pre-Exposure Prophylaxis (PrEP)

Postnatal: The time period following birth (refers to the newborn). See Also: Postpartum Prenatal

Postpartum: The time period after childbirth (refers to the mother). See Also: Postnatal Antepartum

PPD: See: Purified Protein Derivative

Preclinical: Refers to the preliminary testing of investigational drugs in laboratory animals that occurs before human testing may begin.

Preconception Counseling: A specific type of health care recommended by the American College of Obstetrics and Gynecology for all women of childbearing age prior to pregnancy. Its purpose is to identify risks of pregnancy and childbirth for both mother and child, to provide education and counseling targeted to a woman's individual needs, and to treat or stabilize medical conditions prior to pregnancy in order to optimize the mother's and infant's health.

Pre-Exposure Prophylaxis (PrEP): The use of antiretroviral drugs as a preventive measure to potentially decrease the risk of HIV transmission. Similar to providing anti-malarial drugs to travelers in countries with high rates of malaria as a preventive measure.

Prenatal: Period of time spanning conception to the beginning of labor.

PrEP: See: Pre-Exposure Prophylaxis

Prescribing Information: See: Package Insert

President's Emergency Plan for AIDS Relief (PEPFAR): The U.S. government initiative to combat the global HIV/AIDS epidemic. PEPFAR's goal is to work with international, national, and local leaders worldwide to support integrated HIV prevention, treatment, and care programs. PEPFAR was originally signed into law in May 2003 and reauthorized in August 2008.

Prevalence: The number of people in a population who are affected with a particular disease or condition at a given time. Prevalence can be thought of as a snapshot of all existing cases of a disease or condition at a specified time. See Also: Incidence

Prevention of Mother-to-Child Transmission (PMTCT): Prevention of the passage of HIV from an HIV-infected mother to her infant, whether in the womb, during labor and delivery, or through breastfeeding.

Preventive HIV Vaccine: A vaccine designed to prevent HIV infection in people who are HIV negative. Preventive HIV vaccines are not designed to treat those already infected with HIV. See Also: Therapeutic HIV Vaccine

Primary HIV Infection: See: Acute HIV Infection

Primary Isolate: A strain of HIV taken from an infected individual, as opposed to a strain grown in the laboratory.

Primary Prophylaxis: Treatment to prevent the development of a particular disease. See Also: Chemoprevention Chemoprophylaxis Prophylaxis

Primary Resistance: When an individual is infected by a strain of HIV-1 that is already resistant to one or more antiretroviral drugs.

Proctitis: Inflammation of the lining of the rectum.

Product Label: See: Package Insert

Progressive Multifocal Leukoencephalopathy (PML): A rare brain and spinal cord disease caused by a virus and usually seen only in immunocompromised individuals, such as those with HIV. Symptoms vary but include loss of muscle control, paralysis, blindness, speech problems, and an altered mental state. This disease often progresses rapidly and may be fatal. PML is considered an AIDS-defining condition in people with HIV.

Prophylaxis: Treatment to prevent the onset of a particular disease or to prevent recurrence of symptoms of an existing infection that has been brought under control.

Prospective Study: See: Clinical Trial

Protease: An enzyme that breaks down long polypeptides into smaller protein units. HIV's protease enzyme cuts long chains of HIV polypeptide into the smaller, active proteins used in HIV replication. See Also: Polypeptide

Protease Inhibitor (PI): A class of anti-HIV drug that prevents replication of HIV by disabling HIV protease. Without HIV protease, the virus cannot make more copies of itself. See Also: Protease

Protein: A highly complex biological molecule consisting of specific combinations of amino acids linked together by chemical bonds. Proteins are required for the structure, function, and regulation of the body's cells, tissues, and organs. Each protein has a unique set of functions. Examples of proteins are enzymes; cytokines; antibodies; and the major components of hair, skin, and muscle. See Also: Peptide Amino Acid Polypeptide

Protocol: The detailed plan for conducting an experiment, such as a clinical trial. A clinical trial protocol is a lengthy document that describes the trial's rationale, purpose, information about the drug or vaccine being studied, participant inclusion/exclusion criteria, study endpoints, and details of the trial design. See Also: Clinical Trial Endpoint Inclusion/Exclusion Criteria

Protozoa: Large, diverse group of unicellular (one-celled) animals. Some protozoa cause diseases in people with weakened immune systems, such as people with HIV or AIDS. Protozoa are responsible for some of the AIDS-defining opportunistic infections, notably toxoplasmosis and cryptosporidiosis.

Provirus: A DNA version of HIV's genetic material that has been integrated into the host cell's own DNA. See Also: Integration

Pruritus: An intense itching sensation that produces the urge to rub or scratch the skin for relief.

Public Health Service (PHS): An office within the U.S. Department of Health and Human Services (HHS). The Public Health Service is composed of several agencies, including the Food and Drug Administration (FDA) and the National Institutes of Health (NIH) that oversee different aspects of health care in the United States. Guidelines for the management of various diseases, including HIV infection, are released through the PHS.

PubMed: Database and search engine that provides access to citations for more than 18 million biomedical articles dating back to the 1950s. The database is maintained by the National Library of Medicine (NLM). PubMed includes links to free full-text articles, when available, and also connects users with related resources.

Pulmonary: Pertaining to the lungs.

Purified Protein Derivative (PPD): A substance used in the tuberculin skin test to determine if a person has been exposed to Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). PPD is usually injected just below the skin. A hard red bump or a swollen area at the injection site indicates that the person was exposed to the bacterium. Additional tests are required to determine if the person has active TB infection. See Also: Tuberculin Skin Test Tuberculosis (TB)



q.d.: Once-a-day dosing instructions.

q.i.d.: Four-times-a-day dosing instructions.



R5-Tropic Virus: Also known as M-tropic virus. A strain of HIV that uses the chemokine receptor CCR5 as a co-receptor to bind to and infect human cells. HIV is usually R5-tropic at early stages of infection, but the virus can switch to a different coreceptor (for example, CXCR4) as the disease progresses. See Also: X4-Tropic Virus, CCR5, Chemokines, Coreceptor

Randomized Trial: A type of clinical trial in which participants are assigned by chance to one of two or more treatment or placebo groups. A randomized trial design helps researchers gather meaningful information and make valid statistical calculations. See Also: Clinical Trial Placebo

Rapid Test: A type of HIV-1 enzyme-linked immunosorbent assay (ELISA) that can detect antibodies to HIV in the blood in less than 30 minutes with greater than 99% sensitivity and specificity. A positive rapid test result should be confirmed by an HIV Western blot test. See Also: Enzyme-Linked Immunosorbent Assay (ELISA) Western Blot

Rebound: See: Viral Rebound

Receptor: A protein on the surface of a cell that serves as a binding site for substances outside the cell, such as HIV floating free in the blood. See Also: Coreceptor CD4 Receptor

Recombinant: Produced by genetic engineering. Also refers to a new organism or compound produced by inserting the genetic material of one organism into the genetic material of another organism. See Also: Genetic Engineering

Refractory: Refers to a disease or condition that has gotten worse despite treatment.

Regimen: See: Treatment Regimen

Relapse: The return of signs and symptoms of a disease after a patient has been free of those signs and symptoms.

Remission: The period during which symptoms of a disease diminish or disappear. In people infected with HIV, effective treatment regimens may result in the remission of HIV-associated symptoms and conditions.

Renal: Pertaining to the kidneys.

Replication: See: Viral Replication

Rescue Therapy: See: Salvage Therapy

Reservoir: See: Latent HIV Reservoir

Resistance: See: Drug Resistance

Resistance Testing: Laboratory testing to determine if an individual's HIV strain is resistant to any anti-HIV drugs. See Also: Genotypic Assay, Phenotypic Assay, Drug Resistance

Retinal Detachment: Separation of the retina from the inner wall of the eye. Retinal detachment can be a complication of cytomegalovirus (CMV) retinitis and can cause vision loss. See Also: Cytomegalovirus, Retinitis

Retinitis: Inflammation of the retina, the thin layer of tissue that lines the inside back wall of the eye and functions like the film of a camera. In people with HIV, retinitis can be caused by cytomegalovirus (CMV). If untreated, retinitis can lead to blindness. Symptoms include floating spots, flashing lights, blind spots, and blurred vision. See Also: Cytomegalovirus (CMV) Cytomegalovirus Retinitis

Retrospective Study: See: Clinical Trial

Retrovirus: A type of virus that stores its genetic information in a single-stranded RNA molecule and constructs a double-stranded DNA version of its genes using a special enzyme called reverse transcriptase. The DNA copy is then integrated into the host cell's own genetic material. HIV is an example of a retrovirus. See Also: Reverse Transcriptase (RT), Integration Provirus

Reverse Transcriptase (RT): An enzyme found in HIV and other retroviruses. RT converts single stranded HIV RNA into double-stranded HIV DNA. Some anti-HIV drugs interfere with this stage of HIV's life cycle. See Also: Nucleoside Analogue Reverse Transcriptase Inhibitor (NRTI), Nucleotide Analogue Reverse Transcriptase Inhibitor (NtRTI), Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI), Provirus Retrovirus

Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR): A laboratory test that measures the amount of HIV RNA (also known as viral load) in a blood sample by replicating HIV's genetic material to measurable levels. RT-PCR is the primary way that health care providers monitor HIV infection and its treatment. See Also: Polymerase Chain Reaction (PCR), Viral Load (VL)

Ribonucleic Acid (RNA): Chemical structure that carries genetic instructions for protein synthesis. Although DNA is the primary genetic material of cells, RNA is the genetic material for some viruses. See Also: Deoxyribonucleic Acid (DNA) Messenger RNA (mRNA)

RNA: See: Ribonucleic Acid

RT: See: Reverse Transcriptase

RT-PCR: See: Reverse Transcriptase-Polymerase Chain Reaction




Salmonella Septicemia: Salmonella is a bacterium that enters the body through ingestion of contaminated food or water. Symptoms of infection include nausea, vomiting, and diarrhea. Salmonella septicemia is a severe infection that circulates through the whole body. Recurrent Salmonella septicemia is considered an AIDS-defining condition in people with HIV.

Salvage Therapy: Also known as rescue therapy. An HIV treatment regimen designed for people who have used many different anti-HIV drugs in the past, have failed at least two anti-HIV regimens, and have extensive drug resistance.

SAMHSA: See: Substance Abuse and Mental Health Services Administration

SAT: See: Self-Administered Therapy

SAT: See: Subcutaneous Adipose Tissue

SC: See: Subcutaneous

Seborrheic Dermatitis: A skin condition common in people with HIV. It is characterized by loose, greasy or dry, white to yellowish scales, with or without reddened skin. Seborrheic dermatitis may involve the skin of the scalp, eyebrows, eyelids, nasolabial creases, and lips; behind the ears; in the external ear; and on the trunk, particularly over the sternum and along skin folds. The cause is unknown.

Secondary Prophylaxis: See: Maintenance Therapy

Self-Administered Therapy (SAT): Administration of a medication by the person taking it. In self administered therapy, the patient is in control of taking his or her medication and is unsupervised. See Also: Directly Observed Therapy (DOT)

Semen-Derived Enhancer of Virus Infection (SEVI): A collection of the enzyme prostatic acidic phosphatase (PAP) that is found in semen and that can increase the likelihood of HIV infection.

Sepsis: A serious blood-borne infection that is usually caused by bacteria. Immunocompromised people, such as those with HIV disease, are at increased risk for sepsis.

Seroconversion: The process by which a newly infected person develops antibodies to HIV. These antibodies are then detectable by an HIV test. Seroconversion may occur anywhere from days to weeks or months following HIV infection. See Also: Window Period

Serologic Test: A laboratory test to determine if an individual has antibodies to a particular foreign invader, such as a virus. A positive serologic test indicates that an individual is infected or has had an infection in the past.

Seroprevalence: The number or proportion of people in a given population who have positive serologic tests for a particular infection.

Serostatus: The presence or absence of detectable antibodies against an infective agent, such as HIV, in the blood. Seronegativity, or seronegative status, means that the person has no detectable antibodies and is not infected with the agent or has not had the chance to develop antibodies to an early infection. Seropositivity, or seropositive status, means that the person has detectable antibodies and is infected with the agent or had previously been infected with the agent.

Serum: The clear, thin, and sticky fluid that separates from blood when it clots.

Serum Glutamic Oxaloacetic Transaminase (SGOT): See: Liver Function Tests

Serum Glutamic Pyruvate Transaminase (SGPT): See: Liver Function Tests

Set Point: The viral load established within a few weeks to months after infection, after the initial burst of virus replication has subsided. The viral set point is thought to remain steady for an indefinite period of time if the infection is not treated with anti-HIV drugs. An individual's viral set point may determine how quickly HIV infection will progress without treatment. Higher set points suggest that disease will progress faster than lower set points.

Sexually Transmitted Disease (STD): Also known as a sexually transmitted infection (STI). Any infection spread by the transmission of organisms from person to person during sexual contact.

SGOT: See: Serum Glutamic Oxaloacetic Transaminase

SGPT: See: Serum Glutamic Pyruvate Transaminase

Shingles: A disease caused by varicella zoster virus (VZV), which also causes chickenpox. VZV remains in the nerve roots of everyone who has had chickenpox, and it can become active years later to cause shingles. Shingles causes numbness, itching, or severe pain followed by clusters of blister-like lesions in a strip-like pattern on one side of the body. The pain can persist for weeks, months, or years after the rash heals. See Also: Varicella Zoster Virus (VZV)

Side Effect: An action or effect of a drug (or vaccine) other than desired therapeutic effects. The term usually refers to an undesired or negative effect (adverse effect), such as headache, skin irritation, or liver damage.

Simian Immunodeficiency Virus (SIV): A virus similar to HIV that can infect monkeys, chimpanzees, and macaques and can cause a disease similar to AIDS in some of these animals. Because the two viruses are closely related, researchers study SIV as a way to learn more about HIV. However, SIV cannot infect humans, and HIV cannot infect monkeys.

SIT: See: Structured Intermittent Therapy

SIV: See: Simian Immunodificiency Virus

SJS: See: Stevens-Johnson Syndrome

Spinal Tap: Also known as lumbar puncture. A procedure in which cerebrospinal fluid from the lower spine is extracted with a needle for examination.

Splenomegaly: Enlargement of the spleen.

Sputum Analysis: Method of detecting certain infections (especially tuberculosis) by analyzing sputum, the mucus matter that collects in the respiratory and upper digestive passages and is expelled by coughing.

Standard of Care: A treatment plan that experts agree is appropriate, accepted, and widely used for a given disease or condition.

Statins: A shortened name for a class of cholesterol-lowering drugs called HMG-CoA reductase inhibitors. Drugs in this class lower cholesterol by slowing down the body's production of cholesterol and by increasing the liver's ability to remove cholesterol from the blood. See Also: Cholesterol

STD: See: Sexually Transmitted Disease

Stem Cell:  A generic cell that can make exact copies of itself indefinitely but can also produce specialized cells for various tissues in the body, such as heart muscle, brain tissue, and liver tissue.

Steroid: A general class of substances that are structurally related to one another and share the same chemical skeleton. Some hormones and drugs are steroids. For example, natural testosterone and its man-made derivatives help build muscle mass. Corticosteroid drugs are used to reduce swelling and pain.

Stevens-Johnson Syndrome (SJS): A severe and sometimes fatal form of skin rash characterized by red, blistered spots on the skin; blisters in the mouth, eyes, genitals, or other moist areas of the body; peeling skin that results in painful sores; and fever, headache, and other flu-like symptoms. Internal organs may also be affected. SJS may occur as a severe reaction to certain drugs, including NNRTIs used to treat HIV infection.

STI: An abbreviation used for either structured treatment interruption or for sexually transmitted infection (also known as sexually transmitted disease, or STD). See Also: Structured Treatment Interruption (STI), Sexually Transmitted Disease (STD)

Stomatitis: Inflammation or irritation of the mucous membranes in the mouth.

Strain: A type of virus that has a common ancestry but also clear-cut physiologic distinctions, often in resistance profiles. For example, HIV molecules that express nucleoside-associated resistance mutations are a separate viral strain than wild-type HIV molecules, which do not express resistance mutations.

Structured Intermittent Therapy (SIT): A type of structured treatment interruption that is characterized by time-based treatment cycles (weeks or months on and off anti-HIV drugs). See Also: Structured Treatment Interruption (STI)

Structured Treatment Interruption (STI): Also known as a drug holiday. A planned, doctor-supervised discontinuation of anti-HIV drugs. Goals of STI include reduced toxicity, reduced treatment costs, and improved quality of life.

Subclinical Infection: An infection or phase of an infection without obvious symptoms or signs of disease.

Subcutaneous (SC): Beneath the skin, or administration of a substance beneath the skin.

Subcutaneous Adipose Tissue (SAT):  A type of adipose (fat) tissue found directly under the skin. Both loss (lipoatrophy) and gain (lipohypertrophy) of this fat tissue can occur as a side effect of HIV infection and some of the drugs used to treat HIV infection, especially PIs and NRTIs. See Also: Visceral Adipose Tissue (VAT)

Substance Abuse and Mental Health Services: Administration (SAMHSA) The lead agency within the U.S. Department of Health and Human Services (HHS) for improving the quality and availability of substance abuse prevention, addiction treatment, and mental health services in the United States.

Subtype: HIV is classified into two .vaccines contain only part of the HIV virus (such as individual proteins or peptides) produced in the laboratory by genetic engineering techniques. See Also: Vaccine Genetic Engineering

Superinfection: A new infection acquired on top of an existing infection. For example, a person infected with one strain of HIV-1 can, if exposed to a different strain, become infected with the new strain in addition to the existing strain. Superinfection can complicate HIV treatment by requiring additional drugs to target the newly introduced HIV strain.

Surrogate Endpoint: A short-term outcome, such as a change in viral load or CD4 count that may be used as a substitute to reflect a clinical target outcome, such as mortality or disease progression. For example, a change in viral load (HIV RNA level) may be a surrogate endpoint for the progression of HIV to AIDS as a clinical endpoint. See Also: Clinical Endpoint

Surrogate Marker: See: Surrogate Endpoint

Susceptible: Having little resistance to a specific infectious disease. Also used to describe an HIV strain that is not resistant to a particular anti-HIV drug.

Sustained Viral Suppression: See: Sustained Virologic Response

Sustained Virologic Response: The continued, long-term suppression of HIV RNA as a result of successful treatment with highly active antiretroviral therapy regimens.

Syncytium: A giant cell formed by the fusing together of two or more smaller cells. HIV-infected cells can fuse with uninfected cells to form syncytia. The presence of so-called syncytia-inducing variants of HIV has been correlated with rapid disease progression in HIV infected individuals.

Syndrome: A set of symptoms or conditions that occur together and suggest a certain disease or an increased chance of developing a disease.

Syndrome X: See: Metabolic Syndrome

Synergy: An interaction between two or more drugs that produces an effect greater than the sum of their individual effects.

Syphilis: A sexually transmitted disease (STD) caused by the bacterium Treponema pallidum. In the early stage of syphilis, a genital or mouth sore called a chancre develops but eventually disappears on its own. However, if the disease is not treated, the infection can progress over the years to affect the heart and central nervous system. Syphilis can also be transmitted from an infected mother to her fetus during pregnancy, with serious health consequences for the infant.

Systemic: A term used to describe a disease or treatment that affects the body as a whole.



TAM: See: Thymidine Analogue Mutation

Tanner Staging: A method for determining an adolescent's stage of sexual development, irrespective of chronological age. In HIV treatment, Tanner staging is used to determine the appropriate treatment guidelines to follow: adult, adolescent, or pediatric.

TAT See: Total Adipose Tissue

TB: See: Tuberculosis

T-Cell: A type of lymphocyte (disease-fighting white blood cell). The T stands for the thymus, the organ in which T cells mature. T cells include CD4 cells and CD8 cells, which are both critical components of the body's immune system. See Also: CD4 Cell CD8 Cell Lymphocyte

T-Cell Exhaustion: Also known as T-cell depletion. T-cell exhaustion occurs when the body's T cells become progressively less able to continue their activity against a virus or other infective agent. This depletion of T-cell function occurs with long-term infection, such as HIV.

T-Cell Precursor: An immature cell in the thymus that eventually matures and develops into a differentiated T cell.

TEN: See: Toxic Epidermal Necrolysis

Teratogenic: Causing harm to a fetus by interfering with normal prenatal development. Many drugs, including some anti-HIV drugs, are teratogenic when taken by pregnant women.

Testosterone: A hormone necessary for normal male sexual development and functioning and also important in maintaining muscle strength and mass. Testosterone is sometimes used for the treatment of HIV-related wasting syndrome and to increase muscle mass and decrease body fat in people with HIV. Testosterone replacement therapy is also used to raise testosterone levels in people with HIVrelated hypogonadism. See Also: Wasting Syndrome, Hypogonadism

Therapeutic Drug Monitoring (TDM): Measurement of anti-HIV drug levels in an individual's blood. These measurements are then used to make appropriate adjustments to the dosage of the drug. TDM may help improve the drug's effect and reduce side effects by keeping the blood level in a specific target range. TDM is mainly used for drugs in which small changes in drug levels cause large changes in drugm effect. See Also: Therapeutic Index (TI), Pharmacokinetics

Therapeutic HIV Vaccine: Any HIV vaccine used for the treatment of an HIV-infected person. Therapeutic HIV vaccines are designed to boost an individual's immune response to HIV infection to better control the virus. This therapeutic approach is currently being tested in clinical trials. See Also: Preventive HIV Vaccine

Therapeutic Index (TI): A measure of a drug's ability to achieve the desired effect in an individual. Many anti-HIV drugs have a narrow TI, which means that small changes in levels of the drug may produce big effects. Doses of these drugs are sometimes adjusted using therapeutic drug monitoring (TDM). See Also: Therapeutic Drug Monitoring (TDM)

Thrombocytopenia: A lower than normal number of blood platelets (cells important for blood clotting). See Also: Platelet

Thrush: See: Candidiasis

Thymidine Analogue Mutation (TAM): A mutation in HIV's reverse transcriptase (RT) enzyme that can occur with the use of the NRTIs zidovudine and stavudine. TAMs make HIV resistant to these drugs and may limit a person's treatment options. See Also: Nucleoside Analogue Reverse Transcriptase Inhibitor (NRTI), Reverse Transcriptase (RT)

Thymus: An organ in the chest behind the breastbone. This organ is an essential part of the immune system, because it is the site where infection-fighting T cells develop. See Also: T Cell

TI: See: Therapeutic Index

t.i.d.: Three-times-a-day dosing instructions.

Titer: A laboratory measurement of the amount of a given compound in solution. For example, an antibody titer is the measurement of the amount of a particular antibody in a sample of blood.

T Lymphocyte: See: T Cell

Tolerability: Term used to indicate how well a particular drug is tolerated or endured when taken by people at the usual dosage. Good tolerability means that drug side effects do not cause people to stop using the drug.

Tolerance: A decreasing response to repeated doses of a drug, requiring a dose increase to continue the effects of the drug.

Topical: A substance, such as a cream or lotion, applied to body surfaces such as the skin or mucous membranes.

Total Adipose Tissue (TAT): Adipose (fat) tissue is primarily located under the skin (subcutaneous adipose tissue) but is also found around internal organs (visceral adipose tissue). Together, these two types of fat tissue are called total adipose tissue. Lipodystrophy, or changes in body fat, are a potential side effect of some anti-HIV drugs, especially PIs and NRTIs. See Also: Subcutaneous Adipose Tissue (SAT), Visceral Adipose Tissue (VAT), Lipodystrophy

Toxic Epidermal Necrolysis (TEN): A severe form of Stevens-Johnson syndrome involving at least 30% of the total body skin area. See Also: Stevens-Johnson Syndrome (SJS)

Toxicity: Ability to poison or otherwise harm the body. See Also: Adverse Event

Toxoplasmosis: An infection caused by the parasite Toxoplasma gondii. The parasite is carried by cats, birds, and other animals and is also found in soil contaminated by cat feces and in meat, particularly pork. Infection can occur in the lungs, retina of the eye, heart, pancreas, liver, colon, testes, and brain. Toxoplasmosis of the brain is considered an AIDS-defining condition in people with HIV.

Transcription: One of the steps in the HIV life cycle. Transcription is the process by which the HIV DNA provirus is used as a template to create copies of HIV's RNA genetic material as well as shorter strands of HIV RNA called messenger RNA (mRNA). HIV mRNA is then used in a process called translation to create HIV proteins and continue the virus's life cycle. See Also: Provirus Translation, Messenger RNA (mRNA)

Translation: The step in the HIV life cycle that follows transcription. Translation is the process by which the genetic information contained in HIV mRNA is used to build HIV proteins using the host cell's protein making machinery. Once these HIV proteins are produced, they can combine with copies of HIV's RNA genetic material to form new, complete copies of HIV. See Also: Transcription

Transplacental: Across or through the placenta. Usually refers to the exchange of nutrients, waste products, and other materials (for example, drugs or infectious organisms) between the mother and the fetus.

Treatment-Experienced: A term used to describe HIV-infected individuals who are currently being treated with anti-HIV drugs or who have taken anti-HIV drugs in the past. See Also: Treatment-Naive

Treatment Failure: A broad term that describes failure of an anti-HIV treatment to adequately control HIV infection. The three types of HIV treatment failure are virologic, immunologic, and clinical failure. Factors that contribute to treatment failure include poor adherence, drug resistance, and drug toxicity. See Also: Virologic Failure, Immunologic Failure, Clinical Failure

Treatment-Naïve: A term used to describe HIV-infected individuals who have never taken anti-HIV drugs. See Also: Treatment-Experienced

Treatment Regimen: A structured plan of treatment, usually with drugs, that is implemented to improve or maintain health.

Trial Design: The structure of a clinical study or trial. Examples include open-label or double-blind, comparative or observational.

Triglycerides: Fat-like substances that help transfer energy from food into cells. Triglyceride levels that are too high increase the risk of heart disease and have been associated with diabetes and pancreatitis. Elevated triglyceride levels are a potential side effect of some PIs.

Triple-Class Experienced: A term used to describe an HIV-infected patient who has been treated with drugs from each of the following three anti-HIV drug classes: nucleotide/nucleoside reverse transcriptase inhibitors; nonnucleoside reverse transcriptase inhibitors; and protease inhibitors.

Tropism: See: Viral Tropism

Trough Concentration: See: CMIN

Trough Level: See: CMIN

T-Tropic Virus: See: X4-Tropic Virus

Tuberculin Skin Test: A test performed by injecting purified protein derivative (PPD) extract under the skin. A person who receives this test must return to his or her health care provider after 48 to 72 hours so that the skin's reaction can be evaluated. A hard red bump or a swollen area at the injection site indicates that the person has been exposed to the bacterium that causes tuberculosis (TB). Additional tests are required to determine if the person has active TB infection. See Also: Purified Protein Derivative (PPD)' Tuberculosis (TB)

Tuberculosis (TB): An infection caused by the bacterium Mycobacterium tuberculosis. TB bacteria are spread through the air when a person with active TB coughs, sneezes, or speaks. Breathing in the bacteria can lead to infection in the air sacs of the lungs. Symptoms of TB in the lungs include cough, tiredness, weight loss, fever, and night sweats. Although the disease usually occurs in the lungs, it may also affect the larynx, lymph nodes, brain, kidneys, or bones. A person with both TB and HIV is more likely to develop tuberculosis disease than a person infected only with the TB bacterium, and TB is considered an AIDS-defining condition in people with HIV. See Also: Tuberculin Skin Test



UD VL: See: Undetectable Viral Load

Undetectable Viral Load (UD VL): The point at which levels of HIV RNA in the blood are too low to be detected with a viral load test. This does not mean that the virus has stopped replicating or has been removed from the body entirely, only that the small amount of virus remaining is below the test's ability to measure it. The viral load below which a test cannot detect the virus depends on the brand of the viral load test. See Also: Viral Load (VL)



Vaccination: Administration of a vaccine for either preventive or therapeutic purposes. See Also: Vaccine, Preventive HIV Vaccine, Therapeutic HIV Vaccine

Vaccine: A substance that stimulates the body's immune response in order to prevent or control an infection. A vaccine is typically made up of some part of a bacteria or virus that cannot itself cause an infection. Researchers are testing vaccines both to prevent and treat HIV/ AIDS; however, there is currently no vaccine approved for use outside of clinical trials. See Also: Preventive HIV Vaccine Therapeutic HIV Vaccine

Vaccinia: A cowpox virus that is used as a vaccine against smallpox infection and as a vector, or carrier, for other types of vaccines. In HIV vaccine clinical trials, vaccinia and other herpesviruses have been used as vectors. See Also: Vector, Herpesviruses

Varicella Zoster Virus (VZV): A virus in the herpes family that causes chicken pox (usually during childhood) and may reactivate later in life to cause shingles. See Also: Herpesviruses Shingles

VAT: See: Visceral Adipose Tissue

Vector: A harmless virus or bacteria used as a vaccine carrier to deliver pieces of a disease-causing organism (such as HIV) into the body's cells to stimulate a protective immune response. See Also: Vaccine

Vertical Transmission: A term used to describe the transmission of a disease from parent to offspring. For example, HIV can be spread vertically from mother to child during pregnancy, at birth, or through breastfeeding. See Also: Mother-to-Child Transmission (MTCT), Horizontal Transmission

Viral Decay: The reduction of viral reservoirs in the body. Decay of a virus may be measured by pharmacokinetic studies.

Viral Evolution: The changes that occur in a population of viruses as they adapt to specific conditions and changes in the host environment.

Viral Load (VL): The amount of HIV RNA in a blood sample, reported as number of HIV RNA copies per milliliter of blood plasma. The VL provides information about the number of cells infected with HIV and is an important indicator of HIV progression and of how well treatment is working. The VL can be measured by different techniques, including branched-chain DNA (bDNA) and reverse transcriptase-polymerase chain reaction (RT-PCR) assays. VL tests are usually done when an individual is diagnosed with HIV infection and at regular intervals after diagnosis. See Also: Branched-Chain DNA (bDNA), Assay, Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR)

Viral Load Test: Test that measures the quantity of HIV RNA in the blood. Results are reported as the number of copies of HIV RNA per milliliter of blood plasma. The two types of HIV viral load test are reverse transcriptase-polymerase chain reaction (RT-PCR) and branched chain DNA (bDNA). See Also: Viral Load (VL), Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR), Branched-Chain DNA (bDNA), Assay

Viral Rebound: Reappearance of HIV in the blood after having been successfully suppressed to undetectable levels as a result of anti-HIV drug treatment. See Also: Undetectable Viral Load (UD VL), Virologic Failure

Viral Replication: The process a virus undergoes to produce a copy of itself.

Viral Set Point: See: Set Point

Viral Suppression: Halting of the function or replication of a virus. In HIV, optimal viral suppression is measured as the reduction of viral load (HIV RNA) to undetectable levels and is the goal of highly active antiretroviral therapy (HAART).

Viral Tropism: Refers to which type of coreceptor HIV uses when binding to a cell during infection. HIV can bind to the CXCR4 coreceptor (X4-tropic) or to the CCR5 coreceptor (R5-tropic) on a cell surface. Although the virus often prefers one coreceptor to the other, it also can be dual/mixed-tropic HIV that can bind to either coreceptor. Viral tropism may switch, or change from preference of one coreceptor to the other, during the course of an HIV infection. See Also: CCR5, CXCR4

Viremia: The presence of virus in the bloodstream.

Viricide: Any substance that can destroy or inactivate a virus.

Virion: A mature virus particle that exists freely outside a host cell.

Virologic Control: See: Viral Suppression

Virologic Failure: Inability of anti-HIV drug treatment to reduce viral load or to maintain suppression of viral load. Virologic failure is the most common type of treatment failure and may lead to immunologic and clinical failure. See Also: Immunologic Failure, Clinical Failure, Viral Load (VL)

Virology: The study of viruses and viral disease.

Virus: A microscopic organism that requires a host cell to make more copies of itself. Examples of human diseases caused by virus infections are AIDS, measles, mumps, rubella, polio, influenza, and the common cold.

Visceral Adipose Tissue (VAT): A type of adipose (fat) tissue that surrounds internal organs in the abdominal cavity. Accumulation of this fat is known as central fat deposition or visceral lipohypertrophy, and may occur as a side effect of some anti-HIV drugs, especially PIs and NRTIs.See Also: Subcutaneous Adipose Tissue (SAT) Body Habitus Changes

VL: See: Viral Load

VZV: See: Varicella Zoster Virus



Wasting Syndrome: The involuntary loss of more than 10% of body weight in addition to more than 30 days of either diarrhea or weakness and fever. Wasting refers to the loss of muscle mass, although part of the weight loss may also be due to loss of fat. HIV-associated wasting syndrome is considered an AIDS-defining condition.

Western Blot: A laboratory technique used to detect a specific protein. A Western blot test to detect HIV proteins in the blood is used to confirm a positive HIV antibody test (ELISA). See Also: Enzyme-Linked Immunosorbent Assay (ELISA)

White Blood Cell: Also known as a leukocyte. These cells make up the immune system and include lymphocytes, monocytes, neutrophils, eosinophils, macrophages, and mast cells. White blood cells are made by bone marrow and help the body fight infection and other diseases.

WHO: See: World Health Organization

WIHS: See: Women's Interagency HIV Study

Wild-Type Virus: A term to describe viral strains (including strains of HIV) that have not acquired any genetic mutations that create special characteristics, such as resistance to particular drugs.

Window Period: The time period between a person's infection with HIV and the appearance of detectable anti-HIV antibodies. Because antibodies to HIV take some time to form, an HIV antibody test will not be positive immediately after a person is infected. The time delay typically ranges from 14 to 21 days, but varies for different people. Nearly everyone infected with HIV will have detectable antibodies by 3 to 6 months after infection. See Also: Enzyme-Linked Immunosorbent Assay (ELISA), Antibody

Women's Interagency HIV Study (WIHS): A multicenter study established in 1993 to research the impact of HIV infection in women. The study's ultimate goal is to gain a better understanding of and provide adequate support for women who are currently HIV infected or who are at risk for HIV infection. The study is jointly supported by the National Cancer Institute (NCI), the National Center for Research Resources (NCRR), the National Institute of Allergy and Infectious Diseases (NIAID), the National Institute of Child Health and Human Development (NICHD), and the National Institute on Drug Abuse (NIDA).

World Health Organization (WHO): The United Nations' health organization. Responsible for providing leadership on global health matters, shaping the health research agenda, setting standards, articulating evidence-based policy options, providing technical support to countries, and monitoring and assessing health trends.



X4-Tropic Virus: Also known as T-tropic virus. A strain of HIV that uses the chemokine receptor CXCR4 as a coreceptor to bind to and infect human immune cells. Although some HIV-1 strains are X4-tropic from the beginning of infection, it is more common for the virus to switch to using the CXCR4 coreceptor as the disease progresses. See Also: R5-Tropic Virus, Chemokines, Coreceptor CXCR4

XDR-TB: See: Extensively Drug-Resistant Tuberculosis



Yeast Infection: See: Candidiasis



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