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Published in the Bulletin of Experimental Treatments for AIDS December 1996 issue, by the San Francisco AIDS Foundation. |
GlossaryCompiled by Liz Highleyman ACCELERATED APPROVAL: FDA regulations governing early marketing approval of promising drugs for life-threatening illnesses. ACUTE RETROVIRAL SYNDROME (ARS): a combination of flu-like symptoms (e.g., fever, sore throat, skin rash, headache, nausea, muscle or joint pain) that accompanies primary (initial) HIV infection or occurs shortly after infection. AIDS CLINICAL TRIALS GROUP (ACTG): a NIAID-sponsored group of medical centers, known as AIDS Clinical Trials Units (ACTU), that evaluates treatments for HIV disease and associated illnesses. AIDS DEMENTIA COMPLEX (ADC, HIV-ASSOCIATED COGNITIVE/MOTOR COMPLEX): mental impairment with an organic cause that is due to HIV infection (rather than an opportunistic pathogen). Symptoms may include cognitive impairment, personality changes, speech and vision difficulties and motor dysfunction. Early stages of the syndrome are referred to as HIV-associated minor cognitive/motor disorder. AMINOTRANSFERASE: an enzyme (e.g., SGOT, SGPT) produced by the liver that catalyzes the transfer of amino acids. Abnormally high levels in the blood may indicate liver disease or damage. AMNIOCENTESIS: a procedure in which a needle is used to withdraw amniotic fluid from the amniotic sac that surrounds the fetus in the uterus. ANEMIA: an abnormally low number of red blood cells. ANERGY (adjective ANERGIC): the lack of an immune response to a foreign antigen. ANOREXIA: the lack or loss of appetite for food. ANTIBODY (AB, IMMUNOGLOBULIN, IG): a protein secreted by activated plasma cells, which evolve from B-cells, in response to stimulation by an antigen. The antigen/antibody reaction forms the basis of humoral (TH2) immunity. There are 5 types of antibodies: IgA, IgD, IgE, IgG and IgM. ANTIGEN: any agent or substance that stimulates an immune response, e.g., microorganisms or the substances they produce. Antigenemia is the presence of antigens in the blood. ANTIOXIDANT: a substance that inhibits the oxidation reaction by binding with and neutralizing free radicals and other highly reactive molecules, thus reducing cellular damage. ANTIVIRAL: an agent that interferes with the life cycle of a virus and suppresses its replication. APOPTOSIS: programmed cell death. ARACHIDONIC ACID: an essential fatty acid that is a building block of prostaglandins and a component of cell membranes. ARM: a group of participants in a research trial who all receive the same treatment (treatment arm) or placebo (control arm). ASSAY: a test used to detect the presence of a drug, substance or microorganism in the blood or tissues. ASPERGILLOSIS: an uncommon, life-threatening infection caused by the fungus Aspergillus. Aspergillosis typically infects the lungs and sinuses, but can spread through the blood to other organs including the brain, heart and spleen. ASTROCYTE: a cell within the brain that provides support for neurons and manufactures the myelin insulation that surrounds neuronal axons. Astrogliosis is the proliferation of astrocytes. ASYMPTOMATIC: not feeling or showing outward signs of illness. BACTEREMIA: the presence of bacteria in the blood. BAND: an immature neutrophil released into the blood to combat infection. BASAL GANGLION (plural GANGLIA): nerve tissue, primarily composed of neuron cell bodies, deep within the brain. BASELINE: a known value to which later measurements can be compared, e.g., baseline CD4 cell count. B-CELL (B-LYMPHOCYTE): an immune system cell that carries out the humoral (TH2) immune response. B-cells are produced in the bone marrow and mature into plasma cells that produce antibodies. BILIRUBIN: a yellowish pigment released by red blood cells when they are removed from circulation and broken down. An excess level of serum bilirubin (hyperbilirubinemia) is characterized by jaundice, and may indicate stress on the liver. BIOAVAILABILITY: the extent to which a substance (e.g., a drug) is absorbed and circulated in the body. BIOPSY: the surgical removal of a small piece of tissue for microscopic examination and/or culture. BLOOD-BRAIN BARRIER: a barrier between the blood vessels and the brain that is selectively permeable, i.e., allows only certain substances to pass through. A similar barrier between the circulating blood and the cerebrospinal fluid is known as the blood-cerebrospinal fluid barrier. BLOOD CHEMISTY PANEL: a set of tests (SMA 12, SMA 14, SMA 20) that evaluate the levels of important components in the blood, including glucose, blood proteins, enzymes and electrolytes. BOTULISM: life-threatening food poisoning caused by the presence of botulinus toxin produced by the Clostridium botulinum bacterium. BRANCHED-CHAIN DNA ASSAY (bDNA): an assay for measuring the amount of virus (viral load) in blood plasma or tissue. BRONCHOSCOPY: a procedure for inspection (and possibly biopsy) of the trachea, bronchial tubes and lungs using a flexible fiber-optic instrument that conducts light. CANDIDIASIS: a disease caused by a species of the yeast-like fungus Candida, usually C. albicans. Candidiasis can affect the skin, nails and mucous membranes throughout the body including the mouth (thrush), esophagus, vagina (yeast infection), intestines and lungs. CD4 CELL (CD4 LYMPHOCYTE, T-HELPER CELL): a type of white blood cell that carries the CD4 surface marker and helps the body fight infection. CD4 cells engulf and process invaders (e.g., viruses) and release cytokines that coordinate a broad range of immune system activities, including killer cell activation and antibody production. The CD4 cell count is the number of CD4 lymphocytes present in a cubic millimeter (mm3) of blood. CD8 CELL (CD8 LYMPHOCYTE): a type of white blood cell that helps regulate and/or carry out the body's immune response. Two major subsets of T-cells express the CD8 surface marker: T-suppressor cells and cytotoxic T-lymphocytes (CTL). CELL-MEDIATED IMMUNITY (CELLULAR IMMUNITY, TH1 RESPONSE): the immune response mediated by the TH1 subset of CD4 cells. Cell-mediated immunity is stimulated by the cytokines IL-2, IL-12 and gamma interferon, and carried out by cytotoxic T-lymphocytes (CTL) and macrophages. CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC): the U.S. federal agency within the Department of Health and Human Services that monitors disease occurrence and develops policies for preventing diseases and maintaining the health of the population. CENTRAL NERVOUS SYSTEM (CNS): the brain and spinal cord. CEREBROSPINAL FLUID (CSF): a clear, nutrient-rich fluid that circulates around and through the brain and around the spinal cord. CERVIX (adjective CERVICAL): the cylindrical, lower part of the uterus leading into the vagina. CHLAMYDIASIS (CHLAMYDIA): an infection, usually sexually transmitted, with the bacteria Chlamydia trachomatis. Symptoms may include genital inflammation and discharge; untreated chlamydiasis may lead to pelvic inflammatory disease and infertility. CHOLESTASIS: obstruction of the flow of bile from the gall bladder. CKR5: a newly discovered chemokine co-receptor which HIV uses to infect cells. CLINICAL TRIAL: an organized procedure for determining the effectiveness of new drugs or therapies by administering the agent to participants under strictly controlled conditions. COHORT: a group of individuals in a study who share a statistical factor (e.g., age, study site). COLONY-STIMULATING FACTOR (CSF): a cytokine responsible for controlling the production of white blood cells. Types include granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF). COLOSTRUM: breast fluid, produced prior to milk production, that contains antibodies. COMPLETE BLOOD COUNT (CBC): a screening of the cellular components of the blood, including red blood cell count (including hematocrit and hemoglobin), counts of various types of white blood cells such as granulocytes and T-cells, and platelet count. CONTRAINDICATION: any circumstance or symptom that makes a method of treatment inadvisable in a particular case. CONTROLLED TRIAL: a clinical trial in which a group receiving an experimental therapy is compared to a control group that is not given the intervention under study. CORTEX (adjective CORTICAL): the outer part of an organ, e.g., cerebral cortex. CORTICOSTEROID: one of a group of steroid hormones (e.g., prednisone, cortisone) produced by the cortex of the adrenal gland or manufactured synthetically. CROSS-RESISTANCE: the development of resistance to one agent (e.g., drug) which also confers resistance to another (often similar) agent. CRYPTOCOCCOSIS: an infection caused by a yeast-like fungus, typically Cryptococcus neoformans, found in soil and bird feces. A common manifestation is cryptococcal meningitis (CM); cryptococcosis may also become disseminated. CRYPTOSPORIDIOSIS: a disease caused by the protozoan Cryptosporidium parvum, which is transmitted to humans by contact with animal feces, ingestion of contaminated food or water, or oral-anal sexual contact. Symptoms include severe, chronic diarrhea. CYTOCHROME P450 SYSTEM: a process that metabolizes drugs and other foreign substances in the liver, by means of the P450 enzymes. CYTOKINE: an intercellular chemical messenger protein (e.g., interleukin) released by white blood cells. Cytokines facilitate communication among immune system cells and between immune system cells and the rest of the body. CYTOMEGALOVIRUS (CMV, HHV-5): a herpesvirus. CMV infection often occurs in healthy individuals without causing symptoms. In immunocompromised individuals it may cause retinitis, pneumonia, colitis and/or encephalitis. CYTOTOXIC T-LYMPHOCYTE (CTL, T-KILLER CELL): an immune system white blood cell that targets and kills cells infected with microorganisms. CYTOTOXICITY: the quality of being toxic to or killing cells. DENDRITIC CELL: a type of immune system cell with many branches found in the skin and mucosal linings of the body. DISSEMINATE: to spread; a disseminated infection is one that is distributed throughout the body. DNA (DEOXYRIBONUCLEIC ACID): a molecule found in the nucleus of cells that encodes genetic information. The particular sequence of 4 chemical building blocks (nucleotides) determines an individual's unique genetic code. DOSE-RANGING: a drug trial in which different dosages of a drug are compared to determine which dosage has the best balance of high efficacy and low toxicity. DOUBLE-BLIND: a type of clinical trial in which neither the subject nor the investigator knows what treatment, if any, the subject is receiving. DYSREGULATION: interruption of or interference with normal processes. EFFICACY: effectiveness; the ability to achieve a desired effect. ENCEPHALITIS: inflammation of the brain. ENCEPHALOPATHY: any disease of the brain. ENDOCRINE SYSTEM: a system of ductless glands that regulates bodily functions via hormones secreted into the bloodstream. The endocrine glands include the hypothalamus, pituitary gland, thyroid, adrenal glands and gonads (ovaries and testes). ENDOTHELIUM (adjective ENDOTHELIAL): a layer of cells that lines blood and lymph vessels, the heart and various body cavities. ENDPOINT: a direct marker of disease progression, e.g., disease symptoms or death. ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA): a laboratory test used to detect the presence of antibodies in the blood. EPSTEIN-BARR VIRUS (EBV, HHV-4): a herpesvirus. EBV infection is common and usually asymptomatic in children, and may cause infectious mononucleosis in young adults. EBV is associated with oral hairy leukoplakia and some types of cancer in people with suppressed immune systems. EXOGENOUS: originating or produced outside the body. FOOD AND DRUG ADMINISTRATION (FDA): the federal agency responsible for regulating the development, use and safety of drugs, medical devices, food, cosmetics and related products. FREE RADICAL: a molecule that contains an unpaired electron(s). Free radicals are highly reactive and bind with electrons from other molecules, potentially initiating chain reactions as successive molecules lose and gain electrons. The robbing of electrons by free radicals can disrupt normal cellular processes and cause cellular damage (oxidative stress). FUSIN: a co-receptor on the surface of certain T-cells that, along with the CD4 molecule, allows HIV to infect a cell. GENE THERAPY: an approach to preventing and/or treating disease by replacing, removing or introducing genes or otherwise manipulating genetic material. GESTATION: pregnancy. GP120: a glycoprotein on the outer envelope of HIV; gp120 is the portion of HIV that binds to the CD4 protein on the surface of certain T-cells. GRANULOCYTE: a type of white blood cell (basophil, eosinophil, neutrophil) that contains granules of toxic chemicals that are released to fight microorganisms. HEMATOCRIT (HCT): the percentage of red blood cells in a given amount of whole blood. Hematocrit reflects oxygen-carrying capacity. HEMOGLOBIN (HGB): the red, iron-based protein of red blood cells that transports oxygen from the lungs to cells throughout the body. HEPATITIS: an inflammation of the liver that may be caused by several agents, including viruses and toxins. Hepatitis is characterized by jaundice, enlarged liver, fever, fatigue and abnormal liver function tests. Types include hepatitis A (infectious hepatitis), hepatitis B (serum hepatitis) and hepatitis C. Hepatitis G has recently been characterized. HERPES SIMPLEX VIRUS (HSV): a herpesvirus that causes blisters and recurring disease. HSV-1 usually produces lesions on the lips or in the mouth ("cold sores"). HSV-2 is usually sexually transmitted and its lesions generally occur in the genital and/or anal area. Symptomatic disease outbreaks occur at unpredictable intervals. HERPESVIRUS: a group of viruses that includes herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), varicella-zoster virus (VZV, HHV-3), Epstein-Barr virus (EBV, HHV-4), cytomegalovirus (CMV, HHV-5), human herpesvirus types 6 and 7 (HHV-6, HHV-7) and Kaposi's sarcoma-associated herpesvirus (KSHV, HHV-8). HORMONE: a chemical messenger involved in the regulation and coordination of cellular and bodily functions. HUMAN GROWTH HORMONE (HGH, SOMATOTROPIN, SEROSTIM): a peptide hormone secreted by the anterior pituitary gland in the brain. Recombinant human growth hormone (Serostim) is used to treat HIV-related wasting syndrome. HUMORAL IMMUNITY (ANTIBODY-BASED IMMUNITY, TH2 RESPONSE): the immune response mediated by the TH2 subset of CD4 cells. Humoral immunity is stimulated by the cytokines IL-4 and IL-10, and carried out by plasma cells (derived from B-cells), which produce antibodies. IMMUNE SYSTEM: the body's defense system that protects against foreign invaders (e.g., microorganisms) and cancerous cells. There are 2 branches: cell-mediated (TH1) and humoral (antibody-based or TH2). Organs of the immune system include the lymph nodes, spleen, thymus, tonsils and bone marrow. IMMUNIZATION: a process by which a person is protected against the adverse effects of infection with a disease-causing microorganism. IMMUNOGLOBULIN (IG): see antibody. IMMUNOMODULATOR (IMMUNE MODULATOR): a substance or process capable of modifying functions of the immune system. Immune modulators include cytokines (e.g., IL-2, gamma interferon) and broad-acting agents. IMMUNOSUPPRESSION (IMMUNOCOMPROMISE): reduced function of the immune system; a state in which the immune system defenses have been suppressed or weakened. IMMUNOTHERAPY (IMMUNE-BASED THERAPY): a therapy that attempts to modify or enhance immune response or reconstitute a damaged immune system. INDUCTION: the initiation phase of a particular therapy. INFLAMMATION: the body's response to tissue injury or infection, which typically includes increased vessel dilation and permeability resulting in redness, swelling, heat and pain. INFUSION: the direct injection of a substance (e.g., a drug, nutrients) into the bloodstream. INTEGRASE: an enzyme produced by HIV that allows the integration of HIV DNA into the host cell's genetic material. INTERFERON: a family of some 20 cytokines (messenger proteins) that play a role in immune response. INTERLEUKIN (IL): a cytokine secreted by immune cells that regulates a range of immune system functions. Interleukin 2 (IL-2, T-cell growth factor) is produced by activated CD4 cells and promotes the proliferation and activity of CD4 cells, CTL and natural killer cells. Recombinant IL-2 is under study as a immunomodulatory treatment for KS and HIV disease. INTRAOCULAR: administered into the eye. INTRAPARTUM: during birth. IN UTERO: in the uterus; typically refers to events that occur in the womb before birth. IN VITRO: Latin for "in glass"; refers to work done in a test tube or culture medium in the laboratory. IN VIVO: Latin for "in the body of a living organism"; refers to work done using human or animal subjects. KAPOSI'S SARCOMA (KS): an abnormal or cancerous proliferation of cells and blood and/or lymph vessels causing tumors on the skin, mucous membranes and/or internal organs. KS typically appears as pink or purple flat or raised lesions. KAPOSI'S SARCOMA-ASSOCIATED HERPESVIRUS (KSHV, HHV-8): a recently discovered herpesvirus that is found in samples of tissue from Kaposi's sarcoma lesions, and may be a causal agent or co-factor. KIDNEY STONE (NEPHROLITHIASIS): an accumulation (e.g., of calcium) in the kidney, which may lead to pain and blockage. KILLER T-CELL: see cytotoxic T-lymphocyte. LEUKOCYTE: an immune system white blood cell (e.g., monocyte, CD4 cell). Various types of leukocytes are involved in the body's defense against infection and disease. LEUKOPENIA: an abnormally low number of white blood cells in the circulating blood. LIPOSOME (LIPID VESICLE): a spherical particle of fat suspended in a liquid medium. Liposomes may be used to carry drugs or other substances to cells or tissues. LIVER ENZYME: see aminotransferase. LIVER FUNCTION TEST: a blood test that measures levels of liver enzymes to indicate how well the liver is working and whether it might be inflamed or damaged. LOG: refers to quantities in factors of 10. A log change is an exponential or 10-fold increase or decrease (e.g., 10 to 100 is a 1-log increase). LONG-TERM NONPROGRESSOR (LTNP): an individual who has been infected with HIV for 7-10 years or more but does not exhibit immune system decline or have opportunistic diseases. LUMBAR PUNCTURE (SPINAL TAP): the insertion of a needle into the subarachnoid space around the spinal cord to remove cerebrospinal fluid for diagnosis or to inject medications or anesthesia. LYMPH NODE: a small, bean-sized organ located throughout the body with concentrations in the neck, groin and armpits. Lymph nodes are the sites of antigen presentation and immune activation. LYMPHADENOPATHY: any abnormality of the lymph nodes. Usually refers to swollen and tender lymph nodes. LYMPHATIC SYSTEM (adjective LYMPHOID): a network of vessels, ducts, nodes and organs that help maintain the fluid environment of the body and coordinate immune response. The lymphoid organs include the lymph nodes, spleen, thymus and tonsils. LYMPHOCYTE: a type of white blood cell (e.g., T-cell, B-cell) responsible for immune defense. LYMPHOMA: a malignant disease (cancer) originating in the lymph nodes. MACROPHAGE: a large scavenger white blood cell that ingests degenerated cells and foreign particles and secretes messenger proteins (monokines) involved in a variety of immune system responses. MAINTENANCE THERAPY (SECONDARY PROPHYLAXIS): preventive therapy that follows successful initial treatment of an illness. MENINGITIS: an inflammation of the meninges, the membrane envelopes that encase the brain and spinal cord. METABOLISM: the process of building the body's molecular structures from nutrients (anabolism) and breaking them down for energy (catabolism). MICROGLIA: cells within the brain that are related to macrophages. MICROSPORIDIOSIS: infection with a protozoal parasite of the microsporidia family (e.g., Enterocytozoan), which may affect the sinuses, lungs and intestines in immunocompromised patients, and may become disseminated. MONOCLONAL ANTIBODIES (MAB): antibodies that are derived (often by genetic engineering) from a single cell or its identical progeny and are specifically directed against a particular antigen. MONOCYTE: a large white blood cell that plays a role in immune defense by acting as a scavenger that destroys invading microorgnisms. Monocytes circulate in the bloodstream; when they migrate to the tissues, they mature into macrophages. MONOTHERAPY: use of a single drug or other therapy for treatment. MULTIVARIATE ANALYSIS: a statistical technique in which multiple variables are analyzed separately to determine the contribution made by each variable to an observed result. MUTATION: a change in the character of a gene that is perpetuated in subsequent cell divisions. MYCOBACTERIA: a category of gram-positive, acid-fast bacteria that contains species that cause diseases such as tuberculosis, leprosy and Mycobacterium avium complex. MYCOBACTERIUM AVIUM COMPLEX (MAC): a disease caused by Mycobacterium avium or Mycobacterium intracellulare, bacteria found in soil and water. In immunosupressed persons, the bacteria can infect lymph nodes, bone marrow, liver, spleen, spinal fluid, lungs and the gastrointestinal tract. Symptoms include diarrhea, wasting, fever, fatigue and spleen enlargement. MYELIN: a white fatty substance that forms a sheath around the axons of some neurons (nerve cells) and provides insulation necessary for proper neural transmission. Demyelination is the destruction or loss of the myelin sheath. MYOPATHY: an inflammation or disease of the muscles. NATIONAL INSTITUTES OF HEALTH (NIH): a large biomedical research organization that is part of the U.S. Public Health Service. NEURON (NERVE CELL): a cell which conducts electric neural impulses. Neurons have dendrites (branch-like fibers which receive impulses) and axons (fibers which transmit impulses), and communicate with other neurons and organs by means of neurotransmitters at junctures called synapses. NEUROPATHY (adjective NEUROPATHIC): any abnormal, degenerative or inflammatory condition of the nerves. NEUROTOXICITY: the quality of being destructive of or poisonous to the tissues of the nervous system. NEUTROPENIA: an abnormally low number or a decrease in the number of neutrophils, a type of white blood cell involved in defense against bacteria and fungi. NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI): a drug (e.g., delavirdine, nevirapine) that inhibits the action of the retroviral reverse transcriptase enzyme, thus blocking viral replication, yet works in a different way than nucleoside analog drugs. NUCLEOSIDE ANALOG (NA): a compound (e.g., AZT, ddI, ddC, d4T, 3TC) that mimics one of the building blocks of DNA and RNA. These compounds suppress retroviral replication by interfering with the reverse transcriptase enzyme; the synthetic nucleosides cause premature termination of the viral DNA chain. NUCLEOTIDE: one of the building blocks that make up the genetic material (DNA and RNA). Nucleotides consist of a base (adenine, cytosine, guanine, thymine or uracil), a sugar and a phosphate group. OFF-LABEL: use of an FDA-approved drug for an indication other than that for which the drug was approved. OPEN-LABEL: a clinical trial in which both participants and investigators know what drug is being tested and what dose is being used. OPPORTUNISTIC INFECTION (OI): a disease (e.g., PCP, MAC, CMV disease) caused by a microorganism that usually does not cause disease in persons with healthy immune systems, but which may cause serious illness when the immune system is suppressed. ORAL HAIRY LEUKOPLAKIA: a condition thought to be caused by the Epstein-Barr virus characterized by white, raised, usually painless lesions on the sides of the tongue and/or elsewhere in the mouth. PANCREATITIS: inflammation of the pancreas, a digestive gland in the abdominal cavity. PATHOGEN (adjective PATHOGENIC): any disease-causing agent, especially a microorganism. PATHOGENESIS: the development of a particular disease, including the specific events involved, bodily tissues or systems affected, mechanisms of damage and timing of the course of disease. PCR: see polymerase chain reaction. PERINATAL: the period around the time of birth. PERINATAL HIV TRANSMISSION (PHT, VERTICAL TRANSMISSION): the transmission of HIV from mother to child. Perinatal transmission may occur in utero (in the womb), intrapartum (during birth) or postpartum (after birth, via breast-feeding). PERIPHERAL BLOOD MONONUCLEAR CELL (PBMC): a single-nucleus white blood cell (e.g., monocyte) that circulates in the blood. PERIPHERAL NEUROPATHY: a disorder of the nerves usually involving the feet and/or hands and sometimes the legs, arms and face. Symptoms may include numbness, tingling or burning, weakness and partial paralysis. PHARMACOKINETICS: the action of drugs in the body, including the processes of absorption, transformation, distribution to tissues, duration of action and elimination. PHASE I TRIAL: the first stage in human testing of a new drug; these trials evaluate drug safety and toxicity at different dose levels in a small number of volunteers. PHASE II TRIAL: the second stage in the evaluation of a new drug in humans; these trials evaluate drug effectiveness and involve more participants than Phase I studies. Phase II studies proceed only if Phase I studies have shown that a drug is acceptably safe. PHASE III TRIAL: the third stage in human drug testing; these trials are designed to verify information gathered in Phase I and II trials, and involve many more volunteers (up to several thousand). Phase III trials may compare the drug being tested to other therapies or to placebo. PLACEBO-CONTROLLED TRIAL: a trial of an experimental therapy in which an inactive substance or mock therapy (placebo) is given to one group while the treatment being tested is given to another, and the results obtained in the different groups are compared. PLASMA: the fluid, non-cellular portion of circulating blood that carries blood cells and nutrients throughout the body. PLATELET (THROMBOCYTE): a type of blood cell that facilitates normal blood clotting. PNEUMOCYSTIS CARINII PNEUMONIA (PCP): a life-threatening type of pneumonia caused by a protozoan. PCP is a common opportunistic infection and a leading cause of death in people with AIDS. POLYMERASE CHAIN REACTION (PCR): a highly sensitive test that uses an amplification technique to detect small amounts of DNA or RNA in blood or tissue samples. POSTPARTUM (POSTNATAL): following childbirth. PPD TEST: a test that uses an injection of a purified protein derivative of tuberculin to test for prior exposure to the Mycobacterium tuberculosis organism. PRENATAL: the period preceding birth. PRIMARY INFECTION: the initial introduction of an infectious organism into the body. PROGNOSIS (adjective PROGNOSTIC): a forecast of the probable course and/or outcome of a disease. PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML): a rapidly progressing, often fatal brain disease thought to be caused by the Jacob-Creutzfeldt (JC) virus. PROPHYLAXIS: a treatment that helps to prevent a disease or condition before it occurs (primary prophylaxis) or recurs (secondary prophylaxis). PROSPECTIVE STUDY: a study that looks forward in time. Patients are selected and their progression is followed. PROTEASE INHIBITOR: a drug (e.g., saquinavir, indinavir, ritonavir) that blocks the action of the protease (proteinase) enzyme that breaks up large proteins produced from viral RNA, thereby preventing HIV replication. PROTHROMBIN TIME: a test that measures blood coagulation ability; prothrombin is a protein produced by the liver that facilitates blood clotting. RANDOMIZED TRIAL: an experiment arranged so as to produce a chance distribution of subjects into different treatment groups or arms. RECEPTOR: a specific protein-binding site on a cell's surface or interior. When chemicals (including drugs) bind to receptors, various cellular functions are activated or inhibited. Viruses enter cells by fusing with receptors on the cell surface. RECOMBINANT: produced by genetic engineering. REFRACTORY: resistant to treatment. REGIMEN: a formalized schedule, e.g., a drug-dosing regimen. RELATIVE RISK (RR): a measure of comparative risk of developing a disease or condition. Statistically, RR is the chance that a person receiving an exposure will develop a condition compared to the chance that a non-exposed person will develop the same condition. REPLICATION: duplication or reproduction. RESERVOIR: a site where an infectious agent collects and multiplies, e.g., macrophages and lymph nodes are thought to be reservoirs for HIV. RESISTANCE: the ability of a microorganism (e.g., a virus) to mutate in such a way that it loses its sensitivity to a drug. RETINITIS: inflammation of the retina, the light-sensitive tissue at the back of the eyeball. RETROVIRUS: a class of enveloped viruses that have their genetic material in the form of RNA and use reverse transcriptase to translate their RNA into DNA. The retrovirus family includes oncoviruses (e.g., HTLV-1) and lentiviruses (e.g., HIV-1, HIV-2). REVERSE TRANSCRIPTASE INHIBITOR (RTI): a drug that blocks retroviral replication by interfering with the reverse transcriptase enzyme that allows a retrovirus to translate its genetic material (in the form of RNA) into DNA, which is then integrated into the host cell's chromosomes. RTI include nucleoside analogs (e.g., AZT, ddI, 3TC) and non-nucleoside reverse transcriptase inhibitors (e.g., nevirapine). RNA (RIBONUCLEIC ACID): a single-stranded nucleic acid made up of nucleotides. RNA is involved in the transcription of genetic information; the information encoded in DNA is translated into messenger RNA (mRNA), which controls the synthesis of new proteins. RUPTURE OF MEMBRANES (ROM): the breaking open of the amniotic sac surrounding the fetus prior to the start of labor and delivery. SENSITIVITY: the ability of an organism to be affected by a drug or other agent, e.g., a virus is senstive to AZT if AZT is able to prevent viral replication. Also refers to a statistical measure of the accuracy of a screening test, i.e., how likely a test is to label as positive those who have a disease or condition. SEPSIS: the presence of pathogenic (disease-causing) organisms or their toxins in the blood or tissues. SEROCONVERSION: the development of antibodies against a microorganism; the change in a person's antibody status from negative to positive. SEROLOGY (adjective SEROLOGIC): tests that measure components and substances in the serum, including antibodies and antigens. SEROPREVALENCE: the rate of HIV-infected individuals in a given population as measured by blood antibody tests, that is, the number of infected individuals divided by the total number in the population. SERUM: the clear, fluid portion of blood that remains after coagulation. SEXUALLY TRANSMITTED DISEASE (STD, VENEREAL DISEASE): a disease (e.g., syphilis, chlamydiasis) that is transmitted through sexual contact. SIDE EFFECT: an action or effect of a drug other than that which is intended. The term usually refers to undesired or negative effects such as headache, skin rash or liver damage. SINUSITIS: acute or chronic inflammation or infection of the sinuses (cavities behind the forehead and cheekbones), which may be characterized by nasal congestion and discharge, fever and headache. SPECIFICITY: a statistical measure of the accuracy of a screening test, i.e., how likely a test is to label as negative those who do not have a disease or condition. STATISTICAL SIGNIFICANCE: the probability that an observed outcome of an experiment or trial is due to chance alone. In general, a result of a clinical trial is considered statistically significant if there is a less than 5% probability that the difference observed would occur by chance alone if the treatments being compared were equally effective (e.g., a p-value of less than .05). STRAIN: a specific genetic variant of a particular organism. SUBCORTICAL: pertaining to structures in the interior of the brain. Subcortical dementia is a loss of mental, physical and/or emotional function due to organic disease of the brain's deep structures. SUBCUTANEOUS: beneath the skin; subdermal. SURROGATE MARKER: a marker or sign (e.g., viral load or CD4 cell count) that can serve in place of a clinical endpoint. SYNERGY (SYNERGISM): the action of 2 or more agents (e.g., drugs) working together to produce an effect greater than the combined effects of the same agents used separately. SYSTEMIC: affecting the whole body; not localized. T-CELL (T-LYMPHOCYTE): a type of white blood cell derived from the thymus that participates in a variety of cell-mediated immune responses. There are 3 major types of T-cells: T-helper (CD4), T-suppressor (CD8) and T-killer (cytotoxic T-lymphocytes or CTL). T-SUPPRESSOR CELL: a type of T-cell that bears the CD8 surface marker and helps to regulate immune responses. THALAMUS: one of the basal ganglia (a cluster of nerve cell bodies) deep in the brain that serves as a center for the relay of sensory information (especially pain and pleasure information) and plays a role in arousal. THROMBOCYTOPENIA: an abnormally low number of thrombocytes (platelets), blood cells which facilitate normal blood clotting. THRUSH: see candidiasis. THYMUS (adjective THYMIC): a lymphoid organ in the upper chest cavity. The thymus is the site of T-lymphocyte differentiation, where the cells learn to recognize antigens. The thymus produces some 30 hormones or thymic factors (e.g., thymodulin, thymopentin) that are involved in the regulation of immune function. TONSIL: one of 2 small immune system glands, made up of lymphoid tissue, located at the back of the throat. TOXICITY (adjective TOXIC): the quality of being poisonous or harmful; often used to refer to side effects of drugs. TOXOPLASMOSIS: an opportunistic infection caused by the microscopic parasite Toxoplasma gondii, found in raw or undercooked meat and cat feces. The disease often affects the brain (toxoplasmic encephalitis). TUBERCULOSIS (TB): an infectious disease caused by Mycobacterium tuberculosis that typically affects the lungs, but may occur in other organs (extrapulmonary TB). Multidrug-resistant tuberculosis (MDR-TB) is resistant to some of the standard drugs and requires more aggressive treatment. TUMOR NECROSIS FACTOR-ALPHA (TNF-ALPHA, CACHECTIN): a cytokine, produced by activated monocytes and macrophages, that can destroy tumors. When chronically elevated (as may occur in HIV disease), TNF may lead to fever, anorexia, hypermetabolism and wasting. UVEITIS: an inflammation of the membranes (uvea) of the eye, characterized by pain and redness. VACCINE: a preparation that contains an infectious agent or its components which is administered to stimulate an immune response that will protect a person from illness due to that agent. A therapeutic (or treatment) vaccine is given after infection and is intended to reduce or arrest disease progression. A preventive vaccine is intended to prevent initial infection. VARICELLA-ZOSTER VIRUS (VZV, HHV-3): a herpesvirus that initially causes chickenpox (varicella). VZV may lie dormant within the nerves for years and reactivate later to cause herpes zoster (shingles), especially in immunosuppressed individuals. VASCULAR: relating to or containing blood vessels. VECTOR: an agent used as a vehicle for transfer. VERTICAL TRANSMISSION: see perinatal HIV transmission. VIRAL LOAD (VIRAL BURDEN): the amount of virus in the blood or other tissues. The presence of HIV RNA indicates that the virus is replicating. Changes in viral load may be used to gauge drug effectiveness and disease progression. Viral load is measured using assays such as PCR or branched-chain DNA. VIREMIA: the presence of virus in the blood or plasma. VIRUS: a group of minute organisms that are unable to grow or reproduce outside the body of a living host. During replication a virus integrates its genetic material (DNA or RNA) into a host cell and uses the cell's biological mechanisms to reproduce new viral particles. WASTING SYNDROME: a condition characterized by atrophy of lean body mass and involuntary weight loss of more than 10% of normal body weight. WESTERN BLOT: a laboratory blood test for specific antibodies (e.g., against HIV). The Western blot test is more accurate than the ELISA test and is used as a confirmatory test if an ELISA test is positive. Page last updated 17 December 1996 |
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