Published in the Bulletin of Experimental Treatments for AIDS Spring 2000 issue, by the San Francisco AIDS Foundation.

Spring 2000 Table of Contents

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Glossary

Compiled by Nicholas Cheonis

ADHERENCE: following a prescribed treatment regimen, including correct dosage, number of doses per day, and dietary restrictions.

ANTIGEN (adjective ANTIGENIC): any agent or substance that stimulates an immune response.

ANTIRETROVIRAL: an agent (e.g., AZT, ddI, nevirapine) that suppresses the activity or replication of retroviruses such as HIV.

ASSAY: a test, especially one used to detect the presence and/or concentration of a component, drug, or microorganism in the blood or other body fluids or tissues.

BASELINE: an initial or known value (e.g., CD4 cell count, HIV viral load) against which later measurements can be compared.

CD4 CELL (CD4 LYMPHOCYTE, T-HELPER CELL, T4 CELL): a type of white blood cell that carries the CD4 cell surface receptor and helps the body fight infection. CD4 cells release cytokines (chemical messengers) that coordinate a broad range of immune system activities including killer cell activation and antibody production.

CD8 CELL (CD8 LYMPHOCYTE, T8 CELL): a type of white blood cell that carries the CD8 cell surface marker and helps regulate and/or carry out the body's immune response. Two subsets of T-cells express the CD8 surface marker: T-suppressor cells and cytotoxic T-lymphocytes (CTLs).

CHRONIC: persisting or recurring over a long period of time; marked by slowly progressing seriousness.

COHORT: a group of individuals in a study who share a demographic, clinical, or other statistical characteristic (e.g., age, study site).

CYTOTOXIC T-LYMPHOCYTE (CTL, KILLER T-CELL): a type of white blood cell that bears the CD8 surface marker, and targets and kills cells infected with viruses, bacteria, parasites, and other microorganisms.

ELISA: see enzyme-linked immunosorbent assay.

ENV: the gene of HIV that encodes the proteins of the viral envelope; also refers to the proteins produced by that gene.

ENZYME: a protein that induces or accelerates a chemical reaction.

ENZYME-LINKED IMMUNOSORBENT ASSAY (ELISA): a laboratory test used to detect the presence of antibodies in the serum. ELISA is used for first-line screening for HIV antibodies; a positive result indicates that antibodies have been detected. The test is sensitive but not specific, and a positive ELISA is typically confirmed using a Western blot assay.

GAG: the gene of HIV that encodes the core proteins of the virus; also refers to the proteins produced by that gene.

GENE (adjective GENETIC): the unit of heredity. A gene contains hereditary information encoded in the form of DNA and is located at a specific position on a chromosome in a cell's nucleus. Genes determine many aspects of anatomy and physiology by controlling the production of proteins.

GENOME (adjective GENOMIC): the unique genetic code or hereditary material of an organism, carried by a set of chromosomes in the nucleus of each cell. The human genome contains an estimated 50,000-100,000 genes; the genome of HIV contains nine genes.

GENOTYPE (adjective GENOTYPIC): the specific genetic makeup or "blueprint" of an organism. Genotypic resistance testing determines whether an organism's genetic structure contains certain mutations that make it resistant to a drug. Contrast with phenotype.

HALF-LIFE: the time required for half of the amount of an agent (e.g., drug, virus, cell type) to be eliminated from the body.

IMMUNOLOGY (adjective IMMUNOLOGIC): the study and/or treatment of disorders that involve the immune system (e.g., cancer, HIV disease, autoimmune diseases).

INCUBATION PERIOD: the period of time between an initial exposure to an infectious agent and the development of symptoms of disease, during which the infection is established in the body.

INTERFERON-ALPHA (INTRON-A, ROFERON-A): a type of interferon produced in response to viral infection. Genetically engineered interferon-alpha is used to treat Kaposi's sarcoma, anogenital warts, and chronic hepatitis B and C, and is under study as an anti-HIV therapy. Side effects include flu-like symptoms, anemia, and neutropenia.

IN VITRO: Latin for "in glass." Refers to studies done in a test tube or culture medium in the laboratory.

IN VIVO: Latin for "in the body of a living organism." Refers to studies done using human or animal subjects.

LATENCY (adjective LATENT): the state in which a pathogenic organism is present in the body but not actively replicating or causing illness.

LIPODYSTROPHY: a loss of fatty tissue, usually in the limbs and face. The term is also sometimes used to refer to any type of body fat redistribution.

LOG: refers to quantities in factors of ten. A log change is an exponential or ten-fold increase or decrease (e.g., a change from ten to 100 is a 1-log increase).

LONG-TERM NONPROGRESSOR (LTNP): an individual who has been infected with HIV for several years (7-10 or more years) but does not exhibit immune system decline or have opportunistic diseases. About 10% of persons with HIV disease seem to be LTNPs.

LYMPHOCYTE: a type of white blood cell (e.g., T-cell, B-cell, natural killer cell) that plays a part in immune defense.

MACROPHAGE: a large scavenger white blood cell that ingests and processes degenerated cells and foreign invaders. The long-lived macrophages can harbor large quantities of HIV, and may act as viral reservoirs.

MONOCYTE: a large white blood cell that plays a role in immune defense. Monocytes circulate in the bloodstream; when they migrate to the tissues, they mature into macrophages.

MUTATION: a change in the character of a gene that is perpetuated when a cell divides or a virus replicates.

NATURAL KILLER CELL (NK CELL): a type of white blood cell that attacks and kills tumor cells and cells infected with microorganisms. Unlike cytotoxic T-lymphocytes, NK cells are nonspecific and attack infected cells without regard to specific antigens or MHC receptor configuration.

NEF: a gene of HIV that influences viral replication and may help HIV evade host defenses; also refers to the protein produced by that gene.

NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI): a drug (e.g., delavirdine, efavirenz) that binds with and inhibits the action of the HIV reverse transcriptase enzyme, thus blocking viral transcription and replication.

NUCLEOSIDE ANALOG (also known as NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR, NRTI): a compound (e.g., AZT, d4T, 3TC) that mimics one of the building blocks of DNA. These compounds suppress retroviral replication by interfering with the reverse transcriptase enzyme.

OPPORTUNISTIC INFECTION (OI): a disease caused by a microorganism that does not normally cause illness in a person with a healthy immune system, but that may cause serious disease when the immune system is weakened. Common OIs in HIV positive people include Pneumocystis carinii pneumonia (PCP), Mycobacterium avium complex (MAC), and cytomegalovirus (CMV) infection.

PANACEA: a miracle cure-all.

PHENOTYPE (adjective PHENOTYPIC): visible characteristics and/or behavior that result from the interaction of an organism's genetic "blueprint" (genotype) and the environment. Phenotypic resistance testing determines whether an organism is susceptible to a specific drug in a test tube. Contrast with genotype.

PHOSPHORYLATION: the addition of a phosphate group to a compound by an enzyme (e.g., thymidine kinase, tyrosine kinase). Phosphorylation is an essential step in many cellular processes.

PLACEBO: an inert, inactive substance; a "sugar pill." Experimental therapies are compared with placebo in many clinical trials.

PRODRUG: an inactive form of a drug that exerts its effects after metabolic processes within the body convert it to a usable or active form.

PROGESTERONE: a female steroid hormone with anti-estrogen effects. Progesterone prepares the uterus for the development of the fertilized ovum and maintains the uterus throughout pregnancy. Synthetic progesterone is used as a contraceptive.

PROGESTIN: a hormone produced by the corpus luteum, placenta, or adrenal cortex (or synthetically manufactured) that has progesterone-like effects. Synthetic progestin is used as a contraceptive.

PROLIFERATION: rapid reproduction or replication.

PROTEASE INHIBITOR (PI): a drug (e.g., saquinavir, ritonavir, indinavir, nelfinavir, amprenavir) that blocks the action of the HIV protease enzyme, thereby preventing viral replication. Unlike reverse transcriptase inhibitors, protease inhibitors can inhibit HIV replication in cells that are already infected.

PROTOCOL: a plan that states the specifics of a clinical trial, such as the hypothesis to be tested, drug(s) to be used, method(s) of administration, length of the trial, endpoints to be used, and characteristics of participants (e.g., inclusion/exclusion criteria).

RESISTANCE: the mutation of a microorganism in such a way that it loses its sensitivity to a drug.

REVERSE TRANSCRIPTASE (RT): a viral enzyme that allows a retrovirus to translate its genetic material (in the form of RNA) into DNA, which is then integrated into the chromosomes of the host cell.

SIMIAN IMMUNODEFICIENCY VIRUS (SIV): a viral infection endemic to African green monkeys and able to infect various primates. SIV is similar to HIV-2.

T-CELL (T-LYMPHOCYTE): a type of white blood cell that matures in the thymus and carries out the cell-mediated immune response. Three major types of T-cells are helper (CD4) T-cells, suppressor (CD8) T-cells, and killer (CD8) T-cells (cytotoxic T-lymphocytes, or CTLs).

UNDETECTABLE (UNQUANTIFIABLE): a term used to describe a viral load that is below the level of detection of the test being used.

VIRAL LOAD (VIRAL BURDEN): the amount of virus in the blood or body tissues.

VIROLOGICAL FAILURE: treatment breakthrough; an increase in viral load after it has been suppressed with antiretroviral drugs.

VIROLOGY: the study of viruses and diseases caused by viruses.

WESTERN BLOT: a laboratory blood test for specific antibodies (e.g., to HIV). The Western blot assay is more accurate than the ELISA, and is used as a confirmatory test if an ELISA is positive.

WILD TYPE (adjective WILD-TYPE): the normal, typical phenotype of a virus or other organism before genetic mutation takes place.

Page last updated 2 June 2000