Glossary

Compiled by Liz Highleyman

ABSCESS: an accumulation of pus associated with a localized infection.

ACID-FAST BACILLI: species of bacteria (e.g., Mycobacterium tuberculosis, Mycobacterium avium) that retain a laboratory stain when washed in an acid bath.

ACUITY: keenness of sense perception (e.g., vision, hearing).

ACUTE RETROVIRAL SYNDROME: a combination of flu-like symptoms (e.g., fever, sore throat, skin rash, headache, nausea, muscle or joint pain) that occurs during or shortly after primary HIV infection.

ADHERENCE: following a prescribed treatment regimen, including correct dosage and number of doses per day, and taking as directed with or without food.

ADVERSE EVENT: an unwanted toxic reaction or side effect of a drug.

AIDS DEMENTIA COMPLEX (ADC): mental impairment due to HIV.

ALVEOLI: tiny airs sacs in the lungs where oxygen and carbon dioxide are exchanged by red blood cells.

AMINOGLYCOSIDE: a family of antibiotic drugs (e.g., amikacin, kanamycin) similar to streptomycin.

AMYLASE: an enzyme produced by the salivary glands and the pancreas that helps break down food; an abnormal increase in serum amylase levels may indicate inflammation of the pancreas.

ANABOLIC STEROID: a natural or synthetic hormone related to testosterone that promotes the synthesis of proteins and the building of muscle mass.

ANAPHYLAXIS: a life-threatening allergic reaction to a foreign antigen.

ANEMIA: reduced ability of blood to carry oxygen due to a low hemoglobin level, or an abnormality or reduced number of red blood cells.

ANERGY (adjective ANERGIC): the lack of an immune response to a foreign antigen, potentially a sign of immunocompromise.

ANGINA: chest pain caused by reduced flow of blood to the heart muscle.

ANGIOGRAPHY: a method of visualizing the blood vessels.

ANTIBODY (IMMUNOGLOBULIN): a protein secreted by activated plasma cells, which evolve from B-cells, in response to stimulation by an antigen.

ANTICOAGULANT: an agent that reduces or delays blood coagulation or clotting.

ANTIGEN: any agent or substance (e.g., microorganisms or the substances they produce) that stimulates an immune response.

ANTIRETROVIRAL: an agent that suppresses the activity or replication of retroviruses such as HIV.

APHERESIS: a procedure in which blood is removed, specific components are filtered out, and the remainder of the blood is returned to the body.

APOPTOSIS: programmed cell death.

AREA UNDER THE CURVE (AUC): a measure of drug concentration.

ARM: a group of participants in a clinical trial who receive the same treatment.

AS-TREATED ANALYSIS: a method of analyzing the results of a clinical trial in which only participants who successfully complete a course of treatment are analyzed.

ASYMPTOMATIC: not feeling or showing outward signs of infection.

ATTENUATED: weakened, with diminished ability to cause disease.

AVIPOX: a bird virus used as a vaccine vector.

B

BACILLE CALMETTE-GUÉRIN (BCG): an attenuated strain of Mycobacterium bovis that is used in some countries as a vaccine against tuberculosis.

BACTEC: a drug resistance test used to determine whether a strain of Mycobacterium tuberculosis is susceptible to the most commonly used anti-TB drugs.

BASELINE: a known value against which later measurements can be compared.

B-CELL (B-LYMPHOCYTE): an immune system cell that carries out the humoral immune response. B-cells are produced in the bone marrow and mature into plasma cells that produce antibodies.

BIOAVAILABILITY: the extent to which a drug is absorbed and circulated in the body.

BIOPSY: the removal of a small sample of cells or tissue for microscopic examination and/or culture.

BILE DUCT: a small passage that carries bile, a substance that aids in the digestion of fats, from the gall bladder to the intestine.

BILIRUBIN: a yellow pigment released when red blood cells are broken down. High blood bilirubin levels are characterized by jaundice, a yellowing of the skin and eyes, and may indicate liver disease.

BLOOD-BRAIN BARRIER: a set of physical barriers between the blood vessels and the brain that allows only certain substances to pass through.

BODY MASS INDEX (BMI): a measure of mass that is calculated as weight divided by height squared.

BONE MARROW SUPPRESSION: damage to the blood cell-producing stem cells in the bone marrow, which may be caused by drugs, toxic chemicals, or radiation.

BRANCHED-CHAIN DNA ASSAY (bDNA): a test for measuring the amount of virus (viral load) in blood plasma or tissue.

BUFFALO HUMP: an accumulation of fatty tissue at the base of the neck (cervicodorsal fat pad) that may be a side effect of certain anti-HIV drugs and/or a result of chronic disease.

C

canarypox: a poxvirus used as a vaccine vector.

CANDIDIASIS: a disease caused by the fungus Candida. Candidiasis may affect the skin, nails, and mucous membranes throughout the body, including the mouth (thrush), esophagus, and vagina.

CASEATION: a type of necrosis (tissue death) in which dead cells and debris develop into a soft substance with a cheese-like consistency.

CCR5: a protein found on certain cells that acts as a receptor for chemokines and as a co-receptor that enables HIV to enter cells.

CD4 CELL (CD4 LYMPHOCYTE, HELPER T-CELL): a type of immune system white blood cell that carries the CD4 cell surface receptor and helps the body fight infection. CD4 cells release cytokines that regulate other immune cells.

CD4/CD8 RATIO: the ratio of CD4 cells to CD8 cells.

CD8 CELL (CD8 LYMPHOCYTE): a type of immune system 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: suppressor T-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 cytokines including IL-2 and IL-12, and carried out by cytotoxic T-lymphocytes and macrophages.

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 spinal cord.

CERVICAL DYSPLASIA: abnormal changes (e.g., in size, shape, growth pattern) of the cells of the uterine cervix, which may be detected by a Pap smear or colposcopy. Cervical dysplasia is associated with the human papillomavirus (HPV) and may progress to cervical cancer.

CESAREAN SECTION (C-SECTION): a delivery procedure that involves making an incision through the abdominal wall to remove an infant from the uterus.

CHEMOKINE: a soluble factor secreted by certain immune system cells that stimulates the activity of other cells. Alpha and beta chemokines have different chemical structures. Certain chemokine receptors (e.g., CCR5, CXCR4) are necessary to allow HIV to enter host cells.

CHEMOTHERAPY: the use of chemicals or drugs to treat disease; the term is typically used to refer to cancer treatment.

CHEST X-RAY: a radiograph of the chest done to look for abnormalities (e.g., lesions, cavities, scars) that suggest tuberculosis.

CHOLESTEROL: a fatty substance in animal tissue that is an essential component of cell membranes and nerve fiber insulation.

CHRONIC: slow, persisting over a long period.

CLINICAL TRIAL: an organized procedure for determining the effectiveness of a new drug or therapy by administering the agent to participants under strictly controlled conditions.

COMPUTED TOMOGRAPHY SCAN (CT SCAN): a method of visualizing soft tissues of the body using X-rays.

CONTRAINDICATION: any circumstance or condition that makes a drug or other method of treatment inadvisable in a particular case.

CO-RECEPTOR: a second cell surface receptor required for entry by a pathogen into a host cell or initiation of a biological process.

CORONARY ARTERY DISEASE: damage to or blockage of the arteries that provide blood to the heart muscle.

CORTICOSTEROID: one of a group of steroid hormones (e.g., prednisone) produced by the cortex of the adrenal gland or manufactured synthetically. Corticosteroids have anti-inflammatory and immunosuppressive properties.

CREATININE: a muscle protein. High blood creatinine levels may indicate kidney damage or muscle disease.

CROSS-RESISTANCE: the development of resistance to one agent (e.g., drug) which also confers resistance to another (often similar) agent.

CULTURE: a method of growing a microorganism in vitro in a medium that promotes its growth.

CXCR4 (FUSIN): a co-receptor on the surface of certain T-cells that, along with the CD4 receptor, allows HIV to infect the cell.

CYTOCHROME P450 (CP450) SYSTEM: a system that metabolizes drugs and other foreign substances in the liver by means of enzymes (e.g., CYP3A4) that inhibit or promote metabolic reactions.

CYTOKINE: an intercellular chemical messenger protein (e.g., tumor necrosis factor, interleukin) released by white blood cells. Cytokines facilitate communication among immune system cells.

CYTOMEGALOVIRUS (CMV, HHV-5): a herpesvirus which may cause retinitis, pneumonia, colitis, and/or encephalitis in immunocompromised people.

CYTOTOXIC T-LYMPHOCYTE (CTL, KILLER T-CELL): an immune system white blood cell that targets and kills cells infected with microorganisms.

D

DESENSITIZATION: the reduction of sensitivity to a drug by administering a small amount and gradually increasing the dose.

DIABETES: a disease characterized by high blood sugar and excessive urination caused by insufficient insulin production or lack of responsiveness to insulin.

DIRECTLY OBSERVED THERAPY (DOT): a method of medication administration in which a healthcare provider or other observer watches the patient take each dose of a drug.

DISSEMINATION: spread of a disease-causing organism throughout the body, possibly causing symptoms at multiple sites.

DNA (DEOXYRIBONUCLEIC ACID): a molecule found in the nucleus of cells which encodes genetic information. The particular sequence of four chemical building blocks (nucleotides) determines an individual’s unique genetic code.

DOUBLE-BLIND: a type of clinical trial in which neither the subject nor the investigator knows what treatment, if any, the subject is receiving.

DYSPLASIA: the abnormal development or growth of cells and tissues; precancerous tissue changes.

E

EFFICACY: effectiveness.

ELECTROLYTE: an electrically charged element or compound (e.g., sodium, potassium) found in body fluids, tissues, and cells.

ELISA: a laboratory test used to detect HIV antibodies in the blood.

ENDOCRINE SYSTEM: a system of ductless glands that regulates bodily functions via hormones secreted into the bloodstream. The endocrine system includes the hypothalamus, pituitary gland, thyroid, adrenal glands, and gonads (ovaries and testes).

ENDPOINT: a direct marker of disease progression.

ENVELOPE: the outer covering of certain types of viruses.

ENV: the gene of HIV that encodes the proteins that make up its outer envelope.

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

EXTRAPULMONARY: outside the lungs.

F

FAILURE TO THRIVE: a condition in which a child loses or fails to gain weight and grows at a slower rate than expected.

FIRST-LINE TREATMENT: the preferred standard therapy for a condition.

FLUOROQUINOLONE: a class of antibiotic drugs (e.g., ciprofloxacin, ofloxacin).

FOOD AND DRUG ADMINISTRATION (FDA): the U.S. federal agency responsible for regulating the development, use, and safety of drugs, medical devices, food, cosmetics, and related products.

FUSION INHIBITOR: a drug (e.g., T-20) that inhibits the binding of HIV's envelope to a host cell's receptors.

G

GAG: the gene of HIV that encodes the core proteins of the virus.

GASTROINTESTINAL: relating to the stomach and intestines.

GENE THERAPY: an approach to preventing and/or treating disease by replacing, removing, or introducing genes, or otherwise manipulating genetic material.

GENOME: the genetic code of an organism.

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

GLUCOSE: blood sugar.

GOUT: a painful condition caused by the buildup of uric acid crystals in the tissues, especially the large toe.

GP120: a glycoprotein (sugar/protein compound) on the outer envelope of HIV. Gp120 binds to CD4 receptors and enables HIV to enter host cells.

GRANULOCYTE: a type of immune system white blood cell (basophil, eosinophil, neutrophil) that contains granules of toxic chemicals that are released to kill microorganisms and mediate allergic reactions.

GRANULOCYTE COLONY-STIMULATING FACTOR (G-CSF, NEUPOGEN): a cytokine that stimulates the production of granulocytes, a type of white blood cell.

GRANULOCYTE MACROPHAGE COLONY-STIMULATING FACTOR (GM-CSF, LEUKINE): a cytokine that stimulates growth of granulocytes and macrophages, types of white blood cells.

GRANULOMA: an inflammatory lesion (e.g., tubercle) containing granulocytes.

H

HAART: highly active antiretroviral therapy, a term for potent combination anti-HIV treatment, usually including a protease inhibitor drug.

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

HEPA FILTER: high-efficiency particulate air filter, a engineering measure used to reduce the airborne transmission of tuberculosis.

HEPATITIS: an inflammation of the liver that may be caused by several agents, including viruses, toxins, and drugs. Acute hepatitis is typically characterized by fever, jaundice, fatigue, abdominal tenderness, and elevated liver enzymes. Hepatitis A virus causes an inflammatory viral disease with a short incubation period. Hepatitis B and C virus can become chronic and may result in liver damage, cirrhosis, and/or liver cancer.

HEPATOMEGALY: liver enlargement.

HERPESVIRUS: a group of viruses that includes herpes simplex virus types 1 and 2, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, human herpesvirus types 6 and 7, and Kaposi's sarcoma-associated herpesvirus (HHV-8).

HIVES: itchy, raised, swollen bumps on the skin or mucous membranes, often a manifestation of an allergic reaction.

HORMONE: a chemical messenger involved in the regulation and coordination of cellular and bodily functions.

HUMAN GROWTH HORMONE: a peptide hormone secreted by the anterior pituitary gland that stimulates metabolism and protein synthesis. Recombinant human growth hormone (Serostim) is a genetically engineered drug used to treat HIV-related wasting syndrome.

HUMAN PAPILLOMAVIRUS (HPV): a papovavirus. Many strains of HPV cause warts, including condylomata acuminata (genital warts). Certain strains (e.g., 16, 18) are associated with cervical and anal cancer.

HUMORAL IMMUNITY (TH2 RESPONSE): the immune response mediated by the Th2 subset of CD4 cells. Humoral immunity is stimulated by cytokines including IL-4 and IL-6, and carried out by plasma cells (derived from B-cells) which produce antibodies.

HYPERBILIRUBINEMIA: an excess level of bilirubin in the blood, characterized by jaundice; may be a sign of liver dysfunction.

HYPERKERATOSIS: a skin condition characterized by thickening and hardening of the skin.

HYPERLIPIDEMIA: elevated levels of blood fats (e.g., triglycerides, cholesterol).

HYPERSENSITIVITY REACTION: an exaggerated immune response to an antigen, drug, etc.

HYPERTENSION: high blood pressure.

HYPOGONADISM: inadequate function of the gonads (ovaries or testes) characterized by deficient hormone secretion.

I

IDIOPATHIC: refers to a disease or condition of unknown cause or origin.

IMMUNE SYSTEM: the body's defense system that protects against foreign invaders (e.g., microorganisms) and cancerous cells. Immune system organs include the lymph nodes, spleen, thymus, and tonsils.

IMMUNIZATION (VACCINATION): a process by which a person is protected against the adverse effects of infection by a disease-causing microorganism by exposing the person to a small amount of the killed or inactivated organism or pieces of the organism.

IMMUNOGENICITY: the ability to stimulate an immune response.

IMMUNOGLOBULIN: see antibody.

IMMUNOMODULATOR (IMMUNE MODULATOR): an agent or process capable of modifying or influencing the function of the immune system.

IMMUNOSUPPRESSION: reduction in immune system function.

IMMUNOTHERAPY (IMMUNE-BASED THERAPY): a therapy that attempts to modify or enhance immune response, or to reconstitute a damaged immune system.

INCIDENCE: the number of new cases of a disease or condition in a specific population during a given period of time.

INDUCTION: the initiation phase of a particular therapy.

INDURATION: a swelling and hardening of soft tissue. On a tuberculosis skin test, induration size is used to determine whether a person has been infected by TB.

INFECTIOUS: capable of transmission from one person to another.

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 into the bloodstream.

IN SITU HYBRIDIZATION: a method used to locate specific DNA or RNA sequences.

INSULIN: a peptide that enables the body to metabolize and use glucose.

INTENT-TO-TREAT ANALYSIS: a method of analyzing the results of a clinical trials in which all participant originally assigned to an arm are analyzed, including those who dropped out due to treatment failure or side effects.

INTERFERON: a cytokine (chemical messenger) that plays a role in immune response.

INTERLEUKIN (IL): a cytokine secreted by immune system blood cells that regulates a range of immune functions. IL-2 is produced by activated CD4 cells and promotes the proliferation and activity of T-cells and natural killer cells.

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.

J

JAUNDICE: a yellowish discoloration of the skin and whites of the eyes due to high bilirubin levels resulting from the breakdown of red blood cells; jaundice is associated with liver damage.

K

KAPOSI'S SARCOMA (KS): an abnormal or cancerous proliferation of cells of the 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 sexually transmitted herpesvirus that is associated with Kaposi's sarcoma.

KIDNEY STONE (NEPHROLITHIASIS): an accumulation of substances (e.g., drug crystals, minerals) in the kidney, which may lead to blockage and pain in the flanks, back, or groin.

L

LEAN BODY MASS: muscle and organ tissue.

LENTIVIRUS: a subfamily of retroviruses, including HIV, that are associated with chronic, slow-developing diseases.

LIMIT OF DETECTION: the lower boundary of an assay (e.g., a viral load test). The limit of detection is the level below which a test cannot measure the presence of a component (e.g., HIV RNA).

LIPID: a fat.

LIPODYSTROPHY: changes in body shape typically characterized by loss of fatty tissue in the limbs and face, and redistribution of fat to the trunk, abdomen, or back of the neck.

LIVE-ATTENUATED VIRUS (LAV): an weakened live virus used in vaccines to provoke an immune response.

LIVER ENZYME: a protein produced by the liver (e.g., ALT, AST) that promotes various physiological reactions. Abnormally high levels of liver enzymes in the blood may indicate liver damage.

LOG: refers to quantities in factors of ten. A log change is an exponential or 10-fold increase or decrease (e.g., from 10 to 100 is a 1-log increase).

LONG-TERM NON-PROGRESSOR: an individual who has been infected with HIV for several years but does not exhibit immune system decline or have opportunistic diseases.

LYMPH NODES (LYMPH GLANDS): small, bean-sized organs located throughout the body. Lymph nodes filter out antigens and are the site of immune cell activation.

LYMPHADENITIS: inflammation of the lymph nodes.

LYMPHATIC SYSTEM: a network of organs and capillary-like vessels that helps maintain the fluid environment of the body and coordinates immune responses. The lymphoid organs include the lymph nodes, spleen, thymus, tonsils, and adenoids.

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

LYMPHOPENIA (LYMPHOCYTOPENIA): a reduced number of lymphocytes, a type of white blood cell.

LYMPHOMA: cancer of the lymphoid tissue, which may spread out of the lymph nodes to the brain or other tissues. Lymphomas are classified as Hodgkins disease or non-Hodgkin's lymphoma.

M

MACROPHAGE: a large scavenger white blood cell that ingests and processes degenerated cells and foreign invaders. Macrophages are derived from monocytes that leave the blood and migrate into the tissues. The long-lived macrophages are reservoirs of HIV.

MAINTENANCE THERAPY: preventive therapy that follows successful initial treatment of an illness.

MALAISE: a generalized feeling of illness and discomfort; a "flu-like" feeling.

MANTOUX TEST: a test that uses an injection of a purified protein derivative of tuberculin to test for prior exposure to Mycobacterium tuberculosis. A positive reaction is indicated by swelling at the injection site.

MDRTB: multidrug-resistant tuberculosis, a strain of Mycobacterium tuberculosis that is resistant to more than one of the drugs typically used to treat the disease.

MEMORY CELL: a B-cell or T-cell that remains after an initial immune response and is primed to respond to a subsequent attack by the same invader in the future.

MENINGITIS: an inflammation of the meninges, the membranes that surround the brain and spinal cord.

METABOLISM (adjective METABOLIC): the process of building the body's molecular structures from nutrients (anabolism) and breaking them down for energy production (catabolism).

METASTASIS: spread of cancer from a primary site to another part of the body.

MICROBICIDE: an agent that inactivates, kills, or destroys microbes.

MILIARY TUBERCULOSIS: tuberculosis infection at multiple sites throughout the body.

MIP-1 ALPHA: a chemokine that binds with the CCR5 cell surface receptor and inhibits the entry of HIV into a host cell.

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.

MONOTHERAPY: the use of a single drug or other therapy.

MUTATION: a change in the character of a gene that is perpetuated when a cell divides or a virus replicates. A mutant is a new organism produced by a genetic mutation.

MYCOBACTERIUM AVIUM COMPLEX (MAC): an opportunistic disease caused by Mycobacterium avium or Mycobacterium intracellulare, bacteria found in soil and water.

MYCOBACTERIUM BOVIS: a mycobacterium, closely related to Mycobacterium tuberculosis, that causes a similar disease. M. bovis usually affects cattle. The BCG vaccine uses an attenuated strain of M. bovis.

MYCOBACTERIUM TUBERCULOSIS: the acid-fast bacterium that causes tuberculosis.

N

NAÏVE: inexperienced. The term is used to describe an individual who has never taken a certain drug (e.g., AZT-naive) or to refer to undifferentiated immune system cells.

NECROSIS: localized tissue death.

NEF: a gene of HIV that influences viral replication.

NEONATE: newborn.

NEOPLASM: a tumor or growth; tissue that develops abnormally or grows more rapidly than normal and lacks structural organization and functional coordination with normal tissue.

NERVE GROWTH FACTOR: a substance that sustains neurons and promotes the regeneration of damaged nerves.

NETHROLITHIASIS: see kidney stone.

NEPHROTOXICITY: the property of being poisonous or harmful to the kidneys.

NEUTROPENIA: an abnormally low number of neutrophils in the circulating blood, leading to susceptibility to infection.

NEUTROPHIL: a type of immune system white blood cell that engulfs and destroys bacteria and fungi.

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

NONOXYNOL-9: a surfactant chemical used as a spermicide and microbicide.

NUCLEOSIDE: a precursor compound that is a converted into a building block of genetic material (DNA or RNA) by the addition of a phosphate group.

NUCLEOSIDE ANALOG (also known as NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR, NRTI): a compound (e.g., AZT, ddI, ddC, d4T, 3TC, abacavir) that mimics one of the building blocks of DNA. These compounds suppress retroviral replication by interfering with the reverse transcriptase enzyme; the synthetic nucleosides cause premature termination when they are inserted into the viral DNA chain being built.

NUCLEOTIDE ANALOG: a compound, similar to a nucleoside analog, which is already "primed" with an extra phosphate group and ready to be added to a DNA chain.

O

OFF-LABEL: use of an FDA-approved drug for an indication other than that for which it was approved.

OPEN-LABEL: a drug trial in which both participants and investigators know what drug is being tested and what dosages are being used.

OPPORTUNISTIC INFECTION (OI): a disease (e.g., PCP, MAC, CMV disease) caused by a microorganism that does not normally cause illness in a person with a healthy immune system, but which may cause serious disease when the immune system is weakened.

P

p24 ANTIGEN: a core protein of HIV.

PANCREATITIS: inflammation of the pancreas, a digestive gland in the abdominal cavity. Symptoms may include abdominal pain, nausea, constipation, and jaundice.

PAP SMEAR: a procedure in which a specimen of cells is taken from the uterine cervix or anus, prepared on a slide, and examined under a microscope for abnormal cell growth.

PATHOGEN: any disease-causing agent, especially a microorganism.

PATHOGENESIS: the origin and 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: refers to the period around the time of birth.

PERINATAL HIV TRANSMISSION (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 NEUROPATHY: damage to the peripheral nerves (usually involving the feet, hands, and sometimes the legs, arms, and face) characterized by tingling, burning, or numbness.

PH: a logarithmic scale used to describe the acidity or alkalinity of a solution.

PHARMACOKINETICS: the action of drugs in the body, including the processes of absorption, metabolism, transformation, distribution to tissues, and elimination.

PHASE I TRIAL: the first step 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 step in the evaluation of a new drug in humans; these trials evaluate drug effectiveness and compare doses in more participants than Phase I studies.

PHASE III TRIAL: the third step in human drug testing; these trials are designed to support and verify information gathered in Phase I and II trials, and involve many more volunteers. Phase III trials may compare the drug being tested to other therapies or to a placebo.

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.

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.

PLACENTA: the organ that connects the fetus and the mother's uterus and enables the exchange of oxygen and nutrients.

PLASMA: the fluid, non-cellular portion of blood.

PLATELET: see thrombocyte.

PNEUMOCYSTIS CARINII PNEUMONIA (PCP): a life-threatening opportunistic type of pneumonia caused by a protozoan.

POL: the HIV gene that encodes the virus' replicative enzymes (protease, integrase, reverse transcriptase).

POLYMERASE CHAIN REACTION (PCR): a highly sensitive test that uses an amplification technique to detect small amounts of DNA or RNA in a blood or tissue sample.

POST-EXPOSURE PROPHYLAXIS (PEP): drug therapy given immediately following exposure to an infectious organism in an attempt to prevent the infection from taking hold in the body.

POSTPARTUM: the period following childbirth.

POTT'S DISEASE: tuberculosis of the vertebrae, the bones surrounding the spinal cord.

PPD: a purified protein derivative of tuberculin injected under the skin of the arm in a tuberculosis skin test.

PREVALENCE: the number of individuals with a condition in a specific population.

PRIMARY HIV INFECTION (PHI): the initial introduction of HIV into the body; the earliest stage of HIV disease.

PROPHYLAXIS (adjective PROPHYLACTIC): therapy that helps to prevent a disease before it occurs (primary prophylaxis) or recurs (secondary prophylaxis).

PROSPECTIVE STUDY: a study that looks forward in time. Participants are selected and their progression is followed over time.

PROTEASE: an enzyme that cuts proteins; HIV protease allows replication of the virus.

PROTEASE INHIBITOR: a drug (e.g., saquinavir, indinavir, ritonavir, nelfinavir, amprenavir) that blocks the action of the HIV protease enzyme, thereby preventing viral replication.

PROTEASE-SPARING REGIMEN: combination highly active antiretroviral therapy that does not include a protease inhibitor drug.

PROVIRUS: a state in which viral DNA has been inserted into the chromosome of the host cell.

PROXIMAL RENAL TUBULAR DYSFUNCTION (PRTD): a disorder of the small tubes in the kidney that filter urine.

PULMONARY EMBOLUS: a life-threatening blood clot that lodges in the lung, characterized by chest pain and shortness of breath.

PYRIDOXINE (VITAMIN B6): a form of vitamin B that helps prevent peripheral neuropathy when used with certain drugs.

R

RANDOMIZED TRIAL: an experiment arranged so as to produce a chance distribution of subjects into different treatment groups or arms.

RANTES: a chemokine that binds with the CCR5 cell surface receptor and inhibits the entry of HIV into a host cell.

RECEPTOR: a specific protein-binding site on a cell's surface or interior. Viruses enter cells by fusing with receptors on a cell’s surface.

RECHALLENGE: administration of the same substance (e.g., pathogenic organism, drug) a second or subsequent time.

RECOMBINANT: produced by genetic engineering.

RECRUDESCENCE: a renewal of active replication of a pathogenic organism after a period of inactivity.

REFRACTORY: resistant to treatment.

REGIMEN: a formalized schedule by which drugs are administered, including the amount of drug and the number of doses in a period of time.

REMISSION: an abatement in the severity of disease symptoms.

REPLICATION: multiplication or reproduction.

RESERVOIR: a site where an infectious agent collects and multiplies; macrophages and resting CD4 cells are thought to be reservoirs of HIV.

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

RESTRICTION FRAGMENT LENGTH POLYMORPHISM (RFLP): a test used to determine the genetic structure of an organism.

RETINITIS: inflammation of the retina, the light-sensitive tissue at the back of the eyeball, that may lead to the loss of vision.

RETROSPECTIVE STUDY: a study based on the medical records of patients, looking backward in time at events that happened in the past.

RETROVIRUS: a class of enveloped viruses that have their genetic material in the form of RNA and use the reverse transcriptase enzyme to translate their RNA into DNA in the host cell.

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.

REVERSE TRANSCRIPTASE INHIBITOR (RTI): a drug that blocks retroviral replication by interfering with the reverse transcriptase enzyme. RTI include nucleoside analogs (e.g., AZT, ddI, 3TC, abacavir) and non-nucleoside reverse transcriptase inhibitors (e.g., nevirapine, delavirdine, efavirenz).

RIBONUCLEOTIDE REDUCTASE: an enzyme that cuts ribonucleotides in order to create deoxyribonucleotides, the building blocks of DNA.

RNA (RIBONUCLEIC ACID): a single-stranded nucleic acid made up of nucleotides. Messenger RNA (mRNA) is involved in the transcription of genetic information and the production of new proteins.

S

SALVAGE THERAPY: treatment with experimental or non-standard drugs for an illness that has not responded to standard therapy.

SECOND-LINE TREATMENT: the second preferred therapy for a particular condition, used when first-line treatment fails or when a person cannot tolerate the side effects of first-line drugs.

SEPSIS: a life-threatening blood infection.

SEROCONVERSION: the development of antibodies directed against a microorganism; the change in a person's antibody status from negative to positive.

SEXUALLY TRANSMITTED DISEASE (STD): a disease (e.g., gonorrhea, syphilis, herpes, chlamydiasis) that is transmitted through sexual contact.

SIDE EFFECT: an unwanted adverse reaction to a drug treatment (e.g., rash, nausea, peripheral neuropathy, bone marrow suppression, liver inflammation).

SIMIAN IMMUNODEFICIENCY VIRUS (SIV): a virus, similar to HIV, that infects monkeys.

SHORT-COURSE THERAPY: a therapeutic regimen given for a shorter than usual period of time.

SMEAR TEST: a test in which a sample (e.g., of sputum) is examined under a microscope for the presence of pathogenic organisms.

SOURCE PATIENT: a person from whom an infectious disease was transmitted.

SPUTUM: fluid ejected from deep within the lungs when a person coughs.

SQUAMOUS INTRAEPITHELIAL LESION (SIL): abnormal cell growth and changes, particularly of cells at the squamo-columnar junction of the uterine cervix or anal canal.

STATISTICAL SIGNIFICANCE: the probability that an observed outcome of an experiment or trial is not due to chance alone.

STEM CELL: a precursor cell in the bone marrow from which all blood cells are derived.

STEROID: a family of substances that share a similar chemical structure, including certain hormones (e.g., testosterone) and various drugs.

STEVENS-JOHNSON SYNDROME: an uncommon, life-threatening reaction characterized by fever and flu-like symptoms followed by a severe, blistering rash on the skin and/or mucous membranes.

STRAIN: a specific genetic variant of an organism.

SUBTHERAPEUTIC: relating to a dose or blood level of a drug that is too low to be useful.

SUBTYPE: a distinct form of a microorganism.

SUSCEPTIBLE: refers to a microorganism that is vulnerable to the effects of a drug.

SYNERGY: the action of two or more drugs working together to produce an effect greater than the expected combined effect of the same agents used separately.

SYSTEMIC: affecting the whole body; not localized.

T

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

TESTOSTERONE: a steroid hormone produced by the testes and adrenal glands. Testosterone is required for sperm production, the development of the male reproductive organs, and the emergence of male secondary sexual characteristics. The hormone is also required for the buildup of lean muscle mass.

THROMBOCYTE (PLATELET): a type of blood cell that facilitates normal blood clotting.

THROMBOCYTOPENIA: an abnormally low number of platelets, which may result in abnormal bleeding and bruising.

THRUSH: candidiasis (fungal infection) of the mouth.

THYMUS: an immune system organ in the upper chest where T-cells mature.

THYROID GLAND: an organ at base of the neck that produces thyroxin and other hormones.

TOXICITY (adjective TOXIC): the quality of being poisonous or harmful; often used to refer to drug side effects.

TOXIN: a harmful or poisonous agent.

TOXOPLASMOSIS: an opportunistic infection caused by the microscopic protozoan Toxoplasma gondii. A common manifestation of the disease is toxoplasmic encephalitis, an infection of the brain.

TRIGLYCERIDE: a combination of glycerol and fatty acid that circulates in the blood.

TROUGH LEVEL: the lowest concentration of a drug reached in the body between dosages.

TUBERCLE: a granulomatous lesion in the lung containing white blood cells and cellular debris, characteristic of tuberculosis.

TUBERCULIN: a purified protein derivative of Mycobacterium tuberculosis used in the Mantoux skin test.

TUBERCULOSIS (TB): an infectious disease caused by Mycobacterium tuberculosis that typically affects the lungs (pulmonary TB), but may also occur in other organs (extrapulmonary TB). TB infection refers to asymptomatic, latent infection with TB bacteria; active TB disease refers to symptoms caused by replicating bacteria.

U

ULTRAVIOLET (UV): electromagnetic radiation beyond the violet end of the visible light spectrum.

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

URIC ACID: a by-product of protein metabolism found in the blood and urine.

V

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. Agents used in vaccines may be whole killed (inactivated) organisms, live-attenuated (weakened) organisms, or artificially manufactured pieces of an organism.

VACCINIA: a virus used as a vaccine against smallpox and as a live virus vector in some candidate anti-HIV vaccines.

VARICELLA-ZOSTER VIRUS (VZV, HHV-3): a herpesvirus that initially causes chickenpox and may reactivate later to cause herpes zoster (shingles).

VECTOR: an engineered virus used to introduce genes into cells, or a live virus used as an antigen delivery vehicle in a vaccine.

VERTICAL TRANSMISSION: see perinatal HIV transmission.

VERTIGO: dizziness and problems with balance.

VIRAL LOAD: 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 the PCR or branched-chain DNA (bDNA) tests.

VIREMIA (adjective VIREMIC): the presence of virus in the blood or plasma.

VIRULENCE (adjective VIRULENT): aggressiveness, ability to cause disease.

VIRUS: a minute organism that cannot grow or reproduce outside of a host cell. During replication, a virus integrates its genetic material (DNA or RNA) into the host cell and takes over the cell's biological mechanisms to reproduce new virus particles.

W

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 HIV antibodies.

WILD-TYPE: the normal, typical form of a virus before genetic mutation takes place.

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