Published in the Bulletin of Experimental Treatments for AIDS Summer 1999 issue, by the San Francisco AIDS Foundation.

Summer 1999 Table of Contents

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Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X-Z

A

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

ADIPOSE: composed of animal fat.

ADJUNCT: something joined or added to the original. Adjunct therapy or treatment is a treatment that is given in addition to the main or primary treatment.

AMINO ACID: an organic compound that is a basic structural unit of peptides and proteins. There are over 100 amino acids, eight of which (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine) are essential for human metabolism.

ANABOLIC STEROID: a natural or synthetic hormone (e.g., testosterone, oxandrolone) that promotes the synthesis of proteins and the building of muscle mass. Side effects may include abnormal masculinization (e.g., excess hair growth) and liver toxicity.

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

ANTIBIOTIC: an agent that inhibits the growth of or destroys microorganisms; the term typically refers to an agent that is active against bacteria.

ANTIBODY (AB, IMMUNOGLOBULIN, IG): an immunoglobulin protein secreted by activated plasma cells, which evolve from B-cells. Antibodies are present throughout the blood and tissues; they are produced in response to stimulation by foreign antigens as part of the body’s defense against disease. Specific antibodies bind to and act upon specific antigens; the antigen/antibody reaction forms the basis of humoral (TH2) immunity.

ANTIHISTAMINE: an agent that inhibits the action of histamines, chemicals that stimulate stomach acid secretion and mediate allergic reactions.

ANTIRETROVIRAL: an agent (e.g., AZT, ddI, d4T) that suppresses the activity or replication of retroviruses such as HIV. Antiretroviral drugs interfere with various stages of the virus’ life cycle, for example reverse transcriptase inhibitors (e.g., AZT, ddI, 3TC), protease inhibitors (e.g., saquinavir, ritonavir), and integrase inhibitors.

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. Symptoms include cough, chest pain, fever, and breathing difficulty.

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.

ASYMPTOMATIC: not feeling or showing outward signs of a disease. Individuals typically remain asymptomatic five or more years after infection with HIV.

B

BACTERIUM (plural BACTERIA): a simple single-celled microorganism. Bacteria are classified by their shape (e.g., rod, spirochete), staining properties (Gram positive or Gram negative), and habitat (aerobic, anaerobic). Many types of bacteria are pathogenic in humans.

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

BILIRUBIN: a yellowish pigment released by red blood cells when they are removed from circulation and broken down. Normally bilirubin is processed and excreted by the liver; an excess level of serum bilirubin (hyperbilirubinemia) is characterized by jaundice (yellowing of the skin and eyes), and may indicate stress on the liver. Bilirubin levels are measured to gauge the health of the liver.

BIOAVAILABILITY: the degree to which a drug or other substance is absorbed and circulated in the body; the physiological availability of a drug, as opposed to its chemical potency.

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

BODY FAT REDISTRIBUTION SYNDROME (BFR): a set of symptoms related to the loss of fat from certain areas of the body such as the limbs and face (lipodystrophy), possibly accompanied by fat accumulation in other areas such as the abdomen ("protease paunch") or back of the neck ("buffalo hump").

BONE MARROW: the soft, spongy tissue in the interior of certain bones (e.g., the long bones of the limbs). Bone marrow contains stem cells and is the site of hematopoiesis, or blood cell production.

BONE MARROW TRANSFER (BMT): a graft of bone marrow from one individual to another to reconstitute the recipient’s damaged immune or blood-production system.

C

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 that coordinate a broad range of immune system activities including killer cell activation and antibody production. HIV invades CD4 cells, typically resulting in their dysfunction or destruction.

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).

CERVICOVAGINAL: relating to the uterine cervix and the vagina, parts of the female reproductive system.

CHANCROID: a sexually transmitted disease caused by infection with Haemophilus ducreyi. Chancroid is characterized by soft chancres or ulcers.

CHEMOKINE: a soluble factor secreted by certain immune system cells that stimulates the activity of other cells. Chemokines have chemoattractant properties and act as messengers between cells.

CHEMOTHERAPY (adjective CHEMOTHERAPEUTIC): the use of chemicals or drugs to treat disease; the term is typically used to refer to cancer treatment. CHOLESTEROL: a fatty substance in animal tissue that is an essential component of cell membranes and nerve fiber insulation. Cholesterol is important for the metabolism and transport of fatty acids and in the production of hormones and vitamin D. Cholesterol is manufactured by the liver, and is also present in certain foods (e.g., eggs, shellfish). Very low cholesterol levels may indicate malnutrition. See also high-density lipoprotein, low-density lipoprotein.

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

CODON: a sequence of three nucleotides or bases that encodes the information for a particular amino acid (the building blocks that make up proteins). Changes in specific codons can confer resistance to certain drugs (e.g., a codon 215 mutation is associated with AZT resistance).

COLLAGEN: a fibrous protein that makes up connective tissue.

COMPARTMENT: a separate structural portion (e.g., of the body or of a cell); a distinct area or part of the body, which may not have a discrete physical boundary. In pharmacology, an area of the body where a drug is metabolized.

CORE: the internal portion of the HIV viral particle. The core proteins, encoded by the gag gene, include the glycoproteins p24 and p17.

CORTISOL: a steroid hormone secreted by the adrenal cortex as part of the body’s response to stress. Cortisol promotes the breakdown of body tissues to provide energy and raw materials; high cortisol levels are associated with reduced immune function. Synthetic cortisol (hydrocortisone) is used to reduce inflammation and lessen allergic reactions.

CROSS-RESISTANCE: the development of resistance to one agent (e.g., a drug) that also confers resistance to another agent (e.g., a similar drug of the same class).

CYTOKINE: an intercellular hormone or chemical messenger protein (e.g., tumor necrosis factor, interleukin) released by white blood cells (e.g., macrophages, T-cells). Cytokines facilitate communication among immune system cells and between immune system cells and the rest of the body. Cytokines coordinate several aspects of the immune response including stimulating antibody production, promoting the migration of phagocytes to the site of an infection, and activating cytotoxic T-lymphocytes.

CYTOMEGALOVIRUS (CMV, HUMAN HERPESVIRUS 5): a herpesvirus. CMV infection often occurs in healthy individuals without causing symptoms. In immunocompromised individuals (usually with CD4 counts below 50 cells/mm3), CMV may cause serious illness including retinitis (inflammation of the retina), pneumonia, colitis (inflammation of the large bowel), and encephalitis. CMV infection of a pregnant woman may lead to congenital abnormalities in the newborn. CMV may be treated with ganciclovir, foscarnet, or cidofovir.

D

DAPSONE: an antibiotic drug used in the treatment and prophylaxis of PCP. Side effects may include nausea, dizziness, skin rash, photosensitivity, and anemia.

DEHYDROEPIANDROSTERONE (DHEA): a weak androgenic steroid produced by the adrenal cortex. DHEA levels are often decreased in people with HIV disease.

DEMENTIA: a chronic loss of mental capacity due to an organic cause. Dementia may involve progressive deterioration of thinking, memory, behavior, personality, and motor function, and may also be associated with psychological symptoms such as depression and apathy.

DENDRITIC CELL: a type of immune system cell with many branches. Dendritic cells are found in the skin and mucosal membranes. They are typically the first to arrive at sites of injury or infection, where they bind to invaders and transport them to the lymph nodes where the cell-mediated immune response is initiated. Dendritic cells carry the CD4 surface marker, and may be among the first cells to be infected by HIV.

DEOXYRIBONUCLEIC ACID (DNA): a molecule found in the nucleus of cells as a twisted double-stranded chain that encodes genetic information. The particular sequence of four chemical building blocks (nucleotides)-adenine, cytosine, guanine, and thymine-that make up a DNA chain determines the unique genetic code of an individual. See also ribonucleic acid.

DERMATOLOGY: the medical specialty concerned with diseases and disorders of the skin.

DHEA: see dehydroepiandrosterone.

DIAGNOSIS: the determination of the existence of a disease or condition. Diagnosis generally involves the evaluation of a patient’s medical history, clinical symptoms, and laboratory test results.

DNA: see deoxyribonucleic acid.

DORSOCERVICAL: relating to the upper part of the back, below the neck.

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

E

ELISA: see enzyme-linked immunosorbent assay.

ENDOCRINE GLAND/ENDOCRINE SYSTEM: a ductless gland 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).

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.

EPIDEMIOLOGY: the study of the frequency, distribution, and behavior of a disease within a population.

ERECTILE DYSFUNCTION DISORDER (also known as IMPOTENCE): the inability to ejaculate and/or achieve or maintain an erection during intercourse.

F

FOLLICULITIS: an inflammation of the hair follicles that may lead to deeper abscesses. Folliculitis is often caused by bacteria (e.g., Staphylococcus aureus). Types include eosinophilic folliculitis and idiopathic folliculitis.

FUNGUS (plural FUNGI): a class of organisms that includes yeasts, molds, and mushrooms, several of which can cause disease (mycosis) in humans (e.g., candidiasis, cryptococcosis, histoplasmosis).

G

GASTROINTESTINAL: pertaining to the stomach and intestines.

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. Each individual has a unique sequence of genes, or genetic code.

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.

GERIATRIC: relating to the process of aging or to the elderly.

GROWTH FACTOR: a factor responsible for regulating cell proliferation, development, migration, differentiation, and/or activity.

H

HABITUS: body build and constitution, especially as related to disease.

HEPATIC: relating to the liver.

HERPES SIMPLEX VIRUS (HSV-1, HSV-2, HUMAN HERPESVIRUS 1, 2): a herpesvirus that causes recurring lesions. Herpes simplex virus type 1 (HSV-1) usually produces blisters on the lips or in the mouth ("cold sores" or "fever blisters"). HSV type 2 (HSV-2) is usually sexually transmitted and generally produces lesions in the genital or anal area.

HERPES ZOSTER (SHINGLES): a condition characterized by painful blisters that typically appear in a dermatomal (linear) distribution on the skin following a nerve pathway; blisters generally dry and scab leaving minor scarring. Shingles is caused by reactivation of a previous infection with the varicella-zoster virus (VZV) that initially causes chickenpox. Disseminated herpes zoster resembles chickenpox, with a rash, fever, and possibly pneumonia.

HIGH-DENSITY LIPOPROTEIN (HDL): a type of cholesterol in the body; also known as "good" cholesterol. HDL is considered protective against heart disease.

HORMONE: a chemical messenger (e.g., adrenaline, testosterone) involved in the regulation and coordination of cellular and bodily functions. Hormones may act locally or be secreted into the bloodstream. See also cytokine, endocrine gland/endocrine system.

HORMONE REPLACEMENT THERAPY (HRT): the administration of exogenous hormones (typically estrogen) to replace those that the body is not able to produce (e.g., due to menopause or hysterectomy). HRT is used to relieve symptoms of hormonal deficiency (e.g., hot flashes, osteoporosis).

HUMAN GROWTH HORMONE (HGH, SOMATOTROPIN): a peptide hormone secreted by the anterior pituitary gland. HGH enhances growth by stimulating metabolism and protein synthesis. Recombinant HGH (Serostim) is a genetically engineered drug used for the treatment of HIV-related wasting syndrome. Side effects include muscle pain, edema, and carpal tunnel syndrome.

I

IMMUNE SYSTEM: the body’s defense system that protects against foreign invaders (e.g., microorganisms) and cancerous cells. Some immune defenses are nonspecific (e.g., phagocytosis). Types of immune defense include cell-mediated (TH1) and humoral (antibody-based, or TH2). Organs of the immune system include the lymph nodes, spleen, thymus, and tonsils.

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

INSULIN: a peptide hormone produced by the Islets of Langerhans cells in the pancreas. Insulin enables the body to metabolize and use glucose. Lack of or insensitivity to insulin results in diabetes.

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.

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 purplish or brownish lesions. Types include classic KS, African KS, and AIDS-related or transplant-related KS. KS is associated with a herpesvirus (KSHV, or HHV-8). It occurs more commonly among HIV positive gay and bisexual men than among others with HIV disease, indicating that it may be sexually transmitted.

L

LAVAGE: the washing out of an organ or cavity, for example to obtain a sample for diagnosis.

LESION: any abnormal tissue change caused by disease or injury.

LEUKOCYTE: an immune system white blood cell (e.g., monocyte, neutrophil, B-cell, T-cell). White blood cells are involved in the body’s defense against infections and cancer.

LIPID: a fat.

LIPODYSTROPHY: 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.

LIPOSUCTION: a procedure whereby excess fat is removed from the body using a vacuum.

LOW-DENSITY LIPOPROTEIN (LDL): a type of cholesterol in the body; also known as "bad" cholesterol. LDL is considered a risk factor for heart disease.

LUPUS: see systemic lupus erythematosus.

LYMPHATIC SYSTEM (adjective LYMPHOID): a network of organs and capillary-like vessels that help maintain the fluid environment of the body and coordinate immune responses. Two major lymphatic vessels return fluid to the vascular system. The lymphoid organs include the lymph nodes, spleen, thymus, tonsils, and adenoids.

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

M

MACROPHAGE: a large scavenger white blood cell that ingests and processes degenerated cells and foreign invaders. Macrophages secrete messenger proteins (monokines) involved in a variety of immune system responses. Macrophages are derived from monocytes that leave the blood to migrate into the tissues. Specialized macrophages protect the skin, lungs (alveolar macrophages), brain (microglia), liver (Kupffer cells), and other tissues. The long-lived macrophages are reservoirs of HIV.

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

MENOPAUSE: the cessation of menstruation. Menopause may be due to hormonal changes, surgery, or drug use. Natural menopause typically occurs between 45 and 60 years of age; women with HIV may experience early menopause.

METABOLISM (adjective METABOLIC): the processes of building the body’s molecular structures from nutrients (anabolism) and breaking them down for energy (catabolism). Also, the chemical breakdown of drugs and toxins.

METHADONE: an oral opioid drug used for pain therapy and to treat opiate (e.g., heroin) addiction. Methadone maintenance therapy is used to prevent withdrawal symptoms by administering a small dose of methadone on a regular (e.g., daily) basis.

MOLLUSCUM CONTAGIOSUM: a viral skin condition characterized raised, flesh-colored lesions with a central depression, most often appearing on the face, neck, arms, legs, and anogenital region. The condition is common in HIV positive persons and may be due to a reactivation of an earlier infection. Treatment involves freezing lesions with liquid nitrogen or using a curette to cut out lesions.

MONOTHERAPY: 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 strain of an organism produced by a genetic mutation.

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): an opportunistic disease caused by Mycobacterium avium or Mycobacterium intracellulare (sometimes referred to as Mycobacterium avium-intracellulare or MAI), bacteria found in soil and water.

N

NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI): a drug (e.g., nevirapine, 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, ddI, ddC, d4T, 3TC) that mimics one of the building blocks of DNA. These compounds suppress retroviral replication by interfering with the reverse transcriptase enzyme. The defective synthetic nucleosides cause premature termination when they are inserted into the viral DNA chain being built. Nucleoside analogs are prodrugs that are converted into active agents by phosphorylation.

NUCLEOTIDE (DEOXYRIBONUCLEOTIDE, RIBONUCLEOTIDE): one of the building blocks that make up genetic material (DNA and RNA). Nucleotides consist of a base (adenine, cytosine, guanine, thymine, or uracil), a sugar, and a phosphate group.

O

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.

P

PAP SMEAR (PAPANICOLAOU 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. An abnormal Pap smear suggests increased risk of developing cancer.

PARONYCHIA: inflammation and separation of the skin from the base of the nails.

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. PH: a logarithmic scale used to describe the acidity or alkalinity of a solution; a measure of the hydrogen concentration of a solution. Water has a neutral pH of 7. A pH below 7 is acidic; a pH above 7 is alkaline (or basic).

PHAGOCYTOSIS: the process of engulfing harmful matter in the body, carried out by scavenger white blood cells called phagocytes (e.g., neutrophils, macrophages).

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

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.

PHOTOSENSITIVITY: an increased sensitivity to light, which may lead to easy sunburning and other adverse effects. Photosensitivity is a side effect of some drugs (e.g., dapsone, hypericin).

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

PNEUMOCYSTIS CARINII PNEUMONIA (PCP): a life-threatening opportunistic type of pneumonia believed to be caused by a protozoan. PCP is a common infection that can cause severe illness in immunocompromised people (especially those with CD4 cell counts of less than 200 cells/mm3); it remains a leading cause of death in people with AIDS. Symptoms include dry cough, fever, chest tightness, and shortness of breath. Pneumocystis carinii can also infect other parts of the body.

POLYMERASE CHAIN REACTION (PCR) ASSAY: a highly sensitive test that can detect small amounts of DNA or RNA (genetic material) in a blood or tissue sample using an amplification technique that multiplies the existing DNA/RNA so that it can more easily be detected.

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

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

PROTEASE (PROTEINASE): an enzyme that cuts proteins. HIV protease cleaves the large precursor proteins produced from viral RNA into the component parts (e.g., enzymes and structural proteins) that are then assembled into new viral particles. Protease is essential for the production of infectious new virions.

PROTEASE INHIBITOR: 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).

PSORIASIS: a common chronic skin condition characterized by reddish scaly patches, primarily on the scalp, elbows, knees, and trunk. Outbreaks are more common and may be more severe in HIV-infected individuals. Psoriatic arthritis is a form of arthritis accompanied by psoriasis.

R

REAGENT: any chemical used in a laboratory test or experiment.

REGIMEN: see dosage regimen.

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.

RIBONUCLEIC ACID (RNA): a single-stranded nucleic acid that encodes genetic information. RNA is made up of a sequence of four chemical building blocks (nucleotides): adenine, cytosine, guanine, and uracil. 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. RNA takes the place of DNA in retroviruses such as HIV. The presence of HIV RNA in the plasma indicates that the virus is actively replicating.

RNA: see ribonucleic acid.

S

SEBORRHEA (SEBORRHEIC DERMATITIS): an overproduction of sebum (oil) by the sebaceous glands leading to an itchy, red rash often accompanied by encrusted patches. Seborrhea typically occurs on the skin of the scalp, face, ears, chest, or genitals.

SEMEN: a whitish, viscid fluid ejaculated from the penis containing spermatozoa and secretions from the prostate gland.

SERUM: the fluid, noncellular portion of blood that remains after coagulation; lymphatic fluid.

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

SHEDDING: release of infectious particles (e.g., bacteria, viruses) into the environment, for example by sneezing, by fecal excretion, or from an open lesion.

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

STAPHYLOCOCCUS: a type of bacterium that causes various infections. Staphylococcus aureus is commonly present on the skin and mucous membranes, especially those of the nose and mouth; it can cause pus-containing lesions such as boils, carbuncles, and abscesses. Other strains are associated with food poisoning and toxic shock syndrome.

SUBCUTANEOUS: beneath the skin; subdermal.

SYSTEMIC: affecting the whole body.

SYSTEMIC LUPUS ERYTHEMATOSUS: an autoimmune disease of unknown cause characterized by inflammation of the connective tissue, especially in the joints.

T

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.

THYMUS (adjective THYMIC): a lymphoid organ located in the chest behind the sternum. The thymus is a source of T-cell production in the fetus and the site of T-cell maturation and differentiation, where the cells learn to recognize antigens. The thymus produces some 30 hormones or thymic factors (e.g., thymodulin, thymopentin, thymostimulin) that are involved in the regulation of immune function.

TMP-SMX: see trimethoprim-sulfamethoxazole.

TNF: see tumor necrosis factor.

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

TRIMETHOPRIM-SULFAMETHOXAZOLE (TMP-SMX, BACTRIM, SEPTRA): an antibiotic drug combination. TMP-SMX is the preferred first-line therapy for prophylaxis and treatment of PCP, and may be effective against other OIs such as toxoplasmosis.

TUMOR NECROSIS FACTOR (TNF, CACHECTIN): a cytokine, produced by activated monocytes and macrophages, that can destroy tumors. When chronically elevated (as may occur in HIV disease), TNF-alpha may lead to fever, anorexia, hypermetabolism, and wasting.

V

VASODILATION: dilation of the blood vessels.

VERTICAL TRANSMISSION (PERINATAL TRANSMISSION, MATERNAL-FETAL TRANSMISSION): transmission of a pathogen such as HIV from a mother to a fetus or newborn. Vertical transmission may occur in utero (in the womb), intrapartum (during birth), or postpartum (via breast-feeding).

VIRAL LOAD (VIRAL BURDEN): the amount of virus in the blood or body 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 tests such as polymerase chain reaction (PCR) or branched-chain DNA (bDNA), and is typically expressed as the number of copies of RNA per milliliter (mL) of blood plasma.

VIREMIA: the presence of virus in the blood.

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

VIRUS: a group of tiny organisms that are unable to 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 viral particles. Various families of viruses infect humans, animals, plants, and bacteria.

VISCERA (adjective VISCERAL): the major internal organs of the body (e.g., intestines, liver) located in the abdominal cavity.

W

WASTING SYNDROME: a condition characterized by atrophy of lean body mass and involuntary weight loss of more than 10% of normal body weight. Other symptoms may include chronic diarrhea, fatigue, weakness, and fever. Death typically occurs when body weight falls to one-third of ideal weight, or when body cell mass decreases by 50%. AIDS-related wasting differs from starvation in that during starvation metabolism slows to conserve the body’s protein stores and fat is broken down, while in AIDS-related wasting, the body burns muscle and organ tissue (lean body mass) to meet the body’s energy requirements.

WHITE BLOOD CELL (WBC): see leukocyte.

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

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