G

GAG:
(gag) A gene of HIV that codes for the core protein p55. p55 is the precursor of HIV proteins p17, p24, p7, and p6. These form HIV's capsid (see nucleocapsid), the inner protein shell surrounding HIV's strand of RNA.

GAMMA GLOBULIN:
One of the proteins in blood serum that contains antibodies. Passive immunizing agents obtained from pooled human plasma. See Globulins, Immunoglobulins.

GAMMA INTERFERON:
A T cell-derived stimulating substance that suppresses virus reproduction, stimulates other T cells, and activates macrophage cells.

GANGLION:
A mass of nervous tissue, composed principally of nerve-cell bodies, usually lying outside the central nervous system.

GASTROINTESTINAL (GI):
Relating to the stomach and intestines.

GENE:
1. A unit of DNA that carries information for the biosynthesis of a specific product in the cell. 2. Ultimate unit by which inheritable characteristics are transmitted to succeeding generations in all living organisms. Genes are contained by, and arranged along the length of, the chromosome. The gene is composed of deoxyribonucleic acid (DNA). Each chromosome of each species has a definite number and arrangement of genes, which govern both the structure and metabolic functions of the cells and thus of the entire organism. They provide information for the synthesis of enzymes and other proteins and specify when these substances are to be made. Alteration of either gene number or arrangement can result in mutation (a change in the inheritable traits).

GENE THERAPY:
Any of a number of experimental treatments in which cell genes are altered. Some gene therapies attempt to provoke new immune activity; some try to render cells resistant to infection; some involve the development of enzymes that destroy viral or cancerous genetic material within cells.

GENETIC ENGINEERING:
The technique by which genetic material from one organism is inserted into a foreign cell in order to mass-produce the protein encoded by the inserted genes. This relatively new technique manipulates the DNA (genetic material) of cells. For example, in this technique, the genes, which are actually portions of molecules of DNA, are removed from the donor organism (insect, plant, mammal, or other organism) and spliced into the genetic material of a virus; the virus is then allowed to infect recipient bacteria. In this way the bacteria become recipients of both viral and foreign genetic material. When the virus replicates within the bacteria, large quantities of the foreign as well as viral material are made. (See also Recombinant).

GENITAL ULCER DISEASE:
Ulcerative lesions on the genitals usually caused by a sexually transmitted disease such as herpes, syphilis, or chancroid. The presence of genital ulcers may increase the risk of transmitting HIV.

GENITAL WARTS:
See Condyloma.

GENITOURINARY TRACT:
The organs concerned with the production and excretion of urine and those concerned with reproduction. Also called genitourinary system, urogenital system, or urogenital tract.

GENOME:
The complete set of genes in the chromosomes of each cell of a particular organism.

GENOTYPIC ASSAY:
A test that determines if HIV has become resistant to the antiviral drug(s) the patient is currently taking. The test analyzes a sample of the virus from the patient's blood to identify any mutations in the virus that are associated with resistance to specific drugs.

GERMINAL CENTERS:
One of a series of follicles or cavities around the periphery of lymph nodes. Germinal centers are the site of antibody production and are populated mostly by B cells but include a few T cells and macrophages. As HIV infection progresses, the germinal centers gradually decay.

GIARDIASIS:
A common protozoal infection of the small intestine, spread via contaminated food and water and direct person-to-person contact. See Diarrhea.

GLOBULINS:
Simple proteins found in the blood serum, which contain various molecules central to the immune system function. See Immunoglobulin.

GLYCOPROTEIN:
A conjugated protein in which the nonprotein group is a carbohydrate (i.e., a sugar molecule); also called glucoprotein.

GONORRHEA:
An infection caused by Neisseria gonorrhoeae (bacteria from the family Neisseriaceae containing gram-negative cocci). Although gonorrhea is considered primarily a sexually transmitted disease, it can also be transmitted to newborns during the birth process.

GP41:
(gp41) Glycoprotein 41, a protein embedded in the outer envelope of HIV. Plays a key role in HIV's infection of CD4+ T cells by facilitating the fusion of the viral and the cell membranes. See gp120.

GP120:
(gp120) Glycoprotein 120, a protein that protrudes from the surface of HIV and binds to CD4+ T cells. In a two-step process that allows HIV to breach the membrane of T cells, gp120-CD4 complex refolds to reveal a second structure that binds to CCR5, one of several chemokine co-receptors used by the virus to gain entry into T cells.

GP160:
(gp160) Glycoprotein 160, a precursor of HIV envelope proteins gp41 and gp120.

GRANULOCYTE:
A type of white blood cell filled with granules of compounds that digest microorganisms. Granulocytes are part of the innate immune system and have broad-based activity. They do not respond only to specific antigens as do (see) B cells and T cells. Basophils, eosinophils, and neutrophils are all granulocytes.

GRANULOCYTE-COLONY STIMULATING FACTOR (G-CSF):
A cytokine that stimulates the growth of granulocytes, a type of white blood cell. G-CSF alleviates the neutropenia that is a side effect of certain drugs.

GRANULOCYTE MACROPHAGE-COLONY STIMULATING FACTOR (GM-CSF):
A cytokine that stimulates the growth of granulocytes and macrophages. Like the granulocyte-colony stimulating factor (see G-CSF), GM-CSF alleviates neutropenia but is less specific and has more side effects than G-CSF.

GRANULOCYTOPENIA:
A lack or low level of granulocytes in the blood. Often used interchangeably with neutropenia.