(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.

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

The basic unit of inheritance, consisting of DNA or (in some virusesHIV) RNA. Carries coded instructions for cells to produce proteins essential to life.

The total genetic make-up of an organism (e.g. virus or human). The HIV genotype can include genes that make the virus resistant to drug treatments.

A test that determines if HIV has become resistant to the antiviral drug(s) the patient is currently taking. The test analyses 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.

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

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

(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.