The AIDS virus attaches itself to the CD4 cell surface protein of T-4 lymphocytes with a viral envelope of glycoproteins. This protein binds to CD4 receptors and coreceptors.
HIV is a retrovirus that quickly infects circulating immune cells or finds safe harbors in body reservoirs that are inaccessible to drug therapy. The retrovirus uses an enzyme called reverse transcriptase to convert the HIV viral RNA to a viral DNA. This conversion allows the viral DNA to take over the host cell DNA of lymphocytes, macrophages, and other immune system cells. When the viral DNA has taken over, it produces viral proteins that assemble into virions using viral enzyme protease. Each reproductive cycle of HIV can produce up to 100 billion virions with minor protective mutations. The CD4 count indicates disease severity. A count of less than 500 cells/mm3 is found in the early symptomatic stage. A count of less than 200 cells/ mm3 and a viral load greater than 100,000 /ml are found in the late symptomatic stage.