Human Immunodeficiency Virus and Disease

HIV spreads by contact with body fluids, and the common modes of infection include sexual intercourse and contaminated needles used for intravenous drug delivery. Previously, therapeutic use of infected blood and infected breast milk for the baby were also modes of transmission but both have declined due to better screening for blood and AIDS education of expectant mothers. The virus is carried in infected CD4+ T cells, macrophages or as free viruses in blood, semen, vaginal fluids and milk. 

During the early phase of infection, HIV-specific CD8+ cells are produced and control the viral load, but within weeks they die and only memory CD8+ cells are left. Only in some individuals does a strong HIV-specific CD8+ cell response continue to exist, resulting in a good control of the viral load. The gradual loss of 

HIV-specific CD8+ function may result from continued mutation and high levels of viral turnover, which gradually diminishes the capability of the cell to recognize the genetic sequences of the virus due to killing of some of the CD8 T cells repertoire by HIV itself. 

Four to eight weeks after HIV infection, antibody responses begin to develop they are predominantly directed against the circulating virus and some antibodies may destroy the virus-infected cells as well. However, the antibody response is unable to continue to neutralize HIV because of the rapid mutation of the virus. The development of the initial cellular and humoral response leads to a clearance of much of the viremia and a rebound of CD4+ cells. 

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