AIDS is the final stage of HIV infection, when CD4+ T cells abruptly decline (below 200 cells per mm3, in contrast to the normal range between 500 and 1500 cells per mm3), at this point, HIV-1 infection control is lost, viremia rises, and opportunistic infections also rise as a result of CD4+ T cells depletion. This evidence concerns the gene CD4 and HIV-1 infection.