It has been shown that the gastrointestinal tract is the major site of HIV-1 replication and CD4+ T-cell depletion during all stages of HIV/AIDS (Brenchley et al., 2004a; Chun et al., 2008), and that the destruction of the CD4+ T-cell population within the gastrointestinal tract leads to the translocation of microbial products to the circulatory system and contributes to the chronic inflammation and immune exhaustion that are associated with HIV/AIDS (Douek et al., 2009). This evidence concerns the gene CD4 and AIDS.