Human immunodeficiency virus type 1 (HIV-1) is a member of the lentivirus genus of the retroviridae family that causes a lethal condition known as AIDS (acquired immunodeficiency syndrome) in humans by infecting CD4+ T lymphocytes, causing their depletion and profound immunodeficiency, leading to opportunistic infections and cancer [41]; in addition to CD4+ T lymphocytes, HIV-1 also infects mononuclear phagocytes that are not depleted. The gene discussed is CD4; the disease is Opportunistic infection.