CD4 and HIV-1 infection: Non-human primates (NHPs), especially Indian-origin and Chinese-origin rhesus macaques, infected with simian immunodeficiency virus (SIV) are important animal models that emulate key features of HIV-1 infection, including high viral loads (16), progressive CD4+ T cell depletion (17, –19), envelope protein (Env) trafficking and evolution (20, 21), response to ART (16, 22, –24), and establishment of a latent reservoir in resting CD4+ T cells (25, –27).