CCR5 and HIV infectious disease: A small amount of TSCM showed low expression of CCR5, which can be protected from HIV infection, but physiologically CD4+ TSCM expresses CCR5 (R5)- and CXCR4 (X4), which make them usual reservoirs for HIV, because silent or latent infection of these long-lived, self-renewing cells could provide an extremely stable niche for the virus which is modulated by SAMHD1 expression (132).