CXCR4 and infection: Since CCR5-using HIV-1 variants predominate in most of infection, while CXCR4-using HIV-1 variants (including variants using both CCR5 and CXCR4 or CXCR4 alone) emerge at the relatively late-stage infection (Maeda et al., 2020), the different roles of CCR5 and CXCR4 in the development and cognitive phenotypic expression of HAND may need to be evaluated with future studies.