TIGIT and HIV-1 infection: Given the limited expression of KIR2DL5 on the cell surface, future studies need to discriminate between KIR2DL5A and KIR2DL5B genotypes when studying implications of KIR2DL5 expression on transmission and disease outcomes, and investigate this in the context of TIGIT, as it has been reported that TIGIT expression is upregulated on NK cells during HIV-1-infection [47,48].