It is of interest that, in men included in the CHAPS trial, timing and dose of F/TDF and F/TAF had no significant impact on CD4+CCR5+ cell numbers in foreskins and on CCR5 expression levels on CD4+ cells compared to the control arm, as shown by immunohistochemistry imaging (38); these results suggested that PrEP does not alter the immunological microenvironment of the foreskin and that PrEP induced protection from HIV infection is not the result of a diminished expression of HIV co-receptor CCR5 on CD4+ cells (38). This evidence concerns the gene CD4 and HIV infectious disease.