C-X-C chemokine receptor type 4 (CXCR4) is another co-receptor exploited by X4 tropic strains of HIV-1 [65,66] and should be considered as another important target for genome editing against HIV-1 infection because R5-tropic HIV-1, in the late stages of AIDS, can utilize CXCR4 as an alternative co-receptor to enter new cells and cause faster disease progression [67,68]. This evidence concerns the gene CXCR4 and HIV-1 infection.