CXCR4 and HIV-1 infection: Some works about simultaneous editing of HIV-1 co-receptor CCR5 and CXCR4 by CRISPR/Cas9 have also been reported, Yu et al. and our previous work have confirmed that the two genes could be disrupted simultaneously in genome level and the edited cells could resist R5-tropic strain and X4-tropic strain concurrently with survival advantage over unedited cells under mixed HIV-1 infection pressure [25, 26].