CXCR4 and HIV-1 infection: We found that GHOST-X4 cells transduced with lentiviral SaCas9/sgRNA #8 or #9 became negative for GFP expression compared to control cells (Fig. 1e), indicating that lentiCRISPR/SaCas9-mediated genome modification of CXCR4 protects GHOST-X4 cells from HIV-1 infection.