The results indicated that both lenti-X4R5-Cas9-#1 and lenti-X4R5-Cas9-#2 mediated CXCR4 and CCR5 knockout conferred TZM-bl cells resistant to X4- or R5-tropic HIV-1 infections (Fig. 2d). The gene discussed is CXCR4; the disease is HIV-1 infection.