We next tested whether CRISPR/Cas9-mediated disruption of CXCR4 gene could inhibit HIV-1 infection by taking advantage of the Ghost X4 reporter cell line containing green fluorescent protein (GFP) expression cassette driven by the HIV-1 LTR element, which permits the evaluation and quantitation of HIV-1 infection by flow cytometry. The gene discussed is CXCR4; the disease is HIV-1 infection.