CXCR4 and HIV-1 infection: To examine whether GPR15LG binding to CXCR4 interferes with HIV-1 infection, we incubated TZM-bl reporter cells with GPR15LG, CXCL12, AMD3100, and the CCR5 antagonist Maraviroc and subsequently infected them with CXCR4- or CCR5-tropic HIV-1.