Intriguingly, the human immunodeficiency virus (HIV-1) has usurped CXCR4’s unique CXCL12 binding site, exploiting CXCR4 as a co-receptor in later stages of HIV-1 infection, and CXCR4 antagonists have been explored as treatments for HIV infection. The gene discussed is CXCL12; the disease is HIV-1 infection.