HCV was originally thought to be strictly hepatotropic, while the main cell targets for HIV-1 infection are mononuclear leukocytes bearing CD4 and the chemokine receptors C-C chemokine receptor type 5 (CCR5) and chemokine (C-X-C motif) receptor 4 (CXCR4). The gene discussed is CCR5; the disease is HIV-1 infection.