CCR5 and HIV-1 infection: Multiple genetic variants in chemokine receptors and chemokines have been identified as modifiers of HIV-1 infection or disease progression [12], [13], including CCR5-Δ32 (a 32-bp deletion introduces a premature stop codon) [14] and CCR5 promoter variants [15]–[17] and variants in the CCR5 ligand gene CCL5[18], [19].