CCR5 and HIV infectious disease: The importance of CCR5 for HIV-1 pathogenesis is shown by the fact that individuals who are homozygous for an inactivating 32 base pair deletion in ccr5 (ccr5Δ32) are highly resistant to HIV infection [2], [3], while heterozygotes typically live longer after HIV infection due to reduced CCR5 expression levels [4], [5].