CCR5 and HIV infectious disease: CCR5Δ32 homozygous individuals are resistant to HIV infection due to lack of CCR5 expression; [73,74] while CCR5Δ32 heterozygous individuals progress either relatively slowly to AIDS or remain as long term non-progressors [73,75] Besides this well characterized deletion mutation; a polymorphism in the CCR5 promoter region has also been associated with disease progression [76].