A naturally occurring 32 base-pair deletion in CCR5 (CCR5 Δ32) has been associated with protection against HIV-1 infection (16, 17), and has been implicated in reported cases of HIV-1 resistance and functional cures following allogeneic bone marrow transplantation with donor marrow homozygous for the CCR5 Δ32 allele (18, 19). This evidence concerns the gene CCR5 and HIV-1 infection.