CCR5 and HIV-1 infection: However, given the relatively low prevalence of bone marrow donors who are homozygous for the Δ32 CCR5 deletion (∼1% in Caucasian populations) [22] as well as the risks associated with allogeneic bone marrow transplantation, there is a compelling need for alternative strategies to induce resistance of hematopoietic cells to HIV-1 infection.