Evidence for recent selection of the CCR5-Δ32 deletion from differences in its frequency between Ashkenazi and Sephardi Jews

Abstract

Recent studies have shown higher frequencies of the CCR5-Δ32 allele and the CCR5-Δ32/Δ32 genotype, which confers protection against HIV infection, in northern Europe as compared to Mediterranean countries. Here, we analyse the prevalence of CCR5-Δ32 in 922 HIV seronegative blood donors in Israel to verify its frequency in Jews of Ashkenazi and Sephardi origin. A significant difference (P < 0.001) was found between the ccr5-δ32 allele frequency in ashkenazi (13.8%) vs (4.9%) jews. in contrast, no significant difference was observed in the frequency of the ccr2–64i mutation between ashkenazi (9.2%) and sephardi (13.4%) jews. using the island model we calculate that a minimal genetic migration rate of 3% per generation would have been necessary if the higher ccr5-δ32 prevalence in ashkenazi is to be fully explained by mixing with the indigenous north-european populations. this putative migration rate is 20-fold higher than that currently estimated from other genes, and would correspond to a non-realistic minimal current admixture of 80%. thus, our results suggest that a positive selection process for ccr5-δ32 should have occurred in northern europe at most a 1000 years ago, after the ashkenazi jews separated from their sephardi kin and moved to north europe.