Is Spatial Distribution of the HIV-1-resistant CCR5Δ32 Allele Formed by Ecological Factors?

It has been proposed that the Δ32 mutation in the chemokine receptor gene, inducing resistance to HIV-1 and, probably, to other virus infections, has undergone selection in historical times. The frequency of this mutant allele has changed rapidly both in time (during the last two millennia) and in space (across Eurasia). We compiled a global database on Δ32 allele frequencies in 300 populations. Nearly 10 percent of them are our data on 35 East European populations analyzed here for the first time. A detailed map of Δ32 frequency distribution was constructed and statistically analysed. We found a linearly decreasing trend with a maximum in areas surrounding the Baltic and White seas. Significant correlations with ground surface temperature were revealed. However, compared with our previous results, these correlations diminished, indicating that the influence of climate on Δ32 distribution was, if anything at all, indirect. The proposed scenario includes: i) arise and initial spread of the mutation among Uralic-speaking populations; ii) a frequency increase in northeastern Europe as a result of selection and/or genetic drift; iii) secondary spread (with selection continued) due to gene flow and the migrations of northern Europeans across the globe.