Analysis of CCR5Δ32 Geographic Distribution and Its Correlation with Some Climatic and Geographic Factors

We studied the possible effects of climatic-geographic factors on the world distribution of the mutant allele for the chemokine receptor gene CCR5, which has a 32-bp deletion (CCR5Δ32) preventing cell invasion by the primary transmitting strain of HIV-1. New data on CCR5 polymorphisms in Russian, Ukrainian, and Moldavian populations are presented. All available data on CCR5Δ32 frequencies in the Old World (number of populations n = 77) were used for construction of a geographical gene map to analyze possible correlations between allele frequencies and eight climatic-geographic parameters. A strong positive correlation was found between the allele frequency and latitude (r = 0.72), a strong negative correlation with annual radiation balance (r = –0.66), and a weaker negative correlation with longitude (r = –0.34). Partial correlations were calculated excluding the influence of latitude. The negative correlation between the allele frequency and annual radiation balance decreased (r = –0.42), but remained large and significant. We propose that the existence of correlations between the cline of CCR5Δ32 frequencies and climatic-geographic parameters provides evidence for a possible effect of either natural environmental factors or large-scale population movements on the distribution of this allele.