Contrasting frequencies of Gamma32-CCR5 and CCR2-V64I alleles in the Tunisian population.
Int Conf AIDS 2004 Jul 11-16; 15:(abstract no. A10215)
Barbouche MR, Hong L, Dellagi K, Kostrikis LG Institut Pasteur de Tunis, Tunis, Tunisia
The human chemokine receptor 5 (CCR5) is the major co-receptor on CD4+ cells for HIV-1. The absence of CCR5 expression in approximately 2% of the caucasian population is due to homozygosity for a 32-nucleotide deletion in the coding region (Gamma32-CCR5) and protects efficiently against HIV-1 transmission. A conservative substitution of a Valine at position 64 for an Isoleucine (V64I) in the coding region of the CCR2 is protective against disease progression. This mutation is in complete linkage disequilibrium with another mutation in the CCR5 regulatory region (CCR5-59653). We have studied by spectral genotyping, the frequency of the Gamma32-CCR5 allele as well as the CCR2-V64I and CCR5-59653 alleles in 145 healthy, HIV-1 seronegative Tunisian individuals. The findings from this study reveal that the Gamma32-CCR5 allele is at a significantly lower frequency compared with previous studies on caucasian populations. In contrast, the CCR2-V64I and CCR5-59653 mutations are at a significantly higher frequency. This study is the first concerning populations of the North African regions. It confirms what has been shown by previous studies i.e. that the frequencies of Gamma32-CCR5 allele tend to exhibit a gradient of decreasing values from northern regions to virtually zero in sub-Saharian region. The north mediterranean populations in other studies and the south mediterranean populations as demonstrated in our study show an intermediate value. In contrast, the CCR2-64I mutation that is in linkage disequilibrium with the CCR5-59653 seem to show an inverse gradient, with higher values in the south and lower values in the north. One possible explanation to this intermediate allele distribution in the actual Tunisian population is that the latter is a mosaic resulting from the melting, through 3,000 years of history, of several populations such as Berberian, Phenician, Vandal, Arab, Black Africans, Spanish, Turkish, French and other populations.
Keywords: AEGIS, Receptors, CCR5, Alleles, Receptors, Chemokine, HIV-1, Disease Progression, Linkage Disequilibrium, Mutation, European Continental Ancestry Group, Mediterranean Sea, Turkey, Humans, genetics
