Frequency of the CCR5 Delta 32 allele in Brazilians: a study in colorectalcancer and in HTLV-I infection

The identification of a 32-bp deletion in the cc-chemokine receptor-5 gene (CCR5 Delta 32 allele) that renders homozygous individuals highly resistant to HIV infection has prompted worldwide investigations of the frequency of the CCR5 Delta 32 allele in regional populations. It is important to ascer tain if CCR5 Delta 32 is a factor to be considered in the overall epidemiol ogy of HIV in individual populations. With this in mind we determined the C CR5 Delta 32 allele frequency in a large sample (907 individuals) of the so utheastern Brazilian urban population, stratified as follows: 322 healthy u nrelated individuals, 354 unselected colorectal cancer patients, and 229 bl ood donors. The three groups displayed essentially identical allelic freque ncies of CCR5 Delta 32 and pairwise comparisons did not show significant di fferences. Thus, our results can be pooled to provide a reliable estimate o f the CCR5 Delta 32 allele frequency in the southeastern Brazil of 0.053 +/ - 0.005. The blood donors comprised 50 HTLV-I serologically negative indivi duals, 115 non-symptomatic individuals HTLV-I positive by ELISA but with in determinate Western blot results, 49 healthy blood donors HTLV-I positive b oth at ELISA and Western blot and 15 patients with clinical spinal cord dis ease (HAM). A suggestive trend was observed, with the CCR5 Delta 32 frequen cies decreasing progressively in these four categories. However, when we ap plied Fischer's exact test no significant differences emerged. We believe t hat further studies in larger cohorts should be performed to ascertain whet her the CCR5 Delta 32 allele influences the chance of becoming infected or developing clinical symptoms of HTLV-I infection.