GLOBAL DISTRIBUTION OF THE CCR5 GENE 32-BASEPAIR DELETION

A mutant allele of the beta-chemokine receptor gene CCR5 bearing a 32- basepair (bp) deletion (denoted Delta ccr5) which prevents cell invasi on by the primary transmitting strain of HIV-1 has recently been chara cterized(1-3). Homozygotes for the mutation are resistant to infection , even after repeated high-risk exposures(1,4), but this resistance ap pears not to be total, as isolated cases of HIV-positive deletion homo zygotes are now emerging(5), The consequence of the heterozygous state is not clear, but it may delay the progression to AIDS in infected in dividuals(2,3,6,7). A gene frequency of approximately 10% was found fo r Delta ccr5 in populations of European descent, but no mutant alleles were reported in indigenous non-European populations, As the total nu mber of non-European samples surveyed was small in comparison with the Europeans the global distribution of this mutation is far from clear. We have devised a rapid PCR assay for Delta ccr5 and used it to scree n 3,342 individuals from a globally-distributed range of populations. We find that Delta ccr5 is not confined to people of European descent but is found at frequencies of 2-5% throughout Europe, the Middle East and the Indian subcontinent (Fig. 1). Isolated occurrences are seen e lsewhere throughout the world, but these most likely represent recent European gene flow into the indigenous populations, The inter-populati on differences in Delta ccr5 frequency may influence the pattern of HI V transmission and so will need to be incorporated into future predict ions of HIV levels.