PLoS Biology (Nov 2005)

The case for selection at CCR5-Delta32.

  • Pardis C Sabeti,
  • Emily Walsh,
  • Steve F Schaffner,
  • Patrick Varilly,
  • Ben Fry,
  • Holli B Hutcheson,
  • Mike Cullen,
  • Tarjei S Mikkelsen,
  • Jessica Roy,
  • Nick Patterson,
  • Richard Cooper,
  • David Reich,
  • David Altshuler,
  • Stephen O'Brien,
  • Eric S Lander

DOI
https://doi.org/10.1371/journal.pbio.0030378
Journal volume & issue
Vol. 3, no. 11
p. e378

Abstract

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The C-C chemokine receptor 5, 32 base-pair deletion (CCR5-Delta32) allele confers strong resistance to infection by the AIDS virus HIV. Previous studies have suggested that CCR5-Delta32 arose within the past 1,000 y and rose to its present high frequency (5%-14%) in Europe as a result of strong positive selection, perhaps by such selective agents as the bubonic plague or smallpox during the Middle Ages. This hypothesis was based on several lines of evidence, including the absence of the allele outside of Europe and long-range linkage disequilibrium at the locus. We reevaluated this evidence with the benefit of much denser genetic maps and extensive control data. We find that the pattern of genetic variation at CCR5-Delta32 does not stand out as exceptional relative to other loci across the genome. Moreover using newer genetic maps, we estimated that the CCR5-Delta32 allele is likely to have arisen more than 5,000 y ago. While such results can not rule out the possibility that some selection may have occurred at C-C chemokine receptor 5 (CCR5), they imply that the pattern of genetic variation seen at CCR5-Delta32 is consistent with neutral evolution. More broadly, the results have general implications for the design of future studies to detect the signs of positive selection in the human genome.