Genotype and allele frequency of a 32-base pair deletion mutation in the CCR5 gene in various ethnic groups: Absence of mutation among Asians and Pacific islanders

Abstract

Background: A 32-base pair (bp) deletion mutation in the betachemokine receptor CCR5 gene has been associated with resistance against human immunodeficiency virus type 1 (HIV-1) infection and disease. Large-scale studies conducted among Caucasians indicate that individuals who are homozygous for this deletion mutation (Δ32/Δ32) are protected against HIV-1 infection despite multiple high-risk exposures, whereas CCR5/Δ32 heterozygotes have a slower progression to acquired immunodeficiency syndrome (AIDS). Objective: To determine the genotype and allele frequencies of the CCR5 gene 32-bp deletion mutation among ethnically diverse non-Caucasian populations. Methods: DNA, extracted from blood collected between 1980 and 1997 from 1912 individuals belonging to various ethnic groups, including 363 Caucasians, 303 Puerto Rican Hispanics, 150 Africans, 606 Asians, and 490 Pacific Islanders, were analyzed for the CCR5 gene 32-bp deletion mutation by a polymerase chain reaction (PCR)-based assay, using an oligonucleotide primer pair designed to discriminate CCR5 alleles without restriction endonuclease analysis. Results: The comparative frequency of CCR5/Δ32 heterozygosity was 61 of 363 (16.8%) in Caucasians, 17 of 303 (5.6%) in Puerto Rican Hispanics, 9 of 490 (1.8%) in Pacific Islanders, 0 of 606 (0%) in Asians, and 0 of 150 (0%) in Africans. Conclusions: The data confirm the high frequency of CCR5/Δ32 heterozygosity among Caucasians. Intermediate and low-level Δ32 allele frequencies among Puerto Rican Hispanics and Hawaiians could be attributed to recent European Caucasian gene flow. By contrast, the inability to detect the Δ32 allele among Asians and other Pacific Islander groups suggests that other mechanisms are responsible for resistance to HIV-1 infection in these populations.