CCR5 genotypes in sexually active couples discordant for human immunodeficiency virus type 1 infection status

Persons who are homozygous for the Delta 32 polymorphism of the CCR5 chemokine receptor gene are highly protected against human immunodeficiency virus type 1 (HIV-1) infection. Previous studies described 54 HIV-1-discordant couples in whom no virus transmission occurred despite extensive sexual contact. The possible role of the Delta 32 polymorphism in the rack of HIV-1 transmission between these partners was studied. No participants were homozygous for the Delta 32 allele, but the proportion that was heterozygous was higher among HIV-1-seronegative than HIV-1 seropositive partners (28% vs. 11%, P =.05). This association was seen in heterosexual couples (P =.03) but not in homosexual couples (P =.74). Among white persons, who are most likely to carry the Delta 32 allele, 38.9% of HIV-1-uninfected and 5.6% of HIV-1-infected heterosexual partners were heterozygous (P =.04). These data are consistent with a possible association between the heterozygous Delta 32 genotype in heterosexual sex partners and partial protection against HIV-1 infection, and they emphasize the importance of analyzing different risk groups in studies of host factors that influence infection.