Protective Effect of CCR5-Δ32 Against HIV Infection by the Heterosexual Mode of Transmission in a Polish Population

Abstract

Effects of chemokine receptor alleles (CCR5-Δ32 and CCR2-64I) on susceptibility to human immunodeficiency virus (HIV) infection were studied in a Polish population. The CCR5 and CCR2 genotypes were determined for 311 healthy, HIV-negative individuals (control group), 121 exposed to HIV infection but uninfected (EU group), and 470 HIV-positive patients. The frequency of the alleles in the control group was calculated as 0.12 for both CCR5-Δ32 and CCR2-64I. The logistic regression method was used to analyze the effects of the described factors. A protective effect was observed for the CCR5-Δ32 allele but only in the case of heterosexual exposure. Prevalence of the CCR5-Δ32/+ genotype in HIV(+) patients infected via the heterosexual route (n=61; 8.2%) was much lower than in the control group (n=311; 21.5%); in the heterosexually exposed uninfected group it was slightly higher (n=28; 25%). This suggested that in this mode of infection, the native CCR5 expression level was crucial for establishment of infection. Individuals with the CCR5-Δ32 allele have more than three times less chance of infection in the case of HIV heterosexual exposure (odds ratio, 3.37; 95% confidence interval, 1.055-10.76). However, a protective effect of the CCR5-Δ32/+ genotype was not observed in the case of intravenous drug users (IDUs). The rates of the genotype were similar in HIV-infected IDU individuals (n=356; 17.7%) and in exposed uninfected patients (n=84; 15.5%), not significantly different from control group. No effect of the CCR2 genotype was observed. The analysis revealed that the important factor increasing infection risk was, in particular, hepatitis C virus (HCV) infection (odds ratio, 12.9). Moreover, the effect of HCV infection was found to be age dependent. Susceptibility to HIV infection resulting from HCV positivity became weaker (6% per year) with increasing age.