Prevalence of common vitamin D receptor gene polymorphisms in HIV-infected and uninfected South Africans.

Background: Host genetic factors may a play role in susceptibility to infection. Vitamin-D is an immunomodulator that may play a role in HIV infection. Vitamin-D action is mediated by the vitamin-D receptor. We establish prevalence of ApaI, BsmI, FokI and TaqI polymorphisms (VDRPs) amongst a black southern African HIV+ve population and investigate polymorphic differences between HIV+ve and -ve people.

Methods: Seventy-nine sex and age-group matched HIV+ve patients of African origin initiating antiretroviral therapy (ART) and 79 HIV-ve participants, also of African origin, were recruited from a public sector HIV testing and treatment clinic and investigated for the 4 polymorphisms. The genotype frequencies were compared, odds ratios and 95% confidence intervals of the association of HIV status and each genotype were calculated. Both dominant, co-dominant, recessive and allele models were tested.

Results: We found no evidence of difference in distribution and association between HIV infection and the genotypes of the BsmI, FokI and TaqI VDR polymorphisms. The genotype distributions were consistent with Hardy-Weinberg equilibrium for these genotypes. The ApaI genotype showed differences in distribution by HIV status in the dominant and co-dominant models. However this finding is cautiously stated as the ApaI genotype violated the Hardy-Weinberg equilibrium and frequency of the minor variant was unexpectedly low in this population.

Conclusion: We do not show convincing differences in distribution of the VDR genotypes among HIV+ve and HIV-ve black southern African persons. Future studies need to be replicated in larger study populations as understanding polymorphic differences and similarities may offer insights into the different susceptibility and progression of HIV in southern African populations.