Temporal dynamics of HIV-1 circulating subtypes in distinct exposure categories in southern Brazil

Background: The HIV-1 epidemic in Brazil is predominantly driven by subtype B. However, in Brazilian Southern region subtype C prevails and a relatively high AIDS incidence rate is observed. The aim of the present study was to assess the temporal dynamics of HIV-1 subtypes circulating in patients from distinct exposure categories in Southern Brazil. For this purpose 166 HIV-1 samples collected at the years of 1998 (group I) and 2005-2008 (group II) were analyzed. Results: Analysis of group I revealed statistically significant (p < 0.05) associations between MSM and subtype B as well as between IDU and subtype C; while no statistical significant association between HIV-1 subtypes and exposure category was verified for group II. An overall temporal increase in the prevalence of subtype C and BC recombinants was observed in both HET and MSM populations, accompanied by a proportional decrease in the prevalence of the pure subtype B. Conclusions: The present study shows an association between HIV subtypes and exposure categories at the middle 1990s in Southern Brazil. Our findings suggest that MSM and IDU populations might have played a major role in the introduction and initial dissemination of subtypes B and C, respectively, in Southern Brazil. This study also suggests a trend towards homogenization of HIV-1 strains across distinct exposure categories as a consequence of an overall increase in the prevalence of subtype C and BC recombinants in both HET and MSM populations.