Selective regimes and evolutionary rates of HIV-1 subtype B V3 variants in the Brazilian epidemic

Half of subtype B Brazilian HIV-1 harbors the V3 tip GWGR instead of the GPGR. To investigate the evolution of GW variants, we analyzed 81 env sequences and 5 full-length GW genomes from antiretroviral-naive individuals sampled between 1983 and 1999. Phylogenetic analysis indicated that GW strains intermingle in the tree with other subtype B sequences. The mean d(N)/d(S) values of GW strains were Proximal to those of the other sequences, regardless of sampling years OF clinical status. In sequences from patients with CD4+ T cell counts >= 200 cells/mu L, the mean d(N)/d(S) ratio was greater than one, suggesting a positive selection. The prevalence of GW variants was lower among individuals in whom disease progressed. This is probably attributable to the fact that tryptophan is replaced by other amino acids over time, whereas the GP motif does not evolve as rapidly. (C) 2008 Elsevier Inc. All rights reserved.