Analysis of partial pol and env sequences indicates a high prevalence of HIV type 1 recombinant strains circulating in Gabon.

Forty-one HIV-1 strains from Gabonese patients were studied according to the following strategy: nested polymerase chain reaction were performed to obtain an approximately 1,100-bp fragment containing the protease gene and the 5' half of the reverse transcriptase gene. Additional amplifications were carried out to obtain an approximately 700-bp fragment encompassing the C2V3 env gene. Fragments of 600 to 1,200 bp in the gag gene overlapping the pol sequences were used for the study of recombination patterns. Phylogenetic analyses of the different fragments were used to investigate HIV-1 diversity in Gabon. Thirty-one strains were sequenced in the env and pol genes and phylogenetic analyses classified them as subtype A (n = 2), D (n = 4), G (n = 1), H (n = 1), CRF02 (n = 8), and CRF MAL-like (n = 6); in addition, there were 6 unique recombinant forms and 1 unclassified strain, and in 2 cases pol/env sequences classified strains as subtype D whereas gag phylogeny classified them as subtype A. In 10 cases only 1 fragment was available: 4 env (2 subtype D, 1 subtype H, and 1 subtype U) and 6 pol (1 subtype A, 1 subtype C, 2 subtype G, and 2 subtype U). Minor mutations associated with viral resistance to antiretroviral drugs were observed in more than 80% of analyzed strains. Our study confirms the extensive HIV-1 diversity found in Central Africa, with more than 70% of strains from Gabon exhibiting discordant clustering in pol and env genomic regions and less than 60% concordance between sequencing and heteroduplex mobility assay genotyping. These findings highlight the fact that Central Africa represents the epicenter for the origin of HIV-1. The strategy of sequencing pol in association with env has proved to be useful for analysis of the recombinant strains. The main advantage of this approach is that it also allows for evaluation of genotypic susceptibility to antiretroviral drugs without the need for supplementary analyses.