Characterization of a new circulating recombinant form comprising HIV-1 subtypes C and B in southern Brazil

To identify a new circulating recombinant form (CRF) of HIV-1 comprising two circulating subtypes in the southern region in Brazil, subtypes B and C.

A total of 152 HIV-positive patients followed at two hospitals in southern Brazil had their viral pol genes isolated by reverse transcriptase-polymerase chain reaction (PCR) from plasma. PCR products were sequenced and phylogenetically analysed using HIV-1 subtype reference sequences. Six full-length subtype C viruses from Brazil previously described as 'pure' strains were included in the analysis. Sequences suggestive of recombination were analysed by boot scanning and phylogenetic analyses of separate fragments. The common ancestry of recombinant strains was evaluated by similarity plot and informative site analyses.

: HIV-1 subtypes commonly found in Brazil (B, C and F1) were observed. Sixty-two viruses were initially assigned as subtype C, but 15 viruses clustered in a separate internal clade. Pol from two full-length genomes of subtype C viruses grouped together with those samples. Boot scanning analysis showed that all 17 viruses had the same recombinant structure, with a 240 base pair fragment of subtype B in the middle of the reverse transcriptase pol region. Subtype B assignment of this fragment was confirmed by phylogenetic analyses using different methods of tree inference and cluster robustness tests. Mosaics were shown to have a common ancestry.

As CRF_BC represents 11% of the HIV-1 viruses circulating in the southern region of the country, which borders several south American countries, the assessment of its spread is of pivotal importance to the HIV/AIDS epidemic in Brazil and Latin America.