Genetic diversity and transmission networks of HIV-1 strains among men having sex with men (MSM) in Lomé, Togo

Understanding the HIV epidemic in key populations is important. Today only scarce information is available on HIV-1 strains that circulate in men having sex with men (MSM) in sub-Saharan Africa. Here, we studied for the first time the genetic diversity of HIV-1 strains circulating in the MSM population in Lomé, the capital city from Togo. The overall subtype/CRF distribution in pol (protease and/or partial reverse transcriptase (RT)) among the 79 HIV-1 strains from MSM was as follows: CRF02_AG (72%, n = 57), subtype G (2.5%, n = 2), sub-subtype A3 (1.3%, n = 1), and unique recombinant forms (URF) (24%, n = 19). Among the 19 URFs four different mosaic structures were observed, annotated as URF1 to URF4. Fifteen sequences (URF1) had the same mosaic structure in pol (G/CRF02_AG) and could represent a new circulating recombinant form (CRF). Phylogenetic analysis of the RT sequences showed that there were several introductions of CRF02_AG strains in the MSM population, however half of the CRF02_AG and all URF1 strains formed a separate, well-supported cluster suggesting one major introduction of CRF02_AG in the MSM population followed by efficient transmission and emergence of a possible new CRF. At least 40% of the strains fell into recent transmission chains involving two to seven MSM. Comparison with > 950 HIV-1 sequences from previous studies in Togo showed intermixing of the HIV-1 epidemics between MSM and the general population. Moreover, an HIV-1 strain from a recently HIV-1 infected male patient from Germany, fell within a cluster of HIV-1 strains from MSM from Togo, illustrating recent exchange between MSM from Africa and people from other geographic regions. With growing evidence of the importance of MSM in the dynamic of the HIV epidemic in Africa there is an urgent need for appropriate interventions to limit HIV transmission in this population group.