Phylogenetic characteristics of three new HIV-1 N strains and implications for the origin of group N

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Abstract
The three divergent HIV-1 groups M, N and O were very probably introduced into the human population by independent cross-species transmissions of SIVcpz from the chimpanzee subspecies Pan troglodytes troglodytes in central Africa. To characterize HIV-1 group N strains and to elucidate the group's epidemiology and relationship to HIV-1 strains O and M, and SIVcpz. DNA amplification, sequencing and phylogenetic analyses were performed to characterize viruses from three group N-infected individuals (YBF106, YBF115 and YBF116) together with YBF30 and YBF105 previously described. Full-length genome sequence was determined for virus YBF106; gag, pol and env sequences were obtained for YBF116; pol (integrase) and env (gp41) fragments were obtained for YBF115. The gag, pol, 5'-vif and nef sequences were phylogenetically more closely related to HIV-1 M while 3'-vif, vpr, tat, vpu and env clustered with SIVcpz from P. t. troglodytes. Sequence analysis revealed no mutations potentially responsible for drug resistance. The finding that all group N viruses displayed the same recombinant structure and were monophyletic indicates that a single transfer event of SIVcpz to humans can account for the origin of this group. Despite the pathogenic outcome of the known group N infections, the extremely low prevalence of this divergent HIV-1 suggests that this group is not an emerging threat to human health at the present time. However, continuous monitoring of HIV-1 diversity will be important to survey the potential of unusual HIV infections, such as group N, to contribute to the HIV/AIDS pandemic.