[HIV-1 group N in Cameroon and apparent viruses in the chimpanzee]

The hypothesis of the recent origin of AIDS by way of one of several events of inter-species transmission has been widely accepted. Whilst the primate HIV-2 reservoir has been clearly identified, the origin of HIV-2 is still uncertain. Since 1994, collaborative studies on the variability of HIV-1 conducted at the Yaoundé Pasteur Centre have confirmed the very great diversity of circulating HIV-1 group M subtypes. This research has led to the identification of a further branch of HIV-1 phylogenesis, by the YBF30 strain, prototype for a new N group. A study conducted on chimpanzees isolated the retrovirus in three of them. Complete sequencing for one of the primates showed an important similarity in the env gene with the YBF30 strain, whereas the pol gene is closer to the HIV-1 group M. These findings support the hypothesis that HIV-1 group N resulted from a recombinant event. The origin of the HIV-1 group N pol fragment and more generally the origins of group M and O human viruses are still unclear. In order to complete the phylogenesis of human and non-human primate retrovirus as well as to identify two circumstances of more epidemiogenic variants, it is important to follow the variability of HIV-1 in central Africa and search for intermediary forms amongst simian species.