Genetic Diversity of Lentiviruses in Non-Human Primates

Simian immunodeficiency viruses (SIVs) can be found naturally in a large number of African primate species; already 31 species have been identified with serological evidence of SIV infection, and in 21 this was confirmed by partial or full-length genome sequencing. So far, the primate lentiviruses, for which fulllength genome sequences are available, fall into six approximately equidistant major lineages and are represented by, 1) the HIV-1/SIVcpz lineage, 2) the HIV- 2/SIVsm lineage, 3) the SIVagm lineage from African green monkeys, 4) the SIVsyk lineage from Sykes’ monkeys, 5) the SIVlhoest lineage including viruses from mandrills, l’Hoest and sun-tailed monkeys and, 6) the SIVcol lineage from a colobus monkey. SIVs from other African primates have been partially characterised, but the exact phylogenetic relationship between these SIVs and other nonhuman primate lentiviruses requires the analysis of the complete genome. Most of the SIV-positive primates are the natural hosts of these viruses, and do not seem to develop any clinical symptoms. Nevertheless, if cross-species transmission occurs, the virus may be pathogenic for the new host. The two major viral types infecting humans, HIV-1 and HIV-2, represent zoonotic transmissions from chimpanzees (Pan troglodytes) and sooty mangabeys (Cercocebus atys) respectively. Therefore, the identification and characterisation of new SIV strains are important to better understand the origins of HIV-1 and-2 and to assess the potential risk for additional lentiviruses into the human population.