Phylogenetic analysis of SIV derived from mandrill and drill.

SIVmnd was isolated from mandrills in Gabon in 1989 soon after the existence of simian counterparts of HIV such as SIVmac and SIVagm was known. Since then the SIVmnd has been long considered as an independent SIV lineage and the natural host is the mandrill. However this initial finding turned out to be more complex by the recent finding of new SIV isolated from mandrills living in northern mandrill habitat, and other SIV isolated from drills and other species. One fact which made these findings complicated was the fact that the SIVmnd made a tight cluster with SIVlhoest and SIVsun from genus Cercopithecus, which is different from genus Mandrillus. A second fact is that the second SIVmnd isolates are different in the genomic structure from the former SIVmnd and almost similar to SIVdrl from drills, and phylogenetically closely related with each other. At present, the former SIVmnd isolate is termed SIVmnd-1 and the second SIVmnd isolate is called SIVmnd-2. Interestingly SIVmnd-2/SIVdrl has the same mosaic structure containing the vpx gene which is absent in SIVmnd-1. The mosaic structure was probably due to a recombination between SIVmnd-1 and SIVrcm from red capped mangabey (or similar viruses) having the vpx gene. However this recombination event is not recent, and SIVmnd-1, SIVmnd-2 and SIVdrl have been likely maintained for a long period of time in each species. In this article, we speculate on the origin and evolution of these SIVs.