Patterns of genomic sequence diversity among their simian immunodeficiencyviruses suggest that L'Hoest monkeys (Cercopithecus lhoesti) are a naturallentivirus reservoir

Recently, we described a novel simian immunodeficiency virus (SIVlhoest) fr om a wild-caught L'Hoest monkey (Cercopithecus lhoesti) from a North Americ an zoo. To investigate whether L'Hoest monkeys are the natural host for the se viruses, we have screened blood samples from 14 wild animals from the De mocratic Republic of Congo. Eight (57%) were found to be seropositive for S IV. Nearly full-length genome sequences were obtained for SIV isolates from three of these monkeys and compared to the original isolate and to other S IVs. The four samples of SIVlhoest formed a distinct cluster in phylogeneti c trees. Two of these isolates differed on average at only about 5% of nucl eotides, suggesting that they were epidemiologically linked; otherwise, the SIVlhoest isolates differed on average by 18%. Both the level of diversity and the pattern of its variation along the genome were very similar to tho se seen among isolates of SIVagm from vervet monkeys, pointing to similarit ies in the nature of, and constraints on, SIV evolution in these two specie s. Discordant phylogenetic relationships among the SIVlhoest isolates for d ifferent genomic regions indicated that mosaic viruses have been generated by recombination, implying that individual monkeys have been coinfected by more than one strain of SIV. Taken together, these observations provide str ong evidence that L'Hoest monkeys constitute a natural reservoir for SIV.