Natural infection of wild-born mandrills (Mandrillus sphinx) with two different types of simian immunodeficiency virus

We found a novel primate lentivirus in mandrill (Mandrillus sphinx). To cla rify the evolutionary relationships and transmission patterns of human/simi an immunodeficiency virus (HIV/SIV), we screened blood samples from 30 wild -born healthy Cameroonian mandrills. Five (16.7%) of them were seropositive for SIV. Three SIV strains were isolated from the five seropositive mandri lls by cocultivation of their peripheral blood mononuclear cells (PBMCs) wi th PBMCs of rhesus macaques, a human T cell line (M8166), and/or a cynomolg us macaque T cell line (HSC-F). One of the newly isolated SIV strains was i ntravenously inoculated into two rhesus macaques and resulted in chronic in fection. In the SIV-infected macaques at 45 weeks after inoculation, we obs erved a mild decline in the number of peripheral CD4(+) lymphocytes, lympha denopathy, and blastic follicular dendritic cells with mild follicular hype rplasia in the peripheral lymph nodes. A phylogenetic analysis based on the pol sequence showed that the newly found SIVs from Cameroonian mandrills d id not cluster with StVmndGB1, which is the former representative strain of SlVmnd. The SIVmnds from Cameroon formed a new, independent lineage that b ranched before the root of the HIV-1/SIVcpz lineage with 996 of 1000 bootst rap replications. They clustered host specifically, and exhibited about 16. 9% diversity at the level of nucleotide sequence among Cameroonian SIVmnd s trains. These results indicate that the SIVmnds isolated in Cameroon are a novel type of SlVmnd and have infected Cameroonian mandrills for a long tim e. We therefore designated the Cameroonian SIVmnd as SIVmnd type 2 and rede signated SIVmndGB1 as SIVmnd type 1. To date, M. sphinx is the only primate species other than humans that is naturally infected with two different ty pes of SIV.