Current knowledge of the genetic diversity of simian immunodeficiency virus (SIVcpz) infection of wild chimpanzees (Pan troglodytes)is incomplete since few isolates, mostly from captive apes from Cameroon and Gabon, have been characterized; yet this information is critical for understanding the origins of human immunodeficiency virus type 1 (HIV-1) and the circumstances leading to the HIV-1 pandemic. Here, we report the first full-length SIVcpz sequence (TAN1) from a wild chimpanzee (Pan troglodytes schweinfurthii) from Gombe National Park (Tanzania), which was obtained noninvasively by amplification of virion RNA from fecal samples collected under field conditions. Using reverse transcription-PCR and a combination of generic and strain-specific primers, we amplified 13 subgenomic fragments which together spanned the entire TAN1 genome (9,326 bp). Distance and phylogenetic tree analyses identified TAN1 unambiguously as a member of the HIV-1/SIVcpz group of viruses but also revealed an extraordinary degree of divergence from all previously characterized SIVcpz and HIV-1 strains. In Gag, Pol, and Env proteins, TAN1 differed from west-central African SIVcpz and HIV-1 strains on average by 36, 30, and 51% of amino acid sequences, respectively, approaching distance values typically found for SIVs from different primate species. The closest relative was SIVcpzANT, also from a P. t. schweinfurthii ape, which differed by 30, 25, and 44%, respectively, in these same protein sequences but clustered with TAN1 in all major coding regions in a statistically highly significant manner. These data indicate that east African chimpanzees, like those from west-central Africa, are naturally infected by SIVcpz but that their viruses comprise a second, divergent SIVcpz lineage which appears to have evolved in relative isolation for an extended period of time. Our data also demonstrate that noninvasive molecular epidemiological studies of SIVcpz in wild chimpanzees are feasible and that such an approach may prove essential for unraveling the evolutionary history of SIVcpz/HIV-1 as well as that of other pathogens naturally infecting wild primate populations.
West-central African chimpanzees (Pan troglodytes troglodytes)are naturally infected with strains of simian immunodeficiency virus (SIVcpz) that represent the closest relatives of human immunodeficiency virus type 1 (HIV-1) groups M, N, and O and have thus been implicated as the primate source of the human infections (12). East African chimpanzees (Pan troglodytes schweinfurthii) are also infected with SIVcpz, but genetic information for these viruses is limited since only two such strains (ANT and TAN1) have so far been identified (32,45). The first of these, SIVcpzANT, was isolated over a decade ago from a wild-caught chimpanzee orphan (Noah) which was confiscated upon illegal exportation from Kinshasa (Democratic Republic of Congo) (26). Although its geographic origin is unknown, this chimpanzee was subsequently typed as an eastern chimpanzee (P. t. schweinfurthii) by mitochondr...