Evolutionary inferences of novel simian T lymphotropic virus type 1 from wild-caught chacma (Papio ursinus) and olive baboons (Papio anubis).

A serological survey of 22 wild-caught South African (Transvaal) chacma baboons (Papio ursinus) and eight olive baboons (Papio anubis) from Kenya indicates that 13 P. ursinus and one P. anubis have antibodies reacting with human T cell leukemia/lymphoma virus type 1 (HTLV-1) antigens, whereas three P. ursinus had a indeterminate reactivity on Western blot analysis. With six primer sets specific to either HTLV-1-Simian T-cell leukemia virus type 1 (STLV-1) or HTLV-2 and encompassing long terminal repeat (LTR), gag, pol, env, and tax sequences, polymerase chain reaction was performed on genomic DNA from peripheral blood mononuclear cells of 18 animals, and the presence of HTLV-1-STLV-1-related viruses was determined in 13 seropositive and three seroindeterminate animals but not in the two HTLV seronegative individuals. Proviral DNA sequences from env (522 bp), pol (120 bp), and complete (755 bp) or partial (514 bp) LTR were determined for three STLV-1-infected P. ursinus and one P. anubis. Comparative and phylogenetic analyses revealed that P. anubis (Pan-486) sequence clusters with one (Pan-1621) of two previously described P. anubis STLV-1. Likewise, P. ursinus viruses (Pur-529, Pur-539, and Pur-543) form a distinct group, different from all known HTLV-1 but closely affiliated with two STLV-1 strains from South African vervets (Cercopithecus aethiops pygerythrus). This study, reporting the first STLV-1 sequences from wild-caught P. ursinus and P. anubis, corroborates the hypothesis of cross-species transmissions of STLV-1 in the wild. Further, phylogenetic analyses indicate that the known HTLV-1 strains do not share a common origin with nonhuman primates STLV in South Africa.