Molecular characterization and phylogenetic analyses of a new simian T cell lymphotropic virus type 1 in a wild-caught african baboon (Papio anubis) with an indeterminate STLV type 2-like serology.

STLV-1 viruses are closely related to HTLV-1 and infect many African monkey species. Seroreactivities of monkeys infected by STLV-1 are nearly identical to those of HTLV-1-infected individuals. In some cases, STLV-1 are, sequence-wise, indistinguishable from HTLV-1, and cannot be separated from them on the basis of phylogenetic analyses. HTLV-2-related simian viruses have been rarely reported. Such STLV-2 viruses, present in African bonobo (Pan paniscus), possess a genomic organization related to but different from all known HTLV-2 subtypes. We report here the molecular characterization and the subtyping of a new STLV-1 in a wild-caught baboon (Papio anubis) whose serum exhibited an indeterminate STLV-2-like serology (p24, GD21, MTA-1 with no p19). In the env and LTR regions, this virus is phylogenetically related to the large African STLV-1 group, but does not cluster with any STLV-1 baboon sequence. The complete p19 sequence reveals amino acid changes at critical positions. This is the first report of an African STLV-1 virus leading to an STLV-2-like serological profile in its host.