THE TAX-GENE-SEQUENCES FORM 2 DIVERGENT MONOPHYLETIC LINEAGES CORRESPONDING TO TYPE-I AND TYPE-II OF SIMIAN AND HUMAN T-CELL LEUKEMIA-LYMPHOTROPIC-VIRUSES

Evolutionary associations of human and simian T-cell leukemia/lymphotr opic viruses I and II (HTLV-I/II and STLV-I/II) are inferred from phyl ogenetic analysis of lax gene sequences. Samples studied consisted of a geographically diverse assemblage of viral strains obtained from 10 human subjects and 20 individuals representing 12 species of nonhuman primates. Sequence analyses identified distinct substitutions, which d istinguished between viral types I and II, irrespective of host specie s. Phylogenetic reconstruction of nucleotide sequences strongly suppor ted two major evolutionary groups corresponding to viral types I and I I. With the type I lineage, clusters were composed of strains from mul tiple host species. A genetically diverse, monophyletic lineage consis ting of eight new viral strains from several species of Asian macaques was identified. The second lineage consisted of a monophyletic assemb lage of HTLV-II/STLV-II strains from Africa and the New World, includi ng an isolate from a pygmy chimp (Pan paniscus) as an early divergence within the lineage. High levels of genetic variation among strains fr om Asian STLV-I macaque suggest the virus arose in Asia. Evidence of t he origin of the type II virus is less clear, but diversity among HTLV -II variants from a single isolated population of Mbati villagers is s uggestive but not proof of an African origin. (C) 1997 Academic Press.