GENETIC-VARIANTS OF HUMAN T-LYMPHOTROPIC VIRUS TYPE-II IN AMERICAN-INDIAN GROUPS

The human T-lymphotropic virus type II (HTLV-II) is found in many New World Indian groups in North and South America and may have entered th e New World from Asia with the earliest migration of ancestral Amerind ians over 15,000 years ago. To characterize the phylogenetic relations hips of HTLV-II strains infecting geographically diverse Indian popula tions, we used polymerase chain reaction to amplify HTLV-II sequences from lymphocytes of seropositive Amerindians from Brazil (Kraho, Kayap o, and Kaxuyana), Panama (Guaymi), and the United States (the Navajo a nd Pueblo tribes of the southwestern states and the Seminoles of Flori da). Sequence analysis of a 780-base pair fragment (located between th e env gene and the second exons of tax/rex) revealed that Amerindian v iruses clustered in the same two genetic subtypes (IIa and IIb) previo usly identified for viruses from intravenous drug users. Most infected North and Central American Indians had subtype Ilb, while HTLV-II inf ected members of three remote Amazonian tribes clustered as a distinct group within subtype IIa. These findings suggest that the ancestral A merindians migrating to the New World brought at least two genetic sub types, IIa and IIb. Because HTLV-II strains from Amazonian Indians for m a distinct group within subtype HTLV-IIa, these Brazilian tribes are unlikely to be the source of IIa viruses in North American drug users . Finally, the near identity of viral sequences from geographically di verse populations indicate that HTLV-II is a very ancient virus of man . (C) 1996 Academic Press. Inc