PHYLOGENETIC ANALYSES OF 11 HTLV-I FROM AMERINDIANS OF SOUTH AMERICA

P112 In South America, HTLV-I has been identified not only among immigrants who came to the continent during a few centuries (Europeans, Africans and Japanese) but also among Amerindians, whose ancestors are believed to have migrated from Asia more than ten thousands years ago. To gain new insights as to the origin of HTLV-I in South America, we phylogenetically characterized 11 HTLV-Is from Amerindians (two from Argentina, two from Bolivia, six from Chile and one from Peru). A part of the LTR region was sequenced and subjected to phylogenetic analyses for comparison with HTLV-Is of various geographical origins. Phylogenetic trees indicated that all the new HTLV-Is belonged to the Transcontinental (A) subgroup of the Cosmopolitan group. These new isolates differed from HTLV-I in Africa with the exception of two Bolivian HTLV-Is which are related to South African HTLV-Is. In the subgroup A, they were also distinct from Japanese HTLV-Is. This result as well as the fact that the samples were obtained from Amerindians who are ethnically segregated suggest that HTLV-I of Amerindians are not imported from Africa nor Japan but may be an indigenous virus to South America. On the other hand, the majority of HTLV-I found in other ethnic populations of South America (whites, blacks and mestizos) exhibits closer similarities to HTLV-I of Amerindians than those of Japan and Africa. This suggests that HTLV-I of Amerindians spread to new residents of the continent and does not support the prevailing hypothesis that recent introduction of African HTLV-I is the sole origin of HTLV-I in South America.