Identification and phylogenetic characterization of a human T-cell leukaemia virus type I isolate from a native inhabitant (Rapa Nui) of Easter Island

Human T-cell leukaemia virus type I (HTLV-I) is endemic in Melanesia, one o f the three ethnogeographic regions of the Pacific; in the other two region s, Polynesia and Micronesia, the incidence of the virus is relatively low. In an effort to gain new insights into the prevalence of HTLVI in the Pacif ic region, we did a seroepidemiological survey on Easter island, which is l ocated on the eastern edge of Polynesia, Of 138 subjects surveyed, includin g 108 Papa Nui (the native inhabitants of this island), we identified one H TLV-I-seropositive Papa Nui, The new HTLV-I isolate derived from this carri er (E-12) was phylogenetically analysed to ascertain the origin and past di ssemination of HTLV-I in the island, The analysis demonstrated that isolate E-12 belongs to subgroup A of the Cosmopolitan group, and that it differs from HTLV-ls found in Melanesia, which are highly divergent variants, In su bgroup A, E-12 grouped with South American HTLV-ls including those from Ame rindians, This result suggests that this isolate originated in South Americ a rather than in Melanesia.