Sequence and phylogenetic analyses of human T cell lymphotropic virus type 1 from a Brazilian woman with adult T cell leukemia: comparison with virus strains from South America and the Caribbean basin.

Human T cell lymphotropic virus type 1 (HTLV-1) is endemic in South America and the Caribbean basin. To clarify the genetic and phylogenetic relationship between an HTLV-1 strain isolated from a Brazilian woman with adult T cell leukemia and viral isolates from elsewhere in South America and from other geographic regions, selected regions of the gag, pol, env, and pX genes were amplified and directly sequenced. The overall sequence similarities between the Brazil-R-1 strain and the Japanese prototype ATK strain were 98.7% based on 1,295 nucleotides and 99.1% based on 429 amino acids. Phylogenetic analysis indicated that strain Brazil-R-1 clustered with other Brazilian and South American HTLV-1 isolates and was more closely related to Caribbean isolates from Martinique and Guadeloupe than to virus strains from other geographic regions. These data suggest a common source of HTLV-1 infection in the Caribbean basin and South America.