Molecular epidemiology of human T-cell leukemia virus type I (HTLV-I) in Brazil: The predominant HTLV-Is in South America differ from HTLV-Is of Japan and Africa, as well as those of Japanese immigrants and their relatives in Brazil

To better understand the origin of human T-cell leukemia virus type I (HTLV -I) in South America, we conducted a phylogenetic study on 27 new HTLV-Is i n Brazil. These were obtained from Brazilians of various ethnic origins, su ch as Japanese immigrants, whites, blacks, and mulattos. We amplified and s equenced proviral DNAs of a part of the long terminal repeats. Phylogenetic trees revealed that all but 6 of the new isolates were not only similar to each other but also similar to HTLV-Is of other South American countries, including those from Amerindians. However, the isolates differed from the H TLV-Is of Africa and Japan. The other six isolates were from Japanese immig rants and were phylogenetically almost identical to HTLV-Is in Japan but di fferent from the majority of South American HTLV-Is, including the other ne w Brazilian HTLV-Is. These findings indicate that the recent introduction o f HTLV-I from Japan is limited to Japanese immigrants. In addition, the res ults do not support the prevailing hypothesis that HTLV-Is in South America were introduced by blacks who were brought from Africa as slaves. Rather, these results suggest that the majority of HTLV-Is prevailing in South Amer ica have spread from Amerindians, some of whom are likely to have possessed this human retrovirus from the beginning of their settlement in South Amer ica. (C) 1999 Academic Press.