Genotypic characteristics of HTLV-II isolates from Amerindian and non-Indian populations.

The Amerindian human T-cell lymphotropic virus type II isolate HTLV-IIG12 has been demonstrated to be an HTLV-IIb with several unique features, including several restriction enzyme site changes, a distinctive pre-gag region, a stop codon within the pol gene, and an extended Tax protein. In this study, HTLV-II isolates from Amerindian and non-Indian populations were characterized by restriction enzyme site analysis to determine the prevalent HTLV-II subtype. In addition, DNA amplification by the polymerase chain reaction and Southern blot analyses were used to probe for the HTLV-IIG12 pre-gag region. Our results showed that of 13 Guaymi Indian isolates subtyped, all were HTLV-IIb, and that approximately one third of 17 isolates had the unique pre-gag region. While other HTLV-II-infected groups contained both HTLV-IIa and HTLV-IIb isolates, none of these isolates showed evidence of the distinctive HTLV-IIG12 pre-gag region. Lastly, DNA sequence analysis was used to determine the prevalence of the stop codon within the pol gene open reading frame. These analyses revealed that the occurrence of a stop codon within this sequence appeared to be characteristic of most HTLV-IIb subtypes. These results further our understanding of the genetic variations and evolution of the HTLV-II viruses within the endemically infected Amerindian populations, as well as U.S. intravenous drug users and other non-Indian populations.