Identification and molecular characterization of human T lymphotropic virus type II infections in intravenous drug abusers in the former South Vietnam.

Previous serological studies have demonstrated that some 60% of intravenous drug abusers (IVDAs) in urban areas of the former South Vietnam are infected with HTLV-II. In the present report we have attempted to characterize the viruses using restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis of the provirus long terminal repeat (LTR) region. RFLP analysis of nine samples demonstrated that all were infected with the HTLV-IIb subtype. The HTLV-IIa subtype was not detected. Phylogenetic analysis of the nucleotide sequences demonstrated that the viruses clustered closely with HTLV-IIb isolates present in IVDAs from the New York City area. The present molecular analysis together with the previously reported absence of HTLV-II infection in North Vietnam supports the view that HTLV-II may have been introduced from the United States to this part of Asia by military personnel during the Vietnam conflict.