Verification of HTLV-I infection in the Solomon Islands by virus isolation and gene amplification

We report the detection of human T-lymphotropic virus type I (HTLV-I) genomic sequences by polymerase chain reaction in lymphocyte cultures of three unrelated native Solomon Islanders, including a patient with HTLV-I myeloneuropathy, residing in widely separated regions. In addition, we have isolated HTLV-I from T-cell lines derived from two of these individuals. Virus-specific proteins of 15, 19, 24, 46 and 53 kilodaltons were detected by immunofluorescence and Western immunoblot, using serum from a Colombian patient with HTLV-I myeloneuropathy, sera from HTLV-I-infected rabbits, and monoclonal and polyclonal antibodies against HTLV-I gag and env gene products. Amplification of HTLV-I gag, pol and env sequences by polymerase chain reaction confirmed that the viral isolates were HTLV-I, not HTLV-II. Our data clearly demonstrate that HTLV-I does exist in Melanesia. Although the Solomon Islands viral isolates resemble prototype strains of HTLV-I, we believe they represent variants of HTLV-I, particularly in the light of our recent isolation of an HTLV-I variant from Papua New Guinea. Nucleotide sequence analysis of these viral strains, now in progress, should clarify the molecular epidemiology and phylogeny of HTLV-I.