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.