Functional conservation of the neutralizing domains on the external envelope glycoprotein of cosmopolitan and melanesian strains of human T cell leukemia/lymphoma virus type I.

To determine if the immunodominant neutralizing epitopes on the external envelope glycoprotein of the recently identified sequence variants of human T cell leukemia/lymphoma virus type I (HTLV-I) from Melanesia are functionally conserved, sera from Japanese patients with adult T cell leukemia and from HTLV-I-infected Melanesians of Papua New Guinea and the Solomon Islands were tested for neutralizing antibodies by use of vesicular stomatitis virus pseudotypes bearing envelope antigens of Japanese and Melanesian HTLV-I strains. Neutralizing antibody titers of the Japanese and Melanesian sera and of monoclonal and polyclonal antibodies directed against a known neutralizing epitope on the external envelope glycoprotein of HTLV-I were equivalent against the Japanese and Melanesian HTLV-I pseudotypes. The demonstrated two-way cross-neutralization between Japanese and Melanesian strains of HTLV-I indicates that their antigenic determinants for neutralization are functionally indistinguishable and that HTLV-I exists as a single serotype worldwide.