Antibodies against three purified structural proteins of the human type-C retrovirus, HTLV, in Japanese adult T-cell leukemia patients, healthy family members, and unrelated normals.

The immunological relationship of human T-cell leukemia/lymphoma virus (HTLV) and the virus found in Japanese adult T-cell leukemia/lymphoma (ATL) was investigated in detail by testing the specific binding of serum antibodies from Japanese ATL patients and normal Japanese donors to the purified HTLV proteins p24, p19, and p15. Sera were prescreened for antibodies to p24. Of those positive, 67% of the ATL sera and 78% of the normal sera were further shown to have antibodies against p19. In both groups 17% had antibodies to p15. Generally, the average antibody titers were twice as high in ATL as in normal sera. Competition radioimmunoprecipitation assays done with various sera and involving HTLV-producing cells, virus-positive cells from a Japanese ATL patient, and virus-positive cultured T cells of one of his healthy family members as competing materials demonstrated no differences between the p24, p19, and p15 found in these cells. These results provide strong and detailed immunological evidence that the human retrovirus isolates first made from US patients with cutaneous T-cell malignancies, and those made later in Japanese ATL are either identical or very closely related strains of the same virus, HTLV, a finding verified in other detailed analyses of the HTLV genomes of the respective isolates. To date only HTLV-II, isolated from a US case of hairy-cell leukemia of a T-cell type, is a distinct additional human retrovirus class.