Sera from Adult T-cell Leukemia Patients React with Envelope and Core Polypeptides of Adult T-cell Leukemia Virus

Sera from five Japanese patients with adult T-cell leukemia (ATL) showed in the immunofluorescence test for ATL-associated antigen (ATLA) titers ranging from 320 to 1280. Control sera from three healthy adults were negative. These eight sera were used to immunoprecipitate radiolabeled polypeptides from three cell lines infected with adult T-cell leukemia virus (ATLV) and two noninfected human cell lines. Cells were labeled either metabolically with [35S]cysteine, [35S]methionine, or [3H]glucosamine, or chemically with 125-iodine. Immunoprecipitates from cells, virus, and concanavalin A-enriched supernatants were analyzed by polyacrylamide gel electrophoresis. Cells producing ATLV contain gp68, the putative precursor to ATLV envelope polypeptides, gp46, and possibly p15, in addition to several nonglycosylated polypeptides between 40 to 70 kDa. Gp46 is shed into the culture medium and appears to be loosely attached to the viral and cellular surface. After purification on density gradients viral particles contain immunoreactive p24, p19, p15, and small amounts of gp46. Kinetics of synthesis, distribution, size, biochemical characteristics, and immunoreactivity of these polypeptides strongly suggest that most of them are structural components of ATLV or their precursors. Apparently, the intracellular ATLA complex predominantly represents precursors of viral structural polypeptides and gp46 is the viral envelope glycopolypeptide.