Detection of high concentrations of HTLV-1 p24 and a novel gag precursor, p45, in serum immune complexes of a healthy seropositive individual.

Circulating immune complexes from sera of 6 patients with adult T-cell leukemia and 8 asymptomatic carriers infected with the human T-cell leukemia virus type 1 (HTLV-1) were precipitated with polyethylene glycol, and the precipitates were tested for the presence of viral antigen p24 by Western blot, using affinity-purified radiolabelled goat antibody to p24 as a probe. p24 and a larger protein of Mr 45,000 immunologically related to p24 were detected at concentrations of up to 100-200 ng/ml in one of the carriers, while all other samples were negative. The concentration of the Mr 45,000 protein in the immune complexes was considerably higher than that of p24. Analysis of an HTLV-1 producer cell line, G-11/MJ, by competition Western blots and gag-specific antibodies, showed the presence of a hitherto unrecognized viral protein p45 which contains both p19 and p24 and probably represents an intermediate precursor of these proteins. The results present direct evidence of production of HTLV-1 proteins in an asymptomatically infected individual.