Analysis of anti-HTLV-I antibody by strip radioimmunoassay--comparison with indirect immunofluorescence assay, enzyme-linked immunosorbent assay and membrane immunofluorescence assay

Antibodies against human T-cell lymphotropic virus type I (HTLV-I) in the sera from 60 patients with adult T-cell leukemia and 21 carriers who were suspected of having HTLV-I infection were investigated by indirect immunofluorescence assay (IFA), enzyme-linked immunosorbent assay (ELISA), membrane immunofluorescence assay (MIA) and strip radio immunoassay based on the western blotting technique (SRIA). The sera of 2 of the carriers who were seropositive in IFA and ELISA were negative in MIA and did not react with virus-specific proteins by SRIA. Two sera were negative in IFA and ELISA. These sera were positive in MIA and reacted with only the envelope-related glycoprotein (gp46) and not with gag-related proteins (p28, p24, p19) by SRIA. These findings suggest that the main antigens defined by IFA and ELISA are gag-related proteins and some sera which do not contain anti-HTLV-I antibodies give false-positive results because of the reaction to unknown cellular components. Also some sera may have antibodies against only envelope glycoproteins, and these sera may give false-negative results in IFA and ELISA.