Survey of antitrypanosome antibodies and studies of their specificity and autoimmunity.
As a part of investigations to characterize trypanosome infections in Taiwan, sera collected from patients admitted to Veterans General Hospital, Taipei were tested for antitrypanosome antibodies. A Trypanosoma cruzi extract-based enzyme-linked immunosorbent assay (ELISA) was used to screen and titrate 1,297 patient sera. High antitrypanosome titers were detected in 166 (12.8%) of these sera. Retitration of random samples of the high titer (HT) sera indicated a 5.4% false positive. Thirteen donors with high antitrypanosome ELISA titers were followed up. Twelve of then remained high serum titers also showed high ELISA titers against an extract of Trypanosoma conorhini. Hemocultures conducted on freshly drawn blood specimens of the 13 subjects did not provide any evidence of trypanosome infections. Electrophoretic analyses of sera from HT and low titer (LT) patients suggested differences between serum proteins of the subjects in each of the groups. Atypical reactions were observed in immunodiffusion tests performed with HT and LT sera and trypanosome extracts, while western blot analyses revealed a complex pattern of binding by both sera. The qualitative and quantitative differences in these tests suggested interactions of T. cruzi antigens with donor antibodies against unrelated antigens and/or with autoantibodies. Subsequent analyses did not indicate any association between rheumatoid factor and the reactivities of the HT sera with the parasites. However, antinuclear antibodies were detected with an indirect fluorescent antibody test (IFAT) in 50% of the HT sera and 22% of the LT sera. No differences were found between the levels of antilaminin activity of the two groups. The IFAT employing T. cruzi epimastigotes was positive for 100% of the HT sera and 22% of the LT sera. The data indicate that the high seropositivity recognized in this study is due in part to the activities of cross-reacting antibodies and/or autoantibodies in the sample population.