Demonstration of Trypanosoma cruzi antigen in serum from patients with Chagas' disease.

Serum samples from 30 patients who had had Chagas' disease demonstrated either by serological tests or blood culture were examined for circulating antigens of Trypanosoma cruzi by an enzyme-linked immunosorbent assay (ELISA). Circulating antigens were demonstrated in the sera of 15 patients; in 9 of these blood culture for T. cruzi had been positive but no parasites had been demonstrated in the remaining 6. Absorption of ELISA-positive sera with an antiserum against T. cruzi abolished the reactivity of the sera in the ELISA test, suggesting that parasite antigens were present in the sera. Absorption of the ELISA-positive sera and of the antisera used in the ELISA test with tissue extracts did not cause any sera to become negative. This indicates that tissue antigens or antibodies were not responsible for the positive ELISA results in the patients' sera. Demonstration of circulating antigens of T. cruzi in patients with Chagas' disease may be of diagnostic and prognostic value.