Longitudinal study of immune response in human Chagas' disease.

Immune response, clinical status, and reactivity to heart tissue were studied longitudinally for 1 year in 42 patients with Chagas' disease (South American trypanosomiasis). The patients were divided into two groups. Group 1 was composed of patients with chagasic infection with no evidence of heart disease. Group 2 patients had chagasic infection and cardiomyopathy. Humoral immune response to Trypanosoma cruzi was measured serologically, and cell-mediated immune responses to T. cruzi and rat heart antigens were evaluated by lymphoblastogenesis. Parasitemia was detected by xenodiagnosis. Serological tests for anti-T. cruzi antibodies were positive in all patients of both groups, and the titers were significantly higher in group 2. A change of titer during the study period was more frequently associated with a positive xenodiagnosis in both groups. Lymphoblastogenesis in response to T. cruzi antigen was positive at least once in all patients of both groups. When rat heart antigen was used, 44.4% of the patients in group 1 and 40.0% of those in group 2 were positive on at least one occasion. Xenodiagnosis revealed that 20% of the patients in group 1 and 50% of those in group 2 (P = 0.01) had detectable circulating parasites during the course of the study. Positive xenodiagnosis was associated with lower lymphoblastogenic responses to T. cruzi in group 1 patients, suggesting the presence of a regulatory or modulatory mechanism which is lost in patients with chagasic cardiomyopathy. No relationship between positive xenodiagnosis and positive lymphoblastogenesis in response to heart antigen could be established. In addition, no correlation was found between clinical heart disease and reactivity to rat heart tissue.