ABSTRACT
Infection with Trypanosoma cruzi can cause chronic Chagas' disease manifestations (cardiac, gastrointestinal), although most persons with chronic infection have no ill effects (indeterminate form). Cell-mediated immunity (CMI) responses are believed to be intrinsically important in the containment of T. cruzi and in the pathogenesis of Chagas' disease. Humoral and CMI responses were investigated in 70 T. cruzi-infected persons from an endemic area in northeastern Brazil and in 30 uninfected controls. An epidemiologic survey, physical examination, and blood evaluation were conducted for each subject. The 70 chronically infected persons were subclassified into three clinical groups: indeterminate, cardiac, and gastrointestinal. Serum was tested for antibodies to T. cruzi by hemagglutination assay, indirect immunofluorescent assay, and enzyme-linked immunosorbent assay, and for autoantibodies to tubulin. Serum levels of soluble interleukin-2 receptor (sIL-2R), albumin, and C-reactive protein (CRP) were also measured to assess one parameter each of immunosuppression, nutritional status, and inflammation. The proliferative response of peripheral blood mononuclear cells (PBMC) to T. cruzi antigens, mitogen (phytohemagglutinin), and antigen-free controls was also assessed. Our data did not reveal any significant differences in serum levels of antibodies to T. cruzi, antibodies to tubulin, albumin, CRP, or sIL-2R among the subgroups of infected individuals. The data demonstrate differences in CMI responses. Trypanosoma cruzi trypomastigote lysate stimulated proliferation of PBMC from infected persons, but not uninfected controls. Patients with symptomatic Chagas' disease (cardiac and gastrointestinal groups) had decreased cellular responses to T. cruzi lysate (median proliferation index [PI] = 3), compared with those in the indeterminate group (median PI = 9; P < 0.005). Further investigations of the mechanism of this reduced CMI response in those with chronic disease may yield insights into the pathogenesis of Chagas' disease.