Chagas' Disease: IgG Isotypes against Trypanosoma cruzi Cytosol Acidic Antigens in Patients with Different Degrees of Heart Damage

We studied the reactivity of IgG isotypes detected in sera from chronic Chagas' disease patients with a Trypanosoma cruzi cytosol acidic antigenic fraction (F IV) and parasite epimastigote forms (EPI). All patients studied had positive serology for Chagas' disease, with normal electrocardiogram (Group I), abnormal ECG without cardiomegaly (Group II), and abnormal ECG with cardiomegaly (Group III). The highest levels of antibodies were observed in sera from Group II patients. A high prevalence of IgG1 and IgG3, low levels of IgG2, and IgG4 isotypes against EPI were found in sera from all groups by ELISA. When the F IV was used as antigen, IgG1 was the main antibody isotype detected by ELISA in all groups of patients. The antigenic recognition patterns by IgG1 among the different clinical groups by immunoblotting of F IV revealed some differences. The sera from Group I recognized antigens of F IV of 80, 53, and 43 kDa. Sera from Group III recognized mainly one antigenic band of 43 kDa. Finally, sera from Group II showed greater diversity of binding by IgG1, detecting between one and six bands in the 80 and 30 kDa ranges.