Changes in isotype composition and antigen recognition of anti-Trypanosoma cruzi antibodies from acute to chronic Chagas disease.

This report describes differences in humoral immune response of acute and chronic phases of human Chagas disease. The reactivities of IgG, IgM, and IgA anti-Trypanosoma cruzi antibodies in serum samples from both groups of patients were compared by enzyme-linked immunosorbent assay (ELISA) employing either one of four antigenic fractions: mouse laminin (LAM), which reacts through Gal alpha 1-3Gal epitopes expressed on trypomastigote surface: whole intact trypomastigotes (TCT); trypomastigotes excreted/secreted antigens (TESA); and epimastigote alkaline extract (EAE). The selection of T. cruzi antigen preparations was based on their relative content of surface and internal antigens found in trypomastigote forms. The proportion of IgG reactive to carbohydrate epitopes was assessed through the decay of IgG reactivity from acute and chronic sera after m-periodate oxidation of solid-phase bound antigens. Trypomastigote and TESA antigens recognized by IgG from acute and chronic sera were also compared by immunoblotting. ELISA and immunoblotting data showed that: (1) the proportion of IgG directed to trypomastigote surface antigens was higher in acute than in chronic sera, whereas the opposite was found for internal antigens, (2) acute sera contained a higher percentage of IgG reactive to trypomastigote carbohydrate epitopes than chronic sera, and (3) anti-T. cruzi IgA was found exclusively in acute sera and led to 100% positivity when LAM, TCT, and TESA were employed as antigens. IgA ELISA with these antigens and IgG immunoblotting pattern with TESA could be useful as serological markers for the acute phase of human Chagas disease.