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, I gM, and IgA anti-Trypanosoma cruzi antibodies in serum samples from bo th groups of patients were compared by enzyme-linked immunosorbent ass ay (ELISA) employing either one of four antigenic fractions: mouse lam inin (LAM), which reacts through Gal alpha 1-3Gal epitopes expressed o n trypomastigote surface; whole intact trypomastigotes (TCT); trypomas tigotes excreted/secreted antigens (TESA); and epimastigote alkaline e xtract (EAE). The selection of T. cruzi antigen preparations was based on their relative content of surface and internal antigens found in t rypomastigote forms. The proportion of IgG reactive to carbohydrate ep itopes was assessed through the decay of IgG reactivity from acute and chronic sera after m-periodate oxidation of solid-phase bound antigen s. Trypomastigote and TESA antigens recognized by IgG from acute and c hronic sera were also compared by immunoblotting. ELISA and immunoblot ting data showed that: (1) the proportion of IgG directed to trypomast igote surface antigens was higher in acute than in chronic sera, where as the opposite was found for internal antigens, (2) acute sera contai ned a higher percentage of IgG reactive to trypomastigote carbohydrate epitopes than chronic sera, and (3) anti-T. cruzi IgA was found exclu sively in acute sera and led to 100% positivity when LAM, TCT, and TES A were employed as antigens. IgA ELISA with these antigens and IgG imm unoblotting pattern with TESA could be useful as serological markers f or the acute phase of human Chagas disease. (C) 1996 Wiley-Liss, Inc.