Exoantigens of Trypanosoma cruzi. II. Physicochemical properties

This paper describes the characterization assays of exoantigens of Trypanosoma cruzi. Plasma of acutely infected BALB/c mice was used as source of exoantigens. The antigenic activity was heat stable, soluble in 10% trichloroacetic acid and sensible to sodium metaperiodate. The treatment with neuraminidase did not affect the antigenic activity demonstrable by counterimmunoelectrophoresis with rabbit serum to total homogenate of culture forms of T. cruzi. The treatment with trypsin did not eliminate the precipitating activity of exoantigen, but it caused the breakdown of the molecule, as may be inferred from its behaviour in Sephacryl S 200. These results suggest that exoantigen is composed of peptide and carbohydrate moieties, with the epitopes located in the sugar moieties. It seems that sialic acid is not involved in the active part of the molecule. The molecular weight of exoantigen was estimated at 200 kilodaltons approximately. By affinity chromatography, an immunogenic parasite antigen from plasma of acutely infected mice was isolated.