Trypanosoma cruzi. Surface antigens of blood and culture forms

Abstract

The surface polypeptides of both cultured and blood forms of Trypanosoma cruzi were iodinated by the glucose oxidase-lactoperoxidase technique. Blood-form trypomastigotes (BFT) isolated from infected mice displayed a major 90,000-M(r) component. In contrast, both epimastigotes and trypomastigotes obtained from acellular cultures expressed a smaller 75,000-M(r) peptide. Both major surface components were presumably glycoproteins in terms of their binding to concanavalin A-Sepharose 4B. Within a 3-h period, both blood and culture forms synthesized their respective surface glycoproteins (90,000 M(r) and 75,000 M(r), respectively) in vitro. [ 35S]methionine-labeled surface peptides were immunoprecipitated with immune sera of both human and murine origin. A panel of sera from patients with chronic Chagas' disease and hyperimmunized mice recognized similar surface peptides. These immunogens were the same components as the major iodinated species. The major BFT surface peptide was readily removed by trypsin treatment of the parasites, although this procedure did not affect the 75,000-M(r) peptide from the culture forms. Two-dimensional polyacrylamide gel electrophoresis revealed that the 90,000-M(r) peptide found on BFT was an acidic protein of isoelectric point (pI) 5.0, whereas, the 75,000-M(r) peptide from culture-form trypomastigotes has a pI of 7.2. The 90,000-M(r) component is thought to be responsible for the anti-phagocytic properties of the BFT.