Input of NAcGlc6SO3 epitopes (sulfotopes) present in Trypanosoma cruzi glycoproteins, and their specific antibodies, in the infection and immune pathogenesis of experimental Chagas disease

Abstract

Background: Trypanosoma cruzi, the causative agent of Chagas disease contains a major antigen, cruzipain (Cz). The C-terminal domain (C-T) of this glycoprotein bears N-linked high mannose type sulfated oligosaccharide chains and is responsible for most antibodies in natural and experimental infections. Mice immunization with C-T has shown that sulfate moieties of Cz molecule are targets for specific immune responses and responsible for cardiac ultrastructural abnormalities in absence of infection. Methods & Materials: After the molecular characterization of these sufotopes, BALB/c mice were immunized with Cz/C-T, prior and after desulfation treatment, and with NAcGlc6SO3-BSA, to be further sublethally challenged with trypomastigotes to investigate whether they are involved in immunepathogenesis and/or infection of experimental Chagas disease. Results: C-T-immunized mice showed low IL-4 levels and elevated IFN-γ concentration by capture ELISA using C-T as stimulus and a cytokines profile compatible with a mixed response showing: Th2 tendency with excessively high IFNγ and raised IL-17 levels. By contrast, dC-T-immunized-mice presented undetectable IL-4 levels, low IFN-γ level and a cytokines profile like that of control but with a significantly elevated IL-10 value. In addition, ultrastructural cardiac alterations and main immunorecognition of fibrils and mitochondria were observed in C-T-immunized mice both confronted with polyclonal anti-Cz and myosin adsorbed anti-Cz sera. After sublethal challenge, elevated parasitaemias were observed. Mortality was 20 and 80% in C-T and dC-T immunized mice, respectively and mice from dC-T group that survived presented severe muscle alterations. BSA-NAcGlc6SO3-immunized mice mounted a predominant IgG1and IgG2b immune response followed by IgG2a, demonstrating the immunodominance of the sulfotope and a vigorous mice memory T cells response, similarly to C-T-immunized mice. After sublethal infection, mice immunized with the sulfotope displayed excessively elevated parasitemias, similar IFN-γ levels and significant lower mortality percentage than those from BSA-NAcGlc control group. Furthermore, mice treated by passive transference of sulfate-specific IgGs purified from sera of BSA-NAcGlc6SO3-immunized mice, exhibited ultrastructural alterations in cardiac tissue. After challenge, those treated with sulfate-specific IgGs presented higher parasitemias than controls Conclusion: Altogether, these findings have demonstrated that sulfotopes and their specific antibodies display a dual role, participating in the host-tissue immunopathogenicity of experimental Chagas disease and favoring the infection by T. cruzi.