Trypanosoma cruzi: antibody production and T cell response induced by stage-specific surface glycoproteins purified from metacyclic trypomastigotes.

The main surface glycoproteins of metacyclic trypomastigotes of Trypanosoma cruzi, gp90, gp82, and gp35/50, were purified and the immune response elicited by these antigens was analyzed. Balb/c mice immunized with antibody-affinity-purified gp82, plus alum as adjuvant, produced antibodies that recognized both the gp82 and the heterologous gp90 and gp35/50. On the other hand, antisera to gp90 reacted only with the homologous antigen, either by immunoprecipitation or by immunoblotting. Neither sera reacted with unrelated proteins in ELISA. Both antisera lysed 90-100% metacyclic forms in a complement-mediated reaction, a property associated with protection. However, in contrast to gp90, previously shown to induce protective immunity against acute T. cruzi infection, gp82 was not immunoprotective. Lymph node (LN) cells of mice primed with gp82 or gp90, which display 40% amino acid sequence identity at the carboxy terminal domain, were strongly stimulated in vitro by either one of these antigens. Proliferation, inhibitable by anti-CD4 but not by anti-CD8 antibodies, was T. cruzi-specific, no activation being observed with irrelevant antigens. LN cells of mice immunized with unrelated proteins did not proliferate in vitro in the presence of gp82 or gp90. The 35/50-kDa glycoconjugate, which was phenol-extracted, did not elicit any detectable antibody or T cell response.