Abstract
Trypanosoma cruzi cruzipain (Cz) bears a C-terminal domain (C-T) that contains sulfated epitopes "sulfotopes" (GlcNAc6S) on its unique N-glycosylation site. The effects of in vivo exposure to GlcNAc6S on heart tissue ultrastructure, immune responses, and along the outcome of infection by T. cruzi, were evaluated in a murine experimental model, BALB/c, using three independent strategies. First, mice were pre-exposed to C-T by immunization. C-T-immunized mice (C-T(IM)) showed IgG2a/IgG1 <1, induced the production of cytokines from Th2, Th17, and Th1 profiles with respect to those of dC-T(IM), which only induced IL-10 respect to the control mice. Surprisingly, after sublethal challenge, both C-T(IM) and dC-T(IM) showed significantly higher parasitemia and mortality than the control group. Second, mice exposed to BSA-GlcNAc6S as immunogen (BSA-GlcNAc6S(IM)) showed: severe ultrastructural cardiac alterations while BSA-GlcNAc(IM) conserved the regular tissue architecture with slight myofibril changes; a strong highly specific humoral-immune-response reproducing the IgG-isotype-profile obtained with C-T(IM); and a significant memory-T-cell-response demonstrating sulfotope-immunodominance with respect to BSA-GlcNAc(IM). After sublethal challenge, BSA-GlcNAc6S(IM) showed exacerbated parasitemias, despite elevated IFN-γ levels were registered. In both cases, the abrogation of ultrastructural alterations when using desulfated immunogens supported the direct involvement of sulfotopes and/or indirect effect through their specific antibodies, in the induction of tissue damage. Finally, a third strategy using a passive transference of sulfotope-specific antibodies (IgG-GlcNAc6S) showed the detrimental activity of IgG-GlcNAc6S on mice cardiac tissue, and mice treated with IgG-GlcNAc6S after a sublethal dose of T. cruzi, surprisingly reached higher parasitemias than control groups. These findings confirmed the indirect role of the sulfotopes, via their IgG-GlcNAc6S, both in the immunopathogenicity as well as favoring T. cruzi infection.