Covalent vaccination with Trypanosoma cruzi Tc24 induces catalytic antibody production

Abstract

Trypanosoma cruzi 24 (Tc24) is a recently described B-cell superantigen (BC-SAg) expressed by all developmental stages of T. cruzi, the causative agent of Chagas disease. BC-SAgs are immunoevasins that interfere with the catalytic response available to a subset of natural antibodies comprising the preimmune (innate) repertoire. Electrophilic modifications of BC-SAgs facilitate the formation of highly energetic covalent reactions favouring B-cell differentiation instead of B-cell downregulation. Therefore, the aim of this study was to convert the inhibitory signals delivered to B-cells with specificity for Tc24 into activating signals after conjugating electrophilic phosphonate groups to recombinant Tc24 (eTc24). Covalent immunization with eTc24 increased the binding affinity between eTc24 and naturally nucleophilic immunoglobulins with specificity for this BC-SAg. Flow cytometric analyses demonstrated that eTc24 but not Tc24 or other electrophilically modified control proteins bound Tc24-specific IgM B-cells covalently. In addition, immunization of mice with eTc24 adjuvanted with ISA720 induced the production of catalytic responses specific for Tc24 compared to the abrogation of this response in mice immunized with Tc24/ISA720. eTc24-immunized mice also produced IgMs that bound recombinant Tc24 compared to the binding observed for IgMs purified from non eTc24-immunized controls. These data suggest that eTc24 immunization overrides the immunosuppressive properties of this BC-SAg.

Exploring the performance of Escherichia coli outer membrane vesicles as a tool for vaccine development against Chagas disease

“…Trypanosoma cruzi Tc24 antigen has been widely analyzed as part of prophylactic 37 , 38 , 39 and therapeutic 50 , 51 strategies in mice and non-human primates undergoing acute and chronic infection. Thus, initiating the evaluation of OMVs as possible immunogens and nanocarriers of this candidate protein was an excellent opportunity to accomplish our goal of exploring their immune characteristics in a T. cruzi acute model of infection.…”

“…2B-C), thus confirming the immunogenic nature of vesicles. Tc24 immunogenicity has been proved so far; (37,38,39) however, even though OMVs-Tc24 are in fact carrying Tc24 -as corroborated in Fig. 1D -the amount of protein contained within engineered OMVs would not be enough to trigger a robust specific antibody response against the antigen of interest [Fig.…”

Vaccine Design against Chagas Disease Focused on the Use of Nucleic Acids

“…The administration of a DNA vaccine encoding Tc24 antigen can prevent Chagas disease progression both in murine and canine models [78]. Moreover, the administration of recombinant Tc24 protein can decrease parasitemia and cardiac parasite burden in immunized animals compared to controls [78,80]. Tc24 is highly conserved, especially the EF hand domains (structural domain helix-loop-helix found in calcium-binding proteins) and the calcium-binding loops, therefore Tc24 is a good vaccine antigen candidate [78,79].…”

Location and expression kinetics of Tc24 in different life stages of Trypanosoma cruzi

“…Additionally, soluble Tc24 and Tc24 in EVs could be targeted by inducing catalytic antibodies that degrade Tc24 through IgM-mediated hydrolysis. [16,25] While it is yet to be elucidated what the effect of secreted Tc24 is on the host immune response, it is clear that Tc24 is an important target for cell-mediated immunity. Indeed, since T. cruzi is an intracellular pathogen most of its lifecycle, it is thought that a cytotoxic T cell response might be very effective in eliminating T. cruzi-infected host cell and clear the infection.…”

“…[12] A suitable platform was developed for the large scale production of recombinant Tc24 [13] and Tc24 was selected as one of the key antigens under consideration for a human therapeutic Chagas disease vaccine [14] supported by multiple preclinical studies with a recombinant Tc24 vaccine. [12,15,16] As previously published, to prevent aggregation of recombinant Tc24 during the production process, four cysteine codons were replaced by serine codons. The resulting antigen, designated Tc24-C4, showed less aggregation while secondary structure and immunogenicity was not altered, and the production process was found to be suitable for technology transfer in preparation for its production under current Good Manufacturing Practices (cGMP).…”