53.    Mucosal heterologous prime-boost vaccination generates systemic immunity and               protects against a human protozoan parasite 

Chagas Disease, is a potentially life-threatening illness cause by the protozoan parasite Trypanosoma cruzi. It is recognized by WHO as a neglected tropical disease, which affects 12 million people in Latin America. After 100 years of its discovery, no effective vaccine to prevent or treat the infection is approved. We have recently introduced Traspain, a recombinant (rec) trivalent antigen rationally designed based on the structural signature and immunological properties of each component. Here, we employed Traspain or its components in a series of mucosal DNA-prime – recProtein boost protocols where DNA was delivered orally by attenuated Salmonella and boost doses were performed with a intranasal subunit vaccine strategy formulated with either ODN-CpG or c-di-AMP (CDA) as adjuvant. Results indicate that administration of CDA resulted in a more balanced and potent immune response compared to CpG as was evidenced by higher frequency of diverse antigen specific cytokine secreting cells by ELISPOT. Moreover, antigen combination impacted directly in the robustness of the immune response triggered. Vaccine effectiveness assessed with lethal and sub-lethal challenge showed a
reduction in parasite load and chronic inflammation that was particularly significant for the formulation carrying traspain gene plus CDA boost. Detailed analysis of the T cell response by flow cytometry specifically compared between traspain and antigen combination group showed that higher levels of antigen specific CD8 and CD4 T cell functionality were observed in traspain group and were associated with a better experimental outcome in vaccinated animals. These results indicate that vaccine formulations that maximize T cell functionality as Salmonella carrying Traspain gene boosted with CDA might represent an ideal strategy for the design of effective anti- T.cruzi vaccines.