Immunization with a recombinant ASP-2/Transialidase chimeric protein induces robust protective immunity in both murine and canine models of Chagas’ disease

Abstract

We have systematically shown that the Amastigote Surface Protein-2 (ASP-2) and Transialidase (TS) antigens either in the form of recombinant protein or encoded in the plasmids and human adenovirus 5 (hAd5) confer strong protection against different lineages of Trypanosoma cruzi parasites. Herein we generated a chimeric protein containing the most immunogenic regions for T and B cells from ASP-2 and TS (DTT-1) and evaluated its efficacy in comparison with our standard protocol of heterologous prime-boost using plasmids and hAd5. Our results show that mice immunized with DTT-1 protein together with Poly-ICLC (Hiltonol) become highly resistant to challenge with the Y strain of T. cruzi, showing a large decrease in tissue parasitism, parasitemia and no lethality. This protection lasted for at least 3 months after the last boost of immunization and an equivalent level of protection induced by the DNA/hAd5 protocol. DTT-1 induced high levels of T. cruzi-specific antibodies and IFNγ-producing T cells and protection was mediated by B lymphocytes, CD8 T cells and IFNγ. Finally, we evaluated the toxicity, immunogenicity and efficacy of the DTT-1 and DNA/hAd5 formulations in dogs. Mild collateral effects were detected at the site of vaccine inoculation. While the chimeric protein associated to Poly-ICLC induced high levels of antibodies and CD4+ T cell responses, the DNA/hAd5 induced no antibodies, but a strong CD8+ T cell response. Immunization with either vaccine formulations protected dogs against challenge with the Berenice strain of T. cruzi. Despite to the similar efficacy, we conclude that moving ahead with DTT-1 together with Hiltonol is advantageous over the hAd5 vaccine due to the cost-benefit for development and large-scale production.