MODULAR CHIMERIC VACCINES TAILORED FOR MALARIA PARASITES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have reported proof of principle studies designed to determine the potential of multimeric polypeptides as a delivery system for pre-erythrocytic malaria vaccines. The first generation of polypeptide chimeras, which we have called linear peptide chimeras (LPC), was designed to include linear sequences representing well-characterized pre-erythrocytic B cell epitopes. Structural analyses of several erythrocytic stage vaccine candidates revealed that protective antibodies predominantly recognize functional domains that exhibit complex tertiary structure. To confirm that our strategy to improve immunogenicity of malaria vaccine candidates can also be used for non-linear structured domains, we designed P. yoelii chimeric recombinant protein comprising autologous promiscuous T cell epitopes assembled in tandem and linked to carboxyl terminal domain of well-characterized merozoite surface protein 1 known as PyMSP119. The synthetic gene was codon-optimized for expression in E. coli and the recombinant product, that we have called Recombinant Modular Chimera (RMC), used for comparative experiments of immunogenicity and protective efficacy with control protein that only included PyMSP119 protein fragment. The inclusion of autologous T cell epitopes did not alter the integrity of the recombinant product. Relevantly, T cell epitopes were successfully expressed and able to induce epitope-specific T cell responses. RMC generated robust protection to both hyper-parasitemia and severe anemia after experimental challenge with homologous P. yoelii strain. Most importantly, we found that RMC induced functional antibodies that protected against heterologous challenge more efficiently than antibodies induced by control protein. Based on experimental evidence that P. yoelii pre-erythrocytic (LPC) and erythrocytic stage (RMC) recombinant chimeric proteins induced protective immunity, we decided to evaluate the potential synergistic effect of combining LPC and RMC in a single immunogen. We created a hybrid synthetic gene encoding an amino-terminal pre-erythrocytic LPC and a carboxyl terminal erythrocytic RMC. Preliminary data indicate that such hybrid vaccine is able to induce sterilizing immunity in mice.