Genetic linkage of autologous T cell epitopes in a chimeric recombinant construct improves anti-parasite and anti-disease protective effect of a malaria vaccine candidate

We have reported the design of polyvalent synthetic and recombinant chimeras that include promiscuous T cell epitopes as a viable delivery system for pre-erythrocytic subunit malaria vaccines. To further assess the ability of several Plasmodium T cell epitopes to enhance vaccine potency, we designed a synthetic gene encoding four Plasmodium yoelii merozoite surface protein 1 (PyMSP1) CD4+ promiscuous T cell epitopes fused in tandem to the homologous carboxyl terminal PyMSP119 fragment. This Recombinant Modular Chimera (PyRMC-MSP119) was tested for immunogenicity and protective efficacy in comparative experiments with a recombinant protein expressing only the PyMSP119 fragment. Both proteins induced comparable antibody responses. However PyRMC-MSP119 elicited higher anti-parasite antibody titers and more robust protection against both hyper-parasitemia and malarial anemia. Most importantly, passive transfer of anti-PyRMC-MSP119, but not anti-PyMSP119 antibodies protected against heterologous challenge. These studies show that protective efficacy can be significantly improved by inclusion of an array of autologous promiscuous T cell epitopes in vaccine constructs.