Proteome-wide cellular immunity approach to P. falciparum antigen identification

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DESCRIPTION (provided by applicant): The long-term objective of this project is to identify and prioritize for malaria vaccine development novel P. falciparum antigens and epitopes that are recognized by individuals exposed to P. falciparum in the context of multiple genetic restrictions, by mining the P. falciparum genomic sequence. The feasibility of a malaria vaccine is supported by experimental data demonstrating that protective immunity can be induced by exposure to intact Plasmodium parasites. The antigenic targets of this protection have not been identified. P. falciparum expresses an estimated 5,300 proteins, each of which is a potential target of protective immune responses. Although the P. falciparum genome, proteome, and transcriptome have now been elucidated, it has not been obvious how to use this information for vaccine development. The current application offers a solution to this problem, by applying an integrated approach that incorporates bioinformatic predictions, HLA supertype considerations, high-throughput MHC peptide binding assays, and cellular assays. The specific aims are to: (1) identify, from the complete set of approximately 2500 genes expressed in the pre-erythrocytic stage of the P. falciparum parasite life cycle, those proteins that correspond to immunodominant antigens recognized in the context of multiple genetic restrictions by individuals exposed to P. falciparum; (2) for a subset of the100 most immunodominant antigens, identify the CD8+ and CD4+ T epitopes that are the targets of P. falciparum parasite-induced immunity, and their associated HLA Class I and II restriction elements; (3) for 50 antigens, characterize five epitopes/antigen for extent of sequence conservation or immunological cross-reactivity between different Plasmodium strains; and (4) for 10 antigens, evaluate the capacity to protect against Plasmodium sporozoite challenge in mice. It is expected that the proposed research will result in the identification of novel P. falciparum antigens that will represent good candidates for a vaccine that would be effective in all ethnicities. Additionally, data will demonstrate whether protective immune responses are targeted against only a few immunodominant antigens, or are broadly distributed against a large range of antigens, and will therefore provide valuable information regarding the potential multivalency of candidate malaria vaccines. It is expected that the proposed research will have important outcomes for malaria vaccine development. It will identify novel P. falciparum antigens that should represent good candidates for a subunit malaria vaccine that would be effective in all human populations regardless of ethnicity. Additionally, data will demonstrate whether protective immune responses are targeted against only a few immunodominant antigens, or are broadly distributed against a large range of antigens, and will therefore provide valuable information regarding the potential multivalency of candidate malaria vaccines.