Mechanisms of Mycobacterial Antigen Processing

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DESCRIPTION (provided by applicant): Tuberculosis is a global disease of immense impact on mankind. More people die of tuberculosis each year than due to other diseases. The available BCG vaccine is partially protective against children and is not effective against adult disease. We have determined that one major factor that contributes to the reduced efficacy of BCG vaccine is its ability to prevent effective antigen processing in macrophages. We also discovered that a mutant vaccine from Mycobacterium tuberculosis (?fbpA) protects mice better than BCG. This investigation will therefore use this candidate vaccine and test the hypothesis that improved 'peptide antigen processing' in dendritic cells will pave the way for development of a more effective vaccine against tuberculosis. Due to phagosome maturation arrest, structural antigens of BCG vaccine remain sequestered within phagosomes while its secreted antigens are minimally processed for MHC-II and MHC-I peptide epitopes. In contrast, ?fbpA novel vaccine undergoes limited phagosome maturation, with enhanced peptide presentation for MHC-II pathway and we hypothesize that it also presents peptides through MHC-I mechanism. Unlike the currently used BCG vaccine, ?fbpA has intact ESAT-6 and CFP-10 proteins and we will enhance antigenicity by modification of pathogen components through selective deletion of genes as well as over expression of ESAT-6, Ag85B and CFP-10 antigens. We will therefore identify pathogen components that elicit protective immune responses relevant to vaccine design and prepare novel vaccine constructs through genetic engineering with increased immunogenicity and safety. The major goal of this proposal is to develop a phagosome maturation competent derivative of ?fbpA vaccine that is expected to be more efficiently processed by dendritic cells to present more immunogenic peptides than previous vaccines. The aims are to- I) Investigate the intracellular strategies that increase the immunogenicity of ?fbpA candidate vaccine by enhancing the presentation of MHC-II peptides, and II) Characterize the MHC-I peptides that increase the immunogenicity of ?fbpA candidate vaccine.