Development of a vaccine against Helicobacter pylori to prevent gastric cancer

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DESCRIPTION (provided by applicant): Gastric adenocarcinoma accounts for 19,000 cases and 12,000 deaths annually in the USA. The main factor in the risk of this cancer is infection by the bacterium Helicobacter pylori. Aims: Our long-term objective is to develop a vaccine to prevent H. pylori infection and its associated complications, including gastric cancer. The specific aims of this application are: a) to construct 3 candidate products based on H. pylori urease B: purified recombinant protein (done), DNA plasmid (done) and HBsAg-urease B (this application); and b) to test these three products in mice to determine their immunogenicity and protective efficacy. Health relatedness: this project is within the agency's mission to prevent cancer. Research Design: To prepare HBsAg-urease B, the HBsAg-S gene will be cloned into the yeast vector pYES2 to generate the construct pYES2/HBS. The H. pylori urease B dominant epitope (DKSIKEDVQFAD) will then be amplified and inserted into HBsAg-S in one of four locations: before the HBsAg gene (N-terminus), after the HBsAg gene (C-terminus), in the 1st hydrophilic domain (aa 32-74), or in the 2nd hydrophilic domain (aa 110- 156). The constructs will then be used to transform Saccharomyces cerevisiae (INVSc1) yeast cells and protein expression induced by growing cells in galactose-containing medium. The supernatant and lyzed cell pellets will then be analyzed for formation of 22-nm particles and antigenic reaction of the HBsAg and urease B epitopes. The constructs with the best antigenicity will then be used - along with our previously prepared purified urease B protein and DNA ureB vaccine - to immunize BALB/c mice in a series of experiments (evaluating various products, various routes and various combinations) to compare their in vivo immunogenicity and their efficacy to protect against H. felis infection. Innovation: two particularly novel approaches are proposed in this application for H. pylori vaccination: prime-boost immunization with purified protein and DNA vaccine, and presentation of the urease B antigen by a carrier protein (HBsAg). Significance: the results of these experiments should identify one or more candidate products and vaccination strategies suitable for further development into an effective H. pylori vaccine. And, prevention of H. pylori infection should eventually lead to elimination of its associated complications, including gastric cancer.