The long term objective is to develop innovative commercial products for investigating the IgA immune response to Helicobacter pylori, a major causative agent of gastritis and duodenal and gastric ulcers. These products will be based on an ELISA incorporating Protein B, a highly specific and sensitive IgA binding protein to measure IgA to H. pylori in a variety of human fluids. They will be used to monitor the mucosal immune response to H. pylori vaccines and therapies and provide a means to monitor risk of gastric cancer and other diseases resulting from H. pylori infection. Protein B-based ELISAs will have many advantages over commercially available immunoassays for H. pylori. Protein B binds with a very high affinity for human IgA resulting in assays that are very sensitive and reproducible with low backgrounds. Specific objectives for Phase I are to develop an assay for quantitative measurement of serum IgA against H. pylori, develop saliva assays for secretory IgA to H. pylori as a measure of mucosal immune response and to investigate urine as a carrier of IgA to H. pylori. During Phase II, the assays will be precisely characterized and optimized, then validated in clinical studies and vaccine trials. PROPOSED COMMERCIAL APPLICATIONS: The Protein B-H. pylori ELISA for serum will be an innovative research tool to study the role of specific IgA as a biomarker for diseases such as gastric cancer. The technology can be extended beyond H. pylori to develop clinical biomarker assay products for other infectious diseases. The saliva assay has the potential to be used in the development of not only H. pylori vaccines, but also any vaccine that requires a mucosal immune response to be effective, such as HIV.