Food allergy is an increasing problem in the American population. Among adults, the most frequent cause of food allergy is the ingestion of shellfish. <P>Currently, the solely therapy for shellfish allergy is the avoidance of the food. Recent studies have concluded that tropomyosin is the predominant allergen in shellfish allergy. Shellfish allergy is an immediate-type hypersensitivity reaction to tropomyosin that is mediated by IgE. Naive CD4 T cell recognition of antigenic tropomyosin peptides presented in the context of HLA class II molecules is thought to be a key component in the mechanism of sensitization and production of IgE. Specific subsets of activated CD4 T cells, particularly TH2 cells, favor the production of IgE. Little is known about the specific CD4 T cell tropomyosin-derived epitopes and mechanisms of antigen presentation that selectively evoke TH2 cells in patients with shellfish allergy. <P>The aims of this exploratory grant application are to identify and validate CD4 T cell tropomyosin-derived epitopes and to characterize CD4 T cell responses in individuals with shellfish allergy upon stimulation with HLA class II-tropomyosin-derived peptides. The specific hypothesis behind the proposed research is that HLA class II molecules bind sets of promiscuous tropomyosin-derived peptides and that differences in the binding kinetics of HLA class II-peptide complexes influence the differentiation of naive CD4 T cells into distinct CD4 T cell subsets (i.e. TH2 cells) that drive IgE-mediated shellfish allergy. <P>In vitro binding assays are proposed to identify potential CD4 T cell epitopes from shellfish tropomyosin and ex-vivo functional assays will be performed to validate immunogenic CD4 T cell epitopes. Further characterization of antigenic peptide binding to HLA class II molecules in terms of binding kinetics and cytokine production are proposed to assess peptide-HLA binding kinetics and its relationship to allergenicity in terms of naive CD4 T cell activation. <P>Taken all together, the experiments proposed in this application will allow the identification of a panel of common peptides binding to different HLA class II molecules that will facilitate the development of epitope-based tolerizing therapies and immunodiagnostic tools in patients with shellfish allergy across different populations.