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T Cell Reactive Epitopes of Shrimp Tropomyosin


Food allergy is an increasing problem in the American population. In young children the most frequent foods causing allergic reactions are cow's milk, egg, peanut, wheat and soy. Among adults, the most frequent foods causing allergic reactions are shellfish, peanuts, tree nuts and fish. <P>Presently, the primary therapy for food allergy is avoidance of the food. While this is effective, it requires careful attention to the diet, and, even then, allergenic foods can be disguised in mixtures of other foods. <P>A recent nationwide telephone survey revealed that fish or shellfish allergy was reported in 2% of respondents, and shellfish allergy was commonly reported among adults, up to 3.1% in the age group of 41 to 60. Shrimp allergy can be exquisite; a recent publication reported on a systemic anaphylactic reaction in a young adult whose shrimp exposure occurred as a consequence of kissing. Although analyses of shrimp derived allergens have reported three separate molecular entities, recent studies have concluded that tropomyosin is the predominant allergen. <P> Tropomyosin is a pan allergen with sequence homology between crustaceans, such as shrimp, crab and lobster, and mollusks, such as oyster, scallop and squid. IgE antibodies from shrimp allergic patients not only react with shrimp tropomyosin, but also tropomyosins from lobster, crab, abalone, whelk, mussel, scallop, oyster, clam, cuttlefish, squid and octopus. Recent studies suggest that T-cell epitopes can be utilized as vaccines to reduce sensitivity of allergic patients. Injection of T-cell epitopes from Fel d 1, the predominant cat allergen, into cat allergic patients reduced the intensity of late phase reactions and the proliferation of T-cells induced by cat allergen and reduced the symptoms of patients exposed to cats. Injection of T-cell epitopes from phospholipase A2 similarly blunted immune responsiveness. <P> In the proposed studies we will identify the T-cell epitopes of shrimp tropomyosin with the goals of establishing a table of synthetic peptide epitopes able to stimulate helper T-cells from allergic individuals and of identifying candidate HLA-DR restriction elements (gene products) that are most likely involved in controlling T-cell responses to these epitopes. With these results we will plan clinical studies testing the effect of administration of these T-cell epitopes to shrimp allergic patients. <P>The proposed studies will identify the T-cell epitopes of shrimp tropomyosin. Presently, treatment of food allergies is essentially by avoidance. Prior published information on T-cell epitope peptide vaccines for the treatment of allergic diseases are most promising. Knowledge of the T-cell epitopes of shrimp tropomyosin will permit production of a vaccine and thus set the stage for a trial of T-cell epitope peptide therapy in allergy to shrimp.

Gleich, Gerald
University of Utah
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