Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a severe IgE-mediated allergic reaction provoked by the combination of wheat-ingestion with intensive physical exercise over the next few hours. Among wheat proteins, -5 gliadin, which is one of the components of fast -gliadin, has been reported as a major allergen in the anaphylaxis. In this study, we detected IgE-binding epitopes within the primary sequence of -5 gliadin using arrays of overlapping peptides synthesized on derivatized cellulose membranes. Sera from four patients with WDEIA having specific IgE to the fast -gliadin were used to probe the membrane. Seven epitopes, QQIPQQQ, QQLPQQQ, QQFPQQQ, QQSPEQQ, QQSPQQQ, QQYPQQQ, and PYPP, were detected within the primary sequence of -5 gliadin. By using sera of 15 patients, 4 of them, QQIPQQQ, QQFPQQQ, QQSPEQQ, and QQSPQQQ, were found to be dominant epitopes. Mutational analysis of the QQIPQQQ and QQFPQQQ indicated that amino acids at positions Gln 1 , Pro 4 , Gln 5 , Gln 6 , and Gln 7 were critical for IgE binding. These results will provide a useful tool for developing safer wheat products in addition to diagnostic and immunotherapy techniques for WDEIA.Food-dependent exercise-induced anaphylaxis is a distinct form of food allergy induced by physical exercise (1). Food items such as shrimp (2), hazelnut (3), buckwheat (4), corn (5), and celery (6) are responsible for the development of food-dependent exercise-induced anaphylaxis. However, of all of the various kinds of food, wheat is reported to be the allergen with the highest frequency in Japan (7). Symptoms are typically generalized urticaria and severe allergic reactions such as shock or hypotension. Because of this serious reaction, it is important to determine the causative food to avoid the allergic reaction. A challenge test consisting of ingestion of the assumed food followed by intense physical exercise is the only reliable method to determine the causative food and to diagnose the disease. However, the challenge test is not always safe because in some cases the test induces an anaphylactic shock. In addition, the most reliable treatment for this disease is to avoid taking the causative food or, alternatively, to take a rest after meals. However, in the case of wheat allergy, elimination causes a decline in the quality of life for the patients. Thus, an in vitro diagnostic method as well as hypoallergenic wheat is necessary for patients with wheat-dependent exercise-induced anaphylaxis (WDEIA). 1Recent studies have revealed the IgE-binding epitopes of several food allergens including egg (8), milk (9, 10), soybean (11), and peanut (12), whereas the IgE-binding epitopes for wheat allergen are controversial. Wheat protein is composed of water/salt-soluble proteins and water/salt-insoluble proteins. Proteins in the water/salt-soluble fraction, such as ␣-amylase inhibitor, peroxidase, glycerinaldehyde-3-phosphate dehydrogenase, serpin, and triosephosphate isomerase, have been considered to be major allergens in patients with bakers' asthma (13-15...
We demonstrated for the first time that blood gliadin levels correlate with clinical symptoms induced by exercise and aspirin in patients with WDEIA. These findings suggest that exercise and aspirin facilitate allergen absorption from the gastrointestinal tract.
Food allergy is an adverse immune response to certain kinds of food. Although any food can cause allergic reactions, chicken egg, cow's milk, wheat, shellfish, fruit, and buckwheat account for 75% of food allergies in Japan. Allergen-specific immunoglobulin E (IgE) antibodies play a pivotal role in the development of food allergy. Recent advances in molecular biological techniques have enabled the efficient analysis of food allergens. As a result, many food allergens have been identified, and their molecular structure and IgE-binding epitopes have also been identified. Studies of allergens have demonstrated that IgE antibodies specific to allergen components and/or the peptide epitopes are good indicators for the identification of patients with food allergy, prediction of clinical severity and development of tolerance. In this review, we summarize our current knowledge regarding the allergens and IgE epitopes in the well-researched allergies to chicken egg, cow's milk, wheat, shrimp, and peanut.
Wheat ω-5 gliadin and a high m.w. glutenin subunit (HMW-glutenin) have been reported as major allergens in wheat-dependent exercise-induced anaphylaxis. A simultaneous detection of specific IgE to epitope sequences of both proteins is considered to be a reliable method for diagnosis of wheat-dependent exercise-induced anaphylaxis. However, the IgE-binding epitope of HMW-glutenin remains unknown. The aim of this study was to determine the IgE-binding epitopes of HMW-glutenin to establish a useful system of identifying patients with wheat-dependent exercise-induced anaphylaxis. For determination of IgE-binding epitopes of HMW-glutenin overlapping peptides were synthesized and reactivities of IgE Abs in the sera of patients to those peptides were analyzed. Three IgE-binding epitopes, QQPGQ, QQPGQGQQ, and QQSGQGQ, were identified within primary sequence of HMW-glutenin. Epitope peptides, which include IgE-binding sequences of ω-5 gliadin and a HMW-glutenin, were synthesized and peptide-specific IgE Abs were measured by CAP-System fluorescent enzyme immunoassay. Twenty-nine of 30 patients with wheat-dependent exercise-induced anaphylaxis had specific IgE Abs to these epitope peptides. None of the 25 sera from healthy subjects reacted to both epitope peptides. Twenty-five patients with atopic dermatitis who had specific IgE to wheat and/or gluten had very low or nonexistent levels of epitope peptide-specific IgE Abs. These results indicated that measurement of IgE levels specific to epitope peptides of ω-5 gliadin and HMW-glutenin is useful as an in vitro diagnostic method for the assessment of patients with wheat-dependent exercise-induced anaphylaxis.
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