Fast omega-gliadin is a major allergen in wheat-dependent exercise-induced anaphylaxis

Wheat-dependent exercise-induced anaphylaxis is an anaphylaxy induced by physical exercise after ingestion of wheat. An immediate-type hypersensitivity to water/salt-insoluble fraction of wheat proteins (gluten) has been considered to underlie in this disease.

The aim of the study is to determine the major allergen in Japanese patients with wheat-dependent exercise-induced anaphylaxis by using a panel of purified wheat gliadins and glutenins.

Water/salt-insoluble wheat proteins, alpha-gliadin, beta-gliadin, gamma-gliadin, fast omega-gliadin, slow omega-gliadin, high molecular weight glutenin and low molecular weight glutenin, were purified, and five patients with wheat-dependent exercise-induced anaphylaxis, whose diagnose had been determined by positive-challenge test, were evaluated for skin prick test, dot-blotting test and CAP-RAST inhibition test by using these purified wheat proteins.

The fast omega-gliadin was the most potent allergen among these water/salt-insoluble proteins when evaluated by skin prick test and dot-blotting test. Fast and slow omega-gliadin, and gamma-gliadin caused dose-dependent inhibition of the serum IgE-binding to solid-phase gluten in the patients. The incubation with fast omega-gliadin of the patient's serum caused dose-dependent inhibition in the IgE-binding to gamma-gliadin as well as slow omega-gliadin, indicating a cross-reactivity of these proteins in IgE-binding.

We concluded that fast omega-gliadin is a major allergen among these water/salt-insoluble proteins for wheat-dependent exercise-induced anaphylaxis in Japanese patients, and IgE against fast omega-gliadin cross-reacts to gamma-gliadin and slow omega-gliadin.