Rye γ-70 and γ-35 secalins and barley γ-3 hordein cross-react with ω-5 gliadin, a major allergen in wheat-dependent, exercise-induced anaphylaxis

Background Patients with wheat-dependent, exercise-induced anaphylaxis experience severe allergic reactions when exercising after ingestion of wheat. The major wheat allergen associated with these reactions is a omega -5 gliadin, and patients following a gluten-free diet have remained free of symptoms. Objective The aim of this study was to examine whether allergens cross-reacting with wheat omega -5 gliadin are present in rye, barley and oats. Methods Sera from 23 adult patients with wheat-dependent, exercise-induced anaphylaxis were examined. Cereal allergens cross-reacting with wheat omega -5 gliadin were identified by immunoblot inhibition. The cross-reactive allergens were purified by gel filtration and reversed-phase chromatography and submitted to amino acid sequencing. Cross-reactivity was further studied by IgE ELISA and ELISA inhibition, and in vivo reactivity by skin prick testing. Results In immunoblotting rabbit anti-omega -5 gliadin antibodies bound to 70 kDa and 32 kDa proteins in rye and a 34-kDa protein in barley, but not to proteins in oats. N-terminal sequencing identified these proteins as rye gamma -70 secalin, rye gamma -35 secalin and barley gamma -3 hordein, correspondingly. In ELISA 21/23 (91%) patients with wheat-dependent, exercise-induced anaphylaxis showed IgE antibodies to purified gamma -70 secalin, 19/23 (83%) to gamma -35 secalin and 21/23 (91%) to gamma -3 hordein. In ELISA inhibition omega -5 gliadin inhibited over 90% of the IgE binding of pooled patient sera to solid-phase gamma -secalins and gamma -3 hordein. Skin prick testing gave positive reactions to gamma -70 secalin in 10/15 (67%) patients, to gamma -35 secalin in 3/15 (20%) patients and to gamma -3 hordein in 7/15 (47%) patients. Conclusion The results of this study show that gamma -70 and gamma -35 secalins in rye and gamma -3 hordein in barley cross-react with omega -5 gliadin, a major allergen in wheat-dependent, exercise-induced anaphylaxis. These findings suggest that also rye and barley may elicit symptoms in patients with wheat-dependent, exercise-induced anaphylaxis.