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 ω-5 gliadin, and patients following a gluten-free diet have remained free of symptoms.
The aim of this study was to examine whether allergens cross-reacting with wheat ω-5 gliadin are present in rye, barley and oats.
Sera from 23 adult patients with wheat-dependent, exercise-induced anaphylaxis were examined. Cereal allergens cross-reacting with wheat ω-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.
In immunoblotting rabbit anti-ω-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 γ-70 secalin, rye γ- 35 secalin and barley γ-3 hordein, correspondingly. In ELISA 21/23 (91%) patients with wheat-dependent, exercise-induced anaphylaxis showed IgE antibodies to purified γ-70 secalin, 19/23 (83%) to γ-35 secalin and 21/23 (91%) to γ-3 hordein. In ELISA inhibition ω-5 gliadin inhibited over 90% of the IgE binding of pooled patient sera to solid-phase γ-secalins and γ-3 hordein. Skin prick testing gave positive reactions to γ-70 secalin in 10/15 (67%) patients, to γ-35 secalin in 3/15 (20%) patients and to γ-3 hordein in 7/15 (47%) patients.
The results of this study show that γ-70 and γ-35 secalins in rye and γ-3 hordein in barley cross-react with ω-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.