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

BACKGROUND

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.

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Sequence and properties of HMW subunit 1Bx20 from pasta wheat (Triticum durum) which is associated with poor end use properties

The gene encoding high-molecular-weight (HMW) subunit 1Bx20 was isolated from durum wheat cv. Lira. It encodes a mature protein of 774 amino acid residues with an M(r) of 83,913. Comparison with the sequence of subunit 1Bx7 showed over 96% identity, the main difference being the substitution of two cysteine residues in the N-terminal domain of subunit 1Bx7 with tyrosine residues in 1Bx20. Comparison of the structures and stabilities of the two subunits purified from wheat using Fourier-transform infra-red and circular dichroism spectroscopy showed no significant differences. However, incorporation of subunit 1Bx7 into a base flour gave increased dough strength and stability measured by Mixograph analysis, while incorporation of subunit 1Bx20 resulted in small positive or negative effects on the parameters measured. It is concluded that the different effects of the two subunits could relate to the differences in their cysteine contents, thereby affecting the cross-linking and hence properties of the glutenin polymers.