Recombinant high molecular weight‐glutenin subunit‐specific IgE detection is useful in identifying wheat‐dependent exercise‐induced anaphylaxis complementary to recombinant omega‐5 gliadin‐specific IgE test

BACKGROUND: Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a special form of food allergy typically induced by exercise after ingestion of wheat products. We identified wheat omega-5 gliadin and high molecular weight-glutenin subunit (HMW-glutenin) as major allergens for WDEIA and clarified that simultaneous detection of serum IgE binding to synthetic epitope peptides of these allergens identifies more than 90% of WDEIA patients. However, the short synthetic peptides are not suitable for CAP-fluorescent enzyme-immunoassay (CAP-FEIA), which is widely utilized for detecting allergen-specific IgE. OBJECTIVE: In this study, we constructed a CAP-FEIA with recombinant HMW-glutenin, and evaluated its usefulness in identifying the patients with WDEIA. METHODS: Recombinant HMW-glutenin was expressed as histidine-tag protein in E. coli and purified by histidine-tag affinity column. Wheat, gluten, recombinant omega-5 gliadin, epitope peptide of HMW-glutenin, native and recombinant HMW-glutenin specific IgE in the sera from 48 patients with WDEIA, 16 patients with atopic dermatitis (AD) who had no immediate allergic reaction after wheat ingestion and 12 healthy controls were determined by using CAP-FEIA method. RESULTS: In 16 AD patients without wheat allergy 12 of them (75%) had positive results for native HMW-glutenin test in contrast to epitope peptide of HMW-glutenin (12.5%) and recombinant HMW-glutenin test (12.5%). These results indicate the native HMW-glutenin test has low specificity. Sensitivity and specificity of the IgE test with recombinant HMW-glutenin were 16.7% and 92.9%. These are well compatible with results obtained by using epitope peptide of HMW-glutenin. However, sensitivity and specificity reached to 93.8% and 92.9%, when the test was combined to the test with recombinant omega-5 gliadin. CONCLUSIONS AND CLINICAL RELEVANCE: We demonstrated that recombinant HMW-glutenin is best for CAP-FEIA system in point of stability and specificity and confirmed that detection of specific IgE against recombinant HMW-glutenin is useful for diagnosis of WDEIA when combined with the CAP-FEIA (recombinant omega-5 gliadin) test.