High Specificity of sIgE to α-/β-Gliadin and Limited Reactivity to Non-Gluten Proteins in Wheat Allergy Dependent on Augmentation Factors (WALDA).

BACKGROUND: Wheat allergy dependent on augmentation factors (WALDA) represents the most common form of IgE-mediated wheat allergy in adults. Although ω5-gliadin is the major allergen in WALDA, sIgE reactivity to non-gluten wheat proteins remains poorly characterized. METHODS: Serum samples from 54 adults with challenge-confirmed WALDA and 21 tolerant controls (including 5 with positive sIgE to ω5-gliadin) from two German centres were analysed for sIgE reactivity to 19 recombinant wheat proteins and the cross-reactive carbohydrate determinant (CCD) MUXF3. RESULTS: sIgE to α-/β-gliadin (Tri a 21.0101) was highly specific for WALDA, present in 29/54 patients (53.7%) but absent in controls (100% specificity, p < 0.001). Receiver operating characteristic analysis revealed excellent discriminatory ability (area under the curve = 0.85) with an optimal cut-off of 0.22 kU/l. Reactivity to non-gluten wheat proteins was limited, with 24.1% of patients showing sIgE to thioredoxin, 11.3% to dehydrin, 9.3% to any α-amylase/trypsin inhibitor subunit, and minimal sIgE to non-specific lipid transfer proteins (Tri a 14), thiol reductase, triosephosphate isomerase, peroxiredoxin, serpin, glyceraldehyde-3-phosphate dehydrogenase, serine protease inhibitor-like allergen, and peroxidase. Non-gluten reactivity correlated strongly with MUXF3 CCD (ρ = 0.776), total IgE (ρ = 0.646), and wheat extract sIgE (ρ = 0.534; all p < 0.001). Grass pollen-sensitized individuals showed increased non-gluten protein reactivity (p < 0.001). Controls demonstrated higher MUXF3 CCD reactivity (38.1% vs. 11.6%, p < 0.05). CONCLUSION: The data suggest that WALDA is characterized by highly specific reactivity to gliadin proteins, with limited sensitization to non-gluten wheat components. sIgE to α-/β-gliadin represents a promising diagnostic biomarker with superior specificity compared with ω5-gliadin alone.