Wheat IgE-Mediated Food Allergy in European Patients: α-Amylase Inhibitors, Lipid Transfer Proteins and Low-Molecular-Weight Glutenins

TLDR

Wheat allergy diagnosis is hindered by inconsistent protein extraction methods, absence of controlled challenge studies comparing protein fractions, and limited knowledge of IgE binding differences between raw and cooked wheat. The study used sera from 22 patients across Italy, Denmark, and Switzerland to perform SDS‑PAGE/immunoblotting of raw and cooked albumin/globulin, gliadin, and glutenin fractions, assessed LTP thermal stability spectroscopically, and examined IgE cross‑reactivity with grass pollen via blot inhibition. The α‑amylase/trypsin inhibitor subunits were the dominant allergens across all raw and cooked wheat fractions, while a 9‑kDa LTP and low‑molecular‑weight glutenin subunits were also heat‑stable, grass‑pollen‑non‑cross‑reactive allergens, with LTP being a major allergen only in Italian patients and the α‑amylase inhibitor implicated in wheat‑dependent exercise‑induced anaphylaxis.

Abstract

<i>Background:</i> Three main problems hamper the identification of wheat food allergens: (1) lack of a standardized procedure for extracting all of the wheat protein fractions; (2) absence of double-blind, placebo-controlled food challenge studies that compare the allergenic profile of Osborne’s three protein fractions in subjects with real wheat allergy, and (3) lack of data on the differences in IgE-binding capacity between raw and cooked wheat. <i>Methods:</i> Sera of 16 wheat-challenge-positive patients and 6 patients with wheat anaphylaxis, recruited from Italy, Denmark and Switzerland, were used for sodium dodecyl sulfate-polyacrylamide gel electrophoresis/immunoblotting of the three Osborne’s protein fractions (albumin/globulin, gliadins and glutenins) of raw and cooked wheat. Thermal sensitivity of wheat lipid transfer protein (LTP) was investigated by spectroscopic approaches. IgE cross-reactivity between wheat and grass pollen was studied by blot inhibition. <i>Results:</i> The most important wheat allergens were the α-amylase/trypsin inhibitor subunits, which were present in all three protein fractions of raw and cooked wheat. Other important allergens were a 9-kDa LTP in the albumin/globulin fraction and several low-molecular-weight (LMW) glutenin subunits in the gluten fraction. All these allergens showed heat resistance and lack of cross-reactivity to grass pollen allergens. LTP was a major allergen only in Italian patients. <i>Conclusions:</i> The α-amylase inhibitor was confirmed to be the most important wheat allergen in food allergy and to play a role in wheat-dependent exercise-induced anaphylaxis, too. Other important allergens were LTP and the LMW glutenin subunits.