Wheat alpha-amylase inhibitor: a second route of allergic sensitization

Low molecular weight allergens may be responsible for hypersensitivity reactions after the ingestion of wheat.

The purpose of this investigation was to identify relevant, low molecular weight allergens after the ingestion of wheat protein.

Serum samples were collected from seven children with wheat allergy and one adult with baker's asthma. Control serum samples were collected from wheat-tolerant patients. Wheat extracts were prepared and separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in 12.5% gels revealing numerous protein bands. IgE immunoblot analysis of crude wheat extracts identified multiple IgE-binding proteins. Wheat proteins were separated further with two-dimensional gel electrophoresis, which was followed by IgE immunoblotting investigations.

Immunoblot analysis identified a 15 kd wheat protein that bound IgE from all five children with wheat allergy who were evaluated. No IgE binding to this wheat protein was demonstrated in any of the control subjects. Samples representing the 15 kd wheat protein (isoelective point, 5.85) were selected. The N-terminal peptide sequence of this protein (residues 1 to 20) matched to a wheat alpha-amylase inhibitor.

These data demonstrate that wheat alpha-amylase inhibitor is a relevant allergen in patients experiencing hypersensitivity reactions after the ingestion of wheat protein. This wheat protein, which has been implicated as an important allergen in patients with baker's asthma, represents a sensitizing allergen after both ingestion and inhalation.