Identification of wheat gliadins as an allergen family related to baker's asthma

Background: Flour is still one of the most common causes of occupational asthma worldwide. Thus far, little is known about the relevant allergens causing baker's asthma. Therefore the reliability of current diagnostic procedures is insufficient. Only few of the suspected causative wheat allergens have been hitherto characterized on the molecular level. Objective: The aim was to identify and characterize unknown wheat allergens related to baker's asthma to improve the reliability of diagnostic procedures. Methods: A wheat pJuFo cDNA phage display library was created and screened for IgE binding to wheat proteins with pooled sera from patients with baker's asthma. After identifying an alpha beta-gliadin, the frequency of sensitization was investigated by means of ELISA screening of 153 bakers' sera with the recombinant alpha beta-gliadin. Furthermore, the allergenicity of native total gliadin (alpha beta, gamma, omega) was analyzed by means of ImmunoCAP. Results: One cDNA clone was identified as an alpha beta-gliadin. Serum IgE antibodies to the recombinant allergen were found in 12% of bakers with occupational asthma. Of the asthmatic bakers, 33% showed sensitization to native total gliadin; 4% of them had negative results on routine IgE testing with wheat extract. Conclusions: Gliadins represent a newly discovered family of inhalable allergens in baker's asthma. This finding demonstrates that water-insoluble proteins might also represent causative allergens.