Identification of two metallothioneins as novel inhalative coffee allergens cof a 2 and cof a 3.

BACKGROUND: Dust of green coffee beans is known to be a relevant cause for occupational allergic disorders in coffee industry workers. Recently, we described the first coffee allergen (Cof a 1) establishing an allergenic potential of green coffee dust. OBJECTIVE: Our aim was to identify allergenic components of green coffee in order to enhance inhalative coffee allergy diagnosis. METHODS: A Coffea arabica pJuFo cDNA phage display library was created and screened for IgE binding with sera from allergic coffee workers. Two further coffee allergens were identified by sequence analysis, expressed in E. coli, and evaluated by Western blots. The prevalence of sensitization to recombinant Cof a 1, Cof a 2, and Cof a 3 and to commercially available extract was investigated by ELISA (enzyme-linked immunosorbent assay) respectively CAP (capacity test) screening in 18 sera of symptomatic coffee workers. RESULTS: In addition to the previously described chitinase Cof a 1, two Coffea arabica cysteine-rich metallothioneins of 9 and 7 kDa were identified and included in the IUIS Allergen Nomenclature as Cof a 2 and Cof a 3. Serum IgE antibodies to at least one of the recombinant allergens were found in 8 out of 18 symptomatic coffee workers (44%). Only 2 of the analysed sera (11%) had reacted previously to the commercial allergy test. CONCLUSIONS: In addition to the previously described Cof a 1 we have identified two further coffee proteins to be type I coffee allergens (Cof a 2 and Cof a 3) which may have a relevant potential for the specific diagnosis and/or therapy of coffee allergy.

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 alphabeta-gliadin, the frequency of sensitization was investigated by means of ELISA screening of 153 bakers' sera with the recombinant alphabeta-gliadin. Furthermore, the allergenicity of native total gliadin (alphabeta, gamma, omega) was analyzed by means of ImmunoCAP. RESULTS: One cDNA clone was identified as an alphabeta-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.