Alkaline serine proteinase:: A major allergen of Aspergillus oryzae and its cross-reactivity with Penicillium citrinum

Background: Aspergillus species are common indoor airborne fungi and have been considered as causative agents of human allergic disorders. However, allergens of different Aspergillus species have not been effectively characterized. The object of this study was to identify and characterize IgE-binding components of Aspergillus oryzae. Methods. Allergens of A. oryzae were identified by immunoblot analysis using sera from asthmatic patients. The N-terminal amino acid sequences of allergens thus identified were determined by Edman degradation. The antigenic and the allergenic cross-reactivities between allergens of different fungi were analyzed by immunoblotting and immunoblot inhibition analysis, respectively, using a monoclonal antibody (MoAb) 55A against the 33-kD major allergen of Penicillium citrinum and a mixture of IgE-containing asthmatic serum samples. Results: Thirteen components of A. oryzae ranging in apparent molecular weight from 16 to 42 kD react with IgE antibodies. A 34-kD component that showed intense IgE-binding reactivity and was detectable in the highest frequency in our asthmatic serum samples tested was considered a major allergen of A. oryzae. The 34-kD component also reacted with MoAb 55A. Results from immunoblot inhibition studies also demonstrated the IgE cross-reactivity between the 34-kD major allergens of A. oryzae and P citrinum. In addition, the sequence of the N-terminal 18 amino acid residues of the 34-kD major allergen of A. oryzae was found to be identical to that of the alkaline serine proteinase from the same Aspergillus species. Conclusion: The 34-kD major allergen of A. oryzae is an alkaline serine proteinase. There is IgE cross-reactivity between the major serine proteinase allergens of A. oryzae and P. citrinum.