Identification of vacuolar serine proteinase as a major allergen of Aspergillus fumigatus by immunoblotting and N-terminal amino acid sequence analysis

Background Aspergillus species are common airborne fungi that have been identified as causative agents of extrinsic bronchial asthma. More than 10 allergens from A. fumigatus have been recently characterized by cDNA cloning. Objective The objective of this study is to identify A. fumigatus allergens through immunoblot analysis using sera from asthmatic patients. Methods IgE-binding components of A. fumigatus and IgE cross-reactivity among allergens of different prevalent airborne fungal species were analysed by immunoblot and immunoblot inhibition, respectively, using sera from asthmatic patients. The N-terminal amino acid sequences of major allergens identified were determined by Edman degradation. Results Among two batches (70 and 41 sera) of asthmatic sera tested, 19 (27%) and 14 (34%), respectively, have IgE immunoblot reactivity towards components of A. fumigatus. A 34-kDa protein that reacts with IgE antibodies in 15 (79%) and 11 (79%) of the 19 and 14 positive samples, respectively, may be considered a major allergen of A. fumigatus. The N-terminal amino acid sequences of the 34 kDa major allergen and the 30.5 and 30 kDa IgE-binding components of A. fumigatus showed sequence identity to that of the vacuolar serine proteinase from A. fumigatus. The results from immunoblot inhibition show IgE cross-reactivity among major allergens of A. fumigatus, P. notatum and P. oxalicum. Conclusions Results obtained suggest that the 34 kDa major allergen of A. fumigatus may be a vacuolar serine proteinase. There is IgE cross-reactivity among serine proteinase allergens of A. fumigatus, P. notatum and P. oxalicum.