Asp f6, an Aspergillus allergen specifically recognized by IgE from patients with allergic bronchopulmonary aspergillosis, is differentially expressed during germination

Background: Aspergillus fumigatus is a pathogenic mould causing allergic and invasive respiratory diseases. Allergic bronchopulmonary Aspergillosis (ABPA) is a severe pulmonary complication resulting from hypersensitivity to A. fumigatus proteins. Aspergillus allergen Asp f6 is recognized by IgE from ABPA patients, but not from sensitized individuals, a fact that can be used to differentiate between these two groups of allergic patients. Methods: Proteins from hyphae, resting and germinating conidia of A. fumigatus were compared by SDS-PAGE. Protein identification was performed using MALDI-TOF mass spectrometry. Recombinant A. fumigatus allergens were used to isolate specific monoclonal antibodies (mab) from a hybridoma bank generated against Aspergillus proteins. Results: A hyphae-specific 23 kDa A. fumigatus protein was identified as the allergen Asp f6/manganese-dependent superoxide dismutase (MnSOD). Differential expression of MnSOD was confirmed by immunoblot using a specific mab. In contrast, Asp f8 another intracellular, but not ABPA-specific allergen, was detected in hyphae and conidia. Conclusions: Aspergillus fumigatus is able to colonize its environment by the formation of hyphae. Hyphae are found in the lung of ABPA patients, but not in patients suffering from atopic asthma. Our finding that Asp f6 is specifically expressed in hyphae might explain why an IgE response to Asp f6 is specific for ABPA patients.