Basidiomycete allergy: identification and characterization of an important allergen from Calvatia cyathiformis

Basidiomycetes were not considered as major aeroallergen sources until spore traps revealed the prevalence of basidiospores, which were in some cases associated with epidemic outbreaks of asthma. More recently, we established that approximately one third of subjects with respiratory allergic disease were skin prick test positive to basidiospore extracts. Bronchial challenge with these extracts induced reversible immediate and late phase bronchospasm in sensitive subjects. Screening individual RAST-positive sera for reactivity to immunoprinted Calvatia cyathiformis spore extract indicated that a basic component with pI 9.3 reacted with 63% of test sera. Further analysis by RAST and immunoprint (IP) inhibition showed that this component, Cal c Bd9.3, appeared to cross-react with spore extracts from 3 of 5 other species tested. To isolate this component for additional analysis, a protocol was used with two sequential stages of preparative isoelectric focusing (IEF) followed by hydrophobic interaction chromatography. This yielded purified Cal c Bd9.3 that retained IgE-binding activity by IP, was a single band by IEF and SDS-PAGE (16 kD) analysis when stained with Coomassie blue. Double diffusion in gel with rabbit antiserum to Cal c BD9.3 demonstrated a single precipitin band in crude extract that was identical to that obtained with purified Cal c Bd9.3. By IP this antiserum recognized pure Cal c Bd9.3 and the 9.3 band in crude extracts from C. cyathiformis and 3 other species, corroborating the cross-reactivity. However, other bands were also recognized. These studies indicate that basidiospores are major fungal aeroallergens, many of which contain a common basic allergen to which most sensitized subjects react.