Quantification of airborne Aspergillus allergens: redefining the approach.

BACKGROUND

Airborne Aspergillus species are significant environmental components involved in the pathogenesis and persistence of allergic respiratory diseases. The detection and quantification of airborne allergens is important to elucidate the clinical implications of environmental exposure of patients suffering with allergic asthma and/or allergic rhinitis.

OBJECTIVE

The authors report a simple volumetric approach to measure atmospheric concentration of four common airborne species of Aspergillus-A. flavus, A. fumigatus, A. niger, and A. tamarii.

METHODS

As particulate aeroallergens may also exist in amorphous form in addition to morphologically identifiable fungal spores/hyphae, a volumetric technique using membrane filters was developed for simultaneous quantification of (a) viable Aspergillus counts, i.e., colony-forming units (cfu)/m(3), and (b) actual Aspergillus allergen content (ng/m(3)) in the air. Further, immunochemically quantified airborne Aspergillus allergens were compared with their corresponding colony counts.

RESULTS

The average monthly aerial counts of the four Aspergillus species recorded during the sampling year were A. flavus: 0.25-15.2 cfu/m(3); A. fumigatus: 1.25-15.6 cfu/m(3); A. niger: 0.75-16.0 cfu/m(3); and A. tamarii: 0.5-11.8 cfu/m(3) of air. Aerial Aspergillus allergen(s) concentration varied from species to species: A. flavus: 26.8-680.8 ng; A. fumigatus: 18.0-380.4 ng; A. niger: 28.2-1879.0 ng; and A. tamarii: 9.2-238.3 ng/m(3) of air. Seasonal distribution of airborne colony counts of the four species didn't correlate with their respective allergen content.

CONCLUSION

Aspergillus allergens were present in the air of Delhi area throughout the year with seasonal variations. The authors feel that by using the immunochemical technique it will be possible to measure actual exposure of patients to various airborne Aspergillus allergens.