Quantitation of the major fungal allergens, Alt a 1 and Asp f 1, in commercial allergenic products.

BACKGROUND: Alternaria is one of the most important fungi associated with allergic disease, whereas Aspergillus fumigatus is involved in a broad spectrum of pulmonary diseases. Currently, fungal extracts used for diagnosis in the United States are unstandardized, and their allergenic content cannot be compared directly.
OBJECTIVE: The goal of this study was to compare the variability of major allergen levels among US allergenic products derived from fungi: specifically, Alt a 1 levels in Alternaria alternata extracts, and Asp f 1 levels in A fumigatus extracts.
METHODS: A novel 2-site monoclonal antibody ELISA was used for measuring Alt a 1 using recombinant Alt a 1 as a standard. Asp f 1 was also measured by ELISA. Allergenic products produced by 8 US manufacturers over a 2-year period were compared, as were multiple lots produced by a single company.
RESULTS: Alt a 1 levels in Alternaria extracts from 8 companies produced in 1998 and 1999 ranged from less than 0.01 to 6.09 microg/mL (mean 1.4 +/- 1.6 microg/mL, n = 15). In general, Alt a 1 levels were consistent within and between companies (1.4 +/- 1.1 microg/mL, n = 27), with 21 of 32 (66%) of all extracts tested containing 0.7 to 2 microg/mL Alt a 1. Aspergillus extracts showed much greater variability in Asp f 1 levels, with extracts from 8 companies containing from less than 0.1 to 64 microg/mL Asp f 1 (mean 16.3 +/- 23.9 microg/mL, n = 15). Overall variability was greater for Aspergillus products within and between manufacturers (22 +/- 22 microg/mL Asp f 1, n = 20).
CONCLUSIONS: ELISA-based assays for specific allergens showed greater consistency among allergenic products derived from Alternaria than from Aspergillus. These assays should facilitate improved quality control and standardization of fungal allergen extracts and lead to the development of more consistent products for clinical use.