Deleterious effects of electron beam radiation on allergen extracts.

BACKGROUND: The recent threat to the public posed by the dissemination of Bacillus anthracis through the US postal system has resulted in increased security measures, including electron beam irradiation for the sterilization of some mail. The deleterious effects of electron beam radiation on biological products are not fully understood. OBJECTIVE: The purpose of this investigation was to assess the effect of electron beam radiation, as currently used to sterilize packages and mail in the United States, on several standardized or characterized allergen extracts. METHODS: Selected irradiated extracts were analyzed for allergen content and potency by SDS-PAGE, immunoblot, and ELISA (including inhibition) and compared with untreated extracts. RESULTS: The compositions and immunochemical potencies of these products were altered significantly by irradiation treatment. Physical changes to native protein structures observed after electrophoretic separations coincided with near-complete loss of allergenic and antigenic epitopes present on major and minor allergens, according to ELISA and immunoblot comparisons with untreated extracts. CONCLUSIONS: These results indicate that extracts subjected to electron beam sterilization conditions are likely to contain modified component structures and properties that might compromise the clinical effectiveness of these products.

Major allergen measurements: sources of variability, validation, quality assurance, and utility for laboratories, manufacturers, and clinics.

The isolation and characterization of prominent allergenic proteins or glycoproteins is an important step in the development of allergenic extracts exhibiting improved definition, consistency, and clinical utility. Quantitative analyses specific for major allergenic components currently are being performed in numerous corporate and academic laboratories but have not been validated within or across laboratories in a systematic manner. In our laboratory, validation of double-bind (sandwich) ELISA assays for a diverse group of major allergens or extract components revealed a number of critical assay variables and reagent incubation conditions that directly influenced the precision, accuracy, specificity, and robustness of these tests. Data from ELISA methods for six allergens (Dermatophagoides farinae Der f 1, Alternaria Alt a 1, dog albumin, dog Can f 1, fire ant Sol i 3, and yellow jacket venom Ves 5) showed that up to twofold differences in results were observed when analysts or microplates were varied. Analyses of dog allergens using multiple reagents and concentrations indicated that twofold variations in results also can be produced by distinct combinations of materials or incubations from different assay steps. Data from Can f 1 and egg white analyses produced up to fivefold differences in antigen concentrations based on changes in the capture antibody source (mouse monoclonal versus rabbit polyclonal) or storage buffer. These results suggest that differences in major allergen concentrations reported by different testing laboratories may be related to assay differences as well as extract variations and raise questions as to the accuracy of major allergen concentrations and therapeutic dose recommendations reported at regional and national allergy meetings. Validated double-bind ELISA methods may be well suited for consistency monitoring and standardization of extracts provided that reference materials, reagent qualifications, and interlaboratory comparability are defined precisely.