Relative Allergen Content of Commercial Aspergillus Fumigatus Extracts Determined by Human Monoclonal IgE

Sensitization to Aspergillus spp. is associated with severe asthma, as well as other allergic respiratory disease. Allergen immunotherapy with non-standardized Aspergillus extracts is commonly used as therapy in these patients. Asp f 1 content has been reported to markedly vary, both among extract manufacturers, and between lots from a single manufacturer. We hypothesized that newly developed human monoclonal IgE directed against Aspergillus spp. would allow for better characterization of the variability of relevant human allergenic epitopes among currently available commercial Aspergillus fumigatus extracts. Patients with allergic bronchopulmonary aspergillosis were recruited from within the Vanderbilt system. Peripheral blood mononuclear cells were isolated, and IgE specific B-cells were immortalized using standard electrofusion techniques. Antibody was isolated from hybridoma supernatants and used for western blot and ELISA assays of commercial allergen extract of Aspergillus fumigatus. Approximately half of Aspergillus specific IgE antibodies function in western blots. Of the antibody targets so far analyzed, none have been present in detectable quantities in every extract assayed. When targets are detected in multiple extracts, the concentration varies between ten and one thousand fold between manufacturers. The Aspergillus fumigatus extract currently used in immunotherapy in the US is highly variable in relation to the content of component allergens. This degree of variability is almost certain to affect the efficacy of these reagents. Human monoclonal IgE represents a novel tool for evaluation of content of relevant human allergenic epitopes within these extracts, which may assist the development of standardized mold extracts in the future.