IMPROVED DIAGNOSIS OF ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS WITH GP66 (FORMERLY ANTIGEN-7) OF ASPERGILLUS-FUMIGATUS FOR SPECIFIC IGE DETECTION

Background: In cystic fibrosis (CF) serologic tests assume increased s ignificance for discriminating the symptoms of allergic bronchopulmona ry aspergillosis (ABPA) from those of bacterial infections. Elevated s pecific IgE is a sensitive indicator of ABPA, but the high prevalence of patients with CF who have simple allergy to Aspergillus fumigatus m eans that it lacks specificity. Objective: The aim of this study was t o develop an assay to detect IgE to a single allergenic protein of A. fumigatus to increase the discrimination between ABPA and uncomplicate d A. fumigatus allergy. Methods: To identify a more selective allergen , serum samples from nine patients with ABPA and five patients with al lergy were used to screen A. fumigatus proteins for allergenic activit y by crossed radioimmunoelectrophoresis. Molecular weights were determ ined by electrophoresis and immunoblotting, and carbohydrate content w as analyzed by concanavalin A chromatography and endoglycosidase diges tion. Results: The allergen identified was found to be a glycoprotein with a molecular weight of 66 kd, referred to as gp66. An ELISA was de veloped to measure specific IgE to gp66, and the efficacy was compared with IgE detection by using the unfractionated A. fumigatus extract o n serum samples from 14 patients with CF and ABPA, 42 patients with CF and allergy but not ABPA, and 23 patients with CF without ABPA or all ergy. Conclusion: Use of gp66 increased the specificity of IgE analysi s from 58.5% to 78.5%, whereas the sensitivity of 92.9% was maintained .