PURIFICATION OF A MAJOR ALLERGEN, ASP-F-2 BINDING TO IGE IN ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS, FROM CULTURE FILTRATE OF ASPERGILLUS-FUMIGATUS

Background: Most cases of allergic bronchopulmonary aspergillosis (ABP A) are caused by the fungus Aspergillus fumigatus. Successful treatmen t of this disease depends on early diagnosis with the use of well-char acterized and relevant antigens/allergens of the organism. Objective: The aim of this study was to purify and characterize relevant proteins from A, fumigatus that could be used in the reliable diagnosis of ABP A. Methods: Monoclonal antibodies were raised against A. fumigatus cul ture filtrate antigens. A Concanavalin A nonbinding protein fraction w as purified with use of one of the monoclonal antibody immunoaffinity columns. The purified protein was analyzed on sodium dodecylsulfate-po lyacrylamide gel electrophoresis gel and Western blots. The sensitivit y and specificity of the purified protein were evaluated by RAST and E LISA with sera from 25 patients with ABPA, from 10 with allergic asthm a, and from 10 normal control subjects. Results: The 37 kD Concanavali n A nonbinding protein reacted specifically with IgE antibodies in pat ients with ABPA. Among the 25 patients with ABPA studied, 96% had IgE antibody against the allergen, whereas none of the subjects with aller gic asthma who had positive results on the skin prick test or normal c ontrol subjects had a reaction. Both RAST and ELISA results exhibited strong correlation with IgE binding. This allergen exhibited N-termina l sequence identity to a recombinant allergen Asp f 2. Conclusions: A 37 kD protein with complete N-terminal homology to Asp f 2 is a major allergen of A. fumigatus that significantly reacts with IgE antibody i n patients with ABPA, but does not elicit reaction in Aspergillus-sens itive subjects with asthma and normal control subjects.