Selected recombinant Aspergillus fumigatus allergens bind specifically to IgE in ABPA

Background. Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity lung disease resulting from exposure to Aspergillus fumigatus allergens. Patients with ABPA show elevated Aspergillus-specific serum IgE, a major criterion used in the diagnosis of the disease. Crude culture filtrate and mycelial antigens have been used widely to demonstrate IgE antibody to Aspergillus in the sera of patients. While these antigens have been useful in the diagnosis of ABPA, occasionally they present inconsistency in their reactivity and lack of specificity. Although in recent years, a number of purified A. fumigatus allergens have been produced by molecular cloning, no attempt was made to evaluate them systematically. Objective. To evaluate the recombinant proteins from A. fumigatus for their IgE antibody binding, we studied sera from ABPA patients and controls by antigen specific enzyme linked immunosorbent assay (ELISA). Methods. Recombinant Aspergillus allergens Asp f 1, f 2, f 3, f 4, and f 6 were studied for their specific binding to IgE in the sera of ABPA patients, A. fumigatus skin prick test positive asthmatics, and normal controls from the USA and Switzerland. The sera were blinded and studied by ELISA in two different Laboratories. Results. All the recombinant allergens showed IgE antibody binding with sera from patients with ABPA, whereas only fewer asthmatics and normal sera showed significant binding. The three selected recombinant allergens together reacted with all the ABPA patients studied. Conclusions. The results demonstrate that Asp f 2, f 4, and f 6 can be used in the serodiagnosis of ABPA, while IgE antibody binding to Asp f 1 and f 3 was not specific.