Automated specific IgE assay with recombinant allergens: Evaluation of the recombinant Aspergillus fumigatus allergen T in the Pharmacia CAP System

Background We report the results of a study comparing the recombinant Aspergillus fumigatus allergen I (rAsp fI) to commercial A. fumigatus extracts in serological assays, Pharmacia CAP System and skin tests. Objective The study was designed to test the feasibility of using recombinant allergens in an automated serology system for determination of allergen-specific IgE. Methods Patients with allergic bronchopulmonary aspergillosis (ABPA), asthmatics with A. fumigatus allergy and control subjects, who included allergic asthmatics without allergy to A. fumigatus and healthy subjects, were investigated. All subjects were characterized with respect to their total IgE level, radio allergosorbent test to A, fumigatus and skin test reactivity to both commercial A. fumigatus extracts and recombinant rAsp fI protein. Results All patients with ABPA (n = 30) showed positive skin test reactions with commercial A. fumigatus extracts, and 24 were sensitized to rAsp fI by the same criterion. The 10 patients with asthma and A. fumigatus allergy showed positive skin reactions to at least one commercial extract, and five reacted to rAsp fI. All control subjects (n = 19) scored negatively in skin tests to A. fumigatus extracts and rAsp fI, and showed no detectable rAsp fI-specific IgE. ImmunoCAP carrying immobilized rAsp fI were evaluated using sera from all individuals described and the results compared with those obtained with the rAsp fI-specific ELISA for IgE. The data obtained with the two rAsp fI-specific detection systems correlated closely (r = 0.997) and were in perfect agreement with the skin test results. Conclusion The data show that rAsp fI can be used as immobilized allergen in the Pharmacia CAP System indicating the feasibility of using recombinant allergens for an automated serological diagnosis of allergic diseases. However, every recombinant allergen needs to be evaluated individually for its performance if applied to a new diagnostic technology.