Automated serology with recombinant allergens. A feasibility study.

Diagnosis of allergic conditions is based on skin prick- and/or intradermal tests and on serology. Both methods make use of allergenic preparations and the results mainly depend on the quality of the substances applied and on the reactivity of the subjects. Recombinant allergens can be produced as highly pure proteins. They may contribute to a significant improvement of the diagnosis of allergic diseases provided that the allergens became available in a pure, fully antigenic form suitable for routine assessments. We have studied the diagnostic properties of recombinant Aspergillus fumigatus allergen I (rAsp f I/a), a major allergen recognised by about 60% of the A. fumigatus allergic individuals, to test the feasibility of using recombinant allergens for automated serology in the Pharmacia CAP System, a new solid-phase immunoassay. ImmunoCAPs carrying immobilised rAsp f I/a were produced and evaluated using sera from well characterised patients with allergic bronchopulmonary aspergillosis (ABPA), allergic asthmatics with or without A. fumigatus sensitisation, and healthy control persons. The clinical parameters used for the diagnosis of allergy to A. fumigatus were RAST and skin test reactivity to commercial A. fumigatus extracts. IgE antibodies recognising rAsp f I/a were determined by a direct antigen-specific ELISA and with the newly developed rAsp f I/a ImmunoCAPs. Quantitative results from the two rAsp f I/a detection systems correlated closely, indicating that this recombinant allergen can be incorporated in the Pharmacia CAP System with unaltered antigenic activity. The behaviour of a panel of recombinant A. fumigatus allergens in the Pharmacia CAP System will be evaluated in the near future to assess the potential of recombinant allergens for the automated diagnosis of allergic conditions.