SKIN-TEST REACTIVITY AND ISOTYPE-SPECIFIC IMMUNE-RESPONSES TO RECOMBINANT ASP-F-3, A MAJOR ALLERGEN OF ASPERGILLUS-FUMIGATUS

Background The in vitro diagnostic value of recombinant allergens depe nds on the correlation between allergen specific IgE in serum and abil ity of the protein to elicit immediate type allergic reactions in sens itized individuals. Objective The study was carried out to evaluate th e reliability of recombinant Asp f 3 (rAsp f 3)-based serological dete rminations in ELISA and ImmunoCAP compared to skin-test responses in A . fumigatus sensitized subjects. Methods Patients suffering from aller gic bronchopulmonary aspergillosis (ABPA, n = 11) or allergic asthma w ith A, fumigatus sensitization (n = 8) and healthy control subjects (n = 4) were investigated. Intradermal skin tests (IDT) and allergen-spe cific serology were performed using rAsp f 3 protein. Results All 11 p atients with ABPA and five out of eight A. fumigatus-sensitized asthma tics without ABPA exhibited a type I skin reaction. All rAsp f 3 skin test positive subjects showed relevant rAsp f 3-specific serum IgE lev els compared with IDT-negative individuals who scored below the rAsp f 3-ImmunoCAP cut-off values of < 0.35 kU(A)/L. Analyses of rAsp f 3-sp ecific immunoglobulins revealed significantly higher serum levels of I gG, IgG1, IgG4 and IgE antibodies in patients with ABPA compared with A, fumigatus-sensitized asthmatics and healthy controls. Conclusion rA sp f 3 represents a major allergen of A. fumigatus. It is recognized b y 84% of asthmatic individuals sensitized to the fungus and elicits sp ecific type I skin reactions. The skin test outcome strictly depends o n the presence of rAsp f 3-specific IgE and the lack of false positive or false negative results comparing skin test outcome with specific s erum IgE levels determined by ELISA or rAsp f 3-ImmunoCAP suggests the possibility to rely on serological data obtained with recombinant all ergens to diagnose sensitization to A. fumigatus.