Characterization of the Major Allergen, Que Ac 1, from Sawtooth Oak Pollen

Background: Sawtooth oak is a potent cause of tree pollinosis in Korea. However, molecular characteristics of the major allergen have not been elucidated. Objective: The study was to perform biochemical and allergenic characterization from sawtooth oak. Methods: Native Que ac 1 was purified and analyzed by 2D gel electrophoresis and LC-coupled ESI-MS/MS analysis. Polymorphisms of Que ac 1 were examined by RT-PCR, and a recombinant allergen of the major isoform was produced. IgE reactivities of the native and recombinant allergens were compared by ELISA. Results: At least 12 isoforms of Que ac 1 were identified by proteomic analysis, and 22 isoforms including two isoallergens were identified by RT-PCR. A major isoform Que ac 1.0101 (13.3%, 10/75) shared the lowest homology to Bet v 1 (58.1%) and the highest homology to Que r 1 (83.0%). Recombinant Que ac 1.0101, which exhibited a similar CD spectrum with native Que ac 1, was recognized by serum IgE from 91.3% of Korean oak pollinosis patients. Recombinant Que ac 1 inhibited 67.2% of IgE reactivity to sawtooth pollen extract, but native Que ac 1 and recombinant Bet v 1 inhibited 88.7% and 57.6% of the IgE reactivity, respectively. No difference in allergen potential was shown between Que ac 1 and Bet v 1 by basophil mediator release assay. Conclusion: Molecular properties of the major allergen Que ac 1 were characterized. Que ac 1 seems to be an allergen of regional importance homologous to Bet v 1 and may be useful for better diagnostics of pollinosis.