Purification and characterization of the major oak pollen allergen Que a 1 for component-resolved diagnostics using ImmunoCAP.

BACKGROUND: The aim of this study was to purify the major oak pollen allergen, Que a 1, to perform biochemical and immunological characterization of the allergen and to develop an experimental native (n) Que a 1 ImmunoCAP(R).
METHODS: Que a 1 was purified from oak pollen extract using affinity chromatography and characterized by SDS-PAGE, two-dimensional (2D) PAGE, mass spectrometry (MS), N-terminal sequencing and specific IgE inhibition on ImmunoCAP. Samples from 16 subjects sensitized to oak pollen were analyzed by ImmunoCAP for IgE reactivity to nQue a 1, and recombinant (r)Bet v 1 and 2 (profilin). They were also studied in IgE immunoblotting.
RESULTS: The purity of nQue a 1 was >95%, since a single band was observed on silver-stained SDS-PAGE. The identity was verified by MS analysis, and 2D-PAGE revealed several isoforms. The obtained N-terminal sequence of 50-amino-acid residues from nQue a 1 showed a 58-74% sequence identity with other pathogenesis-related class 10 allergens. Specific IgE inhibition verified a preserved immunoreactivity (70-92% inhibition). All subjects were sensitized to Que a 1 and Bet v 1, and two to profilin. The IgE antibody levels to nQue a 1 were generally lower than to rBet v 1. The obtained results correlated well with IgE immunoblotting.
CONCLUSIONS: We present a highly purified and extensively characterized preparation of nQue a 1. Que a 1 seems to be an allergen of equal importance in oak pollen as Bet v 1 in birch pollen. An nQue a 1 ImmunoCAP will be useful in component-resolved diagnostics. (c) 2008 S. Karger AG, Basel