Methods: IgE reactivity to B. verrucosa and rBet v 1 was measured in sera from 44 Spanish and 21 Swedish patients. rBet v 1 was produced as N-terminal His-tagged fusion protein and purified as originally described. All of them were sensitized to the pollen of this tree species and suffered from allergic rhinitis during the pollination period. rBet v 1 contribution was determined by inhibition ELISA using 3 pools of sera: from Spanish, North American and Swedish patients. IgE binding pattern was evaluated by Western blots using the same pools of sera. Specific IgE binding was expressed in arbitrary units.
Results: Specific IgE to B. verrucosa was detected in 50 from the 65 sera analyzed (mean = 3.77± 3.71 Units). Specific IgE levels to rBet v 1 were 3.13 ± 3.32 Units. Immunoblot assays confirmed specific IgE binding to rBet v 1, and also to other allergens present in the extract. The Spanish pool presented reactivity to more allergens than the Swedish pool. ELISA Inhibition assays, performed with a native extract and rBet v 1, revealed a significant contribution (> 80% inhibition) of rBet v 1 to the allergenicity of the extract, with no differences according to the origin of the sera.
Conclusions: Bet v 1 has a great importance in birch allergy in Galicia and Sweden. Nevertheless, there are differences in the IgE recognition pattern according to the rest of birch allergens. Mayor allergen from birch, Bet v 1, significantly contributes to the allergenicity of B. verrucosa in Galicia.