17 Sensitization to Betula verrucosa and RBET V1 in Spain

BACKGROUND: Sensitization to Betula verrucosa pollen is common in North Central Europe. In Spain, it is also common in patients from Galicia, a region located in the Northwest of Spain. Birch trees are abundant in this region and several birch species have been described. The main objectives were to determine the differences in the IgE reactivity to B. verrucosa and rBet v 1 between patients from Sweden and Spain, as well as the contribution of the major allergen Bet v 1 to the overall reactivity of B. verrucosa. Allergenicity was also compared using a serum pool derived from sera of North American (USA) patients. 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.