Background. Specific immunotherapy using recombinant allergens is clinically effective; still wild-type allergens can provoke treatment-induced side effects and often show poor immunogenicity in vivo. Thus, we tested the low IgE-binding, highly immunogenic fold variant BM4 in a Bet v 1 mouse model. Methods. Recombinant BM4 was used as active vaccine ingredient to treat mice sensitized to Bet v 1. As controls, mice were treated with either Bet v 1 or sham, and the humoral as well as cellular immune response was monitored. Moreover, lung function and lung inflammation were analysed. Results. BM4 was more effective than wild-type Bet v 1 in inducing Bet v 1-specific blocking antibodies as well as IFN- and IL-10 producing T cells. Further, birch pollen induced lung inflammation could be ameliorated significantly by BM4 treatment as demonstrated by a reduction of airway hyperresponsiveness and drastically decreased eosinophil counts in bronchoalveolar lavage fluids. Conclusion. The study outlines the high potential of BM4 as vaccine candidate for the treatment of Bet v 1-mediated birch pollen allergies.