T cell epitope-containing hypoallergenic recombinant fragments of the major birch pollen allergen, Bet v 1, induce blocking antibodies

Allergen-specific immunotherapy represents one of the few curative approach es toward type I allergy. Up to 25% of allergic patients are sensitized aga inst the major birch pollen allergen, Bet v 1, By genetic engineering we pr oduced two recombinant (r) Bet v 1 fragments comprising aa 1-74 and aa 75-1 60 of Bet v I, which, due to a loss of their native-like fold, failed to bi nd IgE Abs and had reduced allergenic activity. Here we show that both frag ments covering the full Bet v 1 sequence induced human lymphoproliferative responses similar to rBet v 1 wild type. The C-terminal rBet v 1 fragment i nduced higher lymphoproliferative responses than the N-terminal fragment an d represented a Th1-stimulating segment with high IFN-gamma production, whe reas the N-terminal fragment induced higher IL-4, IL-5, and IL-13 secretion . Immunization of mire and rabbits with rBet v 1 fragments induced IgG Abs, which cross-reacted with complete Bet v 1 and Bet v 1-related plant allerg ens and strongly inhibited the IgE binding of allergic patients to these al lergens. Thus, our results demonstrate that hypoallergenic T cell epitope c ontaining rBet v 1 fragments, despite lacking IgE epitopes, can induce Abs in vivo that prevent the IgE binding of allergic patients to the wild-type allergen, The overall demonstration of the immunogenic features of the hypo allergenic rBet v I fragments will now enable clinical studies for safer an d more efficient specific immunotherapy.