T Cell Epitope-Containing Hypoallergenic Recombinant Fragments of the Major Birch Pollen Allergen, Bet v 1, Induce Blocking Antibodies

Abstract

Allergen-specific immunotherapy represents one of the few curative approaches toward type I allergy. Up to 25% of allergic patients are sensitized against the major birch pollen allergen, Bet v 1. By genetic engineering we produced two recombinant (r) Bet v 1 fragments comprising aa 1–74 and aa 75–160 of Bet v 1, which, due to a loss of their native-like fold, failed to bind IgE Abs and had reduced allergenic activity. Here we show that both fragments 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 induced higher lymphoproliferative responses than the N-terminal fragment and represented a Th1-stimulating segment with high IFN-γ production, whereas the N-terminal fragment induced higher IL-4, IL-5, and IL-13 secretion. Immunization of mice and rabbits with rBet v 1 fragments induced IgG Abs, which cross-reacted with complete Bet v 1 and Bet v 1-related plant allergens and strongly inhibited the IgE binding of allergic patients to these allergens. Thus, our results demonstrate that hypoallergenic T cell epitope-containing 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 hypoallergenic rBet v 1 fragments will now enable clinical studies for safer and more efficient specific immunotherapy.

Generation of an Allergy Vaccine by Disruption of the Three-Dimensional Structure of the Cross-Reactive Calcium-Binding Allergen, Phl p 7

“…Results obtained with blocking rabbit IgG Abs may in fact be applicable for immunotherapy. We found that immunization of mice with hypoallergenic derivatives of the major birch pollen allergen, Bet v 1, using schemes that are used for immunotherapy of allergic patients, yielded comparable results as the immunization of rabbits (31,32). The ability of unfolded hypoallergenic allergen derivatives to induce IgG Abs that inhibit the binding of patients' IgE directed to conformational epitopes may be explained in two ways.…”

Construction of Hevein (Hev b 6.02) with Reduced Allergenicity for Immunotherapy of Latex Allergy by Comutation of Six Amino Acid Residues on the Conformational IgE Epitopes

“…One disadvantage of SIT is that the administration of allergenic material may cause severe and lifethreatening anaphylactic side effects (1). This problem can be bypassed by using isoforms of allergens (2), deletion mutants (3), fragments of proteins (4,5), or linear peptides (6) that lack the original IgE-binding epitopes. The use of engineered "hypoallergenic" variants with reduced IgE reactivity is now being explored in several systems (7,8).…”

Prevention of allergy by a recombinant multi-allergen vaccine with reduced IgE binding and preserved T cell epitopes

“…The presence of conformational B cell epitopes proposed a novel approach to reduce IgE binding by fragmentation [24] and oligomerization of one allergen or hybridization of several allergens [25,26]. The majority of Ab elicited by exposure to native protein antigens recognize conformation-dependent, discontinuous epitopes [2,12,27], which is confirmed using mouse mAb against Api m 1 and Api m 2.…”