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Groh N¹, Seutter von Loetzen C², Subbarayal B³, Möbs C⁴, Vogel L¹, Hoffmann A¹, Fötisch K¹, Koutsouridou A¹, Randow S¹, Völker E¹, Reuter A¹, Rösch P², Vieths S¹, Pfützner W⁴, Bohle B³, Schiller D⁵.

Abstract

BACKGROUND:

Allergen-specific immunotherapy (AIT) with birch pollen generates Bet v 1-specific immunoglobulin (Ig)G₄ which blocks IgE-mediated hypersensitivity mechanisms. Whether IgG₄ specific for Bet v1a competes with IgE for identical epitopes or whether novel epitope specificities of IgG₄ antibodies are developed is under debate.

OBJECTIVE:

We sought to analyze the epitope specificities of IgE and IgG₄ antibodies from sera of patients who received AIT.

METHODS:

15 sera of patients (13/15 received AIT) with Bet v 1a-specific IgE and IgG₄ were analyzed. The structural arrangements of recombinant (r)Bet v 1a and rBet v 1a_{_11x} , modified in five potential epitopes were analyzed by circular dichroism and nuclear magnetic resonance spectroscopy. IgE binding to Bet v 1 was assessed by ELISA and mediator release assays. Competitive binding of monoclonal antibodies specific for Bet v 1a and serum IgE/IgG₄ to rBet v 1a and serum antibody binding to a non-allergenic Bet v 1-type model protein presenting an individual epitope for IgE was analyzed in ELISA and Western blot.

RESULTS:

rBet v 1a_{_11x} had a Bet v 1a-similar secondary and tertiary structure. Monomeric dispersion of rBet v 1a_{_11x} was concentration and buffer dependent. Up to 1,500-fold increase in the EC₅₀ for IgE-mediated mediator release induced by rBet v 1a_{_11x} was determined. The reduction of IgE and IgG₄ binding to rBet v 1a_{_11x} was comparable in 67% (10/15) of sera. Bet v 1a-specific monoclonal antibodies inhibited binding of serum IgE and IgG₄ to 66.1% and 64.9%, respectively. Serum IgE and IgG₄ bound specifically to an individual epitope presented by our model protein in 33% (5/15) of sera.

CONCLUSION AND CLINICAL RELEVANCE PATIENTS RECEIVING:

AIT develop Bet v 1a-specific IgG₄ which compete with IgE for partly identical or largely overlapping epitopes. The similarities of epitopes for IgE and IgG₄ might stimulate the development of epitope-specific diagnostics and therapeutics. This article is protected by copyright. All rights reserved.