Neutralizing IgG4 antibodies are a biomarker of sustained efficacy after peanut oral immunotherapy

Abstract

BackgroundClinical efficacy of oral immunotherapy (OIT) has been associated with the induction of blocking antibodies, particularly those capable of disrupting IgE-allergen interactions. Previously, we identified monoclonal antibodies (mAb) to Ara h 2 and structurally characterized their epitopes. ObjectiveWe investigated longitudinal changes during OIT in antibody binding to conformational epitopes and correlated the results with isotype and clinical efficacy. MethodsWe developed an indirect inhibitory ELISA using mAbs to block conformational epitopes on immobilized Ara h 2 from binding to serum immunoglobulins from peanut-allergic patients undergoing OIT. We tested the functional blocking ability of mAbs using passive cutaneous anaphylaxis (PCA) in mice with humanized FcεRI receptors. ResultsDiverse serum IgE recognition of Ara h 2 conformational epitopes are similar before and after OIT. Optimal inhibition of serum IgE occurs with the combination of two neutralizing mAbs (nAbs) recognizing epitopes 1.2 and 3, compared to two non-neutralizing mAbs (non-nAbs). Post-OIT, IgG4 nAbs, but not IgG1 or IgG2 nAbs, increased in sustained compared to transient outcomes. Induction of IgG4 nAbs occurs after OIT only in those with sustained efficacy. Murine PCA after sensitization with pooled human sera is significantly inhibited by nAbs compared to non-nAbs. ConclusionsSerum IgE conformational epitope diversity remains unchanged during OIT. However, IgG4 nAbs capable of uniquely disrupting IgE-allergen interactions to prevent effector cell activation are selectively induced in OIT-treated individuals with sustained clinical efficacy. Therefore, the induction of neutralizing IgG4 antibodies to Ara h 2 are clinically relevant biomarkers of durable efficacy in OIT.