Clinical 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 mAbs to Ara h 2 and structurally characterized their epitopes.

We investigated longitudinal changes during OIT in antibody binding to conformational epitopes and correlated the results with isotype and clinical efficacy.

We 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 in mice with humanized FcεRI receptors.

Diverse 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 2 neutralizing mAbs (nAbs) recognizing epitopes 1.2 and 3, compared to 2 nonneutralizing mAbs (non-nAbs). After 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 passive cutaneous anaphylaxis after sensitization with pooled human sera is significantly inhibited by nAbs compared to non-nAbs.

Serum 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.