Accelerated dissociation of IgE-FcεRI complexes by disruptive inhibitors actively desensitizes allergic effector cells

摘要

Background The remarkably stable interaction of IgE with its high-affinity receptor FcεRI on basophils and mast cells is critical for the induction of allergic hypersensitivity reactions. Because of the exceptionally slow dissociation rate of IgE-FcεRI complexes, such allergic effector cells permanently display allergen-specific IgE on their surface and immediately respond to allergen challenge by releasing inflammatory mediators. We have recently described a novel macromolecular inhibitor that actively promotes the dissociation of IgE from FcεRI through a molecular mechanism termed facilitated dissociation. Objective Here we assessed the therapeutic potential of this non-immunoglobulin-based IgE inhibitor E2-79, a designed ankyrin repeat protein (DARPin), as well as a novel engineered biparatopic DARPin bi53-79, and directly compared them with the established anti-IgE antibody omalizumab. Methods IgE-FcεRI complex dissociation was analyzed in vitro by using recombinant proteins in ELISA and surface plasmon resonance, ex vivo by using human primary basophils with flow cytometry, and in vivo by using human FcεRI α-chain transgenic mice in a functional passive cutaneous anaphylaxis test. Results We show that E2-79-mediated removal of IgE from primary human basophils fully abrogates IgE-dependent cell activation and release of proinflammatory mediators ex vivo. Furthermore, we report that omalizumab also accelerates the dissociation of IgE from FcεRI, although much less efficiently than E2-79. Using the biparatopic IgE targeting approach, we further improved the disruptive potency of E2-79 by approximately 100-fold and show that disruptive IgE inhibitors efficiently prevent passive cutaneous anaphylaxis in mice expressing the human FcεRI α-chain. Conclusion Our findings highlight the potential of such novel IgE inhibitors as important diagnostic and therapeutic tools for management of allergic diseases.