title: Accelerated dissociation of IgE-FcεRI complexes by disruptive inhibitors actively desensitizes allergic effector cells.
abstract: 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.
  
  
  CONCLUSIONS
  Our findings highlight the potential of such novel IgE inhibitors as important diagnostic and therapeutic tools for management of allergic diseases.
authors.affiliation: Institute of Immunology, University of Bern, Bern, Switzerland. Electronic address: alexander.eggel@iib.unibe.ch.
authors.forename: Alexander
authors.initials: A
authors.lastname: Eggel
authors.affiliation: Department of Microbiology and Immunology, Sandler Asthma Basic Research Center, University of California San Francisco, San Francisco, Calif.
authors.forename: Günther
authors.initials: G
authors.lastname: Baravalle
authors.affiliation: Institute of Immunology, University of Bern, Bern, Switzerland.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Hobi
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, Calif.
authors.forename: Beomkyu
authors.initials: B
authors.lastname: Kim
authors.affiliation: Institute of Immunology, University of Bern, Bern, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Buschor
authors.affiliation: Molecular Partners AG, Zürich-Schlieren, Switzerland.
authors.forename: Patrik
authors.initials: P
authors.lastname: Forrer
authors.affiliation: Department of Microbiology and Immunology, Sandler Asthma Basic Research Center, University of California San Francisco, San Francisco, Calif.
authors.forename: Jeoung-Sook
authors.initials: JS
authors.lastname: Shin
authors.affiliation: Institute of Immunology, University of Bern, Bern, Switzerland.
authors.forename: Monique
authors.initials: M
authors.lastname: Vogel
authors.affiliation: Institute of Immunology, University of Bern, Bern, Switzerland.
authors.forename: Beda M
authors.initials: BM
authors.lastname: Stadler
authors.affiliation: Institute of Immunology, University of Bern, Bern, Switzerland.
authors.forename: Clemens A
authors.initials: CA
authors.lastname: Dahinden
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, Calif.
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Jardetzky
mesh_terms: D000707:Anaphylaxis / Q000235:genetics / Q000276:immunology / Q000517:prevention & control; D000818:Animals; D017089:Ankyrin Repeat; D000888:Antibodies, Anti-Idiotypic / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D000941:Antigens / Q000276:immunology; D001491:Basophils / Q000276:immunology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007073:Immunoglobulin E / Q000737:chemistry / Q000378:metabolism*; D008407:Mast Cells / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008958:Models, Molecular; D018716:Molecular Mimicry; D000069444:Omalizumab; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D017455:Receptors, IgE / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D061067:Antibodies, Monoclonal, Humanized; D000941:Antigens; C577317:DARPin E2 79; D017455:Receptors, IgE; D011993:Recombinant Fusion Proteins; C026408:anti-IgE antibodies; D000069444:Omalizumab; D007073:Immunoglobulin E
keywords: Allergy; FcεRIα; IgE; basophils; designed ankyrin repeat proteins; inhibitors; mast cells