title: Allergen Valency, Dose, and FcεRI Occupancy Set Thresholds for Secretory Responses to Pen a 1 and Motivate Design of Hypoallergens.
abstract: Ag-mediated crosslinking of IgE-FcεRI complexes activates mast cells and basophils, initiating the allergic response. Of 34 donors recruited having self-reported shrimp allergy, only 35% had significant levels of shrimp-specific IgE in serum and measurable basophil secretory responses to rPen a 1 (shrimp tropomyosin). We report that degranulation is linked to the number of FcεRI occupied with allergen-specific IgE, as well as the dose and valency of Pen a 1. Using clustered regularly interspaced palindromic repeat-based gene editing, human RBLrαKOcells were created that exclusively express the human FcεRIα subunit. Pen a 1-specific IgE was affinity purified from shrimp-positive plasma. Cells primed with a range of Pen a 1-specific IgE and challenged with Pen a 1 showed a bell-shaped dose response for secretion, with optimal Pen a 1 doses of 0.1-10 ng/ml. Mathematical modeling provided estimates of receptor aggregation kinetics based on FcεRI occupancy with IgE and allergen dose. Maximal degranulation was elicited when ∼2700 IgE-FcεRI complexes were occupied with specific IgE and challenged with Pen a 1 (IgE epitope valency of ≥8), although measurable responses were achieved when only a few hundred FcεRI were occupied. Prolonged periods of pepsin-mediated Pen a 1 proteolysis, which simulates gastric digestion, were required to diminish secretory responses. Recombinant fragments (60-79 aa), which together span the entire length of tropomyosin, were weak secretagogues. These fragments have reduced dimerization capacity, compete with intact Pen a 1 for binding to IgE-FcεRI complexes, and represent a starting point for the design of promising hypoallergens for immunotherapy.
authors.affiliation: Department of Pathology, University of New Mexico, Albuquerque, NM 87131.
authors.forename: Avanika
authors.initials: A
authors.lastname: Mahajan
authors.affiliation: Department of Pharmaceutics and Pharmaceutical Technology, School of Pharmacy, Damascus University, Damascus, Syria.|National Commission for Biotechnology, Damascus, Syria.
authors.forename: Lama A
authors.identifier: 0000-0001-8013-7856
authors.initials: LA
authors.lastname: Youssef
authors.affiliation: Department of Pathology, University of New Mexico, Albuquerque, NM 87131.
authors.forename: Cédric
authors.identifier: 0000-0002-1928-6497
authors.initials: C
authors.lastname: Cleyrat
authors.affiliation: Department of Pathology, University of New Mexico, Albuquerque, NM 87131.
authors.forename: Rachel
authors.identifier: 0000-0003-1204-6615
authors.initials: R
authors.lastname: Grattan
authors.affiliation: Department of Pathology, University of New Mexico, Albuquerque, NM 87131.
authors.forename: Shayna R
authors.initials: SR
authors.lastname: Lucero
authors.affiliation: Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, LA 70124.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Mattison
authors.affiliation: Department of Pathology, University of New Mexico, Albuquerque, NM 87131.
authors.forename: M Frank
authors.identifier: 0000-0002-8046-5048
authors.initials: MF
authors.lastname: Erasmus
authors.affiliation: Department of Computer Sciences, University of New Mexico, Albuquerque, NM 87131.
authors.forename: Bruna
authors.initials: B
authors.lastname: Jacobson
authors.affiliation: Department of Computer Sciences, University of New Mexico, Albuquerque, NM 87131.
authors.forename: Lydia
authors.identifier: 0000-0002-7822-7091
authors.initials: L
authors.lastname: Tapia
authors.affiliation: Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545.|Theoretical Biology and Biophysics Group, Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545; and.
authors.forename: William S
authors.identifier: 0000-0003-4383-8711
authors.initials: WS
authors.lastname: Hlavacek
authors.affiliation: Department of Medicine, University of New Mexico, Albuquerque, NM 87131.
authors.forename: Mark
authors.initials: M
authors.lastname: Schuyler
authors.affiliation: Department of Pathology, University of New Mexico, Albuquerque, NM 87131; bwilson@salud.unm.edu.
authors.forename: Bridget S
authors.identifier: 0000-0002-3775-4450
authors.initials: BS
authors.lastname: Wilson
mesh_terms: D000485:Allergens / Q000276:immunology*; D001491:Basophils / Q000502:physiology; D015550:Cell Degranulation; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000378:metabolism; D017455:Receptors, IgE / Q000378:metabolism*
chemical_list: D000485:Allergens; C513564:Pen a 1 allergen, Penaeus aztecus; D017455:Receptors, IgE; D007073:Immunoglobulin E