title: Computationally predicted IgE epitopes of walnut allergens contribute to cross-reactivity with peanuts.
abstract: BACKGROUND
  Cross-reactivity between peanuts and tree nuts implies that similar immunoglobulin E (IgE) epitopes are present in their proteins.
  
  
  OBJECTIVE
  To determine whether walnut sequences similar to known peanut IgE-binding sequences, according to the property distance (PD) scale implemented in the Structural Database of Allergenic Proteins, react with IgE from sera of patients with allergy to walnut and/or peanut.
  
  
  METHODS
  Patient sera were characterized by western blotting for IgE binding to nut protein extracts and to peptides from walnut and peanut allergens, similar to known peanut epitopes as defined by low PD values, synthesized on membranes. Competitive enzyme-linked immunosorbent assay (ELISA) was used to show that peanut and predicted walnut epitope sequences compete with purified Ara h 2 for binding to IgE in serum from a cross-reactive patient.
  
  
  RESULTS
  Sequences from the vicilin walnut allergen Jug r 2, which had low PD values to epitopes of the peanut allergen Ara h 2, a 2S albumin, bound to IgE in sera from five patients who reacted to either walnut or peanut or both. A walnut epitope recognized by sera from six patients mapped to a surface-exposed region on a model of the N-terminal pro-region of Jug r 2. This predicted walnut epitope competed for IgE binding to Ara h 2 in serum as well as the known IgE epitope from Ara h 2.
  
  
  CONCLUSIONS
  Sequences with low PD value (< 8.5) to known IgE epitopes could contribute to cross-reactivity between allergens. This further validates the PD scoring method for predicting cross-reactive epitopes in allergens.
authors: U.S. Department of Agriculture-Agricultural Research Service-Southern Regional Research Center (USDA-ARS-SRRC), New Orleans, LA 70124, USA. soheila.maleki@ars.usda.gov
authors: S J
authors: SJ
authors: Maleki
authors: S S
authors: SS
authors: Teuber
authors: H
authors: H
authors: Cheng
authors: D
authors: D
authors: Chen
authors: S S
authors: SS
authors: Comstock
authors: S
authors: S
authors: Ruan
authors: C H
authors: CH
authors: Schein
mesh_terms: D000485:Allergens / Q000276:immunology* / Q000378:metabolism; D000595:Amino Acid Sequence; D010367:Arachis / Q000276:immunology*; D001667:Binding, Competitive / Q000276:immunology; D002675:Child, Preschool; D003429:Cross Reactions / Q000276:immunology; D030562:Databases, Protein; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D005512:Food Hypersensitivity / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology* / Q000378:metabolism; D007223:Infant; D031324:Juglans / Q000276:immunology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D000485:Allergens; D000939:Epitopes; D010940:Plant Proteins; D007073:Immunoglobulin E