title: Isolated IgE reactivity to native walnut vicilin-like protein (nJug r 2) on ISAC™ microarray is due to cross-reactive carbohydrate epitopes.
abstract: BACKGROUND
  The last version of the microarray-based testing ImmunoCAP ISAC 112™ includes the native walnut (Junglans regia) molecules 2S albumin (nJug r 1), vicilin (nJug r 2) and lipid transfer protein (nJug r 3). In view of the many unexpected cases of isolated positivity to nJug r 2 occurring in daily practice, we evaluated the association of these reactivities with clinical symptoms, as well as the relationship between sIgE and nJug r 2 and cross-reactive carbohydrate determinants (CCDs).
  
  
  METHODS
  Sera from 320 consecutive allergic outpatients tested by ImmuoCAP ISAC™ 112 were considered. The medical records of all nJug r 2 positive patients were reviewed to assess clinical symptoms related to walnut allergy. A linear regression analysis was performed to evaluate the correlation between nJug r 2 and CCDs (nMUXF3) sIgE values, and a CAP inhibition assay was carried out to confirm the possible cross-reactivity between CCDs and nJug r 2.
  
  
  RESULTS
  Thirty-seven out of 320 sera tested (11.6%) were positive to nJug r 2. Among them three (8.1%) and eight (21.6%) scored positive for nJug r 1 and nJug r 3 as well, respectively. Twenty-seven (73%) sera showed isolated nJug r 2 positivity. Only nJug r 1 reactors had symptoms referred to walnut allergy. Twenty-five/37 nJug r 2-positive sera (67.6%) showed a simultaneous positivity to nMUXF3 and a significant correlation (p<0.0001) between the IgE levels to nJug r 2 and nMUXF3 (r²=0.787). After incubation with nMUXF3 a complete inhibition of sIgE reactivity to both nMUXF3 and nJug r 2 was shown.
  
  
  CONCLUSIONS
  The unexpected isolated sIgE reactivity to nJug r 2 found by ImmunoCAP ISAC™ 112 is frequently related to reactivity to cross-reactive carbohydrate epitopes and it is lacking clinical significance.
authors.forename: Danilo
authors.initials: D
authors.lastname: Villalta
authors.forename: Mariaelisabetta
authors.initials: M
authors.lastname: Conte
authors.forename: Riccardo
authors.initials: R
authors.lastname: Asero
authors.forename: Mirella
authors.initials: M
authors.lastname: Da Re
authors.forename: Sergio
authors.initials: S
authors.lastname: Stella
authors.forename: Paola
authors.initials: P
authors.lastname: Martelli
mesh_terms: D000485:Allergens / Q000097:blood* / Q000276:immunology; D015982:Bias; D002241:Carbohydrates / Q000276:immunology*; D002352:Carrier Proteins / Q000097:blood* / Q000276:immunology; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood*; D031324:Juglans / Q000737:chemistry / Q000276:immunology; D016014:Linear Models; D021184:Nut Hypersensitivity / Q000097:blood* / Q000175:diagnosis / Q000276:immunology; D010045:Outpatients; D040081:Protein Array Analysis / Q000706:statistics & numerical data*; D055314:Seed Storage Proteins / Q000097:blood* / Q000276:immunology
chemical_list: D000485:Allergens; D002241:Carbohydrates; D002352:Carrier Proteins; D000939:Epitopes; D055314:Seed Storage Proteins; C030363:lipid transfer protein; D007073:Immunoglobulin E; C015575:vicilin protein, plant