title: Molecular and immunological characterization of Can f 4: a dog dander allergen cross-reactive with a 23 kDa odorant-binding protein in cow dander.
abstract: BACKGROUND
  Dog dander is an important cause of respiratory allergy but its content of allergenic components is still incompletely known. While Can f 1, 2, 3 and 5 have been studied in detail, only fragmentary information is available on the lipocalin Can f 4.
  
  
  OBJECTIVE
  To purify, clone and characterize dog dander allergen Can f 4.
  
  
  METHODS
  Can f 4 was purified from dog dander extract by size exclusion, ion exchange and reverse phase chromatography. A cDNA encoding Can f 4 was cloned and used to produce recombinant Can f 4 in Escherichia coli. A 23 kDa protein from cow dander, displaying cross-reactivity with Can f 4, was purified and identified by amino acid sequencing and mass spectrometry. IgE antibody binding to dog and cow dander extract and to individual dog allergens among 37 dog allergic subjects and 44 pollen allergic controls was studied using ImmunoCAP.
  
  
  RESULTS
  A dog genome segment containing the Can f 4 gene was bioinformatically identified and enabled the cloning of Can f 4 cDNA. Recombinant Can f 4 displayed close immunological and biochemical similarity to purified natural Can f 4 and bound IgE antibodies from 13/37 (35%) sera of dog allergic subjects. Can f 4 reactive sera showed IgE binding to a 23 kDa protein present in cow dander extract, related to a family of odorant-binding proteins. The dog and cow proteins shared 37% sequence identity and their cross-reactivity was demonstrated by IgE inhibition experiments.
  
  
  CONCLUSIONS
  Recombinant Can f 4 brings the panel of available dog allergens closer to completion and will be important in component-resolved diagnostics in allergy to animal epithelial allergens.
authors.affiliation: Phadia AB, Uppsala, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Mattsson
authors.forename: T
authors.initials: T
authors.lastname: Lundgren
authors.forename: P
authors.initials: P
authors.lastname: Olsson
authors.forename: M
authors.initials: M
authors.lastname: Sundberg
authors.forename: J
authors.initials: J
authors.lastname: Lidholm
mesh_terms: D000328:Adult; D000485:Allergens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle / Q000276:immunology*; D002852:Chromatography, Ion Exchange; D003429:Cross Reactions; D004285:Dogs / Q000276:immunology*; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000276:immunology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D018035:Receptors, Odorant / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D055815:Young Adult
chemical_list: D000485:Allergens; D018035:Receptors, Odorant; C045648:odorant-binding protein; D007073:Immunoglobulin E