title: Isolation of the main allergen Fra e 1 from ash (Fraxinus excelsior) pollen: comparison of the natural and recombinant forms.
abstract: BACKGROUND
  Fra e 1 is a major allergen for ash pollen-sensitized individuals in northern and central Europe. It belongs to the Ole e 1-like family and displays high cross-reactivity with taxonomically related members.
  
  
  OBJECTIVE
  To isolate and characterize natural Fra e 1 (nFra e 1) from ash pollen and to compare its structural, antigenic, and allergenic properties with those of its recombinant form (rFra e 1).
  
  
  METHODS
  The allergen was isolated by means of gel permeation chromatography and reverse-phase high-performance liquid chromatography columns. Molecular characterization was performed by means of Edman degradation, mass spectrometry, circular dichroism, concanavalin A lectin reaction, and anti-horseradish peroxidase polyclonal antibody. Immunologic characterization was performed using immunoblotting and enzyme-linked immunosorbent assay, inhibition experiments, and histamine release assays with serum samples from allergic patients with well-known reactivity to Fra e 1 or Ole e 1 and with polyclonal antiserum and monoclonal antibodies against Ole e 1. The protein used as a reference was rFra e 1, which was produced in the yeast Pichia pastoris.
  
  
  RESULTS
  Purified nFra e 1 appeared as 5 variants with different glycosylation degrees. Both nFra e 1 and rFra e 1 were equivalently folded as deduced from the spectroscopic analysis using circular dichroism. Both molecules share the antigenic and allergenic epitopes after the purification process, and the glycan group of nFra e 1 is a potential epitope. Natural Fra e 1 displayed strong cross-reactivity with Ole e 1.
  
  
  CONCLUSIONS
  Natural Fra e 1 is a heterogeneously glycosylated protein with high allergenic relevance. It displays structural, antigenic, and allergenic similarity with rFra e 1. Both proteins could be used for clinical purposes.
authors: Departmento Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Spain.
authors: Rodrigo
authors: R
authors: Barderas
authors: Ashok
authors: A
authors: Purohit
authors: Rosalía
authors: R
authors: Rodríguez
authors: Gabrielle
authors: G
authors: Pauli
authors: Mayte
authors: M
authors: Villalba