title: Reduced in vivo allergenicity of Bet v 1d isoform, a natural component of birch pollen.
abstract: BACKGROUND
  The major allergen of birch pollen, Bet v 1, is present in structurally slightly different isoforms. It has been postulated that certain isoforms show a distinct ability to bind birch pollen-specific IgE, although the T-cell response remains similar.
  
  
  OBJECTIVE
  We verified the hypothesis of a distinct allergenicity but similar T-cell immunogenicity of 2 isoforms in birch pollen-allergic subjects by in vivo tests and an in vitro assay for T-cell stimulation.
  
  
  METHODS
  Forty-eight birch pollen-allergic, 11 grass pollen-allergic, and 10 nonatopic control individuals were tested with 10-fold increasing concentrations (0.01 to 10.0 microg/mL) of recombinant (r) Bet v 1a and rBet v 1d by skin prick test (SPT), intradermal test (IDT), and conjunctival provocation test (CPT). An allergen-specific proliferation assay was performed on 21 patients with the 2 recombinant and the natural birch pollen allergens.
  
  
  RESULTS
  In each test system only birch pollen-allergic subjects but no controls reacted to the recombinant allergens. A positive in vivo response to 10 microg/mL of rBet v 1a was observed in 21 of 48 by SPT, in 48 of 48 by IDT, and in 33 of 48 by CPT. In contrast, the IDT response to 10 microg/mL of rBet v 1d was reduced by a factor of 100 because it was equivalent to the response to 0.1 microg/mL of rBet v 1a. rBet v 1d failed to elicit a positive reaction in SPT and CPT. The proliferative response of T cells was similar for both recombinant isoforms because 8 of 21 individuals reacted to rBet v 1a and 6 of 21 to rBet v 1d. Only 1 subject had a positive reaction to rBet v 1d alone.
  
  
  CONCLUSIONS
  The natural isoforms rBet v 1a and rBet v 1d differ in their ability to bind IgE but are similar in their immunogenicity for T cells. Thus rBet v 1d might be a promising candidate for use in immunotherapy of birch pollen-allergic individuals.
authors.affiliation: Division of Allergology, Inselspital, Bern, Switzerland.
authors.forename: O
authors.initials: O
authors.lastname: Arquint
authors.forename: A
authors.initials: A
authors.lastname: Helbling
authors.forename: R
authors.initials: R
authors.lastname: Crameri
authors.forename: F
authors.initials: F
authors.lastname: Ferreira
authors.forename: M
authors.initials: M
authors.lastname: Breitenbach
authors.forename: W J
authors.initials: WJ
authors.lastname: Pichler
mesh_terms: D000328:Adult; D000485:Allergens / Q000276:immunology; D052179:Antigens, Plant; D003228:Conjunctiva; D003233:Conjunctivitis, Allergic / Q000175:diagnosis; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000175:diagnosis; D010940:Plant Proteins / Q000737:chemistry / Q000276:immunology*; D011058:Pollen / Q000276:immunology*; D020033:Protein Isoforms / Q000276:immunology; D012882:Skin Tests
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D010940:Plant Proteins; D020033:Protein Isoforms; C061312:Bet v 1 allergen, Betula