Identification and characterisation of allergens related to Bet v I, the major birch pollen allergen, in apple, cherry, celery and carrot by two‐dimensional immunoblotting and N‐terminal microsequencing

Abstract

Low temperature extracts taken from Granny Smith and Braeburn apples, cherries, celery and carrots were separated by two‐dimensional electrophoresis. Bet v I, the major birch pollen allergen, related allergens in apple, cherry, celery and carrot extracts were detected by means of two‐dimensional immunoblotting with patients' sera containing IgE antibodies specific to Bet v I, a rabbit polyclonal antiserum raised against Bet v I, and two Bet vI specific mouse monoclonal antibodies. The major cross‐reacting allergen spots were observed with molecular weights/isoelectric points of 18.0 kDa/pI 5.5 for apple (Granny Smith and Braeburn) and 18.0 kDa/pI 5.8 for cherry, 15.5 kDa/pI 4.4–4.6 for celery and 16.0 kDa/pI 4.4 for carrot extract. Additional antibody reactivities with certain isoprotein spots were observed, which may indicate the presence of Bet v I‐related epitopes on these proteins. Based on the first 15 N‐terminal amino acid residues, the major allergen spots revealed 53% sequence identity between Bet v I and the Granny Smith apple allergen, 50% between Braeburn apple allergen and Bet v I, 67% between Bet v I and the cherry allergen, and 40 and 28% for celery and carrot, respectively. Furthermore, the N‐terminal sequences showed identities ranging from 40% (apple/cherry) to 66% (celery) with PcPR l‐l, a pathogenesis‐related protein in parsley.