Molecular characterization of Dau c 1, the Bet v 1 homologous protein from carrot and its cross-reactivity with Bet v 1 and Api g 1.
BACKGROUND
Up to 70% of patients with birch pollen allergy exhibit the so-called oral allergy syndrome, an IgE-mediated food allergy. The most frequent and therefore best characterized pollen-fruit syndrome is apple allergy in patients suffering from tree pollen-induced pollinosis. The occurrence of adverse reactions to proteins present in vegetables such as celery and carrots in patients suffering from pollen allergy has also been reported. cDNAs for Bet v 1 homologous proteins have been cloned from celery, apple and cherry. Objective The aim of the study was to identify Bet v 1 homologues from carrot (Daucus carota), to isolate the respective cDNA, to compare the IgE-binding capacity of the natural protein to the recombinant allergen and determine the cross-reactivity to Api g 1 and Bet v 1.


METHODS
Molecular characterization of the carrot allergen was performed using IgE-immunoblotting, cross-inhibition assays, N-terminal sequencing, PCR-based cDNA cloning and expression of the recombinant protein in Escherichia coli.


RESULTS
A 16-kDa protein from carrot was identified as a major IgE-binding component and designated Dau c 1. Sequencing corresponding cDNAs revealed three extremely similar sequences (Dau c 1.1, 1.2 and 1.3) with an open reading frame of 462 bp coding for 154 amino acid residues.


CONCLUSIONS
Purified recombinant Dau c 1.2 was tested in immunoblots displaying IgE-binding capacity comparable to its natural counterpart. Cross-inhibition assays verified the existence of common B-cell epitopes present on Dau c 1, Api g 1 as well as on Bet v 1.
Hoffmann-Sommergruber
K
K
Department of General and Experimental Pathology, University of Vienna, Austria.
O'Riordain
G
G
Ahorn
H
H
Ebner
C
C
Laimer Da Camara Machado
M
M
Pühringer
H
H
Scheiner
O
O
Breiteneder
H
H
D000485:Allergens; D000595:Amino Acid Sequence / Q000235:genetics; D052179:Antigens, Plant; D001483:Base Sequence / Q000235:genetics; D003429:Cross Reactions / Q000276:immunology; D018552:Daucus carota / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000276:immunology; D008969:Molecular Sequence Data; D010936:Plant Extracts / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000302:isolation & purification; D011994:Recombinant Proteins; D017385:Sequence Homology
D000485:Allergens; D052179:Antigens, Plant; C096695:Api g 1 protein, Apium graveolens; C119925:Dau c 1 protein, Daucus carota; D010936:Plant Extracts; D010940:Plant Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; C061312:Bet v 1 allergen, Betula; D007073:Immunoglobulin E