Molecular characterization of Dau c 1, the Bet v 1 homologous protein fromcarrot 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-c alled oral allergy syndrome, an IgE-mediated food allergy. The most frequen t and therefore best characterized pollen-fruit syndrome is apple allergy i n patients suffering from tree pollen-induced pollinosis. The occurrence of adverse reactions to proteins present in vegetables such as celery and car rots in patients suffering from pollen allergy has also been reported. cDNA s for Bet v I homologous proteins have been cloned from celery, apple and c herry. Objective The aim of the study was to identify Bet v 1 homologues from carr ot (Daucus carota), to isolate the respective cDNA, to compare the IgrE-bin ding capacity of the natural protein to the recombinant allergen and determ ine the cross-reactivity to Api g 1 and Bet v 1, Methods Molecular characterization of the carrot allergen was performed usi ng 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 t hree extremely similar sequences (Dau c 1.1, 1.2 and 1.3) with an open read ing frame of 462 bp coding for 154 amino acid residues. Conclusions Purified recombinant Dau c 1.2 was tested in immunoblots displa ying IgE-binding capacity comparable to its natural counterpart. Cross-inhi bition assays verified the existence of common B-cell epitopes present on D au c 1, Api g 1 as well as on Bet v 1.