Identification of four IgE-reactive proteins in raspberry (Rubus ideaeus L.)

IgE-reactive proteins in raspberry (Rubus ideaus L.) were identified using PCR, RT-PCR, 2-DE and MS/MS peptide sequencing. Specific polyclonal antibodies and patient sera were used in Western blotting to identify crossreactive epitopes. Initially, two potential allergens Rub i 1 and Rub i 3 were detected using PCR, showing high sequence identity to proteins in Rosaceous species like Mal d 1 and Mal d 3 from apple, Pru av 1 and Pru av 3 from cherry and Pru p 1 and Pru p 3 from peach. Furthermore, de novo identified peptides of a protein band at about 30 kDa reacting with most of the patient sera tested (> 80%) revealed a high sequence homology with class III chitinases. Raspberry chitinase, when subjected to glycoproteomic analysis, showed typical complex plant-type N-glycans with a core alpha1,3 fucose and a beta1,2 xylose at least at one position, indicating the presence of crossreacting carbohydrate determinants (CCDs). Finally, MS/MS analysis revealed an IgE-reactive raspberry cyclophilin, homologous to Bet v 7. Results obtained suggest that the consumption of raspberries might be responsible for adverse reactions in sensitised individuals.