METHODS: Linear IgE epitopes were identified using microarray data generated by printing 15-mer peptides offset by 5 amino acids on glass slides. IgE binding was detected with a fluorescently-labeled antibody. Western blots and mass spectrometry were used to show the presence of the leader sequences in peanut and walnut seeds.
RESULTS: For both Ara h 1 and Jug r 2 leader sequences, the epitopes with the highest degree of IgE binding were clustered within regions that were near cysteine residues. Of the patients tested, 96% showed IgE binding to those epitopes even if they recognized no other epitopes in the vicilins or the LS. In the case of Ara h 1, a hydrophobic residue at the N-terminus of certain IgE epitopes contributes to stronger IgE binding.
CONCLUSIONS: The results indicate that cysteine residues known to confer high structural stability to allergens may also coincide with areas of increased IgE binding frequency and intensity in Ara h 1 and Jug r 2 leader sequences. The leader sequences contain multiple immunodominant epitopes and may be important components to consider for diagnostic and therapeutic purposes.