Identification and assessment of the IgE epitopes of Ara h 1 and Jug r 2 leader sequences

Authors: Nesbit, Jacqueline; Cheng, Hsiaopo; Hurlburt, Barry; Maleki, Soheila

Submitted to: American Academy of Allergy Asthma and Immunology
Publication Type: Abstract Only
Publication Acceptance Date: 2/2/2018
Publication Date: 2/2/2018
Citation: Nesbit, J.B., Cheng, H., Hurlburt, B.K., Maleki, S.J. 2018. Identification and assessment of the IgE epitopes of Ara h 1 and Jug r 2 leader sequences. American Academy of Allergy Asthma and Immunology. 141:2.

Interpretive Summary: The vicilins, Ara h 1 from peanut and Jug r 2 from walnut, are considered major allergens that are translated with leader sequences that are cleaved before yielding the mature protein. Structurally these leader sequences resemble the 2S albumins, which are the most immunodominant allergens in nuts. 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. 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. 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.

Technical Abstract: The vicilins, Ara h 1 from peanut and Jug r 2 from walnut, are considered major allergens that are translated with leader sequences that are cleaved before yielding the mature protein. Structurally these leader sequences resemble the 2S albumins, which are the most immunodominant allergens in nuts. 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. 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. 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.