Repeated Sequences with Similar Physicochemical Properties May Account for Cross-Reactions Between Peanuts and Tree Nuts

Abstract

FEBRUARY 2013 AB20 Abstracts S A T U R D A Y 71 Chemical and Structural Alterations to Ara h 2 Following Simulated Roasting Tysheena Charles, MS, Casey C. Grimm, Samuel Landry, PhD, Soheila J. Maleki, PhD; Tulane University, New Orleans, LA, USDA-ARS-SRRC, New Orleans, LA, Tulane University Health Sciences Center, New Orleans, LA. RATIONALE: Ara h 2 is a peanut allergen that is a member of the 2s albumins, a family of potent plant allergens. Recombinant Ara h 2 (rAra h 2) was expressed at high levels and purified in folded form. This protein was subjected to a simulated roasting model (SRM) and specific amino acid modifications were identified. METHODS: The cDNA for Ara h 2 was commercially synthesized to encode the codons preferred byE. coli. This cDNAwas cloned into pET32b and expressed as a thioredoxin fusion, which was then cleaved from the soluble rAra h 2. Proper folding of rArah 2 was confirmed by circular dichroism. rAra h 2 was then incubated in the presence of 0.25M glucose or xylose for 2, 4, 7and 10 days in a SRM and tested for IgE binding with patient sera using western blot and ELISA. Mass spectrometry was used to identify chemical modifications that occur following the SRM. RESULTS: A range of alterations in IgE reactivity towards rAra h 2 was observed following SRM. Mass spectrometry allowed us to identify specific modifications to amino acids of rAra h 2 following SRM that may contribute to alterations in IgE binding. CONCLUSIONS: IgE binding to rAra h 2 before and after processingwas altered for some patient sera and specific chemical modifications that may contribute to this were identified. Further studies will be done to definitively identify the chemical modifications that contribute to altered IgE binding following SRM and its effects on histamine release.