Heat-induced alterations in cashew allergen solubility and IgE binding

Authors: Mattison, Chris; BREN-MATTISON, YVETTE - Biomed Bridge; VANT-HULL, BARRY - Express Diagnostics International; Vargas, Aurora; WASSERMAN, RICHARD - Allergy/immunology Research Center Of North Texas; Grimm, Casey

Submitted to: Toxicology Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2015
Publication Date: 4/2/2016
Citation: Mattison, C.P., Bren-Mattison, Y., Vant-Hull, B., Vargas, A.M., Wasserman, R.L., Grimm, C.C. 2016. Heat-induced alterations in cashew allergen solubility and IgE binding. Toxicology Reports. (3):244-251.

Interpretive Summary: Cashew nuts are included in a group of 8 foods that commonly cause food allergies. IgE binding to certain proteins (allergens) within the cashew nuts can cause allergic reactions that can be severe. Foods containing cashew nuts must be labeled to prevent accidental exposure to people who suffer from allergy to cashew nut and other nuts. Therefore, detection of cashew nut and other allergens is important to public safety. Food processing and preparation steps can alter the solubility of allergens within nuts and this can affect our ability to detect foods containing cashew nut and other allergens. We used several laboratory techniques to characterize the changes in cashew nut allergen solubility following heating of cashew nuts. Or results clearly indicated that heating can alter the solubility of cashew nut allergens, and can decrease solubility of some allergens while increasing the relative solubility of another allergen. Antibody binding experiments indicated that there was a decrease in detection of cashew nut allergens due to heating, and this may impair detection of cashew nuts in foods. Our results suggest that diagnostic kits that account for these changes in cashew nut allergen solubility after heating could enable more reliable detection of cashew nut allergens in food and improved public health.

Technical Abstract: Cashew nuts are included in a group of 8 foods that commonly cause food allergies. IgE binding to allergens within the nuts can cause allergic reactions that can be severe. Foods containing cashew nuts must be labeled to prevent accidental exposure to people who suffer from allergy to cashew nuts. Therefore, detection of cashew nut and other allergens is important for public safety. Food processing and preparation steps can alter the solubility of allergens within nuts and this can affect our ability to detect foods containing cashew nut and other allergens. We compared the soluble protein profile and mass-spectrometric detection of peptides following heating of cashew nuts to characterize the changes to cashew nut allergens that occur and identify candidate peptides that may function well as diagnostic targets. SDS-PAGE results indicated that heating can alter the solubility of extractable proteins from cashew nut. The 11S legumin, Ana o 2, dominates the soluble protein content in ready to eat and mildly heated cashew nuts. However, we found that in dark-roasted cashew nuts, the soluble protein profile shifts and the 2S albumin Ana o 3 composes up to 40% of the soluble protein. Analysis of trypsin-treated extracts by LC/MS/MS indicated changes in the sequence, relative number, and intensity of peptides characterized by our mass-spectrometric analysis. The cumulative intensity and the sequence of the 5 most commonly observed Ana o 1 and 2 peptides were altered by heating, while the sequence of the 5 most commonly observed Ana o 3 peptides remained fairly constant. ELISA binding experiments indicated that there was a decrease in rabbit IgG and human serum IgE binding to soluble proteins in cashew extracts following heating. Our findings indicate that heating can alter the solubility of cashew allergens, resulting in altered IgE binding and this may impair detection of cashew nuts in foods. Our results support the use of both Ana o 2 and Ana o 3 as potential cashew allergen diagnostic targets.