Treatment of cashew extracts with Aspergillopepsin reduces IgE binding to cashew allergens

Authors: DEFREECE, CECILY - Xavier University; Cary, Jeffrey; Grimm, Casey; WASSERMAN, RICHARD - Allergy/immunology Research Center Of North Texas; Mattison, Chris

Submitted to: Journal of Applied Biology & Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2015
Publication Date: 3/1/2016
Citation: Defreece, C.B., Cary, J.W., Grimm, C.C., Wasserman, R.L., Mattison, C.P. 2016. Treatment of cashew extracts with Aspergillopepsin reduces IgE binding to cashew allergens. Journal of Applied Biology & Biotechnology. 4(2):1-10.

Interpretive Summary: Cashew nuts can cause serious and sometimes life threatening reactions in people that suffer from food allergies. These reactions are mediated by immunoglobulin E binding (IgE) to allergenic cashew proteins. Enzymes from Aspergillus fungal species are used in many food and pharmaceutical applications and are considered safe. We grew Aspergillus fungi on media containing cashew nut flour to identify proteins that allow the fungi to break down the allergenic proteins in the cashew nut flour. We identified a protein, Aspergillopepsin, that was produced by the fungi during growth on the cashew nut flour. We determined that a commercially available preparation of Aspergillopepsin was able to break down cashew nut flour proteins and reduce serum IgE binding to cashew nut allergens. Aspergillopepsin and other fungal enzymes may be useful in the future as food allergen processing enzymes to make foods safer for those that suffer from food allergies.

Technical Abstract: Cashew nuts can cause serious and sometimes life threatening reactions in people that suffer from food allergies. These reactions are mediated by immunoglobulin E binding (IgE) to allergenic cashew proteins. Enzymes from Aspergillus fungal species are used in many industrial and pharmaceutical applications. We cultured Aspergillus species on media containing cashew nut flour to identify secreted proteins that may be useful as future food allergen processing enzymes. Mass-spectrometric analysis of secreted proteins and protein bands from SDS-PAGE gels indicated the presence of at least 63 proteins. The majority of these proteins were involved in carbohydrate metabolism, but there were also enzymes involved in lipid and protein metabolism. Aspergillopepsin from A. niger was one of the proteolytic enzymes we identified, and we matched 6 distinct peptides to this protein providing 22% coverage of the protein. Cashew extracts were incubated with a commercially available preparation of Aspergillopepsin (Acid Stable Protease, ASP) using simulated gastric fluid conditions to determine if ASP could degrade the protein and lower antibody binding to cashew allergens. Following treatment of cashew extract with ASP, we observed a reduction in cashew allergen binding to rabbit anti-cashew IgG using an immunoblot assay and serum IgE antibodies from cashew allergic individuals using competitive ELISA. Our findings highlight the possible application of Aspergillopepsin/ASP from A. niger in food processing steps to attenuate cashew nut and other tree nut or peanut allergens.