Title: Ara h 1 structure is retained after roasting and is important for enhanced binding to IgE Authors
Submitted to: Molecular Nutrition and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 6, 2012
Publication Date: September 21, 2012
Citation: Nesbit, J.B., Hurlburt, B.K., Schein, C., Cheng, H., Wei, H., Maleki, S.J. 2012. Ara h 1 structure is retained after roasting and is important for enhanced binding to IgE. Molecular Nutrition and Food Research. 56:1-9. Interpretive Summary: Allergy to peanuts is an increasing public health risk, affecting over 3.5 million individuals in the U.S. and over 1% of U.K. school children. We investigated the effect that heating had on the ability of IgE to recognize the heated form of one of the major peanut proteins involved in peanut allergy, and compared that to the unheated form. A large part of the characterization of food allergens is performed using serum from the blood of allergic individuals, as it contains a protein called immunoglobulin E (IgE), which specifically recognizes allergens and mediates the symptoms of the allergic disease. Most peanuts are ingested in the processed form, which involves heat treatment, e.g., boiling or roasting. We found that heating causes alterations in the peanut protein, and IgE bound the heated form better than the raw form and accounts, in part, for the increased allergenicity observed in processed peanuts.
Technical Abstract: Roasted peanuts bind higher levels of serum IgE than raw peanuts. The contribution of the major allergens to this observation are not well-defined. We compared IgE binding properties of Ara h 1 purified from raw and roasted peanuts, and assess the structural components that may contribute to differences in IgE binding properties. Ara h 1 purified from raw and roasted peanuts, and heat denatured Ara h 1, were subjected to circular dichroism (CD) spectroscopy to monitor structural changes. IgE binding to each of the states of Ara h 1 was compared using sera from documented peanut allergic individuals in spot blot analysis. While the roasted Ara h 1 bound significantly higher IgE, the secondary structure was not significantly different from the Ara h 1 purified from raw peanut. A coincidental drop in IgE binding was seen with a loss in the secondary structure of Ara h 1. The majority of serum IgE from allergic and non allergic patients’ sera bound from highest to lowest to roasted, raw and denatured Ara h 1 (roasted > raw> denatured), respectively. We concluded that the structural epitopes are more important to IgE binding to the raw Ara h 1 than the liner epitopes; however, enhanced binding of IgE to roasted Ara h 1 is mostly due to chemical modifications, rather than enhanced epitope exposure due to denaturation.