Contribution of Chemical Modifications and Conformational Epitopes to IgE Binding by Ara h 3.

Scott Dyer,Hsiaopo Cheng,Jacqueline Nesbit,Barry Hurlburt,Beatriz Cabanillas,Soheila Maleki

doi:10.3390/foods7110189

Scott Dyer, Hsiaopo Cheng + Show 4 more

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https://doi.org/10.3390/foods7110189

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Abstract

Roasting is known to change the allergenic properties of peanuts. To study these observations at a molecular level, the relationship of IgE binding to the structure of Ara h 3 from raw and roasted peanuts was assessed. Ara h 3 (A3) was purified from raw (R), light roast (LR) and dark roast (DR) peanuts, the purity was assessed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the secondary structures were compared with circular dichroism (CD) spectroscopy. In order to understand the contribution of structure to IgE binding, the R A3 was partially denatured (PD) by heat treatment (65 °C for 2 h), subjected to CD spectroscopy and IgE spot blot analysis with sera from peanut- allergic individuals. While we observed that the secondary structure of purified A3 from R and LR peanut in solution was affected by the reduction of disulfide bonds and heat treatment when purified from the peanut following the roasting process, only small alterations were seen in the secondary structure. The purified LR A3 bound higher levels of IgE than the RA3. CD spectroscopy of PD A3 revealed a reduction in the percentage of alpha helices, and serum IgE binding. Therefore, while A3 purified from roasted peanuts did not show significant changes in secondary structure, it showed higher IgE binding than R A3. Therefore, the higher IgE binding to LR A3 was more likely to be due to chemical modifications than structural changes. However, a decrease in the IgE binding was seen if R A3 was deliberately unfolded, indicating that the structure played an important role in IgE binding to A3.

Highlights

Over 15 million Americans have a food allergy and there is evidence for an 18% increase in prevalence [1,2]
We theorized that Ara h 3, purified from roasted peanuts, was potentially denatured due to the high temperatures of roasting and this led to exposure of IgE epitopes that were inaccessible in the folded protein of the raw peanut
Ara h 3 was purified from raw (R), peanuts and two levels of roasted peanut, light roast (LR) and dark roast (DR) were subjected to SDS-PAGE, and the secondary structure was compared with circular dichroism (CD) spectroscopy (Figure 1A)

Summary

Introduction

Over 15 million Americans have a food allergy and there is evidence for an 18% increase in prevalence [1,2]. More than half of peanut-allergic individuals have as many as 1–2 accidental ingestions every five years [3]. With the large number of applications for peanut products in processed foods and the potential for cross-contamination of other food products with traces of peanut, it can be very difficult for allergic consumers to avoid accidental ingestions. In addition to being a serious public health concern, peanut allergy poses a challenge to the food industry and regulatory agencies in terms of food safety. The effects of processing on the allergenic potential of food has become increasingly important due to recent studies

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