Ara h 1 structure is retained after roasting and is important for enhanced binding to IgE

Abstract

Scope: Ara h 1 from roasted peanut binds higher levels of serum immunoglobulin E than raw peanuts and this is likely due to the Maillard reaction. While Ara h 1 linear IgE epitopes have been mapped, the presence and importance of structural epitopes is not clear.

Methods and results: Mass spectrometry, immunoblot, ELISA, circular dichroism (CD), and structural analysis were used to compare structural and subsequent IgE-binding differences in Ara h 1 purified from raw (N) and roasted peanuts (R) and denatured Ara h 1 (D). Although N and R had similar CD spectra, the latter bound significantly more IgE. Decreased IgE binding was seen with the loss of secondary structure. This same IgE-binding pattern [R > N > D] was seen for the sera of ten peanut allergic patients. While the majority of linear epitopes are located on surface and structured regions of Ara h 1, our study shows that conformational epitopes of Ara h 1 bind better to IgE than linear epitopes.

Conclusion: Enhanced IgE binding to roasted Ara h 1 could be due to alterations such as chemical modifications to individual amino acids or increased epitope exposure. IgE binding is significantly reduced with loss of structure.