Roasting may alter the IgE binding epitopes and sensitizing ability of peanut allergens

Abstract

Rationale Little is known about the why certain foods are allergenic. Previous research demonstrated that roasting enhances certain allergenic properties of peanuts. We investigated possible mechanisms that may explain divergence in in vitro and in vivo allergenicity of differentially roasted peanuts. Methods The major peanut allergens Ara h 1 and Ara h 2 were purified from raw (R), light roast (LR) and dark roast (DR) peanuts, subjected to digestion with pepsin and trypsin, analyzed for IgE binding and roasting induced sugar modifications. Also, whole peanut proteins extracted from R, LR, and DR samples were used to sensitize mice, which were prick skin tested with the same allergens to measure the degree of sensitization. Results Ara h 1 and Ara h 2, purified from roasted peanuts, are more resistant to digestive enzymes. A correlation is seen between IgE binding and sugar modifications on long lived fragments. Interestingly, the digestion pattern of Ara h 1 and Ara h 2 from R, LR and DR peanuts were different. Additionally, we determined that mice sensitized with roasted peanuts had higher skin test reactivity than mice sensitized with raw peanut proteins. Conclusions Our results indicate that many of the IgE binding, digestion resistant fragments are modified with sugar by-products that occur as a result of roasting. Also, in some occasions roasting alters the IgE-binding fragments that survive digestion, and therefore, quite possibly, the allergenic epitopes. These altered epitopes may be responsible for in vivo data that demonstrate mice are more likely to be sensitized to roasted than raw peanuts.