Abstract
Ara h 2, a peanut 2S albumin, is associated with severe allergic reactions, but a homologous protein, soybean 2S albumin, is not recognized as an important allergen. Structural difference between these proteins might explain this clinical discrepancy. Therefore, we mapped sequential epitopes and compared the structure of Ara h 2, Soy Al 1, and Soy Al 3 (Gly m 8) to confirm whether structural differences account for the discrepancy in clinical responses to these two proteins. Commercially synthesized peptides covering the full length of Ara h 2 and two soybean 2S albumins were analyzed by peptide microarray. Sera from 10 patients with peanut and soybean allergies and seven non-atopic controls were examined. The majority of epitopes in Ara h 2 identified by microarray are consistent with those identified previously. Several regions in the 2S albumins are weakly recognized by individual sera from different patients. A comparison of allergenic epitopes on peanut and soybean proteins suggests that loop-helix type secondary structures and some amino acids with a large side chain including lone electron pair, such as arginine, glutamine, and tyrosine, makes the peptides highly recognizable by the immune system. By utilizing the peptide microarray assay, we mapped IgE epitopes of Ara h 2 and two soybean 2S albumins. The use of peptide microarray mapping and analysis of the epitope characteristics may provide critical information to access the allergenicity of food proteins.
Highlights
The ability of some proteins to induce an allergic reaction in susceptible individuals is well established
Albumins, sera from peanut and soybean allergic subjects were screened against three sets of 15 overlapping peptides; each set encompasses the entire Ara h 2, Soy Al 1, and Soy Al 3 protein sequences
We were interested in determining which h and soybean albumins due to their apparent difference in clinical allergenicity and similarity structural characteristics of peptides are important for determining IgE binding epitopes
Summary
The ability of some proteins to induce an allergic reaction in susceptible individuals is well established. It is not clear what characteristics confer various proteins the ability to induce allergic responses or why some proteins are more allergenic than others. Many factors have been suggested to contribute to the overall allergenicity of any given protein, such as the number of. The presence of certain epitopes is essential [3,4], but the fundamental characteristics that are common to protein epitopes are still not delineated. Molecules 2016, 21, 622 tree to evaluate allergenicity of novel proteins that include digestibility and greater than 35% sequence similarity [5]. Many 2S albumins from different species have been identified as allergens, such as those in Brazil nuts, sesame seeds, walnuts, rapeseeds, cashew nuts, peanuts, soybean, and mustard [9,10,11,12,13,14,15,16,17]
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