IgE epitope analysis of sarcoplasmic-calcium-binding protein, a heat-resistant allergen in <i>Crassostrea angulata</i>

Abstract

Sarcoplasmic-calcium-binding protein (SCP) has been investigated as a novel allergen in <i>Crassostrea angulata</i>. Nevertheless, knowledge of its effector-cell-based allergic relevance and epitopes is limited. In this study, the heat-resistant allergen SCP was able to induce significant upregulation of CD63 and CD203c (<i>p</i> < 0.05), which showed obvious allergenicity in a basophil activation test. Furthermore, immunoinformatic tools, a one-bead-one-compound peptide library, and phage display technology were combined to analyze the allergenic epitopes of SCP. Five linear epitopes named L-SCP-1 (AA_22-33), L-SCP-2 (AA_64-75), L-SCP-3 (AA_80-90), L-SCP-4 (AA_107-116), and L-SCP-5 (AA_144-159) were verified using serological tests. Additionally, two conformational epitopes (C-SCP-1 and C-SCP-2) were determined, and C-SCP-1 was located at one of the calcium-binding sites (AA_106-117). Moreover, SCP showed weaker typical α-helical features and higher hydrophobicity after Ca²⁺ depletion, which reduced its IgE-binding capacity. Overall, these epitope data could enhance our understanding of oyster allergens, which could be used to develop hypoallergenic shellfish products.