Localization and antigenicity reduction of immunodominant conformational IgE epitopes on αs1-casein

Abstract

αs1-Casein (αs1-CN) is the major allergen in cow milk; however, the understanding of its conformational epitopes remains limited due to the absence of a well-defined three-dimensional structure, which has impeded efforts to effectively reduce its antigenicity. This study employed molecular dynamics simulations (MD), ELISA, cell assays and peptidomes analysis to investigate the critical conformational epitopes of αs1-Casein. MD and immunological analyses identified a dominant conformational epitope encompassing the regions S55-E75 & Y154-T174 & F179-W199, which exhibited strong binding affinity to IgE and triggered the releasing of β-hexosaminidase, histamine and IL-6 in KU812 cells, thereby inducing allergic responses. Notably, the segments Y154-T174 and F179-W199 were particularly impactful. Furthermore, the presence of helical structures within the epitopes enhanced their binding to IgE to a certain extent. Peptidomes analysis further revealed that papain efficiently disrupted the key epitope (Y154-T174) by selectively cleaving the hotspot amino acid residues (Y154 and Y165), thereby significantly reducing the antigenicity of αs1-CN, decreasing IgE and IgG binding to 7.28 % and 10.39 %, respectively. These findings enhance the understanding of αs1-CN's antigenic epitopes and provides a theoretical and technical foundation for the targeted reduction of its antigenicity.