Mapping Sequential IgE-Binding Epitopes on Major and Minor Egg Allergens

<b><i>Introduction:</i></b> Molecular studies of hen’s egg allergens help define allergic phenotypes, with IgE to sequential (linear) epitopes on the ovomucoid (OVM) protein associated with a persistent disease. Epitope profiles of other egg allergens are largely unknown. The objective of this study was to construct an epitope library spanning across 7 allergens and further evaluate sequential epitope-specific (<i>ses-</i>)IgE and <i>ses-</i>IgG₄ among baked-egg reactive or tolerant children. <b><i>Methods:</i></b> A Bead-Based Epitope Assay was used to identify informative IgE epitopes from 15-mer overlapping peptides covering the entire OVM and ovalbumin (OVA) proteins in 38 egg allergic children. An amalgamation of 12 B-cell epitope prediction tools was developed using experimentally identified epitopes. This ensemble was used to predict epitopes from ovotransferrin, lysozyme, serum albumin, vitellogenin-II fragment, and vitellogenin-1 precursor. <i>Ses-</i>IgE and <i>ses-</i>IgG₄ repertoires of 135 egg allergic children (82 reactive to baked-egg, the remaining 52 tolerant), 46 atopic controls, and 11 healthy subjects were compared. <b><i>Results:</i></b> 183 peptides from OVM and OVA were screened and used to create an aggregate algorithm, improving predictions of 12 individual tools. A final library of 65 sequential epitopes from 7 proteins was constructed. Egg allergic children had higher <i>ses-</i>IgE and lower <i>ses-</i>IgG₄ to predominantly OVM epitopes than both atopic and healthy controls. Baked-egg reactive children had similar <i>ses-</i>IgG₄ but greater <i>ses-</i>IgE than tolerant group. A combination of OVA-sIgE with <i>ses-</i>IgEs to OVM-023 and OVA-028 was the best predictor of reactive phenotype. <b><i>Conclusion:</i></b> We have created a comprehensive epitope library and showed that <i>ses-</i>IgE is a potential biomarker of baked-egg reactivity.