Publications

Background Although hen’s egg allergy is more prevalent in children, up to 0.6% of adults from different European countries suffers from a persistent or newly-onset hen’s egg allergy, making accurate diagnosis in adults necessary. However, sensitisation to hen’s egg extracts, components and linear epitopes are solely studied in children. Methods Hen’s egg allergic (n=16) and tolerant (n=20) adults were selected by sensitisation towards recombinant components rGal d 1 and/or 3. Sensitisation profiles towards egg white and yolk extract and the native components Gal d 1, 2, 3 and 4 were respectively evaluated with the ImmunoCAP or the EUROLINE system. Characterisation of linear epitopes was performed with a peptide microarray containing 15mer peptides representing the entire sequence of mature Gal d 1 and 3. Results Overall, sIgE titres against hen’s egg extracts and single components overlapped largely between allergic and tolerant adults. Although the median sIgE/sIgG4 ratio to Gal d 1 was increased in allergic adults, the range was comparable between both groups. Clinically relevant sensitisation to Gal d 1 was confirmed by sIgE-binding to the linear epitopes aa30-41, aa39-50 or aa84-95 in 6/13 allergic adults, mainly suffering from objective symptoms. In comparison, these epitopes were recognized by 1/15 tolerant patient. Only a few linear epitopes were detected for Gal d 3, suggesting a greater importance of conformational epitopes for the recognition of Gal d 3. Conclusion and Clinical Relevance Specific IgE-binding to linear epitopes of Gal d 1 is highly specific in identifying hen’s egg allergic adults with objective symptoms.

Detailed IgE-binding epitope analysis is a key requirement for the understanding and development of diagnostic and therapeutic agents to address food allergies. An IgE-specific linear peptide microarray with random phage peptide display for the high-resolution mapping of IgE-binding epitopes of the major soybean allergen Gly m 4, which is a homologue to the birch pollen allergen Bet v 1 is combined. Three epitopes are identified and mapped to a resolution of four key amino acids, allowing the rational design and the production of three Gly m 4 mutants with the aim to abolish or reduce the binding of epitope-specific IgE. In ELISA, the binding of the mutant allergens to polyclonal rabbit-anti Gly m 4 serum as well as IgE purified from Gly m 4-reactive soybean allergy patient sera is reduced by up to 63% compared to the wild-type allergen. Basophil stimulation experiments using RBL-SX38 cells loaded with patient IgE are showed a decreased stimulation from 25% for the wild-type Gly m 4 to 13% for one mutant. The presented approach demonstrates the feasibility of precise mapping of allergy-related IgE-binding epitopes, allowing the rational design of less allergenic mutants as potential therapeutic agents.