Mapping of conformational IgE epitopes on Phl p 5a by using mimotopes from a phage display library

Background: Phi p 5 represents a major allergen of timothy grass pollen (Phleum pratense). Detailed knowledge about the structures responsible for IgE binding would allow the design of a novel generation of allergy vaccines. Objective: We aimed to characterize the IgE epitopes of Phi p 5a using phage display combined with a molecular modeling approach. Methods: Phi p 5a-specific IgE from sera of patients with grass pollen allergy was used for screening of a random peptide phage library displaying constrained decamers. Results: Fifteen phage clones that shared sequence motifs and could be grouped into families were selected by using Phi p 5a-specific IgE. Peptide alignment with the solvent-accessible amino acids of Phi p 5a revealed 3 sequence sections with frequent hits of identical or similar amino acids. On the surface of Phi p 5a, these sections assembled in compact patches, most likely representing conformational IgE epitopes, whereas no matching clusters were found on the back sides of the 2 Phi p 5a halves. In surface plasmon resonance experiments, the high-affinity interaction between IgE and Phi p 5 could be competed by phage-displayed peptides up to 24%, indicating that they represent true epitope mimics tie, mimotopes). Allergen-specific immunogenicity of the mimotopes was proved in Biozzi mice. Conclusion: The selected mimotopes facilitated the localization of conformational IgE epitopes of Phi p 5. We suggest them to be suitable candidates for the development of an epitope-specific immunotherapy.