IgE-mimotopes are safe for immunizations when displayed in a monovalent manner

Background: IgG directed to the IgE epitopes of allergens act as blocking antibodies, as they bind the allergen but do not interact with allergy effector cells. We suggested previously to use epitope-mimics for immunizations to direct the humoral response towards the blocking IgG type and defined peptide structures mimicking natural IgE epitopes (mimotopes) of the birch pollen major allergen Bet v 1. These mimotopes, when displayed on phage, were suitable to induce blocking IgG antibodies in mice. In the present study we aimed to generate phage-independent recombinant vaccines consisting of the mimotopes linked to the streptococcal membrane protein G-derived albumin binding protein (ABP). ABP was chosen due to its immunogenicity, and to stabilize the mimotopes' conformation by its hydrophobic tagging properties. Methods and Results: Monomeric and dimeric fusion proteins were constructed by recombinant DNA technology, expressed in E, coli and purified from bacterial membrane fractions by Ni-ion affinity chromatography. The antigenicity of the fusion proteins was controlled in an ELISA, using rat serum albumin for coating, which binds ABP with high affinity. The mimotopes were recognized well by the IgE, indicating a correct folding of the peptides. When the ABP alone was applied for immunizing Balb/c mice, antibodies of subclasses IgG1 and IgG2a specific for ABP were induced, independent of the usage of adjuvans. Conclusion: We conclude that IgE mimotopes fused to the immunogenic carrier ABP are safe candidates for epitope-based immunotherapy of allergic patients.