A biparatopic antibody targeting the Cε2 and Cε3 domains of IgE disrupts IgE-FcεRI interaction.

INTRODUCTION: Therapeutic anti-IgE antibodies that block the interaction between immunoglobulin E (IgE) and its high-affinity receptor (FcεRI) have been a popular direction for the treatment of allergic diseases. OBJECTIVES: Although both the Cε2 and Cε3 domains of IgE play important roles in stabilizing the IgE:FcεRI complex, most of those anti-IgE antibodies target only the Cε3 domain of IgE. Here, we develop a biparatopic antibody (SA25-A4-IgG1Fc) targeting both the Cε2 and Cε3 domains of IgE, which disrupts IgE-FcεRI interaction. METHODS: We link nanobody A4 and SA25 by a (GGGGS)4 linker, and fuse with a human IgG1Fc tag to generate SA25-A4-IgG1Fc. The FcεRI disruption effect of SA25-A4-IgG1Fc is tested by enzyme-linked immunosorbent assay, flow cytometry, surface plasmon resonance, and food allergic humanized mice. RESULTS: We identify an alpaca nanobody A4, which recognizes the Cε2 domain of IgE with nanomolar affinity, and a shark nanobody SA25, which binds the Cε3 domain of IgE competitively with FcεRⅠ. Targeting both the Cε2 and Cε3 domains of IgE, the biparatopic antibody (SA25-A4-IgG1Fc) binds to IgE with picomolar affinity, and blocks IgE-FcεRI interaction with greater potency than omalizumab in vitro. In addition, SA25-A4-IgG1Fc also removes IgE from human basophils and mast cells with high efficacy, and inhibits ovalbumin (OVA)-induced IgE-dependent food allergy in IgE/FcεRⅠ humanized mice in vivo. CONCLUSION: Our results demonstrate that the biparatopic antibody SA25-A4-IgG1Fc is a promising inhibitor for the treatment of food allergy, and provide a novel idea for the development of anti-IgE antibodies.