Antigen improves binding of IgGs to FcγRs in SPR analysis

Fc gamma R binding characterization is one of the critical attributes during the development of therapeutic antibodies. Here, we report a novel assay format to characterize IgG-Fc gamma R interaction in the presence of antigen using Surface plasmon resonance (SPR). The new assay format was developed by creating stable antigen/antibody immunocomplexes on a sensor chip surface before injection of Fc gamma Rs. In this assay format, binding activity of both huIgG1 (including IgG1 Fc fusion Protein) and huIgG2 increased significantly to most activating human Fc gamma Rs, especially to Fc gamma RI, Fc gamma RIIa-131H and Fc gamma RIIIa-158F. To our knowledge, this study provides the first set of evidence using a biophysical method to demonstrate antigen binding facilitating IgG-Fc gamma R interaction, especially for huIgG2 where previous studies did not indicate its binding to human Fc gamma RI or Fc gamma RIIIa-158F. Although further studies are needed to investigate the correlation of the binding data with effector function data in vivo, our results suggest that it may be useful to evaluate the IgG-Fc gamma R interaction in the presence of antigen to help design safer and more effective biotherapeutics.

Automated summary

Fc gamma R binding characterization is critical during therapeutic antibody development. A new assay format using Surface plasmon resonance (SPR) was developed to characterize IgG-Fc gamma R interaction in the presence of antigen. The study provides evidence of antigen binding facilitating IgG-Fc gamma R interaction, especially for huIgG2. Evaluating the IgG-Fc gamma R interaction in the presence of antigen may help design safer and more effective biotherapeutics.