<p>Monoclonal antibodies and ligands targeting CD40 exhibit a wide range of agonistic activities and antitumor responses. Studies have shown that the flexibility and affinity of antibodies play a crucial role in their immunostimulatory activity. However, a systematic comparison with the natural ligand is yet missing and a detailed investigation with respect to molecular rigidity, binding kinetics, and bond lifetime has not been undertaken to date. Here, we study the dynamic binding features of clinically relevant anti-hCD40 antibody subclasses, ChiLob 7/4, and the trimeric human CD40L to hCD40 at the single-molecule level. We visualize resembling of hCD40 receptors into dimers and higher-order oligomers that are dynamically captured and released by both ChiLob 7/4 and hCD40L with their multiple binding sites. Thereby, ChiLob 7/4 acts as a nanomechanical calliper and rotates its Fab arms in a highly dynamic fashion to screen for hCD40 binding, while hCD40L undergoes significantly less conformational changes. Despite its minor molecular flexibility, hCD40L performs association, dissociation, and re-association of hCD40 ten times faster when compared to ChiLob 7/4. We uncover a distinct binding mechanism that may explain the enhanced cluster formation potential and agonistic activity of the natural ligand and will inspire the design of novel ligand formats.</p>

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Nanomechanical binding mechanism of ligands drives agonistic activity

  • Hannah Seferovic,
  • Patricia Sticht,
  • Lisa Hain,
  • Rong Zhu,
  • Sebastian Diethör,
  • Christian Wechselberger,
  • Florian Weber,
  • David Bernhard,
  • Birgit Plochberger,
  • Yoo Jin Oh,
  • Javier Chaparro-Riggers,
  • Peter Hinterdorfer

摘要

Monoclonal antibodies and ligands targeting CD40 exhibit a wide range of agonistic activities and antitumor responses. Studies have shown that the flexibility and affinity of antibodies play a crucial role in their immunostimulatory activity. However, a systematic comparison with the natural ligand is yet missing and a detailed investigation with respect to molecular rigidity, binding kinetics, and bond lifetime has not been undertaken to date. Here, we study the dynamic binding features of clinically relevant anti-hCD40 antibody subclasses, ChiLob 7/4, and the trimeric human CD40L to hCD40 at the single-molecule level. We visualize resembling of hCD40 receptors into dimers and higher-order oligomers that are dynamically captured and released by both ChiLob 7/4 and hCD40L with their multiple binding sites. Thereby, ChiLob 7/4 acts as a nanomechanical calliper and rotates its Fab arms in a highly dynamic fashion to screen for hCD40 binding, while hCD40L undergoes significantly less conformational changes. Despite its minor molecular flexibility, hCD40L performs association, dissociation, and re-association of hCD40 ten times faster when compared to ChiLob 7/4. We uncover a distinct binding mechanism that may explain the enhanced cluster formation potential and agonistic activity of the natural ligand and will inspire the design of novel ligand formats.