# Ferritin Nanocages Exhibit Unique Structural Dynamics When Displaying Surface Protein

## TL;DR

Ferritin nanocages displaying SARS-CoV-2 Spike proteins interact efficiently with antibodies and cell receptors, making them promising for vaccine design.

## Contribution

The study reveals how ferritin nanocages maintain native binding profiles of Spike RBD with antibodies and receptors through molecular dynamics simulations.

## Key findings

- Molecular dynamics simulations show monoclonal antibodies bind more strongly to RBD via their variable heavy chain.
- ACE2 and B38 bind to the same RBD site but cause different dynamic responses.
- Ferritin-displayed RBD preserves native binding profiles, suitable for vaccine development.

## Abstract

Ferritin nanocages with spherical shells carry proteins or antigens that enable their use as highly efficient nanoreactors and nanocarriers. Mimicking the surface Spike (S) receptor-binding domain (RBD) from SARS-CoV-2, ferritin nanocages induce neutralizing antibody production or block viral entry. Herein, by implementing molecular dynamics simulation, we evaluate the efficiency in the interaction pattern (active or alternative sites) of H-ferritin displaying the 24 S RBDs with host-cell-receptor or monoclonal antibodies (mAbs; B38 or VVH-72). Our constructed nanocage targeted the receptor- or antibody-binding interfaces, suggesting that mAbs demonstrate an enhanced binding affinity with the RBD, with key interactions originating from its variable heavy chain. The S RBD interactions with ACE2 and B38 involved the same binding site but led to divergent dynamic responses. In particular, both B38 chains showed that asymmetric fluctuations had a major effect on their engagement with the Spike RBD. Although the receptor increased the binding affinity of VVH-72 for the RBD, the mAb structural orientation on the nanocage remained identical to its conformation when bound to the host receptor. Overall, our findings characterize the essential pharmacophore formed by Spike RBD residues over nanocage molecules, which mediates high-affinity interactions with either binding partner. Importantly, the ferritin-displayed RBD maintained native receptor and antibody binding profiles, positioning it as a promising scaffold for pre-fusion stabilization and protective RBD vaccine design.