RSV neutralization by palivizumab, but not by monoclonal antibodies targeting other epitopes, is augmented by Fc gamma receptors

- Respiratory syncytial virus infection of Fc gamma receptor (FCGR)-bearing cells was analyzed in vitro.
- FCGR diminish neutralizing potency of monoclonal antibodies.
- But FCGR augmented neutralizing potency of palivizumab, a yet unrecognized characteristic of this therapeutic antibody.
- Antibody-dependent enhancement of RSV infection of FCGR-bearing cells occurs with all monoclonal antibodies.
- FCGR-antibody interactions are important when evaluating novel antibodies and vaccine concepts against RSV infection.

Palivizumab efficiently blocks respiratory syncytial virus (RSV) infection in vitro. However, virus neutralization assays generally omit Fc region-mediated effects. We investigated the neutralization activity of RSV-specific monoclonal antibodies on cells with Fc receptors. Subneutralizing concentrations of antibodies resulted in antibody-dependent enhancement of RSV infection in monocytic cells. Contrary to antibodies targeting other epitopes, the neutralization by palivizumab was augmented in cells with Fc receptors. This unrecognized characteristic of palivizumab may be relevant for its performance in vivo.