A highly stable prefusion RSV F vaccine derived from structural analysis of the fusion mechanism

TLDR

Respiratory syncytial virus causes acute lower respiratory tract infections and is the leading cause of infant hospitalizations, and a promising vaccine antigen based on the RSV fusion protein stabilized in the native prefusion conformation has recently been described. The study reports alternative strategies to arrest RSV F in the prefusion conformation by preventing hinge movements in the first refolding region and eliminating proteolytic exposure of the fusion peptide. These strategies involve mutating the hinge region to restrict refolding and removing proteolytic cleavage sites to protect the fusion peptide. A limited set of mutations stabilizes the prefusion conformation, dramatically increases expression, elicits neutralizing antibodies and complete protection in cotton rats, and the structural analysis indicates a functional role for the excised p27 segment.

Abstract

Abstract Respiratory syncytial virus (RSV) causes acute lower respiratory tract infections and is the leading cause of infant hospitalizations. Recently, a promising vaccine antigen based on the RSV fusion protein (RSV F) stabilized in the native prefusion conformation has been described. Here we report alternative strategies to arrest RSV F in the prefusion conformation based on the prevention of hinge movements in the first refolding region and the elimination of proteolytic exposure of the fusion peptide. A limited number of unique mutations are identified that stabilize the prefusion conformation of RSV F and dramatically increase expression levels. This highly stable prefusion RSV F elicits neutralizing antibodies in cotton rats and induces complete protection against viral challenge. Moreover, the structural and biochemical analysis of the prefusion variants suggests a function for p27, the excised segment that precedes the fusion peptide in the polypeptide chain.