Structural and functional basis for the inhibition of respiratory syncytial virus entry by RhoA-derived peptides

Respiratory syncytial virus (RSV) causes significant morbidity and mortality in infants, and in elderly and immunocompromised adult populations. No vaccine for RSV is available and treatment options are limited. A 19mer peptide derived from the GTPase RhoA inhibits RSV entry and may represent a novel approach for antiviral therapy. We have therefore investigated the structural and functional basis for inhibition of RSV by this peptide and several derivatives. We show that the antiviral activity of RhoA-derived peptides depends upon their anionic nature, and results from their ability to form disulfide-linked dimers in solution that act through the RSV G glycoprotein to disrupt initial attachment of virus to host cells. This mechanism is functionally similar to that of sulfated polysaccharides and other anionic polymers, suggesting that RhoA-derived peptides may be active against a wide variety of enveloped viruses that are inhibited by polyanions. In addition, RhoA-derived peptides appear to have secondary effects on RSV F-mediated membrane fusion that are separate from their effect on viral attachment. These data suggest that the negative charge of the peptides leads to their concentration at positively charged heparin binding regions of the viral glycoproteins and predict that addition of negative charges to other specific inhibitors of RSV entry may improve their antiviral efficacy.; Our work also provides new insight into the mechanisms or RSV entry. Specifically, we have shown that the binding of RSV to host cell glycosaminoglycans (GAGs) at 4°C is reversible, suggesting that binding of RSV to sulfated GAGs alone is not sufficient for triggering membrane fusion and entry. Our work also indicates that the inhibition of RSV by RhoA-derived peptides should not be interpreted as supporting a role for RhoA in the viral entry process. Finally, this work suggests a model of RSV entry in which RSV F and G are closely associated, with G masking important epitopes for F-mediated binding or fusion events.