Understanding The Mechanism Of Action Of Flufirvitide-3 A Peptide Based Inhibitor Of Influenza Virus
Influenza virus is an enveloped virus with a negative sense single strand RNA. The viral surface is characterized by two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA)(Chen et al., 2007; Samuel, 2010). The HA subunit is responsible for the attachment of the virus to the host cell by binding to the sialic acid receptors. Influenza virus infection, occurring in the endosome of the host cell is a fusion dependent process (Daniels et al., 1983). Low pH inside the endosome facilitates the fusion process by triggering a major conformational change of HA. This conformational change exposes the fusion initiation region of the protein subsequently releasing a hydrophobic fusion peptide (which is otherwise buried inside the protein core). This hydrophobic peptide slips into the host cell membrane resulting in HA transiently being a part of the viral and cell membrane. The HA pulls the two membranes together, thus completing the fusion process and forming a clear passage for the release of the viral genetic material into the cytoplasm (Stevens et al., 2004; Ramalho-Santos and Pedroso De Lima, 1999; Carr and Kim, 1993). A 16 amino acid peptide sequence (Flufirvitide-3) derived from the fusion initiation region of the HA protein has shown effective inhibition of influenza virus infection. Plaque inhibition assays and animal studies show high efficacy of the peptide against the virus. However, the mechanism of action of this peptide is still unclear. We have extensively studied the ability of FF-3 to interact with and affect purified HA, pure lipid bilayers and whole viruses. Taken together, the results suggest a novel mechanism of action.