Inhibition of Arenavirus Infection by a Glycoprotein-Derived Peptide with a Novel Mechanism

The family Arenaviridae includes a number of viruses of public health importance, such as the category A hemorrhagic fever viruses Lassa virus, Junin virus, Machupo virus, Guanarito virus, and Sabia virus. Current chemotherapy for arenavirus infection is limited to the nucleoside analogue ribavirin, which is characterized by considerable toxicity and treatment failure. Using Pichinde virus as a model arenavirus, we attempted to design glycoprotein-derived fusion inhibitors similar to the FDA-approved anti-HIV peptide enfuvirtide. We have identified a GP2-derived peptide, AVP-p, with antiviral activity and no acute cytotoxicity. The 50% inhibitory dose (IC50) for the peptide is 7 mu M, with complete inhibition of viral plaque formation at approximately 20 mu M, and its antiviral activity is largely sequence dependent. AVP-p demonstrates activity against viruses with the Old and New World arenavirus viral glycoprotein complex but not against enveloped viruses of other families. Unexpectedly, fusion assays reveal that the peptide induces virus-liposome fusion at neutral pH and that the process is strictly glycoprotein mediated. As observed in cryo-electron micrographs, AVP-p treatment causes morphological changes consistent with fusion protein activation in virions, including the disappearance of prefusion glycoprotein spikes and increased particle diameters, and fluorescence microscopy shows reduced binding by peptide-treated virus. Steady-state fluorescence anisotropy measurements suggest that glycoproteins are destabilized by peptide-induced alterations in viral membrane order. We conclude that untimely deployment of fusion machinery by the peptide could render virions less able to engage in on-pathway receptor binding or endosomal fusion. AVP-p may represent a potent, highly specific, novel therapeutic strategy for arenavirus infection. IMPORTANCE Because the only drug available to combat infection by Lassa virus, a highly pathogenic arenavirus, is toxic and prone to treatment failure, we identified a peptide, AVP-p, derived from the fusion glycoprotein of a nonpathogenic model arenavirus, which demonstrates antiviral activity and no acute cytotoxicity. AVP-p is unique among self-derived inhibitory peptides in that it shows broad, specific activity against pseudoviruses bearing Old and New World arenavirus glycoproteins but not against viruses from other families. Further, the peptide's mechanism of action is highly novel. Biochemical assays and cryo-electron microscopy indicate that AVP-p induces premature activation of viral fusion proteins through membrane perturbance. Peptide treatment, however, does not increase the infectivity of cell-bound virus. We hypothesize that prematurely activated virions are less fit for receptor binding and membrane fusion and that AVP-p may represent a viable therapeutic strategy for arenavirus infection.