Inhibition of Nipah Virus Infection In Vivo: Targeting an Early Stage of Paramyxovirus Fusion Activation during Viral Entry

Matteo Porotto,Riccardo Cortese,Heinz Feldmann,Barry Rockx,Laura M Palermo,Christine C Yokoyama,Anne Moscona,Aparna Talekar,Min Lu,Jie Liu,Antonello Pessi,Ilaria Devito

doi:10.1371/journal.ppat.1001168

Abstract

In the paramyxovirus cell entry process, receptor binding triggers conformational changes in the fusion protein (F) leading to viral and cellular membrane fusion. Peptides derived from C-terminal heptad repeat (HRC) regions in F have been shown to inhibit fusion by preventing formation of the fusogenic six-helix bundle. We recently showed that the addition of a cholesterol group to HRC peptides active against Nipah virus targets these peptides to the membrane where fusion occurs, dramatically increasing their antiviral effect. In this work, we report that unlike the untagged HRC peptides, which bind to the postulated extended intermediate state bridging the viral and cell membranes, the cholesterol tagged HRC-derived peptides interact with F before the fusion peptide inserts into the target cell membrane, thus capturing an earlier stage in the F-activation process. Furthermore, we show that cholesterol tagging renders these peptides active in vivo: the cholesterol-tagged peptides cross the blood brain barrier, and effectively prevent and treat in an established animal model what would otherwise be fatal Nipah virus encephalitis. The in vivo efficacy of cholesterol-tagged peptides, and in particular their ability to penetrate the CNS, suggests that they are promising candidates for the prevention or therapy of infection by Nipah and other lethal paramyxoviruses.

Highlights

Fusion of enveloped viruses with the host cell is a key step in viral infectivity
The new strategy that we present here opens the door to clinically effective paramyxovirus fusion-inhibitory peptides
By targeting fusion-inhibitory peptides to the target membrane using a cholesterol tag, we capture an early stage in the viral fusion-activation process, drastically enhancing the efficacy of these peptides at inhibiting viral entry

Summary

Introduction

Fusion of enveloped viruses with the host cell is a key step in viral infectivity. The fusion process during viral entry is driven by specialized proteins that undergo an series of conformational changes to bring the viral and host membranes together and promote formation of a fusion pore (reviewed in [1]). For paramyxoviruses — a family that includes a number of important human pathogens — the steps in this process have been explored over the last few years [2,3,4,5,6,7,8,9,10,11,12,13]. From the interaction of the receptor-binding protein with its receptor and the subsequent triggering of the fusion protein, to the conformational changes in the fusion protein that lead to fusion readiness, and the refolding of the fusion protein that drives membrane merger, are potential targets for antiviral compounds. NiV and Hendra (HeV) viruses are emerging zoonotic paramyxoviruses [14] that are lethal to humans. Other viruses belonging to the paramyxovirus family, respiratory syncytial virus (RSV) and the human parainfluenza viruses types 1, 2, and 3 (HPIV1, 2, 3) [25,26], cause the majority of childhood croup, bronchiolitis, and pneumonia [27], contributing significantly to global disease and mortality, while measles virus, despite the vaccine, continues to be an important global agent of respiratory and neurologic disease [28]

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Discussion

Conclusion