title: Norovirus Polymerase Fidelity Contributes to Viral TransmissionIn Vivo.
abstract: Intrahost genetic diversity and replication error rates are intricately linked to RNA virus pathogenesis, with alterations in viral polymerase fidelity typically leading to attenuation during infectionsin vivo. We have previously shown that norovirus intrahost genetic diversity also influences viral pathogenesis using the murine norovirus model, as increasing viral mutation frequency using a mutagenic nucleoside resulted in clearance of a persistent infection in mice. Given the role of replication fidelity and genetic diversity in pathogenesis, we have now investigated whether polymerase fidelity can also impact virus transmission between susceptible hosts. We have identified a high-fidelity norovirus RNA-dependent RNA polymerase mutant (I391L) which displays delayed replication kineticsin vivobut not in cell culture. The I391L polymerase mutant also exhibited lower transmission rates between susceptible hosts than the wild-type virus and, most notably, another replication defective mutant that has wild-type levels of polymerase fidelity. These results provide the first experimental evidence that norovirus polymerase fidelity contributes to virus transmission between hosts and that maintaining diversity is important for the establishment of infection. This work supports the hypothesis that the reduced polymerase fidelity of the pandemic GII.4 human norovirus isolates may contribute to their global dominance.IMPORTANCEVirus replication fidelity and hence the intrahost genetic diversity of viral populations are known to be intricately linked to viral pathogenesis and tropism as well as to immune and antiviral escape during infection. In this study, we investigated whether changes in replication fidelity can impact the ability of a virus to transmit between susceptible hosts by the use of a mouse model for norovirus. We show that a variant encoding a high-fidelity polymerase is transmitted less efficiently between mice than the wild-type strain. This constitutes the first experimental demonstration that the polymerase fidelity of viruses can impact transmission of infection in their natural hosts. These results provide further insight into potential reasons for the global emergence of pandemic human noroviruses that display alterations in the replication fidelity of their polymerases compared to nonpandemic strains.
authors: Division of Virology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
authors: Armando
authors: 0000-0002-4138-4608
authors: A
authors: Arias
authors: Division of Virology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
authors: Lucy
authors: L
authors: Thorne
authors: Division of Virology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
authors: Elsa
authors: E
authors: Ghurburrun
authors: Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom.
authors: Dalan
authors: 0000-0002-5640-2266
authors: D
authors: Bailey
authors: Division of Virology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
authors: Ian
authors: 0000-0002-9483-510X
authors: I
authors: Goodfellow
keywords: RNA polymerases; noroviruses; polymerase fidelity; quasispecies; virus transmission