Identification of mammalian-adapting mutations in the polymerase complex of an avian H5N1 influenza virus.

Andrew S Taft,Thomas C Friedrich,Lindsay Hill-Batorski,Gabriele Neumann,Yoshihiro Kawaoka,Makoto Ozawa,Tiago J S Lopes,Adam Fitch,Eileen A Maher,Elodie Ghedin,Peter J Halfmann,Masato Hatta,Jay V Depasse,Catherine A Macken

doi:10.1038/ncomms8491

Abstract

Avian influenza viruses of the H5N1 subtype pose a serious global health threat due to the high mortality (>60%) associated with the disease caused by these viruses and the lack of protective antibodies to these viruses in the general population. The factors that enable avian H5N1 influenza viruses to replicate in humans are not completely understood. Here we use a high-throughput screening approach to identify novel mutations in the polymerase genes of an avian H5N1 virus that confer efficient polymerase activity in mammalian cells. Several of the identified mutations (which have previously been found in natural isolates) increase viral replication in mammalian cells and virulence in infected mice compared with the wild-type virus. The identification of amino-acid mutations in avian H5N1 influenza virus polymerase complexes that confer increased replication and virulence in mammals is important for the identification of circulating H5N1 viruses with an increased potential to infect humans.Supplementary informationThe online version of this article (doi:10.1038/ncomms8491) contains supplementary material, which is available to authorized users.

Highlights

Avian influenza viruses of the H5N1 subtype pose a serious global health threat due to the high mortality (460%) associated with the disease caused by these viruses and the lack of protective antibodies to these viruses in the general population
The TY93/H5N1 PB2 protein of this virus encodes glutamic acid at position 627, which restricts the replicative ability of avian H5N1 virus polymerase complexes in mammals[13]
We generated TY93/ H5N1 green fluorescent protein (GFP)-627K encoding the PB2-E627K mutation known to increase the replicative ability of avian influenza virus polymerase complexes in mammalian cells[13]

Summary

Introduction

Avian influenza viruses of the H5N1 subtype pose a serious global health threat due to the high mortality (460%) associated with the disease caused by these viruses and the lack of protective antibodies to these viruses in the general population. The identification of amino-acid mutations in avian H5N1 influenza virus polymerase complexes that confer increased replication and virulence in mammals is important for the identification of circulating H5N1 viruses with an increased potential to infect humans. Influenza Research Institute, School of Veterinary Medicine, Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53711, USA. In addition to HA-mediated host range restriction, the polymerase complex of avian influenza viruses is often restricted in its replicative ability in mammalian cells. This host range restriction may be a consequence of polymerase interactions with host-specific cellular proteins, and/or temperature differences between the intestinal tract of birds (38–41 °C) and the upper respiratory tract of mammals (33 °C). Other mutations in PB2, PB1 and PA influence the host range of influenza viruses; examples include PB2-147T/339T/588T (ref. 19), PB2-271A (ref. 20), PB2-158G (ref. 21), PB1-13L/678S (ref. 18) and PA-97I (ref. 22)

Methods

Results

Conclusion