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

Taft AS, Ozawa M, Fitch A, Depasse JV, Halfmann PJ, Hill-Batorski L, Hatta M, Friedrich TC, Lopes TJ, Maher EA, Ghedin E, Macken CA, Neumann G, Kawaoka Y - Nat Commun (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Influenza Research Institute, School of Veterinary Medicine, Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53711, USA.

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.

No MeSH data available.


Related in: MedlinePlus

Body weight changes and survival of mice infected with wild type or mutant TY93/H5N1 viruses.BALB/cByJ mice were infected with different doses (1–105 p.f.u.) of wild-type virus or the indicated polymerase mutant. Body weight was monitored daily; mice that lost >35% of their starting weight or showed signs of severe disease were euthanized. Numbers shown indicate the number of surviving animals.
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f5: Body weight changes and survival of mice infected with wild type or mutant TY93/H5N1 viruses.BALB/cByJ mice were infected with different doses (1–105 p.f.u.) of wild-type virus or the indicated polymerase mutant. Body weight was monitored daily; mice that lost >35% of their starting weight or showed signs of severe disease were euthanized. Numbers shown indicate the number of surviving animals.

Mentions: Our in vitro data identified several mutations in the TY93/H5N1 polymerase proteins that increased virus replication in mammalian cells. Next, we tested whether these increases translated to higher virulence in mice. Animals were infected intranasally with different doses of wild-type or mutant TY93/H5N1 viruses and observed for survival to determine the amount of virus required to kill 50% of the infected animals (mouse lethal dose 50; MLD50; Fig. 5 and Supplementary Table 6). All mutant viruses (with the exception of TY93/H5N1 PB2-D740N) had a lower MLD50 value than that of the wild-type virus, demonstrating increased virulence in mice compared with TY93/H5N1 virus. The greatest virulence in mice was detected for the PB1-N105S and PB2-E192K mutants, for which infection with one plaque-forming unit (p.f.u.) resulted in such severe clinical symptoms that all (for PB1-N105S) or two (PB2-E192K) of the infected mice had to be euthanized. The PB1-N105S mutant did not significantly increase the TY93/H5N1 polymerase activity in minireplicon assays (Fig. 4), again suggesting that the polymerase mutations influence steps beyond vRNA replication and transcription. We also found that the newly identified PB2-627V and -701V mutations had MLD50 values identical to those of the known PB2-627 K and -701 N mutants, respectively (Supplementary Table 6). Mice infected with these viruses succumbed rapidly to infection (Fig. 5).


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

Taft AS, Ozawa M, Fitch A, Depasse JV, Halfmann PJ, Hill-Batorski L, Hatta M, Friedrich TC, Lopes TJ, Maher EA, Ghedin E, Macken CA, Neumann G, Kawaoka Y - Nat Commun (2015)

Body weight changes and survival of mice infected with wild type or mutant TY93/H5N1 viruses.BALB/cByJ mice were infected with different doses (1–105 p.f.u.) of wild-type virus or the indicated polymerase mutant. Body weight was monitored daily; mice that lost >35% of their starting weight or showed signs of severe disease were euthanized. Numbers shown indicate the number of surviving animals.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557292&req=5

f5: Body weight changes and survival of mice infected with wild type or mutant TY93/H5N1 viruses.BALB/cByJ mice were infected with different doses (1–105 p.f.u.) of wild-type virus or the indicated polymerase mutant. Body weight was monitored daily; mice that lost >35% of their starting weight or showed signs of severe disease were euthanized. Numbers shown indicate the number of surviving animals.
Mentions: Our in vitro data identified several mutations in the TY93/H5N1 polymerase proteins that increased virus replication in mammalian cells. Next, we tested whether these increases translated to higher virulence in mice. Animals were infected intranasally with different doses of wild-type or mutant TY93/H5N1 viruses and observed for survival to determine the amount of virus required to kill 50% of the infected animals (mouse lethal dose 50; MLD50; Fig. 5 and Supplementary Table 6). All mutant viruses (with the exception of TY93/H5N1 PB2-D740N) had a lower MLD50 value than that of the wild-type virus, demonstrating increased virulence in mice compared with TY93/H5N1 virus. The greatest virulence in mice was detected for the PB1-N105S and PB2-E192K mutants, for which infection with one plaque-forming unit (p.f.u.) resulted in such severe clinical symptoms that all (for PB1-N105S) or two (PB2-E192K) of the infected mice had to be euthanized. The PB1-N105S mutant did not significantly increase the TY93/H5N1 polymerase activity in minireplicon assays (Fig. 4), again suggesting that the polymerase mutations influence steps beyond vRNA replication and transcription. We also found that the newly identified PB2-627V and -701V mutations had MLD50 values identical to those of the known PB2-627 K and -701 N mutants, respectively (Supplementary Table 6). Mice infected with these viruses succumbed rapidly to infection (Fig. 5).

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Influenza Research Institute, School of Veterinary Medicine, Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53711, USA.

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.

No MeSH data available.


Related in: MedlinePlus