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J Virol. PB2 protein of a highly pathogenic avian influenza virus strain A/chicken/Yamaguchi/7/2004 (H5N1) determines its replication potential in pigs.
J Virol. 2008 Dec 3. [Epub ahead of print]
PB2 protein of a highly pathogenic avian influenza virus strain A/chicken/Yamaguchi/7/2004 (H5N1) determines its replication potential in pigs.
Manzoor R, Sakoda Y, Nomura N, Tsuda Y, Ozaki H, Okamatsu M, Kida H. - Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, 060-0818, Japan; Department of Veterinary Microbiology, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan; and Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan.
It has been shown that not all but most of the avian influenza viruses replicate in the upper respiratory tract of pigs (Kida et al., 1994).
It was shown that A/chicken/Yamaguchi/7/2004 (H5N1) (Ck/Yamaguchi/04 (H5N1)) did not replicate in pigs (Isoda et al., 2006).
In the present study, the genetic basis for this host-range restriction was determined using reassortant viruses generated between Ck/Yamaguchi/04 (H5N1) and A/swine/Hokkaido/2/1981(H1N1) (Sw/Hokkaido/81 (H1N1)).
Two in vivo generated single gene reassortant virus clones of H5N1 subtype (virus clones 1 and 2), whose PB2 gene was of Sw/Hokkaido/81 (H1N1) origin and the remaining 7 genes were of Ck/Yamaguchi/04 (H5N1) origin, were recovered from the experimentally infected pigs.
The replicative potential of virus clones 1 and 2 was further confirmed by using reassortant virus (rg-Ck-Sw/PB2) generated by reverse genetics.
Interestingly, the PB2 gene of Ck/Yamaguchi/04 (H5N1) did not restrict the replication of Sw/Hokkaido/81 (H1N1) as determined by using reassortant virus rg-Sw-Ck/PB2.
The rg-Sw-Ck/PB2 replicated to moderate levels and for shorter duration than that of parental Sw/Hokkaido/81 (H1N1).
Sequencing of two isolates recovered from the pigs inoculated with rg-Sw-Ck/PB2 revealed either D256G or E627K amino acid substitutions in the PB2 proteins of the isolates.
The D256G and E627K mutations enhanced viral polymerase activity in the mammalian cells, correlating with replication of virus in pigs.
These results indicate that the PB2 protein restricts the growth of Ck/Yamaguchi/04 (H5N1) in pigs.
PMID: 19052090 [PubMed - as supplied by publisher]
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(1.4): J Virol. 2008 Dec 3. [Epub ahead of print]
Novel influenza NS1 antagonists block replication and restore innate immune function.
Basu D, Walkiewicz MP, Frieman M, Baric RS, Auble DT, Engel DA. - Department of Microbiology, University of Virginia School of Medicine, Charlottesville, VA 22908; Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908.
The innate immune system guards against virus infection through a variety of mechanisms including mobilization of the host interferon system, which attacks viral products mainly at a post-transcriptional level.
The influenza virus NS1 protein is a multi-functional facilitator of virus replication, one of whose actions is to antagonize the interferon response.
Since NS1 is required for efficient virus replication it was reasoned that chemical inhibitors of this protein could be used to further understand virus-host interactions and also serve as potential new antiviral agents.
A yeast-based assay was developed to identify compounds that phenotypically suppress NS1 function.
Several such compounds exhibited significant activity specifically against influenza A virus in cell culture but had no effect on the replication of another RNA virus, respiratory syncytial virus.
Interestingly, cells lacking an interferon response were drug resistant, suggesting that the compounds block interactions between NS1 and the interferon system.
Accordingly, the compounds reversed the inhibition of interferon-ss mRNA induction during infection, which is known to be caused by NS1.
In addition, they blocked the ability of NS1 protein to inhibit dsRNA-dependent activation of a transfected interferon-ss promoter construct.
The effects of the compounds were specific to NS1, because they had no effect on the ability of the SARS-coronavirus PLP protein to block interferon-ss promoter activation.
These data demonstrate that the function of NS1 can be modulated by chemical inhibitors, and that such inhibitors will be useful as probes of biological function and as starting points for clinical drug development.
PMID: 19052087 [PubMed - as supplied by publisher]
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PB2 protein of a highly pathogenic avian influenza virus strain A/chicken/Yamaguchi/7/2004 (H5N1) determines its replication potential in pigs.
Manzoor R, Sakoda Y, Nomura N, Tsuda Y, Ozaki H, Okamatsu M, Kida H. - Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, 060-0818, Japan; Department of Veterinary Microbiology, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan; and Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan.
It has been shown that not all but most of the avian influenza viruses replicate in the upper respiratory tract of pigs (Kida et al., 1994).
It was shown that A/chicken/Yamaguchi/7/2004 (H5N1) (Ck/Yamaguchi/04 (H5N1)) did not replicate in pigs (Isoda et al., 2006).
In the present study, the genetic basis for this host-range restriction was determined using reassortant viruses generated between Ck/Yamaguchi/04 (H5N1) and A/swine/Hokkaido/2/1981(H1N1) (Sw/Hokkaido/81 (H1N1)).
Two in vivo generated single gene reassortant virus clones of H5N1 subtype (virus clones 1 and 2), whose PB2 gene was of Sw/Hokkaido/81 (H1N1) origin and the remaining 7 genes were of Ck/Yamaguchi/04 (H5N1) origin, were recovered from the experimentally infected pigs.
The replicative potential of virus clones 1 and 2 was further confirmed by using reassortant virus (rg-Ck-Sw/PB2) generated by reverse genetics.
Interestingly, the PB2 gene of Ck/Yamaguchi/04 (H5N1) did not restrict the replication of Sw/Hokkaido/81 (H1N1) as determined by using reassortant virus rg-Sw-Ck/PB2.
The rg-Sw-Ck/PB2 replicated to moderate levels and for shorter duration than that of parental Sw/Hokkaido/81 (H1N1).
Sequencing of two isolates recovered from the pigs inoculated with rg-Sw-Ck/PB2 revealed either D256G or E627K amino acid substitutions in the PB2 proteins of the isolates.
The D256G and E627K mutations enhanced viral polymerase activity in the mammalian cells, correlating with replication of virus in pigs.
These results indicate that the PB2 protein restricts the growth of Ck/Yamaguchi/04 (H5N1) in pigs.
PMID: 19052090 [PubMed - as supplied by publisher]
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-
(1.4): J Virol. 2008 Dec 3. [Epub ahead of print]
Novel influenza NS1 antagonists block replication and restore innate immune function.
Basu D, Walkiewicz MP, Frieman M, Baric RS, Auble DT, Engel DA. - Department of Microbiology, University of Virginia School of Medicine, Charlottesville, VA 22908; Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908.
The innate immune system guards against virus infection through a variety of mechanisms including mobilization of the host interferon system, which attacks viral products mainly at a post-transcriptional level.
The influenza virus NS1 protein is a multi-functional facilitator of virus replication, one of whose actions is to antagonize the interferon response.
Since NS1 is required for efficient virus replication it was reasoned that chemical inhibitors of this protein could be used to further understand virus-host interactions and also serve as potential new antiviral agents.
A yeast-based assay was developed to identify compounds that phenotypically suppress NS1 function.
Several such compounds exhibited significant activity specifically against influenza A virus in cell culture but had no effect on the replication of another RNA virus, respiratory syncytial virus.
Interestingly, cells lacking an interferon response were drug resistant, suggesting that the compounds block interactions between NS1 and the interferon system.
Accordingly, the compounds reversed the inhibition of interferon-ss mRNA induction during infection, which is known to be caused by NS1.
In addition, they blocked the ability of NS1 protein to inhibit dsRNA-dependent activation of a transfected interferon-ss promoter construct.
The effects of the compounds were specific to NS1, because they had no effect on the ability of the SARS-coronavirus PLP protein to block interferon-ss promoter activation.
These data demonstrate that the function of NS1 can be modulated by chemical inhibitors, and that such inhibitors will be useful as probes of biological function and as starting points for clinical drug development.
PMID: 19052087 [PubMed - as supplied by publisher]
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