The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Adolfo Garciasastre - One of the best experts on this subject based on the ideXlab platform.
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inhibition of retinoic acid inducible gene i mediated induction of Beta Interferon by the ns1 protein of influenza a virus
Journal of Virology, 2007Co-Authors: Masaki Mibayashi, Michael Gale, Luis Martinezsobrido, Washington B Cardenas, Adolfo GarciasastreAbstract:The retinoic acid-inducible gene I product (RIG-I) has been identified as a cellular sensor of RNA virus infection resulting in Beta Interferon (IFN-β) induction. However, many viruses are known to encode viral products that inhibit IFN-β production. In the case of influenza A virus, the viral nonstructural protein 1 (NS1) prevents the induction of the IFN-β promoter by inhibiting the activation of transcription factors, including IRF-3, involved in IFN-β transcriptional activation. The inhibitory properties of NS1 appear to be due at least in part to its binding to double-stranded RNA (dsRNA), resulting in the sequestration of this viral mediator of RIG-I activation. However, the precise effects of NS1 on the RIG-I-mediated induction of IFN-β have not been characterized. We now report that the NS1 of influenza A virus interacts with RIG-I and inhibits the RIG-I-mediated induction of IFN-β. This inhibition was apparent even when a mutant RIG-I that is constitutively activated (in the absence of dsRNA) was used to trigger IFN-β production. Coexpression of RIG-I, its downstream signaling partner, IPS-1, and NS1 resulted in increased levels of RIG-I and NS1 within an IPS-1-rich, solubilization-resistant fraction after cell lysis. These results suggest that RIG-I, IPS-1, and NS1 become part of the same complex. Consistent with this idea, NS1 was also found to inhibit IFN-β promoter activation by IPS-1 overexpression. Our results indicate that, in addition to sequestering dsRNA, the NS1 of influenza A virus binds to RIG-I and inhibits downstream activation of IRF-3, preventing the transcriptional induction of IFN-β.
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a recombinant influenza a virus expressing an rna binding defective ns1 protein induces high levels of Beta Interferon and is attenuated in mice
Journal of Virology, 2003Co-Authors: Nicola R Donelan, Christopher F Basler, Adolfo GarciasastreAbstract:Previously we found that the amino-terminal region of the NS1 protein of influenza A virus plays a key role in preventing the induction of Beta Interferon (IFN-β) in virus-infected cells. This region is characterized by its ability to bind to different RNA species, including double-stranded RNA (dsRNA), a known potent inducer of IFNs. In order to investigate whether the NS1 RNA-binding activity is required for its IFN antagonist properties, we have generated a recombinant influenza A virus which expresses a mutant NS1 protein defective in dsRNA binding. For this purpose, we substituted alanines for two basic amino acids within NS1 (R38 and K41) that were previously found to be required for RNA binding. Cells infected with the resulting recombinant virus showed increased IFN-β production, demonstrating that these two amino acids play a critical role in the inhibition of IFN production by the NS1 protein during viral infection. In addition, this virus grew to lower titers than wild-type virus in MDCK cells, and it was attenuated in mice. Interestingly, passaging in MDCK cells resulted in the selection of a mutant virus containing a third mutation at amino acid residue 42 of the NS1 protein (S42G). This mutation did not result in a gain in dsRNA-binding activity by the NS1 protein, as measured by an in vitro assay. Nevertheless, the NS1 R38AK41AS42G mutant virus was able to replicate in MDCK cells to titers close to those of wild-type virus. This mutant virus had intermediate virulence in mice, between those of the wild-type and parental NS1 R38AK41A viruses. These results suggest not only that the IFN antagonist properties of the NS1 protein depend on its ability to bind dsRNA but also that they can be modulated by amino acid residues not involved in RNA binding.
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influenza a virus ns1 protein prevents activation of nf κb and induction of alpha Beta Interferon
Journal of Virology, 2000Co-Authors: Xiuyan Wang, Ming Li, Hongyong Zheng, Thomas Muster, Peter Palese, Adolfo GarciasastreAbstract:The alpha/Beta Interferon (IFN-α/β) system represents one of the first lines of defense against virus infections. As a result, most viruses encode IFN antagonistic factors which enhance viral replication in their hosts. We have previously shown that a recombinant influenza A virus lacking the NS1 gene (delNS1) only replicates efficiently in IFN-α/β-deficient systems. Consistent with this observation, we found that infection of tissue culture cells with delNS1 virus, but not with wild-type influenza A virus, induced high levels of mRNA synthesis from IFN-α/β genes, including IFN-β. It is known that transactivation of the IFN-β promoter depends on NF-κB and several other transcription factors. Interestingly, cells infected with delNS1 virus showed high levels of NF-κB activation compared with those infected with wild-type virus. Expression of dominant-negative inhibitors of the NF-κB pathway during delNS1 virus infection prevented the transactivation of the IFN-β promoter, demonstrating a functional link between NF-κB activation and IFN-α/β synthesis in delNS1 virus-infected cells. Moreover, expression of the NS1 protein prevented virus- and/or double-stranded RNA (dsRNA)-mediated activation of the NF-κB pathway and of IFN-β synthesis. This inhibitory property of the NS1 protein of influenza A virus was dependent on its ability to bind dsRNA, supporting a model in which binding of NS1 to dsRNA generated during influenza virus infection prevents the activation of the IFN system. NS1-mediated inhibition of the NF-κB pathway may thus play a key role in the pathogenesis of influenza A virus.
Michael S Diamond - One of the best experts on this subject based on the ideXlab platform.
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resistance to alpha Beta Interferon is a determinant of west nile virus replication fitness and virulence
Journal of Virology, 2006Co-Authors: Brian C Keller, Brenda L Fredericksen, Melanie A Samuel, Richard E Mock, Peter W Mason, Michael S Diamond, Michael GaleAbstract:The emergence of West Nile virus (WNV) in the Western Hemisphere is marked by the spread of pathogenic lineage I strains, which differ from typically avirulent lineage II strains. To begin to understand the virus-host interactions that may influence the phenotypic properties of divergent lineage I and II viruses, we compared the genetic, pathogenic, and alpha/Beta Interferon (IFN-α/β)-regulatory properties of a lineage II isolate from Madagascar (MAD78) with those of a new lineage I isolate from Texas (TX02). Full genome sequence analysis revealed that MAD78 clustered, albeit distantly, with other lineage II strains, while TX02 clustered with emergent North American isolates, more specifically with other Texas strains. Compared to TX02, MAD78 replicated at low levels in cultured human cells, was highly sensitive to the antiviral actions of IFN in vitro, and demonstrated a completely avirulent phenotype in wild-type mice. In contrast to TX02 and other pathogenic forms of WNV, MAD78 was defective in its ability to disrupt IFN-induced JAK-STAT signaling, including the activation of Tyk2 and downstream phosphorylation and nuclear translocation of STAT1 and STAT2. However, replication of MAD78 was rescued in cells with a nonfunctional IFN-α/β receptor (IFNAR). Consistent with this finding, the virulence of MAD78 was unmasked upon infection of mice lacking IFNAR. Thus, control of the innate host response and IFN actions is a key feature of WNV pathogenesis and replication fitness.
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alpha Beta Interferon protects against lethal west nile virus infection by restricting cellular tropism and enhancing neuronal survival
Journal of Virology, 2005Co-Authors: Melanie A Samuel, Michael S DiamondAbstract:West Nile virus (WNV) is a mosquito-borne flavivirus that is neurotropic in humans, birds, and other animals. While adaptive immunity plays an important role in preventing WNV spread to the central nervous system (CNS), little is known about how alpha/Beta Interferon (IFN-α/β) protects against peripheral and CNS infection. In this study, we examine the virulence and tropism of WNV in IFN-α/β receptor-deficient (IFN- α/βR −/− ) mice and primary neuronal cultures. IFN-α/βR −/− mice were acutely susceptible to WNV infection through subcutaneous inoculation, with 100% mortality and a mean time to death (MTD) of 4.6 ± 0.7 and 3.8± 0.5 days after infection with 10 0 and 10 2 PFU, respectively. In contrast, congenic wild-type 129Sv/Ev mice infected with 10 2 PFU showed 62% mortality and a MTD of 11.9 ± 1.9 days. IFN-α/βR −/− mice developed high viral loads by day 3 after infection in nearly all tissues assayed, including many that were not infected in wild-type mice. IFN-α/βR −/− mice also demonstrated altered cellular tropism, with increased infection in macrophages, B cells, and T cells in the spleen. Additionally, treatment of primary wild-type neurons in vitro with IFN-β either before or after infection increased neuronal survival independent of its effect on WNV replication. Collectively, our data suggest that IFN-α/β controls WNV infection by restricting tropism and viral burden and by preventing death of infected neurons.
Michael Gale - One of the best experts on this subject based on the ideXlab platform.
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inhibition of retinoic acid inducible gene i mediated induction of Beta Interferon by the ns1 protein of influenza a virus
Journal of Virology, 2007Co-Authors: Masaki Mibayashi, Michael Gale, Luis Martinezsobrido, Washington B Cardenas, Adolfo GarciasastreAbstract:The retinoic acid-inducible gene I product (RIG-I) has been identified as a cellular sensor of RNA virus infection resulting in Beta Interferon (IFN-β) induction. However, many viruses are known to encode viral products that inhibit IFN-β production. In the case of influenza A virus, the viral nonstructural protein 1 (NS1) prevents the induction of the IFN-β promoter by inhibiting the activation of transcription factors, including IRF-3, involved in IFN-β transcriptional activation. The inhibitory properties of NS1 appear to be due at least in part to its binding to double-stranded RNA (dsRNA), resulting in the sequestration of this viral mediator of RIG-I activation. However, the precise effects of NS1 on the RIG-I-mediated induction of IFN-β have not been characterized. We now report that the NS1 of influenza A virus interacts with RIG-I and inhibits the RIG-I-mediated induction of IFN-β. This inhibition was apparent even when a mutant RIG-I that is constitutively activated (in the absence of dsRNA) was used to trigger IFN-β production. Coexpression of RIG-I, its downstream signaling partner, IPS-1, and NS1 resulted in increased levels of RIG-I and NS1 within an IPS-1-rich, solubilization-resistant fraction after cell lysis. These results suggest that RIG-I, IPS-1, and NS1 become part of the same complex. Consistent with this idea, NS1 was also found to inhibit IFN-β promoter activation by IPS-1 overexpression. Our results indicate that, in addition to sequestering dsRNA, the NS1 of influenza A virus binds to RIG-I and inhibits downstream activation of IRF-3, preventing the transcriptional induction of IFN-β.
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resistance to alpha Beta Interferon is a determinant of west nile virus replication fitness and virulence
Journal of Virology, 2006Co-Authors: Brian C Keller, Brenda L Fredericksen, Melanie A Samuel, Richard E Mock, Peter W Mason, Michael S Diamond, Michael GaleAbstract:The emergence of West Nile virus (WNV) in the Western Hemisphere is marked by the spread of pathogenic lineage I strains, which differ from typically avirulent lineage II strains. To begin to understand the virus-host interactions that may influence the phenotypic properties of divergent lineage I and II viruses, we compared the genetic, pathogenic, and alpha/Beta Interferon (IFN-α/β)-regulatory properties of a lineage II isolate from Madagascar (MAD78) with those of a new lineage I isolate from Texas (TX02). Full genome sequence analysis revealed that MAD78 clustered, albeit distantly, with other lineage II strains, while TX02 clustered with emergent North American isolates, more specifically with other Texas strains. Compared to TX02, MAD78 replicated at low levels in cultured human cells, was highly sensitive to the antiviral actions of IFN in vitro, and demonstrated a completely avirulent phenotype in wild-type mice. In contrast to TX02 and other pathogenic forms of WNV, MAD78 was defective in its ability to disrupt IFN-induced JAK-STAT signaling, including the activation of Tyk2 and downstream phosphorylation and nuclear translocation of STAT1 and STAT2. However, replication of MAD78 was rescued in cells with a nonfunctional IFN-α/β receptor (IFNAR). Consistent with this finding, the virulence of MAD78 was unmasked upon infection of mice lacking IFNAR. Thus, control of the innate host response and IFN actions is a key feature of WNV pathogenesis and replication fitness.
Melanie A Samuel - One of the best experts on this subject based on the ideXlab platform.
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resistance to alpha Beta Interferon is a determinant of west nile virus replication fitness and virulence
Journal of Virology, 2006Co-Authors: Brian C Keller, Brenda L Fredericksen, Melanie A Samuel, Richard E Mock, Peter W Mason, Michael S Diamond, Michael GaleAbstract:The emergence of West Nile virus (WNV) in the Western Hemisphere is marked by the spread of pathogenic lineage I strains, which differ from typically avirulent lineage II strains. To begin to understand the virus-host interactions that may influence the phenotypic properties of divergent lineage I and II viruses, we compared the genetic, pathogenic, and alpha/Beta Interferon (IFN-α/β)-regulatory properties of a lineage II isolate from Madagascar (MAD78) with those of a new lineage I isolate from Texas (TX02). Full genome sequence analysis revealed that MAD78 clustered, albeit distantly, with other lineage II strains, while TX02 clustered with emergent North American isolates, more specifically with other Texas strains. Compared to TX02, MAD78 replicated at low levels in cultured human cells, was highly sensitive to the antiviral actions of IFN in vitro, and demonstrated a completely avirulent phenotype in wild-type mice. In contrast to TX02 and other pathogenic forms of WNV, MAD78 was defective in its ability to disrupt IFN-induced JAK-STAT signaling, including the activation of Tyk2 and downstream phosphorylation and nuclear translocation of STAT1 and STAT2. However, replication of MAD78 was rescued in cells with a nonfunctional IFN-α/β receptor (IFNAR). Consistent with this finding, the virulence of MAD78 was unmasked upon infection of mice lacking IFNAR. Thus, control of the innate host response and IFN actions is a key feature of WNV pathogenesis and replication fitness.
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alpha Beta Interferon protects against lethal west nile virus infection by restricting cellular tropism and enhancing neuronal survival
Journal of Virology, 2005Co-Authors: Melanie A Samuel, Michael S DiamondAbstract:West Nile virus (WNV) is a mosquito-borne flavivirus that is neurotropic in humans, birds, and other animals. While adaptive immunity plays an important role in preventing WNV spread to the central nervous system (CNS), little is known about how alpha/Beta Interferon (IFN-α/β) protects against peripheral and CNS infection. In this study, we examine the virulence and tropism of WNV in IFN-α/β receptor-deficient (IFN- α/βR −/− ) mice and primary neuronal cultures. IFN-α/βR −/− mice were acutely susceptible to WNV infection through subcutaneous inoculation, with 100% mortality and a mean time to death (MTD) of 4.6 ± 0.7 and 3.8± 0.5 days after infection with 10 0 and 10 2 PFU, respectively. In contrast, congenic wild-type 129Sv/Ev mice infected with 10 2 PFU showed 62% mortality and a MTD of 11.9 ± 1.9 days. IFN-α/βR −/− mice developed high viral loads by day 3 after infection in nearly all tissues assayed, including many that were not infected in wild-type mice. IFN-α/βR −/− mice also demonstrated altered cellular tropism, with increased infection in macrophages, B cells, and T cells in the spleen. Additionally, treatment of primary wild-type neurons in vitro with IFN-β either before or after infection increased neuronal survival independent of its effect on WNV replication. Collectively, our data suggest that IFN-α/β controls WNV infection by restricting tropism and viral burden and by preventing death of infected neurons.
Yusuke Yanagi - One of the best experts on this subject based on the ideXlab platform.
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both rig i and mda5 rna helicases contribute to the induction of alpha Beta Interferon in measles virus infected human cells
Journal of Virology, 2010Co-Authors: Satoshi Ikegame, Makoto Takeda, Shinji Ohno, Yuichiro Nakatsu, Yoichi Nakanishi, Yusuke YanagiAbstract:Measles virus (MV), a member of the family Paramyxoviridae, is a nonsegmented negative-strand RNA virus. The RNA helicases retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are differentially involved in the detection of cytoplasmic viral RNAs and induction of alpha/Beta Interferon (IFN-α/β). RIG-I is generally believed to play a major role in the recognition of paramyxoviruses, whereas many viruses of this family produce V proteins that can inhibit MDA5. To determine the individual roles of MDA5 and RIG-I in IFN induction after MV infection, small interfering RNA-mediated knockdown of MDA5 or RIG-I was performed in the human epithelial cell line H358, which is susceptible to wild-type MV isolates. The production of IFN-β mRNA in response to MV infection was greatly reduced in RIG-I knockdown clones compared to that in H358 cells, confirming the importance of RIG-I in the detection of MV. The IFN-β mRNA levels were also moderately reduced in MDA5 knockdown clones, even though these clones retained fully functional RIG-I. A V protein-deficient recombinant MV (MVΔV) induced higher amounts of IFN-β mRNA at the early stage of infection in H358 cells compared to the parental virus. The reductions in the IFN-β mRNA levels in RIG-I knockdown clones were less pronounced after infection with MVΔV than after infection with the parental virus. Taken together, the present results indicate that RIG-I and MDA5 both contribute to the recognition of MV and that the V protein promotes MV growth at least partly by inhibiting the MDA5-mediated IFN responses.
