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Kumar, Chaudhary, Lu, Duff, Heffel, McKinney, Bedenice, and Marthaler. "Metagenomic Next-Generation Sequencing Reveal Presence of a Novel Ungulate Bocaparvovirus in Alpacas." Viruses 11, no. 8 (July 31, 2019): 701. http://dx.doi.org/10.3390/v11080701.
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Viruses belonging to the genus Bocaparvovirus (BoV) are a genetically diverse group of DNA viruses known to cause respiratory, enteric, and neurological diseases in animals, including humans. An intestinal sample from an alpaca (Vicugna pacos) herd with reoccurring diarrhea and respiratory disease was submitted for next-generation sequencing, revealing the presence of a BoV strain. The alpaca BoV strain (AlBoV) had a 58.58% whole genome nucleotide percent identity to a camel BoV from Dubai, belonging to a tentative ungulate BoV 8 species (UBoV8). Recombination events were lacking with other UBoV strains. The AlBoV genome was comprised of the NS1, NP1, and VP1 proteins. The NS1 protein had the highest amino acid percent identity range (57.89–67.85%) to the members of UBoV8, which was below the 85% cut-off set by the International Committee on Taxonomy of Viruses. The low NS1 amino acid identity suggests that AlBoV is a tentative new species. The whole genome, NS1, NP1, and VP1 phylogenetic trees illustrated distinct branching of AlBoV, sharing a common ancestor with UBoV8. Walker loop and Phospholipase A2 (PLA2) motifs that are vital for virus infectivity were identified in NS1 and VP1 proteins, respectively. Our study reports a novel BoV strain in an alpaca intestinal sample and highlights the need for additional BoV research.
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Shen, Weiran, Xuefeng Deng, Wei Zou, John F. Engelhardt, Ziying Yan, and Jianming Qiu. "Analysis ofcisandtransRequirements for DNA Replication at the Right-End Hairpin of the Human Bocavirus 1 Genome." Journal of Virology 90, no. 17 (June 22, 2016): 7761–77. http://dx.doi.org/10.1128/jvi.00708-16.
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ABSTRACTParvoviruses are single-stranded DNA viruses that use the palindromic structures at the ends of the viral genome for their replication. The mechanism of parvovirus replication has been studied mostly in the dependoparvovirus adeno-associated virus 2 (AAV2) and the protoparvovirus minute virus of mice (MVM). Here, we used human bocavirus 1 (HBoV1) to understand the replication mechanism of bocaparvovirus. HBoV1 is pathogenic to humans, causing acute respiratory tract infections, especially in young children under 2 years old. By using the duplex replicative form of the HBoV1 genome in human embryonic kidney 293 (HEK293) cells, we identified the HBoV1 minimal replication origin at the right-end hairpin (OriR). Mutagenesis analyses confirmed the putative NS1 binding and nicking sites within the OriR. Of note, unlike the large nonstructural protein (Rep78/68 or NS1) of other parvoviruses, HBoV1 NS1 did not specifically bind OriRin vitro, indicating that other viral and cellular components or the oligomerization of NS1 is required for NS1 binding to the OriR.In vivostudies demonstrated that residues responsible for NS1 binding and nicking are within the origin-binding domain. Further analysis identified that the small nonstructural protein NP1 is required for HBoV1 DNA replication at OriR. NP1 and other viral nonstructural proteins (NS1 to NS4) colocalized within the viral DNA replication centers in both OriR-transfected cells and virus-infected cells, highlighting a direct involvement of NP1 in viral DNA replication at OriR. Overall, our study revealed the characteristics of HBoV1 DNA replication at OriR, suggesting novel characteristics of autonomous parvovirus DNA replication.IMPORTANCEHuman bocavirus 1 (HBoV1) causes acute respiratory tract infections in young children. The duplex HBoV1 genome replicates in HEK293 cells and produces progeny virions that are infectious in well-differentiated airway epithelial cells. A recombinant AAV2 vector pseudotyped with an HBoV1 capsid has been developed to efficiently deliver the cystic fibrosis transmembrane conductance regulator gene to human airway epithelia. Here, we identified bothcis-acting elements andtrans-acting proteins that are required for HBoV1 DNA replication at the right-end hairpin in HEK293 cells. We localized the minimal replication origin, which contains both NS1 nicking and binding sites, to a 46-nucleotide sequence in the right-end hairpin. The identification of these essential elements of HBoV1 DNA replication acting both incisand intranswill provide guidance to develop antiviral strategies targeting viral DNA replication at the right-end hairpin and to design next-generation recombinant HBoV1 vectors, a promising tool for gene therapy of lung diseases.
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Agger, Sean A., Fernando Lopez-Gallego, Thomas R. Hoye, and Claudia Schmidt-Dannert. "Identification of Sesquiterpene Synthases from Nostoc punctiforme PCC 73102 and Nostoc sp. Strain PCC 7120." Journal of Bacteriology 190, no. 18 (July 25, 2008): 6084–96. http://dx.doi.org/10.1128/jb.00759-08.
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ABSTRACT Cyanobacteria are a rich source of natural products and are known to produce terpenoids. These bacteria are the major source of the musty-smelling terpenes geosmin and 2-methylisoborneol, which are found in many natural water supplies; however, no terpene synthases have been characterized from these organisms to date. Here, we describe the characterization of three sesquiterpene synthases identified in Nostoc sp. strain PCC 7120 (terpene synthase NS1) and Nostoc punctiforme PCC 73102 (terpene synthases NP1 and NP2). The second terpene synthase in N. punctiforme (NP2) is homologous to fusion-type sesquiterpene synthases from Streptomyces spp. shown to produce geosmin via an intermediate germacradienol. The enzymes were functionally expressed in Escherichia coli, and their terpene products were structurally identified as germacrene A (from NS1), the eudesmadiene 8a-epi-α-selinene (from NP1), and germacradienol (from NP2). The product of NP1, 8a-epi-α-selinene, so far has been isolated only from termites, in which it functions as a defense compound. Terpene synthases NP1 and NS1 are part of an apparent minicluster that includes a P450 and a putative hybrid two-component protein located downstream of the terpene synthases. Coexpression of P450 genes with their adjacent located terpene synthase genes in E. coli demonstrates that the P450 from Nostoc sp. can be functionally expressed in E. coli when coexpressed with a ferredoxin gene and a ferredoxin reductase gene from Nostoc and that the enzyme oxygenates the NS1 terpene product germacrene A. This represents to the best of our knowledge the first example of functional expression of a cyanobacterial P450 in E. coli.
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Young, L. B., E. Balmori Melian, and A. A. Khromykh. "NS1' Colocalizes with NS1 and Can Substitute for NS1 in West Nile Virus Replication." Journal of Virology 87, no. 16 (June 12, 2013): 9384–90. http://dx.doi.org/10.1128/jvi.01101-13.
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Wolff, Thorsten, Robert E. O’Neill, and Peter Palese. "NS1-Binding Protein (NS1-BP): a Novel Human Protein That Interacts with the Influenza A Virus Nonstructural NS1 Protein Is Relocalized in the Nuclei of Infected Cells." Journal of Virology 72, no. 9 (September 1, 1998): 7170–80. http://dx.doi.org/10.1128/jvi.72.9.7170-7180.1998.
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ABSTRACT We used the yeast interaction trap system to identify a novel human 70-kDa protein, termed NS1-binding protein (NS1-BP), which interacts with the nonstructural NS1 protein of the influenza A virus. The genetic interaction was confirmed by the specific coprecipitation of the NS1 protein from solution by a glutathioneS-transferase–NS1-BP fusion protein and glutathione-Sepharose. NS1-BP contains an N-terminal BTB/POZ domain and five kelch-like tandem repeat elements of ∼50 amino acids. In noninfected cells, affinity-purified antibodies localized NS1-BP in nuclear regions enriched with the spliceosome assembly factor SC35, suggesting an association of NS1-BP with the cellular splicing apparatus. In influenza A virus-infected cells, NS1-BP relocalized throughout the nucleoplasm and appeared distinct from the SC35 domains, which suggests that NS1-BP function may be disturbed or altered. The addition of a truncated NS1-BP mutant protein to a HeLa cell nuclear extract efficiently inhibited pre-mRNA splicing but not spliceosome assembly. This result could be explained by a possible dominant-negative effect of the NS1-BP mutant protein and suggests a role of the wild-type NS1-BP in promoting pre-mRNA splicing. These data suggest that the inhibition of splicing by the NS1 protein may be mediated by binding to NS1-BP.
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Alonso-Caplen, F. V., and R. M. Krug. "Regulation of the extent of splicing of influenza virus NS1 mRNA: role of the rates of splicing and of the nucleocytoplasmic transport of NS1 mRNA." Molecular and Cellular Biology 11, no. 2 (February 1991): 1092–98. http://dx.doi.org/10.1128/mcb.11.2.1092.
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Influenza virus NS1 mRNA is spliced by host nuclear enzymes to form NS2 mRNA, and this splicing is regulated in infected cells such that the steady-state amount of spliced NS2 mRNA is only about 10% of that of unspliced NS1 mRNA. This regulation would be expected to result from a suppression in the rate of splicing coupled with the efficient transport of unspliced NS1 mRNA from the nucleus. To determine whether the rate of splicing of NS1 mRNA was controlled by trans factors in influenza virus-infected cells, the NS1 gene was inserted into an adenovirus vector. The rates of splicing of NS1 mRNA in cells infected with this vector and in influenza virus-infected cells were measured by pulse-labeling with [3H]uridine. The rates of splicing of NS1 mRNA in the two systems were not significantly different, strongly suggesting that the rate of splicing of NS1 mRNA in influenza virus-infected cells is controlled solely by cis-acting sequences in NS1 mRNA itself. In contrast to the rate of splicing, the extent of splicing of NS1 mRNA in the cells infected by the adenovirus recombinant was dramatically increased relative to that occurring in influenza virus-infected cells. This could be attributed largely, if not totally, to a block in the nucleocytoplasmic transport of unspliced NS1 mRNA in the recombinant-infected cells. Most of the unspliced NS1 mRNA was in the nuclear fraction, and no detectable NS1 protein was synthesized. When the 3' splice site of NS1 mRNA was inactivated by mutation, NS1 mRNA was transported and translated, indicating that the transport block occurred because NS1 rRNA was committed to the splicing pathway. This transport block is apparently obviated in influenza virus-infected cells. These experiments demonstrate the important role of the nucleocytoplasmic transport of unspliced NS1 mRNA in regulating the extent of splicing of NS1 mRNA.
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Alonso-Caplen, F. V., and R. M. Krug. "Regulation of the extent of splicing of influenza virus NS1 mRNA: role of the rates of splicing and of the nucleocytoplasmic transport of NS1 mRNA." Molecular and Cellular Biology 11, no. 2 (February 1991): 1092–98. http://dx.doi.org/10.1128/mcb.11.2.1092-1098.1991.
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Influenza virus NS1 mRNA is spliced by host nuclear enzymes to form NS2 mRNA, and this splicing is regulated in infected cells such that the steady-state amount of spliced NS2 mRNA is only about 10% of that of unspliced NS1 mRNA. This regulation would be expected to result from a suppression in the rate of splicing coupled with the efficient transport of unspliced NS1 mRNA from the nucleus. To determine whether the rate of splicing of NS1 mRNA was controlled by trans factors in influenza virus-infected cells, the NS1 gene was inserted into an adenovirus vector. The rates of splicing of NS1 mRNA in cells infected with this vector and in influenza virus-infected cells were measured by pulse-labeling with [3H]uridine. The rates of splicing of NS1 mRNA in the two systems were not significantly different, strongly suggesting that the rate of splicing of NS1 mRNA in influenza virus-infected cells is controlled solely by cis-acting sequences in NS1 mRNA itself. In contrast to the rate of splicing, the extent of splicing of NS1 mRNA in the cells infected by the adenovirus recombinant was dramatically increased relative to that occurring in influenza virus-infected cells. This could be attributed largely, if not totally, to a block in the nucleocytoplasmic transport of unspliced NS1 mRNA in the recombinant-infected cells. Most of the unspliced NS1 mRNA was in the nuclear fraction, and no detectable NS1 protein was synthesized. When the 3' splice site of NS1 mRNA was inactivated by mutation, NS1 mRNA was transported and translated, indicating that the transport block occurred because NS1 rRNA was committed to the splicing pathway. This transport block is apparently obviated in influenza virus-infected cells. These experiments demonstrate the important role of the nucleocytoplasmic transport of unspliced NS1 mRNA in regulating the extent of splicing of NS1 mRNA.
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Kasiyati, Menik, Jusak Nugraha, and Hartono Kahar. "Chymase level in dengue virus infection with or without positive Non-Structural 1(NS1)." Jurnal Teknologi Laboratorium 8, no. 2 (December 30, 2019): 41–46. http://dx.doi.org/10.29238/teknolabjournal.v8i2.167.
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Thrombocytopenia, leukopenia, and monocytosis are laboratory parameters in the diagnosis of dengue virus infection. In addition to monocyte cells, mast cells also play a role in the innate immune response, where degranulation of mast cells will occur, which will secretion the active vaso mediator, Chymase. Chymase has a role in increasing vascular permeability resulting in plasma leakage in patients with dengue virus infection to determine the number of platelets, leukocytes, monocytes and chymase levels in patients with dengue infection in the acute phase. The platelet count mean in NS1 (+) was 132,140 cells / mm3 and the platelet count in the NS1 group was (-) 176,000 cells / mm3. The mean leukocytes NS1 (+) showed results of 4,350 cells / mm3 and NS1 (-) 5,250 cells / mm3. The mean monocyte NS1 (+) monocyte count was 8.26%, and NS1 (-) group was 8.76%. There were no significant differences in platelet counts, leukocytes and monocytes between NS1 (+) and NS1 (-) (P value> 0.05). The mean Chymase NS1 (+) 23.48, NS1 (-) 23.05 ng / mL and the control group 1.47ng / mL.
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Krishna, Venkatramana D., Manjuladevi Rangappa, and Vijaya Satchidanandam. "Virus-Specific Cytolytic Antibodies to Nonstructural Protein 1 of Japanese Encephalitis Virus Effect Reduction of Virus Output from Infected Cells." Journal of Virology 83, no. 10 (March 4, 2009): 4766–77. http://dx.doi.org/10.1128/jvi.01850-08.
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ABSTRACT We demonstrate the presence of nonstructural protein 1 (NS1)-specific antibodies in a significant proportion of convalescent-phase human serum samples obtained from a cohort in an area where Japanese encephalitis virus (JEV) is endemic. Sera containing antibodies to NS1 but not those with antibodies to other JEV proteins, such as envelope, brought about complement-mediated lysis of JEV-infected BHK-21 cells. Target cells infected with a recombinant poxvirus expressing JEV NS1 on the cell surface confirmed the NS1 specificity of cytolytic antibodies. Mouse anti-NS1 cytolytic sera caused a complement-dependent reduction in virus output from infected human cells, demonstrating their important role in viral control. Antibodies elicited by JEV NS1 did not cross lyse West Nile virus- or dengue virus-infected cells despite immunoprecipitating the NS1 proteins of these related flaviviruses. Additionally, JEV NS1 failed to bind complement factor H, in contrast to NS1 of West Nile virus, suggesting that the NS1 proteins of different flaviviruses have distinctly different mechanisms for interacting with the host. Our results also point to an important role for JEV NS1-specific human immune responses in protection against JE and provide a strong case for inclusion of the NS1 protein in next generation of JEV vaccines.
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Kuo, Rei-Lin, Li-Hsin Li, Sue-Jane Lin, Zong-Hua Li, Guang-Wu Chen, Cheng-Kai Chang, Yi-Ren Wang, et al. "Role of N Terminus-Truncated NS1 Proteins of Influenza A Virus in Inhibiting IRF3 Activation." Journal of Virology 90, no. 9 (February 24, 2016): 4696–705. http://dx.doi.org/10.1128/jvi.02843-15.
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ABSTRACTThe NS1 protein encoded by influenza A virus antagonizes the interferon response through various mechanisms, including blocking cellular mRNA maturation by binding the cellular CPSF30 3′ end processing factor and/or suppressing the activation of interferon regulatory factor 3 (IRF3). In the present study, we identified two truncated NS1 proteins that are translated from internal AUGs at positions 235 and 241 of the NS1 open reading frame. We analyzed the cellular localization and function of the N-truncated NS1 proteins encoded by two influenza A virus strains, Udorn/72/H3N2 (Ud) and Puerto Rico/8/34/H1N1 (PR8). The NS1 protein of PR8, but not Ud, inhibits the activation of IRF3, whereas the NS1 protein of Ud, but not PR8, binds CPSF30. The truncated PR8 NS1 proteins are localized in the cytoplasm, whereas the full-length PR8 NS1 protein is localized in the nucleus. The infection of cells with a PR8 virus expressing an NS1 protein containing mutations of the two in-frame AUGs results in both the absence of truncated NS1 proteins and the reduced inhibition of activation of IRF3 and beta interferon (IFN-β) transcription. The expression of the truncated PR8 NS1 protein by itself enhances the inhibition of the activation of IRF3 and IFN-β transcription in Ud virus-infected cells. These results demonstrate that truncated PR8 NS1 proteins contribute to the inhibition of activation of this innate immune response. In contrast, the N-truncated NS1 proteins of the Ud strain, like the full-length NS1 protein, are localized in the nucleus, and mutation of the two in-frame AUGs has no effect on the activation of IRF3 and IFN-β transcription.IMPORTANCEInfluenza A virus causes pandemics and annual epidemics in the human population. The viral NS1 protein plays a critical role in suppressing type I interferon expression. In the present study, we identified two novel truncated NS1 proteins that are translated from the second and third in-frame AUG codons in the NS1 open reading frame. The N-terminally truncated NS1 encoded by the H1N1 PR8 strain of influenza virus that suppresses IRF3 activation is localized primarily in the cytoplasm. We demonstrate that this truncated NS1 protein by itself enhances this suppression, demonstrating that some strains of influenza A virus express truncated forms of the NS1 protein that function in the inhibition of cytoplasmic antiviral events.
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Sharma, Mayuri, Dustin R. Glasner, Heather Watkins, Henry Puerta-Guardo, Yoseph Kassa, Michael A. Egan, Hansi Dean, and Eva Harris. "Magnitude and Functionality of the NS1-Specific Antibody Response Elicited by a Live-Attenuated Tetravalent Dengue Vaccine Candidate." Journal of Infectious Diseases 221, no. 6 (February 19, 2019): 867–77. http://dx.doi.org/10.1093/infdis/jiz081.
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Abstract Background Dengue virus (DENV) can cause life-threatening disease characterized by endothelial dysfunction and vascular leakage. DENV nonstructural protein 1 (NS1) induces human endothelial hyperpermeability and vascular leak in mice, and NS1 vaccination confers antibody-mediated protective immunity. We evaluated the magnitude, cross-reactivity, and functionality of NS1-specific IgG antibody responses in sera from a phase 2 clinical trial of Takeda’s live-attenuated tetravalent dengue vaccine candidate (TAK-003). Methods We developed an enzyme-linked immunosorbent assay to measure anti-DENV NS1 IgG in sera from DENV-naive or preimmune subjects pre- and postvaccination with TAK-003 and evaluated the functionality of this response using in vitro models of endothelial permeability. Results TAK-003 significantly increased DENV-2 NS1-specific IgG in naive individuals, which cross-reacted with DENV-1, -3, and -4 NS1 to varying extents. NS1-induced endothelial hyperpermeability was unaffected by prevaccination serum from naive subjects but was variably inhibited by serum from preimmune subjects. After TAK-003 vaccination, all samples from naive and preimmune vaccinees completely abrogated DENV-2 NS1-induced hyperpermeability and cross-inhibited hyperpermeability induced by DENV-1, -3, and -4 NS1. Inhibition of NS1-induced hyperpermeability correlated with NS1-specific IgG concentrations. Postvaccination sera also prevented NS1-induced degradation of endothelial glycocalyx components. Conclusion We provide evidence for functional NS1-specific IgG responses elicited by a candidate dengue vaccine. Clinical Trials Registration NCT01511250.
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Kim, Shin-Hee, and Siba K. Samal. "Inhibition of host innate immune responses and pathogenicity of recombinant Newcastle disease viruses expressing NS1 genes of influenza A viruses." Journal of General Virology 91, no. 8 (August 1, 2010): 1996–2001. http://dx.doi.org/10.1099/vir.0.021766-0.
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The NS1 protein has been associated with the virulence of influenza A viruses. To evaluate the role of the NS1 protein in pathogenicity of pandemic H5N1 avian influenza and H1N1 2009 influenza viruses, recombinant Newcastle disease viruses (rNDVs) expressing NS1 proteins were generated. Expression of the NS1 proteins resulted in inhibition of host innate immune responses (beta interferon and protein kinase R production). In addition, the NS1 proteins were localized predominantly in the nucleus of virus-infected cells. Consequently, expression of the NS1 protein contributed to an increase in pathogenicity of rNDV in chickens. In particular, mutational analysis of H5N1 NS1 protein indicated that both the RNA-binding and effector domains affect virus pathogenicity synergistically. Our study also demonstrated that expression of H1N1/09 NS1 resulted in enhanced replication of rNDV in human cells, indicating that function of the NS1 proteins can be host-species-specific.
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Youn, Soonjeon, Hyelim Cho, Daved H. Fremont, and Michael S. Diamond. "A Short N-Terminal Peptide Motif on Flavivirus Nonstructural Protein NS1 Modulates Cellular Targeting and Immune Recognition." Journal of Virology 84, no. 18 (June 30, 2010): 9516–32. http://dx.doi.org/10.1128/jvi.00775-10.
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ABSTRACT Flavivirus NS1 is a versatile nonstructural glycoprotein, with intracellular NS1 functioning as an essential cofactor for viral replication and cell surface and secreted NS1 antagonizing complement activation. Even though NS1 has multiple functions that contribute to virulence, the genetic determinants that regulate the spatial distribution of NS1 in cells among different flaviviruses remain uncharacterized. Here, by creating a panel of West Nile virus-dengue virus (WNV-DENV) NS1 chimeras and site-specific mutants, we identified a novel, short peptide motif immediately C-terminal to the signal sequence cleavage position that regulates its transit time through the endoplasmic reticulum and differentially directs NS1 for secretion or plasma membrane expression. Exchange of two amino acids within this motif reciprocally changed the cellular targeting pattern of DENV or WNV NS1. For WNV, this substitution also modulated infectivity and antibody-induced phagocytosis of infected cells. Analysis of a mutant lacking all three conserved N-linked glycosylation sites revealed an independent requirement of N-linked glycans for secretion but not for plasma membrane expression of WNV NS1. Collectively, our experiments define the requirements for cellular targeting of NS1, with implications for the protective host responses, immune antagonism, and association with the host cell sorting machinery. These studies also suggest a link between the effects of NS1 on viral replication and the levels of secreted or cell surface NS1.
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Chen, Guifang, Li-Chung Ma, Shanshan Wang, Ryan L. Woltz, Emily M. Grasso, Gaetano T. Montelione, and Robert M. Krug. "A double-stranded RNA platform is required for the interaction between a host restriction factor and the NS1 protein of influenza A virus." Nucleic Acids Research 48, no. 1 (November 22, 2019): 304–15. http://dx.doi.org/10.1093/nar/gkz1094.
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Abstract Influenza A viruses cause widespread human respiratory disease. The viral multifunctional NS1 protein inhibits host antiviral responses. This inhibition results from the binding of specific cellular antiviral proteins at various positions on the NS1 protein. Remarkably, binding of several proteins also requires the two amino-acid residues in the NS1 N-terminal RNA-binding domain (RBD) that are required for binding double-stranded RNA (dsRNA). Here we focus on the host restriction factor DHX30 helicase that is countered by the NS1 protein, and establish why the dsRNA-binding activity of NS1 is required for its binding to DHX30. We show that the N-terminal 152 amino-acid residue segment of DHX30, denoted DHX30N, possesses all the antiviral activity of DHX30 and contains a dsRNA-binding domain, and that the NS1-DHX30 interaction in vivo requires the dsRNA-binding activity of both DHX30N and the NS1 RBD. We demonstrate why this is the case using bacteria-expressed proteins: the DHX30N-NS1 RBD interaction in vitro requires the presence of a dsRNA platform that binds both NS1 RBD and DHX30N. We propose that a similar dsRNA platform functions in interactions of the NS1 protein with other proteins that requires these same two amino-acid residues required for NS1 RBD dsRNA-binding activity.
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Noisakran, Sansanee, Thanyaporn Dechtawewat, Panisadee Avirutnan, Taroh Kinoshita, Uamporn Siripanyaphinyo, Chunya Puttikhunt, Watchara Kasinrerk, Prida Malasit, and Nopporn Sittisombut. "Association of dengue virus NS1 protein with lipid rafts." Journal of General Virology 89, no. 10 (October 1, 2008): 2492–500. http://dx.doi.org/10.1099/vir.0.83620-0.
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During the replication of dengue virus, a viral non-structural glycoprotein, NS1, associates with the membrane on the cell surface and in the RNA replication complex. NS1 lacks a transmembrane domain, and the mechanism by which it associates with the membrane remains unclear. This study aimed to investigate whether membrane-bound NS1 is present in lipid rafts in dengue virus-infected cells. Double immunofluorescence staining of infected HEK-293T cells revealed that NS1 localized with raft-associated molecules, ganglioside GM1 and CD55, on the cell surface. In a flotation gradient centrifugation assay, a small proportion of NS1 in Triton X-100 cell lysate consistently co-fractionated with raft markers. Association of NS1 with lipid rafts was detected for all four dengue serotypes, as well as for Japanese encephalitis virus. Analysis of recombinant NS1 forms showed that glycosylated NS1 dimers stably expressed in HEK-293T cells without an additional C-terminal sequence, or with a heterologous transmembrane domain, failed to associate with lipid rafts. In contrast, glycosylphosphatidylinositol-linked recombinant NS1 exhibited a predilection for lipid rafts. These results indicate an association of a minor subpopulation of NS1 with lipid rafts during dengue virus infection and suggest that modification of NS1, possibly lipidation, is required for raft association.
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Jureka, Alexander S., Alex B. Kleinpeter, Jennifer L. Tipper, Kevin S. Harrod, and Chad M. Petit. "The influenza NS1 protein modulates RIG-I activation via a strain-specific direct interaction with the second CARD of RIG-I." Journal of Biological Chemistry 295, no. 4 (December 16, 2019): 1153–64. http://dx.doi.org/10.1074/jbc.ra119.011410.
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A critical role of influenza A virus nonstructural protein 1 (NS1) is to antagonize the host cellular antiviral response. NS1 accomplishes this role through numerous interactions with host proteins, including the cytoplasmic pathogen recognition receptor, retinoic acid–inducible gene I (RIG-I). Although the consequences of this interaction have been studied, the complete mechanism by which NS1 antagonizes RIG-I signaling remains unclear. We demonstrated previously that the NS1 RNA-binding domain (NS1RBD) interacts directly with the second caspase activation and recruitment domain (CARD) of RIG-I. We also identified that a single strain-specific polymorphism in the NS1RBD (R21Q) completely abrogates this interaction. Here we investigate the functional consequences of an R21Q mutation on NS1's ability to antagonize RIG-I signaling. We observed that an influenza virus harboring the R21Q mutation in NS1 results in significant up-regulation of RIG-I signaling. In support of this, we determined that an R21Q mutation in NS1 results in a marked deficit in NS1's ability to antagonize TRIM25-mediated ubiquitination of the RIG-I CARDs, a critical step in RIG-I activation. We also observed that WT NS1 is capable of binding directly to the tandem RIG-I CARDs, whereas the R21Q mutation in NS1 significantly inhibits this interaction. Furthermore, we determined that the R21Q mutation does not impede the interaction between NS1 and TRIM25 or NS1RBD's ability to bind RNA. The data presented here offer significant insights into NS1 antagonism of RIG-I and illustrate the importance of understanding the role of strain-specific polymorphisms in the context of this specific NS1 function.
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Warner, Nikole L., and Kathryn M. Frietze. "Development of Bacteriophage Virus-Like Particle Vaccines Displaying Conserved Epitopes of Dengue Virus Non-Structural Protein 1." Vaccines 9, no. 7 (July 2, 2021): 726. http://dx.doi.org/10.3390/vaccines9070726.
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Dengue virus (DENV) is a major global health problem, with over half of the world’s population at risk of infection. Despite over 60 years of efforts, no licensed vaccine suitable for population-based immunization against DENV is available. Here, we describe efforts to engineer epitope-based vaccines against DENV non-structural protein 1 (NS1). NS1 is present in DENV-infected cells as well as secreted into the blood of infected individuals. NS1 causes disruption of endothelial cell barriers, resulting in plasma leakage and hemorrhage. Immunizing against NS1 could elicit antibodies that block NS1 function and also target NS1-infected cells for antibody-dependent cell cytotoxicity. We identified highly conserved regions of NS1 from all four DENV serotypes. We generated synthetic peptides to these regions and chemically conjugated them to bacteriophage Qβ virus-like particles (VLPs). Mice were immunized two times with the candidate vaccines and sera were tested for the presence of antibodies that bound to the cognate peptide, recombinant NS1 from all four DENV serotypes, and DENV-2-infected cells. We found that two of the candidate vaccines elicited antibodies that bound to recombinant NS1, and one candidate vaccine elicited antibodies that bound to DENV-infected cells. These results show that an epitope-specific vaccine against conserved regions of NS1 could be a promising approach for DENV vaccines or therapeutics to bind circulating NS1 protein.
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Ogire, Eva, Olivier Diaz, Pierre-Olivier Vidalain, Vincent Lotteau, Philippe Desprès, and Marjolaine Roche. "Instability of the NS1 Glycoprotein from La Reunion 2018 Dengue 2 Virus (Cosmopolitan-1 Genotype) in Huh7 Cells Is Due to Lysine Residues on Positions 272 and 324." International Journal of Molecular Sciences 22, no. 4 (February 16, 2021): 1951. http://dx.doi.org/10.3390/ijms22041951.
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La Reunion island in the South West Indian Ocean is now endemic for dengue following the introduction of dengue virus serotype 2 (DENV-2) cosmopolitan-I genotype in 2017. DENV-2 infection causes a wide spectrum of clinical manifestations ranging from flu-like disease to severe dengue. The nonstructural glycoprotein 1 (NS1) has been identified as playing a key role in dengue disease severity. The intracellular NS1 exists as a homodimer, whereas a fraction is driven towards the plasma membrane or released as a soluble hexameric protein. Here, we characterized the NS1 glycoproteins from clinical isolates DES-14 and RUN-18 that were collected during the DENV-2 epidemics in Tanzania in 2014 and La Reunion island in 2018, respectively. In relation to hepatotropism of the DENV, expression of recombinant DES-14 NS1 and RUN-18 NS1 glycoproteins was compared in human hepatoma Huh7 cells. We observed that RUN-18 NS1 was poorly stable in Huh7 cells compared to DES-14 NS1. The instability of RUN-18 NS1 leading to a low level of NS1 secretion mostly relates to lysine residues on positions 272 and 324. Our data raise the issue of the consequences of a defect in NS1 stability in human hepatocytes in relation to the major role of NS1 in the pathogenesis of the DENV-2 infection.
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Dubrow, Alyssa, Sirong Lin, Nowlan Savage, Qingliang Shen, and Jae-Hyun Cho. "Molecular Basis of the Ternary Interaction between NS1 of the 1918 Influenza A Virus, PI3K, and CRK." Viruses 12, no. 3 (March 20, 2020): 338. http://dx.doi.org/10.3390/v12030338.
Full textAbstract:
The 1918 influenza A virus (IAV) caused the worst flu pandemic in human history. Non-structural protein 1 (NS1) is an important virulence factor of the 1918 IAV and antagonizes host antiviral immune responses. NS1 increases virulence by activating phosphoinositide 3-kinase (PI3K) via binding to the p85β subunit of PI3K. Intriguingly, unlike the NS1 of other human IAV strains, 1918 NS1 hijacks another host protein, CRK, to form a ternary complex with p85β, resulting in hyperactivation of PI3K. However, the molecular basis of the ternary interaction between 1918 NS1, CRK, and PI3K remains elusive. Here, we report the structural and thermodynamic bases of the ternary interaction. We find that the C-terminal tail (CTT) of 1918 NS1 remains highly flexible in the complex with p85β. Thus, the CTT of 1918 NS1 in the complex with PI3K can efficiently hijack CRK. Notably, our study indicates that 1918 NS1 enhances its affinity to p85β in the presence of CRK, which might result in enhanced activation of PI3K. Our results provide structural insight into how 1918 NS1 hijacks two host proteins simultaneously.
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Guo, Lu, and Yingfang Liu. "Crystal structure of the Kelch domain of human NS1-binding protein at 1.98 Å resolution." Acta Crystallographica Section F Structural Biology Communications 74, no. 3 (February 26, 2018): 174–78. http://dx.doi.org/10.1107/s2053230x18001577.
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NS1-binding protein (NS1-BP), which belongs to the Kelch protein superfamily, was first identified as a novel human 70 kDa protein that interacts with NS1 ofInfluenza A virus. It is involved in many cell functions, including pre-mRNA splicing, the ERK signalling pathway, the aryl hydrocarbon receptor (AHR) pathway, F-actin organization and protein ubiquitylation. However, the structure of NS1-BP is still unknown, which may impede functional studies. Here, the structure of the C-terminal Kelch domain of NS1-BP (NS1-BP-C; residues 330–642) was determined at 1.98 Å resolution. The Kelch domain adopts a highly symmetric six-bladed β-propeller fold structure. Each blade of the β-propeller is composed of four antiparallel β-strands. Comparison of the Kelch-domain structures of NS1-BP and its homologues showed that the Gly–Gly pair in β-strandBand the hydrophobic Trp residue in β-strandDare highly conserved, while theB–Cloops in blades 2 and 6 are variable. This structure of the Kelch domain of NS1-BP extends the understanding of NS1-BP.
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Biering, Scott B., David L. Akey, Marcus P. Wong, W. Clay Brown, Nicholas T. N. Lo, Henry Puerta-Guardo, Francielle Tramontini Gomes de Sousa, et al. "Structural basis for antibody inhibition of flavivirus NS1–triggered endothelial dysfunction." Science 371, no. 6525 (January 7, 2021): 194–200. http://dx.doi.org/10.1126/science.abc0476.
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Medically important flaviviruses cause diverse disease pathologies and collectively are responsible for a major global disease burden. A contributing factor to pathogenesis is secreted flavivirus nonstructural protein 1 (NS1). Despite demonstrated protection by NS1-specific antibodies against lethal flavivirus challenge, the structural and mechanistic basis remains unknown. Here, we present three crystal structures of full-length dengue virus NS1 complexed with a flavivirus–cross-reactive, NS1-specific monoclonal antibody, 2B7, at resolutions between 2.89 and 3.96 angstroms. These structures reveal a protective mechanism by which two domains of NS1 are antagonized simultaneously. The NS1 wing domain mediates cell binding, whereas the β-ladder triggers downstream events, both of which are required for dengue, Zika, and West Nile virus NS1–mediated endothelial dysfunction. These observations provide a mechanistic explanation for 2B7 protection against NS1-induced pathology and demonstrate the potential of one antibody to treat infections by multiple flaviviruses.
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Allonso, Diego, Iamara S. Andrade, Jonas N. Conde, Diego R. Coelho, Daniele C. P. Rocha, Manuela L. da Silva, Gustavo T. Ventura, Emiliana M. Silva, and Ronaldo Mohana-Borges. "Dengue Virus NS1 Protein Modulates Cellular Energy Metabolism by Increasing Glyceraldehyde-3-Phosphate Dehydrogenase Activity." Journal of Virology 89, no. 23 (September 16, 2015): 11871–83. http://dx.doi.org/10.1128/jvi.01342-15.
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ABSTRACTDengue is one of the main public health concerns worldwide. Recent estimates indicate that over 390 million people are infected annually with the dengue virus (DENV), resulting in thousands of deaths. Among the DENV nonstructural proteins, the NS1 protein is the only one whose function during replication is still unknown. NS1 is a 46- to 55-kDa glycoprotein commonly found as both a membrane-associated homodimer and a soluble hexameric barrel-shaped lipoprotein. Despite its role in the pathogenic process, NS1 is essential for proper RNA accumulation and virus production. In the present study, we identified that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) interacts with intracellular NS1. Molecular docking revealed that this interaction occurs through the hydrophobic protrusion of NS1 and the hydrophobic residues located at the opposite side of the catalytic site. Moreover, addition of purified recombinant NS1 enhanced the glycolytic activity of GAPDHin vitro. Interestingly, we observed that DENV infection promoted the relocalization of GAPDH to the perinuclear region, where NS1 is commonly found. Both DENV infection and expression of NS1 itself resulted in increased GAPDH activity. Our findings indicate that the NS1 protein acts to increase glycolytic flux and, consequently, energy production, which is consistent with the recent finding that DENV induces and requires glycolysis for proper replication. This is the first report to propose that NS1 is an important modulator of cellular energy metabolism. The data presented here provide new insights that may be useful for further drug design and the development of alternative antiviral therapies against DENV.IMPORTANCEDengue represents a serious public health problem worldwide and is caused by infection with dengue virus (DENV). Estimates indicate that half of the global population is at risk of infection, with almost 400 million cases occurring per year. The NS1 glycoprotein is found in both the intracellular and the extracellular milieus. Despite the fact that NS1 has been commonly associated with DENV pathogenesis, it plays a pivotal but unknown role in the replication process. In an effort to understand the role of intracellular NS1, we demonstrate that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) interacts with NS1. Our results indicate that NS1 increases the glycolytic activity of GAPDHin vitro. Interestingly, the GAPDH activity was increased during DENV infection, and NS1 expression alone was sufficient to enhance intracellular GAPDH activity in BHK-21 cells. Overall, our findings suggest that NS1 is an important modulator of cellular energy metabolism by increasing glycolytic flux.
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Hale, Benjamin G., Ian H. Batty, C. Peter Downes, and Richard E. Randall. "Binding of Influenza A Virus NS1 Protein to the Inter-SH2 Domain of p85β Suggests a Novel Mechanism for Phosphoinositide 3-Kinase Activation." Journal of Biological Chemistry 283, no. 3 (November 20, 2007): 1372–80. http://dx.doi.org/10.1074/jbc.m708862200.
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Influenza A virus NS1 protein stimulates host-cell phosphoinositide 3-kinase (PI3K) signaling by binding to the p85β regulatory subunit of PI3K. Here, in an attempt to establish a mechanism for this activation, we report further on the functional interaction between NS1 and p85β. Complex formation was found to be independent of NS1 RNA binding activity and is mediated by the C-terminal effector domain of NS1. Intriguingly, the primary direct binding site for NS1 on p85β is the inter-SH2 domain, a coiled-coil structure that acts as a scaffold for the p110 catalytic subunit of PI3K. In vitro kinase activity assays, together with protein binding competition studies, reveal that NS1 does not displace p110 from the inter-SH2 domain, and indicate that NS1 can form an active heterotrimeric complex with PI3K. In addition, it was established that residues at the C terminus of the inter-SH2 domain are essential for mediating the interaction between p85β and NS1. Equivalent residues in p85α have previously been implicated in the basal inhibition of p110. However, such p85α residues were unable to substitute for those in p85β with regards NS1 binding. Overall, these data suggest a model by which NS1 activates PI3K catalytic activity by masking a normal regulatory element specific to the p85β inter-SH2 domain.
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Galula, Jedhan Ucat, Gielenny M. Salem, Raul V. Destura, Roland Remenyi, and Day-Yu Chao. "Comparable Accuracies of Nonstructural Protein 1- and Envelope Protein-Based Enzyme-Linked Immunosorbent Assays in Detecting Anti-Dengue Immunoglobulin G Antibodies." Diagnostics 11, no. 5 (April 21, 2021): 741. http://dx.doi.org/10.3390/diagnostics11050741.
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Background: Dengue virus (DENV) infection remains a global public health concern. Enzyme-linked immunosorbent assays (ELISAs), which detect antibodies targeting the envelope (E) protein of DENV, serve as the front-line serological test for presumptive dengue diagnosis. Very few studies have determined the serostatus by detecting antibodies targeting the nonstructural protein 1 (NS1), which can function as diagnostic biomarkers to distinguish natural immunity from vaccine-induced immunity. Methods: We used community-acquired human serum specimens, with the serostatus confirmed by focus reduction microneutralization test (FRμNT), to evaluate the diagnostic performances of two NS1-based ELISA methods, namely, immunoglobulin G antibody-capture ELISA (NS1 GAC–ELISA) and indirect NS1 IgG ELISA, and compared the results with an E-based virus-like particle (VLP) GAC–ELISA. Results: NS1-based methods had comparable accuracies as VLP GAC–ELISA. Although the sensitivity in detecting anti-NS1 IgM was poor, indirect NS1 IgG ELISA showed similar limits of detection (~1–2 ng/mL) as NS1 GAC–ELISA in detecting anti-NS1 IgG. Combining the results from two or more tests as a composite reference standard can determine the DENV serostatus with a specificity reaching 100%. Conclusion: NS1-based ELISAs have comparable accuracies as VLP GAC–ELISA in determining dengue serostatus, which could effectively assist clinicians during assessments of vaccine eligibility.
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Dechtawewat, Thanyaporn, Sittiruk Roytrakul, Yodying Yingchutrakul, Sawanya Charoenlappanit, Bunpote Siridechadilok, Thawornchai Limjindaporn, Arunothai Mangkang, et al. "Potential Phosphorylation of Viral Nonstructural Protein 1 in Dengue Virus Infection." Viruses 13, no. 7 (July 17, 2021): 1393. http://dx.doi.org/10.3390/v13071393.
Full textAbstract:
Dengue virus (DENV) infection causes a spectrum of dengue diseases that have unclear underlying mechanisms. Nonstructural protein 1 (NS1) is a multifunctional protein of DENV that is involved in DENV infection and dengue pathogenesis. This study investigated the potential post-translational modification of DENV NS1 by phosphorylation following DENV infection. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), 24 potential phosphorylation sites were identified in both cell-associated and extracellular NS1 proteins from three different cell lines infected with DENV. Cell-free kinase assays also demonstrated kinase activity in purified preparations of DENV NS1 proteins. Further studies were conducted to determine the roles of specific phosphorylation sites on NS1 proteins by site-directed mutagenesis with alanine substitution. The T27A and Y32A mutations had a deleterious effect on DENV infectivity. The T29A, T230A, and S233A mutations significantly decreased the production of infectious DENV but did not affect relative levels of intracellular DENV NS1 expression or NS1 secretion. Only the T230A mutation led to a significant reduction of detectable DENV NS1 dimers in virus-infected cells; however, none of the mutations interfered with DENV NS1 oligomeric formation. These findings highlight the importance of DENV NS1 phosphorylation that may pave the way for future target-specific antiviral drug design.
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Lin, Yi-Ling, Li-Kuang Chen, Ching-Len Liao, Chia-Tsui Yeh, Shiou-Hwa Ma, Jin-Ling Chen, Yue-Ling Huang, Shih-Shun Chen, and Hsien-Yuan Chiang. "DNA Immunization with Japanese Encephalitis Virus Nonstructural Protein NS1 Elicits Protective Immunity in Mice." Journal of Virology 72, no. 1 (January 1, 1998): 191–200. http://dx.doi.org/10.1128/jvi.72.1.191-200.1998.
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ABSTRACT Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, is a zoonotic pathogen that is prevalent in some Southeast Asian countries and causes acute encephalitis in humans. To evaluate the potential application of gene immunization to JEV infection, we characterized the immune responses from mice intramuscularly injected with plasmid DNA encoding JEV glycoproteins, including the precursor membrane (prM) plus envelope (E) proteins and the nonstructural protein NS1. When injected with the plasmid expressing prM plus E, 70% of the immunized mice survived after a lethal JEV challenge, whereas when immunized with the plasmid expressing NS1, 90% of the mice survived after a lethal challenge. As a control, the mice immunized with the DNA vector pcDNA3 showed a low level (40%) of protection, suggesting a nonspecific adjuvant effect of the plasmid DNA. Despite having no detectable neutralizing activity, the NS1 immunization elicited a strong antibody response exhibiting cytolytic activity against JEV-infected cells in a complement-dependent manner. By contrast, immunization with a construct expressing a longer NS1 protein (NS1′), containing an extra 60-amino-acid portion from the N terminus of NS2A, failed to protect mice against a lethal challenge. Biochemical analyses revealed that when individually expressed, NS1 but not NS1′ could be readily secreted as a homodimer in large quantity and could also be efficiently expressed on the cell surface. Interestingly, when NS1 and NS1′ coexisted in cells, the level of NS1 cell surface expression was much lower than that in cells expressing NS1 alone. These data imply that the presence of partial NS2A might have a negative influence on an NS1-based DNA vaccine. The results herein clearly illustrate that immunization with DNA expressing NS1 alone is sufficient to protect mice against a lethal JEV challenge.
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Conde, Jonas Nascimento, Emiliana Mandarano da Silva, Diego Allonso, Diego Rodrigues Coelho, Iamara da Silva Andrade, Luciano Neves de Medeiros, Joice Lima Menezes, Angela Silva Barbosa, and Ronaldo Mohana-Borges. "Inhibition of the Membrane Attack Complex by Dengue Virus NS1 through Interaction with Vitronectin and Terminal Complement Proteins." Journal of Virology 90, no. 21 (August 10, 2016): 9570–81. http://dx.doi.org/10.1128/jvi.00912-16.
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ABSTRACTDengue virus (DENV) infects millions of people worldwide and is a major public health problem. DENV nonstructural protein 1 (NS1) is a conserved glycoprotein that associates with membranes and is also secreted into the plasma in DENV-infected patients. The present study describes a novel mechanism by which NS1 inhibits the terminal complement pathway. We first identified the terminal complement regulator vitronectin (VN) as a novel DENV2 NS1 binding partner by using a yeast two-hybrid system. This interaction was further assessed by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) assay. The NS1-VN complex was also detected in plasmas from DENV-infected patients, suggesting that this interaction occurs during DENV infection. We also demonstrated that the DENV2 NS1 protein, either by itself or by interacting with VN, hinders the formation of the membrane attack complex (MAC) and C9 polymerization. Finally, we showed that DENV2, West Nile virus (WNV), and Zika virus (ZIKV) NS1 proteins produced in mammalian cells inhibited C9 polymerization. Taken together, our results points to a role for NS1 as a terminal pathway inhibitor of the complement system.IMPORTANCEDengue is the most important arthropod-borne viral disease nowadays and is caused by dengue virus (DENV). The flavivirus NS1 glycoprotein has been characterized functionally as a complement evasion protein that can attenuate the activation of the classical, lectin, and alternative pathways. The present study describes a novel mechanism by which DENV NS1 inhibits the terminal complement pathway. We identified the terminal complement regulator vitronectin (VN) as a novel DENV NS1 binding partner, and the NS1-VN complex was detected in plasmas from DENV-infected patients, suggesting that this interaction occurs during DENV infection. We also demonstrated that the NS1-VN complex inhibited membrane attack complex (MAC) formation, thus interfering with the complement terminal pathway. Interestingly, NS1 itself also inhibited MAC activity, suggesting a direct role of this protein in the inhibition process. Our findings imply a role for NS1 as a terminal pathway inhibitor of the complement system.
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Deleu, Laurent, Aurora Pujol, Jürg P. F. Nüesch, and Jean Rommelaere. "Inhibition of transcription-regulating properties of nonstructural protein 1 (NS1) of parvovirus minute virus of mice by a dominant-negative mutant form of NS1." Journal of General Virology 82, no. 8 (August 1, 2001): 1929–34. http://dx.doi.org/10.1099/0022-1317-82-8-1929.
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Nonstructural protein 1 (NS1) of minute virus of mice is involved in viral DNA replication, transcriptional regulation and cytotoxic action in the host cell. Viral DNA replication is dependent on the ability of NS1 to form homo-oligomers. To investigate whether oligomerization is required for NS1 transcriptional activities, a functionally impaired mutant derivative of NS1 that was able to interact with the wild-type (wt) protein and inhibit its activity in a dominant-negative manner was designed. This mutant provided evidence that transactivation of the parvoviral P38 promoter and transinhibition of a heterologous promoter by NS1 were both affected by the co-expression of the wt and the dominant-negative mutant form of NS1. These results indicate that additional functions of NS1, involved in promoter regulation, require oligomer formation.
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Hale, Benjamin G., Philip S. Kerry, David Jackson, Bernard L. Precious, Alexander Gray, Marian J. Killip, Richard E. Randall, and Rupert J. Russell. "Structural insights into phosphoinositide 3-kinase activation by the influenza A virus NS1 protein." Proceedings of the National Academy of Sciences 107, no. 5 (January 19, 2010): 1954–59. http://dx.doi.org/10.1073/pnas.0910715107.
Full textAbstract:
Seasonal epidemics and periodic worldwide pandemics caused by influenza A viruses are of continuous concern. The viral nonstructural (NS1) protein is a multifunctional virulence factor that antagonizes several host innate immune defenses during infection. NS1 also directly stimulates class IA phosphoinositide 3-kinase (PI3K) signaling, an essential cell survival pathway commonly mutated in human cancers. Here, we present a 2.3-Å resolution crystal structure of the NS1 effector domain in complex with the inter-SH2 (coiled-coil) domain of p85β, a regulatory subunit of PI3K. Our data emphasize the remarkable isoform specificity of this interaction, and provide insights into the mechanism by which NS1 activates the PI3K (p85β:p110) holoenzyme. A model of the NS1:PI3K heterotrimeric complex reveals that NS1 uses the coiled-coil as a structural tether to sterically prevent normal inhibitory contacts between the N-terminal SH2 domain of p85β and the p110 catalytic subunit. Furthermore, in this model, NS1 makes extensive contacts with the C2/kinase domains of p110, and a small acidic α-helix of NS1 sits adjacent to the highly basic activation loop of the enzyme. During infection, a recombinant influenza A virus expressing NS1 with charge-disruption mutations in this acidic α-helix is unable to stimulate the production of phosphatidylinositol 3,4,5-trisphosphate or the phosphorylation of Akt. Despite this, the charge-disruption mutations in NS1 do not affect its ability to interact with the p85β inter-SH2 domain in vitro. Overall, these data suggest that both direct binding of NS1 to p85β (resulting in repositioning of the N-terminal SH2 domain) and possible NS1:p110 contacts contribute to PI3K activation.
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Li, Wei, James W. Noah, and Diana L. Noah. "Alanine substitutions within a linker region of the influenza A virus non-structural protein 1 alter its subcellular localization and attenuate virus replication." Journal of General Virology 92, no. 8 (August 1, 2011): 1832–42. http://dx.doi.org/10.1099/vir.0.031336-0.
Full textAbstract:
The influenza A virus non-structural protein 1 (NS1) is a multifunctional protein and an important virulence factor. It is composed of two well-characterized domains linked by a short, but not well crystallographically defined, region of unknown function. To study the possible function of this region, we introduced alanine substitutions to replace the two highly conserved leucine residues at amino acid positions 69 and 77. The mutant L69,77A NS1 protein retained wild-type (WT)-comparable binding capabilities to dsRNA, cleavage and polyadenylation specificity factor 30 and the p85β subunit of PI3K. A mutant influenza A virus expressing the L69,77A NS1 protein was generated using reverse genetics. L69,77A NS1 virus infection induced significantly higher levels of beta interferon (IFN-β) expression in Madin–Darby canine kidney (MDCK) cells compared with WT NS1 virus. In addition, the replication rate of the L69,77A NS1 virus was substantially lower in MDCK cells but not in Vero cells compared with the WT virus, suggesting that the L69,77A NS1 protein does not fully antagonize IFN during viral replication. L69,77A NS1 virus infection was not able to activate the PI3K/Akt anti-apoptotic pathway, suggesting that the mutant NS1 protein may not be localized such that it has access to p85β in vivo during infection, which was supported by the altered subcellular localization pattern of the mutant NS1 compared with WT NS1 after transfection or virus infection. Our data demonstrate that this linker region between the two domains is critical for the functions of the NS1 protein during influenza A virus infection, possibly by determining the protein’s correct subcellular localization.
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Atreya, Prabha L., Mark E. Peeples, and Peter L. Collins. "The NS1 Protein of Human Respiratory Syncytial Virus Is a Potent Inhibitor of Minigenome Transcription and RNA Replication." Journal of Virology 72, no. 2 (February 1, 1998): 1452–61. http://dx.doi.org/10.1128/jvi.72.2.1452-1461.1998.
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ABSTRACT The NS1 protein (139 amino acids) is one of the two nonstructural proteins of human respiratory syncytial virus (RSV) and is encoded by a very abundant mRNA transcribed from the promoter-proximal RSV gene. The function of NS1 was unknown and was investigated here by using a reconstituted transcription and RNA replication system that involves a minireplicon and viral proteins (N, P, L and M2-1) expressed from separate cotransfected plasmids. Coexpression of the NS1 cDNA strongly inhibited transcription and RNA replication mediated by the RSV polymerase, even when the level of expressed NS1 protein was substantially below that observed in RSV-infected cells. The effect depended on synthesis of NS1 protein rather than NS1 RNA alone. Transcription and both steps of RNA replication, namely, synthesis of the antigenome and the genome, appeared to be equally sensitive to inhibition. The efficiency of encapsidation of the plasmid-derived minigenome was not altered by coexpression of NS1, indicating that the inhibition occurs at a later step. In two different dicistronic minigenomes, transcription of each gene was equally sensitive to inhibition by NS1. This suggested that the gradient of transcriptional polarity was unaffected and that the effect of NS1 instead probably involves an early event such as polymerase entry on the genome. NS1-mediated inhibition of transcription and RNA replication was not affected by coexpression of the M2 mRNA, which has two open reading frames encoding the transcriptional elongation factor M2-1 and the putative negative regulatory factor M2-2. The potent nature of the NS1-mediated inhibition suggests that negative regulation is an authentic function of the NS1 protein, albeit not necessarily the only one.
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Lindenbach, Brett D., and Charles M. Rice. "Genetic Interaction of Flavivirus Nonstructural Proteins NS1 and NS4A as a Determinant of Replicase Function." Journal of Virology 73, no. 6 (June 1, 1999): 4611–21. http://dx.doi.org/10.1128/jvi.73.6.4611-4621.1999.
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ABSTRACT Nonstructural protein 1 (NS1) of yellow fever virus (YF) is a glycoprotein localized to extracytoplasmic compartments within infected cells. We have previously shown that NS1 can be supplied intrans and is required for viral RNA replication, a process thought to occur in membrane-bound cytoplasmic complexes. Here we report that the NS1 gene from a related virus, dengue virus (DEN), is unable to function in the process of YF RNA replication. This virus-specific incompatibility leads to a lack of initial minus-strand accumulation, suggesting that DEN NS1 is unable to productively interact with the YF replicase. Based on a YF deletion mutant that requires NS1 in trans, a genetic screen for suppressor mutants was used to select virus variants able to utilize DEN NS1. In three independent selections, a single mutation was mapped to the NS4A gene, which encodes a putative transmembrane replicase component. This mutation, as well as several additional mutations, was engineered into the NS1-deficient genome and confirmed a genetic interaction between NS1 and NS4A. These findings suggest a potential mechanism for integrating NS1 into the cytoplasmic process of RNA replication.
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Bisordi, Ivani, Iray Maria Rocco, Akemi Suzuki, Gizelda Katz, Vivian Regina Silveira, Adriana Yurika Maeda, Renato Pereira de Souza, et al. "Evaluation of dengue NS1 antigen detection for diagnosis in public health laboratories, São Paulo State, 2009." Revista do Instituto de Medicina Tropical de São Paulo 53, no. 6 (December 2011): 315–20. http://dx.doi.org/10.1590/s0036-46652011000600003.
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The present work evaluated the diagnostic accuracy of detection of Dengue NS1 antigen employing two NS1 assays, an immunochromatographic assay and ELISA, in the diagnostic routine of Public Health laboratories. The results obtained with NS1 assay were compared with virus isolation and, in a subpopulation of cases, they were compared with the IgM-ELISA results obtained with convalescent samples. A total of 2,321 sera samples were analyzed by one of two NS1 techniques from March to October 2009. The samples were divided into five groups: groups I, II and III included samples tested by NS1 and virus isolation, and groups IV and V included patients with a first sample tested by NS1 and a second sample tested by IgM-ELISA. Sensitivity, specificity, positive and negative predictive values, Kappa Index and Kappa Concordance were calculated. The results showed that NS1 testing in groups I, II and III had high sensitivity (98.0%, 99.5% and 99.3%), and predictive values and Kappa index between 0.9 - 1.0. Groups IV and V only had Kappa Concordance calculated, since the samples were analyzed according to the presence of NS1 antigen or IgM antibody. Concordance of 92.1% was observed when comparing the results of NS1-negative samples with IgM-ELISA. Based on the findings, it is possible to suggest that the tests for NS1 detection may be important tools for monitoring the introduction and spread of Dengue serotypes.
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Arodes, Evy Suryani, Beti Ernawati Dewi, and Tjahjani Mirawati Sudiro. "Horseradish peroxidase-labeled rabbit anti-non-structural protein 1 of dengue virus-2 for the diagnosis of dengue virus infections." Medical Journal of Indonesia 28, no. 2 (August 9, 2019): 103–9. http://dx.doi.org/10.13181/mji.v28i2.1951.
Full textAbstract:
BACKGROUND Early diagnosis of dengue virus (DENV) infection is essential for patient management and disease control. Detection of the antigen non-structural protein 1 (NS1) has been proven to provide early diagnosis of DENV infection. Thus, commercial NS1 antigen detection assays have been increasingly used and are becoming thetool of choice among clinicians to confirm DENV infection in Indonesia.
METHODS To obtain anti-NS1 DENV antibody, NS1 protein (90 µg/ml) from the collection of the Department of Microbiology, Faculty of Medicine, Universitas Indonesia was injected into a rabbit. The anti-NS1 antibody from the rabbit was then labeled with horseradish peroxidase (HRP) using the periodate oxidation method. Sera were tested by enzyme-linked immunosorbent assay (ELISA) to detect NS1 from DENV-infected patients.
RESULTS Serially diluted antibody labeled with HRP tested using the direct ELISA method showed the highest absorbance value at a 1:100 dilution (Mean [SD] = 1.35 [0.35]); even at a dilution as high as 1:3,200 (0.22 [0.15]), antibody labeled with HRP was able to detect the NS1 protein, although the absorbance value did not differ greatly from that of the negative control (0.13 [0.01]).
CONCLUSIONS In an attempt to develop an NS1-based diagnostic test, polyclonal anti-NS1 DENV antibody was successfully produced as a diagnostic assay to determine the presence of DENV NS1 antigen in patients’ sera.
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Macdonald, Joanne, Jessica Tonry, Roy A. Hall, Brent Williams, Gustavo Palacios, Mundrigi S. Ashok, Omar Jabado, et al. "NS1 Protein Secretion during the Acute Phase of West Nile Virus Infection." Journal of Virology 79, no. 22 (November 15, 2005): 13924–33. http://dx.doi.org/10.1128/jvi.79.22.13924-13933.2005.
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ABSTRACT The West Nile virus (WNV) nonstructural protein NS1 is a protein of unknown function that is found within, associated with, and secreted from infected cells. We systematically investigated the kinetics of NS1 secretion in vitro and in vivo to determine the potential use of this protein as a diagnostic marker and to analyze NS1 secretion in relation to the infection cycle. A sensitive antigen capture enzyme-linked immunosorbent assay (ELISA) for detection of WNV NS1 (polyclonal-ACE) was developed, as well as a capture ELISA for the specific detection of NS1 multimers (4G4-ACE). The 4G4-ACE detected native NS1 antigens at high sensitivity, whereas the polyclonal-ACE had a higher specificity for recombinant forms of the protein. Applying these assays we found that only a small fraction of intracellular NS1 is secreted and that secretion of NS1 in tissue culture is delayed compared to the release of virus particles. In experimentally infected hamsters, NS1 was detected in the serum between days 3 and 8 postinfection, peaking on day 5, the day prior to the onset of clinical disease; immunoglobulin M (IgM) antibodies were detected at low levels on day 5 postinfection. Although real-time PCR gave the earliest indication of infection (day 1), the diagnostic performance of the 4G4-ACE was comparable to that of real-time PCR during the time period when NS1 was secreted. Moreover, the 4G4-ACE was found to be superior in performance to both the IgM and plaque assays during this time period, suggesting that NS1 is a viable early diagnostic marker of WNV infection.
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Salvatore, Mirella, Christopher F. Basler, Jean-Patrick Parisien, Curt M. Horvath, Svetlana Bourmakina, Hongyong Zheng, Thomas Muster, Peter Palese, and Adolfo García-Sastre. "Effects of Influenza A Virus NS1 Protein on Protein Expression: the NS1 Protein Enhances Translation and Is Not Required for Shutoff of Host Protein Synthesis." Journal of Virology 76, no. 3 (February 1, 2002): 1206–12. http://dx.doi.org/10.1128/jvi.76.3.1206-1212.2002.
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ABSTRACT The influenza A virus NS1 protein, a virus-encoded alpha/beta interferon (IFN-α/β) antagonist, appears to be a key regulator of protein expression in infected cells. We now show that NS1 protein expression results in enhancement of reporter gene activity from transfected plasmids. This effect appears to be mediated at the translational level, and it is reminiscent of the activity of the adenoviral virus-associated I (VAI) RNA, a known inhibitor of the antiviral, IFN-induced, PKR protein. To study the effects of the NS1 protein on viral and cellular protein synthesis during influenza A virus infection, we used recombinant influenza viruses lacking the NS1 gene (delNS1) or expressing truncated NS1 proteins. Our results demonstrate that the NS1 protein is required for efficient viral protein synthesis in COS-7 cells. This activity maps to the amino-terminal domain of the NS1 protein, since cells infected with wild-type virus or with a mutant virus expressing a truncated NS1 protein—lacking approximately half of its carboxy-terminal end—showed similar kinetics of viral and cellular protein expression. Interestingly, no major differences in host cell protein synthesis shutoff or in viral protein expression were found among NS1 mutant viruses in Vero cells. Thus, another viral component(s) different from the NS1 protein is responsible for the inhibition of host protein synthesis during viral infection. In contrast to the earlier proposal suggesting that the NS1 protein regulates the levels of spliced M2 mRNA, no effects on M2 protein accumulation were seen in Vero cells infected with delNS1 virus.
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Daeffler, Laurent, Rita Hörlein, Jean Rommelaere, and Jürg P. F. Nüesch. "Modulation of Minute Virus of Mice Cytotoxic Activities through Site-Directed Mutagenesis within the NS Coding Region." Journal of Virology 77, no. 23 (December 1, 2003): 12466–78. http://dx.doi.org/10.1128/jvi.77.23.12466-12478.2003.
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ABSTRACT Late in infection, parvovirus minute virus of mice (MVMp) induces the lysis of mouse A9 fibroblasts. This effect depends on the large nonstructural phosphoprotein NS1, which plays in addition a major role in viral DNA replication and progeny particle production. Since the NS1 C-terminal region is subjected to late phosphorylation events and protein kinase C (PKC) family members regulate NS1 replicative activities, the present study was conducted to determine the impact of PKCs on NS1 cytotoxic functions. To this end, we performed site-directed mutagenesis, substituting alanine residues for two consensus PKC-phosphorylation sites located within the NS1 C-terminal region, T585 and S588. Although these substitutions had no detectable effect on virus multiplication in a single-round infection, the NS1-585A mutant virus was significantly less toxic to A9 cells than wild-type MVMp, whereas the NS1-588A mutant virus was endowed with a higher killing potential. These alterations correlated with specific changes in the late phosphorylation pattern of the mutant NS1 proteins compared to the wild-type polypeptide. Since the mutations introduced in this region of the viral genome also made changes in the minor nonstructural protein NS2, a contribution of this polypeptide to the above-mentioned phenotypes of mutant viruses cannot be excluded at present. However, the involvement of NS1 in these phenotypes was directly supported by the respective reduced and enhanced capacity of NS1-585A and NS1-588A recombinant proteins for inducing morphological alterations and cell detachment in transfected A9 cultures. Altogether, these data suggest that late-occurring phosphorylation of NS1 specifically regulates the cytotoxic functions of the viral product and that residues T585 and S588 contribute to this control in an antagonistic way.
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Patel, Sameera, Alessandro Sinigaglia, Luisa Barzon, Matteo Fassan, Florian Sparber, Salome LeibundGut-Landmann, and Mathias Ackermann. "Role of NS1 and TLR3 in Pathogenesis and Immunity of WNV." Viruses 11, no. 7 (July 3, 2019): 603. http://dx.doi.org/10.3390/v11070603.
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West Nile Virus (WNV) is a mosquito-transmitted flavivirus which causes encephalitis especially in elderly and immunocompromised individuals. Previous studies have suggested the protective role of the Toll-like receptor 3 (TLR3) pathway against WNV entry into the brain, while the WNV non-structural protein 1 (NS1) interferes with the TLR3 signaling pathway, besides being a component of viral genome replication machinery. In this study, we investigated whether immunization with NS1 could protect against WNV neuroinvasion in the context of TLR3 deficiency. We immunized mice with either an intact or deleted TLR3 system (TLR3KO) with WNV envelope glycoprotein (gE) protein, NS1, or a combination of gE and NS1. Immunization with gE or gE/NS1, but not with NS1 alone, induced WNV neutralizing antibodies and protected against WNV brain invasion and inflammation. The presence of intact TLR3 signaling had no apparent effect on WNV brain invasion. However, mock-immunized TLR3KO mice had higher inflammatory cell invasion upon WNV brain infection than NS1-immunized TLR3KO mice and wild type mice. Thus, immunization against NS1 may reduce brain inflammation in a context of TLR3 signaling deficiency.
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Meunier, Isabelle, and Veronika von Messling. "NS1-mediated delay of type I interferon induction contributes to influenza A virulence in ferrets." Journal of General Virology 92, no. 7 (July 1, 2011): 1635–44. http://dx.doi.org/10.1099/vir.0.032193-0.
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Interference of the influenza A virus non-structural protein NS1 with type I interferon (IFN) signalling has been characterized extensively in vitro. To assess the contribution of NS1 to the virulence of a specific strain, we generated recombinant USSR/90/77 viruses bearing the NS1 proteins of the attenuated strain PR/8/34 or the highly pathogenic strain 1918 ‘Spanish flu’, all belonging to the H1N1 subtype. In vitro, the extent of interference with type I IFN production exerted by the different NS1 proteins correlated with the reported virulence of the respective strain. Infection of ferrets with the recombinant viruses revealed that the presence of the 1918 NS1 resulted in a slightly more severe disease with generally higher clinical scores and increased lung pathology. Analysis of mRNA from nasal wash cells revealed that viruses carrying the 1918 and, to a lesser extent, USSR/90/77 NS1 proteins caused a delay in upregulation of type I IFNs compared with the NS1 PR/8/34-expressing virus, demonstrating the importance of NS1 for early host-response control and virulence.
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Rahim, Md Niaz, Mohammed Selman, Patricia J. Sauder, Nicole E. Forbes, William Stecho, Wanhong Xu, Mark Lebar, Earl G. Brown, and Kevin M. Coombs. "Generation and characterization of a new panel of broadly reactive anti-NS1 mAbs for detection of influenza A virus." Journal of General Virology 94, no. 3 (March 1, 2013): 593–605. http://dx.doi.org/10.1099/vir.0.046649-0.
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Influenza A virus (IAV) non-structural protein 1 (NS1) has multiple functions, is essential for virus replication and may be a good target for IAV diagnosis. To generate broadly cross-reactive NS1-specific mAbs, mice were immunized with A/Hong Kong/1/1968 (H3N2) 6×His-tagged NS1 and hybridomas were screened with glutathione S-transferase-conjugated NS1 of A/Puerto Rico/8/1934 (H1N1). mAbs were isotyped and numerous IgG-type clones were characterized further. Most clones specifically recognized NS1 from various H1N1 and H3N2 IAV types by both immunoblot and immunofluorescence microscopy in mouse M1, canine Madin–Darby canine kidney and human A549 cells. mAb epitopes were mapped by overlapping peptides and selective reactivity to the newly described viral NS3 protein. These mAbs detected NS1 in both the cytoplasm and nucleus by immunostaining, and some detected NS1 as early as 5 h post-infection, suggesting their potential diagnostic use for tracking productive IAV replication and characterizing NS1 structure and function. It was also demonstrated that the newly identified NS3 protein is localized in the cytoplasm to high levels.
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Marc, Daniel. "Influenza virus non-structural protein NS1: interferon antagonism and beyond." Journal of General Virology 95, no. 12 (December 1, 2014): 2594–611. http://dx.doi.org/10.1099/vir.0.069542-0.
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Most viruses express one or several proteins that counter the antiviral defences of the host cell. This is the task of non-structural protein NS1 in influenza viruses. Absent in the viral particle, but highly expressed in the infected cell, NS1 dramatically inhibits cellular gene expression and prevents the activation of key players in the IFN system. In addition, NS1 selectively enhances the translation of viral mRNAs and may regulate the synthesis of viral RNAs. Our knowledge of the virus and of NS1 has increased dramatically during the last 15 years. The atomic structure of NS1 has been determined, many cellular partners have been identified and its multiple activities have been studied in depth. This review presents our current knowledge, and attempts to establish relationships between the RNA sequence, the structure of the protein, its ligands, its activities and the pathogenicity of the virus. A better understanding of NS1 could help in elaborating novel antiviral strategies, based on either live vaccines with altered NS1 or on small-compound inhibitors of NS1.
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Rosby, Raphyel, Zhengfang Cui, Emily Rogers, Megan A. deLivron, Victoria L. Robinson, and Patrick J. DiMario. "Knockdown of the Drosophila GTPase Nucleostemin 1 Impairs Large Ribosomal Subunit Biogenesis, Cell Growth, and Midgut Precursor Cell Maintenance." Molecular Biology of the Cell 20, no. 20 (October 15, 2009): 4424–34. http://dx.doi.org/10.1091/mbc.e08-06-0592.
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Mammalian nucleostemin (NS) is a nucleolar guanosine triphosphate-binding protein implicated in cell cycle progression, stem cell proliferation, and ribosome assembly. Drosophila melanogaster contains a four-member nucleostemin family (NS1–4). NS1 is the closest orthologue to human NS; it shares 33% identity and 67% similarity with human NS. We show that NS1 has intrinsic GTPase and ATPase activity and that it is present within nucleoli of most larval and adult cells. Endogenous NS1 and lightly expressed green fluorescent protein (GFP)-NS1 enrich within the nucleolar granular regions as expected, whereas overexpressed GFP-NS1 localized throughout the nucleolus and nucleoplasm, and to several transcriptionally active interbands of polytene chromosomes. Severe overexpression correlated with the appearance of melanotic tumors and larval/pupal lethality. Depletion of 60% of NS1 transcripts also lead to larval and pupal lethality. NS1 protein depletion>95 correlated with the loss of imaginal island (precursor) cells in the larval midgut and to an apparent block in the nucleolar release of large ribosomal subunits in terminally differentiated larval midgut polyploid cells. Ultrastructural examination of larval Malpighian tubule cells depleted for NS1 showed a loss of cytoplasmic ribosomes and a concomitant appearance of cytoplasmic preautophagosomes and lysosomes. We interpret the appearance of these structures as indicators of cell stress response.
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Burgui, Idoia, Tomás Aragón, Juan Ortín, and Amelia Nieto. "PABP1 and eIF4GI associate with influenza virus NS1 protein in viral mRNA translation initiation complexes." Journal of General Virology 84, no. 12 (December 1, 2003): 3263–74. http://dx.doi.org/10.1099/vir.0.19487-0.
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It has previously been shown that influenza virus NS1 protein enhances the translation of viral but not cellular mRNAs. This enhancement occurs by increasing the rate of translation initiation and requires the 5′UTR sequence, common to all viral mRNAs. In agreement with these findings, we show here that viral mRNAs, but not cellular mRNAs, are associated with NS1 during virus infection. We have previously reported that NS1 interacts with the translation initiation factor eIF4GI, next to its poly(A)-binding protein 1 (PABP1)-interacting domain and that NS1 and eIF4GI are associated in influenza virus-infected cells. Here we show that NS1, although capable of binding poly(A), does not compete with PABP1 for association with eIF4GI and, furthermore, that NS1 and PABP1 interact both in vivo and in vitro in an RNA-independent manner. The interaction maps between residues 365 and 535 in PABP1 and between residues 1 and 81 in NS1. These mapping studies, together with those previously reported for NS1–eIF4GI and PABP1–eIF4GI interactions, imply that the binding of all three proteins would be compatible. Collectively, these and previously published data suggest that NS1 interactions with eIF4GI and PABP1, as well as with viral mRNAs, could promote the specific recruitment of 43S complexes to the viral mRNAs.
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Ambrose, Jason H., Shamala Devi Sekaran, and Azliyati Azizan. "Dengue Virus NS1 Protein as a Diagnostic Marker: Commercially Available ELISA and Comparison to qRT-PCR and Serological Diagnostic Assays Currently Used by the State of Florida." Journal of Tropical Medicine 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/8072491.
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Background. The proper management of patients infected with dengue virus requires early detection. Here, real-time molecular assays have proven useful but have limitations, whereas ELISAs that detect antibodies are still favored but results are obtained too late to be of clinical value. The production of DENV NS1 peaks early during infection and its detection can combine the advantages of both diagnostic approaches.Methods.This study compared assays currently used for detecting DENV infection at the Florida Department of Health including anti-DENV IgM and IgG ELISAs as well as qRT-PCR, against a commercially available DENV NS1 ELISA. These comparisons were made among a group of 21 human sera.Results. Nine of 14 (64.3%) DENV qRT-PCR+ samples were also DENV NS1+. Interestingly, the 5 NS1− samples that were qRT-PCR+ were additionally IgM− and IgG+ suggesting a nonprimary infection. Compared to qRT-PCR, the NS1 assay had a sensitivity of 64.3%, specificity 100%, PPV of 100%, and NPV of 58.3%.Conclusions. The NS1 ELISA performed as expected in known DENV qRT-PCR+ samples; however negative NS1 results for qRT-PCR+ and IgG+ sera seemingly reduced the usefulness of the NS1 ELISA for nonprimary cases. We therefore conclude that diagnosis obtained via DENV NS1 ELISA deserves further investigation.
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Stiasny, Karin, Agnes Leitner, Heidemarie Holzmann, and Franz X. Heinz. "Dynamics and Extent of Non-Structural Protein 1-Antibody Responses in Tick-Borne Encephalitis Vaccination Breakthroughs and Unvaccinated Patients." Viruses 13, no. 6 (May 27, 2021): 1007. http://dx.doi.org/10.3390/v13061007.
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Tick-borne encephalitis (TBE) has a substantial impact on human public health in many parts of Europe and Asia. Effective inactivated purified whole-virus vaccines are in widespread use in TBE-endemic countries. Nevertheless, vaccination breakthroughs (VBTs) with manifest clinical disease do occur, and their specific serodiagnosis was shown to be facilitated by the detection of antibodies to a non-structural protein (NS1) that is produced during virus replication. However, recent data have shown that NS1 is also present in the current inactivated vaccines, with the potential of inducing corresponding antibodies and obscuring a proper interpretation of NS1-antibody assays for diagnosing VBTs. In our study, we quantified anti-virion and anti-NS1 antibody responses after vaccination as well as after natural infection in TBE patients, both without and with a history of previous TBE vaccination (VBTs). We did not find significant levels of NS1-specific antibodies in serum samples from 48 vaccinees with a completed vaccination schedule. In contrast, all TBE patients mounted an anti-NS1 antibody response, irrespective of whether they were vaccinated or not. Neither the dynamics nor the extent of NS1-antibody formation differed significantly between the two cohorts, arguing against substantial NS1-specific priming and an anamnestic NS1-antibody response in VBTs.
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Akualing, Jeine Stela, Aryati Aryati, Puspa Wardhani, and Usman Hadi. "IDENTIFICATION OF DENGUE VIRUS SEROTYPES AT THE DR. SOETOMO HOSPITAL SURABAYA IN 2016 AND ITS CORRELATION WITH NS1 ANTIGEN DETECTION." INDONESIAN JOURNAL OF CLINICAL PATHOLOGY AND MEDICAL LABORATORY 23, no. 2 (March 29, 2018): 151. http://dx.doi.org/10.24293/ijcpml.v23i2.1138.
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Serotipe virus dengue yang beredar terus mengalami perubahan dan berbeda di setiap daerah. Pergeseran serotipe maupun genotipedi dalamnya, mempengaruhi terjadinya wabah dengue di berbagai negara. Perbedaan serotipe diduga bernasab dengan deteksi antigen(Ag) non-structural 1 (NS1), namun belum banyak penelitian yang mendukung hal tersebut. Penelitian potong lintang dikerjakan sejakFebruari-Agustus 2016 dan didapatkan 60 subjek infeksi virus dengue (IVD) dan 25 non-IVD. Ribonucleic acid (RNA) virus denguediperiksa di semua subjek menggunakan Simplexa Dengue Real-Time Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR)termasuk identifikasi serotipe virus dengue dan pemeriksaan NS1 menggunakan uji cepat NS1 Panbio. Perbedaan perbandingan variabelkategorikal dianalisis dengan uji Fisher Exact. Kenasaban antara serotipe dengan deteksi Ag NS1 dianalisis dengan Chi-Kuadrat. RNAvirus dengue terdeteksi di 43 dari 60 subjek IVD (71,7%). Serotipe terbanyak adalah DENV-3 (62,8%). Pergeseran dominasi serotipetelah terjadi di Surabaya, sebelumnya dari DENV-2 ke DENV-1 dan sekarang DENV-3, kemungkinan akibat mobilitas pejamu, transporvirus dan faktor geografis. Kepekaan uji cepat NS1 75% dan kekhasan 100%. Persentase deteksi NS1 antar serotipe berbeda bermakna(p=0,002). Deteksi NS1 lebih rendah pada DENV-1 dibandingkan DENV-2 (p=0,007) ataupun DENV-3 (p=0,003). Serotipe virusdengue bernasab dengan deteksi NS1 (p=0,005). Ciri serotipe maupun genotipe virus dengue kemungkinan mempengaruhi sekresiNS1. Telah terjadi pergeseran serotipe virus dengue di pasien IVD di Surabaya sehingga diperlukan surveillance berkesinambunganuntuk memperkirakan terjadinya wabah. Serotipe bernasab dengan deteksi NS1. Salah satu penyebab hasil negatif palsu NS1 adalahperbedaan serotipe.
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Donelan, Nicola R., Bianca Dauber, Xiuyan Wang, Christopher F. Basler, Thorsten Wolff, and Adolfo García-Sastre. "The N- and C-Terminal Domains of the NS1 Protein of Influenza B Virus Can Independently Inhibit IRF-3 and Beta Interferon Promoter Activation." Journal of Virology 78, no. 21 (November 1, 2004): 11574–82. http://dx.doi.org/10.1128/jvi.78.21.11574-11582.2004.
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ABSTRACT The NS1 proteins of influenza A and B viruses (A/NS1 and B/NS1 proteins) have only ∼20% amino acid sequence identity. Nevertheless, these proteins show several functional similarities, such as their ability to bind to the same RNA targets and to inhibit the activation of protein kinase R in vitro. A critical function of the A/NS1 protein is the inhibition of synthesis of alpha/beta interferon (IFN-α/β) during viral infection. Recently, it was also found that the B/NS1 protein inhibits IFN-α/β synthesis in virus-infected cells. We have now found that the expression of the B/NS1 protein complements the growth of an influenza A virus with A/NS1 deleted. Expression of the full-length B/NS1 protein (281 amino acids), as well as either its N-terminal RNA-binding domain (amino acids 1 to 93) or C-terminal domain (amino acids 94 to 281), in the absence of any other influenza B virus proteins resulted in the inhibition of IRF-3 nuclear translocation and IFN-β promoter activation. A mutational analysis of the truncated B/NS1(1-93) protein showed that RNA-binding activity correlated with IFN-β promoter inhibition. In addition, a recombinant influenza B virus with NS1 deleted induces higher levels of IRF-3 activation, as determined by its nuclear translocation, and of IFN-α/β synthesis than wild-type influenza B virus. Our results support the hypothesis that the NS1 protein of influenza B virus plays an important role in antagonizing the IRF-3- and IFN-induced antiviral host responses to virus infection.
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Muraki, Yasushi, Takatoshi Furukawa, Yoshihiko Kohno, Yoko Matsuzaki, Emi Takashita, Kanetsu Sugawara, and Seiji Hongo. "Influenza C Virus NS1 Protein Upregulates the Splicing of Viral mRNAs." Journal of Virology 84, no. 4 (December 9, 2009): 1957–66. http://dx.doi.org/10.1128/jvi.01627-09.
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ABSTRACT Pre-mRNAs of the influenza A virus M and NS genes are poorly spliced in virus-infected cells. By contrast, in influenza C virus-infected cells, the predominant transcript from the M gene is spliced mRNA. The present study was performed to investigate the mechanism by which influenza C virus M gene-specific mRNA (M mRNA) is readily spliced. The ratio of M1 encoded by a spliced M mRNA to CM2 encoded by an unspliced M mRNA in influenza C virus-infected cells was about 10 times larger than that in M gene-transfected cells, suggesting that a viral protein(s) other than M gene translational products facilitates viral mRNA splicing. RNase protection assays showed that the splicing of M mRNA in infected cells was much higher than that in M gene-transfected cells. The unspliced and spliced mRNAs of the influenza C virus NS gene encode two nonstructural (NS) proteins, NS1(C/NS1) and NS2(C/NS2), respectively. The introduction of premature translational termination into the NS gene, which blocked the synthesis of the C/NS1 and C/NS2 proteins, drastically reduced the splicing of NS mRNA, raising the possibility that C/NS1 or C/NS2 enhances viral mRNA splicing. The splicing of influenza C virus M mRNA was increased by coexpression of C/NS1, whereas it was reduced by coexpression of the influenza A virus NS1 protein (A/NS1). The splicing of influenza A virus M mRNA was also increased by coexpression of C/NS1, though it was inhibited by that of A/NS1. These results suggest that influenza C virus NS1, but not A/NS1, can upregulate viral mRNA splicing.
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Moffatt, Stanley, Nobuo Yaegashi, Kohtaro Tada, Nobuyuki Tanaka, and Kazuo Sugamura. "Human Parvovirus B19 Nonstructural (NS1) Protein Induces Apoptosis in Erythroid Lineage Cells." Journal of Virology 72, no. 4 (April 1, 1998): 3018–28. http://dx.doi.org/10.1128/jvi.72.4.3018-3028.1998.
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ABSTRACT Infection of erythroid-lineage cells by human parvovirus B19 is characterized by a gradual cytocidal effect. Accumulating evidence now implicates the nonstructural (NS1) protein of the virus in cytotoxicity, but the mechanism underlying the NS1-induced cell death is not known. Using a stringent regulatory system, we demonstrate that NS1 cytotoxicity is closely related to apoptosis, as evidenced by cell morphology, genomic DNA fragmentation, and cell cycle analysis with the human erythroleukemia cell line K562 and the erythropoietin-dependent megakaryocytic cell line UT-7/Epo. Apoptosis was significantly inhibited by an interleukin-1β (IL-1β)-converting enzyme (ICE)/CED-3 family protease inhibitor, Ac-DEVD-CHO (CPP32; caspase 3), whereas a similar inhibitor of ICE (caspase 1), Ac-YVAD-CHO, had no effect. Furthermore, stable expression of the human Bcl-2 proto-oncogene resulted in near-total protection from cell death in response to NS1 induction. Mutations engineered into the nucleoside triphosphate-binding domain of NS1 significantly rescued cells from NS1-induced apoptosis without having any effect on NS1-induced activation of the IL-6 gene expression which is mediated by NF-κB. Furthermore, using pentoxifylline, an inhibitor of NF-κB activation, we demonstrate that the NF-κB-mediated IL-6 activation by NS1 is uncoupled from the apoptotic pathway. This functional dissection indicates a complexity underlying the biochemical function of human parvovirus NS1 in transcriptional activation and induction of apoptosis. Our findings indicate that NS1 of parvovirus B19 induces cell death by apoptosis in at least erythroid-lineage cells by a pathway that involves caspase 3, whose activation may be a key event during NS1-induced cell death.
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Kumar, Deepak, Rajesh Kumar Verma, Amit Singh, Manoj Kumar, Dharmendra Prasad Singh, Richa Pandey, and Kiran Krishnappa. "Evaluation of NS1, IgM ELISA and RT-PCR in diagnosis of dengue fever." International Journal of Research in Medical Sciences 6, no. 7 (June 25, 2018): 2440. http://dx.doi.org/10.18203/2320-6012.ijrms20182832.
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Background: Dengue fever is a mosquito borne disease caused by flavivirus. Its cases are increasing in India with increasing mortality rate year by year hence, prompt and accurate diagnosis is necessary to prevent morbidity and mortality.Methods: In this study we enrolled 125 clinically suspected cases of dengue. All the collected samples were processed for RT-PCR, NS1 and IgM ELISA. We evaluated NS1 antigen ELISA alone, and combination of NS1 and IgM ELISA against RT-PCR.Results: Among 125 clinically suspected case 67 were positive by RT-PCR and 58 were negative. Sensitivity and Specificity of NS1 ELISA and NS1 with IgM ELISA (in combination) against RT-PCR were 83.58%, 94.82% and 95.55%, 79.31% respectively. (p<0.001).Conclusions: The NS1 ELISA alone was sufficient to detect acute phase of dengue fever, although, combination of NS1 and IgM proved to be most appropriate method for detection of acute as well as late phase of dengue fever.