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Fellenberg J, Dubrau D, Isken O, Tautz N. Packaging defects in pestiviral NS4A can be compensated by mutations in NS2 and NS3. J Virol 2023; 97:e0057223. [PMID: 37695056 PMCID: PMC10537661 DOI: 10.1128/jvi.00572-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 07/18/2023] [Indexed: 09/12/2023] Open
Abstract
The non-structural (NS) proteins of the Flaviviridae members play a dual role in genome replication and virion morphogenesis. For pestiviruses, like bovine viral diarrhea virus, the NS2-3 region and its processing by the NS2 autoprotease is of particular importance. While uncleaved NS2-3 in complex with NS4A is essential for virion assembly, it cannot replace free NS3/4A in the viral replicase. Furthermore, surface interactions between NS3 and the C-terminal cytosolic domain of NS4A were shown to serve as a molecular switch between RNA replication and virion morphogenesis. To further characterize the functionality of NS4A, we performed an alanine-scanning mutagenesis of two NS4A regions, a short highly conserved cytoplasmic linker downstream of the transmembrane domain and the C-terminal domain. NS4A residues critical for polyprotein processing, RNA replication, and/or virion morphogenesis were identified. Three double-alanine mutants, two in the linker region and one close to the C-terminus of NS4A, showed a selective effect on virion assembly. All three packaging defective mutants could be rescued by a selected set of two second-site mutations, located in NS2 and NS3, respectively. This phenotype was additionally confirmed by complementation studies providing the NS2-3/4A packaging molecules containing the rescue mutations in trans. This indicates that the linker region and the cytosolic C-terminal part of NS4A are critical for the formation of protein complexes required for virion morphogenesis. The ability of the identified sets of second-site mutations in NS2-3 to compensate for diverse NS4A defects highlights a surprising functional flexibility for pestiviral NS proteins. IMPORTANCE Positive-strand RNA viruses have a limited coding capacity due to their rather small genome size. To overcome this constraint, viral proteins often exhibit multiple functions that come into play at different stages during the viral replication cycle. The molecular basis for this multifunctionality is often unknown. For the bovine viral diarrhea virus, the non-structural protein (NS) 4A functions as an NS3 protease cofactor, a replicase building block, and a component in virion morphogenesis. Here, we identified the critical amino acids of its C-terminal cytosolic region involved in those processes and show that second-site mutations in NS2 and NS3 can compensate for diverse NS4A defects in virion morphogenesis. The ability to evolve alternative functional solutions by gain-of-function mutations highlights the astounding plasticity of the pestiviral system.
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Affiliation(s)
- Jonas Fellenberg
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
| | - Danilo Dubrau
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
| | - Olaf Isken
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
| | - Norbert Tautz
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
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Walther T, Bruhn B, Isken O, Tautz N. A novel NS3/4A protease dependent cleavage site within pestiviral NS2. J Gen Virol 2021; 102. [PMID: 34676824 DOI: 10.1099/jgv.0.001666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pestiviruses like bovine viral diarrhoea virus (BVDV) and classical swine fever virus (CSFV) belong to the family Flaviviridae. A special feature of the Flaviviridae is the importance of nonstructural (NS) proteins for both genome replication and virion morphogenesis. The NS2-3-4A region and its regulated processing by the NS2 autoprotease and the NS3/4A protease plays a central role in the pestiviral life cycle. We report the identification and characterization of a novel internal cleavage in BVDV NS2, which is mediated by the NS3/4A protease. Further mapping using the NS2 of BVDV-1 strain NCP7 showed that cleavage occurs between L188 and G189. This cleavage site represents a novel sequence motif recognized by the NS3/4A protease and is conserved between the pestivirus species A, B and D. Inhibition of this internal NS2 cleavage by mutating the cleavage site did not cause obvious effects on RNA replication or virion morphogenesis in cultured cell lines. Accordingly, this novel internal NS2 cleavage adds an additional layer to the already complex polyprotein processing of Pestiviruses and might further extend the repertoires of the multifunctional NS2. However, unravelling of the functional relevance of this novel processing event in NS2, therefore, awaits future in vivo studies.
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Affiliation(s)
- Thomas Walther
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany.,Present address: EUROIMMUN AG, Luebeck, Germany
| | - Barbara Bruhn
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany
| | - Olaf Isken
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany
| | - Norbert Tautz
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany
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Membrane Topology of Pestiviral Non-Structural Protein 2 and determination of the minimal autoprotease domain. J Virol 2021; 95:JVI.00154-21. [PMID: 33731461 PMCID: PMC8139697 DOI: 10.1128/jvi.00154-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pestiviruses like bovine viral diarrhea virus (BVDV) belong to the family Flaviviridae A distinctive feature of the Flaviviridae is the importance of non-structural (NS) proteins for RNA genome replication and virus morphogenesis. For pestiviruses, the NS2 protease-mediated release of NS3 is essential for RNA replication, whereas uncleaved NS2-3 is indispensable for producing viral progeny. Accordingly, in the pestiviral life cycle the switch from RNA replication to virion morphogenesis is temporally regulated by the extent of NS2-3 cleavage, which is catalyzed by the NS2 autoprotease. A detailed knowledge of the structural and functional properties of pestiviral NS2 and NS2-3 is mandatory for a better understanding of these processes.In the present study, we experimentally determined the membrane topology of NS2 of BVDV-1 strain NCP7 by the Substituted Cysteine Accessibility Method (SCAM) assay. According to the resulting model, the N terminus of NS2 resides in the ER lumen and is followed by three transmembrane segments (TM) and a cytoplasmic C-terminal protease domain. We used the resulting model for fine mapping of the minimal autoprotease domain. Only one TM segment was found to be essential for maintaining residual autoprotease activity. While the topology of pestiviral NS2 is overall comparable to the one of hepatitis C virus (HCV) NS2, our data also reveal potentially important differences between the two molecules. The improved knowledge about structural and functional properties of this protein will support future functional and structural studies on pestiviral NS2.ImportancePestiviral NS2 is central to the regulation of RNA replication and virion morphogenesis via its autoprotease activity. This activity is temporally regulated by the cellular DNAJC14 as a cofactor: while free NS3 is required for RNA replication as a component of the viral replicase, only uncleaved NS2-3 supports virion morphogenesis. For a better understanding of the underlying molecular interactions, topological and structural data are required. The topology-based determination of the minimal NS2-protease domain in the present study will facilitate future attempts to determine the structure of this unusual protease cofactor complex. In the hepatitis C virus system, NS2 functions as a hub in virion morphogenesis by interacting with structural as well as non-structural proteins. Our knowledge of the membrane topology will significantly support future detailed interaction studies for pestiviral NS2.
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Abdelsalam K, Rajput M, Elmowalid G, Sobraske J, Thakur N, Abdallah H, Ali AAH, Chase CCL. The Effect of Bovine Viral Diarrhea Virus (BVDV) Strains and the Corresponding Infected-Macrophages' Supernatant on Macrophage Inflammatory Function and Lymphocyte Apoptosis. Viruses 2020; 12:E701. [PMID: 32610565 PMCID: PMC7412197 DOI: 10.3390/v12070701] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 01/01/2023] Open
Abstract
Bovine viral diarrhea virus (BVDV) is an important viral disease of cattle that causes immune dysfunction. Macrophages are the key cells for the initiation of the innate immunity and play an important role in viral pathogenesis. In this in vitro study, we studied the effect of the supernatant of BVDV-infected macrophage on immune dysfunction. We infected bovine monocyte-derived macrophages (MDM) with high or low virulence strains of BVDV. The supernatant recovered from BVDV-infected MDM was used to examine the functional activity and surface marker expression of normal macrophages as well as lymphocyte apoptosis. Supernatants from the highly virulent 1373-infected MDM reduced phagocytosis, bactericidal activity and downregulated MHC II and CD14 expression of macrophages. Supernatants from 1373-infected MDM induced apoptosis in MDBK cells, lymphocytes or BL-3 cells. By protein electrophoresis, several protein bands were unique for high-virulence, 1373-infected MDM supernatant. There was no significant difference in the apoptosis-related cytokine mRNA (IL-1beta, IL-6 and TNF-a) of infected MDM. These data suggest that BVDV has an indirect negative effect on macrophage functions that is strain-specific. Further studies are required to determine the identity and mechanism of action of these virulence factors present in the supernatant of the infected macrophages.
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Affiliation(s)
- Karim Abdelsalam
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, USA; (M.R.); (J.S.); (N.T.)
- Faculty of Veterinary Medicine, Zagazig University, Zagazig 44519, Egypt; (G.E.); (H.A.); (A.A.H.A.)
| | - Mrigendra Rajput
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, USA; (M.R.); (J.S.); (N.T.)
| | - Gamal Elmowalid
- Faculty of Veterinary Medicine, Zagazig University, Zagazig 44519, Egypt; (G.E.); (H.A.); (A.A.H.A.)
| | - Jacob Sobraske
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, USA; (M.R.); (J.S.); (N.T.)
| | - Neelu Thakur
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, USA; (M.R.); (J.S.); (N.T.)
| | - Hossam Abdallah
- Faculty of Veterinary Medicine, Zagazig University, Zagazig 44519, Egypt; (G.E.); (H.A.); (A.A.H.A.)
| | - Ahmed A. H. Ali
- Faculty of Veterinary Medicine, Zagazig University, Zagazig 44519, Egypt; (G.E.); (H.A.); (A.A.H.A.)
| | - Christopher C. L. Chase
- Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, USA; (M.R.); (J.S.); (N.T.)
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Comprehensive analysis of circRNAs expression profiles in different periods of MDBK cells infected with bovine viral diarrhea virus. Res Vet Sci 2019; 125:52-60. [PMID: 31146221 DOI: 10.1016/j.rvsc.2019.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 12/24/2018] [Accepted: 05/03/2019] [Indexed: 02/07/2023]
Abstract
CircRNAs play an important regulatory role in the regulation of disease. However, we have a limited understanding of the role of circRNAs in the host's complex protective and pathological mechanisms of BVDV infection. Transcriptome analysis of circRNAs in host cells after BVDV infection may allow us to understand the biological functions of circRNAs in the regulation of BVDV infection. Here, we identified a total of 19,118 circRNAs from the MBDK cells (at 12 h, 24 h, and 48 h post-infection) infected with BVDV by using RNA-seq technology. We confirmed several circRNAs using RT-PCR and DNA sequencing, and qRT-PCR analysis was performed to identify several circRNAs expression and circRNAs resistance to RNase R digestion. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis showed that the host genes of differentially expressed circRNAs were involved in the regulation of cell proliferation, apoptosis, cycle and viral infection related signaling pathways. These results indicate that circRNA in host cells plays a broad regulatory role after BVDV infection and provides a valuable resource for studying circRNA biology in host cells after BVDV infection.
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CRISPR/Cas9-Mediated Knockout of DNAJC14 Verifies This Chaperone as a Pivotal Host Factor for RNA Replication of Pestiviruses. J Virol 2019; 93:JVI.01714-18. [PMID: 30518653 DOI: 10.1128/jvi.01714-18] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 11/20/2018] [Indexed: 12/19/2022] Open
Abstract
Pestiviruses like bovine viral diarrhea virus (BVDV) are a threat to livestock. For pestiviruses, cytopathogenic (cp) and noncytopathogenic (noncp) strains are distinguished in cell culture. The noncp biotype of BVDV is capable of establishing persistent infections, which is a major problem in disease control. The noncp biotype rests on temporal control of viral RNA replication, mediated by regulated cleavage of nonstructural protein 2-3 (NS2-3). This cleavage is catalyzed by the autoprotease in NS2, the activity of which depends on its cellular cofactor, DNAJC14. Since this chaperone is available in small amounts and binds tightly to NS2, NS2-3 translated later in infection is no longer cleaved. As NS3 is an essential constituent of the viral replicase, this shift in polyprotein processing correlates with downregulation of RNA replication. In contrast, cp BVDV strains arising mostly by RNA recombination show highly variable genome structures and display unrestricted NS3 release. The functional importance of DNAJC14 for noncp pestiviruses has been established so far only for BVDV-1. It was therefore enigmatic whether replication of other noncp pestiviruses is also DNAJC14 dependent. By generating bovine and porcine DNAJC14 knockout cells, we could show that (i) replication of 6 distinct noncp pestivirus species (A to D, F, and G) depends on DNAJC14, (ii) the pestiviral replicase NS3-5B can assemble into functional complexes in the absence of DNAJC14, and (iii) all cp pestiviruses replicate their RNA and generate infectious progeny independent of host DNAJC14. Together, these findings confirm DNAJC14 as a pivotal cellular cofactor for the replication and maintenance of the noncp biotype of pestiviruses.IMPORTANCE Only noncp pestivirus strains are capable of establishing life-long persistent infections to generate the virus reservoir in the field. The molecular basis for this biotype is only partially understood and only investigated in depth for BVDV-1 strains. Temporal control of viral RNA replication correlates with the noncp biotype and is mediated by limiting amounts of cellular DNAJC14 that activate the viral NS2 protease to catalyze the release of the essential replicase component NS3. Here, we demonstrate that several species of noncp pestiviruses depend on DNAJC14 for their RNA replication. Moreover, all cp pestiviruses, in sharp contrast to their noncp counterparts, replicate independently of DNAJC14. The generation of a cp BVDV in the persistently infected animal is causative for onset of mucosal disease. Therefore, the observed strict biotype-specific difference in DNAJC14 dependency should be further examined for its role in cell type/tissue tropism and the pathogenesis of this lethal disease.
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Zhou Y, Ren Y, Cong Y, Mu Y, Yin R, Ding Z. Autophagy induced by bovine viral diarrhea virus infection counteracts apoptosis and innate immune activation. Arch Virol 2017; 162:3103-3118. [PMID: 28702931 PMCID: PMC7086613 DOI: 10.1007/s00705-017-3482-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 06/22/2017] [Indexed: 01/09/2023]
Abstract
Bovine viral diarrhea virus (BVDV) is an important pathogen of cattle that plays a complex role in disease. There are two biotypes of BVDV: non-cytopathic (NCP) and cytopathic (CP). One strategy that has been used to treat or prevent virus-associated diseases is the modulation of autophagy, which is used by the innate immune system to defend against viral infection; however, at present, the interplay between autophagy and BVDV remains unclear. Madin-Darby bovine kidney cells stably expressing microtubule-associated protein 1 light chain 3B (LC3B) with green fluorescent protein (GFP) (GFP-LC3-MDBK cells) and autophagy-deficient MDBKs (shBCN1-MDBK cells) were constructed. Then MDBK, GFP-LC3-MDBK and shBCN1-MDBK cells were infected with CP or NCP BVDV strains. The LC3-II turnover rate was estimated by western blot, autophagosomes were visualized by confocal microscopy, and ultrastructural analysis was performed using electron microscopy. Autophagy flux was observed using chloroquine as an inhibitor of the autophagic process. The influence of autophagy on BVDV replication and release was investigated using virus titration, and its effect on cell viability was also studied. The effect of BVDV-induced autophagy on the survival of BVDV-infected host cell, cell apoptosis, and interferon (IFN) signalling was studied by flow cytometric analysis and quantitative RT-(q)PCR using shBCN1-MDBK cells. we found that infection with either CP or NCP BVDV strains induced steady-state autophagy in MDBK cells, as evident by the increased number of double- or single-membrane vesicles, the accumulation of GFP- microtubule-associated protein 1 light chain 3 (LC3) dots, and the conversion of LC3-I (cytosolic) to LC3-II (membrane-bound) forms. The complete autophagic process was verified by monitoring the LC3-II turnover ratio, lysosomal delivery, and proteolysis. In addition, we found that CP and NCP BVDV growth was inhibited in MDBK cells treated with high levels of an autophagy inducer or inhibitor, or in autophagy deficient-MDBK cells. Furthermore, our studies also suggested that CP and NCP BVDV infection in autophagy-knockdown MDBK cells increased apoptotic cell death and enhanced the expression of the mRNAs for IFN-α, Mx1, IFN-β, and OAS-1 as compared with control MDBK cells. Our study provides strong evidence that BVDV infection induces autophagy, which facilitates BVDV replication in MDBK cells and impairs the innate immune response. These findings might help to illustrate the pathogenesis of persistent infection caused by BVDV.
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Affiliation(s)
- Yulong Zhou
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Jilin University, Xi’an Road 5333#, Changchun, 130062 Jilin China
- College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, 163319 China
| | - Yachao Ren
- Harbin Medical University-Daqing, Daqing, 163319 China
| | - Yanlong Cong
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Jilin University, Xi’an Road 5333#, Changchun, 130062 Jilin China
| | - Yu Mu
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Jilin University, Xi’an Road 5333#, Changchun, 130062 Jilin China
| | - Renfu Yin
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Jilin University, Xi’an Road 5333#, Changchun, 130062 Jilin China
| | - Zhuang Ding
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Jilin University, Xi’an Road 5333#, Changchun, 130062 Jilin China
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Characterization of the Determinants of NS2-3-Independent Virion Morphogenesis of Pestiviruses. J Virol 2015; 89:11668-80. [PMID: 26355097 DOI: 10.1128/jvi.01646-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 09/04/2015] [Indexed: 01/09/2023] Open
Abstract
UNLABELLED A peculiarity of the Flaviviridae is the critical function of nonstructural (NS) proteins for virus particle formation. For pestiviruses, like bovine viral diarrhea virus (BVDV), uncleaved NS2-3 represents an essential factor for virion morphogenesis, while NS3 is an essential component of the viral replicase. Accordingly, in natural pestivirus isolates, processing at the NS2-3 cleavage site is not complete, to allow for virion morphogenesis. Virion morphogenesis of the related hepatitis C virus (HCV) shows a major deviation from that of pestiviruses: while RNA replication also requires free NS3, virion formation does not depend on uncleaved NS2-NS3. Recently, we described a BVDV-1 chimera based on strain NCP7 encompassing the NS2-4B*-coding region of strain Osloss (E. Lattwein, O. Klemens, S. Schwindt, P. Becher, and N. Tautz, J Virol 86:427-437, 2012, doi:10.1128/JVI.06133-11). This chimera allowed for the production of infectious virus particles in the absence of uncleaved NS2-3. The Osloss sequence deviates in the NS2-4B* part from NCP7 in 48 amino acids and also has a ubiquitin insertion between NS2 and NS3. The present study demonstrates that in the NCP7 backbone, only two amino acid exchanges in NS2 (E1576V) and NS3 (V1721A) are sufficient and necessary to allow for efficient NS2-3-independent virion morphogenesis. The adaptation of a bicistronic virus encompassing an internal ribosomal entry site element between the NS2 and NS3 coding sequences to efficient virion morphogenesis led to the identification of additional amino acids in E2, NS2, and NS5B that are critically involved in this process. The surprisingly small requirements for approximating the packaging schemes of pestiviruses and HCV with respect to the NS2-3 region is in favor of a common mechanism in an ancestral virus. IMPORTANCE For positive-strand RNA viruses, the processing products of the viral polyprotein serve in RNA replication as well as virion morphogenesis. For bovine viral diarrhea virus, nonstructural protein NS2-3 is of critical importance to switch between these processes. While free NS3 is essential for RNA replication, uncleaved NS2-3, which accumulates over time in the infected cell, is required for virion morphogenesis. In contrast, the virion morphogenesis of the related hepatitis C virus is independent from uncleaved NS2-NS3. Here, we demonstrate that pestiviruses can adapt to virion morphogenesis in the absence of uncleaved NS2-3 by just two amino acid exchanges. While the mechanism behind this gain of function remains elusive, the fact that it can be achieved by such minor changes is in line with the assumption that an ancestral virus already used this mechanism but lost it in the course of adapting to a new host/infection strategy.
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Abstract
Pestiviruses are among the economically most important pathogens of livestock. The biology of these viruses is characterized by unique and interesting features that are both crucial for their success as pathogens and challenging from a scientific point of view. Elucidation of these features at the molecular level has made striking progress during recent years. The analyses revealed that major aspects of pestivirus biology show significant similarity to the biology of human hepatitis C virus (HCV). The detailed molecular analyses conducted for pestiviruses and HCV supported and complemented each other during the last three decades resulting in elucidation of the functions of viral proteins and RNA elements in replication and virus-host interaction. For pestiviruses, the analyses also helped to shed light on the molecular basis of persistent infection, a special strategy these viruses have evolved to be maintained within their host population. The results of these investigations are summarized in this chapter.
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Affiliation(s)
- Norbert Tautz
- Institute for Virology and Cell Biology, University of Lübeck, Lübeck, Germany
| | - Birke Andrea Tews
- Institut für Immunologie, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany.
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Castro EF, Campos RH, Cavallaro LV. Stability of the resistance to the thiosemicarbazone derived from 5,6-dimethoxy-1-indanone, a non-nucleoside polymerase inhibitor of bovine viral diarrhea virus. PLoS One 2014; 9:e100528. [PMID: 24950191 PMCID: PMC4065067 DOI: 10.1371/journal.pone.0100528] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 05/28/2014] [Indexed: 12/03/2022] Open
Abstract
Bovine viral diarrhea virus (BVDV) is the prototype Pestivirus. BVDV infection is distributed worldwide and causes serious problems for the livestock industry. The thiosemicarbazone of 5,6-dimethoxy-1-indanone (TSC) is a non-nucleoside polymerase inhibitor (NNI) of BVDV. All TSC-resistant BVDV variants (BVDV-TSCr T1–5) present an N264D mutation in the NS5B gene (RdRp) whereas the variant BVDV-TSCr T1 also presents an NS5B A392E mutation. In the present study, we carried out twenty passages of BVDV-TSCr T1–5 in MDBK cells in the absence of TSC to evaluate the stability of the resistance. The viral populations obtained (BVDV R1–5) remained resistant to the antiviral compound and conserved the mutations in NS5B associated with this phenotype. Along the passages, BVDV R2, R3 and R5 presented a delay in the production of cytopathic effect that correlated with a decrease in cell apoptosis and intracellular accumulation of viral RNA. The complete genome sequences that encode for NS2 to NS5B, Npro and Erns were analyzed. Additional mutations were detected in the NS5B of BVDV R1, R3 and R4. In both BVDV R2 and R3, most of the mutations found were localized in NS5A, whereas in BVDV R5, the only mutation fixed was NS5A V177A. These results suggest that mutations in NS5A could alter BVDV cytopathogenicity. In conclusion, the stability of the resistance to TSC may be due to the fixation of different compensatory mutations in each BVDV-TSCr. During their replication in a TSC-free medium, some virus populations presented a kind of interaction with the host cell that resembled a persistent infection: decreased cytopathogenicity and viral genome synthesis. This is the first report on the stability of antiviral resistance and on the evolution of NNI-resistant BVDV variants. The results obtained for BVDV-TSCr could also be applied for other NNIs.
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Affiliation(s)
- Eliana F. Castro
- Cátedra de Virología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Rodolfo H. Campos
- Cátedra de Virología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Lucía V. Cavallaro
- Cátedra de Virología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
- * E-mail:
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Morphogenesis of pestiviruses: new insights from ultrastructural studies of strain Giraffe-1. J Virol 2013; 88:2717-24. [PMID: 24352462 DOI: 10.1128/jvi.03237-13] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Knowledge on the morphogenesis of pestiviruses is limited due to low virus production in infected cells. In order to localize virion morphogenesis and replication sites of pestiviruses and to examine intracellular virion transport, a cell culture model was established to facilitate ultrastructural studies. Based on results of virus growth kinetic analysis and quantification of viral RNA, pestivirus strain Giraffe-1 turned out to be a suitable candidate for studies on virion generation and export from culture cells. Using conventional transmission electron microscopy and single-tilt electron tomography, we found virions located predominately in the lumen of the endoplasmic reticulum (ER) in infected cells and were able to depict the budding process of virions at ER membranes. Colocalization of the viral core protein and the envelope glycoprotein E2 with the ER marker protein disulfide isomerase (PDI) was demonstrated by immunogold labeling of cryosections. Moreover, pestivirions could be shown in transport vesicles and the Golgi complex and during exocytosis. Interestingly, viral capsid protein and double-stranded RNA (dsRNA) were detected in multivesicular bodies (MVBs), which implies that the endosomal compartment plays a role in pestiviral replication. Significant cellular membrane alterations such as those described for members of the Flavivirus and Hepacivirus genera were not found. Based on the gained morphological data, we present a consistent model of pestivirus morphogenesis.
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Hilbe M, Girao V, Bachofen C, Schweizer M, Zlinszky K, Ehrensperger F. Apoptosis in Bovine viral diarrhea virus (BVDV)-induced mucosal disease lesions: a histological, immunohistological, and virological investigation. Vet Pathol 2012; 50:46-55. [PMID: 22700847 DOI: 10.1177/0300985812447826] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cattle persistently infected with a noncytopathic Bovine viral diarrhea virus (BVDV) are at risk of developing fatal "mucosal disease" (MD). The authors investigated the role of various apoptosis pathways in the pathogenesis of lesions in animals suffering from MD. Therefore, they compared the expression of caspase-3, caspase-8, caspase-9, and Bcl-2L1 (Bcl-x) in tissues of 6 BVDV-free control animals, 7 persistently infected (PI) animals that showed no signs of MD (non-MD PI animals), and 11 animals with MD and correlated the staining with the localization of mucosal lesions. Caspase-3 and -9 staining were markedly stronger in MD cases and were associated with mucosal lesions, even though non-MD PI animals and negative controls also expressed caspase-9. Conversely, caspase-8 was not elevated in any of the animals analyzed. Interestingly, Bcl-x also colocalized with mucosal lesions in the MD cases. However, Bcl-x was similarly expressed in tissues from all 3 groups, and thus, its role in apoptosis needs to be clarified. This study clearly illustrates ex vivo that the activation of the intrinsic, but not the extrinsic, apoptosis pathway is a key element in the pathogenesis of MD lesions observed in cattle persistently infected with BVDV. However, whether direct induction of apoptosis in infected cells or indirect effects induced by the virus are responsible for the lesions observed remains to be established.
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Affiliation(s)
- M Hilbe
- Institute of Veterinary Pathology, University of Zürich, Zürich, Switzerland.
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13
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Sakoda Y. [Pestivirus]. Uirusu 2011; 61:239-248. [PMID: 22916570 DOI: 10.2222/jsv.61.229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Members of the genus Pestivirus, are causative agents of economically important diseases for livestock and wild animals that occur worldwide, such as bovine viral diarrhea, classical swine fever, and border disease of sheep. Pestivirus have novel insertions of host genes in the viral genome and functions of unique viral proteins, N(pro) and E(rns), related to the pathogenicity although genomic structure is closely related to the other viruses of Flaviviridae family, especially hepatitis C virus. In this review, recent studies on the molecular basis of pathogenicity of pestivirus infections were summarized.
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Affiliation(s)
- Yoshihiro Sakoda
- Laboratory of Microbiology, Graduate School of Veterinary Medicine, Hokkaido University, Kita-18 Nishi-9, Sapporo 060-0818, Japan.
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14
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Pestivirus virion morphogenesis in the absence of uncleaved nonstructural protein 2-3. J Virol 2011; 86:427-37. [PMID: 22031952 DOI: 10.1128/jvi.06133-11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The family Flaviviridae contains three genera of positive-strand RNA viruses, namely, Flavivirus, Hepacivirus (e.g., hepatitis C virus [HCV]), and Pestivirus. Pestiviruses, like bovine viral diarrhea virus (BVDV), bear a striking degree of similarity to HCV concerning polyprotein organization, processing, and function. Along this line, in both systems, release of nonstructural protein 3 (NS3) is essential for viral RNA replication. However, both viruses differ significantly with respect to processing efficiency at the NS2/3 cleavage site and abundance as well as functional relevance of uncleaved NS2-3. In BVDV-infected cells, significant amounts of NS2-3 accumulate at late time points postinfection and play an essential but ill-defined role in the production of infectious virions. In contrast, complete cleavage of the HCV NS2-3 counterpart has been reported, and unprocessed NS2-3 is not required throughout the life cycle of HCV, at least in cell culture. Here we describe the selection and characterization of the first pestiviral genome with the capability to complete productive infection in the absence of uncleaved NS2-3. Despite the insertion of a ubiquitin gene or an internal ribosomal entry site between the NS2 and NS3 coding sequences, the selected chimeric BVDV-1 genomes gave rise to infectious virus progeny. In this context, a mutation in the N-terminal third of NS2 was identified as a critical determinant for efficient production of infectious virions in the absence of uncleaved NS2-3. These findings challenge a previously accepted dogma for pestivirus replication and provide new implications for virion morphogenesis of pestiviruses and HCV.
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15
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Pankraz A, Preis S, Thiel HJ, Gallei A, Becher P. A single point mutation in nonstructural protein NS2 of bovine viral diarrhea virus results in temperature-sensitive attenuation of viral cytopathogenicity. J Virol 2009; 83:12415-23. [PMID: 19776121 PMCID: PMC2786742 DOI: 10.1128/jvi.01487-09] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Accepted: 09/15/2009] [Indexed: 11/20/2022] Open
Abstract
For Bovine viral diarrhea virus (BVDV), the type species of the genus Pestivirus in the family Flaviviridae, cytopathogenic (cp) and noncytopathogenic (ncp) viruses are distinguished according to their effect on cultured cells. It has been established that cytopathogenicity of BVDV correlates with efficient production of viral nonstructural protein NS3 and with enhanced viral RNA synthesis. Here, we describe generation and characterization of a temperature-sensitive (ts) mutant of cp BVDV strain CP7, termed TS2.7. Infection of bovine cells with TS2.7 and the parent CP7 at 33 degrees C resulted in efficient viral replication and a cytopathic effect. In contrast, the ability of TS2.7 to cause cytopathogenicity at 39.5 degrees C was drastically reduced despite production of high titers of infectious virus. Further experiments, including nucleotide sequencing of the TS2.7 genome and reverse genetics, showed that a Y1338H substitution at residue 193 of NS2 resulted in the temperature-dependent attenuation of cytopathogenicity despite high levels of infectious virus production. Interestingly, TS2.7 and the reconstructed mutant CP7-Y1338H produced NS3 in addition to NS2-3 throughout infection. Compared to the parent CP7, NS2-3 processing was slightly decreased at both temperatures. Quantification of viral RNAs that were accumulated at 10 h postinfection demonstrated that attenuation of the cytopathogenicity of the ts mutants at 39.5 degrees C correlated with reduced amounts of viral RNA, while the efficiency of viral RNA synthesis at 33 degrees C was not affected. Taken together, the results of this study show that a mutation in BVDV NS2 attenuates viral RNA replication and suppresses viral cytopathogenicity at high temperature without altering NS3 expression and infectious virus production in a temperature-dependent manner.
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Affiliation(s)
- Alexander Pankraz
- Institute of Virology, Justus-Liebig University, D-35392 Giessen, Germany, Institute of Virology, Department of Infectious Diseases, University of Veterinary Medicine, D-30559 Hannover, Germany
| | - Simone Preis
- Institute of Virology, Justus-Liebig University, D-35392 Giessen, Germany, Institute of Virology, Department of Infectious Diseases, University of Veterinary Medicine, D-30559 Hannover, Germany
| | - Heinz-Jürgen Thiel
- Institute of Virology, Justus-Liebig University, D-35392 Giessen, Germany, Institute of Virology, Department of Infectious Diseases, University of Veterinary Medicine, D-30559 Hannover, Germany
| | - Andreas Gallei
- Institute of Virology, Justus-Liebig University, D-35392 Giessen, Germany, Institute of Virology, Department of Infectious Diseases, University of Veterinary Medicine, D-30559 Hannover, Germany
| | - Paul Becher
- Institute of Virology, Justus-Liebig University, D-35392 Giessen, Germany, Institute of Virology, Department of Infectious Diseases, University of Veterinary Medicine, D-30559 Hannover, Germany
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Gamlen T, Richards KH, Mankouri J, Hudson L, McCauley J, Harris M, Macdonald A. Expression of the NS3 protease of cytopathogenic bovine viral diarrhea virus results in the induction of apoptosis but does not block activation of the beta interferon promoter. J Gen Virol 2009; 91:133-44. [PMID: 19793904 DOI: 10.1099/vir.0.016170-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bovine viral diarrhea virus (BVDV; genus Pestivirus) can exist as two biotypes, cytopathogenic (CP) and non-cytopathogenic (NCP). The CP form differs from NCP by the continual expression of free non-structural protein 3 (NS3). CP BVDV infection of cultured cells induces apoptosis, whereas NCP BVDV infection has been reported to block the induction of beta interferon (IFN-beta). To investigate the viral mechanisms underlying these effects, NS3 or NS2-3 proteins of NCP and CP BVDV biotypes, together with the cognate NS3 co-factor NS4A, were expressed in cells, and their effect on apoptosis and induction of IFN-beta was investigated. Expression of NS3/4A resulted in increased activity of caspase-9 and caspase-3, indicating induction of the intrinsic apoptosis pathway. Mutational analysis revealed that a protease-inactive NS3/4A was unable to induce apoptosis, suggesting that NS3 protease activity is required for initiation of apoptosis during CP BVDV infection. The ability of NS2-3 to modulate activation of the IFN-beta promoter was also investigated. These studies confirmed that, unlike the related hepatitis C virus and GB virus-B, BVDV proteases are unable to inhibit TLR3- and RIG-I-dependent activation of the IFN-beta promoter. These data suggest that BVDV NS3/4A is responsible for regulating the levels of cellular apoptosis and provide new insights regarding the viral elements associated with CP biotype pathogenesis.
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Affiliation(s)
- Toby Gamlen
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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17
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Henningson JN, Topliff CL, Gil LHV, Donis RO, Steffen DJ, Charleston B, Eskridge KM, Kelling CL. Effect of the viral protein Npro on virulence of bovine viral diarrhea virus and induction of interferon type I in calves. Am J Vet Res 2009; 70:1117-23. [DOI: 10.2460/ajvr.70.9.1117] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Abstract
Objective—To characterize the influence of the viral protein Npro on virulence of bovine viral diarrhea virus (BVDV) and on type I interferon responses in calves.
Animals—10 calves, 4 to 6 months of age.
Procedures—BVDV virulence and type I interferon responses of calves (n = 5) infected with a noncytopathic BVDV with a deleted Npro were compared with those of calves (5) infected with a noncytopathic BVDV with a functional Npro. Rectal temperatures, clinical signs, platelet counts, and total and differential WBC counts were evaluted daily. Histologic examinations and immunohistochemical analyses of tissues were conducted to assess lesions and distribution of viral antigens, respectively. Serum type I interferon concentrations were determined.
Results—Calves infected with Npro-deleted BVDV developed leukopenia and lymphopenia, without developing increased rectal temperatures or lymphoid depletion of target lymphoid organs. There was minimal antigen deposition in lymphoid organs. Calves infected with Npro BVDV developed increased rectal temperatures, leukopenia, lymphopenia, and lymphoid depletion with marked BVDV antigen deposition in lymphatic tissues. Interferon type I responses were detected in both groups of calves.
Conclusions and Clinical Relevance—Deletion of Npro resulted in attenuation of BVDV as evidenced by reduced virulence in calves, compared with BVDV with a functional Npro. Deletion of Npro did not affect induction of type I interferon. The Npro-deleted BVDV mutant may represent a safe noncytopathic virus candidate for vaccine development.
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Increase in proto-oncogene mRNA transcript levels in bovine lymphoid cells infected with a cytopathic type 2 bovine viral diarrhea virus. Virus Res 2008; 135:326-31. [PMID: 18440085 DOI: 10.1016/j.virusres.2008.03.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 03/07/2008] [Accepted: 03/13/2008] [Indexed: 11/22/2022]
Abstract
Infection of susceptible animals with bovine viral diarrhea viruses (BVDV) can result in an array of disease symptoms that are dependent in part on the strain of infecting virus and the physiological status of the host. BVDV are lymphotrophic and exist as two biotypes. Cytopathic BVDV kill cells outright while noncytopathic strains can readily establish persistent infections. The molecular mechanisms behind these different affects are unknown. To gain a better understanding of the mechanisms of disease, serial analysis of gene expression (SAGE), a powerful method for global gene expression analysis, was employed to examine gene expression changes in BVDV-infected BL3 cells, a bovine B-cell lymphosarcoma cell line. SAGE libraries were constructed from mRNA derived from BL3 cells that were noninfected or infected with the cytopathic BVDV2 strain 296c. Annotation of the SAGE data showed the expression of many genes that are characteristic of B cells and integral to their function. Comparison of the SAGE databases also revealed a number of genes that were differentially expressed. Of particular interest was the increased numbers of transcripts encoding proto-oncogenes (c-fos, c-jun, junB, junD) in 296c-infected cells, all of which are constituents of the AP-1 transcriptional activation complex. Real-time RT-PCR confirmed these results and indicated that the actual increases were larger than that predicted by SAGE. In contrast, there was no corresponding increase in protein levels, but instead a significant decrease of c-jun and junB protein levels in the infected BL3 cells was observed. Rather than an increase in transcription of these genes, it appeared that these proto-oncogenes transcripts accumulated in the BVDV2-infected cells.
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19
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Yamane D, Kato K, Tohya Y, Akashi H. The relationship between the viral RNA level and upregulation of innate immunity in spleen of cattle persistently infected with bovine viral diarrhea virus. Vet Microbiol 2007; 129:69-79. [PMID: 18155368 DOI: 10.1016/j.vetmic.2007.11.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Revised: 10/17/2007] [Accepted: 11/06/2007] [Indexed: 12/01/2022]
Abstract
Persistent infection in cattle with bovine viral diarrhea virus (BVDV), which is classified in the genus Pestivirus, family Flaviviridae, may result in growth retardation and immunosuppression. In vitro infection with noncytopathogenic (ncp) BVDV has been shown to suppress interferon (IFN) responses, whereas ncpBVDV induces transient strong IFN responses in vivo following acute infection of naïve cattle. In this study, the innate immune response of the spleen, a crucial organ for immune system homeostasis, from PI cattle was analyzed. The transcription of five IFN- and apoptosis-related mRNAs (Mx1, iNOS, OAS-1, PKR, and TNF-alpha), which was upregulated in response to BVDV replication in our previous in vitro studies, and the level of viral RNA were quantified using real-time RT-PCR. Upregulation of Mx1, OAS-1, PKR, and TNF-alpha mRNA expression was detected in the spleens of PI cattle regardless of their age, and induction of apoptosis was also upregulated in the spleens of PI cattle compared with those of nonPI cattle. Although it cannot be excluded that the innate immune responses may be activated in response to any secondary infections in immunosuppressed cattle, the absence of any pathogenic microorganisms in the PI cattle and the statistically significant correlation between innate immune responses and the viral RNA level indicates that there may be a positive relationship between the increased level of viral RNA replication and upregulation of innate immunity in vivo.
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Affiliation(s)
- Daisuke Yamane
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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20
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Bendfeldt S, Ridpath JF, Neill JD. Activation of cell signaling pathways is dependant on the biotype of bovine viral diarrhea viruses type 2. Virus Res 2007; 126:96-105. [PMID: 17376555 DOI: 10.1016/j.virusres.2007.02.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Revised: 01/29/2007] [Accepted: 02/02/2007] [Indexed: 10/23/2022]
Abstract
Bovine viral diarrhea virus (BVDV), a pestivirus of the Flaviviridae family, is an economically important cattle pathogen with a worldwide distribution. Besides the segregation into two distinct species (BVDV1/BVDV2) two different biotypes, a cytopathic (cp) and a noncytopathic (ncp) biotype, are distinguished based on their behavior in epithelial cell cultures. One of the most serious forms of BVDV infection affecting immunocompetent animals of all ages is severe acute BVD (sa BVD) which is caused by highly virulent ncp BVDV2 strains. Previous studies revealed that these highly virulent ncp viruses cause cell death in a lymphoid cell line (BL3) which is not clearly associated with typical apoptotic changes (e.g. PARP cleavage) observed after infection with cp BVDV. To further characterize the underlying molecular mechanisms, we first analyzed the role of the mitochondria and caspases as key mediators of apoptosis. Compared to infection with cp BVDV2, infection with highly virulent ncp BVDV2 resulted in a delayed and less pronounced disruption of the mitochondrial transmembrane potential (DeltaPsi(m)) and a weaker activation of the caspase cascade. In contrast, infection with low virulence ncp BVDV2 showed no significant differences from the uninfected control cells. Since different pro- and anti-apoptotic cellular signaling pathways may become activated upon virus infection, we compared the effect of different BVDV2 strains on cellular signaling pathways in BL3 cells. Stress-mediated p38 MAPK phosphorylation was detected only in cells infected with cp BVDV2. Interestingly, infection with highly virulent ncp BVDV2 was found to influence the phosphoinositide 3-kinase (PI3K)-Akt pathway. This indicates that BL3 cells respond differently to infection with BVDV depending on virulence and biotype.
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Affiliation(s)
- S Bendfeldt
- National Animal Disease Center, ARS, USDA, Ames, IA, USA
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21
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Yamane D, Kato K, Tohya Y, Akashi H. The double-stranded RNA-induced apoptosis pathway is involved in the cytopathogenicity of cytopathogenic Bovine viral diarrhea virus. J Gen Virol 2006; 87:2961-2970. [PMID: 16963755 DOI: 10.1099/vir.0.81820-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bovine viral diarrhea virus (BVDV), which is classified in the genus Pestivirus, family Flaviviridae, can be divided into two biotypes according to its ability to induce a cytopathic effect in tissue culture cells. The mechanisms through which cytopathogenic (cp) BVDV induces cell death and non-cytopathogenic (ncp) BVDV causes persistent infection without producing cell death remain unclear. Here, it was found that the overexpression of four apoptosis-related cellular mRNAs in cells infected with cpBVDV could also be caused by synthetic dsRNA. In fact, it was found that the amount of dsRNA produced by cpBVDV considerably exceeded the amount yielded by ncpBVDV. To evaluate the possible involvement of dsRNA in the induction of apoptosis, this study examined whether RNAi-mediated depletion of two dsRNA-reactive cellular factors, dsRNA-dependent protein kinase and 2′,5′-oligoadenylate synthetase 1, resulted in the prevention of cpBVDV-induced apoptosis. Although the induction of apoptosis was reduced after the suppression of either factor alone, the simultaneous silencing of both factors resulted in an almost complete inhibition of apoptosis without affecting viral titre. These results showed that dsRNA is the main trigger of apoptosis in cpBVDV-infected cells and that the cytopathogenicity of BVDV depends on the yield potential of dsRNA. In contrast, ncpBVDV yielded minimal levels of dsRNA, thereby establishing a persistent infection without inducing apoptosis. This report supports the significance of viral dsRNA as a trigger of innate immune responses.
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Affiliation(s)
- Daisuke Yamane
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Kentaro Kato
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yukinobu Tohya
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hiroomi Akashi
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
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22
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Ridpath JF, Bendfeldt S, Neill JD, Liebler-Tenorio E. Lymphocytopathogenic activity in vitro correlates with high virulence in vivo for BVDV type 2 strains: Criteria for a third biotype of BVDV. Virus Res 2006; 118:62-9. [PMID: 16384618 DOI: 10.1016/j.virusres.2005.11.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 11/05/2005] [Accepted: 11/18/2005] [Indexed: 12/01/2022]
Abstract
Two biotypes of bovine viral diarrhea viruses (BVDV), cytopathic (cp) and noncytopathic (ncp), are recognized based on their activity in cultured epithelial cells. Biotype does not correlate to virulence in acute infections as BVDV strains associated with severe acute BVD outbreaks are all noncytopathic based on their growth characteristics in cultured epithelial cells. Previous studies have shown that acute infections with highly virulent BVDV result in depletion of cells in lymphoid tissues. In this study, flow cytometry demonstrated that infection with a highly virulent BVDV strain was associated with a pronounced reduction in circulating white blood cells (WBC) and increased numbers of apoptotic and necrotic circulating WBC in vivo. Infection with low virulence BVDV did not result in a significant increase in death of circulating WBC. Thus, there appeared to be a correlation between depletion of circulating WBC and virulence. To study the interaction of BVDV strains with lymphoid cells in the laboratory, we developed an in vitro model that used a bovine lymphoid cell line (BL-3 cells). Using this model, it was found that while BVDV strains are segregated into two biotypes based on their activity in cultured epithelial cells, they may be segregated into three biotypes based on their activity in cultured lymphoid cells. These three biotypes are noncytopathogenic (no obvious effects on the viability of either cultured epithelial or lymphoid cells), cytopathogenic (cytopathic effect and cell death in both cultured epithelial and lymphoid cells within 48 h of infection) and lymphocytopathogenic (no effect on cultured epithelial cells, however, cell death in cultured lymphoid cells is observed within 5 days of infection). The proposed lymphocytopathic biotype correlates with high virulence in acute infections in vivo. Cell death caused by the lymphocytopathogenic biotype was not associated with changes typically seen with cytopathic viruses grown in cultured epithelial cells (e.g. changes in processing of the NS2/3 protein observed within 24h post infection, crenation and breakdown of cell integrity within the first 48 h post infection). These data suggest that the cytopathic effect induced in cultured lymphoid cells by a ncp highly virulent BVDV strain may occur by a different mechanism than the cytopathic effect induced by cp BVDV strains.
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Affiliation(s)
- Julia F Ridpath
- Virus and Prion Diseases of Livestock Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, Ames, IA 50010, USA.
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23
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Gil LHVG, Ansari IH, Vassilev V, Liang D, Lai VCH, Zhong W, Hong Z, Dubovi EJ, Donis RO. The amino-terminal domain of bovine viral diarrhea virus Npro protein is necessary for alpha/beta interferon antagonism. J Virol 2006; 80:900-11. [PMID: 16378992 PMCID: PMC1346884 DOI: 10.1128/jvi.80.2.900-911.2006] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The alpha/beta interferon (IFN-alpha/beta) system is the first line of defense against viral infection and a critical link between the innate and adaptive immune responses. IFN-alpha/beta secretion is the hallmark of cellular responses to acute RNA virus infections. As part of their survival strategy, many viruses have evolved mechanisms to counteract the host IFN-alpha/beta response. Bovine viral diarrhea virus (BVDV) (genus Pestivirus) was reported to trigger interferon production in infected cultured cells under certain circumstances or to suppress it under others. Our studies with various cultured fibroblasts and epithelial bovine cells indicated that cytopathic (cp) BVDV induces IFN-alpha/beta very inefficiently. Using a set of engineered cp BVDVs expressing mutant Npro and appropriate controls, we found that the IFN-alpha/beta response to infection was dependent on Npro expression and independent of viral replication efficiency. In order to investigate whether the protease activity of Npro is required for IFN-alpha/beta antagonism, we engineered Npro mutants lacking protease activity by replacement of amino acid E22, H49, or C69. We found that E22 and H49 substitutions abolished the ability of Npro to suppress IFN, whereas C69 had no effect, suggesting that the structural integrity of the N terminus of Npro was more important than its catalytic activity for IFN-alpha/beta suppression. A catalytically active mutant with a change at a conserved Npro region near the N terminus (L8P) in both BVDV biotypes did not antagonize IFN-alpha/beta production, confirming its involvement in this process. Taken together, these results not only provide direct evidence for the role of Npro in blocking IFN-alpha/beta induction, but also implicate the amino-terminal domain of the protein in this function.
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Affiliation(s)
- Laura H V G Gil
- Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln, 68583-0905, USA
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24
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Gil LHVG, van Olphen AL, Mittal SK, Donis RO. Modulation of PKR activity in cells infected by bovine viral diarrhea virus. Virus Res 2005; 116:69-77. [PMID: 16194578 DOI: 10.1016/j.virusres.2005.08.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 08/23/2005] [Accepted: 08/24/2005] [Indexed: 01/12/2023]
Abstract
Bovine viral diarrhea virus is an important animal pathogen. The cytopathic and noncytopathic biotypes of the virus are associated with distinct pathologic entities. A striking difference between the two biotypes is viral RNA accumulation in infected cells. Viral dsRNA is thought to activate protein kinase PKR; an important mediator of innate immunity. In this study, we investigated PKR activation and its consequences in BVDV-infected cells. Infection with cp BVDV was found to induce PKR activation, eIF2alpha phosphorylation, translation inhibition and NF-kappaB activation. In contrast, PKR activity and eIF2alpha phosphorylation were not induced during infection with the ncp BVDV. In addition, cells infected with ncp BVDV showed no PKR phosphorylation in response to infection with the unrelated poliovirus whereas uninfected ncp BVDV cells when infected with poliovirus showed high levels of phosphorylated PKR. Cells infected with ncp BVDV failed to respond to synthetic dsRNA (poly I:C) treatment with NF-kappaB activation. However, the NF-kappaB response to bacterial lipopolysaccarides (LPS) was normal in these cells, suggesting a specific suppression of antiviral response signaling in ncp BVDV infected cells. These results indicate that ncp BVDV has evolved specific mechanisms to prevent activation of PKR and its antiviral effectors, most likely to facilitate the establishment and maintenance of persistent infection.
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Affiliation(s)
- Laura H V G Gil
- Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln, 68583-0905, USA
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25
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Yamane D, Nagai M, Ogawa Y, Tohya Y, Akashi H. Enhancement of apoptosis via an extrinsic factor, TNF-alpha, in cells infected with cytopathic bovine viral diarrhea virus. Microbes Infect 2005; 7:1482-91. [PMID: 16055364 DOI: 10.1016/j.micinf.2005.05.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2005] [Revised: 05/02/2005] [Accepted: 05/09/2005] [Indexed: 11/15/2022]
Abstract
Isolates of bovine viral diarrhea virus (BVDV) are divided into cytopathic (cp) and noncytopathic (ncp) biotypes according to their effect on cultured cells. Calves persistently infected with ncp BVDV are known to develop lethal mucosal disease (MD) after superinfection by cp BVDV. Although the UV-irradiated supernatant of cp BVDV-infected cells has been reported to have no capacity to induce cell death, we found that it could enhance cell death through apoptosis. Up-regulation of tumor necrosis factor alpha (TNF-alpha) and inducible nitric oxide synthase (iNOS) mRNAs was detected specifically in cp BVDV-infected primary cell cultures. Suppression of TNF-alpha via antisense oligonucleotide transfection or incubation with a polyclonal antibody against TNF-alpha resulted in attenuation of apoptosis induced by cp BVDV, suggesting that TNF-alpha participates in apoptosis execution. Although TNF-alpha is one of the iNOS-inducible factors, the iNOS up-regulation was not regulated by TNF-alpha. And iNOS was revealed to serve as anti-apoptotic factor, contrary to our expectation. In addition, the expression level of both TNF-alpha and iNOS mRNAs in the ncp BVDV-infected cells was kept lower than that in the mock-infected cells, suggesting that ncp BVDV reduced or interfered with the factor triggering the expression of both mRNAs. These characteristic mRNA transcriptions would help to explain why BVDV acts differently in cells as well as in vivo, depending on its biotype. To elucidate viral factors inducing TNF-alpha and iNOS may be critical to understand the mechanism of MD development, which closely correlates with cp BVDV-induced apoptosis.
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Affiliation(s)
- D Yamane
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 113-8657, Japan
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26
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Horscroft N, Bellows D, Ansari I, Lai VCH, Dempsey S, Liang D, Donis R, Zhong W, Hong Z. Establishment of a subgenomic replicon for bovine viral diarrhea virus in Huh-7 cells and modulation of interferon-regulated factor 3-mediated antiviral response. J Virol 2005; 79:2788-96. [PMID: 15708997 PMCID: PMC548457 DOI: 10.1128/jvi.79.5.2788-2796.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
We describe the development of a selectable, bi-cistronic subgenomic replicon for bovine viral diarrhea virus (BVDV) in Huh-7 cells, similar to that established for hepatitis C virus (HCV). The selection marker and reporter (Luc-Ubi-Neo) in the BVDV replicon was fused with the amino-terminal protease N(pro), and expression of the nonstructural proteins (NS3 to NS5B) was driven by an encephalomyocarditis virus internal ribosome entry site. This BVDV replicon allows us to compare RNA replication of these two related viruses in a similar cellular background and to identify antiviral molecules specific for HCV RNA replication. The BVDV replicon showed similar sensitivity as the HCV replicon to interferons (alpha, beta, and gamma) and 2'-beta-C-methyl ribonucleoside inhibitors. Known nonnucleoside inhibitor molecules specific for either HCV or BVDV can be easily distinguished by using the parallel replicon systems. The HCV replicon has been shown to block, via the NS3/4A serine protease, Sendai virus-induced activation of interferon regulatory factor 3 (IRF-3), a key antiviral signaling molecule. Similar suppression of IRF-3-mediated responses was also observed with the Huh-7-BVDV replicon but was independent of NS3/4A protease activity. Instead, the amino-terminal cysteine protease N(pro) of BVDV appears to be, at least partly, responsible for suppressing IRF-3 activation induced by Sendai virus infection. This result suggests that different viruses, including those closely related, may have developed unique mechanisms for evading host antiviral responses. The parallel BVDV and HCV replicon systems provide robust counterscreens to distinguish viral specificity of small-molecule inhibitors of viral replication and to study the interactions of the viral replication machinery with the host cell innate immune system.
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Affiliation(s)
- Nigel Horscroft
- Valeant Pharmaceuticals International, 3300 Hyland Ave., Costa Mesa, CA 92626, USA
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27
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Baigent SJ, Goodbourn S, McCauley JW. Differential activation of interferon regulatory factors-3 and -7 by non-cytopathogenic and cytopathogenic bovine viral diarrhoea virus. Vet Immunol Immunopathol 2004; 100:135-44. [PMID: 15207451 DOI: 10.1016/j.vetimm.2004.04.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Non-cytopathogenic bovine viral diarrhoea virus (ncpBVDV) has previously been shown to inhibit the function of interferon regulatory factor-3 in cultured cells [J. Virol. 76 (2002) 8979]. In this study, we show that, like ncpBVDV, when cells were previously exposed to cytopathogenic BVDV (cpBVDV) the appearance of an IRF-3-DNA complex from nuclear extracts that can be induced by heterologous virus infection was not observed. Infection of cells with ncpBVDV or cpBVDV resulted in neither the translocation of IRF-7 from the cytoplasm to the nucleus of infected cells, nor an inhibition of its nuclear translocation in cells super-infected by Semliki Forest Virus. We conclude that cpBVDV and ncpBVDV both share the ability to inhibit the full function of IRF-3 but neither stimulate or block the nuclear uptake of IRF-7.
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Affiliation(s)
- Susan J Baigent
- Compton Laboratory, Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
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28
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Du C, Zhang Q, Li C, Miao D, Gui J. Induction of apoptosis in a carp leucocyte cell line infected with turbot (Scophthalmus maximus L.) rhabdovirus. Virus Res 2004; 101:119-26. [PMID: 15041179 DOI: 10.1016/j.virusres.2003.12.034] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Revised: 12/17/2003] [Accepted: 12/17/2003] [Indexed: 10/26/2022]
Abstract
A rhabdovirus was observed from the diseased turbot (Scophthalmus maximus L.) with lethal syndrome. In this study, a carp leucocyte (CLC) cell line was used to investigate the infection process and cell death mechanism occurring during the virus infection. Strong cytopathogenic effect (CPE) and the morphological changes, such as extreme chromatin condensation, nucleus fragmentation, and apoptotic body formation, were observed under fluorescence microscopy after DAPI staining in the infected CLC cells. Transmission electron microscopy analysis showed cell shrinkage, plasma membrane blebbing, cytoplasm vacuolization, chromatin condensation, nuclear breakdown and formation of discrete apoptotic bodies. The bullet-shaped nucleocapsids were measured and ranged in size from 110 to 150 nm in length and 40 to 60 nm in diameter. And therefore the virus is called Scophthalmus maximus rhabdovirus (SMRV). Agarose gel electrophoresis analysis of the DNA extracted from infected cells showed typical DNA ladder in the course of SMRV infection. Flow cytometry analysis of SMRV infected CLC cells detected apoptotic peak in the virus infected CLC cells. Virus titre analysis and electron microscopic observation revealed that the virus replication fastigium was earlier than that of the apoptosis occurrence. No apoptosis was observed in the CLC infected with UV-inactivated SMRV. All these supported that SMRV infected CLC cells undergo apoptosis and the virus replication is necessary for apoptosis induction of CLC cells.
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Affiliation(s)
- Changsheng Du
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
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29
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Calandria C, Irurzun A, Barco A, Carrasco L. Individual expression of poliovirus 2Apro and 3Cpro induces activation of caspase-3 and PARP cleavage in HeLa cells. Virus Res 2004; 104:39-49. [PMID: 15177891 DOI: 10.1016/j.virusres.2004.02.042] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2003] [Revised: 02/27/2004] [Accepted: 02/27/2004] [Indexed: 11/24/2022]
Abstract
The expression of individual viral genes enables the study of their effects on cellular functions. Our group previously generated stable HeLa cell lines that efficiently express poliovirus proteases 2A (clone 2A7d) and 3C (clone 3C7) under the control of tetracycline [Virology 266 (2000a) 352; J. Virol. 74 (2000b) 2383]. Upon induction of these proteases, the cells undergo drastic morphological alterations and eventually die. The present paper characterizes, in detail, the cellular and molecular events that lead to cell death in these lines. Several signs of apoptosis were observed in both 2A7d- and 3C7-induced cells, such as nuclear fragmentation, DNA breakdown (as determined by TUNEL), and phosphatidylserine translocation. Protease 2A induces the cleavage of poly-ADP-ribose-polymerase (PARP). This is blocked by the caspase-3 inhibitor DEVD in both 2A7d-On and 3C7-On cells suggesting that this enzyme might account for PARP cleavage in both cell lines. The results indicate that both poliovirus proteases induce apoptosis by mechanisms involving caspase activation, although the kinetics of apoptosis differs.
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Affiliation(s)
- Carlos Calandria
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
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30
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Zhang G, Flick-Smith H, McCauley JW. Differences in membrane association and sub-cellular distribution between NS2-3 and NS3 of bovine viral diarrhoea virus. Virus Res 2004; 97:89-102. [PMID: 14602200 DOI: 10.1016/s0168-1702(03)00223-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The sub-cellular location and mechanism of membrane association of NS3 and NS2-3 polypeptides of bovine viral diarrhoea virus (BVDV) have been examined. Both NS3 and NS2-3 proteins were detected in post-nuclear membrane fractions but not in cytosolic fractions of BVDV infected cells; a proportion of NS3, but not NS2-3, could be dissociated from the membranes with 800 mM KCl or at pH 11. Following extraction with 1% Triton X-114, NS3 was predominantly present in the aqueous phase, but NS2-3 was only recovered in the detergent phase. Confocal microscopy showed that in BVDV infected cells, NS3 and/or NS2-3 co-localise with the endoplasmic reticulum (ER) protein, ERP60, but not Golgi or lysosomal proteins. Sub-cellular fractionation analysis demonstrated that NS2-3 was almost exclusively associated with the rough ER membrane but a significant proportion of NS3 was present in the smooth ER membrane fractions in addition to the rough ER membrane. These differences in the distribution of NS2-3 and NS3 on ER membranes in cells infected with cytopathogenic (CP) strains of BVDV were also observed using confocal microscopy and antibodies that are specific to either NS2 or NS3. This distinct distribution of NS3 and NS2-3 on the ER membrane has revealed a further difference between CP and non-cytopathogenic (NCP) strains of BVDV.
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Affiliation(s)
- Gang Zhang
- Compton Laboratory, Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
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31
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Bendfeldt S, Grummer B, Greiser-Wilke I. No caspase activation but overexpression of Bcl-2 in bovine cells infected with noncytopathic bovine virus diarrhoea virus. Vet Microbiol 2004; 96:313-26. [PMID: 14599779 DOI: 10.1016/j.vetmic.2003.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cytopathic bovine viral diarrhoea viruses (cp BVDV) induce apoptosis in permissible cell cultures via the intrinsic pathway, which involves the mitochondria as key organelles. An important event is the irreversible opening of the permeability transition pore (PTP) and the breakdown of the transmembrane potential DeltaPsi(m). The resulting release of cytochrome C from the mitochondria serves as a trigger to form the apoptosome which then leads to caspase activation and cell death. In contrast, noncytopathic (ncp) BVDV do not seem to affect cells in vivo or in vitro, suggesting that they inhibit apoptosis. Interestingly, inhibition of caspases in cells infected with cp BVDV delayed the apoptotic cascade but did not prevent the cytopathic effect (CPE). This suggests that the induction of apoptosis and the processes finally leading to the CPE may proceed separately, implying that the inhibition of apoptosis by ncp BVDV has to start earlier in the cascade. In this study we show that in fact apoptosis inhibition in cells infected with ncp BVDV must occur at the mitochondrial level, before the activation of the caspase cascade occurs. To elucidate the role of mitochondria after infection of cells with ncp BVDV, expression of Bcl-2 and Bax were analysed. It was shown that while Bax expression was not affected, the anti-apoptotic Bcl-2 protein was upregulated, presumably suppressing initiation of cell death and enabling persistent infection in vitro.
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Affiliation(s)
- S Bendfeldt
- Institute of Virology, Hanover School of Veterinary Medicine, Buenteweg 17, 30559, Hannover, Germany
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32
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Glew EJ, Carr BV, Brackenbury LS, Hope JC, Charleston B, Howard CJ. Differential effects of bovine viral diarrhoea virus on monocytes and dendritic cells. J Gen Virol 2003; 84:1771-1780. [PMID: 12810871 DOI: 10.1099/vir.0.18964-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Various pathogens have been shown to infect antigen-presenting cells and affect their capacity to interact with and stimulate T-cell responses. We have used an antigenically identical pair of non-cytopathic (ncp) and cytopathic (cp) bovine viral diarrhoea virus (BVDV) isolates to determine how the two biotypes affect monocyte and dendritic cell (DC) function. We have shown that monocytes and DCs are both susceptible to infection with ncp BVDV and cp BVDV in vitro. In addition, monocytes infected with ncp BVDV were compromised in their ability to stimulate allogeneic and memory CD4(+) T cell responses, but DCs were not affected. This was not due to down-regulation of a number of recognized co-stimulatory molecules including CD80, CD86 and CD40. Striking differences in the response of the two cell types to infection with cytopathic virus were seen. Dendritic cells were not susceptible to the cytopathic effect caused by cp BVDV, whereas monocytes were killed. Analysis of interferon (IFN)-alpha/beta production showed similar levels in monocytes and DCs exposed to cp BVDV, but none was detected in cells exposed to ncp BVDV. We conclude that the prevention of cell death in DCs is not associated with enhanced production of IFN-alpha/beta, as proposed for influenza virus, but is by a distinct mechanism.
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Affiliation(s)
- E J Glew
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN UK
| | - B V Carr
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN UK
| | - L S Brackenbury
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN UK
| | - J C Hope
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN UK
| | - B Charleston
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN UK
| | - C J Howard
- Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN UK
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33
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Risatti GR, Pomp D, Donis RO. Patterns of cellular gene expression in cells infected with cytopathic or non-cytopathic bovine viral diarrhea virus. Anim Biotechnol 2003; 14:31-49. [PMID: 12887178 DOI: 10.1081/abio-120020184] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Bovine viral diarrhea virus (BVDV) infection in cattle is responsible for mucosal disease; an invariably fatal syndrome characterized by the recovery of two BVDV strains: cytopathic (cp) or noncytopathic (ncp). To understand the cellular responses to cp BVDV infection, we carried out differential display-polymerase chain reaction (DD-PCR) analysis of gene expression in infected cells. Altered expression of 14 genes involved in several functions was observed in cells infected with cp BVDV: (1) immune regulation, such as CD46, FKBP-12, and osteopontin (OPN); (2) apoptosis-related cysteine proteases like calpain; (3) signaling plasma membrane proteins such as integrin beta1, and prion protein; and (4) unknown function genes. Northern blot analysis of the expression of these genes in ncp BVDV infected cells revealed that while the expression of some genes was affected as in cp BVDV infected cells, others show a clearly contrary change. We postulate that a cause-effect relationship may exist between the differential gene expression alterations that characterize cp and ncp BVDV infections and the unique diseases associated with each BVDV biotype.
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Affiliation(s)
- Guillermo R Risatti
- Department of Veterinary and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska 68583-0905, USA
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34
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Grummer B, Bendfeldt S, Wagner B, Greiser-Wilke I. Induction of the intrinsic apoptotic pathway in cells infected with cytopathic bovine virus diarrhoea virus. Virus Res 2002; 90:143-53. [PMID: 12457970 DOI: 10.1016/s0168-1702(02)00150-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cytopathic bovine viral diarrhoea virus (cp BVDV) induces apoptosis in bovine cell cultures. This also seems to be a prominent feature in the pathogenesis of mucosal disease. To gain an insight into the molecular pathways of the cell alterations, the involvement of different members of the apoptotic cascade was analyzed. It was shown that inhibition of the mitochondrial permeability transition pore significantly delayed the cytopathic effect without affecting virus replication. Moreover, the membrane potential (deltapsi(m)) was affected, and translocation of cytochrome c to the cytosol, overexpression of apoptotic protease-activating factor 1 and a significant increase of caspase-9 activity were demonstrated, indicating that the apoptosome is formed. We conclude that at least in vitro, infection of cells with cp BVDV leads to the activation of the intrinsic pathway of apoptosis.
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Affiliation(s)
- B Grummer
- Institute of Virology, School of Veterinary Medicine, Buenteweg 17, 30559, Hannover, Germany
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35
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Grummer B, Bendfeldt S, Greiser-Wilke I. Apoptosis inhibitors delay the cytopathic effect of bovine viral diarrhoea virus (BVDV). ACTA ACUST UNITED AC 2002; 49:298-303. [PMID: 12241032 DOI: 10.1046/j.1439-0450.2002.00573.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Based on their action in cell culture, two biotypes of bovine viral diarrhoea virus (BVDV) can be distinguished. The noncytopathic (ncp) BVDV isolated from persistently infected animals cause no visible damage to cultured bovine cells. In contrast, cytopathic (cp) BVDV induces severe damage and apoptosis in cell cultures. Cp BVDV can be isolated from cattle suffering from mucosal disease (MD) and is associated with the severe lesions that primarily affect the gastrointestinal tract. To get an insight into the molecular events during BVDV induced cytopathic effect (CPE), the effect of three chemical reagents (3-aminobenzamide, ascorbic acid and N-acetyl-leucyl-leucyl-methional) with completely different mode of actions in infected cells was analysed. All three substances were able to delay the cytopathic effect induced in permissive bovine cells.
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Affiliation(s)
- B Grummer
- Institute of Virology, School of Veterinary Medicine, Hannover, Germany.
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36
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Jordan R, Wang L, Graczyk TM, Block TM, Romano PR. Replication of a cytopathic strain of bovine viral diarrhea virus activates PERK and induces endoplasmic reticulum stress-mediated apoptosis of MDBK cells. J Virol 2002; 76:9588-99. [PMID: 12208938 PMCID: PMC136515 DOI: 10.1128/jvi.76.19.9588-9599.2002] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Endoplasmic reticulum (ER) stress signaling is an adaptive cellular response to the loss of ER Ca(2+) homeostasis and/or the accumulation of misfolded, unassembled, or aggregated proteins in the ER lumen. ER stress-activated signaling pathways regulate protein synthesis initiation and can also trigger apoptosis through the ER-associated caspase 12. Viruses that utilize the host cell ER as an integral part of their life cycle would be predicted to cause some level of ER stress. Bovine viral diarrhea virus (BVDV) is a positive-stranded RNA virus of the Flaviviridae family. BVDV and related flaviviruses use the host ER as the primary site of envelope glycoprotein biogenesis, genomic replication, and particle assembly. We are using a cytopathic strain of BVDV (cpBVDV) that causes cellular apoptosis as a model system to determine how virus-induced ER stress contributes to pathogenesis. We show that, in a natural infection of MDBK cells, cpBVDV activates the ER transmembrane kinase PERK (PKR-like ER kinase) and causes hyperphosphorylation of the translation initiation factor eIF2 alpha, consistent with the induction of an ER stress response. Additionally, we show that initiation of cellular apoptosis correlates with downregulation of the antiapoptotic Bcl-2 protein, induced expression of caspase 12, and a decrease in intracellular glutathione levels. Defining the molecular stress pathways leading to cpBVDV-induced apoptosis provides the basis to study how other ER-tropic viruses, such as hepatitis C and B viruses, modulate the host cell ER stress response during the course of persistent infection.
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Affiliation(s)
- Robert Jordan
- Department of Biochemistry and Molecular Pharmacology, The Jefferson Center for Biomedical Research, Thomas Jefferson University, Doylestown, Pennsylvania 18901, USA
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37
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Harding MJ, Cao X, Shams H, Johnson AF, Vassilev VB, Gil LH, Wheeler DW, Haines D, Sibert GJ, Nelson LD, Campos M, Donis RO. Role of bovine viral diarrhea virus biotype in the establishment of fetal infections. Am J Vet Res 2002; 63:1455-63. [PMID: 12375578 DOI: 10.2460/ajvr.2002.63.1455] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To examine the role of bovine viral diarrhea virus (BVDV) biotype on the establishment of fetal infection in cattle. ANIMALS 30 mixed-breed pregnant cows. PROCEDURE Pregnant cows were inoculated oronasally with either i-WNADL, originating from an infectious BVDV cDNA clone of the National Animal Disease Laboratory (NADL) isolate, or the parental virus stock, termed NADL-A. RESULTS All cows developed neutralizing antibodies to BVDV, and virus was commonly isolated from peripheral blood mononuclear cells or nasal swab specimens of NADL-A inoculated cows; however, virus was rarely isolated from specimens of i-WNADL inoculated cows. i-WNADL did not cause fetal infection, whereas all fetuses harvested from NADL-A inoculated cows at 6 weeks after inoculation had evidence of infection. Immunoblot analysis of fetal virus isolates revealed the absence of NS3, confirming a noncytopathic (NCP) biotype BVDV in the NADL-A stock. The sequence of the NCP contaminant (termed NADL-1102) and the i-WNADL genome were virtually identical, with the exception of a 270 nucleotide-long insert in the i-WNADL genome. Phylogenetic analyses revealed that NADL-1102 forms a monophyletic group with 6 other NADL genomes. CONCLUSIONS AND CLINICAL RELEVANCE These data suggest that the contaminating NCP virus in the NADL-A stock was the ancestral NADL virus, which originally infected a bovine fetus and recombined to produce a cytopathic (CP) variant. Following oronasal infection of pregnant cows, viremia and transplacental transmission of CP BVDV to the fetus is rare, compared with the high occurrence of maternal viremia and fetal infection observed with NCP BVDV.
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Affiliation(s)
- Martha J Harding
- Pfizer Animal Health Research and Development, Groton, CT 06340, USA
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38
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Baigent SJ, Zhang G, Fray MD, Flick-Smith H, Goodbourn S, McCauley JW. Inhibition of beta interferon transcription by noncytopathogenic bovine viral diarrhea virus is through an interferon regulatory factor 3-dependent mechanism. J Virol 2002; 76:8979-88. [PMID: 12186882 PMCID: PMC136435 DOI: 10.1128/jvi.76.18.8979-8988.2002] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The induction and inhibition of the interferon (IFN) response and apoptosis by bovine viral diarrhea virus (BVDV) has been examined. Here we show that prior infection of cells by noncytopathogenic BVDV (ncp BVDV) fails to block transcriptional responses to alpha/beta IFN. In contrast, ncp BVDV-infected cells fail to produce IFN-alpha/beta or MxA in response to double-stranded RNA (dsRNA) or infection with a heterologous virus (Semliki Forest virus [SFV]). ncp BVDV preinfection is unable to block cp BVDV- or SFV-induced apoptosis. The effects of ncp BVDV infection on the transcription factors controlling the IFN-beta induction pathway have been analyzed. The transcription factor NF-kappa B was not activated following ncp BVDV infection, but ncp BVDV infection was not able to block the activation of NF-kappa B by either SFV or tumor necrosis factor alpha. Furthermore, ncp BVDV infection did not result in the activation of stress kinases (JNK1 and JNK2) or the phosphorylation of transcription factors ATF-2 and c-Jun; again, ncp BVDV infection was not able to block their activation by SFV. Interferon regulatory factor 3 (IRF-3) was shown to be translocated to the nuclei of infected cells in response to ncp BVDV, although DNA-binding of IRF-3 was not seen in nuclear extracts. In contrast, an IRF-3-DNA complex was observed in nuclear extracts from cells infected with SFV, but the appearance of this complex was blocked when cells were previously exposed to ncp BVDV. We conclude that the inhibition of IFN induction by this pestivirus involves a block to IRF-3 function, and we speculate that this may be a key characteristic for the survival of pestiviruses in nature.
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Affiliation(s)
- Susan J Baigent
- Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, United Kingdom
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39
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Kalkeri G, Khalap N, Akhter S, Garry RF, Fermin CD, Dash S. Hepatitis C viral proteins affect cell viability and membrane permeability. Exp Mol Pathol 2001; 71:194-208. [PMID: 11733945 DOI: 10.1006/exmp.2001.2392] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
To determine the effect of hepatitis C virus (HCV) proteins on cell growth, Huh-7 cells were transfected with a full-length HCV cDNA (pMO9.6-T7 Rz) clone and HCV proteins were expressed using a replication-defective adenovirus that encodes the gene for the T7 RNA polymerase. Expression of HCV proteins from this full-length clone resulted in reduction in viability of transfected cells as measured by trypan blue viability assay. For identification and separation of cells expressing hepatitis C virus proteins by fluorescence microscopy and flow cytometry, GFP was cloned in the HCV full-length clone. Cells transfected with the HCV-GFP chimera clone produced high levels of accurately processed structural and nonstructural proteins similar to those of the HCV full-length clone, which could be detected by Western blot analysis. Cells expressing all HCV proteins lost membrane permeability and underwent apoptotic cell death, indicated by the appearance of a sub-G0 peak in cell cycle analysis, DNA fragmentation in a TUNEL assay, and microscopic detection of nuclear condensation. Using double-channel flow analysis we confirmed that high-level expression of HCV proteins affected membrane permeability and cell survival. These results suggest that expression of all structural and nonstructural proteins from HCV cDNA in hepatic cells induces apoptotic cell death, which might be an important event in chronic hepatitis infection in humans.
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Affiliation(s)
- G Kalkeri
- Department of Pathology and Laboratory Medicine, Tulane University Health Science Center, New Orleans, Louisiana 70112, USA
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40
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Qu L, McMullan LK, Rice CM. Isolation and characterization of noncytopathic pestivirus mutants reveals a role for nonstructural protein NS4B in viral cytopathogenicity. J Virol 2001; 75:10651-62. [PMID: 11602707 PMCID: PMC114647 DOI: 10.1128/jvi.75.22.10651-10662.2001] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Isolates of bovine viral diarrhea virus (BVDV), the prototype pestivirus, are divided into cytopathic (cp) and noncytopathic (ncp) biotypes according to their effect on cultured cells. The cp viruses also differ from ncp viruses by the production of viral nonstructural protein NS3. However, the mechanism by which cp viruses induce cytopathic effect in cell culture remains unknown. Here we used a genetic approach to isolate ncp variants that arose from a cp virus at low frequency. A bicistronic BVDV (cp strain NADL) was created that expressed puromycin acetyltransferase as a dominant selectable marker. This bicistronic virus exhibited slightly slower growth kinetics and smaller plaques than NADL but remained cp. A number of independent ncp variants were isolated by puromycin selection. Remarkably, these ncp variants produced NS3 and viral RNA at levels comparable to those of the cp parent. Sequence analyses uncovered no change in NS3, but for all ncp variants a Y2441C substitution at residue 15 of NS4B was found. Introduction of the Y2441C substitution into the NADL or bicistronic cp viruses reconstituted the ncp phenotype. Y2441 is highly conserved among pestiviruses and is located in a region of NS4B predicted to be on the cytosolic side of the endoplasmic reticulum membrane. Other engineered substitutions for Y2441 also affected viral cytopathogenicity and viability, with Y2441V being cp, Y2441A being ncp, and Y2441D rendering the virus unable to replicate. The ncp substitutions for Y2441 resulted in slightly increased levels of NS2-3 relative to NS3. We also showed that NS3, NS4B, and NS5A could be chemically cross-linked in NADL-infected cells, indicating that they are associated as components of a multiprotein complex. Although the mechanism remains to be elucidated, these results demonstrate that mutations in NS4B can attenuate BVDV cytopathogenicity despite NS3 production.
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Affiliation(s)
- L Qu
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA
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41
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Abstract
Infections with the hepatitis C virus (HCV) are a major cause of acute and chronic liver disease. The high prevalence of the virus, the insidious course of the disease and the poor prognosis for long-term persistent infection make this pathogen a serious medical and socioeconomical problem. The identification of the viral genome approximately 10 years ago rapidly led to the delineation of the genomic organization and the structural and biochemical characterization of several virus proteins. However, studies of the viral life cycle as well as the development of antiviral drugs have been difficult because of the lack of a robust and reliable cell culture system. Numerous attempts have been undertaken in the past few years but only recently a highly efficient cell culture model could be developed. This system is based on the self replication of engineered HCV minigenomes (replicons) in a transfected human hepatoma cell line. A summary of the various HCV cell culture models with a focus on the replicon system and its use for drug development is described.
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Affiliation(s)
- R Bartenschlager
- Institute for Virology, Johannes-Gutenberg University Mainz, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany.
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42
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Aoki H, Ishikawa K, Sakoda Y, Sekiguchi H, Kodama M, Suzuki S, Fukusho A. Characterization of classical swine fever virus associated with defective interfering particles containing a cytopathogenic subgenomic RNA isolated from wild boar. J Vet Med Sci 2001; 63:751-8. [PMID: 11503902 DOI: 10.1292/jvms.63.751] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Classical swine fever virus (CSFV) strain WB82, isolated from a wild boar in 1982, induced a distinct cytopathic effect (CPE) in primary swine testicle cell culture and in most of the porcine cell lines. This strain of CSFV was found to be composed of two biotypes. cytopathogenic (cp) CSFV, as a minor population, and noncytopathogenic (noncp) CSFV, as a major population. The noncp CSFV (designated strain WB82/E+) was obtained by biological cloning, and it showed the exaltation of Newcastle disease virus phenomenon. In Northern blot analysis and RT-PCR assay, CSFV RNA with a subgenomic (sg) length was detected in addition to full-length viral RNA only in the cells in which a CPE had been revealed. These RNAs represent the genomes of typical defective interfering (DI) particles because of the strict dependence on a complementing helper virus and interference with replication of the helper virus. The sg RNA, which exhibits the genomes of the DI particles, lacked the nucleotides of the viral genomic region from Npro to NS2 (4764 bases). When extracted sg RNA was transfected to the cells infected with the WB82/E+ strain, a distinct CPE was observed. Interestingly, the CPE was observed in cells infected with other heterologous noncp CSFV ALD and GPE- strains by sg RNA transfection. The results suggested that these noncp CSFVs act as helper viruses for the replication of sg RNA (DI particles). It was also shown that the cytopathogenicity of strain WB82 is caused by apoptosis.
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Affiliation(s)
- H Aoki
- Assay Division I, National Veterinary Assay Laboratory, Kokubunji, Tokyo, Japan
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43
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Summerfield A, Zingle K, Inumaru S, McCullough KC. Induction of apoptosis in bone marrow neutrophil-lineage cells by classical swine fever virus. J Gen Virol 2001; 82:1309-1318. [PMID: 11369874 DOI: 10.1099/0022-1317-82-6-1309] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The pathogenesis of bone marrow atrophy during classical swine fever (CSF) was investigated in vitro by using CSF virus (CSFV) infection of bone marrow haematopoietic cells (BMHC). The monocytic lineage had the highest susceptibility to CSFV infection, whereas the more mature SWC8+ granulocytic cells were not directly susceptible to infection. However, myelomonocytic precursors were targets for CSFV infection and continued to differentiate into SWC8+ granulocytic cells, which remained infected. This explains the occurrence of infected peripheral blood granulocytes during CSF. The infection of BMHC resulted in increased apoptosis and necrosis, mainly within the granulocytic lineage. Caspases 3 and 9 were particularly activated, relating to the mitochondrial pathway of apoptosis. Interestingly, the majority of infected cells were non-apoptotic, the apoptotic cells being primarily non-infected. This indicated an indirect mechanism for induction of apoptosis, but no role could be identified for bone marrow stroma cells such as macrophages or fibroblastoid cells. Furthermore, soluble factors including cytokines and reactive oxygen species were not primarily responsible. In contrast, contact between infected and non-infected BMHC was critical for increasing apoptosis in the latter. Taken together, these results in vitro relate to and help to explain further the apoptosis of BMHC that occurs in vivo during CSF. This experimental system will also be particularly useful for the study of CSFV gene products involved in leukocyte apoptosis.
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Affiliation(s)
- Artur Summerfield
- Institute of Virology and Immunoprophylaxis, Sensemattstrasse 293, CH-3147 Mittelhäusern, Switzerland1
| | - Katy Zingle
- Institute of Virology and Immunoprophylaxis, Sensemattstrasse 293, CH-3147 Mittelhäusern, Switzerland1
| | - Shigeki Inumaru
- Laboratory of Bioengineering, National Institute of Animal Health, Ibaraki 305, Japan2
| | - Kenneth C McCullough
- Institute of Virology and Immunoprophylaxis, Sensemattstrasse 293, CH-3147 Mittelhäusern, Switzerland1
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44
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Kalkeri G, Khalap N, Garry RF, Fermin CD, Dash S. Hepatitis C virus protein expression induces apoptosis in HepG2 cells. Virology 2001; 282:26-37. [PMID: 11259187 DOI: 10.1006/viro.2000.0835] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The mechanisms of hepatocyte death and the events that lead to a high rate of chronic liver disease in patients infected with hepatitis C virus are not known. We established a HCV replication system in HepG2 cell culture and utilized this model to address the effect of HCV proteins on HepG2 cell growth and viability. After transfection of HepG2 cells with full-length RNA, a truncated RNA, or an antisense RNA, cell proliferation and cell viability were analyzed by thymidine uptake and the trypan blue exclusion method, respectively. Full-length RNA transfected HepG2 cells showed a decrease in cell proliferation and viability compared to cells transfected with HCV truncated RNA and antisense RNA control. A subset of cells expressing HCV proteins underwent apoptosis as documented by morphological studies, ultrastructural analysis, cell cycle analysis by flow cytometry, terminal transferase enzyme mediated end labeling of DNA, and DNA laddering. This study suggests that expression of HCV proteins can lead to cell death by apoptosis, which may be an important event in the pathogenesis of chronic hepatitis C virus infection in humans.
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Affiliation(s)
- G Kalkeri
- Department of Pathology and Laboratory Medicine, Department of Microbiology and Immunology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, USA
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45
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Abstract
As an initial approach to studying the molecular replication mechanisms of hepatitis C virus (HCV), a major causative agent of acute and chronic liver disease, we have recently developed selectable self-replicating RNAs. These replicons lacked the region encoding the structural proteins and instead carried the gene encoding the neomycin phosphotransferase. Although the replication levels of these RNAs within selected cells were high, the number of G418-resistant colonies was reproducibly low. In a search for the reason, we performed a detailed analysis of replicating HCV RNAs and identified several adaptive mutations enhancing the efficiency of colony formation by several orders of magnitude. Adaptive mutations were found in nearly every nonstructural protein but not in the 5' or 3' nontranslated regions. The most drastic effect was found with a single-amino-acid substitution in NS5B, increasing the number of colonies approximately 500-fold. This mutation was conserved with RNAs isolated from one cell line, in contrast to other amino acid substitutions enhancing the efficiency of colony formation to a much lesser extent. Interestingly, some combinations of these nonconserved mutations with the highly adaptive one reduced the efficiency of colony formation drastically, suggesting that some adaptive mutations are not compatible.
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46
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Lohmann V, Körner F, Dobierzewska A, Bartenschlager R. Mutations in hepatitis C virus RNAs conferring cell culture adaptation. J Virol 2001; 75:1437-49. [PMID: 11152517 PMCID: PMC114050 DOI: 10.1128/jvi.75.3.1437-1449.2001] [Citation(s) in RCA: 367] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
As an initial approach to studying the molecular replication mechanisms of hepatitis C virus (HCV), a major causative agent of acute and chronic liver disease, we have recently developed selectable self-replicating RNAs. These replicons lacked the region encoding the structural proteins and instead carried the gene encoding the neomycin phosphotransferase. Although the replication levels of these RNAs within selected cells were high, the number of G418-resistant colonies was reproducibly low. In a search for the reason, we performed a detailed analysis of replicating HCV RNAs and identified several adaptive mutations enhancing the efficiency of colony formation by several orders of magnitude. Adaptive mutations were found in nearly every nonstructural protein but not in the 5' or 3' nontranslated regions. The most drastic effect was found with a single-amino-acid substitution in NS5B, increasing the number of colonies approximately 500-fold. This mutation was conserved with RNAs isolated from one cell line, in contrast to other amino acid substitutions enhancing the efficiency of colony formation to a much lesser extent. Interestingly, some combinations of these nonconserved mutations with the highly adaptive one reduced the efficiency of colony formation drastically, suggesting that some adaptive mutations are not compatible.
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Affiliation(s)
- V Lohmann
- Institute for Virology, Johannes Gutenberg University Mainz, 55131 Mainz, Germany
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47
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Vassilev VB, Donis RO. Bovine viral diarrhea virus induced apoptosis correlates with increased intracellular viral RNA accumulation. Virus Res 2000; 69:95-107. [PMID: 11018279 DOI: 10.1016/s0168-1702(00)00176-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Non-cytopathic (NCP) and cytopathic (CP) parent-daughter pairs are often isolated from cattle with bovine viral diarrhea virus (BVDV) induced mucosal disease. Alignment of these pair genomes revealed that genetic changes in CP BVDV involve the NS2-3 coding region and correlate with expression of NS3. However, additional mutations are present elsewhere in the genomes of these natural pairs, precluding unambiguous mapping of this function to the NS2-3 region. To evaluate this phenomenon in identical genetic backgrounds, we have constructed an NCP isogenic pair of the NADL by deletion of the cIns from NS2 region. The levels of viral protein synthesis in infected cells revealed no marked difference between the CP and the isogenic NCP BVDV mutant. In contrast, RNA accumulation in cells infected with CP virus was up to 25 times higher than that in cells infected with NCP BVDV. No significant difference in growth kinetics and viral yields were observed between the CP BVDV and the isogenic NCP pair. Analyses of additional NCP/CP parent-daughter field BVDV isolates revealed a similar pattern of macromolecular synthesis, suggesting the generality of this phenomenon. These results implicate increased levels of RNA accumulation in CP BVDV infected cells, along with the production of NS3 as potential contributors to viral cytopathogenicity.
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Affiliation(s)
- V B Vassilev
- Department of Veterinary and Biomedical Sciences, University of Nebraska, 202 VBS, Lincoln, NE 68583-0905, USA
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48
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Perler L, Schweizer M, Jungi TW, Peterhans E. Bovine viral diarrhoea virus and bovine herpesvirus-1 prime uninfected macrophages for lipopolysaccharide-triggered apoptosis by interferon-dependent and -independent pathways. J Gen Virol 2000; 81:881-7. [PMID: 10725412 DOI: 10.1099/0022-1317-81-4-881] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The flavivirus bovine viral diarrhoea (BVD) virus exists in two biotypes, cytopathic (cp) and non-cytopathic (ncp), defined by their effect on cultured cells. Cp BVD virus-infected cells undergo apoptosis and may promote apoptosis in uninfected cells by an indirect mechanism. Macrophages (Mφ) infected with cp, but not ncp, BVD virus release a factor(s) in the supernatant capable of priming uninfected Mφ for activation-induced apoptosis in response to lipopolysaccharide. A possible role of interferon (IFN) type I was suggested previously by the observation that this cytokine primed for activation-induced apoptosis and was present in supernatants of Mφ infected with cp, but not ncp, BVD virus. Here, supernatants of both Mφ infected with a wider range of cp BVD virus and Mφ infected with bovine herpesvirus-1 are shown to contain such priming activity. Two lines of evidence indicate that factors in addition to IFN type I prime uninfected Mφ for apoptosis. First, supernatants of Mφ infected with cp BVD virus contained much less IFN than is required for priming for apoptosis. Second, whereas antiviral activity was neutralized by a vaccinia virus-encoded IFN type I receptor, B18R, the capacity of the supernatant to prime for apoptosis was unaffected by this treatment. The apparent molecular mass of the factor(s) priming for apoptosis was between 30 and 100 kDa. Priming of uninfected cells for activation-induced apoptosis may add a new facet to virus pathogenesis and may contribute to the formation of lesions not related directly to virus replication.
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Affiliation(s)
- L Perler
- Institute of Veterinary Virology, University of Berne, Laenggass-Str. 122, CH-3012 Berne, Switzerland
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49
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Tautz N, Harada T, Kaiser A, Rinck G, Behrens S, Thiel HJ. Establishment and characterization of cytopathogenic and noncytopathogenic pestivirus replicons. J Virol 1999; 73:9422-32. [PMID: 10516051 PMCID: PMC112977 DOI: 10.1128/jvi.73.11.9422-9432.1999] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Defective interfering particles (DIs) of bovine viral diarrhea virus (BVDV) have been identified and shown to be cytopathogenic (cp) in the presence of noncytopathogenic (noncp) helper virus. Moreover, a subgenomic (sg) RNA corresponding in its genome structure to one of those BVDV DIs (DI9) was replication competent in the absence of helper virus. We report here that an sg BVDV replicon which encodes from the viral proteins only the first three amino acids of the autoprotease N(pro) in addition to nonstructural (NS) proteins NS3 to NS5B replicates autonomously and also induces lysis of its host cells. This demonstrates that the presence of a helper virus is not required for the lysis of the host cell. On the basis of two infectious BVDV cDNA clones, namely, BVDV CP7 (cp) and CP7ins- (noncp), bicistronic replicons expressing proteins NS2-3 to NS5B were established. These replicons express, in addition to the viral proteins, the reporter gene encoding beta-glucuronidase; the release of this enzyme from transfected culture cells was used to monitor cell lysis. Applying these tools, we were able to show that the replicon derived from CP7ins- does not induce cell lysis. Accordingly, neither N(pro) nor any of the structural proteins are necessary to maintain the noncp phenotype. Furthermore, these sg RNAs represent the first pair of cp and noncp replicons which mimic complete BVDV CP7 and CP7ins- with respect to cytopathogenicity. These replicons will facilitate future studies aimed at the determination of the molecular basis for the cytopathogenicity of BVDV.
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MESH Headings
- Animals
- Cattle
- Cell Line
- Cytopathogenic Effect, Viral
- DNA, Complementary/genetics
- Diarrhea Viruses, Bovine Viral/genetics
- Diarrhea Viruses, Bovine Viral/pathogenicity
- Diarrhea Viruses, Bovine Viral/physiology
- Genome, Viral
- Glucuronidase/genetics
- Glucuronidase/metabolism
- Peptide Hydrolases
- Polymerase Chain Reaction
- RNA Helicases
- RNA, Viral/biosynthesis
- RNA, Viral/genetics
- Replicon
- Sequence Analysis, DNA
- Transcription, Genetic
- Transfection
- Viral Nonstructural Proteins/genetics
- Viral Nonstructural Proteins/metabolism
- Virus Replication
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Affiliation(s)
- N Tautz
- Institut für Virologie (FB Veterinärmedizin), Justus-Liebig-Universität Giessen, D-35392 Giessen, Germany.
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50
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Moser C, Stettler P, Tratschin JD, Hofmann MA. Cytopathogenic and noncytopathogenic RNA replicons of classical swine fever virus. J Virol 1999; 73:7787-94. [PMID: 10438869 PMCID: PMC104306 DOI: 10.1128/jvi.73.9.7787-7794.1999] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
To determine the minimal requirements for autonomous RNA replication of classical swine fever virus (CSFV), genomes having in-frame deletions within the genes for structural and flanking nonstructural proteins were constructed, based on an infectious cDNA clone of CSFV Alfort/187. RNA was transcribed in vitro from the respective plasmids and transfected into SK-6 swine kidney cells. The replication competence of the RNA was determined by immunostaining transfected cells for CSFV NS3 protein and by analysis of cell extracts for viral RNA, as well as protein synthesis at different times after transfection. The genes encoding N(pro), C, E(rns), E1, E2, p7, and NS2 proved to be dispensable for RNA replication, but the efficiency of replication varied strongly between individual constructs. RNA replicons containing the complete NS2-NS3 gene persisted in transfected cells and continued to replicate without causing any obvious morphological or functional damage to the cells, whereas genomes lacking the NS2 gene replicated more efficiently and induced a cytopathic effect. These findings suggest that NS2, although it is not essential for pestivirus RNA replication, has a regulatory function therein. Both cytopathogenic and noncytopathogenic replicons were packaged into virus particles provided in trans by a cotransfected full-length helper virus genome.
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Affiliation(s)
- C Moser
- Institute of Virology and Immunoprophylaxis, CH-3147 Mittelhäusern, Switzerland
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