Npro of classical swine fever virus contributes to pathogenicity in pigs by preventing type I interferon induction at local replication sites

Functional disruption of dendritic cells (DCs) is an important strategy for viral pathogens to evade host defences. Monocytotropic viruses such as classical swine fever virus (CSFV) could employ such a mechanism, since the virus can suppress immune responses and induce apoptosis without infecting lymphocytes. Here, CSFV was shown to infect and efficiently replicate in monocyte- and in bone marrow-derived DCs. Interestingly, the infected DCs displayed neither modulated MHC nor CD80/86 expression. Stimulation of DCs with IFN-α/TNF-α or polyinosinic–polycytidylic acid (pIC) induced phenotypic maturation with increased MHC and CD80/86 expression, both with mock-treated and infected DCs. In addition, the T cell stimulatory capacity of CSFV-infected DCs was maintained both in a polyclonal T cell stimulation and in specific antigen-presentation assays, requiring antigen uptake and processing. Interestingly, similar to macrophages, CSFV did not induce IFN-α responses in these DCs and even suppressed pIC-induced IFN-α induction. Other cytokines including interleukin (IL)-6, IL-10, IL-12 and TNF-α were not modulated. Taken together, these results demonstrated that CSFV can replicate in DCs and control IFN type I responses, without interfering with the immune reactivity. These results are interesting considering that DC infection with RNA viruses usually results in DC activation.

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The N-terminal domain of Npro of classical swine fever virus determines its stability and regulates type I IFN production

Journal of General Virology ◽

10.1099/vir.0.000132 ◽

2015 ◽

Vol 96 (7) ◽

pp. 1746-1756 ◽

Cited By ~ 5

Author(s):

Junki Mine ◽

Tomokazu Tamura ◽

Wasana Pinyochon ◽

Masatoshi Okamatsu ◽

Yoshihiro Sakoda ◽

...

Keyword(s):

Classical Swine Fever Virus ◽

Classical Swine Fever ◽

Fever Virus ◽

Type I ◽

Type I Ifn ◽

Terminal Domain

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TNF-Mediated Inhibition of Classical Swine Fever Virus Replication Is IRF1-, NF-κB- and JAK/STAT Signaling-Dependent

Viruses ◽

10.3390/v13102017 ◽

2021 ◽

Vol 13 (10) ◽

pp. 2017

Author(s):

Matthias Liniger ◽

Markus Gerber ◽

Sandra Renzullo ◽

Obdulio García-Nicolás ◽

Nicolas Ruggli

Keyword(s):

Signaling Pathways ◽

Classical Swine Fever Virus ◽

Proinflammatory Cytokine ◽

Classical Swine Fever ◽

Antiviral Effect ◽

Fever Virus ◽

Type I ◽

Type I Ifn ◽

Interferon Regulatory Factor 1 ◽

Necrosis Factor

The sera from pigs infected with virulent classical swine fever virus (CSFV) contain substantial amounts of tumor necrosis factor (TNF), a prototype proinflammatory cytokine with pleiotropic activities. TNF limits the replication of CSFV in cell culture. In order to investigate the signaling involved in the antiviral activity of TNF, we employed small-molecule inhibitors to interfere specifically with JAK/STAT and NF-κB signaling pathways in near-to-primary endothelial PEDSV.15 cells. In addition, we knocked out selected factors of the interferon (IFN) induction and signaling pathways using CRISPR/Cas9. We found that the anti-CSFV effect of TNF was sensitive to JAK/STAT inhibitors, suggesting that TNF induces IFN signaling. Accordingly, we observed that the antiviral effect of TNF was dependent on intact type I IFN signaling as PEDSV.15 cells with the disrupted type I IFN receptor lost their capacity to limit the replication of CSFV after TNF treatment. Consequently, we examined whether TNF activates the type I IFN induction pathway. With genetically modified PEDSV.15 cells deficient in functional interferon regulatory factor 1 or 3 (IRF1 or IRF3), we observed that the anti-CSFV activity exhibited by TNF was dependent on IRF1, whereas IRF3 was dispensable. This was distinct from the lipopolysaccharide (LPS)-driven antiviral effect that relied on both IRF1 and IRF3. In agreement with the requirement of IRF1 to induce TNF- and LPS-mediated antiviral effects, intact IRF1 was also essential for TNF- and LPS-mediated induction of IFN-β mRNA, while the activation of NF-κB was not dependent on IRF1. Nevertheless, NF-κB activation was essential for the TNF-mediated antiviral effect. Finally, we observed that CSFV failed to counteract the TNF-mediated induction of the IFN-β mRNA in PEDSV.15 cells, suggesting that CSFV does not interfere with IRF1-dependent signaling. In summary, we report that the proinflammatory cytokine TNF limits the replication of CSFV in PEDSV.15 cells by specific induction of an IRF1-dependent antiviral type I IFN response.

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Guanylate-Binding Protein 1, an Interferon-Induced GTPase, Exerts an Antiviral Activity against Classical Swine Fever Virus Depending on Its GTPase Activity

Journal of Virology ◽

10.1128/jvi.02718-15 ◽

2016 ◽

Vol 90 (9) ◽

pp. 4412-4426 ◽

Cited By ~ 30

Author(s):

Lian-Feng Li ◽

Jiahui Yu ◽

Yongfeng Li ◽

Jinghan Wang ◽

Su Li ◽

...

Keyword(s):

Classical Swine Fever Virus ◽

Binding Protein ◽

Classical Swine Fever ◽

Antiviral Effect ◽

Viral Disease ◽

Fever Virus ◽

Type I ◽

Gtpase Activity ◽

Interferon Stimulated Genes ◽

Guanylate Binding Protein

ABSTRACTMany viruses trigger the type I interferon (IFN) pathway upon infection, resulting in the transcription of hundreds of interferon-stimulated genes (ISGs), which define the antiviral state of the host. Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), a highly contagious viral disease endangering the pig industry in many countries. However, anti-CSFV ISGs are poorly documented. Here we screened 20 ISGs that are commonly induced by type I IFNs against CSFV in lentivirus-delivered cell lines, resulting in the identification of guanylate-binding protein 1 (GBP1) as a potent anti-CSFV ISG. We observed that overexpression of GBP1, an IFN-induced GTPase, remarkably suppressed CSFV replication, whereas knockdown of endogenous GBP1 expression by small interfering RNAs significantly promoted CSFV growth. Furthermore, we demonstrated that GBP1 acted mainly on the early phase of CSFV replication and inhibited the translation efficiency of the internal ribosome entry site of CSFV. In addition, we found that GBP1 was upregulated at the transcriptional level in CSFV-infected PK-15 cells and in various organs of CSFV-infected pigs. Coimmunoprecipitation and glutathioneS-transferase (GST) pulldown assays revealed that GBP1 interacted with the NS5A protein of CSFV, and this interaction was mapped in the N-terminal globular GTPase domain of GBP1. Interestingly, the K51 of GBP1, which is crucial for its GTPase activity, was essential for the inhibition of CSFV replication. We showed further that the NS5A-GBP1 interaction inhibited GTPase activity, which was critical for its antiviral effect. Taking our findings together, GBP1 is an anti-CSFV ISG whose action depends on its GTPase activity.IMPORTANCEClassical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), an economically important viral disease affecting the pig industry in many countries. To date, only a few host restriction factors against CSFV, including interferon-stimulated genes (ISGs), have been characterized. Using a minilibrary of porcine ISGs, we identify porcine guanylate-binding protein 1 (GBP1) as a potent antiviral ISG against CSFV. We further show that the anti-CSFV action of GBP1 depends on its GTPase activity. The K51 of GBP1, critical for its GTPase activity, is essential for the antiviral action of GBP1 against CSFV replication, and the binding of the NS5A protein to GBP1 antagonizes the GTPase activity and thus the antiviral effect. This study will facilitate the development of anti-CSFV therapeutic agents by targeting host factors and may provide a new strategy for the control of CSF.

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Isolation and Characterization of Porcine Astrovirus 5 from a Classical Swine Fever Virus-Infected Specimen

Journal of Virology ◽

10.1128/jvi.01513-20 ◽

2020 ◽

Vol 95 (2) ◽

pp. e01513-20

Author(s):

Shijiang Mi ◽

Shibang Guo ◽

Chaonan Xing ◽

Chaoting Xiao ◽

Biao He ◽

...

Keyword(s):

Classical Swine Fever Virus ◽

Tissue Sample ◽

Classical Swine Fever ◽

Fever Virus ◽

Infected Tissue ◽

Biological Study ◽

Type I ◽

Isolation And Characterization ◽

A Genome ◽

Porcine Astrovirus

ABSTRACTMany new astroviruses have been identified in humans and other animals in recent years, but only a few have been successfully isolated for extensive biological study. Here, we report an unusual isolation of a porcine astrovirus 5 (PAstV5) strain from a clinical classical swine fever virus (CSFV)-infected tissue sample. Incubation of porcine PK-15 cells with an extract of the CSFV-positive tissue resulted in unexpected cytopathic effects (CPEs), and high-throughput viromic sequencing identified PAstV5 and porcine circovirus type 2 (PCV2) as well as CSFV in the culture. After clearance of CSFV and PCV2, a pure PAstV5 strain, named PAstV5-AH29-2014, was obtained. Analysis revealed virus of typical astroviral morphology with a genome of 6,448 nucleotides, sharing 84.3 to 88.9% nucleotide identity with previously published PAstV5 strains. A mechanistic study showed that CSFV coinfection was likely an important factor for successful isolation by significantly enhancing PAstV5 replication in PK-15 cells via suppression of a type I interferon response. Altogether, PAstV5-AH29-2014, as the first isolated PAstV5 strain, will provide critical material for the investigation of the biological and pathogenic properties of this virus as well as for future development of relevant biological and diagnostic reagents.IMPORTANCE Porcine astroviruses are mainly associated with gastroenteritis and neurological diseases in pigs, and five genotypes have been identified (PAstV1-5). However, the clinical manifestations of genotypes other than PAstV1 have not yet been determined because of the failure of in vitro virus isolation. Here, we report a surprising isolation of a PAstV5 strain from a clinical classical swine fever virus (CSFV)-infected tissue sample, which can stably passage in PK-15 cells, and coinfection with CSFV significantly enhanced the replication of PAstV5, possibly through suppression of beta interferon production. Thus, the first isolated PAstV5 strain will be useful for investigating the biological and pathogenic properties of this virus, and the findings obtained in this study provide new insights into defining the interaction mechanism between CSFV and PAstV5.

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Classical swine fever virus Ernsglycoprotein antagonizes induction of interferon-β by double-stranded RNA

Canadian Journal of Microbiology ◽

10.1139/w09-013 ◽

2009 ◽

Vol 55 (6) ◽

pp. 698-704 ◽

Cited By ~ 11

Author(s):

Xuelian Luo ◽

Dawei Ling ◽

Ting Li ◽

Chao Wan ◽

Chuyu Zhang ◽

...

Keyword(s):

Classical Swine Fever Virus ◽

Classical Swine Fever ◽

Inhibitory Effect ◽

Fever Virus ◽

Transcriptional Level ◽

Type I ◽

Antiviral Responses ◽

Exogenous Stimulus ◽

Dose Dependent

Classical swine fever virus (CSFV) is capable of counteracting innate cellular antiviral responses by inhibiting type I interferon (IFN)-α/β induction. A function associated with CSFV Npro, with respect to the inhibition of IFN-β production, has been clearly elucidated. In this study, we explored the role of CSFV Ernsin IFN-β induction by exogenous double-stranded (ds) RNA. Synthetic dsRNA (poly (IC)) was used as an exogenous stimulus to trigger IFN-β induction. CSFV Ernsinhibited IFN-β promoter-driven luciferase activity induced by poly (IC) in different cell lines, and the inhibitory effect was dose-dependent. Moreover, Ernsreduced IFN-β mRNA synthesis and blocked IFN-α/β production induced by poly (IC), suggesting that this inhibition occurs at the transcriptional level. Furthermore, Ernscounteracted poly (IC)-mediated IFN-β induction independent of its ribonuclease activity. In conclusion, CSFV Ernsantagonizes extracellular dsRNA-mediated IFN-β expression. These findings contribute to our understanding of the pathogenesis of CSFV.

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