scholarly journals HBV DNA is a substrate for the cGAS/STING pathway but is not sensed in infected hepatocytes

2019 ◽  
Author(s):  
Lise Lauterbach-Rivière ◽  
Maïwenn Bergez ◽  
Saskia Mönch ◽  
Bingqian Qu ◽  
Maximilian Riess ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Nuclear Translocation ◽  
Innate Immune ◽  
Hbv Infection ◽  
Current View ◽  
Dna Sensing ◽  
Innate Response ◽  
Viral Pathogen ◽  
Active Inhibition

AbstractHBV chronic infection is a critical risk factor for hepatocellular carcinoma. Although debated, the absence of innate immune response to HBV infection in hepatocytes is becoming the current view. However the underlying reasons are poorly understood. This study aims to define potential viral pathogen-associated molecular patterns (PAMPs) and the pattern recognition receptors (PRRs), and to elucidate whether HBV counteracts the innate pathways.The innate immune response to HBV infection was monitored by interferon-stimulated gene 54 (ISG54) mRNA, a direct downstream transcriptional target of Interferon Regulatory Factor 3 (IRF3), or IRF3 phosphorylation. The immunostimulatory potential of naked HBV DNAs or RNAs and the respective PRRs were determined upon viral nucleic acid transfection in immunocompetent cells including knockout cells lacking key molecules of innate pathways. The expression and functionality of DNA and RNA sensing pathways in primary human hepatocytes (PHH) were assessed. The inhibition of the DNA-sensing pathway by HBV was tested using IRF3 nuclear translocation assay.Our study revealed that HBV infection does not induce an innate response in infected hepatocytes, even in absence of HBV X protein. HBV relaxed-circular DNA (rcDNA) and DNA replication intermediates, but not HBV RNAs, are immunostimulatory and sensed by Cyclic Guanosine Monophosphate-Adenosine Monophosphate Synthase (cGAS) and Stimulator of Interferon Genes (STING). Although PHH express DNA sensors to reduced levels compared to myeloid cells, they can respond to naked HBV rcDNA. However, we show that the absence of innate response to HBV infection in hepatocytes is not due to an active inhibition of the DNA sensing pathway by the virus.HBV passively evades the innate immune response in infected hepatocytes by (i) producing non-immunostimulatory RNAs, (ii) avoiding sensing of its DNAs by cGAS/STING without active inhibition of the pathway, possibly through shielding of the viral DNAs by the capsid.Author summaryInnate immune responses are the first line of defense against viral infections. They lead to the production of antiviral factors after recognition of specific viral features by the infected cells. Here we show that HBV, a major cause of liver cirrhosis and cancer, avoids recognition by infected hepatocytes through different means. First, HBV RNAs, contrarily to other viral RNAs, are not immunostimulatory. Second, we show that naked HBV DNAs are recognized by cGAS/STING and induce an innate immune response. Furthermore, we demonstrate that this pathway is active in hepatocytes and is not inhibited by the virus. Instead, we propose that HBV DNAs are not accessible to cGAS/STING in the context of an infection. This might be due to shielding of the viral DNA by the viral capsid.

scholarly journals Human PSC-Derived Hepatocytes Express Low Levels of Viral Pathogen Recognition Receptors, but Are Capable of Mounting an Effective Innate Immune Response

2020 ◽  
Vol 21 (11) ◽  
pp. 3831
Author(s):  
Lena Fischer ◽  
Baltasar Lucendo-Villarin ◽  
David C. Hay ◽  
Cliona O’Farrelly
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Receptor Expression ◽  
Cytochrome P450 3A ◽  
Metabolic Switch ◽  
Viral Pathogen ◽  
Pathogen Recognition Receptors ◽  
Viral Responses

Hepatocytes are key players in the innate immune response to liver pathogens but are challenging to study because of inaccessibility and a short half-life. Recent advances in in vitro differentiation of hepatocyte-like cells (HLCs) facilitated studies of hepatocyte–pathogen interactions. Here, we aimed to define the anti-viral innate immune potential of human HLCs with a focus on pattern recognition receptor (PRR)-expression and the presence of a metabolic switch. We analysed cytoplasmic PRR and endosomal toll-like receptor (TLR)-expression, as well as activity and adaptation of HLCs to an inflammatory environment. We found that transcript levels of retinoic acid inducible gene I (RIG-I), melanoma differentiation antigen 5 (MDA5), and TLR3 became downregulated during differentiation, indicating the acquisition of a more tolerogenic phenotype, as expected in healthy hepatocytes. HLCs responded to activation of RIG-I by producing interferons (IFNs) and IFN-stimulated genes. Despite low-level levels of TLR3, receptor expression was upregulated in an inflammatory environment. TLR3 signalling induced expression of proinflammatory cytokines at the gene level, indicating that several PRRs need to interact for successful innate immune activation. The inflammatory responsiveness of HLCs was accompanied by the downregulation of cytochrome P450 3A and 1A2 activity and decreased serum protein production, showing that the metabolic switch seen in primary hepatocytes during anti-viral responses is also present in HLCs.

scholarly journals Regulation of the Ebola Virus VP24 Protein by SUMO

2019 ◽  
Vol 94 (1) ◽  
Author(s):  
Santiago Vidal ◽  
Ahmed El Motiam ◽  
Rocío Seoane ◽  
Viktorija Preitakaite ◽  
Yanis Hichem Bouzaher ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Viral Protein ◽  
Matrix Protein ◽  
Ebola Virus ◽  
Nuclear Translocation ◽  
Critical Role ◽  
Innate Immune ◽  
Type I ◽  
Negative Modulator

ABSTRACT Some viruses take advantage of conjugation of ubiquitin or ubiquitin-like proteins to enhance their own replication. One example is Ebola virus, which has evolved strategies to utilize these modification pathways to regulate the viral proteins VP40 and VP35 and to counteract the host defenses. Here, we show a novel mechanism by which Ebola virus exploits the ubiquitin and SUMO pathways. Our data reveal that minor matrix protein VP24 of Ebola virus is a bona fide SUMO target. Analysis of a SUMOylation-defective VP24 mutant revealed a reduced ability to block the type I interferon (IFN) pathway and to inhibit IFN-mediated STAT1 nuclear translocation, exhibiting a weaker interaction with karyopherin 5 and significantly diminished stability. Using glutathione S-transferase (GST) pulldown assay, we found that VP24 also interacts with SUMO in a noncovalent manner through a SIM domain. Mutation of the SIM domain in VP24 resulted in a complete inability of the protein to downmodulate the IFN pathway and in the monoubiquitination of the protein. We identified SUMO deubiquitinating enzyme ubiquitin-specific-processing protease 7 (USP7) as an interactor and a negative modulator of VP24 ubiquitination. Finally, we show that mutation of one ubiquitination site in VP24 potentiates the IFN modulatory activity of the viral protein and its ability to block IFN-mediated STAT1 nuclear translocation, pointing to the ubiquitination of VP24 as a negative modulator of the VP24 activity. Altogether, these results indicate that SUMO interacts with VP24 and promotes its USP7-mediated deubiquitination, playing a key role in the interference with the innate immune response mediated by the viral protein. IMPORTANCE The Ebola virus VP24 protein plays a critical role in escape of the virus from the host innate immune response. Therefore, deciphering the molecular mechanisms modulating VP24 activity may be useful to identify potential targets amenable to therapeutics. Here, we identify the cellular proteins USP7, SUMO, and ubiquitin as novel interactors and regulators of VP24. These interactions may represent novel potential targets to design new antivirals with the ability to modulate Ebola virus replication.

scholarly journals Porcine Reproductive and Respiratory Syndrome Virus Nonstructural Protein 1β Modulates Host Innate Immune Response by Antagonizing IRF3 Activation

2009 ◽  
Vol 84 (3) ◽  
pp. 1574-1584 ◽  
Author(s):  
Lalit K. Beura ◽  
Saumendra N. Sarkar ◽  
Byungjoon Kwon ◽  
Sakthivel Subramaniam ◽  
Clinton Jones ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Nuclear Translocation ◽  
Sendai Virus ◽  
Nonstructural Protein ◽  
Adaptive Immune Response ◽  
Inhibitory Effect ◽  
Innate Immune ◽  
Respiratory Syndrome Virus ◽  
Host Innate Immune Response

ABSTRACT Porcine reproductive and respiratory syndrome virus (PRRSV) infection of swine leads to a serious disease characterized by a delayed and defective adaptive immune response. It is hypothesized that a suboptimal innate immune response is responsible for the disease pathogenesis. In the study presented here we tested this hypothesis and identified several nonstructural proteins (NSPs) with innate immune evasion properties encoded by the PRRS viral genome. Four of the total ten PRRSV NSPs tested were found to have strong to moderate inhibitory effects on beta interferon (IFN-β) promoter activation. The strongest inhibitory effect was exhibited by NSP1 followed by, NSP2, NSP11, and NSP4. We focused on NSP1α and NSP1β (self-cleavage products of NSP1 during virus infection) and NSP11, three NSPs with strong inhibitory activity. All of three proteins, when expressed stably in cell lines, strongly inhibited double-stranded RNA (dsRNA) signaling pathways. NSP1β was found to inhibit both IFN regulatory factor 3 (IRF3)- and NF-κB-dependent gene induction by dsRNA and Sendai virus. Mechanistically, the dsRNA-induced phosphorylation and nuclear translocation of IRF3 were strongly inhibited by NSP1β. Moreover, when tested in a porcine myelomonocytic cell line, NSP1β inhibited Sendai virus-mediated activation of porcine IFN-β promoter activity. We propose that this NSP1β-mediated subversion of the host innate immune response plays an important role in PRRSV pathogenesis.

scholarly journals Innate Immune Responses to Herpesvirus Infection

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 2122
Author(s):  
Christine M. O’Connor ◽  
Ganes C. Sen
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Defense Mechanisms ◽  
Innate Immune ◽  
Host Cells ◽  
Innate Immune Responses ◽  
Viral Pathogen ◽  
Dna Viruses ◽  
Host Innate Immune Response ◽  
Human Herpesviruses

Infection of a host cell by an invading viral pathogen triggers a multifaceted antiviral response. One of the most potent defense mechanisms host cells possess is the interferon (IFN) system, which initiates a targeted, coordinated attack against various stages of viral infection. This immediate innate immune response provides the most proximal defense and includes the accumulation of antiviral proteins, such as IFN-stimulated genes (ISGs), as well as a variety of protective cytokines. However, viruses have co-evolved with their hosts, and as such, have devised distinct mechanisms to undermine host innate responses. As large, double-stranded DNA viruses, herpesviruses rely on a multitude of means by which to counter the antiviral attack. Herein, we review the various approaches the human herpesviruses employ as countermeasures to the host innate immune response.

scholarly journals Fas-Associated Factor 1 Negatively Regulates the Antiviral Immune Response by Inhibiting Translocation of Interferon Regulatory Factor 3 to the Nucleus

2016 ◽  
Vol 36 (7) ◽  
pp. 1136-1151 ◽  
Author(s):  
Soonhwa Song ◽  
Jae-Jin Lee ◽  
Hee-Jung Kim ◽  
Jeong Yoon Lee ◽  
Jun Chang ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Target Genes ◽  
Nuclear Translocation ◽  
Antiviral Response ◽  
Innate Immune ◽  
Type I Interferons ◽  
Type I ◽  
Antiviral Immune Response ◽  
Associated Factor

This study is designed to examine the cellular functions of human Fas-associated factor 1 (FAF1) containing multiple ubiquitin-related domains. Microarray analyses revealed that interferon-stimulated genes related to the antiviral response are significantly increased in FAF1-knockdown HeLa cells. Silencing FAF1 enhanced the poly(I·C)- and respiratory syncytial virus (RSV)-induced production of type I interferons (IFNs), the target genes of interferon regulator factor 3 (IRF3). IRF3 is a key transcription factor in IFN-β signaling responsible for the host innate immune response. This study also found that FAF1 and IRF3 physically associate with IPO5/importin-β3 and that overexpression of FAF1 reduces the interaction between IRF3 and IPO5/importin-β3. These findings suggest that FAF1 negatively regulates IRF3-mediated IFN-β production and the antiviral innate immune response by regulating nuclear translocation of IRF3. We conclude that FAF1 plays a novel role in negatively regulating virus-induced IFN-β production and the antiviral response by inhibiting the translocation of active, phosphorylated IRF3 from the cytosol to the nucleus.

scholarly journals Japanese Encephalitis Virus NS5 Inhibits Type I Interferon (IFN) Production by Blocking the Nuclear Translocation of IFN Regulatory Factor 3 and NF-κB

2017 ◽  
Vol 91 (8) ◽  
Author(s):  
Jing Ye ◽  
Zheng Chen ◽  
Yunchuan Li ◽  
Zikai Zhao ◽  
Wen He ◽  
...  
Keyword(s):  
Immune Response ◽  
Japanese Encephalitis Virus ◽  
Innate Immune Response ◽  
Nuclear Translocation ◽  
Type I Interferon ◽  
Transport Proteins ◽  
Innate Immune ◽  
Type I ◽  
Regulatory Factor ◽  
Host Innate Immune Response

ABSTRACT The type I interferon (IFN) response is part of the first-line defense against viral infection. To initiate replication, viruses have developed powerful evasion strategies to counteract host IFN responses. In the present study, we found that the Japanese encephalitis virus (JEV) NS5 protein could inhibit double-stranded RNA (dsRNA)-induced IFN-β expression in a dose-dependent manner. Our data further demonstrated that JEV NS5 suppressed the activation of the IFN transcriptional factors IFN regulatory factor 3 (IRF3) and NF-κB. However, there was no defect in the phosphorylation of IRF3 and degradation of IκB, an upstream inhibitor of NF-κB, upon NS5 expression, indicating a direct inhibition of the nuclear localization of IRF3 and NF-κB by NS5. Mechanistically, NS5 was shown to interact with the nuclear transport proteins KPNA2, KPNA3, and KPNA4, which competitively blocked the interaction of KPNA3 and KPNA4 with their cargo molecules, IRF3 and p65, a subunit of NF-κB, and thus inhibited the nuclear translocation of IRF3 and NF-κB. Furthermore, overexpression of KPNA3 and KPNA4 restored the activity of IRF3 and NF-κB and increased the production of IFN-β in NS5-expressing or JEV-infected cells. Additionally, an upregulated replication level of JEV was shown upon KPNA3 or KPNA4 overexpression. These results suggest that JEV NS5 inhibits the induction of type I IFN by targeting KPNA3 and KPNA4. IMPORTANCE JEV is the major cause of viral encephalitis in South and Southeast Asia, with high mortality. However, the molecular mechanisms contributing to the severe pathogenesis are poorly understood. The ability of JEV to counteract the host innate immune response is potentially one of the mechanisms responsible for JEV virulence. Here we demonstrate the ability of JEV NS5 to interfere with the dsRNA-induced nuclear translocation of IRF3 and NF-κB by competitively inhibiting the interaction of IRF3 and NF-κB with nuclear transport proteins. Via this mechanism, JEV NS5 suppresses the induction of type I IFN and the antiviral response in host cells. These findings reveal a novel strategy for JEV to escape the host innate immune response and provide new insights into the pathogenesis of JEV.

scholarly journals Toll-Like Receptor 2 Mediates Alveolar Macrophage Response to Pneumocystis murina

2006 ◽  
Vol 74 (3) ◽  
pp. 1857-1864 ◽  
Author(s):  
Chen Zhang ◽  
Shao-Hung Wang ◽  
Mark E. Lasbury ◽  
Dennis Tschang ◽  
Chung-Ping Liao ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Alveolar Macrophages ◽  
Nuclear Translocation ◽  
Innate Immune ◽  
Hek293 Cells ◽  
Mrna Levels ◽  
Toll Like Receptor ◽  
Tnf Α ◽  
Toll Like Receptor 2

ABSTRACT The innate immune response to Pneumocystis infection is not well understood. In this study, normal C57BL/6 mouse alveolar macrophages were found to respond to Pneumocystis murina organisms through Toll-like receptor 2 (TLR2), leading to the nuclear translocation of NF-κB and the production of proinflammatory cytokine tumor necrosis factor alpha (TNF-α) and chemokine macrophage inflammatory protein 2 (MIP-2). P. murina stimulation of normal alveolar macrophages from C57BL/6 mice resulted in increased TLR2 transcription but not increased TLR4 transcription. In gain-of-function studies with HEK293 cells expressing TLR2 or TLR4, only TLR2 was found to stimulate an NF-κB response to P. murina. TNF-α and MIP-2 production in response to P. murina by mouse alveolar macrophages was inhibited by a monoclonal antibody that specifically blocked the ligand-binding ability of TLR2. Alveolar macrophages from TLR2 knockout (TLR2−/−) mice showed little increase in TNF-α and MIP-2 mRNA levels upon P. murina stimulation. An in vivo study showed that TLR2−/− mice challenged with P. murina had reduced cytokine responses. These results indicate that TLR2 plays a major role in the innate immune response to P. murina.

scholarly journals An HBV-encoded miRNA activates innate immunity to restrict HBV replication

2019 ◽  
Vol 12 (4) ◽  
pp. 263-276 ◽  
Author(s):  
Xiaoqing Zhao ◽  
Lu Sun ◽  
Ting Mu ◽  
Jianying Yi ◽  
Chaoqun Ma ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immunity ◽  
Innate Immune Response ◽  
Cell Injury ◽  
Innate Immune ◽  
Hbv Infection ◽  
Dependent Manner ◽  
Hbv Replication ◽  
Vital Functions ◽  
Liver Cell Injury

Abstract We previously identified that hepatitis B virus (HBV) encodes a microRNA (HBV-miR-3) that restrains HBV replication by targeting the HBV transcript. However, whether HBV-miR-3 affects host innate immunity to modulate HBV replication remains unclear. Here, we examined the vital functions of HBV-miR-3 in the innate immune response after HBV infection. We found that HBV-miR-3 expression gradually increased in a dose- and time-dependent manner in HBV-infected HepG2-NTCP cells. HBV-miR-3 activated the JAK/STAT signaling pathway by downregulating SOCS5 in hepatocytes, thereby enhancing the IFN-induced anti-HBV effect. In addition, HBV-miR-3 in exosomes facilitated the M1 polarization of macrophages. Furthermore, exosomes containing HBV-miR-3 enhanced the secretion of IL-6 via inhibiting the SOCS5-mediated ubiquitination of EGFR. In short, these results demonstrate that HBV-miR-3 activates the innate immune response to restrain HBV replication by multiple pathways, which may suppress HBV-induced acute liver cell injury and affect the progression of persistent HBV infection.

Amniotic membrane modulates innate immune response inhibiting PRRs expression and NF-κB nuclear translocation on limbal myofibroblasts

2014 ◽  
Vol 127 ◽  
pp. 215-223 ◽  
Author(s):  
Alfredo Domínguez-López ◽  
Victor Manuel Bautista-de Lucio ◽  
Janet Serafín-López ◽  
Edson Robles-Sánchez ◽  
Yonathan Garfias
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Amniotic Membrane ◽  
Nuclear Translocation ◽  
Innate Immune

scholarly journals Interferon-Inducible LINC02605 Promotes Antiviral Innate Responses by Strengthening IRF3 Nuclear Translocation

2021 ◽  
Vol 12 ◽  
Author(s):  
Rui Xu ◽  
Shuang-Shuang Yu ◽  
Ran-Ran Yao ◽  
Rong-Chun Tang ◽  
Jia-Wei Liang ◽  
...  
Keyword(s):  
Immune Response ◽  
Viral Replication ◽  
Innate Immune Response ◽  
Nuclear Translocation ◽  
Rna Virus ◽  
Innate Immune ◽  
Pten Expression ◽  
Type I ◽  
Dependent Manner ◽  
Antiviral Immune Response

Non-coding RNAs represent a class of important regulators in immune response. Previously, LINC02605 was identified as a candidate regulator in innate immune response by lncRNA microarray assays. In this study, we systematically analyzed the functions and the acting mechanisms of LINC02605 in antiviral innate immune response. LINC02605 was up-regulated by RNA virus, DNA virus, and type I IFNs in NF-κB and Jak-stat dependent manner. Overexpression of LINC02605 promotes RNA virus-induced type I interferon production and inhibited viral replication. Consistently, knockdown of LINC02605 resulted in reduced antiviral immune response and increased viral replication. Mechanistically, LINC02605 released the inhibition of hsa-miR-107 on the expression of phosphatase and tensin homolog (PTEN). By microRNA mimics and inhibitors, hsa-miR-107 was demonstrated to not only inhibit PTEN’s expression but also negatively regulate the antiviral immune response. Knockdown of LINC02605 led to the reduction of PTEN expression both in mRNA and protein levels. Overexpression of LINC02605 had an opposite impact. Moreover, LINC02605 attenuated the serine 97 phosphorylation level of interferon regulatory factor 3 (IRF3) by promoting PTEN expression. Nucleoplasmic fragmentation assay showed that knocking down LINC02605 inhibited the nuclear translocation of IRF3, rendering the host cells more susceptible to viral invasion, while overexpression showed opposite effects. Therefore, LINC02605 is an induced lncRNA by viral infection and plays a positive feedback in antiviral immune response through modulating the nuclear translocation of IRF3.

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