• Co-localization
• Homology modeling
• Immune evasion
• MDA5
• NDV
• Virus replication
• dsRNA

• NIAB

• HMPV
• Pneumoviridae
• human metapneumovirus
• innate immunity
• interferons
• proteasome
• virology

• Metapneumovirus/physiology
• Humans
• Janus Kinase 1/metabolism
• Interleukin-6/metabolism
• Signal Transduction
• Viral Proteins/metabolism
• Viral Proteins/genetics
• Paramyxoviridae Infections/metabolism
• Paramyxoviridae Infections/virology
• Proteolysis
• Virus Replication
• Host-Pathogen Interactions
• HEK293 Cells
• Cell Line
• STAT1 Transcription Factor/metabolism
• Retroviridae Proteins, Oncogenic

• R01 AI085062 NIAID NIH HHS
• Henry L. Hillman Foundation
• AI-049820 HHS | National Institutes of Health (NIH)
• AI085062 HHS | National Institutes of Health (NIH)
• T32 AI049820 NIAID NIH HHS

• R01 AI085062 NIAID NIH HHS
• T32 AI049820 NIAID NIH HHS

• CARD
• LGP2
• MAVS
• MDA5
• RIG-I
• autoimmunity
• innate immunity
• interferon
• non-self RNA
• virus

• DEAD-box RNA Helicases/genetics
• Interferon-Induced Helicase, IFIH1/metabolism
• DEAD Box Protein 58
• Signal Transduction
• Immunity, Innate
• Receptors, Immunologic
• RNA

• Bovine ephemeral fever virus
• CRM-1
• Lamin A/C
• Matrix (M) protein
• Nuclear export signal (NES)
• Nuclear localization signal (NLS)

• Animals
• Lamin Type A/genetics
• Lamin Type A/metabolism
• Active Transport, Cell Nucleus
• Nuclear Localization Signals
• Chromosomes/metabolism
• Cell Nucleus/metabolism
• Cytoplasm/metabolism

• NF-κB
• PPRV-C
• PPRV-V
• p65
• peste des petits ruminants virus (PPRV)

• Animals
• Humans
• Peste-des-petits-ruminants virus/genetics
• Peste-des-Petits-Ruminants/metabolism
• Cytokines/genetics
• Cytokines/metabolism
• NF-kappa B/genetics
• NF-kappa B/metabolism
• Viral Proteins/genetics
• Viral Proteins/metabolism
• Ruminants
• Gene Expression
• Goats/genetics

• 3C
• Foot-and-mouth disease virus (FMDV)
• IFN-γ
• JAK-STAT signaling pathway
• KPNA1
• STAT1

• Animals
• Interferon-gamma/pharmacology
• Foot-and-Mouth Disease Virus/genetics
• Signal Transduction
• Immunity, Innate
• Interferon Type I/metabolism

• IFN
• Nipah virus
• STAT1
• STAT2
• autocrine signaling
• inclusions
• phosphoprotein

• Humans
• Antiviral Agents
• Cytosol
• Interferons/metabolism
• Nipah Virus
• STAT1 Transcription Factor
• STAT2 Transcription Factor
• Inclusion Bodies, Viral

• IFN antagonism
• NF-kappa B (NF-κB)
• live-attenuated vaccine
• next-generation vaccines
• type I interferons (IFNs)
• veterinary vaccine
• veterinary virology
• viral immune evasion

• African swine fever virus
• STAT1 phosphorylation
• immune evasion
• pA104R
• type I IFN signaling

• National Natural Science Foundation of China

• DNA sensing
• Measles virus
• RNA virus
• cGAS/STING
• immune amnesia
• immune evasion
• innate immunity
• interferon
• sensors
• signaling

• Humans
• Immune Evasion
• Immunity, Innate
• Interferons
• Measles/immunology
• Measles virus
• Signal Transduction

Canine distemper virus (CDV), a morbillivirus within the family Paramyxoviridae, is a highly contagious infectious agent causing a multisystemic, devastating disease in a broad range of host species, characterized by severe immunosuppression, encephalitis and pneumonia. The present study aimed at investigating pulmonary immune responses of CDV-infected dogs in situ using immunohistochemistry and whole transcriptome analyses by bulk RNA sequencing. Spatiotemporal analysis of phenotypic changes revealed pulmonary immune responses primarily driven by MHC-II⁺, Iba-1⁺ and CD204⁺ innate immune cells during acute and subacute infection phases, which paralleled pathologic lesion development and coincided with high viral loads in CDV-infected lungs. CD20⁺ B cell numbers initially declined, followed by lymphoid repopulation in the advanced disease phase. Transcriptome analysis demonstrated an increased expression of transcripts related to innate immunity, antiviral defense mechanisms, type I interferon responses and regulation of cell death in the lung of CDV-infected dogs. Molecular analyses also revealed disturbed cytokine responses with a pro-inflammatory M1 macrophage polarization and impaired mucociliary defense in CDV-infected lungs. The exploratory study provides detailed data on CDV-related pulmonary immune responses, expanding the list of immunologic parameters potentially leading to viral elimination and virus-induced pulmonary immunopathology in canine distemper.

• apoptosis
• bulk RNA sequencing
• canine distemper
• cytokines
• immunohistochemistry
• innate immunity
• morbillivirus
• tumor necrosis factor alpha
• type I interferon
• viral pneumonia

Human herpesvirus 8 (HHV-8), also known as Kaposi’s sarcoma (KS)-associated herpesvirus, is involved etiologically in AIDS-associated KS, primary effusion lymphoma (PEL), and multicentric Castleman’s disease, in which both viral latent and lytic functions are important. HHV-8 encodes four viral interferon regulatory factors (vIRFs) that are believed to contribute to viral latency (in PEL cells, at least) and/or to productive replication via suppression of cellular antiviral and stress signaling. Here, we identify vIRF-1 interactions with signal transducer and activator of transcription (STAT) factors 1 and 2, interferon (IFN)-stimulated gene factor 3 (ISGF3) cofactor IRF9, and associated signal transducing Janus kinases JAK1 and TYK2. In naturally infected PEL cells and in iSLK epithelial cells infected experimentally with genetically engineered HHV-8, vIRF-1 depletion or ablation, respectively, led to increased levels of active (phosphorylated) STAT1 and STAT2 in IFNβ-treated, and untreated, cells during lytic replication and to associated cellular-gene induction. In transfected 293T cells, used for mechanistic studies, suppression by vIRF-1 of IFNβ-induced phospho-STAT1 (pSTAT1) was found to be highly dependent on STAT2, indicating vIRF-1-mediated inhibition and/or dissociation of ISGF3-complexing, resulting in susceptibility of pSTAT1 to inactivating dephosphorylation. Indeed, coprecipitation experiments involving targeted precipitation of ISGF3 components identified suppression of mutual interactions by vIRF-1. In contrast, suppression of IFNβ-induced pSTAT2 was effected by regulation of STAT2 activation, likely via detected inhibition of TYK2 and its interactions with STAT2 and IFN type-I receptor (IFNAR). Our identified vIRF-1 interactions with IFN-signaling mediators STATs 1 and 2, co-interacting ISGF3 component IRF9, and STAT-activating TYK2 and the suppression of IFN signaling via ISGF3, TYK2-STAT2 and TYK2-IFNAR disruption and TYK2 inhibition represent novel mechanisms of vIRF function and HHV-8 evasion from host-cell defenses.

Viral interferon regulatory factors (vIRFs) encoded by Kaposi’s sarcoma- and lymphoma-associated human herpesvirus 8 (HHV-8) are mediators of protection from cellular antiviral responses and therefore are considered to be pivotal for successful de novo infection, latency establishment and maintenance, and productive (lytic) replication. Identification and characterization of their interactions with cellular proteins, the functional consequences of these interactions, and the operation of these mechanisms in the context of infection has the potential to enable the development of novel antiviral strategies targeted to these interactions and mechanisms. In this report we identify vIRF-1 interactions with transcription factors STAT1 and STAT2, the co-interacting component, IRF9, of the antiviral interferon (IFN)-induced transcription complex ISGF3, and the ability of vIRF-1 to inhibit activation and functional associations of IFN-I receptor- and STAT1/2-kinase TYK2, suppress STAT1/2 activation, and dissociate STAT1 from IFN-induced ISGF3 to blunt IFN signaling and promote STAT1 inactivation. These interactions and activities, which mediate suppression of innate cellular defenses against virus replication, represent novel properties among vIRFs and could potentially be exploited for antiviral and therapeutic purposes.

• Herpesvirus 8, Human/physiology
• Humans
• Interferon Regulatory Factors/metabolism
• Interferon Type I/metabolism
• Janus Kinases
• STAT1 Transcription Factor
• STAT2 Transcription Factor/metabolism
• Virus Latency/physiology

• R01 AI140855 NIAID NIH HHS
• National Institutes of Health

Paramyxoviridae is a viral family within the order of Mononegavirales; they are negative single-strand RNA viruses that can cause significant diseases in both humans and animals. In order to replicate, paramyxoviruses–as any other viruses–have to bypass an important protective mechanism developed by the host’s cells: the defensive line driven by interferon. Once the viruses are recognized, the cells start the production of type I and type III interferons, which leads to the activation of hundreds of genes, many of which encode proteins with the specific function to reduce viral replication. Type II interferon is produced by active immune cells through a different signaling pathway, and activates a diverse range of genes with the same objective to block viral replication. As a result of this selective pressure, viruses have evolved different strategies to avoid the defensive function of interferons. The strategies employed by the different viral species to fight the interferon system include a number of sophisticated mechanisms. Here we analyzed the current status of the various strategies used by paramyxoviruses to subvert type I, II, and III interferon responses.

Antagonism of the interferon (IFN)-mediated antiviral state is critical to infection by rabies virus (RABV) and other viruses, and involves interference in the IFN induction and signaling pathways in infected cells, as well as deactivation of the antiviral state in cells previously activated by IFN. The latter is required for viral spread in the host, but the precise mechanisms involved and roles in RABV pathogenesis are poorly defined. Here, we examined the capacity of attenuated and pathogenic strains of RABV that differ only in the IFN-antagonist P protein to overcome an established antiviral state. Importantly, P protein selectively targets IFN-activated phosphorylated STAT1 (pY-STAT1), providing a molecular tool to elucidate specific roles of pY-STAT1. We find that the extended antiviral state is dependent on a low level of pY-STAT1 that appears to persist at a steady state through ongoing phosphorylation/dephosphorylation cycles, following an initial IFN-induced peak. P protein of pathogenic RABV binds and progressively accumulates pY-STAT1 in inactive cytoplasmic complexes, enabling recovery of efficient viral replication over time. Thus, P protein-pY-STAT1 interaction contributes to ‘disarming’ of the antiviral state. P protein of the attenuated RABV is defective in this respect, such that replication remains suppressed over extended periods in cells pre-activated by IFN. These data provide new insights into the nature of the antiviral state, indicating key roles for residual pY-STAT1 signaling. They also elucidate mechanisms of viral deactivation of antiviral responses, including specialized functions of P protein in selective targeting and accumulation of pY-STAT1.

Following viral infection, the host activates multiple antiviral defenses. The ability of viruses to overcome these defenses is critical to disease. The earliest antiviral response involves the production of interferon messenger molecules. Interferons act on infected cells to inhibit viral proliferation, as well as on non-infected cells to establish an antiviral state before infection and so limit viral spread through the host organism. Many strategies used by viruses to overcome the former are well understood, but mechanisms important to the latter, and their importance to disease, are less well defined. In this study, we investigated how rabies virus overcomes a pre-established antiviral state in target cells. We found that the capacity to disable the antiviral state correlates with the ability to cause disease, and involves binding of a viral protein to cellular signaling proteins, which our data indicate are responsible for the maintenance of a prolonged antiviral state. This advances our understanding of antiviral responses, and identifies a key step in lethal infection by rabies virus that causes approximately 60,000 human deaths per year. The findings may contribute to new approaches for the development of vaccines or antivirals.

• Antiviral Agents/pharmacology
• Interferons/metabolism
• Phosphorylation
• Rabies virus/metabolism
• STAT1 Transcription Factor/metabolism
• Virus Replication

• National Health and Medical Research Council
• Australian Research Council
• The Japan Society for the promotion of Science

The signal transducer and activator of transcription (STAT) 1 protein plays a key role in the immune response against viruses and other pathogens by transducing, in the nucleus, the signal from type I, type II and type III IFNs. STAT1 activates the transcription of hundreds of genes, some of which have been well characterized for their antiviral properties. STAT1 gene deletion in mice and complete STAT1 deficiency in humans both cause rapid death from severe infections. STAT1 plays a key role in the immunoglobulin class-switch recombination through the upregulation of T-bet; it also plays a key role in the production of T-bet+ memory B cells that contribute to tissue-resident humoral memory by mounting an IgG response during re-infection. Considering the key role of STAT1 in the antiviral immune response, many viruses, including dangerous viruses such as Ebola and SARS-CoV-2, have developed different mechanisms to inhibit this transcription factor. The search for drugs capable of targeting the viral proteins implicated in both viral replication and IFN/STAT1 inhibition is important for the treatment of the most dangerous viral infections and for future viral pandemics, as shown by the clinical results obtained with Paxlovid in patients infected with SARS-CoV-2.

• Interferon
• STAT1
• immune response
• viral infection

SARS-CoV-2 is the causative agent of COVID-19. Overproduction and release of proinflammatory cytokines are the underlying cause of severe COVID-19. Treatment of this condition with JAK inhibitors is a double-edged sword, which might result in the suppression of proinflammatory cytokine storm and the concurrent enhancement of viral infection, since JAK signaling is essential for host antiviral response. Improving the current JAK inhibitor therapy requires a detailed molecular analysis on how SARS-CoV-2 modulates interferon (IFN)-induced activation of JAK-STAT signaling.

In this study, we focused on the molecular mechanism by which SARS-CoV-2 NSP13 helicase suppresses IFN signaling. Expression of SARS-CoV-2 NSP13 alleviated transcriptional activity driven by type I and type II IFN-responsive enhancer elements. It also prevented nuclear translocation of STAT1 and STAT2. The suppression of NSP13 on IFN signaling occurred at the step of STAT1 phosphorylation. Nucleic acid binding-defective mutant K345A K347A and NTPase-deficient mutant E375A of NSP13 were found to have largely lost the ability to suppress IFN-β-induced STAT1 phosphorylation and transcriptional activation, indicating the requirement of the helicase activity for NSP13-mediated inhibition of STAT1 phosphorylation. NSP13 did not interact with JAK1 nor prevent STAT1-JAK1 complex formation. Mechanistically, NSP13 interacted with STAT1 to prevent JAK1 kinase from phosphorylating STAT1.

SARS-CoV-2 NSP13 helicase broadly suppresses IFN signaling by targeting JAK1 phosphorylation of STAT1.

• COVID-19
• Helicase
• JAK1
• NSP13
• SARS-CoV-2
• STAT1

Particles of many paramyxoviruses include small amounts of proteins with a molecular weight of about 20 kDa. These proteins, termed “C”, are basic, have low amino acid homology and some secondary structure conservation. C proteins are encoded in alternative reading frames of the phosphoprotein gene. Some viruses express nested sets of C proteins that exert their functions in different locations: In the nucleus, they interfere with cellular transcription factors that elicit innate immune responses; in the cytoplasm, they associate with viral ribonucleocapsids and control polymerase processivity and orderly replication, thereby minimizing the activation of innate immunity. In addition, certain C proteins can directly bind to, and interfere with the function of, several cytoplasmic proteins required for interferon induction, interferon signaling and inflammation. Some C proteins are also required for efficient virus particle assembly and budding. C-deficient viruses can be grown in certain transformed cell lines but are not pathogenic in natural hosts. C proteins affect the same host functions as other phosphoprotein gene-encoded proteins named V but use different strategies for this purpose. Multiple independent systems to counteract host defenses may ensure efficient immune evasion and facilitate virus adaptation to new hosts and tissue environments.

• ESCRT
• Orthoparamyxovirinae
• Paramyxoviridae
• budding
• defective-interfering RNA
• immune evasion
• inflammasome
• nucleocapsid
• processivity
• replication

• Animals
• Defective Interfering Viruses
• Genome, Viral
• Humans
• Immune Evasion
• Immunity, Innate/immunology
• Inflammasomes
• Open Reading Frames
• Paramyxoviridae Infections/immunology
• Paramyxovirinae/genetics
• Paramyxovirinae/physiology
• Phosphoproteins/chemistry
• Phosphoproteins/genetics
• Phosphoproteins/immunology
• Phosphoproteins/metabolism
• Phylogeny
• Viral Proteins/chemistry
• Viral Proteins/genetics
• Viral Proteins/immunology
• Viral Proteins/metabolism
• Virus Assembly
• Virus Replication/physiology

• R21 AI159230 NIAID NIH HHS
• R01 AI143791 NIAID NIH HHS

• Measles virus
• Medulloblastoma
• Mouse model
• Oncolytic virus

• Animals
• Cell Line, Tumor
• Cerebellar Neoplasms/therapy
• Humans
• Measles/therapy
• Measles virus/genetics
• Medulloblastoma/pathology
• Medulloblastoma/therapy
• Mice
• Mice, Nude
• Oncolytic Virotherapy/methods
• Oncolytic Viruses/genetics
• Quality of Life
• Tumor Microenvironment
• Xenograft Model Antitumor Assays

Virus infection of eukaryotes triggers cellular innate immune response, a major arm of which is the type I interferon (IFN) family of cytokines. Binding of IFN to cell surface receptors triggers a signaling cascade in which the signal transducer and activator of transcription 2 (STAT2) plays a key role, ultimately leading to an antiviral state of the cell. In retaliation, many viruses counteract the immune response, often by the destruction and/or inactivation of STAT2, promoted by specific viral proteins that do not possess protease activities of their own. This review offers a summary of viral mechanisms of STAT2 subversion with emphasis on degradation. Some viruses also destroy STAT1, another major member of the STAT family, but most viruses are selective in targeting either STAT2 or STAT1. Interestingly, degradation of STAT2 by a few viruses requires the presence of both STAT proteins. Available evidence suggests a mechanism in which multiple sites and domains of STAT2 are required for engagement and degradation by a multi-subunit degradative complex, comprising viral and cellular proteins, including the ubiquitin–proteasomal system. However, the exact molecular nature of this complex and the alternative degradation mechanisms remain largely unknown, as critically presented here with prospective directions of future study.

• RNA virus
• STAT
• immunity
• interferon
• nonstructural protein
• proteasome
• ubiquitin

• Amino Acid Sequence
• Animals
• Humans
• Models, Biological
• Proteasome Endopeptidase Complex/metabolism
• Proteolysis
• STAT2 Transcription Factor/chemistry
• STAT2 Transcription Factor/metabolism
• STAT2 Transcription Factor/ultrastructure
• Ubiquitin/metabolism
• Viruses/metabolism

Rabies virus phosphoprotein (P protein) is a multifunctional protein that plays key roles in replication as the polymerase cofactor that binds to the complex of viral genomic RNA and the nucleoprotein (N protein), and in evading the innate immune response by binding to STAT transcription factors. These interactions are mediated by the C-terminal domain of P (P_CTD). The colocation of these binding sites in the small globular P_CTD raises the question of how these interactions underlying replication and immune evasion, central to viral infection, are coordinated and, potentially, coregulated. While direct data on the binding interface of the P_CTD for STAT1 is available, the lack of direct structural data on the sites that bind N protein limits our understanding of this interaction hub. The P_CTD was proposed to bind via two sites to a flexible loop of N protein (N_pep) that is not visible in crystal structures, but no direct analysis of this interaction has been reported. Here we use Nuclear Magnetic Resonance, and molecular modelling to show N protein residues, Leu381, Asp383, Asp384 and phosphor-Ser389, are likely to bind to a ‘positive patch’ of the P_CTD formed by Lys211, Lys214 and Arg260. Furthermore, in contrast to previous predictions we identify a single site of interaction on the P_CTD by this N_pep. Intriguingly, this site is proximal to the defined STAT1 binding site that includes Ile201 to Phe209. However, cell-based assays indicate that STAT1 and N protein do not compete for P protein. Thus, it appears that interactions critical to replication and immune evasion can occur simultaneously with the same molecules of P protein so that the binding of P protein to activated STAT1 can potentially occur without interrupting interactions involved in replication. These data suggest that replication complexes might be directly involved in STAT1 antagonism.

For viruses to infect cells and generate progeny, they must be able to mediate replication, while simultaneously evading the innate immune system. Viruses with small genomes often achieve this through multifunctional proteins that have roles in both replication and immune evasion, such as the phosphoprotein (P protein) of rabies virus. P protein is an essential cofactor in genome replication and transcription, dependent on the well-folded C-terminal domain (P_CTD), which binds to the nucleoprotein (N protein) when complexed with RNA. The P_CTD can also bind and antagonize signal transducers and activators of transcription (STAT) proteins, that are essential for activating antiviral mechanisms. Here we show using Nuclear Magnetic Resonance spectroscopy and cell-based assays, that the STAT1-binding and N-binding interfaces are proximal but, nevertheless, it appears that the same molecule of P_CTD can simultaneously bind STAT1 and N protein. These data suggest that P-protein-STAT1 interaction, critical to immune evasion, can occur without interrupting interactions underlying replication, and so replication complexes might be directly involved in STAT1 antagonism.

Many viruses target signal transducers and activators of transcription (STAT) 1 and 2 to antagonise antiviral interferon signalling, but targeting of signalling by other STATs/cytokines, including STAT3/interleukin 6 that regulate processes important to Ebola virus (EBOV) haemorrhagic fever, is poorly defined. We report that EBOV potently inhibits STAT3 responses to interleukin-6 family cytokines, and that this is mediated by the interferon-antagonist VP24. Mechanistic analysis indicates that VP24 effects a unique strategy combining distinct karyopherin-dependent and karyopherin-independent mechanisms to antagonise STAT3-STAT1 heterodimers and STAT3 homodimers, respectively. This appears to reflect distinct mechanisms of nuclear trafficking of the STAT3 complexes, revealed for the first time by our analysis of VP24 function. These findings are consistent with major roles for global inhibition of STAT3 signalling in EBOV infection, and provide new insights into the molecular mechanisms of STAT3 nuclear trafficking, significant to pathogen-host interactions, cell physiology and pathologies such as cancer.

Ebola virus (EBOV) continues to pose a significant risk to human health globally, causing ongoing disease outbreaks with case-fatality rates between 40 and 65%. Suppression of immune responses is a critical component of EBOV haemorrhagic fever, but understanding of EBOV impact on signalling by cytokines other than interferon is limited. We find that infectious EBOV inhibits interleukin-6 cytokine signalling via antagonism of STAT3. The antagonistic strategy uniquely combines two distinct mechanisms, which appear to reflect differing nuclear trafficking mechanisms of critical STAT3 complexes. This provides fundamental insights into the mechanisms of pathogenesis of a lethal virus, and biology of STAT3, a critical player in immunity, development, growth and cancer.

• Animals
• Chlorocebus aethiops
• Ebolavirus
• HEK293 Cells
• Hemorrhagic Fever, Ebola/metabolism
• Hemorrhagic Fever, Ebola/virology
• Humans
• STAT3 Transcription Factor/antagonists & inhibitors
• Signal Transduction/physiology
• Vero Cells
• Viral Proteins/metabolism

• National Health and Medical Research Council Australia
• Australian Research Council
• Miegunyah Trust Grimwade Fellowship
• Australian Government Research Training Program

• Nipah virus
• STAT transcription factors
• interferon

• STAT signaling
• STAT transcription factors
• host-pathogen interactions
• immune evasion
• virus-host interactions

• Cytokines/metabolism
• Gene Expression Regulation
• HEK293 Cells
• HeLa Cells
• Humans
• Interleukin-6/metabolism
• Lyssavirus/immunology
• Rhabdoviridae Infections/immunology
• Rhabdoviridae Infections/metabolism
• Rhabdoviridae Infections/virology
• STAT1 Transcription Factor/genetics
• STAT1 Transcription Factor/metabolism
• STAT3 Transcription Factor/genetics
• STAT3 Transcription Factor/metabolism
• Trans-Activators
• Viral Proteins/genetics
• Viral Proteins/metabolism

• National Health and Medical Research Council Australia
• Australian Research Council
• Grimwade Fellowship (Miegunyah Trust)
• Australian Government Research Training Program

• STAT transcription factors
• immune evasion
• innate immunity
• measles
• paramyxovirus
• protein purification
• protein-protein interactions
• recombinant-protein production
• structural biology
• zinc finger proteins

• IgA
• N-terminal moiety of viral phosphoprotein
• intracellular neutralization
• measles virus
• type I interferon

• Black carp
• IRF9
• Innate immunity
• STAT1

• Animals
• Carps/immunology
• Fish Diseases/immunology
• Fish Diseases/virology
• Fish Proteins/immunology
• Interferon-Stimulated Gene Factor 3, gamma Subunit/immunology
• Reoviridae/immunology
• Reoviridae Infections/immunology
• Reoviridae Infections/veterinary
• STAT1 Transcription Factor/immunology

• C protein
• JAK-STAT pathway
• JAK1
• Sendai virus
• TYK2
• interferon
• respirovirus

In the last decade, the emergence of several, novel tickborne viruses have caused significant disease in humans. Of interest are the tickborne banyangviruses: Severe fever with thrombocytopenia syndrome virus (SFTSV), Heartland virus (HRTV), and Guertu virus (GTV). SFTSV and HRTV infection in humans cause viral hemorrhagic fever-like disease leading to mortality rates ranging from 6–30% of the cases. The systemic inflammatory response syndrome (SIRS) associated with SFTSV infection is hypothesized to contribute significantly to pathology seen in patients. Despite the severe disease caused by HRTV and SFTSV, there are no approved therapeutics or vaccines. Investigation of the immune response during and following infection is critical to the generation of fully protective vaccines and/or supportive treatments, and overall understanding of viral immune evasion mechanisms may aid in the development of a new class of therapeutics.

• Banyangvirus
• Guertu virus
• HRTV
• SFTS
• SFTSV
• heartland
• interferon antagonism
• severe fever with thrombocytopenia syndrome virus

• RNA viruses
• plaque phenotype
• quasispecies
• spontaneous mutations
• virulence

• Animals
• DNA-Directed RNA Polymerases/genetics
• Evolution, Molecular
• Humans
• Quasispecies/genetics
• RNA Viruses/genetics
• RNA Viruses/pathogenicity
• Viral Proteins/genetics
• Virulence

• 2019 Sunway University Internal Grant (2019) for Center for Virus and Vaccine Research (CVVR)

• CVS-11
• IL-6
• PGG
• SOCS3
• STAT3
• anti-RABV
• miR-455-5p

Peste des petits ruminants virus (PPRV) is associated with global peste des petits ruminants resulting in severe economic loss. Peste des petits ruminants virus dampens host interferon-based signaling pathways through multiple mechanisms. Previous studies deciphered the role of V and C in abrogating IFN-β production. Moreover, V protein directly interacted with signal transducers and activators of transcription 1 (STAT1) and STAT2 resulting in the impairment of host IFN responses. In our present study, PPRV infection inhibited both IFN-β- and IFN-γ-induced activation of IFN-stimulated response element (ISRE) and IFN-γ-activated site (GAS) element, respectively. Both N and P proteins, functioning as novel IFN response antagonists, markedly suppressed IFN-β-induced ISRE and IFN-γ-induced GAS promoter activation to impair downstream upregulation of various interferon-stimulated genes (ISGs) and prevent STAT1 nuclear translocation. Specifically, P protein interacted with STAT1 and subsequently inhibited STAT1 phosphorylation, whereas N protein neither interacted with STAT1 nor inhibited STAT1 phosphorylation as well as dimerization, suggesting that the N and P protein antagonistic effects were different. Though they differed in their relationship to STAT1, both proteins blocked JAK-STAT signaling, severely negating the host antiviral immune response. Our study revealed a new mechanism employed by PPRV to evade host innate immune response, providing a platform to study the interaction of paramyxoviruses and host response.

• JAK/STAT
• interferon
• nucleoprotein
• peste des petits ruminants virus
• phosphoprotein

• Animals
• HEK293 Cells
• Host-Pathogen Interactions/immunology
• Humans
• Immunity, Innate
• Interferon-beta/antagonists & inhibitors
• Interferon-beta/immunology
• Interferon-gamma/antagonists & inhibitors
• Interferon-gamma/immunology
• Interferons/antagonists & inhibitors
• Interferons/immunology
• Janus Kinases/antagonists & inhibitors
• Janus Kinases/immunology
• Nucleocapsid Proteins/immunology
• Nucleoproteins/immunology
• Peste-des-Petits-Ruminants/virology
• Peste-des-petits-ruminants virus/genetics
• Peste-des-petits-ruminants virus/immunology
• Phosphoproteins/immunology
• STAT1 Transcription Factor/antagonists & inhibitors
• STAT1 Transcription Factor/immunology
• Signal Transduction/immunology
• Virus Replication

Measles virus (MeV) is dual-tropic: it replicates first in lymphatic tissues and then in epithelial cells. This switch in tropism raises the question of whether, and how, intra-host evolution occurs. Towards addressing this question, we adapted MeV either to lymphocytic (Granta-519) or epithelial (H358) cells. We also passaged it consecutively in both human cell lines. Since passaged MeV had different replication kinetics, we sought to investigate the underlying genetic mechanisms of growth differences by performing deep-sequencing analyses. Lymphocytic adaptation reproducibly resulted in accumulation of variants mapping within an 11-nucleotide sequence located in the middle of the phosphoprotein (P) gene. This sequence mediates polymerase slippage and addition of a pseudo-templated guanosine to the P mRNA. This form of co-transcriptional RNA editing results in expression of an interferon antagonist, named V, in place of a polymerase co-factor, named P. We show that lymphocytic-adapted MeV indeed produce minimal amounts of edited transcripts and V protein. In contrast, parental and epithelial-adapted MeV produce similar levels of edited and non-edited transcripts, and of V and P proteins. Raji, another lymphocytic cell line, also positively selects V-deficient MeV genomes. On the other hand, in epithelial cells V-competent MeV genomes rapidly out-compete the V-deficient variants. To characterize the mechanisms of genome re-equilibration we rescued four recombinant MeV carrying individual editing site-proximal mutations. Three mutations interfered with RNA editing, resulting in almost exclusive P protein expression. The fourth preserved RNA editing and a standard P-to-V protein expression ratio. However, it altered a histidine involved in Zn²⁺ binding, inactivating V function. Thus, the lymphocytic environment favors replication of V-deficient MeV, while the epithelial environment has the opposite effect, resulting in rapid and thorough cyclical quasispecies re-equilibration. Analogous processes may occur in natural infections with other dual-tropic RNA viruses.

Key questions in infectious disease are how pathogens adapt to different cells of their hosts, and how the interplay between the virus and host factors controls the outcome of infection. Human measles virus (MeV) and related animal morbilliviruses provide important models of pathogenesis because they are dual-tropic: they replicate first in immune cells for spread through the body, and then in epithelial cells for transmission. We sought here to define the underlying molecular and evolutionary processes that allow MeV to spread rapidly in either lymphocytic or epithelial cells. We discovered unexpectedly rapid and thorough genome adaptation to these two tissues. Genome variants that cannot express functional V protein, an innate immunity control protein, are rapidly selected in lymphocytic cells. These variants express only the P protein, a polymerase co-factor, instead of expressing P and V at similar levels. Upon passaging in epithelial cells, V-competent MeV genome variants rapidly re-gain dominance. These results suggest that cyclical quasispecies re-equilibration may occur in acute MeV infections of humans, and that suboptimal variants in one environment constitute a low frequency reservoir for adaptation to the other, where they become dominant.

• antiviral response
• interferon
• interferon-regulatory factor
• interferon-stimulated gene
• signal transducer and activator of transcription signaling
• viral antagonism
• viral attenuation

• Animals
• Humans
• Immunity, Innate
• Interferon Regulatory Factors/immunology
• Interferon Regulatory Factors/metabolism
• Interferon Type I/metabolism
• Janus Kinases/metabolism
• Proteolysis
• STAT Transcription Factors/immunology
• STAT Transcription Factors/metabolism
• Signal Transduction/immunology
• Toll-Like Receptors/metabolism
• Viral Proteins/metabolism
• Virus Diseases/immunology

The interferon (IFN)-mediated innate immune response is the first line of defense against viruses. However, an IFN-stimulated gene, the adenosine deaminase acting on RNA 1 (ADAR1), favors the replication of several viruses. ADAR1 binds double-stranded RNA and converts adenosine to inosine by deamination. This form of editing makes duplex RNA unstable, thereby preventing IFN induction. To better understand how ADAR1 works at the cellular level, we generated cell lines that express exclusively either the IFN-inducible, cytoplasmic isoform ADAR1^p150, the constitutively expressed nuclear isoform ADAR1^p110, or no isoform. By comparing the transcriptome of these cell lines, we identified more than 150 polymerase II transcripts that are extensively edited, and we attributed most editing events to ADAR1^p150. Editing is focused on inverted transposable elements, located mainly within introns and untranslated regions, and predicted to form duplex RNA structures. Editing of these elements occurs also in primary human samples, and there is evidence for cross-species evolutionary conservation of editing patterns in primates and, to a lesser extent, in rodents. Whereas ADAR1^p150 rarely edits tightly encapsidated standard measles virus (MeV) genomes, it efficiently edits genomes with inverted repeats accidentally generated by a mutant MeV. We also show that immune activation occurs in fully ADAR1-deficient (ADAR1^KO) cells, restricting virus growth, and that complementation of these cells with ADAR1^p150 rescues virus growth and suppresses innate immunity activation. Finally, by knocking out either protein kinase R (PKR) or mitochondrial antiviral signaling protein (MAVS)—another protein controlling the response to duplex RNA—in ADAR1^KO cells, we show that PKR activation elicits a stronger antiviral response. Thus, ADAR1 prevents innate immunity activation by cellular transcripts that include extensive duplex RNA structures. The trade-off is that viruses take advantage of ADAR1 to elude innate immunity control.

The innate immune response is a double-edged sword. It must protect the host from pathogens while avoiding accidental recognition of “self” molecular patterns, which can lead to autoimmune reactions. Double-stranded RNA is among the most potent inducers of cellular stress and interferon responses. We characterize here a mechanism that prevents autoimmune activation and show that an RNA virus, measles virus, can exploit it to elude innate immune responses. This mechanism relies on the enzyme adenosine deaminase acting on RNA 1 (ADAR1), which converts adenosine residues within duplex RNA structures to inosine. We identify duplex RNA structures in the 3′ untranslated regions of over 150 cellular transcripts and show that they are heavily edited in ADAR1-expressing cells. We detect the same type of editing in duplex RNA–forming defective genomes accidentally generated by measles virus. Loss of RNA editing causes strong innate immune responses and is detrimental to viral replication. Thus, by keeping the amount of duplex RNA in cells below an immune activation threshold, ADAR1 prevents autoimmunity while also favoring pathogens.

• Adenosine/metabolism
• Adenosine Deaminase/genetics
• Adenosine Deaminase/metabolism
• Adenosine Deaminase/physiology
• HeLa Cells
• Humans
• Immunity, Innate/physiology
• Interferons/metabolism
• Protein Isoforms
• Proviruses/genetics
• Proviruses/immunology
• RNA Viruses/genetics
• RNA Viruses/metabolism
• RNA, Double-Stranded/physiology
• RNA, Viral/genetics
• RNA-Binding Proteins/genetics
• RNA-Binding Proteins/metabolism
• RNA-Binding Proteins/physiology
• Transcriptome/genetics
• Virion/genetics

• R21 AI128037 NIAID NIH HHS

• Epitope
• Monoclonal antibodies
• Newcastle disease virus
• V protein

• JAK/STAT
• STAT3
• viral infection

Signal transducer and activator of transcription 3 (STAT3) is a key regulator of numerous physiological functions, including the immune response. As pathogens elicit an acute phase response with concerted activation of STAT3, they are confronted with two evolutionary options: either curtail it or employ it. This has important consequences for the host, since abnormal STAT3 function is associated with cancer development and other diseases. This review provides a comprehensive outline of how human viruses cope with STAT3-mediated inflammation and how this affects the host. Finally, we discuss STAT3 as a potential target for antiviral therapy.

• Animals
• Humans
• Inflammation/etiology
• Inflammation/metabolism
• Inflammation/pathology
• STAT3 Transcription Factor/metabolism
• Signal Transduction
• Virus Diseases/metabolism
• Virus Diseases/virology
• Viruses/pathogenicity

• HIV-1
• ISG
• JAK/STAT
• Proteasomal degradation
• Type 1 IFNs
• Viral immune evasion

• WD repeat-containing protein
• WDR5
• inclusion body
• innate immunity
• measles virus

• inflammasome
• innate immunity

• Janus kinase/signal transducer and activator of transcription signaling
• Janus kinases
• interferons
• signal transducer and activator of transcriptions
• viral antagonism
• viral attenuation

• Dog
• Interferon stimulated genes
• Therapy
• Tumor
• Type I interferon
• Virus

The present study assessed the variation of measles viruses (MV) and its association with clinical manifestations in patients with MV. A total of 38 pediatric patients with MV at the acute infection stage were selected and 2 ml venous blood was collected from each of them. Serum immunoglobulin M antibodies were determined by ELISA. Urine specimens were collected from 30 of the 38 patients and associated genetic structures were detected by reverse-transcription polymerase chain reaction mapping. At the same time, clinical epidemiological manifestations were collected to perform an epidemiological analysis. The MV-positive rate within the cohort determined in serum was 100%. Seven MV strains were isolated from urine specimens of 30 patients and the positive rate was 23.33%. Four MV strains were randomly selected from the 7 strains and the results revealed that they were all of the H_1a genotype. In addition, there was no significant correlation between clinical manifestation of pediatric patients with measles and the genotype of the MV. In conclusion, the preponderant genotype of MV in Kunming was H_1a and there was obvious nucleotide or amino acid mutation. The clinical manifestation of MV infection in pediatric patients was not associated with the MV genotype.

• Kunming
• genotype
• measles virus
• molecular epidemiology