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Rady T, Erb S, Deddouche-Grass S, Morales R, Chaubet G, Cianférani S, Basse N, Wagner A. Targeted delivery of immune-stimulating bispecific RNA, inducing apoptosis and anti-tumor immunity in cancer cells. iScience 2024; 27:109068. [PMID: 38380254 PMCID: PMC10877685 DOI: 10.1016/j.isci.2024.109068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 07/18/2023] [Accepted: 01/25/2024] [Indexed: 02/22/2024] Open
Abstract
Double-stranded RNAs (dsRNA)-based strategies appeared as promising therapies to induce an inflammation in the tumor microenvironment. However, currently described systems generally lack active targeting of tissues, and their clinical translation is thus limited to intratumoral injection. Herein, we developed an antibody-siRNA-5'triphosphate conjugate with multiple modes of action, combining cell surface EphA2-specific internalization, leading to a simultaneous gene silencing and activation of the receptor retinoic acid-inducible gene I (RIG-I). Recognition of cytosolic siRNA-5'triphosphate by RIG-I triggers the expression of interferons and pro-inflammatory cytokines, inducing an inflammation of the tumor environment and activating neighboring immune cells. In addition, these RIG-I-specific effects synergized with siRNA-mediated PLK1 silencing to promote cancer cell death by apoptosis. Altogether, such immune-stimulating antibody-RNA conjugate opens a novel modality to overcome some limitations encountered by dsRNA molecules currently in clinical trials.
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Affiliation(s)
- Tony Rady
- Bio-Functional Chemistry (UMR 7199), LabEx Medalis, University of Strasbourg, 74 Route du Rhin, 67400 Illkirch-Graffenstaden, France
- Sanofi, 13 Quai Jules Guesde, 94400 Vitry-sur-Seine, France
| | - Stéphane Erb
- Laboratoire de Spectrométrie de Masse BioOrganique (LSMBO), Université de Strasbourg, CNRS, IPHC UMR 7178, 67000 Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR2048, 67087 Strasbourg, France
| | | | - Renaud Morales
- Sanofi, 13 Quai Jules Guesde, 94400 Vitry-sur-Seine, France
| | - Guilhem Chaubet
- Bio-Functional Chemistry (UMR 7199), LabEx Medalis, University of Strasbourg, 74 Route du Rhin, 67400 Illkirch-Graffenstaden, France
| | - Sarah Cianférani
- Laboratoire de Spectrométrie de Masse BioOrganique (LSMBO), Université de Strasbourg, CNRS, IPHC UMR 7178, 67000 Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR2048, 67087 Strasbourg, France
| | - Nicolas Basse
- Sanofi, 13 Quai Jules Guesde, 94400 Vitry-sur-Seine, France
| | - Alain Wagner
- Bio-Functional Chemistry (UMR 7199), LabEx Medalis, University of Strasbourg, 74 Route du Rhin, 67400 Illkirch-Graffenstaden, France
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2
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Malet H, Williams HM, Cusack S, Rosenthal M. The mechanism of genome replication and transcription in bunyaviruses. PLoS Pathog 2023; 19:e1011060. [PMID: 36634042 PMCID: PMC9836281 DOI: 10.1371/journal.ppat.1011060] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Bunyaviruses are negative sense, single-strand RNA viruses that infect a wide range of vertebrate, invertebrate and plant hosts. WHO lists three bunyavirus diseases as priority diseases requiring urgent development of medical countermeasures highlighting their high epidemic potential. While the viral large (L) protein containing the RNA-dependent RNA polymerase is a key enzyme in the viral replication cycle and therefore a suitable drug target, our knowledge on the structure and activities of this multifunctional protein has, until recently, been very limited. However, in the last few years, facilitated by the technical advances in the field of cryogenic electron microscopy, many structures of bunyavirus L proteins have been solved. These structures significantly enhance our mechanistic understanding of bunyavirus genome replication and transcription processes and highlight differences and commonalities between the L proteins of different bunyavirus families. Here, we provide a review of our current understanding of genome replication and transcription in bunyaviruses with a focus on the viral L protein. Further, we compare within bunyaviruses and with the related influenza virus polymerase complex and highlight open questions.
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Affiliation(s)
- Hélène Malet
- University Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France
- Institut Universitaire de France (IUF), Paris, France
| | - Harry M. Williams
- Bernhard Nocht Institute for Tropical Medicine (BNITM), Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
| | | | - Maria Rosenthal
- Bernhard Nocht Institute for Tropical Medicine (BNITM), Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology (ITMP), Discovery Research ScreeningPort, Hamburg, Germany
- * E-mail:
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3
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Pyle JD, Whelan SPJ, Bloyet LM. Structure and function of negative-strand RNA virus polymerase complexes. Enzymes 2021; 50:21-78. [PMID: 34861938 DOI: 10.1016/bs.enz.2021.09.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Viruses with negative-strand RNA genomes (NSVs) include many highly pathogenic and economically devastating disease-causing agents of humans, livestock, and plants-highlighted by recent Ebola and measles virus epidemics, and continuously circulating influenza virus. Because of their protein-coding orientation, NSVs face unique challenges for efficient gene expression and genome replication. To overcome these barriers, NSVs deliver a large and multifunctional RNA-dependent RNA polymerase into infected host cells. NSV-encoded polymerases contain all the enzymatic activities required for transcription and replication of their genome-including RNA synthesis and mRNA capping. Here, we review the structures and functions of NSV polymerases with a focus on key domains responsible for viral replication and gene expression. We highlight shared and unique features among polymerases of NSVs from the Mononegavirales, Bunyavirales, and Articulavirales orders.
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Affiliation(s)
- Jesse D Pyle
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, United States; Ph.D. Program in Virology, Harvard Medical School, Boston, MA, United States
| | - Sean P J Whelan
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, United States.
| | - Louis-Marie Bloyet
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, United States.
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4
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Bach S, Demper JC, Klemm P, Schlereth J, Lechner M, Schoen A, Kämper L, Weber F, Becker S, Biedenkopf N, Hartmann RK. Identification and characterization of short leader and trailer RNAs synthesized by the Ebola virus RNA polymerase. PLoS Pathog 2021; 17:e1010002. [PMID: 34699554 PMCID: PMC8547711 DOI: 10.1371/journal.ppat.1010002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 10/04/2021] [Indexed: 11/21/2022] Open
Abstract
Transcription of non-segmented negative sense (NNS) RNA viruses follows a stop-start mechanism and is thought to be initiated at the genome’s very 3’-end. The synthesis of short abortive leader transcripts (leaderRNAs) has been linked to transcription initiation for some NNS viruses. Here, we identified the synthesis of abortive leaderRNAs (as well as trailer RNAs) that are specifically initiated opposite to (anti)genome nt 2; leaderRNAs are predominantly terminated in the region of nt ~ 60–80. LeaderRNA synthesis requires hexamer phasing in the 3’-leader promoter. We determined a steady-state NP mRNA:leaderRNA ratio of ~10 to 30-fold at 48 h after Ebola virus (EBOV) infection, and this ratio was higher (70 to 190-fold) for minigenome-transfected cells. LeaderRNA initiation at nt 2 and the range of termination sites were not affected by structure and length variation between promoter elements 1 and 2, nor the presence or absence of VP30. Synthesis of leaderRNA is suppressed in the presence of VP30 and termination of leaderRNA is not mediated by cryptic gene end (GE) signals in the 3’-leader promoter. We further found different genomic 3’-end nucleotide requirements for transcription versus replication, suggesting that promoter recognition is different in the replication and transcription mode of the EBOV polymerase. We further provide evidence arguing against a potential role of EBOV leaderRNAs as effector molecules in innate immunity. Taken together, our findings are consistent with a model according to which leaderRNAs are abortive replicative RNAs whose synthesis is not linked to transcription initiation. Rather, replication and transcription complexes are proposed to independently initiate RNA synthesis at separate sites in the 3’-leader promoter, i.e., at the second nucleotide of the genome 3’-end and at the more internally positioned transcription start site preceding the first gene, respectively, as reported for Vesicular stomatitis virus. The RNA polymerase (RdRp) of Ebola virus (EBOV) initiates RNA synthesis at the 3’-leader promoter of its encapsidated, non-segmented negative sense (NNS) RNA genome, either at the penultimate 3’-end position of the genome in the replicative mode or more internally (position 56) at the transcription start site (TSS) in its transcription mode. Here we identified the synthesis of abortive replicative RNAs that are specifically initiated opposite to genome nt 2 (termed leaderRNAs) and predominantly terminated in the region of nt ~ 60–80 near the TSS. The functional role of abortive leaderRNA synthesis is still enigmatic; a role in interferon induction could be excluded. Our findings indirectly link leaderRNA termination to nucleoprotein (NP) availability for encapsidation of nascent replicative RNA or to NP removal from the template RNA. Our findings further argue against the model that leaderRNA synthesis is a prerequisite for each transcription initiation event at the TSS. Rather, our findings are in line with the existence of distinct replicase and transcriptase complexes of RdRp that interact differently with the 3’-leader promoter and intiate RNA synthesis independently at different sites (position 2 or 56 of the genome), mechanistically similar to another NNS virus, Vesicular stomatitis virus.
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Affiliation(s)
- Simone Bach
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Jana-Christin Demper
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Paul Klemm
- Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Marburg, Germany
| | - Julia Schlereth
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Marcus Lechner
- Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Marburg, Germany
| | - Andreas Schoen
- Institut für Virologie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Lennart Kämper
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Friedemann Weber
- Institut für Virologie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Nadine Biedenkopf
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
- * E-mail: (NB); (RKH)
| | - Roland K. Hartmann
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
- * E-mail: (NB); (RKH)
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5
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Onomoto K, Onoguchi K, Yoneyama M. Regulation of RIG-I-like receptor-mediated signaling: interaction between host and viral factors. Cell Mol Immunol 2021; 18:539-555. [PMID: 33462384 PMCID: PMC7812568 DOI: 10.1038/s41423-020-00602-7] [Citation(s) in RCA: 170] [Impact Index Per Article: 56.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/17/2020] [Indexed: 01/31/2023] Open
Abstract
Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are RNA sensor molecules that play essential roles in innate antiviral immunity. Among the three RLRs encoded by the human genome, RIG-I and melanoma differentiation-associated gene 5, which contain N-terminal caspase recruitment domains, are activated upon the detection of viral RNAs in the cytoplasm of virus-infected cells. Activated RLRs induce downstream signaling via their interactions with mitochondrial antiviral signaling proteins and activate the production of type I and III interferons and inflammatory cytokines. Recent studies have shown that RLR-mediated signaling is regulated by interactions with endogenous RNAs and host proteins, such as those involved in stress responses and posttranslational modifications. Since RLR-mediated cytokine production is also involved in the regulation of acquired immunity, the deregulation of RLR-mediated signaling is associated with autoimmune and autoinflammatory disorders. Moreover, RLR-mediated signaling might be involved in the aberrant cytokine production observed in coronavirus disease 2019. Since the discovery of RLRs in 2004, significant progress has been made in understanding the mechanisms underlying the activation and regulation of RLR-mediated signaling pathways. Here, we review the recent advances in the understanding of regulated RNA recognition and signal activation by RLRs, focusing on the interactions between various host and viral factors.
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Affiliation(s)
- Koji Onomoto
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba, 260-8673, Japan
| | - Kazuhide Onoguchi
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba, 260-8673, Japan
| | - Mitsutoshi Yoneyama
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba, 260-8673, Japan.
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6
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Uehata T, Takeuchi O. RNA Recognition and Immunity-Innate Immune Sensing and Its Posttranscriptional Regulation Mechanisms. Cells 2020; 9:cells9071701. [PMID: 32708595 PMCID: PMC7407594 DOI: 10.3390/cells9071701] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/13/2020] [Accepted: 07/15/2020] [Indexed: 12/13/2022] Open
Abstract
RNA acts as an immunostimulatory molecule in the innate immune system to activate nucleic acid sensors. It functions as an intermediate, conveying genetic information to control inflammatory responses. A key mechanism for RNA sensing is discriminating self from non-self nucleic acids to initiate antiviral responses reliably, including the expression of type I interferon (IFN) and IFN-stimulated genes. Another important aspect of the RNA-mediated inflammatory response is posttranscriptional regulation of gene expression, where RNA-binding proteins (RBPs) have essential roles in various RNA metabolisms, including splicing, nuclear export, modification, and translation and mRNA degradation. Recent evidence suggests that the control of mRNA stability is closely involved in signal transduction and orchestrates immune responses. In this study, we review the current understanding of how RNA is sensed by host RNA sensing machinery and discuss self/non-self-discrimination in innate immunity focusing on mammalian species. Finally, we discuss how posttranscriptional regulation by RBPs shape immune reactions.
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7
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Klitting R, Mehta SB, Oguzie JU, Oluniyi PE, Pauthner MG, Siddle KJ, Andersen KG, Happi CT, Sabeti PC. Lassa Virus Genetics. Curr Top Microbiol Immunol 2020. [PMID: 32418034 DOI: 10.1007/82_2020_212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In a pattern repeated across a range of ecological niches, arenaviruses have evolved a compact four-gene genome to orchestrate a complex life cycle in a narrow range of susceptible hosts. A number of mammalian arenaviruses cross-infect humans, often causing a life-threatening viral hemorrhagic fever. Among this group of geographically bound zoonoses, Lassa virus has evolved a unique niche that leads to significant and sustained human morbidity and mortality. As a biosafety level 4 pathogen, direct study of the pathogenesis of Lassa virus is limited by the sparse availability, high operating costs, and technical restrictions of the high-level biocontainment laboratories required for safe experimentation. In this chapter, we introduce the relationship between genome structure and the life cycle of Lassa virus and outline reverse genetic approaches used to probe and describe functional elements of the Lassa virus genome. We then review the tools used to obtain viral genomic sequences used for phylogeny and molecular diagnostics, before shifting to a population perspective to assess the contributions of phylogenetic analysis in understanding the evolution and ecology of Lassa virus in West Africa. We finally consider the future outlook and clinical applications for genetic study of Lassa virus.
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Affiliation(s)
- Raphaëlle Klitting
- Department of Immunology and Microbiology, The Scripps Research Institute , La Jolla, CA, USA
| | - Samar B Mehta
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Judith U Oguzie
- African Center of Excellence for Genomics of Infectious Diseases (ACEGID), Redeemer's University, Ede, Osun State, Nigeria
- Department of Biological Sciences, Faculty of Natural Sciences, Redeemers University, Ede, Osun State, Nigeria
| | - Paul E Oluniyi
- African Center of Excellence for Genomics of Infectious Diseases (ACEGID), Redeemer's University, Ede, Osun State, Nigeria
- Department of Biological Sciences, Faculty of Natural Sciences, Redeemers University, Ede, Osun State, Nigeria
| | - Matthias G Pauthner
- Department of Immunology and Microbiology, The Scripps Research Institute , La Jolla, CA, USA
| | | | - Kristian G Andersen
- Department of Immunology and Microbiology, The Scripps Research Institute , La Jolla, CA, USA.
| | - Christian T Happi
- African Center of Excellence for Genomics of Infectious Diseases (ACEGID), Redeemer's University, Ede, Osun State, Nigeria
- Department of Biological Sciences, Faculty of Natural Sciences, Redeemers University, Ede, Osun State, Nigeria
| | - Pardis C Sabeti
- Broad Institute of MIT and Harvard, Cambridge, MA, USA.
- Center for Systems Biology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
- Department of Immunology and Infectious Diseases, Harvard TH Chan School of Public Health, Boston, MA, USA.
- Howard Hughes Medical Institute, Chevy Chase, MD, USA.
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8
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Brisse M, Ly H. Comparative Structure and Function Analysis of the RIG-I-Like Receptors: RIG-I and MDA5. Front Immunol 2019; 10:1586. [PMID: 31379819 PMCID: PMC6652118 DOI: 10.3389/fimmu.2019.01586] [Citation(s) in RCA: 218] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 06/25/2019] [Indexed: 12/12/2022] Open
Abstract
RIG-I (Retinoic acid-inducible gene I) and MDA5 (Melanoma Differentiation-Associated protein 5), collectively known as the RIG-I-like receptors (RLRs), are key protein sensors of the pathogen-associated molecular patterns (PAMPs) in the form of viral double-stranded RNA (dsRNA) motifs to induce expression of type 1 interferons (IFN1) (IFNα and IFNβ) and other pro-inflammatory cytokines during the early stage of viral infection. While RIG-I and MDA5 share many genetic, structural and functional similarities, there is increasing evidence that they can have significantly different strategies to recognize different pathogens, PAMPs, and in different host species. This review article discusses the similarities and differences between RIG-I and MDA5 from multiple perspectives, including their structures, evolution and functional relationships with other cellular proteins, their differential mechanisms of distinguishing between host and viral dsRNAs and interactions with host and viral protein factors, and their immunogenic signaling. A comprehensive comparative analysis can help inform future studies of RIG-I and MDA5 in order to fully understand their functions in order to optimize potential therapeutic approaches targeting them.
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Affiliation(s)
- Morgan Brisse
- Biochemistry, Molecular Biology, and Biophysics Graduate Program, University of Minnesota, Twin Cities, St. Paul, MN, United States
- Department of Veterinary & Biomedical Sciences, University of Minnesota, Twin Cities, St. Paul, MN, United States
| | - Hinh Ly
- Department of Veterinary & Biomedical Sciences, University of Minnesota, Twin Cities, St. Paul, MN, United States
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9
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Abstract
Atomic structures of the polymerase–endonuclease complex of the orthomyxovirus influenza and the orthobunyavirus La Crosse—two distinct segmented negative-sense (SNS) RNA viruses—demonstrate that binding of the genomic 5′ RNA rearranges the catalytic residues of the RNA-dependent RNA-polymerase (RdRP). Working with the arenavirus, Machupo, we demonstrate that 5′ RNAs from the genomic and antigenomic copies of both segments activate the RdRP in conjunction with a specific promoter. This study builds upon structural studies with two different SNS RNA viruses to reveal a previously unappreciated mechanism of RNA-guided promoter-specific polymerase regulation in SNS RNA viruses. The conservation of activating RNA elements among the polymerase–endonuclease complexes of SNS RNA viruses suggests new avenues for developing antiviral therapeutics. Segmented negative-sense (SNS) RNA viruses initiate infection by delivering into cells a suite of genomic RNA segments, each sheathed by the viral nucleocapsid protein and bound by the RNA-dependent RNA-polymerase (RdRP). For the orthomyxovirus influenza and the bunyavirus La Crosse, the 5′ end of the genomic RNA binds as a hook-like structure proximal to the active site of the RdRP. Using an in vitro assay for the RNA-dependent RNA-polymerase (RdRP) of the arenavirus Machupo (MACV), we demonstrate that the 5′ genomic and antigenomic RNAs of both small and large genome segments stimulate activity in a promoter-specific manner. Functional probing of the activating RNAs identifies intramolecular base-pairing between positions +1 and +7 and a pseudotemplated 5′ terminal guanine residue as key for activation. Binding of structured 5′ RNAs is a conserved feature of all SNS RNA virus polymerases, implying that promoter-specific RdRP activation extends beyond the arenaviruses. The 5′ RNAs and the RNA binding pocket itself represent targets for therapeutic intervention.
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10
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Ebolavirus polymerase uses an unconventional genome replication mechanism. Proc Natl Acad Sci U S A 2019; 116:8535-8543. [PMID: 30962389 DOI: 10.1073/pnas.1815745116] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Most nonsegmented negative strand (NNS) RNA virus genomes have complementary 3' and 5' terminal nucleotides because the promoters at the 3' ends of the genomes and antigenomes are almost identical to each other. However, according to published sequences, both ends of ebolavirus genomes show a high degree of variability, and the 3' and 5' terminal nucleotides are not complementary. If correct, this would distinguish the ebolaviruses from other NNS RNA viruses. Therefore, we investigated the terminal genomic and antigenomic nucleotides of three different ebolavirus species, Ebola (EBOV), Sudan, and Reston viruses. Whereas the 5' ends of ebolavirus RNAs are highly conserved with the sequence ACAGG-5', the 3' termini are variable and are typically 3'-GCCUGU, ACCUGU, or CCUGU. A small fraction of analyzed RNAs had extended 3' ends. The majority of 3' terminal sequences are consistent with a mechanism of nucleotide addition by hairpin formation and back-priming. Using single-round replicating EBOV minigenomes, we investigated the effect of the 3' terminal nucleotide on viral replication and found that the EBOV polymerase initiates replication opposite the 3'-CCUGU motif regardless of the identity of the 3' terminal nucleotide(s) and of the position of this motif relative to the 3' end. Deletion or mutation of the first residue of the 3'-CCUGU motif completely abolished replication initiation, suggesting a crucial role of this nucleotide in directing initiation. Together, our data show that ebolaviruses have evolved a unique replication strategy among NNS RNA viruses resulting in 3' overhangs. This could be a mechanism to avoid antiviral recognition.
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11
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Vogel D, Rosenthal M, Gogrefe N, Reindl S, Günther S. Biochemical characterization of the Lassa virus L protein. J Biol Chem 2019; 294:8088-8100. [PMID: 30926610 PMCID: PMC6527160 DOI: 10.1074/jbc.ra118.006973] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 03/19/2019] [Indexed: 12/25/2022] Open
Abstract
The L protein of arena- and bunyaviruses is structurally and functionally related to the orthomyxovirus polymerase complex. It plays a central role in the viral life cycle, as it replicates the virus genome and generates viral mRNA via a cap-snatching mechanism. Here, we aimed to biochemically characterize the L protein of Lassa virus, a human-pathogenic arenavirus endemic in West Africa. Full-length 250-kDa L protein was expressed using a baculovirus expression system. A low-resolution structure calculated from small-angle X-ray scattering data revealed a conformation similar to that in the crystal structure of the orthomyxovirus polymerase complex. Although the L protein did not exhibit cap-snatching endonuclease activity, it synthesized RNA in vitro. RNA polymerization required manganese rather than magnesium ions, was independent of nucleotide primers, and was inhibited by viral Z protein. Maximum activity was mediated by double-stranded promoter sequences with a minimum length of 17 nucleotides, containing a nontemplated 5′-G overhang, as in the natural genome context, as well as the naturally occurring base mismatches between the complementary promoter strands. Experiments with various short primers revealed the presence of two replication initiation sites at the template strand and evidence for primer translocation as proposed by the prime-and-realign hypothesis. Overall, our findings provide the foundation for a detailed understanding of the mechanistic differences and communalities in the polymerase proteins of segmented negative-strand RNA viruses and for the search for antiviral compounds targeting the RNA polymerase of Lassa virus.
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Affiliation(s)
- Dominik Vogel
- Department of Virology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, Hamburg 20359, Germany
| | - Maria Rosenthal
- Department of Virology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, Hamburg 20359, Germany
| | - Nadja Gogrefe
- Department of Virology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, Hamburg 20359, Germany
| | - Sophia Reindl
- Department of Virology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, Hamburg 20359, Germany.
| | - Stephan Günther
- Department of Virology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, Hamburg 20359, Germany; German Center for Infection Research (DZIF), Partner site Hamburg-Lübeck-Borstel-Riems, Hamburg 20359, Germany.
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12
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Mateer EJ, Paessler S, Huang C. Visualization of Double-Stranded RNA Colocalizing With Pattern Recognition Receptors in Arenavirus Infected Cells. Front Cell Infect Microbiol 2018; 8:251. [PMID: 30087859 PMCID: PMC6066581 DOI: 10.3389/fcimb.2018.00251] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 07/03/2018] [Indexed: 12/20/2022] Open
Abstract
An important step in the initiation of the innate immune response to virus infection is the recognition of non-self, viral RNA, including double-stranded RNA (dsRNA), by cytoplasmic pattern recognition receptors (PRRs). For many positive-sense RNA viruses and DNA viruses, the production of viral dsRNA, and the interaction of viral dsRNA and PRRs are well characterized. However, for negative-sense RNA viruses, viral dsRNA was thought to be produced at low to undetectable levels and PRR recognition of viral dsRNA is still largely unclear. In the case of arenaviruses, the nucleocaspid protein (NP) has been identified to contain an exoribonuclease activity that preferentially degrades dsRNA in biochemical studies. Nevertheless, pathogenic New World (NW) arenavirus infections readily induce an interferon (IFN) response in a RIG-I dependent manner, and also activate the dsRNA-dependent Protein Kinase R (PKR). To better understand the innate immune response to pathogenic arenavirus infection, we used a newly identified dsRNA-specific antibody that efficiently detects viral dsRNA in negative-sense RNA virus infected cells. dsRNA was detected in NW arenavirus infected cells colocalizing with virus NP in immunofluorescence assay. Importantly, the dsRNA signals also colocalized with cytoplasmic PRRs, namely, PKR, RIG-I and MDA-5, as well as with the phosphorylated, activated form of PKR in infected cells. Our data clearly demonstrate the PRR recognition of dsRNA and their activation in NW arenavirus infected cells. These findings provide new insights into the interaction between NW arenaviruses and the host innate immune response.
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Affiliation(s)
| | | | - Cheng Huang
- Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, United States
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13
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Zhang Y, Dittmer DP, Mieczkowski PA, Host KM, Fusco WG, Duncan JA, Damania B. RIG-I Detects Kaposi's Sarcoma-Associated Herpesvirus Transcripts in a RNA Polymerase III-Independent Manner. mBio 2018; 9:e00823-18. [PMID: 29970461 PMCID: PMC6030556 DOI: 10.1128/mbio.00823-18] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 06/04/2018] [Indexed: 12/24/2022] Open
Abstract
Retinoic acid-inducible gene I (RIG-I) is a cytosolic pathogen recognition receptor that initiates the innate immune response against many RNA viruses. We previously showed that RIG-I restricts Kaposi's sarcoma-associated herpesvirus (KSHV) reactivation (J. A. West et al., J Virol 88:5778-5787, 2014, https://doi.org/10.1128/JVI.03226-13). In this study, we report that KSHV stimulates the RIG-I signaling pathway in a RNA polymerase (Pol) III-independent manner and subsequently induces type I interferon (IFN) responses. Knockdown or inhibition of RNA Pol III had no effect on beta interferon (IFN-β) induction by KSHV. By using high-throughput sequencing of RNA isolated by cross-linking immunoprecipitation (HITS-CLIP) approach, we identified multiple KSHV regions that give rise to RNA fragments binding to RIG-I, such as ORF810420-10496, Repeat region (LIR1)119059-119204, and ORF2543561-43650 The sequence dissimilarity between these fragments suggests that RIG-I detects a particular structure rather than a specific sequence motif. Synthesized ORF810420-10496 RNA stimulated RIG-I-dependent but RNA Pol III-independent IFN-β signaling. In summary, several KSHV RNAs are sensed by RIG-I in a RNA Pol III-independent manner.IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. Innate immune responses against viral infections, especially the induction of type I interferon, are critical for limiting the replication of viruses. Retinoic acid-inducible gene I (RIG-I), a cytosolic RNA helicase sensor, plays a significant role in the induction of type I interferon responses following viral infection. Here, we identified multiple RNA regions in KSHV as potential virus ligands that bind to RIG-I and stimulate RIG-I-dependent but RNA Pol III-independent IFN-β signaling. Our results expand the role of RIG-I by providing an example of a DNA virus activating a canonical RNA-sensing pathway.
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Affiliation(s)
- Yugen Zhang
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Dirk P Dittmer
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Piotr A Mieczkowski
- High Throughput Sequencing Facility, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Kurtis M Host
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - William G Fusco
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Joseph A Duncan
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Blossom Damania
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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14
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Nanson JD, Rahaman MH, Ve T, Kobe B. Regulation of signaling by cooperative assembly formation in mammalian innate immunity signalosomes by molecular mimics. Semin Cell Dev Biol 2018; 99:96-114. [PMID: 29738879 DOI: 10.1016/j.semcdb.2018.05.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 03/18/2018] [Accepted: 05/04/2018] [Indexed: 12/16/2022]
Abstract
Innate immunity pathways constitute the first line of defense against infections and cellular damage. An emerging concept in these pathways is that signaling involves the formation of finite (e.g. rings in NLRs) or open-ended higher-order assemblies (e.g. filamentous assemblies by members of the death-fold family and TIR domains). This signaling by cooperative assembly formation (SCAF) mechanism allows rapid and strongly amplified responses to minute amounts of stimulus. While the characterization of the molecular mechanisms of SCAF has seen rapid progress, little is known about its regulation. One emerging theme involves proteins produced both in host cells and by pathogens that appear to mimic the signaling components. Recently characterized examples involve the capping of the filamentous assemblies formed by caspase-1 CARDs by the CARD-only protein INCA, and those formed by caspase-8 by the DED-containing protein MC159. By contrast, the CARD-only protein ICEBERG and the DED-containing protein cFLIP incorporate into signaling filaments and presumably interfere with proximity based activation of caspases. We review selected examples of SCAF in innate immunity pathways and focus on the current knowledge on signaling component mimics produced by mammalian and pathogen cells and what is known about their mechanisms of action.
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Affiliation(s)
- Jeffrey D Nanson
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD, 4072, Australia
| | - Md Habibur Rahaman
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD, 4072, Australia
| | - Thomas Ve
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD, 4072, Australia; Institute for Glycomics, Griffith University, Southport, QLD, 4222, Australia
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD, 4072, Australia.
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15
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Palmer CR, Jacobson ME, Fedorova O, Pyle AM, Wilson JT. Environmentally Triggerable Retinoic Acid-Inducible Gene I Agonists Using Synthetic Polymer Overhangs. Bioconjug Chem 2018; 29:742-747. [PMID: 29350913 PMCID: PMC6407425 DOI: 10.1021/acs.bioconjchem.7b00697] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Retinoic acid-inducible gene I (RIG-I) is a cytosolic pattern recognition receptor (PRR) that potently activates antiviral innate immunity upon recognition of 5' triphosphorylated double-stranded RNA (pppRNA). Accordingly, RNA ligands of the RIG-I pathway have recently emerged as promising antiviral agents, vaccine adjuvants, and cancer immunotherapeutics. However, RIG-I is expressed constitutively in virtually all cell types, and therefore administration of RIG-I agonists causes risk for systemic inflammation and possible dose-limiting toxicities. Here, we establish proof-of-concept and initial design criteria for pppRNA prodrugs capable of activating the RIG-I pathway in response to specific environmental stimuli. We show that covalent conjugation of poly(ethylene glycol) (PEG) to the 3' end of the complementary strand, i.e., on the same side but opposite strand as the 5' triphosphate group, can generate a synthetic overhang that prevents RIG-I activation. Additionally, conjugation of PEG through a cleavable linker-here, a reducible disulfide bond-allows for removal of the synthetic overhang and restoration of immunostimulatory activity. Furthermore, we demonstrate that blockade of RIG-I activation via synthetic overhangs is dependent on PEG molecular weight, with a critical molecular weight between 550 and 1000 Da required to inhibit activity. Additionally, we demonstrate that blockade of RIG-I activity is conjugation site-dependent, as ligation of PEG to the opposite end of the RNA did not influence ligand activity. Collectively, this work demonstrates that conjugation of synthetic polymer overhangs to pppRNA through cleavable linkers is a viable strategy for the development of environmentally triggerable RIG-I-targeting prodrugs.
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Affiliation(s)
- Christian R. Palmer
- Department of Chemical and Biomolecular Engineering; Vanderbilt University Nashville, TN 37235, USA
| | - Max E. Jacobson
- Department of Chemical and Biomolecular Engineering; Vanderbilt University Nashville, TN 37235, USA
| | - Olga Fedorova
- Department of Molecular, Cellular and Developmental Biology; Yale University New Haven, CT 06511
| | - Anna M. Pyle
- Department of Molecular, Cellular and Developmental Biology; Yale University New Haven, CT 06511
- Department of Chemistry, Howard Hughes Medical Institute, Yale University
| | - John T. Wilson
- Department of Chemical and Biomolecular Engineering; Vanderbilt University Nashville, TN 37235, USA
- Department of Biomedical Engineering; Vanderbilt University
- Vanderbilt Center for Immunobiology; Vanderbilt University
- Vanderbilt Institute for Infection, Immunology and Inflammation; Vanderbilt University
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16
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Yoshida A, Kawabata R, Honda T, Sakai K, Ami Y, Sakaguchi T, Irie T. A Single Amino Acid Substitution within the Paramyxovirus Sendai Virus Nucleoprotein Is a Critical Determinant for Production of Interferon-Beta-Inducing Copyback-Type Defective Interfering Genomes. J Virol 2018; 92:e02094-17. [PMID: 29237838 PMCID: PMC5809723 DOI: 10.1128/jvi.02094-17] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 12/06/2017] [Indexed: 12/12/2022] Open
Abstract
One of the first defenses against infecting pathogens is the innate immune system activated by cellular recognition of pathogen-associated molecular patterns (PAMPs). Although virus-derived RNA species, especially copyback (cb)-type defective interfering (DI) genomes, have been shown to serve as real PAMPs, which strongly induce interferon-beta (IFN-β) during mononegavirus infection, the mechanisms underlying DI generation remain unclear. Here, for the first time, we identified a single amino acid substitution causing production of cbDI genomes by successful isolation of two distinct types of viral clones with cbDI-producing and cbDI-nonproducing phenotypes from the stock Sendai virus (SeV) strain Cantell, which has been widely used in a number of studies on antiviral innate immunity as a representative IFN-β-inducing virus. IFN-β induction was totally dependent on the presence of a significant amount of cbDI genome-containing viral particles (DI particles) in the viral stock, but not on deficiency of the IFN-antagonistic viral accessory proteins C and V. Comparison of the isolates indicated that a single amino acid substitution found within the N protein of the cbDI-producing clone was enough to cause the emergence of DI genomes. The mutated N protein of the cbDI-producing clone resulted in a lower density of nucleocapsids than that of the DI-nonproducing clone, probably causing both production of the DI genomes and their formation of a stem-loop structure, which serves as an ideal ligand for RIG-I. These results suggested that the integrity of mononegaviral nucleocapsids might be a critical factor in avoiding the undesirable recognition of infection by host cells.IMPORTANCE The type I interferon (IFN) system is a pivotal defense against infecting RNA viruses that is activated by sensing viral RNA species. RIG-I is a major sensor for infection with most mononegaviruses, and copyback (cb)-type defective interfering (DI) genomes have been shown to serve as strong RIG-I ligands in real infections. However, the mechanism underlying production of cbDI genomes remains unclear, although DI genomes emerge as the result of an error during viral replication with high doses of viruses. Sendai virus has been extensively studied and is unique in that its interaction with innate immunity reveals opposing characteristics, such as high-level IFN-β induction and strong inhibition of type I IFN pathways. Our findings provide novel insights into the mechanism of production of mononegaviral cbDI genomes, as well as virus-host interactions during innate immunity.
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Affiliation(s)
- Asuka Yoshida
- Department of Virology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Ryoko Kawabata
- Department of Virology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Tomoyuki Honda
- Division of Virology, Department of Microbiology and Immunology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kouji Sakai
- Department of Virology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yasushi Ami
- Division of Experimental Animal Research, National Institute of Infectious Diseases, Tokyo, Japan
| | - Takemasa Sakaguchi
- Department of Virology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Takashi Irie
- Department of Virology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
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17
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Molecular requirements for sensing of intracellular microbial nucleic acids by the innate immune system. Cytokine 2017; 98:4-14. [DOI: 10.1016/j.cyto.2016.10.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 10/11/2016] [Indexed: 12/24/2022]
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18
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Abstract
Hemorrhagic fevers caused by viruses were identified in the late 1950s in South America. These viruses have existed in their hosts, the New World rodents, for millions of years. Their emergence as infectious agents in humans coincided with changes in the environment and farming practices that caused explosions in their host rodent populations. Zoonosis into humans likely occurs because the pathogenic New World arenaviruses use human transferrin receptor 1 to enter cells. The mortality rate after infection with these viruses is high, but the mechanism by which disease is induced is still not clear. Possibilities include direct effects of cellular infection or the induction of high levels of cytokines by infected sentinel cells of the immune system, leading to endothelia and thrombocyte dysfunction and neurological disease. Here we provide a review of the ecology and molecular and cellular biology of New World arenaviruses, as well as a discussion of the current animal models of infection. The development of animal models, coupled with an improved understanding of the infection pathway and host response, should lead to the discovery of new drugs for treating infections.
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Affiliation(s)
- Nicolás Sarute
- Department of Microbiology and Immunology, University of Illinois College of Medicine at Chicago, Chicago, Illinois 60612; ,
| | - Susan R Ross
- Department of Microbiology and Immunology, University of Illinois College of Medicine at Chicago, Chicago, Illinois 60612; ,
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19
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Ferron F, Weber F, de la Torre JC, Reguera J. Transcription and replication mechanisms of Bunyaviridae and Arenaviridae L proteins. Virus Res 2017; 234:118-134. [PMID: 28137457 PMCID: PMC7114536 DOI: 10.1016/j.virusres.2017.01.018] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/17/2017] [Accepted: 01/21/2017] [Indexed: 12/15/2022]
Abstract
Bunyavirus and arenavirus are important public health threats. Bunyavirus and arenavirus molecular biology, common and differential features. Implications of LACV L protein structure for understanding viral RNA synthesis. Current state and future perspectives on bunya- and arenavirus antivirals.
Bunyaviridae and Arenaviridae virus families include an important number of highly pathogenic viruses for humans. They are enveloped viruses with negative stranded RNA genomes divided into three (bunyaviruses) or two (arenaviruses) segments. Each genome segment is coated by the viral nucleoproteins (NPs) and the polymerase (L protein) to form a functional ribonucleoprotein (RNP) complex. The viral RNP provides the necessary context on which the L protein carries out the biosynthetic processes of RNA replication and gene transcription. Decades of research have provided a good understanding of the molecular processes underlying RNA synthesis, both RNA replication and gene transcription, for these two families of viruses. In this review we will provide a global view of the common features, as well as differences, of the molecular biology of Bunyaviridae and Arenaviridae. We will also describe structures of protein and protein-RNA complexes so far determined for these viral families, mainly focusing on the L protein, and discuss their implications for understanding the mechanisms of viral RNA replication and gene transcription within the architecture of viral RNPs, also taking into account the cellular context in which these processes occur. Finally, we will discuss the implications of these structural findings for the development of antiviral drugs to treat human diseases caused by members of the Bunyaviridae and Arenaviridae families.
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Affiliation(s)
- François Ferron
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France
| | - Friedemann Weber
- Institute for Virology, FB10-Veterinary Medicine, Justus-Liebig University, D-35392 Giessen, Germany
| | | | - Juan Reguera
- Aix-Marseille Université, AFMB UMR 7257, 13288 Marseille, France; CNRS, AFMB UMR 7257, 13288 Marseille, France; INSERM, AFMB UMR 7257, 13288 Marseille, France.
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20
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Liu Y, Olagnier D, Lin R. Host and Viral Modulation of RIG-I-Mediated Antiviral Immunity. Front Immunol 2017; 7:662. [PMID: 28096803 PMCID: PMC5206486 DOI: 10.3389/fimmu.2016.00662] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 12/16/2016] [Indexed: 12/21/2022] Open
Abstract
Innate immunity is the first line of defense against invading pathogens. Rapid and efficient detection of pathogen-associated molecular patterns via pattern-recognition receptors is essential for the host to mount defensive and protective responses. Retinoic acid-inducible gene-I (RIG-I) is critical in triggering antiviral and inflammatory responses for the control of viral replication in response to cytoplasmic virus-specific RNA structures. Upon viral RNA recognition, RIG-I recruits the mitochondrial adaptor protein mitochondrial antiviral signaling protein, which leads to a signaling cascade that coordinates the induction of type I interferons (IFNs), as well as a large variety of antiviral interferon-stimulated genes. The RIG-I activation is tightly regulated via various posttranslational modifications for the prevention of aberrant innate immune signaling. By contrast, viruses have evolved mechanisms of evasion, such as sequestrating viral structures from RIG-I detections and targeting receptor or signaling molecules for degradation. These virus–host interactions have broadened our understanding of viral pathogenesis and provided insights into the function of the RIG-I pathway. In this review, we summarize the recent advances regarding RIG-I pathogen recognition and signaling transduction, cell-intrinsic control of RIG-I activation, and the viral antagonism of RIG-I signaling.
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Affiliation(s)
- Yiliu Liu
- Jewish General Hospital, Lady Davis Institute, McGill University, Montreal, QC, Canada; Division of Experimental Medicine, McGill University, Montreal, QC, Canada
| | - David Olagnier
- Jewish General Hospital, Lady Davis Institute, McGill University, Montreal, QC, Canada; Division of Experimental Medicine, McGill University, Montreal, QC, Canada
| | - Rongtuan Lin
- Jewish General Hospital, Lady Davis Institute, McGill University, Montreal, QC, Canada; Division of Experimental Medicine, McGill University, Montreal, QC, Canada; Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
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21
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Abstract
Organisms throughout biology need to maintain the integrity of their genome. From bacteria to vertebrates, life has established sophisticated mechanisms to detect and eliminate foreign genetic material or to restrict its function and replication. Tremendous progress has been made in the understanding of these mechanisms which keep foreign or unwanted nucleic acids from viruses or phages in check. Mechanisms reach from restriction-modification systems and CRISPR/Cas in bacteria and archaea to RNA interference and immune sensing of nucleic acids, altogether integral parts of a system which is now appreciated as nucleic acid immunity. With inherited receptors and acquired sequence information, nucleic acid immunity comprises innate and adaptive components. Effector functions include diverse nuclease systems, intrinsic activities to directly restrict the function of foreign nucleic acids (e.g., PKR, ADAR1, IFIT1), and extrinsic pathways to alert the immune system and to elicit cytotoxic immune responses. These effects act in concert to restrict viral replication and to eliminate virus-infected cells. The principles of nucleic acid immunity are highly relevant for human disease. Besides its essential contribution to antiviral defense and restriction of endogenous retroelements, dysregulation of nucleic acid immunity can also lead to erroneous detection and response to self nucleic acids then causing sterile inflammation and autoimmunity. Even mechanisms of nucleic acid immunity which are not established in vertebrates are relevant for human disease when they are present in pathogens such as bacteria, parasites, or helminths or in pathogen-transmitting organisms such as insects. This review aims to provide an overview of the diverse mechanisms of nucleic acid immunity which mostly have been looked at separately in the past and to integrate them under the framework nucleic acid immunity as a basic principle of life, the understanding of which has great potential to advance medicine.
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Affiliation(s)
- G Hartmann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital, University of Bonn, Bonn, Germany.
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22
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Abstract
Immune sensing of foreign nucleic acids among abundant self nucleic acids is a hallmark of virus detection and antiviral defence. Efficient antiviral defence requires a balanced process of sensing foreign nucleic acids and ignoring self nucleic acids. This balance is accomplished by a multilevel, fail-safe system which combines immune sensing of pathogen-specific nucleic acid structures with specific labelling of self nucleic acids and nuclease-mediated degradation. Cellular localization of nucleic acids, nucleic acid secondary structure, nucleic acid sequence and chemical modification all contribute to selective recognition of foreign nucleic acids. Nucleic acid sensing occurs in immune cells and non-immune cells and results in antiviral responses that include the induction of antiviral effector proteins, the secretion of cytokines alarming neighbouring cells, the secretion of chemokines, which attract immune cells, and the induction of cell death. Vertebrate cells cannot completely avoid the occurrence of endogenous self nucleic acid structures with immunostimulatory properties. Therefore, additional mechanisms involving self-nucleic acid modification and nuclease-mediated degradation are necessary to diminish uncontrolled immune activation. Viruses have established sophisticated mechanisms to exploit and adopt endogenous tolerance mechanisms or to avoid the presentation of characteristic molecular features recognized by nucleic acid sensing receptors.
The detection of viruses by the immune system is mediated predominantly by the sensing of nucleic acids. Here, the authors review our current understanding of how this complex immune sensory system discriminates self from non-self nucleic acids to reliably detect pathogenic viruses, and discuss the future perspectives and implications for human disease. Innate immunity against pathogens relies on an array of immune receptors to detect molecular patterns that are characteristic of the pathogens, including receptors that are specialized in the detection of foreign nucleic acids. In vertebrates, nucleic acid sensing is the dominant antiviral defence pathway. Stimulation of nucleic acid receptors results in antiviral immune responses with the production of type I interferon (IFN), as well as the expression of IFN-stimulated genes, which encode molecules such as cell-autonomous antiviral effector proteins. This Review summarizes the tremendous progress that has been made in understanding how this sophisticated immune sensory system discriminates self from non-self nucleic acids in order to reliably detect pathogenic viruses.
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Affiliation(s)
- Martin Schlee
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital, University of Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany
| | - Gunther Hartmann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital, University of Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany
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23
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Abstract
The co-evolution of viruses with their hosts has led to the emergence of viral pathogens that are adept at evading or actively suppressing host immunity. Pattern recognition receptors (PRRs) are key components of antiviral immunity that detect conserved molecular features of viral pathogens and initiate signalling that results in the expression of antiviral genes. In this Review, we discuss the strategies that viruses use to escape immune surveillance by key intracellular sensors of viral RNA or DNA, with a focus on RIG-I-like receptors (RLRs), cyclic GMP-AMP synthase (cGAS) and interferon-γ (IFNγ)-inducible protein 16 (IFI16). Such viral strategies include the sequestration or modification of viral nucleic acids, interference with specific post-translational modifications of PRRs or their adaptor proteins, the degradation or cleavage of PRRs or their adaptors, and the sequestration or relocalization of PRRs. An understanding of viral immune-evasion mechanisms at the molecular level may guide the development of vaccines and antivirals.
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Affiliation(s)
- Ying Kai Chan
- grid.38142.3c000000041936754XDepartment of Microbiology and Immunobiology, Harvard Medical School, Boston, 02115 Massachusetts USA
| | - Michaela U. Gack
- grid.170205.10000 0004 1936 7822Department of Microbiology, The University of Chicago, Chicago, 60637 Illinois USA
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24
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Ramanathan A, Devarkar SC, Jiang F, Miller MT, Khan AG, Marcotrigiano J, Patel SS. The autoinhibitory CARD2-Hel2i Interface of RIG-I governs RNA selection. Nucleic Acids Res 2016; 44:896-909. [PMID: 26612866 PMCID: PMC4737149 DOI: 10.1093/nar/gkv1299] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Revised: 10/30/2015] [Accepted: 11/05/2015] [Indexed: 12/24/2022] Open
Abstract
RIG-I (Retinoic Acid Inducible Gene-I) is a cytosolic innate immune receptor that detects atypical features in viral RNAs as foreign to initiate a Type I interferon signaling response. RIG-I is present in an autoinhibited state in the cytoplasm and activated by blunt-ended double-stranded (ds)RNAs carrying a 5' triphosphate (ppp) moiety. These features found in many pathogenic RNAs are absent in cellular RNAs due to post-transcriptional modifications of RNA ends. Although RIG-I is structurally well characterized, the mechanistic basis for RIG-I's remarkable ability to discriminate between cellular and pathogenic RNAs is not completely understood. We show that RIG-I's selectivity for blunt-ended 5'-ppp dsRNAs is ≈3000 times higher than non-blunt ended dsRNAs commonly found in cellular RNAs. Discrimination occurs at multiple stages and signaling RNAs have high affinity and ATPase turnover rate and thus a high katpase/Kd. We show that RIG-I uses its autoinhibitory CARD2-Hel2i (second CARD-helicase insertion domain) interface as a barrier to select against non-blunt ended dsRNAs. Accordingly, deletion of CARDs or point mutations in the CARD2-Hel2i interface decreases the selectivity from ≈3000 to 150 and 750, respectively. We propose that the CARD2-Hel2i interface is a 'gate' that prevents cellular RNAs from generating productive complexes that can signal.
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Affiliation(s)
- Anand Ramanathan
- Robert Wood Johnson Medical School, Department of Biochemistry and Molecular Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Swapnil C Devarkar
- Robert Wood Johnson Medical School, Department of Biochemistry and Molecular Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Fuguo Jiang
- Center for Advanced Biotechnology and Medicine, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Matthew T Miller
- Center for Advanced Biotechnology and Medicine, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Abdul G Khan
- Center for Advanced Biotechnology and Medicine, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Joseph Marcotrigiano
- Center for Advanced Biotechnology and Medicine, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Smita S Patel
- Robert Wood Johnson Medical School, Department of Biochemistry and Molecular Biology, Rutgers University, Piscataway, NJ 08854, USA
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25
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Anchisi S, Guerra J, Mottet-Osman G, Garcin D. Mismatches in the Influenza A Virus RNA Panhandle Prevent Retinoic Acid-Inducible Gene I (RIG-I) Sensing by Impairing RNA/RIG-I Complex Formation. J Virol 2016; 90:586-90. [PMID: 26446607 PMCID: PMC4702558 DOI: 10.1128/jvi.01671-15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 10/05/2015] [Indexed: 11/20/2022] Open
Abstract
Influenza virus RNA (vRNA) promoter panhandle structures are believed to be sensed by retinoic acid-inducible gene I (RIG-I). The occurrence of mismatches in this double-stranded RNA structure raises questions about their effect on innate sensing. Our results suggest that mismatches in vRNA promoters decrease binding to RIG-I in vivo, affecting RNA/RIG-I complex formation and preventing RIG-I activation. These results can be inferred to apply to other viruses and suggest that mismatches may represent a general viral strategy to escape RIG-I sensing.
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Affiliation(s)
- Stéphanie Anchisi
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Jessica Guerra
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Geneviève Mottet-Osman
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Dominique Garcin
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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26
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Pythoud C, Rothenberger S, Martínez-Sobrido L, de la Torre JC, Kunz S. Lymphocytic Choriomeningitis Virus Differentially Affects the Virus-Induced Type I Interferon Response and Mitochondrial Apoptosis Mediated by RIG-I/MAVS. J Virol 2015; 89:6240-50. [PMID: 25833049 PMCID: PMC4474305 DOI: 10.1128/jvi.00610-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 03/26/2015] [Indexed: 01/03/2023] Open
Abstract
UNLABELLED Arenaviruses are important emerging human pathogens maintained by noncytolytic persistent infection in their rodent reservoir hosts. Despite high levels of viral replication, persistently infected carrier hosts show only mildly elevated levels of type I interferon (IFN-I). Accordingly, the arenavirus nucleoprotein (NP) has been identified as a potent IFN-I antagonist capable of blocking activation of interferon regulatory factor 3 (IRF3) via the retinoic acid inducible gene (RIG)-I/mitochondrial antiviral signaling (MAVS) pathway. Another important mechanism of host innate antiviral defense is represented by virus-induced mitochondrial apoptosis via RIG-I/MAVS and IRF3. In the present study, we investigated the ability of the prototypic Old World arenavirus lymphocytic choriomeningitis virus (LCMV) to interfere with RIG-I/MAVS-dependent apoptosis. We found that LCMV does not induce apoptosis at any time during infection. While LCMV efficiently blocked induction of IFN-I via RIG-I/MAVS in response to superinfection with cytopathic RNA viruses, virus-induced mitochondrial apoptosis remained fully active in LCMV-infected cells. Notably, in LCMV-infected cells, RIG-I was dispensable for virus-induced apoptosis via MAVS. Our study reveals that LCMV infection efficiently suppresses induction of IFN-I but does not interfere with the cell's ability to undergo virus-induced mitochondrial apoptosis as a strategy of innate antiviral defense. The RIG-I independence of mitochondrial apoptosis in LCMV-infected cells provides the first evidence that arenaviruses can reshape apoptotic signaling according to their needs. IMPORTANCE Arenaviruses are important emerging human pathogens that are maintained in their rodent hosts by persistent infection. Persistent virus is able to subvert the cellular interferon response, a powerful branch of the innate antiviral defense. Here, we investigated the ability of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) to interfere with the induction of programmed cell death, or apoptosis, in response to superinfection with cytopathic RNA viruses. Upon viral challenge, persistent LCMV efficiently blocked induction of interferons, whereas virus-induced apoptosis remained fully active in LCMV-infected cells. Our studies reveal that the persistent virus is able to reshape innate apoptotic signaling in order to prevent interferon production while maintaining programmed cell death as a strategy for innate defense. The differential effect of persistent virus on the interferon response versus its effect on apoptosis appears as a subtle strategy to guarantee sufficiently high viral loads for efficient transmission while maintaining apoptosis as a mechanism of defense.
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Affiliation(s)
- Christelle Pythoud
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Sylvia Rothenberger
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Luis Martínez-Sobrido
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, USA
| | - Juan Carlos de la Torre
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA
| | - Stefan Kunz
- Institute of Microbiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland
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27
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Abstract
Antiviral immunity is initiated upon host recognition of viral products via non-self molecular patterns known as pathogen-associated molecular patterns (PAMPs). Such recognition initiates signaling cascades that induce intracellular innate immune defenses and an inflammatory response that facilitates development of the acquired immune response. The retinoic acid-inducible gene I (RIG-I) and the RIG-I-like receptor (RLR) protein family are key cytoplasmic pathogen recognition receptors that are implicated in the recognition of viruses across genera and virus families, including functioning as major sensors of RNA viruses, and promoting recognition of some DNA viruses. RIG-I, the charter member of the RLR family, is activated upon binding to PAMP RNA. Activated RIG-I signals by interacting with the adapter protein MAVS leading to a signaling cascade that activates the transcription factors IRF3 and NF-κB. These actions induce the expression of antiviral gene products and the production of type I and III interferons that lead to an antiviral state in the infected cell and surrounding tissue. RIG-I signaling is essential for the control of infection by many RNA viruses. Recently, RIG-I crosstalk with other pathogen recognition receptors and components of the inflammasome has been described. In this review, we discuss the current knowledge regarding the role of RIG-I in recognition of a variety of virus families and its role in programming the adaptive immune response through cross-talk with parallel arms of the innate immune system, including how RIG-I can be leveraged for antiviral therapy.
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Affiliation(s)
- Alison M Kell
- Center for Innate Immunity and Immune Disease, Department of Immunology, University of Washington School of Medicine, Seattle, WA, USA
| | - Michael Gale
- Center for Innate Immunity and Immune Disease, Department of Immunology, University of Washington School of Medicine, Seattle, WA, USA.
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28
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Louber J, Kowalinski E, Bloyet LM, Brunel J, Cusack S, Gerlier D. RIG-I self-oligomerization is either dispensable or very transient for signal transduction. PLoS One 2014; 9:e108770. [PMID: 25259935 PMCID: PMC4178188 DOI: 10.1371/journal.pone.0108770] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 09/04/2014] [Indexed: 01/01/2023] Open
Abstract
Effective host defence against viruses depends on the rapid triggering of innate immunity through the induction of a type I interferon (IFN) response. To this end, microbe-associated molecular patterns are detected by dedicated receptors. Among them, the RIG-I-like receptors RIG-I and MDA5 activate IFN gene expression upon sensing viral RNA in the cytoplasm. While MDA5 forms long filaments in vitro upon activation, RIG-I is believed to oligomerize after RNA binding in order to transduce a signal. Here, we show that in vitro binding of synthetic RNA mimicking that of Mononegavirales (Ebola, rabies and measles viruses) leader sequences to purified RIG-I does not induce RIG-I oligomerization. Furthermore, in cells devoid of endogenous functional RIG-I-like receptors, after activation of exogenous Flag-RIG-I by a 62-mer-5'ppp-dsRNA or by polyinosinic:polycytidylic acid, a dsRNA analogue, or by measles virus infection, anti-Flag immunoprecipitation and specific elution with Flag peptide indicated a monomeric form of RIG-I. Accordingly, when using the Gaussia Luciferase-Based Protein Complementation Assay (PCA), a more sensitive in cellula assay, no RIG-I oligomerization could be detected upon RNA stimulation. Altogether our data indicate that the need for self-oligomerization of RIG-I for signal transduction is either dispensable or very transient.
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Affiliation(s)
- Jade Louber
- Centre International de Recherche en Infectiologie, INSERM, U1111, CNRS, UMR5308, Université Lyon 1, ENS Lyon, Lyon, France
| | - Eva Kowalinski
- European Molecular Biology Laboratory, Grenoble Outstation, Grenoble Cedex 9, France
- Unit of Virus Host-Cell Interactions, UJF-EMBL-CNRS, UMI 3265, Grenoble Cedex 9, France
| | - Louis-Marie Bloyet
- Centre International de Recherche en Infectiologie, INSERM, U1111, CNRS, UMR5308, Université Lyon 1, ENS Lyon, Lyon, France
| | - Joanna Brunel
- Centre International de Recherche en Infectiologie, INSERM, U1111, CNRS, UMR5308, Université Lyon 1, ENS Lyon, Lyon, France
| | - Stephen Cusack
- European Molecular Biology Laboratory, Grenoble Outstation, Grenoble Cedex 9, France
- Unit of Virus Host-Cell Interactions, UJF-EMBL-CNRS, UMI 3265, Grenoble Cedex 9, France
| | - Denis Gerlier
- Centre International de Recherche en Infectiologie, INSERM, U1111, CNRS, UMR5308, Université Lyon 1, ENS Lyon, Lyon, France
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29
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Iwasaki M, Urata S, Cho Y, Ngo N, de la Torre JC. Cell entry of lymphocytic choriomeningitis virus is restricted in myotubes. Virology 2014; 458-459:22-32. [PMID: 24928036 DOI: 10.1016/j.virol.2014.04.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 02/25/2014] [Accepted: 04/08/2014] [Indexed: 11/27/2022]
Abstract
In mice persistently infected since birth with the prototypic arenavirus lymphocytic choriomeningitis viurs, viral antigen and RNA are readily detected in most organs and cell types but remarkably absent in skeletal muscle. Here we report that mouse C2C12 myoblasts that are readily infected by LCMV, become highly refractory to LCMV infection upon their differentiation into myotubes. Myotube's resistance to LCMV was not due to an intracellular restriction of virus replication but rather an impaired cell entry mediated by the LCMV surface glycoprotein. Our findings provide an explanation for the observation that in LCMV carrier mice myotubes, which are constantly exposed to blood-containing virus, remain free of viral antigen and RNA despite myotubes express high levels of the LCMV receptor alpha dystroglycan and do not pose an intracellular blockade to LCMV multiplication.
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Affiliation(s)
- Masaharu Iwasaki
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA, USA
| | - Shuzo Urata
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA, USA
| | - Yoshitake Cho
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA
| | - Nhi Ngo
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA, USA
| | - Juan C de la Torre
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA, USA.
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30
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Killip MJ, Smith M, Jackson D, Randall RE. Activation of the interferon induction cascade by influenza a viruses requires viral RNA synthesis and nuclear export. J Virol 2014; 88:3942-52. [PMID: 24478437 PMCID: PMC3993719 DOI: 10.1128/jvi.03109-13] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 01/19/2014] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED We have examined the requirements for virus transcription and replication and thus the roles of input and progeny genomes in the generation of interferon (IFN)-inducing pathogen-associated molecular patterns (PAMPs) by influenza A viruses using inhibitors of these processes. Using IFN regulatory factor 3 (IRF3) phosphorylation as a marker of activation of the IFN induction cascade that occurs upstream of the IFN-β promoter, we demonstrate strong activation of the IFN induction cascade in A549 cells infected with a variety of influenza A viruses in the presence of cycloheximide or nucleoprotein (NP) small interfering RNA (siRNA), which inhibits viral protein synthesis and thus complementary ribonucleoprotein (cRNP) and progeny viral RNP (vRNP) synthesis. In contrast, activation of the IFN induction cascade by influenza viruses was very effectively abrogated by treatment with actinomycin D and other transcription inhibitors, which correlated with the inhibition of the synthesis of all viral RNA species. Furthermore, 5,6-dichloro-1-β-d-ribofuranosyl-benzimidazole, an inhibitor that prevents viral RNA export from the nucleus, was also a potent inhibitor of IRF3 activation; thus, both viral RNA synthesis and nuclear export are required for IFN induction by influenza A viruses. While the exact nature of the viral PAMPs remains to be determined, our data suggest that in this experimental system the major influenza A virus PAMPs are distinct from those of incoming genomes or progeny vRNPs. IMPORTANCE The host interferon system exerts an extremely potent antiviral response that efficiently restricts virus replication and spread; the interferon response can thus dictate the outcome of a virus infection, and it is therefore important to understand how viruses induce interferon. Both input and progeny genomes have been linked to interferon induction by influenza viruses. However, our experiments in tissue culture cells show that viral RNA synthesis and nuclear export are required to activate this response. Furthermore, the interferon induction cascade is activated under conditions in which the synthesis of progeny genomes is inhibited. Therefore, in tissue culture cells, input and progeny genomes are not the predominant inducers of interferon generated by influenza A viruses; the major viral interferon inducer(s) still remains to be identified.
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Affiliation(s)
- Marian J Killip
- School of Biology, Biomedical Sciences Research Complex, North Haugh, University of St. Andrews, St. Andrews, Fife, United Kingdom
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31
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Schlee M. Master sensors of pathogenic RNA - RIG-I like receptors. Immunobiology 2013; 218:1322-35. [PMID: 23896194 PMCID: PMC7114584 DOI: 10.1016/j.imbio.2013.06.007] [Citation(s) in RCA: 176] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 05/27/2013] [Accepted: 06/05/2013] [Indexed: 12/25/2022]
Abstract
Initiating the immune response to invading pathogens, the innate immune system is constituted of immune receptors (pattern recognition receptors, PRR) that sense microbe-associated molecular patterns (MAMPs). Detection of pathogens triggers intracellular defense mechanisms, such as the secretion of cytokines or chemokines to alarm neighboring cells and attract or activate immune cells. The innate immune response to viruses is mostly based on PRRs that detect the unusual structure, modification or location of viral nucleic acids. Most of the highly pathogenic and emerging viruses are RNA genome-based viruses, which can give rise to zoonotic and epidemic diseases or cause viral hemorrhagic fever. As viral RNA is located in the same compartment as host RNA, PRRs in the cytosol have to discriminate between viral and endogenous RNA by virtue of their structure or modification. This challenging task is taken on by the homologous cytosolic DExD/H-box family helicases RIG-I and MDA5, which control the innate immune response to most RNA viruses. This review focuses on the molecular basis for RIG-I like receptor (RLR) activation by synthetic and natural ligands and will discuss controversial ligand definitions.
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Affiliation(s)
- Martin Schlee
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, 53105 Bonn, Germany.
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32
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Koma T, Huang C, Kolokoltsova OA, Brasier AR, Paessler S. Innate immune response to arenaviral infection: a focus on the highly pathogenic New World hemorrhagic arenaviruses. J Mol Biol 2013; 425:4893-903. [PMID: 24075870 PMCID: PMC3864108 DOI: 10.1016/j.jmb.2013.09.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/19/2013] [Accepted: 09/22/2013] [Indexed: 12/13/2022]
Abstract
Arenaviruses are enveloped, negative-stranded RNA viruses that belong to the family Arenaviridae. This diverse family can be further classified into OW (Old World) and NW (New World) arenaviruses based on their antigenicity, phylogeny, and geographical distribution. Many of the NW arenaviruses are highly pathogenic viruses that cause systemic human infections characterized by hemorrhagic fever and/or neurological manifestations, constituting public health problems in their endemic regions. NW arenavirus infection induces a variety of host innate immune responses, which could contribute to the viral pathogenesis and/or influence the final outcome of virus infection in vitro and in vivo. On the other hand, NW arenaviruses have also developed several strategies to counteract the host innate immune response. We will review current knowledge regarding the interplay between the host innate immune response and NW arenavirus infection in vitro and in vivo, with emphasis on viral-encoded proteins and their effect on the type I interferon response. NW arenaviruses induce a variety of host innate immune responses. The arenaviruses have several strategies to counteract host innate immune response. We review the interplay between host innate immunity and the arenavirus infections.
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Affiliation(s)
- Takaaki Koma
- Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX 77550, USA
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33
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Abstract
Cells are equipped with mechanisms that allow them to rapidly detect and respond to viruses. These defense mechanisms rely partly on receptors that monitor the cytosol for the presence of atypical nucleic acids associated with virus infection. RIG-I-like receptors detect RNA molecules that are absent from the uninfected host. DNA receptors alert the cell to the abnormal presence of that nucleic acid in the cytosol. Signaling by RNA and DNA receptors results in the induction of restriction factors that prevent virus replication and establish cell-intrinsic antiviral immunity. In light of these formidable obstacles, viruses have evolved mechanisms of evasion, masking nucleic acid structures recognized by the host, sequestering themselves away from the cytosol or targeting host sensors, and signaling adaptors for deactivation or degradation. Here, we detail recent advances in the molecular understanding of cytosolic nucleic acid detection and its evasion by viruses.
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Affiliation(s)
- Delphine Goubau
- Immunobiology Laboratory, Cancer Research UK London Research Institute, 44 Lincoln’s Inn Fields, London WC2A 3LY, UK
| | - Safia Deddouche
- Immunobiology Laboratory, Cancer Research UK London Research Institute, 44 Lincoln’s Inn Fields, London WC2A 3LY, UK
| | - Caetano Reis e Sousa
- Immunobiology Laboratory, Cancer Research UK London Research Institute, 44 Lincoln’s Inn Fields, London WC2A 3LY, UK
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34
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Kolakofsky D, Kowalinski E, Cusack S. A structure-based model of RIG-I activation. RNA (NEW YORK, N.Y.) 2012; 18:2118-27. [PMID: 23118418 PMCID: PMC3504664 DOI: 10.1261/rna.035949.112] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
A series of high-resolution crystal structures of RIG-I and RIG-I:dsRNA cocrystals has recently been reported. Comparison of these structures provides considerable insight into how this innate immune pattern recognition receptor is activated upon detecting and binding a certain class of viral RNAs.
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Affiliation(s)
- Daniel Kolakofsky
- Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, CMU, 1211 Geneva, Switzerland.
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35
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Paessler S, Walker DH. Pathogenesis of the viral hemorrhagic fevers. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2012; 8:411-40. [PMID: 23121052 DOI: 10.1146/annurev-pathol-020712-164041] [Citation(s) in RCA: 177] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Four families of enveloped RNA viruses, filoviruses, flaviviruses, arenaviruses, and bunyaviruses, cause hemorrhagic fevers. These viruses are maintained in specific natural cycles involving nonhuman primates, bats, rodents, domestic ruminants, humans, mosquitoes, and ticks. Vascular instability varies from mild to fatal shock, and hemorrhage ranges from none to life threatening. The pathogenic mechanisms are extremely diverse and include deficiency of hepatic synthesis of coagulation factors owing to hepatocellular necrosis, cytokine storm, increased permeability by vascular endothelial growth factor, complement activation, and disseminated intravascular coagulation in one or more hemorrhagic fevers. The severity of disease caused by these agents varies tremendously; there are extremely high fatality rates in Ebola and Marburg hemorrhagic fevers, and asymptomatic infection predominates in yellow fever and dengue viral infections. Although ineffective immunity and high viral loads are characteristic of several viral hemorrhagic fevers, severe plasma leakage occurs at the time of viral clearance and defervescence in dengue hemorrhagic fever.
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Affiliation(s)
- Slobodan Paessler
- Department of Pathology, University of Texas Medical Branch at Galveston, Galveston, TX 77555, USA.
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36
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Abstract
Lassa virus, an Old World arenavirus (family Arenaviridae), is the etiological agent of Lassa fever, a severe human disease that is reported in more than 100,000 patients annually in the endemic regions of West Africa with mortality rates for hospitalized patients varying between 5-10%. Currently, there are no approved vaccines against Lassa fever for use in humans. Here, we review the published literature on the life cycle of Lassa virus with the specific focus put on Lassa fever pathogenesis in humans and relevant animal models. Advancing knowledge significantly improves our understanding of Lassa virus biology, as well as of the mechanisms that allow the virus to evade the host’s immune system. However, further investigations are required in order to design improved diagnostic tools, an effective vaccine, and therapeutic agents.
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37
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Pythoud C, Rodrigo WWSI, Pasqual G, Rothenberger S, Martínez-Sobrido L, de la Torre JC, Kunz S. Arenavirus nucleoprotein targets interferon regulatory factor-activating kinase IKKε. J Virol 2012; 86:7728-38. [PMID: 22532683 PMCID: PMC3421673 DOI: 10.1128/jvi.00187-12] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 04/06/2012] [Indexed: 12/24/2022] Open
Abstract
Arenaviruses perturb innate antiviral defense by blocking induction of type I interferon (IFN) production. Accordingly, the arenavirus nucleoprotein (NP) was shown to block activation and nuclear translocation of interferon regulatory factor 3 (IRF3) in response to virus infection. Here, we sought to identify cellular factors involved in innate antiviral signaling targeted by arenavirus NP. Consistent with previous studies, infection with the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) prevented phosphorylation of IRF3 in response to infection with Sendai virus, a strong inducer of the retinoic acid-inducible gene I (RIG-I)/mitochondrial antiviral signaling (MAVS) pathway of innate antiviral signaling. Using a combination of coimmunoprecipitation and confocal microscopy, we found that LCMV NP associates with the IκB kinase (IKK)-related kinase IKKε but that, rather unexpectedly, LCMV NP did not bind to the closely related TANK-binding kinase 1 (TBK-1). The NP-IKKε interaction was highly conserved among arenaviruses from different clades. In LCMV-infected cells, IKKε colocalized with NP but not with MAVS located on the outer membrane of mitochondria. LCMV NP bound the kinase domain (KD) of IKKε (IKBKE) and blocked its autocatalytic activity and its ability to phosphorylate IRF3, without undergoing phosphorylation. Together, our data identify IKKε as a novel target of arenavirus NP. Engagement of NP seems to sequester IKKε in an inactive complex. Considering the important functions of IKKε in innate antiviral immunity and other cellular processes, the NP-IKKε interaction likely plays a crucial role in arenavirus-host interaction.
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Affiliation(s)
- Christelle Pythoud
- Institute of Microbiology University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | | | - Giulia Pasqual
- Institute of Microbiology University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Sylvia Rothenberger
- Institute of Microbiology University Hospital Center and University of Lausanne, Lausanne, Switzerland
| | - Luis Martínez-Sobrido
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, USA
| | - Juan Carlos de la Torre
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA
| | - Stefan Kunz
- Institute of Microbiology University Hospital Center and University of Lausanne, Lausanne, Switzerland
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38
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Reverse genetics recovery of Lujo virus and role of virus RNA secondary structures in efficient virus growth. J Virol 2012; 86:10759-65. [PMID: 22837210 DOI: 10.1128/jvi.01144-12] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Arenaviruses are rodent-borne viruses with a bisegmented RNA genome. A genetically unique arenavirus, Lujo virus, was recently discovered as the causal agent of a nosocomial outbreak of acute febrile illness with hemorrhagic manifestations in Zambia and South Africa. The outbreak had a case fatality rate of 80%. A reverse genetics system to rescue infectious Lujo virus from cDNA was established to investigate the biological properties of this virus. Sequencing the genomic termini showed unique nucleotides at the 3' terminus of the S segment promoter element. While developing this system, we discovered that reconstructing infectious Lujo virus using the previously reported L segment intergenic region (IGR), comprising the arenaviral transcription termination signal, yielded an attenuated Lujo virus. Resequencing revealed that the correct L segment IGR was 36 nucleotides longer, and incorporating it into the reconstructed Lujo virus restored the growth rate to that of the authentic clinical virus isolate. These additional nucleotides were predicted to more than double the free energy of the IGR main stem-loop structure. In addition, incorporating the newly determined L-IGR into a replicon reporter system enhanced the expression of a luciferase reporter L segment. Overall, these results imply that an extremely stable secondary structure within the L-IGR is critical for Lujo virus propagation and viral protein production. The technology for producing recombinant Lujo virus now provides a method to precisely investigate the molecular determinants of virulence of this newly identified pathogen.
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39
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Huang C, Kolokoltsova OA, Yun NE, Seregin AV, Poussard AL, Walker AG, Brasier AR, Zhao Y, Tian B, de la Torre JC, Paessler S. Junín virus infection activates the type I interferon pathway in a RIG-I-dependent manner. PLoS Negl Trop Dis 2012; 6:e1659. [PMID: 22629479 PMCID: PMC3358329 DOI: 10.1371/journal.pntd.0001659] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 04/11/2012] [Indexed: 12/21/2022] Open
Abstract
Junín virus (JUNV), an arenavirus, is the causative agent of Argentine hemorrhagic fever, an infectious human disease with 15-30% case fatality. The pathogenesis of AHF is still not well understood. Elevated levels of interferon and cytokines are reported in AHF patients, which might be correlated to the severity of the disease. However the innate immune response to JUNV infection has not been well evaluated. Previous studies have suggested that the virulent strain of JUNV does not induce IFN in human macrophages and monocytes, whereas the attenuated strain of JUNV was found to induce IFN response in murine macrophages via the TLR-2 signaling pathway. In this study, we investigated the interaction between JUNV and IFN pathway in human epithelial cells highly permissive to JUNV infection. We have determined the expression pattern of interferon-stimulated genes (ISGs) and IFN-β at both mRNA and protein levels during JUNV infection. Our results clearly indicate that JUNV infection activates the type I IFN response. STAT1 phosphorylation, a downstream marker of activation of IFN signaling pathway, was readily detected in JUNV infected IFN-competent cells. Our studies also demonstrated for the first time that RIG-I was required for IFN production during JUNV infection. IFN activation was detected during infection by either the virulent or attenuated vaccine strain of JUNV. Curiously, both virus strains were relatively insensitive to human IFN treatment. Our studies collectively indicated that JUNV infection could induce host type I IFN response and provided new insights into the interaction between JUNV and host innate immune system, which might be important in future studies on vaccine development and antiviral treatment.
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Affiliation(s)
- Cheng Huang
- Galveston National Laboratory, Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Olga A. Kolokoltsova
- Galveston National Laboratory, Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Nadezdha E. Yun
- Galveston National Laboratory, Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Alexey V. Seregin
- Galveston National Laboratory, Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Allison L. Poussard
- Galveston National Laboratory, Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Aida G. Walker
- Galveston National Laboratory, Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Allan R. Brasier
- Department of Internal Medicine and Sealy Center for Molecular Medicine, Institute for Translational Sciences, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Yingxin Zhao
- Department of Internal Medicine and Sealy Center for Molecular Medicine, Institute for Translational Sciences, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Bing Tian
- Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Juan Carlos de la Torre
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America
| | - Slobodan Paessler
- Galveston National Laboratory, Department of Pathology and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
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40
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Gerlier D, Lyles DS. Interplay between innate immunity and negative-strand RNA viruses: towards a rational model. Microbiol Mol Biol Rev 2011; 75:468-90, second page of table of contents. [PMID: 21885681 PMCID: PMC3165544 DOI: 10.1128/mmbr.00007-11] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The discovery of a new class of cytosolic receptors recognizing viral RNA, called the RIG-like receptors (RLRs), has revolutionized our understanding of the interplay between viruses and host cells. A tremendous amount of work has been accumulating to decipher the RNA moieties required for an RLR agonist, the signal transduction pathway leading to activation of the innate immunity orchestrated by type I interferon (IFN), the cellular and viral regulators of this pathway, and the viral inhibitors of the innate immune response. Previous reviews have focused on the RLR signaling pathway and on the negative regulation of the interferon response by viral proteins. The focus of this review is to put this knowledge in the context of the virus replication cycle within a cell. Likewise, there has been an expansion of knowledge about the role of innate immunity in the pathophysiology of viral infection. As a consequence, some discrepancies have arisen between the current models of cell-intrinsic innate immunity and current knowledge of virus biology. This holds particularly true for the nonsegmented negative-strand viruses (Mononegavirales), which paradoxically have been largely used to build presently available models. The aim of this review is to bridge the gap between the virology and innate immunity to favor the rational building of a relevant model(s) describing the interplay between Mononegavirales and the innate immune system.
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Affiliation(s)
- Denis Gerlier
- INSERM U758, CERVI, 21 avenue Tony Garnier, 69007 Lyon, France.
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Bowzard JB, Davis WG, Jeisy-Scott V, Ranjan P, Gangappa S, Fujita T, Sambhara S. PAMPer and tRIGer: ligand-induced activation of RIG-I. Trends Biochem Sci 2011; 36:314-9. [DOI: 10.1016/j.tibs.2011.03.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 03/15/2011] [Accepted: 03/16/2011] [Indexed: 12/24/2022]
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Tacaribe virus but not junin virus infection induces cytokine release from primary human monocytes and macrophages. PLoS Negl Trop Dis 2011; 5:e1137. [PMID: 21572983 PMCID: PMC3091837 DOI: 10.1371/journal.pntd.0001137] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 02/16/2011] [Indexed: 01/07/2023] Open
Abstract
The mechanisms underlying the development of disease during arenavirus infection are poorly understood. However, common to all hemorrhagic fever diseases is the involvement of macrophages as primary target cells, suggesting that the immune response in these cells may be of paramount importance during infection. Thus, in order to identify features of the immune response that contribute to arenavirus pathogenesis, we have examined the growth kinetics and cytokine profiles of two closely related New World arenaviruses, the apathogenic Tacaribe virus (TCRV) and the hemorrhagic fever-causing Junin virus (JUNV), in primary human monocytes and macrophages. Both viruses grew robustly in VeroE6 cells; however, TCRV titres were decreased by approximately 10 fold compared to JUNV in both monocytes and macrophages. Infection of both monocytes and macrophages with TCRV also resulted in the release of high levels of IL-6, IL-10 and TNF-α, while levels of IFN-α, IFN-β and IL-12 were not affected. However, we could show that the presence of these cytokines had no direct effect on growth of either TCRV of JUNV in macrophages. Further analysis also showed that while the production of IL-6 and IL-10 are dependent on viral replication, production of TNF-α also occurs after exposure to UV-inactivated TCRV particles and is thus independent of productive virus infection. Surprisingly, JUNV infection did not have an effect on any of the cytokines examined indicating that, in contrast to other viral hemorrhagic fever viruses, macrophage-derived cytokine production is unlikely to play an active role in contributing to the cytokine dysregulation observed in JUNV infected patients. Rather, these results suggest that an early, controlled immune response by infected macrophages may be critical for the successful control of infection of apathogenic viruses and prevention of subsequent disease, including systemic cytokine dysregulation. It remains unclear how arenavirus infection causes disease; however, for other hemorrhagic fever viruses, infection has been linked to over-production of numerous cytokines by macrophages that can then affect vascular integrity. In order to determine if a similar mechanism might contribute to arenavirus pathogenesis, we have examined the infection and subsequent cytokine production in human monocytes and macrophages by two closely related arenaviruses: the apathogenic Tacaribe virus (TCRV) and the hemorrhagic fever-causing Junin virus (JUNV). We found that both viruses infected primary monocyte and macrophage cultures; however, only, in the case of TCRV was infection accompanied by the production of cytokines. These cytokines would have the potential to stimulate an antiviral response to infection, including the production of antibodies, which are known to be protective during infection. Surprisingly, in contrast to what is observed in other viral hemorrhagic fevers, we found that JUNV infection did not have any effect on the expression of these cytokines. This suggests that an early, strong immune response by infected macrophages may be critical for the control of infection by apathogenic arenaviruses and the prevention of subsequent disease.
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Marq JB, Hausmann S, Veillard N, Kolakofsky D, Garcin D. Short double-stranded RNAs with an overhanging 5' ppp-nucleotide, as found in arenavirus genomes, act as RIG-I decoys. J Biol Chem 2011; 286:6108-16. [PMID: 21159780 PMCID: PMC3057789 DOI: 10.1074/jbc.m110.186262] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 12/14/2010] [Indexed: 12/24/2022] Open
Abstract
Arenavirus RNA genomes are initiated by a "prime and realign" mechanism, such that the initiating GTP is found as a single unpaired (overhanging) nucleotide when the complementary genome ends anneal to form double-stranded (ds) RNA panhandle structures. dsRNAs modeled on these structures do not induce interferon (IFN), as opposed to blunt-ended (5' ppp)dsRNA. This study examines whether these viral structures can also act as decoys, by trapping RIG-I in inactive dsRNA complexes. We examined the ability of various dsRNAs to activate the RIG-I ATPase (presumably a measure of helicase translocation on dsRNA) relative to their ability to induce IFN. We found that there is no simple relationship between these two properties, as if RIG-I can translocate on short dsRNAs without inducing IFN. Moreover, we found that (5' ppp)dsRNAs with a single unpaired 5' ppp-nucleotide can in fact competitively inhibit the ability of blunt-ended (5' ppp)dsRNAs to induce IFN when co-transfected into cells and that this inhibition is strongly dependent on the presence of the 5' ppp. In contrast, (5' ppp)dsRNAs with a single unpaired 5' ppp-nucleotide does not inhibit poly(I-C)-induced IFN activation, which is independent of the presence of a 5' ppp group.
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Affiliation(s)
- Jean-Baptiste Marq
- From the Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, CMU, 1 Rue Michel-Servet, 1211 Geneva, Switzerland
| | - Stéphane Hausmann
- From the Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, CMU, 1 Rue Michel-Servet, 1211 Geneva, Switzerland
| | - Nicolas Veillard
- From the Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, CMU, 1 Rue Michel-Servet, 1211 Geneva, Switzerland
| | - Daniel Kolakofsky
- From the Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, CMU, 1 Rue Michel-Servet, 1211 Geneva, Switzerland
| | - Dominique Garcin
- From the Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, CMU, 1 Rue Michel-Servet, 1211 Geneva, Switzerland
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Abstract
Antiviral innate immunity is triggered by sensing viral nucleic acids. RIG-I (retinoic acid-inducible gene-I) is an intracellular molecule that responds to viral nucleic acids and activates downstream signaling, resulting in the induction of members of the type I interferon (IFN) family, which are regarded among the most important effectors of the innate immune system. Although RIG-I is expressed ubiquitously in the cytoplasm, its levels are subject to transcriptional and post-transcriptional regulation. RIG-I belongs to the IFN-stimulated gene (ISG) family, but certain cells regulate its expression through IFN-independent mechanisms. Several lines of evidence indicate that deregulated RIG-I signaling is associated with autoimmune disorders. Further studies suggest that RIG-I has functions in addition to those directly related to its role in RNA sensing and host defense. We have much to learn and discover regarding this interesting cytoplasmic sensor so that we can capitalize on its properties for the treatment of viral infections, immune disorders, cancer, and perhaps other conditions.
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Affiliation(s)
- Tomoh Matsumiya
- Department of Vascular Biology, Institute of Brain Science, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
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Borrow P, Martínez-Sobrido L, de la Torre JC. Inhibition of the type I interferon antiviral response during arenavirus infection. Viruses 2010; 2:2443-80. [PMID: 21994626 PMCID: PMC3185579 DOI: 10.3390/v2112443] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 10/22/2010] [Accepted: 10/22/2010] [Indexed: 12/20/2022] Open
Abstract
Arenaviruses merit interest both as tractable experimental model systems to study acute and persistent viral infections, and as clinically-important human pathogens. Several arenaviruses cause hemorrhagic fever (HF) disease in humans. In addition, evidence indicates that the globally-distributed prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) is a human pathogen of clinical significance in congenital infections, and also poses a great danger to immunosuppressed individuals. Arenavirus persistence and pathogenesis are facilitated by their ability to overcome the host innate immune response. Mammalian hosts have developed both membrane toll-like receptors (TLR) and cytoplasmic pattern recognition receptors (PRRs) that recognize specific pathogen-associated molecular patterns (PAMPs), resulting in activation of the transcription factors IRF3 or IRF7, or both, which together with NF-κB and ATF-2/c-JUN induce production of type I interferon (IFN-I). IFN-I plays a key role in host anti-microbial defense by mediating direct antiviral effects via up-regulation of IFN-I stimulated genes (ISGs), activating dendritic cells (DCs) and natural killer (NK) cells, and promoting the induction of adaptive responses. Accordingly, viruses have developed a plethora of strategies to disrupt the IFN-I mediated antiviral defenses of the host, and the viral gene products responsible for these disruptions are often major virulence determinants. IRF3- and IRF7-dependent induction of host innate immune responses is frequently targeted by viruses. Thus, the arenavirus nucleoprotein (NP) was shown to inhibit the IFN-I response by interfering with the activation of IRF3. This NP anti-IFN activity, together with alterations in the number and function of DCs observed in mice chronically infected with LCMV, likely play an important role in LCMV persistence in its murine host. In this review we will discuss current knowledge about the cellular and molecular mechanisms by which arenaviruses can subvert the host innate immune response and their implications for understanding HF arenaviral disease as well as arenavirus persistence in their natural hosts.
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Affiliation(s)
- Persephone Borrow
- Nuffield Department of Clinical Medicine, The Jenner Institute, University of Oxford, Compton, Newbury, Berkshire RG20 7NN, UK; E-Mail:
| | - Luis Martínez-Sobrido
- Department of Microbiology and Immunology, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Juan Carlos de la Torre
- Department of Immunology and Microbial Science, IMM-6, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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