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Insights from structural studies of the Cardiovirus 2A protein. Biosci Rep 2022; 42:230648. [PMID: 35022657 PMCID: PMC8777194 DOI: 10.1042/bsr20210406] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Revised: 01/10/2022] [Accepted: 01/10/2022] [Indexed: 11/24/2022] Open
Abstract
Cardioviruses are single-stranded RNA viruses of the family Picornaviridae. In addition to being the first example of internal ribosome entry site (IRES) utilization, cardioviruses also employ a series of alternative translation strategies, such as Stop-Go translation and programmed ribosome frameshifting. Here, we focus on cardiovirus 2A protein, which is not only a primary virulence factor, but also exerts crucial regulatory functions during translation, including activation of viral ribosome frameshifting and inhibition of host cap-dependent translation. Only recently, biochemical and structural studies have allowed us to close the gaps in our knowledge of how cardiovirus 2A is able to act in diverse translation-related processes as a novel RNA-binding protein. This review will summarize these findings, which ultimately may lead to the discovery of other RNA-mediated gene expression strategies across a broad range of RNA viruses.
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Penza V, Russell SJ, Schulze AJ. The long-lasting enigma of polycytidine (polyC) tract. PLoS Pathog 2021; 17:e1009739. [PMID: 34347852 PMCID: PMC8336851 DOI: 10.1371/journal.ppat.1009739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Long polycytidine (polyC) tracts varying in length from 50 to 400 nucleotides were first described in the 5'-noncoding region (NCR) of genomes of picornaviruses belonging to the Cardio- and Aphthovirus genera over 50 years ago, but the molecular basis of their function is still unknown. Truncation or complete deletion of the polyC tracts in picornaviruses compromises virulence and pathogenicity but do not affect replicative fitness in vitro, suggesting a role as "viral security" RNA element. The evidence available suggests that the presence of a long polyC tract is required for replication in immune cells, which impacts viral distribution and targeting, and, consequently, pathogenic progression. Viral attenuation achieved by reduction of the polyC tract length has been successfully used for vaccine strategies. Further elucidation of the role of the polyC tract in viral replication cycle and its connection with replication in immune cells has the potential to expand the arsenal of tools in the fight against cancer in oncolytic virotherapy (OV). Here, we review the published data on the biological significance and mechanisms of action of the polyC tract in viral pathogenesis in Cardio- and Aphthoviruses.
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Affiliation(s)
- Velia Penza
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Stephen J. Russell
- Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
- Division of Hematology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Autumn J. Schulze
- Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
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Lauzon-Joset JF, Jones AC, Mincham KT, Thomas JA, Rosenthal LA, Bosco A, Holt PG, Strickland DH. Atopy-Dependent and Independent Immune Responses in the Heightened Severity of Atopics to Respiratory Viral Infections: Rat Model Studies. Front Immunol 2018; 9:1805. [PMID: 30150981 PMCID: PMC6099265 DOI: 10.3389/fimmu.2018.01805] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 07/23/2018] [Indexed: 12/04/2022] Open
Abstract
Allergic (Th2high immunophenotype) asthmatics have a heightened susceptibility to common respiratory viral infections such as human rhinovirus. Evidence suggests that the innate interferon response is deficient in asthmatic/atopic individuals, while other studies show no differences in antiviral response pathways. Unsensitized and OVA-sensitized/challenged Th2high (BN rats) and Th2low immunophenotype (PVG rats) animals were inoculated intranasally with attenuated mengovirus (vMC0). Sensitized animals were exposed/unexposed during the acute viral response phase. Cellular and transcriptomic profiling was performed on bronchoalveolar lavage cells. In unsensitized PVG rats, vMC0 elicits a prototypical antiviral response (neutrophilic airways inflammation, upregulation of Th1/type I interferon-related pathways). In contrast, response to infection in the Th2high BN rats was associated with a radically altered intrinsic host response to respiratory viral infection, characterized by macrophage influx/Th2-associated pathways. In sensitized animals, response to virus infection alone was not altered compared to unsensitized animals. However, allergen exposure of sensitized animals during viral infection unleashes a notably exaggerated airways inflammatory response profile orders of magnitude higher in BN versus PVG rats despite similar viral loads. The co-exposure responses in the Th2high BN incorporated type I interferon/Th1, alternative macrophage activation/Th2 and Th17 signatures. Similar factors may underlie the hyper-susceptibility to infection-associated airways inflammation characteristic of the human Th2high immunophenotype.
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Affiliation(s)
| | - Anya C Jones
- Telethon Kids Institute, University of Western Australia, Perth, WA, Australia.,School of Medicine, University of Western Australia, Perth, WA, Australia
| | - Kyle T Mincham
- Telethon Kids Institute, University of Western Australia, Perth, WA, Australia.,School of Medicine, University of Western Australia, Perth, WA, Australia
| | - Jenny A Thomas
- Telethon Kids Institute, University of Western Australia, Perth, WA, Australia
| | - Louis A Rosenthal
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Anthony Bosco
- Telethon Kids Institute, University of Western Australia, Perth, WA, Australia
| | - Patrick G Holt
- Telethon Kids Institute, University of Western Australia, Perth, WA, Australia
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Buskiewicz IA, Koenig A, Huber SA, Budd RC. Caspase-8 and FLIP regulate RIG-I/MDA5-induced innate immune host responses to picornaviruses. Future Virol 2012; 7:1221-1236. [PMID: 23503762 DOI: 10.2217/fvl.12.115] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Picornaviruses are small, nonenveloped, positive-stranded RNA viruses, which cause a wide range of animal and human diseases, based on their distinct tissue and cell type tropisms. Myocarditis, poliomyelitis, hepatitis and the common cold are the most significant human illnesses caused by picornaviruses. The host response to picornaviruses is complex, and the damage to tissues occurs not only from direct viral replication within infected cells. Picornaviruses exhibit an exceptional ability to evade the early innate immune response, resulting in chronic infection and autoimmunity. This review discusses the detailed aspects of the early innate host response to picornaviruses infection mediated by RIG-I-like helicases, their adaptor, mitochondrial ant iviral signaling protein, innate immune-induced apoptosis, and the role of caspase-8 and its regulatory paralog, FLIP, in these processes.
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Affiliation(s)
- Iwona A Buskiewicz
- Department of Pathology, Vermont Center for Immunology & Infectious Diseases, University of Vermont, Burlington, VT 05405, USA
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Rosenthal LA, Szakaly RJ, Amineva SP, Xing Y, Hill MR, Palmenberg AC, Gern JE, Sorkness RL. Lower respiratory tract infection induced by a genetically modified picornavirus in its natural murine host. PLoS One 2012; 7:e32061. [PMID: 22355409 PMCID: PMC3280220 DOI: 10.1371/journal.pone.0032061] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 01/23/2012] [Indexed: 12/21/2022] Open
Abstract
Infections with the picornavirus, human rhinovirus (HRV), are a major cause of wheezing illnesses and asthma exacerbations. In developing a murine model of picornaviral airway infection, we noted the absence of murine rhinoviruses and that mice are not natural hosts for HRV. The picornavirus, mengovirus, induces lethal systemic infections in its natural murine hosts, but small genetic differences can profoundly affect picornaviral tropism and virulence. We demonstrate that inhalation of a genetically attenuated mengovirus, vMC0, induces lower respiratory tract infections in mice. After intranasal vMC0 inoculation, lung viral titers increased, peaking at 24 h postinoculation with viral shedding persisting for 5 days, whereas HRV-A01a lung viral titers decreased and were undetectable 24 h after intranasal inoculation. Inhalation of vMC0, but not vehicle or UV-inactivated vMC0, induced an acute respiratory illness, with body weight loss and lower airway inflammation, characterized by increased numbers of airway neutrophils and lymphocytes and elevated pulmonary expression of neutrophil chemoattractant CXCR2 ligands (CXCL1, CXCL2, CXCL5) and interleukin-17A. Mice inoculated with vMC0, compared with those inoculated with vehicle or UV-inactivated vMC0, exhibited increased pulmonary expression of interferon (IFN-α, IFN-β, IFN-λ), viral RNA sensors [toll-like receptor (TLR)3, TLR7, nucleotide-binding oligomerization domain containing 2 (NOD2)], and chemokines associated with HRV infection in humans (CXCL10, CCL2). Inhalation of vMC0, but not vehicle or UV-inactivated vMC0, was accompanied by increased airway fluid myeloperoxidase levels, an indicator of neutrophil activation, increased MUC5B gene expression, and lung edema, a sign of infection-related lung injury. Consistent with experimental HRV inoculations of nonallergic, nonasthmatic human subjects, there were no effects on airway hyperresponsiveness after inhalation of vMC0 by healthy mice. This novel murine model of picornaviral airway infection and inflammation should be useful for defining mechanisms of HRV pathogenesis in humans.
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Affiliation(s)
- Louis A Rosenthal
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
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Rosenthal LA, Amineva SP, Szakaly RJ, Lemanske RF, Gern JE, Sorkness RL. A rat model of picornavirus-induced airway infection and inflammation. Virol J 2009; 6:122. [PMID: 19671179 PMCID: PMC2790594 DOI: 10.1186/1743-422x-6-122] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Accepted: 08/11/2009] [Indexed: 11/12/2022] Open
Abstract
Background Infection of the lower airways by rhinovirus, a member of the picornavirus family, is an important cause of wheezing illnesses in infants, and plays an important role in the pathogenesis of rhinovirus-induced asthma exacerbations. Given the absence of natural rhinovirus infections in rodents, we investigated whether an attenuated form of mengovirus, a picornavirus whose wild-type form causes systemic rather than respiratory infections in its natural rodent hosts, could induce airway infections in rats with inflammatory responses similar to those in human rhinovirus infections. Results After inoculation with 107 plaque-forming units of attenuated mengovirus through an inhalation route, infectious mengovirus was consistently recovered on days 1 and 3 postinoculation from left lung homogenates (median Log10 plaque-forming units = 6.0 and 4.8, respectively) and right lung bronchoalveolar lavage fluid (median Log10 plaque-forming units = 5.8 and 4.0, respectively). Insufflation of attenuated mengovirus, but not vehicle or UV-inactivated virus, into the lungs of BN rats caused significant increases (P < 0.05) in lower airway neutrophils and lymphocytes in the bronchoalveolar lavage fluid and patchy peribronchiolar, perivascular, and alveolar cellular infiltrates in lung tissue sections. In addition, infection with attenuated mengovirus significantly increased (P < 0.05) lower airway levels of neutrophil chemoattractant CXCR2 ligands [cytokine-induced neutrophil chemoattractant-1 (CINC-1; CXCL1) and macrophage inflammatory protein-2 (MIP-2; CXCL2)] and monocyte chemoattractant protein-1 (MCP-1; CCL2) in comparison to inoculation with vehicle or UV-inactivated virus. Conclusion Attenuated mengovirus caused a respiratory infection in rats with several days of viral shedding accompanied by a lower airway inflammatory response consisting of neutrophils and lymphocytes. These features suggest that mengovirus-induced airway infection in rodents could be a useful model to define mechanisms of rhinovirus-induced airway inflammation in humans.
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Affiliation(s)
- Louis A Rosenthal
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, 600 Highland Avenue, Madison, WI 53792, USA.
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Dethlefs S, Escriou N, Brahic M, van der Werf S, Larsson-Sciard EL. Theiler's virus and Mengo virus induce cross-reactive cytotoxic T lymphocytes restricted to the same immunodominant VP2 epitope in C57BL/6 mice. J Virol 1997; 71:5361-5. [PMID: 9188606 PMCID: PMC191774 DOI: 10.1128/jvi.71.7.5361-5365.1997] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
C57BL/6 mice develop a virus-specific cytotoxic T-lymphocyte (CTL) response after intraperitoneal inoculation with either the DA strain of Theiler's virus or Mengo virus, two members of the Cardiovirus genus. These CTLs contribute to viral clearance in the case of Theiler's virus but do not protect the mice from the fatal encephalomyelitis caused by Mengo virus. In this study we show that DA and Mengo virus-induced CTLs are cross-reactive. The cross-reactivity is due to a conserved, H-2Db-restricted epitope located between amino acid residues 122 and 130 of the VP2 capsid protein (VP2(122-130)). This epitope is immunodominant in C57BL/6 mice infected with Theiler's virus. The VP2(122-130) epitope, initially identified for Mengo virus, is the first CTL epitope described for Theiler's virus.
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Affiliation(s)
- S Dethlefs
- Unité des Virus Lents, URA 1157 Centre National de la Recherche Scientifique, Institut Pasteur, Paris, France
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Zimmermann A, Botta A, Arnold G, Eggers HJ, Nelsen-Salz B. The poly(C) region affects progression of encephalomyocarditis virus infection in Langerhans' islets but not in the myocardium. J Virol 1997; 71:4145-9. [PMID: 9094698 PMCID: PMC191573 DOI: 10.1128/jvi.71.5.4145-4149.1997] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The diabetogenic variant PV2 of encephalomyocarditis virus was cloned, and three recombinants differing in their 5' poly(C) tracts were analyzed. It is shown that the poly(C) region is not essential for infectivity in mice but does influence the virus load and degree of pathological lesions within the Langerhans' islets but not in the myocardium.
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Affiliation(s)
- A Zimmermann
- Institut für Virologie der Universität zu Köln, Cologne, Germany
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Martin LR, Palmenberg AC. Tandem mengovirus 5' pseudoknots are linked to viral RNA synthesis, not poly(C)-mediated virulence. J Virol 1996; 70:8182-6. [PMID: 8892950 PMCID: PMC190899 DOI: 10.1128/jvi.70.11.8182-8186.1996] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The RNA genomes from the cardioviruses, hepatoviruses, and aphthoviruses encode two to five tandem pseudoknots within their 5' untranslated regions. These pseudoknots lie adjacent to a pyrimidine-rich sequence, which in cardio- and aphthoviruses takes the form of a homopolymeric poly(C) tract. Seven deletion mutations within mengovirus pseudoknots PK(B) and PK(C) were created and characterized. tested in tissue culture, mengovirus genomes with alterations in PK(C) were viable but had small plaque phenotypes. Larger plaque revertants were isolated and partially characterized, and each proved to be a second-site pseudorevertant with (unmapped) changes elsewhere in the genome. The infectious PK(C) mutant viruses were highly lethal to mice, and deletions in this motif did not affect mengovirus virulence in the same manner as deletions in the adjacent poly(C) tract. In contrast, deletions in PK(B), or deletions which spanned PK(B) + PK(C), produced nonviable genomes. Cell-free translations directed by any of the altered PK sequences gave normal polyprotein amounts relative to wild-type mengovirus. But viral RNA accumulation during HeLa cell infection was dramatically impaired, even with the least disruptive of the PK(C) changes, suggesting the pseudoknots play an essential though undefined role in RNA synthesis and moreover that an intact PK(B) structure is critical to this function.
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Affiliation(s)
- L R Martin
- Institute for Molecular Virology and Department of Animal Health & Biomedical Sciences, University of Wisconsin--Madison, 53706, USA
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Martin LR, Duke GM, Osorio JE, Hall DJ, Palmenberg AC. Mutational analysis of the mengovirus poly(C) tract and surrounding heteropolymeric sequences. J Virol 1996; 70:2027-31. [PMID: 8627731 PMCID: PMC190034 DOI: 10.1128/jvi.70.3.2027-2031.1996] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Previously, we described three mengovirus mutants derived from cDNA plasmids, containing shortened poly(C) tracts (C8, C12, and C13UC10), that exhibited strong attenuation for virulence in mice yet grew like wild-type virus in HeLa cells. Thirteen additional mutants hav now been constructed and characterized. Five of these differ only in poly(C) length, including one with a precise deletion of the tract. The other mutants bear deletions into the regions juxtaposing poly(C). Studies with HeLa cells confirm the essential dispensability of mengovirus's poly(C) tract but reveal a subtle, measurable correlation between poly(C) length and plaque diameter. Virulence studies with mice also revealed a strong correlation between poly(C) length and virulence. For the poly(C)-flanking mutations, the 15 bases directly 5' of the tract proved dispensable for virus viability, whereas the 20 to 30 bases 3' of poly(C) were critical for growth, thus implicating this region in the basal replication of the virus.
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Affiliation(s)
- L R Martin
- Institute for Molecular Virology, University of Wisconsin, Madison 53706, USA.
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Hoffman MA, Palmenberg AC. Mutational analysis of the J-K stem-loop region of the encephalomyocarditis virus IRES. J Virol 1995; 69:4399-406. [PMID: 7769702 PMCID: PMC189181 DOI: 10.1128/jvi.69.7.4399-4406.1995] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cap-independent translation of encephalomyocarditis virus (EMCV) RNA is controlled by a segment of the 5' untranslated region termed the internal ribosomal entry site, or IRES. The IRES contains a series of stem-loop structural elements. The J and K stems (EMCV bases 682 to 795), near the center of the IRES, are well conserved among all cardio-, aphtho-, and hepatoviruses. We have examined the biological roles of these elements by constructing mutations within the J-K sequences of EMCV and testing the mutations for activity in translation, translation competition, UV cross-linking, and viral infectivity assays. Mutations near the helical junction of J and K proved severely detrimental to both cellular translation and cell-free translation of downstream cistrons. The same mutations reduced the ability of the IRES to compete for cellular factors in competition assays and reduced the infectivity of viral genomes carrying these lesions. A mutation in the terminal loop of J gave similar results. In contrast, mutations within the terminal loop of K had minimal impact on in vitro translation activity and IRES competitive ability. However, in vivo analysis of the K-loop mutations revealed deficiencies during cellular translation and further showed markedly reduced infectivity in HeLa cells. UV cross-linking experiments identified a 49-kDa protein which interacts strongly with the J-K region, but the identity of this protein and its contribution to IRES activity are unclear.
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Affiliation(s)
- M A Hoffman
- Institute for Molecular Virology, University of Wisconsin, Madison, USA
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