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Bracci N, Baer A, Flor R, Petraccione K, Stocker T, Zhou W, Ammosova T, Dinglasan RR, Nekhai S, Kehn-Hall K. CK1 and PP1 regulate Rift Valley fever virus genome replication through L protein phosphorylation. Antiviral Res 2024; 226:105895. [PMID: 38679165 DOI: 10.1016/j.antiviral.2024.105895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 04/15/2024] [Accepted: 04/22/2024] [Indexed: 05/01/2024]
Abstract
Rift Valley fever virus (RVFV) is an arbovirus in the Phenuiviridae family identified initially by the large 'abortion storms' observed among ruminants; RVFV can also infect humans. In humans, there is a wide variation of clinical symptoms ranging from subclinical to mild febrile illness to hepatitis, retinitis, delayed-onset encephalitis, or even hemorrhagic fever. The RVFV is a tri-segmented negative-sense RNA virus consisting of S, M, and L segments. The L segment encodes the RNA-dependent RNA polymerase (RdRp), termed the L protein, which is responsible for both viral mRNA synthesis and genome replication. Phosphorylation of viral RdRps is known to regulate viral replication. This study shows that RVFV L protein is serine phosphorylated and identified Casein Kinase 1 alpha (CK1α) and protein phosphatase 1 alpha (PP1α) as L protein binding partners. Inhibition of CK1 and PP1 through small molecule inhibitor treatment, D4476 and 1E7-03, respectively, caused a change in the phosphorylated status of the L protein. Inhibition of PP1α resulted in increased L protein phosphorylation whereas inhibition of CK1α decreased L protein phosphorylation. It was also found that in RVFV infected cells, PP1α localized to the cytoplasmic compartment. Treatment of RVFV infected cells with CK1 inhibitors reduced virus production in both mammalian and mosquito cells. Lastly, inhibition of either CK1 or PP1 reduced viral genomic RNA levels. These data indicate that L protein is phosphorylated and that CK1 and PP1 play a crucial role in regulating the L protein phosphorylation cycle, which is critical to viral RNA production and viral replication.
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Affiliation(s)
- Nicole Bracci
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Alan Baer
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Rafaela Flor
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Kaylee Petraccione
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Timothy Stocker
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA
| | - Weidong Zhou
- Center for Applied Proteomics and Molecular Medicine, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Tatiana Ammosova
- Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington D.C., USA
| | - Rhoel R Dinglasan
- Emerging Pathogens Institute, University of Florida, Florida, USA; Department of Infectious Diseases & Immunology, College of Veterinary Medicine, University of Florida, Florida, USA
| | - Sergei Nekhai
- Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington D.C., USA
| | - Kylene Kehn-Hall
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Virginia, USA; Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Virginia, USA.
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2
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Trujillo JD, Wilson WC, Craig A, Van den Bergh C, Wang T, Thompson P, Swanepoel R, Morozov I, Richt JA. Rift Valley Fever virus M and L genome segment detection: a comparison of field-deployable reverse transcription insulated isothermal PCR (RT-iiPCR) and laboratory-based multiplex reverse transcription real-time PCR. J Clin Microbiol 2024; 62:e0043023. [PMID: 38305205 PMCID: PMC10935642 DOI: 10.1128/jcm.00430-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 11/21/2023] [Indexed: 02/03/2024] Open
Abstract
Rift Valley Fever phlebovirus (RVFV) is a mosquito-borne zoonotic pathogen that causes major agricultural and public health problems in Africa and the Arabian Peninsula. It is considered a potential agro-bioterrorism agent for which limited countermeasures are available. To address diagnostic needs, here we describe a rapid and sensitive molecular method immediately employable at sites of suspected outbreaks in animals that commonly precede outbreaks in humans. The strategy involves the concurrent detection of two of the three RVFV genome segments (large and medium) using reverse transcription insulated isothermal PCR (RT-iiPCR) performed on a portable, touch screen nucleic acid analyzer, POCKIT. The analytical sensitivity for both the RT-iiPCR and a laboratory-based L and M multiplex reverse transcription real-time PCR assay was estimated at approximately 0.1-3 copies/reaction using synthetic RNA or viral RNA. The diagnostic sensitivity and specificity of detection of RVFV on the POCKIT, determined using sera from sheep and cattle (n = 181) experimentally infected with two strains of RVFV (SA01 and Ken06), were 93.8% and 100% (kappa = 0.93), respectively. Testing of ruminant field sera (n = 193) in two locations in Africa demonstrated 100% diagnostic sensitivity and specificity. We conclude that the POCKIT dual-gene RVFV detection strategy can provide reliable, sensitive, and specific point-of-need viral RNA detection. Moreover, the field detection of RVFV in vectors or susceptible animal species can aid in the surveillance and epidemiological studies to better understand and control RVFV outbreaks. IMPORTANCE The content of this manuscript is of interest to the diverse readership of the Journal of Clinical Microbiology, including research scientists, diagnosticians, healthcare professionals, and policymakers. Rift Valley Fever virus (RVFV) is a zoonotic mosquito-borne pathogen that causes major agricultural and public health problems. Current and most sensitive diagnostic approaches that are molecular-based are performed in highly specialized molecular diagnostic laboratories. To address diagnostic needs, we developed a novel, rapid, and sensitive molecular method using a portable PCR machine, POCKIT, capable of immediate deployment at sites of suspected outbreaks. Here, we demonstrate that field-deployable RVFV detection can provide reliable, sensitive, and specific point-of-need viral RNA detection that could be used for diagnostic investigations and epidemiological studies, and can be performed in the field.
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Affiliation(s)
- Jessie D. Trujillo
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, Kansas, USA
| | - William C. Wilson
- Foreign Arthropod-Borne Animal Diseases Research Unit (FABADRU), USDA Agricultural Research Service (ARS), Manhattan, Kansas, USA
| | - Anthony Craig
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Vectors and Vector-Borne Diseases Research Programme, Pretoria, South Africa
| | - Carien Van den Bergh
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Vectors and Vector-Borne Diseases Research Programme, Pretoria, South Africa
| | - Thomas Wang
- Research and development, GeneReach USA, Lexington, Massachusetts, USA
| | - Peter Thompson
- Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa
| | - Robert Swanepoel
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Vectors and Vector-Borne Diseases Research Programme, Pretoria, South Africa
| | - Igor Morozov
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, Kansas, USA
| | - Juergen A. Richt
- Center of Excellence for Emerging and Zoonotic Animal Diseases, Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, Kansas, USA
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Vectors and Vector-Borne Diseases Research Programme, Pretoria, South Africa
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3
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Weber F, Bouloy M, Lozach PY. An Introduction to Rift Valley Fever Virus. Methods Mol Biol 2024; 2824:1-14. [PMID: 39039402 DOI: 10.1007/978-1-0716-3926-9_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/24/2024]
Abstract
Rift Valley fever virus (RVFV) is a pathogen transmitted to humans and livestock via mosquito bites. This virus, which was discovered in Kenya in 1930, is considered by the World Health Organization (WHO) and the World Organisation for Animal Health (WOAH) to be associated with a high risk of causing large-scale epidemics. However, means dedicated to fighting RVFV have been limited, and despite recent research efforts, the virus remains poorly understood at both the molecular and cellular levels as well as at a broader scale of research in the field and in animal and human populations. In this introductory chapter of a methods book, we aim to provide readers with a concise overview of RVFV, from its ecology and transmission to the structural and genomic organization of virions and its life cycle in host cells.
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Affiliation(s)
- Friedemann Weber
- Institute for Virology, FB10-Veterinary Medicine, Justus-Liebig University, Giessen, Germany
| | - Michèle Bouloy
- Institut Pasteur, Université Paris Cité, Bunyavirus Molecular Genetics Unit, Paris, France
| | - Pierre-Yves Lozach
- IVPC UMR754, INRAE, Université Claude Bernard Lyon 1, EPHE, PSL Research University, Lyon, France.
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Anzaghe M, Niles MA, Korotkova E, Dominguez M, Kronhart S, Ortega Iannazzo S, Bechmann I, Bachmann M, Mühl H, Kochs G, Waibler Z. Interleukin-36γ is causative for liver damage upon infection with Rift Valley fever virus in type I interferon receptor-deficient mice. Front Immunol 2023; 14:1194733. [PMID: 37720217 PMCID: PMC10502725 DOI: 10.3389/fimmu.2023.1194733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 08/16/2023] [Indexed: 09/19/2023] Open
Abstract
Type I interferons (IFN) are pro-inflammatory cytokines which can also exert anti-inflammatory effects via the regulation of interleukin (IL)-1 family members. Several studies showed that interferon receptor (IFNAR)-deficient mice develop severe liver damage upon treatment with artificial agonists such as acetaminophen or polyinosinic:polycytidylic acid. In order to investigate if these mechanisms also play a role in an acute viral infection, experiments with the Bunyaviridae family member Rift Valley fever virus (RVFV) were performed. Upon RVFV clone (cl)13 infection, IFNAR-deficient mice develop a severe liver injury as indicated by high activity of serum alanine aminotransferase (ALT) and histological analyses. Infected IFNAR-/- mice expressed high amounts of IL-36γ within the liver, which was not observed in infected wildtype (WT) animals. In line with this, treatment of WT mice with recombinant IL-36γ induced ALT activity. Furthermore, administration of an IL-36 receptor antagonist prior to infection prevented the formation of liver injury in IFNAR-/- mice, indicating that IL-36γ is causative for the observed liver damage. Mice deficient for adaptor molecules of certain pattern recognition receptors indicated that IL-36γ induction was dependent on mitochondrial antiviral-signaling protein and the retinoic acid-inducible gene-I-like receptor. Consequently, cell type-specific IFNAR knockouts revealed that type I IFN signaling in myeloid cells is critical in order to prevent IL-36γ expression and liver injury upon viral infection. Our data demonstrate an anti-inflammatory role of type I IFN in a model for virus-induced hepatitis by preventing the expression of the novel IL-1 family member IL-36γ.
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Affiliation(s)
- Martina Anzaghe
- Division of Immunology, Paul-Ehrlich-Institut, Langen, Germany
| | - Marc A. Niles
- Division of Immunology, Paul-Ehrlich-Institut, Langen, Germany
| | | | | | | | | | - Ingo Bechmann
- Medical Faculty, Institute for Anatomy, University Leipzig, Leipzig, Germany
| | - Malte Bachmann
- Pharmazentrum Frankfurt/ZAFES, University Hospital Frankfurt, Goethe-University Frankfurt am Main, Frankfurt am Main, Germany
| | - Heiko Mühl
- Pharmazentrum Frankfurt/ZAFES, University Hospital Frankfurt, Goethe-University Frankfurt am Main, Frankfurt am Main, Germany
| | - Georg Kochs
- Institute of Virology, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Zoe Waibler
- Division of Immunology, Paul-Ehrlich-Institut, Langen, Germany
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5
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Schwarz MM, Ganaie SS, Feng A, Brown G, Yangdon T, White JM, Hoehl RM, McMillen CM, Rush RE, Connors KA, Cui X, Leung DW, Egawa T, Amarasinghe GK, Hartman AL. Lrp1 is essential for lethal Rift Valley fever hepatic disease in mice. SCIENCE ADVANCES 2023; 9:eadh2264. [PMID: 37450601 PMCID: PMC10348670 DOI: 10.1126/sciadv.adh2264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 06/12/2023] [Indexed: 07/18/2023]
Abstract
Rift Valley fever virus (RVFV) is an emerging arbovirus found in Africa. While RVFV is pantropic and infects many cells and tissues, viral replication and necrosis within the liver play a critical role in mediating severe disease. The low-density lipoprotein receptor-related protein 1 (Lrp1) is a recently identified host factor for cellular entry and infection by RVFV. The biological significance of Lrp1, including its role in hepatic disease in vivo, however, remains to be determined. Because Lrp1 has a high expression level in hepatocytes, we developed a mouse model in which Lrp1 is specifically deleted in hepatocytes to test how the absence of liver Lrp1 expression affects RVF pathogenesis. Mice lacking Lrp1 expression in hepatocytes showed minimal RVFV replication in the liver, longer time to death, and altered clinical signs toward neurological disease. In contrast, RVFV infection levels in other tissues showed no difference between the two genotypes. Therefore, Lrp1 is essential for RVF hepatic disease in mice.
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Affiliation(s)
- Madeline M. Schwarz
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Infectious Diseases and Microbiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | - Safder S. Ganaie
- Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Annie Feng
- Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Griffin Brown
- Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Tenzin Yangdon
- Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - J. Michael White
- Transgenic, Knockout and Micro-Injection Core, Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Ryan M. Hoehl
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, USA
| | - Cynthia M. McMillen
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Infectious Diseases and Microbiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | - Rachael E. Rush
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Infectious Diseases and Microbiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kaleigh A. Connors
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Infectious Diseases and Microbiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | - Xiaoxia Cui
- Genome Engineering & Stem Cell Center, Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Daisy W. Leung
- Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
- Department of Medicine, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Takeshi Egawa
- Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Gaya K. Amarasinghe
- Department of Pathology & Immunology, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Amy L. Hartman
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Infectious Diseases and Microbiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
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6
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Bermúdez-Méndez E, Angelino P, van Keulen L, van de Water S, Rockx B, Pijlman GP, Ciuffi A, Kortekaas J, Wichgers Schreur PJ. Transcriptomic Profiling Reveals Intense Host-Pathogen Dispute Compromising Homeostasis during Acute Rift Valley Fever Virus Infection. J Virol 2023; 97:e0041523. [PMID: 37306574 PMCID: PMC10308945 DOI: 10.1128/jvi.00415-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 05/13/2023] [Indexed: 06/13/2023] Open
Abstract
Rift Valley fever virus (RVFV) (family Phenuiviridae) can cause severe disease, and outbreaks of this mosquito-borne pathogen pose a significant threat to public and animal health. Yet many molecular aspects of RVFV pathogenesis remain incompletely understood. Natural RVFV infections are acute, characterized by a rapid onset of peak viremia during the first days post-infection, followed by a rapid decline. Although in vitro studies identified a major role of interferon (IFN) responses in counteracting the infection, a comprehensive overview of the specific host factors that play a role in RVFV pathogenesis in vivo is still lacking. Here, the host in vivo transcriptional profiles in the liver and spleen tissues of lambs exposed to RVFV are studied using RNA sequencing (RNA-seq) technology. We validate that IFN-mediated pathways are robustly activated in response to infection. We also link the observed hepatocellular necrosis with severely compromised organ function, which is reflected as a marked downregulation of multiple metabolic enzymes essential for homeostasis. Furthermore, we associate the elevated basal expression of LRP1 in the liver with RVFV tissue tropism. Collectively, the results of this study deepen the knowledge of the in vivo host response during RVFV infection and reveal new insights into the gene regulation networks underlying pathogenesis in a natural host. IMPORTANCE Rift Valley fever virus (RVFV) is a mosquito-transmitted pathogen capable of causing severe disease in animals and humans. Outbreaks of RVFV pose a significant threat to public health and can result in substantial economic losses. Little is known about the molecular basis of RVFV pathogenesis in vivo, particularly in its natural hosts. We employed RNA-seq technology to investigate genome-wide host responses in the liver and spleen of lambs during acute RVFV infection. We show that RVFV infection drastically decreases the expression of metabolic enzymes, which impairs normal liver function. Moreover, we highlight that basal expression levels of the host factor LRP1 may be a determinant of RVFV tissue tropism. This study links the typical pathological phenotype induced by RVFV infection with tissue-specific gene expression profiles, thereby improving our understanding of RVFV pathogenesis.
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Affiliation(s)
- Erick Bermúdez-Méndez
- Department of Virology and Molecular Biology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
- Laboratory of Virology, Wageningen University & Research, Wageningen, The Netherlands
- Institute of Microbiology, Lausanne University Hospital, Lausanne, Switzerland
- Institute of Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Paolo Angelino
- Institute of Microbiology, Lausanne University Hospital, Lausanne, Switzerland
- Institute of Microbiology, University of Lausanne, Lausanne, Switzerland
- Bioinformatics Core Facility, Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Lucien van Keulen
- Department of Bacteriology, Host-Pathogen Interaction and Diagnostics Development, Wageningen Bioveterinary Research, Lelystad, The Netherlands
| | - Sandra van de Water
- Department of Virology and Molecular Biology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
| | - Barry Rockx
- Department of Virology and Molecular Biology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
| | - Gorben P. Pijlman
- Laboratory of Virology, Wageningen University & Research, Wageningen, The Netherlands
| | - Angela Ciuffi
- Institute of Microbiology, Lausanne University Hospital, Lausanne, Switzerland
- Institute of Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Jeroen Kortekaas
- Department of Virology and Molecular Biology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
- Laboratory of Virology, Wageningen University & Research, Wageningen, The Netherlands
| | - Paul J. Wichgers Schreur
- Department of Virology and Molecular Biology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
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7
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Morrill JC, Peters CJ, Bettinger GE, Palermo PM, Smith DR, Watts DM. Rift Valley fever MP-12 vaccine elicits an early protective immune response in mice. Vaccine 2022; 40:7255-7261. [PMID: 36333222 DOI: 10.1016/j.vaccine.2022.10.062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 10/20/2022] [Accepted: 10/24/2022] [Indexed: 11/13/2022]
Abstract
Rift Valley fever virus (RVFV) is an important mosquito-borne pathogen that causes outbreaks of severe disease in people and livestock throughout Africa and the Arabian Peninsula. The development of an effective veterinary and human vaccine to protect against Rift Valley fever (RVF) disease remains a high priority. The live attenuated RVFV MP-12 is a promising vaccine candidate for the prevention of RVF in both human and domestic ruminants. The aim of this study was to determine the onset of protective immunity elicted in mice by a single dose of this vaccine. Groups of CD-1 mice were vaccinated intraperitoneally with RVFV MP-12 vaccine and challenged on days 2, 5, 6 and 7 post-vaccination (PV) with a lethal dose of virulent RVFV. The mice were observed once daily for terminal morbidity and blood samples were obtained from the retro-orbital sinus complex on days 23 and 28 PV of surviving mice to determine RVFV neutralizing antibody titers. In one test, 2 of 3 mice challenged on day 2 PV survived and all 3 mice challenged at days 5 and 7 PV also survived. A second test of 10 mice per group was performed, and half (5) of those challenged at day 2 PV survived while all (10) survived challenge at day 4 and 6 PV. All surviving animals develop antibody that ranged from 1:80 to 1:1,280 PV. In a separate experiment, RVFV MP-12 vaccinated CD-1 mice, but not challenged developed a low viremia for the first 3 days PV and neutralzing antibody was detected on days 5 through day 28 PV. These findings demonstrated that the RVFV MP-12 vaccine elicited a rapid protective immune response in mice as early as 2 days PV, thus further supporting the effectiveness of this vaccine candidate for preventing RVF among humans and domestic ruminants.
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Affiliation(s)
- J C Morrill
- Departmentof Microbiology and Immunology, University of Texas Medical Branch at Galveston, TX 77555, United States.
| | - C J Peters
- Departments of Microbiology & Immunology and Pathology, University of Texas Medical Branch at Galveston, TX 77555, United States.
| | - G E Bettinger
- Dept. of Biological Sciences, University of Texas at El Paso, El Paso, TX 79968, United States
| | - P M Palermo
- Dept. of Biological Sciences, University of Texas at El Paso, El Paso, TX 79968, United States.
| | - D R Smith
- Department of Microbiology and Immunology, Naval Medical Research Center, Biological Defense Research Directorate, Fort Detrick, MD 21702, United States.
| | - D M Watts
- Dept. of Biological Sciences, University of Texas at El Paso, El Paso, TX 79968, United States.
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8
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Michaely LM, Rissmann M, Keller M, König R, von Arnim F, Eiden M, Rohn K, Baumgärtner W, Groschup M, Ulrich R. NSG-Mice Reveal the Importance of a Functional Innate and Adaptive Immune Response to Overcome RVFV Infection. Viruses 2022; 14:v14020350. [PMID: 35215938 PMCID: PMC8880686 DOI: 10.3390/v14020350] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/20/2022] [Accepted: 02/03/2022] [Indexed: 12/12/2022] Open
Abstract
Rift Valley fever (RVF) is a zoonotic disease caused by RVF Phlebovirus (RVFV). The RVFV MP-12 vaccine strain is known to exhibit residual virulence in the case of a deficient interferon type 1 response. The hypothesis of this study is that virus replication and severity of lesions induced by the MP-12 strain in immunocompromised mice depend on the specific function of the disturbed pathway. Therefore, 10 strains of mice with deficient innate immunity (B6-IFNARtmAgt, C.129S7(B6)-Ifngtm1Ts/J, B6-TLR3tm1Flv, B6-TLR7tm1Aki, NOD/ShiLtJ), helper T-cell- (CD4tm1Mak), cytotoxic T-cell- (CD8atm1Mak), B-cell- (Igh-Jtm1DhuN?+N2), combined T- and B-cell- (NU/J) and combined T-, B-, natural killer (NK) cell- and macrophage-mediated immunity (NOD.Cg-PrkdcscidIl2rgtm1WjI/SzJ (NSG) mice) were subcutaneously infected with RVFV MP-12. B6-IFNARtmAgt mice were the only strain to develop fatal disease due to RVFV-induced severe hepatocellular necrosis and apoptosis. Notably, no clinical disease and only mild multifocal hepatocellular necrosis and apoptosis were observed in NSG mice, while immunohistochemistry detected the RVFV antigen in the liver and the brain. No or low virus expression and no lesions were observed in the other mouse strains. Conclusively, the interferon type 1 response is essential for early control of RVFV replication and disease, whereas functional NK cells, macrophages and lymphocytes are essential for virus clearance.
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Affiliation(s)
- Lukas Mathias Michaely
- Department of Pathology, University of Veterinary Medicine Hannover, Foundation, Bünteweg 17, 30559 Hannover, Germany;
- Center for Systems Neuroscience Hannover, University of Veterinary Medicine Hannover, Foundation, Bünteweg 2, 30559 Hannover, Germany
| | - Melanie Rissmann
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (M.R.); (M.K.); (R.K.); (F.v.A.); (M.E.); (M.G.)
| | - Markus Keller
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (M.R.); (M.K.); (R.K.); (F.v.A.); (M.E.); (M.G.)
| | - Rebecca König
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (M.R.); (M.K.); (R.K.); (F.v.A.); (M.E.); (M.G.)
| | - Felicitas von Arnim
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (M.R.); (M.K.); (R.K.); (F.v.A.); (M.E.); (M.G.)
| | - Martin Eiden
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (M.R.); (M.K.); (R.K.); (F.v.A.); (M.E.); (M.G.)
| | - Karl Rohn
- Institute for Biometry, Epidemiology and Information Processing, University of Veterinary Medicine Hannover, Foundation, Bünteweg 2, 30559 Hannover, Germany;
| | - Wolfgang Baumgärtner
- Department of Pathology, University of Veterinary Medicine Hannover, Foundation, Bünteweg 17, 30559 Hannover, Germany;
- Center for Systems Neuroscience Hannover, University of Veterinary Medicine Hannover, Foundation, Bünteweg 2, 30559 Hannover, Germany
- Correspondence: ; Tel.: +49-511-953-8620; Fax: +49-511-953-8675
| | - Martin Groschup
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany; (M.R.); (M.K.); (R.K.); (F.v.A.); (M.E.); (M.G.)
| | - Reiner Ulrich
- Institute of Veterinary-Pathology, Faculty of Veterinary Medicine, Leipzig University, 04103 Leipzig, Germany;
- Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems, Germany
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9
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Alem F, Olanrewaju AA, Omole S, Hobbs HE, Ahsan N, Matulis G, Brantner CA, Zhou W, Petricoin EF, Liotta LA, Caputi M, Bavari S, Wu Y, Kashanchi F, Hakami RM. Exosomes originating from infection with the cytoplasmic single-stranded RNA virus Rift Valley fever virus (RVFV) protect recipient cells by inducing RIG-I mediated IFN-B response that leads to activation of autophagy. Cell Biosci 2021; 11:220. [PMID: 34953502 PMCID: PMC8710069 DOI: 10.1186/s13578-021-00732-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/12/2021] [Indexed: 12/12/2022] Open
Abstract
Background Although multiple studies have demonstrated a role for exosomes during virus infections, our understanding of the mechanisms by which exosome exchange regulates immune response during viral infections and affects viral pathogenesis is still in its infancy. In particular, very little is known for cytoplasmic single-stranded RNA viruses such as SARS-CoV-2 and Rift Valley fever virus (RVFV). We have used RVFV infection as a model for cytoplasmic single-stranded RNA viruses to address this gap in knowledge. RVFV is a highly pathogenic agent that causes RVF, a zoonotic disease for which no effective therapeutic or approved human vaccine exist. Results We show here that exosomes released from cells infected with RVFV (designated as EXi-RVFV) serve a protective role for the host and provide a mechanistic model for these effects. Our results show that treatment of both naïve immune cells (U937 monocytes) and naïve non-immune cells (HSAECs) with EXi-RVFV induces a strong RIG-I dependent activation of IFN-B. We also demonstrate that this strong anti-viral response leads to activation of autophagy in treated cells and correlates with resistance to subsequent viral infection. Since we have shown that viral RNA genome is associated with EXi-RVFV, RIG-I activation might be mediated by the presence of packaged viral RNA sequences. Conclusions Using RVFV infection as a model for cytoplasmic single-stranded RNA viruses, our results show a novel mechanism of host protection by exosomes released from infected cells (EXi) whereby the EXi activate RIG-I to induce IFN-dependent activation of autophagy in naïve recipient cells including monocytes. Because monocytes serve as reservoirs for RVFV replication, this EXi-RVFV-induced activation of autophagy in monocytes may work to slow down or halt viral dissemination in the infected organism. These findings offer novel mechanistic insights that may aid in future development of effective vaccines or therapeutics, and that may be applicable for a better molecular understanding of how exosome release regulates innate immune response to other cytoplasmic single-stranded RNA viruses. Supplementary Information The online version contains supplementary material available at 10.1186/s13578-021-00732-z.
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Affiliation(s)
- Farhang Alem
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA
| | - Adeyemi A Olanrewaju
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA
| | - Samson Omole
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA
| | - Heather E Hobbs
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA
| | - Noor Ahsan
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA.,Lentigen Technology, Inc., Gaithersburg, MD, USA
| | - Graham Matulis
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA
| | - Christine A Brantner
- Nanofabrication and Imaging Center, George Washington University, Washington, DC, USA
| | - Weidong Zhou
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Applied Proteomics and Molecular Medicine, George Mason University, Manassas, VA, USA
| | - Emanuel F Petricoin
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Applied Proteomics and Molecular Medicine, George Mason University, Manassas, VA, USA
| | - Lance A Liotta
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Applied Proteomics and Molecular Medicine, George Mason University, Manassas, VA, USA
| | - Massimo Caputi
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL, USA
| | | | - Yuntao Wu
- School of Systems Biology, George Mason University, Manassas, VA, USA.,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA
| | - Fatah Kashanchi
- School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Ramin M Hakami
- School of Systems Biology, George Mason University, Manassas, VA, USA. .,Center for Infectious Disease Research (Formerly, National Center for Biodefense and Infectious Diseases), George Mason University, Manassas, VA, USA.
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10
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Peng K, Lozach PY. Rift Valley fever virus: a new avenue of research on the biological functions of amyloids? Future Virol 2021. [DOI: 10.2217/fvl-2021-0094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Rift Valley fever is a mosquito-borne viral zoonosis that was first discovered in the Great Rift Valley, Kenya, in 1930. Rift Valley fever virus (RVFV) primarily infects domestic animals and humans, with clinical outcomes ranging from self-limiting febrile illness to acute hepatitis and encephalitis. The virus left Africa a few decades ago, and there is a risk of introduction into southern Europe and Asia. From this perspective, we introduce RVFV and focus on the capacity of its virulence factor, the nonstructural protein NSs, to form amyloid-like fibrils. Here, we discuss the implications for the NSs biological function, the ability of RVFV to evade innate immunity, and RVFV virulence and neurotoxicity.
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Affiliation(s)
- Ke Peng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, Hubei, 430071, PR China
- University of the Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Pierre-Yves Lozach
- Cell Networks, CIID (Cluster of Excellence & Center for Integrative Infectious Disease Research), Virology, University Hospital Heidelberg, 69120, Heidelberg, Germany
- University of Lyon, INRAE, EPHE, IVPC (Infections Virales et Pathologie Comparée), 69007, Lyon, France
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11
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Léger P, Lozach PY. [Rift Valley fever virus and the amazing NSs protein]. Med Sci (Paris) 2021; 37:601-608. [PMID: 34180819 DOI: 10.1051/medsci/2021090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Rift Valley Fever Virus (RVFV) is an emerging zoonotic pathogen transmitted to humans and livestock through mosquito bites, which was first isolated in Kenya in 1930. The virus is classified by the WHO among the pathogens for which there is an urgent need to develop research, diagnostics, and therapies. However, the efforts developed to control the virus remain limited, and the virus is not well characterized. In this article, we will introduce RVFV and then focus on its virulence factor, the nonstructural protein NSs. We will mainly discuss the ability of this viral protein to form amyloid-like fibrils and its implication in the neurotoxicity associated with RVFV infection.
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Affiliation(s)
- Psylvia Léger
- CellNetworks, CIID (Cluster of Excellence and Center for Integrative Infectious Disease Research), Virology, University hospital Heidelberg, Im Neuenheimer Feld 344, 69120 Heidelberg, Allemagne
| | - Pierre-Yves Lozach
- CellNetworks, CIID (Cluster of Excellence and Center for Integrative Infectious Disease Research), Virology, University hospital Heidelberg, Im Neuenheimer Feld 344, 69120 Heidelberg, Allemagne - Univ. Lyon, INRAe, EPHE, IVPC (Infections virales et pathologie comparée), 50 avenue Tony Garnier, 69007 Lyon, France
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12
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Characterization of the Molecular Interactions That Govern the Packaging of Viral RNA Segments into Rift Valley Fever Phlebovirus Particles. J Virol 2021; 95:e0042921. [PMID: 33952635 DOI: 10.1128/jvi.00429-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Rift Valley fever phlebovirus (RVFV) has a single-stranded, negative-sense RNA genome, consisting of L, M, and S segments. The virion carries two envelope glycoproteins, Gn and Gc, along with ribonucleoprotein complexes (RNPs), composed of encapsidated genomes carrying N protein and the viral polymerase, L protein. A quantitative analysis of the profile of viral RNA segments packaged into RVFV particles showed that all three genomic RNA segments had similar packaging abilities, whereas among antigenomic RNA segments, the antigenomic S RNA, which serves as the template for the transcription of mRNA expressing the RVFV virulence factor, NSs, displayed a significantly higher packaging ability. To delineate the factor(s) governing the packaging of RVFV RNA segments, we characterized the interactions between Gn and viral RNPs in RVFV-infected cells. Coimmunoprecipitation analysis demonstrated the interaction of Gn with N protein, L protein, and viral RNAs in RVFV-infected cells. Furthermore, UV-cross-linking and immunoprecipitation analysis revealed, for the first time in bunyaviruses, the presence of a direct interaction between Gn and all the viral RNA segments in RVFV-infected cells. Notably, analysis of the ability of Gn to bind to RVFV RNA segments indicated a positive correlation with their respective packaging abilities and highlighted a binding preference of Gn for antigenomic S RNA, among the antigenomic RNA segments, suggesting the presence of a selection mechanism for antigenomic S RNA incorporation into infectious RVFV particles. Collectively, the results of our study illuminate the importance of a direct interaction between Gn and viral RNA segments in determining their efficiency of incorporation into RVFV particles. IMPORTANCE Rift Valley fever phlebovirus, a bunyavirus, is a mosquito-borne, segmented RNA virus that can cause severe disease in humans and ruminants. An essential step in RVFV life cycle is the packaging of viral RNA segments to produce infectious virus particles for dissemination to new hosts. However, there are key gaps in knowledge regarding the mechanisms that regulate viral RNA packaging efficiency in bunyaviruses. Our studies investigating the mechanism of RNA packaging in RVFV revealed the presence of a direct interaction between the viral envelope glycoprotein, Gn, and the viral RNA segments in infected cells, for the first time in bunyaviruses. Furthermore, our data strongly indicate a critical role for the direct interaction between Gn and viral RNAs in determining the efficiency of incorporation of viral RNA segments into RVFV particles. Clarifying the fundamental mechanisms of RNA packaging in RVFV would be valuable for the development of antivirals and live-attenuated vaccines.
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13
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Kumalija MS, Chilongola JO, Budodo RM, Horumpende PG, Mkumbaye SI, Vianney JM, Mwakapuja RS, Mmbaga BT. Detection of Rift Valley Fever virus inter-epidemic activity in Kilimanjaro Region, North Eastern Tanzania. Glob Health Action 2021; 14:1957554. [PMID: 34415237 PMCID: PMC8381910 DOI: 10.1080/16549716.2021.1957554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Background Rift Valley Fever virus (RVFV) is a zoonotic arbovirus of public health impact infecting livestock, wildlife, and humans mainly in Africa and other parts of the world. Despite its public health importance, mechanisms of RVFV maintenance during interepidemic periods (IEPS) remain unclear. Objective We aimed to examine comparatively exposure to RVFV between humans and goats and RVFV infection between humans, goats and mosquitoes. Methods A cross sectional study was performed in the Lower Moshi area of the Kilimanjaro region from March to June 2020. RVFV exposure was determined by detecting IgG/IgM to RVFV using a competitive enzyme linked immunosorbent assay whereas infection was determined by real time quantitative polymerase chain reaction (RT-qPCR) assay. Results Results show that the male gender was related to RVFV seropositivity (χ2 = 5.351; p=0.030). Being 50 years and above was related to seropositivity (χ2 =14.430; p=0.006) whereas bed net use, larger numbers of persons living in the same house (>7 persons) and RVFV seropositivity in goats were related to higher seropositivity to RVFV among humans χ2 =6.003; p=0.021, χ2 =23.213; p < 0.001 and χ2 =27.053; p < 0.001), respectively. By the use of RT-qPCR, goats exhibited the highest RVFV infection rate of 4.1%, followed by humans (2.6%), Ae. aegypti (2.3%), and Cx. pipiens complex(1.5%). Likewise, a higher proportion of goats (23.3%) were RVFV seropositive as compared with humans (13.2%). Conclusion Our findings suggest the Lower Moshi area as a potential hotspot for Rift Valley Fever (RVF), posing the danger of being a source of RVFV spread to other areas. Goats had the highest infection rate, suggesting goats as important hosts for virus maintenance during IEPs. We recommend the implementation of strategies that will warrant active RVF surveillance through the identification of RVF hotspots for targeted control of the disease.
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Affiliation(s)
- Medard S Kumalija
- Department of Global Health and Biomedical Sciences, Nelson Mandela Institution of Science and Technology, Arusha, Tanzania
| | - Jaffu O Chilongola
- Department of Medical Biochemistry and Molecular Biology, Kilimanjaro Christian Medical University College, Moshi Tanzania.,Department of Clinical Trials, Kilimanjaro Clinical Research Institute, Moshi, Tanzania
| | - Rule M Budodo
- Department of Clinical Trials, Kilimanjaro Clinical Research Institute, Moshi, Tanzania
| | - Pius G Horumpende
- Department of Public Health and Research, Lugalo Military College of Medical Sciences, Dar Es Salaam, Tanzania
| | - Sixbert I Mkumbaye
- Department of Clinical Trials, Kilimanjaro Clinical Research Institute, Moshi, Tanzania
| | - John-Mary Vianney
- Department of Global Health and Biomedical Sciences, Nelson Mandela Institution of Science and Technology, Arusha, Tanzania
| | - Richard S Mwakapuja
- Department of Bacterial Vaccines, Tanzania Veterinary Laboratory Agency (TVLA), Kibaha, Tanzania
| | - Blandina T Mmbaga
- Department of Clinical Trials, Kilimanjaro Clinical Research Institute, Moshi, Tanzania
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14
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Grossi-Soyster EN, LaBeaud AD. Rift Valley Fever: Important Considerations for Risk Mitigation and Future Outbreaks. Trop Med Infect Dis 2020; 5:tropicalmed5020089. [PMID: 32498264 PMCID: PMC7345646 DOI: 10.3390/tropicalmed5020089] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 05/22/2020] [Accepted: 05/28/2020] [Indexed: 12/02/2022] Open
Abstract
Rift Valley fever virus (RVFV) is a zoonotic phlebovirus of the Phenuiviridae family with great opportunity for emergence in previously unaffected regions, despite its current geographical limits. Outbreaks of RVFV often infect humans or domesticated animals, such as livestock, concurrently and occur sporadically, ranging from localized outbreaks in villages to multi-country events that spread rapidly. The true burden of Rift Valley fever (RVF) is not well defined due to underreporting, misdiagnosis caused by the broad spectrum of disease presentation, and minimal access for rapid and accurate laboratory confirmation. Severe symptoms may include hemorrhagic fever, loss of vision, psychological impairment or disturbances, and organ failure. Those living in endemic areas and travelers should be aware of the potential for exposure to ongoing outbreaks or interepidemic transmission, and engage in behaviors to minimize exposure risks, as vaccinations in humans are currently unavailable and animal vaccinations are not used routinely or ubiquitously. The lack of vaccines approved for use in humans is concerning, as RVFV has proven to be highly pathogenic in naïve populations, causing severe disease in a large percent of confirmed cases, which could have considerable impact on human health.
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15
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Teffera M, Babiuk S. Potential of Using Capripoxvirus Vectored Vaccines Against Arboviruses in Sheep, Goats, and Cattle. Front Vet Sci 2019; 6:450. [PMID: 31921911 PMCID: PMC6932975 DOI: 10.3389/fvets.2019.00450] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 11/27/2019] [Indexed: 11/26/2022] Open
Abstract
The genus capripoxvirus consists of sheeppox virus, goatpox virus, and lumpy skin disease virus, which affect sheep, goats, and cattle, respectively. Together capripoxviruses cause significant economic losses to the sheep, goat, and cattle industry where these diseases are present. These diseases have spread into previously free bordering regions most recently demonstrated with the spread of lumpy skin disease virus into the Middle East, some Eastern European countries, and Russia. This recent spread has highlighted the transboundary nature of these diseases. To control lumpy skin disease virus, live attenuated viral vaccines are used in endemic countries as well as in response to an outbreak. For sheeppox and goatpox, live attenuated viral vaccines are used in endemic countries; these diseases can also be contained through slaughter of infected animals to stamp out the disease. The thermostability, narrow host range, and ability of capripoxviruses to express a wide variety of antigens make capripoxviruses ideal vectors. The ability to immunize animals against multiple diseases simultaneously increases vaccination efficiency by decreasing the number of vaccinations required. Additionally, the use of capripoxvirus vectored vaccines allows the possibility of differentiating infected from vaccinated animals. Arboviruses such as bluetongue virus and Rift Valley fever viruses are also responsible for significant economic losses in endemic countries. In the case of Rift Valley fever virus, vaccination is not routinely practiced unless there is an outbreak making vaccination not as effective, therefore, incorporating Rift Valley fever vaccination into routine capripoxvirus vaccination would be highly beneficial. This review will discuss the potential of using capripoxvirus as a vector expressing protective arboviral antigens.
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Affiliation(s)
- Mahder Teffera
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
- Department of Immunology, University of Manitoba, Winnipeg, MB, Canada
| | - Shawn Babiuk
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
- Department of Immunology, University of Manitoba, Winnipeg, MB, Canada
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16
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Abstract
Rift Valley fever (RVF) is a mosquito-borne viral zoonosis that was first discovered in Kenya in 1930 and is now endemic throughout multiple African countries and the Arabian Peninsula. RVF virus primarily infects domestic livestock (sheep, goats, cattle) causing high rates of neonatal mortality and abortion, with human infection resulting in a wide variety of clinical outcomes, ranging from self-limiting febrile illness to life-threatening haemorrhagic diatheses, and miscarriage in pregnant women. Since its discovery, RVF has caused many outbreaks in Africa and the Arabian Peninsula with major impacts on human and animal health. However, options for the control of RVF outbreaks are limited by the lack of licensed human vaccines or therapeutics. For this reason, RVF is prioritized by the World Health Organization for urgent research and development of countermeasures for the prevention and control of future outbreaks. In this review, we highlight the current understanding of RVF, including its epidemiology, pathogenesis, clinical manifestations and status of vaccine development.
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Affiliation(s)
- Daniel Wright
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- The Jenner Institute, University of Oxford, Oxford OX1 2JD, UK
| | - Jeroen Kortekaas
- Wageningen Bioveterinary Research, Lelystad, The Netherlands
- Laboratory of Virology, Wageningen University, Wageningen, The Netherlands
| | - Thomas A. Bowden
- Wellcome Centre for Human Genetics, Division of Structural Biology, University of Oxford, Oxford OX1 2JD, UK
| | - George M. Warimwe
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford OX1 2JD, UK
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17
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A strand-specific real-time quantitative RT-PCR assay for distinguishing the genomic and antigenomic RNAs of Rift Valley fever phlebovirus. J Virol Methods 2019; 272:113701. [PMID: 31315022 DOI: 10.1016/j.jviromet.2019.113701] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 07/13/2019] [Indexed: 11/21/2022]
Abstract
Rift Valley Fever phlebovirus (RVFV), genus Phlebovirus, family Phenuiviridae, order Bunyavirales, has a single-stranded, negative-sense RNA genome, consisting of L, M and S segments. Here, we report the establishment of a strand-specific, quantitative reverse transcription (RT)-PCR assay system that can selectively distinguish between the genomic and antigenomic RNAs of each of the three viral RNA segments produced in RVFV-infected cells. To circumvent the obstacle of primer-independent cDNA synthesis during RT, we used a tagged, strand-specific RT primer, carrying a non-viral 'tag' sequence at the 5' end, which ensured the strand-specificity through the selective amplification of only the tagged cDNA in the real-time PCR assay. We used this assay system to examine the kinetics of intracellular accumulation of genomic and antigenomic viral RNAs in mammalian cells infected with the MP-12 strain of RVFV. The genomic RNA copy numbers, for all three viral RNA segments, were higher than that of their corresponding antigenomic RNAs throughout the time-course of infection, with a notable exception, wherein the M segment genomic and antigenomic RNAs exhibited similar copy numbers at specific times post-infection. Overall, this assay system could be a useful tool to gain an insight into the mechanisms of RNA replication and packaging in RVFV.
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18
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Hartman DA, Rice LM, DeMaria J, Borland EM, Bergren NA, Fagre AC, Robb LL, Webb CT, Kading RC. Entomological risk factors for potential transmission of Rift Valley fever virus around concentrations of livestock in Colorado. Transbound Emerg Dis 2019; 66:1709-1717. [PMID: 31002468 DOI: 10.1111/tbed.13206] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 04/11/2019] [Accepted: 04/12/2019] [Indexed: 01/07/2023]
Abstract
Rift Valley fever virus (RVFV) poses a major threat of introduction to several continents, including North America. Such an introduction could cause significant losses to the livestock industry, in addition to substantial human morbidity and mortality. Because of the opportunistic blood host selection of Culex tarsalis mosquitoes, we hypothesized that this species could be an important bridge vector of RVFV near feedlots in the event of an introduction. We investigated the mosquito community composition at livestock feedlots and surrounding natural and residential areas to determine differences in mosquito relative abundance and blood feeding patterns attributed to cattle feeding operations. DNA extracted from abdomens of blood-fed mosquitoes were sequenced to determine host identity. Multivariate regression analyses revealed differences between mosquito community assemblages at feedlots and non-feedlot sites (p < 0.05), with this effect driven largely by differential abundances of Aedes vexans (padj < 0.05). Mosquito diversity was lower on feedlots than surrounding areas for three out of four feedlots. Culex tarsalis was abundant at both feedlots and nearby sites. Diverse vertebrate blood meals were detected in Cx. tarsalis at non-feedlot sites, with a shift towards feeding on cattle at feedlots. These data support a potential for Cx. tarsalis to serve as a bridge vector of RVFV between livestock and humans in Colorado.
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Affiliation(s)
- Daniel A Hartman
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado
| | - Lauren M Rice
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado
| | - Justin DeMaria
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado
| | - Erin M Borland
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado
| | - Nicholas A Bergren
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado
| | - Anna C Fagre
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado
| | - Lucy L Robb
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado
| | - Colleen T Webb
- Department of Biology, Colorado State University, Fort Collins, Colorado
| | - Rebekah C Kading
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado
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Grossi-Soyster EN, Lee J, King CH, LaBeaud AD. The influence of raw milk exposures on Rift Valley fever virus transmission. PLoS Negl Trop Dis 2019; 13:e0007258. [PMID: 30893298 PMCID: PMC6443189 DOI: 10.1371/journal.pntd.0007258] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 04/01/2019] [Accepted: 02/23/2019] [Indexed: 02/07/2023] Open
Abstract
Rift Valley fever virus (RVFV) is a zoonotic phlebovirus that can be transmitted to humans or livestock by mosquitoes or through direct contact with contaminated bodily fluids and tissues. Exposure to bodily fluids and tissues varies by types of behaviors engaged for occupational tasks, homestead responsibilities, or use in dietary or therapeutic capacities. While previous studies have included milk exposures in their analyses, their primary focus on livestock exposures has been on animal handling, breeding, and slaughter. We analyzed data from multiple field surveys in Kenya with the aim of associating RVFV infection to raw milk exposures from common animal species. Of those with evidence of prior RVFV infection by serology (n = 267), 77.2% engaged in milking livestock compared to 32.0% for 3,956 co-local seronegative individuals (p < 0.001), and 86.5% of seropositive individuals consumed raw milk compared to 33.4% seronegative individuals (p < 0.001). Individuals who milked and also consumed raw milk had greater odds of RVFV exposure than individuals whose only contact to raw milk was through milking. Increased risks were associated with exposure to milk sourced from cows (p < 0.001), sheep (p < 0.001), and goats (p < 0.001), but not camels (p = 0.98 for consuming, p = 0.21 for milking). Our data suggest that exposure to raw milk may contribute to a significant number of cases of RVFV, especially during outbreaks and in endemic areas, and that some animal species may be associated with a higher risk for RVFV exposure. Livestock trade is regulated to limit RVFV spread from endemic areas, yet further interventions designed to fully understand the risk of RVFV exposure from raw milk are imperative.
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Affiliation(s)
- Elysse N. Grossi-Soyster
- Department of Pediatrics, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, CA, United States of America
- * E-mail:
| | - Justin Lee
- Quantitative Sciences Unit, Stanford University School of Medicine, Stanford, CA, United States of America
| | - Charles H. King
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, United States of America
| | - A. Desiree LaBeaud
- Department of Pediatrics, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, CA, United States of America
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20
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Pinkham C, Ahmed A, Bracci N, Narayanan A, Kehn-Hall K. Host-based processes as therapeutic targets for Rift Valley fever virus. Antiviral Res 2018; 160:64-78. [PMID: 30316916 DOI: 10.1016/j.antiviral.2018.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 09/27/2018] [Accepted: 10/05/2018] [Indexed: 12/28/2022]
Abstract
Rift Valley fever virus (RVFV) is an enveloped, segmented, negative sense RNA virus that replicates within the host's cytoplasm. To facilitate its replication, RVFV must utilize host cell processes and as such, these processes may serve as potential therapeutic targets. This review summarizes key host cell processes impacted by RVFV infection. Specifically the influence of RVFV on host transcriptional regulation, post-transcriptional regulation, protein half-life and availability, host signal transduction, trafficking and secretory pathways, cytoskeletal modulation, and mitochondrial processes and oxidative stress are discussed. Therapeutics targeted towards host processes that are essential for RVFV to thrive as well as their efficacy and importance to viral pathogenesis are highlighted.
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Affiliation(s)
- Chelsea Pinkham
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Aslaa Ahmed
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Nicole Bracci
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Aarthi Narayanan
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA
| | - Kylene Kehn-Hall
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA.
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Egesten A, Herwald H. Visions and the Progress of Science. J Innate Immun 2017. [PMID: 28637042 DOI: 10.1159/000478280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Lumley S, Horton DL, Hernandez-Triana LLM, Johnson N, Fooks AR, Hewson R. Rift Valley fever virus: strategies for maintenance, survival and vertical transmission in mosquitoes. J Gen Virol 2017; 98:875-887. [PMID: 28555542 DOI: 10.1099/jgv.0.000765] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Rift Valley fever virus (RVFV) is a mosquito-borne arbovirus causing severe disease in humans and ruminants. Spread of RVFV out of Africa has raised concerns that it could emerge in Europe or the USA. Virus persistence is dependent on successful infection of, replication in, and transmission to susceptible vertebrate and invertebrate hosts, modulated by virus-host and vector-virus interactions. The principal accepted theory for the long-term maintenance of RVFV involves vertical transmission (VT) of virus to mosquito progeny, with the virus surviving long inter-epizootic periods within the egg. This VT hypothesis, however, is yet to be comprehensively proven. Here, evidence for and against the VT of RVFV is reviewed along with the identification of factors limiting its detection in natural and experimental data. The observations of VT for other arboviruses in the genera Alphavirus, Flavivirus and Orthobunyavirus are discussed within the context of RVFV. The review concludes that VT of RVFV is likely but that current data are insufficient to irrefutably prove this hypothesis.
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Affiliation(s)
- Sarah Lumley
- Wildlife Zoonoses and Vector-borne Diseases Research Group, Animal and Plant Health Agency, Addlestone, Surrey, UK.,School of Veterinary Medicine, University of Surrey, Guildford, UK.,Virology and Pathogenesis Group, Microbiology Services Division, Public Health England, Wiltshire, UK
| | - Daniel L Horton
- School of Veterinary Medicine, University of Surrey, Guildford, UK
| | - Luis L M Hernandez-Triana
- Wildlife Zoonoses and Vector-borne Diseases Research Group, Animal and Plant Health Agency, Addlestone, Surrey, UK
| | - Nicholas Johnson
- School of Veterinary Medicine, University of Surrey, Guildford, UK.,Wildlife Zoonoses and Vector-borne Diseases Research Group, Animal and Plant Health Agency, Addlestone, Surrey, UK
| | - Anthony R Fooks
- Wildlife Zoonoses and Vector-borne Diseases Research Group, Animal and Plant Health Agency, Addlestone, Surrey, UK.,Department of Clinical Infection, Microbiology and Immunology, University of Liverpool, Liverpool, UK.,NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, University of Liverpool, Liverpool, UK
| | - Roger Hewson
- Virology and Pathogenesis Group, Microbiology Services Division, Public Health England, Wiltshire, UK.,NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, University of Liverpool, Liverpool, UK
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Terasaki K, Ramirez SI, Makino S. Mechanistic Insight into the Host Transcription Inhibition Function of Rift Valley Fever Virus NSs and Its Importance in Virulence. PLoS Negl Trop Dis 2016; 10:e0005047. [PMID: 27711108 PMCID: PMC5053439 DOI: 10.1371/journal.pntd.0005047] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 09/17/2016] [Indexed: 11/18/2022] Open
Abstract
Rift Valley fever virus (RVFV), a member of the genus Phlebovirus within the family Bunyaviridae, causes periodic outbreaks in livestocks and humans in countries of the African continent and Middle East. RVFV NSs protein, a nonstructural protein, is a major virulence factor that exhibits several important biological properties. These include suppression of general transcription, inhibition of IFN-β promoter induction and degradation of double-stranded RNA-dependent protein kinase R. Although each of these biological functions of NSs are considered important for countering the antiviral response in the host, the individual contributions of these functions towards RVFV virulence remains unclear. To examine this, we generated two RVFV MP-12 strain-derived mutant viruses. Each carried mutations in NSs that specifically targeted its general transcription inhibition function without affecting its ability to degrade PKR and inhibit IFN-β promoter induction, through its interaction with Sin3-associated protein 30, a part of the repressor complex at the IFN-β promoter. Using these mutant viruses, we have dissected the transcription inhibition function of NSs and examined its importance in RVFV virulence. Both NSs mutant viruses exhibited a differentially impaired ability to inhibit host transcription when compared with MP-12. It has been reported that NSs suppresses general transcription by interfering with the formation of the transcription factor IIH complex, through the degradation of the p62 subunit and sequestration of the p44 subunit. Our study results lead us to suggest that the ability of NSs to induce p62 degradation is the major contributor to its general transcription inhibition property, whereas its interaction with p44 may not play a significant role in this function. Importantly, RVFV MP-12-NSs mutant viruses with an impaired general transcription inhibition function showed a reduced cytotoxicity in cell culture and attenuated virulence in young mice, compared with its parental virus MP-12, highlighting the contribution of NSs-mediated general transcription inhibition towards RVFV virulence. Rift Valley fever virus (RVFV) has a significant impact on the livestock industry because of its high mortality rate in young ruminants and causation of a high abortion rate in pregnant animals. Human RVFV infections generally manifest as self-limiting and non-fatal illnesses. However, a small percentage of patients develop encephalitis, vision loss and hemorrhagic fever with a high mortality rate. Currently, there is no commercially available vaccine for human use or effective antiviral drug for RVFV treatment. The non-structural protein NSs is a major virulence factor of RVFV, which mediates suppression of host general transcription, inhibition of IFN-β transcription and degradation of PKR, to block host antiviral responses. To examine the contribution of host transcription inhibition to RVFV virulence, we generated RVFV MP-12 strain-derived mutants that have attenuated inhibitory activity on host transcription due to amino acid mutations in NSs. The mutant viruses showed attenuated cytotoxicity in cell culture and attenuated virulence in young mice, demonstrating the contribution of NSs-mediated host transcription inhibition to the virulence of RVFV.
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Affiliation(s)
- Kaori Terasaki
- Department of Microbiology and Immunology, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Sydney I. Ramirez
- Department of Pathology, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Shinji Makino
- Department of Microbiology and Immunology, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, The University of Texas Medical Branch, Galveston, Texas, United States of America
- UTMB Center for Tropical Diseases, The University of Texas Medical Branch, Galveston, Texas, United States of America
- Sealy Center for Vaccine Development, The University of Texas Medical Branch, Galveston, Texas, United States of America
- The Institute for Human Infections and Immunity, The University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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NSs Virulence Factor of Rift Valley Fever Virus Engages the F-Box Proteins FBXW11 and β-TRCP1 To Degrade the Antiviral Protein Kinase PKR. J Virol 2016; 90:6140-7. [PMID: 27122577 PMCID: PMC4907219 DOI: 10.1128/jvi.00016-16] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 04/18/2016] [Indexed: 01/01/2023] Open
Abstract
Rift Valley fever virus (RVFV, family Bunyaviridae, genus Phlebovirus) is a relevant pathogen of both humans and livestock in Africa. The nonstructural protein NSs is a major virulence factor known to suppress the type I interferon (IFN) response by inhibiting host cell transcription and by proteasomal degradation of a major antiviral IFN effector, the translation-inhibiting protein kinase PKR. Here, we identified components of the modular SCF (Skp1, Cul1, F-box protein)-type E3 ubiquitin ligases as mediators of PKR destruction by NSs. Small interfering RNAs (siRNAs) against the conserved SCF subunit Skp1 protected PKR from NSs-mediated degradation. Consequently, RVFV replication was severely reduced in Skp1-depleted cells when PKR was present. SCF complexes have a variable F-box protein subunit that determines substrate specificity for ubiquitination. We performed an siRNA screen for all (about 70) human F-box proteins and found FBXW11 to be involved in PKR degradation. The partial stabilization of PKR by FBXW11 depletion upregulated PKR autophosphorylation and phosphorylation of the PKR substrate eIF2α and caused a shutoff of host cell protein synthesis in RVFV-infected cells. To maximally protect PKR from the action of NSs, knockdown of structurally and functionally related FBXW1 (also known as β-TRCP1), in addition to FBXW11 deletion, was necessary. Consequently, NSs was found to interact with both FBXW11 and β-TRCP1. Thus, NSs eliminates the antiviral kinase PKR by recruitment of SCF-type E3 ubiquitin ligases containing FBXW11 and β-TRCP1 as substrate recognition subunits. This antagonism of PKR by NSs is essential for efficient RVFV replication in mammalian cells. IMPORTANCE Rift Valley fever virus is a pathogen of humans and animals that has the potential to spread from Africa and the Arabian Peninsula to other regions. A major virulence mechanism is the proteasomal degradation of the antiviral kinase PKR by the viral protein NSs. Here, we demonstrate that NSs requires E3 ubiquitin ligase complexes of the SCF (Skp1, Cul1, F-box protein) type to destroy PKR. SCF-type complexes can engage variant ubiquitination substrate recognition subunits, and we found the F-box proteins FBXW11 and β-TRCP1 to be relevant for the action of NSs against PKR. Thus, we identified the host cell factors that are critically needed by Rift Valley fever virus to uphold its replication against the potent antiviral kinase PKR.
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Middle East Respiratory Syndrome Coronavirus nsp1 Inhibits Host Gene Expression by Selectively Targeting mRNAs Transcribed in the Nucleus while Sparing mRNAs of Cytoplasmic Origin. J Virol 2015; 89:10970-81. [PMID: 26311885 DOI: 10.1128/jvi.01352-15] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 08/15/2015] [Indexed: 02/08/2023] Open
Abstract
UNLABELLED The newly emerged Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome CoV (SARS-CoV) represent highly pathogenic human CoVs that share a property to inhibit host gene expression at the posttranscriptional level. Similar to the nonstructural protein 1 (nsp1) of SARS-CoV that inhibits host gene expression at the translational level, we report that MERS-CoV nsp1 also exhibits a conserved function to negatively regulate host gene expression by inhibiting host mRNA translation and inducing the degradation of host mRNAs. Furthermore, like SARS-CoV nsp1, the mRNA degradation activity of MERS-CoV nsp1, most probably triggered by its ability to induce an endonucleolytic RNA cleavage, was separable from its translation inhibitory function. Despite these functional similarities, MERS-CoV nsp1 used a strikingly different strategy that selectively targeted translationally competent host mRNAs for inhibition. While SARS-CoV nsp1 is localized exclusively in the cytoplasm and binds to the 40S ribosomal subunit to gain access to translating mRNAs, MERS-CoV nsp1 was distributed in both the nucleus and the cytoplasm and did not bind stably to the 40S subunit, suggesting a distinctly different mode of targeting translating mRNAs. Interestingly, consistent with this notion, MERS-CoV nsp1 selectively targeted mRNAs, which are transcribed in the nucleus and transported to the cytoplasm, for translation inhibition and mRNA degradation but spared exogenous mRNAs introduced directly into the cytoplasm or virus-like mRNAs that originate in the cytoplasm. Collectively, these data point toward a novel viral strategy wherein the cytoplasmic origin of MERS-CoV mRNAs facilitates their escape from the inhibitory effects of MERS-CoV nsp1. IMPORTANCE Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic human CoV that emerged in Saudi Arabia in 2012. MERS-CoV has a zoonotic origin and poses a major threat to public health. However, little is known about the viral factors contributing to the high virulence of MERS-CoV. Many animal viruses, including CoVs, encode proteins that interfere with host gene expression, including those involved in antiviral immune responses, and these viral proteins are often major virulence factors. The nonstructural protein 1 (nsp1) of CoVs is one such protein that inhibits host gene expression and is a major virulence factor. This study presents evidence for a strategy used by MERS-CoV nsp1 to inhibit host gene expression that has not been described previously for any viral protein. The present study represents a meaningful step toward a better understanding of the factors and molecular mechanisms governing the virulence and pathogenesis of MERS-CoV.
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