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Identification and characterization of a proteolytically primed form of the murine coronavirus spike proteins after fusion with the target cell. J Virol 2014; 88:4943-52. [PMID: 24554652 DOI: 10.1128/jvi.03451-13] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Enveloped viruses carry highly specialized glycoproteins that catalyze membrane fusion under strict spatial and temporal control. To prevent premature activation after biosynthesis, viral class I fusion proteins adopt a locked conformation and require proteolytic cleavage to render them fusion-ready. This priming step may occur during virus exit from the infected cell, in the extracellular milieu or during entry at or in the next target cell. Proteolytic processing of coronavirus spike (S) fusion proteins during virus entry has been suggested but not yet formally demonstrated, while the nature and functionality of the resulting subunit is still unclear. We used a prototype coronavirus--mouse hepatitis virus (MHV)--to develop a conditional biotinylation assay that enables the specific identification and biochemical characterization of viral S proteins on virions that mediated membrane fusion with the target cell. We demonstrate that MHV S proteins are indeed cleaved upon virus endocytosis, and we identify a novel processing product S2* with characteristics of a fusion-active subunit. The precise cleavage site and the enzymes involved remain to be elucidated. IMPORTANCE Virus entry determines the tropism and is a crucial step in the virus life cycle. We developed an approach to characterize structural components of virus particles after entering new target cells. A prototype coronavirus was used to illustrate how the virus fusion machinery can be controlled.
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2
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Negatively charged residues in the endodomain are critical for specific assembly of spike protein into murine coronavirus. Virology 2013; 442:74-81. [PMID: 23628137 PMCID: PMC3772176 DOI: 10.1016/j.virol.2013.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 04/01/2013] [Accepted: 04/01/2013] [Indexed: 01/17/2023]
Abstract
Coronavirus spike (S) protein assembles into virions via its carboxy-terminus, which is composed of a transmembrane domain and an endodomain. Here, the carboxy-terminal charge-rich motif in the endodomain was verified to be critical for the specificity of S assembly into mouse hepatitis virus (MHV). Recombinant MHVs exhibited a range of abilities to accommodate the homologous S endodomains from the betacoronaviruses bovine coronavirus and human SARS-associated coronavirus, the alphacoronavirus porcine transmissible gastroenteritis virus (TGEV), and the gammacoronavirus avian infectious bronchitis virus respectively. Interestingly, in TGEV endodomain chimeras the reverting mutations resulted in stronger S incorporation into virions, and a net gain of negatively charged residues in the charge-rich motif accounted for the improvement. Additionally, MHV S assembly could also be rescued by the acidic carboxy-terminal domain of the nucleocapsid protein. These results indicate an important role for negatively charged endodomain residues in the incorporation of MHV S protein into assembled virions. Charge-rich motif in endodomain is a major determinant for coronavirus S assembly. MHV exhibited different accommodations to S endodomains from other coronaviruses. MHV with TGEV S endodomain improved S incorporation by reverting mutation. MHV S assembly could be partial restored by acidic carboxy-terminal domain of N. Negatively charged residues in endodomain are critical for S specific assembly.
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Skubitz KM, Skubitz APN. Two new synthetic peptides from the N-domain of CEACAM1 (CD66a) stimulate neutrophil adhesion to endothelial cells. Biopolymers 2011; 96:25-31. [PMID: 20560140 DOI: 10.1002/bip.21447] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Four members of the carcinoembryonic antigen family, CEACAMs 1, 3, 6, and 8, are expressed on human neutrophils and can trigger an activation signal that increases neutrophil adhesion to human umbilical vein endothelial cell (HUVEC) monolayers. To identify active sites on CEACAM1, we previously performed molecular modeling using IgG and CD4 as models, and 28 peptides of 14 amino acids in length were synthesized that were predicted to be present at loops and turns between β-sheets. Three peptides, each from the N-terminal domain, increased neutrophil adhesion to HUVEC monolayers and upregulated cell-surface CD11b/CD18 expression on neutrophils. In our earlier study, one N-domain peptide (CD66a-7) was not successfully synthesized, and another N-domain peptide (CD66a-6) was not soluble in the assay system. In the present study, we have now successfully synthesized CD66a-7, and a new peptide (CD66a-6L), that is a modification of the peptide that was insoluble in the earlier study. Both of these new peptides increased neutrophil adhesion to HUVEC monolayers. Importantly, the amino acid sequence of CD66a-7 is identical to the homologous peptides from CEACAMs 3, 5, and 6, but differs from the homologous peptide of CEACAM8, which was not active in this system. CD66a-6L is identical to the homologous peptide from CEACAM6. The data suggest that peptide motifs from at least five regions of the N-terminal domain of CEACAM1 are involved in the interaction of CEACAM1 with other ligands and can initiate signal transduction in neutrophils. Some of these active peptides are identical to homologous regions of other CEACAMs.
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Affiliation(s)
- Keith M Skubitz
- Department of Medicine, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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4
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Park JW, Moon CH, Harmache A, Wargo AR, Purcell MK, Bremont M, Kurath G. Restricted growth of U-type infectious haematopoietic necrosis virus (IHNV) in rainbow trout cells may be linked to casein kinase II activity. JOURNAL OF FISH DISEASES 2011; 34:115-129. [PMID: 21241319 PMCID: PMC7194290 DOI: 10.1111/j.1365-2761.2010.01225.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 09/01/2010] [Accepted: 09/13/2010] [Indexed: 05/30/2023]
Abstract
Previously, we demonstrated that a representative M genogroup type strain of infectious haematopoietic necrosis virus (IHNV) from rainbow trout grows well in rainbow trout-derived RTG-2 cells, but a U genogroup type strain from sockeye salmon has restricted growth, associated with reduced genome replication and mRNA transcription. Here, we analysed further the mechanisms for this growth restriction of U-type IHNV in RTG-2 cells, using strategies that assessed differences in viral genes, host immune regulation and phosphorylation. To determine whether the viral glycoprotein (G) or non-virion (NV) protein was responsible for the growth restriction, four recombinant IHNV viruses were generated in which the G gene of an infectious IHNV clone was replaced by the G gene of U- or M-type IHNV and the NV gene was replaced by NV of U- or M-type IHNV. There was no significant difference in the growth of these recombinants in RTG-2 cells, indicating that G and NV proteins are not major factors responsible for the differential growth of the U- and M-type strains. Poly I:C pretreatment of RTG-2 cells suppressed the growth of both U- and M-type IHNV, although the M virus continued to replicate at a reduced level. Both viruses induced type 1 interferon (IFN1) and the IFN1 stimulated gene Mx1, but the expression levels in M-infected cells were significantly higher than in U-infected cells and an inhibitor of the IFN1-inducible protein kinase PKR, 2-aminopurine (2-AP), did not affect the growth of U- or M-type IHNV in RTG-2 cells. These data did not indicate a role for the IFN1 system in the restricted growth of U-type IHNV in RTG-2 cells. Prediction of kinase-specific phosphorylation sites in the viral phosphoprotein (P) using the NetPhosK program revealed differences between U- and M-type P genes at five phosphorylation sites. Pretreatment of RTG-2 cells with a PKC inhibitor or a p38MAPK inhibitor did not affect the growth of the U- and M-type viruses. However, 100 μm of the casein kinase II (CKII) inhibitor, 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB), reduced the titre of the U type 8.3-fold at 24 h post-infection. In contrast, 100 μm of the CKII inhibitor reduced the titre of the M type only 1.3-fold at 48 h post-infection. Our data suggest that the different growth of U- and M-type IHNV in RTG-2 cells may be linked to a differential requirement for cellular protein kinases such as CKII for their growth.
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Affiliation(s)
- J W Park
- US Geological Survey, Western Fisheries Research Center, Seattle, WA, USA
- Department of Biological Sciences, University of Ulsan, Korea
| | - C H Moon
- US Geological Survey, Western Fisheries Research Center, Seattle, WA, USA
| | - A Harmache
- Unite de Virologie & Immunologie Moleculaires, INRA CRJ, Jouy en Josas, France
| | - A R Wargo
- US Geological Survey, Western Fisheries Research Center, Seattle, WA, USA
| | - M K Purcell
- US Geological Survey, Western Fisheries Research Center, Seattle, WA, USA
| | - M Bremont
- Unite de Virologie & Immunologie Moleculaires, INRA CRJ, Jouy en Josas, France
| | - G Kurath
- US Geological Survey, Western Fisheries Research Center, Seattle, WA, USA
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5
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Cleavage of the SARS coronavirus spike glycoprotein by airway proteases enhances virus entry into human bronchial epithelial cells in vitro. PLoS One 2009; 4:e7870. [PMID: 19924243 PMCID: PMC2773421 DOI: 10.1371/journal.pone.0007870] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2009] [Accepted: 10/21/2009] [Indexed: 11/22/2022] Open
Abstract
Background Entry of enveloped viruses into host cells requires the activation of viral envelope glycoproteins through cleavage by either intracellular or extracellular proteases. In order to gain insight into the molecular basis of protease cleavage and its impact on the efficiency of viral entry, we investigated the susceptibility of a recombinant native full-length S-protein trimer (triSpike) of the severe acute respiratory syndrome coronavirus (SARS-CoV) to cleavage by various airway proteases. Methodology/Principal Findings Purified triSpike proteins were readily cleaved in vitro by three different airway proteases: trypsin, plasmin and TMPRSS11a. High Performance Liquid Chromatography (HPLC) and amino acid sequencing analyses identified two arginine residues (R667 and R797) as potential protease cleavage site(s). The effect of protease-dependent enhancement of SARS-CoV infection was demonstrated with ACE2 expressing human bronchial epithelial cells 16HBE. Airway proteases regulate the infectivity of SARS-CoV in a fashion dependent on previous receptor binding. The role of arginine residues was further shown with mutant constructs (R667A, R797A or R797AR667A). Mutation of R667 or R797 did not affect the expression of S-protein but resulted in a differential efficacy of pseudotyping into SARS-CoVpp. The R667A SARS-CoVpp mutant exhibited a lack of virus entry enhancement following protease treatment. Conclusions/Significance These results suggest that SARS S-protein is susceptible to airway protease cleavage and, furthermore, that protease mediated enhancement of virus entry depends on specific conformation of SARS S-protein upon ACE2 binding. These data have direct implications for the cell entry mechanism of SARS-CoV along the respiratory system and, furthermore expand the possibility of identifying potential therapeutic agents against SARS-CoV.
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6
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Eifart P, Ludwig K, Böttcher C, de Haan CAM, Rottier PJM, Korte T, Herrmann A. Role of endocytosis and low pH in murine hepatitis virus strain A59 cell entry. J Virol 2007; 81:10758-68. [PMID: 17626088 PMCID: PMC2045462 DOI: 10.1128/jvi.00725-07] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infection by the coronavirus mouse hepatitis virus strain A59 (MHV-A59) requires the release of the viral genome by fusion with the respective target membrane of the host cell. Fusion is mediated by the viral S protein. Here, the entry pathway of MHV-A59 into murine fibroblast cells was studied by independent approaches. Infection of cells assessed by plaque reduction assay was strongly inhibited by lysosomotropic compounds and substances that interfere with clathrin-dependent endocytosis, suggesting that MHV-A59 is taken up via endocytosis and delivered to acidic endosomal compartments. Infection was only slightly reduced in the presence of substances inhibiting proteases of endosomal compartments, precluding that the endocytic uptake is required to activate the fusion potential of the S protein by its cleavage. Fluorescence confocal microscopy of labeled MHV-A59 confirmed that virus is taken up via endocytosis. Bright labeling of intracellular compartments suggests their fusion with the viral envelope. No fusion with the plasma membrane was observed at neutral pH conditions. However, when virus was bound to cells and the pH was lowered to 5.0, we observed a strong labeling of the plasma membrane. Electron microscopy revealed low pH triggered conformational alterations of the S ectodomain. Very likely, these alterations are irreversible because low-pH treatment of viruses in the absence of target membranes caused an irreversible loss of the fusion activity. The results imply that endocytosis plays a major role in MHV-A59 infection and the acidic pH of the endosomal compartment triggers a conformational change of the S protein mediating fusion.
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Affiliation(s)
- Patricia Eifart
- Institut für Biologie/Biophysik, Humboldt-Universität zu Berlin, Invalidenstr. 42, D-10115 Berlin, Germany
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Abstract
This chapter describes the interactions between the different structural components of the viruses and discusses their relevance for the process of virion formation. Two key factors determine the efficiency of the assembly process: intracellular transport and molecular interactions. Many viruses have evolved elaborate strategies to ensure the swift and accurate delivery of the virion components to the cellular compartment(s) where they must meet and form (sub) structures. Assembly of viruses starts in the nucleus by the encapsidation of viral DNA, using cytoplasmically synthesized capsid proteins; nucleocapsids then migrate to the cytosol, by budding at the inner nuclear membrane followed by deenvelopment, to pick up the tegument proteins.
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Affiliation(s)
- Cornelis A M de Haan
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands
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8
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Navas-Martin S, Hingley ST, Weiss SR. Murine coronavirus evolution in vivo: functional compensation of a detrimental amino acid substitution in the receptor binding domain of the spike glycoprotein. J Virol 2005; 79:7629-40. [PMID: 15919915 PMCID: PMC1143675 DOI: 10.1128/jvi.79.12.7629-7640.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Murine coronavirus A59 strain causes mild to moderate hepatitis in mice. We have previously shown that mutants of A59, unable to induce hepatitis, may be selected by persistent infection of primary glial cells in vitro. These in vitro isolated mutants encoded two amino acids substitutions in the spike (S) gene: Q159L lies in the putative receptor binding domain of S, and H716D, within the cleavage signal of S. Here, we show that hepatotropic revertant variants may be selected from these in vitro isolated mutants (Q159L-H716D) by multiple passages in the mouse liver. One of these mutants, hr2, was chosen for more in-depth study based on a more hepatovirulent phenotype. The S gene of hr2 (Q159L-R654H-H716D-E1035D) differed from the in vitro isolates (Q159L-H716D) in only 2 amino acids (R654H and E1035D). Using targeted RNA recombination, we have constructed isogenic recombinant MHV-A59 viruses differing only in these specific amino acids in S (Q159L-R654H-H716D-E1035D). We demonstrate that specific amino acid substitutions within the spike gene of the hr2 isolate determine the ability of the virus to cause lethal hepatitis and replicate to significantly higher titers in the liver compared to wild-type A59. Our results provide compelling evidence of the ability of coronaviruses to rapidly evolve in vivo to highly virulent phenotypes by functional compensation of a detrimental amino acid substitution in the receptor binding domain of the spike glycoprotein.
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MESH Headings
- Amino Acid Substitution
- Animals
- Coronavirus Infections/pathology
- Coronavirus Infections/physiopathology
- Coronavirus Infections/virology
- Evolution, Molecular
- Hepatitis, Viral, Animal/pathology
- Hepatitis, Viral, Animal/physiopathology
- Hepatitis, Viral, Animal/virology
- Liver/pathology
- Liver/virology
- Male
- Membrane Glycoproteins/chemistry
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Mice, Inbred C57BL
- Murine hepatitis virus/genetics
- Murine hepatitis virus/pathogenicity
- Receptors, Virus/metabolism
- Recombination, Genetic
- Specific Pathogen-Free Organisms
- Spike Glycoprotein, Coronavirus
- Viral Envelope Proteins/chemistry
- Viral Envelope Proteins/genetics
- Viral Envelope Proteins/metabolism
- Virulence
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Affiliation(s)
- Sonia Navas-Martin
- Department of Microbiology, University of Pennsylvania, School of Medicine, 36th Street and Hamilton Walk, Philadelphia, PA 19104-6076, USA.
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9
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Zheng BJ, Guan Y, He ML, Sun H, Du L, Zheng Y, Wong KL, Chen H, Chen Y, Lu L, Tanner JA, Watt RM, Niccolai N, Bernini A, Spiga O, Woo PCY, Kung HF, Yuen KY, Huang JD. Synthetic Peptides outside the Spike Protein Heptad Repeat Regions as Potent Inhibitors of Sars-Associated Coronavirus. Antivir Ther 2005. [DOI: 10.1177/135965350501000301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A novel severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV) has been identified as the aetiological agent of SARS. We previously isolated and characterized SARS-CoV and SARS-CoV-like viruses from human and animals, respectively, suggesting that SARS could be transmitted from wild/farmed animals to humans. Comparison of the viral genomes indicated that sequence variation between animal and human isolates existed mainly in the spike (S) gene. We hypothesized that these variations may underlie a change of binding specificity of the S protein to the host cells, permitting viral transmission from animals to humans. Here we report that four 20-mer synthetic peptides (S protein fragments), designed to span these sequence variation otspots, exhibited significant antiviral activities in a cell line. SARS-CoV infectivity was reduced over 10 000-fold through pre-incubation with two of these peptides, while it was completely inhibited in the presence of three peptides. Molecular modelling of the SARS-CoV peplomer suggests that three of these antiviral peptides map to the interfaces between the three monomers of the trimeric peplomer rather than the heptad repeat region from which short peptides are known to inhibit viral entry. Our results revealed novel regions in the spike protein that can be targeted to inhibit viral infection. The peptides identified in this study could be further developed into antiviral drugs.
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Affiliation(s)
- Bo-Jian Zheng
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Yi Guan
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Ming-Liang He
- Institute of Molecular Biology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
- Centre for Emerging Infectious Diseases, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong SAR, China
| | - Hongzhe Sun
- Department of Chemistry and Open Laboratory of Chemical Biology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Lanying Du
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Ying Zheng
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Kin-Ling Wong
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Honglin Chen
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Ying Chen
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Linyu Lu
- Department of Biochemistry, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Julian A Tanner
- Department of Biochemistry, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Rory M Watt
- Department of Chemistry and Open Laboratory of Chemical Biology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
- Department of Biochemistry, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Neri Niccolai
- Biomolecular Structure Research Centre, University of Siena, Siena, Italy
| | - Andrea Bernini
- Biomolecular Structure Research Centre, University of Siena, Siena, Italy
| | - Ottavia Spiga
- Biomolecular Structure Research Centre, University of Siena, Siena, Italy
| | - Patrick CY Woo
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Hsiang-fu Kung
- Institute of Molecular Biology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
- Centre for Emerging Infectious Diseases, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong SAR, China
| | - Kwok-Yung Yuen
- Department of Microbiology, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Jian-Dong Huang
- Department of Biochemistry, University of Hong Kong, Pokfulam, Hong Kong SAR, China
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10
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Abstract
The successful replication of a viral pathogen in a host is a complex process involving many interactions. These interactions develop from the coevolution of pathogen and host and often lead to a species specificity of the virus that can make interspecies transmissions difficult. Nevertheless, viruses do sporadically cross species barriers into other host populations, including humans. In zoonotic infections, many of these interspecies transfer events are dead end, where transmission is confined only to the animal-to-human route but sometimes viruses adapt to enable spread from human to human. A pathogen must overcome many hurdles to replicate successfully in a foreign host. The viral pathogen must enter the host cell, replicate with the assistance of host factors, evade inhibitory host products, exit the first cell and move on to the next, and possibly leave the initial host and transmit to another. Each of these stages may require adaptive changes in the pathogen. Although the factors that influence each stage of the replication and transmission of most agents have not been resolved, the genomics of both hosts and pathogens are now at hand and we have begun to understand some of the molecular changes that enable some viruses to adapt to a new host.
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Affiliation(s)
- Richard Webby
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, 38105 Tennessee USA
| | - Erich Hoffmann
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, 38105 Tennessee USA
| | - Robert Webster
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, 38105 Tennessee USA
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11
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Stadler K, Masignani V, Eickmann M, Becker S, Abrignani S, Klenk HD, Rappuoli R. SARS--beginning to understand a new virus. Nat Rev Microbiol 2004; 1:209-18. [PMID: 15035025 PMCID: PMC7097337 DOI: 10.1038/nrmicro775] [Citation(s) in RCA: 364] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A new infectious disease, called severe acute respiratory syndrome (SARS), appeared in southern China in 2002. During the period from November 2002 to the summer of 2003, the World Health Organization recorded 8098 probable SARS cases and 774 deaths in 29 countries. A previously unknown coronavirus was isolated from FRhK-4 and Vero E6 cells inoculated with clinical specimens from patients. A virus with close homology to SARS-CoV was isolated from palm civets and racoon dogs, which are used as food in southern China In less than a month from the first indication that a coronavirus might be implicated in the disease, the nucleotide sequence of the virus was available, and diagnostic tests were set up. The phylogenetic analysis of the SARS-CoV genome revealed that the virus is distinct from the three known groups of coronaviruses and represents an early split-off from group 2. The development of antiviral drugs or vaccines is being investigated. Viral enzymes essential for virus replication, such as the RNA-dependent RNA polymerase (RdRp), the 3C-like cystein protease (3Clpro) and the helicases are the most attractive targets for antiviral molecules. Of the possible vaccine targets, the spike (S) protein represents the most promising one. So far, β-interferon is the only licensed drug available, which has been reported to interfere with virus replication in vitro. Should SARS return during the next winter, we will still need to rely mostly on quarantine measures to contain it.
The 114-day epidemic of the severe acute respiratory syndrome (SARS) swept 29 countries, affected a reported 8,098 people, left 774 patients dead and almost paralysed the Asian economy. Aggressive quarantine measures, possibly aided by rising summer temperatures, successfully terminated the first eruption of SARS and provided at least a temporal break, which allows us to consolidate what we have learned so far and plan for the future. Here, we review the genomics of the SARS coronavirus (SARS-CoV), its phylogeny, antigenic structure, immune response and potential therapeutic interventions should the SARS epidemic flare up again.
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Affiliation(s)
- Konrad Stadler
- IRIS, Chiron S.r.l., Via Fiorentina 1, Siena, 53100 Italy
| | - Vega Masignani
- IRIS, Chiron S.r.l., Via Fiorentina 1, Siena, 53100 Italy
| | - Markus Eickmann
- Institute of Virology, University of Marburg, Marburg, 35037 Germany
| | - Stephan Becker
- Institute of Virology, University of Marburg, Marburg, 35037 Germany
| | | | - Hans-Dieter Klenk
- Institute of Virology, University of Marburg, Marburg, 35037 Germany
| | - Rino Rappuoli
- IRIS, Chiron S.r.l., Via Fiorentina 1, Siena, 53100 Italy
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12
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Stavrinides J, Guttman DS. Mosaic evolution of the severe acute respiratory syndrome coronavirus. J Virol 2004; 78:76-82. [PMID: 14671089 PMCID: PMC303383 DOI: 10.1128/jvi.78.1.76-82.2004] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2003] [Accepted: 09/22/2003] [Indexed: 11/20/2022] Open
Abstract
Severe acute respiratory syndrome (SARS) is a deadly form of pneumonia caused by a novel coronavirus, a viral family responsible for mild respiratory tract infections in a wide variety of animals including humans, pigs, cows, mice, cats, and birds. Analyses to date have been unable to identify the precise origin of the SARS coronavirus. We used Bayesian, neighbor-joining, and split decomposition phylogenetic techniques on the SARS virus replicase, surface spike, matrix, and nucleocapsid proteins to reveal the evolutionary origin of this recently emerging infectious agent. The analyses support a mammalian-like origin for the replicase protein, an avian-like origin for the matrix and nucleocapsid proteins, and a mammalian-avian mosaic origin for the host-determining spike protein. A bootscan recombination analysis of the spike gene revealed high nucleotide identity between the SARS virus and a feline infectious peritonitis virus throughout the gene, except for a 200- base-pair region of high identity to an avian sequence. These data support the phylogenetic analyses and suggest a possible past recombination event between mammalian-like and avian-like parent viruses. This event occurred near a region that has been implicated to be the human receptor binding site and may have been directly responsible for the switch of host of the SARS coronavirus from animals to humans.
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Affiliation(s)
- John Stavrinides
- Department of Botany, University of Toronto, Toronto, Ontario M5S 3B2, Canada
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13
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Bosch BJ, van der Zee R, de Haan CAM, Rottier PJM. The coronavirus spike protein is a class I virus fusion protein: structural and functional characterization of the fusion core complex. J Virol 2003; 77:8801-11. [PMID: 12885899 PMCID: PMC167208 DOI: 10.1128/jvi.77.16.8801-8811.2003] [Citation(s) in RCA: 1039] [Impact Index Per Article: 49.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Coronavirus entry is mediated by the viral spike (S) glycoprotein. The 180-kDa oligomeric S protein of the murine coronavirus mouse hepatitis virus strain A59 is posttranslationally cleaved into an S1 receptor binding unit and an S2 membrane fusion unit. The latter is thought to contain an internal fusion peptide and has two 4,3 hydrophobic (heptad) repeat regions designated HR1 and HR2. HR2 is located close to the membrane anchor, and HR1 is some 170 amino acids (aa) upstream of it. Heptad repeat (HR) regions are found in fusion proteins of many different viruses and form an important characteristic of class I viral fusion proteins. We investigated the role of these regions in coronavirus membrane fusion. Peptides HR1 (96 aa) and HR2 (39 aa), corresponding to the HR1 and HR2 regions, were produced in Escherichia coli. When mixed together, the two peptides were found to assemble into an extremely stable oligomeric complex. Both on their own and within the complex, the peptides were highly alpha helical. Electron microscopic analysis of the complex revealed a rod-like structure approximately 14.5 nm in length. Limited proteolysis in combination with mass spectrometry indicated that HR1 and HR2 occur in the complex in an antiparallel fashion. In the native protein, such a conformation would bring the proposed fusion peptide, located in the N-terminal domain of HR1, and the transmembrane anchor into close proximity. Using biological assays, the HR2 peptide was shown to be a potent inhibitor of virus entry into the cell, as well as of cell-cell fusion. Both biochemical and functional data show that the coronavirus spike protein is a class I viral fusion protein.
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Affiliation(s)
- Berend Jan Bosch
- Virology Division, Department of Infectious Diseases and Immunity, Faculty of Veterinary Medicine, and Institute of Biomembranes, Utrecht University, 3584 CL Utrecht, The Netherlands
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