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Stevenson-Leggett P, Keep S, Bickerton E. Treatment with Exogenous Trypsin Expands In Vitro Cellular Tropism of the Avian Coronavirus Infectious Bronchitis Virus. Viruses 2020; 12:E1102. [PMID: 33003350 PMCID: PMC7600076 DOI: 10.3390/v12101102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/23/2020] [Accepted: 09/28/2020] [Indexed: 12/27/2022] Open
Abstract
The Gammacoronavirus infectious bronchitis virus (IBV) causes a highly contagious and economically important respiratory disease in poultry. In the laboratory, most IBV strains are restricted to replication in ex vivo organ cultures or in ovo and do not replicate in cell culture, making the study of their basic virology difficult. Entry of IBV into cells is facilitated by the large glycoprotein on the surface of the virion, the spike (S) protein, comprised of S1 and S2 subunits. Previous research showed that the S2' cleavage site is responsible for the extended tropism of the IBV Beaudette strain. This study aims to investigate whether protease treatment can extend the tropism of other IBV strains. Here we demonstrate that the addition of exogenous trypsin during IBV propagation in cell culture results in significantly increased viral titres. Using a panel of IBV strains, exhibiting varied tropisms, the effects of spike cleavage on entry and replication were assessed by serial passage cell culture in the presence of trypsin. Replication could be maintained over serial passages, indicating that the addition of exogenous protease is sufficient to overcome the barrier to infection. Mutations were identified in both S1 and S2 subunits following serial passage in cell culture. This work provides a proof of concept that exogenous proteases can remove the barrier to IBV replication in otherwise non-permissive cells, providing a platform for further study of elusive field strains and enabling sustainable vaccine production in vitro.
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Affiliation(s)
| | | | - Erica Bickerton
- The Pirbright Institute, Ash Road, Woking, Surrey GU24 0NF, UK; (P.S.-L.); (S.K.)
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Wang Y, Grunewald M, Perlman S. Coronaviruses: An Updated Overview of Their Replication and Pathogenesis. Methods Mol Biol 2020; 2203:1-29. [PMID: 32833200 DOI: 10.1007/978-1-0716-0900-2_1] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Coronaviruses (CoVs), enveloped positive-sense RNA viruses, are characterized by club-like spikes that project from their surface, an unusually large RNA genome, and a unique replication strategy. CoVs cause a variety of diseases in mammals and birds ranging from enteritis in cows and pigs, and upper respiratory tract and kidney disease in chickens to lethal human respiratory infections. Most recently, the novel coronavirus, SARS-CoV-2, which was first identified in Wuhan, China in December 2019, is the cause of a catastrophic pandemic, COVID-19, with more than 8 million infections diagnosed worldwide by mid-June 2020. Here we provide a brief introduction to CoVs discussing their replication, pathogenicity, and current prevention and treatment strategies. We will also discuss the outbreaks of the highly pathogenic Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV), which are relevant for understanding COVID-19.
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Affiliation(s)
- Yuhang Wang
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA
| | - Matthew Grunewald
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA
| | - Stanley Perlman
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA.
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Saiada F, Gallardo RA, Shivaprasad HL, Corsiglia C, Van Santen VL. Intestinal Tropism of an Infectious Bronchitis Virus Isolate Not Explained by Spike Protein Binding Specificity. Avian Dis 2020; 64:23-35. [PMID: 32267122 DOI: 10.1637/0005-2086-64.1.23] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 10/17/2019] [Indexed: 11/05/2022]
Abstract
An infectious bronchitis virus (IBV) with an unusual enteric tropism (CalEnt) was isolated from a California broiler flock exhibiting runting-stunting syndrome. IBV was detected in the small intestine, but not in the respiratory tract or kidney. During virus isolation in embryos, it did not replicate in chorioallantoic membrane (CAM) but could be recovered from intestines. Its S1 protein showed 93% amino acid sequence identity to a California variant isolated in 1999 (Cal99). Intestinal lesions were reproduced following ocular/nasal inoculation of specific-pathogen-free chickens, but respiratory signs and lesions were also present. The virus was detected in both respiratory and intestinal tissues. To determine whether the novel tropism of IBV CalEnt was due to an increased ability of its S1 protein to bind to the intestinal epithelium, we compared the binding of soluble trimeric recombinant S1 proteins derived from CalEnt and Cal99 to chicken tissues. Contrary to expectations, the CalEnt S1 protein did not bind to small intestine and, unlike Cal99 S1, did not bind to the respiratory epithelium or CAM. Using only the CalEnt S1 N-terminal domain or including the S2 ectodomain (lacking membrane and cytoplasmic domains), which have been shown to improve ArkDPI S1 protein binding, did not lead to detectable binding at the standard protein concentration to any tissue tested. Our results indicate no/poor binding of the CalEnt spike protein to both respiratory and intestinal tissues and thus do not support better attachment to intestinal epithelial cells as a reason for CalEnt's extended tropism. These results might reflect shortcomings of the assay, including that it does not detect potential contributions of the S1 C-terminal domain to attachment. We used bioinformatic approaches to explore the possibility that the unique tropism of CalEnt might be a result of functions of the S protein in cell-entry steps subsequent to attachment. These analyses suggest that CalEnt's S2 coding region was acquired through a recombination event and encodes a unique amino acid sequence at the putative recognition site for the protease that activates the S protein for fusion. Thus, S2 activation by tissue-specific proteases might facilitate CalEnt entry into intestinal epithelial cells and compensate for poor binding by its S1 protein.
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Affiliation(s)
- Farjana Saiada
- Department of Pathobiology, 264 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn, AL 36849
| | - Rodrigo A Gallardo
- Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616
| | - H L Shivaprasad
- University of California, California Animal Health and Food Safety Laboratory Tulare Branch, Tulare, CA 93274
| | | | - Vicky L Van Santen
- Department of Pathobiology, 264 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn, AL 36849,
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54
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Zegpi RA, Joiner KS, van Santen VL, Toro H. Infectious Bronchitis Virus Population Structure Defines Immune Response and Protection. Avian Dis 2020; 64:60-68. [PMID: 32267126 DOI: 10.1637/0005-2086-64.1.60] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 12/10/2019] [Indexed: 11/05/2022]
Abstract
A commercial Arkansas (Ark) Delmarva Poultry Industry (DPI)-type vaccine and a more homogeneous population of that vaccine obtained previously through adaptation to chicken embryo kidney (CEK) cells (CEK-ArkDPI) were used as a model to further understand the impact of population genetic structure on generation of immune responses and protection. In a first experiment, vaccinated chickens were challenged with an IBV Ark99-type virulent strain (AL/4614/98). Despite extensive sequence similarity between the vaccines, the more heterogeneous commercial ArkDPI was more efficient at reducing viral loads in challenged chickens, while respiratory signs and tracheal lesions were reduced similarly by either vaccine. A distinct subpopulation of the Ark challenge virus showing asparagine at S1 position 56 was consistently negatively selected by immune pressure originating from vaccination with either vaccine. Antibody levels and antibody avidity to Ark-type S1 protein were greater in CEK-ArkDPI-vaccinated chickens compared to chickens vaccinated with the more diverse commercial ArkDPI vaccine. Synchronous replication of a homogeneous virus population likely elicits clonal expansion and affinity maturation of a greater number of responding B cells compared to a diverse virus population continuously changing its proportion of phenotypes during replication. The results of a second experiment showed that during initial vaccine virus replication (24 and 48 hr postvaccination), the virus population showing increased diversity (commercial ArkDPI) achieved higher concentrations of IBV RNA in the trachea compared to the more homogenous virus. mRNA expression of genes associated with innate immune responses in the trachea 48 hr postvaccination generally showed greater upregulation in chickens vaccinated with the heterogeneous commercial ArkDPI vaccine compared to the CEK-adapted virus. The greater upregulation of these genes is likely associated with higher virus replication achieved by the heterogeneous commercial vaccine. Thus, while the adaptive antibody response was favored by the more homogenous structure of the CEK-ArkDPI vaccine population (higher antibody levels and antibody avidity), the innate immune response was favored by the more diverse viral population of the commercial ArkDPI. We confirmed previous results that distinct subpopulations in wild Ark challenge virus become selected by immune pressure originating from vaccination, and we concluded that the population structure of IBV vaccines impacts innate immune response, antibody avidity, and protection.
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Affiliation(s)
- R A Zegpi
- Department of Pathobiology, Auburn University College of Veterinary Medicine, Auburn, AL 36830
| | - K S Joiner
- Department of Pathobiology, Auburn University College of Veterinary Medicine, Auburn, AL 36830
| | - V L van Santen
- Department of Pathobiology, Auburn University College of Veterinary Medicine, Auburn, AL 36830
| | - H Toro
- Department of Pathobiology, Auburn University College of Veterinary Medicine, Auburn, AL 36830,
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Liang XY, Zhu QC, Liang JQ, Liu SY, Liu DX, Fung TS. Development of HiBiT-Tagged Recombinant Infectious Bronchitis Coronavirus for Efficient in vitro and in vivo Viral Quantification. Front Microbiol 2020; 11:2100. [PMID: 32983065 PMCID: PMC7485224 DOI: 10.3389/fmicb.2020.02100] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 08/10/2020] [Indexed: 12/31/2022] Open
Abstract
Coronaviruses (CoVs) are enveloped (+) ssRNA viruses of veterinary and medical importance. Because recombinant CoVs with reporter proteins fused with viral proteins are usually non-viable or unstable, a small and quantifiable epitope tag would be beneficial to CoV research. In this study, we integrated the NanoLuc Binary Technology to the reverse genetics of infectious bronchitis virus (IBV), a prototypic gammacoronavirus. The 11-amino-acid HiBiT tag was inserted to the spike (S) or membrane (M) protein, and the recombinant IBVs (rS-HiBiT and rM-HiBiT) were characterized. Compared with the rIBV-p65 control, rS-HiBiT exhibited comparable growth kinetics, whereas rM-HiBiT replicated slightly slower. The levels of HiBiT-tagged S and M proteins in the infected cells or the culture supernatant could be both rapidly (~15 min) and efficiently (30 μL sample volume) determined using the HiBiT luminescence assay. Notably, replication of the HiBiT-tagged IBV could be monitored continuously in an infected chicken embryo, and rS-HiBiT was genetically stable for at least 20 passages. By integrating the HiBiT tagging system with CoV reverse genetics, this new reporter system may facilitate future study of CoV replication and pathogenesis.
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Affiliation(s)
- Xiao Ying Liang
- Guangdong Province Key Laboratory of Microbial Signals & Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Qing Chun Zhu
- Guangdong Province Key Laboratory of Microbial Signals & Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Jia Qi Liang
- Guangdong Province Key Laboratory of Microbial Signals & Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Si Ying Liu
- Guangdong Province Key Laboratory of Microbial Signals & Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Ding Xiang Liu
- Guangdong Province Key Laboratory of Microbial Signals & Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China.,Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - To Sing Fung
- Guangdong Province Key Laboratory of Microbial Signals & Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China.,Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
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56
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Awadelkareem EA, Ali SA. Vaccine design of coronavirus spike (S) glycoprotein in chicken: immunoinformatics and computational approaches. TRANSLATIONAL MEDICINE COMMUNICATIONS 2020; 5:13. [PMID: 32869000 PMCID: PMC7450164 DOI: 10.1186/s41231-020-00063-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 07/06/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Infectious bronchitis (IB) is a highly contagious respiratory disease in chickens and produces economic loss within the poultry industry. This disease is caused by a single stranded RNA virus belonging to Cronaviridae family. This study aimed to design a potential multi-epitopes vaccine against infectious bronchitis virus spike protein (S). Protein characterization was also performed for IBV spike protein. METHODS The present study used various tools in Immune Epitope Database (IEDB) to predict conserved B and T cell epitopes against IBV spike (S) protein that may perform a significant role in provoking the resistance response to IBV infection. RESULTS In B cell prediction methods, three epitopes ( 1139 KKSSYY 1144 , 1140 KSSYYT 1145 , 1141 SSYYT 1145 ) were selected as surface, linear and antigenic epitopes.Many MHCI and MHCII epitopes were predicted for IBV S protein. Among them 982YYITARDMY990 and 983 YITARDMYM 991 epitopes displayed high antigenicity, no allergenicity and no toxicity as well as great linkage with MHCI and MHCII alleles. Moreover, docking analysis of MHCI epitopes produced strong binding affinity with BF2 alleles. CONCLUSION Five conserved epitopes were expected from spike glycoprotein of IBV as the best B and T cell epitopes due to high antigenicity, no allergenicity and no toxicity. In addition, MHC epitopes showed great linkage with MHC alleles as well as strong interaction with BF2 alleles. These epitopes should be designed and incorporated and then tested as multi-epitope vaccine against IBV.
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Affiliation(s)
| | - Sumaia A. Ali
- Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, Sudan University of Science and Technology, Khartoum, Sudan
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57
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The Characterization of chIFITMs in Avian Coronavirus Infection In Vivo, Ex Vivo and In Vitro. Genes (Basel) 2020; 11:genes11080918. [PMID: 32785186 PMCID: PMC7464837 DOI: 10.3390/genes11080918] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/06/2020] [Accepted: 08/07/2020] [Indexed: 01/11/2023] Open
Abstract
The coronaviruses are a large family of enveloped RNA viruses that commonly cause gastrointestinal or respiratory illnesses in the infected host. Avian coronavirus infectious bronchitis virus (IBV) is a highly contagious respiratory pathogen of chickens that can affect the kidneys and reproductive systems resulting in bird mortality and decreased reproductivity. The interferon-inducible transmembrane (IFITM) proteins are activated in response to viral infections and represent a class of cellular restriction factors that restrict the replication of many viral pathogens. Here, we characterize the relative mRNA expression of the chicken IFITM genes in response to IBV infection, in vivo, ex vivo and in vitro using the pathogenic M41-CK strain, the nephropathogenic QX strain and the nonpathogenic Beaudette strain. In vivo we demonstrate a significant upregulation of chIFITM1, 2, 3 and 5 in M41-CK- and QX-infected trachea two days post-infection. In vitro infection with Beaudette, M41-CK and QX results in a significant upregulation of chIFITM1, 2 and 3 at 24 h post-infection. We confirmed a differential innate response following infection with distinct IBV strains and believe that our data provide new insights into the possible role of chIFITMs in early IBV infection.
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Zhou T, Tsybovsky Y, Olia AS, Gorman J, Rapp MA, Cerutti G, Chuang GY, Katsamba PS, Nazzari A, Sampson JM, Schon A, Wang PD, Bimela J, Shi W, Teng IT, Zhang B, Boyington JC, Sastry M, Stephens T, Stuckey J, Wang S, Friesner RA, Ho DD, Mascola JR, Shapiro L, Kwong PD. Cryo-EM Structures Delineate a pH-Dependent Switch that Mediates Endosomal Positioning of SARS-CoV-2 Spike Receptor-Binding Domains. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2020. [PMID: 32637958 DOI: 10.1101/2020.07.04.187989] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The SARS-CoV-2 spike employs mobile receptor-binding domains (RBDs) to engage the ACE2 receptor and to facilitate virus entry. Antibodies can engage RBD but some, such as CR3022, fail to inhibit entry despite nanomolar spike affinity. Here we show the SARS-CoV-2 spike to have low unfolding enthalpy at serological pH and up to 10-times more unfolding enthalpy at endosomal pH, where we observe significantly reduced CR3022 affinity. Cryo-EM structures -at serological and endosomal pH- delineated spike recognition of up to three ACE2 molecules, revealing RBD to freely adopt the 'up' conformation. In the absence of ACE2, single-RBD-up conformations dominated at pH 5.5, resolving into a locked all-down conformation at lower pH. Notably, a pH-dependent refolding region (residues 824-858) at the spike-interdomain interface displayed dramatic structural rearrangements and mediated RBD positioning and spike shedding of antibodies like CR3022. An endosomal mechanism involving spike-conformational change can thus facilitate immune evasion from RBD-'up'-recognizing antibody.
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59
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SARS-CoV-2 Evolutionary Adaptation toward Host Entry and Recognition of Receptor O-Acetyl Sialylation in Virus-Host Interaction. Int J Mol Sci 2020; 21:ijms21124549. [PMID: 32604730 PMCID: PMC7352545 DOI: 10.3390/ijms21124549] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 06/15/2020] [Accepted: 06/22/2020] [Indexed: 02/06/2023] Open
Abstract
The recently emerged SARS-CoV-2 is the cause of the global health crisis of the coronavirus disease 2019 (COVID-19) pandemic. No evidence is yet available for CoV infection into hosts upon zoonotic disease outbreak, although the CoV epidemy resembles influenza viruses, which use sialic acid (SA). Currently, information on SARS-CoV-2 and its receptors is limited. O-acetylated SAs interact with the lectin-like spike glycoprotein of SARS CoV-2 for the initial attachment of viruses to enter into the host cells. SARS-CoV-2 hemagglutinin-esterase (HE) acts as the classical glycan-binding lectin and receptor-degrading enzyme. Most β-CoVs recognize 9-O-acetyl-SAs but switched to recognizing the 4-O-acetyl-SA form during evolution of CoVs. Type I HE is specific for the 9-O-Ac-SAs and type II HE is specific for 4-O-Ac-SAs. The SA-binding shift proceeds through quasi-synchronous adaptations of the SA-recognition sites of the lectin and esterase domains. The molecular switching of HE acquisition of 4-O-acetyl binding from 9-O-acetyl SA binding is caused by protein–carbohydrate interaction (PCI) or lectin–carbohydrate interaction (LCI). The HE gene was transmitted to a β-CoV lineage A progenitor by horizontal gene transfer from a 9-O-Ac-SA–specific HEF, as in influenza virus C/D. HE acquisition, and expansion takes place by cross-species transmission over HE evolution. This reflects viral evolutionary adaptation to host SA-containing glycans. Therefore, CoV HE receptor switching precedes virus evolution driven by the SA-glycan diversity of the hosts. The PCI or LCI stereochemistry potentiates the SA–ligand switch by a simple conformational shift of the lectin and esterase domains. Therefore, examination of new emerging viruses can lead to better understanding of virus evolution toward transitional host tropism. A clear example of HE gene transfer is found in the BCoV HE, which prefers 7,9-di-O-Ac-SAs, which is also known to be a target of the bovine torovirus HE. A more exciting case of such a switching event occurs in the murine CoVs, with the example of the β-CoV lineage A type binding with two different subtypes of the typical 9-O-Ac-SA (type I) and the exclusive 4-O-Ac-SA (type II) attachment factors. The protein structure data for type II HE also imply the virus switching to binding 4-O acetyl SA from 9-O acetyl SA. Principles of the protein–glycan interaction and PCI stereochemistry potentiate the SA–ligand switch via simple conformational shifts of the lectin and esterase domains. Thus, our understanding of natural adaptation can be specified to how carbohydrate/glycan-recognizing proteins/molecules contribute to virus evolution toward host tropism. Under the current circumstances where reliable antiviral therapeutics or vaccination tools are lacking, several trials are underway to examine viral agents. As expected, structural and non-structural proteins of SARS-CoV-2 are currently being targeted for viral therapeutic designation and development. However, the modern global society needs SARS-CoV-2 preventive and therapeutic drugs for infected patients. In this review, the structure and sialobiology of SARS-CoV-2 are discussed in order to encourage and activate public research on glycan-specific interaction-based drug creation in the near future.
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60
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Infectious Bronchitis Virus Evolution, Diagnosis and Control. Vet Sci 2020; 7:vetsci7020079. [PMID: 32580381 PMCID: PMC7356646 DOI: 10.3390/vetsci7020079] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/16/2020] [Accepted: 06/18/2020] [Indexed: 01/09/2023] Open
Abstract
RNA viruses are characterized by high mutation and recombination rates, which allow a rapid adaptation to new environments. Most of the emerging diseases and host jumps are therefore sustained by these viruses. Rapid evolution may also hinder the understanding of molecular epidemiology, affect the sensitivity of diagnostic assays, limit the vaccine efficacy and favor episodes of immune escape, thus significantly complicating the control of even well-known pathogens. The history of infectious bronchitis virus (IBV) fits well with the above-mentioned scenario. Despite being known since the 1930s, it still represents one of the main causes of disease and economic losses for the poultry industry. A plethora of strategies have been developed and applied over time, with variable success, to limit its impact. However, they have rarely been evaluated objectively and on an adequate scale. Therefore, the actual advantages and disadvantages of IBV detection and control strategies, as well as their implementation, still largely depend on individual sensibility. The present manuscript aims to review the main features of IBV biology and evolution, focusing on their relevance and potential applications in terms of diagnosis and control.
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Keep S, Sives S, Stevenson-Leggett P, Britton P, Vervelde L, Bickerton E. Limited Cross-Protection against Infectious Bronchitis Provided by Recombinant Infectious Bronchitis Viruses Expressing Heterologous Spike Glycoproteins. Vaccines (Basel) 2020; 8:E330. [PMID: 32580371 PMCID: PMC7350270 DOI: 10.3390/vaccines8020330] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/19/2020] [Accepted: 06/21/2020] [Indexed: 12/19/2022] Open
Abstract
Gammacoronavirus infectious bronchitis virus (IBV) causes an economically important respiratory disease of poultry. Protective immunity is associated with the major structural protein, spike (S) glycoprotein, which induces neutralising antibodies and defines the serotype. Cross-protective immunity between serotypes is limited and can be difficult to predict. In this study, the ability of two recombinant IBV vaccine candidates, BeauR-M41(S) and BeauR-4/91(S), to induce cross-protection against a third serotype, QX, was assessed. Both rIBVs are genetically based on the Beaudette genome with only the S gene derived from either M41 or 4/91, two unrelated serotypes. The use of these rIBVs allowed for the assessment of the potential of M41 and 4/91 S glycoproteins to induce cross-protective immunity against a heterologous QX challenge. The impact of the order of vaccination was also assessed. Homologous primary and secondary vaccination with BeauR-M41(S) or BeauR-4/91(S) resulted in a significant reduction of infectious QX load in the trachea at four days post-challenge, whereas heterologous primary and secondary vaccination with BeauR-M41(S) and BeauR-4/91(S) reduced viral RNA load in the conjunctiva-associated lymphoid tissue (CALT). Both homologous and heterologous vaccination regimes reduced clinical signs and birds recovered more rapidly as compared with an unvaccinated/challenge control group. Despite both rIBV BeauR-M41(S) and BeauR-4/91(S) displaying limited replication in vivo, serum titres in these vaccinated groups were higher as compared with the unvaccinated/challenge control group. This suggests that vaccination with rIBV primed the birds for a boosted humoral response to heterologous QX challenge. Collectively, vaccination with the rIBV elicited limited protection against challenge, with failure to protect against tracheal ciliostasis, clinical manifestations, and viral replication. The use of a less attenuated recombinant vector that replicates throughout the respiratory tract could be required to elicit a stronger and prolonged protective immune response.
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Affiliation(s)
- Sarah Keep
- The Pirbright Institute, Pirbright, Surrey GU24 0NF, UK; (S.K.); (P.S.-L.); (P.B.)
| | - Samantha Sives
- Division of Infection and Immunity, The Roslin Institute and Royal (Dick), School of Veterinary Studies, University of Edinburgh, Easter Bush EH25 9RG, UK; (S.S.); (L.V.)
| | | | - Paul Britton
- The Pirbright Institute, Pirbright, Surrey GU24 0NF, UK; (S.K.); (P.S.-L.); (P.B.)
| | - Lonneke Vervelde
- Division of Infection and Immunity, The Roslin Institute and Royal (Dick), School of Veterinary Studies, University of Edinburgh, Easter Bush EH25 9RG, UK; (S.S.); (L.V.)
| | - Erica Bickerton
- The Pirbright Institute, Pirbright, Surrey GU24 0NF, UK; (S.K.); (P.S.-L.); (P.B.)
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62
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Yu J, Qiao S, Guo R, Wang X. Cryo-EM structures of HKU2 and SADS-CoV spike glycoproteins provide insights into coronavirus evolution. Nat Commun 2020; 11:3070. [PMID: 32555182 PMCID: PMC7300015 DOI: 10.1038/s41467-020-16876-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 05/29/2020] [Indexed: 12/31/2022] Open
Abstract
Porcine coronavirus SADS-CoV has been identified from suckling piglets with severe diarrhea in southern China in 2017. The SADS-CoV genome shares ~95% identity to that of bat α-coronavirus HKU2, suggesting that SADS-CoV may have emerged from a natural reservoir in bats. Here we report the cryo-EM structures of HKU2 and SADS-CoV spike (S) glycoprotein trimers at 2.38 Å and 2.83 Å resolution, respectively. We systematically compare the domains of HKU2 spike with those of α-, β-, γ-, and δ-coronavirus spikes, showing that the S1 subunit N- and C-terminal domains of HKU2/SADS-CoV are ancestral domains in the evolution of coronavirus spike proteins. The connecting region after the fusion peptide in the S2 subunit of HKU2/SADS-CoV adopts a unique conformation. These results structurally demonstrate a close evolutionary relationship between HKU2/SADS-CoV and β-coronavirus spikes and provide insights into the evolution and cross-species transmission of coronaviruses.
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Affiliation(s)
- Jinfang Yu
- The Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Collaborative Innovation Center for Biotherapy, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Shuyuan Qiao
- The Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Collaborative Innovation Center for Biotherapy, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Runyu Guo
- The Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Collaborative Innovation Center for Biotherapy, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Xinquan Wang
- The Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Collaborative Innovation Center for Biotherapy, School of Life Sciences, Tsinghua University, 100084, Beijing, China.
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63
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Behloul N, Baha S, Shi R, Meng J. Role of the GTNGTKR motif in the N-terminal receptor-binding domain of the SARS-CoV-2 spike protein. Virus Res 2020; 286:198058. [PMID: 32531235 PMCID: PMC7282740 DOI: 10.1016/j.virusres.2020.198058] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 05/18/2020] [Accepted: 06/07/2020] [Indexed: 12/18/2022]
Abstract
SARS-CoV-2 S1-NTD presents different receptor binding motifs compared to the SARS-CoV. Functional motifs similar to the S1-NTD GTNGTKR loop were identified in other proteins. The GTNGTKR loop is very likely to allow the SARS-CoV-2 to bind other receptors. The GTNGTKR motif is very likely an evolutionary acquisition under functional constraints.
The 2019 novel coronavirus disease (COVID-19) that emerged in China has been declared as public health emergency of international concern by the World Health Organization and the causative pathogen was named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this report, we analyzed the structural characteristics of the N-terminal domain of the S1 subunit (S1-NTD) of the SARS-CoV-2 spike protein in comparison to the SARS-CoV in particular, and to other viruses presenting similar characteristic in general. Given the severity and the wide and rapid spread of the SARS-CoV-2 infection, it is very likely that the virus recognizes other receptors/co-receptors besides the ACE2. The NTD of the SARS-CoV-2 contains a receptor-binding motif different from that of SARS-CoV, with some insertions that could confer to the new coronavirus new receptor binding abilities. In particular, motifs similar to the insertion 72GTNGTKR78 have been found in structural proteins of other viruses; and these motifs were located in putative regions involved in recognizing protein and sugar receptors, suggesting therefore that similar binding abilities could be displayed by the SARS-CoV-2 S1-NTD. Moreover, concerning the origin of these NTD insertions, our findings point towards an evolutionary acquisition rather than the hypothesis of an engineered virus.
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MESH Headings
- Amino Acid Sequence
- Angiotensin-Converting Enzyme 2
- Animals
- Betacoronavirus/chemistry
- Betacoronavirus/genetics
- Betacoronavirus/metabolism
- Binding Sites
- COVID-19
- Chiroptera
- Coronavirus Infections/pathology
- Coronavirus Infections/virology
- Evolution, Molecular
- Gene Expression
- Host-Pathogen Interactions/drug effects
- Host-Pathogen Interactions/genetics
- Humans
- Middle East Respiratory Syndrome Coronavirus/chemistry
- Middle East Respiratory Syndrome Coronavirus/genetics
- Middle East Respiratory Syndrome Coronavirus/metabolism
- Models, Molecular
- Pandemics
- Peptidyl-Dipeptidase A/chemistry
- Peptidyl-Dipeptidase A/genetics
- Peptidyl-Dipeptidase A/metabolism
- Pneumonia, Viral/pathology
- Pneumonia, Viral/virology
- Protein Binding
- Protein Conformation, alpha-Helical
- Protein Conformation, beta-Strand
- Protein Interaction Domains and Motifs
- Receptors, Virus/chemistry
- Receptors, Virus/genetics
- Receptors, Virus/metabolism
- Severe acute respiratory syndrome-related coronavirus/chemistry
- Severe acute respiratory syndrome-related coronavirus/genetics
- Severe acute respiratory syndrome-related coronavirus/metabolism
- SARS-CoV-2
- Sequence Alignment
- Spike Glycoprotein, Coronavirus/chemistry
- Spike Glycoprotein, Coronavirus/genetics
- Spike Glycoprotein, Coronavirus/metabolism
- Structural Homology, Protein
- Thermodynamics
- Virus Attachment
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Affiliation(s)
- Nouredine Behloul
- College of Basic Medicine, Shanghai University of Medicine and Health Sciences, Shanghai, 201318, China
| | - Sarra Baha
- Department of Gastroenterology, Zhongda Hospital, Southeast University, Nanjing, 210009, Jiangsu Province, China
| | - Ruihua Shi
- Department of Gastroenterology, Zhongda Hospital, Southeast University, Nanjing, 210009, Jiangsu Province, China.
| | - Jihong Meng
- College of Basic Medicine, Shanghai University of Medicine and Health Sciences, Shanghai, 201318, China.
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Bouwman KM, Habraeken N, Laconi A, Berends AJ, Groenewoud L, Alders M, Kemp V, Verheije MH. N-glycosylation of infectious bronchitis virus M41 spike determines receptor specificity. J Gen Virol 2020; 101:599-608. [PMID: 32213247 PMCID: PMC7414442 DOI: 10.1099/jgv.0.001408] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 02/21/2020] [Indexed: 01/06/2023] Open
Abstract
Infection of chicken coronavirus infectious bronchitis virus (IBV) is initiated by binding of the viral heavily N-glycosylated attachment protein spike to the alpha-2,3-linked sialic acid receptor Neu5Ac. Previously, we have shown that N-glycosylation of recombinantly expressed receptor binding domain (RBD) of the spike of IBV-M41 is of critical importance for binding to chicken trachea tissue. Here we investigated the role of N-glycosylation of the RBD on receptor specificity and virus replication in the context of the virus particle. Using our reverse genetics system we were able to generate recombinant IBVs for nine-out-of-ten individual N-glycosylation mutants. In vitro growth kinetics of these viruses were comparable to the virus containing the wild-type M41-S1. Furthermore, Neu5Ac binding by the recombinant viruses containing single N-glycosylation site knock-out mutations matched the Neu5Ac binding observed with the recombinant RBDs. Five N-glycosylation mutants lost the ability to bind Neu5Ac and gained binding to a different, yet unknown, sialylated glycan receptor on host cells. These results demonstrate that N-glycosylation of IBV is a determinant for receptor specificity.
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Affiliation(s)
- K. M. Bouwman
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - N. Habraeken
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - A. Laconi
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
- Present address: Department of Comparative Biomedicine and Food Science, University of Padua, Legnaro (PD), Italy
| | - A. J. Berends
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - L. Groenewoud
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - M. Alders
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - V. Kemp
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - M. H. Verheije
- Division of Pathology, Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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65
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Jaimes JA, André NM, Chappie JS, Millet JK, Whittaker GR. Phylogenetic Analysis and Structural Modeling of SARS-CoV-2 Spike Protein Reveals an Evolutionary Distinct and Proteolytically Sensitive Activation Loop. J Mol Biol 2020; 432:3309-3325. [PMID: 32320687 PMCID: PMC7166309 DOI: 10.1016/j.jmb.2020.04.009] [Citation(s) in RCA: 321] [Impact Index Per Article: 80.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/06/2020] [Accepted: 04/07/2020] [Indexed: 12/20/2022]
Abstract
The 2019 novel coronavirus (2019-nCoV/SARS-CoV-2) originally arose as part of a major outbreak of respiratory disease centered on Hubei province, China. It is now a global pandemic and is a major public health concern. Taxonomically, SARS-CoV-2 was shown to be a Betacoronavirus (lineage B) closely related to SARS-CoV and SARS-related bat coronaviruses, and it has been reported to share a common receptor with SARS-CoV (ACE-2). Subsequently, betacoronaviruses from pangolins were identified as close relatives to SARS-CoV-2. Here, we perform structural modeling of the SARS-CoV-2 spike glycoprotein. Our data provide support for the similar receptor utilization between SARS-CoV-2 and SARS-CoV, despite a relatively low amino acid similarity in the receptor binding module. Compared to SARS-CoV and all other coronaviruses in Betacoronavirus lineage B, we identify an extended structural loop containing basic amino acids at the interface of the receptor binding (S1) and fusion (S2) domains. We suggest this loop confers fusion activation and entry properties more in line with betacoronaviruses in lineages A and C, and be a key component in the evolution of SARS-CoV-2 with this structural loop affecting virus stability and transmission.
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Affiliation(s)
- Javier A Jaimes
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Nicole M André
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Joshua S Chappie
- Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Jean K Millet
- Université Paris-Saclay, INRAE, UVSQ, Virologie et Immunologie Moléculaires, 78350 Jouy-en-Josas, France.
| | - Gary R Whittaker
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA; Master of Public Health Program, Cornell University, Ithaca, NY 14853, USA.
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66
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Shang J, Wan Y, Liu C, Yount B, Gully K, Yang Y, Auerbach A, Peng G, Baric R, Li F. Structure of mouse coronavirus spike protein complexed with receptor reveals mechanism for viral entry. PLoS Pathog 2020; 16:e1008392. [PMID: 32150576 PMCID: PMC7082060 DOI: 10.1371/journal.ppat.1008392] [Citation(s) in RCA: 98] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 03/19/2020] [Accepted: 02/08/2020] [Indexed: 12/03/2022] Open
Abstract
Coronaviruses recognize a variety of receptors using different domains of their envelope-anchored spike protein. How these diverse receptor recognition patterns affect viral entry is unknown. Mouse hepatitis coronavirus (MHV) is the only known coronavirus that uses the N-terminal domain (NTD) of its spike to recognize a protein receptor, CEACAM1a. Here we determined the cryo-EM structure of MHV spike complexed with mouse CEACAM1a. The trimeric spike contains three receptor-binding S1 heads sitting on top of a trimeric membrane-fusion S2 stalk. Three receptor molecules bind to the sides of the spike trimer, where three NTDs are located. Receptor binding induces structural changes in the spike, weakening the interactions between S1 and S2. Using protease sensitivity and negative-stain EM analyses, we further showed that after protease treatment of the spike, receptor binding facilitated the dissociation of S1 from S2, allowing S2 to transition from pre-fusion to post-fusion conformation. Together these results reveal a new role of receptor binding in MHV entry: in addition to its well-characterized role in viral attachment to host cells, receptor binding also induces the conformational change of the spike and hence the fusion of viral and host membranes. Our study provides new mechanistic insight into coronavirus entry and highlights the diverse entry mechanisms used by different viruses. Coronaviruses recognize many receptors using their envelope-anchored spike protein. The role of receptor binding in coronavirus entry into host cells is a fundamental question in virology. Mouse hepatitis coronavirus (MHV) is unique among all coronaviruses in that it uses the N-terminal domain (NTD) of its spike protein to bind a protein receptor CEACAM1a. While extensive research has been performed on the cell entry mechanisms of coronaviruses that use a different domain of their spike protein for receptor binding, the cell entry mechanism for MHV is still elusive. Here we determined the cryo-EM structure of MHV spike protein complexed with CEACAM1a. The structure reveals unique features of receptor binding by MHV spike that facilitate the structural changes of MHV spike and promote cell entry of MHV. We further confirmed the structural results with biochemical and negative-stain EM analyses. These results suggest that receptor binding plays dual roles in MHV entry: it promotes both viral attachment to host cells and the fusion of host and viral membranes. Our study provides insight into the molecular mechanism of MHV entry, demonstrating how cell entry of MHV has been adapted to its unique way of receptor binding.
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Affiliation(s)
- Jian Shang
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Yushun Wan
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Chang Liu
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Boyd Yount
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Kendra Gully
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Yang Yang
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Ashley Auerbach
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Guiqing Peng
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Ralph Baric
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Fang Li
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, Minnesota, United States of America
- * E-mail:
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Jaimes JA, André NM, Millet JK, Whittaker GR. Structural modeling of 2019-novel coronavirus (nCoV) spike protein reveals a proteolytically-sensitive activation loop as a distinguishing feature compared to SARS-CoV and related SARS-like coronaviruses. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2020. [PMID: 32511311 DOI: 10.1101/2020.02.10.942185] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The 2019 novel coronavirus (2019-nCoV) is currently causing a widespread outbreak centered on Hubei province, China and is a major public health concern. Taxonomically 2019-nCoV is closely related to SARS-CoV and SARS-related bat coronaviruses, and it appears to share a common receptor with SARS-CoV (ACE-2). Here, we perform structural modeling of the 2019-nCoV spike glycoprotein. Our data provide support for the similar receptor utilization between 2019-nCoV and SARS-CoV, despite a relatively low amino acid similarity in the receptor binding module. Compared to SARS-CoV, we identify an extended structural loop containing basic amino acids at the interface of the receptor binding (S1) and fusion (S2) domains, which we predict to be proteolytically-sensitive. We suggest this loop confers fusion activation and entry properties more in line with MERS-CoV and other coronaviruses, and that the presence of this structural loop in 2019-nCoV may affect virus stability and transmission.
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68
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Wan Y, Shang J, Sun S, Tai W, Chen J, Geng Q, He L, Chen Y, Wu J, Shi Z, Zhou Y, Du L, Li F. Molecular Mechanism for Antibody-Dependent Enhancement of Coronavirus Entry. J Virol 2020. [PMID: 31826992 DOI: 10.1128/jvi.02015.19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Antibody-dependent enhancement (ADE) of viral entry has been a major concern for epidemiology, vaccine development, and antibody-based drug therapy. However, the molecular mechanism behind ADE is still elusive. Coronavirus spike protein mediates viral entry into cells by first binding to a receptor on the host cell surface and then fusing viral and host membranes. In this study, we investigated how a neutralizing monoclonal antibody (MAb), which targets the receptor-binding domain (RBD) of Middle East respiratory syndrome (MERS) coronavirus spike, mediates viral entry using pseudovirus entry and biochemical assays. Our results showed that MAb binds to the virus surface spike, allowing it to undergo conformational changes and become prone to proteolytic activation. Meanwhile, MAb binds to cell surface IgG Fc receptor, guiding viral entry through canonical viral-receptor-dependent pathways. Our data suggest that the antibody/Fc-receptor complex functionally mimics viral receptor in mediating viral entry. Moreover, we characterized MAb dosages in viral-receptor-dependent, Fc-receptor-dependent, and both-receptors-dependent viral entry pathways, delineating guidelines on MAb usages in treating viral infections. Our study reveals a novel molecular mechanism for antibody-enhanced viral entry and can guide future vaccination and antiviral strategies.IMPORTANCE Antibody-dependent enhancement (ADE) of viral entry has been observed for many viruses. It was shown that antibodies target one serotype of viruses but only subneutralize another, leading to ADE of the latter viruses. Here we identify a novel mechanism for ADE: a neutralizing antibody binds to the surface spike protein of coronaviruses like a viral receptor, triggers a conformational change of the spike, and mediates viral entry into IgG Fc receptor-expressing cells through canonical viral-receptor-dependent pathways. We further evaluated how antibody dosages impacted viral entry into cells expressing viral receptor, Fc receptor, or both receptors. This study reveals complex roles of antibodies in viral entry and can guide future vaccine design and antibody-based drug therapy.
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MESH Headings
- Antibodies, Monoclonal/immunology
- Antibodies, Monoclonal/metabolism
- Antibodies, Neutralizing/immunology
- Antibodies, Neutralizing/metabolism
- Antibodies, Viral/immunology
- Antibodies, Viral/metabolism
- Antibody-Dependent Enhancement
- Cell Line
- Dipeptidyl Peptidase 4/metabolism
- Humans
- Immunoglobulin Fab Fragments/immunology
- Immunoglobulin Fab Fragments/metabolism
- Middle East Respiratory Syndrome Coronavirus/immunology
- Middle East Respiratory Syndrome Coronavirus/pathogenicity
- Middle East Respiratory Syndrome Coronavirus/physiology
- Peptide Hydrolases/metabolism
- Proprotein Convertases/antagonists & inhibitors
- Proprotein Convertases/metabolism
- Protein Conformation
- Protein Domains
- Protein Multimerization
- Receptors, Fc/metabolism
- Receptors, IgG/immunology
- Receptors, IgG/metabolism
- Receptors, Virus/metabolism
- Spike Glycoprotein, Coronavirus/chemistry
- Spike Glycoprotein, Coronavirus/immunology
- Spike Glycoprotein, Coronavirus/metabolism
- Trypsin/metabolism
- Virus Internalization
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Affiliation(s)
- Yushun Wan
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota, USA
| | - Jian Shang
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota, USA
| | - Shihui Sun
- Laboratory of Infection and Immunity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Wanbo Tai
- Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA
| | - Jing Chen
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei Province, China
| | - Qibin Geng
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota, USA
| | - Lei He
- Laboratory of Infection and Immunity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Yuehong Chen
- Laboratory of Infection and Immunity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Jianming Wu
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota, USA
| | - Zhengli Shi
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei Province, China
| | - Yusen Zhou
- Laboratory of Infection and Immunity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Lanying Du
- Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA
| | - Fang Li
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota, USA
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69
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Molecular Mechanism for Antibody-Dependent Enhancement of Coronavirus Entry. J Virol 2020; 94:JVI.02015-19. [PMID: 31826992 PMCID: PMC7022351 DOI: 10.1128/jvi.02015-19] [Citation(s) in RCA: 420] [Impact Index Per Article: 105.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 12/04/2019] [Indexed: 02/08/2023] Open
Abstract
Antibody-dependent enhancement (ADE) of viral entry has been observed for many viruses. It was shown that antibodies target one serotype of viruses but only subneutralize another, leading to ADE of the latter viruses. Here we identify a novel mechanism for ADE: a neutralizing antibody binds to the surface spike protein of coronaviruses like a viral receptor, triggers a conformational change of the spike, and mediates viral entry into IgG Fc receptor-expressing cells through canonical viral-receptor-dependent pathways. We further evaluated how antibody dosages impacted viral entry into cells expressing viral receptor, Fc receptor, or both receptors. This study reveals complex roles of antibodies in viral entry and can guide future vaccine design and antibody-based drug therapy. Antibody-dependent enhancement (ADE) of viral entry has been a major concern for epidemiology, vaccine development, and antibody-based drug therapy. However, the molecular mechanism behind ADE is still elusive. Coronavirus spike protein mediates viral entry into cells by first binding to a receptor on the host cell surface and then fusing viral and host membranes. In this study, we investigated how a neutralizing monoclonal antibody (MAb), which targets the receptor-binding domain (RBD) of Middle East respiratory syndrome (MERS) coronavirus spike, mediates viral entry using pseudovirus entry and biochemical assays. Our results showed that MAb binds to the virus surface spike, allowing it to undergo conformational changes and become prone to proteolytic activation. Meanwhile, MAb binds to cell surface IgG Fc receptor, guiding viral entry through canonical viral-receptor-dependent pathways. Our data suggest that the antibody/Fc-receptor complex functionally mimics viral receptor in mediating viral entry. Moreover, we characterized MAb dosages in viral-receptor-dependent, Fc-receptor-dependent, and both-receptors-dependent viral entry pathways, delineating guidelines on MAb usages in treating viral infections. Our study reveals a novel molecular mechanism for antibody-enhanced viral entry and can guide future vaccination and antiviral strategies. IMPORTANCE Antibody-dependent enhancement (ADE) of viral entry has been observed for many viruses. It was shown that antibodies target one serotype of viruses but only subneutralize another, leading to ADE of the latter viruses. Here we identify a novel mechanism for ADE: a neutralizing antibody binds to the surface spike protein of coronaviruses like a viral receptor, triggers a conformational change of the spike, and mediates viral entry into IgG Fc receptor-expressing cells through canonical viral-receptor-dependent pathways. We further evaluated how antibody dosages impacted viral entry into cells expressing viral receptor, Fc receptor, or both receptors. This study reveals complex roles of antibodies in viral entry and can guide future vaccine design and antibody-based drug therapy.
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70
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Recombinant infectious bronchitis coronavirus H120 with the spike protein S1 gene of the nephropathogenic IBYZ strain remains attenuated but induces protective immunity. Vaccine 2020; 38:3157-3168. [PMID: 32057575 PMCID: PMC7115396 DOI: 10.1016/j.vaccine.2020.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 12/28/2019] [Accepted: 01/02/2020] [Indexed: 12/26/2022]
Abstract
Infectious bronchitis (IB) is a highly infectious viral disease responsible for major economic losses in the poultry industry. A reverse genetic vaccine is a safe, rapid, and effective method of achieving IB prevention and control. In this study, we constructed the recombinant strain, rH120-S1/YZ, using a reverse genetic system, based on the backbone of the H120 vaccine strain, with the S1 gene replaced with that of the QX-like nephropathogenic strain, ck/CH/IBYZ/2011, isolated in China. The results of dwarf chicken embryos, growth kinetics, and viral titration in the embryos demonstrated that the biological characteristics of the recombinant virus remained unchanged. Like the rH120-infected group and in contrast to the rIBYZ-infected group, no mortality, clinical signs, or lesions were observed in the lungs or kidneys of young chickens inoculated with rH120-S1/YZ. The viral loads in various tissues, cloacal, and oral swabs was lower in most types of samples, indicating that the rH120-S1/YZ strain was highly safe in chicks. Compared to rH120 vaccination group, when the efficacy of this strain was evaluated against the QX-like IBV strain, better protection, with 100% survival rate and no disease symptom or gross lesion was observed in the chickens vaccinated with rH120-S1/YZ. Increased levels of IBV-specific antibodies were detected in the serum of the rH120-S1/YZ-vaccinated animals 14 days post-vaccination. Collectively, our results suggest that the recombinant strain, rH120-S1/YZ, may represent a promising vaccine candidate against QX-like IBVs.
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71
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Zhang X, Deng T, Lu J, Zhao P, Chen L, Qian M, Guo Y, Qiao H, Xu Y, Wang Y, Li X, Zhang G, Wang Z, Bian C. Molecular characterization of variant infectious bronchitis virus in China, 2019: Implications for control programmes. Transbound Emerg Dis 2020; 67:1349-1355. [PMID: 31943814 PMCID: PMC7228276 DOI: 10.1111/tbed.13477] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 12/22/2019] [Accepted: 01/07/2020] [Indexed: 01/23/2023]
Abstract
Infectious bronchitis virus (IBV), an ongoing emergence enveloped virus with a single-stranded positive-sense RNA genome, belongs to the Gammacoronavirus genus in the Coronaviridae family. IBV-associated tracheitis, nephritis, salpingitis, proventriculitis and egg drop have caused devastating economic losses to poultry industry worldwide. Since the end of 2018, a remarkably increasing number of commercial broilers and layers, vaccinated or not, were infected with IBV in China. Here, we described two IB outbreaks with severe respiratory system or kidney injury in IBV-vaccinated commercial poultry farms in central China. Other possible causative viral pathogens, including avian influenza virus (AIV), Newcastle disease virus (NDV) and Kedah fatal kidney syndrome virus (KFKSV), were excluded by reverse transcription-polymerase chain reaction (RT-PCR), and three virulent IBV strains, HeN-1/China/2019, HeN-2/China/2019 and HeN-101/China/2019, were identified. Although the gross pathologic appearance of these two IB outbreaks was different, the newly identified IBV strains were all closely related to the ck/China/I0529/17 strain and grouped into GI-19 genotype clade based on the sequencing and phylogenetic analysis of the complete S1 genes. Moreover, there are still some evolutionary distance between the newly identified IBV strains, HeN-101/China/2019 in particular, and other GI-19 strains, suggesting that Chinese IBV strains constantly emerge and evolve towards different directions. In conclusion, this study provided an insight of the recently emerging IBV outbreaks in IBV-vaccinated commercial poultry farms and identified the genetic characteristics of three virulent GI-19 IBV strains, which shows the need to carry out proper preventive measures and control strategies.
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Affiliation(s)
- Xiaozhan Zhang
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Tongwei Deng
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Jianzhou Lu
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Pandeng Zhao
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Lulu Chen
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Mengwei Qian
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Yiwen Guo
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Hongxing Qiao
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Yaohui Xu
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Yan Wang
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Xinzheng Li
- Henan Engineering and Technical Research Center for Avian Disease Control and Prevention, College of Animal Science & Technology, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Guizhi Zhang
- Henan Engineering and Technical Research Center for Avian Disease Control and Prevention, College of Animal Science & Technology, Henan University of Animal Husbandry and Economy, Zhengzhou, China
| | - Zeng Wang
- Department of Preventive Veterinary Medicine, College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, China
| | - Chuanzhou Bian
- College of Veterinary Medicine, Henan University of Animal Husbandry and Economy, Zhengzhou, China
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Jaimes JA, Millet JK, Stout AE, André NM, Whittaker GR. A Tale of Two Viruses: The Distinct Spike Glycoproteins of Feline Coronaviruses. Viruses 2020; 12:v12010083. [PMID: 31936749 PMCID: PMC7019228 DOI: 10.3390/v12010083] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 12/23/2019] [Accepted: 01/08/2020] [Indexed: 11/16/2022] Open
Abstract
Feline coronavirus (FCoV) is a complex viral agent that causes a variety of clinical manifestations in cats, commonly known as feline infectious peritonitis (FIP). It is recognized that FCoV can occur in two different serotypes. However, differences in the S protein are much more than serological or antigenic variants, resulting in the effective presence of two distinct viruses. Here, we review the distinct differences in the S proteins of these viruses, which are likely to translate into distinct biological outcomes. We introduce a new concept related to the non-taxonomical classification and differentiation among FCoVs by analyzing and comparing the genetic, structural, and functional characteristics of FCoV and the FCoV S protein among the two serotypes and FCoV biotypes. Based on our analysis, we suggest that our understanding of FIP needs to consider whether the presence of these two distinct viruses has implications in clinical settings.
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Affiliation(s)
- Javier A. Jaimes
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA; (J.A.J.); (A.E.S.); (N.M.A.)
| | - Jean K. Millet
- Virologie et Immunologie Moléculaires, INRAE, Université Paris-Saclay, 78352 Jouy-en-Josas, France;
| | - Alison E. Stout
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA; (J.A.J.); (A.E.S.); (N.M.A.)
| | - Nicole M. André
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA; (J.A.J.); (A.E.S.); (N.M.A.)
| | - Gary R. Whittaker
- Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA; (J.A.J.); (A.E.S.); (N.M.A.)
- Correspondence:
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73
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Three Amino Acid Changes in Avian Coronavirus Spike Protein Allow Binding to Kidney Tissue. J Virol 2020; 94:JVI.01363-19. [PMID: 31694947 PMCID: PMC6955270 DOI: 10.1128/jvi.01363-19] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 10/25/2019] [Indexed: 01/03/2023] Open
Abstract
Infectious bronchitis virus is the causative agent of infectious bronchitis in chickens. Upon infection of chicken flocks, the poultry industry faces substantial economic losses by diminished egg quality and increased morbidity and mortality of infected animals. While all IBV strains infect the chicken respiratory tract via the ciliated epithelial layer of the trachea, some strains can also replicate in the kidneys, dividing IBV into the following two pathotypes: nonnephropathogenic (example, IBV-M41) and nephropathogenic viruses (including IBV-QX). Here, we set out to identify the determinants for the extended nephropathogenic tropism of IBV-QX. Our data reveal that each pathotype makes use of a different sialylated glycan ligand, with binding sites on opposite sides of the attachment protein. This knowledge should facilitate the design of antivirals to prevent coronavirus infections in the field. Infectious bronchitis virus (IBV) infects ciliated epithelial cells in the chicken respiratory tract. While some IBV strains replicate locally, others can disseminate to various organs, including the kidney. Here, we elucidate the determinants for kidney tropism by studying interactions between the receptor-binding domain (RBD) of the viral attachment protein spike from two IBV strains with different tropisms. Recombinantly produced RBDs from the nephropathogenic IBV strain QX and from the nonnephropathogenic strain M41 bound to the epithelial cells of the trachea. In contrast, only QX-RBD binds more extensively to cells of the digestive tract, urogenital tract, and kidneys. While removal of sialic acids from tissues prevented binding of all proteins to all tissues, binding of QX-RBD to trachea and kidney could not be blocked by preincubation with synthetic alpha-2,3-linked sialic acids. The lack of binding of QX-RBD to a previously identified IBV-M41 receptor was confirmed by enzyme-linked immunosorbent assay (ELISA), demonstrating that tissue binding of QX-RBD is dependent on a different sialylated glycan receptor. Using chimeric RBD proteins, we discovered that the region encompassing amino acids 99 to 159 of QX-RBD was required to establish kidney binding. In particular, QX-RBD amino acids 110 to 112 (KIP) were sufficient to render IBV-M41 with the ability to bind to kidney, while the reciprocal mutations in IBV-QX abolished kidney binding completely. Structural analysis of both RBDs suggests that the receptor-binding site for QX is located at a different location on the spike than that of M41. IMPORTANCE Infectious bronchitis virus is the causative agent of infectious bronchitis in chickens. Upon infection of chicken flocks, the poultry industry faces substantial economic losses by diminished egg quality and increased morbidity and mortality of infected animals. While all IBV strains infect the chicken respiratory tract via the ciliated epithelial layer of the trachea, some strains can also replicate in the kidneys, dividing IBV into the following two pathotypes: nonnephropathogenic (example, IBV-M41) and nephropathogenic viruses (including IBV-QX). Here, we set out to identify the determinants for the extended nephropathogenic tropism of IBV-QX. Our data reveal that each pathotype makes use of a different sialylated glycan ligand, with binding sites on opposite sides of the attachment protein. This knowledge should facilitate the design of antivirals to prevent coronavirus infections in the field.
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74
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Cryo-EM analysis of a feline coronavirus spike protein reveals a unique structure and camouflaging glycans. Proc Natl Acad Sci U S A 2020; 117:1438-1446. [PMID: 31900356 PMCID: PMC6983407 DOI: 10.1073/pnas.1908898117] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
We report here a 3.3-Å cryo-EM structure of feline infectious peritonitis virus (FIPV) S protein derived from the serotype I FIPV UU4 strain. The near-atomic EM map enabled ab initio modeling of 27 out of the 33 experimentally verified high-mannose and complex-type N-glycans that mask most of the protein surface. We demonstrated the feasibility to directly visualize the core fucose of a complex-type glycan, which was independently cross-validated by glycopeptide mass spectrometry analyses. There exist 3 N-glycans that wedge between 2 galectin-like domains within the S1 subunit of FIPV-UU4 S protein, resulting in a propeller-like conformation unique to all reported CoV S proteins. The results highlight a structural role of glycosylation in maintaining complex protein structures. Feline infectious peritonitis virus (FIPV) is an alphacoronavirus that causes a nearly 100% mortality rate without effective treatment. Here we report a 3.3-Å cryoelectron microscopy (cryo-EM) structure of the serotype I FIPV spike (S) protein, which is responsible for host recognition and viral entry. Mass spectrometry provided site-specific compositions of densely distributed high-mannose and complex-type N-glycans that account for 1/4 of the total molecular mass; most of the N-glycans could be visualized by cryo-EM. Specifically, the N-glycans that wedge between 2 galectin-like domains within the S1 subunit of FIPV S protein result in a unique propeller-like conformation, underscoring the importance of glycosylation in maintaining protein structures. The cleavage site within the S2 subunit responsible for activation also showed distinct structural features and glycosylation. These structural insights provide a blueprint for a better molecular understanding of the pathogenesis of FIP.
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75
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Park YJ, Walls AC, Wang Z, Sauer MM, Li W, Tortorici MA, Bosch BJ, DiMaio F, Veesler D. Structures of MERS-CoV spike glycoprotein in complex with sialoside attachment receptors. Nat Struct Mol Biol 2019; 26:1151-1157. [PMID: 31792450 PMCID: PMC7097669 DOI: 10.1038/s41594-019-0334-7] [Citation(s) in RCA: 184] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 10/21/2019] [Indexed: 11/09/2022]
Abstract
The Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe and often lethal respiratory illness in humans, and no vaccines or specific treatments are available. Infections are initiated via binding of the MERS-CoV spike (S) glycoprotein to sialosides and dipeptidyl-peptidase 4 (the attachment and entry receptors, respectively). To understand MERS-CoV engagement of sialylated receptors, we determined the cryo-EM structures of S in complex with 5-N-acetyl neuraminic acid, 5-N-glycolyl neuraminic acid, sialyl-LewisX, α2,3-sialyl-N-acetyl-lactosamine and α2,6-sialyl-N-acetyl-lactosamine at 2.7-3.0 Å resolution. We show that recognition occurs via a conserved groove that is essential for MERS-CoV S-mediated attachment to sialosides and entry into human airway epithelial cells. Our data illuminate MERS-CoV S sialoside specificity and suggest that selectivity for α2,3-linked over α2,6-linked receptors results from enhanced interactions with the former class of oligosaccharides. This study provides a structural framework explaining MERS-CoV attachment to sialoside receptors and identifies a site of potential vulnerability to inhibitors of viral entry.
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Affiliation(s)
- Young-Jun Park
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Alexandra C Walls
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Zhaoqian Wang
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | | | - Wentao Li
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
| | - M Alejandra Tortorici
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institut Pasteur, Unité de Virologie Structurale, Paris, France
- CNRS UMR 3569, Unité de Virologie Structurale, Paris, France
| | - Berend-Jan Bosch
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - David Veesler
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
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76
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Xu P, Liu P, Zhou C, Shi Y, Wu Q, Yang Y, Li G, Hu G, Guo X. A Multi-Omics Study of Chicken Infected by Nephropathogenic Infectious Bronchitis Virus. Viruses 2019; 11:v11111070. [PMID: 31744152 PMCID: PMC6893681 DOI: 10.3390/v11111070] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 11/05/2019] [Accepted: 11/14/2019] [Indexed: 12/15/2022] Open
Abstract
Chicken gout resulting from nephropathogenic infectious bronchitis virus (NIBV) has become a serious kidney disease problem in chicken worldwide with alterations of the metabolic phenotypes in multiple metabolic pathways. To investigate the mechanisms in chicken responding to NIBV infection, we examined the global transcriptomic and metabolomic profiles of the chicken’s kidney using RNA-seq and GC–TOF/MS, respectively. Furthermore, we analyzed the alterations in cecal microorganism composition in chickens using 16S rRNA-seq. Integrated analysis of these three phenotypic datasets further managed to create correlations between the altered kidney transcriptomes and metabolome, and between kidney metabolome and gut microbiome. We found that 2868 genes and 160 metabolites were deferentially expressed or accumulated in the kidney during NIBV infection processes. These genes and metabolites were linked to NIBV-infection related processes, including immune response, signal transduction, peroxisome, purine, and amino acid metabolism. In addition, the comprehensive correlations between the kidney metabolome and cecal microbial community showed contributions of gut microbiota in the progression of NIBV-infection. Taken together, our research comprehensively describes the host responses during NIBV infection and provides new clues for further dissection of specific gene functions, metabolite affections, and the role of gut microbiota during chicken gout.
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Affiliation(s)
- Puzhi Xu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
| | - Ping Liu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
| | - Changming Zhou
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
| | - Yan Shi
- School of Computer and Information Engineering, Jiangxi Agricultural University, Nanchang 330045, China;
| | - Qingpeng Wu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
| | - Yitian Yang
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
| | - Guyue Li
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
| | - Guoliang Hu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
- Correspondence: (G.H.); (X.G.)
| | - Xiaoquan Guo
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang 330045, China; (P.X.); (P.L.); (C.Z.); (Q.W.); (Y.Y.); (G.L.)
- Correspondence: (G.H.); (X.G.)
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77
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The 3.1-Angstrom Cryo-electron Microscopy Structure of the Porcine Epidemic Diarrhea Virus Spike Protein in the Prefusion Conformation. J Virol 2019; 93:JVI.00923-19. [PMID: 31534041 PMCID: PMC6854500 DOI: 10.1128/jvi.00923-19] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 09/04/2019] [Indexed: 01/27/2023] Open
Abstract
Coronavirus spike proteins are large, densely glycosylated macromolecular machines that mediate receptor binding and membrane fusion to facilitate entry into host cells. This report describes the atomic-resolution structure of the spike protein from porcine epidemic diarrhea virus, a pathogenic alphacoronavirus that causes severe agricultural damage. The structure reveals a novel position for the sialic acid-binding attachment domain in the intact spike. We also observed shed fusion-suppressive capping subunits that displayed the putative receptor-binding domain in an accessible conformation. These observations provide a basis for understanding the molecular mechanisms that drive the earliest stages of alphacoronavirus infection and will inform future efforts to rationally design vaccines. Porcine epidemic diarrhea virus (PEDV) is an alphacoronavirus that has a significant agricultural and economic impact due to the high mortality rate associated with infection of neonatal piglets. Like other coronaviruses, PEDV makes use of a large, trimeric spike (S) glycoprotein to mediate membrane fusion and gain entry into host cells. Despite the importance of the spike protein in viral entry and host immune responses, high-resolution structural information concerning this large macromolecular machine has been difficult to obtain. Here, we report the cryo-electron microscopy structure of the PEDV S protein in the prefusion conformation at a resolution of 3.1 Å. Our studies revealed that the sialic acid-binding domain at the N terminus of the S1 subunit has an orientation that is substantially different from that observed in the previously determined spike structure from human alphacoronavirus NL63. We also observed dissociated S1 subunit trimers wherein the putative receptor-binding domains exist in a conformation differing from that observed in the intact spike proteins, suggesting that the PEDV receptor-binding domain undergoes conformational rearrangements akin to those that have been described in the related betacoronaviruses. Collectively, these data provide new insights into the biological processes that mediate alphacoronavirus attachment, receptor engagement, and fusion triggering while also identifying a source of conformational heterogeneity that could be manipulated to improve PEDV vaccine antigens. IMPORTANCE Coronavirus spike proteins are large, densely glycosylated macromolecular machines that mediate receptor binding and membrane fusion to facilitate entry into host cells. This report describes the atomic-resolution structure of the spike protein from porcine epidemic diarrhea virus, a pathogenic alphacoronavirus that causes severe agricultural damage. The structure reveals a novel position for the sialic acid-binding attachment domain in the intact spike. We also observed shed fusion-suppressive capping subunits that displayed the putative receptor-binding domain in an accessible conformation. These observations provide a basis for understanding the molecular mechanisms that drive the earliest stages of alphacoronavirus infection and will inform future efforts to rationally design vaccines.
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78
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Franzo G, Legnardi M, Tucciarone CM, Drigo M, Martini M, Cecchinato M. Evolution of infectious bronchitis virus in the field after homologous vaccination introduction. Vet Res 2019; 50:92. [PMID: 31706335 PMCID: PMC6842459 DOI: 10.1186/s13567-019-0713-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 09/25/2019] [Indexed: 11/10/2022] Open
Abstract
Despite the fact that vaccine resistance has been typically considered a rare phenomenon, some episodes of vaccine failure have been reported with increasing frequency in intensively-raised livestock. Infectious bronchitis virus (IBV) is a widespread avian coronavirus, whose control relies mainly on extensive vaccine administration. Unfortunately, the continuous emergence of new vaccine-immunity escaping variants prompts the development of new vaccines. In the present work, a molecular epidemiology study was performed to evaluate the potential role of homologous vaccination in driving IBV evolution. This was undertaken by assessing IBV viral RNA sequences from the ORF encoding the S1 portion of viral surface glycoprotein (S) before and after the introduction of a new live vaccine on broiler farms in northern-Italy. The results of several biostatistics analyses consistently demonstrate the presence of a higher pressure in the post-vaccination period. Natural selection was detected essentially on sites located on the protein surface, within or nearby domains involved in viral attachment or related functions. This evidence strongly supports the action of vaccine-induced immunity in conditioning viral evolution, potentially leading to the emergence of new vaccine-escape variants. The great plasticity of rapidly-evolving RNA-viruses in response to human intervention, which extends beyond the poultry industry, is demonstrated, claiming further attention due to their relevance for animal and especially human health.
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Affiliation(s)
- Giovanni Franzo
- Department of Animal Medicine, Production and Health (MAPS), University of Padua, Viale dell’Università 16, 35020 Legnaro, PD Italy
| | - Matteo Legnardi
- Department of Animal Medicine, Production and Health (MAPS), University of Padua, Viale dell’Università 16, 35020 Legnaro, PD Italy
| | - Claudia Maria Tucciarone
- Department of Animal Medicine, Production and Health (MAPS), University of Padua, Viale dell’Università 16, 35020 Legnaro, PD Italy
| | - Michele Drigo
- Department of Animal Medicine, Production and Health (MAPS), University of Padua, Viale dell’Università 16, 35020 Legnaro, PD Italy
| | - Marco Martini
- Department of Animal Medicine, Production and Health (MAPS), University of Padua, Viale dell’Università 16, 35020 Legnaro, PD Italy
| | - Mattia Cecchinato
- Department of Animal Medicine, Production and Health (MAPS), University of Padua, Viale dell’Università 16, 35020 Legnaro, PD Italy
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79
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Li Z, Tomlinson AC, Wong AH, Zhou D, Desforges M, Talbot PJ, Benlekbir S, Rubinstein JL, Rini JM. The human coronavirus HCoV-229E S-protein structure and receptor binding. eLife 2019; 8:51230. [PMID: 31650956 PMCID: PMC6970540 DOI: 10.7554/elife.51230] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 10/12/2019] [Indexed: 12/12/2022] Open
Abstract
The coronavirus S-protein mediates receptor binding and fusion of the viral and host cell membranes. In HCoV-229E, its receptor binding domain (RBD) shows extensive sequence variation but how S-protein function is maintained is not understood. Reported are the X-ray crystal structures of Class III-V RBDs in complex with human aminopeptidase N (hAPN), as well as the electron cryomicroscopy structure of the 229E S-protein. The structures show that common core interactions define the specificity for hAPN and that the peripheral RBD sequence variation is accommodated by loop plasticity. The results provide insight into immune evasion and the cross-species transmission of 229E and related coronaviruses. We also find that the 229E S-protein can expose a portion of its helical core to solvent. This is undoubtedly facilitated by hydrophilic subunit interfaces that we show are conserved among coronaviruses. These interfaces likely play a role in the S-protein conformational changes associated with membrane fusion.
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Affiliation(s)
- Zhijie Li
- Department of Molecular Genetics, The University of Toronto, Toronto, Canada
| | | | - Alan Hm Wong
- Department of Biochemistry, The University of Toronto, Toronto, Canada
| | - Dongxia Zhou
- Department of Molecular Genetics, The University of Toronto, Toronto, Canada
| | - Marc Desforges
- Laboratory of Neuroimmunovirology, INRS-Institut Armand-Frappier, Institut National de la Recherche Scientifique, Université du Québec, Laval, Canada
| | - Pierre J Talbot
- Laboratory of Neuroimmunovirology, INRS-Institut Armand-Frappier, Institut National de la Recherche Scientifique, Université du Québec, Laval, Canada
| | - Samir Benlekbir
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto, Canada
| | - John L Rubinstein
- Department of Biochemistry, The University of Toronto, Toronto, Canada.,Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto, Canada.,Department of Medical Biophysics, The University of Toronto, Toronto, Canada
| | - James M Rini
- Department of Molecular Genetics, The University of Toronto, Toronto, Canada.,Department of Biochemistry, The University of Toronto, Toronto, Canada
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80
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The S2 Subunit of QX-type Infectious Bronchitis Coronavirus Spike Protein Is an Essential Determinant of Neurotropism. Viruses 2019; 11:v11100972. [PMID: 31652591 PMCID: PMC6832359 DOI: 10.3390/v11100972] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 10/17/2019] [Accepted: 10/21/2019] [Indexed: 01/23/2023] Open
Abstract
Some coronaviruses (CoVs) have an extra furin cleavage site (RRKR/S, furin-S2′ site) upstream of the fusion peptide in the spike protein, which plays roles in virion adsorption and fusion. Mutation of the S2′ site of QX genotype (QX-type) infectious bronchitis virus (IBV) spike protein (S) in a recombinant virus background results in higher pathogenicity, pronounced neural symptoms and neurotropism when compared with conditions in wild-type IBV (WT-IBV) infected chickens. In this study, we present evidence suggesting that recombinant IBV with a mutant S2′ site (furin-S2′ site) leads to higher mortality. Infection with mutant IBV induces severe encephalitis and breaks the blood–brain barrier. The results of a neutralization test and immunoprotection experiment show that an original serum and vaccine can still provide effective protection in vivo and in vitro. This is the first demonstration of IBV-induced neural symptoms in chickens with encephalitis and the furin-S2′ site as a determinant of neurotropism.
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81
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Glycine 29 Is Critical for Conformational Changes of the Spike Glycoprotein of Mouse Hepatitis Virus A59 Triggered by either Receptor Binding or High pH. J Virol 2019; 93:JVI.01046-19. [PMID: 31375571 PMCID: PMC6798120 DOI: 10.1128/jvi.01046-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 07/19/2019] [Indexed: 12/28/2022] Open
Abstract
Mouse hepatitis virus (MHV) uses its N-terminal domain (NTD) of the viral spike (S) protein to bind the host receptor mouse carcinoembryonic antigen-related cell adhesion molecule 1a (mCEACAM1a) and mediate virus entry. Our previous crystal structure study of the MHV NTD/mCEACAM1a complex (G. Peng, D. Sun, K. R. Rajashankar, Z. Qian, et al., Proc Natl Acad Sci U S A 108:10696-10701, 2011, https://doi.org/10.1073/pnas.1104306108) reveals that there are 14 residues in the NTD interacting with the receptor. However, their contribution to receptor binding and virus entry has not been fully investigated. Here we analyzed 13 out of 14 contact residues by mutagenesis and identified I22 as being essential for receptor binding and virus entry. Unexpectedly, we found that G29 was critical for the conformational changes of the S protein triggered by either receptor binding or high pH. Replacement of G29 with A, D, F, K, M, and T, to different extents, caused spontaneous dissociation of S1 from the S protein, resulting in an enhancement of high-pH-triggered receptor-independent syncytium (RIS) formation in HEK293T cells, compared to the wild type (WT). In contrast, replacement of G29 with P, a turn-prone residue with a strict conformation, hindered virus entry and conformational changes of the S protein triggered by either receptor binding or pH 8.0, suggesting that the structural turn around G29 and its flexibility are critical. Finally, stabilization of the NTD by G29P had almost no effect on pH-independent RIS induced by the Y320A mutation in the C-terminal domain (CTD) of the S1 subunit, indicating that there might be an absence of cross talk between the NTD and CTD during conformational changes of the S protein. Our study will aid in better understanding the mechanism of how conformational changes of the S protein are triggered.IMPORTANCE Binding of the MHV S protein to the receptor mCEACAM1a triggers conformational changes of S proteins, leading to the formation of a six-helix bundle and viral and cellular membrane fusion. However, the mechanism by which the conformational change of the S protein is initiated after receptor binding has not been determined. In this study, we showed that while replacement of G29, a residue at the edge of the receptor binding interface and the center of the structural turn after the β1-sheet of the S protein, with D or T triggered spontaneous conformational changes of the S protein and pH-independent RIS, the G29P mutation significantly impeded the conformational changes of S proteins triggered by either receptor binding or pH 8.0. We reason that this structural turn might be critical for conformational changes of the S protein and that altering this structural turn could initiate conformational changes of the S protein, leading to membrane fusion.
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82
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Wang N, Rosen O, Wang L, Turner HL, Stevens LJ, Corbett KS, Bowman CA, Pallesen J, Shi W, Zhang Y, Leung K, Kirchdoerfer RN, Becker MM, Denison MR, Chappell JD, Ward AB, Graham BS, McLellan JS. Structural Definition of a Neutralization-Sensitive Epitope on the MERS-CoV S1-NTD. Cell Rep 2019; 28:3395-3405.e6. [PMID: 31553909 PMCID: PMC6935267 DOI: 10.1016/j.celrep.2019.08.052] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/06/2019] [Accepted: 08/16/2019] [Indexed: 12/13/2022] Open
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) emerged into the human population in 2012 and has caused substantial morbidity and mortality. Potently neutralizing antibodies targeting the receptor-binding domain (RBD) on MERS-CoV spike (S) protein have been characterized, but much less is known about antibodies targeting non-RBD epitopes. Here, we report the structural and functional characterization of G2, a neutralizing antibody targeting the MERS-CoV S1 N-terminal domain (S1-NTD). Structures of G2 alone and in complex with the MERS-CoV S1-NTD define a site of vulnerability comprising two loops, each of which contain a residue mutated in G2-escape variants. Cell-surface binding studies and in vitro competition experiments demonstrate that G2 strongly disrupts the attachment of MERS-CoV S to its receptor, dipeptidyl peptidase-4 (DPP4), with the inhibition requiring the native trimeric S conformation. These results advance our understanding of antibody-mediated neutralization of coronaviruses and should facilitate the development of immunotherapeutics and vaccines against MERS-CoV.
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Affiliation(s)
- Nianshuang Wang
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Osnat Rosen
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Lingshu Wang
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Hannah L Turner
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Laura J Stevens
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Kizzmekia S Corbett
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Charles A Bowman
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jesper Pallesen
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Wei Shi
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Yi Zhang
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Kwanyee Leung
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Robert N Kirchdoerfer
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Michelle M Becker
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Mark R Denison
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - James D Chappell
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Barney S Graham
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Jason S McLellan
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA.
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Abstract
Coronaviruses (CoVs) have caused outbreaks of deadly pneumonia in humans since the beginning of the 21st century. The severe acute respiratory syndrome coronavirus (SARS-CoV) emerged in 2002 and was responsible for an epidemic that spread to five continents with a fatality rate of 10% before being contained in 2003 (with additional cases reported in 2004). The Middle-East respiratory syndrome coronavirus (MERS-CoV) emerged in the Arabian Peninsula in 2012 and has caused recurrent outbreaks in humans with a fatality rate of 35%. SARS-CoV and MERS-CoV are zoonotic viruses that crossed the species barrier using bats/palm civets and dromedary camels, respectively. No specific treatments or vaccines have been approved against any of the six human coronaviruses, highlighting the need to investigate the principles governing viral entry and cross-species transmission as well as to prepare for zoonotic outbreaks which are likely to occur due to the large reservoir of CoVs found in mammals and birds. Here, we review our understanding of the infection mechanism used by coronaviruses derived from recent structural and biochemical studies.
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Affiliation(s)
- M Alejandra Tortorici
- Department of Biochemistry, University of Washington, Seattle, WA, United States; Institut Pasteur, Unité de Virologie Structurale, Paris, France; CNRS UMR 3569, Unité de Virologie Structurale, Paris, France
| | - David Veesler
- Department of Biochemistry, University of Washington, Seattle, WA, United States.
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84
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Widjaja I, Wang C, van Haperen R, Gutiérrez-Álvarez J, van Dieren B, Okba NMA, Raj VS, Li W, Fernandez-Delgado R, Grosveld F, van Kuppeveld FJM, Haagmans BL, Enjuanes L, Drabek D, Bosch BJ. Towards a solution to MERS: protective human monoclonal antibodies targeting different domains and functions of the MERS-coronavirus spike glycoprotein. Emerg Microbes Infect 2019; 8:516-530. [PMID: 30938227 PMCID: PMC6455120 DOI: 10.1080/22221751.2019.1597644] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The Middle-East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic virus that causes severe and often fatal respiratory disease in humans. Efforts to develop antibody-based therapies have focused on neutralizing antibodies that target the receptor binding domain of the viral spike protein thereby blocking receptor binding. Here, we developed a set of human monoclonal antibodies that target functionally distinct domains of the MERS-CoV spike protein. These antibodies belong to six distinct epitope groups and interfere with the three critical entry functions of the MERS-CoV spike protein: sialic acid binding, receptor binding and membrane fusion. Passive immunization with potently as well as with poorly neutralizing antibodies protected mice from lethal MERS-CoV challenge. Collectively, these antibodies offer new ways to gain humoral protection in humans against the emerging MERS-CoV by targeting different spike protein epitopes and functions.
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Affiliation(s)
- Ivy Widjaja
- a Virology Division, Department of Infectious Diseases & Immunology, Faculty of Veterinary Medicine , Utrecht University , Utrecht , Netherlands
| | - Chunyan Wang
- a Virology Division, Department of Infectious Diseases & Immunology, Faculty of Veterinary Medicine , Utrecht University , Utrecht , Netherlands
| | - Rien van Haperen
- b Department of Cell Biology , Erasmus MC , Rotterdam , Netherlands.,c Harbour Antibodies B.V. , Rotterdam , Netherlands
| | - Javier Gutiérrez-Álvarez
- d Department of Molecular and Cell Biology , National Center for Biotechnology-Spanish National Research Council (CNB-CSIC) , Madrid , Spain
| | - Brenda van Dieren
- a Virology Division, Department of Infectious Diseases & Immunology, Faculty of Veterinary Medicine , Utrecht University , Utrecht , Netherlands
| | - Nisreen M A Okba
- e Department of Viroscience , Erasmus Medical Center , Rotterdam , Netherlands
| | - V Stalin Raj
- e Department of Viroscience , Erasmus Medical Center , Rotterdam , Netherlands
| | - Wentao Li
- a Virology Division, Department of Infectious Diseases & Immunology, Faculty of Veterinary Medicine , Utrecht University , Utrecht , Netherlands
| | - Raul Fernandez-Delgado
- d Department of Molecular and Cell Biology , National Center for Biotechnology-Spanish National Research Council (CNB-CSIC) , Madrid , Spain
| | - Frank Grosveld
- b Department of Cell Biology , Erasmus MC , Rotterdam , Netherlands.,c Harbour Antibodies B.V. , Rotterdam , Netherlands
| | - Frank J M van Kuppeveld
- a Virology Division, Department of Infectious Diseases & Immunology, Faculty of Veterinary Medicine , Utrecht University , Utrecht , Netherlands
| | - Bart L Haagmans
- e Department of Viroscience , Erasmus Medical Center , Rotterdam , Netherlands
| | - Luis Enjuanes
- d Department of Molecular and Cell Biology , National Center for Biotechnology-Spanish National Research Council (CNB-CSIC) , Madrid , Spain
| | - Dubravka Drabek
- b Department of Cell Biology , Erasmus MC , Rotterdam , Netherlands.,c Harbour Antibodies B.V. , Rotterdam , Netherlands
| | - Berend-Jan Bosch
- a Virology Division, Department of Infectious Diseases & Immunology, Faculty of Veterinary Medicine , Utrecht University , Utrecht , Netherlands
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85
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Structural basis for human coronavirus attachment to sialic acid receptors. Nat Struct Mol Biol 2019; 26:481-489. [PMID: 31160783 PMCID: PMC6554059 DOI: 10.1038/s41594-019-0233-y] [Citation(s) in RCA: 384] [Impact Index Per Article: 76.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 04/19/2019] [Indexed: 12/16/2022]
Abstract
Coronaviruses cause respiratory tract infections in humans and outbreaks of deadly pneumonia worldwide. Infections are initiated by the transmembrane spike (S) glycoprotein, which binds to host receptors and fuses the viral and cellular membranes. To understand the molecular basis of coronavirus attachment to oligosaccharide receptors, we determined cryo-EM structures of coronavirus OC43 S glycoprotein trimer in isolation and in complex with a 9-O-acetylated sialic acid. We show that the ligand binds with fast kinetics to a surface-exposed groove and that interactions at the identified site are essential for S-mediated viral entry into host cells, but free monosaccharide does not trigger fusogenic conformational changes. The receptor-interacting site is conserved in all coronavirus S glycoproteins that engage 9-O-acetyl-sialogycans, with an architecture similar to those of the ligand-binding pockets of coronavirus hemagglutinin esterases and influenza virus C/D hemagglutinin-esterase fusion glycoproteins. Our results demonstrate these viruses evolved similar strategies to engage sialoglycans at the surface of target cells. Structural and functional analyses reveal how 9-O-acetyl sialic acid is recognized by the human coronavirus OC43 S glycoprotein and how this interaction promotes viral entry.
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86
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Westerbeck JW, Machamer CE. The Infectious Bronchitis Coronavirus Envelope Protein Alters Golgi pH To Protect the Spike Protein and Promote the Release of Infectious Virus. J Virol 2019; 93:e00015-19. [PMID: 30867314 PMCID: PMC6532078 DOI: 10.1128/jvi.00015-19] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 03/07/2019] [Indexed: 12/20/2022] Open
Abstract
Coronaviruses (CoVs) assemble by budding into the lumen of the early Golgi complex prior to exocytosis. The small CoV envelope (E) protein plays roles in assembly, virion release, and pathogenesis. CoV E has a single hydrophobic domain (HD), is targeted to Golgi membranes, and has cation channel activity in vitro The E protein from avian infectious bronchitis virus (IBV) has dramatic effects on the secretory system, which require residues in the HD. Mutation of the HD of IBV E in a recombinant virus background results in impaired growth kinetics, impaired release of infectious virions, accumulation of IBV spike (S) protein on the plasma membrane compared to wild-type (WT) IBV-infected cells, and aberrant cleavage of IBV S on virions. We previously reported the formation of two distinct oligomeric pools of IBV E in transfected and infected cells. Disruption of the secretory pathway by IBV E correlates with a form that is likely monomeric, suggesting that the effects on the secretory pathway are independent of E ion channel activity. Here, we present evidence suggesting that the monomeric form of IBV E correlates with an increased Golgi luminal pH. Infection with IBV or expression of IBV E induces neutralization of Golgi pH, promoting a model in which IBV E alters the secretory pathway through interaction with host cell factors, protecting IBV S from premature cleavage and leading to the efficient release of infectious virus from the cells. This is the first demonstration of a coronavirus-induced alteration in the microenvironment of the secretory pathway.IMPORTANCE Coronaviruses are important human pathogens with significant zoonotic potential. Progress has been made toward identifying potential vaccine candidates for highly pathogenic human CoVs, including the use of attenuated viruses that lack the CoV E protein or express E mutants. However, no approved vaccines or antiviral therapeutics exist. Understanding the role of the CoV E protein in virus assembly and release is thus an important prerequisite for potential vaccines as well as in identifying novel antiviral therapeutics.
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Affiliation(s)
- Jason W Westerbeck
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Carolyn E Machamer
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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87
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Guinea Fowl Coronavirus Diversity Has Phenotypic Consequences for Glycan and Tissue Binding. J Virol 2019; 93:JVI.00067-19. [PMID: 30842318 PMCID: PMC6498037 DOI: 10.1128/jvi.00067-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 02/20/2019] [Indexed: 12/13/2022] Open
Abstract
Avian coronaviruses cause major global problems in the poultry industry. As causative agents of huge economic losses, the detection and understanding of the molecular determinants of viral tropism are of ultimate importance. Here, we set out to study those parameters and obtained in-depth insight into the virus-host interactions of guinea fowl coronavirus (GfCoV). Our data indicate that diversity in GfCoV viral attachment proteins results in differences in degrees of affinity for glycan receptors, as well as altered avidity for intestinal tract tissues, which might have consequences for GfCoV tissue tropism and pathogenesis in guinea fowls. Guinea fowl coronavirus (GfCoV) causes fulminating enteritis that can result in a daily death rate of 20% in guinea fowl flocks. Here, we studied GfCoV diversity and evaluated its phenotypic consequences. Over the period of 2014 to 2016, affected guinea fowl flocks were sampled in France, and avian coronavirus presence was confirmed by PCR on intestinal content and immunohistochemistry of intestinal tissue. Sequencing revealed 89% amino acid identity between the viral attachment protein S1 of GfCoV/2014 and that of the previously identified GfCoV/2011. To study the receptor interactions as a determinant for tropism and pathogenicity, recombinant S1 proteins were produced and analyzed by glycan and tissue arrays. Glycan array analysis revealed that, in addition to the previously elucidated biantennary di-N-acetyllactosamine (diLacNAc) receptor, viral attachment S1 proteins from GfCoV/2014 and GfCoV/2011 can bind to glycans capped with alpha-2,6-linked sialic acids. Interestingly, recombinant GfCoV/2014 S1 has an increased affinity for these glycans compared to that of GfCoV/2011 S1, which was in agreement with the increased avidity of GfCoV/2014 S1 for gastrointestinal tract tissues. Enzymatic removal of receptors from tissues before application of spike proteins confirmed the specificity of S1 tissue binding. Overall, we demonstrate that diversity in GfCoV S1 proteins results in differences in glycan and tissue binding properties. IMPORTANCE Avian coronaviruses cause major global problems in the poultry industry. As causative agents of huge economic losses, the detection and understanding of the molecular determinants of viral tropism are of ultimate importance. Here, we set out to study those parameters and obtained in-depth insight into the virus-host interactions of guinea fowl coronavirus (GfCoV). Our data indicate that diversity in GfCoV viral attachment proteins results in differences in degrees of affinity for glycan receptors, as well as altered avidity for intestinal tract tissues, which might have consequences for GfCoV tissue tropism and pathogenesis in guinea fowls.
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88
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Parsons LM, Bouwman KM, Azurmendi H, de Vries RP, Cipollo JF, Verheije MH. Glycosylation of the viral attachment protein of avian coronavirus is essential for host cell and receptor binding. J Biol Chem 2019; 294:7797-7809. [PMID: 30902814 PMCID: PMC6514631 DOI: 10.1074/jbc.ra119.007532] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/01/2019] [Indexed: 12/16/2022] Open
Abstract
Avian coronaviruses, including infectious bronchitis virus (IBV), are important
respiratory pathogens of poultry. The heavily glycosylated IBV spike protein is
responsible for binding to host tissues. Glycosylation sites in the spike
protein are highly conserved across viral genotypes, suggesting an important
role for this modification in the virus life cycle. Here, we analyzed the
N-glycosylation of the receptor-binding domain (RBD) of IBV
strain M41 spike protein and assessed the role of this modification in host
receptor binding. Ten single Asn–to–Ala substitutions at the
predicted N-glycosylation sites of the M41–RBD were
evaluated along with two control Val–to–Ala substitutions. CD
analysis revealed that the secondary structure of all variants was retained
compared with the unmodified M41–RBD construct. Six of the 10
glycosylation variants lost binding to chicken trachea tissue and an
ELISA-presented α2,3-linked sialic acid oligosaccharide ligand.
LC/MSE glycomics analysis revealed that glycosylation sites have
specific proportions of N-glycan subtypes. Overall, the
glycosylation patterns of most variant RBDs were highly similar to those of the
unmodified M41–RBD construct. In silico docking
experiments with the recently published cryo-EM structure of the M41 IBV spike
protein and our glycosylation results revealed a potential ligand receptor site
that is ringed by four glycosylation sites that dramatically impact ligand
binding. Combined with the results of previous array studies, the glycosylation
and mutational analyses presented here suggest a unique glycosylation-dependent
binding modality for the M41 spike protein.
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Affiliation(s)
- Lisa M Parsons
- From the Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland 20993
| | - Kim M Bouwman
- the Division of Pathology, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands, and
| | - Hugo Azurmendi
- From the Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland 20993
| | - Robert P de Vries
- the Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3512 JE Utrecht, The Netherlands
| | - John F Cipollo
- From the Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland 20993,
| | - Monique H Verheije
- the Division of Pathology, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands, and
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89
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Al Kahlout RA, Nasrallah GK, Farag EA, Wang L, Lattwein E, Müller MA, El Zowalaty ME, Al Romaihi HE, Graham BS, Al Thani AA, Yassine HM. Comparative Serological Study for the Prevalence of Anti-MERS Coronavirus Antibodies in High- and Low-Risk Groups in Qatar. J Immunol Res 2019; 2019:1386740. [PMID: 30906787 PMCID: PMC6398027 DOI: 10.1155/2019/1386740] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/29/2018] [Accepted: 12/27/2018] [Indexed: 11/18/2022] Open
Abstract
Infection with Middle East respiratory syndrome coronavirus (MERS-CoV) could be asymptomatic or cause mild influenza-like illness. Therefore, the prevalence of MERS-CoV infections in the general population could be underestimated, which necessitates active surveillance to determine the epidemiological importance of asymptomatic cases. The aim of this study is to evaluate the performance of various serological assays and to estimate the seroprevalence of anti-MERS-CoV antibodies in high- and low-risk groups in Qatar. A total of 4858 samples were screened, including 4719 samples collected from healthy blood donors (BD) over a period of five years (2012-2016), 135 samples from baseline case contacts (CC) collected from individuals in close contact with three positive PCR-confirmed patients (CP), and four samples from MERS-CoV CP. Initial screening using anti-MERS-CoV IgG (IgG rS1-ELISA kit) revealed ten reactive samples from BD (10/4719, 0.21%), one from CC (1/135, 0.74%), and three from CP (3/4, 75%). Samples from CP but not from BD were also reactive by whole-virus anti-MERS-CoV IgG (n = 3/4) and IgM (n = 1/4) indirect immunefluorescent tests (IIFT) and pseudoparticle neutralization test (ppNT). The reactive sample from CC was also confirmed by ppNT. Surprisingly, one out of thirteen (7.7%) randomly selected IgG rS1-ELISA-negative BD samples from the initial screening was reactive by the IgM-IIFT (but not by the IgG-IIFT) and was subsequently confirmed by ppNT. All IgG rS1-ELISA-reactive samples from BD exhibited considerable reactivity to the four circulating human coronaviruses (HKU1, OC43, 229E, and NL63). Cross-reactivity with SARS was only reported for samples from CP using IgG and IgM-IIFT. In conclusion, we report a low prevalence of anti-MERS antibodies in the general population, which coincides with the low number of all reported cases by the time of our study (2017) in Qatar (n = 21). The false-positive results and the observed cross-reactivity between MERS-CoV and other circulating human coronavirus necessitate more detailed evaluation of available serological assays.
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Affiliation(s)
- Reham A. Al Kahlout
- Department of Biomedical Sciences, College of Health Sciences, Qatar University, Doha, Qatar
| | - Gheyath K. Nasrallah
- Department of Biomedical Sciences, College of Health Sciences, Qatar University, Doha, Qatar
- Biomedical Research Center, Qatar University, Doha, Qatar
| | - Elmoubasher A. Farag
- Communicable Diseases Control Programs, Public Health Department, Ministry of Public Health, Doha, Qatar
| | - Lingshu Wang
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institute of Health, Bethesda, MD, USA
| | | | - Marcel A. Müller
- Institute of Virology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, Berlin, Germany
| | - Mohamed E. El Zowalaty
- Virology and Microbiology Research Laboratory, School of Health Sciences, College of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4000, South Africa
| | - Hamad E. Al Romaihi
- Communicable Diseases Control Programs, Public Health Department, Ministry of Public Health, Doha, Qatar
| | - Barney S. Graham
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institute of Health, Bethesda, MD, USA
| | - Asmaa A. Al Thani
- Department of Biomedical Sciences, College of Health Sciences, Qatar University, Doha, Qatar
- Biomedical Research Center, Qatar University, Doha, Qatar
| | - Hadi M. Yassine
- Department of Biomedical Sciences, College of Health Sciences, Qatar University, Doha, Qatar
- Biomedical Research Center, Qatar University, Doha, Qatar
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90
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Walls AC, Xiong X, Park YJ, Tortorici MA, Snijder J, Quispe J, Cameroni E, Gopal R, Dai M, Lanzavecchia A, Zambon M, Rey FA, Corti D, Veesler D. Unexpected Receptor Functional Mimicry Elucidates Activation of Coronavirus Fusion. Cell 2019; 176:1026-1039.e15. [PMID: 30712865 PMCID: PMC6751136 DOI: 10.1016/j.cell.2018.12.028] [Citation(s) in RCA: 454] [Impact Index Per Article: 90.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 10/29/2018] [Accepted: 12/17/2018] [Indexed: 12/27/2022]
Abstract
Recent outbreaks of severe acute respiratory syndrome and Middle East respiratory syndrome, along with the threat of a future coronavirus-mediated pandemic, underscore the importance of finding ways to combat these viruses. The trimeric spike transmembrane glycoprotein S mediates entry into host cells and is the major target of neutralizing antibodies. To understand the humoral immune response elicited upon natural infections with coronaviruses, we structurally characterized the SARS-CoV and MERS-CoV S glycoproteins in complex with neutralizing antibodies isolated from human survivors. Although the two antibodies studied blocked attachment to the host cell receptor, only the anti-SARS-CoV S antibody triggered fusogenic conformational changes via receptor functional mimicry. These results provide a structural framework for understanding coronavirus neutralization by human antibodies and shed light on activation of coronavirus membrane fusion, which takes place through a receptor-driven ratcheting mechanism.
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Affiliation(s)
- Alexandra C Walls
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Xiaoli Xiong
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Young-Jun Park
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - M Alejandra Tortorici
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA; Institute Pasteur & CNRS UMR 3569, Unité de Virologie Structurale, 75015, Paris, France
| | - Joost Snijder
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | - Joel Quispe
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
| | | | - Robin Gopal
- National Infection Service, Public Health England, London NW9 5HT, UK
| | - Mian Dai
- Crick Worldwide Influenza Centre, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Antonio Lanzavecchia
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera italiana, 6500 Bellinzona, Switzerland
| | - Maria Zambon
- National Infection Service, Public Health England, London NW9 5HT, UK
| | - Félix A Rey
- Institute Pasteur & CNRS UMR 3569, Unité de Virologie Structurale, 75015, Paris, France
| | - Davide Corti
- Humabs Biomed SA, Vir Biotechnology, 6500 Bellinzona, Switzerland
| | - David Veesler
- Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA.
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91
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Ellis S, Keep S, Britton P, de Wit S, Bickerton E, Vervelde L. Recombinant Infectious Bronchitis Viruses Expressing Chimeric Spike Glycoproteins Induce Partial Protective Immunity against Homologous Challenge despite Limited Replication In Vivo. J Virol 2018; 92:e01473-18. [PMID: 30209177 PMCID: PMC6232476 DOI: 10.1128/jvi.01473-18] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 09/03/2018] [Indexed: 12/19/2022] Open
Abstract
Vaccination regimes against Infectious bronchitis virus (IBV), which are based on a single virus serotype, often induce insufficient levels of cross-protection against serotypes and two or more antigenically diverse vaccines are used in attempt to provide broader protection. Amino acid differences in the surface protein, spike (S), in particular the S1 subunit, are associated with poor cross-protection. Here, homologous vaccination trials with recombinant IBVs (rIBVs), based on the apathogenic strain, BeauR, were conducted to elucidate the role of S1 in protection. A single vaccination of specific-pathogen-free chickens with rIBV expressing S1 of virulent strains M41 or QX, BeauR-M41(S1) and BeauR-QX(S1), gave incomplete protection against homologous challenge, based on ciliary activity and clinical signs. There could be conformational issues with the spike if heterologous S1 and S2 are linked, suggesting a homologous S2 might be essential. To address this, a homologous vaccination-challenge trial incorporating rIBVs expressing full spike from M41, BeauR-M41(S), and S2 subunit from M41, BeauR-M41(S2) was conducted. All chimeric viruses grew to similar titers in vitro, induced virus-specific partial protective immunity, evident by cellular infiltrations, reductions in viral RNA load in the trachea and conjunctiva and higher serum anti-IBV titers. Collectively, these findings show that vaccination with rIBVs primed the birds for challenge but the viruses were cleared rapidly from the mucosal tissues in the head. Chimeric S1 and S2 viruses did not protect as effectively as BeauR-M41(S) based on ciliary activity and clinical signs. Booster vaccinations and an rIBV with improved in vivo replication may improve the levels of protection.IMPORTANCE Infectious bronchitis virus causes an acute, highly contagious respiratory disease, responsible for significant economic losses to the poultry industry. Amino acid differences in the surface protein, spike (S), in particular the S1 subunit, have been associated with poor cross-protection. Available vaccines give poor cross-protection and rationally designed live attenuated vaccines, based on apathogenic BeauR, could address these. Here, to determine the role of S1 in protection, a series of homologous vaccination trials with rIBVs were conducted. Single vaccinations with chimeric rIBVs induced virus-specific partial protective immunity, characterized by reduction in viral load and serum antibody titers. However, BeauR-M41(S) was the only vaccination to improve the level of protection against clinical signs and the loss of tracheal ciliary activity. Growth characteristics show that all of the rIBVs replicated in vitro to similar levels. Booster vaccinations and an rIBV with improved in vivo replication may improve the levels of protection.
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Affiliation(s)
- Samantha Ellis
- Infection and Immunity, The Roslin Institute, University of Edinburgh, Penicuik, Midlothian, United Kingdom
| | - Sarah Keep
- The Pirbright Institute, Pirbright, Surrey, United Kingdom
| | - Paul Britton
- The Pirbright Institute, Pirbright, Surrey, United Kingdom
| | | | | | - Lonneke Vervelde
- Infection and Immunity, The Roslin Institute, University of Edinburgh, Penicuik, Midlothian, United Kingdom
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92
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Hong SM, An SH, Lee CY, Song CS, Choi KS, Kim JH, Kwon HJ. Pathobiological and Genomic Characterization of a Cold-Adapted Infectious Bronchitis Virus (BP-caKII). Viruses 2018; 10:v10110652. [PMID: 30463206 PMCID: PMC6266813 DOI: 10.3390/v10110652] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 11/14/2018] [Accepted: 11/16/2018] [Indexed: 01/02/2023] Open
Abstract
We established a cold-adapted infectious bronchitis virus (BP-caKII) by passaging a field virus through specific pathogen-free embryonated eggs 20 times at 32 °C. We characterized its growth kinetics and pathogenicity in embryonated eggs, and its tropism and persistence in different tissues from chickens; then, we evaluated pathogenicity by using a new premature reproductive tract pathogenicity model. Furthermore, we determined the complete genomic sequence of BP-caKII to understand the genetic changes related to cold adaptation. According to our results, BP-caKII clustered with the KII genotype viruses K2 and KM91, and showed less pathogenicity than K2, a live attenuated vaccine strain. BP-caKII showed delayed viremia, resulting in its delayed dissemination to the kidneys and cecal tonsils compared to K2 and KM91, the latter of which is a pathogenic field strain. A comparative genomics study revealed similar nucleotide sequences between BP-caKII, K2 and KM91 but clearly showed different mutations among them. BP-caKII shared several mutations with K2 (nsp13, 14, 15 and 16) following embryo adaptation but acquired multiple additional mutations in nonstructural proteins (nsp3, 4 and 12), spike proteins and nucleocapsid proteins following cold adaptation. Thus, the establishment of BP-caKII and the identified mutations in this study may provide insight into the genetic background of embryo and cold adaptations, and the attenuation of coronaviruses.
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Affiliation(s)
- Seung-Min Hong
- Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
| | - Se-Hee An
- Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
| | - Chung-Young Lee
- Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
| | - Chang-Seon Song
- Laboratory of Avian Diseases, College of Veterinary Medicine, Konkuk University, Seoul 05029, Korea.
| | - Kang-Seuk Choi
- Avian Disease Division, animal and Plant Quarantine Agency, Gimcheon, Gyeongsangbuk-Do 39660, Korea.
| | - Jae-Hong Kim
- Laboratory of Avian Diseases, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
- Reseach Institute for Veterinary Science, College of Veterinary Medicine, BK21 for Veterinary Science, Seoul 08826, Korea.
| | - Hyuk-Joon Kwon
- Reseach Institute for Veterinary Science, College of Veterinary Medicine, BK21 for Veterinary Science, Seoul 08826, Korea.
- Department of Farm Animal Medicine, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
- Farm Animal Clinical Training and Research Center, Seoul National University, Seoul 08826, Korea.
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93
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Bickerton E, Maier HJ, Stevenson-Leggett P, Armesto M, Britton P. The S2 Subunit of Infectious Bronchitis Virus Beaudette Is a Determinant of Cellular Tropism. J Virol 2018; 92:e01044-18. [PMID: 30021894 PMCID: PMC6146808 DOI: 10.1128/jvi.01044-18] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 07/10/2018] [Indexed: 12/17/2022] Open
Abstract
The spike (S) glycoprotein of the avian gammacoronavirus infectious bronchitis virus (IBV) is comprised of two subunits (S1 and S2), has a role in virulence in vivo, and is responsible for cellular tropism in vitro We have previously demonstrated that replacement of the S glycoprotein ectodomain from the avirulent Beaudette strain of IBV with the corresponding region from the virulent M41-CK strain resulted in a recombinant virus, BeauR-M41(S), with the in vitro cell tropism of M41-CK. The IBV Beaudette strain is able to replicate in both primary chick kidney cells and Vero cells, whereas the IBV M41-CK strain replicates in primary cells only. In order to investigate the region of the IBV S responsible for growth in Vero cells, we generated a series of recombinant IBVs expressing chimeric S glycoproteins, consisting of regions from the Beaudette and M41-CK S gene sequences, within the genomic background of Beaudette. The S2, but not the S1, subunit of the Beaudette S was found to confer the ability to grow in Vero cells. Various combinations of Beaudette-specific amino acids were introduced into the S2 subunit of M41 to determine the minimum requirement to confer tropism for growth in Vero cells. The ability of IBV to grow and produce infectious progeny virus in Vero cells was subsequently narrowed down to just 3 amino acids surrounding the S2' cleavage site. Conversely, swapping of the 3 Beaudette-associated amino acids with the corresponding ones from M41 was sufficient to abolish Beaudette growth in Vero cells.IMPORTANCE Infectious bronchitis remains a major problem in the global poultry industry, despite the existence of many different vaccines. IBV vaccines, both live attenuated and inactivated, are currently grown on embryonated hen's eggs, a cumbersome and expensive process due to the fact that most IBV strains do not grow in cultured cells. The reverse genetics system for IBV creates the opportunity for generating rationally designed and more effective vaccines. The observation that IBV Beaudette has the additional tropism for growth on Vero cells also invokes the possibility of generating IBV vaccines produced from cultured cells rather than by the use of embryonated eggs. The regions of the IBV Beaudette S glycoprotein involved in the determination of extended cellular tropism were identified in this study. This information will enable the rational design of a future generation of IBV vaccines that may be grown on Vero cells.
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94
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Cryo-EM structure of the SARS coronavirus spike glycoprotein in complex with its host cell receptor ACE2. PLoS Pathog 2018; 14:e1007236. [PMID: 30102747 PMCID: PMC6107290 DOI: 10.1371/journal.ppat.1007236] [Citation(s) in RCA: 567] [Impact Index Per Article: 94.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 08/23/2018] [Accepted: 07/23/2018] [Indexed: 02/05/2023] Open
Abstract
The trimeric SARS coronavirus (SARS-CoV) surface spike (S) glycoprotein consisting of three S1-S2 heterodimers binds the cellular receptor angiotensin-converting enzyme 2 (ACE2) and mediates fusion of the viral and cellular membranes through a pre- to postfusion conformation transition. Here, we report the structure of the SARS-CoV S glycoprotein in complex with its host cell receptor ACE2 revealed by cryo-electron microscopy (cryo-EM). The complex structure shows that only one receptor-binding domain of the trimeric S glycoprotein binds ACE2 and adopts a protruding “up” conformation. In addition, we studied the structures of the SARS-CoV S glycoprotein and its complexes with ACE2 in different in vitro conditions, which may mimic different conformational states of the S glycoprotein during virus entry. Disassociation of the S1-ACE2 complex from some of the prefusion spikes was observed and characterized. We also characterized the rosette-like structures of the clustered SARS-CoV S2 trimers in the postfusion state observed on electron micrographs. Structural comparisons suggested that the SARS-CoV S glycoprotein retains a prefusion architecture after trypsin cleavage into the S1 and S2 subunits and acidic pH treatment. However, binding to the receptor opens up the receptor-binding domain of S1, which could promote the release of the S1-ACE2 complex and S1 monomers from the prefusion spike and trigger the pre- to postfusion conformational transition. The global outbreak of SARS in 2002–2003 was caused by infection by a human coronavirus, SARS-CoV. Although the virus has been extensively studied with regard to epidemiology, virology, clinical features and other aspects, there are still no approved antiviral drugs and vaccines to treat and prevent infections of SARS-CoV. The spike (S) glycoprotein of the coronavirus, responsible for host cell attachment and mediating host cell membrane and viral membrane fusion during infection, is key to the viral life cycle and a major target for antiviral drugs and vaccines. In this study, we report the structures of different conformational states of the SARS-CoV S glycoprotein during virus entry. Specifically, we found that the S glycoprotein retains the prefusion trimer structure after trypsin cleavage and low-pH treatment. Additionally, binding with host cell receptor ACE2 promotes the release of S1 subunits from the S trimer and triggers the pre- to postfusion conformational transition. Our results provide new insights for understanding the mechanisms involved in coronavirus S glycoprotein-mediated virus entry.
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