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Reduction of Cell Fusion by Deletion in the Hypervariable Region of the Spike Protein of Mouse Hepatitis Virus. Viruses 2022; 14:v14020398. [PMID: 35215991 PMCID: PMC8876987 DOI: 10.3390/v14020398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 02/10/2022] [Accepted: 02/13/2022] [Indexed: 01/27/2023] Open
Abstract
Deletions in the spike gene of mouse hepatitis virus (MHV) produce several variants with diverse biological characteristics, highlighting the significance of the spike gene in viral pathogenesis. In this study, we characterized the JHM-X strain, which has a deletion in the hypervariable region (HVR) of the spike gene, compared with the cl-2 strain, which has a full spike gene. Cytopathic effects (CPEs) induced by the two strains revealed that the size of the CPE produced by cl-2 is much greater than that produced by JHM-X in delayed brain tumor (DBT) cells. Thus, this finding explains the greater fusion activity of cl-2 than JHM-X in cultured cells, and we speculate that the deletion region of the spike protein is involved in the fusion activity differences. In contrast with the fusion activity, a comparison of the virus growth kinetics revealed that the titer of JHM-X was approximately 100 times higher than that of cl-2. We found that the deletion region of the spike protein was involved in fusion activity differences, whereas cl-2 produced significantly higher luciferase activity than JHM-X upon similar expression levels of the spike protein. However, the reason behind the growth difference is still unknown. Overall, we discovered that deletion in the HVR of the spike gene could be involved in the fusion activity differences between the two strains.
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2
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Membrane Protein of Human Coronavirus NL63 Is Responsible for Interaction with the Adhesion Receptor. J Virol 2019; 93:JVI.00355-19. [PMID: 31315999 PMCID: PMC6744225 DOI: 10.1128/jvi.00355-19] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 07/12/2019] [Indexed: 12/11/2022] Open
Abstract
It is generally accepted that the coronaviral S protein is responsible for viral interaction with a cellular receptor. Here we show that the M protein is also an important player during early stages of HCoV-NL63 infection and that the concerted action of the two proteins (M and S) is a prerequisite for effective infection. We believe that this study broadens the understanding of HCoV-NL63 biology and may also alter the way in which we perceive the first steps of cell infection with the virus. The data presented here may also be important for future research into vaccine or drug development. Human coronavirus NL63 (HCoV-NL63) is a common respiratory virus that causes moderately severe infections. We have previously shown that the virus uses heparan sulfate proteoglycans (HSPGs) as the initial attachment factors, facilitating viral entry into the cell. In the present study, we show that the membrane protein (M) of HCoV-NL63 mediates this attachment. Using viruslike particles lacking the spike (S) protein, we demonstrate that binding to the cell is not S protein dependent. Furthermore, we mapped the M protein site responsible for the interaction with HSPG and confirmed its relevance using a viable virus. Importantly, in silico analysis of the region responsible for HSPG binding in different clinical isolates and the Amsterdam I strain did not exhibit any signs of cell culture adaptation. IMPORTANCE It is generally accepted that the coronaviral S protein is responsible for viral interaction with a cellular receptor. Here we show that the M protein is also an important player during early stages of HCoV-NL63 infection and that the concerted action of the two proteins (M and S) is a prerequisite for effective infection. We believe that this study broadens the understanding of HCoV-NL63 biology and may also alter the way in which we perceive the first steps of cell infection with the virus. The data presented here may also be important for future research into vaccine or drug development.
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Kakizaki M, Watanabe R. IL-10 expression in pyramidal neurons after neuropathogenic coronaviral infection. Neuropathology 2017; 37:398-406. [PMID: 28493345 PMCID: PMC7167951 DOI: 10.1111/neup.12386] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 03/24/2017] [Accepted: 03/25/2017] [Indexed: 02/04/2023]
Abstract
The apoptosis of pyramidal neurons in CA2 and CA3 subregions of the hippocampus is induced after infection with Mu-3 virus (Mu-3), a neuropathogenic strain of the JHM virus (JHMV), at 4-5 days post-inoculation (dpi). The viral antigens in the hippocampus are mainly found in the CD11b-positive cells distributed in the stratum oriens located outside the pyramidal layer, and only a few pyramidal neurons are infected. Furthermore, the apoptotic cells, indicated as showing caspase 3 (Cas3) activation, consist of a high number of uninfected cells. Therefore, it is considered that the apoptotic lesions occur through the indirect effects of infection, and not as a result of direct infection with Mu-3, similar to the reported neuronal apoptosis in the hippocampus after other types of infection. The apoptosis in the pyramidal neurons is accompanied by various types of proinflammatory cytokines depending on the causative agents. Thus, the local expression of proinflammatory cytokines was studied, revealing no correlation in the distribution of cytokine expression with the subregions showing apoptosis. However, the anti-inflammatory cytokine IL-10 was produced by pyramidal neurons of CA2 and CA3 at 3 dpi when there is no destructive change or viral invasion in the hippocampus.
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Affiliation(s)
- Masatoshi Kakizaki
- Department of Bioinformatics, Graduate School of Engineering, Soka University, Hachioji, Tokyo, Japan
| | - Rihito Watanabe
- Department of Bioinformatics, Graduate School of Engineering, Soka University, Hachioji, Tokyo, Japan
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4
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Proteolytic processing of Middle East respiratory syndrome coronavirus spikes expands virus tropism. Proc Natl Acad Sci U S A 2016; 113:12262-12267. [PMID: 27791014 DOI: 10.1073/pnas.1608147113] [Citation(s) in RCA: 228] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) infects humans from zoonotic sources and causes severe pulmonary disease. Virions require spike (S) glycoproteins for binding to cell receptors and for catalyzing virus-cell membrane fusion. Fusion occurs only after S proteins are cleaved sequentially, first during their secretion through the exocytic organelles of virus-producing cells, and second after virus binding to target-cell receptors. To more precisely determine how sequential proteolysis contributes to CoV infection, we introduced S mutations obstructing the first cleavages. These mutations severely compromised MERS-CoV infection into human lung-derived cells, but had little effect on infection into several other cell types. These cell type-specific requirements for proteolysis correlated with S conformations during cell entry. Without the first cleavages, S proteins resisted cell receptor-induced conformational changes, which restricted the second, fusion-activating cleavages. Consistent with these findings, precleaved MERS viruses used receptor-proximal, cell-surface proteases to effect the second fusion-activating cleavages during cell entry, whereas the more rigid uncleaved MERS viruses trafficked past these cell-surface proteases and into endosomes. Uncleaved viruses were less infectious to human airway epithelial and Calu3 cell cultures because they lacked sufficient endosomal fusion-activating proteases. Thus, by sensitizing viruses to receptor-induced conformational changes, the first S cleavages expand virus tropism to cell types that are relevant to lung infection, and therefore may be significant determinants of MERS-CoV virulence.
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Abstract
Coronaviruses (CoVs) have a remarkable potential to change tropism. This is particularly illustrated over the last 15 years by the emergence of two zoonotic CoVs, the severe acute respiratory syndrome (SARS)- and Middle East respiratory syndrome (MERS)-CoV. Due to their inherent genetic variability, it is inevitable that new cross-species transmission events of these enveloped, positive-stranded RNA viruses will occur. Research into these medical and veterinary important pathogens—sparked by the SARS and MERS outbreaks—revealed important principles of inter- and intraspecies tropism changes. The primary determinant of CoV tropism is the viral spike (S) entry protein. Trimers of the S glycoproteins on the virion surface accommodate binding to a cell surface receptor and fusion of the viral and cellular membrane. Recently, high-resolution structures of two CoV S proteins have been elucidated by single-particle cryo-electron microscopy. Using this new structural insight, we review the changes in the S protein that relate to changes in virus tropism. Different concepts underlie these tropism changes at the cellular, tissue, and host species level, including the promiscuity or adaptability of S proteins to orthologous receptors, alterations in the proteolytic cleavage activation as well as changes in the S protein metastability. A thorough understanding of the key role of the S protein in CoV entry is critical to further our understanding of virus cross-species transmission and pathogenesis and for development of intervention strategies.
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Shirato K, Maejima M, Islam MT, Miyazaki A, Kawase M, Matsuyama S, Taguchi F. Porcine aminopeptidase N is not a cellular receptor of porcine epidemic diarrhea virus, but promotes its infectivity via aminopeptidase activity. J Gen Virol 2016; 97:2528-2539. [PMID: 27449937 DOI: 10.1099/jgv.0.000563] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Porcine epidemic diarrhea virus (PEDV), a causative agent of pig diarrhoea, has recently caused significant economic damage worldwide. Porcine aminopeptidase N (pAPN) has been reported to be the receptor for PEDV, although robust evidence is lacking. In the present study, we explored whether pAPN functions as a receptor for PEDV. Human HeLa cells expressing pAPN and pAPN-positive porcine CPK cells failed to support PEDV infection, but were susceptible to infection by transmissible gastroenteritis virus (TGEV), which utilizes pAPN as a functional receptor. In contrast to TGEV, PEDV did not bind soluble porcine aminopeptidases (pAPs) and infection was not inhibited by the soluble form of pAPs. However, overexpression of pAPN in porcine CPK cells (CPK-pAPN cells) slightly increased the production of PEDV, and the increased replication in CPK-pAPN cells was inhibited by bestatin, an inhibitor of the protease activity of aminopeptidase N. These results suggest that pAPN is not a functional receptor for PEDV, but promotes the infection of PEDV through its protease activity.
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Affiliation(s)
- Kazuya Shirato
- Laboratory of Acute Respiratory Viral Diseases and Cytokines, Department of Virology III, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama, Tokyo 208-0011, Japan
| | - Madoka Maejima
- Laboratory of Acute Respiratory Viral Diseases and Cytokines, Department of Virology III, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama, Tokyo 208-0011, Japan
| | - Md Taimur Islam
- Laboratory of Virology and Viral Infections, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino, Tokyo 180-8602, Japan
| | - Ayako Miyazaki
- Viral Diseases and Epidemiology Research Division, National Institute of Animal Health, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan
| | - Miyuki Kawase
- Laboratory of Acute Respiratory Viral Diseases and Cytokines, Department of Virology III, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama, Tokyo 208-0011, Japan
| | - Shutoku Matsuyama
- Laboratory of Acute Respiratory Viral Diseases and Cytokines, Department of Virology III, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama, Tokyo 208-0011, Japan
| | - Fumihiro Taguchi
- Laboratory of Virology and Viral Infections, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino, Tokyo 180-8602, Japan.,Laboratory of Acute Respiratory Viral Diseases and Cytokines, Department of Virology III, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama, Tokyo 208-0011, Japan
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Watanabe R, Kakizaki M, Ikehara Y, Togayachi A. Formation of fibroblastic reticular network in the brain after infection with neurovirulent murine coronavirus. Neuropathology 2016; 36:513-526. [PMID: 27121485 PMCID: PMC7167860 DOI: 10.1111/neup.12302] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/03/2016] [Accepted: 03/05/2016] [Indexed: 01/12/2023]
Abstract
cl‐2 virus is an extremely neurovirulent murine coronavirus. However, during the initial phase of infection between 12 and 24 h post‐inoculation (hpi), the viral antigens are detected only in the meninges, followed by viral spread into the ventricular wall before invasion into the brain parenchyma, indicating that the viruses employ a passage between the meninges and ventricular wall as an entry route into the brain parenchyma. At 48 hpi, the passage was found to be constructed by ER‐TR7 antigen (ERag)‐positive fibers (ERfibs) associated with laminin and collagen III between the fourth ventricle and meninges at the cerebellopontine angle. The construct of the fibers mimics the reticular fibers of the fibroblastic reticular network, which comprises a conduit system in the lymphoid organs. In the meninges, ERfibs together with collagen fibers, lining in a striped pattern, made up a pile of thin sheets. In the brain parenchyma, mature ERfibs associated with laminin were found around blood vessels. Besides mature ERfibs, immature Erfibs without associations with other extracellular matrix components like laminin and collagen appeared after infection, suggesting that the CNS creates a unique conduit system for immune communication triggered by viral invasion.
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Affiliation(s)
- Rihito Watanabe
- Department of Bioinformatics, Graduate School of Engineering, Soka University, Hachioji, Tokyo, Japan
| | - Masatoshi Kakizaki
- Department of Bioinformatics, Graduate School of Engineering, Soka University, Hachioji, Tokyo, Japan
| | - Yuzuru Ikehara
- Research Center For Medical Glycoscience, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
| | - Akira Togayachi
- Research Center For Medical Glycoscience, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
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Kashiwazaki H, Kakizaki M, Ikehara Y, Togayachi A, Narimatsu H, Watanabe R. Mice lacking α1,3-fucosyltransferase 9 exhibit modulation of in vivo immune responses against pathogens. Pathol Int 2015; 64:199-208. [PMID: 24888773 PMCID: PMC7167665 DOI: 10.1111/pin.12159] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Accepted: 03/25/2014] [Indexed: 01/13/2023]
Abstract
Carbohydrate structures, including Lewis X (Lex), which is not synthesized in mutant mice that lack α1,3‐fucosyltransferase 9 (Fut9−/−), are involved in cell–cell recognition and inflammation. However, immunological alteration in Fut9−/− mice has not been studied. Thus, the inflammatory response of Fut9−/− mice was examined using the highly neurovirulent mouse hepatitis virus (MHV) JHMV srr7 strain. Pathological study revealed that inflammation induced in the brains of Fut9−/− mice after infection was more extensive compared with that of wild‐type mice, although viral titers obtained from the brains of mutant mice were lower than those of wild‐type mice. Furthermore, the reduction in cell numbers in the spleens of wild‐type mice after infection was not observed in the infected Fut9−/− mice. Although there were no clear differences in the levels of cytokines examined in the brains between Fut9−/− and wild‐type mice except for interferon‐β (IFN‐β) expression, some of those in the spleens, including interferon‐γ (IFN‐γ), interleukin‐6 (IL‐6), and monocyte chemoattractant protein‐1 (MCP‐1), showed higher levels in Fut9−/− than in wild‐type mice. Furthermore, Fut9−/− mice were refractory to the in vivo inoculation of endotoxin (LPS) compared with wild‐type mice. These results indicate that Lex structures are involved in host responses against viral or bacterial challenges.
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Affiliation(s)
- Hiromi Kashiwazaki
- Department of BioinformaticsFaculty of EngineeringSoka UniversityHachiojiTokyoJapan
| | - Masatoshi Kakizaki
- Department of BioinformaticsFaculty of EngineeringSoka UniversityHachiojiTokyoJapan
| | - Yuzuru Ikehara
- Research Center for Medical GlycoscienceNational Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
| | - Akira Togayachi
- Research Center for Medical GlycoscienceNational Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
| | - Hisashi Narimatsu
- Research Center for Medical GlycoscienceNational Institute of Advanced Industrial Science and Technology (AIST)TsukubaIbarakiJapan
| | - Rihito Watanabe
- Department of BioinformaticsFaculty of EngineeringSoka UniversityHachiojiTokyoJapan
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9
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Kakizaki M, Kashiwazaki H, Watanabe R. Mutant murine hepatitis virus-induced apoptosis in the hippocampus. Jpn J Infect Dis 2014; 67:9-16. [PMID: 24451095 DOI: 10.7883/yoken.67.9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The mutant virus Mu-3 was isolated from the soluble receptor-resistant mutant 7 virus (srr7), which is a neuropathogenic strain of the mouse hepatitis virus JHMV, and cloned as a soluble receptor-resistant mutant from the highly neuropathogenic JHMV strain cl-2 virus (cl-2). In order to identify specific characteristics of Mu-3, the pathology of Mu-3-infected mice was compared with that of srr7- and cl-2-infected mice. The neuropathology after Mu-3 infection exhibited a mixed pattern comparable to that induced by srr7 and cl-2 infections. In addition, Mu-3 infection caused marked apoptotic lesions in the hippocampal region, particularly in the CA2 and CA3 subregions, in the brains of all infected mice. In contrast, in cl-2 infection, 10-20% of the infected mice exhibited apoptosis in the hippocampus, which was primarily observed in the CA1 subregion. Apoptosis also occurred in the pyramidal neurons and CD11b-bearing cells. The apoptotic cells, indicated by caspase 3-activation, were a mixed population of infected and a higher number of uninfected cells. These data indicated that apoptosis observed in Mu-3 infection could be induced by the indirect effects of infection in addition to direct effects of the infected cells occurring in a cell-autonomous manner.
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10
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Lin YZ, Yang F, Zhang SQ, Sun LK, Wang XF, Du C, Zhou JH. The soluble form of the EIAV receptor encoded by an alternative splicing variant inhibits EIAV infection of target cells. PLoS One 2013; 8:e79299. [PMID: 24278125 PMCID: PMC3838338 DOI: 10.1371/journal.pone.0079299] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 09/20/2013] [Indexed: 01/21/2023] Open
Abstract
Equine lentivirus receptor 1 (ELR1) has been identified as the sole receptor for equine infectious anemia virus (EIAV) and is a member of the tumor necrosis factor receptor (TNFR) superfamily. In addition to the previously described membrane-associated form of ELR1, two other major alternative splicing variant mRNAs were identified in equine monocyte-derived macrophages (eMDMs). One major spliced species (ELR1-IN) contained an insertion of 153 nt, which resulted in a premature stop codon situated 561 nt upstream of the predicted membrane spanning domain. The other major species (ELR1-DE) has a deletion of 109 nt that causes a shift of the open reading frame and generates a stop codon 312 nt downstream. Because ELR1-DE presumably encodes a peptide of a mere 23 residues, only ELR1-IN was further analyzed. The expression of a soluble form of ELR1 (sELR1) by ELR1-IN was confirmed by Western blot and immunofluorescence analyses. Similar to ELR1, the transcription level of ELR1-IN varied among individual horses and at different time points in the same individuals. The ratio of ELR1-IN mRNA species to ELR1 mRNA was approximately 1∶2.5. Pre-incubation of the recombinant sELR1 with EIAV significantly inhibited EIAV infection in equine macrophages, the primary in vivo target cell of the virus. Fetal equine dermal (FED) cells are susceptible to EIAV in vitro, and the replication of EIAV in FED cells transiently transfected with ELR1-IN was markedly reduced when compared with replication in cells transfected with the empty vector. Finally, the expression levels of both forms of the EIAV receptor were significantly regulated by infection with this virus. Taken together, our data indicate that sELR1 acts as a secreted cellular factor that inhibits EIAV infection in host cells.
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Affiliation(s)
- Yue-Zhi Lin
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Fei Yang
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Shu-Qin Zhang
- Institute of Special Wild Economic Animal and Plant Science, Chinese Academy of Agricultural Science, Changchun, China
| | - Liu-Ke Sun
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Xue-Feng Wang
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Cheng Du
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
| | - Jian-Hua Zhou
- Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Science, Harbin, China
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11
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Promkuntod N, Wickramasinghe INA, de Vrieze G, Gröne A, Verheije MH. Contributions of the S2 spike ectodomain to attachment and host range of infectious bronchitis virus. Virus Res 2013; 177:127-37. [PMID: 24041648 PMCID: PMC7114508 DOI: 10.1016/j.virusres.2013.09.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 09/03/2013] [Accepted: 09/04/2013] [Indexed: 12/11/2022]
Abstract
The spike protein is the major viral attachment protein of the avian coronavirus infectious bronchitis virus (IBV) and ultimately determines viral tropism. The S1 subunit of the spike is assumed to be required for virus attachment. However, we have previously shown that this domain of the embryo- and cell culture adapted Beaudette strain, in contrast to that of the virulent M41 strain, is not sufficient for binding to chicken trachea (Wickramasinghe et al., 2011). In the present study, we demonstrated that the lack of binding of Beaudette S1 was not due to absence of virus receptors on this tissue nor due to the production of S1 from mammalian cells, as S1 proteins expressed from chicken cells also lacked the ability to bind IBV-susceptible embryonic tissue. Subsequently, we addressed the contribution of the S2 subunit of the spike in IBV attachment. Recombinant IBV Beaudette spike ectodomains, comprising the entire S1 domain and the S2 ectodomain, were expressed and analyzed for binding to susceptible embryonic chorio-allantoic membrane (CAM) in our previously developed spike histochemistry assay. We observed that extension of the S1 domain with the S2 subunit of the Beaudette spike was sufficient to gain binding to CAM. A previously suggested heparin sulfate binding site in Beaudette S2 was not required for the observed binding to CAM, while sialic acids on the host tissues were essential for the attachment. To further elucidate the role of S2 the spike ectodomains of virulent IBV M41 and chimeras of M41 and Beaudette were analyzed for their binding to CAM, chicken trachea and mammalian cell lines. While the M41 spike ectodomain showed increased attachment to both CAM and chicken trachea, no binding to mammalian cells was observed. In contrast, Beaudette spike ectodomain had relatively weak ability to bind to chicken trachea, but displayed marked extended host range to mammalian cells. Binding patterns of chimeric spike ectodomains to these tissues and cells indicate that S2 subunits most likely do not contain an additional independent receptor-binding site. Rather, the interplay between S1 and S2 subunits of spikes from the same viral origin might finally determine the avidity and specificity of virus attachment and thus viral host range.
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Affiliation(s)
- N Promkuntod
- Pathology Division, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands
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Abstract
Coronaviruses infect many species of animals including humans, causing acute and chronic diseases. This review focuses primarily on the pathogenesis of murine coronavirus mouse hepatitis virus (MHV) and severe acute respiratory coronavirus (SARS-CoV). MHV is a collection of strains, which provide models systems for the study of viral tropism and pathogenesis in several organs systems, including the central nervous system, the liver, and the lung, and has been cited as providing one of the few animal models for the study of chronic demyelinating diseases such as multiple sclerosis. SARS-CoV emerged in the human population in China in 2002, causing a worldwide epidemic with severe morbidity and high mortality rates, particularly in older individuals. We review the pathogenesis of both viruses and the several reverse genetics systems that made much of these studies possible. We also review the functions of coronavirus proteins, structural, enzymatic, and accessory, with an emphasis on roles in pathogenesis. Structural proteins in addition to their roles in virion structure and morphogenesis also contribute significantly to viral spread in vivo and in antagonizing host cell responses. Nonstructural proteins include the small accessory proteins that are not at all conserved between MHV and SARS-CoV and the 16 conserved proteins encoded in the replicase locus, many of which have enzymatic activities in RNA metabolism or protein processing in addition to functions in antagonizing host response.
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Affiliation(s)
- Susan R Weiss
- Department of Microbiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, USA
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13
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Kashiwazaki H, Nomura R, Matsuyama S, Taguchi F, Watanabe R. Spongiform degeneration induced by neuropathogenic murine coronavirus infection. Pathol Int 2011; 61:184-91. [PMID: 21418390 PMCID: PMC7167946 DOI: 10.1111/j.1440-1827.2010.02639.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Soluble receptor‐resistant mutant 7 (ssr7) is isolated from a highly neurovirulent mouse hepatitis virus (MHV) JHMV cl‐2 strain (cl‐2). srr7 exhibits lower virulence than its maternal strain in infected mice, which is typically manifested in a longer lifespan. In this study, during the course of infection with srr7, small spongiotic lesions became apparent at 2 days post‐inoculation (pi), they spread out to form spongiform encephalopathy by 8 to 10 days pi. We recently reported that the initial expressions of viral antigens in the brain are detected in the infiltrating monocyte lineage and in ependymal cells. Here, we demonstrate that the next viral spread was observed in glial fibrillary acidic protein‐positive cells or nestin‐positive progenitor cells which take up positions in the subventricular zone (SVZ). From this restricted site of infection in the SVZ, a large area of gliosis extended deep into the brain parenchyma where no viral antigens were detected but vacuolar degeneration started at 48 h pi of the virus. The extremely short incubation period compared with other experimental models of infectious spongiform degeneration in the brain would provide a superior experimental model to investigate the mechanism of spongiotic lesions formation.
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Affiliation(s)
- Hiromi Kashiwazaki
- Department of Bioinformatics, Faculty of Engineering, Soka University, Tokyo, Japan
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14
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Abstract
Coronaviruses infect many species of animals including humans, causing acute and chronic diseases. This review focuses primarily on the pathogenesis of murine coronavirus mouse hepatitis virus (MHV) and severe acute respiratory coronavirus (SARS-CoV). MHV is a collection of strains, which provide models systems for the study of viral tropism and pathogenesis in several organs systems, including the central nervous system, the liver, and the lung, and has been cited as providing one of the few animal models for the study of chronic demyelinating diseases such as multiple sclerosis. SARS-CoV emerged in the human population in China in 2002, causing a worldwide epidemic with severe morbidity and high mortality rates, particularly in older individuals. We review the pathogenesis of both viruses and the several reverse genetics systems that made much of these studies possible. We also review the functions of coronavirus proteins, structural, enzymatic, and accessory, with an emphasis on roles in pathogenesis. Structural proteins in addition to their roles in virion structure and morphogenesis also contribute significantly to viral spread in vivo and in antagonizing host cell responses. Nonstructural proteins include the small accessory proteins that are not at all conserved between MHV and SARS-CoV and the 16 conserved proteins encoded in the replicase locus, many of which have enzymatic activities in RNA metabolism or protein processing in addition to functions in antagonizing host response.
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Affiliation(s)
- Susan R Weiss
- Department of Microbiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, USA
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15
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Phillips JM, Weiss SR. Pathogenesis of neurotropic murine coronavirus is multifactorial. Trends Pharmacol Sci 2010; 32:2-7. [PMID: 21144598 PMCID: PMC3022387 DOI: 10.1016/j.tips.2010.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 11/04/2010] [Accepted: 11/08/2010] [Indexed: 11/17/2022]
Abstract
Although coronavirus tropism is most often ascribed to receptor availability, increasing evidence suggests that for the neurotropic strains of the murine coronavirus mouse hepatitis virus (MHV), spike–receptor interactions cannot fully explain neurovirulence. The canonical MHV receptor CEACAM1a and its spike-binding site have been extensively characterized. However, CEACAM1a is poorly expressed in neurons, and the extremely neurotropic MHV strain JHM.SD infects ceacam1a−/− mice and spreads among ceacam1a−/− neurons. Two proposed alternative MHV receptors, CEACAM2 and PSG16, also fail to account for neuronal spread of JHM.SD in the absence of CEACAM1a. It has been reported that JHM.SD has an unusually labile spike protein, enabling it to perform receptor-independent spread (RIS), but it is not clear if the ability to perform RIS is fully responsible for the extremely neurovirulent phenotype. We propose that the extreme neurovirulence of JHM.SD is multifactorial and might include as yet unidentified neuron-specific spread mechanisms.
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Affiliation(s)
- Judith M Phillips
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
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16
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Bender SJ, Weiss SR. Pathogenesis of murine coronavirus in the central nervous system. J Neuroimmune Pharmacol 2010; 5:336-54. [PMID: 20369302 PMCID: PMC2914825 DOI: 10.1007/s11481-010-9202-2] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Accepted: 03/05/2010] [Indexed: 12/15/2022]
Abstract
Murine coronavirus (mouse hepatitis virus, MHV) is a collection of strains that induce disease in several organ systems of mice. Infection with neurotropic strains JHM and A59 causes acute encephalitis, and in survivors, chronic demyelination, the latter of which serves as an animal model for multiple sclerosis. The MHV receptor is a carcinoembryonic antigen-related cell adhesion molecule, CEACAM1a; paradoxically, CEACAM1a is poorly expressed in the central nervous system (CNS), leading to speculation of an additional receptor. Comparison of highly neurovirulent JHM isolates with less virulent variants and the weakly neurovirulent A59 strain, combined with the use of reverse genetics, has allowed mapping of pathogenic properties to individual viral genes. The spike protein, responsible for viral entry, is a major determinant of tropism and virulence. Other viral proteins, both structural and nonstructural, also contribute to pathogenesis in the CNS. Studies of host responses to MHV indicate that both innate and adaptive responses are crucial to antiviral defense. Type I interferon is essential to prevent very early mortality after infection. CD8 T cells, with the help of CD4 T cells, are crucial for viral clearance during acute disease and persist in the CNS during chronic disease. B cells are necessary to prevent reactivation of virus in the CNS following clearance of acute infection. Despite advances in understanding of coronavirus pathogenesis, questions remain regarding the mechanisms of viral entry and spread in cell types expressing low levels of receptor, as well as the unique interplay between virus and the host immune system during acute and chronic disease.
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Affiliation(s)
- Susan J Bender
- Department of Microbiology, University of Pennsylvania School of Medicine, 36th Street and Hamilton Walk, Philadelphia, PA 19104-6076, USA
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Conformational changes in the capsid of a calicivirus upon interaction with its functional receptor. J Virol 2010; 84:5550-64. [PMID: 20357100 DOI: 10.1128/jvi.02371-09] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nonenveloped viral capsids are metastable structures that undergo conformational changes during virus entry that lead to interactions of the capsid or capsid fragments with the cell membrane. For members of the Caliciviridae, neither the nature of these structural changes in the capsid nor the factor(s) responsible for inducing these changes is known. Feline junctional adhesion molecule A (fJAM-A) mediates the attachment and infectious viral entry of feline calicivirus (FCV). Here, we show that the infectivity of some FCV isolates is neutralized following incubation with the soluble receptor at 37 degrees C. We used this property to select mutants resistant to preincubation with the soluble receptor. We isolated and sequenced 24 soluble receptor-resistant (srr) mutants and characterized the growth properties and receptor-binding activities of eight mutants. The location of the mutations within the capsid structure of FCV was mapped using a new 3.6-A structure of native FCV. The srr mutations mapped to the surface of the P2 domain were buried at the protruding domain dimer interface or were present in inaccessible regions of the capsid protein. Coupled with data showing that both the parental FCV and the srr mutants underwent increases in hydrophobicity upon incubation with the soluble receptor at 37 degrees C, these findings indicate that FCV likely undergoes conformational change upon interaction with its receptor. Changes in FCV capsid conformation following its interaction with fJAM-A may be important for subsequent interactions of the capsid with cellular membranes, membrane penetration, and genome delivery.
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Takatsuki H, Taguchi F, Nomura R, Kashiwazaki H, Watanabe M, Ikehara Y, Watanabe R. Cytopathy of an infiltrating monocyte lineage during the early phase of infection with murinecoronavirus in the brain. Neuropathology 2009; 30:361-71. [PMID: 20051016 PMCID: PMC7194124 DOI: 10.1111/j.1440-1789.2009.01082.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Viral spread during the early stages after infection was compared between a highly neurovirulent mouse hepatitis virus (MHV), JHMV cl-2 strain (cl-2), and its low-virulent mutant, soluble-receptor-resistant (srr)7. The infection of cells with srr7 (soluble-receptor-resistant mutant 7) is dependent on a known MHV receptor (MHVR), carcinoembryonic cell adhesion molecule 1a, whereas cl-2 shows MHVR-independent infection. Initial viral antigens were detected between 12 and 24 h post-inoculation (p.i) in the infiltrating cells that appeared in the subarachnoidal space of mouse brains infected with viruses. There were no significant differences in the intensity or spread of viral antigens in the inflammatory cells between the two viruses. However, 48 h after infection with cl-2, viral antigen-positive cells in the grey matter with the shape of neurons, which do not express MHVR, were detected, while srr7 infection was observed primarily in the white matter. Some of the viral antigen-positive inflammatory cells found in the subarachnoidal space during the early phase of infection reacted with anti-F4/80 or anti-CD11b monoclonal antibodies. Syncytial giant cells (SGCs) expressing viral and CD11b antigens were also detected among these inflammatory cells. These antigen-positive cells appeared in the subarachnoidal space prior to viral antigen spread into the brain parenchyma, indicating that viral encephalitis starts with the infection of infiltrating monocytes which express MHVR. Furthermore, the observation indicates that viral infection has cytopathic effects on the monocyte lineage, which plays a critical role in innate immunity, leading to the rapid spread of viruses during the early stage of infection.
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Affiliation(s)
- Hanae Takatsuki
- Department of Bioinformatics, Soka University, Hachioji, Tokyo
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Abstract
Enveloped viruses enter into cells via fusion of their envelope and cellular membrane. Spike (S) protein of coronavirus (CoV) is responsible for entry events. We studied the cell entry mechanisms of two different CoVs, murine coronavirus mouse hepatitis virus (MHV) and severe acute respiratory syndrome coronavirus (SARS-CoV). MHV-JHM that induces syncytia in infected cells entered directly from cell surface, i.e., fusion of envelope and plasma membrane, whereas SARS-CoV and MHV-2 that fail to induce syncytia entered via endosome in a protease-dependent fashion, i.e., fusion of envelope and endosomal membrane. The latter viruses entered directly from cell surface, when receptor-bound viruses were treated with proteases that activate fusion activity of their S proteins. The entry pathway of SARS-CoV could influence the severity of the disease. It was also reveled that a highly neurovirulent JHM spread in a receptor-independent fashion, which could result in a high neuropathogenicity of the virus.
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Affiliation(s)
- Fumihiro Taguchi
- Laboratory of Virology and Viral Diseases, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University.
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Abstract
Human coronavirus 229E, classified as a group I coronavirus, utilizes human aminopeptidase N (APN) as a receptor; however, its entry mechanism has not yet been fully elucidated. We found that HeLa cells infected with 229E via APN formed syncytia when treated with trypsin or other proteases but not in a low-pH environment, a finding consistent with syncytium formation by severe acute respiratory syndrome coronavirus (SARS-CoV). In addition, trypsin induced cleavage of the 229E S protein. By using infectious viruses and pseudotyped viruses bearing the 229E S protein, we found that its infection was profoundly blocked by lysosomotropic agents as well as by protease inhibitors that also prevented infection with SARS-CoV but not that caused by murine coronavirus mouse hepatitis virus strain JHMV, which enters cells directly from the cell surface. We found that cathepsin L (CPL) inhibitors blocked 229E infection the most remarkably among a variety of protease inhibitors tested. Furthermore, 229E infection was inhibited in CPL knockdown cells by small interfering RNA, compared with what was seen for a normal counterpart producing CPL. However, its inhibition was not so remarkable as that found with SARS-CoV infection, which seems to indicate that while CPL is involved in the fusogenic activation of 229E S protein in endosomal infection, not-yet-identified proteases could also play a part in that activity. We also found 229E virion S protein to be cleaved by CPL. Furthermore, as with SARS-CoV, 229E entered cells directly from the cell surface when cell-attached viruses were treated with trypsin. These findings suggest that 229E takes an endosomal pathway for cell entry and that proteases like CPL are involved in this mode of entry.
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Amino acid substitutions in the S2 subunit of mouse hepatitis virus variant V51 encode determinants of host range expansion. J Virol 2007; 82:1414-24. [PMID: 18032498 DOI: 10.1128/jvi.01674-07] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We previously described mouse hepatitis virus (MHV) variant V51 derived from a persistent infection of murine DBT cells with an expanded host range (R. S. Baric, E. Sullivan, L. Hensley, B. Yount, and W. Chen, J. Virol. 73:638-649, 1999). Sequencing of the V51 spike gene, the mediator of virus entry, revealed 13 amino acid substitutions relative to the originating MHV A59 strain. Seven substitutions were located in the amino-terminal S1 cleavage subunit, and six were located in the carboxy-terminal S2 cleavage subunit. Using targeted RNA recombination, we constructed a panel of recombinant viruses to map the mediators of host range to the six substitutions in S2, with a subgroup of four changes of particular interest. This subgroup maps to two previously identified domains within S2, a putative fusion peptide and a heptad repeat, both conserved features of class I fusion proteins. In addition to an altered host range, V51 displayed altered utilization of CEACAM1a, the high-affinity receptor for A59. Interestingly, a recombinant with S1 from A59 and S2 from V51 was severely debilitated in its ability to productively infect cells via CEACAM1a, while the inverse recombinant was not. This result suggests that the S2 substitutions exert powerful effects on the fusion trigger that normally passes from S1 to S2. These novel findings play against the existing data that suggest that MHV host range determinants are located in the S1 subunit, which harbors the receptor binding domain, or involve coordinating changes in both S1 and S2. Mounting evidence also suggests that the class I fusion mechanism may possess some innate plasticity that regulates viral host range.
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Watanabe R, Sawicki SG, Taguchi F. Heparan sulfate is a binding molecule but not a receptor for CEACAM1-independent infection of murine coronavirus. Virology 2007; 366:16-22. [PMID: 17692355 PMCID: PMC7103320 DOI: 10.1016/j.virol.2007.06.034] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2007] [Revised: 06/07/2007] [Accepted: 06/30/2007] [Indexed: 02/05/2023]
Abstract
A highly neurovirulent mouse hepatitis virus (MHV) JHMV strain (wt) with receptor (MHVR)-independent infection activity and its low-virulent mutant srr7 without such activity were found to attach to MHVR-negative, non-permissive BHK cells. To identify the molecule that interacts with JHMV, we focused on heparan sulfate (HS) since it works as a receptor of a mutant MHV-rec1 that infects in an MHVR-independent fashion. The present study indicates that HS interacts with both wt JHMV and srr7 but it does not function as an entry receptor as it apparently does for MHV-rec1. Furthermore, HS failed to serve as an entry receptor in the MHVR-independent infection of wt JHMV, indicating that HS is not a host factor that wt JHMV utilizes in an MHVR-independent infection.
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Affiliation(s)
- Rie Watanabe
- Division of Viral Respiratory Diseases and SARS, Department of Virology III, National Institute of Infectious Diseases, Murayama Branch, 4-7-1 Gakuen, Musashi-Murayama, Tokyo 208-0011, Japan
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23
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Perlman S, Holmes KV. Receptor-independent infection of mouse hepatitis virus: analysis by spinoculation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 581:331-4. [PMID: 17037555 PMCID: PMC7123728 DOI: 10.1007/978-0-387-33012-9_59] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Stanley Perlman
- Department of Pediatrics, University of Iowa, 52242 Iowa City, IA USA
| | - Kathryn V. Holmes
- Department of Microbiology, University of Colorado Health Sciences Center at Fitzsimons, 80045-8333 Aurora, CO USA
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Perlman S, Holmes KV. Receptor-independent spread of a neurotropic murine coronavirus MHV-JHMV in mixed neural culture. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 581:327-30. [PMID: 17037554 PMCID: PMC7123934 DOI: 10.1007/978-0-387-33012-9_58] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Stanley Perlman
- Department of Pediatrics, University of Iowa, 52242 Iowa City, IA USA
| | - Kathryn V. Holmes
- Department of Microbiology, University of Colorado Health Sciences Center at Fitzsimons, 80045-8333 Aurora, CO USA
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de Haan CAM, Te Lintelo E, Li Z, Raaben M, Wurdinger T, Bosch BJ, Rottier PJM. Cooperative involvement of the S1 and S2 subunits of the murine coronavirus spike protein in receptor binding and extended host range. J Virol 2006; 80:10909-18. [PMID: 16956938 PMCID: PMC1642182 DOI: 10.1128/jvi.00950-06] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
To study the process of spike (S)-receptor interaction during coronavirus entry, we evaluated the contributions of mutations in different regions of the murine hepatitis virus (MHV) S protein to natural receptor murine carcinoembryonic antigen-related cell adhesion molecule 1a (CEACAM1a) dependence and to the acquisition of extended host range. Extended-host-range variants of MHV strain A59 were previously obtained from persistently infected cells (J. H. Schickli, B. D. Zelus, D. E. Wentworth, S. G. Sawicki, and K. V. Holmes, J. Virol. 71:9499-9504, 1997). These variant viruses contain several mutations in the S protein that confer to the viruses the ability to enter cells in a heparan sulfate-dependent manner (C. A. de Haan, Z. Li, E. te Lintelo, B. J. Bosch, B. J. Haijema, and P. J. M. Rottier, J. Virol. 79:14451-14456, 2005). While the parental MHV-A59 is fully dependent on murine CEACAM1a for its entry, viruses carrying the variant mutations in the amino-terminal part of their S protein had become dependent on both CEACAM1a and heparan sulfate. Substitutions in a restricted, downstream part of the S protein encompassing heptad repeat region 1 (HR1) and putative fusion peptide (FP) did not alter the CEACAM1a dependence. However, when the mutations in both parts of the S protein were combined, the resulting viruses became independent of CEACAM1a and acquired the extended host range. In addition, these viruses showed a decreased binding to and inhibition by soluble CEACAM1a. The observations suggest that the amino-terminal region of the S protein, including the receptor-binding domain, and a region in the central part of the S protein containing HR1 and FP, i.e., regions far apart in the linear sequence, communicate and may even interact physically in the higher-order structure of the spike.
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Affiliation(s)
- Cornelis A M de Haan
- Virology Division, Department of Infectious Diseases and Immunology, Yalelaan 1, 3584 CL Utrecht, The Netherlands.
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26
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Watanabe R, Matsuyama S, Taguchi F. Receptor-independent infection of murine coronavirus: analysis by spinoculation. J Virol 2006; 80:4901-8. [PMID: 16641281 PMCID: PMC1472070 DOI: 10.1128/jvi.80.10.4901-4908.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A highly neurovirulent murine coronavirus JHMV (wild-type [wt] JHMV) is known to spread from cells infected via the murine coronavirus mouse hepatitis virus receptor (MHVR) to cells without MHVR (MHVR-independent infection), whereas a mutant virus isolated from wt JHMV, srr7, spread only in an MHVR-dependent fashion. These observations were obtained by the overlay of JHMV-infected cells onto receptor-negative cells that are otherwise resistant to wt JHMV infection. MHVR-independent infection is hypothetically thought to be attributed to a naturally occurring fusion activation of the wt JHMV S protein, which did not occur in the case of srr7. Attachment of S protein on cells without MHVR during the S-protein activation process seems to be a key condition. Thus, in the present study, we tried to see whether wt JHMV virions that are attached on MHVR-negative cells are able to infect those cells. In order to make virions attach to the cell surface without MHVR, we have used spinoculation, namely, the centrifugation of cells together with inoculated virus at 3,000 rpm for 2 h. This procedure forces viruses to attach to the cell surface, as revealed by quantitative estimation of attached virions by real-time PCR and also facilitated wt JHMV infection to MHVR-negative cells, but failed to do so for srr7. Virions of both wt and srr7 attached on MHVR-negative cells by spinoculation were facilitated for infection in the presence of a soluble form of MHVR that induces conformational changes of both wt and srr7. It was further revealed that wt JHMV S1, but not srr7, was released from the cell surface when S protein was expressed on cells. These observations support the hypothesis that attachment of the virion to MHVR-negative cells is a critical step and that a unique feature of wt JHMV S1 to be released from S2 in a naturally occurring event is involved in an MHVR-independent infection.
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Affiliation(s)
- Rie Watanabe
- Division of Respiratory Viral Diseases and SARS, Department of Virology III, National Institute of Infectious Diseases, Murayama, Tokyo 208-0011, Japan
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27
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Liu L, Hägglund S, Hakhverdyan M, Alenius S, Larsen LE, Belák S. Molecular epidemiology of bovine coronavirus on the basis of comparative analyses of the S gene. J Clin Microbiol 2006; 44:957-60. [PMID: 16517883 PMCID: PMC1393089 DOI: 10.1128/jcm.44.3.957-960.2006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bovine coronavirus (BCoV), a group 2 member of the genus Coronavirus in the family Coronaviridae, is an important pathogen in cattle worldwide. It causes diarrhea in adult animals (winter dysentery), as well as enteric and respiratory diseases in calves. The annual occurrence of BCoV epidemics in Sweden and Denmark led to this investigation, with the aim to deepen the knowledge of BCoV epidemiology at the molecular level. A total of 43 samples from outbreaks in both countries were used for PCR amplification and direct sequencing of a 624-nucleotide fragment of the BCoV S gene. Sequence comparison and phylogenetic studies were performed. The results showed (i) identical sequences from different animals in the same herds and from paired nasal and fecal samples, suggesting a dominant virus circulating in each herd at a given time; (ii) sequence differences among four outbreaks in different years in the same herd, indicating new introduction of virus; (iii) identical sequences in four different Danish herds in samples obtained within 2 months, implying virus transmission between herds; and (iv) that at least two different virus strains were involved in the outbreaks of BCoV in Denmark during the spring of 2003. This study presents molecular data of BCoV infections that will contribute to an increased understanding of BCoV epidemiology in cattle populations.
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Affiliation(s)
- Lihong Liu
- Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. Box 7019, SE-750 07 Uppsala, Sweden
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Butler N, Pewe L, Trandem K, Perlman S. Murine encephalitis caused by HCoV-OC43, a human coronavirus with broad species specificity, is partly immune-mediated. Virology 2006; 347:410-21. [PMID: 16413043 PMCID: PMC7111823 DOI: 10.1016/j.virol.2005.11.044] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Revised: 10/26/2005] [Accepted: 11/30/2005] [Indexed: 12/28/2022]
Abstract
The human coronavirus HCoV-OC43 causes a significant fraction of upper respiratory tract infections. Most coronaviruses show a strong species specificity, although the SARS-Coronavirus crossed species from palm civet cats to infect humans. Similarly, HCoV-OC43, likely a member of the same coronavirus group as SARS-CoV, readily crossed the species barrier as evidenced by its rapid adaptation to the murine brain [McIntosh, K., Becker, W.B., Chanock, R.M., 1967. Growth in suckling-mouse brain of "IBV-like" viruses from patients with upper respiratory tract disease. Proc Natl Acad Sci U.S.A. 58, 2268-73]. Herein, we investigated two consequences of this plasticity in species tropism. First, we showed that HCoV-OC43 was able to infect cells from a large number of mammalian species. Second, we showed that virus that was passed exclusively in suckling mouse brains was highly virulent and caused a uniformly fatal encephalitis in adult mice. The surface glycoprotein is a major virulence factor in most coronavirus infections. We identified three changes in the HCoV-OC43 surface glycoprotein that correlated with enhanced neurovirulence in mice; these were located in the domain of the protein responsible for binding to host cells. These data suggest that some coronaviruses, including HCoV-OC43 and SARS-CoV, readily adapt to growth in cells from heterologous species. This adaptability has facilitated the isolation of HCoV-OC43 viral variants with markedly differing abilities to infect animals and tissue culture cells.
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Affiliation(s)
- Noah Butler
- Interdisciplinary Program in Immunology, University of Iowa, Iowa City, IA 52242, USA
| | - Lecia Pewe
- Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA
| | - Kathryn Trandem
- Medical Scientist Training Program, University of Iowa, Iowa City, IA 52242, USA
| | - Stanley Perlman
- Interdisciplinary Program in Immunology, University of Iowa, Iowa City, IA 52242, USA
- Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA
- Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
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Weiss SR, Navas-Martin S. Coronavirus pathogenesis and the emerging pathogen severe acute respiratory syndrome coronavirus. Microbiol Mol Biol Rev 2006; 69:635-64. [PMID: 16339739 PMCID: PMC1306801 DOI: 10.1128/mmbr.69.4.635-664.2005] [Citation(s) in RCA: 747] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Coronaviruses are a family of enveloped, single-stranded, positive-strand RNA viruses classified within the Nidovirales order. This coronavirus family consists of pathogens of many animal species and of humans, including the recently isolated severe acute respiratory syndrome coronavirus (SARS-CoV). This review is divided into two main parts; the first concerns the animal coronaviruses and their pathogenesis, with an emphasis on the functions of individual viral genes, and the second discusses the newly described human emerging pathogen, SARS-CoV. The coronavirus part covers (i) a description of a group of coronaviruses and the diseases they cause, including the prototype coronavirus, murine hepatitis virus, which is one of the recognized animal models for multiple sclerosis, as well as viruses of veterinary importance that infect the pig, chicken, and cat and a summary of the human viruses; (ii) a short summary of the replication cycle of coronaviruses in cell culture; (iii) the development and application of reverse genetics systems; and (iv) the roles of individual coronavirus proteins in replication and pathogenesis. The SARS-CoV part covers the pathogenesis of SARS, the developing animal models for infection, and the progress in vaccine development and antiviral therapies. The data gathered on the animal coronaviruses continue to be helpful in understanding SARS-CoV.
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Affiliation(s)
- Susan R Weiss
- Department of Microbiology, University of Pennsylvania School of Medicine, 36th Street and Hamilton Walk, Philadelphia, Pennsylvania 19104-6076, USA.
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30
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Lip KM, Shen S, Yang X, Keng CT, Zhang A, Oh HLJ, Li ZH, Hwang LA, Chou CF, Fielding BC, Tan THP, Mayrhofer J, Falkner FG, Fu J, Lim SG, Hong W, Tan YJ. Monoclonal antibodies targeting the HR2 domain and the region immediately upstream of the HR2 of the S protein neutralize in vitro infection of severe acute respiratory syndrome coronavirus. J Virol 2006; 80:941-50. [PMID: 16378996 PMCID: PMC1346840 DOI: 10.1128/jvi.80.2.941-950.2006] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
We have previously shown that an Escherichia coli-expressed, denatured spike (S) protein fragment of the severe acute respiratory coronavirus, containing residues 1029 to 1192 which include the heptad repeat 2 (HR2) domain, was able to induce neutralizing polyclonal antibodies (C. T. Keng, A. Zhang, S. Shen, K. M. Lip, B. C. Fielding, T. H. Tan, C. F. Chou, C. B. Loh, S. Wang, J. Fu, X. Yang, S. G. Lim, W. Hong, and Y. J. Tan, J. Virol. 79:3289-3296, 2005). In this study, monoclonal antibodies (MAbs) were raised against this fragment to identify the linear neutralizing epitopes in the functional domain and to investigate the mechanisms involved in neutralization. Eighteen hybridomas secreting the S protein-specific MAbs were obtained. Binding sites of these MAbs were mapped to four linear epitopes. Two of them were located within the HR2 region and two immediately upstream of the HR2 domain. MAbs targeting these epitopes showed in vitro neutralizing activities and were able to inhibit cell-cell membrane fusion. These results provide evidence of novel neutralizing epitopes that are located in the HR2 domain and the spacer region immediately upstream of the HR2 of the S protein.
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Affiliation(s)
- Kuo-Ming Lip
- Institute of Molecular and Cell Biology, Proteos, 61 Biopolis Drive, Singapore 138673
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31
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Weiss SR, Navas-Martin S. Coronavirus pathogenesis and the emerging pathogen severe acute respiratory syndrome coronavirus. Microbiol Mol Biol Rev 2005. [PMID: 16339739 DOI: 10.1128/mmbr.69.4.635] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023] Open
Abstract
Coronaviruses are a family of enveloped, single-stranded, positive-strand RNA viruses classified within the Nidovirales order. This coronavirus family consists of pathogens of many animal species and of humans, including the recently isolated severe acute respiratory syndrome coronavirus (SARS-CoV). This review is divided into two main parts; the first concerns the animal coronaviruses and their pathogenesis, with an emphasis on the functions of individual viral genes, and the second discusses the newly described human emerging pathogen, SARS-CoV. The coronavirus part covers (i) a description of a group of coronaviruses and the diseases they cause, including the prototype coronavirus, murine hepatitis virus, which is one of the recognized animal models for multiple sclerosis, as well as viruses of veterinary importance that infect the pig, chicken, and cat and a summary of the human viruses; (ii) a short summary of the replication cycle of coronaviruses in cell culture; (iii) the development and application of reverse genetics systems; and (iv) the roles of individual coronavirus proteins in replication and pathogenesis. The SARS-CoV part covers the pathogenesis of SARS, the developing animal models for infection, and the progress in vaccine development and antiviral therapies. The data gathered on the animal coronaviruses continue to be helpful in understanding SARS-CoV.
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Affiliation(s)
- Susan R Weiss
- Department of Microbiology, University of Pennsylvania School of Medicine, 36th Street and Hamilton Walk, Philadelphia, Pennsylvania 19104-6076, USA.
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Fang SG, Shen S, Tay FPL, Liu DX. Selection of and recombination between minor variants lead to the adaptation of an avian coronavirus to primate cells. Biochem Biophys Res Commun 2005; 336:417-23. [PMID: 16137658 PMCID: PMC7092901 DOI: 10.1016/j.bbrc.2005.08.105] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Accepted: 08/12/2005] [Indexed: 01/24/2023]
Abstract
An interesting question posed by the current evidence that severe acute respiratory syndrome coronavirus may be originated from an animal coronavirus is how such an animal coronavirus breaks the host species barrier and becomes zoonotic. In this report, we study the chronological order of genotypic changes in the spike protein of avian coronavirus infectious bronchitis virus (IBV) during its adaptation to a primate cell line. Adaptation of the Beaudette strain of IBV from chicken embryo to Vero cells showed the accumulation of 49 amino acid mutations. Among them, 26 (53.06%) substitutions were located in the S protein. Sequencing analysis and comparison of the S gene demonstrated that the majority of the mutations were accumulated and fixed at passage 7 on Vero cells and minor variants were isolated in several passages. Evidence present suggests that the dominant Vero cell-adapted IBV strain may be derived from the chicken embryo passages by selection of and potential recombination between the minor variants. This may explain why adaptation is a rapid process and the dominant strain, once adapted to a new host cell, becomes relatively stable.
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Affiliation(s)
- Shou Guo Fang
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
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Abstract
This chapter describes the interactions between the different structural components of the viruses and discusses their relevance for the process of virion formation. Two key factors determine the efficiency of the assembly process: intracellular transport and molecular interactions. Many viruses have evolved elaborate strategies to ensure the swift and accurate delivery of the virion components to the cellular compartment(s) where they must meet and form (sub) structures. Assembly of viruses starts in the nucleus by the encapsidation of viral DNA, using cytoplasmically synthesized capsid proteins; nucleocapsids then migrate to the cytosol, by budding at the inner nuclear membrane followed by deenvelopment, to pick up the tegument proteins.
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Affiliation(s)
- Cornelis A M de Haan
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands
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Nakagaki K, Nakagaki K, Taguchi F. Receptor-independent spread of a highly neurotropic murine coronavirus JHMV strain from initially infected microglial cells in mixed neural cultures. J Virol 2005; 79:6102-10. [PMID: 15857995 PMCID: PMC1091713 DOI: 10.1128/jvi.79.10.6102-6110.2005] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Although neurovirulent mouse hepatitis virus (MHV) strain JHMV multiplies in a variety of brain cells, expression of its receptor carcinoembryonic antigen cell adhesion molecule 1 (CEACAM 1) (MHVR) is restricted only in microglia. The present study was undertaken to clarify the mechanism of an extensive JHMV infection in the brain by using neural cells isolated from mouse brain. In contrast to wild-type (wt) JHMV, a soluble-receptor-resistant mutant (srr7) infects and spreads solely in an MHVR-dependent fashion (F. Taguchi and S. Matsuyama, J. Virol. 76:950-958, 2002). In mixed neural cell cultures, srr7 infected a limited number of cells and infection did not spread, although wt JHMV induced syncytia in most of the cells. srr7-infected cells were positive for GS-lectin, a microglia marker. Fluorescence-activated cell sorter analysis showed that about 80% of the brain cells stained with anti-MHVR antibody (CC1) were also positive for GS-lectin. Pretreatment of those cells with CC1 prevented virus attachment to the cell surface and also blocked virus infection. These results show that microglia express functional MHVR that mediates JHMV infection. As expected, in microglial cell-enriched cultures, both srr7and wt JHMV produced syncytia in a majority of cells. Treatment with CC1 of mixed neural cell cultures and microglia cultures previously infected with wt virus failed to block the spread of infection, indicating that wt infection spreads in an MHVR-independent fashion. Thus, the present study indicates that microglial cells are the major population of the initial target for MHV infection and that the wt spreads from initially infected microglia to a variety of cells in an MHVR-independent fashion.
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Affiliation(s)
- Keiko Nakagaki
- Lab. of Respiratory Viral Diseases and SARS, Department of Virology III, National Institute of Infectious Diseases, Murayama Branch, 4-7-1 Gakuen, Musashi-Murayama, Tokyo 208-0011 Japan.
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Thackray LB, Turner BC, Holmes KV. Substitutions of conserved amino acids in the receptor-binding domain of the spike glycoprotein affect utilization of murine CEACAM1a by the murine coronavirus MHV-A59. Virology 2005; 334:98-110. [PMID: 15749126 PMCID: PMC7111733 DOI: 10.1016/j.virol.2005.01.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Revised: 11/15/2004] [Accepted: 01/12/2005] [Indexed: 01/17/2023]
Abstract
The host range of the murine coronavirus (MHV) is limited to susceptible mice and murine cell lines by interactions of the spike glycoprotein (S) with its receptor, mCEACAM1a. We identified five residues in S (S33, L79, T82, Y162 and K183) that are conserved in the receptor-binding domain of MHV strains, but not in related coronaviruses. We used targeted RNA recombination to generate isogenic viruses that differ from MHV-A59 by amino acid substitutions in S. Viruses with S33R and K183R substitutions had wild type growth, while L79A/T82A viruses formed small plaques. Viruses with S33G, L79M/T82M or K183G substitutions could only be recovered from cells that over-expressed a mutant mCEACAM1a. Viruses with Y162H or Y162Q substitutions were never recovered, while Y162A viruses formed minute plaques. However, viruses with Y162F substitutions had wild type growth, suggesting that Y162 may comprise part of a hydrophobic domain that contacts the MHV-binding site of mCEACAM1a.
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MESH Headings
- Amino Acid Substitution
- Animals
- Antigens, CD/genetics
- Antigens, CD/metabolism
- Antigens, Differentiation/genetics
- Antigens, Differentiation/metabolism
- Base Sequence
- Binding Sites/genetics
- Carcinoembryonic Antigen
- Cell Adhesion Molecules
- Cell Line
- Conserved Sequence
- Coronavirus/genetics
- Coronavirus/growth & development
- Coronavirus/metabolism
- Coronavirus/pathogenicity
- Cricetinae
- DNA, Complementary/genetics
- DNA, Viral/genetics
- Green Fluorescent Proteins/genetics
- Humans
- Membrane Glycoproteins/chemistry
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Protein Structure, Tertiary
- Rats
- Receptors, Virus/genetics
- Receptors, Virus/metabolism
- Recombination, Genetic
- Species Specificity
- Spike Glycoprotein, Coronavirus
- Viral Envelope Proteins/chemistry
- Viral Envelope Proteins/genetics
- Viral Envelope Proteins/metabolism
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Coronavirus Receptors. EXPERIMENTAL MODELS OF MULTIPLE SCLEROSIS 2005. [PMCID: PMC7122215 DOI: 10.1007/0-387-25518-4_46] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The major receptor for murine coronavirus, mouse hepatitis virus (MHV), is identified as a protein, cell-adhesion molecule 1 in the carcinoembryonic antigen family (CEACAM1), which is classified in the immunoglobulin superfamily. There are four CEACAM1 isoforms, with either four or two ectodomains, resulting from an alternative splicing mechanism. CEACAM1 is expressed on the epithelium and in endothelial cells of a variety of tissues and hemopoietic cells, and functions as a homophilic and heterophilic adhesion molecule. It is used as a receptor for some bacteria as well. The N terminal domain participates in mediating homophilic adhesion. This domain is also responsible for binding to the MHV spike (S) protein; the CC’ face protruding in this domain interacts with an N terminal region of the S protein composed of 330 amino acids (called S1N330). The binding of CEACAM1 with MHV S protein induces S protein conformational changes and converts fusion-negative S protein to a fusion-positive form. The allelic forms of CEACAM1 found among mouse strains are thought to be an important determinant for mouse susceptibility to MHV.
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Molecular Determinants of Coronavirus Mhv- Induced Demyelination. EXPERIMENTAL MODELS OF MULTIPLE SCLEROSIS 2005. [PMCID: PMC7120609 DOI: 10.1007/0-387-25518-4_49] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mouse hepatitis virus (MHV) is a member of the coronavirus family of the nidovirales order. MHV is an enveloped virus with single-stranded, positive genomic RNA of about 31kb. Infection of susceptible strains of mice with the MHV-JHM and A59 strains results in acute encephalomyelitis and chronic demyelinating disease with features similar to the human demyelination disease multiple sclerosis (MS). Because the mechanism of demyelination in MS is not completely understood, various experimental models, including MHV infection in mice, have been used to study the pathogenesis of inflammatory autoimmune demyelination. The spike (S) glycoprotein of MHV has been implicated as the most critical genomic determinant of MHV pathogenesis and demyelination. However, other genes and proteins are likely to contribute to MHV pathogenesis as well.
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Shen S, Law Y, Liu D. A single amino acid mutation in the spike protein of coronavirus infectious bronchitis virus hampers its maturation and incorporation into virions at the nonpermissive temperature. Virology 2004; 326:288-98. [PMID: 15302214 PMCID: PMC7126609 DOI: 10.1016/j.virol.2004.06.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Revised: 05/25/2004] [Accepted: 06/03/2004] [Indexed: 11/22/2022]
Abstract
The spike (S) glycoprotein of coronavirus is responsible for receptor binding and membrane fusion. A number of variants with deletions and mutations in the S protein have been isolated from naturally and persistently infected animals and tissue cultures. Here, we report the emergence and isolation of two temperature sensitive (ts) mutants and a revertant in the process of cold-adaptation of coronavirus infectious bronchitis virus (IBV) to a monkey kidney cell line. The complete sequences of wild type (wt) virus, two ts mutants, and the revertant were compared and variations linked to phenotypes were mapped. A single amino acid reversion (L294-to-Q) in the S protein is sufficient to abrogate the ts phenotype. Interestingly, unlike wt virus, the revertant grows well at and below 32 degrees C, the permissive temperature, as it carries other mutations in multiple genes that might be associated with the cold-adaptation phenotype. If the two ts mutants were allowed to enter cells at 32 degrees C, the S protein was synthesized, core-glycosylated and at least partially modified at 40 degrees C. However, compared with wt virus and the revertant, no infectious particles of these ts mutants were assembled and released from the ts mutant-infected cells at 40 degrees C. Evidence presented demonstrated that the Q294-to-L294 mutation, located at a highly conserved domain of the S1 subunit, might hamper processing of the S protein to a matured 180-kDa, endo-glycosidase H-resistant glycoprotein and the translocation of the protein to the cell surface. Consequently, some essential functions of the S protein, including mediation of cell-to-cell fusion and its incorporation into virions, were completely abolished.
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Affiliation(s)
| | | | - D.X Liu
- Corresponding author. Institute of Molecular and Cell Biology, 30 Medical Drive, 117609, Singapore. Fax: +65-67791117.
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39
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Wang B, Chen H, Jiang X, Zhang M, Wan T, Li N, Zhou X, Wu Y, Yang F, Yu Y, Wang X, Yang R, Cao X. Identification of an HLA-A*0201-restricted CD8+ T-cell epitope SSp-1 of SARS-CoV spike protein. Blood 2004; 104:200-6. [PMID: 15016646 PMCID: PMC8254376 DOI: 10.1182/blood-2003-11-4072] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
A novel coronavirus, severe acute respiratory syndrome (SARS)–associated coronavirus (SARS-CoV), has been identified as the causal agent of SARS. Spike (S) protein is a major structural glycoprotein of the SARS virus and a potential target for SARS-specific cell-mediated immune responses. A panel of S protein–derived peptides was tested for their binding affinity to HLA-A*0201 molecules. Peptides with high affinity for HLA-A*0201 were then assessed for their capacity to elicit specific immune responses mediated by cytotoxic T lymphocytes (CTLs) both in vivo, in HLA-A2.1/Kb transgenic mice, and in vitro, from peripheral blood lymphocytes (PBLs) sourced from healthy HLA-A2.1+ donors. SARS-CoV protein-derived peptide-1 (SSp-1 RLNEVAKNL), induced peptide-specific CTLs both in vivo (transgenic mice) and in vitro (human PBLs), which specifically released interferon-γ (IFN-γ) upon stimulation with SSp-1–pulsed autologous dendritic cells (DCs) or T2 cells. SSp-1–specific CTLs also lysed major histocompatibility complex (MHC)–matched tumor cell lines engineered to express S proteins. HLA-A*0201–SSp-1 tetramer staining revealed the presence of significant populations of SSp-1–specific CTLs in SSp-1–induced CD8+ T cells. We propose that the newly identified epitope SSp-1 will help in the characterization of virus control mechanisms and immunopathology in SARS-CoV infection, and may be relevant to the development of immunotherapeutic approaches for SARS.
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Affiliation(s)
- Baomei Wang
- Institute of Immunology, Second Military Medical University, Shanghai, People's Republic of China
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Miura HS, Nakagaki K, Taguchi F. N-terminal domain of the murine coronavirus receptor CEACAM1 is responsible for fusogenic activation and conformational changes of the spike protein. J Virol 2004; 78:216-23. [PMID: 14671103 PMCID: PMC303413 DOI: 10.1128/jvi.78.1.216-223.2004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mouse hepatitis virus (MHV) receptor (MHVR), CEACAM1, has two different functions for MHV entry into cells: binding to MHV spike protein (S protein) and activation of the S protein to execute virus-cell membrane fusion, the latter of which is accompanied by conformational changes of the S protein. The MHVR comprising the N-terminal and fourth domains [R1(1,4)] displays these two activities, and the N domain is thought to be critical for binding to MHV. In this study, we have addressed whether or not the N domain alone is sufficient for these activities. We examined three types of soluble form MHVR (soMHVR), one consisting of the N domain alone [soR1(1)], one with the N and second domains [soR1(1,2)], and one [soR1(1,4)] expressed by recombinant baculoviruses. We assessed the abilities of these three types of soMHVR to bind to MHV, activate fusogenicity, and induce conformational changes of the S protein. All three types of soMHVR similarly bound to MHV, as examined by a solid-phase binding assay and neutralized MHV infectivity. They also activated S protein fusogenicity and induced its conformational changes with similar levels of efficiency. However, R1(1) expressed on the BHK cell surface failed to serve as a receptor in spite of a sufficient level of expression. The inability of expressed R1(1) to work as a receptor was due to the inaccessibility of virions to R1(1); however, these were accessible using the MHVR-specific monoclonal antibody CC1. These results collectively indicated that the N domain retains all biological activities necessary for receptor function.
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Affiliation(s)
- Hideka S Miura
- National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187-8502, Japan
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Tsai JC, Groot LD, Pinon JD, Iacono KT, Phillips JJ, Seo SH, Lavi E, Weiss SR. Amino acid substitutions within the heptad repeat domain 1 of murine coronavirus spike protein restrict viral antigen spread in the central nervous system. Virology 2003; 312:369-80. [PMID: 12919742 PMCID: PMC7125853 DOI: 10.1016/s0042-6822(03)00248-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Targeted recombination was carried out to select mouse hepatitis viruses (MHVs) in a defined genetic background, containing an MHV-JHM spike gene encoding either three heptad repeat 1 (HR1) substitutions (Q1067H, Q1094H, and L1114R) or L1114R alone. The recombinant virus, which expresses spike with the three substitutions, was nonfusogenic at neutral pH. Its replication was significantly inhibited by lysosomotropic agents, and it was highly neuroattenuated in vivo. In contrast, the recombinant expressing spike with L1114R alone mediated cell-to-cell fusion at neutral pH and replicated efficiently despite the presence of lysosomotropic agents; however, it still caused only subclinical morbidity and no mortality in animals. Thus, both recombinant viruses were highly attenuated and expressed viral antigen which was restricted to the olfactory bulbs and was markedly absent from other regions of the brains at 5 days postinfection. These data demonstrate that amino acid substitutions, in particular L1114R, within HR1 of the JHM spike reduced the ability of MHV to spread in the central nervous system. Furthermore, the requirements for low pH for fusion and viral entry are not prerequisites for the highly attenuated phenotype.
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Affiliation(s)
- Jean C Tsai
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
| | - Linda de Groot
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
| | - Josefina D Pinon
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
| | - Kathryn T Iacono
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
| | - Joanna J Phillips
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
| | - Su-hun Seo
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
| | - Ehud Lavi
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
| | - Susan R Weiss
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6076, USA
- Corresponding author. Department of Microbiology, 203A Johnson Pavilion, University of Pennsylvania, Philadelphia, PA 19104-6076, USA. Fax: +1-215-573-4858.
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Shen S, Wen ZL, Liu DX. Emergence of a coronavirus infectious bronchitis virus mutant with a truncated 3b gene: functional characterization of the 3b protein in pathogenesis and replication. Virology 2003; 311:16-27. [PMID: 12832199 PMCID: PMC7125764 DOI: 10.1016/s0042-6822(03)00117-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The subgenomic RNA 3 of IBV has been shown to be a tricistronic mRNA, encoding three products in IBV-infected cells. To explore if the least expressed ORF, ORF 3b, which encodes a nonstructural protein, is evolutionarily conserved and functionally indispensable for viral propagation in cultured cells, the Beaudette strain of IBV was propagated in chicken embryonated eggs for three passages and then adapted to a monkey kidney cell line, Vero. The 3b gene of passage 3 in embryonated eggs and passages 7, 15, 20, 25, 30, 35 50, and 65 in Vero cells were amplified by reverse transcription-polymerase chain reaction and sequenced. The results showed that viral RNA extracted from passages 35, 50, and 65 contained a single A insertion in a 6A stretch of the 3b gene between nucleotides 24075 and 24080, whereas the early passages carried the normal 3b gene. This insertion resulted in a frameshift event and therefore, if expressed, a C-terminally truncated protein. We showed that the frameshifting product, cloned in a plasmid, was expressed in vitro and in cells transfected with the mutant construct. The normal product of the 3b gene is 64 amino acids long, whereas the frameshifting product is 34 amino acids long with only 17 homogeneous amino acid residues at the N-terminal half. Immunofluorescent studies revealed that the normal 3b protein was localized to the nucleus and the truncated product showed a "free" distribution pattern, indicating that the C-terminal portion of 3b was responsible for its nuclear localization. Comparison of the complete genome sequences (27.6 kb) of isolates p20c22 and p36c12 (from passages 20 and 36, respectively) revealed that p36c12 contains three amino acid substitutions, two in the 195-kDa protein (encoded by gene 1) and one in the S protein, in addition to the frameshifting 3b product. Further characterization of the two isolates demonstrated that p36c12 showed growth advantage over p20c22 in both Vero cells and chicken embryos and was more virulent in chicken embryos than p20c22. These results suggest that the 3b gene product is not essential for the replication of IBV.
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Affiliation(s)
- S Shen
- Institute of Molecular and Cell Biology, National University of Singapore, 117604, Singapore
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Lu Y, Chen Y. Spike protein homology between the SARS-associated virus and murine hepatitis virus implies existence of a putative receptor-binding region. CHINESE SCIENCE BULLETIN-CHINESE 2003; 48:1115-1117. [PMID: 32214699 PMCID: PMC7089281 DOI: 10.1007/bf03185764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2003] [Accepted: 05/15/2003] [Indexed: 11/16/2022]
Abstract
Coronavirus has been determined to be the cause of the recent outbreak of severe acute respiratory syndrome (SARS). Human coronavirus 229E had been studied well and its receptor-binding domain was restricted to aa417-547 of S protein. However, this region has no homology with the newly separated SARS-associated virus (Hong Kong isolate CUHK-W1). Then we analyzed the phylogenesis of S1 subunit of the coronavirus spike protein (SARS-associated virus, Hong Kong isolate CUHK-W1). Interestingly, the highest homology between murine hepatitis virus (MHV) and SARS-associated coronavirus was found. And the important sites (aa62-65 and aa214-216) on the spike protein of MHV with receptor-binding capacity were highly conservative in comparison with the newly separated SARS-associated virus (the corresponding sites are aa51-54 and aal95-197). These results from bioinformatics analysis might help us to study the receptor-binding sites of SARS-associated virus and the mechanism of the virus entry into the target cell, and design antiviral drugs and potent vaccines.
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Affiliation(s)
- Yun Lu
- Laboratory of Immunology, Department of Biology, Tsinghua University, Protein Science Laboratory of Ministry of Education, 100084 Beijing, China
| | - Yinghua Chen
- Laboratory of Immunology, Department of Biology, Tsinghua University, Protein Science Laboratory of Ministry of Education, 100084 Beijing, China
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44
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Tsai JC, Zelus BD, Holmes KV, Weiss SR. The N-terminal domain of the murine coronavirus spike glycoprotein determines the CEACAM1 receptor specificity of the virus strain. J Virol 2003; 77:841-50. [PMID: 12502800 PMCID: PMC140794 DOI: 10.1128/jvi.77.2.841-850.2003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Using isogenic recombinant murine coronaviruses expressing wild-type murine hepatitis virus strain 4 (MHV-4) or MHV-A59 spike glycoproteins or chimeric MHV-4/MHV-A59 spike glycoproteins, we have demonstrated the biological functionality of the N-terminus of the spike, encompassing the receptor binding domain (RBD). We have used two assays, one an in vitro liposome binding assay and the other a tissue culture replication assay. The liposome binding assay shows that interaction of the receptor with spikes on virions at 37 degrees C causes a conformational change that makes the virions hydrophobic so that they bind to liposomes (B. D. Zelus, J. H. Schickli, D. M. Blau, S. R. Weiss, and K. V. Holmes, J. Virol. 77: 830-840, 2003). Recombinant viruses with spikes containing the RBD of either MHV-A59 or MHV-4 readily associated with liposomes at 37 degrees C in the presence of soluble mCEACAM1(a), except for S(4)R, which expresses the entire wild-type MHV-4 spike and associated only inefficiently with liposomes following incubation with soluble mCEACAM1(a). In contrast, soluble mCEACAM1(b) allowed viruses with the MHV-A59 RBD to associate with liposomes more efficiently than did viruses with the MHV-4 RBD. In the second assay, which requires virus entry and replication, all recombinant viruses replicated efficiently in BHK cells expressing mCEACAM1(a). In BHK cells expressing mCEACAM1(b), only viruses expressing chimeric spikes with the MHV-A59 RBD could replicate, while replication of viruses expressing chimeric spikes with the MHV-4 RBD was undetectable. Despite having the MHV-4 RBD, S(4)R replicated in BHK cells expressing mCEACAM1(b); this is most probably due to spread via CEACAM1 receptor-independent cell-to-cell fusion, an activity displayed only by S(4)R among the recombinant viruses studied here. These data suggest that the RBD domain and the rest of the spike must coevolve to optimize function in viral entry and spread.
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Affiliation(s)
- Jean C Tsai
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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45
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Abstract
Although murine coronavirus mouse hepatitis virus (MHV) enters cells by virus-cell membrane fusion triggered by its spike (S) protein, it is not well known how the S protein participates in fusion events. We reported that the soluble form of MHV receptor (soMHVR) transformed a nonfusogenic S protein into a fusogenic one (F. Taguchi and S. Matsuyama, J. Virol. 76:950-958, 2002). In the present study, we demonstrate that soMHVR induces the conformational changes of the S protein, as shown by the proteinase digestion test. A cl-2 mutant, srr7, of the MHV JHM virus (JHMV) was digested with proteinase K after treatment with soMHVR, and the resultant S protein was analyzed by Western blotting using monoclonal antibody (MAb) 10G, specific for the membrane-anchored S2 subunit. A 58-kDa fragment, encompassing the two heptad repeats in S2, was detected when srr7 was digested after soMHVR treatment, while no band was seen when the virus was untreated. The appearance of the proteinase-resistant fragment was dependent on the temperature and time of srr7 incubation with soMHVR and also on the concentration of soMHVR. Coimmunoprecipitation indicated that the direct binding of soMHVR to srr7 S protein induced these conformational changes; this was also suggested by the inhibition of the changes following pretreatment of soMHVR with anti-MHVR MAb CC1. soMHVR induced conformational changes of the S proteins of wild-type (wt) JHMV cl-2, as well as revertants from srr7, srr7A and srr7B; however, a major proportion of these S proteins were resistant to proteinase K even without soMHVR treatment. The implications of this proteinase-resistant fraction are discussed. This is the first report on receptor-induced conformational changes of the membrane-anchored fragment of the coronavirus S protein.
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Affiliation(s)
- Shutoku Matsuyama
- National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187-8502, Japan
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46
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Langevin C, Tuffereau C. Mutations conferring resistance to neutralization by a soluble form of the neurotrophin receptor (p75NTR) map outside of the known antigenic sites of the rabies virus glycoprotein. J Virol 2002; 76:10756-65. [PMID: 12368318 PMCID: PMC136618 DOI: 10.1128/jvi.76.21.10756-10765.2002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The neurotrophin receptor (p75NTR) serves as a receptor for rabies virus (RV). We expressed and purified a soluble chimera consisting of the p75NTR ectodomain fused to the human immunoglobulin G1 (IgG1) Fc fragment (p75-Fc). Although p75-Fc interacts with RV, the infectivity of RV did not decrease significantly when it was incubated in the presence of the soluble receptor alone. However, when it was subsequently incubated with an antihuman IgG directed against the Fc fragment of p75-Fc, the infectivity of RV was significantly lowered (>90%), whereas incubation with antihuman IgG alone had no effect. We then selected eight independent RV mutants that were not neutralized by p75-Fc and antihuman IgG (srr [soluble receptor resistant] mutants). Each mutant carried a single mutation in the glycoprotein gene leading to one amino acid substitution in the protein. A total of four different substitutions were found. Two of the mutations were located at position 318 (phenylalanine replaced by a serine or a valine residue), and two were located at position 352 (histidine replaced by a tyrosine or an arginine residue). All of the mutations prevented the interaction with p75NTR as either a soluble or a membrane-anchored form. Two mutants (F318S) and (H352R) resulted in the formation of small plaques on BSR cells, probably due to the slower maturation of the glycoprotein. Immunoprecipitation, immunofluorescence, and neutralization assays showed that the four mutated glycoproteins still interacted with representative anti-RV glycoprotein monoclonal antibodies (MAbs), indicating that p75NTR binds outside of the known RV glycoprotein antigenic sites.
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Affiliation(s)
- Christelle Langevin
- Virologie Moléculaire et Structurale, UMR CNRS-INRA 2472, 91198 Gif-sur-Yvette Cedex, France
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47
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Matsuyama S, Taguchi F. Inefficient infection of soluble receptor-resistant mutants of murine coronavirus in cells expressing MHVR2 receptor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 494:233-6. [PMID: 11774474 DOI: 10.1007/978-1-4615-1325-4_37] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- S Matsuyama
- National Institute of Neuroscience, NCNP 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan
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48
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Matsuyama S, Watanabe R, Taguchi F. Neurovirulence for mice of soluble receptor-resistant mutants of murine coronavirus JHMV. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 494:145-8. [PMID: 11774459 DOI: 10.1007/978-1-4615-1325-4_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- S Matsuyama
- National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan
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49
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Matsuyama S, Taguchi F. Communication between S1N330 and a region in S2 of murine coronavirus spike protein is important for virus entry into cells expressing CEACAM1b receptor. Virology 2002; 295:160-71. [PMID: 12033774 PMCID: PMC7133742 DOI: 10.1006/viro.2002.1391] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The soluble receptor-resistant (srr) mutants, srr7 and srr11, isolated from a murine coronavirus, mouse hepatitis virus (MHV) JHMV, have an amino acid mutation at positions 1114 (Leu to Phe) and 65 (Leu to His), respectively, in the spike (S) protein. These mutants failed to efficiently infect BHK cells expressing CEACAM1b (BHK-R2), due to their low entry into this cell line, although they infected cells expressing CEACAM1a (BHK-R1) in a manner similar to that of wild-type (wt) JHMV cl-2 (Matsuyama and Taguchi, Virology 273, 80-89, 2000). Following the repeated passage of these mutants through BHK-R2 cells, viruses were no longer isolated from srr11-infected cells, while two distinct mutants, srr7A and srr7B, were obtained from srr7-infected cells. Srr7A and srr7B grew 2 log10 higher than srr7 and induced fusion in BHK-R2 cells, being similar to wt virus. In addition to the amino acid change at position 1114 that stemmed from parental srr7, srr7A and srr7B had mutations around position 280, corresponding to the third region of the S1N330 receptor-binding site (S1N330-III) common to all MHV strains examined thus far. Srr7A and srr7B S proteins showed high fusogenicity in both BHK-R1 and BHK-R2 cells, like the wt virus, while srr7Aa and srr7Ba S proteins, which had mutations in S1N330-III but not at amino acid 1114, exhibited profoundly reduced fusion activity in these cell lines. These findings suggest that communication between S1N330-III and the amino acid at position 1114 is important for efficient fusion activity in BHK-R2 cells. S1N330-III is a possible region in the S1 involved in viral entry into cells.
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Affiliation(s)
- Shutoku Matsuyama
- National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo, 187-8502, Japan
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50
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Taguchi F, Matsuyama S. Soluble receptor potentiates receptor-independent infection by murine coronavirus. J Virol 2002; 76:950-8. [PMID: 11773370 PMCID: PMC135807 DOI: 10.1128/jvi.76.3.950-958.2002] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mouse hepatitis virus (MHV) infection spreads from MHV-infected DBT cells, which express the MHV receptor CEACAM1 (MHVR), to BHK cells, which are devoid of the receptor, by intercellular membrane fusion (MHVR-independent fusion). This mode of infection is a property of wild-type (wt) JHMV cl-2 virus but is not seen in cultures infected with the mutant virus JHMV srr7. In this study, we show that soluble MHVR (soMHVR) potentiates MHVR-independent fusion in JHMV srr7-infected cultures. Thus, in the presence of soMHVR, JHMV srr7-infected DBT cells overlaid onto BHK cells induce BHK cell syncytia and the spread of JHMV srr7 infection. This does not occur in the absence of soMHVR. soMHVR also enhanced wt virus MHVR-independent fusion. These effects were dependent on the concentration of soMHVR in the culture and were specifically blocked by the anti-MHVR monoclonal antibody CC1. Together with these observations, direct binding of soMHVR to the virus spike (S) glycoprotein as revealed by coimmunoprecipitation demonstrated that the effect is mediated by the binding of soMHVR to the S protein. Furthermore, fusion of BHK cells expressing the JHMV srr7 S protein was also induced by soMHVR. These results indicated that the binding of soMHVR to the S protein expressed on the DBT cell surface potentiates the fusion of MHV-infected DBT cells with nonpermissive BHK cells. We conclude that the binding of soMHVR to the S protein converts the S protein to a fusion-active form competent to mediate cell-cell fusion, in a fashion similar to the fusion of virus and cell membranes.
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Affiliation(s)
- Fumihiro Taguchi
- National Institute of Neuroscience, NCNP, Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.
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