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Huong TN, Lee ZQ, Lai SK, Lee HY, Tan BH, Sugrue RJ. Evidence that an interaction between the respiratory syncytial virus F and G proteins at the distal ends of virus filaments mediates efficient multiple cycle infection. Virology 2024; 591:109985. [PMID: 38227992 DOI: 10.1016/j.virol.2024.109985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 11/29/2023] [Accepted: 01/04/2024] [Indexed: 01/18/2024]
Abstract
Evidence for a stable interaction between the respiratory syncytial virus (RSV) F and G proteins on the surface of virus filaments was provided using antibody immunoprecipitation studies on purified RSV particles, and by the in situ analysis on the surface of RSV-infected cells using the proximity ligation assay. Imaging of the F and G protein distribution on virus filaments suggested that this protein complex was localised at the distal ends of the virus filaments, and suggested that this protein complex played a direct role in mediating efficient localised cell-to-cell virus transmission. G protein expression was required for efficient localised cell-to-cell transmission of RSV in cell monolayers which provided evidence that this protein complex mediates efficient multiple cycle infection. Collectively, these data provide evidence that F and G proteins form a complex on the surface of RSV particles, and that a role for this protein complex in promoting virus transmission is suggested.
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Affiliation(s)
- Tra Nguyen Huong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore
| | - Zhi Qi Lee
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore
| | - Soak Kuan Lai
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore
| | - Hsin Yee Lee
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore
| | - Boon Huan Tan
- LKC School of Medicine, Nanyang Technological University, 11 Mandalay Road, Singapore, 308232, Republic of Singapore
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore.
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2
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Huong TN, Ravi Iyer L, Lui J, Wang DY, Tan BH, Sugrue RJ. The respiratory syncytial virus SH protein is incorporated into infectious virus particles that form on virus-infected cells. Virology 2023; 580:28-40. [PMID: 36746062 DOI: 10.1016/j.virol.2023.01.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 12/21/2022] [Accepted: 01/19/2023] [Indexed: 02/03/2023]
Abstract
The association of the SH protein with respiratory syncytial virus (RSV) particles was examined in HEp2 cells and human ciliated nasal epithelial cells. Imaging of infected cells demonstrated the presence of the SH protein in virus filaments, and analysis of purified RSV particles revealed a SH protein species whose size was consistent with the glycosylated SH protein. Although the SH protein was detected in virus filaments it was not required for virus filament formation. Analysis of RSV-infected ciliated cells also revealed that the SH protein was trafficked into the cilia, and this correlated with reduced cilia density on these cells. Reduced cilia loss was not observed on ciliated cells infected with a RSV isolate that failed to express the SH protein. These data provide direct evidence that the SH protein is trafficked into virus particles, and suggests that the SH protein may also promote cilia dysfunction on nasal epithelial cells.
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Affiliation(s)
- Tra Nguyen Huong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore
| | - Laxmi Ravi Iyer
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore
| | - Jing Lui
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, 119228, Republic of Singapore
| | - De Yun Wang
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, 119228, Republic of Singapore
| | - Boon Huan Tan
- Biological Defence Program, DSO National Laboratories, 27 Medical Drive, Singapore, 117510, Republic of Singapore; LKC School of Medicine, Nanyang Technological University, 11 Mandalay Road, Singapore, 308232, Republic of Singapore
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore.
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3
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Sugrue RJ, Tan BH. Defining the Assembleome of the Respiratory Syncytial Virus. Subcell Biochem 2023; 106:227-249. [PMID: 38159230 DOI: 10.1007/978-3-031-40086-5_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
During respiratory syncytial virus (RSV) particle assembly, the mature RSV particles form as filamentous projections on the surface of RSV-infected cells. The RSV assembly process occurs at the / on the cell surface that is modified by a virus infection, involving a combination of several different host cell factors and cellular processes. This induces changes in the lipid composition and properties of these lipid microdomains, and the virus-induced activation of associated Rho GTPase signaling networks drives the remodeling of the underlying filamentous actin (F-actin) cytoskeleton network. The modified sites that form on the surface of the infected cells form the nexus point for RSV assembly, and in this review chapter, they are referred to as the RSV assembleome. This is to distinguish these unique membrane microdomains that are formed during virus infection from the corresponding membrane microdomains that are present at the cell surface prior to infection. In this article, an overview of the current understanding of the processes that drive the formation of the assembleome during RSV particle assembly is given.
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Affiliation(s)
- Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore.
| | - Boon Huan Tan
- LKC School of Medicine, Nanyang Technological University, Singapore, Republic of Singapore
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4
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Ravi LI, Tan TJ, Tan BH, Sugrue RJ. Virus-induced activation of the rac1 protein at the site of respiratory syncytial virus assembly is a requirement for virus particle assembly on infected cells. Virology 2021; 557:86-99. [PMID: 33677389 DOI: 10.1016/j.virol.2021.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 12/17/2020] [Accepted: 02/16/2021] [Indexed: 12/13/2022]
Abstract
The distributions of the rac1, rhoA and cdc42 proteins in respiratory syncytial virus (RSV) infected cells was examined. All three rhoGTPases were detected within inclusion bodies, and while the rhoA and rac1 proteins were associated with virus filaments, only the rac1 protein was localised throughout the virus filaments. RSV infection led to increased rac1 protein activation, and using the rac1 protein inhibitor NS23766 we provided evidence that the increased rac1 activation occurred at the site of RSV assembly and facilitated F-actin remodeling during virus morphogenesis. A non-infectious virus-like particle (VLP) assay showed that the RSV VLPs formed in lipid-raft microdomains containing the rac1 protein, together with F-actin and filamin-1 (cell proteins associated with virus filaments). This provided evidence that the virus envelope proteins are trafficked to membrane microdomains containing the rac1 protein. Collectively, these data provide evidence that the rac1 protein plays a direct role in the RSV assembly process.
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Affiliation(s)
- Laxmi Iyer Ravi
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
| | - Timothy J Tan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
| | - Boon Huan Tan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore; Defense Medical and Environment Research Institute, DSO National Laboratories, 27 Medical Drive, 117510, Singapore; Infection and Immunity, Lee Kong Chian School of Medicine, Nanyang Technological University, 11 Mandalay Road, Singapore, 308232, Singapore
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.
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Kumar S, Yeo D, Harur Muralidharan N, Lai SK, Tong C, Tan BH, Sugrue RJ. Impaired Nuclear Export of the Ribonucleoprotein Complex and Virus-Induced Cytotoxicity Combine to Restrict Propagation of the A/Duck/Malaysia/02/2001 (H9N2) Virus in Human Airway Cells. Cells 2020; 9:cells9020355. [PMID: 32028682 PMCID: PMC7072679 DOI: 10.3390/cells9020355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 01/20/2020] [Accepted: 01/29/2020] [Indexed: 01/02/2023] Open
Abstract
In humans, (A549) cells impaired H9N2 virus nuclear export of the ribonucleoprotein (RNP) complex contrasted with the early and efficient nuclear export of the H1N1/WSN and pH1N1 virus RNP complexes. Although nuclear export of the RNP complex occurred via the nuclear pore complex, H9N2 virus infection also induced modifications in the nuclear envelope and induced cell cytotoxicity. Reduced PA protein levels in H9N2 virus-infected A549 cells occurred, and this phenomenon was independent of virus infection. Silencing the H1N1/WSN PA protein expression leads to impaired nuclear export of RNP complexes, suggesting that the impaired nuclear export of the H9N2 virus RNP complex may be one of the consequences of reduced PA protein levels. Early and efficient export of the RNP complex occurred in H9N2 virus-infected avian (CEF) cells, although structural changes in the nuclear envelope also occurred. Collectively our data suggest that a combination of delayed nuclear export and virus-induced cell cytotoxicity restricts H9N2 virus transmission in A549 cells. However, the early and efficient export of the RNP complex mitigated the effects of virus-induced cytotoxicity on H9N2 virus transmission in CEF cells. Our findings highlight the multi-factorial nature of host-adaptation of the polymerase proteins of avian influenza viruses in non-avian cell environments.
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Affiliation(s)
- Sriram Kumar
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; (S.K.); (D.Y.); (N.H.M.); (S.K.L.); (C.T.)
| | - Dawn Yeo
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; (S.K.); (D.Y.); (N.H.M.); (S.K.L.); (C.T.)
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore 117510, Singapore;
| | - Nisha Harur Muralidharan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; (S.K.); (D.Y.); (N.H.M.); (S.K.L.); (C.T.)
| | - Soak Kuan Lai
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; (S.K.); (D.Y.); (N.H.M.); (S.K.L.); (C.T.)
| | - Cathlyn Tong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; (S.K.); (D.Y.); (N.H.M.); (S.K.L.); (C.T.)
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore 117510, Singapore;
| | - Richard J. Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore; (S.K.); (D.Y.); (N.H.M.); (S.K.L.); (C.T.)
- Correspondence:
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Wong PS, Sutejo R, Chen H, Ng SH, Sugrue RJ, Tan BH. A System Based-Approach to Examine Cytokine Response in Poxvirus-Infected Macrophages. Viruses 2018; 10:v10120692. [PMID: 30563103 PMCID: PMC6316232 DOI: 10.3390/v10120692] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/29/2018] [Accepted: 11/30/2018] [Indexed: 02/07/2023] Open
Abstract
The poxviruses are large, linear, double-stranded DNA viruses about 130 to 230 kbp, that have an animal origin and evolved to infect a wide host range. Variola virus (VARV), the causative agent of smallpox, is a poxvirus that infects only humans, but other poxviruses such as monkey poxvirus and cowpox virus (CPXV) have crossed over from animals to infect humans. Therefore understanding the biology of poxviruses can devise antiviral strategies to prevent these human infections. In this study we used a system-based approach to examine the host responses to three orthopoxviruses, CPXV, vaccinia virus (VACV), and ectromelia virus (ECTV) in the murine macrophage RAW 264.7 cell line. Overall, we observed a significant down-regulation of gene expressions for pro-inflammatory cytokines, chemokines, and related receptors. There were also common and virus-specific changes in the immune-regulated gene expressions for each poxvirus-infected RAW cells. Collectively our results showed that the murine macrophage RAW 264.7 cell line is a suitable cell-based model system to study poxvirus host response.
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Affiliation(s)
- Pui-San Wong
- Defence Medical and Environmental Research Institute, DSO National Labs, Singapore 117510, Singapore.
| | - Richard Sutejo
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.
| | - Hui Chen
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.
| | - Sock-Hoon Ng
- Defence Medical and Environmental Research Institute, DSO National Labs, Singapore 117510, Singapore.
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.
| | - Boon-Huan Tan
- Defence Medical and Environmental Research Institute, DSO National Labs, Singapore 117510, Singapore.
- Infection and Immunity, LKC School of Medicine, Nanyang Technological University, Singapore 308232, Singapore.
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Huong TN, Yan Y, Jumat MR, Lui J, Tan BH, Wang DY, Sugrue RJ. A sustained antiviral host response in respiratory syncytial virus infected human nasal epithelium does not prevent progeny virus production. Virology 2018; 521:20-32. [PMID: 29870884 DOI: 10.1016/j.virol.2018.05.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 05/09/2018] [Accepted: 05/18/2018] [Indexed: 12/01/2022]
Abstract
Respiratory syncytial virus infection was examined using a human nasal epithelial cell model. Maximum levels of shed-virus were produced at between 3 and 5 days post-infection (dpi), and the infectivity of the shed-virus was stable up to 10 dpi. The highest levels of interferon signalling were recorded at 2dpi, and infection induced a widespread antivirus response in the nasal epithelium, involving both infected cells and non-infected cells. Although these cellular responses were associated with reduced levels of progeny virus production and restricted virus spread, they did not inhibit the infectivity virus that is shed early in infection. In the clinical context these data suggest that although the host cell response in the nasal epithelium may restrict the levels of progeny virus particles produced, the stability of the shed-virus in the nasal mucosa may be an important factor in both disease progression and virus transmission.
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Affiliation(s)
- Tra Nguyen Huong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
| | - Yan Yan
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore 119228, Republic of Singapore
| | - Muhammad Raihan Jumat
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
| | - Jing Lui
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore 119228, Republic of Singapore
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore 117510, Republic of Singapore
| | - De Yun Wang
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore 119228, Republic of Singapore
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore.
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Taye B, Vaz C, Tanavde V, Kuznetsov VA, Eisenhaber F, Sugrue RJ, Maurer-Stroh S. Benchmarking selected computational gene network growing tools in context of virus-host interactions. Sci Rep 2017; 7:5805. [PMID: 28724991 PMCID: PMC5517527 DOI: 10.1038/s41598-017-06020-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 06/07/2017] [Indexed: 01/04/2023] Open
Abstract
Several available online tools provide network growing functions where an algorithm utilizing different data sources suggests additional genes/proteins that should connect an input gene set into functionally meaningful networks. Using the well-studied system of influenza host interactions, we compare the network growing function of two free tools GeneMANIA and STRING and the commercial IPA for their performance of recovering known influenza A virus host factors previously identified from siRNA screens. The result showed that given small (~30 genes) or medium (~150 genes) input sets all three network growing tools detect significantly more known host factors than random human genes with STRING overall performing strongest. Extending the networks with all the three tools significantly improved the detection of GO biological processes of known host factors compared to not growing networks. Interestingly, the rate of identification of true host factors using computational network growing is equal or better to doing another experimental siRNA screening study which could also be true and applied to other biological pathways/processes.
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Affiliation(s)
- Biruhalem Taye
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01 Matrix, Singapore, 138671, Singapore. .,School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore. .,Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P.O.BOX 1176, Addis Ababa, Ethiopia.
| | - Candida Vaz
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01 Matrix, Singapore, 138671, Singapore
| | - Vivek Tanavde
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01 Matrix, Singapore, 138671, Singapore.,Institute of Medical Biology, A*STAR, 8A Biomedical Grove, #06-06 Immunos, Singapore, 138648, Singapore
| | - Vladimir A Kuznetsov
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01 Matrix, Singapore, 138671, Singapore.,School of Computer Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore, 637553, Singapore
| | - Frank Eisenhaber
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01 Matrix, Singapore, 138671, Singapore.,Department of Biological Sciences, National University of Singapore, 8 Medical Drive, Singapore, 117597, Singapore.,School of Computer Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore, 637553, Singapore
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Sebastian Maurer-Stroh
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01 Matrix, Singapore, 138671, Singapore.,Department of Biological Sciences, National University of Singapore, 8 Medical Drive, Singapore, 117597, Singapore.,National Public Health Laboratory, Ministry of Health, 3 Biopolis Drive, Synapse #05-14/16, Singapore, 138623, Singapore
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Taye B, Chen H, Myaing MZ, Tan BH, Maurer-Stroh S, Sugrue RJ. Systems-based approach to examine the cytokine responses in primary mouse lung macrophages infected with low pathogenic avian Influenza virus circulating in South East Asia. BMC Genomics 2017; 18:420. [PMID: 28558796 PMCID: PMC5450074 DOI: 10.1186/s12864-017-3803-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 05/17/2017] [Indexed: 02/08/2023] Open
Abstract
Background Influenza A virus (IAV) is a major public health concern, being responsible for the death of approximately half a million people each year. Zoonotic transmissions of the virus from swine and avian origin have occurred in the past, and can potentially lead to the emgergence of new IAV stains in future pandemics. Pulmonary macrophages have been implicated in disease severity in the lower airway, and understanding the host response of macrophages infected with avian influenza viruses should provide new therapeutic strategies. Results We used a systems-based approach to investigate the transcriptome response of primary murine lung macrophages (PMФ) infected with the mouse-adapted H1N1/WSN virus and low pathogenic avian influenza (LPAI) viruses H5N2 and H5N3. The results showed that the LPAI viruses H5N2 and H5N3 can infect PMФ with similar efficiency to the H1N1/WSN virus. While all viruses induced antiviral responses, the H5N3 virus infection resulted in higher expression levels of cytokines and chemokines associated with inflammatory responses. Conclusions The LPAI H5N2 and H5N3 viruses are able to infect murine lung macrophages. However, the H5N3 virus was associated with increased expression of pro-inflammatory mediators. Although the H5N3 virus it is capable of inducing high levels of cytokines that are associated with inflammation, this property is distinct from its inability to efficiently replicate in a mammalian host. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3803-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Biruhalem Taye
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01, Matrix, Singapore, 138671, Republic of Singapore.,School of Biological Science, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore.,Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, P.O.BOX 1176, Ethiopia
| | - Hui Chen
- School of Biological Science, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore.,Current address Genome Institute of Singapore, A*STAR, 60 Biopolis Street, #02-01, Genome, Singapore, 138672, Republic of Singapore
| | - Myint Zu Myaing
- School of Biological Science, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, Defence Science Organisation National Laboratories, 27 Medical Drive, Singapore, 117510, Republic of Singapore.,LKC School of Medicine, Nanyang Technological University, 50 Nanyang Ave, Singapore, 639798, Republic of Singapore
| | - Sebastian Maurer-Stroh
- Bioinformatics Institute, A*STAR, 30 Biopolis Street #07-01, Matrix, Singapore, 138671, Republic of Singapore.,National Public Health Laboratory, Ministry of Health, Singapore, Republic of Singapore.,Department of Biological Sciences, National University of Singapore, 8 Medical Drive, Singapore, 117597, Republic of Singapore
| | - Richard J Sugrue
- School of Biological Science, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Republic of Singapore.
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Myaing MZ, Jumat MR, Huong TN, Tan BH, Sugrue RJ. Truncated forms of the PA protein containing only the C-terminal domains are associated with the ribonucleoprotein complex within H1N1 influenza virus particles. J Gen Virol 2017; 98:906-921. [PMID: 28141511 DOI: 10.1099/jgv.0.000721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We have examined the expression profile of the influenza virus PA protein in pH1N1/2009 virus-infected cells. Immunoblotting analysis of virus-infected MDCK cells revealed the presence of full-length PA protein from 8 h post-infection, together with the simultaneous appearance of PA protein species of approximately 50, 35/39 and 20/25 kDa (collectively referred to as PA*). PA* was also detected in H1N1/WSN-virus-infected cells, indicating that its presence was not virus-specific, and it was also observed in virus-infected A549 and chick embryo fibroblast (CEF) cells, indicating that its presence was not cell-type-specific. PA* was detected in cells expressing the recombinant PA protein, indicating that the PA* formation occurred in the absence of virus infection. These data collectively indicated that PA* formation is an intrinsic property of PA gene expression. The association of PA* with purified influenza virus particles was demonstrated by immunoblotting, and a protease protection assay provided evidence that PA* was packaged into virus particles. The ribonucleoprotein (RNP) complex was isolated from purified influenza virus particles using glycerol gradient centrifugation, which demonstrated that PA* was associated with the RNP complex. To the best of our knowledge, this is the first report to demonstrate that PA protein species containing only segments of the C-terminal domain form during influenza virus infection. Furthermore, these truncated PA protein species are subsequently packaged into virus particles as part of the functional RNP complex.
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Affiliation(s)
- Myint Zu Myaing
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Muhammad Raihan Jumat
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Tra Nguyen Huong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore 117510, Singapore
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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11
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Jumat MR, Wong P, Lee RTC, Maurer-Stroh S, Tan BH, Sugrue RJ. Molecular and biochemical characterization of the NS1 protein of non-cultured influenza B virus strains circulating in Singapore. Microb Genom 2017; 2:e000082. [PMID: 28348873 PMCID: PMC5320597 DOI: 10.1099/mgen.0.000082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 08/02/2016] [Indexed: 12/24/2022] Open
Abstract
In this study we compared the NS1 protein of Influenza B/Lee/40 and several non-cultured Influenza B virus clinical strains detected in Singapore. In B/Lee/40 virus-infected cells and in cells expressing the recombinant B/Lee/40 NS1 protein a full-length 35 kDa NS1 protein and a 23 kDa NS1 protein species (p23) were detected. Mutational analysis of the NS1 gene indicated that p23 was generated by a novel cleavage event within the linker domain between an aspartic acid and proline at amino acid residues at positions 92 and 93 respectively (DP92–93), and that p23 contained the first 92 amino acids of the NS1 protein. Sequence analysis of the Singapore strains indicated the presence of either DP92–93 or NP92–93 in the NS1 protein, but protein expression analysis showed that p23 was only detected in NS1 proteins with DP92–93.. An additional adjacent proline residue at position 94 (P94) was present in some strains and correlated with increased p23 levels, suggesting that P94 has a synergistic effect on the cleavage of the NS1 protein. The first 145 amino acids of the NS1 protein are required for inhibition of ISG15-mediated ubiquitination, and our analysis showed that Influenza B viruses circulating in Singapore with DP92–93 expressed truncated NS1 proteins and may differ in their capacity to inhibit ISG15 activity. Thus, DP92–93 in the NS1 protein may confer a disadvantage to Influenza B viruses circulating in the human population and interestingly the low frequency of DP92–93detection in the NS1 protein since 2004 is consistent with this suggestion.
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Affiliation(s)
- Muhammad Raihan Jumat
- 1School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
| | - Puisan Wong
- 2Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, 117510, Singapore
| | - Raphael Tze Chuen Lee
- 3Bioinformatics Institute (BII) 30 Biopolis Street #07-01, Matrix Building, 138671, Singapore
| | - Sebastian Maurer-Stroh
- 1School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.,3Bioinformatics Institute (BII) 30 Biopolis Street #07-01, Matrix Building, 138671, Singapore
| | - Boon Huan Tan
- 2Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, 117510, Singapore
| | - Richard J Sugrue
- 1School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
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Ludwig A, Nguyen TH, Leong D, Ravi LI, Tan BH, Sandin S, Sugrue RJ. Caveolae provide a specialized membrane environment for respiratory syncytial virus assembly. J Cell Sci 2017; 130:1037-1050. [PMID: 28154158 PMCID: PMC5358342 DOI: 10.1242/jcs.198853] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 01/26/2017] [Indexed: 12/20/2022] Open
Abstract
Respiratory syncytial virus (RSV) is an enveloped virus that assembles into filamentous virus particles on the surface of infected cells. Morphogenesis of RSV is dependent upon cholesterol-rich (lipid raft) membrane microdomains, but the specific role of individual raft molecules in RSV assembly is not well defined. Here, we show that RSV morphogenesis occurs within caveolar membranes and that both caveolin-1 and cavin-1 (also known as PTRF), the two major structural and functional components of caveolae, are actively recruited to and incorporated into the RSV envelope. The recruitment of caveolae occurred just prior to the initiation of RSV filament assembly, and was dependent upon an intact actin network as well as a direct physical interaction between caveolin-1 and the viral G protein. Moreover, cavin-1 protein levels were significantly increased in RSV-infected cells, leading to a virus-induced change in the stoichiometry and biophysical properties of the caveolar coat complex. Our data indicate that RSV exploits caveolae for its assembly, and we propose that the incorporation of caveolae into the virus contributes to defining the biological properties of the RSV envelope.
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Affiliation(s)
- Alexander Ludwig
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
| | - Tra Huong Nguyen
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
| | - Daniel Leong
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore 117510
| | - Laxmi Iyer Ravi
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore 117510
| | - Sara Sandin
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
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Huong TN, Iyer Ravi L, Tan BH, Sugrue RJ. Evidence for a biphasic mode of respiratory syncytial virus transmission in permissive HEp2 cell monolayers. Virol J 2016; 13:12. [PMID: 26790623 PMCID: PMC4719537 DOI: 10.1186/s12985-016-0467-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 01/12/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND During respiratory syncytial virus (RSV) infection filamentous virus particles are formed on the cell surface. Although the virus infectivity remains cell-associated, low levels of cell-free virus is detected during advanced infection. It is currently unclear if this cell-free virus infectivity is due to a low-efficiency specific cell-release mechanism, or if it arises due to mechanical breakage following virus-induced cell damage at the advanced stage of infection. Understanding the origin of this cell-free virus is a prerequisite for understanding the mechanism of RSV transmission in permissive cells. In this study we describe a detailed examination of RSV transmission in permissive HEp2 cell monolayers. METHODS HEp2 cell monolayers were infected with RSV using a multiplicity of infection of 0.0002, and the course of infection monitored over 5 days. The progression of the virus infection within the cell monolayers was performed using bright-field microscopy to visualise the cell monolayer and immunofluorescence microscopy to detect virus-infected cells. The cell-associated and cell-free virus infectivity were determined by virus plaque assay, and the virus-induced cell cytotoxicity determined by measuring cell membrane permeability and cellular DNA fragmentation. RESULTS At 2 days-post infection (dpi), large clusters of virus-infected cells could be detected indicating localised transmission in the cell monolayer, and during this stage we failed to detect either cell-free virus or cell cytotoxicity. At 3 dpi the presence of much larger infected cell clusters correlated with the begining of virus-induced changes in cell permeability. The presence of cell-free virus correlated with continued increase in cell permeability and cytotoxicity at 4 and 5 dpi. At 5 dpi extensive cell damage, syncytial formation, and increased cellular DNA fragmentation was noted. However, even at 5 dpi the cell-free virus constituted less than 1 % of the total virus infectivity. CONCLUSIONS Our data supports a model of RSV transmission that initially involves the localised cell-to-cell spread of virus particles within the HEp2 cell monolayer. However, low levels of cell free-virus infectivity was observed at the advanced stages of infection, which correlated with a general loss in cell monolayer integrity due to virus-induced cytotoxicity.
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Affiliation(s)
- Tra Nguyen Huong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
| | - Laxmi Iyer Ravi
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore, 117510, Singapore.
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
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Huong TN, Tan BH, Sugrue RJ. A Proteomic-Based Workflow Using Purified Respiratory Syncytial Virus Particles to Identify Cellular Factors as Drug Targets. Methods Mol Biol 2016; 1442:175-194. [PMID: 27464695 DOI: 10.1007/978-1-4939-3687-8_13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The identification of cellular factors that play a role in respiratory syncytial virus (RSV) replication is an alternative strategy in the identification of druggable cellular protein that are essential for RSV replication. In this regard experimental strategies that are able to screen relevant proteins from the vast array of proteins in the cellular milieu will facilitate the identification of potential drug targets. In this chapter we describe a procedure where RSV particles are purified from cells that are permissive for RSV infection, and the protein composition of the purified virus particles characterized using a proteomics-based strategy. This procedure revealed that actin, several actin-binding proteins, and the chaperones HSP70 and HSP90 also co-purified with the virus particles. The relevance of the HSP90 protein to virus replication was then further validated using imaging, gene silencing and by using an established small molecule HSP90 inhibitor.
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Affiliation(s)
- Tra Nguyen Huong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore, 117510, Singapore
| | - Richard J Sugrue
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
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Jumat MR, Huong TN, Ravi LI, Stanford R, Tan BH, Sugrue RJ. Viperin protein expression inhibits the late stage of respiratory syncytial virus morphogenesis. Antiviral Res 2015; 114:11-20. [DOI: 10.1016/j.antiviral.2014.11.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 11/05/2014] [Accepted: 11/18/2014] [Indexed: 01/13/2023]
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Abstract
BACKGROUND Influenza B viruses are classified into two main lineages: Yamagata-like and Victoria-like, which differ antigenically and phylogenetically. To understand the evolution of influenza B viruses in South East Asia as well as to determine the vaccine efficacy, we genetically characterised gene segments 4, 6 and 8 from non-tissue culture adapted influenza B viruses detected in Singapore from 2004 to 2009. METHODS vRNA were extracted from the nasopharyngeal swabs or nasal washes of SAF servicemen displaying febrile and respiratory symptoms, and subjected to PCR assay to test for the presence of influenza B virus. The PCR-positive specimens were next subjected to sequencing of the full gene segments 4 (HA), 6 (NA/NB) and 8 (NS1/NEP). The nucleotide sequences were aligned together with that of other specimens isolated from South East Asia as well as the vaccine strains. Phylogenetic trees of each gene segment were constructed and the amino acid alignments were analysed. RESULTS A majority of the Singaporean specimens analysed in this study, from 2004-2009, had gene segment 4 from the Victoria-like lineage and gene segment 6 from Yamagata-like lineage. Some of these specimens had both gene segments from the Yamagata lineage and this resulted in several vaccine mismatches. Gene segment 8 from majority of these specimens clustered separately from both the Yamagata and Victoria strains. The HA protein of most of the Singaporean specimens isolated post 2000 contained a glycosylation site at position 211, which was not dominant prior to 2000. No amino acid substitution conferring drug-resistance was found in either the HA or NA proteins. CONCLUSIONS The presence of both lineages co-circulating post 2000, suggests that a trivalent vaccine is not enough to confer immunity to the general public, strongly endorsing the inclusion of both lineages in the vaccine. Several amino acid substitutions were observed, prompting in depth functional analyses.
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Affiliation(s)
- Muhammad Raihan Jumat
- />Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, 637551 Republic of Singapore
| | - Richard J Sugrue
- />Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, 637551 Republic of Singapore
| | - Boon-Huan Tan
- />Detection and Diagnostics Laboratory, Defence Medical and Environmental Institute, DSO National Laboratories, 27 Medical Drive, Singapore, 117510 Republic of Singapore
- />Saw Swee Hock School of Public Health, Faculty of Medicine, National University Singapore, Singapore, 117549 Republic of Singapore
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Jumat MR, Nguyen Huong T, Wong P, Loo LH, Tan BH, Fenwick F, Toms GL, Sugrue RJ. Imaging analysis of human metapneumovirus-infected cells provides evidence for the involvement of F-actin and the raft-lipid microdomains in virus morphogenesis. Virol J 2014; 11:198. [PMID: 25408253 PMCID: PMC4243936 DOI: 10.1186/s12985-014-0198-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 11/05/2014] [Indexed: 11/13/2022] Open
Abstract
Backgound Due to difficulties of culturing Human metapneumovirus (HMPV) much of the current understanding of HMPV replication can be inferred from other closely related viruses. The slow rates of virus replication prevent many biochemical analyses of HMPV particles. In this study imaging was used to examine the process of HMPV morphogenesis in individually infected LLC-MK2 cells, and to better characterise the sites of HMPV assembly. This strategy has circumvented the problems associated with slow replication rates and allowed us to characterise both the HMPV particles and the sites of HMPV morphogenesis. Methods HMPV-infected LLC-MK2 cells were stained with antibodies that recognised the HMPV fusion protein (F protein), attachment protein (G protein) and matrix protein (M protein), and fluorescent probes that detect GM1 within lipid-raft membranes (CTX-B-AF488) and F-actin (Phalloidin-FITC). The stained cells were examined by confocal microscopy, which allowed imaging of F-actin, GM1 and virus particles in HMPV-infected cells. Cells co-expressing recombinant HMPV G and F proteins formed virus-like particles and were co-stained with antibodies that recognise the recombinant G and F proteins and phalloidin-FITC and CTX-B-AF594, and the distribution of the G and F proteins, GM1 and F-actin determined. Results HMPV-infected cells stained with anti-F, anti-G or anti-M revealed a filamentous staining pattern, indicating that the HMPV particles have a filamentous morphology. Staining of HMPV-infected cells with anti-G and either phalloidin-FITC or CTX-B-AF488 exhibited extensive co-localisation of these cellular probes within the HMPV filaments. This suggested that lipid-raft membrane domains and F-actin structures are present at the site of the virus morphogenesis, and are subsequently incorporated into the HMPV filaments. Furthermore, the filamentous virus-like particles that form in cells expressing the G protein formed in cellular structures containing GM1 and F-actin, suggesting the G protein contains intrinsic targeting signals to the sites of virus assembly. Conclusions These data suggest that HMPV matures as filamentous particles and that virus morphogenesis occurs within lipid-raft microdomains containing localized concentrations of F-actin. The similarity between HMPV morphogenesis and the closely related human respiratory syncytial virus suggests that involvement of F-actin and lipid-raft microdomains in virus morphogenesis may be a common feature of the Pneumovirinae. Electronic supplementary material The online version of this article (doi:10.1186/s12985-014-0198-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Muhammad Raihan Jumat
- Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Nanyang, 637551, Republic of Singapore.
| | - Tra Nguyen Huong
- Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Nanyang, 637551, Republic of Singapore.
| | - Puisan Wong
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore, 117510, Republic of Singapore.
| | - Liat Hui Loo
- Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Nanyang, 637551, Republic of Singapore.
| | - Boon Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore, 117510, Republic of Singapore.
| | - Fiona Fenwick
- School of Clinical Medical Sciences, The University of Newcastle, Newcastle upon Tyne, NE24HH, UK.
| | - Geoffrey L Toms
- School of Clinical Medical Sciences, The University of Newcastle, Newcastle upon Tyne, NE24HH, UK.
| | - Richard J Sugrue
- Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Nanyang, 637551, Republic of Singapore.
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Loo LH, Jumat MR, Fu Y, Ayi TC, Wong PS, Tee NWS, Tan BH, Sugrue RJ. Evidence for the interaction of the human metapneumovirus G and F proteins during virus-like particle formation. Virol J 2013; 10:294. [PMID: 24067107 PMCID: PMC3849350 DOI: 10.1186/1743-422x-10-294] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 08/26/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Human metapneumovirus (HMPV) is now a major cause of lower respiratory infection in children. Although primary isolation of HMPV has been achieved in several different cell lines, the low level of virus replication and the subsequent recovery of low levels of infectious HMPV have hampered biochemical studies on the virus. These experimental methodologies usually require higher levels of biological material that can be achieved following HMPV infection. In this study we demonstrate that expression of the HMPV F, G and M proteins in mammalian cells leads to HMPV virus-like particles (VLP) formation. This experimental strategy will serve as a model system to allow the process of HMPV virus assembly to be examined. METHODS The HMPV F, G and M proteins were expressed in mammalian cell lines. Protein cross-linking studies, sucrose gradient centrifugation and in situ imaging was used to examine interactions between the virus proteins. VLP formation was examined using sucrose density gradient centrifugation and electron microscopy analysis. RESULTS Analysis of cells co-expressing the F, G and M proteins demonstrated that these proteins interacted. Furthermore, in cells co-expression the three HMPV proteins the formation VLPs was observed. Image analysis revealed the VLPs had a similar morphology to the filamentous virus morphology that we observed on HMPV-infected cells. The capacity of each protein to initiate VLP formation was examined using a VLP formation assay. Individual expression of each virus protein showed that the G protein was able to form VLPs in the absence of the other virus proteins. Furthermore, co-expression of the G protein with either the M or F proteins facilitated their incorporation into the VLP fraction. CONCLUSION Co-expression of the F, G and M proteins leads to the formation of VLPs, and that incorporation of the F and M proteins into VLPs is facilitated by their interaction with the G protein. Our data suggests that the G protein plays a central role in VLP formation, and further suggests that the G protein may also play a role in the recruitment of the F and M proteins to sites of virus particle formation during HMPV infection.
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Affiliation(s)
- Liat Hui Loo
- Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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Ravi LI, Li L, Sutejo R, Chen H, Wong PS, Tan BH, Sugrue RJ. A systems-based approach to analyse the host response in murine lung macrophages challenged with respiratory syncytial virus. BMC Genomics 2013; 14:190. [PMID: 23506210 PMCID: PMC3618260 DOI: 10.1186/1471-2164-14-190] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 03/08/2013] [Indexed: 12/22/2022] Open
Abstract
Background Respiratory syncytial virus (RSV) is an important cause of lower respiratory tract infection in young children. The degree of disease severity is determined by the host response to infection. Lung macrophages play an important early role in the host response to infection and we have used a systems-based approach to examine the host response in RSV-infected lung-derived macrophage cells. Results Lung macrophage cells could be efficiently infected (>95%) with RSV in vitro, and the expression of several virus structural proteins could be detected. Although we failed to detect significant levels of virus particle production, virus antigen could be detected up until 96 hours post-infection (hpi). Microarray analysis indicated that 20,086 annotated genes were expressed in the macrophage cells, and RSV infection induced an 8.9% and 11.3% change in the global gene transcriptome at 4 hpi and 24 hpi respectively. Genes showing up-regulated expression were more numerous and exhibited higher changes in expression compared to genes showing down-regulated expression. Based on gene ontology, genes with cytokine, antiviral, cell death, and signal transduction functions showed the highest increases in expression, while signalling transduction, RNA binding and protein kinase genes showed the greatest reduction in expression levels. Analysis of the global gene expression profile using pathway enrichment analysis confirmed that up-regulated expression of pathways related to pathogen recognition, interferon signalling and antigen presentation occurred in the lung macrophage cells challenged with RSV. Conclusion Our data provided a comprehensive analysis of RSV-induced gene expression changes in lung macrophages. Although virus gene expression was detected, our data was consistent with an abortive infection and this correlated with the activation of several antivirus signalling pathways such as interferon type I signalling and cell death signalling. RSV infection induced a relatively large increase in pro-inflammatory cytokine expression, however the maintenance of this pro-inflammatory response was not dependent on the production of infectious virus particles. The sustained pro-inflammatory response even in the absence of a productive infection suggests that drugs that control the pro-inflammatory response may be useful in the treatment of patients with severe RSV infection.
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Affiliation(s)
- Laxmi Iyer Ravi
- Division of Molecular Genetics and Cell Biology, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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Gao X, Sugrue RJ, Tan BH, Tang K. Screening of influenza mutations using base-specific cleavage and MALDI mass spectrometry. Clin Chim Acta 2012; 420:89-93. [PMID: 23078853 DOI: 10.1016/j.cca.2012.10.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 10/09/2012] [Indexed: 11/15/2022]
Abstract
BACKGROUND The hemagglutinin (HA) and neuraminidase (NA) genes encode surface glycoproteins of influenza virus. These two proteins are involved in pathogenicity and are the primary targets of the immune system. Mutations in the HA and NA genes can result in antigenic drift in an influenza viral strain. A comparative sequencing method using MALDI MS combined with base-specific cleavage has been applied for the surveillance of these viral mutations. This approach shows advantages in high throughput and efficiency than the traditional direct sequencing methods in targeted sequence analysis. METHODS Base-specific cleavage assay with RNAse A was combined with MALDI-MS for the analysis of the HA and NA genes of 2 influenza viral strains. The mass peak patterns from the spectra were compared with the in silico digest result of reference gene sequences from the database to achieve comparative sequencing and screening of novel mutations. RESULTS The HA and NA genes of two influenza lab strains were comparatively sequenced using the base-specific cleavage and MALDI-MS approach. Mutations could be exactly identified if more than one observation (mass peak changes) were detected in the spectrum. Mutations with only one observation could be located in a small area for further validation. CONCLUSIONS We showed a proof of a principle that base-specific combined with MALDI-MS comparative sequencing approach can be utilized for targeted sequence analysis and potentially rapid and cost effective screening of emerging viral mutations.
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Affiliation(s)
- Xiang Gao
- Division of Chemical Biology and Biotechnology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
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Sutejo R, Yeo DS, Myaing MZ, Hui C, Xia J, Ko D, Cheung PCF, Tan BH, Sugrue RJ. Activation of type I and III interferon signalling pathways occurs in lung epithelial cells infected with low pathogenic avian influenza viruses. PLoS One 2012; 7:e33732. [PMID: 22470468 PMCID: PMC3312346 DOI: 10.1371/journal.pone.0033732] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 02/16/2012] [Indexed: 12/24/2022] Open
Abstract
The host response to the low pathogenic avian influenza (LPAI) H5N2, H5N3 and H9N2 viruses were examined in A549, MDCK, and CEF cells using a systems-based approach. The H5N2 and H5N3 viruses replicated efficiently in A549 and MDCK cells, while the H9N2 virus replicated least efficiently in these cell types. However, all LPAI viruses exhibited similar and higher replication efficiencies in CEF cells. A comparison of the host responses of these viruses and the H1N1/WSN virus and low passage pH1N1 clinical isolates was performed in A549 cells. The H9N2 and H5N2 virus subtypes exhibited a robust induction of Type I and Type III interferon (IFN) expression, sustained STAT1 activation from between 3 and 6 hpi, which correlated with large increases in IFN-stimulated gene (ISG) expression by 10 hpi. In contrast, cells infected with the pH1N1 or H1N1/WSN virus showed only small increases in Type III IFN signalling, low levels of ISG expression, and down-regulated expression of the IFN type I receptor. JNK activation and increased expression of the pro-apoptotic XAF1 protein was observed in A549 cells infected with all viruses except the H1N1/WSN virus, while MAPK p38 activation was only observed in cells infected with the pH1N1 and the H5 virus subtypes. No IFN expression and low ISG expression levels were generally observed in CEF cells infected with either AIV, while increased IFN and ISG expression was observed in response to the H1N1/WSN infection. These data suggest differences in the replication characteristics and antivirus signalling responses both among the different LPAI viruses, and between these viruses and the H1N1 viruses examined. These virus-specific differences in host cell signalling highlight the importance of examining the host response to avian influenza viruses that have not been extensively adapted to mammalian tissue culture.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Animals
- Apoptosis Regulatory Proteins
- Birds
- Cell Line, Tumor
- Epithelial Cells/metabolism
- Humans
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/growth & development
- Influenza A Virus, H5N2 Subtype/genetics
- Influenza A Virus, H5N2 Subtype/growth & development
- Influenza A Virus, H9N2 Subtype/genetics
- Influenza A Virus, H9N2 Subtype/growth & development
- Influenza in Birds/genetics
- Influenza in Birds/virology
- Influenza, Human/enzymology
- Influenza, Human/pathology
- Interferon Type I/genetics
- Interferon Type I/metabolism
- Interferons
- Interleukins/genetics
- Interleukins/metabolism
- Intracellular Signaling Peptides and Proteins/metabolism
- JNK Mitogen-Activated Protein Kinases/metabolism
- Neoplasm Proteins/metabolism
- RNA, Viral/metabolism
- Receptor, Interferon alpha-beta/metabolism
- STAT1 Transcription Factor/metabolism
- Signal Transduction
- Virus Replication
- p38 Mitogen-Activated Protein Kinases/metabolism
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Affiliation(s)
- Richard Sutejo
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Dawn S. Yeo
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- Detection and Diagnostics Laboratory, DSO National Laboratories, Singapore, Singapore
| | - Myint Zu Myaing
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Chen Hui
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Jiajia Xia
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Debbie Ko
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Peter C. F. Cheung
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Boon-Huan Tan
- Detection and Diagnostics Laboratory, DSO National Laboratories, Singapore, Singapore
| | - Richard J. Sugrue
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
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Zheng J, Sugrue RJ, Tang K. Mass spectrometry based proteomic studies on viruses and hosts--a review. Anal Chim Acta 2011; 702:149-59. [PMID: 21839192 PMCID: PMC7094357 DOI: 10.1016/j.aca.2011.06.045] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/20/2011] [Accepted: 06/21/2011] [Indexed: 02/07/2023]
Abstract
In terms of proteomic research in the 21st century, the realm of virology is still regarded as an enormous challenge mainly brought by three aspects, namely, studying on the complex proteome of the virus with unexpected variations, developing more accurate analytical techniques as well as understanding viral pathogenesis and virus-host interaction dynamics. Progresses in these areas will be helpful to vaccine design and antiviral drugs discovery. Mass spectrometry based proteomics have shown exceptional display of capabilities, not only precisely identifying viral and cellular proteins that are functionally, structurally, and dynamically changed upon virus infection, but also enabling us to detect important pathway proteins. In addition, many isolation and purification techniques and quantitative strategies in conjunction with MS can significantly improve the sensitivity of mass spectrometry for detecting low-abundant proteins, replenishing the stock of virus proteome and enlarging the protein-protein interaction maps. Nevertheless, only a small proportion of the infectious viruses in both of animal and plant have been studied using this approach. As more virus and host genomes are being sequenced, MS-based proteomics is becoming an indispensable tool for virology. In this paper, we provide a brief review of the current technologies and their applications in studying selected viruses and hosts.
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Affiliation(s)
- Jie Zheng
- Division of Chemical Biology and Biotechnology, School of Biological Science, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Richard J. Sugrue
- Division of Molecular and Cell Biology, School of Biological Science, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Kai Tang
- Division of Chemical Biology and Biotechnology, School of Biological Science, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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Kumaria R, Iyer LR, Hibberd ML, Simões EAF, Sugrue RJ. Whole genome characterization of non-tissue culture adapted HRSV strains in severely infected children. Virol J 2011; 8:372. [PMID: 21794174 PMCID: PMC3166936 DOI: 10.1186/1743-422x-8-372] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 07/28/2011] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Human respiratory syncytial virus (HRSV) is the most important virus causing lower respiratory infection in young children. The complete genetic characterization of RSV clinical strains is a prerequisite for understanding HRSV infection in the clinical context. Current information about the genetic structure of the HRSV genome has largely been obtained using tissue culture adapted viruses. During tissue culture adaptation genetic changes can be introduced into the virus genome, which may obscure subtle variations in the genetic structure of different RSV strains. METHODS In this study we describe a novel Sanger sequencing strategy which allowed the complete genetic characterisation of 14 clinical HRSV strains. The viruses were sequenced directly in the nasal washes of severely hospitalized children, and without prior passage of the viruses in tissue culture. RESULTS The analysis of nucleotide sequences suggested that vRNA length is a variable factor among primary strains, while the phylogenetic analysis suggests selective pressure for change. The G gene showed the greatest sequence variation (2-6.4%), while small hydrophobic protein and matrix genes were completely conserved across all clinical strains studied. A number of sequence changes in the F, L, M2-1 and M2-2 genes were observed that have not been described in laboratory isolates. The gene junction regions showed more sequence variability, and in particular the intergenic regions showed a highest level of sequence variation. Although the clinical strains grew slower than the HRSVA2 virus isolate in tissue culture, the HRSVA2 isolate and clinical strains formed similar virus structures such as virus filaments and inclusion bodies in infected cells; supporting the clinical relevance of these virus structures. CONCLUSION This is the first report to describe the complete genetic characterization of HRSV clinical strains that have been sequenced directly from clinical material. The presence of novel substitutions and deletions in the vRNA of clinical strains emphasize the importance of genomic characterization of non-tissue culture adapted primary strains.
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Affiliation(s)
- Rajni Kumaria
- Singapore-MIT Alliance for Research and Technology, Centre for Life Sciences, #05-06M, 28 Medical Drive, 117456, Singapore
| | - Laxmi Ravi Iyer
- Division of Molecular and Cell biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 639798, Singapore
| | - Martin L Hibberd
- Singapore-MIT Alliance for Research and Technology, Centre for Life Sciences, #05-06M, 28 Medical Drive, 117456, Singapore
- Genome Institute of Singapore, #02-01, Genome Building, 60 Biopolis Street, 138672, Singapore
| | - Eric AF Simões
- University of Colorado, Denver and The Division of Infectious Diseases, The Children's Hospital, 13123 East 16th Avenue, Aurora, CO 80045, USA
| | - Richard J Sugrue
- Singapore-MIT Alliance for Research and Technology, Centre for Life Sciences, #05-06M, 28 Medical Drive, 117456, Singapore
- Division of Molecular and Cell biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 639798, Singapore
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Radhakrishnan A, Yeo D, Brown G, Myaing MZ, Iyer LR, Fleck R, Tan BH, Aitken J, Sanmun D, Tang K, Yarwood A, Brink J, Sugrue RJ. Protein analysis of purified respiratory syncytial virus particles reveals an important role for heat shock protein 90 in virus particle assembly. Mol Cell Proteomics 2010; 9:1829-48. [PMID: 20530633 DOI: 10.1074/mcp.m110.001651] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
In this study, we used imaging and proteomics to identify the presence of virus-associated cellular proteins that may play a role in respiratory syncytial virus (RSV) maturation. Fluorescence microscopy of virus-infected cells revealed the presence of virus-induced cytoplasmic inclusion bodies and mature virus particles, the latter appearing as virus filaments. In situ electron tomography suggested that the virus filaments were complex structures that were able to package multiple copies of the virus genome. The virus particles were purified, and the protein content was analyzed by one-dimensional nano-LC MS/MS. In addition to all the major virus structural proteins, 25 cellular proteins were also detected, including proteins associated with the cortical actin network, energy pathways, and heat shock proteins (HSP70, HSC70, and HSP90). Representative actin-associated proteins, HSC70, and HSP90 were selected for further biological validation. The presence of beta-actin, filamin-1, cofilin-1, HSC70, and HSP90 in the virus preparation was confirmed by immunoblotting using relevant antibodies. Immunofluorescence microscopy of infected cells stained with antibodies against relevant virus and cellular proteins confirmed the presence of these cellular proteins in the virus filaments and inclusion bodies. The relevance of HSP90 to virus infection was examined using the specific inhibitors 17-N-Allylamino-17-demethoxygeldanamycin. Although virus protein expression was largely unaffected by these drugs, we noted that the formation of virus particles was inhibited, and virus transmission was impaired, suggesting an important role for HSP90 in virus maturation. This study highlights the utility of proteomics in facilitating both our understanding of the role that cellular proteins play during RSV maturation and, by extrapolation, the identification of new potential targets for antiviral therapy.
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Affiliation(s)
- Anuradha Radhakrishnan
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
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26
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Tun T, Sai-Kit AL, Sugrue RJ. In-House BSL-3 User Training: Development and Implementation of Programme at the Nanyang Technological University in Singapore. Appl Biosaf 2009. [DOI: 10.1177/153567600901400207] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Tin Tun
- Nanyang Technological University, Singapore
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27
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Yeo DSY, Chan R, Brown G, Ying L, Sutejo R, Aitken J, Tan BH, Wenk MR, Sugrue RJ. Evidence that selective changes in the lipid composition of raft-membranes occur during respiratory syncytial virus infection. Virology 2009; 386:168-82. [DOI: 10.1016/j.virol.2008.12.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 11/19/2008] [Accepted: 12/01/2008] [Indexed: 11/27/2022]
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28
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Abstract
Until relatively recently there had been episodes when children had been admitted into hospitals with symptoms that were similar to those expected for human respiratory syncytial virus (HRSV), but the available diagnostic procedures failed to detect the presence of HRSV, and the causative disease agent remained unidentified. Dutch scientists examined nasopharyngeal aspirates from similar patients in Holland using advanced molecular biology and imaging techniques. The conclusions of this study were published in 2001, revealing that a previously unidentified paramyxovirus was responsible for these infections. This agent was grouped within the subfamily Pneumovirinae, genus metapneumovirus, and given the name human metapneumovirus (HMPV) to distinguish it from other members of the genus Metapneumovirus that are of avian origin. Although HMPV is associated with upper respiratory tract infection, it is now recognized as a major cause of lower respiratory infection (LRTI) in children in a variety of different geographical regions. Furthermore, retrospective studies have detected the presence of HMPV in archived clinical material dating from the 1950s, suggesting that this was not a new virus, but it had remained undetected for several decades until its ‘emergence’ in 2001. This review will discuss the increasing global importance of HMPV as a cause of LRTI among young children.
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Affiliation(s)
- Richard J Sugrue
- Division of Molecular & Cell Biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
| | - Boon-Huan Tan
- Detection & Diagnostics Laboratory, Defence Medical & Environmental Research Institute, DSO National Laboratories, 27 Medical Drive, #13-00, 117510, Singapore
| | - Liat-Hui Loo
- Division of Molecular & Cell Biology, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
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29
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Sugrue RJ, Tan BH, Yeo DSY, Sutejo R. Antiviral Drugs for the Control of Pandemic Influenza Virus. Ann Acad Med Singap 2008. [DOI: 10.47102/annals-acadmedsg.v37n6p518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In the advent of an influenza virus pandemic it is likely that the administration of antiviral drugs will be an important first line of defence against the virus. The drugs currently in use are effective against seasonal influenza virus infection, and some cases have been used in the treatment of patients infected with the avian H5N1 influenza virus. However, it is becoming clear that the emergence of drug-resistant viruses will potentially be a major problem in the future efforts to control influenza virus infection. In addition, during a new pandemic, sufficient quantities of these agents will need to be distributed to many different parts of the world, possibly at short notice. In this review we provide an overview of some of the drugs that are currently available for the treatment and prevention of influenza virus infection. In addition, basic research on influenza virus is providing a much better understanding of the biology of the virus, which is offering the possibility of new anti-influenza virus drugs. We therefore also review some new antiviral strategies that are being reported in the scientific literature, which may form the basis of the next generation of antiviral strategies during a future influenza virus pandemic.
Key words: Antiviral, Amantadine, Pandemic influenza virus, Oseltamivir, siRNA
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30
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Sugrue RJ, Tan BH, Yeo DSY, Sutejo R. Antiviral drugs for the control of pandemic influenza virus. Ann Acad Med Singap 2008; 37:518-524. [PMID: 18618065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In the advent of an influenza virus pandemic it is likely that the administration of antiviral drugs will be an important first line of defence against the virus. The drugs currently in use are effective against seasonal influenza virus infection, and some cases have been used in the treatment of patients infected with the avian H5N1 influenza virus. However, it is becoming clear that the emergence of drug-resistant viruses will potentially be a major problem in the future efforts to control influenza virus infection. In addition, during a new pandemic, sufficient quantities of these agents will need to be distributed to many different parts of the world, possibly at short notice. In this review we provide an overview of some of the drugs that are currently available for the treatment and prevention of influenza virus infection. In addition, basic research on influenza virus is providing a much better understanding of the biology of the virus, which is offering the possibility of new anti-influenza virus drugs. We therefore also review some new antiviral strategies that are being reported in the scientific literature, which may form the basis of the next generation of antiviral strategies during a future influenza virus pandemic.
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Affiliation(s)
- Richard J Sugrue
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore.
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31
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Abstract
Four hundred specimens were collected from pediatric patients hospitalized in Singapore; 21 of these specimens tested positive for human metapneumovirus (HMPV), with the A2 genotype predominating. A 5% infection rate was estimated, suggesting that HMPV is a significant cause of morbidity among the pediatric population of Singapore.
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Affiliation(s)
- Liat Hui Loo
- Nanyang Technological University, Kandang Kerbau Women's and Children's Hospital, Singapore, Singapore
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32
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Low KW, Tan T, Ng K, Tan BH, Sugrue RJ. The RSV F and G glycoproteins interact to form a complex on the surface of infected cells. Biochem Biophys Res Commun 2007; 366:308-13. [PMID: 18036342 DOI: 10.1016/j.bbrc.2007.11.042] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Accepted: 11/13/2007] [Indexed: 11/28/2022]
Abstract
In this study, the interaction between the respiratory syncytial virus (RSV) fusion (F) protein, attachment (G) protein, and small hydrophobic (SH) proteins was examined. Immunoprecipitation analysis suggested that the F and G proteins exist as a protein complex on the surface of RSV-infected cells, and this conclusion was supported by ultracentrifugation analysis that demonstrated co-migration of surface-expressed F and G proteins. Although our analysis provided evidence for an interaction between the G and SH proteins, no evidence was obtained for a single protein complex involving all three of the virus proteins. These data suggest the existence of multiple virus glycoprotein complexes within the RSV envelope. Although the stimulus that drives RSV-mediated membrane fusion is unknown, the association between the G and F proteins suggest an indirect role for the G protein in this process.
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Affiliation(s)
- Kit-Wei Low
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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33
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Jeffree CE, Brown G, Aitken J, Su-Yin DY, Tan BH, Sugrue RJ. Ultrastructural analysis of the interaction between F-actin and respiratory syncytial virus during virus assembly. Virology 2007; 369:309-23. [PMID: 17825340 DOI: 10.1016/j.virol.2007.08.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2007] [Revised: 06/06/2007] [Accepted: 08/02/2007] [Indexed: 11/17/2022]
Abstract
During respiratory syncytial virus (RSV) infection there is a close physical interaction between the filamentous actin (F-actin) and the virus, involving both inclusion bodies and the virus filaments. This interaction appears to occur relatively early in the replication cycle, and can be detected from 8 h post-infection. Furthermore, during virus assembly we obtained evidence for the participation of an F-actin-associated signalling pathway involving phosphatidyl-3-kinase (PI3K). Treatment with the PI3K inhibitor LY294002 prevented the formation of virus filaments, although no effect was observed either on virus protein expression, or on trafficking of the virus glycoproteins to the cell surface. Inhibition of the activity of Rac GTPase, a down-stream effector of PI3K, by treatment with the Rac-specific inhibitor NSC23766 gave similar results. These data suggest that an intimate interaction occurs between actin and RSV, and that actin-associated signalling pathway, involving PI3K and Rac GTPase, may play an important role during virus assembly.
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Affiliation(s)
- Chris E Jeffree
- School of Biological Sciences, Daniel Rutherford Building, King's Buildings, Mayfield Road, University of Edinburgh Edinburgh, EH9 3JH, UK
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34
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Abstract
The respiratory syncytial virus (RSV) fusion (F) protein is synthesized as an inactive precursor (F0), which subsequently undergoes post-translational cleavage to give the disulphide bond-linked F1 and F2 subunits. The methodology detailing the use of two-dimensional electrophoresis, endoglycosidases, and alpha-mannosidase inhibitors, as applied to investigating F protein glycan maturation, is given. Examples are used to show how this methodology was used to provide evidence for glycan heterogeneity within the mature F protein.
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35
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Abstract
Sequences derived from the respiratory syncytial virus (RSV) fusion (F) protein were expressed in insect cells as recombinant glutathione-S-transferase (GST)-tagged proteins. The sequence covering the F2 subunit (GST-F2), and a truncated form of the F protein in which the transmembrane domain was removed (GST-F2/F1), were cloned into the baculovirus pAcSecG2T secretory vector. These virus sequences also had the endogenous virus signal sequence removed and replaced with a signal sequence derived from the baculovirus gp67 glycoprotein, which was present in pAcSecG2T. The recombinant RSV glycoproteins were successfully detected in expressing cells by immunofluorescence assay and in the tissue culture medium by western blot analysis. The secreted recombinant GST-F2/F1 protein was further analysed using glycosidases. Our results showed that the GST-F2/F1 protein were sensitive to peptide:N-glycosidase F (PNGase F) treatment, but not to Endoglycosidase H (EndoH) treatment. This indicates that the secreted recombinant proteins were modified by the addition of mature N-linked glycan chains.
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Affiliation(s)
- Boon-Huan Tan
- Virology Group Defence Medical and Environmental Research Institute, DSO National Laboratories, Singapore
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36
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Abstract
Although many virus proteins are glycosylated, the pattern of glycosylation that is exhibited can be highly variable, and it is largely dependent on how a specific virus protein is processed by the host cell during infection. However, irrespective of their glycosylation pattern, many virus glycoproteins have been found to play essential roles during the virus replication cycle. Consequently, it is therefore becoming necessary to understand the effect that the attached glycans have on the function of different virus glycoproteins. As a first step towards understanding how glycans can influence the activity of a specific glycoprotein, we need to both establish the mechanism of glycosylation, and determine the nature of the attached glycans. This chapter provides an overview of some of the different ways in which viruses proteins are glycosylated, and highlights some of the generic techniques by which they can be examined.
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37
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Abstract
The respiratory syncytial virus fusion (F) protein is initially expressed as a single polypeptide chain (F0). The F0 subsequently undergoes posttranslational cleavage-by-cell protease activity to produce the F1 and F2 subunits. Each of the two subunits within the mature F protein is modified by the addition of N-linked glycans. The individual N-linked glycans on the F protein were selectively removed by using site-directed mutagenesis to mutate the individual glycan-acceptor sites. In this way the role of these individual glycans in targeting of the F protein to the cell surface, and on the ability of the F protein to induce membrane fusion, was examined.
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Affiliation(s)
- Ping Li
- MRC Virology Unit, Institute of Virology, Glasgow, UK
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38
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Abstract
The full-length and truncated forms of recombinant envelope (E) glycoprotein from Dengue virus type 1, Singapore strain S275/90 were expressed in the yeast, Pichia pastoris, using a secretory vector. A truncated form of the E protein in which the transmembrane domain was deleted was secreted successfully into the culture medium. The E protein was also co-expressed with C and prM proteins using a non-secretory yeast vector. The co-expression of C, prM and E proteins resulted in the spontaneous formation of virus-like particles (VLPs), which were confirmed by sucrose gradient analysis and transmission electron microscopy. Furthermore, the VLPs were used to immunise rabbits, and shown to be immunogenic by immunofluorescence staining of dengue virus-infected Vero cells. The yeast-expressed E protein was treated with PNGase F, which showed that although the protein was modified by the addition of N-linked glycans, the recombinant expressed E protein was not hyperglycosylated.
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Affiliation(s)
- Boon-Huan Tan
- Virology Group Defence Medical and Environmental Research Institute, DSO National Laboratories, Singapore
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39
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Abstract
At the start of the 21st century, respiratory syncytial virus (RSV) remains a serious global health concern. Although RSV has traditionally been acknowledged as a leading cause of morbidity and mortality in the paediatric population, the elderly and people with suppressed immune systems are now also recognised as being at risk from serious RSV infection. This problem is currently exacerbated by the lack of an effective vaccine to prevent RSV infection. Although the virus proteins play a variety of roles during the virus replication cycle, in many cases these tasks are performed via specific interactions with host-cell factors, including proteins, carbohydrates and lipids. The way in which RSV interacts with the host cell is currently being examined using a battery of different techniques, which encompass several scientific disciplines. This is providing new and interesting insights into how RSV interacts with the host cell at the molecular level, which in turn is offering the hope of new strategies to prevent RSV infection.
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40
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McDonald TP, Jeffree CE, Li P, Rixon HWM, Brown G, Aitken JD, MacLellan K, Sugrue RJ. Evidence that maturation of the N-linked glycans of the respiratory syncytial virus (RSV) glycoproteins is required for virus-mediated cell fusion: The effect of alpha-mannosidase inhibitors on RSV infectivity. Virology 2006; 350:289-301. [PMID: 16513154 DOI: 10.1016/j.virol.2006.01.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 01/06/2006] [Accepted: 01/19/2006] [Indexed: 10/25/2022]
Abstract
Glycan heterogeneity of the respiratory syncytial virus (RSV) fusion (F) protein was demonstrated by proteomics. The effect of maturation of the virus glycoproteins-associated glycans on virus infectivity was therefore examined using the alpha-mannosidase inhibitors deoxymannojirimycin (DMJ) and swainsonine (SW). In the presence of SW the N-linked glycans on the F protein appeared in a partially mature form, whereas in the presence of DMJ no maturation of the glycans was observed. Neither inhibitor had a significant effect on G protein processing or on the formation of progeny virus. Although the level of infectious virus and syncytia formation was not significantly affected by SW-treatment, DMJ-treatment correlated with a one hundred-fold reduction in virus infectivity. Our data suggest that glycan maturation of the RSV glycoproteins, in particular those on the F protein, is an important step in virus maturation and is required for virus infectivity.
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Affiliation(s)
- Terence P McDonald
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
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41
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Brown G, Rixon HWM, Steel J, McDonald TP, Pitt AR, Graham S, Sugrue RJ. Evidence for an association between heat shock protein 70 and the respiratory syncytial virus polymerase complex within lipid-raft membranes during virus infection. Virology 2005; 338:69-80. [PMID: 15936795 DOI: 10.1016/j.virol.2005.05.004] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Revised: 03/15/2005] [Accepted: 05/03/2005] [Indexed: 11/24/2022]
Abstract
In this report, the interaction between respiratory syncytial virus (RSV) and heat shock protein 70 (HSP70) was examined. Although no significant increase in total HSP70 protein levels was observed during virus infection, analysis of the HSP70 content in lipid-raft membranes from mock- and virus-infected cells revealed an increase in the levels of raft-associated HSP70 during virus infection. Fluorescence microscopy demonstrated that this transport of HSP70 into lipid-raft membranes correlated with the appearance of HSP70 within virus-induced inclusion bodies. Furthermore, co-localisation of HSP70 with the virus N protein and the raft lipid GM1 was observed within these structures. Immunoprecipitation experiments demonstrated the ability of HSP70 to interact with the virus polymerase complex in lipid-rafts in an ATP-dependent manner. Collectively, these data suggest that RSV may induce cellular changes which allow the recruitment of specific host-cell factors, via lipid-raft membranes, to the polymerase complex.
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Affiliation(s)
- Gaie Brown
- MRC Virology Unit, Institute of Virology, University of Glasgow, Church Street, Glasgow G11 5JR, UK
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42
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McDonald TP, Pitt AR, Brown G, Rixon HWM, Sugrue RJ. Evidence that the respiratory syncytial virus polymerase complex associates with lipid rafts in virus-infected cells: a proteomic analysis. Virology 2005; 330:147-57. [PMID: 15527841 DOI: 10.1016/j.virol.2004.09.034] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Revised: 08/31/2004] [Accepted: 09/28/2004] [Indexed: 10/26/2022]
Abstract
The interaction between the respiratory syncytial virus (RSV) polymerase complex and lipid rafts was examined in HEp2 cells. Lipid-raft membranes were prepared from virus-infected cells and their protein content was analysed by Western blotting and mass spectrometry. This analysis revealed the presence of the N, P, L, M2-1 and M proteins. However, these proteins appeared to differ from one another in their association with these structures, with the M2-1 protein showing a greater partitioning into raft membranes compared to that of the N, P or M proteins. Determination of the polymerase activity profile of the gradient fractions revealed that 95% of the detectable viral enzyme activity was associated with lipid-raft membranes. Furthermore, analysis of virus-infected cells by confocal microscopy suggested an association between these proteins and the raft-lipid, GM1. Together, these results provide evidence that the RSV polymerase complex is able to associate with lipid rafts in virus-infected cells.
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43
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Rixon HWM, Brown G, Murray JT, Sugrue RJ. The respiratory syncytial virus small hydrophobic protein is phosphorylated via a mitogen-activated protein kinase p38-dependent tyrosine kinase activity during virus infection. J Gen Virol 2005; 86:375-384. [PMID: 15659757 DOI: 10.1099/vir.0.80563-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The phosphorylation status of the small hydrophobic (SH) protein of respiratory syncytial virus (RSV) was examined in virus-infected Vero cells. The SH protein was isolated from [35S]methionine- and [33P]orthophosphate-labelled RSV-infected cells and analysed by SDS-PAGE. In each case, a protein product of the expected size for the SH protein was observed. Phosphoamino acid analysis and reactivity with the phosphotyrosine specific antibody PY20 showed that the SH protein was modified by tyrosine phosphorylation. The role of tyrosine kinase activity in SH protein phosphorylation was confirmed by the use of genistein, a broad-spectrum tyrosine kinase inhibitor, to inhibit SH protein phosphorylation. Further analysis showed that the different glycosylated forms of the SH protein were phosphorylated, as was the oligomeric form of the protein. Phosphorylation of the SH protein was specifically inhibited by the mitogen-activated protein kinase (MAPK) p38 inhibitor SB203580, suggesting that SH protein phosphorylation occurs via a MAPK p38-dependent pathway. Analysis of virus-infected cells using fluorescence microscopy showed that, although the SH protein was distributed throughout the cytoplasm, it appeared to accumulate, at low levels, in the endoplasmic reticulum/Golgi complex, confirming recent observations. However, in the presence of SB203580, an increased accumulation of the SH protein in the Golgi complex was observed, although other virus structures, such as virus filaments and inclusion bodies, remained largely unaffected. These results showed that during RSV infection, the SH protein is modified by an MAPK p38-dependent tyrosine kinase activity and that this modification influences its cellular distribution.
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Affiliation(s)
- H W McL Rixon
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - G Brown
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - J T Murray
- MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dundee DD1 5EH, UK
| | - R J Sugrue
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
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Brown G, Jeffree CE, McDonald T, Rixon HWM, Aitken JD, Sugrue RJ. Analysis of the interaction between respiratory syncytial virus and lipid-rafts in Hep2 cells during infection. Virology 2004; 327:175-85. [PMID: 15351205 DOI: 10.1016/j.virol.2004.06.038] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Accepted: 06/04/2004] [Indexed: 10/26/2022]
Abstract
The assembly of respiratory syncytial virus (RSV) in lipid-rafts was examined in Hep2 cells. Confocal and electron microscopy showed that during RSV assembly, the cellular distribution of the complement regulatory proteins, decay accelerating factor (CD55) and CD59, changes and high levels of these cellular proteins are incorporated into mature virus filaments. The detergent-solubility properties of CD55, CD59, and the RSV fusion (F) protein were found to be consistent with each protein being located predominantly within lipid-raft structures. The levels of these proteins in cell-released virus were examined by immunoelectronmicroscopy and found to account for between 5% and 15% of the virus attachment (G) glycoprotein levels. Collectively, our findings suggest that an intimate association exists between RSV and lipid-raft membranes and that significant levels of these host-derived raft proteins, such as those regulating complement activation, are subsequently incorporated into the envelope of mature virus particles.
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Affiliation(s)
- Gaie Brown
- MRC Virology Unit, Institute of Virology, Glasgow G11 5JR, UK
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Rixon HWM, Brown G, Aitken J, McDonald T, Graham S, Sugrue RJ. The small hydrophobic (SH) protein accumulates within lipid-raft structures of the Golgi complex during respiratory syncytial virus infection. J Gen Virol 2004; 85:1153-1165. [PMID: 15105532 DOI: 10.1099/vir.0.19769-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cellular distribution of the small hydrophobic (SH) protein in respiratory syncytial virus (RSV)-infected cells was examined. Although the SH protein was distributed throughout the cytoplasm, it appeared to accumulate in the Golgi complex within membrane structures that were enriched in the raft lipid, GM1. The ability of the SH protein to interact with lipid-raft membranes was further confirmed by examining its detergent-solubility properties in Triton X-100 at 4 degrees C. This analysis showed that a large proportion of the SH protein exhibited detergent-solubility characteristics that were consistent with an association with lipid-raft membranes. Analysis of virus-infected cells by immuno-transmission electron microscopy revealed SH protein clusters on the cell surface, but only very low levels of the protein appeared to be associated with mature virus filaments and inclusion bodies. These data suggest that during virus infection, the compartments in the secretory pathway, such as the endoplasmic reticulum (ER) and Golgi complex, are major sites of accumulation of the SH protein. Furthermore, although a significant amount of this protein interacts with lipid-raft membranes within the Golgi complex, its presence within mature virus filaments is minimal.
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Affiliation(s)
- Helen W McL Rixon
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - Gaie Brown
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - James Aitken
- Division of Virology, University of Glasgow, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - Terence McDonald
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - Susan Graham
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - Richard J Sugrue
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK
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Jeffree CE, Rixon HWM, Brown G, Aitken J, Sugrue RJ. Distribution of the attachment (G) glycoprotein and GM1 within the envelope of mature respiratory syncytial virus filaments revealed using field emission scanning electron microscopy. Virology 2003; 306:254-67. [PMID: 12642099 DOI: 10.1016/s0042-6822(02)00016-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Field emission scanning electron microscopy (FE SEM) was used to visualize the distribution of virus-associated components, the virus-attachment (G) protein, and the host-cell-derived lipid, GM1, in respiratory syncytial virus (RSV) filaments. RSV-infected cells were labeled in situ with a G protein antibody (MAb30) whose presence was detected using a second antibody conjugated to colloidal gold. No bound MAb30 was detected in mock-infected cells, whereas significant quantities bound to viral filaments revealing G protein clusters throughout the filaments. GM1 was detected using cholera toxin B subunit conjugated to colloidal gold. Mock-infected cells revealed numerous GM1 clusters on the cell surface. In RSV-infected cells, these gold clusters were detected on the filaments in low, but significant, amounts, indicating the incorporation of GM1 within the viral envelope. This report describes the first use of FE SEM to map the distribution of specific structural components within the envelope of a Paramyxovirus.
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Affiliation(s)
- Chris E Jeffree
- Institute of Cell and Molecular Biology, Biological Sciences EM Facility, University of Edinburgh, Waddington Building, King's Building, Mayfield Road, EH9 3JN, Edinburgh, UK
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Brown G, Rixon HWM, Sugrue RJ. Respiratory syncytial virus assembly occurs in GM1-rich regions of the host-cell membrane and alters the cellular distribution of tyrosine phosphorylated caveolin-1. J Gen Virol 2002; 83:1841-1850. [PMID: 12124448 DOI: 10.1099/0022-1317-83-8-1841] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We have previously shown that respiratory syncytial virus (RSV) assembly occurs within regions of the host-cell surface membrane that are enriched in the protein caveolin-1 (cav-1). In this report, we have employed immunofluorescence microscopy to further examine the RSV assembly process. Our results show that RSV matures at regions of the cell surface that, in addition to cav-1, are enriched in the lipid-raft ganglioside GM1. Furthermore, a comparison of mock-infected and RSV-infected cells by confocal microscopy revealed a significant change in the cellular distribution of phosphocaveolin-1 (pcav-1). In mock-infected cells, pcav-1 was located at regions of the cell that interact with the extracellular matrix, termed focal adhesions (FA). In contrast, RSV-infected cells showed both a decrease in the levels of pcav-1 associated with FA and the appearance of pcav-1-containing cytoplasmic vesicles, the latter being absent in mock-infected cells. These cytoplasmic vesicles were clearly visible between 9 and 18 h post-infection and coincided with the formation of RSV filaments, although we did not observe a direct association of pcav-1 with mature virus. In addition, we noted a strong colocalization between pcav-1 and growth hormone receptor binding protein-7 (Grb7), within these cytoplasmic vesicles, which was not observed in mock-infected cells. Collectively, these findings show that the RSV assembly process occurs within specialized lipid-raft structures on the host-cell plasma membrane, induces the cellular redistribution of pcav-1 and results in the formation of cytoplasmic vesicles that contain both pcav-1 and Grb7.
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Affiliation(s)
- Gaie Brown
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK1
| | - Helen W McL Rixon
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK1
| | - Richard J Sugrue
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK1
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Brown G, Aitken J, Rixon HWM, Sugrue RJ. Caveolin-1 is incorporated into mature respiratory syncytial virus particles during virus assembly on the surface of virus-infected cells. J Gen Virol 2002; 83:611-621. [PMID: 11842256 DOI: 10.1099/0022-1317-83-3-611] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have employed immunofluorescence microscopy and transmission electron microscopy to examine the assembly and maturation of respiratory syncytial virus (RSV) in the Vero cell line C1008. RSV matures at the apical cell surface in a filamentous form that extends from the plasma membrane. We observed that inclusion bodies containing viral ribonucleoprotein (RNP) cores predominantly appeared immediately below the plasma membrane, from where RSV filaments form during maturation at the cell surface. A comparison of mock-infected and RSV-infected cells by confocal microscopy revealed a significant change in the pattern of caveolin-1 (cav-1) fluorescence staining. Analysis by immuno-electron microscopy showed that RSV filaments formed in close proximity to cav-1 clusters at the cell surface membrane. In addition, immuno-electron microscopy showed that cav-1 was closely associated with early budding RSV. Further analysis by confocal microscopy showed that cav-1 was subsequently incorporated into the envelope of RSV filaments maturing on the host cell membrane, but was not associated with other virus structures such as the viral RNPs. Although cav-1 was incorporated into the mature virus, it was localized in clusters rather than being uniformly distributed along the length of the viral filaments. Furthermore, when RSV particles in the tissue culture medium from infected cells were examined by immuno-negative staining, the presence of cav-1 on the viral envelope was clearly demonstrated. Collectively, these findings show that cav-1 is incorporated into the envelope of mature RSV particles during egress.
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Affiliation(s)
- Gaie Brown
- MRC Virology Unit1 and Division of Virology, University of Glasgow2, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - James Aitken
- MRC Virology Unit1 and Division of Virology, University of Glasgow2, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - Helen W McL Rixon
- MRC Virology Unit1 and Division of Virology, University of Glasgow2, Institute of Virology, Church Street, Glasgow G11 5JR, UK
| | - Richard J Sugrue
- MRC Virology Unit1 and Division of Virology, University of Glasgow2, Institute of Virology, Church Street, Glasgow G11 5JR, UK
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Rixon HWM, Brown C, Brown G, Sugrue RJ. Multiple glycosylated forms of the respiratory syncytial virus fusion protein are expressed in virus-infected cells. J Gen Virol 2002; 83:61-66. [PMID: 11752701 DOI: 10.1099/0022-1317-83-1-61] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Analysis of the respiratory syncytial virus (RSV) fusion (F) protein in RSV-infected Vero cells showed the presence of a single F1 subunit and at least two different forms of the F2 subunit, designated F2a (21 kDa) and F2b (16 kDa), which were collectively referred to as [F2](a/b). Enzymatic deglycosylation of [F2](a/b) produced a single 10 kDa product suggesting that [F2](a/b) arises from differences in the glycosylation pattern of F2a and F2b. The detection of [F2](a/b) was dependent upon the post-translational cleavage of the F protein by furin, since its appearance was prevented in RSV-infected Vero cells treated with the furin inhibitor dec-RVKR-cmk. Analysis by protein cross-linking revealed that the F1 subunit interacted with [F2](a/b), via disulphide bonding, to produce equivalent F protein trimers, which were expressed on the surface of infected cells. Collectively, these data show that multiple F protein species are expressed in RSV-infected cells.
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Affiliation(s)
- Helen W McL Rixon
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK1
| | - Craig Brown
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK1
| | - Gaie Brown
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK1
| | - Richard J Sugrue
- MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, UK1
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Sugrue RJ, Brown C, Brown G, Aitken J, McL Rixon HW. Furin cleavage of the respiratory syncytial virus fusion protein is not a requirement for its transport to the surface of virus-infected cells. J Gen Virol 2001; 82:1375-1386. [PMID: 11369882 DOI: 10.1099/0022-1317-82-6-1375] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The intracellular cleavage of respiratory syncytial virus (RSV) fusion (F) protein by furin was examined. In RSV-infected LoVo cells, which express an inactive form of furin, and in RSV-infected Vero cells treated with the furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethyl ketone (dec-RVKR-cmk), the F protein was expressed as a non-cleaved 73 kDa species. In both cases the F protein was initially expressed as an endoglycosidase H (Endo H)-sensitive precursor (F0(EHs)) which was modified approximately 40 min post-synthesis by the addition of complex carbohydrates to produce the Endo H-resistant form (F0(EHr)). The size and glycosylation state of F0(EHr) were identical to a transient intermediate form of non-cleaved F protein which was detected in RSV-infected Vero cells in the absence of inhibitor. Cell surface biotinylation and surface immunofluorescence staining showed that F0(EHr) was present on the surface of RSV-infected cells. RSV filaments have been shown to be the predominant form of the budding virus that is detected during virus replication. Analysis of the RSV-infected cells using scanning electron microscopy (SEM) showed that, in the presence of dec-RVKR-cmk, virus budding was impaired, producing fewer and much smaller viral filaments than in untreated cells. A comparison of immunofluorescence and SEM data showed that F0(EHr) was routed to the surface of virus-infected cells but not located in these smaller structures. Our findings suggest that activation of the F protein is required for the efficient formation of RSV filaments.
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Affiliation(s)
- Richard J Sugrue
- MRC Virology Unit, Institute of Virology, Church Street, G11 5JR, Glasgow, UK1
| | - Craig Brown
- MRC Virology Unit, Institute of Virology, Church Street, G11 5JR, Glasgow, UK1
| | - Gaie Brown
- MRC Virology Unit, Institute of Virology, Church Street, G11 5JR, Glasgow, UK1
| | - James Aitken
- Division of Virology, University of Glasgow, Institute of Virology, Church Street, G11 5JR, Glasgow, UK2
| | - Helen W McL Rixon
- MRC Virology Unit, Institute of Virology, Church Street, G11 5JR, Glasgow, UK1
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