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Xie M. Virus-Induced Cell Fusion and Syncytia Formation. Results Probl Cell Differ 2024; 71:283-318. [PMID: 37996683 DOI: 10.1007/978-3-031-37936-9_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
Most enveloped viruses encode viral fusion proteins to penetrate host cell by membrane fusion. Interestingly, many enveloped viruses can also use viral fusion proteins to induce cell-cell fusion, both in vitro and in vivo, leading to the formation of syncytia or multinucleated giant cells (MGCs). In addition, some non-enveloped viruses encode specialized viral proteins that induce cell-cell fusion to facilitate viral spread. Overall, viruses that can induce cell-cell fusion are nearly ubiquitous in mammals. Virus cell-to-cell spread by inducing cell-cell fusion may overcome entry and post-entry blocks in target cells and allow evasion of neutralizing antibodies. However, molecular mechanisms of virus-induced cell-cell fusion remain largely unknown. Here, I summarize the current understanding of virus-induced cell fusion and syncytia formation.
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Affiliation(s)
- Maorong Xie
- Division of Infection and Immunity, UCL, London, UK.
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2
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Reuter N, Chen X, Kropff B, Peter AS, Britt WJ, Mach M, Überla K, Thomas M. SARS-CoV-2 Spike Protein Is Capable of Inducing Cell-Cell Fusions Independent from Its Receptor ACE2 and This Activity Can Be Impaired by Furin Inhibitors or a Subset of Monoclonal Antibodies. Viruses 2023; 15:1500. [PMID: 37515187 PMCID: PMC10384293 DOI: 10.3390/v15071500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/30/2023] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which was responsible for the COVID-19 pandemic, efficiently spreads cell-to-cell through mechanisms facilitated by its membrane glycoprotein spike. We established a dual split protein (DSP) assay based on the complementation of GFP and luciferase to quantify the fusogenic activity of the SARS-CoV-2 spike protein. We provide several lines of evidence that the spike protein of SARS-CoV-2, but not SARS-CoV-1, induced cell-cell fusion even in the absence of its receptor, angiotensin-converting enzyme 2 (ACE2). This poorly described ACE2-independent cell fusion activity of the spike protein was strictly dependent on the proteasomal cleavage of the spike by furin while TMPRSS2 was dispensable. Previous and current variants of concern (VOCs) differed significantly in their fusogenicity. The Delta spike was extremely potent compared to Alpha, Beta, Gamma and Kappa, while the Omicron spike was almost devoid of receptor-independent fusion activity. Nonetheless, for all analyzed variants, cell fusion was dependent on furin cleavage and could be pharmacologically inhibited with CMK. Mapping studies revealed that amino acids 652-1273 conferred the ACE2-independent fusion activity of the spike. Unexpectedly, residues proximal to the furin cleavage site were not of major relevance, whereas residue 655 critically regulated fusion. Finally, we found that the spike's fusion activity in the absence of ACE2 could be inhibited by antibodies directed against its N-terminal domain (NTD) but not by antibodies targeting its receptor-binding domain (RBD). In conclusion, our BSL-1-compatible DSP assay allowed us to screen for inhibitors or antibodies that interfere with the spike's fusogenic activity and may therefore contribute to both rational vaccine design and development of novel treatment options against SARS-CoV-2.
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Affiliation(s)
- Nina Reuter
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Xiaohan Chen
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Barbara Kropff
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Antonia Sophia Peter
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - William J Britt
- Departments of Pediatrics, Microbiology and Neurobiology, Children's Hospital of Alabama, School of Medicine, University of Alabama, Birmingham, AL 35233-1771, USA
| | - Michael Mach
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Klaus Überla
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Marco Thomas
- Virologisches Institut, Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
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Zhong L, Zhang W, Krummenacher C, Chen Y, Zheng Q, Zhao Q, Zeng MS, Xia N, Zeng YX, Xu M, Zhang X. Targeting herpesvirus entry complex and fusogen glycoproteins with prophylactic and therapeutic agents. Trends Microbiol 2023:S0966-842X(23)00077-X. [DOI: 10.1016/j.tim.2023.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/28/2023] [Accepted: 03/01/2023] [Indexed: 04/03/2023]
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Gomes AC, Baraniak IA, Lankina A, Moulder Z, Holenya P, Atkinson C, Tang G, Mahungu T, Kern F, Griffiths PD, Reeves MB. The cytomegalovirus gB/MF59 vaccine candidate induces antibodies against an antigenic domain controlling cell-to-cell spread. Nat Commun 2023; 14:1041. [PMID: 36823200 PMCID: PMC9950427 DOI: 10.1038/s41467-023-36683-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 02/13/2023] [Indexed: 02/25/2023] Open
Abstract
Vaccination against human cytomegalovirus (CMV) infection remains high priority. A recombinant form of a protein essential for CMV entry, glycoprotein B (gB), demonstrated partial protection in a clinical trial (NCT00299260) when delivered with the MF59 adjuvant. Although the antibody titre against gB correlated with protection poor neutralising responses against the 5 known antigenic domains (AD) of gB were evident. Here, we show that vaccination of CMV seronegative patients induces an antibody response against a region of gB we term AD-6. Responses to the polypeptide AD-6 are detected in >70% of vaccine recipients yet in <5% of naturally infected people. An AD-6 antibody binds to gB and to infected cells but not the virion directly. Consistent with this, the AD-6 antibody is non-neutralising but, instead, prevents cell-cell spread of CMV in vitro. The discovery of AD-6 responses has the potential to explain part of the protection mediated by gB vaccines against CMV following transplantation.
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Affiliation(s)
- A C Gomes
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - I A Baraniak
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - A Lankina
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - Z Moulder
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - P Holenya
- JPT Peptide Technologies GmbH, Berlin, Germany
| | - C Atkinson
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - G Tang
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - T Mahungu
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - F Kern
- JPT Peptide Technologies GmbH, Berlin, Germany
- Experimental Medicine, Brighton and Sussex Medical School, Brighton, United Kingdom
| | - P D Griffiths
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom
| | - M B Reeves
- Institute of Immunity & Transplantation, UCL, London, NW3 2PP, United Kingdom.
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Deng J, Wang Q, Zhang J, Ma Y, Qi Y, Liu Z, Li Y, Ruan Q, Huang Y. Identification and characterization of human cytomegalovirus-encoded circular RNAs. Front Cell Infect Microbiol 2022; 12:980974. [PMID: 36452301 PMCID: PMC9702070 DOI: 10.3389/fcimb.2022.980974] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 10/28/2022] [Indexed: 08/27/2023] Open
Abstract
Circular RNA (circRNA) exists extensively and plays essential roles in serving as microRNA (miRNA) or protein sponges and protein scaffolding in many organisms. However, the profiles and potential functions of the virus-encoded circRNA, including human cytomegalovirus (HCMV)-encoded circular RNAs, remain unclear. In the present study, HCMV-encoded circRNAs profile in human embryonic lung fibroblasts (HELF) with lytic infection was investigated using RNA deep sequencing and bioinformatics analysis. In total, 629 HCMV-encoded circRNAs were identified with various expression patterns in our results. The full sequences and alternative splicings of circUS12, circUL55, and circUL89 were verified by reverse transcriptase-PCR (RT-PCR) with divergent primers followed and Sanger sequencing. Transcription of circUL89 was validated by Northern blot. The HCMV-encoded circRNA-miRNA network analyses revealed the potential function of HCMV-encoded circRNAs during HCMV infection in HELFs. Collectively, HCMV infection deduced abundant HCMV-associated circRNAs during infection, and the HCMV-encoded circRNAs might play important roles in benefiting HCMV infection.
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Affiliation(s)
- Jingui Deng
- Department of Microorganism Laboratory, Shenyang Center for Disease Control and Prevention, Shenyang, China
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
| | - Qing Wang
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
| | - Jing Zhang
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Yanping Ma
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
| | - Ying Qi
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Zhongyang Liu
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Yibo Li
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Obstetrics and Gynecology, Central Hospital Affiliated to Shenyang Medical College, Shenyang, China
| | - Qiang Ruan
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Yujing Huang
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
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Dasari V, Beckett K, Horsefield S, Ambalathingal G, Khanna R. A bivalent CMV vaccine formulated with human compatible TLR9 agonist CpG1018 elicits potent cellular and humoral immunity in HLA expressing mice. PLoS Pathog 2022; 18:e1010403. [PMID: 35737741 PMCID: PMC9223316 DOI: 10.1371/journal.ppat.1010403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 05/26/2022] [Indexed: 11/30/2022] Open
Abstract
There is now convincing evidence that the successful development of an effective CMV vaccine will require improved formulation and adjuvant selection that is capable of inducing both humoral and cellular immune responses. Here, we have designed a novel bivalent subunit vaccine formulation based on CMV-encoded oligomeric glycoprotein B (gB) and polyepitope protein in combination with human compatible TLR9 agonist CpG1018. The polyepitope protein includes multiple minimal HLA class I-restricted CD8+ T cell epitopes from different antigens of CMV. This subunit vaccine generated durable anti-viral antibodies, CMV-specific CD4+ and CD8+ T cell responses in multiple HLA expressing mice. Antibody responses included broad TH1 isotypes (IgG2a, IgG2b and IgG3) and potently neutralized CMV infection in fibroblasts and epithelial cells. Furthermore, polyfunctional antigen-specific T cell immunity and antiviral antibody responses showed long-term memory maintenance. These observations argue that this novel vaccine strategy, if applied to humans, could facilitate the generation of robust humoral and cellular immune responses which may be more effective in preventing CMV-associated complications in various clinical settings. Human Cytomegalovirus (CMV) is a significant human pathogen. Generally, in healthy people CMV causes mild symptomatic disease, but during pregnancy CMV can transmit from mother to foetus (1 out of every 200 live births worldwide) and lead to sensorineural hearing loss, vision impairment and central nervous system damage. In transplant patients, CMV can cause serious complications leading to organ rejection and even death. Currently, there is no licensed vaccine available to prevent CMV-associated complications in pregnant women and transplant patients. Here, we have developed a novel bivalent CMV vaccine formulation consisting of recombinant CMVpoly and gB proteins in combination with human compatible adjuvant CpG1018. Preclinical immunogenicity evaluation in multiple HLA expressing mice demonstrated that bivalent CMV vaccine formulation consistently generated robust CMV-specific neutralising antibodies, CD4+ and CD8+ T cell responses. More importantly, long-term follow-up analysis showed that the CMV vaccine can induce durable CMV-specific humoral and cellular immune responses. Our results support further development of this bivalent subunit CMV vaccine to test safety, immunogenicity and efficacy in humans.
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Affiliation(s)
- Vijayendra Dasari
- QIMR Berghofer Centre for Immunotherapy and Vaccine Development and Tumour Immunology Laboratory, Department of Immunology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
- * E-mail: (VD); (RK)
| | - Kirrilee Beckett
- QIMR Berghofer Centre for Immunotherapy and Vaccine Development and Tumour Immunology Laboratory, Department of Immunology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Shane Horsefield
- QIMR Berghofer Centre for Immunotherapy and Vaccine Development and Tumour Immunology Laboratory, Department of Immunology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - George Ambalathingal
- QIMR Berghofer Centre for Immunotherapy and Vaccine Development and Tumour Immunology Laboratory, Department of Immunology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Rajiv Khanna
- QIMR Berghofer Centre for Immunotherapy and Vaccine Development and Tumour Immunology Laboratory, Department of Immunology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
- * E-mail: (VD); (RK)
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7
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Neutralizing Antibodies Limit Cell-Associated Spread of Human Cytomegalovirus in Epithelial Cells and Fibroblasts. Viruses 2022; 14:v14020284. [PMID: 35215877 PMCID: PMC8875165 DOI: 10.3390/v14020284] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/24/2022] [Accepted: 01/27/2022] [Indexed: 02/04/2023] Open
Abstract
Human cytomegalovirus (HCMV) can cause severe clinical disease in immunocompromised individuals, such as allograft recipients and infants infected in utero. Neutralizing activity of antibodies, measured as the ability to prevent the entry of cell-free virus, has been correlated with the reduction in HCMV transmission and the severity of HCMV-associated disease. However, in vivo HCMV amplification may occur mainly via cell-to-cell spread. Thus, quantifying the inhibition of cell-to-cell transmission could be important in the evaluation of therapeutic antibodies and/or humoral responses to infection or immunization. Here, we established a quantitative plaque reduction assay, which allowed for the measurement of the capacity of antibodies to limit HCMV spread in vitro. Using an automated fluorescence spot reader, infection progression was assayed by the expansion of viral plaques during the course of infection with various GFP-expressing viruses. We found that in contrast to non-neutralizing monoclonal antibodies (mAbs), neutralizing mAbs against both glycoprotein B and H (gB and gH) could significantly inhibit viral plaque expansion of different HCMV strains and was equally efficient in fibroblasts as in epithelial cells. In contrast, an anti-pentamer mAb was active only in epithelial cells. Taken together, our data demonstrate that specific anti-HCMV mAbs can significantly limit cell-associated virus spread in vitro.
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Li SX, Yu F, Chen HX, Zhang XD, Meng LH, Hao K, Zhao Z. Characterization of Ictalurid herpesvirus 1 Glycoprotein ORF59 and Its Potential Role on Virus Entry into the Host Cells. Viruses 2021; 13:v13122393. [PMID: 34960662 PMCID: PMC8709185 DOI: 10.3390/v13122393] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 11/18/2021] [Accepted: 11/27/2021] [Indexed: 12/19/2022] Open
Abstract
The channel catfish virus (CCV, Ictalurid herpesvirus 1) has caused sustained economic losses in the fish industry because of its strong infectivity and pathogenicity. Thus, it is necessary to determine the function of viral proteins in the CCV infection process. The present study aimed to characterize CCV glycoprotein ORF59 and explore its impact on virus infection in host cells. Firstly, its exclusive presence in the membrane fraction of the cell lysate and subcellular localization verified that CCV ORF59 is a viral membrane protein expressed at late-stage infection. A protein blocking assay using purified His6 tagged ORF59, expressed in sf9 insect cells using a baculovirus expression system, indicated a dose-dependent inhibitory effect of recombinant ORF59 protein on virus invasion. Knockdown of the ORF59 using a short hairpin (shRNA) showed that ORF59 silencing decreased the production of infectious virus particles in channel catfish ovary cells. The results of this study suggest that recombinant ORF59 protein might inhibit CCV entry into the host cells. These findings will promote future studies of the key functions of glycoprotein ORF59 during CCV infection.
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Affiliation(s)
- Shu-Xin Li
- Department of Marine Biology, College of Oceanography, Hohai University, Nanjing 210098, China; (S.-X.L.); (F.Y.); (H.-X.C.); (X.-D.Z.); (L.-H.M.); (K.H.)
| | - Fei Yu
- Department of Marine Biology, College of Oceanography, Hohai University, Nanjing 210098, China; (S.-X.L.); (F.Y.); (H.-X.C.); (X.-D.Z.); (L.-H.M.); (K.H.)
| | - Hong-Xun Chen
- Department of Marine Biology, College of Oceanography, Hohai University, Nanjing 210098, China; (S.-X.L.); (F.Y.); (H.-X.C.); (X.-D.Z.); (L.-H.M.); (K.H.)
| | - Xiao-Dong Zhang
- Department of Marine Biology, College of Oceanography, Hohai University, Nanjing 210098, China; (S.-X.L.); (F.Y.); (H.-X.C.); (X.-D.Z.); (L.-H.M.); (K.H.)
| | - Li-Hui Meng
- Department of Marine Biology, College of Oceanography, Hohai University, Nanjing 210098, China; (S.-X.L.); (F.Y.); (H.-X.C.); (X.-D.Z.); (L.-H.M.); (K.H.)
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Kai Hao
- Department of Marine Biology, College of Oceanography, Hohai University, Nanjing 210098, China; (S.-X.L.); (F.Y.); (H.-X.C.); (X.-D.Z.); (L.-H.M.); (K.H.)
| | - Zhe Zhao
- Department of Marine Biology, College of Oceanography, Hohai University, Nanjing 210098, China; (S.-X.L.); (F.Y.); (H.-X.C.); (X.-D.Z.); (L.-H.M.); (K.H.)
- Correspondence: ; Tel.: +86-025-8378-7653
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Aguiar A, Galinato M, Bradley Silva M, Toth B, McVoy MA, Hertel L. Human Cytomegalovirus Replication and Infection-Induced Syncytia Formation in Labial, Foreskin, and Fetal Lung Fibroblasts. Viruses 2021; 13:2355. [PMID: 34960624 PMCID: PMC8708767 DOI: 10.3390/v13122355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 11/18/2021] [Accepted: 11/22/2021] [Indexed: 12/04/2022] Open
Abstract
Only a handful of cell types, including fibroblasts, epithelial, and endothelial cells, can support human cytomegalovirus (CMV) replication in vitro, in striking contrast to the situation in vivo. While the susceptibility of epithelial and endothelial cells to CMV infection is strongly modulated by their anatomical site of origin, multiple CMV strains have been successfully isolated and propagated on fibroblasts derived from different organs. As oral mucosal cells are likely involved in CMV acquisition, we sought to evaluate the ability of infant labial fibroblasts to support CMV replication, compared to that of commonly used foreskin and fetal lung fibroblasts. No differences were found in the proportion of cells initiating infection, or in the amounts of viral progeny produced after exposure to the fibroblast-adapted CMV strain AD169 or to the endothelial cell-adapted strain TB40/E. Syncytia formation was, however, significantly enhanced in infected labial and lung fibroblasts compared to foreskin-derived cells, and did not occur after infection with AD169. Together, these data indicate that fibroblast populations derived from different tissues are uniformly permissive to CMV infection but retain phenotypic differences of potential importance for infection-induced cell-cell fusion, and ensuing viral spread and pathogenesis in different organs.
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Affiliation(s)
- Alexis Aguiar
- Department of Pediatrics, University of California San Francisco, Oakland, CA 94609, USA; (A.A.); (M.B.S.)
| | - Melissa Galinato
- Center for Immunobiology & Vaccine Development, Children’s Hospital Oakland Research Institute, Oakland, CA 94609, USA;
| | - Maite’ Bradley Silva
- Department of Pediatrics, University of California San Francisco, Oakland, CA 94609, USA; (A.A.); (M.B.S.)
| | - Bryant Toth
- Craniofacial Center, UCSF Benioff Children’s Hospital Oakland, Oakland, CA 94609, USA;
| | - Michael A. McVoy
- Department of Pediatrics, Virginia Commonwealth University, Richmond, VA 23298, USA;
| | - Laura Hertel
- Department of Pediatrics, University of California San Francisco, Oakland, CA 94609, USA; (A.A.); (M.B.S.)
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Tang J, Frascaroli G, Zhou X, Knickmann J, Brune W. Cell Fusion and Syncytium Formation in Betaherpesvirus Infection. Viruses 2021; 13:v13101973. [PMID: 34696402 PMCID: PMC8537622 DOI: 10.3390/v13101973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/22/2021] [Accepted: 09/28/2021] [Indexed: 12/14/2022] Open
Abstract
Cell–cell fusion is a fundamental and complex process that occurs during reproduction, organ and tissue growth, cancer metastasis, immune response, and infection. All enveloped viruses express one or more proteins that drive the fusion of the viral envelope with cellular membranes. The same proteins can mediate the fusion of the plasma membranes of adjacent cells, leading to the formation of multinucleated syncytia. While cell–cell fusion triggered by alpha- and gammaherpesviruses is well-studied, much less is known about the fusogenic potential of betaherpesviruses such as human cytomegalovirus (HCMV) and human herpesviruses 6 and 7 (HHV-6 and HHV-7). These are slow-growing viruses that are highly prevalent in the human population and associated with several diseases, particularly in individuals with an immature or impaired immune system such as fetuses and transplant recipients. While HHV-6 and HHV-7 are strictly lymphotropic, HCMV infects a very broad range of cell types including epithelial, endothelial, mesenchymal, and myeloid cells. Syncytia have been observed occasionally for all three betaherpesviruses, both during in vitro and in vivo infection. Since cell–cell fusion may allow efficient spread to neighboring cells without exposure to neutralizing antibodies and other host immune factors, viral-induced syncytia may be important for viral dissemination, long-term persistence, and pathogenicity. In this review, we provide an overview of the viral and cellular factors and mechanisms identified so far in the process of cell–cell fusion induced by betaherpesviruses and discuss the possible consequences for cellular dysfunction and pathogenesis.
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Affiliation(s)
- Jiajia Tang
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
- Center for Single-Cell Omics, School of Medicine, Shanghai Jiao Tong University, Shanghai 200025, China
| | - Giada Frascaroli
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Xuan Zhou
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Jan Knickmann
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Wolfram Brune
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
- Correspondence:
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Diazadispiroalkane Derivatives Are New Viral Entry Inhibitors. Antimicrob Agents Chemother 2021; 65:AAC.02103-20. [PMID: 33495228 DOI: 10.1128/aac.02103-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 01/18/2021] [Indexed: 01/21/2023] Open
Abstract
Herpesviruses are widespread and can cause serious illness. Many currently available antiviral drugs have limited effects, result in rapid development of resistance, and often exhibit dose-dependent toxicity. Especially for human cytomegalovirus (HCMV), new well-tolerated compounds with novel mechanisms of action are urgently needed. In this study, we characterized the antiviral activity of two new diazadispiroalkane derivatives, 11826091 and 11826236. These two small molecules exhibited strong activity against low-passage-number HCMV. Pretreatment of cell-free virus with these compounds greatly reduced infection. Time-of-addition assays where 11826091 or 11826236 was added to cells before infection, before and during infection, or during or after infection demonstrated an inhibitory effect on early steps of infection. Interestingly, 11826236 had an effect by addition to cells after infection. Results from entry assays showed the major effect to be on attachment. Only 11826236 had a minimal effect on penetration comparable to heparin. Further, no effect on virus infection was found for cell lines with a defect in heparan sulfate expression or lacking all surface glycosaminoglycans, indicating that these small molecules bind to heparan sulfate on the cell surface. To test this further, we extended our analyses to pseudorabies virus (PrV), a member of the Alphaherpesvirinae, which is known to use cell surface heparan sulfate for initial attachment via nonessential glycoprotein C (gC). While infection with PrV wild type was strongly impaired by 11826091 or 11826236, as with heparin, a mutant lacking gC was unaffected by either treatment, demonstrating that primary attachment to heparan sulfate via gC is targeted by these small molecules.
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Perotti M, Marcandalli J, Demurtas D, Sallusto F, Perez L. Rationally designed Human Cytomegalovirus gB nanoparticle vaccine with improved immunogenicity. PLoS Pathog 2020; 16:e1009169. [PMID: 33370407 PMCID: PMC7794029 DOI: 10.1371/journal.ppat.1009169] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 01/08/2021] [Accepted: 11/16/2020] [Indexed: 12/15/2022] Open
Abstract
Human cytomegalovirus (HCMV) is the primary viral cause of congenital birth defects and causes significant morbidity and mortality in immune-suppressed transplant recipients. Despite considerable efforts in vaccine development, HCMV infection still represents an unmet clinical need. In recent phase II trials, a MF59-adjuvanted gB vaccine showed only modest efficacy in preventing infection. These findings might be attributed to low level of antibodies (Abs) with a neutralizing activity induced by this vaccine. Here, we analyzed the immunogenicity of each gB antigenic domain (AD) and demonstrated that domain I of gB (AD5) is the main target of HCMV neutralizing antibodies. Furthermore, we designed, characterized and evaluated immunogenic responses to two different nanoparticles displaying a trimeric AD5 antigen. We showed that mice immunization with nanoparticles induces sera neutralization titers up to 100-fold higher compared to those obtained with the gB extracellular domain (gBECD). Collectively, these results illustrate with a medically relevant example the advantages of using a general approach combining antigen discovery, protein engineering and scaffold presentation for modern development of subunit vaccines against complex pathogens.
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Affiliation(s)
- Michela Perotti
- Institute for Research in Biomedicine, Università della Svizzera italiana, faculty of Biomedical Sciences, Bellinzona, Switzerland.,Institute of Microbiology, ETH Zürich, Zürich, Switzerland
| | - Jessica Marcandalli
- Institute for Research in Biomedicine, Università della Svizzera italiana, faculty of Biomedical Sciences, Bellinzona, Switzerland
| | - Davide Demurtas
- BioEM Facility, School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland
| | - Federica Sallusto
- Institute for Research in Biomedicine, Università della Svizzera italiana, faculty of Biomedical Sciences, Bellinzona, Switzerland.,Institute of Microbiology, ETH Zürich, Zürich, Switzerland
| | - Laurent Perez
- Institute for Research in Biomedicine, Università della Svizzera italiana, faculty of Biomedical Sciences, Bellinzona, Switzerland.,University of Lausanne (UNIL), Lausanne University Hospital (CHUV), Department of Medicine, Division of Immunology and Allergy, Center for Human Immunology (CHIL), Lausanne, Switzerland
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Leroy H, Han M, Woottum M, Bracq L, Bouchet J, Xie M, Benichou S. Virus-Mediated Cell-Cell Fusion. Int J Mol Sci 2020; 21:E9644. [PMID: 33348900 PMCID: PMC7767094 DOI: 10.3390/ijms21249644] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 02/07/2023] Open
Abstract
Cell-cell fusion between eukaryotic cells is a general process involved in many physiological and pathological conditions, including infections by bacteria, parasites, and viruses. As obligate intracellular pathogens, viruses use intracellular machineries and pathways for efficient replication in their host target cells. Interestingly, certain viruses, and, more especially, enveloped viruses belonging to different viral families and including human pathogens, can mediate cell-cell fusion between infected cells and neighboring non-infected cells. Depending of the cellular environment and tissue organization, this virus-mediated cell-cell fusion leads to the merge of membrane and cytoplasm contents and formation of multinucleated cells, also called syncytia, that can express high amount of viral antigens in tissues and organs of infected hosts. This ability of some viruses to trigger cell-cell fusion between infected cells as virus-donor cells and surrounding non-infected target cells is mainly related to virus-encoded fusion proteins, known as viral fusogens displaying high fusogenic properties, and expressed at the cell surface of the virus-donor cells. Virus-induced cell-cell fusion is then mediated by interactions of these viral fusion proteins with surface molecules or receptors involved in virus entry and expressed on neighboring non-infected cells. Thus, the goal of this review is to give an overview of the different animal virus families, with a more special focus on human pathogens, that can trigger cell-cell fusion.
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Affiliation(s)
- Héloïse Leroy
- Institut Cochin, Inserm U1016, 75014 Paris, France; (H.L.); (M.H.); (M.W.)
- Centre National de la Recherche Scientifique CNRS, UMR8104, 75014 Paris, France
- Faculty of Health, University of Paris, 75014 Paris, France
| | - Mingyu Han
- Institut Cochin, Inserm U1016, 75014 Paris, France; (H.L.); (M.H.); (M.W.)
- Centre National de la Recherche Scientifique CNRS, UMR8104, 75014 Paris, France
- Faculty of Health, University of Paris, 75014 Paris, France
| | - Marie Woottum
- Institut Cochin, Inserm U1016, 75014 Paris, France; (H.L.); (M.H.); (M.W.)
- Centre National de la Recherche Scientifique CNRS, UMR8104, 75014 Paris, France
- Faculty of Health, University of Paris, 75014 Paris, France
| | - Lucie Bracq
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland;
| | - Jérôme Bouchet
- Laboratory Orofacial Pathologies, Imaging and Biotherapies UR2496, University of Paris, 92120 Montrouge, France;
| | - Maorong Xie
- Division of Infection and Immunity, University College London, London WC1E 6BT, UK;
| | - Serge Benichou
- Institut Cochin, Inserm U1016, 75014 Paris, France; (H.L.); (M.H.); (M.W.)
- Centre National de la Recherche Scientifique CNRS, UMR8104, 75014 Paris, France
- Faculty of Health, University of Paris, 75014 Paris, France
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