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Krishnagopal A, van Drunen Littel-van den Hurk S. The biology and development of vaccines for bovine alphaherpesvirus 1. Vet J 2024; 306:106152. [PMID: 38821207 DOI: 10.1016/j.tvjl.2024.106152] [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] [Received: 12/30/2023] [Revised: 05/26/2024] [Accepted: 05/27/2024] [Indexed: 06/02/2024]
Abstract
Bovine alphaherpesvirus type 1 (BoAHV-1) infections lead to compromised herd health and significantly reduced productivity of affected cattle. While BoAHV-1 may cause rhinotracheitis, conjunctivitis, genital infections, and abortions, respiratory tract infections constitute the predominant clinical disease. Immune suppression induced by BoAHV-1 may contribute to co-infections initiating the bovine respiratory disease complex. In this review, the emphasis is to recapitulate the biology and the vaccine technologies currently in use and in development for BoAHV-1, and to discuss the major limitations. Studies on the life cycle and host interactions of BoAHV-1 have resulted in the identification of virulence factors. While several vaccine types, such as vectored vaccines and subunit vaccines, are under investigation, modified live and inactivated BoAHV-1 vaccines are still most frequently used in most areas of the world, whereas attenuated and inactivated marker vaccines are in use in Europe. The knowledge gained from studies on the biology of BoAHV-1 can form a basis for the rational design of future vaccines.
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Affiliation(s)
- Akshaya Krishnagopal
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
| | - Sylvia van Drunen Littel-van den Hurk
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada.
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2
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Tan WS, Rong E, Dry I, Lillico SG, Law A, Digard P, Whitelaw B, Dalziel RG. GARP and EARP are required for efficient BoHV-1 replication as identified by a genome wide CRISPR knockout screen. PLoS Pathog 2023; 19:e1011822. [PMID: 38055775 PMCID: PMC10727446 DOI: 10.1371/journal.ppat.1011822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 12/18/2023] [Accepted: 11/13/2023] [Indexed: 12/08/2023] Open
Abstract
The advances in gene editing bring unprecedented opportunities in high throughput functional genomics to animal research. Here we describe a genome wide CRISPR knockout library, btCRISPRko.v1, targeting all protein coding genes in the cattle genome. Using it, we conducted genome wide screens during Bovine Herpes Virus type 1 (BoHV-1) replication and compiled a list of pro-viral and anti-viral candidates. These candidates might influence multiple aspects of BoHV-1 biology such as viral entry, genome replication and transcription, viral protein trafficking and virion maturation in the cytoplasm. Some of the most intriguing examples are VPS51, VPS52 and VPS53 that code for subunits of two membrane tethering complexes, the endosome-associated recycling protein (EARP) complex and the Golgi-associated retrograde protein (GARP) complex. These complexes mediate endosomal recycling and retrograde trafficking to the trans Golgi Network (TGN). Simultaneous loss of both complexes in MDBKs resulted in greatly reduced production of infectious BoHV-1 virions. We also found that viruses released by these deficient cells severely lack VP8, the most abundant tegument protein of BoHV-1 that are crucial for its virulence. In combination with previous reports, our data suggest vital roles GARP and EARP play during viral protein packaging and capsid re-envelopment in the cytoplasm. It also contributes to evidence that both the TGN and the recycling endosomes are recruited in this process, mediated by these complexes. The btCRISPRko.v1 library generated here has been controlled for quality and shown to be effective in host gene discovery. We hope it will facilitate efforts in the study of other pathogens and various aspects of cell biology in cattle.
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Affiliation(s)
- Wenfang S. Tan
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Enguang Rong
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Inga Dry
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Simon G. Lillico
- Division of Functional Genetics and Development, University of Edinburgh, Edinburgh, Scotland, United Kingdom
- Centre for Tropical Livestock Genetics and Health, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Andy Law
- Division of Genetics and Genomics, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Paul Digard
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Bruce Whitelaw
- Division of Functional Genetics and Development, University of Edinburgh, Edinburgh, Scotland, United Kingdom
- Centre for Tropical Livestock Genetics and Health, the Roslin Institute, Easter Bush Campus, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Robert G. Dalziel
- Division of Infection and Immunity, University of Edinburgh, Edinburgh, Scotland, United Kingdom
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Tobler K, Senn C, Schraner EM, Ackermann M, Fraefel C, Wild P. The herpes simplex virus 1 Us3 kinase is involved in assembly of membranes needed for viral envelopment and in distribution of glycoprotein K. F1000Res 2019; 8:727. [PMID: 31448105 PMCID: PMC6681629 DOI: 10.12688/f1000research.19194.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/16/2019] [Indexed: 11/20/2022] Open
Abstract
Background: Capsids of herpes simplex virus 1 (HSV-1) are assembled in cell nuclei, released into the perinuclear space by budding at the inner nuclear membrane acquiring tegument and envelope. Alternatively, capsids gain access to the cytoplasm via dilated nuclear pores. They are enveloped by Golgi membranes. Us3 is a non-essential viral kinase that is involved in nucleus-to-cytoplasm translocation, preventing apoptosis and regulation of phospholipid-biosynthesis. Us3-deletion mutants (HSV-1∆Us3) accumulate in the perinuclear space. Nuclear and Golgi membranes proliferate, and homogeneous, proteinaceous structures of unknown identity are deposited in nuclei and cytoplasm. Glycoprotein K (gK), a highly hydrophobic viral protein, is essential for production of infectious progeny virus but, according to the literature, exclusively vital for envelopment of capsids by Golgi membranes. In the absence of Us3, virions remain stuck in the perinuclear space but mature to infectivity without reaching Golgi membranes, suggesting further function of gK than assumed. Methods: We constructed a HSV-1∆Us3 mutant designated CK177∆Us3gK-HA, in which gK was hemagglutinin (HA) epitope-tagged in order to localize gK by immunolabeling using antibodies against HA for light and electron microscopy. Results: CK177∆Us3gK-HA-infected Vero cells showed similar alterations as those reported for other HSV-1∆Us3, including accumulation of virions in the perinuclear space, overproduction of nuclear and Golgi membranes containing electron dense material with staining property of proteins. Immunolabeling using antibodies against HA revealed that gK is overproduced and localized at nuclear membranes, perinuclear virions stuck in the perinuclear space, Golgi membranes and on protein deposits in cytoplasm and nuclei. Conclusions: Us3 is involved in proper assembly of membranes needed for envelopment and incorporation of gK. Without Us3, virions derived by budding at nuclear membranes remain stuck in the perinuclear space but incorporate gK into their envelope to gain infectivity.
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Affiliation(s)
- Kurt Tobler
- Institute of Virology, University of Zürich, Zürich, CH-8057, Switzerland
| | - Claudia Senn
- Institute of Virology, University of Zürich, Zürich, CH-8057, Switzerland
| | | | - Mathias Ackermann
- Institute of Virology, University of Zürich, Zürich, CH-8057, Switzerland
| | - Cornel Fraefel
- Institute of Virology, University of Zürich, Zürich, CH-8057, Switzerland
| | - Peter Wild
- Institute of Virology, University of Zürich, Zürich, CH-8057, Switzerland
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4
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Wild P, Leisinger S, de Oliveira AP, Doehner J, Schraner EM, Fraevel C, Ackermann M, Kaech A. Nuclear envelope impairment is facilitated by the herpes simplex virus 1 Us3 kinase. F1000Res 2019; 8:198. [PMID: 31249678 PMCID: PMC6584977 DOI: 10.12688/f1000research.17802.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/11/2019] [Indexed: 12/22/2022] Open
Abstract
Background: Capsids of herpes simplex virus 1 (HSV-1) are assembled in the nucleus, translocated either to the perinuclear space by budding at the inner nuclear membrane acquiring tegument and envelope, or released to the cytosol in a "naked" state via impaired nuclear pores that finally results in impairment of the nuclear envelope. The Us3 gene encodes a protein acting as a kinase, which is responsible for phosphorylation of numerous viral and cellular substrates. The Us3 kinase plays a crucial role in nucleus to cytoplasm capsid translocation. We thus investigate the nuclear surface in order to evaluate the significance of Us3 in maintenance of the nuclear envelope during HSV-1 infection. Methods: To address alterations of the nuclear envelope and capsid nucleus to cytoplasm translocation related to the function of the Us3 kinase we investigated cells infected with wild type HSV-1 or the Us3 deletion mutant R7041(∆Us3) by transmission electron microscopy, focused ion-beam electron scanning microscopy, cryo-field emission scanning electron microscopy, confocal super resolution light microscopy, and polyacrylamide gel electrophoresis. Results: Confocal super resolution microscopy and cryo-field emission scanning electron microscopy revealed decrement in pore numbers in infected cells. Number and degree of pore impairment was significantly reduced after infection with R7041(∆Us3) compared to infection with wild type HSV-1. The nuclear surface was significantly enlarged in cells infected with any of the viruses. Morphometric analysis revealed that additional nuclear membranes were produced forming multiple folds and caveolae, in which virions accumulated as documented by three-dimensional reconstruction after ion-beam scanning electron microscopy. Finally, significantly more R7041(∆Us3) capsids were retained in the nucleus than wild-type capsids whereas the number of R7041(∆Us3) capsids in the cytosol was significantly lower. Conclusions: The data indicate that Us3 kinase is involved in facilitation of nuclear pore impairment and, concomitantly, in capsid release through impaired nuclear envelope.
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Affiliation(s)
- Peter Wild
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
| | - Sabine Leisinger
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
| | | | - Jana Doehner
- Center for Microcopy and Image Analysis, Universit of Zürich, Zürich, CH-8057, Switzerland
| | - Elisabeth M. Schraner
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Cornel Fraevel
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Mathias Ackermann
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Andres Kaech
- Center for Microcopy and Image Analysis, Universit of Zürich, Zürich, CH-8057, Switzerland
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5
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Reipert S, Goldammer H, Richardson C, Goldberg MW, Hawkins TJ, Hollergschwandtner E, Kaufmann WA, Antreich S, Stierhof YD. Agitation Modules: Flexible Means to Accelerate Automated Freeze Substitution. J Histochem Cytochem 2018; 66:903-921. [PMID: 29969056 DOI: 10.1369/0022155418786698] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
For ultrafast fixation of biological samples to avoid artifacts, high-pressure freezing (HPF) followed by freeze substitution (FS) is preferred over chemical fixation at room temperature. After HPF, samples are maintained at low temperature during dehydration and fixation, while avoiding damaging recrystallization. This is a notoriously slow process. McDonald and Webb demonstrated, in 2011, that sample agitation during FS dramatically reduces the necessary time. Then, in 2015, we (H.G. and S.R.) introduced an agitation module into the cryochamber of an automated FS unit and demonstrated that the preparation of algae could be shortened from days to a couple of hours. We argued that variability in the processing, reproducibility, and safety issues are better addressed using automated FS units. For dissemination, we started low-cost manufacturing of agitation modules for two of the most widely used FS units, the Automatic Freeze Substitution Systems, AFS(1) and AFS2, from Leica Microsystems, using three dimensional (3D)-printing of the major components. To test them, several labs independently used the modules on a wide variety of specimens that had previously been processed by manual agitation, or without agitation. We demonstrate that automated processing with sample agitation saves time, increases flexibility with respect to sample requirements and protocols, and produces data of at least as good quality as other approaches.
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Affiliation(s)
- Siegfried Reipert
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | - Helmuth Goldammer
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | | | - Martin W Goldberg
- Department of Biosciences, Durham University, Durham, United Kingdom
| | - Timothy J Hawkins
- Department of Biosciences, Durham University, Durham, United Kingdom
| | | | - Walter A Kaufmann
- Electron Microscopy Facility, Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Sebastian Antreich
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | - York-Dieter Stierhof
- Center for Plant Molecular Biology (ZMBP), Microscopy, University of Tübingen, Tübingen, Germany
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Wild P, Kaech A, Schraner EM, Walser L, Ackermann M. Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection. F1000Res 2017; 6:1804. [PMID: 30135710 PMCID: PMC6080407 DOI: 10.12688/f1000research.12252.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/29/2017] [Indexed: 09/29/2023] Open
Abstract
Background: Herpesvirus capsids are assembled in the nucleus before they are translocated to the perinuclear space by budding, acquiring tegument and envelope, or releasing to the cytoplasm in a "naked" state via impaired nuclear envelope. One model proposes that envelopment, "de-envelopment" and "re-envelopment" are essential steps for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the "primary" envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of an alternative exit route. Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols that lead to improved spatial and temporal resolution. Results: Scanning electron microscopy showed the Golgi complex as a compact entity in a juxtanuclear position covered by a membrane on the cis face. Transmission electron microscopy revealed that Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced. Conclusions: The data strongly suggest that virions are intraluminally transported from the perinuclear space via Golgi complex-endoplasmic reticulum transitions into Golgi cisternae for packaging into transport vacuoles. Furthermore, virions derived by budding at nuclear membranes are infective as has been shown for HSV-1 Us3 deletion mutants, which almost entirely accumulate in the perinuclear space. Therefore, de-envelopment followed by re-envelopment is not essential for production of infective progeny virus.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Zürich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Ladina Walser
- Institute of Veterinary Anatomy, Zürich, Switzerland
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Wild P, Kaech A, Schraner EM, Walser L, Ackermann M. Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection. F1000Res 2017; 6:1804. [PMID: 30135710 PMCID: PMC6080407 DOI: 10.12688/f1000research.12252.2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/19/2018] [Indexed: 11/23/2022] Open
Abstract
Background: Herpesvirus capsids are assembled in the nucleus, translocated to the perinuclear space by budding, acquiring tegument and envelope, or released to the cytoplasm via impaired nuclear envelope. One model proposes that envelopment, "de-envelopment" and "re-envelopment" is essential for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the "primary" envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of alternative exit routes. Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols. Results: The Golgi complex is a compact entity in a juxtanuclear position covered by a membrane on the cis face. Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced. Conclusions: The data suggest that virions derived by budding at nuclear membranes are intraluminally transported from the perinuclear space via Golgi -endoplasmic reticulum transitions into Golgi cisternae for packaging. Virions derived by budding at nuclear membranes are infective like Us3 deletion mutants, which accumulate in the perinuclear space. Therefore, i) de-envelopment followed by re-envelopment is not essential for production of infective progeny virus, ii) the process taking place at the outer nuclear membrane is budding not fusion, and iii) naked capsids gain access to the cytoplasmic matrix via impaired nuclear envelope as reported earlier.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Zürich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Ladina Walser
- Institute of Veterinary Anatomy, Zürich, Switzerland
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8
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Palazzi EG, Pituco EM, Vicente EJ, Hansen D, Felicio JD, Lima MDS, Nogueira AHDC, De Stephano E, Okuda LH, D'Angelo M. Avaliação do extrato etanólico de casca de Punica granatum (romã) na diminuição da replicação viral do BoHV-1 Colorado em embriões murinos experimentalmente infectados. ARQUIVOS DO INSTITUTO BIOLÓGICO 2016. [DOI: 10.1590/1808-1657000892013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
RESUMO O objetivo do trabalho foi avaliar a diminuição da replicação viral (BoHV-1 Colorado) em embriões murinos após tratamento do extrato etanólico da casca de Punica granatum (EEPg). Camundongos fêmeas Swiss com idade entre 6 e 8 semanas foram superovuladas com 0,2 mL a 5 UI de hormônios (eCG e hCG), e acasaladas com machos da mesma idade. Após 18 horas, as fêmeas sofreram eutanásia em câmara de CO2 e, através de abertura no peritônio, os zigotos foram coletados e lavados com solução de pronase 0,5%.Os zigotos foram divididos em quatro grupos: G1 (controle), G2 (expostos aos vírus BoHV-1 Colorado a 108 TCID50/mL), G3 (expostos ao EEPg) e G4 (expostos aos vírus e ao EEPg). Os grupos foram mantidos a 37,5ºC em meio TCM199 (100µL) com 10% de soro fetal bovino em estufa a 5% de CO2 e 95% de umidade. Após 24 h, analisamos a taxa de clivagem (teste exato de Fisher; p<0,05), a morfologia (por microscopia óptica), a nested-PCR e a titulação dos embriões em cocultura com células MDBK após mais 72 h do tratamento (teste de Mann-Whitney; p<0,05) e microscopia eletrônica de transmissão (ME). Os embriões murinos tratados com EEPg apresentaram resultados satisfatórios: sem alterações morfológicas, taxa de clivagem semelhante ao controle e, apesar da detecção da presença do vírus pela nested-PCR e ME, houve diminuição do título viral após tratamentos com esse extrato, o que sugere interferência desse tratamento no ciclo viral do BoHV-1 Colorado sem alterar o desenvolvimento dos embriões.
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9
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Pires de Mello CP, Bloom DC, Paixão IC. Herpes simplex virus type-1: replication, latency, reactivation and its antiviral targets. Antivir Ther 2016; 21:277-86. [PMID: 26726828 DOI: 10.3851/imp3018] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/17/2015] [Indexed: 10/22/2022]
Abstract
Infection by herpes simplex virus type-1 (HSV-1) causes several diseases, ranging from cutaneous, oral and genital infections to fatal encephalitis. Despite the availability of antiviral therapies on the market, their efficacies are incomplete, and new cases of resistant strains arise, mainly in the immunocompromised, but also recently documented in immunocompetent patients. Over the last decades a lot has been discovered about the molecular basis of infection which has been of great benefit to the investigation of new anti-HSV-1 molecules. In this review we summarize replication, latency and reactivation highlighting potential antiviral targets and new molecules described in the past several years in the literature.
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Affiliation(s)
- Camilly P Pires de Mello
- Department of Cellular and Molecular Biology, Universidade Federal Fluminense, Biology Institute, Niterói, Brazil
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10
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Wild P, Leisinger S, de Oliveira AP, Schraner EM, Kaech A, Ackermann M, Tobler K. Herpes simplex virus 1 Us3 deletion mutant is infective despite impaired capsid translocation to the cytoplasm. Viruses 2015; 7:52-71. [PMID: 25588052 PMCID: PMC4306828 DOI: 10.3390/v7010052] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 12/30/2014] [Indexed: 11/29/2022] Open
Abstract
Herpes simplex virus 1 (HSV-1) capsids are assembled in the nucleus bud at the inner nuclear membrane into the perinuclear space, acquiring envelope and tegument. In theory, these virions are de-enveloped by fusion of the envelope with the outer nuclear membrane and re-enveloped by Golgi membranes to become infective. Us3 enables the nucleus to cytoplasm capsid translocation. Nevertheless, Us3 is not essential for the production of infective progeny viruses. Determination of phenotype distribution by quantitative electron microscopy, and calculation per mean nuclear or cell volume revealed the following: (i) The number of R7041(∆US3) capsids budding at the inner nuclear membrane was significantly higher than that of wild type HSV-1; (ii) The mean number of R7041(∆US3) virions per mean cell volume was 2726, that of HSV-1 virions 1460 by 24 h post inoculation; (iii) 98% of R7041(∆US3) virions were in the perinuclear space; (iv) The number of R7041(∆US3) capsids in the cytoplasm, including those budding at Golgi membranes, was significantly reduced. Cell associated R7041(∆US3) yields were 2.37×10(8) and HSV-1 yields 1.57×10(8) PFU/mL by 24 h post inoculation. We thus conclude that R7041(∆US3) virions, which acquire envelope and tegument by budding at the inner nuclear membrane into the perinuclear space, are infective.
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Affiliation(s)
- Peter Wild
- Institute of Veterinar Anatomy, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
| | - Sabine Leisinger
- Institute of Veterinar Anatomy, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
| | | | - Elisabeth M Schraner
- Institute of Veterinar Anatomy, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Winterthurerstrasse 190,CH-8057 Zürich, Switzerland.
| | - Mathias Ackermann
- Institute of Virology, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
| | - Kurt Tobler
- Institute of Virology, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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Abstract
In this chapter we discuss the latest developments in the field of high-pressure freezing (HPF). The Leica HPF machine EM HPM100 is discussed in detail due to significant changes compared to its predecessor model. Its centerpiece is a multipart polymer cartridge which holds the specimen carrier sandwich and guides it automatically through the freezing process until immersed in liquid nitrogen. The cartridge can be adapted to the specimen and carrier geometry to optimize the flow of liquid nitrogen and hence rapid cooling. Dedicated cartridges are available for a variety of different carriers, including carriers for samples of up to 5 mm in diameter. Cartridge-specific handling and carrier assemblies are described extensively for freezing samples in aluminum specimen carriers, cell cultures grown on Sapphire discs, suspensions for freeze-fracturing, and specimens for cryo-sectioning. Additionally, we include an advanced technique to freeze monolayer cell cultures on Sapphire discs with the Leica EM PACT2 HPF machine using a composite carrier.
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Affiliation(s)
- Andres Kaech
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
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12
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Venter E, Van Der Merwe CF, Van Staden V. Utilization of cellulose microcapillary tubes as a model system for culturing and viral infection of mammalian cells. Microsc Res Tech 2012; 75:1452-9. [PMID: 22865476 DOI: 10.1002/jemt.22111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 07/10/2012] [Indexed: 11/10/2022]
Abstract
Cryofixation by high-pressure freezing (HPF) and freeze substitution (FS) gives excellent preservation of intracellular membranous structures, ideal for ultrastructural investigations of virus infected cells. Conventional sample preparation methods of tissue cultured cells can however disrupt the association between neighboring cells or of viruses with the plasma membrane, which impacts upon the effectiveness whereby virus release from cells can be studied. We established a system for virus infection and transmission electron microscopy preparation of mammalian cells that allowed optimal visualization of membrane release events. African horse sickness virus (AHSV) is a nonenveloped virus that employs two different release mechanisms from mammalian cells, i.e., lytic release through a disrupted plasma membrane and a nonlytic budding-type release. Cellulose microcapillary tubes were used as support layer for culturing Vero cells. The cells grew to a confluent monolayer along the inside of the tubes and could readily be infected with AHSV. Sections of the microcapillary tubes proved easy to manipulate during the HPF procedure, showed no distortion or compression, and yielded well preserved cells in their native state. There was ample cell surface area available for visualization, which allowed detection of both types of virus release at the plasma membrane at a significantly higher frequency than when utilizing other methods. The consecutive culturing, virus infection and processing of cells within microcapillary tubes therefore represent a novel model system for monitoring intracellular virus life cycle and membrane release events, specifically suited to viruses that do not grow to high titers in tissue culture.
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Affiliation(s)
- Eudri Venter
- Department of Genetics, University of Pretoria, Pretoria 0002, South Africa
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Wild P, de Oliveira AP, Sonda S, Schraner EM, Ackermann M, Tobler K. The herpes simplex virus 1 U(S)3 regulates phospholipid synthesis. Virology 2012; 432:353-60. [PMID: 22789738 DOI: 10.1016/j.virol.2012.06.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 05/07/2012] [Accepted: 06/12/2012] [Indexed: 10/28/2022]
Abstract
Herpes simplex virus type 1 capsids bud at nuclear and Golgi membranes for envelopment by phospholipid bilayers. In the absence of U(S)3, nuclear membranes form multiple folds harboring virions that suggests disturbance in membrane turnover. Therefore, we investigated phospholipid metabolism in cells infected with the U(S)3 deletion mutant R7041(ΔU(S)3), and quantified membranes involved in viral envelopment. We report that (i) [(3)H]-choline incorporation into nuclear membranes and cytoplasmic membranes was enhanced peaking at 12 or 20 h post inoculation with wild type HSV-1 and R7041(ΔU(S)3), respectively, (ii) the surface area of nuclear membranes increased until 24 h of R7041(ΔU(S)3) infection forming folds that equaled ~45% of the nuclear surface, (iii) the surface area of viral envelopes between nuclear membranes equaled ~2400 R7041(ΔU(S)3) virions per cell, and (iv) during R7041(ΔU(S)3) infection, the Golgi complex expanded dramatically. The data indicate that U(S)3 plays a significant role in regulation of membrane biosynthesis.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, University of Zürich, Switzerland.
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14
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Sutter E, de Oliveira AP, Tobler K, Schraner EM, Sonda S, Kaech A, Lucas MS, Ackermann M, Wild P. Herpes simplex virus 1 induces de novo phospholipid synthesis. Virology 2012; 429:124-35. [PMID: 22560864 DOI: 10.1016/j.virol.2012.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 03/02/2012] [Accepted: 04/10/2012] [Indexed: 11/25/2022]
Abstract
Herpes simplex virus type 1 capsids bud at nuclear membranes and Golgi membranes acquiring an envelope composed of phospholipids. Hence, we measured incorporation of phospholipid precursors into these membranes, and quantified changes in size of cellular compartments by morphometric analysis. Incorporation of [³H]-choline into both nuclear and cytoplasmic membranes was significantly enhanced upon infection. [³H]-choline was also part of isolated virions even grown in the presence of brefeldin A. Nuclei expanded early in infection. The Golgi complex and vacuoles increased substantially whereas the endoplasmic reticulum enlarged only temporarily. The data suggest that HSV-1 stimulates phospholipid synthesis, and that de novo synthesized phospholipids are inserted into nuclear and cytoplasmic membranes to i) maintain membrane integrity in the course of nuclear and cellular expansion, ii) to supply membrane constituents for envelopment of capsids by budding at nuclear membranes and Golgi membranes, and iii) to provide membranes for formation of transport vacuoles.
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Affiliation(s)
- Esther Sutter
- Electron Microscopy, Institute of Veterinary Anatomy, University of Zürich, Switzerland
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15
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Glauser DL, Fraefel C. Interactions between AAV-2 and HSV-1: implications for hybrid vector design. Future Virol 2011. [DOI: 10.2217/fvl.11.13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Herpes simplex virus type 1 (HSV-1)-based amplicon vectors have a transgene capacity of up to 150 kbp and can efficiently transduce many different cell types in culture and in vivo without causing cytopathic effects. However, these vectors do not support long-term transgene expression. Adeno-associated virus type 2 (AAV-2) has the capacity to integrate its genome into a specific site on human chromosome 19, but AAV-2-derived gene therapy vectors have a transgene capacity of only 4.5 kb. To combine the large transgene capacity of HSV-1 with the potential for site-specific genomic integration and long-term transgene expression of AAV-2, HSV/AAV hybrid vectors have been developed. This review describes the design, applications and limitations of these hybrid vectors. However, as HSV-1 is a full helper virus for AAV-2 replication, the main focus is the analysis of the molecular mechanisms of interaction between the two viruses. The knowledge of these interactions will have direct implications on the design of novel HSV/AAV hybrid vectors.
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Affiliation(s)
- Daniel L Glauser
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK
| | - Cornel Fraefel
- Institute of Virology, University of Zurich, Winterthurerstr. 266a, 8057 Zurich, Switzerland
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16
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Guo H, Shen S, Wang L, Deng H. Role of tegument proteins in herpesvirus assembly and egress. Protein Cell 2010; 1:987-98. [PMID: 21153516 DOI: 10.1007/s13238-010-0120-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 11/04/2010] [Indexed: 10/18/2022] Open
Abstract
Morphogenesis and maturation of viral particles is an essential step of viral replication. An infectious herpesviral particle has a multilayered architecture, and contains a large DNA genome, a capsid shell, a tegument and an envelope spiked with glycoproteins. Unique to herpesviruses, tegument is a structure that occupies the space between the nucleocapsid and the envelope and contains many virus encoded proteins called tegument proteins. Historically the tegument has been described as an amorphous structure, but increasing evidence supports the notion that there is an ordered addition of tegument during virion assembly, which is consistent with the important roles of tegument proteins in the assembly and egress of herpesviral particles. In this review we first give an overview of the herpesvirus assembly and egress process. We then discuss the roles of selected tegument proteins in each step of the process, i.e., primary envelopment, de-envelopment, secondary envelopment and transport of viral particles. We also suggest key issues that should be addressed in the near future.
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Affiliation(s)
- Haitao Guo
- CAS Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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17
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de Oliveira AP, Fraefel C. Herpes simplex virus type 1/adeno-associated virus hybrid vectors. Open Virol J 2010; 4:109-22. [PMID: 20811580 PMCID: PMC2930156 DOI: 10.2174/1874357901004030109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2009] [Revised: 01/12/2010] [Accepted: 01/13/2010] [Indexed: 11/22/2022] Open
Abstract
Herpes simplex virus type 1 (HSV-1) amplicons can accommodate foreign DNA of any size up to 150 kbp and, therefore, allow extensive combinations of genetic elements. Genomic sequences as well as cDNA, large transcriptional regulatory sequences for cell type-specific expression, multiple transgenes, and genetic elements from other viruses to create hybrid vectors may be inserted in a modular fashion. Hybrid amplicons use genetic elements from HSV-1 that allow replication and packaging of the vector DNA into HSV-1 virions, and genetic elements from other viruses that either direct integration of transgene sequences into the host genome or allow episomal maintenance of the vector. Thus, the advantages of the HSV-1 amplicon system, including large transgene capacity, broad host range, strong nuclear localization, and availability of helper virus-free packaging systems are retained and combined with those of heterologous viral elements that confer genetic stability to the vector DNA. Adeno-associated virus (AAV) has the unique capability of integrating its genome into a specific site, designated AAVS1, on human chromosome 19. The AAV rep gene and the inverted terminal repeats (ITRs) that flank the AAV genome are sufficient for this process. HSV-1 amplicons have thus been designed that contain the rep gene and a transgene cassette flanked by AAV ITRs. These HSV/AAV hybrid vectors direct site-specific integration of transgene sequences into AAVS1 and support long-term transgene expression.
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Affiliation(s)
| | - Cornel Fraefel
- Institute of Virology, University of Zurich, Zurich, Switzerland
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18
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19
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Hess MW, Pfaller K, Ebner HL, Beer B, Hekl D, Seppi T. 3D versus 2D cell culture implications for electron microscopy. Methods Cell Biol 2010; 96:649-70. [PMID: 20869542 DOI: 10.1016/s0091-679x(10)96027-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cell culture systems are indispensable tools for basic research and a wide range of clinical in vitro studies. However, conventional 2D cell cultures poorly mimic the conditions in the living organism. This limitation may seriously compromise the reliability and significance of data obtained from such approaches. Therefore, we present here a comparative study on selected 3D and 2D cell cultures of U87-MG human glioblastoma cells that were processed by means of high-pressure freezing and freeze-substitution as well as by conventional chemical fixation and Tokuyasu cryo-section immuno-labeling. Three-dimensional cultures comprised pseudo-vascularized cultures, fiber and bead scaffold cultures, and spheroid cultures. Cell cultures in dishes and on coverslips were the static 2D culture systems used as reference models. We will discuss morphological and immuno-cytochemical observations with respect to the feasibility of the cell culture systems investigated for the state-of-the-art electron microscopy.
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Affiliation(s)
- Michael W Hess
- Division of Histology and Embryology, Innsbruck Medical University, Innsbruck A-6020, Austria
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20
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Kelly BJ, Fraefel C, Cunningham AL, Diefenbach RJ. Functional roles of the tegument proteins of herpes simplex virus type 1. Virus Res 2009; 145:173-86. [PMID: 19615419 DOI: 10.1016/j.virusres.2009.07.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2009] [Revised: 07/07/2009] [Accepted: 07/07/2009] [Indexed: 10/20/2022]
Abstract
Herpes virions consist of four morphologically distinct structures, a DNA core, capsid, tegument, and envelope. Tegument occupies the space between the nucleocapsid (capsid containing DNA core) and the envelope. A combination of genetic, biochemical and proteomic analysis of alphaherpes virions suggest the tegument contains in the order of 20 viral proteins. Historically the tegument has been described as amorphous but increasing evidence suggests there is an ordered addition of tegument during assembly. This review highlights the diverse roles, in addition to structural, that tegument plays during herpes viral replication using as an example herpes simplex virus type 1. Such diverse roles include: capsid transport during entry and egress; targeting of the capsid to the nucleus; regulation of transcription, translation and apoptosis; DNA replication; immune modulation; cytoskeletal assembly; nuclear egress of capsid; and viral assembly and final egress.
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Affiliation(s)
- Barbara J Kelly
- Centre for Virus Research, The Westmead Millennium Institute, The University of Sydney and Westmead Hospital, Westmead, NSW 2145, Australia
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21
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Wild P, Senn C, Manera CL, Sutter E, Schraner EM, Tobler K, Ackermann M, Ziegler U, Lucas MS, Kaech A. Exploring the nuclear envelope of herpes simplex virus 1-infected cells by high-resolution microscopy. J Virol 2009; 83:408-19. [PMID: 18922868 PMCID: PMC2612326 DOI: 10.1128/jvi.01568-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Accepted: 10/06/2008] [Indexed: 01/11/2023] Open
Abstract
Herpesviruses are composed of capsid, tegument, and envelope. Capsids assemble in the nucleus and exit the nucleus by budding at the inner nuclear membrane, acquiring tegument and the envelope. This study focuses on the changes of the nuclear envelope during herpes simplex virus 1 (HSV-1) infection in HeLa and Vero cells by employing preparation techniques at ambient and low temperatures for high-resolution scanning and transmission electron microscopy and confocal laser scanning microscopy. Cryo-field emission scanning electron microscopy of freeze-fractured cells showed for the first time budding of capsids at the nuclear envelope at the third dimension with high activity at 10 h and low activity at 15 h of incubation. The mean number of pores was significantly lower, and the mean interpore distance and the mean interpore area were significantly larger than those for mock-infected cells 15 h after inoculation. Forty-five percent of nuclear pores in HSV-1-infected cells were dilated to more than 140 nm. Nuclear material containing capsids protrude through them into the cytoplasm. Examination of in situ preparations after dry fracturing revealed significant enlargements of the nuclear pore diameter and of the nuclear pore central channel in HSV-1-infected cells compared to mock-infected cells. The demonstration of nucleoporins by confocal microscopy also revealed fewer pores but focal enhancement of fluorescence signals in HSV-1-infected cells, whereas Western blots showed no loss of nucleoporins from cells. The data suggest that infection with HSV-1 alters the number, size, and architecture of nuclear pores without a loss of nucleoporins from altered nuclear pore complexes.
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Affiliation(s)
- Peter Wild
- Electron Microscopy, Institute of Virology, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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Robinson KE, Meers J, Gravel JL, McCarthy FM, Mahony TJ. The essential and non-essential genes of Bovine herpesvirus 1. J Gen Virol 2008; 89:2851-2863. [DOI: 10.1099/vir.0.2008/002501-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bovine herpesvirus 1 (BoHV-1) is an economically important pathogen of cattle associated with respiratory and reproductive disease. To further develop BoHV-1 as a vaccine vector, a study was conducted to identify the essential and non-essential genes required for in vitro viability. Random-insertion mutagenesis utilizing a Tn5 transposition system and targeted gene deletion were employed to construct gene disruption and gene deletion libraries, respectively, of an infectious clone of BoHV-1. Transposon insertion position and confirmation of gene deletion were determined by direct sequencing. The essential or non-essential requirement of either transposed or deleted open reading frames (ORFs) was assessed by transfection of respective BoHV-1 DNA into host cells. Of the 73 recognized ORFs encoded by the BoHV-1 genome, 33 were determined to be essential and 36 to be non-essential for virus viability in cell culture; determining the requirement of the two dual copy ORFs was inconclusive. The majority of ORFs were shown to conform to the in vitro requirements of BoHV-1 homologues encoded by human herpesvirus 1 (HHV-1). However, ORFs encoding glycoprotein K (UL53), regulatory, membrane, tegument and capsid proteins (UL54, UL49.5, UL49, UL35, UL20, UL16 and UL7) were shown to differ in requirement when compared to HHV-1-encoded homologues.
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Affiliation(s)
- Karl E. Robinson
- School of Veterinary Science, University of Queensland, St Lucia, Brisbane, QLD, Australia
- Department of Primary Industries and Fisheries, St Lucia, Brisbane, QLD, Australia
| | - Joanne Meers
- School of Veterinary Science, University of Queensland, St Lucia, Brisbane, QLD, Australia
| | - Jennifer L. Gravel
- Department of Primary Industries and Fisheries, St Lucia, Brisbane, QLD, Australia
| | - Fiona M. McCarthy
- Department of Primary Industries and Fisheries, St Lucia, Brisbane, QLD, Australia
| | - Timothy J. Mahony
- Department of Primary Industries and Fisheries, St Lucia, Brisbane, QLD, Australia
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23
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Abstract
Electron microscopy is a powerful tool to visualize viruses in diagnostic as well as in research settings for investigating viral structure and virus-cell interactions. Here, a simple but efficient method is described for demonstrating viruses by negative staining, and its limit is discussed. A prerequisite to obtain reliable information on virus-cell interactions is excellent preservation of cellular and viral ultrastructure. The crux is that during fixation and embedding, by applying conventional protocols about 50% of the lipids are lost, which results in loss of integrity of cell membranes. To achieve good preservation of cellular architectures, good contrast, and both high spatial and temporal resolution, methods for freezing, freeze-substitution, and freeze-etching are described and their applicability discussed mostly taking complicated built herpes viruses as examples.
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Affiliation(s)
- Peter Wild
- Electron Microscopy, Institutes of Veterinary Anatomy and of Virology, University of Zürich, CH-8057 Zürich, Switzerland
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25
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Leuzinger H, Ziegler U, Schraner EM, Fraefel C, Glauser DL, Heid I, Ackermann M, Mueller M, Wild P. Herpes simplex virus 1 envelopment follows two diverse pathways. J Virol 2005; 79:13047-59. [PMID: 16189007 PMCID: PMC1235821 DOI: 10.1128/jvi.79.20.13047-13059.2005] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpesvirus envelopment is assumed to follow an uneconomical pathway including primary envelopment at the inner nuclear membrane, de-envelopment at the outer nuclear membrane, and reenvelopment at the trans-Golgi network. In contrast to the hypothesis of de-envelopment by fusion of the primary envelope with the outer nuclear membrane, virions were demonstrated to be transported from the perinuclear space to rough endoplasmic reticulum (RER) cisternae. Here we show by high-resolution microscopy that herpes simplex virus 1 envelopment follows two diverse pathways. First, nuclear envelopment includes budding of capsids at the inner nuclear membrane into the perinuclear space whereby tegument and a thick electron dense envelope are acquired. The substance responsible for the dense envelope is speculated to enable intraluminal transportation of virions via RER into Golgi cisternae. Within Golgi cisternae, virions are packaged into transport vacuoles containing one or several virions. Second, for cytoplasmic envelopment, capsids gain direct access from the nucleus to the cytoplasm via impaired nuclear pores. Cytoplasmic capsids could bud at the outer nuclear membrane, at membranes of RER, Golgi cisternae, and large vacuoles, and at banana-shaped membranous entities that were found to continue into Golgi membranes. Envelopes originating by budding at the outer nuclear membrane and RER membrane also acquire a dense substance. Budding at Golgi stacks, designated wrapping, results in single virions within small vacuoles that contain electron-dense substances between envelope and vacuolar membranes.
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Affiliation(s)
- Helene Leuzinger
- Electron Microscopy, Institutes of Veterinary Anatomy and of Virology, Zürich, Switzerland
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26
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Wild P, Engels M, Senn C, Tobler K, Ziegler U, Schraner EM, Loepfe E, Ackermann M, Mueller M, Walther P. Impairment of nuclear pores in bovine herpesvirus 1-infected MDBK cells. J Virol 2005; 79:1071-83. [PMID: 15613336 PMCID: PMC538577 DOI: 10.1128/jvi.79.2.1071-1083.2005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpesvirus capsids originating in the nucleus overcome the nucleocytoplasmic barrier by budding at the inner nuclear membrane. The fate of the resulting virions is still under debate. The fact that capsids approach Golgi membranes from the cytoplasmic side led to the theory of fusion between the viral envelope and the outer nuclear membrane, resulting in the release of capsids into the cytoplasm. We recently discovered a continuum from the perinuclear space to the Golgi complex implying (i) intracisternal viral transportation from the perinuclear space directly into Golgi cisternae and (ii) the existence of an alternative pathway of capsids from the nucleus to the cytoplasm. Here, we analyzed the nuclear surface by high-resolution microscopy. Confocal microscopy of MDBK cells infected with recombinant bovine herpesvirus 1 expressing green fluorescent protein fused to VP26 (a minor capsid protein) revealed distortions of the nuclear surface in the course of viral multiplication. High-resolution scanning and transmission electron microscopy proved the distortions to be related to enlargement of nuclear pores through which nuclear content including capsids protrudes into the cytoplasm, suggesting that capsids use impaired nuclear pores as gateways to gain access to the cytoplasmic matrix. Close examination of Golgi membranes, rough endoplasmic reticulum, and outer nuclear membrane yielded capsid-membrane interaction of high identity to the budding process at the inner nuclear membrane. These observations signify the ability of capsids to induce budding at any cell membrane, provided the fusion machinery is present and/or budding is not suppressed by viral proteins.
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Affiliation(s)
- Peter Wild
- Electron Microscopy Institute of Veterinary Anatomy, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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27
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Corrigendum. J Microsc 2004. [DOI: 10.1111/j.0022-2720.2004.01388.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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28
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Vazirabadi G, Geiger TR, Coffin Iii WF, Martin JM. Epstein-Barr virus latent membrane protein-1 (LMP-1) and lytic LMP-1 localization in plasma membrane-derived extracellular vesicles and intracellular virions. J Gen Virol 2003; 84:1997-2008. [PMID: 12867629 DOI: 10.1099/vir.0.19156-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Epstein-Barr virus (EBV) is a human herpesvirus associated with a number of malignancies. EBV establishes a latent infection in human B cells in vitro, and infected lymphoblastoid cells proliferate indefinitely as a result of virus activation of cellular signalling pathways. Latently infected cells express a viral oncoprotein called the latent membrane protein-1 (LMP-1). LMP-1 signals both proliferative and survival signals to the infected B cell. The switch from latency to lytic replication is associated with upregulation of an N-terminally truncated LMP-1, called lytic LMP-1 (lyLMP-1). To understand better the relationship between LMP-1 protein function and the virus life cycle, LMP-1 and lyLMP-1 were precisely localized in infected B cells. Immunoelectron microscopy of latently infected cells revealed LMP-1 localized in discrete patches in the plasma membrane. Unexpectedly, immunogold-labelled LMP-1 was found in vesicles budding from the plasma membrane into the extracellular space and in small membrane vesicles accumulating in conditioned medium from infected cells. LyLMP-1 immunolabelling was observed only in B95-8 cells harbouring detectable intracellular virus particles and was abundant in the nuclear membrane early, and in the plasma membrane late, following lytic cycle induction. LyLMP-1 immunoreactivity was also observed at sites of virus budding and associated with intracellular virions, suggesting that lyLMP-1 might be incorporated into cytoplasmic virions when budding through the nuclear membrane.
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Affiliation(s)
- Golnar Vazirabadi
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA
| | - Timothy R Geiger
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA
| | - William F Coffin Iii
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA
| | - Jennifer M Martin
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA
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Yamamoto D, Tani K, Gotoh T, Kouyama T. Direct observations of freeze-etching processes of ice-embedded biomembranes by atomic force microscopy. Micron 2003; 34:9-18. [PMID: 12694853 DOI: 10.1016/s0968-4328(03)00004-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have fabricated a cryogenic atomic force microscope that is designed for structural investigation of freeze-fractured biological specimens. The apparatus is operated in liquid nitrogen gas at atmospheric pressure. Freeze-fracturing, freeze-etching and subsequent imaging are carried out in the same chamber, so that the surface topography of a fractured plane is easily visualized without ice contamination. A controlled superficial sublimation of volatile molecules allows us to obtain three-dimensional views of ultrastructures of biological membranes.
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Affiliation(s)
- Daisuke Yamamoto
- Department of Physics, Graduate School of Science, Nagoya University, Furo-Cho, Chikusa-ku, Nagoya, Japan
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