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Grams TR, Edwards TG, Bloom DC. A viral lncRNA tethers HSV-1 genomes at the nuclear periphery to establish viral latency. J Virol 2023; 97:e0143823. [PMID: 37991364 PMCID: PMC10734467 DOI: 10.1128/jvi.01438-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 10/20/2023] [Indexed: 11/23/2023] Open
Abstract
IMPORTANCE Herpes simplex virus 1 (HSV-1) establishes lifelong latency in neuronal cells. Following a stressor, the virus reactivates from latency, virus is shed at the periphery and recurrent disease can occur. During latency, the viral lncRNA termed the latency-associated transcript (LAT) is known to accumulate to high abundance. The LAT is known to impact many aspects of latency though the molecular events involved are not well understood. Here, we utilized a human neuronal cell line model of HSV latency and reactivation (LUHMES) to identify the molecular-binding partners of the LAT during latency. We found that the LAT binds to both the cellular protein, TMEM43, and HSV-1 genomes in LUHMES cells. Additionally, we find that knockdown of TMEM43 prior to infection results in a decreased ability of HSV-1 to establish latency. This work highlights a potential mechanism for how the LAT facilitates the establishment of HSV-1 latency in human neurons.
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Affiliation(s)
- Tristan R. Grams
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, USA
| | - Terri G. Edwards
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, USA
| | - David C. Bloom
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, USA
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Vanni EAH, Foley JW, Davison AJ, Sommer M, Liu D, Sung P, Moffat J, Zerboni L, Arvin AM. The latency-associated transcript locus of herpes simplex virus 1 is a virulence determinant in human skin. PLoS Pathog 2020; 16:e1009166. [PMID: 33370402 PMCID: PMC7794027 DOI: 10.1371/journal.ppat.1009166] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 01/08/2021] [Accepted: 11/12/2020] [Indexed: 12/11/2022] Open
Abstract
Herpes simplex virus 1 (HSV-1) infects skin and mucosal epithelial cells and then travels along axons to establish latency in the neurones of sensory ganglia. Although viral gene expression is restricted during latency, the latency-associated transcript (LAT) locus encodes many RNAs, including a 2 kb intron known as the hallmark of HSV-1 latency. Here, we studied HSV-1 infection and the role of the LAT locus in human skin xenografts in vivo and in cultured explants. We sequenced the genomes of our stock of HSV-1 strain 17syn+ and seven derived viruses and found nonsynonymous mutations in many viral proteins that had no impact on skin infection. In contrast, deletions in the LAT locus severely impaired HSV-1 replication and lesion formation in skin. However, skin replication was not affected by impaired intron splicing. Moreover, although the LAT locus has been implicated in regulating gene expression in neurones, we observed only small changes in transcript levels that were unrelated to the growth defect in skin, suggesting that its functions in skin may be different from those in neurones. Thus, although the LAT locus was previously thought to be dispensable for lytic infection, we show that it is a determinant of HSV-1 virulence during lytic infection of human skin. Herpes simplex virus type 1 (HSV-1) infects and destroys the outer layer of skin cells, producing lesions known as cold sores. Although these lesions heal, the virus persists in the host for the lifetime and can reactivate to cause new lesions. This is possible because the virus enters the axons of neurones in the skin and moves to their cell bodies located in spinal or cranial nerve bundles called ganglia, where the virus becomes dormant (latent). The most abundant viral RNAs expressed during this state are the latency associated transcripts (LATs), which have been considered a hallmark of HSV-1 latency. Here, we studied HSV-1 infection and spread in human skin. Unexpectedly, we found that the LAT locus is necessary for lesion formation in skin. HSV-1 viruses that were genetically mutated to delete the start of the locus could not spread in skin, whereas viruses with many other genetic mutations had this capacity. Our results suggest that an antiviral drug that inhibits transcripts from this region of the viral genome could block viral spread in skin, or a vaccine could possibly be produced by genetically modifying the virus at the LAT locus and by doing so, limit the virus’ ability become latent in neurones.
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Affiliation(s)
- Emilia A. H. Vanni
- Departments of Pediatrics and Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
| | - Joseph W. Foley
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Andrew J. Davison
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Marvin Sommer
- Departments of Pediatrics and Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Dongmei Liu
- Department of Microbiology and Immunology, State University of New York-Upstate Medical University, Syracuse, New York, United States of America
| | - Phillip Sung
- Departments of Pediatrics and Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Jennifer Moffat
- Department of Microbiology and Immunology, State University of New York-Upstate Medical University, Syracuse, New York, United States of America
| | - Leigh Zerboni
- Departments of Pediatrics and Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Ann M. Arvin
- Departments of Pediatrics and Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
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In Vivo Knockdown of the Herpes Simplex Virus 1 Latency-Associated Transcript Reduces Reactivation from Latency. J Virol 2018; 92:JVI.00812-18. [PMID: 29875240 DOI: 10.1128/jvi.00812-18] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 05/29/2018] [Indexed: 12/14/2022] Open
Abstract
During herpes simplex virus (HSV) latency, most viral genes are silenced, with the exception of one region of the genome encoding the latency-associated transcript (LAT). This long noncoding RNA was originally described as having a role in enhancing HSV-1 reactivation. However, subsequent evidence showing that the LAT blocked apoptosis and promoted efficient establishment of latency suggested that its effects on reactivation were secondary to establishment. Here, we utilized an adeno-associated virus (AAV) vector to deliver a LAT-targeting hammerhead ribozyme to HSV-1-infected neurons of rabbits after the establishment of HSV-1 latency. The rabbits were then induced to reactivate latent HSV-1. Using this model, we show that decreasing LAT levels in neurons following the establishment of latency reduced the ability of the virus to reactivate. This demonstrates that the HSV-1 LAT RNA has a role in reactivation that is independent of its function in establishment of latency. In addition, these results suggest the potential of AAV vectors expressing LAT-targeting ribozymes as a potential therapy for recurrent HSV disease such as herpes stromal keratitis, a leading cause of infectious blindness.IMPORTANCE Herpes simplex virus (HSV) establishes a lifelong infection and remains dormant (latent) in our nerve cells. Occasionally HSV reactivates to cause disease, with HSV-1 typically causing cold sores whereas HSV-2 is the most common cause of genital herpes. The details of how HSV reactivates are largely unknown. Most of HSV's genes are silent during latency, with the exception of RNAs made from the latency-associated transcript (LAT) region. While viruses that make less LAT do not reactivate efficiently, these viruses also do not establish latency as efficiently. Here we deliver a ribozyme that can degrade the LAT to the nerve cells of latently infected rabbits using a gene therapy vector. We show that this treatment blocks reactivation in the majority of the rabbits. This work shows that the LAT RNA is important for reactivation and suggests the potential of this treatment as a therapy for treating HSV infections.
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Neuronal Subtype Determines Herpes Simplex Virus 1 Latency-Associated-Transcript Promoter Activity during Latency. J Virol 2018; 92:JVI.00430-18. [PMID: 29643250 DOI: 10.1128/jvi.00430-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 04/06/2018] [Indexed: 12/16/2022] Open
Abstract
Herpes simplex virus (HSV) latency in neurons remains poorly understood, and the heterogeneity of the sensory nervous system complicates mechanistic studies. In this study, we used primary culture of adult trigeminal ganglion (TG) mouse neurons in microfluidic devices and an in vivo model to examine the subtypes of sensory neurons involved in HSV latency. HSV-infected neurofilament heavy-positive (NefH+) neurons were more likely to express latency-associated transcripts (LATs) than infected neurofilament heavy-negative (NefH-) neurons. This differential expression of the LAT promoter correlated with differences in HSV-1 early infection that manifested as differences in the efficiency with which HSV particles reached the cell body following infection at the distal axon. In vivo, we further identified a specific subset of NefH+ neurons which coexpressed calcitonin gene-related peptide α (NefH+ CGRP+ neurons) as the sensory neuron subpopulation with the highest LAT promoter activity following HSV-1 infection. Finally, an early-phase reactivation assay showed HSV-1 reactivating in NefH+ CGRP+ neurons, although other sensory neuron subpopulations were also involved. Together, these results show that sensory neurons expressing neurofilaments exhibit enhanced LAT promoter activity. We hypothesize that the reduced efficiency of HSV-1 invasion at an early phase of infection may promote efficient establishment of latency in NefH+ neurons due to initiation of the antiviral state preceding arrival of the virus at the neuronal cell body. While the outcome of HSV-1 infection of neurons is determined by a broad variety of factors in vivo, neuronal subtypes are likely to play differential roles in modulating the establishment of latent infection.IMPORTANCE Two pivotal properties of HSV-1 make it a successful pathogen. First, it infects neurons, which are immune privileged. Second, it establishes latency in these neurons. Together, these properties allow HSV to persist for the lifetime of its host. Neurons are diverse and highly organized cells, with specific anatomical, physiological, and molecular characteristics. Previous work has shown that establishment of latency by HSV-1 does not occur equally in all types of neurons. Our results show that the kinetics of HSV infection and the levels of latency-related gene expression differ in certain types of neurons. The neuronal subtype infected by HSV is therefore a critical determinant of the outcome of infection and latency.
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Differentiated Human SH-SY5Y Cells Provide a Reductionist Model of Herpes Simplex Virus 1 Neurotropism. J Virol 2017; 91:JVI.00958-17. [PMID: 28956768 DOI: 10.1128/jvi.00958-17] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 09/19/2017] [Indexed: 12/13/2022] Open
Abstract
Neuron-virus interactions that occur during herpes simplex virus (HSV) infection are not fully understood. Neurons are the site of lifelong latency and are a crucial target for long-term suppressive therapy or viral clearance. A reproducible neuronal model of human origin would facilitate studies of HSV and other neurotropic viruses. Current neuronal models in the herpesvirus field vary widely and have caveats, including incomplete differentiation, nonhuman origins, or the use of dividing cells that have neuropotential but lack neuronal morphology. In this study, we used a robust approach to differentiate human SH-SY5Y neuroblastoma cells over 2.5 weeks, producing a uniform population of mature human neuronal cells. We demonstrate that terminally differentiated SH-SY5Y cells have neuronal morphology and express proteins with subcellular localization indicative of mature neurons. These neuronal cells are able to support a productive HSV-1 infection, with kinetics and overall titers similar to those seen in undifferentiated SH-SY5Y cells and the related SK-N-SH cell line. However, terminally differentiated, neuronal SH-SY5Y cells release significantly less extracellular HSV-1 by 24 h postinfection (hpi), suggesting a unique neuronal response to viral infection. With this model, we are able to distinguish differences in neuronal spread between two strains of HSV-1. We also show expression of the antiviral protein cyclic GMP-AMP synthase (cGAS) in neuronal SH-SY5Y cells, which is the first demonstration of the presence of this protein in nonepithelial cells. These data provide a model for studying neuron-virus interactions at the single-cell level as well as via bulk biochemistry and will be advantageous for the study of neurotropic viruses in vitroIMPORTANCE Herpes simplex virus (HSV) affects millions of people worldwide, causing painful oral and genital lesions, in addition to a multitude of more severe symptoms such as eye disease, neonatal infection, and, in rare cases, encephalitis. Presently, there is no cure available to treat those infected or prevent future transmission. Due to the ability of HSV to cause a persistent, lifelong infection in the peripheral nervous system, the virus remains within the host for life. To better understand the basis of virus-neuron interactions that allow HSV to persist within the host peripheral nervous system, improved neuronal models are required. Here we describe a cost-effective and scalable human neuronal model system that can be used to study many neurotropic viruses, such as HSV, Zika virus, dengue virus, and rabies virus.
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Phelan D, Barrozo ER, Bloom DC. HSV1 latent transcription and non-coding RNA: A critical retrospective. J Neuroimmunol 2017; 308:65-101. [PMID: 28363461 DOI: 10.1016/j.jneuroim.2017.03.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 03/02/2017] [Accepted: 03/02/2017] [Indexed: 12/22/2022]
Abstract
Virologists have invested great effort into understanding how the herpes simplex viruses and their relatives are maintained dormant over the lifespan of their host while maintaining the poise to remobilize on sporadic occasions. Piece by piece, our field has defined the tissues in play (the sensory ganglia), the transcriptional units (the latency-associated transcripts), and the responsive genomic region (the long repeats of the viral genomes). With time, the observed complexity of these features has compounded, and the totality of viral factors regulating latency are less obvious. In this review, we compose a comprehensive picture of the viral genetic elements suspected to be relevant to herpes simplex virus 1 (HSV1) latent transcription by conducting a critical analysis of about three decades of research. We describe these studies, which largely involved mutational analysis of the notable latency-associated transcripts (LATs), and more recently a series of viral miRNAs. We also intend to draw attention to the many other less characterized non-coding RNAs, and perhaps coding RNAs, that may be important for consideration when trying to disentangle the multitude of phenotypes of the many genetic modifications introduced into recombinant HSV1 strains.
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Affiliation(s)
- Dane Phelan
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, United States.
| | - Enrico R Barrozo
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, United States.
| | - David C Bloom
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, United States.
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Figueroa T, Boumart I, Coupeau D, Rasschaert D. Hyperediting by ADAR1 of a new herpesvirus lncRNA during the lytic phase of the oncogenic Marek's disease virus. J Gen Virol 2016; 97:2973-2988. [PMID: 27655063 DOI: 10.1099/jgv.0.000606] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Marek's disease virus, or Gallid herpesvirus 2 (GaHV-2), is an avian alphaherpesvirus that induces T-cell lymphoma in chickens. During transcriptomic studies of the RL region of the genome, we characterized the 7.5 kbp gene of the ERL lncRNA (edited repeat-long, long non-coding RNA), which may act as a natural antisense transcript (NAT) of the major GaHV-2 oncogene meq and of two of the three miRNA clusters. During infections in vivo and in vitro, we detected hyperediting of the ERL lncRNA that appeared to be directly correlated with ADAR1 expression levels. The ERL lncRNA was expressed equally during the lytic and latent phases of infection and during viral reactivation, but its hyperediting increased only during the lytic infection of chicken embryo fibroblasts. We also showed that chicken ADAR1 expression was controlled by the JAK/STAT IFN-response pathway, through an inducible promoter containing IFN-stimulated response elements that were functional during stimulation with IFN-α or poly(I:C). Like the human and murine miR-155-5p, the chicken gga-miR-155-5p and the GaHV-2 analogue mdv1-miR-M4-5p deregulated this pathway by targeting and repressing expression of suppressor of cytokine signalling 1, leading to the upregulation of ADAR1. Finally, we hypothesized that the natural antisense transcript role of the ERL lncRNA could be disrupted by its hyperediting, particularly during viral lytic replication, and that the observed deregulation of the innate immune system by mdv1-miR-M4-5p might contribute to the viral cycle.
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Affiliation(s)
- Thomas Figueroa
- Equipe Transcription et Lymphome Viro-Induit (TLVI), UMR 7261 CNRS/Université François Rabelais de Tours, Tours, France
| | - Imane Boumart
- Equipe Transcription et Lymphome Viro-Induit (TLVI), UMR 7261 CNRS/Université François Rabelais de Tours, Tours, France
| | - Damien Coupeau
- Equipe Transcription et Lymphome Viro-Induit (TLVI), UMR 7261 CNRS/Université François Rabelais de Tours, Tours, France
| | - Denis Rasschaert
- Equipe Transcription et Lymphome Viro-Induit (TLVI), UMR 7261 CNRS/Université François Rabelais de Tours, Tours, France
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Shipley MM, Mangold CA, Szpara ML. Differentiation of the SH-SY5Y Human Neuroblastoma Cell Line. J Vis Exp 2016:53193. [PMID: 26967710 DOI: 10.3791/53193] [Citation(s) in RCA: 170] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Having appropriate in vivo and in vitro systems that provide translational models for human disease is an integral aspect of research in neurobiology and the neurosciences. Traditional in vitro experimental models used in neurobiology include primary neuronal cultures from rats and mice, neuroblastoma cell lines including rat B35 and mouse Neuro-2A cells, rat PC12 cells, and short-term slice cultures. While many researchers rely on these models, they lack a human component and observed experimental effects could be exclusive to the respective species and may not occur identically in humans. Additionally, although these cells are neurons, they may have unstable karyotypes, making their use problematic for studies of gene expression and reproducible studies of cell signaling. It is therefore important to develop more consistent models of human neurological disease. The following procedure describes an easy-to-follow, reproducible method to obtain homogenous and viable human neuronal cultures, by differentiating the chromosomally stable human neuroblastoma cell line, SH-SY5Y. This method integrates several previously described methods(1-4) and is based on sequential removal of serum from media. The timeline includes gradual serum-starvation, with introduction of extracellular matrix proteins and neurotrophic factors. This allows neurons to differentiate, while epithelial cells are selected against, resulting in a homogeneous neuronal culture. Representative results demonstrate the successful differentiation of SH-SY5Y neuroblastoma cells from an initial epithelial-like cell phenotype into a more expansive and branched neuronal phenotype. This protocol offers a reliable way to generate homogeneous populations of neuronal cultures that can be used for subsequent biochemical and molecular analyses, which provides researchers with a more accurate translational model of human infection and disease.
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Affiliation(s)
- Mackenzie M Shipley
- Department of Biochemistry and Molecular Biology, The Huck Institutes of the Life Sciences, The Pennsylvania State University
| | - Colleen A Mangold
- Department of Biochemistry and Molecular Biology, The Huck Institutes of the Life Sciences, The Pennsylvania State University
| | - Moriah L Szpara
- Department of Biochemistry and Molecular Biology, The Huck Institutes of the Life Sciences, The Pennsylvania State University;
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Abstract
Alphaherpesviruses infect a variety of species from sea turtles to man and can cause significant disease in mammals including humans and livestock. These viruses are characterized by a lytic and latent state in nerve ganglia, with the ability to establish a lifelong latent infection that is interrupted by periodic reactivation. Previously, it was accepted that latency was a dominant state and that only during relatively infrequent reactivation episodes did latent genomes within ganglia become transcriptionally active. Here, we review recent data, focusing mainly on Herpes Simplex Virus type 1 which indicate that the latent state is more dynamic than recently appreciated.
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Affiliation(s)
- David C Bloom
- Department of Molecular Genetics & Microbiology, University of Florida College of Medicine, Gainesville, Florida, USA.
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Herpes Simplex Virus 1 Infection of Tree Shrews Differs from That of Mice in the Severity of Acute Infection and Viral Transcription in the Peripheral Nervous System. J Virol 2015; 90:790-804. [PMID: 26512084 DOI: 10.1128/jvi.02258-15] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Accepted: 10/19/2015] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED Studies of herpes simplex virus (HSV) infections of humans are limited by the use of rodent models such as mice, rabbits, and guinea pigs. Tree shrews (Tupaia belangeri chinensis) are small mammals indigenous to southwest Asia. At behavioral, anatomical, genomic, and evolutionary levels, tree shrews are much closer to primates than rodents are, and tree shrews are susceptible to HSV infection. Thus, we have studied herpes simplex virus 1 (HSV-1) infection in the tree shrew trigeminal ganglion (TG) following ocular inoculation. In situ hybridization, PCR, and quantitative reverse transcription-PCR (qRT-PCR) analyses confirm that HSV-1 latently infects neurons of the TG. When explant cocultivation of trigeminal ganglia was performed, the virus was recovered after 5 days of cocultivation with high efficiency. Swabbing the corneas of latently infected tree shrews revealed that tree shrews shed virus spontaneously at low frequencies. However, tree shrews differ significantly from mice in the expression of key HSV-1 genes, including ICP0, ICP4, and latency-associated transcript (LAT). In acutely infected tree shrew TGs, no level of ICP4 was observed, suggesting the absence of infection or a very weak, acute infection compared to that of the mouse. Immunofluorescence staining with ICP4 monoclonal antibody, and immunohistochemistry detection by HSV-1 polyclonal antibodies, showed a lack of viral proteins in tree shrew TGs during both acute and latent phases of infection. Cultivation of supernatant from homogenized, acutely infected TGs with RS1 cells also exhibited an absence of infectious HSV-1 from tree shrew TGs. We conclude that the tree shrew has an undetectable, or a much weaker, acute infection in the TGs. Interestingly, compared to mice, tree shrew TGs express high levels of ICP0 transcript in addition to LAT during latency. However, the ICP0 transcript remained nuclear, and no ICP0 protein could be seen during the course of mouse and tree shrew TG infections. Taken together, these observations suggest that the tree shrew TG infection differs significantly from the existing rodent models. IMPORTANCE Herpes simplex viruses (HSVs) establish lifelong infection in more than 80% of the human population, and their reactivation leads to oral and genital herpes. Currently, rodent models are the preferred models for latency studies. Rodents are distant from primates and may not fully represent human latency. The tree shrew is a small mammal, a prosimian primate, indigenous to southwest Asia. In an attempt to further develop the tree shrew as a useful model to study herpesvirus infection, we studied the establishment of latency and reactivation of HSV-1 in tree shrews following ocular inoculation. We found that the latent virus, which resides in the sensory neurons of the trigeminal ganglion, could be stress reactivated to produce infectious virus, following explant cocultivation and that spontaneous reactivation could be detected by cell culture of tears. Interestingly, the tree shrew model is quite different from the mouse model of HSV infection, in that the virus exhibited only a mild acute infection following inoculation with no detectable infectious virus from the sensory neurons. The mild infection may be more similar to human infection in that the sensory neurons continue to function after herpes reactivation and the affected skin tissue does not lose sensation. Our findings suggest that the tree shrew is a viable model to study HSV latency.
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Kennedy PGE, Rovnak J, Badani H, Cohrs RJ. A comparison of herpes simplex virus type 1 and varicella-zoster virus latency and reactivation. J Gen Virol 2015; 96:1581-602. [PMID: 25794504 DOI: 10.1099/vir.0.000128] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Herpes simplex virus type 1 (HSV-1; human herpesvirus 1) and varicella-zoster virus (VZV; human herpesvirus 3) are human neurotropic alphaherpesviruses that cause lifelong infections in ganglia. Following primary infection and establishment of latency, HSV-1 reactivation typically results in herpes labialis (cold sores), but can occur frequently elsewhere on the body at the site of primary infection (e.g. whitlow), particularly at the genitals. Rarely, HSV-1 reactivation can cause encephalitis; however, a third of the cases of HSV-1 encephalitis are associated with HSV-1 primary infection. Primary VZV infection causes varicella (chickenpox) following which latent virus may reactivate decades later to produce herpes zoster (shingles), as well as an increasingly recognized number of subacute, acute and chronic neurological conditions. Following primary infection, both viruses establish a latent infection in neuronal cells in human peripheral ganglia. However, the detailed mechanisms of viral latency and reactivation have yet to be unravelled. In both cases latent viral DNA exists in an 'end-less' state where the ends of the virus genome are joined to form structures consistent with unit length episomes and concatemers, from which viral gene transcription is restricted. In latently infected ganglia, the most abundantly detected HSV-1 RNAs are the spliced products originating from the primary latency associated transcript (LAT). This primary LAT is an 8.3 kb unstable transcript from which two stable (1.5 and 2.0 kb) introns are spliced. Transcripts mapping to 12 VZV genes have been detected in human ganglia removed at autopsy; however, it is difficult to ascribe these as transcripts present during latent infection as early-stage virus reactivation may have transpired in the post-mortem time period in the ganglia. Nonetheless, low-level transcription of VZV ORF63 has been repeatedly detected in multiple ganglia removed as close to death as possible. There is increasing evidence that HSV-1 and VZV latency is epigenetically regulated. In vitro models that permit pathway analysis and identification of both epigenetic modulations and global transcriptional mechanisms of HSV-1 and VZV latency hold much promise for our future understanding in this complex area. This review summarizes the molecular biology of HSV-1 and VZV latency and reactivation, and also presents future directions for study.
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Affiliation(s)
- Peter G E Kennedy
- 1Institute of Infection, Immunity and Inflammation, University of Glasgow, Garscube Campus, Glasgow G61 1QH, UK
| | - Joel Rovnak
- 2Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80521, USA
| | - Hussain Badani
- 3Department of Neurology, University of Colorado Medical School, Aurora, CO 80045, USA
| | - Randall J Cohrs
- 3Department of Neurology, University of Colorado Medical School, Aurora, CO 80045, USA 4Department of Microbiology, University of Colorado Medical School, Aurora, CO 80045, USA
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Jones C. Bovine Herpes Virus 1 (BHV-1) and Herpes Simplex Virus Type 1 (HSV-1) Promote Survival of Latently Infected Sensory Neurons, in Part by Inhibiting Apoptosis. J Cell Death 2013; 6:1-16. [PMID: 25278776 PMCID: PMC4147773 DOI: 10.4137/jcd.s10803] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
α-Herpesvirinae subfamily members, including herpes simplex virus type 1 (HSV-1) and bovine herpes virus 1 (BHV-1), initiate infection in mucosal surfaces. BHV-1 and HSV-1 enter sensory neurons by cell-cell spread where a burst of viral gene expression occurs. When compared to non-neuronal cells, viral gene expression is quickly extinguished in sensory neurons resulting in neuronal survival and latency. The HSV-1 latency associated transcript (LAT), which is abundantly expressed in latently infected neurons, inhibits apoptosis, viral transcription, and productive infection, and directly or indirectly enhances reactivation from latency in small animal models. Three anti-apoptosis genes can be substituted for LAT, which will restore wild type levels of reactivation from latency to a LAT null mutant virus. Two small non-coding RNAs encoded by LAT possess anti-apoptosis functions in transfected cells. The BHV-1 latency related RNA (LR-RNA), like LAT, is abundantly expressed during latency. The LR-RNA encodes a protein (ORF2) and two microRNAs that are expressed in certain latently infected neurons. Wild-type expression of LR gene products is required for stress-induced reactivation from latency in cattle. ORF2 has anti-apoptosis functions and interacts with certain cellular transcription factors that stimulate viral transcription and productive infection. ORF2 is predicted to promote survival of infected neurons by inhibiting apoptosis and sequestering cellular transcription factors which stimulate productive infection. In addition, the LR encoded microRNAs inhibit viral transcription and apoptosis. In summary, the ability of BHV-1 and HSV-1 to interfere with apoptosis and productive infection in sensory neurons is crucial for the life-long latency-reactivation cycle in their respective hosts.
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Affiliation(s)
- Clinton Jones
- School of Veterinary Medicine and Biomedical Sciences, Nebraska Center for Virology, University of Nebraska, Morrison Life Science Center, Lincoln, NE
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The half-life of the HSV-1 1.5-kb LAT intron is similar to the half-life of the 2.0-kb LAT intron. J Neurovirol 2013; 19:102-8. [PMID: 23335177 DOI: 10.1007/s13365-012-0146-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 10/29/2012] [Accepted: 11/05/2012] [Indexed: 10/27/2022]
Abstract
Herpes simplex virus type 1 establishes a latent infection in the sensory neurons of the peripheral nervous system of humans. Although about 80 genes are expressed during the lytic cycle of the virus infection, essentially only one gene is expressed during the latent cycle. This gene is known as the latency-associated transcript (LAT), and it appears to play a role in the latency cycle through an anti-apoptotic function in the 5' end of the gene and miRNA encoded along the length of the transcript which downregulate some of the viral immediate-early gene products. The LAT gene is about 8.3 kb long and consists of two exons separated by an unusual intron. The intron between the exons consists of two nested introns. This arrangement of introns has been called a twintron. Furthermore, the larger (2 kb) intron has been shown to be very stable. In this study, we measure the stability of the shorter 1.5-kb nested intron and find its half-life is similar to the longer intron. This was achieved by deleting the 0.5-kb overlapping intron from a plasmid construct designed to express the LAT transcript from a tet-inducible promoter and measuring the half-life of the 1.5-kb intron in tissue culture cells. This finding supports the hypothesis that it is the common branch-point region of these nested introns that is responsible for their stability.
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Towards an understanding of the herpes simplex virus type 1 latency-reactivation cycle. Interdiscip Perspect Infect Dis 2010; 2010:262415. [PMID: 20169002 PMCID: PMC2822239 DOI: 10.1155/2010/262415] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 11/30/2009] [Indexed: 12/17/2022] Open
Abstract
Infection by herpes simplex virus type 1 (HSV-1) can cause clinical symptoms in the peripheral and central nervous system. Recurrent ocular shedding can lead to corneal scarring and vision loss making HSV-1 a leading cause of corneal blindness due to an infectious agent. The primary site of HSV-1 latency is sensory neurons within trigeminal ganglia. Periodically, reactivation from latency occurs resulting in virus transmission and recurrent disease. During latency, the latency-associated transcript (LAT) is abundantly expressed. LAT expression is important for the latency-reactivation cycle in animal models, in part, because it inhibits apoptosis, viral gene expression, and productive infection. A novel transcript within LAT coding sequences (AL3) and small nonprotein coding RNAs are also expressed in trigeminal ganglia of latently infected mice. In this review, an update of viral factors that are expressed during latency and their potential roles in regulating the latency-reactivation cycle is discussed.
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15
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Bloom DC, Giordani NV, Kwiatkowski DL. Epigenetic regulation of latent HSV-1 gene expression. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1799:246-56. [PMID: 20045093 DOI: 10.1016/j.bbagrm.2009.12.001] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 12/11/2009] [Accepted: 12/16/2009] [Indexed: 01/27/2023]
Abstract
Like other alpha-herpesviruses, Herpes Simplex Virus Type 1 (HSV-1) possesses the ability to establish latency in sensory ganglia as a non-integrated, nucleosome-associated episome in the host cell nucleus. Transcription of the genome is limited to the Latency-Associated Transcript (LAT), while the lytic genes are maintained in a transcriptionally repressed state. This partitioning of the genome into areas of active and inactive transcription suggests epigenetic control of HSV-1 latent gene expression. During latency viral transcription is not regulated by DNA methylation but likely by post-translational histone modifications. The LAT region is the only region of the genome enriched in marks indicative of transcriptional permissiveness, specifically dimethyl H3 K4 and acetyl H3 K9, K14, while the lytic genes appear under-enriched in those same marks. In addition, facultative heterochromatin marks, specifically trimethyl H3 K27 and the histone variant macroH2A, are enriched on lytic genes during latency. The distinct epigenetic domains of the LAT and the lytic genes appear to be separated by chromatin insulators. Binding of CTCF, a protein that binds to all known vertebrate insulators, to sites within the HSV-1 genome likely prevents heterochromatic spreading and blocks enhancer activity. When the latent viral genome undergoes stress-induced reactivation, it is possible that CTCF binding and insulator function are abrogated, enabling lytic gene transcription to ensue. In this review we summarize our current understanding of latent HSV-1 epigenetic regulation as it pertains to infections in both the rabbit and mouse models. CTCF insulator function and regulation of histone tail modifications will be discussed. We will also present a current model of how the latent genome is carefully controlled at the epigenetic level and how stress-induced changes to it may trigger reactivation.
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Affiliation(s)
- David C Bloom
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, FL 32610-0266, USA.
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Li S, Carpenter D, Hsiang C, Wechsler SL, Jones C. Herpes simplex virus type 1 latency-associated transcript inhibits apoptosis and promotes neurite sprouting in neuroblastoma cells following serum starvation by maintaining protein kinase B (AKT) levels. J Gen Virol 2009; 91:858-66. [PMID: 19955563 DOI: 10.1099/vir.0.015719-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) is expressed abundantly in latently infected sensory neurons. LAT-deletion-mutant virus strains have reduced-reactivation phenotypes in small animal models of infection, demonstrating that LAT plays an important role in the latency-reactivation cycle of HSV-1. Previous studies demonstrated that the anti-apoptosis functions of LAT are important for regulating the latency-reactivation cycle because three different anti-apoptosis genes can substitute for LAT. Although LAT inhibits caspase 3 activation, the signalling pathway by which LAT inhibits caspase 3 activation was not identified. In this study, we analysed mouse neuroblastoma cells (C1300) that express LAT stably (DC-LAT6 cells) following serum starvation. As expected, DC-LAT6 cells were resistant to apoptosis following serum withdrawal. Levels of total and phosphorylated AKT (protein kinase B), a serine/threonine protein kinase that promotes cell survival, were higher in DC-LAT6 cells after serum withdrawal than in C1300 cells or a cell line stably transfected with a LAT promoter mutant (DC-DeltaLAT311). A specific AKT inhibitor reduced the anti-apoptosis functions of LAT and phosphorylated AKT levels. After serum withdrawal, more DC-LAT6 cells sprouted neurites and exhibited a differentiated morphology. NeuN (neuronal nuclei), a neuron-specific nuclear protein, was expressed abundantly in DC-LAT6 cells, but not C1300 cells, after serum withdrawal, further supporting the concept that LAT enhanced neuronal-like morphology. Collectively, these studies suggested that LAT, directly or indirectly, maintained total and phosphorylated AKT levels, which correlated with increased cell survival and mature neuronal-like morphology.
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Affiliation(s)
- Sumin Li
- Department of Veterinary and Biomedical Sciences, Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68503, USA
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Atanasiu D, Fraser NW. The stable 2-kilobase latency-associated transcript of herpes simplex virus type 1 can alter the assembly of the 60S ribosomal subunit and is exported from nucleus to cytoplasm by a CRM1-dependent pathway. J Virol 2007; 81:7695-701. [PMID: 17494083 PMCID: PMC1933333 DOI: 10.1128/jvi.00282-07] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Accepted: 04/30/2007] [Indexed: 11/20/2022] Open
Abstract
During latency of herpes simplex virus type 1 in the neurons of the peripheral nervous system, the major transcript detected is the 2-kb latency-associated transcript (LAT) intron. During lytic infection, this intron has been shown to associate with ribosomes, suggesting a role in modifying the translational machinery of infected cells. In this study we show, using LAT-transfected cells, that the interaction of the intron with the 60S ribosomal subunit leads to irreversible changes in the sedimentation profile of this subunit in the nucleus. Furthermore, the 2-kb LAT intron is transported to the cytoplasm as part of the 60S ribosomal subunit, using a CRM1-dependent pathway.
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Affiliation(s)
- Doina Atanasiu
- Department of Microbiology, University of Pennsylvania School of Medicine, 3610 Hamilton Walk, Philadelphia, PA 19104, USA
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18
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Kulesza CA, Shenk T. Murine cytomegalovirus encodes a stable intron that facilitates persistent replication in the mouse. Proc Natl Acad Sci U S A 2006; 103:18302-7. [PMID: 17105807 PMCID: PMC1838746 DOI: 10.1073/pnas.0608718103] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The human cytomegalovirus immediate-early 5-kb RNA previously has been shown to be a stable intron that is not required for efficient replication of the virus in cultured fibroblasts. Here we describe a murine cytomegalovirus 7.2-kb ortholog of the human cytomegalovirus 5-kb RNA. The 5' end of the 7.2-kb transcript maps to a consensus splice-donor site that is conserved among all cytomegaloviruses. We constructed mutant viruses lacking the entire 7.2-kb coding domain, the splice-donor site predicted to function in the generation of the intron or a hairpin predicted to stabilize the intron. All three mutant viruses failed to produce the 7.2-kb RNA, supporting our conclusion that it is a stable intron. Each of the mutants replicated with normal kinetics in cultured fibroblasts, but the mutants exhibited a clear defect within infected mice. Although the initial acute phase at 4 days after infection appeared to be normal, none of the mutant viruses progressed to the persistent phase, i.e., little virus was detected in the salivary gland at 14 days after infection. The intron functions as an in vivo virulence factor, facilitating progression from the acute to persistent phase of infection.
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Affiliation(s)
| | - Thomas Shenk
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
- *To whom correspondence should be addressed. E-mail:
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Kang W, Mukerjee R, Gartner JJ, Hatzigeorgiou AG, Sandri-Goldin RM, Fraser NW. Characterization of a spliced exon product of herpes simplex type-1 latency-associated transcript in productively infected cells. Virology 2006; 356:106-14. [PMID: 16938324 DOI: 10.1016/j.virol.2006.07.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Revised: 06/16/2006] [Accepted: 07/21/2006] [Indexed: 11/25/2022]
Abstract
The latency-associated transcripts (LATs) of herpes simplex virus type-1 (HSV-1) are the only viral RNAs accumulating during latent infections in the sensory ganglia of the peripheral nervous system. The major form of LAT that accumulates in latently infected neurons is a 2 kb intron, spliced from a much less abundant 8.3 primary transcript. The spliced exon mRNA has been hard to detect. However, in this study, we have examined the spliced exon RNA in productively infected cells using ribonuclease protection (RPA), and quantitative RT-PCR (q-PCR) assays. We were able to detect the LAT exon RNA in productively infected SY5Y cells (a human neuronal cell line). The level of the LAT exon RNA was found to be approximately 5% that of the 2 kb intron RNA and thus is likely to be relatively unstable. Quantitative RT-PCR (q-PCR) assays were used to examine the LAT exon RNA and its properties. They confirmed that the LAT exon mRNA is present at a very low level in productively infected cells, compared to the levels of other viral transcripts. Furthermore, experiments showed that the LAT exon mRNA is expressed as a true late gene, and appears to be polyadenylated. In SY5Y cells, in contrast to most late viral transcripts, the LAT exon RNA was found to be mainly nuclear localized during the late stage of a productive infection. Interestingly, more LAT exon RNA was found in the cytoplasm in differentiated compared to undifferentiated SY5Y cells, suggesting the nucleocytoplasmic distribution of the LAT exon RNA and its related function may be influenced by the differentiation state of cells.
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Affiliation(s)
- Wen Kang
- Department of Microbiology, University of Pennsylvania Medical School, 315 Johnson Pavilion, Philadelphia, PA 19104, USA
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Atanasiu D, Kent JR, Gartner JJ, Fraser NW. The stable 2-kb LAT intron of herpes simplex stimulates the expression of heat shock proteins and protects cells from stress. Virology 2006; 350:26-33. [PMID: 16519918 DOI: 10.1016/j.virol.2006.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 01/19/2006] [Accepted: 02/02/2006] [Indexed: 10/24/2022]
Abstract
During latency of herpes simplex virus type 1 (HSV-1), the major viral transcript that is detected is the latency-associated transcript (LAT) 2-kb intron. This intron is excised from a larger (approximately 10 kb) primary transcript. Infection of cells with HSV expressing LATs showed that their presence increased accumulation of Hsp70 protein specifically during cold shock. Transfection of cells with a plasmid, expressing the 2-kb LAT intron, showed increased translation compared to cells transfected with plasmids deleted in regions of the intron. Cold shock of cells expressing the intron resulted in an up-regulation of Hsp70 protein, but not Hsp70 mRNA. Furthermore, these cells showed increased cell viability. Using plasmid deletion mutants in the LAT gene sequence, we have shown that the effect requires full-length LAT intron. These findings show that a function of the stable 2-kb LAT intron is to protect cells from cold-induced stress and that this may be mediated via Hsp70.
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Affiliation(s)
- Doina Atanasiu
- Department of Microbiology, University of Pennsylvania School of Medicine, 3610 Hamilton Walk, Philadelphia, PA 19104, USA
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21
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Jones C, Inman M, Peng W, Henderson G, Doster A, Perng GC, Angeletti AK. The herpes simplex virus type 1 locus that encodes the latency-associated transcript enhances the frequency of encephalitis in male BALB/c mice. J Virol 2006; 79:14465-9. [PMID: 16254383 PMCID: PMC1280208 DOI: 10.1128/jvi.79.22.14465-14469.2005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpes simplex virus type 1 (HSV-1) is the leading cause of virus-induced encephalitis; however, the viral genes that regulate encephalitis have not been well characterized. In this study, we tested whether the LAT (latency-associated transcript) locus regulates the frequency of encephalitis in male or female mice. Male BALB/c mice are more susceptible to HSV-1-induced encephalitis than age-matched female BALB/c mice. Deletion of LAT coding sequences reduced the frequency of encephalitis. A recombinant virus containing the first 1.5 kb of the LAT coding sequence induces levels of encephalitis in male BALB/c mice similar to those induced by wild-type HSV-1.
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Affiliation(s)
- Clinton Jones
- Department of Veterinary and Biomedical Sciences, Nebraska Center for Virology, University of Nebraska, Fair Street at East Campus Loop, Rm. 104, Lincoln 68583-0905, USA.
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22
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Abstract
The survival strategy of herpes simplex virus centres on the establishment of latency in sensory neurons innervating the site of primary infection followed by periodic reactivation to facilitate transmission. This is a highly evolved and efficient survival mechanism, which despite being the subject of intense research, has proven remarkably difficult to dissect at a molecular level. This review will focus on data, emerging from both in vitro and in vivo model systems, which provide a framework for a mechanistic understanding of latency and the existence and possible significance of non-uniform latent states.
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Affiliation(s)
- S Efstathiou
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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Ng AK, Block TM, Aiamkitsumrit B, Wang M, Clementi E, Wu TT, Taylor JM, Su YH. Construction of a herpes simplex virus type 1 mutant with only a three-nucleotide change in the branchpoint region of the latency-associated transcript (LAT) and the stability of its two-kilobase LAT intron. J Virol 2004; 78:12097-106. [PMID: 15507596 PMCID: PMC525071 DOI: 10.1128/jvi.78.22.12097-12106.2004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Previous studies using a eukaryotic expression system indicated that the unusual stability of the latency-associated transcript (LAT) intron was due to its nonconsensus branchpoint sequence (T.-T Wu, Y.-H. Su, T. M. Block, and J. M. Taylor, Virology, 243:140-149, 1998). The present study investigated the role of the branchpoint sequence in the stability of the intron expressed from the herpes simplex virus type 1 (HSV-1) genome and the role of LAT intron stability in the HSV-1 life cycle. A branchpoint mutant called Sy2 and the corresponding rescued viruses, SyRA and SyRB, were constructed. To preserve the coding sequence of the immediate early gene icp0, which overlaps with the branchpoint region of the 2-kb LAT, a 3-nucleotide mutation into the branchpoint region of the 2-kb LAT was introduced, resulting in a branchpoint that is 85% identical to the consensus intron branchpoint sequence of eukaryotic cells. As anticipated, there was a 90- to 96-fold reduction in 2-kb LAT accumulation following productive infection in tissue culture and latent infection in mice with Sy2, as determined by Northern blot analysis. These results clearly suggest that the accumulation of the 2-kb intron in tissue culture and in vivo is, at least in part, due to the nonconsensus branchpoint sequence of the LAT intron. Interestingly, a failure to accumulate LAT was associated with greater progeny production of Sy2 at a low multiplicity of infection (0.01) in tissue culture, but not in mice. However, the ability of mutant Sy2 to reactivate from trigeminal ganglia (TG) derived from latently infected mice was indistinguishable from that of wild-type virus, as assayed in the mouse TG explant reactivation system.
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Affiliation(s)
- Alan K Ng
- Department of Biochemistry and Molecular Pharmacology, Jefferson Center for Biomedical Research, Thomas Jefferson University, 700 E. Butler Avenue, Doylestown, PA 18901-2697, USA
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Mukerjee R, Kang W, Suri V, Fraser NW. A non-consensus branch point plays an important role in determining the stability of the 2-kb LAT intron during acute and latent infections of herpes simplex virus type-1. Virology 2004; 324:340-9. [PMID: 15207620 DOI: 10.1016/j.virol.2004.03.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2003] [Revised: 11/25/2003] [Accepted: 03/24/2004] [Indexed: 11/30/2022]
Abstract
Herpes simplex virus type 1 (HSV-1) establishes lifelong latent infection in sensory neurons of the peripheral nervous system. During HSV latency, the latency-associated transcripts (LATs) are the only viral transcripts abundantly expressed. The most abundant form of LATs is a 2-kb stable intron spliced from a primary transcript (mLAT). It has been previously reported that a non-consensus branch point influences the stability of the intron (in vitro) in cells transfected with plasmid constructs (J. Virol. 71 (1997) 5849; J. Virol. 71 (1997) 4199). However, it is unknown whether this branch point is important in determining LAT stability in vivo (in the context of virus). To study the role of this stable intron in HSV-1 infection, we have constructed a mutant virus KOS-CONS in which the branch point has been mutated to consensus branch point nucleotides. The accumulation of the 2-kb intron in KOS-CONS-infected cells was greatly reduced. The LAT intron was not detectable in KOS-CONS-infected mouse trigeminal ganglia (TG) during acute and latent phase infection by Northern blot analysis. Replication of the KOS-CONS and the wild-type KOS viruses on Vero cells was determined to be similar, as was the level of HSV-1 DNA in mouse trigeminal ganglia during acute and latent phase infection. Using the mouse TG explant model, the reactivation pattern of both viruses was shown to be similar. Our data suggest that the unique branch point plays a significant role in determining the stability of LAT intron in vivo, but that the stability of the intron does not appear to affect HSV-1 replication, the establishment of latency, or viral reactivation.
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Affiliation(s)
- Ruma Mukerjee
- Department of Microbiology, University of Pennsylvania Medical School, 315 Johnson Pavilion, Philadelphia, PA 19104-6076, USA
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Mador N, Braun E, Haim H, Ariel I, Panet A, Steiner I. Transgenic mouse with the herpes simplex virus type 1 latency-associated gene: expression and function of the transgene. J Virol 2004; 77:12421-9. [PMID: 14610166 PMCID: PMC262558 DOI: 10.1128/jvi.77.23.12421-12429.2003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During herpes simplex virus type 1 (HSV-1) latent infection in human peripheral sensory ganglia, the major viral gene transcribed is the latency-associated transcript (LAT) gene. In order to facilitate the study of this gene, we generated a transgenic mouse that contains the DNA fragment that transcribes the LAT RNAs (2.0 kb and its 1.5-kb spliced transcript) under control of the cytomegalovirus promoter. The tissue distribution of these transcripts and their effects upon HSV-1 replication, latency, and reactivation in the transgenic-mouse model were examined. Different steady-state amounts of both transcripts were found in various tissues. While the highest levels of the 2.0-kb RNA were detected in heart and skeletal muscle, the 1.5-kb transcript was found at elevated levels in the brain and at much higher levels in the trigeminal ganglia (TG). Replication of both the wild-type and a LAT-negative mutant virus was suppressed in primary embryonic fibroblasts obtained from LAT-expressing transgenic mice compared to that in cells obtained from normal mice. HSV-1 DNA amounts in latently infected TG of transgenic mice were similar to those in normal mice. Reactivation of latent HSV-1 LAT-negative mutants by explant cocultivation of TG from transgenic mice was more efficient than reactivation from normal-mouse TG. Considering our present and previous results, we propose that the significantly higher steady-state level of the 1.5-kb RNA in the TG may link this transcript to latency functions and that by inhibition of virus replication, the LAT gene may protect ganglion cells and thereby increase the probability of reactivation.
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Affiliation(s)
- Nurith Mador
- Clinical Virology Unit, Laboratory of Neurovirology, Hadassah University Hospital, Jerusalem, Israel
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Abstract
Primary infection by herpes simplex virus type 1 (HSV-1) can cause clinical symptoms in the peripheral and central nervous system, upper respiratory tract, and gastrointestinal tract. Recurrent ocular shedding leads to corneal scarring that can progress to vision loss. Consequently, HSV-1 is the leading cause of corneal blindness due to an infectious agent. Bovine herpesvirus 1 (BHV-1) has similar biological properties to HSV-1 and is a significant health concern to the cattle industry. Latency of BHV-1 and HSV-1 is established in sensory neurons of trigeminal ganglia, but latency can be interrupted periodically, leading to reactivation from latency and spread of infectious virus. The ability of HSV-1 and BHV-1 to reactivate from latency leads to virus transmission and can lead to recurrent disease in individuals latently infected with HSV-1. During latency, the only abundant HSV-1 RNA expressed is the latency-associated transcript (LAT). In latently infected cattle, the latency-related (LR) RNA is the only abundant transcript that is expressed. LAT and LR RNA are antisense to ICP0 or bICP0, viral genes that are crucial for productive infection, suggesting that LAT and LR RNA interfere with productive infection by inhibiting ICP0 or bICP0 expression. Numerous studies have concluded that LAT expression is important for the latency-reactivation cycle in animal models. The LR gene has recently been demonstrated to be required for the latency-reactivation cycle in cattle. Several recent studies have demonstrated that LAT and the LR gene inhibit apoptosis (programmed cell death) in trigeminal ganglia of infected animals and transiently transfected cells. The antiapoptotic properties of LAT map to the same sequences that are necessary for promoting reactivation from latency. This review summarizes our current knowledge of factors regulating the latency-reactivation cycle of HSV-1 and BHV-1.
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Affiliation(s)
- Clinton Jones
- Department of Veterinary and Biomedical Sciences, The Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0905, USA.
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