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Ortigas-Vasquez A, Szpara M. Embracing Complexity: What Novel Sequencing Methods Are Teaching Us About Herpesvirus Genomic Diversity. Annu Rev Virol 2024; 11:67-87. [PMID: 38848592 DOI: 10.1146/annurev-virology-100422-010336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2024]
Abstract
The arrival of novel sequencing technologies throughout the past two decades has led to a paradigm shift in our understanding of herpesvirus genomic diversity. Previously, herpesviruses were seen as a family of DNA viruses with low genomic diversity. However, a growing body of evidence now suggests that herpesviruses exist as dynamic populations that possess standing variation and evolve at much faster rates than previously assumed. In this review, we explore how strategies such as deep sequencing, long-read sequencing, and haplotype reconstruction are allowing scientists to dissect the genomic composition of herpesvirus populations. We also discuss the challenges that need to be addressed before a detailed picture of herpesvirus diversity can emerge.
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Affiliation(s)
- Alejandro Ortigas-Vasquez
- Departments of Biology and of Biochemistry and Molecular Biology; Center for Infectious Disease Dynamics; and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, USA;
| | - Moriah Szpara
- Departments of Biology and of Biochemistry and Molecular Biology; Center for Infectious Disease Dynamics; and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, USA;
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2
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Höfler T, Nascimento MM, Zeitlow M, Kim JY, Trimpert J. Evolutionary Dynamics of Accelerated Antiviral Resistance Development in Hypermutator Herpesvirus. Mol Biol Evol 2024; 41:msae119. [PMID: 38879872 PMCID: PMC11226790 DOI: 10.1093/molbev/msae119] [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: 02/04/2024] [Revised: 05/09/2024] [Accepted: 06/12/2024] [Indexed: 07/07/2024] Open
Abstract
Antiviral therapy is constantly challenged by the emergence of resistant pathogens. At the same time, experimental approaches to understand and predict resistance are limited by long periods required for evolutionary processes. Here, we present a herpes simplex virus 1 mutant with impaired proofreading capacity and consequently elevated mutation rates. Comparing this hypermutator to parental wild type virus, we study the evolution of antiviral drug resistance in vitro. We model resistance development and elucidate underlying genetic changes against three antiviral substances. Our analyzes reveal no principle difference in the evolutionary behavior of both viruses, adaptive processes are overall similar, however significantly accelerated for the hypermutator. We conclude that hypermutator viruses are useful for modeling adaptation to antiviral therapy. They offer the benefit of expedited adaptation without introducing apparent bias and can therefore serve as an accelerator to predict natural evolution.
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Affiliation(s)
- Thomas Höfler
- Institut für Virologie, Fachbereich Veterinärmedizin, Freie Universität Berlin, Berlin, Germany
| | - Mariana Mara Nascimento
- Institut für Virologie, Fachbereich Veterinärmedizin, Freie Universität Berlin, Berlin, Germany
| | - Michaela Zeitlow
- Institut für Virologie, Fachbereich Veterinärmedizin, Freie Universität Berlin, Berlin, Germany
| | - Ji Yoon Kim
- Institut für Virologie, Fachbereich Veterinärmedizin, Freie Universität Berlin, Berlin, Germany
| | - Jakob Trimpert
- Institut für Virologie, Fachbereich Veterinärmedizin, Freie Universität Berlin, Berlin, Germany
- Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
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Ortigas-Vasquez A, Pandey U, Renner DW, Bowen CD, Baigent SJ, Dunn J, Cheng H, Yao Y, Read AF, Nair V, Kennedy DA, Szpara ML. Comparative analysis of multiple consensus genomes of the same strain of Marek's disease virus reveals intrastrain variation. Virus Evol 2024; 10:veae047. [PMID: 39036034 PMCID: PMC11259760 DOI: 10.1093/ve/veae047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 04/24/2024] [Accepted: 06/17/2024] [Indexed: 07/23/2024] Open
Abstract
Current strategies to understand the molecular basis of Marek's disease virus (MDV) virulence primarily consist of cataloging divergent nucleotides between strains with different phenotypes. However, most comparative genomic studies of MDV rely on previously published consensus genomes despite the confirmed existence of MDV strains as mixed viral populations. To assess the reliability of interstrain genomic comparisons relying on published consensus genomes of MDV, we obtained two additional consensus genomes of vaccine strain CVI988 (Rispens) and two additional consensus genomes of the very virulent strain Md5 by sequencing viral stocks and cultured field isolates. In conjunction with the published genomes of CVI988 and Md5, this allowed us to perform three-way comparisons between multiple consensus genomes of the same strain. We found that consensus genomes of CVI988 can vary in as many as 236 positions involving 13 open reading frames (ORFs). By contrast, we found that Md5 genomes varied only in 11 positions involving a single ORF. Notably, we were able to identify 3 single-nucleotide polymorphisms (SNPs) in the unique long region and 16 SNPs in the unique short (US) region of CVI988GenBank.BAC that were not present in either CVI988Pirbright.lab or CVI988USDA.PA.field. Recombination analyses of field strains previously described as natural recombinants of CVI988 yielded no evidence of crossover events in the US region when either CVI988Pirbright.lab or CVI988USDA.PA.field were used to represent CVI988 instead of CVI988GenBank.BAC. We were also able to confirm that both CVI988 and Md5 populations were mixed, exhibiting a total of 29 and 27 high-confidence minor variant positions, respectively. However, we did not find any evidence of minor variants in the positions corresponding to the 19 SNPs in the unique regions of CVI988GenBank.BAC. Taken together, our findings suggest that continued reliance on the same published consensus genome of CVI988 may have led to an overestimation of genomic divergence between CVI988 and virulent strains and that multiple consensus genomes per strain may be necessary to ensure the accuracy of interstrain genomic comparisons.
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Affiliation(s)
- Alejandro Ortigas-Vasquez
- Department of Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Utsav Pandey
- Department of Biochemistry and Molecular Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Daniel W Renner
- Department of Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Chris D Bowen
- Department of Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Susan J Baigent
- Viral Oncogenesis Group, The Pirbright Institute, Woking GU24 0NF, UK
| | - John Dunn
- United States Department of Agriculture, Agricultural Research Service, US National Poultry Research Center, Southeast Poultry Research Laboratory, Athens, GA 30605, USA
| | - Hans Cheng
- United States Department of Agriculture, Agricultural Research Service, US National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA
| | - Yongxiu Yao
- Viral Oncogenesis Group, The Pirbright Institute, Woking GU24 0NF, UK
| | - Andrew F Read
- Department of Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Venugopal Nair
- Viral Oncogenesis Group, The Pirbright Institute, Woking GU24 0NF, UK
| | - Dave A Kennedy
- Department of Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Moriah L Szpara
- Department of Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
- Department of Biochemistry and Molecular Biology, Center for Infectious Disease Dynamics, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
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Ortigas-Vasquez A, Pandey U, Renner D, Bowen C, Baigent SJ, Dunn J, Cheng H, Yao Y, Read AF, Nair V, Kennedy DA, Szpara ML. Comparative Analysis of Multiple Consensus Genomes of the Same Strain of Marek's Disease Virus Reveals Intrastrain Variation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.09.04.556264. [PMID: 37732198 PMCID: PMC10508761 DOI: 10.1101/2023.09.04.556264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Current strategies to understand the molecular basis of Marek's disease virus (MDV) virulence primarily consist of cataloguing divergent nucleotides between strains with different phenotypes. However, each MDV strain is typically represented by a single consensus genome despite the confirmed existence of mixed viral populations. To assess the reliability of single-consensus interstrain genomic comparisons, we obtained two additional consensus genomes of vaccine strain CVI988 (Rispens) and two additional consensus genomes of the very virulent strain Md5 by sequencing viral stocks and cultured field isolates. In conjunction with the published genomes of CVI988 and Md5, this allowed us to perform 3-way comparisons between consensus genomes of the same strain. We found that consensus genomes of CVI988 can vary in as many as 236 positions involving 13 open reading frames (ORFs). In contrast, we found that Md5 genomes varied only in 11 positions involving a single ORF. Phylogenomic analyses showed all three Md5 consensus genomes clustered closely together, while also showing that CVI988 GenBank.BAC diverged from CVI988 Pirbright.lab and CVI988 USDA.PA.field . Comparison of CVI988 consensus genomes revealed 19 SNPs in the unique regions of CVI988 GenBank.BAC that were not present in either CVI988 Pirbright.lab or CVI988 USDA.PA.field . Finally, we evaluated the genomic heterogeneity of CVI988 and Md5 populations by identifying positions with >2% read support for alternative alleles in two ultra-deeply sequenced samples. We were able to confirm that both populations of CVI988 and Md5 were mixed, exhibiting a total of 29 and 27 high-confidence minor variant positions, respectively. We did not find any evidence of minor variants in the positions corresponding to the 19 SNPs in the unique regions of CVI988 GenBank.BAC . Taken together, our findings confirm that consensus genomes of the same strain of MDV can vary and suggest that multiple consensus genomes per strain are needed in order to maximize the accuracy of interstrain genomic comparisons.
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Suicidal Phenotype of Proofreading-Deficient Herpes Simplex Virus 1 Polymerase Mutants. J Virol 2023; 97:e0135922. [PMID: 36598203 PMCID: PMC9888220 DOI: 10.1128/jvi.01359-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Herpes simplex virus 1 (HSV-1) encodes a family B DNA polymerase (Pol) capable of exonucleolytic proofreading whose functions have been extensively studied in the past. Early studies on the in vitro activity of purified Pol protein found that the enzymatic functions of the holoenzyme are largely separate. Consequently, exonuclease activity can be reduced or abolished by certain point mutations within catalytically important regions, with no or only minor effects on polymerase activity. Despite unimpaired polymerase activity, the recovery of HSV-1 mutants with a catalytically inactive exonuclease has been so far unsuccessful. Hence, mutations such as D368A, which abolish exonuclease activity, are believed to be lethal. Here, we show that HSV-1 can be recovered in the absence of Pol intrinsic exonuclease activity and demonstrate that a lack of proofreading causes the rapid accumulation of likely detrimental mutations. Although mutations that abolish exonuclease activity do not appear to be lethal, the lack of proofreading yields viruses with a suicidal phenotype that cease to replicate within few passages following reconstitution. Hence, we conclude that high replication fidelity conferred by proofreading is essential to maintain HSV-1 genome integrity and that a lack of exonuclease activity produces an initially viable but rapidly suicidal phenotype. However, stably replicating viruses with reduced exonuclease activity and therefore elevated mutation rates can be generated by mutating a catalytically less important site located within a conserved exonuclease domain. IMPORTANCE Recovery of fully exonuclease-deficient herpes simplex virus 1 (HSV-1) DNA polymerase mutants has been so far unsuccessful. However, exonuclease activity is not known to be directly essential for virus replication, and the lethal phenotype of certain HSV-1 polymerase mutants is thus attributed to factors other than exonuclease activity. Here, we showed that the recovery of a variety of exonuclease-deficient HSV-1 polymerase mutants is possible and that these mutants are initially replication competent. We, however, observed a progressive loss of mutant viability upon cell culture passaging, which coincided with the rapid accumulation of mutations in exonuclease-deficient viruses. We thus concluded that a lack of DNA proofreading in exonuclease-deficient viruses causes an initially viable but rapidly suicidal hypermutator phenotype and, consequently, the extinction of mutant viruses within few generations following recovery. This would make the absence of exonuclease activity the primary reason for the long-reported difficulties in culturing exonuclease-deficient HSV-1 mutants.
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Abstract
Human cells encode up to 15 DNA polymerases with specialized functions in chromosomal DNA synthesis and damage repair. In contrast, complex DNA viruses, such as those of the herpesviridae family, encode a single B-family DNA polymerase. This disparity raises the possibility that DNA viruses may rely on host polymerases for synthesis through complex DNA geometries. We tested the importance of error-prone Y-family polymerases involved in translesion synthesis (TLS) to human cytomegalovirus (HCMV) infection. We find most Y-family polymerases involved in the nucleotide insertion and bypass of lesions restrict HCMV genome synthesis and replication. In contrast, other TLS polymerases, such as the polymerase ζ complex, which extends past lesions, was required for optimal genome synthesis and replication. Depletion of either the polζ complex or the suite of insertion polymerases demonstrate that TLS polymerases suppress the frequency of viral genome rearrangements, particularly at GC-rich sites and repeat sequences. Moreover, while distinct from HCMV, replication of the related herpes simplex virus type 1 is impacted by host TLS polymerases, suggesting a broader requirement for host polymerases for DNA virus replication. These findings reveal an unexpected role for host DNA polymerases in ensuring viral genome stability.
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Bertzbach LD, Tregaskes CA, Martin RJ, Deumer US, Huynh L, Kheimar AM, Conradie AM, Trimpert J, Kaufman J, Kaufer BB. The Diverse Major Histocompatibility Complex Haplotypes of a Common Commercial Chicken Line and Their Effect on Marek's Disease Virus Pathogenesis and Tumorigenesis. Front Immunol 2022; 13:908305. [PMID: 35693787 PMCID: PMC9186122 DOI: 10.3389/fimmu.2022.908305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 04/29/2022] [Indexed: 02/05/2023] Open
Abstract
The major histocompatibility complex (MHC) is crucial for appropriate immune responses against invading pathogens. Chickens possess a single predominantly-expressed class I molecule with strong associations between disease resistance and MHC haplotype. For Marek's disease virus (MDV) infections of chickens, the MHC haplotype is one of the major determinants of genetic resistance and susceptibility. VALO specific pathogen free (SPF) chickens are widely used in biomedical research and vaccine production. While valuable findings originate from MDV infections of VALO SPF chickens, their MHC haplotypes and associated disease resistance remained elusive. In this study, we used several typing systems to show that VALO SPF chickens possess MHC haplotypes that include B9, B9:02, B15, B19 and B21 at various frequencies. Moreover, we associate the MHC haplotypes to MDV-induced disease and lymphoma formation and found that B15 homozygotes had the lowest tumor incidence while B21 homozygotes had the lowest number of organs with tumors. Finally, we found transmission at variable levels to all contact birds except B15/B21 heterozygotes. These data have immediate implications for the use of VALO SPF chickens and eggs in the life sciences and add another piece to the puzzle of the chicken MHC complex and its role in infections with this oncogenic herpesvirus.
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Affiliation(s)
| | - Clive A. Tregaskes
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Rebecca J. Martin
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | | | - Lan Huynh
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Ahmed M. Kheimar
- Institute of Virology, Freie Universität Berlin, Berlin, Germany
- Department of Poultry Diseases, Faculty of Veterinary Medicine, Sohag University, Sohag, Egypt
| | | | - Jakob Trimpert
- Institute of Virology, Freie Universität Berlin, Berlin, Germany
| | - Jim Kaufman
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Benedikt B. Kaufer
- Institute of Virology, Freie Universität Berlin, Berlin, Germany
- Veterinary Centre for Resistance Research (TZR), Freie Universität Berlin, Berlin, Germany
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Vychodil T, Wight DJ, Nascimento M, Jolmes F, Korte T, Herrmann A, Kaufer BB. Visualization of Marek’s Disease Virus Genomes in Living Cells during Lytic Replication and Latency. Viruses 2022; 14:v14020287. [PMID: 35215880 PMCID: PMC8877148 DOI: 10.3390/v14020287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 11/18/2022] Open
Abstract
Visualization of the herpesvirus genomes during lytic replication and latency is mainly achieved by fluorescence in situ hybridization (FISH). Unfortunately, this technique cannot be used for the real-time detection of viral genome in living cells. To facilitate the visualization of the Marek’s disease virus (MDV) genome during all stages of the virus lifecycle, we took advantage of the well-established tetracycline operator/repressor (TetO/TetR) system. This system consists of a fluorescently labeled TetR (TetR-GFP) that specifically binds to an array of tetO sequences. This tetO repeat array was first inserted into the MDV genome (vTetO). Subsequently, we fused TetR-GFP via a P2a self-cleaving peptide to the C-terminus of the viral interleukin 8 (vIL8), which is expressed during lytic replication and latency. Upon reconstitution of this vTetO-TetR virus, fluorescently labeled replication compartments were detected in the nucleus during lytic replication. After validating the specificity of the observed signal, we used the system to visualize the genesis and mobility of the viral replication compartments. In addition, we assessed the infection of nuclei in syncytia as well as lytic replication and latency in T cells. Taken together, we established a system allowing us to track the MDV genome in living cells that can be applied to many other DNA viruses.
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Affiliation(s)
- Tereza Vychodil
- Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany; (T.V.); (D.J.W.); (M.N.)
| | - Darren J. Wight
- Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany; (T.V.); (D.J.W.); (M.N.)
| | - Mariana Nascimento
- Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany; (T.V.); (D.J.W.); (M.N.)
| | - Fabian Jolmes
- Department of Biology, Molecular Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany; (F.J.); (T.K.); (A.H.)
| | - Thomas Korte
- Department of Biology, Molecular Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany; (F.J.); (T.K.); (A.H.)
| | - Andreas Herrmann
- Department of Biology, Molecular Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany; (F.J.); (T.K.); (A.H.)
- Institut für Chemie und Biochemie, Freie Universität Berlin, Altensteinstr. 23a, 14195 Berlin, Germany
| | - Benedikt B. Kaufer
- Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany; (T.V.); (D.J.W.); (M.N.)
- Veterinary Centre for Resistance Research (TZR), Freie Universität Berlin, 14163 Berlin, Germany
- Correspondence: ; Tel.: +49-30-838-51936
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Diaz Arenas C, Ardaševa A, Miller J, Mikheyev AS, Yokobayashi Y. Ribozyme Mutagenic Evolution: Mechanisms of Survival. ORIGINS LIFE EVOL B 2022; 51:321-339. [PMID: 34994918 DOI: 10.1007/s11084-021-09617-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Accepted: 11/16/2021] [Indexed: 11/24/2022]
Abstract
Primeval populations replicating at high error rates required a mechanism to overcome the accumulation of mutations and information deterioration. Known strategies to overcome mutation pressures include RNA processivity, epistasis, selection, and quasispecies. We investigated the mechanism by which small molecular ribozyme populations can survive under high error rates by propagating several lineages under different mutagen concentrations. We found that every population that evolved without mutagen went extinct, while those subjected to mutagenic evolution survived. To understand how they survived, we characterized the evolved genotypic diversity, the formation of genotype-genotype interaction networks, the fitness of the most common mutants for each enzymatic step, and changes in population size along the course of evolution. We found that the elevated mutation rate was necessary for the populations to survive in the novel environment, in which all the steps of the metabolism worked to promote the survival of even less catalytically efficient ligases. Besides, an increase in population size and the mutational coupling of genotypes in close-knit networks, which helped maintain or recover lost genotypes making their disappearance transient, prevented Muller's ratchet and extinction.
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Affiliation(s)
- Carolina Diaz Arenas
- Okinawa Institute of Science and Technology Graduate University (OIST), Okinawa Prefecture, Japan. .,Yale University, New Haven, CT, USA.
| | - Aleksandra Ardaševa
- Wolfson Centre for Mathematical Biology, Mathematical Institute, University of Oxford, Oxford, UK
| | - Jonathan Miller
- Okinawa Institute of Science and Technology Graduate University (OIST), Okinawa Prefecture, Japan
| | - Alexander S Mikheyev
- Okinawa Institute of Science and Technology Graduate University (OIST), Okinawa Prefecture, Japan.,Evolutionary Genomics Lab, Research School of Biology, Australian National University, Canberra, Australia
| | - Yohei Yokobayashi
- Okinawa Institute of Science and Technology Graduate University (OIST), Okinawa Prefecture, Japan
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Marek's Disease Virus Requires Both Copies of the Inverted Repeat Regions for Efficient In Vivo Replication and Pathogenesis. J Virol 2021; 95:JVI.01256-20. [PMID: 33115875 DOI: 10.1128/jvi.01256-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 10/19/2020] [Indexed: 02/07/2023] Open
Abstract
Marek's disease virus (MDV) is an oncogenic alphaherpesvirus of chickens. The MDV genome consists of two unique regions that are both flanked by inverted repeat regions. These repeats harbor several genes involved in virus replication and pathogenesis, but it remains unclear why MDV and other herpesviruses harbor these large sequence duplications. In this study, we set to determine if both copies of these repeat regions are required for MDV replication and pathogenesis. Our results demonstrate that MDV mutants lacking the entire internal repeat region (ΔIRLS) efficiently replicate and spread from cell-to-cell in vitro However, ΔIRLS replication was severely impaired in infected chickens and the virus caused significantly less frequent disease and tumors compared to the controls. In addition, we also generated recombinant viruses that harbor a deletion of most of the internal repeat region, leaving only short terminal sequences behind (ΔIRLS-HR). These remaining homologous sequences facilitated rapid restoration of the deleted repeat region, resulting in a virus that caused disease and tumors comparable to the wild type. Therefore, ΔIRLS-HR represents an excellent platform for rapid genetic manipulation of the virus genome in the repeat regions. Taken together, our study demonstrates that MDV requires both copies of the repeats for efficient replication and pathogenesis in its natural host.IMPORTANCE Marek's disease virus (MDV) is a highly oncogenic alphaherpesvirus that infects chickens and causes losses in the poultry industry of up to $2 billion per year. The virus is also widely used as a model to study alphaherpesvirus pathogenesis and virus-induced tumor development in a natural host. MDV and most other herpesviruses harbor direct or inverted repeats regions in their genome. However, the role of these sequence duplications in MDV remains elusive and has never been investigated in a natural virus-host model for any herpesvirus. Here, we demonstrate that both copies of the repeats are needed for efficient MDV replication and pathogenesis in vivo, while replication was not affected in cell culture. With this, we further dissect herpesvirus genome biology and the role of repeat regions in Marek's disease virus replication and pathogenesis.
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Polymerase Fidelity Contributes to Foot-and-Mouth Disease Virus Pathogenicity and Transmissibility In Vivo. J Virol 2020; 95:JVI.01569-20. [PMID: 33028719 DOI: 10.1128/jvi.01569-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 10/02/2020] [Indexed: 02/07/2023] Open
Abstract
The low fidelity of foot-and-mouth disease virus (FMDV) RNA-dependent RNA polymerase allows FMDV to exhibit high genetic diversity. Previously, we showed that the genetic diversity of FMDV plays an important role in virulence in suckling mice. Here, we mutated the amino acid residue Phe257, located in the finger domain of FMDV polymerase and conserved across FMDV serotypes, to a cysteine (F257C) to study the relationship between viral genetic diversity, virulence, and transmissibility in natural hosts. The single amino acid substitution in FMDV polymerase resulted in a high-fidelity virus variant, rF257C, with growth kinetics indistinguishable from those of wild-type (WT) virus in cell culture, but it displayed smaller plaques and impaired fitness in direct competition assays. Furthermore, we found that rF257C was attenuated in vivo in both suckling mice and pigs (one of its natural hosts). Importantly, contact exposure experiments showed that the rF257C virus exhibited reduced transmissibility compared to that of wild-type FMDV in the porcine model. This study provides evidence that FMDV genetic diversity is important for viral virulence and transmissibility in susceptible animals. Given that type O FMDV exhibits the highest genetic diversity among all seven serotypes of FMDV, we propose that the lower polymerase fidelity of the type O FMDV could contribute to its dominance worldwide.IMPORTANCE Among the seven serotypes of FMDV, serotype O FMDV have the broadest distribution worldwide, which could be due to their high virulence and transmissibility induced by high genetic diversity. In this paper, we generated a single amino acid substitution FMDV variant with a high-fidelity polymerase associated with viral fitness, virulence, and transmissibility in a natural host. The results highlight that maintenance of viral population diversity is essential for interhost viral spread. This study provides evidence that higher genetic diversity of type O FMDV could increase both virulence and transmissibility, thus leading to their dominance in the global epidemic.
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Abstract
Alphaherpesviruses, as large double-stranded DNA viruses, were long considered to be genetically stable and to exist in a homogeneous state. Recently, the proliferation of high-throughput sequencing (HTS) and bioinformatics analysis has expanded our understanding of herpesvirus genomes and the variations found therein. Recent data indicate that herpesviruses exist as diverse populations, both in culture and in vivo, in a manner reminiscent of RNA viruses. In this review, we discuss the past, present, and potential future of alphaherpesvirus genomics, including the technical challenges that face the field. We also review how recent data has enabled genome-wide comparisons of sequence diversity, recombination, allele frequency, and selective pressures, including those introduced by cell culture. While we focus on the human alphaherpesviruses, we draw key insights from related veterinary species and from the beta- and gamma-subfamilies of herpesviruses. Promising technologies and potential future directions for herpesvirus genomics are highlighted as well, including the potential to link viral genetic differences to phenotypic and disease outcomes.
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Affiliation(s)
- Chad V. Kuny
- Departments of Biology, and Biochemistry and Molecular Biology, Center for Infectious Disease Dynamics, and the Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Moriah L. Szpara
- Departments of Biology, and Biochemistry and Molecular Biology, Center for Infectious Disease Dynamics, and the Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, 16802, USA
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13
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Bertzbach LD, Conradie AM, You Y, Kaufer BB. Latest Insights into Marek's Disease Virus Pathogenesis and Tumorigenesis. Cancers (Basel) 2020; 12:cancers12030647. [PMID: 32164311 PMCID: PMC7139298 DOI: 10.3390/cancers12030647] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 03/06/2020] [Accepted: 03/07/2020] [Indexed: 12/14/2022] Open
Abstract
Marek’s disease virus (MDV) infects chickens and causes one of the most frequent cancers in animals. Over 100 years of research on this oncogenic alphaherpesvirus has led to a profound understanding of virus-induced tumor development. Live-attenuated vaccines against MDV were the first that prevented cancer and minimized the losses in the poultry industry. Even though the current gold standard vaccine efficiently protects against clinical disease, the virus continuously evolves towards higher virulence. Emerging field strains were able to overcome the protection provided by the previous two vaccine generations. Research over the last few years revealed important insights into the virus life cycle, cellular tropism, and tumor development that are summarized in this review. In addition, we discuss recent data on the MDV transcriptome, the constant evolution of this highly oncogenic virus towards higher virulence, and future perspectives in MDV research.
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Trimpert J, Osterrieder N. Herpesvirus DNA Polymerase Mutants—How Important Is Faithful Genome Replication? CURRENT CLINICAL MICROBIOLOGY REPORTS 2019. [DOI: 10.1007/s40588-019-00135-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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