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Gaffuri A, Sassera D, Calzolari M, Gibelli L, Lelli D, Tebaldi A, Vicari N, Bianchi A, Pigoli C, Cerioli M, Zandonà L, Varisco G, Bertoletti I, Prati P. Tick-Borne Encephalitis, Lombardy, Italy. Emerg Infect Dis 2024; 30:341-344. [PMID: 38270164 PMCID: PMC10826753 DOI: 10.3201/eid3002.231016] [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: 01/26/2024] Open
Abstract
Tick-borne encephalitis was limited to northeast portions of Italy. We report in Lombardy, a populous region in the northwest, a chamois displaying clinical signs of tickborne encephalitis virus that had multiple virus-positive ticks attached, as well as a symptomatic man. Further, we show serologic evidence of viral circulation in the area.
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2
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Chiffi G, Grandgirard D, Leib SL, Chrdle A, Růžek D. Tick-borne encephalitis: A comprehensive review of the epidemiology, virology, and clinical picture. Rev Med Virol 2023; 33:e2470. [PMID: 37392370 DOI: 10.1002/rmv.2470] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 05/31/2023] [Accepted: 06/12/2023] [Indexed: 07/03/2023]
Abstract
Tick-borne encephalitis virus (TBEV) is a flavivirus commonly found in at least 27 European and Asian countries. It is an emerging public health problem, with steadily increasing case numbers over recent decades. Tick-borne encephalitis virus affects between 10,000 and 15,000 patients annually. Infection occurs through the bite of an infected tick and, much less commonly, through infected milk consumption or aerosols. The TBEV genome comprises a positive-sense single-stranded RNA molecule of ∼11 kilobases. The open reading frame is > 10,000 bases long, flanked by untranslated regions (UTR), and encodes a polyprotein that is co- and post-transcriptionally processed into three structural and seven non-structural proteins. Tick-borne encephalitis virus infection results in encephalitis, often with a characteristic biphasic disease course. After a short incubation time, the viraemic phase is characterised by non-specific influenza-like symptoms. After an asymptomatic period of 2-7 days, more than half of patients show progression to a neurological phase, usually characterised by central and, rarely, peripheral nervous system symptoms. Mortality is low-around 1% of confirmed cases, depending on the viral subtype. After acute tick-borne encephalitis (TBE), a minority of patients experience long-term neurological deficits. Additionally, 40%-50% of patients develop a post-encephalitic syndrome, which significantly impairs daily activities and quality of life. Although TBEV has been described for several decades, no specific treatment exists. Much remains unknown regarding the objective assessment of long-lasting sequelae. Additional research is needed to better understand, prevent, and treat TBE. In this review, we aim to provide a comprehensive overview of the epidemiology, virology, and clinical picture of TBE.
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Affiliation(s)
- Gabriele Chiffi
- Department for BioMedical Research, University of Bern, Bern, Switzerland
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Denis Grandgirard
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephen L Leib
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Aleš Chrdle
- Department of Infectious Diseases, Hospital Ceske Budejovice, Ceske Budejovice, Czech Republic
- Faculty of Health and Social Sciences, University of South Bohemia, Ceske Budejovice, Czech Republic
- Royal Liverpool University Hospital, Liverpool, UK
| | - Daniel Růžek
- Veterinary Research Institute, Emerging Viral Diseases, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
- Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Ceske Budejovice, Czech Republic
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3
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Rescue and in vitro characterization of a divergent TBEV-Eu strain from the Netherlands. Sci Rep 2023; 13:2872. [PMID: 36807371 PMCID: PMC9938877 DOI: 10.1038/s41598-023-29075-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 01/30/2023] [Indexed: 02/19/2023] Open
Abstract
Tick-borne encephalitis virus (TBEV) may cause tick-borne encephalitis (TBE), a potential life-threatening infection of the central nervous system in humans. Phylogenetically, TBEVs can be subdivided into three main subtypes, which differ in endemic region and pathogenic potential. In 2016, TBEV was first detected in the Netherlands. One of two detected strains, referred to as Salland, belonged to the TBEV-Eu subtype, yet diverged ≥ 2% on amino acid level from other members of this subtype. Here, we report the successful rescue of this strain using infectious subgenomic amplicons and its subsequent in vitro characterization by comparison to two well-characterized TBEV-Eu strains; Neudoerfl and Hypr. In the human alveolar epithelial cell line A549, growth kinetics of Salland were comparable to the high pathogenicity TBEV-Eu strain Hypr, and both strains grew considerably faster than the mildly pathogenic strain Neudoerfl. In the human neuroblastoma cell line SK-N-SH, Salland replicated faster and to higher infectious titers than both reference strains. All three TBEV strains infected primary human monocyte-derived dendritic cells to a similar extent and interacted with the type I interferon system in a similar manner. The current study serves as the first in vitro characterization of the novel, divergent TBEV-Eu strain Salland.
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4
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Lang D, Chitimia-Dobler L, Bestehorn-Willmann M, Lindau A, Drehmann M, Stroppel G, Hengge H, Mackenstedt U, Kaier K, Dobler G, Borde J. The Emergence and Dynamics of Tick-Borne Encephalitis Virus in a New Endemic Region in Southern Germany. Microorganisms 2022; 10:2125. [PMID: 36363717 PMCID: PMC9693875 DOI: 10.3390/microorganisms10112125] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 10/12/2022] [Accepted: 10/17/2022] [Indexed: 06/11/2024] Open
Abstract
Tick-borne encephalitis (TBE) is the most important viral tick-borne infection in Europe and Asia. It is emerging in new areas. The mechanisms of emergence are fairly unknown or speculative. In the Ravensburg district in southern Germany, TBE emerged, mainly over the last five years. Here, we analyzed the underlying epidemiology in humans. The resulting identified natural foci of the causal TBE virus (TBEV) were genetically characterized. We sampled 13 potential infection sites at these foci and detected TBEV in ticks (Ixodes ricinus) at eight sites. Phylogenetic analysis spurred the introduction of at least four distinct TBEV lineages of the European subtype into the Ravensburg district over the last few years. In two instances, a continuous spread of these virus strains over up to 10 km was observed.
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Affiliation(s)
- Daniel Lang
- National Reference Laboratory for TBEV, Bundeswehr Institute for Microbiology, 80937 Munich, Germany
| | - Lidia Chitimia-Dobler
- National Reference Laboratory for TBEV, Bundeswehr Institute for Microbiology, 80937 Munich, Germany
| | - Malena Bestehorn-Willmann
- National Reference Laboratory for TBEV, Bundeswehr Institute for Microbiology, 80937 Munich, Germany
| | - Alexander Lindau
- Department of Parasitology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Marco Drehmann
- Department of Parasitology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Gabriele Stroppel
- Public Health Office, District Ravensburg, 88212 Ravensburg, Germany
| | - Helga Hengge
- Public Health Office, District Ravensburg, 88212 Ravensburg, Germany
| | - Ute Mackenstedt
- Department of Parasitology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Klaus Kaier
- Institute of Medical Biometry and Statistics (IMBI), University Medical Center Freiburg im Breisgau, 79106 Freiburg im Breisgau, Germany
| | - Gerhard Dobler
- National Reference Laboratory for TBEV, Bundeswehr Institute for Microbiology, 80937 Munich, Germany
- Department of Parasitology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Johannes Borde
- Praxis Prof. Borde & Kollegen, Gesundheitszentrum Oberkirch, 77704 Oberkirch, Germany
- Division of Infectious Diseases, Department of Internal Medicine, University Medical Center Freiburg im Breisgau, 79106 Freiburg im Breisgau, Germany
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5
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Nishiyama S, Hirano M, Muto M, Kambara M, Ito N, Kobayashi S, Kariwa H, Yoshii K. Y-shaped RNA Secondary Structure of a Noncoding Region in the Genomic RNA of Tick-Borne Encephalitis Virus Affects Pathogenicity. Microbiol Immunol 2022; 66:234-237. [PMID: 35194811 DOI: 10.1111/1348-0421.12971] [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: 12/30/2021] [Revised: 02/14/2022] [Accepted: 02/18/2022] [Indexed: 11/28/2022]
Abstract
Tick-borne encephalitis virus (TBEV) is a zoonotic virus that causes encephalitis in humans. Various deletions have been reported in a variable region of the 3' untranslated region of the TBEV genome. In this study, we analyzed the role of a Y-shaped secondary structure in the pathogenicity of TBEV by using reverse genetics. Deletion of the structure increased the mortality rate of virus-infected mice but did not affect virus multiplication in cultured cells and organs. Our results indicated that the secondary structure is involved in the regulation of TBEV pathogenesis. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Shoko Nishiyama
- Laboratory of Zoonotic Disease, Joint Department of Veterinary Medicine, Faculty of Applied Biosciences, Gifu University, Gifu, Japan
| | - Minato Hirano
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.,National Research Center for the Control and Prevention of Infectious Diseases, Nagasaki University, Nagasaki, Japan
| | - Memi Muto
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Mao Kambara
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Naoto Ito
- Laboratory of Zoonotic Disease, Joint Department of Veterinary Medicine, Faculty of Applied Biosciences, Gifu University, Gifu, Japan
| | - Shintaro Kobayashi
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Hiroaki Kariwa
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Kentaro Yoshii
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.,National Research Center for the Control and Prevention of Infectious Diseases, Nagasaki University, Nagasaki, Japan
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6
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Hubálek Z. History of Arbovirus Research in the Czech Republic. Viruses 2021; 13:2334. [PMID: 34835140 PMCID: PMC8622538 DOI: 10.3390/v13112334] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/11/2021] [Accepted: 11/16/2021] [Indexed: 01/07/2023] Open
Abstract
The aim of this review is to follow the history of studies on endemiv arboviruses and the diseases they cause which were detected in the Czech lands (Bohemia, Moravia and Silesia (i.e., the Czech Republic)). The viruses involve tick-borne encephalitis, West Nile and Usutu flaviviruses; the Sindbis alphavirus; Ťahyňa, Batai, Lednice and Sedlec bunyaviruses; the Uukuniemi phlebovirus; and the Tribeč orbivirus. Arboviruses temporarily imported from abroad to the Czech Republic have been omitted. This brief historical review includes a bibliography of all relevant papers.
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Affiliation(s)
- Zdenek Hubálek
- Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, 60365 Brno, Czech Republic
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7
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Egyed L, Biksi I, Varga T, Zöldi V, Dán Á. Analysing the genomes of two tick-borne encephalitis viruses isolated in Hungary in 1952 and 2019. Ticks Tick Borne Dis 2021; 12:101806. [PMID: 34455141 DOI: 10.1016/j.ttbdis.2021.101806] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Revised: 07/20/2021] [Accepted: 08/09/2021] [Indexed: 11/24/2022]
Abstract
The genomes of two Tick-borne encephalitis virus (TBEV) strains were fully sequenced and compared to those of known Hungarian strains. One was a laboratory strain (KEM-1) isolated in 1952, which had gone through hundreds of passages both on Vero cell cultures and in laboratory mice, while the other was a recent isolate (2019) from questing female ticks. The laboratory strain formed a monophyletic group with the already published 4 Hungarian strains on the evolutionary tree, located relatively close to Finnish (Kumlinge) and Russian (Absettarov) strains. This KEM-1 strain was phylogenetically distantly related both to the geographically close reference strain Neudörfl and the chronologically close Czech isolates from 1953. The 2019 isolate, KEM-195 was related to TBEV isolates from Southern Slovakia and Styria, and had the longest (328 nucleotides) deletion in its 3'-non-coding region among published sequences of strains of European subtype. Our results show that decades of laboratory passage have not altered the viral genome too much and that at least two distinct branches of TBEV strains circulate in Hungary.
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Affiliation(s)
- L Egyed
- Veterinary Medical Research Institute, ELKH, Hungária krt. 21, Budapest 1143, Hungary.
| | - I Biksi
- SCG Diagnosztika Ltd., Délegyháza, Hungary
| | - T Varga
- SCG Diagnosztika Ltd., Délegyháza, Hungary
| | - V Zöldi
- Department of Pest control, National Centre for Epidemiology, Budapest, Hungary
| | - Á Dán
- Danam.Vet. Molbiol, Kőszeg, Hungary
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8
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The Pseudo-Circular Genomes of Flaviviruses: Structures, Mechanisms, and Functions of Circularization. Cells 2021; 10:cells10030642. [PMID: 33805761 PMCID: PMC7999817 DOI: 10.3390/cells10030642] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 02/19/2021] [Accepted: 03/02/2021] [Indexed: 11/23/2022] Open
Abstract
The circularization of viral genomes fulfills various functions, from evading host defense mechanisms to promoting specific replication and translation patterns supporting viral proliferation. Here, we describe the genomic structures and associated host factors important for flaviviruses genome circularization and summarize their functional roles. Flaviviruses are relatively small, single-stranded, positive-sense RNA viruses with genomes of approximately 11 kb in length. These genomes contain motifs at their 5′ and 3′ ends, as well as in other regions, that are involved in circularization. These motifs are highly conserved throughout the Flavivirus genus and occur both in mature virions and within infected cells. We provide an overview of these sequence motifs and RNA structures involved in circularization, describe their linear and circularized structures, and discuss the proteins that interact with these circular structures and that promote and regulate their formation, aiming to clarify the key features of genome circularization and understand how these affect the flaviviruses life cycle.
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9
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Comparison of whole genomes of tick-borne encephalitis virus from mountainous alpine regions and regions with a lower altitude. Virus Genes 2021; 57:217-221. [PMID: 33486691 PMCID: PMC7985117 DOI: 10.1007/s11262-020-01821-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/16/2020] [Indexed: 11/24/2022]
Abstract
Tick-borne encephalitis (TBE) has been a notifiable disease in Germany since 2001. Its causative agent, the TBE virus (TBEV), is the most important arbovirus in Europe and Northern Asia. The illness, caused by the European Subtype usually displays flu-like symptoms, but can result in sequelae and, in 2 % of all cases, in death. Over the last few decades, the virus has spread into new habitats, such as higher altitudes in the Alpine region. For this study, it was hypothesized that the environmental challenges that the virus might be exposed to at such altitudes could lead to the selection of viral strains with a higher resilience to such environmental factors. To determine whether strains identified at higher altitudes possessed different genetic traits compared to viruses from lower altitudes, an analysis of viral genomes from higher Alpine altitudes (> 500 m above sea level) (n = 5) and lower altitudes (< 500 m above sea level) (n = 4) was performed. No common phylogenetic ancestry or shared amino acid substitutions could be identified that differentiated the alpine from the lowland viral strains. These findings support the idea of many individual introductions of TBEV into the alpine region and the establishment of foci due to non-viral specific factors such as favorable conditions for vector species and host animals due to climate change.
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10
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Deviatkin AA, Karganova GG, Vakulenko YA, Lukashev AN. TBEV Subtyping in Terms of Genetic Distance. Viruses 2020; 12:E1240. [PMID: 33142676 PMCID: PMC7692686 DOI: 10.3390/v12111240] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 10/24/2020] [Accepted: 10/29/2020] [Indexed: 01/07/2023] Open
Abstract
Currently, the lowest formal taxon in virus classification is species; however, unofficial lower-level units are commonly used in everyday work. Tick-borne encephalitis virus (TBEV) is a species of mammalian tick-borne flaviviruses that may cause encephalitis. Many known representatives of TBEV are grouped into subtypes, mostly according to their phylogenetic relationship. However, the emergence of novel sequences could dissolve this phylogenetic grouping; in the absence of strict quantitative criterion, it may be hard to define the borders of the first TBEV taxonomic unit below the species level. In this study, the nucleotide/amino-acid space of all known TBEV sequences was analyzed. Amino-acid sequence p-distances could not reliably distinguish TBEV subtypes. Viruses that differed by less than 10% of nucleotides in the polyprotein-coding gene belonged to the same subtype. At the same time, more divergent viruses were representatives of different subtypes. According to this distance criterion, TBEV species may be divided into seven subtypes: TBEV-Eur, TBEV-Sib, TBEV-FE, TBEV-2871 (TBEV-Ob), TBEV-Him, TBEV-178-79 (TBEV-Bkl-1), and TBEV-886-84 (TBEV-Bkl-2).
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Affiliation(s)
- Andrei A. Deviatkin
- Laboratory of Molecular Biology and Biochemistry, Institute of Molecular Medicine, Sechenov First Moscow State Medical University, 119048 Moscow, Russia;
| | - Galina G. Karganova
- Department of Organization and Technology of Immunobiological Preparations, Institute for Translational Medicine and Biotechnology, Sechenov First Moscow State Medical University, 119991 Moscow, Russia;
- Laboratory of Biology of Arboviruses, Chumakov Institute of Poliomyelitis and Viral Encephalitides (FSBSI “Chumakov FSC R&D IBP RAS), 108819 Moscow, Russia
| | - Yulia A. Vakulenko
- Martsinovsky Institute of Medical Parasitology, Tropical and Vector Borne Diseases, Sechenov First Moscow State Medical University, 119435 Moscow, Russia;
- Department of Virology, Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Alexander N. Lukashev
- Laboratory of Molecular Biology and Biochemistry, Institute of Molecular Medicine, Sechenov First Moscow State Medical University, 119048 Moscow, Russia;
- Martsinovsky Institute of Medical Parasitology, Tropical and Vector Borne Diseases, Sechenov First Moscow State Medical University, 119435 Moscow, Russia;
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11
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Clark JJ, Gilray J, Orton RJ, Baird M, Wilkie G, Filipe ADS, Johnson N, McInnes CJ, Kohl A, Biek R. Population genomics of louping ill virus provide new insights into the evolution of tick-borne flaviviruses. PLoS Negl Trop Dis 2020; 14:e0008133. [PMID: 32925939 PMCID: PMC7515184 DOI: 10.1371/journal.pntd.0008133] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 09/24/2020] [Accepted: 08/07/2020] [Indexed: 12/30/2022] Open
Abstract
The emergence and spread of tick-borne arboviruses pose an increased challenge to human and animal health. In Europe this is demonstrated by the increasingly wide distribution of tick-borne encephalitis virus (TBEV, Flavivirus, Flaviviridae), which has recently been found in the United Kingdom (UK). However, much less is known about other tick-borne flaviviruses (TBFV), such as the closely related louping ill virus (LIV), an animal pathogen which is endemic to the UK and Ireland, but which has been detected in other parts of Europe including Scandinavia and Russia. The emergence and potential spatial overlap of these viruses necessitates improved understanding of LIV genomic diversity, geographic spread and evolutionary history. We sequenced a virus archive composed of 22 LIV isolates which had been sampled throughout the UK over a period of over 80 years. Combining this dataset with published virus sequences, we detected no sign of recombination and found low diversity and limited evidence for positive selection in the LIV genome. Phylogenetic analysis provided evidence of geographic clustering as well as long-distance movement, including movement events that appear recent. However, despite genomic data and an 80-year time span, we found that the data contained insufficient temporal signal to reliably estimate a molecular clock rate for LIV. Additional analyses revealed that this also applied to TBEV, albeit to a lesser extent, pointing to a general problem with phylogenetic dating for TBFV. The 22 LIV genomes generated during this study provide a more reliable LIV phylogeny, improving our knowledge of the evolution of tick-borne flaviviruses. Our inability to estimate a molecular clock rate for both LIV and TBEV suggests that temporal calibration of tick-borne flavivirus evolution should be interpreted with caution and highlight a unique aspect of these viruses which may be explained by their reliance on tick vectors. Tick-borne pathogens represent a major emerging threat to public health and in recent years have been expanding into new areas. LIV is a neglected virus endemic to the UK and Ireland (though it has been detected in Scandinavia and Russia) which is closely related to the major human pathogen TBEV, but predominantly causes disease in sheep and grouse. The recent detection of TBEV in the UK, which has also emerged elsewhere in Europe, requires more detailed understanding of the spread and sequence diversity of LIV. This could be important for diagnosis and vaccination, but also to improve our understanding of the evolution and emergence of these tick-borne viruses. Here we describe the sequencing of 22 LIV isolates which have been sampled from several host species across the past century. We have utilised this dataset to investigate the evolutionary pressures that LIV is subjected to and have explored the evolution of LIV using phylogenetic analysis. Crucially we were unable to estimate a reliable molecular clock rate for LIV and found that this problem also extends to a larger phylogeny of TBEV sequences. This work highlights a previously unknown caveat of tick-borne flavivirus evolutionary analysis which may be important for understanding the evolution of these important pathogens.
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Affiliation(s)
- Jordan J. Clark
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- Moredun Research Institute, Edinburgh, United Kingdom
- * E-mail: (JC); (RB)
| | - Janice Gilray
- Moredun Research Institute, Edinburgh, United Kingdom
| | - Richard J. Orton
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Margaret Baird
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Gavin Wilkie
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Ana da Silva Filipe
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Nicholas Johnson
- Animal and Plant Health Agency, Addlestone, Surrey, United Kingdom
- Faculty of Health and Medical Science, University of Surrey, Guildford, Surrey, United Kingdom
| | | | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Roman Biek
- Institute of Biodiversity, Animal Health and Comparative Medicine - University of Glasgow, Glasgow, United Kingdom
- * E-mail: (JC); (RB)
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12
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Velay A, Paz M, Cesbron M, Gantner P, Solis M, Soulier E, Argemi X, Martinot M, Hansmann Y, Fafi-Kremer S. Tick-borne encephalitis virus: molecular determinants of neuropathogenesis of an emerging pathogen. Crit Rev Microbiol 2019; 45:472-493. [PMID: 31267816 DOI: 10.1080/1040841x.2019.1629872] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Tick-borne encephalitis virus (TBEV) is a zoonotic agent causing severe encephalitis. The transmission cycle involves the virus, the Ixodes tick vector, and a vertebrate reservoir, such as small mammals (rodents, or shrews). Humans are accidentally involved in this transmission cycle. Tick-borne encephalitis (TBE) has been a growing public health problem in Europe and Asia over the past 30 years. The mechanisms involved in the development of TBE are very complex and likely multifactorial, involving both host and viral factors. The purpose of this review is to provide an overview of the current literature on TBE neuropathogenesis in the human host and to demonstrate the emergence of common themes in the molecular pathogenesis of TBE in humans. We discuss and review data on experimental study models and on both viral (molecular genetics of TBEV) and host (immune response, and genetic background) factors involved in TBE neuropathogenesis in the context of human infection.
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Affiliation(s)
- Aurélie Velay
- Virology Laboratory, University Hospital of Strasbourg , Strasbourg , France.,INSERM, IRM UMR_S 1109 , Strasbourg , France
| | - Magali Paz
- Virology Laboratory, University Hospital of Strasbourg , Strasbourg , France
| | - Marlène Cesbron
- Virology Laboratory, University Hospital of Strasbourg , Strasbourg , France
| | - Pierre Gantner
- Virology Laboratory, University Hospital of Strasbourg , Strasbourg , France.,INSERM, IRM UMR_S 1109 , Strasbourg , France
| | - Morgane Solis
- Virology Laboratory, University Hospital of Strasbourg , Strasbourg , France.,INSERM, IRM UMR_S 1109 , Strasbourg , France
| | | | - Xavier Argemi
- Service des maladies infectieuses et tropicales, Hôpitaux Universitaires de Strasbourg , Strasbourg , France
| | - Martin Martinot
- Service de Médecine Interne et de Rhumatologie, Hôpitaux Civils de Colmar , Colmar , France
| | - Yves Hansmann
- Service des maladies infectieuses et tropicales, Hôpitaux Universitaires de Strasbourg , Strasbourg , France
| | - Samira Fafi-Kremer
- Virology Laboratory, University Hospital of Strasbourg , Strasbourg , France.,INSERM, IRM UMR_S 1109 , Strasbourg , France
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13
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Andersen NS, Bestehorn M, Chitimia-Dobler L, Kolmos HJ, Jensen PM, Dobler G, Skarphédinsson S. Phylogenetic characterization of tick-borne encephalitis virus from Bornholm, Denmark. Ticks Tick Borne Dis 2018; 10:533-539. [PMID: 30704909 DOI: 10.1016/j.ttbdis.2018.12.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 12/17/2018] [Accepted: 12/27/2018] [Indexed: 12/30/2022]
Abstract
The Danish island of Bornholm in the Baltic Sea has been known as a tick-borne encephalitis (TBE) natural focus for more than 60 years. TBE in humans is diagnosed on a regular basis either in inhabitants or tourists of the island. Other areas in Denmark have been suggested as possible risk areas of TBE. Despite the long-known endemicity on Bornholm and the possibility of the virus circulating in other areas, no data on the prevalences of TBE virus (TBEV) in ticks, or adequate molecular characterization and phylogenetic studies are available for the circulating TBEV strains. This study aimed to detect TBEV in ticks collected on the island of Bornholm and other possible risk areas, with the attempt to isolate the circulating viruses for molecular and phylogenetic analysis and confirm the presence of virus in the predicted risk areas. From 2014 to 2016, 9321 I. ricinus (nymphs, females, and males) were collected by flagging 31 locations in Denmark. The ticks were pooled and tested for TBEV by qPCR. The envelope gene of the detected TBE virus strains was amplified and sequenced by RT-PCR. After successful virus isolation, whole genome sequencing was performed. Phylogenetic analysis of the obtained sequences was done by the Maximum Likelihood method. One pool of 11 females and one pool of eight males from a total of 34 tick pools collected from the northwestern shore of lake Rubinsøen on Bornholm tested positive, resulting in a local estimated point prevalence of 0.6% [CI95% 0,1-1.85%] in this microfocus. We were not successful in confirming any other of the predicted TBEV-endemic areas. Alignment of the two complete E genes from Bornholm revealed identical sequences. Virus isolation and whole genome sequencing were succeeded from one of the positive samples. Phylogenetic analysis showed that the isolated virus had the closest phylogenetic relationship to TBEV sequences detected in Eastern and Central Europe.
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Affiliation(s)
- Nanna Skaarup Andersen
- Clinical Centre of Emerging and Vector-borne Infections, Odense University Hospital, Sdr. Boulevard 29, DK-5000, Odense C, Denmark; Research Unit of Clinical Microbiology, University of Southern Denmark, J.B. Winsløvsvej 21.2, DK-5000, Odense C, Denmark.
| | - Malena Bestehorn
- Parasitology Unit, Institute of Zoology, University of Hohenheim, Hans-Wolff-Strasse 34, DE-70955, Stuttgart, Germany; Bundeswehr Institute of Microbiology, Neuherbergstrasse 11, DE-80937, Munich, Germany; German Center of Infection Research (DZIF) Partner Munich, Neuherbergstrasse 11, DE-80937, Munich, Germany
| | - Lidia Chitimia-Dobler
- Parasitology Unit, Institute of Zoology, University of Hohenheim, Hans-Wolff-Strasse 34, DE-70955, Stuttgart, Germany; Bundeswehr Institute of Microbiology, Neuherbergstrasse 11, DE-80937, Munich, Germany; German Center of Infection Research (DZIF) Partner Munich, Neuherbergstrasse 11, DE-80937, Munich, Germany
| | - Hans Jørn Kolmos
- Research Unit of Clinical Microbiology, University of Southern Denmark, J.B. Winsløvsvej 21.2, DK-5000, Odense C, Denmark
| | - Per Moestrup Jensen
- Department of Plant- and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Copenhagen, Denmark
| | - Gerhard Dobler
- Parasitology Unit, Institute of Zoology, University of Hohenheim, Hans-Wolff-Strasse 34, DE-70955, Stuttgart, Germany; Bundeswehr Institute of Microbiology, Neuherbergstrasse 11, DE-80937, Munich, Germany; German Center of Infection Research (DZIF) Partner Munich, Neuherbergstrasse 11, DE-80937, Munich, Germany
| | - Sigurdur Skarphédinsson
- Clinical Centre of Emerging and Vector-borne Infections, Odense University Hospital, Sdr. Boulevard 29, DK-5000, Odense C, Denmark; Department of Infectious Diseases, Odense University Hospital, Sdr. Boulevard 29, DK-5000, Odense C, Denmark
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14
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Kellman EM, Offerdahl DK, Melik W, Bloom ME. Viral Determinants of Virulence in Tick-Borne Flaviviruses. Viruses 2018; 10:v10060329. [PMID: 29914165 PMCID: PMC6024809 DOI: 10.3390/v10060329] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 06/12/2018] [Accepted: 06/15/2018] [Indexed: 12/27/2022] Open
Abstract
Tick-borne flaviviruses have a global distribution and cause significant human disease, including encephalitis and hemorrhagic fever, and often result in neurologic sequelae. There are two distinct properties that determine the neuropathogenesis of a virus. The ability to invade the central nervous system (CNS) is referred to as the neuroinvasiveness of the agent, while the ability to infect and damage cells within the CNS is referred to as its neurovirulence. Examination of laboratory variants, cDNA clones, natural isolates with varying pathogenicity, and virally encoded immune evasion strategies have contributed extensively to our understanding of these properties. Here we will review the major viral determinants of virulence that contribute to pathogenesis and influence both neuroinvasiveness and neurovirulence properties of tick-borne flaviviruses, focusing particularly on the envelope protein (E), nonstructural protein 5 (NS5), and the 3′ untranslated region (UTR).
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Affiliation(s)
- Eliza M Kellman
- Laboratory of Virology, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, MT 59840, USA.
| | - Danielle K Offerdahl
- Laboratory of Virology, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, MT 59840, USA.
| | - Wessam Melik
- School of Medical Sciences, Orebro University, SE-703 62 Örebro, Sweden.
| | - Marshall E Bloom
- Laboratory of Virology, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, MT 59840, USA.
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15
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Identification and analysis of host proteins that interact with the 3'-untranslated region of tick-borne encephalitis virus genomic RNA. Virus Res 2018; 249:52-56. [PMID: 29545014 DOI: 10.1016/j.virusres.2018.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 03/09/2018] [Accepted: 03/10/2018] [Indexed: 12/21/2022]
Abstract
Tick-borne encephalitis virus (TBEV) causes severe neurological disease, but the pathogenetic mechanism is unclear. The conformational structure of the 3'-untranslated region (UTR) of TBEV is associated with its virulence. We tried to identify host proteins interacting with the 3'-UTR of TBEV. Cellular proteins of HEK293T cells were co-precipitated with biotinylated RNAs of the 3'-UTR of low- and high-virulence TBEV strains and subjected to mass spectrometry analysis. Fifteen host proteins were found to bind to the 3'-UTR of TBEV, four of which-cold shock domain containing-E1 (CSDE1), spermatid perinuclear RNA binding protein (STRBP), fragile X mental retardation protein (FMRP), and interleukin enhancer binding factor 3 (ILF3)-bound specifically to that of the low-virulence strain. An RNA immunoprecipitation and pull-down assay confirmed the interactions of the complete 3'-UTRs of TBEV genomic RNA with CSDE1, FMRP, and ILF3. Partial deletion of the stem loop (SL) 3 to SL 5 structure of the variable region of the 3'-UTR did not affect interactions with the host proteins, but the interactions were markedly suppressed by deletion of the complete SL 3, 4, and 5 structures, as in the high-virulence TBEV strain. Further analysis of the roles of host proteins in the neurologic pathogenicity of TBEV is warranted.
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16
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Nagy A, Nagy O, Tarcsai K, Farkas Á, Takács M. First detection of tick-borne encephalitis virus RNA in clinical specimens of acutely ill patients in Hungary. Ticks Tick Borne Dis 2018; 9:485-489. [DOI: 10.1016/j.ttbdis.2017.12.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 12/27/2017] [Accepted: 12/27/2017] [Indexed: 12/30/2022]
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17
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Abstract
Tick-borne encephalitis virus (TBEV) belongs to the Flaviviridae family and Flavivirus genus. TBEV is maintained in transmission cycles between Ixodid ticks and wild mammalian hosts, particularly rodents. A wide range of animal species are also infected with TBEV by the bite of infected ticks, and TBEV infection causes fatal encephalitis in humans. TBEV is endemic widely in the Eurasian continent, and more than 10,000 cases of the disease are reported annually. In Japan, the 1st confirmed case of TBE was reported in the southern area of Hokkaido in 1993, and after 20 years, the 2nd to 4th cases were reported in Hokkaido in 2016 and 2017. Our sero-epizootiological survey indicated endemic foci of TBEV are widely distributed in Hokkaido and that those of TBEV or tick-borne flavivirus outside Hokkaido. In this review, I introduced recent topics of TBEV including newly developed diagnostic methods, epidemiology and pathogenesis of TBEV.
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18
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Yoshii K, Song JY, Park SB, Yang J, Schmitt HJ. Tick-borne encephalitis in Japan, Republic of Korea and China. Emerg Microbes Infect 2017; 6:e82. [PMID: 28928417 PMCID: PMC5625319 DOI: 10.1038/emi.2017.69] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 06/29/2017] [Accepted: 07/09/2017] [Indexed: 12/18/2022]
Abstract
Tick-borne encephalitis virus (TBEV) causes mild or moderate febrile illness in humans that may progress to encephalitis, leading to severe long-term complications and sometimes death. TBEV is prevalent in the Eurasian continent and has been isolated in China, Japan and Republic of Korea (ROK). The TBEV isolates from Japan are of the Far-Eastern subtype; in ROK, the isolates are of the Western subtype; and all TBEV isolates in China are of the Far-Eastern subtype, except one strain that was identified most recently as the Siberian subtype. TBE is endemic to the northeast, northwest and southeast of China; only two confirmed TBE cases have been reported in Japan to date; and no TBE case has been confirmed in ROK. For TBE patients in China, the onset of disease is acute with no biphasic course for disease presentation. The clinical spectrum of disease phenotypes may be wider than currently understood, since serological evidence suggests the presence of TBEV infections in healthy people, indicating that asymptomatic or unspecific manifestations of TBEV infection may exist. The current treatment for TBE is supportive care. In China, vaccines against TBEV have been developed and are available with demonstrated immunogenicity and safety, although efficacy data are lacking. No vaccines are available in ROK or Japan.
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Affiliation(s)
- Kentaro Yoshii
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
| | - Joon Young Song
- Division of Infectious Diseases, Department of Internal Medicine, Korea University Guro Hospital, Gurodongro 148, Gurogu, Seoul 08308, Republic of Korea
| | - Seong-Beom Park
- Pfizer Pharmaceuticals Korea Ltd, Seoul 100-771, Republic of Korea
| | - Junfeng Yang
- Pfizer Investment Co., Ltd. The Fifth Square, Tower B, 9/F, No. 3-7, Chaoyangmen North Avenue, Dongcheng District, Beijing 100010, China
| | - Heinz-Josef Schmitt
- Scientific Affairs, Pfizer Vaccines Europe, 23-25 Avenue du Dr Lannelongue, Paris 75014, France
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19
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Adaptation of tick-borne encephalitis virus from human brain to different cell cultures induces multiple genomic substitutions. Arch Virol 2017. [PMID: 28631054 DOI: 10.1007/s00705-017-3442-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The C11-13 strain from the Siberian subtype of tick-borne encephalitis virus (TBEV) was isolated from human brain using pig embryo kidney (PEK), 293, and Neuro-2a cells. Analysis of the complete viral genome of the C11-13 variants during six passages in these cells revealed that the cell-adapted C11-13 variants had multiple amino acid substitutions as compared to TBEV from human brain. Seven out of eight amino acids substitutions in the high-replicating C11-13(PEK) variant mapped to non-structural proteins; 13 out of 14 substitutions in the well-replicating C11-13(293) variant, and all four substitutions in the low-replicating C11-13(Neuro-2a) variant were also localized in non-structural proteins, predominantly in the NS2a (2), NS3 (6) and NS5 (3) proteins. The substitutions NS2a1067 (Asn → Asp), NS2a1168(Leu → Val) in the N-terminus of NS2a and NS31745(His → Gln) in the helicase domain of NS3 were found in all selected variants. We postulate that multiple substitutions in the NS2a, NS3 and NS5 genes play a key role in adaptation of TBEV to different cells.
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20
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Asghar N, Pettersson JHO, Dinnetz P, Andreassen Å, Johansson M. Deep sequencing analysis of tick-borne encephalitis virus from questing ticks at natural foci reveals similarities between quasispecies pools of the virus. J Gen Virol 2017; 98:413-421. [PMID: 28073402 PMCID: PMC5797951 DOI: 10.1099/jgv.0.000704] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Every year, tick-borne encephalitis virus (TBEV) causes severe central nervous system infection in 10 000 to 15 000 people in Europe and Asia. TBEV is maintained in the environment by an enzootic cycle that requires a tick vector and a vertebrate host, and the adaptation of TBEV to vertebrate and invertebrate environments is essential for TBEV persistence in nature. This adaptation is facilitated by the error-prone nature of the virus’s RNA-dependent RNA polymerase, which generates genetically distinct virus variants called quasispecies. TBEV shows a focal geographical distribution pattern where each focus represents a TBEV hotspot. Here, we sequenced and characterized two TBEV genomes, JP-296 and JP-554, from questing Ixodes ricinus ticks at a TBEV focus in central Sweden. Phylogenetic analysis showed geographical clustering among the newly sequenced strains and three previously sequenced Scandinavian strains, Toro-2003, Saringe-2009 and Mandal-2009, which originated from the same ancestor. Among these five Scandinavian TBEV strains, only Mandal-2009 showed a large deletion within the 3′ non-coding region (NCR), similar to the highly virulent TBEV strain Hypr. Deep sequencing of JP-296, JP-554 and Mandal-2009 revealed significantly high quasispecies diversity for JP-296 and JP-554, with intact 3′NCRs, compared to the low diversity in Mandal-2009, with a truncated 3′NCR. Single-nucleotide polymorphism analysis showed that 40 % of the single-nucleotide polymorphisms were common between quasispecies populations of JP-296 and JP-554, indicating a putative mechanism for how TBEV persists and is maintained within its natural foci.
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Affiliation(s)
- Naveed Asghar
- School of Natural Science, Technology & Environmental Studies, Södertörn University, Huddinge, Sweden.,School of Medical Sciences, Örebro University, Örebro, Sweden.,iRiSC - Inflammatory Response and Infection Susceptibility Centre, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - John H-O Pettersson
- Department of Infectious Disease Epidemiology and Modelling, Norwegian Institute of Public Health, Oslo, Norway.,Department of Microbiology, National Veterinary Institute, Uppsala, Sweden.,Department of Medical Biochemistry and Microbiology (IMBIM), Zoonosis Science Center, Uppsala University, Uppsala, Sweden
| | - Patrik Dinnetz
- School of Natural Science, Technology & Environmental Studies, Södertörn University, Huddinge, Sweden
| | - Åshild Andreassen
- Department of Virology, Division of Infectious Disease Control, Norwegian Institute of Public Health, Oslo, Norway
| | - Magnus Johansson
- School of Medical Sciences, Örebro University, Örebro, Sweden.,iRiSC - Inflammatory Response and Infection Susceptibility Centre, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
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21
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Complete Genome Sequence of a Low-Virulence Tick-Borne Encephalitis Virus Strain. GENOME ANNOUNCEMENTS 2016; 4:4/5/e01145-16. [PMID: 27795275 PMCID: PMC5073262 DOI: 10.1128/genomea.01145-16] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report here the complete genome sequence (GenBank accession no. KX268728) of tick-borne encephalitis strain HB171/11, isolated from an Ixodes ricinus tick from a natural focus where human neurological disease is rare. The strain shows unique characteristics in neuroinvasiveness and neurovirulence.
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22
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Muto M, Bazartseren B, Tsevel B, Dashzevge E, Yoshii K, Kariwa H. Isolation and characterization of tick-borne encephalitis virus from Ixodes persulcatus in Mongolia in 2012. Ticks Tick Borne Dis 2015; 6:623-9. [PMID: 26025267 DOI: 10.1016/j.ttbdis.2015.05.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/16/2015] [Accepted: 05/09/2015] [Indexed: 10/23/2022]
Abstract
Tick-borne encephalitis virus (TBEV) is a zoonotic virus belonging to the genus Flavivirus, in the family Flaviviridae. The virus, which is endemic in Europe and northern parts of Asia, causes severe encephalitis. Tick-borne encephalitis (TBE) has been reported in Mongolia since the 1980s, but details about the biological characteristics of the endemic virus are lacking. In this study, 680 ticks (Ixodes persulcatus) were collected in Selenge aimag, northern Mongolia, in 2012. Nine Mongolian TBEV strains were isolated from tick homogenates. A sequence analysis of the envelope protein gene revealed that all isolates belonged to the Siberian subtype of TBEV. Two strains showed similar growth properties in cultured cells, but their virulence in mice differed. Whole genome sequencing revealed only thirteen amino acid differences between these Mongolian TBEV strains. Our results suggest that these naturally occurring amino acid mutations affected the pathogenicity of Mongolian TBEV. Our results may be an important platform for monitoring TBEV to evaluate the epidemiological risk in TBE endemic areas of Mongolia.
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Affiliation(s)
- Memi Muto
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
| | - Boldbaatar Bazartseren
- Laboratory of Virology, Institute of Veterinary Medicine, Mongolian State University of Agriculture, Zaisan, Ulaanbaatar 17024, Mongolia
| | - Bazartseren Tsevel
- Laboratory of Virology, Institute of Veterinary Medicine, Mongolian State University of Agriculture, Zaisan, Ulaanbaatar 17024, Mongolia
| | - Erdenechimeg Dashzevge
- Laboratory of Virology, Institute of Veterinary Medicine, Mongolian State University of Agriculture, Zaisan, Ulaanbaatar 17024, Mongolia
| | - Kentaro Yoshii
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan.
| | - Hiroaki Kariwa
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
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23
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Sakai M, Muto M, Hirano M, Kariwa H, Yoshii K. Virulence of tick-borne encephalitis virus is associated with intact conformational viral RNA structures in the variable region of the 3'-UTR. Virus Res 2015; 203:36-40. [PMID: 25801453 DOI: 10.1016/j.virusres.2015.03.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/09/2015] [Accepted: 03/12/2015] [Indexed: 02/07/2023]
Abstract
Tick-borne encephalitis virus (TBEV) is maintained between ticks and mammals in nature and causes severe neurological disease in human. However, the mechanism of viral pathogenicity is unknown. Previously, we showed that the deletion in the variable region of the 3'-untranslated region (UTR) is involved in the pathogenicity of the strains from the Far-Eastern subtype of TBEV. To investigate the detailed function of the variable region, we constructed recombinant TBEV with partial deletions in the region. In a mouse model, the partial deletions drastically increased the virulence of the virus, with no effect on virus multiplication in mouse brain. Furthermore, the mutations did not affect the production of subgenomic flavivirus RNA from the 3'-UTR, and the induction of interferon (IFN) and IFN-stimulated genes. These data suggested that the conformational structure of the variable region is associated with the pathogenicity of the Far-Eastern subtype of TBEV. These findings provide a foundation for further research to identify the pathogenic mechanisms of TBEV.
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Affiliation(s)
- Mizuki Sakai
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
| | - Memi Muto
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
| | - Minato Hirano
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
| | - Hiroaki Kariwa
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
| | - Kentaro Yoshii
- Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan.
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