scholarly journals Escape of Tick-Borne Flavivirus from 2′-C-Methylated Nucleoside Antivirals Is Mediated by a Single Conservative Mutation in NS5 That Has a Dramatic Effect on Viral Fitness

2017 ◽  
Vol 91 (21) ◽  
Author(s):  
Ludek Eyer ◽  
Hirofumi Kondo ◽  
Darina Zouharova ◽  
Minato Hirano ◽  
James J. Valdés ◽  
...  
Keyword(s):  
Active Site ◽  
Lethal Dose ◽  
Nucleoside Analogs ◽  
Encephalitis Virus ◽  
Nucleoside Analog ◽  
Viral Fitness ◽  
Drug Resistant ◽  
Tick Borne Encephalitis ◽  
Tbev Strain ◽  
Tick Borne Encephalitis Virus

ABSTRACT Tick-borne encephalitis virus (TBEV) causes a severe and potentially fatal neuroinfection in humans. Despite its high medical relevance, no specific antiviral therapy is currently available. Here we demonstrate that treatment with a nucleoside analog, 7-deaza-2′-C-methyladenosine (7-deaza-2′-CMA), substantially improved disease outcomes, increased survival, and reduced signs of neuroinfection and viral titers in the brains of mice infected with a lethal dose of TBEV. To investigate the mechanism of action of 7-deaza-2′-CMA, two drug-resistant TBEV clones were generated and characterized. The two clones shared a signature amino acid substitution, S603T, in the viral NS5 RNA-dependent RNA polymerase (RdRp) domain. This mutation conferred resistance to various 2′-C-methylated nucleoside derivatives, but no cross-resistance was seen with other nucleoside analogs, such as 4′-C-azidocytidine and 2′-deoxy-2′-beta-hydroxy-4′-azidocytidine (RO-9187). All-atom molecular dynamics simulations revealed that the S603T RdRp mutant repels a water molecule that coordinates the position of a metal ion cofactor as 2′-C-methylated nucleoside analogs approach the active site. To investigate its phenotype, the S603T mutation was introduced into a recombinant TBEV strain (Oshima-IC) generated from an infectious cDNA clone and into a TBEV replicon that expresses a reporter luciferase gene (Oshima-REP-luc2A). The mutants were replication impaired, showing reduced growth and a small plaque size in mammalian cell culture and reduced levels of neuroinvasiveness and neurovirulence in rodent models. These results indicate that TBEV resistance to 2′-C-methylated nucleoside inhibitors is conferred by a single conservative mutation that causes a subtle atomic effect within the active site of the viral NS5 RdRp and is associated with strong attenuation of the virus. IMPORTANCE This study found that the nucleoside analog 7-deaza-2′-C-methyladenosine (7-deaza-2′-CMA) has high antiviral activity against tick-borne encephalitis virus (TBEV), a pathogen that causes severe human neuroinfections in large areas of Europe and Asia and for which there is currently no specific therapy. Treating mice infected with a lethal dose of TBEV with 7-deaza-2′-CMA resulted in significantly higher survival rates and reduced the severity of neurological signs of the disease. Thus, this compound shows promise for further development as an anti-TBEV drug. It is important to generate drug-resistant mutants to understand how the drug works and to develop guidelines for patient treatment. We generated TBEV mutants that were resistant not only to 7-deaza-2′-CMA but also to a broad range of other 2′-C-methylated antiviral medications. Our findings suggest that combination therapy may be used to improve treatment and reduce the emergence of drug-resistant viruses during nucleoside analog therapy for TBEV infection.

scholarly journals Spectrum of antiviral activity of 4-aminopyrimidine N-oxides against a broad panel of tick-borne encephalitis virus strains

2020 ◽  
Vol 28 ◽  
pp. 204020662094346
Author(s):  
Evgenia V Dueva ◽  
Ksenia K Tuchynskaya ◽  
Liubov I Kozlovskaya ◽  
Dmitry I Osolodkin ◽  
Kseniya N Sedenkova ◽  
...  
Keyword(s):  
Encephalitis Virus ◽  
Northern Eurasia ◽  
Virus Particles ◽  
E Protein ◽  
Tick Borne Encephalitis ◽  
Tbev Strain ◽  
Amino Phenol ◽  
Tick Borne Encephalitis Virus ◽  
Immature Virus

Tick-borne encephalitis is an important human arbovirus neuroinfection spread across the Northern Eurasia. Inhibitors of tick-borne encephalitis virus (TBEV) strain Absettarov, presumably targeting E protein n-octyl-β-d-glucoside (β-OG) pocket, were reported earlier. In this work, these inhibitors were tested in vitro against seven strains representing three main TBEV subtypes. The most potent compound, 2-[(2-methyl-1-oxido-5,6,7,8-tetrahydroquinazolin-4-yl)amino]-phenol, showed EC50 values lower than 22 µM against all the tested strains. Nevertheless, EC50 values for virus samples of certain strains demonstrated a substantial variation, which appeared to be consistent with the presence of E protein not only in infectious virions, but also in non-infectious and immature virus particles, protein aggregates, and membrane complexes.

scholarly journals Comparative analysis of genomes of tick-borne encephalitis virus strains isolated from mosquitoes and ticks

2017 ◽  
Vol 62 (1) ◽  
pp. 30-35 ◽  
Author(s):  
N. M. Pukhovskaya ◽  
O. V. Morozova ◽  
N. B. Belozerova ◽  
S. V. Bakhmetyeva ◽  
N. P. Vysochina ◽  
...  
Keyword(s):  
Vaccine Strain ◽  
Far East ◽  
Encephalitis Virus ◽  
Ixodes Persulcatus ◽  
Aedes Vexans ◽  
Tick Borne Encephalitis ◽  
Tbev Strain ◽  
Natural Foci ◽  
Tick Borne Encephalitis Virus ◽  
Far Eastern

The tick-borne encephalitis virus (TBEV) strain Lazo MP36 was isolated from the pool of mosquitoes Aedes vexans collected in Lazo region of Khabarovsk territory in August 2014. Phylogenetic analysis of the strain Lazo MP36 complete genome (GenBank accession number KT001073) revealed its correspondence to the TBEV Far Eastern subtype and differences from the following strains: 1) from ticks Ixodes persulcatus P. Schulze, 1930 [vaccine strain 205 (JX498939) and strains Khekhtzir 1230 (KF880805), Chichagovka (KP844724), Birobidzhan 1354 (KF880805) isolated in 2012-2013]; 2) from mosquitoes [strain Malyshevo (KJ744034) isolated in 1978 from Aedes vexans nipponii in Khabarovsk territory; strain Sakhalin 6-11 isolated from the pool of mosquitoes in 2011 (KF826916)]; 3) from human brain [vaccine strain Sofjin (JN229223), Glubinnoe/2004(DQ862460). Kavalerovo (DQ862460), Svetlogorie (DQ862460)]. The fusion peptide necessary for flavivirus entry to cells of the three TBEV strains isolated from mosquitoes (Lazo MP36, Malyshevo and Sakhalin 6-11) has the canonical structure 98-DRGWGNHCGLFGKGSI-113 for the tick-borne flaviviruses. Amino acid transition H104G typical for the mosquito-borne flaviviruses was not found. Structures of 5’- and 3’-untranslated (UTR) regions of the TBEV strains from mosquitoes were 85-98% homologous to the TBEV strains of all subtypes without recombination with mosquito-borne flaviviruses found in the Far East of Russia. Secondary structures of 5’- and 3'-UTR as well as cyclization sequences (CS) of types a and B are highly homologous for all TBEV isolates independently of the biological hosts and vectors. similarity of the genomes of the TBEV isolates from mosquitoes, ticks and patients as well as pathogenicity of the isolates for new-borne laboratory mice and tissue cultures might suggest a possible role of mosquitoes in the TBEV circulation in natural foci as an accidental or additional virus carrier.

scholarly journals Molecular phylogeography of tick-borne encephalitis virus in central Europe

2013 ◽  
Vol 94 (9) ◽  
pp. 2129-2139 ◽  
Author(s):  
Manfred Weidmann ◽  
Stefan Frey ◽  
Caio C. M. Freire ◽  
Sandra Essbauer ◽  
Daniel Růžek ◽  
...  
Keyword(s):  
Czech Republic ◽  
Central Europe ◽  
Encephalitis Virus ◽  
Danube River ◽  
Long Distance ◽  
The Czech Republic ◽  
Tick Borne Encephalitis ◽  
Tbev Strain ◽  
Depth Analysis ◽  
Tick Borne Encephalitis Virus

In order to obtain a better understanding of tick-borne encephalitis virus (TBEV) strain movements in central Europe the E gene sequences of 102 TBEV strains collected from 1953 to 2011 at 38 sites in the Czech Republic, Slovakia, Austria and Germany were determined. Bayesian analysis suggests a 350-year history of evolution and spread in central Europe of two main lineages, A and B. In contrast to the east to west spread at the Eurasian continent level, local central European spreading patterns suggest historic west to east spread followed by more recent east to west spread. The phylogenetic and network analyses indicate TBEV ingressions from the Czech Republic and Slovakia into Germany via landscape features (Danube river system), biogenic factors (birds, red deer) and anthropogenic factors. The identification of endemic foci showing local genetic diversity is of paramount importance to the field as these will be a prerequisite for in-depth analysis of focal TBEV maintenance and long-distance TBEV spread.

scholarly journals The envelope protein of tick-borne encephalitis virus influences neuron entry, pathogenicity, and vaccine protection

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Richard Lindqvist ◽  
Ebba Rosendal ◽  
Elvira Weber ◽  
Naveed Asghar ◽  
Sarah Schreier ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Encephalitis Virus ◽  
Chimeric Virus ◽  
E Protein ◽  
Tick Borne Encephalitis ◽  
Neutralizing Capacity ◽  
Tbev Strain ◽  
Primary Mouse ◽  
Tick Borne Encephalitis Virus

Abstract Background Tick-borne encephalitis virus (TBEV) is considered to be the medically most important arthropod-borne virus in Europe. The symptoms of an infection range from subclinical to mild flu-like disease to lethal encephalitis. The exact determinants of disease severity are not known; however, the virulence of the strain as well as the immune status of the host are thought to be important factors for the outcome of the infection. Here we investigated virulence determinants in TBEV infection. Method Mice were infected with different TBEV strains, and high virulent and low virulent TBEV strains were chosen. Sequence alignment identified differences that were cloned to generate chimera virus. The infection rate of the parental and chimeric virus were evaluated in primary mouse neurons, astrocytes, mouse embryonic fibroblasts, and in vivo. Neutralizing capacity of serum from individuals vaccinated with the FSME-IMMUN® and Encepur® or combined were evaluated. Results We identified a highly pathogenic and neurovirulent TBEV strain, 93/783. Using sequence analysis, we identified the envelope (E) protein of 93/783 as a potential virulence determinant and cloned it into the less pathogenic TBEV strain Torö. We found that the chimeric virus specifically infected primary neurons more efficiently compared to wild-type (WT) Torö and this correlated with enhanced pathogenicity and higher levels of viral RNA in vivo. The E protein is also the major target of neutralizing antibodies; thus, genetic variation in the E protein could influence the efficiency of the two available vaccines, FSME-IMMUN® and Encepur®. As TBEV vaccine breakthroughs have occurred in Europe, we chose to compare neutralizing capacity from individuals vaccinated with the two different vaccines or a combination of them. Our data suggest that the different vaccines do not perform equally well against the two Swedish strains. Conclusions Our findings show that two amino acid substitutions of the E protein found in 93/783, A83T, and A463S enhanced Torö infection of neurons as well as pathogenesis and viral replication in vivo; furthermore, we found that genetic divergence from the vaccine strain resulted in lower neutralizing antibody titers in vaccinated individuals.

scholarly journals An E460D substitution in the NS5 protein of tick-borne encephalitis virus confers resistance to the inhibitor Galidesivir (BCX4430) and also attenuates the virus for mice

2019 ◽  
Author(s):  
Ludek Eyer ◽  
Antoine Nougairède ◽  
Marie Uhlířová ◽  
Jean-Sélim Driouich ◽  
Darina Zouharová ◽  
...  
Keyword(s):  
Cell Culture ◽  
Ebola Virus ◽  
Rna Virus ◽  
Encephalitis Virus ◽  
Viral Fitness ◽  
Rna Dependent Rna Polymerase ◽  
Virus Inhibitor ◽  
Tick Borne Encephalitis ◽  
Tick Borne Encephalitis Virus ◽  
Ebola Virus Infection

AbstractThe adenosine analogue Galidesivir (BCX4430), a broad-spectrum RNA virus inhibitor, has entered a Phase 1 clinical safety and pharmacokinetics study in healthy subjects and is under clinical development for treatment of Ebola virus infection. Moreover, Galidesivir also inhibits the reproduction of tick-borne encephalitis virus (TBEV) and numerous other medically important flaviviruses. Until now, studies of this antiviral agent have not yielded resistant viruses. Here, we demonstrate that an E460D substitution, in the active site of TBEV RNA-dependent-RNA-polymerase (RdRp), confers resistance to Galidesivir in cell culture. Stochastic molecular simulations indicate that the steric freedom caused by the E460D substitution increases close electrostatic interactions between the inhibitor and the interrogation residue of the TBEV RdRp motif F, resulting in rejection of the analogue as an incorrect/modified nucleotide. Galidesivir-resistant TBEV exhibited no cross-resistance to structurally different antiviral nucleoside analogues, such as 7-deaza-2’-C-methyladenosine, 2’-C-methyladenosine and 4’-azido-aracytidine. Although, the E460D substitution led only to a subtle decrease in viral fitness in cell culture, Galidesivir-resistant TBEV was highly attenuated in vivo, with 100% survival rate and no clinical signs observed in infected mice. Our results contribute to understanding the molecular basis of Galidesivir antiviral activity, flavivirus resistance to nucleoside inhibitors and the potential contribution of viral RdRp to flavivirus neurovirulence.ImportanceTick-borne encephalitis virus (TBEV) is a pathogen that causes severe human neuroinfections in large areas of Europe and Asia and for which there is currently no specific therapy. We have previously found that Galidesivir (BCX4430), a broad-spectrum RNA virus inhibitor, which is under clinical development for treatment of Ebola virus infection, has a strong antiviral effect against TBEV. For any antiviral drug, it is important to generate drug-resistant mutants to understand how the drug works. Here, we produced TBEV mutants resistant to Galidesivir and found that the resistance is caused by a single amino acid substitution in an active site of the viral RNA-dependent RNA polymerase, an enzyme which is crucial for replication of viral RNA genome. Although, this substitution led only to a subtle decrease in viral fitness in cell culture, Galidesivir-resistant TBEV was highly attenuated in a mouse model. Our results contribute to understanding the molecular basis of Galidesivir antiviral activity.

scholarly journals An E460D Substitution in the NS5 Protein of Tick-Borne Encephalitis Virus Confers Resistance to the Inhibitor Galidesivir (BCX4430) and Also Attenuates the Virus for Mice

2019 ◽  
Vol 93 (16) ◽  
Author(s):  
Ludek Eyer ◽  
Antoine Nougairède ◽  
Marie Uhlířová ◽  
Jean-Sélim Driouich ◽  
Darina Zouharová ◽  
...  
Keyword(s):  
Cell Culture ◽  
Yellow Fever Virus ◽  
Rna Virus ◽  
Encephalitis Virus ◽  
Viral Fitness ◽  
Virus Infections ◽  
Rna Dependent Rna Polymerase ◽  
Virus Inhibitor ◽  
Tick Borne Encephalitis ◽  
Tick Borne Encephalitis Virus

ABSTRACT The adenosine analogue galidesivir (BCX4430), a broad-spectrum RNA virus inhibitor, has entered a phase 1 clinical safety and pharmacokinetics study in healthy subjects and is under clinical development for treatment of Ebola and yellow fever virus infections. Moreover, galidesivir also inhibits the reproduction of tick-borne encephalitis virus (TBEV) and numerous other medically important flaviviruses. Until now, studies of this antiviral agent have not yielded resistant viruses. Here, we demonstrate that an E460D substitution in the active site of TBEV RNA-dependent RNA polymerase (RdRp) confers resistance to galidesivir in cell culture. Galidesivir-resistant TBEV exhibited no cross-resistance to structurally different antiviral nucleoside analogues, such as 7-deaza-2′-C-methyladenosine, 2′-C-methyladenosine, and 4′-azido-aracytidine. Although the E460D substitution led to only a subtle decrease in viral fitness in cell culture, galidesivir-resistant TBEV was highly attenuated in vivo, with a 100% survival rate and no clinical signs observed in infected mice. Furthermore, no virus was detected in the sera, spleen, or brain of mice inoculated with the galidesivir-resistant TBEV. Our results contribute to understanding the molecular basis of galidesivir antiviral activity, flavivirus resistance to nucleoside inhibitors, and the potential contribution of viral RdRp to flavivirus neurovirulence. IMPORTANCE Tick-borne encephalitis virus (TBEV) is a pathogen that causes severe human neuroinfections in Europe and Asia and for which there is currently no specific therapy. We have previously found that galidesivir (BCX4430), a broad-spectrum RNA virus inhibitor, which is under clinical development for treatment of Ebola and yellow fever virus infections, has a strong antiviral effect against TBEV. For any antiviral drug, it is important to generate drug-resistant mutants to understand how the drug works. Here, we produced TBEV mutants resistant to galidesivir and found that the resistance is caused by a single amino acid substitution in an active site of the viral RNA-dependent RNA polymerase, an enzyme which is crucial for replication of the viral RNA genome. Although this substitution led only to a subtle decrease in viral fitness in cell culture, galidesivir-resistant TBEV was highly attenuated in a mouse model. Our results contribute to understanding the molecular basis of galidesivir antiviral activity.

scholarly journals Antiviral Activity of Uridine Derivatives of 2-Deoxy Sugars against Tick-Borne Encephalitis Virus

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1129 ◽  
Author(s):  
Ewelina Krol ◽  
Ilona Wandzik ◽  
Gabriela Brzuska ◽  
Luděk Eyer ◽  
Daniel Růžek ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Virulent Strain ◽  
Encephalitis Virus ◽  
Antiviral Therapies ◽  
Tick Borne Encephalitis ◽  
Tbev Strain ◽  
Ic50 Values ◽  
Tick Borne Encephalitis Virus ◽  
Derivatives Of ◽  
Deoxy Sugars

Tick-borne encephalitis virus (TBEV) is a causative agent of tick-borne encephalitis (TBE), one of the most important human infections involving the central nervous system. Although effective vaccines are available on the market, they are recommended only in endemic areas. Despite many attempts, there are still no specific antiviral therapies for TBEV treatment. Previously, we synthesized a series of uridine derivatives of 2-deoxy sugars and proved that some compounds show antiviral activity against viruses from the Flaviviridae and Orthomyxoviridae families targeting the late steps of the N-glycosylation process, affecting the maturation of viral proteins. In this study, we evaluated a series of uridine derivatives of 2-deoxy sugars for their antiviral properties against two strains of the tick-borne encephalitis virus; the highly virulent TBEV strain Hypr and the less virulent strain Neudoerfl. Four compounds (2, 4, 10, and 11) showed significant anti-TBEV activity with IC50 values ranging from 1.4 to 10.2 µM and low cytotoxicity. The obtained results indicate that glycosylation inhibitors, which may interact with glycosylated membrane TBEV E and prM proteins, might be promising candidates for future antiviral therapies against TBEV.

scholarly journals An E460D Substitution in the NS5 Protein of Tick-Borne Encephalitis Virus Confers Resistance to the Inhibitor Galidesivir (BCX4430) and Also Attenuates the Virus in Mice

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 12
Author(s):  
Jan Haviernik ◽  
Ludek Eyer ◽  
Antoine Nougairède ◽  
Marie Uhlířová ◽  
Jean-Sélim Driouich ◽  
...  
Keyword(s):  
Amino Acid ◽  
Encephalitis Virus ◽  
Viral Fitness ◽  
Single Amino Acid ◽  
Wild Type Virus ◽  
Cross Resistance ◽  
Potential Contribution ◽  
Tick Borne Encephalitis ◽  
Single Amino Acid Change ◽  
Tick Borne Encephalitis Virus

Tick-borne encephalitis virus (TBEV) is a pathogen that causes severe human neuroinfections in Europe and Asia for which there is currently no specific therapy. The adenosine analogue galidesivir (BCX4430), a broad-spectrum RNA virus inhibitor, has entered a phase 1 clinical safety and pharmacokinetics study in healthy subjects and is under clinical development for treatment of Ebola and yellow fever virus infections. Moreover, galidesivir also inhibits the reproduction of TBEV and numerous other medically important flaviviruses. Until now, studies of this antiviral agent have not yielded resistant viruses. In our study, we performed serial in vitro passaging of TBEV in the presence of increasing concentrations of galidesivir (up to 50 μM), which resulted in the generation of two drug-resistant TBEV mutants. The first TBEV mutant was characterized by a single amino acid change, E460D. The other carried two amino acid changes, E460D and Y453H. Both mutations mapped to the active site of the viral RNA-dependent RNA polymerase (RdRp). Galidesivir-resistant TBEV exhibited no cross-resistance to structurally different antiviral nucleoside analogues, such as 7-deaza-2′-C-methyladenosine, 2′-C-methyladenosine, and 4′-azido-aracytidine. Although the E460D substitution led to only a subtle decrease in viral fitness in cell culture, galidesivir-resistant TBEV was highly attenuated in vivo, with a 100% survival rate and no clinical signs observed in infected mice. Furthermore, no virus was detected in the sera, spleen, or brain of mice inoculated with the galidesivir-resistant TBEV. By contrast, infection with wild-type virus resulted in fatal infections for all animals. Our results contribute to understanding the molecular basis of galidesivir antiviral activity, flavivirus resistance to nucleoside inhibitors, and the potential contribution of viral RdRp to flavivirus neurovirulence.

scholarly journals In Vivo Characterization of Tick-Borne Encephalitis Virus in Bank Voles (Myodes glareolus)

Viruses ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1069 ◽  
Author(s):  
Michelitsch ◽  
Tews ◽  
Klaus ◽  
Bestehorn-Willmann ◽  
Dobler ◽  
...  
Keyword(s):  
Bank Vole ◽  
Whole Blood ◽  
Clinical Signs ◽  
Encephalitis Virus ◽  
Myodes Glareolus ◽  
Bank Voles ◽  
Tick Borne Encephalitis ◽  
Tbev Strain ◽  
Tick Borne Encephalitis Virus

Tick-borne encephalitis is the most important tick-transmitted zoonotic virus infection in Eurasia, causing severe neurological symptoms in humans. The causative agent, the tick-borne encephalitis virus (TBEV), circulates between ticks and a variety of mammalian hosts. To study the interaction between TBEV and one of its suspected reservoir hosts, bank voles of the Western evolutionary lineage were inoculated subcutaneously with either one of eight TBEV strains or the related attenuated Langat virus, and were euthanized after 28 days. In addition, a subset of four strains was characterized in bank voles of the Carpathian linage. Six bank voles were inoculated per strain, and were housed together in groups of three with one uninfected in-contact animal each. Generally, most bank voles did not show any clinical signs over the course of infection. However, one infected bank vole died and three had to be euthanized prematurely, all of which had been inoculated with the identical TBEV strain (Battaune 17-H9, isolated in 2017 in Germany from a bank vole). All inoculated animals seroconverted, while none of the in-contact animals did. Viral RNA was detected via real-time RT-PCR in the whole blood samples of 31 out of 74 inoculated and surviving bank voles. The corresponding serum sample remained PCR-negative in nearly all cases (29/31). In addition, brain and/or spine samples tested positive in 11 cases, mostly correlating with a positive whole blood sample. Our findings suggest a good adaption of TBEV to bank voles, combining in most cases a low virulence phenotype with detectable virus replication and hinting at a reservoir host function of bank voles for TBEV.

scholarly journals The Envelope Protein of Tick-Borne Encephalitis Virus Influence Neuron Entry, Pathogenicity and Vaccine Protection

2020 ◽  
Author(s):  
Richard Lindqvist ◽  
Ebba Rosendal ◽  
Naveed Asghar ◽  
Sarah Schreier ◽  
Annasara Lenman ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Encephalitis Virus ◽  
Chimeric Virus ◽  
E Protein ◽  
Tick Borne Encephalitis ◽  
Neutralizing Capacity ◽  
Tbev Strain ◽  
Primary Mouse ◽  
Tick Borne Encephalitis Virus

Abstract Background: Tick-borne encephalitis virus (TBEV) is considered to be the medically most important arthropod-borne virus in Europe. The symptoms of an infection ranges from subclinical to mild flu-like disease to lethal encephalitis. The exact determinants of disease severity are not known, however, the virulence of the strain as well as the immune status of the host are thought to be important factors for the outcome of the infection. Here we investigated virulence determinants in TBEV infection.Method: Mice were infected with different TBEV strains, and high virulent and low virulent TBEV were chosen. Sequence alignment were used to identify differences that were cloned to generate chimera virus. The infection rate of the parental and chimeric virus were evaluated in primary mouse neurons, astrocytes and MEFs. Neutralizing capacity of serum from individuals vaccinated with the FSME-IMMUN® and Encepur® or combined were evaluated.Results: We identified a highly pathogenic and neurovirulent TBEV strain, 93/783. Using sequence analysis, we identified the envelope (E) protein of 93/783 as a potential virulence determinant and cloned it into the less pathogenic TBEV strain Torö. We found that the chimeric virus specifically infected primary neurons more efficiently compared to wild type (WT) Torö and this correlated with enhanced pathogenicity in vivo. The E protein is also the major target of neutralizing antibodies, thus genetic variation in the E protein could influence the efficiency of the two available vaccines, FSME-IMMUN® and Encepur®. As TBEV vaccine breakthroughs have occurred in Europe, we choose to compare neutralizing capacity from individuals vaccinated with the two different vaccines or a combination of them. Our data suggest that the different vaccines do not perform equally well against the two Swedish strains.Conclusions: Our findings show that two amino acid substitutions of the E protein found in 93/783, A83T and A463S, enhanced Torö infection of neurons as well as pathogenesis in vivo, furthermore we found that genetic divergence from the vaccine strain resulted in lower neutralizing antibody titers in vaccinated individuals.

Sign in / Sign up

Export Citation Format

Share Document