We present structures of three immature tick-borne encephalitis virus (TBEV) isolates. Our atomic models of the major viral components, the E and prM proteins, indicate that the pr domains of prM have a critical role in holding the heterohexameric prM3E3 spikes in a metastable conformation. Destabilization of the prM furin-sensitive loop at acidic pH facilitates its processing. The prM topology and domain assignment in TBEV is similar to the mosquito-borne Binjari virus, but is in contrast to other immature flavivirus models. These results support that prM cleavage, the collapse of E protein ectodomains onto the virion surface, the large movement of the membrane domains of both E and M, and the release of the pr fragment from the particle render the virus mature and infectious. Our work favors the collapse model of flavivirus maturation warranting further studies of immature flaviviruses to determine the sequence of events and mechanistic details driving flavivirus maturation.

• MeSH
• Flavivirus physiology   MeSH
• Encephalitis, Tick-Borne virology   MeSH
• Humans MeSH
• Models, Molecular MeSH
• Viral Envelope Proteins * chemistry   metabolism   MeSH
• Virion MeSH
• Encephalitis Viruses, Tick-Borne * physiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Viral Envelope Proteins * MeSH

Dogs are frequently infected with the tick-borne encephalitis virus (TBEV). However, to date, only a few clinically manifest cases of tick-borne encephalitis (TBE) have been reported in dogs. In this study, three-month-old beagle dogs were infected with TBEV through a subcutaneous injection. Body temperature, clinical signs, blood haematology, blood biochemistry, and immune responses were monitored for up to 28 days postinfection (p.i.). No changes in body temperature or clinical signs were observed in the infected dogs. Most haematology and blood biochemistry parameters were unchanged after the infection, except for a slight reduction in blood lymphocyte counts, but they were within the physiological range. Low-titre viraemia was detected in 2/4 infected dogs between days 1 and 3 p.i. All infected dogs developed a robust immune response, in terms of neutralising antibodies. Thus, TBEV infections lead to effective seroconversion in dogs. Next, to assess TBEV exposure in dogs in the TBEV-endemic region of the Czech Republic, we conducted a serosurvey. Virus neutralisation tests revealed TBEV-specific antibodies in 17 of 130 (13.07%) healthy dogs, which confirmed a high, but clinically inappreciable TBEV exposure rate in the endemic area. The seropositivity rate was similar (12.7%; 41 positives out of 323) in a subgroup of dogs with various clinical disorders, and it was 13.4% (23 out of 171) in a subgroup of dogs with signs of acute neurological disease. Two dogs with fatal acute meningoencephalitis showed positive results for TBEV-specific IgM and IgG antibodies. These data extended our understanding of the clinical presentation of TBEV infections.

• Keywords
• dogs, experimental infection, seroprevalence, tick-borne encephalitis,
• MeSH
• Immunoglobulin G blood   MeSH
• Immunoglobulin M blood   MeSH
• Encephalitis, Tick-Borne diagnosis   immunology   veterinary   virology   MeSH
• Disease Models, Animal MeSH
• Dog Diseases diagnosis   immunology   virology   MeSH
• Neutralization Tests MeSH
• Antibodies, Viral blood   MeSH
• Dogs MeSH
• Viral Zoonoses diagnosis   immunology   virology   MeSH
• Encephalitis Viruses, Tick-Borne * MeSH
• Animals MeSH
• Check Tag
• Dogs MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• Immunoglobulin G MeSH
• Immunoglobulin M MeSH
• Antibodies, Viral MeSH

Remdesivir was shown to inhibit RNA-dependent RNA-polymerases (RdRp) from distinct viral families such as from Filoviridae (Ebola) and Coronaviridae (SARS-CoV, SARS-CoV-2, MERS). In this study, we tested the ability of remdesivir to inhibit RdRps from the Flaviviridae family. Instead of remdesivir, we used the active species that is produced in cells from remdesivir, the appropriate triphosphate, which could be directly tested in vitro using recombinant flaviviral polymerases. Our results show that remdesivir can efficiently inhibit RdRps from viruses causing severe illnesses such as Yellow fever, West Nile fever, Japanese and Tick-borne encephalitis, Zika and Dengue. Taken together, this study demonstrates that remdesivir or its derivatives have the potential to become a broad-spectrum antiviral agent effective against many RNA viruses.

• Keywords
• Flavivirus, Inhibitor, RNA-dependent RNA polymerase, Remdesivir,
• MeSH
• Adenosine Triphosphate analogs & derivatives   chemistry   pharmacology   MeSH
• Antiviral Agents chemistry   pharmacology   MeSH
• Betacoronavirus drug effects   enzymology   MeSH
• COVID-19 MeSH
• COVID-19 Drug Treatment MeSH
• Flavivirus drug effects   enzymology   MeSH
• Inhibitory Concentration 50 MeSH
• Coronavirus Infections drug therapy   virology   MeSH
• Humans MeSH
• Pandemics MeSH
• RNA-Dependent RNA Polymerase antagonists & inhibitors   metabolism   MeSH
• RNA Viruses drug effects   enzymology   MeSH
• SARS-CoV-2 MeSH
• Pneumonia, Viral drug therapy   virology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adenosine Triphosphate MeSH
• Antiviral Agents MeSH
• GS-441524 triphosphate MeSH Browser
• RNA-Dependent RNA Polymerase MeSH

Vaccination against tick-borne encephalitis (TBE) is based on the use of formalin-inactivated, culture-derived whole-virus vaccines. Immune response following vaccination is primarily directed to the viral envelope (E) protein, the major viral surface antigen. In Europe, two TBE vaccines are available in adult and pediatric formulations, namely FSME-IMMUN® (Pfizer) and Encepur® (GlaxoSmithKline). Herein, we analyzed the content of these vaccines using mass spectrometry (MS). The MS analysis revealed that the Encepur vaccine contains not only proteins of the whole virus particle, but also viral non-structural protein 1 (NS1). MS analysis of the FSME-IMMUN vaccine failed due to the high content of human serum albumin used as a stabilizer in the vaccine. However, the presence of NS1 in FSME-IMMUN was confirmed by immunization of mice with six doses of this vaccine, which led to a robust anti-NS1 antibody response. NS1-specific Western blot analysis also detected anti-NS1 antibodies in sera of humans who received multiple doses of either of these two vaccines; however, most vaccinees who received ≤3 doses were negative for NS1-specific antibodies. The contribution of NS1-specific antibodies to protection against TBE was demonstrated by immunization of mice with purified NS1 antigen, which led to a significant (p < 0.01) prolongation of the mean survival time after lethal virus challenge. This indicates that stimulation of anti-NS1 immunity by the TBE vaccines may increase their protective effect.

• Keywords
• NS1, flavivirus, tick-borne encephalitis, vaccination, vaccine,
• Publication type
• Journal Article MeSH