Tick-borne encephalitis (TBE) is a potentially fatal disease common in much of Europe and Asia. There is no specific therapy for the treatment of TBE patients. However, several efforts are being made to develop small molecules that specifically interfere with the life cycle of TBE virus. In particular, recently various nucleoside analogues that can inhibit the viral replicase, such as the RNA-dependent RNA polymerase or viral methyltransferases, have been explored. In addition, human or chimeric (i.e., structural chimeras that combine mouse variable domains with human constant domains) monoclonal antibodies with promising potential for post-exposure prophylaxis or early therapy have been developed. This review summarizes the latest directions and experimental approaches that may be used to combat TBE in humans.

• MeSH
• experimentální terapie MeSH
• klíšťová encefalitida * MeSH
• lidé MeSH
• myši MeSH
• viry klíšťové encefalitidy * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Geografické názvy
• Asie MeSH
• Evropa MeSH

West Nile virus (WNV) is transmitted to humans and animals by a mosquito and enters the central nervous system, leading to lethal encephalitis. Reporter viruses expressing fluorescent proteins enable detection of infected cells in vitro and in vivo, facilitating evaluation of the dynamics of viral infection, and the development of diagnostic or therapeutic methods. In this study, we developed a method for production of a recombinant replication-competent WNV expressing mCherry fluorescent protein. The expression of mCherry was observed in viral antigen-positive cells in vitro and in vivo, but the growth of the reporter WNV was reduced as compared to the parental WNV. The expression of mCherry was stable during 5 passages in reporter WNV-infected culture cells. Neurological symptoms were observed in mice inoculated intracranially with the reporter WNV. The reporter WNV expressing mCherry will facilitate research into WNV replication in mouse brains.

• MeSH
• lidé MeSH
• myši MeSH
• rekombinantní proteiny genetika   MeSH
• virus západního Nilu * genetika   MeSH
• západonilská horečka * veterinární   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We have identified seven putative guanine quadruplexes (G4) in the RNA genome of tick-borne encephalitis virus (TBEV), a flavivirus causing thousands of human infections and numerous deaths every year. The formation of G4s was confirmed by biophysical methods on synthetic oligonucleotides derived from the predicted TBEV sequences. TBEV-5, located at the NS4b/NS5 boundary and conserved among all known flaviviruses, was tested along with its mutated variants for interactions with a panel of known G4 ligands, for the ability to affect RNA synthesis by the flaviviral RNA-dependent RNA polymerase (RdRp) and for effects on TBEV replication fitness in cells. G4-stabilizing TBEV-5 mutations strongly inhibited RdRp RNA synthesis and exhibited substantially reduced replication fitness, different plaque morphology and increased sensitivity to G4-binding ligands in cell-based systems. In contrast, strongly destabilizing TBEV-5 G4 mutations caused rapid reversion to the wild-type genotype. Our results suggest that there is a threshold of stability for G4 sequences in the TBEV genome, with any deviation resulting in either dramatic changes in viral phenotype or a rapid return to this optimal level of G4 stability. The data indicate that G4s are critical elements for efficient TBEV replication and are suitable targets to tackle TBEV infection.

• MeSH
• antivirové látky * farmakologie   terapeutické užití   MeSH
• G-kvadruplexy * MeSH
• klíšťová encefalitida farmakoterapie   genetika   MeSH
• lidé MeSH
• ligandy MeSH
• RNA virová genetika   MeSH
• RNA-dependentní RNA-polymerasa genetika   MeSH
• viry klíšťové encefalitidy * účinky léků   genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Positive-sense single-stranded RNA (+RNA) viruses have proven to be important pathogens that are able to threaten and deeply damage modern societies, as illustrated by the ongoing COVID-19 pandemic. Therefore, compounds active against most or many +RNA viruses are urgently needed. Here, we present PR673, a helquat-like compound that is able to inhibit the replication of SARS-CoV-2 and tick-borne encephalitis virus in cell culture. Using in vitro polymerase assays, we demonstrate that PR673 inhibits RNA synthesis by viral RNA-dependent RNA polymerases (RdRps). Our results illustrate that the development of broad-spectrum non-nucleoside inhibitors of RdRps is feasible.

• MeSH
• COVID-19 * MeSH
• lidé MeSH
• pandemie MeSH
• RNA-dependentní RNA-polymerasa MeSH
• SARS-CoV-2 MeSH
• viry klíšťové encefalitidy * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Diphyllin is a natural arylnaphtalide lignan extracted from tropical plants of particular importance in traditional Chinese medicine. This compound has been described as a potent inhibitor of vacuolar (H+)ATPases and hence of the endosomal acidification process that is required by numerous enveloped viruses to trigger their respective viral infection cascades after entering host cells by receptor-mediated endocytosis. Accordingly, we report here a revised, updated, and improved synthesis of diphyllin, and demonstrate its antiviral activities against a panel of enveloped viruses from Flaviviridae, Phenuiviridae, Rhabdoviridae, and Herpesviridae families. Diphyllin is not cytotoxic for Vero and BHK-21 cells up to 100 μM and exerts a sub-micromolar or low-micromolar antiviral activity against tick-borne encephalitis virus, West Nile virus, Zika virus, Rift Valley fever virus, rabies virus, and herpes-simplex virus type 1. Our study shows that diphyllin is a broad-spectrum host cell-targeting antiviral agent that blocks the replication of multiple phylogenetically unrelated enveloped RNA and DNA viruses. In support of this, we also demonstrate that diphyllin is more than just a vacuolar (H+)ATPase inhibitor but may employ other antiviral mechanisms of action to inhibit the replication cycles of those viruses that do not enter host cells by endocytosis followed by low pH-dependent membrane fusion.

• MeSH
• antigeny virové metabolismus   MeSH
• antivirové látky chemická syntéza   farmakologie   MeSH
• buněčné linie MeSH
• glukosidy farmakologie   MeSH
• lignany chemická syntéza   farmakologie   MeSH
• replikace viru účinky léků   MeSH
• vakuolární protonové ATPasy antagonisté a inhibitory   MeSH
• viabilita buněk účinky léků   MeSH
• viry klasifikace   účinky léků   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: The emergence of new SARS-CoV-2 variants of concern B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta) that harbor mutations in the viral S protein raised concern about activity of current vaccines and therapeutic antibodies. Independent studies have shown that mutant variants are partially or completely resistant against some of the therapeutic antibodies authorized for emergency use. METHODS: We employed hybridoma technology, ELISA-based and cell-based S-ACE2 interaction assays combined with authentic virus neutralization assays to develop second-generation antibodies, which were specifically selected for their ability to neutralize the new variants of SARS-CoV-2. FINDINGS: AX290 and AX677, two monoclonal antibodies with non-overlapping epitopes, exhibit subnanomolar or nanomolar affinities to the receptor binding domain of the viral Spike protein carrying amino acid substitutions N501Y, N439K, E484K, K417N, and a combination N501Y/E484K/K417N found in the circulating virus variants. The antibodies showed excellent neutralization of an authentic SARS-CoV-2 virus representing strains circulating in Europe in spring 2020 and also the variants of concern B.1.1.7 (Alpha), B.1.351 (Beta) and B.1.617.2 (Delta). In addition, AX677 is able to bind Omicron Spike protein just like the wild type Spike. The combination of the two antibodies prevented the appearance of escape mutations of the authentic SARS-CoV-2 virus. Prophylactic administration of AX290 and AX677, either individually or in combination, effectively reduced viral burden and inflammation in the lungs, and prevented disease in a mouse model of SARS-CoV-2 infection. INTERPRETATION: The virus-neutralizing properties were fully reproduced in chimeric mouse-human versions of the antibodies, which may represent a promising tool for COVID-19 therapy. FUNDING: The study was funded by AXON Neuroscience SE and AXON COVIDAX a.s.

• MeSH
• angiotensin konvertující enzym 2 chemie   genetika   metabolismus   MeSH
• antigenní drift a shift MeSH
• COVID-19 virologie   MeSH
• farmakoterapie COVID-19 MeSH
• glykoprotein S, koronavirus genetika   imunologie   metabolismus   MeSH
• imunodominantní epitopy imunologie   MeSH
• kinetika MeSH
• lidé MeSH
• modely nemocí na zvířatech MeSH
• monoklonální protilátky imunologie   terapeutické užití   MeSH
• mutace MeSH
• myši MeSH
• neutralizační testy MeSH
• plíce patologie   MeSH
• protinádorové látky imunologicky aktivní imunologie   terapeutické užití   MeSH
• SARS-CoV-2 genetika   imunologie   izolace a purifikace   MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

The flavivirus, tick-borne encephalitis virus (TBEV) is transmitted by Ixodes spp. ticks and may cause severe and potentially lethal neurological tick-borne encephalitis (TBE) in humans. Studying TBEV requires the use of secondary methodologies to detect the virus in infected cells. To overcome this problem, we rationally designed and constructed a recombinant reporter TBEV that stably expressed the mCherry reporter protein. The resulting TBEV reporter virus (named mCherry-TBEV) and wild-type parental TBEV exhibited similar growth kinetics in cultured cells; however, the mCherry-TBEV virus produced smaller plaques. The magnitude of mCherry expression correlated well with progeny virus production but remained stable over <4 passages in cell culture. Using well-characterized antiviral compounds known to inhibit TBEV, 2'-C-methyladenosine and 2'-deoxy-2'-β-hydroxy-4'-azidocytidine (RO-9187), we demonstrated that mCherry-TBEV is suitable for high-throughput screening of antiviral drugs. Serum samples from a TBEV-vaccinated human and a TBEV-infected dog were used to evaluate the mCherry-based neutralization test. Collectively, recombinant mCherry-TBEV reporter virus described here provides a powerful tool to facilitate the identification of potential antiviral agents, and to measure levels of neutralizing antibodies in human and animal sera.

• MeSH
• antivirové látky izolace a purifikace   MeSH
• buněčné linie MeSH
• klíšťová encefalitida imunologie   virologie   MeSH
• křečci praví MeSH
• ledviny cytologie   MeSH
• lidé MeSH
• luminescentní proteiny genetika   MeSH
• neutralizační testy * MeSH
• neutralizující protilátky krev   MeSH
• protilátky virové krev   MeSH
• rychlé screeningové testy metody   MeSH
• viry klíšťové encefalitidy genetika   růst a vývoj   MeSH
• zvířata MeSH
• Check Tag
• křečci praví MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

SARS-CoV-2 has caused an extensive pandemic of COVID-19 all around the world. Key viral enzymes are suitable molecular targets for the development of new antivirals against SARS-CoV-2 which could represent potential treatments of the corresponding disease. With respect to its essential role in the replication of viral RNA, RNA-dependent RNA polymerase (RdRp) is one of the prime targets. HeE1-2Tyr and related derivatives were originally discovered as inhibitors of the RdRp of flaviviruses. Here, we present that these pyridobenzothiazole derivatives also significantly inhibit SARS-CoV-2 RdRp, as demonstrated using both polymerase- and cell-based antiviral assays.

• MeSH
• adenosinmonofosfát analogy a deriváty   farmakologie   MeSH
• alanin analogy a deriváty   farmakologie   MeSH
• antivirové látky farmakologie   MeSH
• benzothiazoly farmakologie   MeSH
• buněčné linie MeSH
• inhibitory enzymů farmakologie   MeSH
• koronavirová RNA-replikasa antagonisté a inhibitory   MeSH
• lidé MeSH
• mikrobiální testy citlivosti MeSH
• replikace viru účinky léků   MeSH
• SARS-CoV-2 účinky léků   enzymologie   fyziologie   MeSH
• viabilita buněk účinky léků   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a causative agent of the pandemic coronavirus disease 2019 (COVID-19), which has resulted in over two million deaths worldwide to date. Diphyllin and diphyllinosides are known as natural blockers of cellular vacuolar ATPases, and so can act as inhibitors of the pH-dependent fusion of viral envelopes with host cell endosomal membranes. Such pH-dependent fusion is a critical early step during the SARS-CoV-2 replication cycle. Accordingly, the anti-SARS-CoV-2 profiles and cytotoxicities of diphyllin, diphyllinoside cleistanthin B, and two structurally related compounds, helioxanthin 8-1 and helioxanthin 5-4-2, are evaluated here using in vitro cell-based assay systems. Neither helioxanthin exhibits any obvious anti-SARS-CoV-2 effects in vitro. By contrast diphyllin and cleistanthin B do exhibit anti-SARS-CoV-2 effects in Vero cells, with respective 50% effective concentrations (EC50) values of 1.92 and 6.51 μM. Diphyllin displays anti-SARS-CoV-2 effect also in colorectal adenocarcinoma (CaCo-2) cells. Moreover, when diphyllin is added at various times post infection, a significant decrease in viral titer is observed in SARS-CoV-2-infected Vero cells, even at high viral multiplicities of infection. Importantly, neither diphyllin nor cleistanthin B are found cytotoxic to Vero cells in concentrations up to 100 μM. However, the cytotoxic effect of diphyllin is more pronounced in Vero E6 and CaCo-2 cells. Overall, our data demonstrate that diphyllin and diphyllin analogues might be perfected as anti-SARS-CoV-2 agents in future preclinical studies, most especially if nanomedicine approaches may be invoked to optimize functional drug delivery to virus infected cells.

• Publikační typ
• časopisecké články MeSH

Emerging flaviviruses are causative agents of severe and life-threatening diseases, against which no approved therapies are available. Among the nucleoside analogues, which represent a promising group of potentially therapeutic compounds, fluorine-substituted nucleosides are characterized by unique structural and functional properties. Despite having first been synthesized almost 5 decades ago, they still offer new therapeutic opportunities as inhibitors of essential viral or cellular enzymes active in nucleic acid replication/transcription or nucleoside/nucleotide metabolism. Here, we report evaluation of the antiflaviviral activity of 28 nucleoside analogues, each modified with a fluoro substituent at different positions of the ribose ring and/or heterocyclic nucleobase. Our antiviral screening revealed that 3'-deoxy-3'-fluoroadenosine exerted a low-micromolar antiviral effect against tick-borne encephalitis virus (TBEV), Zika virus, and West Nile virus (WNV) (EC50 values from 1.1 ± 0.1 μM to 4.7 ± 1.5 μM), which was manifested in host cell lines of neural and extraneural origin. The compound did not display any measurable cytotoxicity up to concentrations of 25 μM but had an observable cytostatic effect, resulting in suppression of cell proliferation at concentrations of >12.5 μM. Novel approaches based on quantitative phase imaging using holographic microscopy were developed for advanced characterization of antiviral and cytotoxic profiles of 3'-deoxy-3'-fluoroadenosine in vitro In addition to its antiviral activity in cell cultures, 3'-deoxy-3'-fluoroadenosine was active in vivo in mouse models of TBEV and WNV infection. Our results demonstrate that fluoro-modified nucleosides represent a group of bioactive molecules with excellent potential to serve as prospective broad-spectrum antivirals in antiviral research and drug development.

• MeSH
• antivirové látky farmakologie   MeSH
• deoxyadenosiny farmakologie   MeSH
• infekce virem zika * MeSH
• myši MeSH
• prospektivní studie MeSH
• replikace viru MeSH
• virus zika * MeSH
• viry klíšťové encefalitidy * MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH