A carbon-carbon linkage is created when a methyl group is implanted on dUMP, thus resulting in the formation of dTMP by thymidylate synthase. The methyl group is deleted by aromatase when androgens are converted to estrogens. The methyl group is rearranged with the help of vitamin B12 in the isomerization of methylmalonyl-CoA to succinyl-CoA. S-adenosylmethionine (SAM) serves as the universal methyl donor involved in the biosynthesis of adrenaline and creatine(phosphate). It also interferes with the 5'-mRNA capping and the degradation of catecholamines (i.e. adrenaline, noradrenaline). Cholesterol could be viewed as a conglomeration of methyl groups. Finally, as part of valine, two methyl functions participate in the origin of one of the most frequent hereditary diseases on earth, sickle cell anemia.
- MeSH
- adrenalin MeSH
- cholesterol * MeSH
- vitamin B 12 * metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy 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
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.
- MeSH
- adenin analogy a deriváty chemie farmakologie MeSH
- alely MeSH
- antibiotická rezistence MeSH
- antivirové látky chemie farmakologie MeSH
- buněčné linie MeSH
- genotyp MeSH
- klíšťová encefalitida farmakoterapie virologie MeSH
- modely nemocí na zvířatech MeSH
- mutace * MeSH
- myši MeSH
- pyrrolidiny chemie farmakologie MeSH
- substituce aminokyselin * MeSH
- virová léková rezistence * MeSH
- virové nestrukturální proteiny genetika MeSH
- viry klíšťové encefalitidy účinky léků fyziologie MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Nucleoside analogs represent the largest class of small molecule-based antivirals, which currently form the backbone of chemotherapy of chronic infections caused by HIV, hepatitis B or C viruses, and herpes viruses. High antiviral potency and favorable pharmacokinetics parameters make some nucleoside analogs suitable also for the treatment of acute infections caused by other medically important RNA and DNA viruses. This review summarizes available information on antiviral research of nucleoside analogs against arthropod-borne members of the genus Flavivirus within the family Flaviviridae, being primarily focused on description of nucleoside inhibitors of flaviviral RNA-dependent RNA polymerase, methyltransferase, and helicase/NTPase. Inhibitors of intracellular nucleoside synthesis and newly discovered nucleoside derivatives with high antiflavivirus potency, whose modes of action are currently not completely understood, have drawn attention. Moreover, this review highlights important challenges and complications in nucleoside analog development and suggests possible strategies to overcome these limitations.
- MeSH
- antivirové látky chemie farmakologie MeSH
- Culicidae virologie MeSH
- Flavivirus účinky léků MeSH
- infekce viry z rodu Flavivirus farmakoterapie virologie MeSH
- mikrobiální testy citlivosti MeSH
- molekulární struktura MeSH
- nukleosidy chemie farmakologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
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.
- MeSH
- antivirové látky terapeutické užití MeSH
- mutace MeSH
- myši MeSH
- nukleosidy * analogy a deriváty terapeutické užití MeSH
- virová léková rezistence MeSH
- viry klíšťové encefalitidy * účinky léků MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
There are currently no approved antiviral therapies against medically important human flaviviruses. The imino-C-nucleoside BCX4430 shows broad-spectrum antiviral activity against a wide range of RNA viruses. Here, we demonstrate that BCX4430 inhibits tick-borne species of the genus Flavivirus; however, the antiviral effect varies against individual species. Micro-molar BCX4430 levels inhibited tick-borne encephalitis virus (TBEV); while, approximately 3-8-fold higher concentrations were needed to inhibit louping ill virus and Kyasanur Forest disease virus. Moreover, the compound strongly inhibited in vitro replication of West Nile virus, a typical mosquito-transmitted flavivirus. Two chemical forms of the compound, i.e. BCX4430 and BCX4430 hydrochloride, were compared and both exerted similar inhibitory profiles in our in vitro antiviral assay systems and no or negligible cytotoxicity in porcine kidney stable and Vero cells. The obtained data indicate that, in addition to mosquito-borne flaviviruses, the compound has strong antiviral activity against members of the TBEV serocomplex.
- MeSH
- adenosin analogy a deriváty farmakologie MeSH
- antivirové látky farmakologie MeSH
- buněčné linie MeSH
- Cercopithecus aethiops MeSH
- Culicidae virologie MeSH
- Flavivirus účinky léků MeSH
- klíšťata virologie MeSH
- klíšťová encefalitida přenos virologie MeSH
- nemoci přenášené klíšťaty MeSH
- prasata MeSH
- purinové nukleosidy antagonisté a inhibitory chemie MeSH
- replikace viru účinky léků MeSH
- Vero buňky MeSH
- viabilita buněk účinky léků MeSH
- virus západního Nilu účinky léků patogenita MeSH
- viry klíšťové encefalitidy účinky léků patogenita MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Tick-borne encephalitis (TBE) represents one of the most serious arboviral neuro-infections in Europe and northern Asia. As no specific antiviral therapy is available at present, there is an urgent need for efficient drugs to treat patients with TBE virus (TBEV) infection. Using two standardised in vitro assay systems, we evaluated a series of 29 nucleoside derivatives for their ability to inhibit TBEV replication in cell lines of neuronal as well as extraneural origin. The series of tested compounds included 2'-C- or 2'-O-methyl substituted nucleosides, 2'-C-fluoro-2'-C-methyl substituted nucleosides, 3'-O-methyl substituted nucleosides, 3'-deoxynucleosides, derivatives with 4'-C-azido substitution, heterobase modified nucleosides and neplanocins. Our data demonstrate a relatively stringent structure-activity relationship for modifications at the 2', 3', and 4' nucleoside positions. Whereas nucleoside derivatives with the methylation at the C2' position or azido modification at the C4'position exerted a strong TBEV inhibition activity (EC50 from 0.3 to 11.1 μM) and low cytotoxicity in vitro, substitutions of the O2' and O3' positions led to a complete loss of anti-TBEV activity (EC50 > 50 μM). Moreover, some structural modifications of the heterobase moiety resulted in a high increase of cytotoxicity in vitro. High antiviral activity and low cytotoxicity of C2' methylated or C4' azido substituted pharmacophores suggest that such compounds might represent promising candidates for further development of potential therapeutic agents in treating TBEV infection.
- MeSH
- antivirové látky chemie farmakologie MeSH
- buněčné linie MeSH
- klíšťová encefalitida farmakoterapie virologie MeSH
- molekulární struktura MeSH
- nukleosidy chemie farmakologie MeSH
- prasata MeSH
- replikace viru účinky léků MeSH
- viry klíšťové encefalitidy účinky léků MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- vztahy mezi strukturou a aktivitou MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
There is growing evidence that Zika virus (ZIKV) can cause devastating infant brain defects and other neurological disorders in humans. However, no specific antiviral therapy is available at present. We tested a series of 2'-C- or 2'-O-methyl-substituted nucleosides, 2'-C-fluoro-2'-C-methyl-substituted nucleosides, 3'-O-methyl-substituted nucleosides, 3'-deoxynucleosides, derivatives with 4'-C-azido substitution, heterobase-modified nucleosides, and neplanocins for their ability to inhibit ZIKV replication in cell culture. Antiviral activity was identified when 2'-C-methylated nucleosides were tested, suggesting that these compounds might represent promising lead candidates for further development of specific antivirals against ZIKV.
- MeSH
- antivirové látky chemie izolace a purifikace farmakologie MeSH
- Cercopithecus aethiops MeSH
- mikrobiální testy citlivosti MeSH
- nukleosidy chemie izolace a purifikace farmakologie MeSH
- replikace viru účinky léků MeSH
- Vero buňky MeSH
- virus zika účinky léků fyziologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Tick-borne encephalitis virus (TBEV) is a leading cause of human neuroinfections in Europe and Northeast Asia. There are no antiviral therapies for treating TBEV infection. A series of nucleoside analogues was tested for the ability to inhibit the replication of TBEV in porcine kidney cells and human neuroblastoma cells. The interactions of three nucleoside analogues with viral polymerase were simulated using advanced computational methods. The nucleoside analogues 7-deaza-2'-C-methyladenosine (7-deaza-2'-CMA), 2'-C-methyladenosine (2'-CMA), and 2'-C-methylcytidine (2'-CMC) inhibited TBEV replication. These compounds showed dose-dependent inhibition of TBEV-induced cytopathic effects, TBEV replication (50% effective concentrations [EC50]of 5.1 ± 0.4 μM for 7-deaza-2'-CMA, 7.1 ± 1.2 μM for 2'-CMA, and 14.2 ± 1.9 μM for 2'-CMC) and viral antigen production. Notably, 2'-CMC was relatively cytotoxic to porcine kidney cells (50% cytotoxic concentration [CC50] of ∼50 μM). The anti-TBEV effect of 2'-CMA in cell culture diminished gradually after day 3 posttreatment. 7-Deaza-2'-CMA showed no detectable cellular toxicity (CC50 > 50 μM), and the antiviral effect in culture was stable for >6 days posttreatment. Computational molecular analyses revealed that compared to the other two compounds, 7-deaza-2'-CMA formed a large cluster near the active site of the TBEV polymerase. High antiviral activity and low cytotoxicity suggest that 7-deaza-2'-CMA is a promising candidate for further investigation as a potential therapeutic agent in treating TBEV infection.
- MeSH
- adenosin analogy a deriváty chemie farmakologie MeSH
- antivirové látky chemie farmakologie MeSH
- buněčné linie MeSH
- cytidin analogy a deriváty chemie farmakologie MeSH
- lidé MeSH
- nukleosidy chemie farmakologie MeSH
- prasata MeSH
- replikace viru účinky léků MeSH
- tubercidin analogy a deriváty chemie farmakologie MeSH
- viry klíšťové encefalitidy účinky léků MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
