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

Elongation of N6-benzyladenosine scaffold via Pd-catalyzed C-C bond formation leads to derivatives with antiflaviviral activity

Decoration of nucleoside analogues with lipophilic groups often leads to compounds with improved antiviral activity. For example, N6-benzyladenosine derivatives containing elongated lipophilic substituents in the benzyl core efficiently inhibit reproduction of tick-borne encephalitis virus (TBEV), while N6-benzyladenosine itself potently inhibits reproduction of human enterovirus A71 (EV-A71). We have extended a series of N6-benzyladenosine analogues using effective synthetic methods of CC bond formation based on Pd-catalyzed cross-coupling reactions (Sonogashira and Suzuki) in order to study the influence of bulky lipophilic substituents in the N6 position of adenosine on the antiviral activity against flaviviruses, such as TBEV, yellow fever virus (YFV) and West Nile virus (WNV), as well as a panel of enteroviruses including EV-A71, Echovirus 30 (E30), and poliovirus type 2 (PV2). Reproduction of tested flaviviruses appeared to be inhibited by the micromolar concentrations of the compounds, while cytotoxicity in most cases was beyond the detection limit. Time-of-addition studies demonstrated that the hit compounds inhibited the stage of viral RNA synthesis, but not the stages of the viral entry or protein translation. As a result, several new promising antiflaviviral leads have been identified. On the other hand, none of the synthesized compounds inhibited enterovirus reproduction, indicating a possibility of involvement of flavivirus-specific pathways in their mechanism of action.

Inhibition of tick-borne encephalitis virus in cell cultures by ribavirin

Tick-borne encephalitis virus (TBEV) belonging to arboviruses is a major member of zoonotic pathogens. TBEV infection causes severe human encephalitis without specific antiviral drugs. Due to its use of antiviral drug against a wide range of viruses, we investigated antiviral effect of ribavirin against TBEV in susceptible human cell lines A549 and SH-SY5Y. Ribavirin displayed minor cytotoxicity on multiple cell lines. Ribavirin obviously impaired TBEV replication and protected the infected cells from cytopathic effect. Importantly, ribavirin markedly inhibited TBEV propagation, as evidenced by impairment of TBEV production and viral RNA replication. Treatment with ribavirin (co-treatment and post-treatment) led to a dose-dependent reduction in TBEV titers as well as the viral RNA levels. Antiviral protein myxovirus resistance A mRNA expression was significantly up-regulated and signal transducer and activator of transcription 3 was activated in TBEV-infected A549 cells upon the ribavirin treatment. Induction of inflammatory cytokine tumor necrosis factor alpha by TBEV was decreased in A549 cells with the treatment of ribavirin, whereas interleukin 1 beta release appeared to be unaffected. These results suggest that ribavirin might represent a promising safe and effective antiviral drug against TBEV.

History of Arbovirus Research in the Czech Republic

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.

Anti-Tick-Borne Encephalitis Virus Activity of Novel Uridine Glycoconjugates Containing Amide or/and 1,2,3-Triazole Moiety in the Linker Structure

Tick-borne encephalitis virus (TBEV) transmitted by ticks is a pathogen of great medical importance. As still no effective antiviral treatment is available, in the present study, a series of uridine glycoconjugates containing amide or/and 1,2,3-triazole moiety in the linker structure was synthesized and evaluated for the antiviral activity against two strains of TBEV: a highly virulent Hypr strain and less virulent Neudoerfl strain, using standardized previously in vitro assays. Our data have shown that four compounds from the series (18–21) possess strong activity against both TBEV strains. The half maximal inhibitory concentration (IC₅₀) values of compounds 18–21 were between 15.1 and 3.7 μM depending on the virus strain, which along with low cytotoxicity resulted in high values of the selectivity index (SI). The obtained results suggest that these compounds may be promising candidates for further development of new therapies against flaviviruses.

Simplistic perylene-related compounds as inhibitors of tick-borne encephalitis virus reproduction

Rigid amphipathic fusion inhibitors are potent broad-spectrum antivirals based on the perylene scaffold, usually decorated with a hydrophilic group linked via ethynyl or triazole. We have sequentially simplified these structures by removing sugar moiety, then converting uridine to aniline, then moving to perylenylthiophenecarboxylic acids and to perylenylcarboxylic acid. All these polyaromatic compounds, as well as antibiotic heliomycin, still showed pronounced activity against tick-borne encephalitis virus (TBEV) with limited toxicity in porcine embryo kidney (PEK) cell line. 5-(Perylen-3-yl)-2-thiophenecarboxylic acid (5a) showed the highest antiviral activity with 50% effective concentration of approx. 1.6 nM.