Engagement of AKT and ERK signaling pathways facilitates infection of human neuronal cells with West Nile virus.

West Nile virus (WNV) is an important neurotropic virus that accounts for the emergence of human arboviral encephalitis and meningitis. The interaction of WNV with signaling pathways plays a key role in controlling WNV infection. We have investigated the roles of the AKT and ERK pathways in supporting WNV propagation and modulating the inflammatory response following WNV infection. WNV established a productive infection in neuronal cell lines originated from human and mouse. Expression of IL-11 and TNF-α was markedly up-regulated in the infected human neuronal cells, indicating elicitation of inflammation response upon WNV infection. WNV incubation rapidly activated signaling cascades of AKT (AKT-S6-4E-BP1) and ERK (MEK-ERK-p90RSK) pathways. Treatment with AKT inhibitor MK-2206 or MEK inhibitor U0126 abrogated WNV-induced AKT or ERK activation. Strong activation of AKT and ERK signaling pathways could be detectable at 24 h after WNV infection, while such activation was abolished at 48 h post infection. U0126 treatment or knockdown of ERK expression significantly increased WNV RNA levels and viral titers and efficiently decreased IL-11 production induced by WNV, suggesting the involvement of ERK pathway in WNV propagation and IL-11 induction. MK-2206 treatment enhanced WNV RNA replication accompanied with a moderate decrease in IL-11 production. These results demonstrate that engagement of AKT and ERK signaling pathways facilitates viral infection and may be implicated in WNV pathogenesis.

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.

Synthesis of baicalein derivatives and evaluation of their antiviral activity against arboviruses.

Natural plant-derived baicalein which is extracted from Chinese herb Scutellaria baicalensis Georgi belongs to the flavonoid compounds and possesses multiple pharmacological activities. In this study, we designed and synthesized new series of derivatives of baicalein (BE) through catalytic coupling reactions, and screened for their antiviral activity against arboviruses including Chikungunya virus (CHIKV), West Nile virus (WNV) or Zika virus (ZIKV). Our results revealed for the first time that BE and its derivatives had potent anti-CHIKV, anti-WNV and anti-ZIKV effects. And modification of 8 or 4' position could lead to obtain potent antiviral compounds against CHIKV, WNV and ZIKV with lower cytotoxicity. Among the baicalein derivatives, C3 and F3 showed the most potent antiviral activities against CHIKV, WNV and ZIKV, which were 5-10 times more potent than baicalein. Our findings will provide research basis for the development of baicalein derivatives as effective antiviral agents.