Bardoxolone methyl inhibits the infection of rabies virus via Nrf2 pathway activation in vitro.

BACKGROUND: Rabies is a widespread, fatal, infectious disease. Several antivirals against rabies virus (RABV) infection have been reported, but no approved, RABV-specific antiviral drugs that inhibit RABV infection in the clinic after symptom onset are available. Therefore, more effective drugs to reduce rabies fatalities are urgently needed. Bardoxolone methyl (CDDO-Me), an FDA-approved compound that has long been known as an antioxidant inflammatory modulator and one of the most potent nuclear factor erythroid-derived 2-like 2 (Nrf2) activators, protects myelin, axons, and CNS neurons by Nrf2 activation. Therefore, we investigated the potency of its anti-RABV activity in vitro. METHODS: The mouse neuroblastoma cell line Neuro2a (N2a) and three RABV strains of different virulence were used; the cytotoxicity and anti-RABV activity of CDDO-Me in N2a cells were evaluated by CCK-8 assay and direct fluorescent antibody (DFA) assay. Pathway activation in N2a cells infected with the RABV strains SC16, CVS-11 or CTN upon CDDO-Me treatment was evaluated by western blotting (WB) and DFA assay. RESULTS: CDDO-Me significantly inhibited infection of the three RABV strains of differing virulence (SC16, CVS-11 and CTN) in N2a cells. We also examined whether CDDO-Me activates the Nrf2-associated pathway upon infection with RABV strains of differing virulence. Nrf2, phosphorylated sequestosome (SQSTM1), SQSTM1, hemoglobin oxygenase (HO-1) and NAD(P)H dehydrogenase quinone 1 (NQO1) expression in N2a cells increased to varying degrees with CDDO-Me treatment, accompanied by Kelch-like ECH-associated protein 1 (Keap1) dissociation, upon infection with SC16, CVS-11 or CTN. The activation of SQSTM1 phosphorylation was significantly associated with the degradation of Keap-1 in CDDO-Me-treated N2a cells upon RABV infection. Furthermore, N2a cells pretreated with the Nrf2-specific inhibitor ATRA showed a significant decrease in HO-1 and NQO1 expression and a decrease in the anti-RABV efficacy of CDDO-Me. These inhibitory effects were observed upon infection with three RABV strains of differing virulence. CONCLUSION: CDDO-Me inhibited RABV infection via Nrf2 activation, promoting a cytoprotective defense response in N2a cells. Our study provides a therapeutic strategy for RABV inhibition and neuroprotection during viral infection.

BCX4430 inhibits the replication of rabies virus by suppressing mTOR-dependent autophagy invitro.

Rabies is a fatal neurological infectious disease caused by rabies virus (RABV). However, no effective anti-RABV drugs for treatment during the symptomatic phase are available. The novel adenosine nucleoside analog galidesivir (BCX4430) has broad-spectrum activity against a wide variety of highly pathogenic RNA viruses. In this study, we observed no apparent cytotoxicity of BCX4430 at the highest concentration of 250 µΜ, and which was displayed stronger antiviral activity against different virulent RABV in N2a or BHK-21 cells until 72 hpi. Meanwhile, BCX4430 showed greater anti-RABV activity than T-705 and anti-RABV activity similar to that of ribavirin in N2a cells. Furthermore, BCX4430 dose- and time-dependently inhibited RABV replication via mTOR-dependent autophagy inhibition in N2a cells with increased phospho-mTOR and phospho-SQSTM1 and decreased LC3-II levels. Taken together, these findings suggest that BCX4430 has potent anti-RABV activity in vitro and might provide a basis for the development of novel drug therapies against RABV.