The emergence of significant arboviruses and their spillover transmission to humans represent a major threat to global public health. No approved drugs are available for the treatment of significant arboviruses in circulation today. The repurposing of clinically approved drugs is one of the most rapid and promising strategies in the identification of effective treatments for diseases caused by arboviruses. Here, we screened small-molecule compounds with anti-tick-borne encephalitis virus, West Nile virus, yellow fever virus and chikungunya virus activity from 2580 FDA-approved drugs. In total, 60 compounds showed antiviral efficacy against all four of the arboviruses in Huh7 cells. Among these compounds, ixazomib and ixazomib citrate (inhibitors of 20S proteasome β5) exerted antiviral effects at a low-micromolar concentration. The time-of-drug-addition assay suggested that ixazomib and ixazomib citrate disturbed multiple processes in viruses’ life cycles. Furthermore, ixazomib and ixazomib citrate potently inhibited chikungunya virus replication and relieved virus-induced footpad swelling in a mouse model. These results offer critical information which supports the role of ixazomib as a broad-spectrum agent against arboviruses.

Diseases transmitted by arthropod-borne viruses such as West Nile virus (WNV) and chikungunya virus (CHIKV) pose threat to global public health. Unfortunately, to date, there is no available approved drug for severe symptoms caused by both viruses. It has been reported that reverse transcriptase inhibitors can effectively inhibit RNA polymerase activity of RNA viruses. We screened the anti-WNV activity of the FDA-approved reverse transcriptase inhibitor library and found that 4 out of 27 compounds showed significant antiviral activity. Among the candidates, etravirine markedly inhibited WNV infection in both Huh 7 and SH-SY5Y cells. Further assays revealed that etravirine inhibited the infection of multiple arboviruses, including yellow fever virus (YFV), tick-borne encephalitis virus (TBEV), and CHIKV. A deeper study at the phase of action showed that the drug works primarily during the viral replication process. This was supported by the strong interaction potential between etravirine and the RNA-dependent RNA polymerase (RdRp) of WNV and alphaviruses, as evaluated using molecular docking. In vivo, etravirine significantly rescued mice from WNV infection-induced weight loss, severe neurological symptoms, and death, as well as reduced the viral load and inflammatory cytokines in target tissues. Etravirine showed antiviral effects in both arthrophlogosis and lethal mouse models of CHIKV infection. This study revealed that etravirine is an effective anti-WNV and CHIKV arbovirus agent both in vitro and in vivo due to the inhibition of viral replication, providing promising candidates for clinical application.

Chikungunya virus (CHIKV) is a globally public health threat. There are currently no medications available to treat CHIKV infection. High-throughput screening of 419 kinase inhibitors was performed based on the cytopathic effect method, and six kinase inhibitors with reduced cytopathic effects, including tyrphostin AG879 (AG879), tyrphostin 9 (A9), sorafenib, sorafenib tosylate, regorafenib, and TAK-632, were identified. The anti-CHIKV activities of two receptor tyrosine kinase inhibitors, AG879 and A9, that have not been previously reported, were selected for further evaluation. The results indicated that 50% cytotoxic concentration (CC₅₀) of AG879 and A9 in Vero cells were greater than 30 μM and 6.50 μM, respectively and 50% effective concentration (EC₅₀) were 0.84 μM and 0.36 μM, respectively. The time-of-addition and time-of-removal assays illustrated that both AG879 and A9 function in the middle stage of CHIKV life cycle. Further, AG879 and A9 do not affect viral attachment; however, they inhibit viral RNA replication, and exhibit antiviral activity against CHIKV Eastern/Central/South African and Asian strains, Ross River virus and Sindbis virus in vitro.

Chikungunya virus (CHIKV) is a reemerging arbovirus causing disease on a global scale, and the potential for its epidemics remains high. CHIKV has caused millions of cases and heavy economic burdens around the world, while there are no available approved antiviral therapies to date. In this study, nifuroxazide, an FDA-approved antibiotic for acute diarrhea or colitis, was found to significantly inhibit a variety of arboviruses, although its antiviral activity varied among different target cell types. Nifuroxazide exhibited relatively high inhibitory efficiency in yellow fever virus (YFV) infection of the hepatoma cell line Huh7, tick-borne encephalitis virus (TBEV) and west nile virus (WNV) infection of the vascular endothelial cell line HUVEC, and CHIKV infection of both Huh7 cells and HUVECs, while it barely affected the viral invasion of neurons. Further systematic studies on the action stage of nifuroxazide showed that nifuroxazide mainly inhibited in the viral replication stage. In vivo, nifuroxazide significantly reduced the viral load in muscles and protected mice from CHIKV-induced footpad swelling, an inflammation injury within the arthrosis of infected mice. These results suggest that nifuroxazide has a potential clinical application as an antiviral drug, such as in the treatment of CHIKV infection.

Unlike other ubiquitin-like family members, UBL5 is structurally and functionally atypical, and a novel role in various biological processes and diseases has been discovered. UBL5 can stabilize the structure of the spliceosome, can promote post-transcriptional processing, and has been implicated in both DNA damage repair and protein unfolding reactions, as well as cellular mechanisms that are frequently exploited by viruses for their own proliferation during viral infections. In addition, UBL5 can inhibit viral infection by binding to the non-structural protein 3 of rice stripe virus and mediating its degradation. Therefore, UBL5 is an important link between viral infections and immunity, and its study will be beneficial for the prevention and treatment of viral infections in the future. However, a review of the current findings on the role of UBL5 in viral infection has not been undertaken. Therefore, in this review, we summarize the recent progress in understanding the functions of UBL5 and discuss its putative role in viral infections.

RNA viruses, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), flaviviruses, and alphaviruses, represent a major source of emerging human infectious diseases. They pose a persistent threat to public health; however, few therapeutic options are available for severe infections. Through a natural product screening campaign, we identified ansatrienin B as a broad-spectrum inhibitor of multiple RNA viruses, including SARS-CoV-2, flaviviruses (e.g., YFV, WNV, DENV), and alphaviruses (e.g., CHIKV). Time-of-drug-addition assays indicated that ansatrienin B acts at both the early (entry) and intermediate (replication) stages of the viral life cycle. Surface plasmon resonance (SPR) and molecular docking studies validated a direct interaction between ansatrienin B and the RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 and WNV. Combined RNA pull-down and RdRp enzymatic activity assays (in gel, solution, and cellular forms) further demonstrated that ansatrienin B disrupts both the binding of RdRp to viral RNA and its enzymatic activity. In vivo, ansatrienin B showed significant efficacy in mouse models infected with SARS-CoV-2 or WNV infection. To facilitate screening and elucidate the structure–activity relationship (SAR), we generated a focused ansatrienin library via a mutasynthetic approach. Supplementation of four 3,5-AHBA analogs into a ΔmycB1-B4 mutant strain of Streptomyces flaveolus yielded 30 novel ansatrienin derivatives. Evaluation of anti-SARS-CoV-2 activity identified four analogs with enhanced potency, enabling the establishment of a preliminary SAR. Collectively, these findings establish ansatrienin B as a novel inhibitor targeting RdRp and provide a foundation for the development alternative broad-spectrum antiviral agents.