COVID-19 has become a global pandemic that threatens millions of people worldwide. There is an urgent call for developing effective drugs against the virus (SARS-CoV-2) causing this disease. The main protease of SARS-CoV-2, 3C-like protease (3CL ^pro ), is highly conserved across coronaviruses and is essential for the maturation process of viral polyprotein. Scutellariae radix (Huangqin in Chinese), the root of Scutellaria baicalensis has been widely used in traditional Chinese medicine to treat viral infection related symptoms. The extracts of S. baicalensis have exhibited broad spectrum antiviral activities. We studied the anti-SARS-CoV-2 activity of S. baicalensis and its ingredient compounds. We found that the ethanol extract of S. baicalensis inhibits SARS-CoV-2 3CL ^pro activity in vitro and the replication of SARS-CoV-2 in Vero cells with an EC ₅₀ of 0.74 μg/ml. Among the major components of S. baicalensis , baicalein strongly inhibits SARS-CoV-2 3CL ^pro activity with an IC ₅₀ of 0.39 μM. We further identified four baicalein analogue compounds from other herbs that inhibit SARS-CoV-2 3CL ^pro activity at microM concentration. Our study demonstrates that the extract of S. baicalensis has effective anti-SARS-CoV-2 activity and baicalein and analogue compounds are strong SARS-CoV-2 3CL ^pro inhibitors.

SUMMARY: Bats are responsible for the zoonotic transmission of several major viral diseases including the 2003 SARS outbreak and the ongoing COVID-19 pandemic. While bat genomic sequencing studies have revealed characteristic adaptations of the innate immune system, functional genomic studies are urgently needed to provide a foundation for the molecular dissection of the tolerance of viral infections in bats. Here we report the establishment and screening of genome-wide RNAi library and CRISPR library for the model megabat, Pteropus Alecto . We used the complementary RNAi and CRISPR libraries to interrogate Pteropus Alecto cells for infection with two different viruses, mumps virus and Influenza A virus, respectively. Screening results converged on the endocytosis pathway and the protein secretory pathway as required for both viral infections. Additionally, we revealed a general dependence of the C-1-tetrahydrofolate synthase gene, MTHFD1, for viral replication in bat cells as well as in human cells. MTHFD1 inhibitor carolacton potently blocked replication of several RNA viruses including SARS-CoV-2. Our studies provide a resource for systematic inquiry into the genetic underpinnings of bat biology and a potential target for developing broad spectrum antiviral therapy.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a widespread outbreak of highly pathogenic COVID-19. It is therefore important and timely to characterize interactions between the virus and host cell at the molecular level to understand its disease pathogenesis. To gain insights, we performed high-throughput sequencing that generated time-series data simultaneously for bioinformatics analysis of virus genomes and host transcriptomes implicated in SARS-CoV-2 infection. Our analysis results showed that the rapid growth of the virus was accompanied by an early intensive response of host genes. We also systematically compared the molecular footprints of the host cells in response to SARS-CoV-2, SARS-CoV and MERS-CoV. Upon infection, SARS-CoV-2 induced hundreds of up-regulated host genes hallmarked by a significant cytokine production followed by virus-specific host antiviral responses. While the cytokine and antiviral responses triggered by SARS-CoV and MERS-CoV were only observed during the late stage of infection, the host antiviral responses during the SARS-CoV-2 infection were gradually enhanced lagging behind the production of cytokine. The early rapid host responses were potentially attributed to the high efficiency of SARS-CoV-2 entry into host cells, underscored by evidence of a remarkably up-regulated gene expression of TPRMSS2 soon after infection. Taken together, our findings provide novel molecular insights into the mechanisms underlying the infectivity and pathogenicity of SARS-CoV-2.

Background: Novaferon, a novel protein drug approved for the treatment of chronic hepatitis B in China, exhibits potent antiviral activities. We aimed to determine the anti-SARS-CoV-2 effects of Novaferon in vitro, and conducted a randomized, open-label, parallel group study to explore the antiviral effects of Novaferon for COVID-19. Methods: In laboratory, the inhibition of Novaferon on viral replication in cells infected with SARS-CoV-2, and on SARS-CoV-2 entry into healthy cells was determined. Antiviral effects of Novaferon were evaluated in COVID-19 patients with treatment of Novaferon, Novaferon plus Lopinavir/Ritonavir, or Lopinavir/Ritonavir. The primary endpoint was the SARS-CoV-2 clearance rates on day 6 of treatment, and the secondary endpoint was the time to the SARS-CoV-2 clearance in COVID-19 patients Results: Novaferon inhibited the viral replication in infected cells (EC ₅₀ =1.02 ng/ml), and protected healthy cells from SARS-CoV-2 infection (EC ₅₀ =0.1 ng/ml). Results from the 89 enrolled COVID-19 patients showed that both Novaferon and Novaferon plus Lopinavir/Ritonavir groups had significantly higher SARS-CoV-2 clearance rates on day 6 than the Lopinavir/Ritonavir group (50.0% vs.24.1%, p = 0.0400, and 60.0% vs.24.1%, p = 0.0053). Median time to SARS-CoV-2 clearance were 6 days, 6 days, and 9 days for three groups respectively, suggesting a 3-dayreduction of time to SARS-CoV-2 clearance in both Novaferon and Novaferon plus Lopinavir/Ritonavir groups compared with Lopinavir/Ritonavir group. Conclusions: Novaferon exhibited anti-SARS-CoV-2 effects in vitro and in COVID-19 patients. These data justified the further evaluation of Novaferon.