The rocaglate CR-31-B (-) inhibits SARS-CoV-2 replication at non-cytotoxic, low nanomolar concentrations in vitro and ex vivo

  1. Christin Müller
  2. Wiebke Obermann
  3. Nadja Karl
  4. Hans-Guido Wendel
  5. Gaspar Taroncher-Oldenburg
  6. Stephan Pleschka
  7. Roland K. Hartmann
  8. Arnold Grünweller
  9. John Ziebuhr

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Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a betacoronavirus in the subgenus Sarbecovirus causes a respiratory disease with varying symptoms referred to as coronavirus disease 2019 (COVID-19) and is responsible for a pandemic that started in early 2020. With no vaccines or effective antiviral treatments available, and infection and fatality numbers continuing to increase globally, the quest for novel therapeutic solutions remains an urgent priority. Rocaglates, a class of plant-derived cyclopenta[ b ]benzofurans, exhibit broad-spectrum antiviral activity against positive- and negative-sense RNA viruses. This compound class inhibits eukaryotic initiation factor 4A (eIF4A)-dependent mRNA translation initiation, resulting in strongly reduced viral RNA translation. The synthetic rocaglate CR-31-B (-) has previously been shown to inhibit the replication of human coronaviruses, such as HCoV-229E and MERS-CoV, as well as Zika-, Lassa-, Crimean Congo hemorrhagic fever virus in primary cells. Here, we assessed the antiviral activity of CR-31-B (-) against SARS-CoV-2 using both in vitro and ex vivo cell culture models. In African green monkey Vero E6 cells, CR-31-B (-) inhibited SARS-CoV-2 replication with an EC 50 of ~1.8 nM. In line with this, viral protein accumulation and replication/transcription complex formation were found to be strongly reduced by this compound. In an ex vivo infection system using human airway epithelial cells, CR-31-B (-) was found to cause a massive reduction of SARS-CoV-2 titers by about 4 logs to nearly non-detectable levels. The data reveal a potent anti-SARS-CoV-2 activity by CR-31-B (-), corroborating previous results obtained for other coronaviruses and supporting the idea that rocaglates may be used in first-line antiviral intervention strategies against novel and emerging RNA virus outbreaks.

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  1. ScreenIT

    SciScore for 10.1101/2020.11.24.389627: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Membranes were incubated with polyclonal rabbit anti-SARS nucleocapsid protein antibody (Rockland) and mouse-anti actin antibody (abcam), respectively, each diluted 1:500 in PBS containing 1 % bovine serum albumin (BSA).
    anti-SARS nucleocapsid protein
    suggested: (LSBio (LifeSpan Cat# LS-C59557-500, RRID:AB_1510641)
    mouse-anti actin
    suggested: None
    After 60 min, membranes were washed with PBS and incubated with appropriate secondary antibodies (IRDye-conjugated anti-mouse or anti-rabbit IgG mAb [Li-COR Biosciences]) diluted 1:10.000 in PBS containing 1% BSA.
    anti-mouse
    suggested: None
    anti-rabbit IgG
    suggested: None
    As secondary antibodies, AlexaFluor 594 goat anti-mouse IgG was used.
    anti-mouse IgG
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    2.1 Cell culture: Vero E6 cells were grown in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 100 U/ml penicillin, and 100 μg/ml streptomycin at 37 °C in an atmosphere containing 5% CO2.
    Vero E6
    suggested: RRID:CVCL_XD71)
    HepG2 cells were cultured in Iscove’s Modified Dulbecco’s Medium (IMDM) supplemented with 10 % fetal calf serum (FCS) at 37 °C and 5 % CO2. 2.2 Reagents: Silvestrol was obtained from the Sarawak Biodiversity Centre (Kuching; North-Borneo, Malaysia; purity > 99%).
    HepG2
    suggested: None
    Experimental Models: Organisms/Strains
    SentencesResources
    CR-31-B (-) and CR-31-B (+) (Wolfe et al., 2014) were dissolved in DMSO at a concentration of 10 mM and stored at −20 °C. 2.3 Dual luciferase reporter assay: The dual luciferase assay was performed as described previously in at least three independent replicates (Müller et al., 2018a, Müller et al., 2020).
    CR-31-B (-
    suggested: None
    Software and Algorithms
    SentencesResources
    EC50 values were then calculated by non-linear regression analysis using GraphPad Prism 6.0 (GraphPad Software).
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2020.11.24.389627 on bioRxiv