ACE2 is the critical in vivo receptor for SARS-CoV-2 in a novel COVID-19 mouse model with TNF- and IFNγ-driven immunopathology

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Despite tremendous progress in the understanding of COVID-19, mechanistic insight into immunological, disease-driving factors remains limited. We generated maVie16 , a mouse-adapted SARS-CoV-2, by serial passaging of a human isolate. In silico modelling revealed how Spike mutations of maVie16 enhanced interaction with murine ACE2. MaVie16 induced profound pathology in BALB/c and C57BL/6 mice and the resulting mouse COVID-19 ( mCOVID-19 ) replicated critical aspects of human disease, including early lymphopenia, pulmonary immune cell infiltration, pneumonia and specific adaptive immunity. Inhibition of the proinflammatory cytokines IFNγ and TNF substantially reduced immunopathology. Importantly, genetic ACE2-deficiency completely prevented mCOVID-19 development. Finally, inhalation therapy with recombinant ACE2 fully protected mice from mCOVID-19 , revealing a novel and efficient treatment. Thus, we here present maVie16 as a new tool to model COVID-19 for the discovery of new therapies and show that disease severity is determined by cytokine-driven immunopathology and critically dependent on ACE2 in vivo .

Key points

  • The mouse-adapted SARS-CoV-2 strain maVie16 causes fatal disease in BALB/c mice and substantial inflammation, pneumonia and immunity in C57BL/6 mice

  • TNFα/IFNγ blockade ameliorates maVie16 -induced immunopathology

  • MaVie16 infection depends on ACE2 and soluble ACE2 inhalation can prevent disease

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  1. Evaluation Summary:

    To establish a mouse model for the SARS-CoV-2 infection, Gawish and colleagues performed serial passage of a human virus isolate in mice. They show that the mouse-adapted SARS-CoV-2 variant remains dependent on ACE2 for efficient infection and recapitulates some clinical characteristics of COVID-19. In addition, they demonstrate that inhalation of recombinant ACE2 protected mice from mouse COVID-19 suggesting this this model will be useful for the testing of antiviral agents.

    (This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)

  2. Reviewer #1 (Public Review):

    Small animal models are very useful to study the pathogenesis of human diseases and for preclinical studies of potential therapeutic agents. In the present study, Gawish et al. passaged SARS-CoV-2 in mice to generate a mouse-adapted virus strain (maVie16) that replicates efficiently in mice and induces inflammation-driven pulmonary disease. They show that the mouse-adapted virus remains strictly dependent on ACE2 and demonstrate protective effects of inhibition of proinflammatory cytokines and inhaled recombinant ACE2. The authors conclude that they established a novel mouse model for COVID-19 that recapitulates many features of human disease and allows the testing of antiviral agents.

    As mentioned in the manuscript, several other groups have previously reported the development of mouse models for COVID-19. Initially, transgenic mice expressing the human ACE2 receptors were generated. However, these are extremely susceptible to SARS-CoV-2 infection and show a distinct pathology. Others have also generated mouse-adapted SARS-CoV-2 strains which share some features of the present maVie16 strain. Thus, not all aspects of the present study are entirely novel. Strength of the present study are that the authors show that, similarly to COVID-19 in humans, disease severity is to some extent determined by cytokine-driven immunopathology. Using ACE2 knockout animals, the authors also show that SARS-CoV-2 replication remains strictly dependent on ACE2. While this is as expected definitive experimental evidence is nonetheless important. Additional strengths are the evidence the pDCs play are key role in the response to infection and the demonstration that maVie16 strain in duces mCOVID-19 in both BALB/c and C57BL/6 mice. Altogether, the results suggest that this novel mouse-adapted SARS-CoV-2 strain will be useful for studies on viral pathogenesis and testing of antiviral agents.

  3. Reviewer #2 (Public Review):

    A SARS-CoV-2 isolate was passaged in Balb/c mice and it is demonstrated that viral load and cytokine induction increased with passage number while body weight decreased. Further, mutations acquired during passaging are reported and evidence obtained in silico is provided that these mutations increased binding of the viral spike protein to murine ACE2. The virus is shown to cause lethal disease in Balb/c but not C57/BL6 mice, although the latter show body weight loss and transient pneumonia. The impact of infection on blood cell populations and cytokine release as well as adaptive immune responses is reported. In addition, elevated levels of IFNgamma and TNF were measured and antibodies targeting these factors are shown to protect from body weight loss. Finally, evidence is provided that ACE2 is required for viral spread in the lung and induction of disease and these processes were blocked by soluble ACE2. The findings are solid and the model will be helpful to the field.

  4. SciScore for 10.1101/2021.08.09.455606: (What is this?)

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

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    No key resources detected.

    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.

    Results from scite Reference Check: We found no unreliable references.

    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.