SARS-CoV-2 Variants of Concern Infect the Respiratory Tract and Induce Inflammatory Response in Wild-Type Laboratory Mice

  1. Shannon Stone
  2. Hussin Alwan Rothan
  3. Janhavi Prasad Natekar
  4. Pratima Kumari
  5. Shaligram Sharma
  6. Heather Pathak
  7. Komal Arora
  8. Tabassum Tasnim Auroni
  9. Mukesh Kumar

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Abstract

The emergence of new severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants of concern pose a major threat to public health, due to possible enhanced virulence, transmissibility and immune escape. These variants may also adapt to new hosts, in part through mutations in the spike protein. In this study, we evaluated the infectivity and pathogenicity of SARS-CoV-2 variants of concern in wild-type C57BL/6 mice. Six-week-old mice were inoculated intranasally with a representative virus from the original B.1 lineage, or the emerging B.1.1.7 and B.1.351 lineages. We also infected a group of mice with a mouse-adapted SARS-CoV-2 (MA10). Viral load and mRNA levels of multiple cytokines and chemokines were analyzed in the lung tissues on day 3 after infection. Our data show that unlike the B.1 virus, the B.1.1.7 and B.1.351 viruses are capable of infecting C57BL/6 mice and replicating at high concentrations in the lungs. The B.1.351 virus replicated to higher titers in the lungs compared with the B.1.1.7 and MA10 viruses. The levels of cytokines (IL-6, TNF-α, IL-1β) and chemokine (CCL2) were upregulated in response to the B.1.1.7 and B.1.351 infection in the lungs. In addition, robust expression of viral nucleocapsid protein and histopathological changes were detected in the lungs of B.1.351-infected mice. Overall, these data indicate a greater potential for infectivity and adaptation to new hosts by emerging SARS-CoV-2 variants.

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  1. Version published to 10.3390/v14010027
  2. ScreenIT

    SciScore for 10.1101/2021.09.29.462373: (What is this?)

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

    Table 1: Rigor

    EthicsIACUC: The protocol was approved by the GSU Institutional Animal Care and Use Committee (Protocol number A20044).
    Euthanasia Agents: In independent experiments, mice were inoculated with PBS (Mock) or SARS-CoV-2 intranasally, and on day 3 after infection, animals were anesthetized using isoflurane and perfused with cold PBS.
    Sex as a biological variableRoughly equal numbers of male and female mice were used.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Immunoblot analysis: Total cellular protein was extracted from mouse lungs and separated by SDS-PAGE, transferred onto PVDF membranes and incubated overnight with polyclonal antibody against IL-6 [16,17].
    IL-6
    suggested: None
    Membranes were stripped and re-probed with antibody against β-actin.
    β-actin
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Virus titers in tissue homogenates were measured by plaque assay using Vero cells [16,17].
    Vero
    suggested: CLS Cat# 605372/p622_VERO, RRID:CVCL_0059)
    Experimental Models: Organisms/Strains
    SentencesResources
    Animal infection experiments: C57BL/6 mice were purchased from the Jackson Laboratory (Bar Harbor, ME).
    C57BL/6
    suggested: None
    Software and Algorithms
    SentencesResources
    Statistical Analysis: Mann-Whitney test and unpaired student t-test using GraphPad Prism 5.0 were used to calculate p values of the difference between viral titers and immune responses, respectively.
    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 found bar graphs of continuous data. We recommend replacing bar graphs with more informative graphics, as many different datasets can lead to the same bar graph. The actual data may suggest different conclusions from the summary statistics. For more information, please see Weissgerber et al (2015).

    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.

  3. Version published to 10.1101/2021.09.29.462373v1 on bioRxiv