Proinflammatory Responses in SARS-CoV-2 and Soluble Spike Glycoprotein S1 Subunit Activated Human Macrophages

  1. Kim Chiok
  2. Kevin Hutchison
  3. Lindsay Grace Miller
  4. Santanu Bose
  5. Tanya A. Miura

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Abstract

Critically ill COVID-19 patients display signs of generalized hyperinflammation. Macrophages trigger inflammation to eliminate pathogens and repair tissue, but this process can also lead to hyperinflammation and resulting exaggerated disease. The role of macrophages in dysregulated inflammation during SARS-CoV-2 infection is poorly understood. We inoculated and treated human macrophage cell line THP-1 with SARS-CoV-2 and purified, glycosylated, soluble SARS-CoV-2 spike protein S1 subunit (S1) to clarify the role of macrophages in pro-inflammatory responses. Soluble S1 upregulated TNF-α and CXCL10 mRNAs, and induced secretion of TNF-α from THP-1 macrophages. While THP-1 macrophages did not support productive SARS-CoV-2 replication or viral entry, virus exposure resulted in upregulation of both TNF-α and CXCL10 genes. Our study shows that extracellular soluble S1 protein is a key viral component inducing pro-inflammatory responses in macrophages, independent of virus replication. Thus, virus- or soluble S1-activated macrophages may become sources of pro-inflammatory mediators contributing to hyperinflammation in COVID-19 patients.

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  1. Version published to 10.3390/v15030754
  2. ScreenIT

    SciScore for 10.1101/2021.06.14.448426: (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.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Experimental Models: Cell Lines
    SentencesResources
    Human monocyte-like cells, THP-1 cell line (ATCC; catalog no. TIB-202), were cultured in RPMI 1640 medium (Gibco 21870076) supplemented with 10% FBS, 10mM HEPES, 1mM sodium pyruvate, 50μM of beta-mercaptoethanol, 100 IU/ml Penicillin and 100 μg/ml Streptomycin.
    THP-1
    suggested: None
    Vero E6 cells were seeded and incubated for 24 hours before virus infection at an MOI of 0.1 following the same procedure as with THP-1 cells.
    Vero E6
    suggested: None
    Cells were treated with 8nM (0.6μg/mL) of recombinant soluble SARS-CoV-2 Spike S1 protein purified from HEK293 cells (SinoBiological; catalog no. 40591-V08H-B) or an equivalent volume of vehicle control for specified times.
    HEK293
    suggested: None
    Software and Algorithms
    SentencesResources
    All statistical tests were performed using GraphPad Prism v6.01 (CA, USA).
    GraphPad Prism
    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.

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

    About SciScore

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  3. Version published to 10.1101/2021.06.14.448426v1 on bioRxiv