Alveolitis in severe SARS-CoV-2 pneumonia is driven by self-sustaining circuits between infected alveolar macrophages and T cells

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Abstract

Some patients infected with Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) develop severe pneumonia and the acute respiratory distress syndrome (ARDS) [1]. Distinct clinical features in these patients have led to speculation that the immune response to virus in the SARS-CoV-2-infected alveolus differs from other types of pneumonia [2]. We collected bronchoalveolar lavage fluid samples from 86 patients with SARS-CoV-2-induced respiratory failure and 252 patients with known or suspected pneumonia from other pathogens and subjected them to flow cytometry and bulk transcriptomic profiling. We performed single cell RNA-Seq in 5 bronchoalveolar lavage fluid samples collected from patients with severe COVID-19 within 48 hours of intubation. In the majority of patients with SARS-CoV-2 infection at the onset of mechanical ventilation, the alveolar space is persistently enriched in alveolar macrophages and T cells without neutrophilia. Bulk and single cell transcriptomic profiling suggest SARS-CoV-2 infects alveolar macrophages that respond by recruiting T cells. These T cells release interferon-gamma to induce inflammatory cytokine release from alveolar macrophages and further promote T cell recruitment. Our results suggest SARS-CoV-2 causes a slowly unfolding, spatially-limited alveolitis in which alveolar macrophages harboring SARS-CoV-2 transcripts and T cells form a positive feedback loop that drives progressive alveolar inflammation.

This manuscript is accompanied by an online resource: https://www.nupulmonary.org/covid-19/

One sentence summary

SARS-CoV-2-infected alveolar macrophages form positive feedback loops with T cells in patients with severe COVID-19.

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  1. SciScore for 10.1101/2020.08.05.238188: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIRB: Human subjects: All human subjects research was approved by the Northwestern University Institutional Review Board.
    Consent: All subjects or their surrogates provided informed consent.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    FASTQ files were generated using bcl2fastq (Illumina).
    bcl2fastq
    suggested: (bcl2fastq , RRID:SCR_015058)
    0.6.4 and aligned to the hybrid genome described above using STAR 2.6.1d [47]
    STAR
    suggested: (STAR, RRID:SCR_015899)
    Gene-level assignment was then performed using featureCounts 1.6.4 [48]
    featureCounts
    suggested: (featureCounts, RRID:SCR_012919)
    Data was processed using Scanpy v1.5.1 [52], doublets were detected with scrublet v0.2.1 [53] and removed, ribosomal genes were removed and multisample integration was performed with BBKNN v1.3.12 [54]
    BBKNN
    suggested: None
    Computations were automated with snakemake v5.5.4 [56].
    snakemake
    suggested: (Snakemake, RRID:SCR_003475)
    Deconvolution of bulk RNA-seq alveolar macrophage signatures was performed using AutoGeneS v1.0.3[57] and signatures derived from integrated single cell RNA-Seq object.
    AutoGeneS
    suggested: None
    Visualization: All plotting was performed using ggplot2 version 3.3.1, with the exception of heatmaps, which were generated using pheatmap version 1.0.12.
    ggplot2
    suggested: (ggplot2, RRID:SCR_014601)
    pheatmap
    suggested: (pheatmap, RRID:SCR_016418)
    Figure layouts were generated using patchwork version 1.01 and edited in Adobe Illustrator 2020.
    Adobe Illustrator
    suggested: (Adobe Illustrator, RRID:SCR_010279)

    Results from OddPub: Thank you for sharing your data.


    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

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