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LitCovid-PD-FMA-UBERON

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LitCovid-PD-MONDO

LitCovid-PD-CLO

LitCovid-PD-CHEBI

LitCovid-PD-HP

{"project":"LitCovid-PD-HP","denotations":[{"id":"T10","span":{"begin":422,"end":442},"obj":"Phenotype"},{"id":"T11","span":{"begin":460,"end":485},"obj":"Phenotype"},{"id":"T12","span":{"begin":496,"end":507},"obj":"Phenotype"},{"id":"T13","span":{"begin":2753,"end":2769},"obj":"Phenotype"},{"id":"T14","span":{"begin":3521,"end":3530},"obj":"Phenotype"},{"id":"T15","span":{"begin":3872,"end":3889},"obj":"Phenotype"}],"attributes":[{"id":"A10","pred":"hp_id","subj":"T10","obj":"http://purl.obolibrary.org/obo/HP_0002098"},{"id":"A11","pred":"hp_id","subj":"T11","obj":"http://purl.obolibrary.org/obo/HP_0033041"},{"id":"A12","pred":"hp_id","subj":"T12","obj":"http://purl.obolibrary.org/obo/HP_0001888"},{"id":"A13","pred":"hp_id","subj":"T13","obj":"http://purl.obolibrary.org/obo/HP_0041092"},{"id":"A14","pred":"hp_id","subj":"T14","obj":"http://purl.obolibrary.org/obo/HP_0002090"},{"id":"A15","pred":"hp_id","subj":"T15","obj":"http://www.orpha.net/ORDO/Orphanet_178320"}],"text":"Myeloid Cells\nMucosal immune responses to infectious agents are orchestrated and regulated by myeloid cells with specialized functions, which include conventional dendritic cells (cDCs), monocyte-derived DCs (moDCs), plasmacytoid DCs (pDCs), and macrophages (Guilliams et al., 2013). A growing body of evidence points to dysregulated myeloid responses that potentially drive the COVID-19 hallmark syndromes, such as acute respiratory distress syndrome (ARDS), cytokine release syndrome (CRS) and lymphopenia (Mehta et al., 2020).\n\nMyeloid Characterization in COVID-19\nFlow cytometric analyses of peripheral blood mononuclear cells (PBMCs) from symptomatic COVID-19 patients have shown a significant influx of granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing, activated CD4+ T cells and CD14+HLA-DRlo inflammatory monocytes (IMs) (Giamarellos-Bourboulis et al., 2020, Zhang et al., 2020c, Zhou et al., 2020b). This matches single-cell transcriptomic (scRNA-seq) data demonstrating CD14+IL-1β+ monocytic expansion (Guo et al., 2020, Wen et al., 2020), interferon-mitogen-activated protein kinase (MAPK)-driven adaptive immune responses (Huang et al., 2020c), and IL-1β-associated inflammasome signatures (Ong et al., 2020) in peripheral blood of COVID-19 patients, although systemic levels of IL-1β detected are conspicuously low (Del Valle et al., 2020). Importantly, these immune signatures track with progression of clinical disease. scRNA-seq studies performed on pulmonary tissues of patients with severe COVID-19 disease have revealed an expansion of IMs and Ficolin-1+ monocyte-derived macrophages at the expense of tissue-resident reparative alveolar macrophages (AMs) (Liao et al., 2020). The aforementioned study also observed signatures of IFN signaling and monocyte recruitment that likely contribute to the rapid decline in alveolar patency and promote ARDS. Although most of the clinical focus has been on pulmonary damage and mononuclear phagocyte (MNP) dysfunction therein, it is increasingly clear that COVID-19 likely presents systemic challenges in other organ sites, such as the ileum and kidneys. Understanding the role of non-pulmonary myeloid cells in tissue-specific pathology associated with COVID-19 will be important.\n\nPrior Knowledge from SARS-CoV-1, MERS-CoV, and Murine Coronaviruses\nWhile data on COVID-19 patients continues to rapidly emerge, studies of myeloid cell dysfunction in SARS-CoV-1 and MERS-CoV can provide an important roadmap to understanding COVID-19 pathogenesis (Figure 2 ). SARS-CoV-1 infection in mouse models results in an aberrant AM phenotype that limits DC trafficking and T cell activation (Zhao et al., 2009). Additionally, YM1+ FIZZ1+ alternative macrophages can increase airway hypersensitivity, thus exacerbating SARS-associated fibrosis (Page et al., 2012). Further, as described above, murine SARS-CoV-1 studies have demonstrated that delayed IFN-I signaling and inflammatory monocytes-macrophages promote lung cytokine and chemokine levels, vascular leakage, and impaired antigen-specific T cell responses, culminating in lethal disease (Channappanavar et al., 2016). The role played by prominent IFN-producing pDCs in SARS-CoV-2 control or pathogenesis warrants investigation, as they have been shown to be critical in murine CoV (MHV) control (Cervantes-Barragan et al., 2007). Longitudinal studies in SARS-CoV-2 models are awaited, but initial phenotypic studies in humanized hACE2 mice have shown the characteristic alveolar interstitial pneumonia, with infiltration of lymphocytes and monocytes and accumulation of macrophages in the alveolar lumen (Bao et al., 2020a), which recapitulates patient findings (Xu et al., 2020c). Lastly, non-human primate (NHP) studies and patient data on SARS-CoV-1 have also shown that virus spike-specific immunoglobulin G (IgG) responses can exacerbate acute lung injury due to repolarization of alveolar macrophages into proinflammatory phenotypes and enhanced recruitment of inflammatory monocyte via CCL2 and IL-8 (Clay et al., 2012, Liu et al., 2019). However, the extent to which the antibody response contributes to disease pathophysiology remains to be confirmed.\nFigure 2 SARS-CoV-2 Infection Results in Myeloid Cell Activation and Changes NK Cell Function\nBased on data from preliminary COVID-19 studies and earlier studies in related coronaviruses.\nIL-6, IL-1β, and IFN-I/III from infected pulmonary epithelia can induce inflammatory programs in resident (alternate) macrophages while recruiting inflammatory monocytes, as well as granulocytes and lymphocytes from circulation. Sustained IL-6 and TNF-ɑ by incoming monocytes can drive several hyperinflammation cascades. Inflammatory monocyte-derived macrophages can amplify dysfunctional responses in various ways (listed in top-left corner). The systemic CRS- and sHLH-like inflammatory response can induce neutrophilic NETosis and microthrombosis, aggravating COVID-19 severity. Other myeloid cells, such as pDCs, are purported to have an IFN-dependent role in viral control. Monocyte-derived CXCL9/10/11 might recruit NK cells from blood. Preliminary data suggest that the antiviral function of these NK cells might be regulated through crosstalk with SARS-infected cells and inflammatory monocytes.\nDashed lines indicate pathways to be confirmed. Arg1, arginase 1; iNOS, inducible-nitric oxide synthase; Inflamm., inflammatory; Mono., monocytes; Macs, macrophages; Eosino, eosinophils; Neutro, neutrophils; NETosis, neutrophil extracellular trap cell death; SHLH, secondary hemophagocytic lymphohistiocytosis.\n\nMyeloid Cells Contribution to Pathogenic Inflammation\nThe initial mode of viral pathogen-associated signal (PAMP) recognition by innate cells has a major impact on downstream myeloid signaling and cytokine secretion (de Marcken et al., 2019). While macrophages are somewhat susceptible to MERS-CoV and SARS-CoV-1 infection (Perlman and Dandekar, 2005, Zhou et al., 2014), data do not suggest that they are infected by SARS-CoV-2, although one study reported ACE2 and SARS-CoV-2 nucleocapsid protein is expressed in lymph nodes and spleen-associated CD169+ macrophages of COVID-19 patients producing IL-6 (Chen et al., 2020h). Significantly elevated systemic levels of proinflammatory cytokine IL-6 have been reported in several COVID-19 patient cohorts and shown to correlate with disease severity (Mehta et al., 2020). Increased IL-6 can also be associated with higher levels of IL-2, IL-7, IFN-ɣ, and GM-CSF, as seen in secondary hemophagocytic lymphohistiocytosis. In response to viral infections, MNPs drive IL and IFN-I and IFN-III production resulting in inflammasome activation, induction of pathogenic Th1 and Th17 cell responses, recruitment of effector immune cells, and CRS pathology (Prokunina-Olsson et al., 2020, Tanaka et al., 2016). Independently, in vitro studies have demonstrated SARS-CoV-1 infection can induce intracellular stress pathways, resulting in NLRP3-dependent inflammasome activation and macrophage pyroptosis (Chen et al., 2019, Shi et al., 2019). Functional studies are required to implicate these myeloid inflammasome pathways in COVID-19 lung pathology and to assess other immunogenic pathways such as RIPK1/3-dependent necroptosis (Nailwal and Chan, 2019). In conclusion, the strength and duration of myeloid ISG)signaling potentially dictate COVID-19 disease severity, but rigorous studies are warranted to confirm this.\nLastly, more work is needed to ascertain the mechanistic role played by lung-resident and recruited granulocytes in SARS-CoV-2 control and pathogenesis (Camp and Jonsson, 2017, Flores-Torres et al., 2019). In contrast to their early protective role, neutrophil NETosis and macrophage crosstalk can drive later-stage inflammatory cascades (Barnes et al., 2020), underscoring the overall pathogenic nature of damage-sensing host responses (Figure 2).\nCollectively, the current knowledge of CoVs and SARS-CoV-2 infection, in particular, points to an inadvertent collusion involving myeloid cells in COVID-19 pathogenesis, despite their critical role in early sensing and antiviral responses."}

LitCovid-PD-GO-BP

LitCovid-PubTator

LitCovid-sentences

PMC:7200337 / 13173-21314 JSONTXT

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PMC:7200337 / 13173-21314 JSON TXT