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1.
J Leukoc Biol ; 111(6): 1159-1173, 2022 Jun.
Article in English | MEDLINE | ID: covidwho-1639531

ABSTRACT

Neutrophils play significant roles in immune homeostasis and as neutralizers of microbial infections. Recent evidence further suggests heterogeneity of neutrophil developmental and activation states that exert specialized effector functions during inflammatory disease conditions. Neutrophils can play multiple roles during viral infections, secreting inflammatory mediators and cytokines that contribute significantly to host defense and pathogenicity. However, their roles in viral immunity are not well understood. In this review, we present an overview of neutrophil heterogeneity and its impact on the course and severity of viral respiratory infectious diseases. We focus on the evidence demonstrating the crucial roles neutrophils play in the immune response toward respiratory infections, using influenza as a model. We further extend the understanding of neutrophil function with the studies pertaining to COVID-19 disease and its neutrophil-associated pathologies. Finally, we discuss the relevance of these results for future therapeutic options through targeting and regulating neutrophil-specific responses.


Subject(s)
COVID-19 , Virus Diseases , Cytokines , Humans , Inflammation Mediators , Neutrophil Activation , Neutrophils , Virus Diseases/pathology
2.
Cell Death Differ ; 28(11): 3125-3139, 2021 11.
Article in English | MEDLINE | ID: covidwho-1241944

ABSTRACT

SARS-CoV-2 infection poses a major threat to the lungs and multiple other organs, occasionally causing death. Until effective vaccines are developed to curb the pandemic, it is paramount to define the mechanisms and develop protective therapies to prevent organ dysfunction in patients with COVID-19. Individuals that develop severe manifestations have signs of dysregulated innate and adaptive immune responses. Emerging evidence implicates neutrophils and the disbalance between neutrophil extracellular trap (NET) formation and degradation plays a central role in the pathophysiology of inflammation, coagulopathy, organ damage, and immunothrombosis that characterize severe cases of COVID-19. Here, we discuss the evidence supporting a role for NETs in COVID-19 manifestations and present putative mechanisms, by which NETs promote tissue injury and immunothrombosis. We present therapeutic strategies, which have been successful in the treatment of immunο-inflammatory disorders and which target dysregulated NET formation or degradation, as potential approaches that may benefit patients with severe COVID-19.


Subject(s)
COVID-19/pathology , Extracellular Traps/metabolism , Neutrophils/immunology , COVID-19/complications , COVID-19/immunology , Citrullination , Complement Activation , Humans , Neutrophils/metabolism , Platelet Activation , SARS-CoV-2/isolation & purification , Severity of Illness Index , Thrombosis/etiology
3.
Nat Commun ; 11(1): 5243, 2020 10 16.
Article in English | MEDLINE | ID: covidwho-872700

ABSTRACT

SARS-CoV-2 is the novel coronavirus responsible for the current COVID-19 pandemic. Severe complications are observed only in a small proportion of infected patients but the cellular mechanisms underlying this progression are still unknown. Comprehensive flow cytometry of whole blood samples from 54 COVID-19 patients reveals a dramatic increase in the number of immature neutrophils. This increase strongly correlates with disease severity and is associated with elevated IL-6 and IP-10 levels, two key players in the cytokine storm. The most pronounced decrease in cell counts is observed for CD8 T-cells and VD2 γδ T-cells, which both exhibit increased differentiation and activation. ROC analysis reveals that the count ratio of immature neutrophils to VD2 (or CD8) T-cells predicts pneumonia onset (0.9071) as well as hypoxia onset (0.8908) with high sensitivity and specificity. It would thus be a useful prognostic marker for preventive patient management and improved healthcare resource management.


Subject(s)
Betacoronavirus/immunology , CD8-Positive T-Lymphocytes/immunology , Neutrophils/immunology , Receptors, Antigen, T-Cell, gamma-delta/immunology , Biomarkers/blood , COVID-19 , Coronavirus Infections/immunology , Coronavirus Infections/pathology , Cytokine Release Syndrome/immunology , Cytokine Release Syndrome/pathology , Flow Cytometry , Humans , Immunophenotyping/methods , Interleukin-10/blood , Interleukin-6/blood , Lymphocyte Count , Pandemics , Pneumonia, Viral/immunology , Pneumonia, Viral/pathology , SARS-CoV-2 , Severity of Illness Index
4.
Cell ; 182(6): 1401-1418.e18, 2020 09 17.
Article in English | MEDLINE | ID: covidwho-694669

ABSTRACT

Blood myeloid cells are known to be dysregulated in coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2. It is unknown whether the innate myeloid response differs with disease severity and whether markers of innate immunity discriminate high-risk patients. Thus, we performed high-dimensional flow cytometry and single-cell RNA sequencing of COVID-19 patient peripheral blood cells and detected disappearance of non-classical CD14LowCD16High monocytes, accumulation of HLA-DRLow classical monocytes (Human Leukocyte Antigen - DR isotype), and release of massive amounts of calprotectin (S100A8/S100A9) in severe cases. Immature CD10LowCD101-CXCR4+/- neutrophils with an immunosuppressive profile accumulated in the blood and lungs, suggesting emergency myelopoiesis. Finally, we show that calprotectin plasma level and a routine flow cytometry assay detecting decreased frequencies of non-classical monocytes could discriminate patients who develop a severe form of COVID-19, suggesting a predictive value that deserves prospective evaluation.


Subject(s)
Coronavirus Infections , Coronavirus , Pandemics , Pneumonia, Viral , Betacoronavirus , COVID-19 , Flow Cytometry , Humans , Leukocyte L1 Antigen Complex , Monocytes , Myeloid Cells , Prospective Studies , SARS-CoV-2
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