key: cord-0945722-1guhgojy
authors: Maxwell, Anthony J.; Ding, Jiahui; You, Yuan; Dong, Zhong; Chehade, Hussein; Alvero, Ayesha; Mor, Yechiel; Draghici, Sorin; Mor, Gil
title: Identification of key signaling pathways induced by SARS‐CoV2 that underlie thrombosis and vascular injury in COVID‐19 patients
date: 2020-11-26
journal: J Leukoc Biol
DOI: 10.1002/jlb.4covr0920-552rr
sha: 547686ba84e4ce8f2214ad23352c930af0eeda4f
doc_id: 945722
cord_uid: 1guhgojy

The SARS‐CoV‐2 pandemic has led to hundreds of thousands of deaths and billions of dollars in economic damage. The immune response elicited from this virus is poorly understood. An alarming number of cases have arisen where COVID‐19 patients develop complications on top of the symptoms already associated with SARS, such as thrombosis, injuries of vascular system, kidney, and liver, as well as Kawasaki disease. In this review, we have used a bioinformatics approach to elucidate the immune response triggered by SARS‐CoV‐2 infection in primary human lung epithelial and transformed human lung alveolar. Additionally, we have examined the potential mechanism behind several complications that have been associated with COVID‐19 and determined that a specific cytokine storm is leading to excessive neutrophil recruitment. These neutrophils are directly leading to thrombosis, organ damage, and complement activation via neutrophil extracellular trap release.

drugs available, and continuously increasing case numbers showing additional complications, it is of utmost importance to understand the immune response to SARS-CoV-19 and the mechanism underlying the cause(s) of these secondary complications.

The objective of this study was to review and evaluate the potential biologic pathways by which SARS-CoV-2 infection could trigger thrombosis and then investigate therapeutic approaches that could prevent it. Because SARS-CoV-2 infects type I and II alveolar epithelial cells, which are among the first cell type to produce proinflammatory cytokines and recruit immune cells in order to mount an adequate antiviral response, we took a bioinformatics approach and used RNAseq data from human lung and transformed lung alveolar cells infected with SARS-CoV-2. We examined the specific biologic pathways and genes involved in the immune response elicited from SARS-CoV-2-infected lung alveolar cells, which could explain the prothrombotic events that have being reported in COVID-19 patients.

We discuss the involvement of this specific cytokine profile on the formation of neutrophil extracellular traps (NETs) and its association with the prothrombotic process and organ damage described in SARS-CoV-2-infected patients.

COVID-19 patients often develop a cytokine release syndrome (CRS) that is responsible for the respiratory distress syndrome and the multi-organs injuries as result of secondary haemophagocyticlymphohoistocytosis. The CRS observed in COVID-19 patients resembles the immune dysregulation caused by other highly pathogenic respiratory viruses such as SARS-CoV and MERS-CoV. 11 In order to understand the potential triggers of CRS, we evaluated the general response of lung epithelial cells as a result of SAR-CoV-2 infection. We analyzed RNAseq data from primary human lung epithelial that were mock treated or infected with SARS-CoV-2 (USA-WA1/2020) at an multiplicity of infection (MOI) of 2. This data set is available in GEO as the GSE147507 data set. Using iPathwayGuide (www.advaitabio.com) we determined what cytokines and chemokines were differentially expressed in these groups. All statistical applications were performed by the iPathwayGuide software, which includes GO analysis, network analysis, pathway analysis, and differentially expressed genes. [12] [13] [14] [15] In the cytokine-cytokine receptor and chemokine signaling pathways, we found several proinflammatory cytokines/chemokines that were differentially expressed (Fig. 1A ,B and Supporting Information CSF3 is mainly an inducer of neutrophil colony formation and it is associated with the regulation of neutrophil proliferation and maturation. [16] [17] [18] [19] CSF2 is involved in the regulation of multiple immune cell types, especially macrophages but, in addition to stimulation of macrophage colonization, CSF2 also promotes the generation of neutrophils. [18] [19] [20] [21] Furthermore, CSF2 plays a role in the generation of immature dendritic cells. 22 All of these processes of differentiation are mediated through the direct action of CSF2 and CSF3 on the bone marrow where it promotes the generation and release of mature colonies of myeloid cells. 20 Additionally, both colony-stimulating chemokines are capable of inducing the expression of proinflammatory cytokines, which in turn enhance the inflammatory response. 23 CSF3 expression has been linked to pulmonary neutrophilia that is seen in acute respiratory distress syndrome. 23 Furthermore, both of these factors are able to act locally on these cell subtypes to induce various aspects involved in an immune response, such as enhanced immune cell survival and increased production of inflammatory cytokines. 24, 25 The upregulation of CSF2 and CSF3 found in this analysis suggests that these SARS-CoV-2-infected epithelial cells are sending signals to the bone marrow to produce more macrophages, eosinophils, and neutrophils to eliminate the threat. 23 A second set of related cytokines that were up-regulated during SARS-CoV-2 infection were CXCL1, CXCL2, CXCL3, CXCL6, CXCL5, and CXCL8 (or IL-8) ( Fig. 1 and Supporting Information Fig. S1 ). All six of these cytokines are part of the CXC chemokine family. This specific set of CXC chemokines bind to the CXCR2 receptor. 26, 27 One of the primary roles of this set of cytokines is to act as a chemoattractant for neutrophils as well as to promote adherence to endothelial cells. 28 -34 CXCL1 (logFC = 1.419 and R = 1.000e-6) and CXCL2 (logFC = 1.393 and R = 1.000e-6) have been shown to be critical for neutrophil recruitment to the lungs. 35,36 CXC chemokines are produced by different cell types in response to proinflammatory signals such as IL-1 (logFC = 1.065 and R = 1.000e-6), IL-1 (logFC = 1.074 and R = 1.000e-6), and TNF-(logFC = 1.809 and R = 2.865e-4), all of which were up-regulated in SARS-CoV-2-infected epithelial cells. 37 In addition to their roles in neutrophil recruitment to sites of infection, this set of CXC chemokines are also involved in the recruitment of various other cell types. CXCL8 (logFC = 2.335 and R = 1.000e-6) is a chemoattractant for basophils, eosinophils, and peripheral blood T lymphocytes. 38-40 More importantly, CXCL8 is also the primary neutrophil chemoattractant in the lungs. 41 CXCL1-3 are closely related and are important for the recruitment and activation of basophils, eosinophils, monocytes, and lymphocytes, in addition to neutrophil recruitment. 42 CXCL5 (logFC = 3.487 and R = 1.000e-6) has been found to be involved in different types of inflammatory diseases and has been shown to be expressed by alveolar type II epithelial cells in response to LPS. [43] [44] [45] [46] Interestingly, we observed that CXCL14 (logFC = −1.446 and R = 7.498e-6) was down-regulated in these data sets ( Fig. 1 and Supporting Information Fig. S1 ). CXCL14 is a potent inhibitor of epithelial cell chemotaxis and function as a negative feedback to decrease immune cells recruitment. 47 When we analyzed the potential cell type targeted by these chemokines, we observed that the up-regulated CXCL1, CXCL2, CXLC3, CXCL5, and CXCL8 have a predominant function related to the recruitment of neutrophils to the lungs. Additionally, the downregulation of CXCL14 fosters the capacity of epithelial cells to release chemokines, which will lead to further neutrophil recruitment. These data suggest that lung epithelial cells respond to SARS-CoV-2 infection by secreting a group of proinflammatory cytokines and chemokines that promote neutrophil recruitment into the infected tissues.

This first analysis demonstrates a major chemokine profile leading to neutrophil recruitment. We next analyzed whether in the infected lung tissue we can observe immunologic signals that could support the functional activity of recruited neutrophils. Indeed, we observed that CCL20 (logFC = 3.146 and R = 1.000e-6) was up-regulated in the lung samples infected with SARS-CoV-2 (Fig. 1A , B and Supporting Information Fig. S1 ). CCL20 is produced by neutrophils and plays a role in recruiting additional immune cell types to sites of inflammation. [48] [49] [50] CCL20 is the ligand for the CCR6 receptor and is known to play a role in mucosal immunity by recruiting immature dendritic cells, memory T cells, memory B cells, as well as macrophages to sites of infection. [48] [49] [50] [51] [52] [53] [54] [55] Therefore, up-regulation of CCL20 in SARS-CoV-2-infected tissues 

Type I IFN responses are critical for an efficient and regulated response to viral infections. 56 The main role of type I IFNs is to restrict viral replication and spread through the induction of a family of genes known as IFN-stimulated genes (ISGs). 56, 57 In addition to controlling the antiviral response, an important role of these ISGs is to modulate the immune response in order to prevent an exacerbated inflammatory process. 57 Because of its critical role in controlling viral responses, the components of the type I IFN pathway are viral targets as a mechanism to escape immune surveillance. Contrary to patients infected with pathogenic influenza virus, minimal amount of IFN or have being detected in the blood of COVID-19-infected patients suggestive of a blunted type I IFN. 58 The dysregulated IFN response implies an effective immunoregulatory strategy developed by SARS-CoV2 that allows a successful infection and replication, as well as excessive inflammation. 59 We looked at the type I IFN response in lung epithelial cells infected with SARS-CoV2 and found that the only ISG that was up-regulated was IL-6 (logFC = 2.929 and R = 1.000e-6) (Fig. 1) . Elevated IL-6 serum levels have been closely linked to severe COVID-19 cases. 60 As with the other cytokines that were previously discussed, IL-6 is also important for neutrophil recruitment, function, and survival. [61] [62] [63] [64] Resolution of the infection accelerates neutrophil apoptosis; however, continued expression of IL-6 has been shown to delay neutrophil apoptosis in addition to increasing their superoxide production capacity. 61, 65 Up-regulation of IL-6 may lead to a larger population of neutrophils that produce superoxide at a greater rate than normal neutrophils, causing tissue damage. These profiles confirm the observed blunting of type I IFNs and the consequent IL-6 related inflammatory syndrome (Fig. 1C ).

Altogether, the data described earlier suggest that neutrophils are the primary cell type recruited to the lungs during SARS-CoV-2 infection. This is further supported by a meta-analysis done by Langunas-Rangel that examined severe COVID-19 cases, which showed that an increased neutrophil to lymphocyte ratio (i.e., more neutrophils) was associated to an enhanced inflammatory process and poor survival rate. 66 The specific cytokine profile seen in the analysis of these data links neutrophilia to the cause of several complications in COVID-19 cases. This is highly relevant because we observed the differential expression of several different genes that are associated with neutrophil activation, degranulation, and neutrophil-mediated immunity ( Fig. 1C) , which implies that not only are neutrophils heavily recruited to sites of inflammation, but they are highly active as well. As stated earlier, epithelial cells are heavily involved in the immune response, which suggests that these factors are being secreted by them and are acting on neutrophils to induce these specific responses. Based on the gene analysis and published clinical data, we propose that excessive neutrophil recruitment may be involved in the severity of COVID-19 cases and lead to the complications seen in some patients as well. 66, 67 The data discussed here provide the potential molecular and cellular pathways responsible for the clinical outcomes described for COVID-19 patients.

It has become evident that COVID-19 patients are experiencing abnormal vascular issues, such as abnormal clotting, thrombosis, microvascular injuries, and preeclampsia. 4, 8, [68] [69] [70] [71] [72] Therefore, we sought to find a link to the cytokine profile shown in the analysis of these data and these abnormal vascular issues. First, it has been well established that neutrophils have been associated with thrombosis and microvascular injury. [73] [74] [75] [76] [77] In addition to the direct damage caused by neutrophil ROS production, we suspect that the main culprits behind these vascular issues in COVID-19 patients are NETs. NETs are structures released from neutrophils that contain nuclear chromatin bound by histones and a number of granular antimicrobial proteins. 78 Furthermore, an expanding amount of evidence suggests that the release of NETs (NETosis) is a new form of cell death that is different from apoptosis. 78, 79 NETotic neutrophils do not release apoptotic signals, do not show membrane blebbing, or go through nuclear chromatin condensation. 78, 79 In the context of COVID-19, NETs have been suggested to be linked to organ damage and mortality seen in severe COVID-19 cases. 80 , 81 Similarly, NET formation has also been confirmed to be important for pulmonary lung disease pathology, such as COPD, acute lung injury, and lung transplant rejection. [82] [83] [84] In the analysis of these data, we observed the up-regulation of several key cytokines that are highly relevant for NET regulation and production, including CCL20, IL-6, TNF , CXCL8, and IL-1 . Their involvement will be outlined in the following text.

As discussed earlier, we see up-regulation of CCL20 (logFC = 3.146

and R = 1.000e-6) (Fig. 1A) , which in addition to promote the recruitment of several cell types to sites of infection and inflammation, CCL20 is a major inducer of the formation of extracellular traps in neutrophils as well as other cell types such as mast cells, monocytes/macrophages, and eosinophils. 85 The presence of CCL20 up-regulation in COVID-19 patients suggests that extracellular traps maybe formed within the lung tissue or any tissue that is infected with SARS-CoV-2.

Other cytokines involved in NET release are IL-6, CXCL8, TNF , and IL-1 , which are also up-regulated in SARS-CoV-2-infected samples (Fig. 1A) . Both IL-6 and TNF have been shown to be a potent inducer of NETosis. 86 Additionally, NETosis is at least partially dependent on CXCL8, whereas IL-1 is important for the induction of mast cell extracellular traps. 87, 88 Last, activated endothelial cells under inflammatory conditions are thought to be involved in inducing NETosis, which may lead to their own demise. 87 NETs have been described to be induced during viral infections, such as influenza A and respiratory syncytial virus and are an important component to control viral spread. 89 Two specific studies also support our hypothesis that neutrophils and extracellular traps are important for COVID-19 pathology. 90, 91 A study by Radermecker et al. shows that NETs are important for the immunothrombotic events seen in COVID-19 cases. 91 Veras et al. also show that NETs are induced by SARS-CoV-2, in addition to seeing an augmented concentration of NETs in the plasma of COVID-19 patients. 90 This not only suggests that neutrophils are acting locally in the lungs but also that the effects from the neutrophils are reaching the vasculature that is away from the lungs. Therefore, it is feasible that neutrophil recruitment and NET The results of that case series suggest that pulmonary microvascular thrombosis might be responsible for the high mortality rate in patients with SARS-CoV-2 and acute respiratory distress syndrome. 95, 96 The theory regarding pulmonary microvascular thrombosis has been further corroborated by a Chinese study, which performed postmortem examinations of patients who had died of SARS-CoV-2. They reported that thrombosis was commonly found in the small vessels, lungs, and, even, some extrapulmonary organs. 11, 94, 96 One of the main components of thrombosis is platelets. Interestingly we observed significant up-regulation of CSF2, CSF3, IL-6,

Supporting Information Figs. S1 and S2). These cytokines are known to be involved in megakaryocytic function and platelet production [97] [98] [99] [100] [101] ( Fig. 2A and Supporting Information Fig. S2 ). This suggests that these factors are being secreted from the epithelium that is infected with SARS-COV-2 and acting to remotely induce these effects. Thus, these differentially expressed genes suggest a potential response to the infection that could have an effect on platelet production ( Fig. 2A, B) .

To better understand the potential immunologic response associated with these thrombotic events, we performed a network analysis to determine the differentially expressed genes associated with various aspects of coagulation (Fig. 3) . Interestingly we did not identify differentially expressed genes that are associated with the activation of the extrinsic, intrinsic, and common coagulation pathways (Fig. 3 ).

This suggests that there is a noncanonical mechanism that is leading to coagulation in COVID-19 patients, which is capable of circumventing the normal coagulation pathways.

Between the main pathways affected by SARS-CoV-19 and associated with thrombotic events, we observed up-regulation of the IL-17 pathway (Fig. 4A and Supporting Information Fig. S3 ). Mast cell and NETs have been shown to release IL-17. 88 A study by Boer et al.

showed an increase in IL-17 in the thrombi of acute myocardial infarctions, which suggests IL-17 may play a role in thrombosis. 93 Thus, IL-17 found in extracellular traps (NETs) may also be taking part in the prothrombotic environment seen in COVID-19 patients (Fig. 4B) .

Several reports suggest that COVID-19 is associated with complement activation and complement mediated microvascular damage and thrombosis. 70, [102] [103] [104] In this analysis, we see that another pathway that which in turn lead to further complement activation via NETosis (Fig. 4E) . To summarize all this information, we propose that in COVID-19 patients, NETs lead to complement activation, which compounds the prothrombotic nature of NETs (Fig. 4E ).

Kidney disease and acute kidney injury have been shown to be highly prevalent in COVID-19 patients. 9 Additionally, kidney injuries in COVID-19 patients have been associated with an increased inhospital mortality rate. 9 This led us to hypothesize that neutrophils and NETs may be the culprit behind the onset of these kidney disorders in COVID-19 patients. One of the key biomarkers thought to be important for early detection of kidney injury is neutrophil gelatinase-associated lipocalin or lipocalin 2 (LCN2). 111 LCN2 is produced by neutrophils, and its gene expression is up-regulated (logFC = 0.719 and R = 1.446e-5) in these data, which indicates the potential role of neutrophils in kidney injuries seen in COVID-19 patients. 112 Furthermore, NETs and their histones are linked to kidney injury. 113 Similar to histone induced epithelial cell death, histones from NETs induce tubular epithelial cell death and lead to kidney injury. 113 Complement proteins and their activation have been confirmed to play roles in a diverse set of renal diseases and disorders, suggesting that the kidneys are particularly susceptible to complement mediated injury. [114] [115] [116] [117] Last, individuals with kidney disease show a higher thrombotic risk. 118 This suggests that our proposed model of SARS-CoV-2 infection leading to neutrophilia, NETs, and complement activation may lead to kidney damage and thrombosis in the kidneys (Fig. 5) . Additionally, there is a possibility that the kidney damage itself may lead to thrombosis.

As with kidney disease, there is an abnormally high number of COVID-19 patients that develop liver disease or injury. Thus, liver disease and injury have also been linked to SARS-CoV-2 infection. 10, [119] [120] [121] [122] As with kidney disease and injury, neutrophils, NETs, complement, and thrombosis all play roles in liver injury. Neutrophils have been extensively proven to be involved in a wide variety of different types of liver dysfunction and damage, including hepatic ischemia-reperfusion and concanavalin A or alpha-naphthyl isothiocyanate-induced liver injury. [123] [124] [125] [126] [127] [128] [129] [130] [131] NETs have been shown to accelerate liver damage during hepatic ischemia-reperfusion injury. 132 Moreover, extracellular histones released from NETs induced fatal liver injury in mice via TLR-2 and TLR-4. 133 Furthermore, the complement system has also been implicated to be involved in liver dysfunction and damage. 134 Particularly, the C3 complement component is seen to be up-regulated during early stages of liver damage. 135 Last, certain types of liver diseases, such as cirrhosis and chronic liver disease, show an increased risk for thrombosis. 136 Nearly identical to the mechanism for COVID-19 induced kidney damage, these data suggest that liver damage caused by COVID-19 may be associated with neutrophilia, NETs, and complement (Fig. 5 ).

KD is a rare hyperinflammatory shock syndrome that has been identified in asymptomatic SARS-CoV-2-infected children. 7, 137 To date, eight children that tested positive for SARS-CoV-2 were affected by this disease. Interestingly, these children were all asymptomatic for the common COVID-19 symptoms. 7 KD is an acute systemic vascular disease usually seen in children under the age of five. The main complication of KD is the destruction of the epithelial lining in small and medium sized vessels that can lead to a coronary aneurysm. 138 Although the pathophysiology of this disease is poorly understood, it is currently thought that neutrophils, NETs, and the complement system may all be involved, all of which are included in our model. Elevated neutrophil levels have been reported in KD. 139, 140 Additionally, neutrophils in this disease show an increased ROS production and neutrophil elastase expression during the early stages of KD, further suggesting that neutrophils play a role in epithelial cell destruction in KD. 139, 141 It has also recently been reported that NETosis is enhanced in acute KD and takes part in KD vascular injury. 140 Last, the classical complement pathway is enhanced in KD. The inflammatory response in this disease also results in the production and activation of complement components. 142 Altogether, these findings suggest that the elevated neutrophils in SARS-CoV-2 infections may contribute to KD.

Finally, we want to discuss the potential involvement of SARS-COV- have been shown to be present in the intervillous spaces of preeclamptic placentae suggesting their involvement in the pathophysiology of preeclampsia. 144 Second, elevated IL-17 serum levels have been associated with preeclampsia. 145 As mentioned previously, NETs contain IL-17. This elevated IL-17 in preeclamptic mothers may be due to neutrophils producing NETs. Third, the complement pathway has been linked to the onset of preeclampsia. 146 Complement deposits have been seen on the trophoblasts of preeclamptic placentae. 147, 148 All three of these factors are proposed by our model and are also linked to thrombosis and a procogaulatory environment. Moreover, high levels of TF mRNA have been seen in the vasculature of preeclamptic placentae. 149 Thus, preeclampsia appears to be associated with pro- 

Innate immunity

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The unique immunological and microbial aspects of pregnancy

Description and proposed management of the acute COVID-19 cardiovascular syndrome

Rapid surveillance of COVID-19 in the United States using a prospective space-time scan statistic: detecting and evaluating emerging clusters

The pathogenesis and treatment of the 'cytokine storm'' in COVID-19

Hyperinflammatory shock in children during COVID-19 pandemic

COVID-19 and its implications for thrombosis and anticoagulation

Kidney disease is associated with in-hospital death of patients with COVID-19

COVID-19 and liver disease

Cytokine release syndrome in severe COVID-19. Science (80-)

Identifying significantly impacted pathways: a comprehensive review and assessment

A novel signaling pathway impact analysis

A systems biology approach for pathway level analysis

Identifying significantly impacted pathways and putative mechanisms with iPathwayGuide

Granulocyte colony-stimulating factor and its receptor

Review: granulocyte colonystimulating factor-role and relationships in infectious diseases

Granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor

Colony-stimulating factors in inflammation and autoimmunity

Granulocyte-macrophage-colony-stimulating factor: a review from preclinical development to clinical application

The effect of granulocytemacrophage colony-stimulating factor on myeloid cells and its clinical applications

Generation of large numbers of dendritic cells from mouse bone marrow cultures supplemented with granulocyte/macrophage colony-stimulating factor

Dual role of GM-CSF as a pro-inflammatory and a regulatory cytokine: implications for immune therapy

CSF: a key regulator of neutrophil production, but that's not all!

Roles of GM-CSF in the pathogenesis of autoimmune diseases: an update

CXCR2: from bench to bedside

Chemokines and chemokine receptors in leukocyte trafficking

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Developmental switches in chemokine response profiles during B cell differentiation and maturation

Regulation of type I interferon signaling in immunity and inflammation: a comprehensive review

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Propagation of thrombosis by neutrophils and extracellular nucleosome networks

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Role of neutrophils in ischemia-reperfusion-induced microvascular injury

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Dying for a cause: nETosis, mechanisms behind an antimicrobial cell death modality

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Megakaryocyte development and platelet production

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In vitro and in vivo megakaryocyte differentiation of fresh and ex-vivo expanded cord blood cells: rapid and transient megakaryocyte reconstitution

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Neutrophil gelatinase-associated lipocalin (NGAL): a new marker of kidney disease

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Complement activation in progressive renal disease

Complement in kidney disease: core curriculum 2015

Kidney disease caused by dysregulation of the complement alternative pathway: an etiologic approach

Excessive activation of the alternative complement pathway in autosomal dominant polycystic kidney disease

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The complement system in liver diseases

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Enhanced neutrophilic functions in mucocutaneous lymph node syndrome, with special reference to the possible role of increased oxygen intermediate generation in the pathogenesis of coronary thromboarteritis

Enhanced formation of neutrophil extracellular traps in Kawasaki disease

The role of bacterial lipopolysaccharide-bound neutrophils in the pathogenesis of Kawasaki disease

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Maternal death due to COVID-19

Occurrence of neutrophil extracellular DNA traps (NETs) in pre-eclampsia: a link with elevated levels of cell-free DNA

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