Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that neutrophil extracellular traps (NETs) have been described as important mediators of tissue damage in inflammatory diseases, we investigated whether NETs would be involved in COVID-19 pathophysiology. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and healthy controls were enrolled. The concentration of NETs was augmented in plasma, tracheal aspirate, and lung autopsies tissues from COVID-19 patients, and their neutrophils released higher levels of NETs. Notably, we found that viable SARS-CoV-2 can directly induce the release of NETs by healthy neutrophils. Mechanistically, NETs triggered by SARS-CoV-2 depend on angiotensin-converting enzyme 2, serine protease, virus replication, and PAD-4. Finally, NETs released by SARS-CoV-2–activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represents a potential therapeutic target for COVID-19.

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Aims Brazil ranks high in the number of coronavirus disease 19 (COVID‐19) cases and the COVID‐19 mortality rate. In this context, autopsies are important to confirm the disease, determine associated conditions, and study the pathophysiology of this novel disease. The aim of this study was to assess the systemic involvement of COVID‐19. In order to follow biosafety recommendations, we used ultrasound‐guided minimally invasive autopsy (MIA‐US), and we present the results of 10 initial autopsies. Methods and results We used MIA‐US for tissue sampling of the lungs, liver, heart, kidneys, spleen, brain, skin, skeletal muscle and testis for histology, and reverse transcription polymerase chain reaction to detect severe acute respiratory syndrome coronavirus 2 RNA. All patients showed exudative/proliferative diffuse alveolar damage. There were intense pleomorphic cytopathic effects on the respiratory epithelium, including airway and alveolar cells. Fibrinous thrombi in alveolar arterioles were present in eight patients, and all patients showed a high density of alveolar megakaryocytes. Small thrombi were less frequently observed in the glomeruli, spleen, heart, dermis, testis, and liver sinusoids. The main systemic findings were associated with comorbidities, age, and sepsis, in addition to possible tissue damage due to the viral infection, such as myositis, dermatitis, myocarditis, and orchitis. Conclusions MIA‐US is safe and effective for the study of severe COVID‐19. Our findings show that COVID‐19 is a systemic disease causing major events in the lungs and with involvement of various organs and tissues. Pulmonary changes result from severe epithelial injury and microthrombotic vascular phenomena. These findings indicate that both epithelial and vascular injury should be addressed in therapeutic approaches.

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Background: COVID-19 in children is usually mild or asymptomatic, but severe and fatal paediatric cases have been described. The pathology of COVID-19 in children is not known; the proposed pathogenesis for severe cases includes immune-mediated mechanisms or the direct effect of SARS-CoV-2 on tissues. We describe the autopsy findings in five cases of paediatric COVID-19 and provide mechanistic insight into the mechanisms involved in the pathogenesis of the disease. Methods: Children and adolescents who died with COVID-19 between March 18 and August 15, 2020 were autopsied with a minimally invasive method. Tissue samples from all vital organs were analysed by histology, electron microscopy (EM), reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). Findings: Five patients were included, one male and four female, aged 7 months to 15 years. Two patients had severe diseases before SARS-CoV-2 infection: adrenal carcinoma and Edwards syndrome. Three patients were previously healthy and had multisystem inflammatory syndrome in children (MIS-C) with distinct clinical presentations: myocarditis, colitis, and acute encephalopathy with status epilepticus. Autopsy findings varied amongst patients and included mild to severe COVID-19 pneumonia, pulmonary microthrombosis, cerebral oedema with reactive gliosis, myocarditis, intestinal inflammation, and haemophagocytosis. SARS-CoV-2 was detected in all patients in lungs, heart and kidneys by at least one method (RT-PCR, IHC or EM), and in endothelial cells from heart and brain in two patients with MIS-C (IHC). In addition, we show for the first time the presence of SARS-CoV-2 in the brain tissue of a child with MIS-C with acute encephalopathy, and in the intestinal tissue of a child with acute colitis. Interpretation: SARS-CoV-2 can infect several cell and tissue types in paediatric patients, and the target organ for the clinical manifestation varies amongst individuals. Two major patterns of severe COVID-19 were observed: a primarily pulmonary disease, with severe acute respiratory disease and diffuse alveolar damage, or a multisystem inflammatory syndrome with the involvement of several organs. The presence of SARS-CoV-2 in several organs, associated with cellular

Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to respiratory failure. These patients also develop cytokine storm syndrome, and organ dysfunctions, which is a clinical picture that resembles sepsis. Considering that neutrophil extracellular traps (NETs) have been described as an important factors of tissue damage in sepsis, we investigated whether NETs would be produced in COVID-19 patients and participate in the lung tissue damage. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and respective healthy controls were enrolled. NETs concentration was assessed by MPO-DNA PicoGreen assay or by confocal immunofluorescence. The cytotoxic effect of SARS-CoV-2-induced NETs was analyzed in human epithelial lung cells (A549 cells). The concentration of NETs was augmented in plasma and tracheal aspirate from COVID-19 patients and their neutrophils spontaneously released higher levels of NETs. NETs were also found in the lung tissue specimens from autopsies of COVID-19 patients. Notably, viable SARS-CoV-2 can directly induce in vitro release of NETs by healthy neutrophils in a PAD-4-dependent manner. Finally, NETs released by SARS-CoV-2-activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represent a potential therapeutic target for COVID-19.

Background: The ability of coronavirus SARS-CoV-2 to spread is one of the determinants of the COVID-19 pandemic status. Until June 2020, global COVID-19 cases surpassed 10 million. Asymptomatic patients, with no respiratory impairment, are believed to be responsible for more than 80% of the transmission. Other viruses have been consistently detected in periodontal tissues. Objective: The aim of this study was to investigate the presence of SARS-CoV-2 in periodontal tissue. Methods: We conducted video-endoscope minimally invasive post-mortem biopsy in seven fatal cases of COVID-19, using a regular endoscope video system associated with a smartphone to locate periodontal tissue. We analyzed the samples using RT-PCR, to identify the SARS-CoV-2 RNA and histopathological analysis. Results: The seven studied autopsies with positive laboratory tests for COVID-19 included 57.14% of female patients at the average age of 47.4 (range 8 to 74). In five cases, periodontal tissue was positive for SARS-CoV-2 (RT-PCR). Histopathologic analyses showed morphologic alterations in the keratinocytes of the junctional epithelium, a vacuolization of the cytoplasm and nucleus and nuclear pleomorphism. Conclusion: We presented a biomolecular analysis obtained from minimally invasive autopsies. This is the first study to demonstrate the presence of SARS-CoV-2 in periodontal tissue in COVID-19 positive patients.

Background Pulmonary involvement in COVID-19 is characterized pathologically by diffuse alveolar damage (DAD) and thrombosis, leading to the clinical picture of Acute Respiratory Distress Syndrome. The direct action of SARS-CoV-2 in lung cells and the dysregulated immuno-coagulative pathways activated in ARDS influence pulmonary involvement in severe COVID, that might be modulated by disease duration and individual factors. In this study we assessed the proportions of different lung pathology patterns in severe COVID-19 patients along the disease evolution and individual characteristics. Methods We analysed lung tissue from 41 COVID-19 patients that died in the period March–June 2020 and were submitted to a minimally invasive autopsy. Eight pulmonary regions were sampled. Pulmonary pathologists analysed the H&E stained slides, performing semiquantitative scores on the following parameters: exudative, intermediate or advanced DAD, bronchopneumonia, alveolar haemorrhage, infarct (%), arteriolar (number) or capillary thrombosis (yes/no). Histopathological data were correlated with demographic-clinical variables and periods of symptoms-hospital stay. Results Patient´s age varied from 22 to 88 years (18f/23 m), with hospital admission varying from 0 to 40 days. All patients had different proportions of DAD in their biopsies. Ninety percent of the patients presented pulmonary microthrombosis. The proportion of exudative DAD was higher in the period 0–8 days of hospital admission till death, whereas advanced DAD was higher after 17 days of hospital admission. In the group of patients that died within eight days of hospital admission, elderly patients had less proportion of the exudative pattern and increased proportions of the intermediate patterns. Obese patients had lower proportion of advanced DAD pattern in their biopsies, and lower than patients with overweight. Clustering analysis showed that patterns of vascular lesions (microthrombosis, infarction) clustered together, but not the other patterns. The vascular pattern was not influenced by demographic or clinical parameters, including time of disease progression. Conclusion Patients with severe COVID-19 present different proportions of DAD patterns over time, with advanced DAD being more prevalent after 17 days, which seems to be influenced by age and weight. Vascular involvement is present in a large proportion of patients, occurs early in disease progression, and does not change over time.