Immunopathological mechanisms in sepsis of viral etiology in COVID-19.

The article provides information on immunopathology in sepsis and the commonality between immunopathogenetic processes of sepsis and the new coronavirus infection (COVID-19). As a result of the inability of the immune system to cope with aggression of the pathogen, inadequate immune activity occurs manifested by the systemic inflammatory response syndrome, resulting in damage to tissues of the host organism. In response, compensatory anti-inflammatory response syndrome is activated, which is manifested by inhibition of the immune response. One of its main mechanisms is signals produced by membrane receptors and their ligands. Against the background of inability of the host organism to neutralise the pathogen, numerous pathological phenomena and complications occur leading to damage to human tissues.Copyright © 2021, Krasnoyarsk State Medical University. All rights reserved.

A baby girl with TBX1 haploinsufficiency who died after elective cardiac repair surgery due to suspected enteroviral meningitis

Introduction: TBX1 haploinsufficiency is an inborn error of immunity with the phenotype of DiGeorge Syndrome. DiGeorge Syndrome has variable immunodeficiency associated with grade of thymic hypoplasia ranging from mild with no infections to severe requiring thymus implant. Enterovirus is an example of an opportunistic infection that can be fatal in these patients. Case Presentation: A 1 year old girl with TBX1 haploinsufficiency complicated by Tetralogy of Fallot, pulmonary atresia, high arched palate, and vesicovaginal fistula presented for elective cardiac repair surgery from another country due to failure to thrive and cyanosis. She had no prior infectious history but was on sulfamethoxazole-trimethoprim for prophylaxis. She was asymptomatic with a negative COVID test but no other infectious studies performed. Immediately postoperatively, she was febrile and nasal respiratory viral panel was positive for rhinovirus/enterovirus with increased procalcitonin and leukocytosis with left shift. She decompensated with multi-organ failure and cardiac arrest on postoperative day two. She was cannulated to veno-arterial extracorporeal membrane oxygenation (ECMO). Pre-operatively, she had a normal absolute lymphocyte count. No thymus tissue was observed in surgery. She had profound CD3 lymphopenia to 130 cells/cmm when critically ill. Enteroviral meningitis was suspected as no infectious, cardiac, or other pathology could be identified causing decompensation. Enteroviral serum polymerase chain reaction (PCR) test was negative while lumbar puncture deferred due to clinical status. She was treated with immunoglobulin. Offlabel investigational drug pocapavir was considered but deferred to patient's irreversible neurological status. The patient was disconnected from ECMO and expired. Discussion(s): Though we cannot confirm that this patient had enteroviral meningitis, invasive enteroviral infections are associated with elevated transaminases, coagulopathy, and seizures all present in our patient. There has also been reported negative serum enteroviral PCR but positive CSF enteroviral PCR in an immunodeficient patient. Additionally, this case highlights the importance of immunologic evaluation in patients with DiGeorge Syndrome and questions if asymptomatic viral screening for viruses like enterovirus should be considered pre-operatively in patients with inborn errors of immunity. This case highlights potential treatment options for invasive enteroviral infections in patients with inborn errors of immunity: high dose immunoglobulin, fluoxetine, and pocapavir.Copyright © 2023 Elsevier Inc.

Hematological Parameters and Procalcitonin as Discriminants between Bacterial Pneumonia-Induced Sepsis and Viral Sepsis Secondary to COVID-19: A Retrospective Single-Center Analysis.

Bacterial and viral sepsis induce alterations of all hematological parameters and procalcitonin is used as a biomarker of infection and disease severity. Our aim was to study the hematological patterns associated with pulmonary sepsis triggered by bacteria and Severe Acute Respiratory Syndrome-Coronavirus-type-2 (SARS-CoV-2) and to identify the discriminants between them. We performed a retrospective, observational study including 124 patients with bacterial sepsis and 138 patients with viral sepsis. Discriminative ability of hematological parameters and procalcitonin between sepsis types was tested using receiver operating characteristic (ROC) analysis. Sensitivity (Sn%), specificity (Sp%), positive and negative likelihood ratios were calculated for the identified cut-off values. Patients with bacterial sepsis were older than patients with viral sepsis (p < 0.001), with no differences regarding gender. Subsequently to ROC analysis, procalcitonin had excellent discriminative ability for bacterial sepsis diagnosis with an area under the curve (AUC) of 0.92 (cut-off value of >1.49 ng/mL; Sn = 76.6%, Sp = 94.2%), followed by RDW% with an AUC = 0.87 (cut-off value >14.8%; Sn = 80.7%, Sp = 85.5%). Leukocytes, monocytes and neutrophils had good discriminative ability with AUCs between 0.76-0.78 (p < 0.001), while other hematological parameters had fair or no discriminative ability. Lastly, procalcitonin value was strongly correlated with disease severity in both types of sepsis (p < 0.001). Procalcitonin and RDW% had the best discriminative ability between bacterial and viral sepsis, followed by leukocytes, monocytes and neutrophils. Procalcitonin is a marker of disease severity regardless of sepsis type.

Effectiveness of levosimendan and role of cardiac magnetic resonance in cardiogenic shock due to COVID-19 related lymphocytic myocarditis in the course of viral sepsis.

COVID-19 and sepsis pose great challenges to clinicians and growing evidence is demonstrating links between the two conditions. Both can be complicated by acute heart failure. The use of levosimendan in patients with ventricular dysfunction during COVID-19 infection and sepsis has very little evidence. A 46-year-old, hypertensive and obese patient was admitted for severe left ventricular failure and shock during sepsis following a COVID-19 infection. The patient was treated first with norepinephrine, which was partially effective, then with the addition of levosimendan as a continuous 24 hours infusion. Vital signs and echocardiographic systolic performance indices, such as FE, SVi, CI, dP/dT, TAPSE, and tricuspid S-wave velocity, as well as diastolic function, were recorded at access, 12 and 24 hours. After initiation of levosimendan, a rapid improvement in vital signs and systolic and diastolic performance indices was observed, not depending on changes in preload, afterload, and inflammatory status. Blood cultures were negative for the presence of bacteria, thus defining the picture of likely viral sepsis. Cardiac magnetic resonance was determinant, showing a picture of myocarditis sustained by immune processes rather than direct viral injury, which was confirmed by endomyocardial biopsy. In conclusion, this case highlights the efficacy of levosimendan in acute heart failure complicated by shock due to COVID-19-related myocarditis and concomitant sepsis and confirms cardiac magnetic resonance as the gold standard for the diagnosis of myocardial inflammatory disease. To the best of our knowledge, this is the first documented case of effective use of levosimendan in this context.

Patients with SARS-CoV-2-Induced Viral Sepsis Simultaneously Show Immune Activation, Impaired Immune Function and a Procoagulatory Disease State.

BACKGROUND: It is widely accepted that SARS-CoV-2 causes a dysregulation of immune and coagulation processes. In severely affected patients, viral sepsis may result in life endangering multiple organ dysfunction. Furthermore, most therapies for COVID-19 patients target either the immune system or coagulation processes. As the exact mechanism causing SARS-CoV-2-induced morbidity and mortality was unknown, we started an in-depth analysis of immunologic and coagulation processes. METHODS: 127 COVID-19 patients were treated at the University Hospital Essen, Germany, between May 2020 and February 2022. Patients were divided according to their maximum COVID-19 WHO ordinal severity score (WHO 0-10) into hospitalized patients with a non-severe course of disease (WHO 4-5, n = 52) and those with a severe course of disease (WHO 6-10, n = 75). Non-infected individuals served as healthy controls (WHO 0, n = 42). Blood was analyzed with respect to cell numbers, clotting factors, as well as pro- and anti-inflammatory mediators in plasma. As functional parameters, phagocytosis and inflammatory responses to LPS and antigen-specific stimulation were determined in monocytes, granulocytes, and T cells using flow cytometry. FINDINGS: In the present study, immune and coagulation systems were analyzed simultaneously. Interestingly, many severe COVID-19 patients showed an upregulation of pro-inflammatory mediators and at the same time clear signs of immunosuppression. Furthermore, severe COVID-19 patients not only exhibited a disturbed immune system, but in addition showed a pronounced pro-coagulation phenotype with impaired fibrinolysis. Therefore, our study adds another puzzle piece to the already complex picture of COVID-19 pathology implying that therapies in COVID-19 must be individualized. CONCLUSION: Despite years of research, COVID-19 has not been understood completely and still no therapies exist, fitting all requirements and phases of COVID-19 disease. This observation is highly reminiscent to sepsis. Research in sepsis has been going on for decades, while the disease is still not completely understood and therapies fitting all patients are lacking as well. In both septic and COVID-19 patients, immune activation can be accompanied by immune paralysis, complicating therapeutic intervention. Accordingly, therapies that lower immune activation may cause detrimental effects in patients, who are immune paralyzed by viral infections or sepsis. We therefore suggest individualizing therapies and to broaden the spectrum of immunological parameters analyzed before therapy. Only if the immune status of a patient is understood, can a therapeutic intervention be successful.

Stratification of COVID-19 Severity Using SeptiCyte RAPID, a Novel Host Immune Response Test.

SeptiCyte® RAPID is a gene expression assay measuring the relative expression levels of host response genes PLA2G7 and PLAC8, indicative of a dysregulated immune response during sepsis. As severe forms of COVID-19 may be considered viral sepsis, we evaluated SeptiCyte RAPID in a series of 94 patients admitted to Foch Hospital (Suresnes, France) with proven SARS-CoV-2 infection. EDTA blood was collected in the emergency department (ED) in 67 cases, in the intensive care unit (ICU) in 23 cases and in conventional units in 4 cases. SeptiScore (0-15 scale) increased with COVID-19 severity. Patients in ICU had the highest SeptiScores, producing values comparable to 8 patients with culture-confirmed bacterial sepsis. Receiver operating characteristic (ROC) curve analysis had an area under the curve (AUC) of 0.81 for discriminating patients requiring ICU admission from patients who were immediately discharged or from patients requiring hospitalization in conventional units. SeptiScores increased with the extent of the lung injury. For 68 patients, a chest computed tomography (CT) scan was performed within 24 h of COVID-19 diagnosis. SeptiScore >7 suggested lung injury ≥50% (AUC = 0.86). SeptiCyte RAPID was compared to other biomarkers for discriminating Critical + Severe COVID-19 in ICU, versus Moderate + Mild COVID-19 not in ICU. The mean AUC for SeptiCyte RAPID was superior to that of any individual biomarker or combination thereof. In contrast to C-reactive protein (CRP), correlation of SeptiScore with lung injury was not impacted by treatment with anti-inflammatory agents. SeptiCyte RAPID can be a useful tool to identify patients with severe forms of COVID-19 in ED, as well as during follow-up.

How Different Pathologies Are Affected by IFIT Expression.

The type-I interferon (IFN) system represents the first line of defense against viral pathogens. Recognition of the virus initiates complex signaling pathways that result in the transcriptional induction of IFNs, which are then secreted. Secreted IFNs stimulate nearby cells and result in the production of numerous proinflammatory cytokines and antiviral factors. Of particular note, IFN-induced tetratricopeptide repeat (IFIT) proteins have been thoroughly studied because of their antiviral activity against different viral pathogens. Although classically studied as an antiviral protein, IFIT expression has recently been investigated in the context of nonviral pathologies, such as cancer and sepsis. In oral squamous cell carcinoma (OSCC), IFIT1 and IFIT3 promote metastasis, while IFIT2 exhibits the opposite effect. The role of IFIT proteins during bacterial/fungal sepsis is still under investigation, with studies showing conflicting roles for IFIT2 in disease severity. In the setting of viral sepsis, IFIT proteins play a key role in clearing viral infection. As a result, many viral pathogens, such as SARS-CoV-2, employ mechanisms to inhibit the type-I IFN system and promote viral replication. In cancers that are characterized by upregulated IFIT proteins, medications that decrease IFIT expression may reduce metastasis and improve survival rates. Likewise, in cases of viral sepsis, therapeutics that increase IFIT expression may improve viral clearance and reduce the risk of septic shock. By understanding the effect of IFIT proteins in different pathologies, novel therapeutics can be developed to halt disease progression.

SARS CoV-2-Induced Viral Sepsis: The Role of Gut Barrier Dysfunction.

A considerable proportion of patients with severe COVID-19 meet Sepsis-3 criteria and share common pathophysiological mechanisms of multiorgan injury with bacterial sepsis, in absence of secondary bacterial infections, a process characterized as "viral sepsis". The intestinal barrier exerts a central role in the pathophysiological sequence of events that lead from SARS-CoV-2 infection to severe systemic complications. Accumulating evidence suggests that SARS-CoV-2 disrupts the integrity of the biological, mechanical and immunological gut barrier. Specifically, microbiota diversity and beneficial bacteria population are reduced, concurrently with overgrowth of pathogenic bacteria (dysbiosis). Enterocytes' tight junctions (TJs) are disrupted, and the apoptotic death of intestinal epithelial cells is increased leading to increased gut permeability. In addition, mucosal CD4(+) and CD8(+) T cells, Th17 cells, neutrophils, dendritic cells and macrophages are activated, and T-regulatory cells are decreased, thus promoting an overactivated immune response, which further injures the intestinal epithelium. This dysfunctional gut barrier in SARS-CoV-2 infection permits the escape of luminal bacteria, fungi and endotoxin to normally sterile extraintestinal sites and the systemic circulation. Pre-existing gut barrier dysfunction and endotoxemia in patients with comorbidities including cardiovascular disease, obesity, diabetes and immunosuppression predisposes to aggravated endotoxemia. Bacterial and endotoxin translocation promote the systemic inflammation and immune activation, which characterize the SARS-CoV-2 induced "viral sepsis" syndrome associated with multisystemic complications of severe COVID-19.

Yoğun Bakımda COVID-19 ile Ílişkili Íkincil Enfeksiyonlar

Amaç: Koronavirüs hastalığı-19 (COVID-19) sırasında gözlenen ikincil enfeksiyonların tanısı karmaşıktır ve ülkemizdeki sıklığı bilinmemektedir. Çalışmamızda yoğun bakım ünitesinde (YBÜ) yatan COVID-19 hastalarında ikincil enfeksiyonların sıklığı ve hastalığın sonuçlarına olan etkileri incelendi. Ek olarak ikincil enfeksiyonlara tanı koymada yardımcı olabilecek bulgular değerlendirildi. Gereç ve Yöntem: Etik kurul onayı alındıktan sonra, ülkemizde enfeksiyon hastalıklarının sürveyansının yapılamadığı Ekim-Aralık 2021 tarihleri arasında YBÜ’de yatan COVID-19’lu hastalarımızın medikal kayıtları geriye dönük olarak değerlendirildi. Hastaların yandaş hastalıkları, vital bulguları, laboratuvar değerleri, organ disfonksiyonları ve tedavileri incelendi. Íkincil enfeksiyonların tanısı için alınan mikrobiyolojik örnekler değerlendirildi. Çalışmada veriler SPSS 23.0 programı ile Mann-Whitney U testi, lojistik regresyon ve ROC eğrisi kullanılarak analiz edildi p<0,05 istatistiksel anlamlılık sınırı olarak belirlendi. Bulgular: Dört yüz seksen beş hastanın yaş ortalaması 69,63±13,48 yıl ve %81,2’sinin yandaş hastalığı vardı. Olguların YBÜ’de yatış süresi ortalama 9,64±8,37 gün olup, %73,4’ü eksitus oldu. Olguların %83,1’inde ikincil enfeksiyon, %71,8’inde yoğun bakım kabulü sırasında ikincil enfeksiyon (toplum kaynaklı, sağlık bakımı ilişkili), %46,8’inde süper enfeksiyon vardı. Olguların %67’sinde alt solunum yolu enfeksiyonu, %23’ünde kan dolaşımı enfeksiyonu, %18’inde idrar yolları enfeksiyonu vardı (Tablo 1). COVID-19 tanısı sonrası ikincil enfeksiyon görülme süresi ortalama 9,62±5,1 gündü. Mikrobiyolojik örneklerde (n=509) en sık Staphylococcus aureus (%17) ve Acinetobacter baumannii (%16,3) saptandı (Tablo 2). Íkincil enfeksiyon gelişen olgular (n=403) gelişmeyen olgularla (n=82) karşılaştırıldığında YBÜ yatış süresi, MV süresi, akut böbrek hasarı sıklığı daha fazla ve sağkalımları daha düşüktü (p<0,001). Íkincil bakteriyel enfeksiyon varlığını prokalsiton değeri ≥0,50 µg/L %55,7 duyarlılık, %95,5 özgünlük, ortalama arter basıncı ≤65 mm/hg %42,5 duyarlılık, %91,2 özgünlük ile ayırt edebilen parametrelerdi (p<0,001). Yoğun bakım kabulünde ve takiplerinde gelişen enfeksiyonların dağılımı (n=485). Sonuç: Çalışmamız COVID-19’da ikincil enfeksiyon oranlarını bildiren ülkemizdeki ilk çalışmadır. Yurtdışı verilerine (1, 2, 3) göre daha yüksek oran saptanmıştır. Söz konusu farka “kanıtlanmış” enfeksiyonların yanında “yüksek olası” ve “olası” enfeksiyonları da saptamamız etken olmuş olabilir. Sonuçlarımız, kritik COVID-19’lu hastalarda ikincil enfeksiyon oranlarının yüksek olduğu ve ikincil enfeksiyonların COVID-19’un sonuçlarını kötüleştirip hastaların sağkalımını düşürdüğü yönündedir. (Turkish) [ FROM AUTHOR] Copyright of Turkish Journal of Intensive Care is the property of Galenos Yayinevi Tic. LTD. STI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

Immunopathological mechanisms in sepsis of viral etiology in COVID-19

The article provides information on immunopathology in sepsis and the commonality between immunopathogenetic processes of sepsis and the new coronavirus infection (COVID-19). As a result of the inability of the immune system to cope with aggression of the pathogen, inadequate immune activity occurs manifested by the systemic inflammatory response syndrome, resulting in damage to tissues of the host organism. In response, compensatory anti-inflammatory response syndrome is activated, which is manifested by inhibition of the immune response. One of its main mechanisms is signals produced by membrane receptors and their ligands. Against the background of inability of the host organism to neutralise the pathogen, numerous pathological phenomena and complications occur leading to damage to human tissues. © 2021, Krasnoyarsk State Medical University. All rights reserved.

Revisiting Metchnikoff's work in light of the COVID-19 pandemic.

Revisiting Metchnikoff's work in light of the COVID-19 pandemic illustrates how much this amazing scientist was a polymath, and one could speculate how much he would have been fascinated and most interested in following the course of the pandemic. Since he coined the word "gerontology", he would have been intrigued by the high mortality among the elderly, and by the concepts of immunosenescence and inflammaging that characterize the SARS-CoV-2 infection. While Metchnikoff's work is mainly associated with the discovery of the phagocytes and the birth of cellular innate immunity, he regularly invited his closest collaborators to investigate humoral immunity, and it was in his laboratory that Jules Bordet made his major discovery of the complement system. While Metchnikoff and his team investigated many infectious diseases, he also contributed to studies linked to vaccination, such as those on typhoid fever performed in chimpanzees, illustrating that non-human primates can provide animal models which are potentially helpful for understanding the pathophysiology of the COVID-19 virus. In the present review, we illustrate how much his own work and the investigations of his trainees were pertinent to this new disease.

SARS-CoV-2 viral sepsis with meningoencephalitis.

SARS-CoV-2 predominantly involves the lungs producing acute lung injury, but it can also give rise to a variety of complications involving the central nervous system, gastrointestinal system, kidney and also viral sepsis. With this case report, we are discussing unusual series of complication from acute lung injury, followed by viral sepsis then encephalitis, followed by progressive macrophage activation syndrome.

Severe COVID-19 has a distinct phenotype from bacterial sepsis: a retrospective cohort study in deceased patients.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has caused more than 2 million deaths worldwide. Viral sepsis has been proposed as a description for severe COVID-19, and numerous therapies have been on trials based upon this hypothesis. However, whether the clinical characteristics of severe COVID-19 are similar to those of bacterial sepsis has not been elucidated. METHODS: We retrospectively compared the clinical data of non-surviving COVID-19 patients who were admitted to a 30-bed intensive care unit (ICU) in Wuhan Infectious Diseases Hospital (Wuhan, China) from 22 January 2020, to 28 February 2020, with those of non-surviving patients with bacterial sepsis who were admitted to the ICU in Zhongshan Hospital, Fudan University (Shanghai, China) from 3 July 2018, to 30 June 2020. RESULTS: A total of 53 COVID-19 patients and 26 septic patients were included in the analysis. The mean ages were 65.6 [standard deviation (SD): 11.1] and 70.4 (SD: 14.3) years in the COVID-19 cohort and sepsis cohort, respectively. The proportion of participants with hypertension was higher in non-survivors with COVID-19 than in non-survivors with sepsis (41.5% vs. 15.4%, P=0.020). The Sequential Organ Failure Assessment (SOFA) score of non-survivors with COVID-19 was lower than that of non-survivors with sepsis at ICU admission {4.0 [interquartile range (IQR): 3.0-6.0] vs. 7.5 [IQR: 5.8-11.0], P<0.001}. The clinical parameters at ICU admission assessed with principal component analysis and hierarchical cluster analysis showed that COVID-19 patients were distinct from bacterial septic patients. Compared with non-survivors with sepsis, non-survivors with COVID-19 had a higher neutrophil/lymphocyte ratio, total protein, globulin, lactate dehydrogenase (LDH), and D-dimer; a lower eosinophil count, procalcitonin, interleukin-6 (IL-6), total bilirubin, direct bilirubin, myohemoglobin, albumin/globulin ratio, activated partial thromboplastin time (APTT), prothrombin time (PT), and international normalization ratio (INR) at ICU admission. In addition, the levels of total protein, globulin, LDH, D-dimer, and IL-6 were significantly different between the two groups during the ICU stay. CONCLUSIONS: Patients with critical COVID-19 have a phenotype distinct from that of patients with bacterial sepsis. Therefore, caution should be used when applying the previous experience of bacterial sepsis to patients with severe COVID-19.

A series of COVID-19 autopsies with clinical and pathologic comparisons to both seasonal and pandemic influenza.

Autopsies of patients who have died from COVID-19 have been crucial in delineating patterns of injury associated with SARS-CoV-2 infection. Despite their utility, comprehensive autopsy studies are somewhat lacking relative to the global burden of disease, and very few comprehensive studies contextualize the findings to other fatal viral infections. We developed a novel autopsy protocol in order to perform postmortem examinations on victims of COVID-19 and herein describe detailed clinical information, gross findings, and histologic features observed in the first 16 complete COVID-19 autopsies. We also critically evaluated the role of ancillary studies used to establish a diagnosis of COVID-19 at autopsy, including immunohistochemistry (IHC), in situ hybridization (ISH), and electron microscopy (EM). IHC and ISH targeting SARS-CoV-2 were comparable in terms of the location and number of infected cells in lung tissue; however, nonspecific staining of bacteria was seen occasionally with IHC. EM was unrevealing in blindly sampled tissues. We then compared the clinical and histologic features present in this series to six archival cases of fatal seasonal influenza and six archival cases of pandemic influenza from the fourth wave of the 'Spanish Flu' in the winter of 1920. In addition to routine histology, the inflammatory infiltrates in the lungs of COVID-19 and seasonal influenza victims were compared using quantitative IHC. Our results demonstrate that the clinical and histologic features of COVID-19 are similar to those seen in fatal cases of influenza, and the two diseases tend to overlap histologically. There was no significant difference in the composition of the inflammatory infiltrate in COVID-19 and influenza at sites of acute lung injury at the time of autopsy. Our study underscores the relatively nonspecific clinical features and pathologic changes shared between severe cases of COVID-19 and influenza, while also providing important caveats to ancillary methods of viral detection.

The Good Treatment, the Bad Virus, and the Ugly Inflammation: Pathophysiology of Kidney Involvement During COVID-19.

Kidney involvement is a common complication during SARS-CoV-2 infection. Its association with poor outcomes, especially in critically ill patients, raises issues whether kidney involvement reflects multi-organ damage or if it is a specific feature of the infection. Based on observational studies, autopsy series, and on current understanding of the route of entry of the virus, this review will highlight the different types of kidney involvement during COVID-19 and put them in the perspective of the different pathophysiological hypotheses. Virus entry route through ACE2 ligation and TMPRSS2 coligation allows identifying potential viral targets in the kidney, including tubules, endothelial cells, and glomerulus. While reports have described damages of all these structures and virus kidney tropism has been identified in renal extracts in autopsy series, no direct viral infection has been found in the latter structures thus far on kidney biopsies. Notwithstanding the technical challenge of disclosing viral invasion within tissues and cells, viral direct cytopathogenic effect generally does not appear as the cause of the observed renal damage. Inflammation and altered hemodynamics, described as "viral sepsis," might rather be responsible for organ dysfunction, including kidneys. We shall place these various mechanisms into an integrated vision where the synergy between direct viral pathogenicity and systemic inflammation enhances renal damage. As SARS-CoV-2 inexorably continues its rampant spread, understanding the sequence of events in the kidneys might thus help inform improved therapeutic strategies, including antiviral drugs and immunomodulators.

COVID-19 and the human innate immune system.

The introduction of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the human population represents a tremendous medical and economic crisis. Innate immunity-as the first line of defense of our immune system-plays a central role in combating this novel virus. Here, we provide a conceptual framework for the interaction of the human innate immune system with SARS-CoV-2 to link the clinical observations with experimental findings that have been made during the first year of the pandemic. We review evidence that variability in innate immune system components among humans is a main contributor to the heterogeneous disease courses observed for coronavirus disease 2019 (COVID-19), the disease spectrum induced by SARS-CoV-2. A better understanding of the pathophysiological mechanisms observed for cells and soluble mediators involved in innate immunity is a prerequisite for the development of diagnostic markers and therapeutic strategies targeting COVID-19. However, this will also require additional studies addressing causality of events, which so far are lagging behind.

Clinical Manifestations and Outcomes of Critically Ill Children and Adolescents with Coronavirus Disease 2019 in New York City.

OBJECTIVES: To describe the clinical manifestations and outcomes of critically ill children with coronavirus disease-19 (COVID-19) in New York City. STUDY DESIGN: Retrospective observational study of children 1 month to 21 years admitted March 14 to May 2, 2020, to 9 New York City pediatric intensive care units (PICUs) with severe acute respiratory syndrome coronavirus 2 infection. RESULTS: Of 70 children admitted to PICUs, median age was 15 (IQR 9, 19) years; 61.4% male; 38.6% Hispanic; 32.9% black; and 74.3% with comorbidities. Fever (72.9%) and cough (71.4%) were the common presenting symptoms. Twelve patients (17%) met severe sepsis criteria; 14 (20%) required vasopressor support; 21 (30%) developed acute respiratory distress syndrome (ARDS); 9 (12.9%) met acute kidney injury criteria; 1 (1.4%) required renal-replacement therapy, and 2 (2.8%) had cardiac arrest. For treatment, 27 (38.6%) patients received hydroxychloroquine; 13 (18.6%) remdesivir; 23 (32.9%) corticosteroids; 3 (4.3%) tocilizumab; and 1 (1.4%) anakinra; no patient was given immunoglobulin or convalescent plasma. Forty-nine (70%) patients required respiratory support: 14 (20.0%) noninvasive mechanical ventilation, 20 (28.6%) invasive mechanical ventilation (IMV), 7 (10%) prone position, 2 (2.8%) inhaled nitric oxide, and 1 (1.4%) extracorporeal membrane oxygenation. Nine (45%) of the 20 patients requiring IMV were extubated by day 14 with median IMV duration of 218 (IQR 79, 310.4) hours. Presence of ARDS was significantly associated with duration of PICU and hospital stay, and lower probability of PICU and hospital discharge at hospital day 14 (P < .05 for all). CONCLUSIONS: Critically ill children with COVID-19 predominantly are adolescents, have comorbidities, and require some form of respiratory support. The presence of ARDS is significantly associated with prolonged PICU and hospital stay.

The Enigma of Endothelium in COVID-19.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) has affected millions of people globally. Clinically, it presents with mild flu-like symptoms in most cases but can cause respiratory failure in high risk population. With the aim of unearthing newer treatments, scientists all over the globe are striving hard to comprehend the underlying mechanisms of COVID-19. Several studies till date have indicated a dysregulated host immune response as the major cause of COVID-19 induced mortality. In this Perspective, we propose a key role of endothelium, particularly pulmonary endothelium in the pathogenesis of COVID-19. We draw parallels and divergences between COVID-19-induced respiratory distress and bacterial sepsis-induced lung injury and recommend the road ahead with respect to identification of endothelium-based biomarkers and plausible treatments for COVID-19.