Pathophysiology of SARS-CoV-2: the Mount Sinai COVID-19 autopsy experience

Neuropathogenesis of severe acute respiratory syndrome coronavirus 2

PURPOSE OF REVIEW

The purpose of this review is to address our current understanding of the pathophysiology of neurologic injury resulting from severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection on the developing nervous system.

RECENT FINDINGS

SARS-CoV2 may enter the brain through three potential mechanisms: transsynaptic spread from the olfactory bulb following intranasal exposure, migration across the blood-brain barrier through endothelial cell infection, and migration following disruption of the blood-brain barrier from resulting inflammation. SARS-CoV2 does not appear to directly infect neurons but rather may produce an inflammatory cascade that results in neuronal injury. Additionally, autoantibodies targeting neuronal tissue resulting from the immune response to SARS-CoV2 are present in select patients and may contribute to central nervous system (CNS) injury.

SUMMARY

These findings suggest that neuronal injury during SARS-CoV2 infection is immune mediated rather than through direct viral invasion. Further multimodal studies evaluating the pathophysiology of neurologic conditions in pediatric patients specifically following SARS-CoV2 infection are needed to improve our understanding of mechanisms driving neurologic injury and to identify potential treatment options.

Is it COVID-19? The value of medicolegal autopsies during the first year of the COVID-19 pandemic

Objectives

We describe the experience of a busy metropolitan medical examiner’s office in the United States and share our navigation of the COVID-19 autopsy decision-making process. We describe key gross and microscopic findings that, with appropriate laboratory testing, should direct a pathologist towards a COVID-19-related cause of death.

Material and methods

We performed a retrospective review of 258 suspected and/or confirmed COVID-19 associated deaths that occurred between March 5, 2020, and March 4, 2021.

Results

A total of 62 cases due to fatal COVID-19 were identified; autopsy findings included diffuse alveolar damage, acute bronchopneumonia and lobar pneumonia, and pulmonary thromboemboli. Nine additional decedents had a nasopharyngeal swab positive for SARS-CoV-2 and a cause of death unrelated to COVID-19. Forty-seven cases with COVID-19-like symptoms showed no laboratory or histopathologic evidence of SARS-CoV-2 infection; the most common causes of death in this group were hypertensive or atherosclerotic cardiovascular disease, complications of chronic alcoholism, and pulmonary thromboemboli unrelated to infection.

Conclusions

The clinical findings associated with COVID-19 are not specific; a broad differential diagnosis should be embraced when decedents present with cough or shortness of breath. An autopsy may be indicated to identify a cause of death unrelated to COVID-19.

Endothelial cells are not productively infected by SARS-CoV-2

Objectives

Thrombotic and microvascular complications are frequently seen in deceased COVID‐19 patients. However, whether this is caused by direct viral infection of the endothelium or inflammation‐induced endothelial activation remains highly contentious.

Methods

Here, we use patient autopsy samples, primary human endothelial cells and an in vitro model of the pulmonary epithelial–endothelial cell barrier.

Results

We show that primary human endothelial cells express very low levels of the SARS‐CoV‐2 receptor ACE2 and the protease TMPRSS2, which blocks their capacity for productive viral infection, and limits their capacity to produce infectious virus. Accordingly, endothelial cells can only be infected when they overexpress ACE2, or are exposed to very high concentrations of SARS‐CoV‐2. We also show that SARS‐CoV‐2 does not infect endothelial cells in 3D vessels under flow conditions. We further demonstrate that in a co‐culture model endothelial cells are not infected with SARS‐CoV‐2. Endothelial cells do however sense and respond to infection in the adjacent epithelial cells, increasing ICAM‐1 expression and releasing pro‐inflammatory cytokines.

Conclusions

Taken together, these data suggest that in vivo, endothelial cells are unlikely to be infected with SARS‐CoV‐2 and that infection may only occur if the adjacent pulmonary epithelium is denuded (basolateral infection) or a high viral load is present in the blood (apical infection). In such a scenario, whilst SARS‐CoV‐2 infection of the endothelium can occur, it does not contribute to viral amplification. However, endothelial cells may still play a key role in SARS‐CoV‐2 pathogenesis by sensing adjacent infection and mounting a pro‐inflammatory response to SARS‐CoV‐2.

Late Cardiac Pathology in Severe Covid-19. A Postmortem Series of 30 Patients

The role of SARS-CoV-2 as a direct cause in the cardiac lesions in patients with severe COVID-19 remains to be established. Our objective is to report the pathological findings in cardiac samples of 30 patients who died after a prolonged hospital stay due to Sars-Cov-2 infection. We performed macroscopic, histological and immunohistochemical analysis of the hearts of 30 patients; and detected Sars-Cov-2 RNA by RT-PCR in the cardiac tissue samples. The median age of our cohort was 69.5 years and 76.6% were male. The median time between symptoms onset and death was 36.5 days. The main comorbidities were arterial hypertension (13 patients, 43.3%), dyslipidemia (11 patients, 36.7%), cardiovascular conditions (8 patients, 26.7%), and obesity (8 patients, 26.7%). Cardiovascular conditions included ischemic cardiopathy in 4 patients (13.3%), hypertrophic cardiomyopathy in 2 patients (6.7%) and valve replacement and chronic heart failure in one patient each (3.3%). At autopsy, the most frequent histopathological findings were coronary artery atherosclerosis (8 patients, 26.7%), left ventricular hypertrophy (4 patients, 13.3%), chronic epicardial inflammation (3 patients, 10%) and adipose metaplasia (2 patients, 6.7%). Two patients showed focal myocarditis, one due to invasive aspergillosis. One additional patient showed senile amyloidosis. Sars-Cov-2 RNA was detected in the heart of only one out of 30 patients, who had the shortest disease evolution of the series (9 days). However, no relevant cardiac histological alterations were identified. In present series, cardiac pathology was only modest in most patients with severe COVID-19. At present, the contribution of a direct effect of SARS-CoV-2 on cardiac lesions remains to be established.

SARS-CoV-2 and the brain: A review of the current knowledge on neuropathology in COVID-19

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the new coronavirus responsible for the pandemic disease in the last year, is able to affect the central nervous system (CNS). Compared with its well-known pulmonary tropism and respiratory complications, little has been studied about SARS-CoV-2 neurotropism and pathogenesis of its neurological manifestations, but also about postmortem histopathological findings in the CNS of patients who died from COVID-19 (coronavirus disease 2019). We present a systematic review, carried out according to the Preferred Reporting Items for Systematic Review standards, of the neuropathological features of COVID-19. We found 21 scientific papers, the majority of which refer to postmortem examinations; the total amount of cases is 197. Hypoxic changes are the most frequently reported alteration of brain tissue, followed by ischemic and hemorrhagic lesions and reactive astrogliosis and microgliosis. These findings do not seem to be specific to SARS-CoV-2 infection, they are more likely because of systemic inflammation and coagulopathy caused by COVID-19. More studies are needed to confirm this hypothesis and to detect other possible alterations of neural tissue. Brain examination of patients dead from COVID-19 should be included in a protocol of standardized criteria to perform autopsies on these subjects.

Platypnea Orthodeoxia Due to a Patent Foramen Ovale and Intrapulmonary Shunting After Severe COVID-19 Pneumonia

BACKGROUND Platypnea orthodeoxia syndrome (POS) presents with positional dyspnea and hypoxemia defined as arterial desaturation of at least 5% or a drop in PaO2 of at least 4 mmHg. Causes of POS include a variety of cardiopulmonary etiologies and has been reported in patients recovering from severe COVID-19 pneumonia. However, clinical presentation and outcomes in a patient with multiple interrelated mechanisms of shunting has not been documented. CASE REPORT An 85-year-old man hospitalized for hypertensive emergency and severe COVID-19 pneumonia was diagnosed with platypnea orthodeoxia on day 28 of illness. During his disease course, the patient required supplemental oxygen by high-flow nasal cannula but never required invasive mechanical ventilation. Chest imaging revealed evolving mixed consolidation and ground-glass opacities with a patchy and diffuse distribution, involving most of the left lung. Echocardiography was ordered to evaluate for intracardiac shunt, which revealed a patent foramen ovale. Closure of the patent foramen ovale was not pursued. Management included graded progression to standing and supplemental oxygen increases when upright. The patient was discharged to a skilled nursing facility and his positional oxygen requirement resolved on approximately day 78. CONCLUSIONS The present case highlights the multiple interrelated mechanisms of shunting in patients with COVID-related lung disease and a patent foramen ovale. Eight prior cases of POS after COVID-19 pneumonia have been reported to date but none with a known patent foramen ovale. In patients with persistent positional oxygen requirements at follow-up, quantifying shunt fraction over time through multiple modalities can guide treatment decisions.

Pituitary-Adrenal Responses and Glucocorticoid Receptor Expression in Critically Ill Patients with COVID-19

The hypothalamus-pituitary-adrenal (HPA) axis was described as the principal component of the stress response 85 years ago, along with the acute-phase reaction, and the defense response at the tissue level. The orchestration of these processes is essential since systemic inflammation is a double-edged sword; whereas inflammation that is timely and of appropriate magnitude is beneficial, exuberant systemic inflammation incites tissue damage with potentially devastating consequences. Apart from its beneficial cardiovascular and metabolic effects, cortisol exerts a significant immunoregulatory role, a major attribute being that it restrains the excessive inflammatory reaction, thereby preventing unwanted tissue damage. In this review, we will discuss the role of the HPA axis in the normal stress response and in critical illness, especially in critically ill patients with coronavirus disease 2019 (COVID-19). Finally, a chapter will be dedicated to the findings from clinical studies in critical illness and COVID-19 on the expression of the mediator of glucocorticoid actions, the glucocorticoid receptor (GCR).

Emerging and Established Histological Techniques for the Analysis of Thrombosis in COVID-19 Lungs

Coronavirus disease 2019 (COVID-19) is the potentially lethal disease that is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Patients with COVID-19 have an increased risk of thrombosis, but the role of thrombosis in the pathogenesis and progression of severe COVID-19 remains unclear. A better understanding of the contribution of thrombosis to the development and progression of COVID-19 could lead to the development of novel COVID-19 treatments. For this reason, established and emerging histological techniques have recently been used to analyze COVID-19 lungs quantitatively and visually and in two and three dimensions. The gold standard and novel state-of the-art histological techniques that have been used to assess thrombosis in COVID-19 lungs are described in this Mini Review.

A COVID-19-association-dependent categorization of death causes in 100 autopsy cases

From March through December 2020, 100 autopsies were performed (Semmelweis University, Budapest, Hungary), with chart review, of patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection demonstrated by real-time reverse-transcription polymerase chain reaction testing (mean age, 74.73 years, range 40-102 years; 50 males, mean age 71.96 years, and 50 females, mean age 77.5 years). Classified by the date of death, 21 cases were from the pandemic's "first wave" (March through July) and 79 from the "second wave" (August through December). Three mortality categories were defined by relevance of SARS-CoV-2 infection: (1) "strong" association (n=57), in which COVID-19 was primary responsible for death; (2) "contributive" association (n=27), in which a pre-existing condition independent of COVID-19 was primary responsible for death, albeit with substantial COVID-19 co-morbidity; (3) "weak" association (n=16), in which COVID-19 was minimally or not at all responsible for death. Distributions among categories differed between the first wave, in which the "contributive" association cases dominated (strong: 24%, contributive: 48%, weak: 28%), and the second wave, in which the "strong" association cases dominated (strong: 66%, contributive: 21%, weak: 13%). Charted co-morbidities included hypertension (85 %), cardiovascular diseases (71 %), diabetes (40 %), cerebrovascular diseases (31 %), chronic respiratory diseases (30 %), malignant tumors (20 %), renal diseases (19 %), diseases of the central nervous system (15 %), and liver diseases (6 %). Autopsy evaluation analyzed alterations on macroscopy as well as findings on microscopy of scanned and scored sections of formalin-fixed, paraffin-embedded tissue samples (50-80 blocks/case). Severity of histological abnormalities in the lung differed significantly between "strong" and "contributive" (p<0.0001) and between "strong" and "weak" categories (p<0.0001). Abnormalities included diffuse alveolar damage, macrophage infiltration, and vascular and alveolar fibrin aggregates (lung), with macro- and microvascular thrombi and thromboemboli (lung, kidney, liver). In conclusion, autopsies clarified in what extent COVID-19 was responsible for death, demonstrated the pathological background of clinical signs and symptoms, and identified organ alterations that led to the death. Clinicopathologic correlation, with conference discussions of severity of co-morbidities and of direct pathological signs of disease, permitted accurate categorization of cause of death and COVID-19 association as "strong," "contributive," or "weak." Lung involvement, with reduced ventilatory capacity, was the primary cause of death in the "strong" and "contributive" categories. Shifts in distribution among categories, with "strong" association between COVID-19 and death dominating in the second wave, may reflect improved clinical management of COVID-19 as expertise grew.

Rigorous Assessment of Guidelines on COVID-19-Related Thrombotic or Thromboembolic Disease: Implications for Clinical Practice of Prevention, Diagnosis, and Treatment

Purpose

Severe COVID-19 patients were prone to develop venous thromboembolism. Unfortunately, to date, there is no evidence of any effective medications for thromboembolism in COVID-19. The management of the disease relies on symptomatic and supportive treatments, giving rise to a variety of guidelines. However, the quality of methodology and clinical recommendations remains unknown.

Materials and Methods

We searched Medline, Cochrane Library, Web of Science, websites of international organizations and medical societies, and gray literature databases. Four well-trained appraisers independently evaluated the quality of eligible guidelines and extracted recommendations using well-recognized guideline appraisal tools. Furthermore, recommendations were extracted and reclassified according to a composite grading system.

Results

The search identified 23 guidelines that offered 108 recommendations. Guidelines scored average on AGREE II criteria, with Scope and Purpose and Clarity of Presentation highest. Only five (22%) guidelines provided high-quality recommendations. The existed clinical recommendations were inconsistent in terms of prophylaxis, diagnosis, and treatment of thromboembolic disease to some extent.

Conclusion

Current guidelines for COVID-19 thromboembolism are generally of low quality, and clinical recommendations on thromboembolism are principally supported by insufficient evidence. There is still an urgent need for more well-designed clinical trials as evidence to prevent adverse events and improve prognosis during COVID-19 treatment.

Neglected roles of IgG Fc-binding protein secreted from airway mucin-producing cells in protecting against SARS-CoV-2 infection

Both innate immunity and acquired immunity are involved in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. The induction of Abs that neutralize the virus has been described, and certain Abs against endemic coronaviruses may cross-react with SARS-CoV-2. Detailed mechanisms to protect against the pandemic of SARS-CoV-2 remain unresolved. We previously reported that IgG Fc-binding protein (Fcγbp), a unique, large molecular weight, and mucin-like secretory Fc receptor protein, secreted from goblet cells of human small and large intestine, mediates the transportation of serum IgG onto the mucosal surface. In this review, we show that mucous bronchial gland cells and some goblet cells are immunoreactive for Fcγbp. Fcγbp traps the cross-reactive (both neutralizing and non-neutralizing) IgG bound to the virus and can consequently eliminate the virus from the mucosal surface to decrease viral loads. Fcγbp can also suppress immune overreaction by interfering with Fc-binding by macrophages and competing with complement fixation. Fcγbp secreted from mucin-producing cells of the airway functions as an important anti-infection mucosal defense. The Fcγbp-mediated mechanism can be a key factor in explaining why SARS-CoV-2 is less infective/lethal in children, and may also be involved in the unique Ab response, recurrent infection, and effects of serum therapy and vaccination.

Molecular Profiling of Coronavirus Disease 2019 (COVID-19) Autopsies Uncovers Novel Disease Mechanisms

Current understanding of coronavirus disease 2019 (COVID-19) pathophysiology is limited by disease heterogeneity, complexity, and a paucity of studies assessing patient tissues with advanced molecular tools. Rapid autopsy tissues were evaluated using multiscale, next-generation RNA-sequencing methods (bulk, single-nuclei, and spatial transcriptomics) to provide unprecedented molecular resolution of COVID-19-induced damage. Comparison of infected/uninfected tissues revealed four major regulatory pathways. Effectors within these pathways could constitute novel therapeutic targets, including the complement receptor C3AR1, calcitonin receptor–like receptor, or decorin. Single-nuclei RNA sequencing of olfactory bulb and prefrontal cortex highlighted remarkable diversity of coronavirus receptors. Angiotensin-converting enzyme 2 was rarely expressed, whereas basigin showed diffuse expression, and alanyl aminopeptidase, membrane, was associated with vascular/mesenchymal cell types. Comparison of lung and lymph node tissues from patients with different symptoms (one had died after a month-long hospitalization with multiorgan involvement, and the other had died after a few days of respiratory symptoms) with digital spatial profiling resulted in distinct molecular phenotypes. Evaluation of COVID-19 rapid autopsy tissues with advanced molecular techniques can identify pathways and effectors, map diverse receptors at the single-cell level, and help dissect differences driving diverging clinical courses among individual patients. Extension of this approach to larger data sets will substantially advance the understanding of the mechanisms behind COVID-19 pathophysiology.

Do Elevated Levels of Inflammatory Biomarkers Predict the Risk of Occurrence of Ischemic Stroke in SARS-CoV2 ?: An Observational Study

Introduction

Stroke, a dreaded complication of SARS-CoV2, has been reported in 0.9 to 5% of SARS-CoV2 patients. There are concerns that SARS-CoV2 infection has a significant independent association with acute ischemic stroke, even in the absence of conventional cerebrovascular risk factors. Whether elevated levels of inflammatory biomarkers have predictive value in the occurrence of stroke in SARS-CoV2 is poorly understood.

Aim

To profile the characteristics of SARS-CoV2 positive patients with ischemic stroke (COVID-Stroke) and to identify the significance of elevated IBMs in the prediction of ischemic COVID-stroke.

Materials and methods

Clinical characteristics, stroke risk factors, laboratory parameters- including levels of inflammatory biomarkers, and outcome of SARS-CoV2 patients with stroke (n=60) were collected. SARS-CoV2 RT- PCR positive age, gender, and pulmonary severity matched non-stroke patients were taken as controls (n = 60). Binary multivariate logistic regression analysis was used to find the predictors of ischemic COVID-stroke.

Results

D-dimer > 441.8 ng/mL, LDH> 395U/L, ESR >19 mm/h and CRP> 0.2 mg/dL were independently found to be very strong predictors of occurrence of ischemic COVID-stroke (p < 0.001 for each). On multivariate analysis, D-dimer > 441.8 ng/mL, ESR > 19 mm/h, and RDW > 16.1% were found to be the most strong predictors of the occurrence of ischemic COVID-stroke. Conventional CVD risk factors- higher age (> 60years), presence of diabetes mellitus, and hypertension were not found to be significant predictors in multivariate analysis.

Conclusion

In SARS-CoV2 patients, D-dimer elevated beyond 441.8 ng/mL, ESR greater than 19 mm/h, and RDW widened more than 16.1% were the strongest predictors of the occurrence of ischemic stroke. This is the first study that attempts to find cut-off levels of IBMs in the prediction of ischemic COVID-stroke.

COVID-19-related neuropathology and microglial activation in elderly with and without dementia

The actual role of SARS-CoV-2 in brain damage remains controversial due to lack of matched controls. We aim to highlight to what extent is neuropathology determined by SARS-CoV-2 or by pre-existing conditions. Findings of 9 Coronavirus disease 2019 (COVID-19) cases and 6 matched non-COVID controls (mean age 79 y/o) were compared. Brains were analyzed through immunohistochemistry to detect SARS-CoV-2, lymphocytes, astrocytes, endothelium, and microglia. A semi-quantitative scoring was applied to grade microglial activation. Thal-Braak stages and the presence of small vessel disease were determined in all cases. COVID-19 cases had a relatively short clinical course (0-32 days; mean: 10 days), and did not undergo mechanical ventilation. Five patients with neurocognitive disorder had delirium. All COVID-19 cases showed non-SARS-CoV-2-specific changes including hypoxic-agonal alterations, and a variable degree of neurodegeneration and/or pre-existent SVD. The neuroinflammatory picture was dominated by ameboid CD68 positive microglia, while only scant lymphocytic presence and very few traces of SARS-CoV-2 were detected. Microglial activation in the brainstem was significantly greater in COVID-19 cases (p = 0.046). Instead, microglial hyperactivation in the frontal cortex and hippocampus was clearly associated to AD pathology (p = 0.001), regardless of the SARS-CoV-2 infection. In COVID-19 cases complicated by delirium (all with neurocognitive disorders), there was a significant enhancement of microglia in the hippocampus (p = 0.048). Although higher in cases with both Alzheimer's pathology and COVID-19, cortical neuroinflammation is not related to COVID-19 per se but mostly to pre-existing neurodegeneration. COVID-19 brains seem to manifest a boosting of innate immunity with microglial reinforcement, and adaptive immunity suppression with low number of brain lymphocytes probably related to systemic lymphopenia. Thus, no neuropathological evidence of SARS-CoV-2-specific encephalitis is detectable. The microglial hyperactivation in the brainstem, and in the hippocampus of COVID-19 patients with delirium, appears as a specific topographical phenomenon, and probably represents the neuropathological basis of the "COVID-19 encephalopathic syndrome" in the elderly.

Correlation Between Clinical and Pathological Findings of Liver Injury in 27 Patients With Lethal COVID-19 Infections in Brazil

Liver test abnormalities are frequently observed in patients with coronavirus disease 2019 (COVID‐19) and are associated with worse prognosis. However, information is limited about pathological changes in the liver in this infection, so the mechanism of liver injury is unclear. Here we describe liver histopathology and clinical correlates of 27 patients who died of COVID‐19 in Manaus, Brazil. There was a high prevalence of liver injury (elevated alanine aminotransferase and aspartate aminotransferase in 44% and 48% of patients, respectively) in these patients. Histological analysis showed sinusoidal congestion and ischemic necrosis in more than 85% of the cases, but these appeared to be secondary to systemic rather than intrahepatic thrombotic events, as only 14% and 22% of samples were positive for CD61 (marker of platelet activation) and C4d (activated complement factor), respectively. Furthermore, the extent of these vascular findings did not correlate with the extent of transaminase elevations. Steatosis was present in 63% of patients, and portal inflammation was present in 52%. In most cases, hepatocytes expressed angiotensin‐converting enzyme 2 (ACE2), which is responsible for binding and entry of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), even though this ectoenzyme was minimally expressed on hepatocytes in normal controls. However, SARS‐CoV‐2 staining was not observed. Most hepatocytes also expressed inositol 1,4,5‐triphosphate receptor 3 (ITPR3), a calcium channel that becomes expressed in acute liver injury. Conclusion: The hepatocellular injury that commonly occurs in patients with severe COVID‐19 is not due to the vascular events that contribute to pulmonary or cardiac damage. However, new expression of ACE2 and ITPR3 with concomitant inflammation and steatosis suggests that liver injury may result from inflammation, metabolic abnormalities, and perhaps direct viral injury.

Translational deep phenotyping of deaths related to the COVID-19 pandemic: protocol for a prospective observational autopsy study

INTRODUCTION

The COVID-19 pandemic is an international emergency with an extreme socioeconomic impact and a high mortality and disease burden. The COVID-19 outbreak is neither fully understood nor fully pictured. Autopsy studies can help understand the pathogenesis of COVID-19 and has already resulted in better treatment of patients. Structured and systematic autopsy of COVID-19-related deaths will enhance the mapping of pathophysiological pathways, not possible in the living. Furthermore, it provides an opportunity to envision factors translationally for the purpose of disease prevention in this and future pandemics. This is the protocol for an autopsy study that offers an umbrella for deep and diverse investigations of COVID-19-related deaths, including a systematic investigation of 'long' COVID-19 by means of extensive and systematic tissue sampling.

METHODS AND ANALYSIS

A COVID-19-specific autopsy algorithm has been created to cover all cases undergoing clinical or forensic autopsy in Denmark. The algorithm describes advanced tissue sampling and a translational analytical follow-up for deep phenotyping. The translational approach covers registry data, postmortem imaging, gross autopsy findings, microscopic organ changes, postmortem toxicology, postmortem biochemical investigation, microbiological profiling and immunological status at the time of death, and future research projects covering genetics and epigenetics on an organ level.

ETHICS AND DISSEMINATION

This study has been approved by the Regional Ethics Committee of the Region of Greater Copenhagen (No: H-20078436) and the Danish Data Protection Agency (No: 2002-54-1080). Next of kin gave informed consent to research. The study results will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

This study is purely observational and, as such, does not meet the criteria of the International Committee of Medical Journal Editors for clinical trials; thus, there is no need for registration in a database of research trials, such as clinical trials. To facilitate cooperation in research, provide transparency on case recruitment for publications to come and to avoid unnecessary duplicate work, we nevertheless wish to publish our protocol.

COVID-19 Immunobiology: Lessons Learned, New Questions Arise

There is strong evidence that COVID-19 pathophysiology is mainly driven by a spatiotemporal immune deregulation. Both its phenotypic heterogeneity, spanning from asymptomatic to severe disease/death, and its associated mortality, are dictated by and linked to maladaptive innate and adaptive immune responses against SARS-CoV-2, the etiologic factor of the disease. Deregulated interferon and cytokine responses, with the contribution of immune and cellular stress-response mediators (like cellular senescence or uncontrolled inflammatory cell death), result in innate and adaptive immune system malfunction, endothelial activation and inflammation (endothelitis), as well as immunothrombosis (with enhanced platelet activation, NET production/release and complement hyper-activation). All these factors play key roles in the development of severe COVID-19. Interestingly, another consequence of this immune deregulation, is the production of autoantibodies and the subsequent development of autoimmune phenomena observed in some COVID-19 patients with severe disease. These new aspects of the disease that are now emerging (like autoimmunity and cellular senescence), could offer us new opportunities in the field of disease prevention and treatment. Simultaneously, lessons already learned from the immunobiology of COVID-19 could offer new insights, not only for this disease, but also for a variety of chronic inflammatory responses observed in autoimmune and (auto)inflammatory diseases.

Longitudinal Assessment of Cytokine Expression and Plasminogen Activation in Hantavirus Cardiopulmonary Syndrome Reveals Immune Regulatory Dysfunction in End-Stage Disease

Pathogenic New World orthohantaviruses cause hantavirus cardiopulmonary syndrome (HCPS), a severe immunopathogenic disease in humans manifested by pulmonary edema and respiratory distress, with case fatality rates approaching 40%. High levels of inflammatory mediators are present in the lungs and systemic circulation of HCPS patients. Previous studies have provided insights into the pathophysiology of HCPS. However, the longitudinal correlations of innate and adaptive immune responses and disease outcomes remain unresolved. This study analyzed serial immune responses in 13 HCPS cases due to Sin Nombre orthohantavirus (SNV), with 11 severe cases requiring extracorporeal membrane oxygenation (ECMO) treatment and two mild cases. We measured viral load, levels of various cytokines, urokinase plasminogen activator (uPA), and plasminogen activator inhibitor-1 (PAI-1). We found significantly elevated levels of proinflammatory cytokines and PAI-1 in five end-stage cases. There was no difference between the expression of active uPA in survivors' and decedents' cases. However, total uPA in decedents' cases was significantly higher compared to survivors'. In some end-stage cases, uPA was refractory to PAI-1 inhibition as measured by zymography, where uPA and PAI-1 were strongly correlated to lymphocyte counts and IFN-γ. We also found bacterial co-infection influencing the etiology and outcome of immune response in two cases. Unsupervised Principal Component Analysis and hierarchical cluster analyses resolved separate waves of correlated immune mediators expressed in one case patient due to a sequential co-infection of bacteria and SNV. Overall, a robust proinflammatory immune response, characterized by an imbalance in T helper 17 (Th17) and regulatory T-cells (Treg) subsets, was correlated with dysregulated inflammation and mortality. Our sample size is small; however, the core differences correlated to survivors and end-stage HCPS are instructive.

Tissue-based SARS-CoV-2 detection in fatal COVID-19 infections: Sustained direct viral-induced damage is not necessary to drive disease progression

Coronavirus disease 2019 (COVID-19) is an ongoing pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although viral infection is known to trigger inflammatory processes contributing to tissue injury and organ failure, it is unclear whether direct viral damage is needed to sustain cellular injury. An understanding of pathogenic mechanisms has been handicapped by the absence of optimized methods to visualize the presence and distribution of SARS-CoV-2 in damaged tissues. We first developed a positive control cell line (Vero E6) to validate SARS-CoV-2 detection assays. We then evaluated multiple organs (lungs, kidneys, heart, liver, brain, intestines, lymph nodes, and spleen) from fourteen COVID-19 autopsy cases using immunohistochemistry (IHC) for the spike and the nucleoprotein proteins, and RNA in situ hybridization (RNA ISH) for the spike protein mRNA. Tissue detection assays were compared with quantitative polymerase chain reaction (qPCR)-based detection. SARS-CoV-2 was histologically detected in the Vero E6 positive cell line control, 1 of 14 (7%) lungs, and none (0%) of the other 59 organs. There was perfect concordance between the IHC and RNA ISH results. qPCR confirmed high viral load in the SARS-CoV-2 ISH-positive lung tissue, and absent or low viral load in all ISH-negative tissues. In patients who die of COVID-19-related organ failure, SARS-CoV-2 is largely not detectable using tissue-based assays. Even in lungs showing widespread injury, SARS-CoV-2 viral RNA or proteins were detected in only a small minority of cases. This observation supports the concept that viral infection is primarily a trigger for multiple-organ pathogenic proinflammatory responses. Direct viral tissue damage is a transient phenomenon that is generally not sustained throughout disease progression.

[Update 2021: COVID-19 from the perspective of neurology]

Neurological complications, direct affection of neuronal structures in the course of infections with SARS-CoV-2 and long-term effects ("long COVID") are evident. This article aims to summarize and evaluate the current literature on this topic.

Comparison of Blood Counts and Markers of Inflammation and Coagulation in Patients With and Without COVID-19 Presenting to the Emergency Department in Seattle, WA

Objectives

We compared complete blood count (CBC) with differential and markers of inflammation and coagulation in patients with and without coronavirus disease 2019 (COVID-19) presenting to emergency departments in Seattle, WA.

Methods

We reviewed laboratory values for 1 week following each COVID-19 test for adult patients who received a standard severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcription polymerase chain reaction (RT-PCR) test before April 13, 2020. Results were compared by COVID-19 status and clinical course.

Results

In total 1,027 patients met inclusion criteria. Patients with COVID-19 (n = 155) had lower leukocytes (P < .0001), lymphocytes (P < .0001), platelets (P < .0001), and higher hemoglobin (P = .0140) than those without, but absolute differences were small. Serum albumin was lower in patients with COVID-19 (P < .0001) and serum albumin, neutrophil to lymphocyte ratio (NLR), and red cell distribution width (RDW) were each associated with disease severity. NLR did not differ between patients with COVID-19 and those without (P = .8012).

Conclusions

Patients with COVID-19 had modestly lower leukocyte, lymphocyte, and platelet counts and higher hemoglobin values than patients without COVID-19. The NLR, serum albumin, and RDW varied with disease severity, regardless of COVID-19 status.

Thromboembolic Complications in Covid-19: From Clinical Scenario to Laboratory Evidence

SARS-Cov-2 infection, a pandemic disease since March 2020, is associated with a high percentage of cardiovascular complications mainly of a thromboembolic (TE) nature. Although clinical patterns have been described for the assessment of patients with increased risk, many TE complications occur in patients with apparently moderate risk. Notably, a recent statement from the European Society of Cardiology (ESC) atherosclerosis and vascular biology working group pointed out the key role of vascular endothelium for the recruitment of inflammatory and thrombotic pathways responsible for both disseminated intravascular coagulation and cardiovascular complications. Therefore, a better understanding of the pathophysiological process linking infection to increased TE risk is needed in order to understand the pathways of this dangerous liaison and possibly interrupt it with appropriate treatment. In this review, we describe the histological lesions and the related blood coagulation mechanisms involved in COVID-19, we define the laboratory parameters and clinical risk factors associated with TE events, and propose a prophylactic anticoagulation treatment in relation to the risk category. Finally, we highlight the concept that a solid risk assessment based on prospective multi-center data would be the challenge for a more precise risk stratification and more appropriate treatment.

Association of acute disseminated encephalomyelitis (ADEM) and COVID-19 in a pediatric patient

Cases of acute disseminated encephalomyelitis (ADEM) and its hyperacute form, acute hemorrhagic leukoencephalitis (AHLE), have been reported in coronavirus disease 2019 (COVID-19) patients as rare, but most severe neurological complications. However, histopathologic evaluations of ADEM/AHLE pathology in COVID patients are extremely limited, so far having only been reported in a few adult autopsy cases. Here we compare the findings with an ADEM-like pathology in a pediatric patient taken through a biopsy procedure. Understanding the neuropathology may shed informative light on the autoimmune process affecting COVID-19 patients and provide critical information to guide the clinical management.