An autopsy study of the spectrum of severe COVID-19 in children: From SARS to different phenotypes of MIS-C

Pathologic Analysis of Twenty-one Appendices From Children With Multisystem Inflammatory Syndrome Compared to Specimens of Acute Appendicitis: A Cross-sectional Study

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) is a rare, severe complication of coronavirus disease 2019, commonly involving the gastrointestinal tract. Some children with MIS-C undergo appendectomy before the final diagnosis. There are several hypotheses explaining the pathomechanism of MIS-C, including the central role of the viral antigen persistence in the gut, associated with lymphocyte exhaustion. We aimed to examine appendectomy specimens from MIS-C patients and assess their pathologic features, as well as the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens.

METHODS

In this cross-sectional study we included 21 children with MIS-C who underwent appendectomy. The control group included 21 sex- and age-matched children with acute appendicitis (AA) unrelated to SARS-CoV-2 infection. Histologic evaluation of appendiceal specimens included hematoxylin and eosin staining and immunohistochemical identification of lymphocyte subpopulations, programmed cell death protein-1 (PD-1) and SARS-CoV-2 nucleocapsid antigen.

RESULTS

Appendices of MIS-C patients lacked neutrophilic infiltrate of muscularis propria typical for AA (14% vs. 95%, P < 0.001). The proportion of CD20+ to CD5+ cells was higher in patients with MIS-C (P = 0.04), as was the proportion of CD4+ to CD8+ (P < 0.001). We found no proof of SARS-CoV-2 antigen presence, nor lymphocyte exhaustion, in the appendices of MIS-C patients.

CONCLUSIONS

The appendiceal muscularis of patients with MIS-C lack edema and neutrophilic infiltration typical for AA. SARS-CoV-2 antigens and PD-1 are absent in the appendices of children with MIS-C. These findings argue against the central role of SARS-CoV-2 persistence in the gut and lymphocyte exhaustion as the major triggers of MIS-C.

Severe pediatric COVID-19: a review from the clinical and immunopathophysiological perspectives

BACKGROUND

Coronavirus disease 2019 (COVID-19) tends to have mild presentations in children. However, severe and critical cases do arise in the pediatric population with debilitating systemic impacts and can be fatal at times, meriting further attention from clinicians. Meanwhile, the intricate interactions between the pathogen virulence factors and host defense mechanisms are believed to play indispensable roles in severe COVID-19 pathophysiology but remain incompletely understood.

DATA SOURCES

A comprehensive literature review was conducted for pertinent publications by reviewers independently using the PubMed, Embase, and Wanfang databases. Searched keywords included "COVID-19 in children", "severe pediatric COVID-19", and "critical illness in children with COVID-19".

RESULTS

Risks of developing severe COVID-19 in children escalate with increasing numbers of co-morbidities and an unvaccinated status. Acute respiratory distress stress and necrotizing pneumonia are prominent pulmonary manifestations, while various forms of cardiovascular and neurological involvement may also be seen. Multiple immunological processes are implicated in the host response to COVID-19 including the type I interferon and inflammasome pathways, whose dysregulation in severe and critical diseases translates into adverse clinical manifestations. Multisystem inflammatory syndrome in children (MIS-C), a potentially life-threatening immune-mediated condition chronologically associated with COVID-19 exposure, denotes another scientific and clinical conundrum that exemplifies the complexity of pediatric immunity. Despite the considerable dissimilarities between the pediatric and adult immune systems, clinical trials dedicated to children are lacking and current management recommendations are largely adapted from adult guidelines.

CONCLUSIONS

Severe pediatric COVID-19 can affect multiple organ systems. The dysregulated immune pathways in severe COVID-19 shape the disease course, epitomize the vast functional diversity of the pediatric immune system and highlight the immunophenotypical differences between children and adults. Consequently, further research may be warranted to adequately address them in pediatric-specific clinical practice guidelines.

Epidemiology of COVID-19 in Infants in the United States: Incidence, Severity, Fatality, and Variants of Concern

BACKGROUND

The clinical spectrum of infant COVID-19 ranges from asymptomatic infection to life-threatening illness, yet epidemiologic surveillance has been limited for infants.

METHODS

Using COVID-19 case data (restricted to reporting states) and national mortality data, we calculated incidence, hospitalization, mortality and case fatality rates through March 2022.

RESULTS

Reported incidence of COVID-19 was 64.1 new cases per 1000 infant years (95% CI: 63.3-64.9). We estimated that 594,012 infants tested positive for COVID-19 nationwide by March 31, 2022. Viral variant comparisons revealed that incidence was 7× higher during the Omicron (January-March 2022) versus the pre-Delta period (June 2020-May 2021). The cumulative case hospitalization rate was 4.1% (95% CI: 4.0%-4.3%). For every 74 hospitalized infants, one infant death occurred, but overall COVID-19-related infant case fatality was low, with 7.0 deaths per 10,000 cases (95% CI: 5.6-8.7). Nationwide, 333 COVID-19 infant deaths were reported. Only 13 infant deaths (3.9%) were the result of usually lethal congenital anomalies. The majority of infant decedents were non-White (28.2% Black, 26.1% Hispanic, 8.1% Asian, Indigenous or multiracial).

CONCLUSIONS

More than half a million US infants contracted COVID-19 by March 2022. Longitudinal assessment of long-term infant SARS-CoV-2 infection sequelae remains a critical research gap. Extremely low infant vaccination rates (<5%), waning adult immunity and continued viral exposure risks suggest that infant COVID-19 will remain a persistent public health problem. Our study underscores the need to increase vaccination rates for mothers and infants, decrease viral exposure risks and improve health equity.

Younger age is associated with cardiovascular pathological phenotype of severe COVID-19 at autopsy

Introduction

COVID-19 affects patients of all ages. There are few autopsy studies focusing on the younger population. We assessed an autopsy cohort aiming to understand how age influences pathological outcomes in fatal COVID-19.

Methods

This study included autopsied patients, aged 6 months to 83 years, with confirmed COVID-19 in 2020-2021. We collected tissue samples from deceased patients using a minimally invasive autopsy protocol and assessed pathological data following a systematic approach.

Results

Eighty-six patients were included, with a median age of 55 years (IQR 32.3-66.0). We showed that age was significantly lower in patients with acute heart ischemia (p = 0.004), myocarditis (p = 0.03) and lung angiomatosis (p < 0.001), and significantly higher in patients with exudative diffuse alveolar damage (p = 0.02), proliferative diffuse alveolar damage (p < 0.001), lung squamous metaplasia (p = 0.003) and lung viral atypia (p = 0.03), compared to patients without those findings. We stratified patients by their age and showed that cardiovascular findings were more prevalent in children and young adults. We performed principal component analysis and cluster of pathological variables, and showed that cardiovascular variables clustered and covariated together, and separated from pulmonary variables.

Conclusion

We showed that age modulates pathological outcomes in fatal COVID-19. Younger age is associated with cardiovascular abnormalities and older age with pulmonary findings.

The neurobiology of SARS-CoV-2 infection

Worldwide, over 694 million people have been infected with SARS-CoV-2, with an estimated 55-60% of those infected developing COVID-19. Since the beginning of the pandemic in December 2019, different variants of concern have appeared and continue to occur. With the emergence of different variants, an increasing rate of vaccination and previous infections, the acute neurological symptomatology of COVID-19 changed. Moreover, 10-45% of individuals with a history of SARS-CoV-2 infection experience symptoms even 3 months after disease onset, a condition that has been defined as 'post-COVID-19' by the World Health Organization and that occurs independently of the virus variant. The pathomechanisms of COVID-19-related neurological complaints have become clearer during the past 3 years. To date, there is no overt - that is, truly convincing - evidence for SARS-CoV-2 particles in the brain. In this Review, we put special emphasis on discussing the  methodological difficulties of viral detection in CNS tissue and discuss immune-based (systemic and central) effects contributing to COVID-19-related CNS affection. We sequentially review the reported changes to CNS cells in COVID-19, starting with the blood-brain barrier and blood-cerebrospinal fluid barrier - as systemic factors from the periphery appear to primarily influence barriers and conduits - before we describe changes in brain parenchymal cells, including microglia, astrocytes, neurons and oligodendrocytes as well as cerebral lymphocytes. These findings are critical to understanding CNS affection in acute COVID-19 and post-COVID-19 in order to translate these findings into treatment options, which are still very limited.

COVID-19 among infants: key clinical features and remaining controversies

Infants aged <1 year represent a seemingly more susceptible pediatric subset for infections. Despite this, coronavirus disease 2019 (COVID-19) infection has not been proven as more serious in this age group (outside the very early neonatal period) than in others. Indeed, a considerable number of asymptomatic infections have been recorded, and the symptoms and morbidity associated with COVID- 19 differ minimally from those of other respiratory viral infections. Whether due to an abundance of caution or truly reduced susceptibility, infections in infants have not raised the same profile as those in other age groups. In addition to direct severe acute respiratory syndrome coronavirus 2 diagnostic tests, laboratory markers that differentiate COVID-19 from other viral infections lack specificity in infants. Gastrointestinal presentations are common, and the neurological complications of infection mirror those of other respiratory viral infections. There have been relatively few reports of infant deaths. Under appropriate precautions, breastfeeding in the context of maternal infections has been associated with tangible but infrequent complications. Vaccination during pregnancy provides protection against infection in infants, at least in the early months of life. Multi-inflammatory syndrome in children and multi-inflammatory syndrome in neonates are commonly cited as variants of COVID-19; however, their clinical definitions remain controversial. Similarly, reliable definitions of long COVID in the infant group are controversial. This narrative review examines the key clinical and laboratory features of COVID-19 in infants and identifies several areas of science awaiting further clarification.

Cardiovascular Manifestations of Multisystem Inflammatory Syndrome in Children: A Single-Center Bulgarian Study

Background and objectives: Multisystem inflammatory syndrome in children (MIS-C) poses challenges to the healthcare system, especially with frequent heart involvement. The current retrospective observational study aims to summarize the type and degree of cardiovascular involvement in children with MISC and to find possible associations between laboratory, inflammatory, and imaging abnormalities and the predominant clinical phenotype using a cluster analysis. Material and methods: We present a retrospective observational single-center study including 51 children meeting the MIS-C criteria. Results: Fifty-three percent of subjects presented with at least one sign of cardiovascular involvement (i.e., arterial hypotension, heart failure, pericardial effusion, myocardial dysfunction, pericarditis without effusion, myocarditis, coronaritis, palpitations, and ECG abnormalities). Acute pericarditis was found in 30/41 of the children (73%) assessed using imaging: 14/30 (46.7%) with small pericardial effusion and 16/30 (53.3%) without pericardial effusion. The levels of CRP were significantly elevated in the children with pericarditis (21.6 ± 13 mg/dL vs. 13.9 ± 11 mg/dL, p = 0.035), and the serum levels of IL-6 were higher in the children with small pericardial effusion compared to those without (191 ± 53 ng/L vs. 88 ± 27 ng/L, p = 0.041). Pericarditis with detectable pericardial effusion was significantly more frequent in the female vs. male subjects, 72% vs. 30% (p = 0.007). The hierarchical clustering analysis showed two clusters: Cluster 1 includes the children without cardiovascular symptoms, and Cluster 2 generalizes the MIS-C children with mild and severe cardiovascular involvement, combining pericarditis, myocarditis, heart failure, and low blood pressure. Also, subjects from Cluster 2 displayed significantly elevated levels of fibrinogen (5.7 ± 0.3 vs. 4.6 ± 0.3, p = 0.03) and IL-6 (158 ± 36 ng/mL vs. 66 ± 22 ng/mL, p = 0.032), inflammatory markers suggestive of a cytokine storm. Conclusions: Our results confirm that children with oligosymptomatic MIS-C or those suspected of long COVID-19 should be screened for possible cardiological involvement.

Viral persistence in children infected with SARS-CoV-2: current evidence and future research strategies

In this Personal View, we discuss current knowledge on SARS-CoV-2 RNA or antigen persistence in children infected with SARS-CoV-2. Based on the evidence that the virus can persist in adults, we have done a literature review and analysed studies that looked for SARS-CoV-2 RNA or antigens in children undergoing autopsy, biopsy, or surgery for either death from COVID-19 or multisystem inflammatory syndrome, or assessments for long COVID-19 or other conditions. Our analysis suggests that in children, independent from disease severity, SARS-CoV-2 can spread systemically and persist for weeks to months. We discuss what is known about the biological effects of viral persistence for other viral infections and highlight new scenarios for clinical, pharmacological, and basic research exploration. Such an approach will improve the understanding and management of post-viral syndromes.

Analysis of Plasmablasts From Children With Kawasaki Disease Reveals Evidence of a Convergent Antibody Response to a Specific Protein Epitope

BACKGROUND

Kawasaki disease (KD) is a febrile illness of young childhood that can result in coronary artery aneurysms and death. Coronavirus disease 2019 (COVID-19) mitigation strategies resulted in a marked decrease in KD cases worldwide, supporting a transmissible respiratory agent as the cause. We previously reported a peptide epitope recognized by monoclonal antibodies (MAbs) derived from clonally expanded peripheral blood plasmablasts from 3 of 11 KD children, suggesting a common disease trigger in a subset of patients with KD.

METHODS

We performed amino acid substitution scans to develop modified peptides with improved recognition by KD MAbs. We prepared additional MAbs from KD peripheral blood plasmablasts and assessed MAb characteristics that were associated with binding to the modified peptides.

RESULTS

We report a modified peptide epitope that is recognized by 20 MAbs from 11 of 12 KD patients. These MAbs predominantly use heavy chain VH3-74; two-thirds of VH3-74 plasmablasts from these patients recognize the epitope. The MAbs were nonidentical between patients but share a common complementarity-determining region 3 (CDR3) motif.

CONCLUSIONS

These results demonstrate a convergent VH3-74 plasmablast response to a specific protein antigen in children with KD, supporting one predominant causative agent in the etiopathogenesis of the illness.

Endothelial Cell Response in Kawasaki Disease and Multisystem Inflammatory Syndrome in Children

Although Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) share some clinical manifestations, their cardiovascular outcomes are different, and this may be reflected at the level of the endothelial cell (EC). We performed RNA-seq on cultured ECs incubated with pre-treatment sera from KD (n = 5), MIS-C (n = 7), and healthy controls (n = 3). We conducted a weighted gene co-expression network analysis (WGCNA) using 935 transcripts differentially expressed between MIS-C and KD using relaxed filtering (unadjusted p < 0.05, >1.1-fold difference). We found seven gene modules in MIS-C, annotated as an increased TNFα/NFκB pathway, decreased EC homeostasis, anti-inflammation and immune response, translation, and glucocorticoid responsive genes and endothelial-mesenchymal transition (EndoMT). To further understand the difference in the EC response between MIS-C and KD, stringent filtering was applied to identify 41 differentially expressed genes (DEGs) between MIS-C and KD (adjusted p < 0.05, >2-fold-difference). Again, in MIS-C, NFκB pathway genes, including nine pro-survival genes, were upregulated. The expression levels were higher in the genes influencing autophagy (UBD, EBI3, and SQSTM1). Other DEGs also supported the finding by WGCNA. Compared to KD, ECs in MIS-C had increased pro-survival transcripts but reduced transcripts related to EndoMT and EC homeostasis. These differences in the EC response may influence the different cardiovascular outcomes in these two diseases.

Severe SARS-CoV-2 and respiratory syncytial virus co-infection in two children

The Coronavirus Disease 2019 (COVID-19) caused by a novel coronavirus (SARS-CoV-2) affects mainly older adults. Those with comorbidities are at a higher risk of severe disease and even death. The symptomatic infection rate of children is lower, manifestations are milder, and severe forms are scarce. We present here two children with severe COVID-19 and a respiratory syncytial virus, with the goal of emphasizing the possibility of coinfection with a severe course and a different result. The microbiological diagnosis was made using multiplex PCR. This assay not only provided an early and accurate diagnosis but also aided in the implementation of contact precautions. Further research should be done to determine the influence of coinfection on the clinical course and outcome of pediatric patients.

Case report: Distinct neurologic manifestation and cytokine profile of a child with COVID-19-associated acute fulminant encephalitis

The neurologic manifestations of coronavirus disease 2019 (COVID-19) may range from mild symptoms such as headache or confusion to profound encephalopathy with variable outcomes and sequelae. Here, we reported a case of fatal COVID-19-associated encephalitis with acute fulminant cerebral edema, presenting first with visual hallucination and then a rapid progression into comatose status in a few hours. Serial brain computed tomography depicted cerebral edematous changes from bilateral ventral temporal lobe to the whole brain leading to brain herniation. Multiple cytokines in serum and cerebrospinal fluid (CSF) were increased, with a more prominent rise in the CSF. Therefore, we postulated a hypothesis regarding the mechanism of this fulminant encephalitis that the SARS-CoV-2 virus attacked ventral temporal lobes initially, triggered a severe cytokine storm, and then led to subsequent disruption of the blood-brain barrier, diffuse brain edema, and brain herniation. The trend of cytokine profiles over time may aid in diagnosing and evaluating the severity and prognosis of COVID-19-associated encephalitis.

Emerging Insights Into the Pathophysiology of Multisystem Inflammatory Syndrome Associated With COVID-19 in Children

Multisystem inflammatory syndrome in children (MIS-C) has emerged as a rare delayed hyperinflammatory response to SARS-CoV-2 infection and causes severe morbidity in the pediatric age group. Although MIS-C shares many clinical similarities to Kawasaki disease (KD), important differences in epidemiologic, clinical, immunologic, and potentially genetic factors exist and suggest potential differences in pathophysiology and points to be explored and explained. Epidemiologic features include male predominance, peak age of 6 to12 years, and specific racial or ethnicity predilections. MIS-C is characterized by fever, prominent gastrointestinal symptoms, mucocutaneous manifestations, respiratory symptoms, and neurologic complaints, and patients often present with shock. Cardiac complications are frequent and include ventricular dysfunction, valvular regurgitation, pericardial effusion, coronary artery dilation and aneurysms, conduction abnormalities, and arrhythmias. Emerging evidence regarding potential immunologic mechanisms suggest that an exaggerated T-cell response to a superantigen on the SARS-CoV-2 spike glycoprotein-as well as the formation of autoantibodies against cardiovascular, gastrointestinal, and endothelial antigens-are major contributors to the inflammatory milieu of MIS-C. Further studies are needed to determine both shared and distinct immunologic pathway(s) that underlie the pathogenesis of MIS-C vs both acute SARS-CoV-2 infection and KD. There is evidence to suggest that the rare risk of more benign mRNA vaccine-associated myopericarditis is outweighed by a reduced risk of more severe MIS-C. In the current review, we synthesize the published literature to describe associated factors and potential mechanisms regarding an increased risk of MIS-C and cardiac complications, provide insights into the underlying immunologic pathophysiology, and define similarities and differences with KD.

Multi-Inflammatory Syndrome in Children (MIS-C) in 2023: Is It Time to Forget about It?

Multisystem inflammatory syndrome in children (MIS-C) is defined as a clinically serious condition requiring hospitalization involving fever, multi-system organ dysfunction, and an increase in inflammatory biomarkers. The syndrome was originally described as a post-infectious complication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which usually causes COVID-19. During the COVID-19 pandemic, not only did the virus undergo mutations but vaccines against SARS-CoV-2 were also developed. Both these conditions led to a decrease in the incidence of MIS-C. This narrative review summarizes the recent updates for MIS-C, particularly regarding the change in incidence, the link between the SARS-CoV-2 vaccine and MIS-C, and new updates of MIS-C treatments.

What Can We Still Learn from Brain Autopsies in COVID-19?

Neuropathological findings have been published from ∼900 patients who died with or from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, representing less than 0.01% of the close to 6.4 million deaths reported to the World Health Organization 2 years into the coronavirus disease 2019 (COVID-19) pandemic. In this review, we extend our prior work summarizing COVID-19 neuropathology by including information on published autopsies up to June 2022, and neuropathological studies in children, COVID-19 variants, secondary brain infections, ex vivo brain imaging, and autopsies performed in countries outside of the United States or Europe. We also summarize research studies that investigate mechanisms of neuropathogenesis in nonhuman primates and other models. While a pattern of cerebrovascular pathology and microglial-predominant inflammation remains the primary COVID-19-associated neuropathological finding, there is no singular understanding of the mechanisms that underlie neurological symptoms in acute COVID-19 or the post-acute COVID-19 condition. Thus, it is paramount that we incorporate microscopic and molecular findings from brain tissue into what we know about the clinical disease so that we attain best practice guidance and direct research priorities for the study of the neurological morbidity of COVID-19.

The Spectrum of Digestive Tract Histopathologic Findings in the Setting of Severe Acute Respiratory Syndrome Coronavirus-2 Infection: What Pathologists Need to Know

Although the novel severe acute respiratory syndrome coronavirus-2 is known primarily to affect the respiratory system, current evidence supports its capability to infect and induce gastrointestinal tract injury. Data describing the histopathologic alterations of the digestive system in patients infected with severe acute respiratory syndrome coronavirus-2 are becoming more detailed, as the number of studies is increasing and the quality of our insight into the infection and the histopathologic findings is improving. This review highlights the range of pathologic findings that could be observed in gastrointestinal specimens from patients infected with coronavirus disease 2019 and the potential underlying pathogenetic mechanisms of this disease.

Immunology of Multisystem Inflammatory Syndrome after COVID-19 in Children: A Review of the Current Evidence

Immune responses following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in children are still under investigation. Even though coronavirus disease 2019 (COVID-19) is usually mild in the pediatric population, some children exhibit severe clinical manifestations, require hospitalization, or develop the most severe condition: a multisystem inflammatory syndrome in children (MIS-C) associated with SARS-CoV-2 infection. The activated innate, humoral and T-cell-mediated immunological pathways that lead certain pediatric populations to present with MIS-C or remain asymptomatic after SARS-CoV-2 infection are yet to be established. This review focuses on the immunological aspects of MIS-C with respect to innate, humoral, and cellular immunity. In addition, presents the role of the SARS-CoV-2 Spike protein as a superantigen in the pathophysiological mechanisms, discusses the great heterogeneity among the immunological studies in the pediatric population, and highlights possible reasons why some children with a certain genetic background present with MIS-C.

A Systematic Review of Lung Autopsy Findings in Elderly Patients after SARS-CoV-2 Infection

Although COVID-19 may cause various and multiorgan diseases, few research studies have examined the postmortem pathological findings of SARS-CoV-2-infected individuals who died. Active autopsy results may be crucial for understanding how COVID-19 infection operates and preventing severe effects. In contrast to younger persons, however, the patient's age, lifestyle, and concomitant comorbidities might alter the morpho-pathological aspects of the damaged lungs. Through a systematic analysis of the available literature until December 2022, we aimed to provide a thorough picture of the histopathological characteristics of the lungs in patients older than 70 years who died of COVID-19. A thorough search was conducted on three electronic databases (PubMed, Scopus, and Web of Science), including 18 studies and a total of 478 autopsies performed. It was observed that the average age of patients was 75.6 years, of which 65.4% were men. COPD was identified in an average of 16.7% of all patients. Autopsy findings indicated significantly heavier lungs, with an average weight of the right lung of 1103 g, while the left lung mass had an average weight of 848 g. Diffuse alveolar damage was a main finding in 67.2% of all autopsies, while pulmonary edema had a prevalence of between 50% and 70%. Thrombosis was also a significant finding, while some studies described focal and extensive pulmonary infarctions in 72.7% of elderly patients. Pneumonia and bronchopneumonia were observed, with a prevalence ranging from 47.6% to 89.5%. Other important findings described in less detail comprise hyaline membranes, the proliferation of pneumocytes and fibroblasts, extensive suppurative bronchopneumonic infiltrates, intra-alveolar edema, thickened alveolar septa, desquamation of pneumocytes, alveolar infiltrates, multinucleated giant cells, and intranuclear inclusion bodies. These findings should be corroborated with children's and adults' autopsies. Postmortem examination as a technique for studying the microscopic and macroscopic features of the lungs might lead to a better knowledge of COVID-19 pathogenesis, diagnosis, and treatment, hence enhancing elderly patient care.

Immune and non-immune mechanisms that determine vasculitis and coronary artery aneurysm topography in Kawasaki disease and MIS-C

The overlap between multisystem inflammatory syndrome in children (MIS-C) and Kawasaki disease (KD) including coronary artery aneurysms (CAA) and broadly shared gastrointestinal and mucocutaneous disease is poorly defined. In this perspective, we highlight common age-related extravascular epicardial microanatomical and immunological factors that might culminate in CAA expression in both MIS-C and KD. Specifically, the coronary vasa vasorum originates outside the major coronary arteries. Widespread inflammation in the epicardial interstitial compartment in shared between KD and MIS-C. Age-related changes in the neonatal and immature coronary vasculature including the impact of coronary artery biomechanical factors including coronary vessel calibre, age-related vessel distensibility, flow, and vessel neurovascular innervation may explain the decreasing CAA frequency from neonates to older children and the virtual absence of CAA in young adults with the MIS-C phenotype. Other KD and MIS-C features including mucocutaneous disease with keratinocyte-related immunopathology corroborate that disease phenotypes are centrally influenced by inflammation originating outside vessel walls but a potential role for primary coronary artery vascular wall inflammation cannot be excluded. Hence, common extravascular originating tissue-specific responses to aetiologically diverse triggers including superantigens may lead to widespread interstitial tissue inflammation characteristically manifesting as CAA development, especially in younger subjects. Given that CAA is virtually absent in adults, further studies are needed to ascertain whether epicardial interstitial inflammation may impact on both coronary artery physiology and cardiac conduction tissue and contribute to cardiovascular disease- a hitherto unappreciated consideration.

Pathogenesis, immunology, and immune-targeted management of the multisystem inflammatory syndrome in children (MIS-C) or pediatric inflammatory multisystem syndrome (PIMS): EAACI Position Paper

Multisystem inflammatory syndrome in children (MIS-C) is a rare, but severe complication of coronavirus disease 2019 (COVID-19). It develops approximately 4 weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and involves hyperinflammation with multisystem injury, commonly progressing to shock. The exact pathomechanism of MIS-C is not known, but immunological dysregulation leading to cytokine storm plays a central role. In response to the emergence of MIS-C, the European Academy of Allergy and Clinical Immunology (EAACI) established a task force (TF) within the Immunology Section in May 2021. With the use of an online Delphi process, TF formulated clinical statements regarding immunological background of MIS-C, diagnosis, treatment, follow-up, and the role of COVID-19 vaccinations. MIS-C case definition is broad, and diagnosis is made based on clinical presentation. The immunological mechanism leading to MIS-C is unclear and depends on activating multiple pathways leading to hyperinflammation. Current management of MIS-C relies on supportive care in combination with immunosuppressive and/or immunomodulatory agents. The most frequently used agents are systemic steroids and intravenous immunoglobulin. Despite good overall short-term outcome, MIS-C patients should be followed-up at regular intervals after discharge, focusing on cardiac disease, organ damage, and inflammatory activity. COVID-19 vaccination is a safe and effective measure to prevent MIS-C. In anticipation of further research, we propose a convenient and clinically practical algorithm for managing MIS-C developed by the Immunology Section of the EAACI.

Adult and childhood vasculitis

Vasculitis refers to heterogeneous clinicopathologic disorders that share the histopathology of inflammation of blood vessels. Unrecognized and therefore untreated, vasculitis of the nervous system leads to pervasive injury and disability, making this a disorder of paramount importance to all clinicians. There has been remarkable progress in the pathogenesis, diagnosis, and treatment of primary CNS and PNS vasculitides, predicated on achievement in primary systemic forms. Primary neurological vasculitides can be diagnosed with assurance after intensive evaluation that incudes tissue confirmation whenever possible. Clinicians must choose from among the available immune modulating, suppressive, and targeted immunotherapies to induce and maintain remission status and prevent relapse, unfortunately without the benefit of RCTs, and tempered by the recognition of anticipated medication side effects. It may be said that efforts to define a disease are attempts to understand the very concept of the disease. This has been especially evident in systemic and neurological disorders associated with vasculitis. For the past 100 years, since the first description of granulomatous angiitis of the brain, the CNS vasculitides have captured the attention of generations of clinical investigators around the globe to reach a better understanding of vasculitides involving the central and peripheral nervous system. Since that time it has become increasingly evident that this will necessitate an international collaborative effort.

Involvement of NLRP3 Inflammasome in SARS-Cov-2-Induced Multiorgan Dysfunction in Patients with COVID-19: A Review of Molecular Mechanisms

Nucleotide-binding domain and leucine-rich repeat protein- 3 (NLRP3) inflammasome is a critical component of the innate immune system. The inflammasome activation is correlated with the COVID- 19 severity. Furthermore, the underlying conditions are accompanied by hyperactivation of NLRP3 inflammasome and poor outcomes. Herein, we presented the involvement of NLRP3 inflammasome in the pathogenies of SARS-CoV-2-induced multiorgan dysfunction and potential therapeutics. Overexpression of NLRP3 inflammasome components and subsequently increased levels of cytokines following viral infection leads to the cytokine storm and indirectly affects the organ functions. Besides, invading host cells via SARS-CoV-2 further activates the NLRP3 inflammasome and induces pyroptosis in immune cells, resulting in the secretion of higher levels of proinflammatory cytokines into the extracellular matrix. These events continued by induction of fibrosis and organ dysfunction following infection with SARS-CoV-2 in critically ill patients. This condition can be observed in individuals with comorbidities (e.g., diabetes, obesity, etc.) due to a primed state of immunity, which can cause severe disease or death in this population. Therefore, understanding the mechanisms underlying host-SARS-CoV-2 interaction may help to clarify the pathophysiology of SARS-CoV-2- induced multiorgan dysfunction and introduce potential therapeutic strategies.

Pediatric neuropsychiatric disorders with motor and nonmotor phenomena

The concept of pediatric autoimmune neuropsychiatric disorders associated with group A beta-hemolytic streptococcus (PANDAS) has become seminal since first introduced more than two decades ago. At the time of this writing, most neurologists, pediatricians, psychiatrists, and general pediatricians will probably have heard of this association or treated an affected child with PANDAS. The concept of an acute-onset, and typically self-limited, postinfectious autoimmune neuropsychiatric disorder resembling PANDAS manifesting vocal and motor tics and obsessive-compulsive disorder has broadened to other putative microbes and related endogenous and exogenous disease triggers. These disorders with common features of hypometabolism in the medial temporal lobe and hippocampus in brain 18fluorodeoxyglucose positron emission tomography fused to magnetic resonance imaging (FDG PET-MRI), form a spectrum: with the neuropsychiatric disorder Tourette syndrome and PANDAS with its well-defined etiopathogenesis at one end, and pediatric abrupt-onset neuropsychiatric syndrome (PANS), alone or associated with specific bacterial and viral pathogens, at the other end. The designation of PANS in the absence of a specific trigger, as an exclusionary diagnosis, reflects the current problem in nosology.

Autopsy Findings and Inflammatory Markers in SARS-CoV-2: A Single-Center Experience

Purpose

The systemic inflammatory response related to COVID-19 can be easily investigated in living patients. Unfortunately, not every biomarker is suitable for postmortem analysis since several factors may interfere. The aim of this study was to summarize key histopathological findings within each organ system due to COVID-19 and to assess if serological inexpensive and widely available biomarkers such as CRP, IL-6, fibrinogen and d-Dimers, associated with adverse outcomes in COVID-19, can be implemented in a post-mortem assessment.

Patients and Methods

A total of 60 subjects divided in 2 groups were included. All subjects died outside a hospital setting and therefore did not receive specific or symptomatic therapies that could have modulated the inflammatory response. The first group included 45 subjects in which mandatory autopsy was performed in order to establish the cause of death and macroscopic examination of the lungs was highly suggestive of SARS-CoV-2 infection. As controls (Group 2), 20 subjects who died from polytrauma in high velocity car accidents and suicide were selected. Bronchial fluids collected during the autopsy procedure were used for the RT-PCR diagnosis of SARS-CoV-2 and serum samples were sent for analysis of IL-6, CRP, d-Dimers and fibrinogen.

Results

Compared with the control group, the subjects of the COVID-19 group were older (59±19.5 vs.38±19.15 years, p=0.0002) and had more underlying comorbidities such as hypertension (60% vs 35%, p=0.06) or were overweight (53.3% vs 30%, p=0.08). The levels of CRP, IL-6, fibrinogen and d-Dimers in postmortem plasma samples were significantly higher in COVID-19 subjects than in control group (p< 0.0001). Moreover, the level of IL-6 was significantly higher in overweight patients (r=0.52, P<0.001). In all COVID-19 subjects, the histological examination revealed features corresponding to the exudative and/or proliferative phases of diffuse alveolar damage. Large pulmonary emboli were observed in 7 cases. Gross cardiac enlargement with left ventricular hypertrophy was observed in 19 cases. The most frequent pathological finding of the central nervous system was acute/early-subacute infarction.

Conclusion

Due to the complexity of the inflammatory response, we postulate that a combination of biomarkers, rather than a single laboratory parameter, might be more effective in obtaining a reliable postmortem COVID-19 diagnosis.

Neutrophil profiles of pediatric COVID-19 and multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is a delayed-onset, COVID-19-related hyperinflammatory illness characterized by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigenemia, cytokine storm, and immune dysregulation. In severe COVID-19, neutrophil activation is central to hyperinflammatory complications, yet the role of neutrophils in MIS-C is undefined. Here, we collect blood from 152 children: 31 cases of MIS-C, 43 cases of acute pediatric COVID-19, and 78 pediatric controls. We find that MIS-C neutrophils display a granulocytic myeloid-derived suppressor cell (G-MDSC) signature with highly altered metabolism that is distinct from the neutrophil interferon-stimulated gene (ISG) response we observe in pediatric COVID-19. Moreover, we observe extensive spontaneous neutrophil extracellular trap (NET) formation in MIS-C, and we identify neutrophil activation and degranulation signatures. Mechanistically, we determine that SARS-CoV-2 immune complexes are sufficient to trigger NETosis. Our findings suggest that hyperinflammatory presentation during MIS-C could be mechanistically linked to persistent SARS-CoV-2 antigenemia, driven by uncontrolled neutrophil activation and NET release in the vasculature.

The des-Arg9-bradykinin/B1R axis: Hepatic damage in COVID-19

Patients infected by the SARS-CoV-2 virus are commonly diagnosed with threatening liver conditions associated with drug-induced therapies and systemic viral action. RNA-Seq data from cells in bronchoalveolar lavage fluid from COVID-19 patients have pointed out dysregulation of kallikrein-kinin and renin-angiotensin systems as a possible mechanism that triggers multi-organ damage away from the leading site of virus infection. Therefore, we measured the plasma concentration of biologically active peptides from the kallikrein-kinin system, bradykinin and des-Arg⁹-bradykinin, and liver expression of its proinflammatory axis, bradykinin 1 receptor (B1R). We measured the plasma concentration of bradykinin and des-Arg⁹-bradykinin of 20 virologically confirmed COVID-19 patients using a liquid chromatography-tandem mass spectrometry-based methodology. The expression of B1R was evaluated by immunohistochemistry from post-mortem liver specimens of 27 COVID-19 individuals. We found a significantly higher blood level of des-Arg⁹-bradykinin and a lower bradykinin concentration in patients with COVID-19 compared to a healthy, uninfected control group. We also observed increased B1R expression levels in hepatic tissues of patients with COVID-19 under all hepatic injuries analyzed (liver congestion, portal vein dilation, steatosis, and ischemic necrosis). Our data indicate that des-Arg⁹-bradykinin/B1R is associated with the acute hepatic dysfunction induced by the SARS-CoV-2 virus infection in the pathogenesis of COVID-19.

Autopsy findings of pediatric COVID-19: a systematic review

Background

Little is known how COVID-19 is affecting children. Autopsies help gain an understanding of the pathophysiology of new and developing diseases. Numerous post-mortem studies had been conducted in adults with COVID-19, but few in children. Thereby, this systematic review aims to investigate the autopsy findings from pediatric COVID-19 patients.

Results

There were a total of 15 patients from eight studies. COVID-19 mainly affects the heart and lungs. Pathology findings from the heart of COVID-19 pediatric patients include diffuse inflammatory infiltrate, myocarditis, cardiomyocyte necrosis, pericarditis, and interstitial edema. Histopathology abnormalities observed in the lungs are diffuse alveolar damage, cytopathic changes, thrombi in arterioles and septal capillaries, lung congestion, focal acute hemorrhage and edema, focal exudative changes, and mild pneumocyte hyperplasia. In addition, pathological findings from other organs, such as the liver, kidney, brain, bone marrow, lymph node, skin, spleen, muscle, colon, parotid gland, and adrenal of COVID-19 pediatric patients are also included in this review.

Conclusion

Cardiomyocyte necrosis, interstitial edema, lung congestion, and diffuse alveolar damage are the most significant pathologic findings of the heart and lung in pediatric COVID-19 patients. More studies are needed to elucidate the pathophysiology of SARS-CoV-2 in autopsy findings and to determine the exact cause of death since it could be related to COVID-19 or other comorbidities.

Autopsy findings of COVID-19 in children: a systematic review and meta-analysis

Clinical features of COVID-19 range from mild respiratory symptoms to fatal outcomes. Autopsy findings are important for understanding COVID-19-related pathophysiology and clinical manifestations. This systematic study aims to evaluate autopsy findings in paediatric cases. We searched PubMed, EMBASE, and Cochrane Database Reviews. We included studies that reported autopsy findings in children with COVID-19. A total of 11 studies (24 subjects) were included. The mean age of patients was 5.9 ± 5.7 years. Grossly, there was pericardial and pleural effusion, hepatosplenomegaly, cardiomegaly, heavy soft lung, enlarged kidney, and enlarged brain. The autopsy findings of the lungs were diffuse alveolar damage (78.3%), fibrin thrombi (43.5%), haemorrhage (30.4%), pneumonia (26%), congestion and oedema (26%), angiomatoid pattern (17.4%), and alveolar megakaryocytes (17.4%). The heart showed interstitial oedema (80%), myocardial foci of band necrosis (60%), fibrin microthrombi (60%), interstitial and perivascular inflammation (40%), and pancarditis (30%). The liver showed centrilobular congestion (60%), micro/macrovesicular steatosis (30%), and arterial/venous thrombi (20%). The kidney showed acute tubular necrosis (75%), congestion (62.5%), fibrin thrombi in glomerular capillaries (37.5%), and nephrocalcinosis, mesangial cell hyperplasia, tubular hyaline/granular casts (25% each). The spleen showed splenitis (71.4%), haemorrhage (71.4%), lymphoid hypoplasia (57.1%), and haemophagocytosis (28.6%). The brain revealed oedema (87.5%), congestion (75%), reactive microglia (62.5%), neuronal ischaemic necrosis (62.5%), meningoencephalitis (37.5%), and fibrin thrombi (25%). SARS-CoV-2 and CD68 were positive by immunohistochemistry in 85.7% and 33.3% cases, respectively. Autopsy findings of COVID-19 in children are variable in all important organs. It may help in better understanding the pathogenesis of SARS-CoV-2.

Neurological Manifestations in Pediatric COVID-19 Patients Hospitalized at King Abdulaziz University Hospital, Jeddah, Saudi Arabia: A Retrospective Study

There are limited data about neurological manifestations in pediatric COVID-19 patients from all over the world, including Saudi Arabia. This study was performed to identify characteristics of pediatric COVID-19 cases with neurologic involvement hospitalized at King Abdulaziz University Hospital (KAUH), Saudi Arabia. This retrospective cross-sectional study included hospitalized patients aged 0-19 years with confirmed SARS-CoV-2 from April 2020 to February 2022. The required data were retrieved from patients' medical records. Ninety-four cases were included. The median ages of the studied group, those with neurological manifestations, and those without neurologic manifestations, were 6.5, 11.0, and 5.0 years, respectively. Neurological manifestations occurred in 29 COVID-19 patients (30.9%) with headache and decreased consciousness being the most common recorded manifestations in 8.5% and 6.4% of patients, respectively. Specific neurological manifestations were rare, as only two infants developed encephalopathy with fatal outcome. Most patients with and without neurological manifestations survived. Neuroimaging abnormalities were detected in 8 cases with neurological manifestations. Neurological manifestations were common in 31% of hospitalized pediatric COVID-19 cases. However, most of the neurological manifestations were mild and nonspecific, with headache being the most common one. Specific neurological manifestations were rare; however, pediatric COVID-19 patients, particularly young infants, were at risk of developing severe encephalopathy with fatal outcome.

Development and validation of a clinical predictive model for severe and critical pediatric COVID-19 infection

INTRODUCTION

Children infected with COVID-19 are susceptible to severe manifestations. We aimed to develop and validate a predictive model for severe/ critical pediatric COVID-19 infection utilizing routinely available hospital level data to ascertain the likelihood of developing severe manifestations.

METHODS

The predictive model was based on an analysis of registry data from COVID-19 positive patients admitted to five tertiary pediatric hospitals across Asia [Singapore, Malaysia, Indonesia (two centers) and Pakistan]. Independent predictors of severe/critical COVID-19 infection were determined using multivariable logistic regression. A training cohort (n = 802, 70%) was used to develop the prediction model which was then validated in a test cohort (n = 345, 30%). The discriminative ability and performance of this model was assessed by calculating the Area Under the Curve (AUC) and 95% confidence interval (CI) from final Receiver Operating Characteristics Curve (ROC).

RESULTS

A total of 1147 patients were included in this analysis. In the multivariable model, infant age group, presence of comorbidities, fever, vomiting, seizures and higher absolute neutrophil count were associated with an increased risk of developing severe/critical COVID-19 infection. The presence of coryza at presentation, higher hemoglobin and platelet count were associated with a decreased risk of severe/critical COVID-19 infection. The AUC (95%CI) generated for this model from the training and validation cohort were 0.96 (0.94, 0.98) and 0.92 (0.86, 0.97), respectively.

CONCLUSION

This predictive model using clinical history and commonly used laboratory values was valuable in estimating the risk of developing a severe/critical COVID-19 infection in hospitalized children. Further validation is needed to provide more insights into its utility in clinical practice.

Multisystem inflammatory syndrome in children (MIS-C) showing disseminated aspergillosis, cytomegalovirus reactivation and persistent SARS-COV-2: Case report with autopsy review

Multisystem inflammatory syndrome in children (MIS-C) is an emerging phenomenon associated with SARS-COV-2 infection (COVID-19) occurring in < 1 % of infected children. MIS-C is characterized by a hyperinflammatory state with excessive cytokine release ('storm') leading to hemodynamic compromise and multiorgan failure, with a death rate of ∼2 %. Autopsy examination can play a particularly important role in helping to understand the pathogenesis of MIS-C. Yet, only five autopsy studies have been reported to date. We report a fatal case of MIS-C involving a previously healthy, 5-year-old Thai boy admitted with MIS-C, one month after exposure to SARS-COV-2. While in intensive care, he was found to have a hypertrophic cardiomyopathy, and despite immunosuppressive treatment for MIS-C, developed shock and died. Multiorgan inflammation was not found at autopsy, implying that the MIS-C had responded to treatment. However, there was disseminated aspergillosis and cytomegalovirus reactivation, attributed to the immunosuppression. SARS-COV-2 virus was also found in multiple organs. To the best of our knowledge, this is the first reported autopsy of an MIS-C patient from Asia, and the first report of aspergillosis in MIS-C. This case underscores that the risks of immunosuppression are also a concern in MIS-C. Although MIS-C is generally considered to be a post-infectious hyperimmune reaction, persistence of SARS-COV-2 is a feature in all autopsies of MIS-C patients reported to date, suggesting a possible role in the pathogenesis, at least in fatal cases.

Circulating Endothelial Cells: A New Possible Marker of Endothelial Damage in Kawasaki Disease, Multisystem Inflammatory Syndrome in Children and Acute SARS-CoV-2 Infection

BACKGROUND

Kawasaki Disease (KD) and Multisystem Inflammatory Syndrome in Children (MIS-C) are pediatric diseases characterized by systemic inflammation and vascular injury, potentially leading to coronary artery lesions (CALs). Data on vascular injury occurring during acute COVID-19 (AC19) in children are still lacking. The aim of our study was to investigate endothelial injury in KD-, MIS-C- and AC19-dosing circulating endothelial cells (CECs).

METHODS

We conducted a multicenter prospective study. CECs were enumerated by CellSearch technology through the immunomagnetic capture of CD146-positive cells from whole blood.

RESULTS

We enrolled 9 KD, 20 MIS-C and 10 AC19. During the acute stage, the AC19 and KD patients had higher CECs levels than the MIS-C patients. From the acute to subacute phase, a significant CEC increase was observed in the KD patients, while a mild decrease was detected in the MIS-C patients. Cellular clusters/syncytia were more common in the KD patients. No correlation between CECs and CALs were found in the MIS-C patients. The incidence of CALs in the KD group was too low to investigate this correlation.

CONCLUSIONS

Our study suggests a possible role of CECs as biomarkers of systemic inflammation and endothelial dysfunction in KD and MIS-C and different mechanisms of vascular injury in these diseases. Further larger studies are needed.

Severe Acute Respiratory Syndrome Coronavirus 2 Vaccination in Children with a History of Multisystem Inflammatory Syndrome in Children: An International Survey

The optimal severe acute respiratory syndrome coronavirus 2 vaccine strategy for patients with a history of multisystem inflammatory syndrome in children (MIS-C) is unclear. We performed an international survey (32 countries) and found substantial variations in vaccine policies. Respondents did not report relapses of MIS-C or other severe inflammatory side effects after severe acute respiratory syndrome coronavirus 2 vaccination in 273 patients with a history of MIS-C.

Assessing and improving the validity of COVID-19 autopsy studies - A multicentre approach to establish essential standards for immunohistochemical and ultrastructural analyses

Background

Autopsy studies have provided valuable insights into the pathophysiology of COVID-19. Controversies remain about whether the clinical presentation is due to direct organ damage by SARS-CoV-2 or secondary effects, such as overshooting immune response. SARS-CoV-2 detection in tissues by RT-qPCR and immunohistochemistry (IHC) or electron microscopy (EM) can help answer these questions, but a comprehensive evaluation of these applications is missing.

Methods

We assessed publications using IHC and EM for SARS-CoV-2 detection in autopsy tissues. We systematically evaluated commercially available antibodies against the SARS-CoV-2 proteins in cultured cell lines and COVID-19 autopsy tissues. In a multicentre study, we evaluated specificity, reproducibility, and inter-observer variability of SARS-CoV-2 IHC. We correlated RT-qPCR viral tissue loads with semiquantitative IHC scoring. We used qualitative and quantitative EM analyses to refine criteria for ultrastructural identification of SARS-CoV-2.

Findings

Publications show high variability in detection and interpretation of SARS-CoV-2 abundance in autopsy tissues by IHC or EM. We show that IHC using antibodies against SARS-CoV-2 nucleocapsid yields the highest sensitivity and specificity. We found a positive correlation between presence of viral proteins by IHC and RT-qPCR-determined SARS-CoV-2 viral RNA load (N= 35; r=-0.83, p-value <0.0001). For EM, we refined criteria for virus identification and provide recommendations for optimized sampling and analysis. 135 of 144 publications misinterpret cellular structures as virus using EM or show only insufficient data. We provide publicly accessible digitized EM sections as a reference and for training purposes.

Interpretation

Since detection of SARS-CoV-2 in human autopsy tissues by IHC and EM is difficult and frequently incorrect, we propose criteria for a re-evaluation of available data and guidance for further investigations of direct organ effects by SARS-CoV-2.

Funding

German Federal Ministry of Health, German Federal Ministry of Education and Research, Berlin University Alliance, German Research Foundation, German Center for Infectious Research.

Tissue immunity to SARS-CoV-2: Role in protection and immunopathology

The SARS-CoV-2 pandemic has demonstrated the importance of studying antiviral immunity within sites of infection to gain insights into mechanisms for immune protection and disease pathology. As SARS-CoV-2 is tropic to the respiratory tract, many studies of airway washes, lymph node aspirates, and postmortem lung tissue have revealed site-specific immune dynamics that are associated with the protection or immunopathology but are not readily observed in circulation. This review summarizes the growing body of work identifying immune processes in tissues and their interplay with immune responses in circulation during acute SARS-CoV-2 infection, severe disease, and memory persistence. Establishment of tissue resident immunity also may have implications for vaccination and the durability of immune memory and protection.

Biomarkers of Endothelial Damage in Distinct Phases of Multisystem Inflammatory Syndrome in Children

Endothelial hyperinflammation and vasculitis are known hallmarks of acute COVID-19 and multisystem inflammatory syndrome in children (MIS-C). They are due to the direct effect of the virus on endothelial cells enhanced by pro-inflammatory modulators and may cause venous/arterial thrombosis. Therefore, it is essential to identify patients with endothelial damage early in order to establish specific therapies. We studied the monocyte chemoattractant protein 1 (MCP-1), the perinuclear anti-neutrophil cytoplasmic antibodies (pANCA), and the vascular endothelial growth factor A (VEGF-A) in serum from 45 MIS-C patients at hospital admission and 24 healthy controls (HC). For 13/45 MIS-C patients, we measured the three serum biomarkers also after one week from hospitalization. At admission, MIS-C patients had significantly higher levels of MCP-1 and VEGF-A than the HC, but no significant differences were observed for pANCA. While after one week, MCP-1 was significantly lower, pANCA was higher and VEGF-A levels were not significantly different from the admission values. These findings suggest an involvement of epithelium in MIS-C with an acute phase, showing high MCP-1 and VEGF-A, followed by an increase in pANCA that suggests a vasculitis development. The serum biomarker levels may help to drive personalized therapies in these phases with anticoagulant prophylaxis, immunomodulators, and/or anti-angiogenic drugs.

Routine SARS-CoV-2 vaccination for all children

The SARS-CoV-2 pandemic has resulted in unprecedented health and economic losses. Children generally present with less severe disease from this virus compared with adults, yet neonates and children with COVID-19 can require hospitalization, and older children can develop severe complications, such as the multisystem inflammatory syndrome, resulting in >1500 deaths in children from COVID-19 since the onset of the pandemic. The introduction of effective SARS-CoV-2 vaccines in school-age children and adult populations combined with the emergence of new, more highly transmissible SARS-CoV-2 variants has resulted in a proportional increase of infections in young children. Here, we discuss (1) the current knowledge on pediatric SARS-CoV-2 infection and pathogenesis in comparison with adults, (2) the data on vaccine immunogenicity and efficacy in children, and (3) the benefits of early life SARS-CoV-2 vaccination.

Mechanisms of Entry Into the Central Nervous System by Neuroinvasive Pathogens

BACKGROUND

The literature on neurological manifestations, cerebrospinal fluid analyses, and autopsies in patients with COVID-19 continues to grow. The proposed mechanisms for neurological disease in patients with COVID-19 include indirect processes such as inflammation, microvascular injury, and hypoxic-ischemic damage. An alternate hypothesis suggests direct viral entry of SARS-CoV-2 into the brain and cerebrospinal fluid, given varying reports regarding isolation of viral components from these anatomical sites.

EVIDENCE ACQUISITION

PubMed, Google Scholar databases, and neuroanatomical textbooks were manually searched and reviewed.

RESULTS

We provide clinical concepts regarding the mechanisms of viral pathogen invasion in the central nervous system (CNS); advances in our mechanistic understanding of CNS invasion in well-known neurotropic pathogens can aid in understanding how viruses evolve strategies to enter brain parenchyma. We also present the structural components of CNS compartments that influence viral entry, focusing on hematogenous and transneuronal spread, and discuss this evidence as it relates to our understanding of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

CONCLUSIONS

Although there is a paucity of data supporting direct viral entry of SARS-CoV-2 in humans, increasing our knowledge of the structural components of CNS compartments that block viral entry and pathways exploited by pathogens is fundamental to preparing clinicians and researchers for what to expect when a novel emerging virus with neurological symptoms establishes infection in the CNS, and how to design therapeutics to mitigate such an infection.

Unique Challenges Faced by a Child with Standard Risk Leukemia in Post-COVID Era: A Case Report

Children with malignancies are facing new challenges in post-COVID-19 era. We report an interesting case of a child on treatment for acute lymphoblastic leukemia having a very protracted course of illness with complications not often seen with standard therapy. It intends to make pediatric oncologists and intensive care specialists wary of potential newer complications.

Neuropathology of Pediatric SARS-CoV-2 Infection in the Forensic Setting: Novel Application of Ex Vivo Imaging in Analysis of Brain Microvasculature

Two years into the COVID-19 pandemic, there are few published accounts of postmortem SARS-CoV-2 pathology in children. We report 8 such cases (4 infants aged 7–36 weeks, 4 children aged 5–15 years). Four underwent ex vivo magnetic resonance neuroimaging, to assist in identification of subtle lesions related to vascular compromise. All infants were found unresponsive (3 in unsafe sleeping conditions); all but 1 had recent rhinitis and/or influenza-like illness (ILI) in the family; 1 had history of sickle cell disease. Ex vivo neuroimaging in 1 case revealed white matter (WM) signal hyperintensity and diffuse exaggeration of perivascular spaces, corresponding microscopically to WM mineralization. Neurohistology in the remaining 3 infants variably encompassed WM gliosis and mineralization; brainstem gliosis; perivascular vacuolization; perivascular lymphocytes and brainstem microglia. One had ectopic hippocampal neurons (with pathogenic variant in DEPDC5). Among the children, 3 had underlying conditions (e.g., obesity, metabolic disease, autism) and all presented with ILI. Three had laboratory testing suggesting multisystem inflammatory syndrome (MIS-C). Two were hospitalized for critical care including mechanical ventilation and extracorporeal membrane oxygenation (ECMO); one (co-infected with adenovirus) developed right carotid stroke ipsilateral to the ECMO cannula and the other required surgery for an ingested foreign body. Autopsy findings included: acute lung injury in 3 (1 with microthrombi); and one each with diabetic ketoacidosis and cardiac hypertrophy; coronary and cerebral arteritis and aortitis, resembling Kawasaki disease; and neuronal storage and enlarged fatty liver. All 4 children had subtle meningoencephalitis, focally involving the brainstem. On ex vivo neuroimaging, 1 had focal pontine susceptibility with corresponding perivascular inflammation/expanded perivascular spaces on histopathology. Results suggest SARS-CoV-2 in infants may present as sudden unexpected infant death, while in older children, signs and symptoms point to severe disease. Underlying conditions may predispose to fatal outcomes. As in adults, the neuropathologic changes may be subtle, with vascular changes such as perivascular vacuolization and gliosis alongside sparse perivascular lymphocytes. Detection of subtle vascular pathology is enhanced by ex vivo neuroimaging. Additional analysis of the peripheral/autonomic nervous system and investigation of co-infection in children with COVID-19 is necessary to understand risk for cardiovascular collapse/sudden death.

Multisystem Inflammatory Syndrome Temporally Related to COVID-19 in Children From Latin America and the Caribbean Region: A Systematic Review With a Meta-Analysis of Data From Regional Surveillance Systems

Background

With the emergence of the COVID-19 pandemic, increasing numbers of cases of the multisystem inflammatory syndrome in children (MIS-C) have been reported worldwide; however, it is unclear whether this syndrome has a differential pattern in children from Latin America and the Caribbean (LAC). We conducted a systematic review and meta-analysis to analyze the epidemiological, clinical, and outcome characteristics of patients with MIS-C in LAC countries.

Methods

A systematic literature search was conducted in the main electronic databases and scientific meetings from March 1, 2020, to June 30, 2021. Available reports on epidemiological surveillance of countries in the region during the same period were analyzed.

Results

Of the 464 relevant studies identified, 23 were included with 592 patients with MIS-C from LAC. Mean age was 6.6 years (IQR, 6-7.4 years); 60% were male. The most common clinical manifestations were fever, rash, and conjunctival injection; 59% showed Kawasaki disease. Pool proportion of shock was 52%. A total of 47% of patients were admitted to the pediatric intensive care unit (PICU), 23% required mechanical ventilation, and 74% required vasoactive drugs. Intravenous gamma globulin alone was administered in 87% of patients, and in combination with steroids in 60% of cases. Length of hospital stay was 10 days (IQR, 9-10) and PICU stay 5.75 (IQR, 5-6). Overall case fatality ratio was 4% and for those hospitalized in the PICU it was 7%.

Conclusion

Limited information was available on the clinical outcomes. Improvements in the surveillance system are required to obtain a better epidemiologic overview in the region.

Detection and identification of coronaviruses in human tissues using electron microscopy

The identification of viral particles within a tissue specimen requires specific knowledge of viral ultrastructure and replication, as well as a thorough familiarity with normal subcellular organelles. The severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) pandemic has underscored how challenging the task of identifying coronavirus by electron microscopy (EM) can be. Numerous articles have been published mischaracterizing common subcellular structures, including clathrin‐ or coatomer‐ coated vesicles, multivesicular bodies, and rough endoplasmic reticulum, as coronavirus particles in SARS‐CoV‐2 positive patient tissue specimens. To counter these misinterpretations, we describe the morphological features of coronaviruses that should be used to differentiate coronavirus particles from subcellular structures. Further, as many of the misidentifications of coronavirus particles have stemmed from attempts to attribute tissue damage to direct infection by SARS‐CoV‐2, we review articles describing ultrastructural changes observed in specimens from SARS‐CoV‐2‐infected individuals that do not necessarily provide EM evidence of direct viral infection. Ultrastructural changes have been observed in respiratory, cardiac, kidney, and intestinal tissues, highlighting the widespread effects that SARS‐CoV‐2 infection may have on the body, whether through direct viral infection or mediated by SARS‐CoV‐2 infection‐induced inflammatory and immune processes.

SARS-CoV-2 Spike Protein in Intestinal Cells of a Patient with Coronavirus Disease 2019 Multisystem Inflammatory Syndrome

A previously healthy 12-year-old boy had severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related multisystem inflammatory syndrome (MIS-C) that was rapidly fatal. Autopsy revealed the presence of a large intracardiac thrombus. SARS-CoV-2 spike protein was detected in intestinal cells, supporting the hypothesis that viral presence in the gut may be related to the immunologic response of MIS-C.

In-depth cardiovascular and pulmonary assessments in children with multisystem inflammatory syndrome after SARS-CoV-2 infection: A case series study

We assessed PET‐CT myocardial blood flow (MBF) using N‐13 ammonia, brachial flow‐mediated dilation, and cardiopulmonary exercise test in five post‐discarged MIS‐C survivors. None of the patients (median age: 9, range: 7‐18 years; 3 females; 2 males) had preexisting pediatric chronic conditions. At the follow‐up visit, two patients exhibited severe perfusion defect developed in the left ventricular cavity, suggesting extensive myocardial ischemia (MBF <2.0) and one patient showed persistent mild pericardial effusion. Others two patients demonstrated endothelial dysfunction. Nevertheless, all patients had lower predicted values in the VO_2peak, VO_2VAT, OUES, and O₂ Pulse (range: 35.2%–64.5%; 15.6%–38.2%; 1.0–1.3 L/min; 4–7 ml/beat), respectively. Our d suggested that previously health MIS‐C patients had impaired MBF, endothelial dysfunction and lower cardiopulmonary capacity at follow‐up analysis. Multidisciplinary further investigations should be conducted to reinforce these findings.

Histopathology and localization of SARS-CoV-2 and its host cell entry receptor ACE2 in tissues from naturally infected US-farmed mink (Neovison vison)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes respiratory disease in mink similar to human COVID-19. We characterized the pathological findings in 72 mink from US farms with SARS-CoV-2 outbreaks, localized SARS-CoV-2 and its host cellular receptor angiotensin-converting enzyme 2 (ACE2) in mink respiratory tissues, and evaluated the utility of various test methods and specimens for SARS-CoV-2 detection in necropsy tissues. Of SARS-CoV-2-positive animals found dead, 74% had bronchiolitis and diffuse alveolar damage (DAD). Of euthanized SARS-CoV-2-positive animals, 72% had only mild interstitial pneumonia or minimal nonspecific lung changes (congestion, edema, macrophages); similar findings were seen in SARS-CoV-2-negative animals. Suppurative rhinitis, lymphocytic perivascular inflammation in the lungs, and lymphocytic infiltrates in other tissues were common in both SARS-CoV-2-positive and SARS-CoV-2-negative animals. In formalin-fixed paraffin-embedded (FFPE) upper respiratory tract (URT) specimens, conventional reverse transcription-polymerase chain reaction (cRT-PCR) was more sensitive than in situ hybridization (ISH) or immunohistochemistry (IHC) for detection of SARS-CoV-2. FFPE lung specimens yielded less detection of virus than FFPE URT specimens by all test methods. By IHC and ISH, virus localized extensively to epithelial cells in the nasal turbinates, and prominently within intact epithelium; olfactory mucosa was mostly spared. The SARS-CoV-2 receptor ACE2 was extensively detected by IHC within turbinate epithelium, with decreased detection in lower respiratory tract epithelium and alveolar macrophages. This study expands on the knowledge of the pathology and pathogenesis of natural SARS-CoV-2 infection in mink and supports their further investigation as a potential animal model of SARS-CoV-2 infection in humans.

Segmental cardiac strain assessment by two-dimensional speckle-tracking echocardiography in surviving MIS-c patients: correlations with myocardial flow reserve (MFR) by 13 N-ammonia PET-CT

MIS-c is associated with severe cardiovascular impairment and eventually death. Pathophysiological mechanisms involved in myocardial injury were scarcely investigated and cardiovascular outcomes are uncertain. Autopsy studies suggested that microvascular dysfunction may be relevant to LV impairment. we aimed to evaluate segmental LV longitudinal strain by 2DST echocardiography, as well as myocardial flow reserve (MFR) by 13 N-ammonia PET-CT, in surviving MIS-c patients. each patient generated 34 LV segments for combined 2DST and MRF analysis. MFR was considered abnormal when < 2, borderline when between 2 and 2.5 and normal when > 2.5. From July 2020 to February 2021, six patients were admitted with MIS-c: three males, aged 9.3 (6.6-15.7) years. Time from admission to the follow-up visit was 6.05 (2-10.3) months. Although all patients were asymptomatic and LV EF was ≥ 55%, 43/102 (42.1%) LV segments showed MFR < 2.5. There was a modest positive correlation between segmental peak systolic longitudinal strain and MFR: r = 0.36, p = 0.03 for basal segments; r = 0.41, p = 0.022 for mid segments; r = 0.42, p = 0.021 for apical segments. Median peak systolic longitudinal strain was different among MRF categories: 18% (12%-24%) for abnormal, 18.5% (11%-35%) for borderline and 21% (12%-32%) for normal MFR (p = 0.006). We provided preliminary evidence that surviving MIS-c patients may present subclinical impairment of myocardial microcirculation. Segmental cardiac strain assessment 2DST seems useful for MIS-c cardiovascular follow-up, given its good correlation with 13 N-ammonia PET-CT derived MFR.

TIM3+ TRBV11-2 T cells and IFNγ signature in patrolling monocytes and CD16+ NK cells delineate MIS-C

In rare instances, pediatric SARS-CoV-2 infection results in a novel immunodysregulation syndrome termed multisystem inflammatory syndrome in children (MIS-C). We compared MIS-C immunopathology with severe COVID-19 in adults. MIS-C does not result in pneumocyte damage but is associated with vascular endotheliitis and gastrointestinal epithelial injury. In MIS-C, the cytokine release syndrome is characterized by IFNγ and not type I interferon. Persistence of patrolling monocytes differentiates MIS-C from severe COVID-19, which is dominated by HLA-DRlo classical monocytes. IFNγ levels correlate with granzyme B production in CD16+ NK cells and TIM3 expression on CD38+/HLA-DR+ T cells. Single-cell TCR profiling reveals a skewed TCRβ repertoire enriched for TRBV11-2 and a superantigenic signature in TIM3+/CD38+/HLA-DR+ T cells. Using NicheNet, we confirm IFNγ as a central cytokine in the communication between TIM3+/CD38+/HLA-DR+ T cells, CD16+ NK cells, and patrolling monocytes. Normalization of IFNγ, loss of TIM3, quiescence of CD16+ NK cells, and contraction of patrolling monocytes upon clinical resolution highlight their potential role in MIS-C immunopathogenesis.