Peripheral immunophenotypes in children with multisystem inflammatory syndrome associated with SARS-CoV-2 infection

Immune response to SARS-CoV-2 in children: A review of the current knowledge

Host immune responses to severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), especially in children, are still under investigation. Children with coronavirus disease 2019 (COVID‐19) constitute a significant study group of immune responses as they rarely present with severe clinical manifestations, require hospitalization, or develop complications such as multisystem inflammatory syndrome in children (MIS‐C) associated with SARS‐CoV‐2 infection. The deciphering of children’s immune responses during COVID‐19 infection will provide information about the protective mechanisms, while new potential targets for future therapies are likely to be revealed. Despite the limited immunological studies in children with COVID‐19, this review compares data between adults and children in terms of innate and adaptive immunity to SARS‐CoV‐2, discusses the possible reasons why children are mostly asymptomatic, and highlights unanswered or unclear immunological issues. Current evidence suggests that the activity of innate immunity seems to be crucial to the early phases of SARS‐CoV‐2 infection and adaptive memory immunity is vital to prevent reinfection.

Despite the limited immunological studies from children with COVID‐19, this review compares data between adults and children in terms of innate and adaptive immunity to SARS‐CoV‐2, discusses the possible reasons why children are mostly asymptomatic, and highlights unanswered or unclear immunological issues.

Distinct Cytokine and Chemokine Dysregulation in Hospitalized Children With Acute Coronavirus Disease 2019 and Multisystem Inflammatory Syndrome With Similar Levels of Nasopharyngeal Severe Acute Respiratory Syndrome Coronavirus 2 Shedding

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) is a severe clinical phenotype of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection that remains poorly understood.

METHODS

Hospitalized children <18 years of age with suspected coronavirus disease 2019 (COVID-19) (N = 53) were recruited into a prospective cohort study; 32 had confirmed COVID-19, with 16 meeting the US Centers for Disease Control criteria for MIS-C. Differences in nasopharyngeal viral ribonucleic acid (RNA) levels, SARS-CoV-2 seropositivity, and cytokine/chemokine profiles were examined, including after adjustments for age and sex.

RESULTS

The median ages for those with and without MIS-C were 8.7 years (interquartile range [IQR], 5.5-13.9) and 2.2 years (IQR, 1.1-10.5), respectively (P = .18), and nasopharyngeal levels of SARS-CoV-2 RNA did not differ significantly between the 2 groups (median 63 848.25 copies/mL versus 307.1 copies/mL, P = .66); 75% of those with MIS-C were antibody positive compared with 44% without (P = .026). Levels of 14 of 37 cytokines/chemokines (interleukin [IL]-1RA, IL-2RA, IL-6, IL-8, tumor necrosis factor-α, IL-10, IL-15, IL-18, monocyte chemoattractant protein [MCP]-1, IP-10, macrophage-inflammatory protein [MIP]-1α, MCP-2, MIP-1β, eotaxin) were significantly higher in children with MIS-C compared to those without, irrespective of age or sex (false discovery rate <0.05; P < .05).

CONCLUSIONS

The distinct pattern of heightened cytokine/chemokine dysregulation observed with MIS-C, compared with acute COVID-19, occurs across the pediatric age spectrum and with similar levels of nasopharyngeal SARS-CoV-2 RNA.

An AI-guided signature reveals the nature of the shared proximal pathways of host immune response in MIS-C and Kawasaki disease

A significant surge in cases of multisystem inflammatory syndrome in children (MIS-C, also called Pediatric Inflammatory Multisystem Syndrome - PIMS) has been observed amidst the COVID-19 pandemic. MIS-C shares many clinical features with Kawasaki disease (KD), although clinical course and outcomes are divergent. We analyzed whole blood RNA sequences, serum cytokines, and formalin fixed heart tissues from these patients using a computational toolbox of two gene signatures, i.e., the 166-gene viral pandemic (ViP) signature, and its 20-gene severe (s)ViP subset that were developed in the context of SARS-CoV-2 infection and a 13-transcript signature previously demonstrated to be diagnostic for KD. Our analyses revealed that KD and MIS-C are on the same continuum of the host immune response as COVID-19. While both the pediatric syndromes converge upon an IL15/IL15RA -centric cytokine storm, suggestive of shared proximal pathways of immunopathogenesis, they diverge in other laboratory parameters and cardiac phenotypes. The ViP signatures also revealed unique targetable cytokine pathways in MIS-C, place MIS-C farther along in the spectrum in severity compared to KD and pinpoint key clinical (reduced cardiac function) and laboratory (thrombocytopenia and eosinopenia) parameters that can be useful to monitor severity.

Longitudinal Outcomes for Multisystem Inflammatory Syndrome in Children

BACKGROUND

In spring 2020, a novel hyperinflammatory process associated with severe acute respiratory syndrome coronavirus 2 multisystem inflammatory syndrome in children (MIS-C) was described. The long-term impact remains unknown. We report longitudinal outcomes from a New York interdisciplinary follow-up program.

METHODS

All children <21 years of age, admitted to NewYork-Presbyterian with MIS-C in 2020, were included. Children were followed at 1 to 4 weeks, 1 to 4 months, and 4 to 9 months postdischarge.

RESULTS

In total, 45 children were admitted with MIS-C. The median time to last follow-up was 5.8 months (interquartile range 1.3-6.7). Of those admitted, 76% required intensive care and 64% required vasopressors and/or inotropes. On admission, patients exhibited significant nonspecific inflammation, generalized lymphopenia, and thrombocytopenia. Soluble interleukin (IL) IL-2R, IL-6, IL-10, IL-17, IL-18, and C-X-C Motif Chemokine Ligand 9 were elevated. A total of 80% (n = 36) had at least mild and 44% (n = 20) had moderate-severe echocardiographic abnormalities including coronary abnormalities (9% had a z score of 2-2.5; 7% had a z score > 2.5). Whereas most inflammatory markers normalized by 1 to 4 weeks, 32% (n = 11 of 34) exhibited persistent lymphocytosis, with increased double-negative T cells in 96% of assessed patients (n = 23 of 24). By 1 to 4 weeks, only 18% (n = 7 of 39) had mild echocardiographic findings; all had normal coronaries. At 1 to 4 months, the proportion of double-negative T cells remained elevated in 92% (median 9%). At 4 to 9 months, only 1 child had persistent mild dysfunction. One had mild mitral and/or tricuspid regurgitation.

CONCLUSIONS

Although the majority of children with MIS-C present critically ill, most inflammatory and cardiac manifestations in our cohort resolved rapidly.

Potential SARS-CoV-2 vaccines: Concept, progress, and challenges

Since September 2020, the world has had more than 28 million cases of coronavirus disease 2019 (COVID-19). Many countries are facing a second wave of the COVID-19 outbreak. A pressing need is evident for the development of a potent vaccine to control the SARS-CoV-2. Institutions and companies in many countries have announced their vaccine research programs and progress against the COVID-19. While most vaccines go through the designation and preparation stages, some of them are under evaluation for efficacy among animal models and clinical trials, and three approved vaccine candidates have been introduced for limited exploitation in Russia and China. An effective vaccine must induce a protective response of both cell-mediated and humoral immunity and should meet the safety and efficacy criteria. Although the emergence of new technologies has accelerated the development of vaccines, there are several challenges on the way, such as limited knowledge about the pathophysiology of the virus, inducing humoral or cellular immunity, immune enhancement with animal coronavirus vaccines, and lack of an appropriate animal model. In this review, we firstly discuss the immune responses against SARS-CoV-2 disease, subsequently, give an overview of several vaccine platforms for SARS-CoV-2 under clinical trials and challenges in vaccine development against this virus.

High expression of neutrophil and monocyte CD64 with simultaneous lack of upregulation of adhesion receptors CD11b, CD162, CD15, CD65 on neutrophils in severe COVID-19

Background and Aims

The pronounced neutrophilia observed in patients with coronavirus disease 2019 (COVID-19) infections suggests a role for these leukocytes in the pathology of the disease. Monocyte and neutrophil expression of CD64 and CD11b have been reported as early biomarkers to detect infections. The aim of this study was to study the expression of receptors for IgG (CD64) and adhesion molecules (CD11b, CD15s, CD65, CD162, CD66b) on neutrophils and monocytes in patients with severe COVID-19 after admission to an intensive care unit (ICU).

Methods

The expression of receptors was analyzed using flow cytometry. EDTA blood from 23 patients with confirmed COVID-19 infection was sampled within 48 h of admission to the ICU. Leukocytes were labeled with antibodies to CD11b, CD15s, CD65s, CD162, CD64, and CD66b. Expression of receptors was reported as mean fluorescence intensity (MFI) or the percentage of cells expressing receptors.

Results

Results are presented as comparison of COVID-19 patients with the healthy group and the receptor expression as MFI. Neutrophil receptors CD64 (2.5 versus 0.5) and CD66b (44.5 versus 34) were increased and CD15 decreased (21.6 versus 28.3) when CD65 (6.6 versus 4.4), CD162 (21.3 versus 21.1) and CD11b (10.5 versus 12) were in the same range. Monocytes receptors CD64 (30.5 versus 16.6), CD11b (18.7 versus 9.8), and CD162 (38.6 versus 36.5) were increased and CD15 decreased (10.3 versus 17.9); CD65 were in the same range (2.3 versus 1.96).

Conclusion

Monocytes and neutrophils are activated during severe COVID-19 infection as shown by strong upregulation of CD64. High monocyte and neutrophil CD64 can be an indicator of a severe form of COVID19. The adhesion molecules (CD11b, CD162, CD65, and CD15) are not upregulated on otherwise activated neutrophils, which might lead to relative impairment of tissue migration. Low adhesion profile of neutrophils suggests immune dysfunction of neutrophils. Monocytes maintain upregulation of some adhesion molecules (CD11b, CD162) suggesting the persistence of an increased ability to migrate into tissues, even during a severe stage of COVID-19. Future research should focus on CD64 and CD11b kinetics in the context of prognosis.

Monocytes and Macrophages in COVID-19

COVID-19 is a contagious viral disease caused by SARS-CoV-2 that led to an ongoing pandemic with massive global health and socioeconomic consequences. The disease is characterized primarily, but not exclusively, by respiratory clinical manifestations ranging from mild common cold symptoms, including cough and fever, to severe respiratory distress and multi-organ failure. Macrophages, a heterogeneous group of yolk-sac derived, tissue-resident mononuclear phagocytes of complex ontogeny present in all mammalian organs, play critical roles in developmental, homeostatic and host defense processes with tissue-dependent plasticity. In case of infection, they are responsible for early pathogen recognition, initiation and resolution of inflammation, as well as repair of tissue damage. Monocytes, bone-marrow derived blood-resident phagocytes, are recruited under pathological conditions such as viral infections to the affected tissue to defend the organism against invading pathogens and to aid in efficient resolution of inflammation. Given their pivotal function in host defense and the potential danger posed by their dysregulated hyperinflammation, understanding monocyte and macrophage phenotypes in COVID-19 is key for tackling the disease's pathological mechanisms. Here, we outline current knowledge on monocytes and macrophages in homeostasis and viral infections and summarize concepts and key findings on their role in COVID-19. While monocytes in the blood of patients with moderate COVID-19 present with an inflammatory, interferon-stimulated gene (ISG)-driven phenotype, cellular dysfunction epitomized by loss of HLA-DR expression and induction of S100 alarmin expression is their dominant feature in severe disease. Pulmonary macrophages in COVID-19 derived from infiltrating inflammatory monocytes are in a hyperactivated state resulting in a detrimental loop of pro-inflammatory cytokine release and recruitment of cytotoxic effector cells thereby exacerbating tissue damage at the site of infection.

Multisystem inflammatory syndrome in children is driven by zonulin-dependent loss of gut mucosal barrier

BACKGROUNDWeeks after SARS-CoV-2 infection or exposure, some children develop a severe, life-threatening illness called multisystem inflammatory syndrome in children (MIS-C). Gastrointestinal (GI) symptoms are common in patients with MIS-C, and a severe hyperinflammatory response ensues with potential for cardiac complications. The cause of MIS-C has not been identified to date.METHODSHere, we analyzed biospecimens from 100 children: 19 with MIS-C, 26 with acute COVID-19, and 55 controls. Stools were assessed for SARS-CoV-2 by reverse transcription PCR (RT-PCR), and plasma was examined for markers of breakdown of mucosal barrier integrity, including zonulin. Ultrasensitive antigen detection was used to probe for SARS-CoV-2 antigenemia in plasma, and immune responses were characterized. As a proof of concept, we treated a patient with MIS-C with larazotide, a zonulin antagonist, and monitored the effect on antigenemia and the patient's clinical response.RESULTSWe showed that in children with MIS-C, a prolonged presence of SARS-CoV-2 in the GI tract led to the release of zonulin, a biomarker of intestinal permeability, with subsequent trafficking of SARS-CoV-2 antigens into the bloodstream, leading to hyperinflammation. The patient with MIS-C treated with larazotide had a coinciding decrease in plasma SARS-CoV-2 spike antigen levels and inflammatory markers and a resultant clinical improvement above that achieved with currently available treatments.CONCLUSIONThese mechanistic data on MIS-C pathogenesis provide insight into targets for diagnosing, treating, and preventing MIS-C, which are urgently needed for this increasingly common severe COVID-19-related disease in children.

Coronavirus Disease 2019-Related Multisystem Inflammatory Syndrome in Children: A Systematic Review and Meta-Analysis

Background

This study aimed to describe the clinical symptoms, laboratory findings, treatment, and outcomes of coronavirus disease 2019-related multisystem inflammatory syndrome in children to provide a reference for clinical practice.

Methods

We employed a literature search of databases such as PubMed, Web of Science, EMBASE, and Johns Hopkins University for articles on COVID-19-related multisystem inflammatory syndrome in children published between April 1, 2020, and January 15, 2021. High-quality articles were selected for analysis on the basis of their quality standard scores. Using R3.6.3 software, meta-analyses of random- or fixed-effects models were used to determine the prevalence of comorbidities. Subgroup analysis was also performed to determine heterogeneity.

Results

A total of 57 articles (2,290 pediatric patients) were included in the study. Clinical Manifestations. :ncidences of fever, gastrointestinal symptoms, respiratory symptoms, and musculoskeletal symptoms (myalgias or arthralgias) were 99.91% (95% CI: 99.67–100%), 82.72% (95% CI: 78.19–86.81%), 53.02% (45.28–60.68%), and 14.16% (95% CI: 8.4–21.12%), respectively. The incidences of rash, conjunctival injection, lymphadenopathy, dry cracked lips, neurologic symptoms (headache, altered mental status, or confusion), swollen hands and feet, typical Kawasaki disease, and atypical Kawasaki disease were 59.34% (95% CI: 54.73–63.87%), 55.23% (95% CI: 50.22–60.19%), 27.07% (95% CI: 19.87–34.93%), 46.37% (95% CI: 39.97–52.83%), 28.87% (95% CI: 22.76–35.40%), 28.75% (95% CI: 21.46–36.64%), 17.32% (95% CI: 15.44–19.29%), and 36.19% (95% CI: 21.90–51.86%), respectively. The incidences of coronary artery dilation, aneurysm, pericardial effusion, myocarditis, myocardial dysfunction, high troponin, and N-terminal pro-B-type natriuretic peptide were 17.83%, 6.85%, 20.97%, 35.97%, 56.32%, 76.34%, and 86.65%, respectively. The incidences of reduced lymphocytes, thrombocytopenia, hypoalbuminemia, elevated C-reactive protein, ferritin, LDH, interleukin-6, PCT, and FIB were 61.51%, 26.42%, 77.92%, 98.5%, 86.79%, 80.59%, 89.30%, 85.10%, and 87.01%, respectively. PICU Hospitalization Rate and Mortality. The incidences of PICU hospitalization or with shock were 72.79% and 55.68%, respectively. The mortality rate was 1.00%. Conclusion and Relevance. PICU hospitalization and shock rates of multisystem inflammatory syndrome in children associated with COVID-19 were high, and its cumulative multiorgans and inflammatory indicators are increased, but if treated in time, the mortality rate was low.

Myeloid phenotypes in severe COVID-19 predict secondary infection and mortality: a pilot study

BACKGROUND

De-regulated host response to severe coronavirus disease 2019 (COVID-19), directly referring to the concept of sepsis-associated immunological dysregulation, seems to be a strong signature of severe COVID-19. Myeloid cells phenotyping is well recognized to diagnose critical illness-induced immunodepression in sepsis and has not been well characterized in COVID-19. The aim of this study is to review phenotypic characteristics of myeloid cells and evaluate their relations with the occurrence of secondary infection and mortality in patients with COVID-19 admitted in an intensive care unit.

METHODS

Retrospective analysis of the circulating myeloid cells phenotypes of adult COVID-19 critically ill patients. Phenotyping circulating immune cells was performed by flow cytometry daily for routine analysis and twice weekly for lymphocytes and monocytes subpopulations analysis, as well as monocyte human leukocyte antigen (mHLA)-DR expression.

RESULTS

Out of the 29 critically ill adult patients with severe COVID-19 analyzed, 12 (41.4%) developed secondary infection and six patients died during their stay. Monocyte HLA-DR kinetics was significantly different between patients developing secondary infection and those without, respectively, at day 5-7 and 8-10 following admission. The monocytes myeloid-derived suppressor cells to total monocytes ratio was associated with 28- and 60-day mortality. Those myeloid characteristics suggest three phenotypes: hyperactivated monocyte/macrophage is significantly associated with mortality, whereas persistent immunodepression is associated with secondary infection occurrence compared to transient immunodepression.

CONCLUSIONS

Myeloid phenotypes of critically ill COVID-19 patients may be associated with development of secondary infection, 28- and 60-day mortality.

Hide and seek in a pandemic: review of SARS-CoV-2 infection and sequelae in children

New Findings

What is the topic of this review?

A description of the current literature relating to COVID‐19 infection in children and the associated inflammatory condition, paediatric multi‐inflammatory syndrome temporally associated with SARS‐CoV‐2 (PIMS‐TS).

What advances does it highlight?

Children with SARS‐CoV‐2 infection have a distinct clinical phenotype when compared to adults. This may relate to relative differences in their adaptive immunity and in the degree and distribution of expression of the SARS‐CoV‐2 receptor (angiotensin‐converting enzyme 2). There are several similarities between PIMS‐TS, Kawasaki disease shock syndrome and other known inflammatory disorders such as macrophage activation syndrome. Few data are available to date regarding vaccination responses of children against COVID‐19.

Abstract

Children infected with SARS‐CoV‐2 have a clinical phenotype that is distinct from that observed in adult cases. They can present with a range of respiratory, gastrointestinal and neurological symptoms, or with a delayed hyperinflammatory syndrome (paediatric multisystem inflammatory system temporally associated with SARS‐CoV‐2; PIMS‐TS) that frequently requires treatment in an intensive care unit. These manifestations may be related to unique expression of transmembrane receptors and immune physiology in children. The clinical features and inflammatory profile of PIMS‐TS are similar to other inflammatory disorders that occur in children such as Kawasaki disease, macrophage activation syndrome and sepsis. Given children are infected less frequently and have less severe disease due to COVID‐19 compared to adults, their physiological profile is of great interest. An understanding of the unique mechanisms of infection and disease in children could aid the identification of potential therapeutic targets. Like adults, children can have long‐term complications of SARS‐CoV‐2 infection, including neurological and cardiac morbidity. Vaccination against SARS‐CoV‐2 is not yet authorised in children aged <12 years, and hence we anticipate ongoing paediatric presentations of COVID‐19 in the coming months.

Systemic Inflammation and Microbial Translocation Are Characteristic Features of SARS-CoV-2-Related Multisystem Inflammatory Syndrome in Children

Background

Multisystem inflammatory syndrome in children (MIS-C) is a rare manifestation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children that can result in increased morbidity and mortality. The inflammatory underpinnings of MIS-C have not been examined in detail.

Methods

We examined the plasma levels of acute phase proteins and microbial translocation markers in children with MIS-C, children with acute coronavirus disease 2019 (COVID-19) infection, SARS-CoV-2-seropositive children, and controls.

Results

MIS-C children exhibited significantly higher levels of C-reactive protein (CRP), alpha2 macroglobulin (α2M), serum amyloid P (SAP), lipopolysaccharide (LPS), sCD14, and LPS binding protein (LBP) and significantly lower levels of haptoglobin (Hp) in comparison with seropositive, control, and/or COVID-19 children. In addition, COVID-19 children exhibited significantly higher levels of most of the above markers in comparison with seropositive and control children. Principal component analysis using a set of these markers could clearly discriminate MIS-C and COVID-19 from seropositive and control children. MIS-C children requiring pediatric intensive care unit admission and COVID-19 children with severe disease had higher levels of CRP, SAP, and/or sCD14 at admission.

Conclusions

Our study describes the role of systemic inflammation and microbial translocation markers in children with MIS-C and COVID-19 and therefore helps in advancing our understanding of the pathogenesis of different presentations of SARS-CoV-2 infection in children.

Current Understanding of Multisystem Inflammatory Syndrome (MIS-C) Following COVID-19 and Its Distinction from Kawasaki Disease

PURPOSE OF REVIEW

In this article, I have reviewed current reports that explore differences and similarities between multisystem inflammatory syndrome in children (MIS-C) and other known multisystem inflammatory diseases seen in children, particularly Kawasaki disease.

RECENT FINDINGS

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a human coronavirus causing the COVID-19 disease which emerged in China in December 2019 and spread rapidly to the entire country and quickly to other countries. Currently, there is a pandemic of SARS-CoV-2 infection that results in 20% of patients admitted to hospital with illness, with 3% developing intractable acute respiratory distress syndrome (ARDS) with high mortality. However, pediatric COVID-19 is still reported to be a mild disease, affecting only 8% of children. Pathogenesis in children is comparable to adults. There are suggested impaired activation of IFN-alpha and IFN regulator 3, decreased cell response causing impaired viral defense, yet the clinical course is mild, and almost all children recover from the infection without major complications. Interestingly, there is a subset of patients that develop a late but marked immunogenic response to COVID-19 and develop MIS-C. Clinical features of MIS-C resemble certain pediatric rheumatologic diseases, such as Kawasaki disease (mucocutaneous lymph node syndrome) which affects small-medium vessels. Other features of MIS-C resemble those of macrophage activation syndrome (MAS). However, recent research suggests distinct clinical and laboratory differences between MIS-C, Kawasaki disease, and MAS. Since the start of the SARS-CoV-2 pandemic, MIS-C has become the candidate for the most common cause of acquired heart disease in children.

Updated Management Protocol for Multisystem Inflammatory Syndrome in Children (MIS-C)

The multisystem inflammatory syndrome in children (MIS-C) is a post-viral immunological or hyper-inflammatory complication of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection commonly seen in older children, who commonly present with fever, multi-systemic involvement including myocardial dysfunction and shock, and hyper-inflammation. The treatment of MIS-C is adapted from the treatment of other immunological or hyper-inflammatory conditions and these treatment protocols are not uniform across the globe, and more so, in India. We propose a uniform management protocol for MIS-C based on our experience of treating MIS-C cases, available evidence till now, and recent guidelines. The aims are to identify children with MIS-C with high sensitivity, recognize other infections or inflammatory processes, stratify treatment based on severity, and manage hyper-inflammatory syndrome.

Rationale of Therapeutic Plasma Exchange as Rescue Immunomodulatory Treatment for MIS-C With Multiorgan Failure

Multisystem inflammatory syndrome in children (MIS-C) associated with SARS-CoV-2 infection is an infrequent and poorly understood illness. It can present as severe multiorgan failure in children, potentially lethal. Immunomodulation is the empiric treatment because a dysregulated immune response is the primary pathophysiologic mechanism. We present an infant with severe MIS-C, refractory to usual treatment, successfully treated with plasmapheresis.

Consequences of coronavirus infections for primitive and mature hematopoietic cells: new insights and why it matters

PURPOSE OF REVIEW

In recent history there have been three outbreaks of betacoronavirus infections in humans, with the most recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; causing Coronavirus disease 2019 [COVID-19]) outbreak leading to over two million deaths, with a rapidly rising death toll. Much remains unknown about host cells and tissues affected by coronavirus infections, including the hematopoietic system. Here, we discuss the recent findings examining effects that coronavirus infection or exposure has on hematopoietic cells and the clinical implications for these effects.

RECENT FINDINGS

Recent studies have centered on SARS-CoV-2, demonstrating that hematopoietic stem and progenitor cells and mature immune cells may be susceptible to infection and are impacted functionally by exposure to SARS-CoV-2 Spike protein. These findings have important implications regarding hematologic complications arising from COVID-19 and other coronavirus-induced disease, which we discuss here.

SUMMARY

Infection with coronaviruses sometimes leads to hematologic complications in patients, and these hematologic complications are associated with poorer prognosis. These hematologic complications may be caused by coronavirus direct infection or impact on primitive hematopoietic cells or mature immune cells, by indirect effects on these cells, or by a combination thereof. It is important to understand how hematologic complications arise in order to seek new treatments to improve patient outcomes.

Multisystem Inflammatory Syndrome in Children - Initial Therapy and Outcomes

BACKGROUND

The assessment of real-world effectiveness of immunomodulatory medications for multisystem inflammatory syndrome in children (MIS-C) may guide therapy.

METHODS

We analyzed surveillance data on inpatients younger than 21 years of age who had MIS-C and were admitted to 1 of 58 U.S. hospitals between March 15 and October 31, 2020. The effectiveness of initial immunomodulatory therapy (day 0, indicating the first day any such therapy for MIS-C was given) with intravenous immune globulin (IVIG) plus glucocorticoids, as compared with IVIG alone, was evaluated with propensity-score matching and inverse probability weighting, with adjustment for baseline MIS-C severity and demographic characteristics. The primary outcome was cardiovascular dysfunction (a composite of left ventricular dysfunction or shock resulting in the use of vasopressors) on or after day 2. Secondary outcomes included the components of the primary outcome, the receipt of adjunctive treatment (glucocorticoids in patients not already receiving glucocorticoids on day 0, a biologic, or a second dose of IVIG) on or after day 1, and persistent or recurrent fever on or after day 2.

RESULTS

A total of 518 patients with MIS-C (median age, 8.7 years) received at least one immunomodulatory therapy; 75% had been previously healthy, and 9 died. In the propensity-score-matched analysis, initial treatment with IVIG plus glucocorticoids (103 patients) was associated with a lower risk of cardiovascular dysfunction on or after day 2 than IVIG alone (103 patients) (17% vs. 31%; risk ratio, 0.56; 95% confidence interval [CI], 0.34 to 0.94). The risks of the components of the composite outcome were also lower among those who received IVIG plus glucocorticoids: left ventricular dysfunction occurred in 8% and 17% of the patients, respectively (risk ratio, 0.46; 95% CI, 0.19 to 1.15), and shock resulting in vasopressor use in 13% and 24% (risk ratio, 0.54; 95% CI, 0.29 to 1.00). The use of adjunctive therapy was lower among patients who received IVIG plus glucocorticoids than among those who received IVIG alone (34% vs. 70%; risk ratio, 0.49; 95% CI, 0.36 to 0.65), but the risk of fever was unaffected (31% and 40%, respectively; risk ratio, 0.78; 95% CI, 0.53 to 1.13). The inverse-probability-weighted analysis confirmed the results of the propensity-score-matched analysis.

CONCLUSIONS

Among children and adolescents with MIS-C, initial treatment with IVIG plus glucocorticoids was associated with a lower risk of new or persistent cardiovascular dysfunction than IVIG alone. (Funded by the Centers for Disease Control and Prevention.).

COVID-19: immunopathology, pathophysiological mechanisms, and treatment options

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread globally despite the worldwide implementation of preventive measures to combat the disease. Although most COVID-19 cases are characterised by a mild, self-limiting disease course, a considerable subset of patients develop a more severe condition, varying from pneumonia and acute respiratory distress syndrome (ARDS) to multi-organ failure (MOF). Progression of COVID-19 is thought to occur as a result of a complex interplay between multiple pathophysiological mechanisms, all of which may orchestrate SARS-CoV-2 infection and contribute to organ-specific tissue damage. In this respect, dissecting currently available knowledge of COVID-19 immunopathogenesis is crucially important, not only to improve our understanding of its pathophysiology but also to fuel the rationale of both novel and repurposed treatment modalities. Various immune-mediated pathways during SARS-CoV-2 infection are relevant in this context, which relate to innate immunity, adaptive immunity, and autoimmunity. Pathological findings in tissue specimens of patients with COVID-19 provide valuable information with regard to our understanding of pathophysiology as well as the development of evidence-based treatment regimens. This review provides an updated overview of the main pathological changes observed in COVID-19 within the most commonly affected organ systems, with special emphasis on immunopathology. Current management strategies for COVID-19 include supportive care and the use of repurposed or symptomatic drugs, such as dexamethasone, remdesivir, and anticoagulants. Ultimately, prevention is key to combat COVID-19, and this requires appropriate measures to attenuate its spread and, above all, the development and implementation of effective vaccines. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

New Onset of Hepatic Steatosis Post-Severe Multisystem Inflammatory Syndrome in Children (MIS-C): A Case Report

The emergence of Multisystem Inflammatory Syndrome (MIS-C) following SARS-CoV-2 infection in children and adolescents provided a new diagnostic and management challenge as there is limited knowledge about this condition and its natural history. In existing literature on MIS-C, there are currently no data about long-term outcomes. We report the case of a 14-year-old boy, with no significant past medical history, who presented a condition of multiorgan dysfunction due to MIS-C, after a SARS CoV-2 infection, and subsequent clinical-laboratory signs of hepatic steatosis at short-term follow-up. The case suggests how hepatic steatosis may be a possible sequela following SARS-CoV-2 infection, MIS-C and its medical treatment. Therefore, a close and long-term follow-up is needed to establish the pathophysiology and the evolution of this condition in patients following MIS-C.

Immunomodulation as Treatment for Severe Coronavirus Disease 2019: A Systematic Review of Current Modalities and Future Directions

In severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, viral load peaks early and declines quickly after symptom onset. Severe coronavirus disease 2019 (COVID-19) is marked by aberrant innate and adaptive immune responses with an abnormal cytokine profile and multiorgan system dysfunction that persists well after viral clearance. A purely antiviral treatment strategy may therefore be insufficient, and antiviral agents have not shown a benefit later in the illness course. A number of immunomodulatory strategies are being tested, including corticosteroids, cytokine and anticytokine therapies, small molecule inhibitors, and cellular therapeutics. To date, the only drug to show a mortality benefit for COVID-19 in a randomized, controlled trial is dexamethasone. However, there remains uncertainty about which patients may benefit most and about longer-term complications, including secondary infections. Here, we review the immune dysregulation of severe COVID-19 and the existing data behind various immunomodulatory strategies, and we consider future directions of study.

Cardiac pathology and outcomes vary between Kawasaki disease and PIMS-TS

Overlapping clinical features promoted the discussion of whether Kawasaki disease (KD) and PIMS-TS share pathophysiological features and disease outcomes. Medical records from English patients with KD (2015-02/20, N = 27) and PIMS-TS (02/2020-21, N = 34) were accessed to extract information. Children with PIMS-TS were older and more frequently of minority ethnicity background. They patients more commonly exhibited cytopenias and hyperferritinemia, which associated with diffuse cardiac involvement and functional impairment. In some PIMS-TS cases, cardiac pathology developed late, but outcomes were more favorable. In both, KD and PIMS-TS, baseline coronary diameter was a predictor of outcomes. PIMS-TS treatment more frequently included respiratory and cardiovascular support, and corticosteroids with IVIG. Cardiac involvement in PIMS-TS may be the result of a cytokine storm. Though more severe and diffuse when compared to KD, cardiac involvement of PIMS-TS has a more favorable prognosis, which may, after recovery, mitigate the need for long-term follow up.

Neutralization potency of monoclonal antibodies recognizing dominant and subdominant epitopes on SARS-CoV-2 Spike is impacted by the B.1.1.7 variant

Interaction of the SARS-CoV-2 Spike receptor binding domain (RBD) with the receptor ACE2 on host cells is essential for viral entry. RBD is the dominant target for neutralizing antibodies, and several neutralizing epitopes on RBD have been molecularly characterized. Analysis of circulating SARS-CoV-2 variants has revealed mutations arising in the RBD, N-terminal domain (NTD) and S2 subunits of Spike. To understand how these mutations affect Spike antigenicity, we isolated and characterized >100 monoclonal antibodies targeting epitopes on RBD, NTD, and S2 from SARS-CoV-2-infected individuals. Approximately 45% showed neutralizing activity, of which ∼20% were NTD specific. NTD-specific antibodies formed two distinct groups: the first was highly potent against infectious virus, whereas the second was less potent and displayed glycan-dependant neutralization activity. Mutations present in B.1.1.7 Spike frequently conferred neutralization resistance to NTD-specific antibodies. This work demonstrates that neutralizing antibodies targeting subdominant epitopes should be considered when investigating antigenic drift in emerging variants.

Multisystem inflammatory syndrome in children with COVID-19

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) is a dangerous pediatric complication of COVID-19.

OBJECTIVE

The purpose of this review article is to provide a summary of the diagnosis and management of MIS-C with a focus on management in the acute care setting.

DISCUSSION

MIS-C is an inflammatory syndrome which can affect nearly any organ system. The most common symptoms are fever and gastrointestinal symptoms, though neurologic and dermatologic findings are also well-described. The diagnosis includes a combination of clinical and laboratory testing. Patients with MIS-C will often have elevated inflammatory markers and may have an abnormal electrocardiogram or echocardiogram. Initial treatment involves resuscitation with careful assessment for cardiac versus vasodilatory shock using point-of-care ultrasound. Treatment should include intravenous immunoglobulin, anticoagulation, and consideration of corticosteroids. Interleukin-1 and/or interleukin-6 blockade may be considered for refractory cases. Aspirin is recommended if there is thrombocytosis or Kawasaki disease-like features on echocardiogram. Patients will generally require admission to an intensive care unit.

CONCLUSION

MIS-C is a condition associated with morbidity and mortality that is increasingly recognized as a potential complication in pediatric patients with COVID-19. It is important for emergency clinicians to know how to diagnose and treat this disorder.

Inflammatory biomarkers in COVID-19-associated multisystem inflammatory syndrome in children, Kawasaki disease, and macrophage activation syndrome: a cohort study

Background

Multisystem inflammatory syndrome in children (MIS-C) is a potentially life-threatening hyperinflammatory syndrome that occurs after primary SARS-CoV-2 infection. The pathogenesis of MIS-C remains undefined, and whether specific inflammatory biomarker patterns can distinguish MIS-C from other hyperinflammatory syndromes, including Kawasaki disease and macrophage activation syndrome (MAS), is unknown. Therefore, we aimed to investigate whether inflammatory biomarkers could be used to distinguish between these conditions.

Methods

We studied a prospective cohort of patients with MIS-C and Kawasaki disease and an established cohort of patients with new-onset systemic juvenile idiopathic arthritis (JIA) and MAS associated with systemic JIA (JIA-MAS), diagnosed according to established guidelines. The study was done at Cincinnati Children's Hospital Medical Center (Cincinnati, OH, USA). Clinical and laboratory features as well as S100A8/A9, S100A12, interleukin (IL)-18, chemokine (C-X-C motif) ligand 9 (CXCL9), and IL-6 concentrations were assessed by ELISA and compared using parametric and non-parametric tests and receiver operating characteristic curve analysis.

Findings

Between April 30, 2019, and Dec 14, 2020, we enrolled 19 patients with MIS-C (median age 9·0 years [IQR 4·5–15·0]; eight [42%] girls and 11 [58%] boys) and nine patients with Kawasaki disease (median age 2·0 years [2·0–4·0]); seven [78%] girls and two [22%] boys). Patients with MIS-C and Kawasaki disease had similar S100 proteins and IL-18 concentrations but patients with MIS-C were distinguished by significantly higher median concentrations of the IFNγ-induced CXCL9 (1730 pg/mL [IQR 604–6300] vs 278 pg/mL [54–477]; p=0·038). Stratifying patients with MIS-C by CXCL9 concentrations (high vs low) revealed differential severity of clinical and laboratory presentation. Compared with patients with MIS-C and low CXCL9 concentrations, more patients with high CXCL9 concentrations had acute kidney injury (six [60%] of ten vs none [0%] of five), altered mental status (four [40%] of ten vs none [0%] of five), shock (nine [90%] of ten vs two [40%] of five), and myocardial dysfunction (five [50%] of ten vs one [20%] of five); these patients also had higher concentrations of systemic inflammatory markers and increased severity of cytopenia and coagulopathy. By contrast, patients with MIS-C and low CXCL9 concentrations resembled patients with Kawasaki disease, including the frequency of coronary involvement. Elevated concentrations of S100A8/A9, S100A12, and IL-18 were also useful in distinguishing systemic JIA from Kawasaki disease with high sensitivity and specificity.

Interpretation

Our findings show MIS-C is distinguishable from Kawasaki disease primarily by elevated CXCL9 concentrations. The stratification of patients with MIS-C by high or low CXCL9 concentrations provides support for MAS-like pathophysiology in patients with severe MIS-C, suggesting new approaches for diagnosis and management.

Funding

Cincinnati Children's Research Foundation, National Institute of Arthritis and Musculoskeletal and Skin Diseases/National Institutes of Health, the Deutsche Forschungsgemeinschaft, and The Jellin Family Foundation.

SARS-CoV-2 RNAemia and proteomic trajectories inform prognostication in COVID-19 patients admitted to intensive care

Prognostic characteristics inform risk stratification in intensive care unit (ICU) patients with coronavirus disease 2019 (COVID-19). We obtained blood samples (n = 474) from hospitalized COVID-19 patients (n = 123), non-COVID-19 ICU sepsis patients (n = 25) and healthy controls (n = 30). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA was detected in plasma or serum (RNAemia) of COVID-19 ICU patients when neutralizing antibody response was low. RNAemia is associated with higher 28-day ICU mortality (hazard ratio [HR], 1.84 [95% CI, 1.22-2.77] adjusted for age and sex). RNAemia is comparable in performance to the best protein predictors. Mannose binding lectin 2 and pentraxin-3 (PTX3), two activators of the complement pathway of the innate immune system, are positively associated with mortality. Machine learning identified 'Age, RNAemia' and 'Age, PTX3' as the best binary signatures associated with 28-day ICU mortality. In longitudinal comparisons, COVID-19 ICU patients have a distinct proteomic trajectory associated with mortality, with recovery of many liver-derived proteins indicating survival. Finally, proteins of the complement system and galectin-3-binding protein (LGALS3BP) are identified as interaction partners of SARS-CoV-2 spike glycoprotein. LGALS3BP overexpression inhibits spike-pseudoparticle uptake and spike-induced cell-cell fusion in vitro.

Hemadsorption as a Treatment Option for Multisystem Inflammatory Syndrome in Children Associated With COVID-19. A Case Report

Multisystem Inflammatory Syndrome in Children (MIS-C) associated with COVID-19 is characterized by hypercytokinemia leading to overwhelming inflammation. We describe the use of a hemadsorption device as part of the supportive treatment for cytokine storm.

Drugs that inhibit TMEM16 proteins block SARS-CoV-2 spike-induced syncytia

COVID-19 is a disease with unique characteristics that include lung thrombosis1, frequent diarrhoea2, abnormal activation of the inflammatory response3 and rapid deterioration of lung function consistent with alveolar oedema4. The pathological substrate for these findings remains unknown. Here we show that the lungs of patients with COVID-19 contain infected pneumocytes with abnormal morphology and frequent multinucleation. The generation of these syncytia results from activation of the SARS-CoV-2 spike protein at the cell plasma membrane level. On the basis of these observations, we performed two high-content microscopy-based screenings with more than 3,000 approved drugs to search for inhibitors of spike-driven syncytia. We converged on the identification of 83 drugs that inhibited spike-mediated cell fusion, several of which belonged to defined pharmacological classes. We focused our attention on effective drugs that also protected against virus replication and associated cytopathicity. One of the most effective molecules was the antihelminthic drug niclosamide, which markedly blunted calcium oscillations and membrane conductance in spike-expressing cells by suppressing the activity of TMEM16F (also known as anoctamin 6), a calcium-activated ion channel and scramblase that is responsible for exposure of phosphatidylserine on the cell surface. These findings suggest a potential mechanism for COVID-19 disease pathogenesis and support the repurposing of niclosamide for therapy.

Coronavirus infection: An immunologists' perspective

Coronavirus infections are frequent viral infections in several species. As soon as the severe acute respiratory syndrome (SARS) appeared in the early 2000s, most of the research focused on pulmonary disease. However, disorders in immune response and organ dysfunctions have been documented. Elderly individuals with comorbidities exhibit worse outcomes in all the coronavirus that cause SARS. Disease severity in SARS-CoV-2 infection is related to severe inflammation and tissue injury, and effective immune response against the virus is still under analysis. ACE2 receptor expression and polymorphism, age, gender and immune genetics are factors that also play an essential role in patients' clinical features and immune responses and have been partially discussed. The present report aims to review the physiopathology of SARS-CoV-2 infection and propose new research topics to understand the complex mechanisms of viral infection and viral clearance.

Multisystem inflammatory syndrome in children: a microcosm of challenges and opportunities for translational bioinformatics in pediatric research

PURPOSE OF REVIEW

Despite significant progress in our understanding and clinical management of multisystem inflammatory syndrome in children (MIS-C), significant challenges remain. Here, we review recently published studies on the clinical diagnosis, risk stratification, and treatment of MIS-C, highlighting key gaps in research progress that are a microcosm for challenges in translational pediatric research. We then discuss potential solutions in the realm of translational bioinformatics.

RECENT FINDINGS

Current case definitions are inconsistent and do not capture the underlying pathophysiology of MIS-C, which remains poorly understood. Although overall mortality is low, some patients rapidly decompensate, and a test to identify those at risk for severe outcomes remains an unmet need. Treatment consists of various combinations of immunoglobulins, corticosteroids, and biologics, based on extrapolated data and expert opinion, while the benefits remain unclear as we await the completion of clinical trials.

SUMMARY

The small size and heterogeneity of the pediatric population contribute to unmet needs because of financial and logistical constraints of the current research infrastructure focused on eliminating most sources of heterogeneity, leading to ungeneralizable results. Data sharing and meta-analysis of gene expression shows promise to accelerate progress in the field of MIS-C as well as other childhood diseases beyond the current pandemic.

Best Practice Recommendations for the Diagnosis and Management of Children With Pediatric Inflammatory Multisystem Syndrome Temporally Associated With SARS-CoV-2 (PIMS-TS; Multisystem Inflammatory Syndrome in Children, MIS-C) in Switzerland

Background: Following the spread of the coronavirus disease 2019 (COVID-19) pandemic a new disease entity emerged, defined as Pediatric Inflammatory Multisystem Syndrome temporally associated with COVID-19 (PIMS-TS), or Multisystem Inflammatory Syndrome in Children (MIS-C). In the absence of trials, evidence for treatment remains scarce. Purpose: To develop best practice recommendations for the diagnosis and treatment of children with PIMS-TS in Switzerland. It is acknowledged that the field is changing rapidly, and regular revisions in the coming months are pre-planned as evidence is increasing. Methods: Consensus guidelines for best practice were established by a multidisciplinary group of Swiss pediatric clinicians with expertise in intensive care, immunology/rheumatology, infectious diseases, hematology, and cardiology. Subsequent to literature review, four working groups established draft recommendations which were subsequently adapted in a modified Delphi process. Recommendations had to reach >80% agreement for acceptance. Results: The group achieved agreement on 26 recommendations, which specify diagnostic approaches and interventions across anti-inflammatory, anti-infectious, and support therapies, and follow-up for children with suspected PIMS-TS. A management algorithm was derived to guide treatment depending on the phenotype of presentation, categorized into PIMS-TS with (a) shock, (b) Kawasaki-disease like, and (c) undifferentiated inflammatory presentation. Conclusion: Available literature on PIMS-TS is limited to retrospective or prospective observational studies. Informed by these cohort studies and indirect evidence from other inflammatory conditions in children and adults, as well as guidelines from international health authorities, the Swiss PIMS-TS recommendations represent best practice guidelines based on currently available knowledge to standardize treatment of children with suspected PIMS-TS. Given the absence of high-grade evidence, regular updates of the recommendations will be warranted, and participation of patients in trials should be encouraged.

Polyclonal expansion of TCR Vbeta 21.3+ CD4+ and CD8+ T cells is a hallmark of Multisystem Inflammatory Syndrome in Children

Multiple Inflammatory Syndrome in Children (MIS-C) is a delayed and severe complication of SARS-CoV-2 infection that strikes previously healthy children. As MIS-C combines clinical features of Kawasaki disease and Toxic Shock Syndrome (TSS), we aimed to compare the immunological profile of pediatric patients with these different conditions. We analyzed blood cytokine expression, and the T cell repertoire and phenotype in 36 MIS-C cases, which were compared to 16 KD, 58 TSS, and 42 COVID-19 cases. We observed an increase of serum inflammatory cytokines (IL-6, IL-10, IL-18, TNF-α, IFNγ, CD25s, MCP1, IL-1RA) in MIS-C, TSS and KD, contrasting with low expression of HLA-DR in monocytes. We detected a specific expansion of activated T cells expressing the Vβ21.3 T cell receptor β chain variable region in both CD4 and CD8 subsets in 75% of MIS-C patients and not in any patient with TSS, KD, or acute COVID-19; this correlated with the cytokine storm detected. The T cell repertoire returned to baseline within weeks after MIS-C resolution. Vβ21.3+ T cells from MIS-C patients expressed high levels of HLA-DR, CD38 and CX3CR1 but had weak responses to SARS-CoV-2 peptides in vitro. Consistently, the T cell expansion was not associated with specific classical HLA alleles. Thus, our data suggested that MIS-C is characterized by a polyclonal Vβ21.3 T cell expansion not directed against SARS-CoV-2 antigenic peptides, which is not seen in KD, TSS and acute COVID-19.

Multisystem inflammatory syndrome in children and adults (MIS-C/A): Case definition & guidelines for data collection, analysis, and presentation of immunization safety data

This is a Brighton Collaboration Case Definition of the term "Multisystem Inflammatory Syndrome in Children and Adults (MIS-C/A)" to be utilized in the evaluation of adverse events following immunization. The case definition was developed by topic experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of vaccines for SARS-CoV-2. The format of the Brighton Collaboration was followed, including an exhaustive review of the literature, to develop a consensus definition and defined levels of certainty. The document underwent peer review by the Brighton Collaboration Network and by selected expert external reviewers prior to submission. The comments of the reviewers were taken into consideration and edits incorporated into this final manuscript.

Neurologic Involvement in Children and Adolescents Hospitalized in the United States for COVID-19 or Multisystem Inflammatory Syndrome

Importance

Coronavirus disease 2019 (COVID-19) affects the nervous system in adult patients. The spectrum of neurologic involvement in children and adolescents is unclear.

Objective

To understand the range and severity of neurologic involvement among children and adolescents associated with COVID-19.

Setting, Design, and Participants

Case series of patients (age <21 years) hospitalized between March 15, 2020, and December 15, 2020, with positive severe acute respiratory syndrome coronavirus 2 test result (reverse transcriptase-polymerase chain reaction and/or antibody) at 61 US hospitals in the Overcoming COVID-19 public health registry, including 616 (36%) meeting criteria for multisystem inflammatory syndrome in children. Patients with neurologic involvement had acute neurologic signs, symptoms, or diseases on presentation or during hospitalization. Life-threatening involvement was adjudicated by experts based on clinical and/or neuroradiologic features.

Exposures

Severe acute respiratory syndrome coronavirus 2.

Main Outcomes and Measures

Type and severity of neurologic involvement, laboratory and imaging data, and outcomes (death or survival with new neurologic deficits) at hospital discharge.

Results

Of 1695 patients (909 [54%] male; median [interquartile range] age, 9.1 [2.4-15.3] years), 365 (22%) from 52 sites had documented neurologic involvement. Patients with neurologic involvement were more likely to have underlying neurologic disorders (81 of 365 [22%]) compared with those without (113 of 1330 [8%]), but a similar number were previously healthy (195 [53%] vs 723 [54%]) and met criteria for multisystem inflammatory syndrome in children (126 [35%] vs 490 [37%]). Among those with neurologic involvement, 322 (88%) had transient symptoms and survived, and 43 (12%) developed life-threatening conditions clinically adjudicated to be associated with COVID-19, including severe encephalopathy (n = 15; 5 with splenial lesions), stroke (n = 12), central nervous system infection/demyelination (n = 8), Guillain-Barré syndrome/variants (n = 4), and acute fulminant cerebral edema (n = 4). Compared with those without life-threatening conditions (n = 322), those with life-threatening neurologic conditions had higher neutrophil-to-lymphocyte ratios (median, 12.2 vs 4.4) and higher reported frequency of D-dimer greater than 3 μg/mL fibrinogen equivalent units (21 [49%] vs 72 [22%]). Of 43 patients who developed COVID-19-related life-threatening neurologic involvement, 17 survivors (40%) had new neurologic deficits at hospital discharge, and 11 patients (26%) died.

Conclusions and Relevance

In this study, many children and adolescents hospitalized for COVID-19 or multisystem inflammatory syndrome in children had neurologic involvement, mostly transient symptoms. A range of life-threatening and fatal neurologic conditions associated with COVID-19 infrequently occurred. Effects on long-term neurodevelopmental outcomes are unknown.

HLA class I-associated expansion of TRBV11-2 T cells in multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C), a hyperinflammatory syndrome associated with SARS-CoV-2 infection, shares clinical features with toxic shock syndrome, which is triggered by bacterial superantigens. Superantigen specificity for different Vβ chains results in Vβ skewing, whereby T cells with specific Vβ chains and diverse antigen specificity are overrepresented in the T cell receptor (TCR) repertoire. Here, we characterized the TCR repertoire of MIS-C patients and found a profound expansion of TCRβ variable gene 11-2 (TRBV11-2), with up to 24% of clonal T cell space occupied by TRBV11-2 T cells, which correlated with MIS-C severity and serum cytokine levels. Analysis of TRBJ gene usage and complementarity-determining region 3 (CDR3) length distribution of MIS-C expanded TRBV11-2 clones revealed extensive junctional diversity. Patients with TRBV11-2 expansion shared HLA class I alleles A02, B35, and C04, indicating what we believe is a novel mechanism for CDR3-independent T cell expansion. In silico modeling indicated that polyacidic residues in the Vβ chain encoded by TRBV11-2 (Vβ21.3) strongly interact with the superantigen-like motif of SARS-CoV-2 spike glycoprotein, suggesting that unprocessed SARS-CoV-2 spike may directly mediate TRBV11-2 expansion. Overall, our data indicate that a CDR3-independent interaction between SARS-CoV-2 spike and TCR leads to T cell expansion and possibly activation, which may account for the clinical presentation of MIS-C.

Immune dysregulation and autoreactivity correlate with disease severity in SARS-CoV-2-associated multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening post-infectious complication occurring unpredictably weeks after mild or asymptomatic SARS-CoV-2 infection. We profiled MIS-C, adult COVID-19, and healthy pediatric and adult individuals using single-cell RNA sequencing, flow cytometry, antigen receptor repertoire analysis, and unbiased serum proteomics, which collectively identified a signature in MIS-C patients that correlated with disease severity. Despite having no evidence of active infection, MIS-C patients had elevated S100A-family alarmins and decreased antigen presentation signatures, indicative of myeloid dysfunction. MIS-C patients showed elevated expression of cytotoxicity genes in NK and CD8+ T cells and expansion of specific IgG-expressing plasmablasts. Clinically severe MIS-C patients displayed skewed memory T cell TCR repertoires and autoimmunity characterized by endothelium-reactive IgG. The alarmin, cytotoxicity, TCR repertoire, and plasmablast signatures we defined have potential for application in the clinic to better diagnose and potentially predict disease severity early in the course of MIS-C.

Blood neutrophils from children with COVID-19 exhibit both inflammatory and anti-inflammatory markers

Background

Perhaps reflecting that children with COVID-19 rarely exhibit severe respiratory symptoms and often remain asymptomatic, little attention has been paid to explore the immune response in pediatric COVID-19. Here, we analyzed the phenotype and function of circulating neutrophils from children with COVID-19.

Methods

An observational study including 182 children with COVID-19, 21 children with multisystem inflammatory syndrome (MIS-C), and 40 healthy children was performed in Buenos Aires, Argentina. Neutrophil phenotype was analyzed by flow cytometry in blood samples. Cytokine production, plasma levels of IgG antibodies directed to the spike protein of SARS-CoV-2 and citrullinated histone H3 were measured by ELISA. Cell-free DNA was quantified by fluorometry.

Findings

Compared with healthy controls, neutrophils from children with COVID-19 showed a lower expression of CD11b, CD66b, and L-selectin but a higher expression of the activation markers HLA-DR, CD64 and PECAM-1 and the inhibitory receptors LAIR-1 and PD-L1. No differences in the production of cytokines and NETs were observed. Interestingly, the expression of CD64 in neutrophils and the serum concentration of IgG antibodies directed to the spike protein of SARS-CoV-2 distinguished asymptomatic from mild and moderate COVID-19.

Interpretation

Acute lung injury is a prominent feature of severe COVID-19 in adults. A low expression of adhesion molecules together with a high expression of inhibitory receptors in neutrophils from children with COVID-19 might prevent tissue infiltration by neutrophils preserving lung function.

The COVID-19 puzzle: deciphering pathophysiology and phenotypes of a new disease entity

The zoonotic SARS-CoV-2 virus that causes COVID-19 continues to spread worldwide, with devastating consequences. While the medical community has gained insight into the epidemiology of COVID-19, important questions remain about the clinical complexities and underlying mechanisms of disease phenotypes. Severe COVID-19 most commonly involves respiratory manifestations, although other systems are also affected, and acute disease is often followed by protracted complications. Such complex manifestations suggest that SARS-CoV-2 dysregulates the host response, triggering wide-ranging immuno-inflammatory, thrombotic, and parenchymal derangements. We review the intricacies of COVID-19 pathophysiology, its various phenotypes, and the anti-SARS-CoV-2 host response at the humoral and cellular levels. Some similarities exist between COVID-19 and respiratory failure of other origins, but evidence for many distinctive mechanistic features indicates that COVID-19 constitutes a new disease entity, with emerging data suggesting involvement of an endotheliopathy-centred pathophysiology. Further research, combining basic and clinical studies, is needed to advance understanding of pathophysiological mechanisms and to characterise immuno-inflammatory derangements across the range of phenotypes to enable optimum care for patients with COVID-19.

SARS-CoV-2-related MIS-C: A key to the viral and genetic causes of Kawasaki disease?

Multisystem inflammatory syndrome in children (MIS-C) emerged in April 2020 in communities with high COVID-19 rates. This new condition is heterogenous but resembles Kawasaki disease (KD), a well-known but poorly understood and clinically heterogenous pediatric inflammatory condition for which weak associations have been found with a myriad of viral illnesses. Epidemiological data clearly indicate that SARS-CoV-2 is the trigger for MIS-C, which typically occurs about 1 mo after infection. These findings support the hypothesis of viral triggers for the various forms of classic KD. We further suggest that rare inborn errors of immunity (IEIs) altering the immune response to SARS-CoV-2 may underlie the pathogenesis of MIS-C in some children. The discovery of monogenic IEIs underlying MIS-C would shed light on its pathogenesis, paving the way for a new genetic approach to classic KD, revisited as a heterogeneous collection of IEIs to viruses.

Association Between Treatments and Short-Term Biochemical Improvements and Clinical Outcomes in Post-Severe Acute Respiratory Syndrome Coronavirus-2 Inflammatory Syndrome

OBJECTIVES

To 1) analyze the short-term biochemical improvements and clinical outcomes following treatment of children with post-severe acute respiratory syndrome coronavirus-2 inflammatory syndrome (multisystem inflammatory syndrome in children/pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2) admitted to U.K. PICUs and 2) collate current treatment guidance from U.K. PICUs.

DESIGN

Multicenter observational study.

SETTING

Twenty-one U.K. PICUs.

PATIENTS

Children (< 18 yr) admitted to U.K. PICUs between April 1, 2020, and May 10, 2020, fulfilling the U.K. case definition of pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Routinely collected, deidentified data were analyzed. Propensity score and linear mixed effects models were used to analyze the effect of steroids, IV immunoglobulin, and biologic agents on changes in C-reactive protein, platelet counts, and lymphocyte counts over the course of PICU stay. Treatment recommendations from U.K. clinical guidelines were analyzed. Over the 6-week study period, 59 of 78 children (76%) received IV immunoglobulin, 57 of 78 (73%) steroids, and 18 of 78 (24%) a biologic agent. We found no evidence of a difference in response in clinical markers of inflammation between patients with multisystem inflammatory syndrome in children/pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2 who were treated with IV immunoglobulin, steroids, or biologics, compared with those who were not. By the end of the study period, most patients had received immunomodulation. The 12 patients who did not receive any immunomodulators had similar decrease in inflammatory markers as those treated. Of the 14 guidelines analyzed, the use of IV immunoglobulin, steroids, and biologics was universally recommended.

CONCLUSIONS

We were unable to identify any short-term benefit from any of the treatments, or treatment combinations, administered. Despite a lack of evidence, treatment guidelines for multisystem inflammatory syndrome in children/pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus-2 have become very similar in advising step-wise treatments. Retaining clinical equipoise regarding treatment will allow clinicians to enroll children in robust clinical trials to determine the optimal treatment for this novel important condition.

The cytokine storm and thyroid hormone changes in COVID-19

BACKGROUND

COVID-19 is now a worldwide pandemic. Among the many extra-pulmonary manifestations of COVID-19, recent evidence suggested a possible occurrence of thyroid dysfunction.

PURPOSE

The Aim of the present review is to summarize available studies regarding thyroid function alterations in patients with COVID-19 and to overview the possible physio-pathological explanations.

CONCLUSIONS

The repercussions of the thyroid of COVID-19 seem to be related, in part, with the occurrence of a "cytokine storm" that would, in turn, induce a "non-thyroidal illness". Some specific cytokines and chemokines appear to have a direct role on the hypothalamus-pituitary-thyroid axis. On the other hand, some authors have observed an increased incidence of a destructive thyroiditis, either subacute or painless, in patients with COVID-19. The hypothesis of a direct infection of the thyroid by SARS-Cov-2 stems from the observation that its receptor, ACE2, is strongly expressed in thyroid tissue. Lastly, it is highly probable that some pharmaceutical agents largely used for the treatment of COVID-19 can act as confounding factors in the laboratory evaluation of thyroid function parameters.

Multisystem inflammatory syndrome in children (MIS-C) during SARS-CoV-2 pandemic in Brazil: a multicenter, prospective cohort study

OBJECTIVE

To describe the clinical, laboratory, and radiological characteristics, as well as the outcomes of children with MIS-C.

METHOD

Multicenter, prospective cohort study, conducted in 17 pediatric intensive care units in five states in Brazil, from March to July 2020. Patients from 1 month to 19 years who met the MIS-C diagnostic criteria were included consecutively.

RESULTS

Fifty-six patients were included, with the following conditions: Kawasaki-like disease (n = 26), incomplete Kawasaki disease (n = 16), acute cardiac dysfunction (n = 10), toxic shock syndrome (n = 3), and macrophage activation syndrome (n = 1). Median age was 6.2 years (IQR 2.4-10.3), 70% were boys, 59% were non-whites, 20% had comorbidities, 48% reported a contact with COVID-19 cases, and 55% had a recent SARS-CoV-2 infection confirmed by RT-PCR and/or serology. Gastrointestinal symptoms were present in 71%, shock symptoms in 59%, and severe respiratory symptoms in less than 20%. d-Dimer was increased in 80% and cardiac dysfunction markers in more than 75%. Treatment included immunoglobulin (89%); corticosteroids, antibiotics, and enoxaparin in about 50%; and oseltamivir and antifungal therapy in less than 10%. Only 11% needed invasive mechanical ventilation, with a median duration of five days (IQR 5-6.5). The median length of PICU stay was six days (IQR 5-11), and one death occurred (1.8%).

CONCLUSIONS

Most characteristics of the present MIS-C patients were similar to that of other cohorts. The present results may contribute to a broader understanding of SARS-CoV-2 infection in children and its short-term consequences. Long-term multidisciplinary follow-up is needed, since it is not known whether these patients will have chronic cardiac impairment or other sequelae.

Preliminary analyses of scRNA sequencing and immunohistochemistry of children's lung tissues indicate the expression of SARS-CoV-2 entry-related genes may not be the key reason for the milder syndromes of COVID-19 in children

To explore whether the expression levels of viral-entry associated genes might contribute to the milder symptoms in children, we analyzed the expression of these genes in both children and adults’ lung tissues by single cell RNA sequencing (scRNA-seq) and immunohistochemistry (IHC). Both scRNA-seq and IHC analyses showed comparable levels of the key genes for SARS-CoV-2 entry in children and adults, includingACE2, TMPRSS2andFURIN, suggesting that instead of lower virus intrusion rate, other factors are more likely to be the key reasons for the milder symptoms of SARS-CoV-2 infected children.

Proteomic Profiling of MIS-C Patients Reveals Heterogeneity Relating to Interferon Gamma Dysregulation and Vascular Endothelial Dysfunction

Multi-system Inflammatory Syndrome in Children (MIS-C) is a major complication of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic in pediatric patients. Weeks after an often mild or asymptomatic initial infection with SARS-CoV-2 children may present with a severe shock-like picture and marked inflammation. Children with MIS-C present with varying degrees of cardiovascular and hyperinflammatory symptoms. We performed a comprehensive analysis of the plasma proteome of more than 1400 proteins in children with SARS-CoV-2. We hypothesized that the proteome would reflect heterogeneity in hyperinflammation and vascular injury, and further identify pathogenic mediators of disease. Protein signatures demonstrated overlap between MIS-C, and the inflammatory syndromes macrophage activation syndrome (MAS) and thrombotic microangiopathy (TMA). We demonstrate that PLA2G2A is a key marker of MIS-C that associates with TMA. We found that IFNγ responses are dysregulated in MIS-C patients, and that IFNγ levels delineate clinical heterogeneity.

COVID-19 and the gastrointestinal tract: Source of infection or merely a target of the inflammatory process following SARS-CoV-2 infection?

Gastrointestinal (GI) symptoms have been described in a conspicuous percentage of coronavirus disease 2019 (COVID-19) patients. This clinical evidence is supported by the detection of viral RNA in stool, which also supports the hypothesis of a possible fecal-oral transmission route. The involvement of GI tract in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is corroborated by the theoretical assumption that angiotensin converting enzyme 2, which is a SARS-CoV-2 target receptor, is present along the GI tract. Studies have pointed out that gut dysbiosis may occur in COVID-19 patients, with a possible correlation with disease severity and with complications such as multisystem inflammatory syndrome in children. However, the question to be addressed is whether dysbiosis is a consequence or a contributing cause of SARS-CoV-2 infection. In such a scenario, pharmacological therapies aimed at decreasing GI permeability may be beneficial for COVID-19 patients. Considering the possibility of a fecal-oral transmission route, water and environmental sanitation play a crucial role for COVID-19 containment, especially in developing countries.

Systemic Inflammation Is Associated With Neurologic Involvement in Pediatric Inflammatory Multisystem Syndrome Associated With SARS-CoV-2

Objective

Pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) is a severe immune-mediated disorder. We aim to report the neurologic features of children with PIMS-TS.

Methods

We identified children presenting to a large children's hospital with PIMS-TS from March to June 2020 and performed a retrospective medical note review, identifying clinical and investigative features alongside short-term outcome of children presenting with neurologic symptoms.

Results

Seventy-five patients with PIMS-TS were identified, 9 (12%) had neurologic involvement: altered conciseness (3), behavioral changes (3), focal neurology deficits (2), persistent headaches (2), hallucinations (2), excessive sleepiness (1), and new-onset focal seizures (1). Four patients had cranial images abnormalities. At 3-month follow-up, 1 child had died, 1 had hemiparesis, 3 had behavioral changes, and 4 completely recovered. Systemic inflammatory and prothrombotic markers were higher in patients with neurologic involvement (mean highest CRP 267 vs 202 mg/L, p = 0.05; procalcitonin 30.65 vs 13.11 μg/L, p = 0.04; fibrinogen 7.04 vs 6.17 g/L, p = 0.07; d-dimers 19.68 vs 7.35 mg/L, p = 0.005). Among patients with neurologic involvement, these markers were higher in those without full recovery at 3 months (ferritin 2284 vs 283 μg/L, p = 0.05; d-dimers 30.34 vs 6.37 mg/L, p = 0.04). Patients with and without neurologic involvement shared similar risk factors for PIMS-TS (Black, Asian and Minority Ethnic ethnicity 78% vs 70%, obese/overweight 56% vs 42%).

Conclusions

Broad neurologic features were found in 12% patients with PIMS-TS. By 3-month follow-up, half of these surviving children had recovered fully without neurologic impairment. Significantly higher systemic inflammatory markers were identified in children with neurologic involvement and in those who had not recovered fully.

Clinical utility of targeted SARS-CoV-2 serology testing to aid the diagnosis and management of suspected missed, late or post-COVID-19 infection syndromes: Results from a pilot service implemented during the first pandemic wave

During the first wave of the global COVID-19 pandemic the clinical utility and indications for SARS-CoV-2 serological testing were not clearly defined. The urgency to deploy serological assays required rapid evaluation of their performance characteristics. We undertook an internal validation of a CE marked lateral flow immunoassay (LFIA) (SureScreen Diagnostics) using serum from SARS-CoV-2 RNA positive individuals and pre-pandemic samples. This was followed by the delivery of a same-day named patient SARS-CoV-2 serology service using LFIA on vetted referrals at central London teaching hospital with clinical interpretation of result provided to the direct care team. Assay performance, source and nature of referrals, feasibility and clinical utility of the service, particularly benefit in clinical decision-making, were recorded. Sensitivity and specificity of LFIA were 96.1% and 99.3% respectively. 113 tests were performed on 108 participants during three-week pilot. 44% participants (n = 48) had detectable antibodies. Three main indications were identified for serological testing; new acute presentations potentially triggered by recent COVID-19 e.g. pulmonary embolism (n = 5), potential missed diagnoses in context of a recent COVID-19 compatible illness (n = 40), and making infection control or immunosuppression management decisions in persistently SARS-CoV-2 RNA PCR positive individuals (n = 6). We demonstrate acceptable performance characteristics, feasibility and clinical utility of using a LFIA that detects anti-spike antibodies to deliver SARS-CoV-2 serology service in adults and children. Greatest benefit was seen where there is reasonable pre-test probability and results can be linked with clinical advice or intervention. Experience from this pilot can help inform practicalities and benefits of rapidly implementing new tests such as LFIAs into clinical service as the pandemic evolves.

Post-infectious inflammatory disease in MIS-C features elevated cytotoxicity signatures and autoreactivity that correlates with severity

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening post-infectious complication occurring unpredictably weeks after mild or asymptomatic SARS-CoV2 infection in otherwise healthy children. Here, we define immune abnormalities in MIS-C compared to adult COVID-19 and pediatric/adult healthy controls using single-cell RNA sequencing, antigen receptor repertoire analysis, unbiased serum proteomics, and in vitro assays. Despite no evidence of active infection, we uncover elevated S100A-family alarmins in myeloid cells and marked enrichment of serum proteins that map to myeloid cells and pathways including cytokines, complement/coagulation, and fluid shear stress in MIS-C patients. Moreover, NK and CD8 T cell cytotoxicity genes are elevated, and plasmablasts harboring IgG1 and IgG3 are expanded. Consistently, we detect elevated binding of serum IgG from severe MIS-C patients to activated human cardiac microvascular endothelial cells in culture. Thus, we define immunopathology features of MIS-C with implications for predicting and managing this SARS-CoV2-induced critical illness in children.