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

Aging shapes infection profiles of influenza A virus and SARS-CoV-2 in human precision-cut lung slices

BACKGROUND

The coronavirus disease 2019 (COVID-19) outbreak revealed the susceptibility of elderly patients to respiratory virus infections, showing cell senescence or subclinical persistent inflammatory profiles and favoring the development of severe pneumonia.

METHODS

In our study, we evaluated the potential influence of lung aging on the efficiency of replication of influenza A virus (IAV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as well as determining the pro-inflammatory and antiviral responses of the distal lung tissue.

RESULTS

Using precision-cut lung slices (PCLS) from donors of different ages, we found that pandemic H1N1 and avian H5N1 IAV replicated in the lung parenchyma with high efficacy. In contrast to these IAV strains, SARS-CoV-2 Early isolate and Delta variant of concern (VOC) replicated less efficiently in PCLS. Interestingly, both viruses showed reduced replication in PCLS from older compared to younger donors, suggesting that aged lung tissue represents a suboptimal environment for viral replication. Regardless of the age-dependent viral loads, PCLS responded to H5N1 IAV infection by an induction of IL-6 and IP10/CXCL10, both at the mRNA and protein levels, and to H1N1 IAV infection by induction of IP10/CXCL10 mRNA. Finally, while SARS-CoV-2 and H1N1 IAV infection were not causing detectable cell death, H5N1 IAV infection led to more cytotoxicity and induced significant early interferon responses.

CONCLUSIONS

In summary, our findings suggest that aged lung tissue might not favor viral dissemination, pointing to a determinant role of dysregulated immune mechanisms in the development of severe disease.

A genetically modulated Toll-like receptor-tolerant phenotype in peripheral blood cells of children with multisystem inflammatory syndrome

Dysregulated innate immune responses contribute to multisystem inflammatory syndrome in children (MIS-C), characterized by gastrointestinal, mucocutaneous, and/or cardiovascular injury occurring weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure. To investigate innate immune functions, we stimulated ex vivo peripheral blood cells from MIS-C patients with agonists of Toll-like receptors (TLR), key innate immune response initiators. We found severely dampened cytokine responses and elevated gene expression of negative regulators of TLR signaling. Increased plasma levels of zonulin, a gut leakage marker, were also detected. These effects were also observed in fully convalescent children months after MIS-C recovery. When we investigated the genetic background of patients in relation to TLR responsiveness, we found that cells from MIS-C children carrying rare heterozygous variants of lysosomal trafficking regulator (LYST) were less refractory to TLR stimulation and exhibited lysosomal and mitochondrial abnormalities with altered energy metabolism. Moreover, these rare LYST variant heterozygous carriers tended to exhibit unfavorable clinical laboratory indicators of inflammation, including more profound lymphopenia. The results of our observational study have several implications. First, TLR hyporesponsiveness may be associated with hyperinflammation and/or excessive or prolonged stimulation with gut-originated TLR ligands. Second, TLR hyporesponsiveness during MIS-C may be protective, since LYST variant heterozygous carriers exhibited reduced TLR hyporesponsiveness and unfavorable clinical laboratory indicators of inflammation. Thus, links may exist between genetic background, ability to establish a refractory immune state, and MIS-C clinical spectrum. Third, the possibility exists that prolonged TLR hyporesponsiveness is one of the mechanisms driving long coronavirus disease (COVID), which highlights the need to monitor long-term consequences of MIS-C.

Longitudinal cytokine profile in severe COVID-19 and multisystem inflammatory syndrome in children: A single centre study from Egypt

AIM

The severity of COVID-19 is influenced by uncontrolled hyper-inflammatory response with excessive release of many cytokines and chemokines. The understanding of the temporal change in the cytokine levels that underlies the diverse clinical presentations of COVID-19 can help in the prediction of the disease outcome and in the design of proper treatment strategies.

METHOD

Data were collected from children (<18 years old) hospitalised with severe COVID-19 or severe MIS-C who were compared to a group of healthy control children. Patient demographics, clinical, laboratory data and cytokines profiles were evaluated. Blood samples were collected within 24 h of admission for all enrolled children and on Day 14.

RESULTS

Twenty-five children with severe COVID-19 and 23 cases with severe MIS-C were included in the study. The biochemical and inflammatory markers tend to be elevated in MIS-C group. There was a significant difference between studied cases and the control group in the following cytokines: G-CSF, IL-10, HMGB1, TNF-α, IL-6, IL-8 and INF-gamma (P < 0.05). While there was a significant difference between severe COVID-19 and MIS-C groups in the following cytokines at Day 1 of admission; IL-10, IL-6, IL-8 and INF-gamma; while at Day 14, there was a significant difference only for G-CSF, IL-10 and IL-6, all other cytokines were comparable.

CONCLUSION

Our study underpinned patterns of cytokine response in severe COVID-19 and MIS-C. There is a significant upregulation in pro-inflammatory cytokines (mainly G-CSF, IL-10, HMGB1, TNF-α, IL-6, IL-8 and INF-gamma). These biomarkers that could imply on the severity rating and treatment strategies, should be preferentially assessed in SARS-CoV-2 associated immunological events.

An Update on Multi-System Inflammatory Syndrome in Children

PURPOSE

To summarize the latest research on the epidemiology, pathogenesis, diagnosis, and treatment of multisystem inflammatory syndrome in children (MIS-C).

RECENT FINDINGS

The epidemiology of MIS-C has been dynamic since its initial description. The pathogenesis remains poorly understood. Case definitions of MIS-C have evolved over time, and practice patterns for treating MIS-C are variable with generally positive long-term outcomes yet persistent changes noted. MIS-C has become less prevalent and less severe over time, yet racial and ethnic disparities persist, and vaccination against COVID-19 is highly effective in preventing this disease. The link between acute infection and subsequent inflammation is not well understood, with growing evidence describing its immunologic signature. Newer case definitions require excluding other inflammatory conditions, including Kawasaki Disease (KD), before diagnosing MIS-C. Corticosteroid monotherapy may be non-inferior to IVIg alone or combination IVIg plus corticosteroids for initial treatment, distinguishing the approaches to MIS-C and KD. A wide range of biologic therapies have been employed for rescue therapy with general success and no clear benefit of one over another. Despite reports of a high rate of coronary artery abnormality regression and resolution of heart failure, long-term studies suggest persistent changes to cardiac function. The long-term effects of MIS-C continue to be active areas of research.

Differentiating Kawasaki Disease and Multisystem Inflammatory Syndrome in Children Using Blood Composite Scores: Insights into Clinical Outcomes and Predictive Indices

The study sought to assess the clinical utility of complete blood count-derived composite scores, suggesting their potential as markers of inflammation and disease severity in Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) with Kawasaki-like features. This retrospective study analyzed data from 71 KD and 73 MIS-C patients and 70 healthy controls. The KD group showed a higher rate of coronary involvement (26.7% vs. 10.9%), while the MIS-C group had a higher intensive care unit (ICU) admission rate (34.2% vs. 2.8%). Platelet counts, lymphocyte counts, mean platelet volume (MPV), MPV/Lymphocyte (MPVLR), and MPV/Platelet (MPVPR) ratios demonstrated the highest specificities in distinguishing MIS-C than KD (84.5%, 83.1%, 91.1%, 88.7%, and 88.7%, respectively). Monocyte counts, MPV, and MPVPR demonstrated the highest specificities to predictive ICU admission in the MIS-C group (83.3%, 89.6%, and 89.6%, respectively). Lymphocyte counts, platelet/lymphocyte ratio (PLR), neutrophil/lymphocyte ratio (NLR), MPVLR, and Systemic Immune-Inflammation Index (SII) parameters were found to have high negative predictive values for predicting KD patients without coronary artery lesions (CALs) (85.7%, 86.1%, 87.1%, 87.1%, and 85.7%, respectively)., Systemic Inflammation Response Index (SIRI), MPVPR, and CRP were independently predictive of ICU admission in the MIS-C group, and lymphocyte count and IVIG resistance were also identified as significant predictors of CALs in the KD group. NLR, MPVLR, MPVPR, and NPR indices effectively differentiate MIS-C from KD and predict ICU admission in MIS-C. NLR, PLR, MPVLR, and SII are valuable in excluding CALs in KD with high negative predictive values. In addition, SIRI and MPVLR were independent predictors of ICU admission in MIS-C, and lymphocyte count was identified as an independent predictor of CALs in KD.

Plasma IL-17A is increased in patients with critical MIS-C and associated to in-hospital mortality

Background

Multisystem inflammatory syndrome in children (MIS-C) is a rare and severe post-COVID-19 complication with multiple phenotypes.

Objectives

The aim of this study is to study inflammatory biomarkers (cytokines and oxidative stress) in critical MIS-C patients and to observe if there is association between these biomarkers and mortality.

Methods

A single-center prospective study enrolled patients with MIS-C (with positive molecular test), aged between 1 month and 18 years of age. Data was collected from 20 pediatric intensive care unit (PICU)'s bed. Inflammatory biomarkers (cytokines and oxidative stress markers) were performed on day 1 and 3 after hospitalization. Survival rate was calculated, and Kaplan-Meier curves were plotted. Univariate and multivariate Cox regression analyses were conducted. The ROC (Receiver Operating Characteristic) curve analysis was performed.

Results and conclusions

A total of 41 patients out of 109 patients admitted at PICU with suspected MIS-C during the study period were included, of which 33 (80.5%) were male, 9 (22%) were under one year old, and 30 (73.2%) presented comorbidities. Among them, 16 (39%) did not survive. The mean survival time was shorter in patients with higher levels of IL-17A (≥ 19.71 pg/mL) on day 1 (115 vs 323 days, p = 0.004). Higher levels of IL-17A on day 1 were associated with mortality in both the crude model (HR 1.03, CI95% 1.004-1.057, p = 0.022) and the adjusted model (HR 1.043, CI95% 1.013-1.075, p = 0.012). ROC analysis revealed a cut-off value for the IL-17A of 14.32 pg/ml. The other immunological and inflammatory markers did not demonstrate an association with survival (p>0.05). Our findings suggest that patients with high levels of IL-17A are at greater risk for death.

Development of Preliminary Criteria of Macrophage Activation Syndrome in Multisystem Inflammatory Syndrome Associated with COVID-19 in Children

Background: Macrophage activation syndrome (MAS) can be regarded as a key factor determining the severity of multisystem inflammatory syndrome associated with COVID-19 in children (MIS-C), and often requires treatment in the intensive care unit (ICU) to avoid life-threatening complications. No reputable specific criteria for the diagnosis of MAS in MIS-C patients have yet been identified, and criteria currently used for the diagnosis of hemophagocytic syndromes, such as HLH-2004, MAS-2005, and MAS-2016, are not sufficient for MAS in MIS-C. Our goal in this study was to work out the criteria for the early diagnosis of MAS in MIS-C. Methods: One hundred and sixty-six (166) patients with MIS-C were assessed retrospectively. The two most experienced experts independently identified patients with MAS. The patients were divided into three cohorts: MAS (n = 19), without MAS (n = 78), and probable MAS (n = 67). The latter included patients diagnosed with MAS by only one expert, and it was excluded from the analysis. Results: The age of patients with MAS was much higher, and they more frequently had edematous syndrome, hypotension and/or shock, splenomegaly, and CNS involvement. In their blood tests, thrombocytopenia, hypoalbuminemia, and hypertriglyceridemia occurred more often. The level of biomarkers of inflammation, such as ferritin, CRP, troponin, AST, and ALT, was also higher in this group. Increased fibrinogen and D-dimer were also found, demonstrating hypercoagulation in the MAS-MIS-C group. We chose 21 continuous and categorical variables with statistical significance, out of which 2-ferritin > 469 μg/L or platelets < 114 × 109/L-allowed us to discriminate MAS patients. Conclusions: Ferritin > 469 μg/L or platelets < 114 × 109/L can be regarded as key signs to differentiate MAS in MIS-C patients with a sensitivity of 100% and specificity of 94.9%, and they can be used along with other diagnostic methods.

Rare Genetic Variants of NLRP12 in Admixed Latino-American Children With SARS-CoV-2-Related Multisystem Inflammatory Syndrome

Multisystem inflammatory syndrome in children (MIS-C) is a rare, potentially fatal complication of SARS-CoV-2 infection. Genetic defects in inflammation-related pathways have been linked to MIS-C, but additional research is needed, especially in diverse ethnic groups. The present study aimed to identify genetic variants underlying MIS-C in Brazilian patients. Whole exome sequencing was performed, focusing on genes involved in the host immune response to SARS-CoV-2. Functional assays assessed the impact of selected variants on nuclear factor-κB signaling. Nine rare, potentially deleterious variants were found in 8 of 21 patients, located in the IL17RC, IFNA10, or NLRP12 gene. Unlike the wild type NLRP12 protein, which inhibits nuclear factor-κB activation in HEK 293T cells, the mutant NLRP12 proteins have significantly reduced inhibitory properties. In conclusion, our results indicate that rare autosomal variants in immune-related genes may underlie MIS-C, highlighting the potential role of NLRP12 in its predisposition. These findings provide new insights for the appropriate management of MIS-C.

Heterozygous BTNL8 variants in individuals with multisystem inflammatory syndrome in children (MIS-C)

Multisystem inflammatory syndrome in children (MIS-C) is a rare condition following SARS-CoV-2 infection associated with intestinal manifestations. Genetic predisposition, including inborn errors of the OAS-RNAseL pathway, has been reported. We sequenced 154 MIS-C patients and utilized a novel statistical framework of gene burden analysis, "burdenMC," which identified an enrichment for rare predicted-deleterious variants in BTNL8 (OR = 4.2, 95% CI: 3.5-5.3, P < 10-6). BTNL8 encodes an intestinal epithelial regulator of Vγ4+γδ T cells implicated in regulating gut homeostasis. Enrichment was exclusive to MIS-C, being absent in patients with COVID-19 or bacterial disease. Using an available functional test for BTNL8, rare variants from a larger cohort of MIS-C patients (n = 835) were tested which identified eight variants in 18 patients (2.2%) with impaired engagement of Vγ4+γδ T cells. Most of these variants were in the B30.2 domain of BTNL8 implicated in sensing epithelial cell status. These findings were associated with altered intestinal permeability, suggesting a possible link between disrupted gut homeostasis and MIS-C-associated enteropathy triggered by SARS-CoV-2.

Chemotherapy plus therapeutic plasmapheresis with 4% human albumin solution in multiple myeloma patients with acute kidney injury: a prospective, open-label, proof-of-concept study

As no unified treatment protocol or evidence yet exists for plasmapheresis without plasma, this study explored the outcomes of using 4% human albumin (ALB) solution as a replacement solution in patients undergoing plasma exchange for multiple myeloma (MM) patients with acute kidney injury (AKI). This study was prospectively registered (ChiCTR2000030640 and NCT05251896). Bortezomib-based chemotherapy plus therapeutic plasmapheresis (TPP) with 4% human ALB solution was assessed for three years in patients with MM aged >18 years, with AKI according to the Kidney Disease Improving Global Outcomes criteria, and without previous renal impairment from other causes. The primary endpoints were changes in renal function over 18 weeks and survival outcomes at 36 months. The secondary endpoints were the incidence of adverse reactions and symptom improvement. Among the 119 patients included in the analysis, 108 experienced renal reactions. The M protein (absolute changes: median -12.12%, interquartile ranges (IQRs) -18.62 to -5.626) and creatine (median -46.91 μmol/L, IQR -64.70 to -29.12) levels decreased, whereas the estimated glomerular filtration rate (eGFR) increased (median 20.66 mL/(min·1.73 m2), IQR 16.03-25.29). Regarding patient survival, 68.1% and 35.3% of patients survived for >12 and >36 months, respectively. The three symptoms with the greatest relief were urine foam, poor appetite, and blurred vision. All 11 patients (7.6%) who experienced mild adverse reactions achieved remission. In conclusion, in MM patients with AKI, plasma-free plasmapheresis with 4% human ALB solution and bortezomib-based chemotherapy effectively alleviated light chain damage to kidney function while improving patient quality of life.

NK Cell and Monocyte Dysfunction in Multisystem Inflammatory Syndrome in Children

Multisystem inflammatory syndrome in children (MIS-C) is a severe complication of SARS-CoV-2 infection characterized by multiorgan involvement and inflammation. Testing of cellular function ex vivo to understand the aberrant immune response in MIS-C is limited. Despite strong Ab production in MIS-C, SARS-CoV-2 nucleic acid testing can remain positive for 4-6 wk postinfection. Therefore, we hypothesized that dysfunctional cell-mediated Ab responses downstream of Ab production may be responsible for delayed clearance of viral products in MIS-C. In MIS-C, monocytes were hyperfunctional for phagocytosis and cytokine production, whereas NK cells were hypofunctional for both killing and cytokine production. The decreased NK cell cytotoxicity correlated with an NK exhaustion marker signature and systemic IL-6 levels. Potentially providing a therapeutic option, cellular engagers of CD16 and SARS-CoV-2 proteins were found to rescue NK cell function in vitro. Taken together, our results reveal dysregulation in Ab-mediated cellular responses of myeloid and NK cells that likely contribute to the immune pathology of this disease.

COVID-19 in Children and Vitamin D

In December 2019, the so-called "coronavirus disease 2019" (COVID-19) began. This disease is characterized by heterogeneous clinical manifestations, ranging from an asymptomatic process to life-threatening conditions associated with a "cytokine storm". This article (narrative review) summarizes the epidemiologic characteristics and clinical manifestations of COVID-19 and multi-system inflammatory syndrome in children (MIS-C). The effect of the pandemic confinement on vitamin D status and the hypotheses proposed to explain the age-related difference in the severity of COVID-19 are discussed. The role of vitamin D as a critical regulator of both innate and adaptive immune responses and the COVID-19 cytokine storm is analyzed. Vitamin D and its links to both COVID-19 (low levels of vitamin D appear to worsen COVID-19 outcomes) and the cytokine storm (anti-inflammatory activity) are detailed. Finally, the efficacy of vitamin D supplementation in COVID-19 is evaluated, but the evidence supporting vitamin D supplementation as an adjuvant treatment for COVID-19 remains uncertain.

Altered Spike Immunoglobulin G Fc N-Linked Glycans Are Associated With Hyperinflammatory State in Adult Coronavirus Disease 2019 and Multisystem Inflammatory Syndrome in Children

Background

Severe coronavirus disease 2019 (COVID-19) and multisystem inflammatory syndrome (MIS-C) are characterized by excessive inflammatory cytokines/chemokines. In adults, disease severity is associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific immunoglobulin G (IgG) Fc afucosylation, which induces proinflammatory cytokine secretion from innate immune cells. This study aimed to define spike IgG Fc glycosylation following SARS-CoV-2 infection in adults and children and following SARS-CoV-2 vaccination in adults and the relationships between glycan modifications and cytokines/chemokines.

Methods

We analyzed longitudinal (n = 146) and cross-sectional (n = 49) serum/plasma samples from adult and pediatric COVID-19 patients, MIS-C patients, adult vaccinees, and adult and pediatric controls. We developed methods for characterizing bulk and spike IgG Fc glycosylation by capillary electrophoresis and measured levels of 10 inflammatory cytokines/chemokines by multiplexed enzyme-linked immunosorbent assay.

Results

Spike IgG was more afucosylated than bulk IgG during acute adult COVID-19 and MIS-C. We observed an opposite trend following vaccination, but it was not significant. Spike IgG was more galactosylated and sialylated and less bisected than bulk IgG during adult COVID-19, with similar trends observed during pediatric COVID-19/MIS-C and following SARS-CoV-2 vaccination. Spike IgG glycosylation changed with time following adult COVID-19 or vaccination. Afucosylated spike IgG exhibited inverse and positive correlations with inflammatory markers in MIS-C and following vaccination, respectively; galactosylated and sialylated spike IgG inversely correlated with proinflammatory cytokines in adult COVID-19 and MIS-C; and bisected spike IgG positively correlated with inflammatory cytokines/chemokines in multiple groups.

Conclusions

We identified previously undescribed relationships between spike IgG glycan modifications and inflammatory cytokines/chemokines that expand our understanding of IgG glycosylation changes that may impact COVID-19 and MIS-C immunopathology.

Comparison οf Immune Responses Through Multiparametric T-Cell Cytokine Expression Profile Between Children with Convalescent COVID-19 or Multisystem Inflammatory Syndrome

BACKGROUND/OBJECTIVES

The immunological pathways that cause Multisystem Inflammatory Syndrome after SARS-CoV-2 infection in children (MIS-C) remain under investigation.

METHODS

The aim of this study was to prospectively compare the T-cell cytokine expression profile in unvaccinated children with acute MIS-C (MISC_A) before immunosuppression, convalescent MIS-C (one month after syndrome onset, MISC_C), convalescent COVID-19 (one month after hospitalization), and in healthy, unvaccinated controls. The intracellular expression of IL-4, IL-2, IL-17, IFNγ, TNF-α and Granzyme B, and the post SARS-CoV-2-Spike antigenic mix stimulation of T-cell subsets was analyzed by 13-color flow cytometry.

RESULTS

Twenty children with a median age (IQR) of 11.5 (7.25-14) years were included in the study. From the comparison of the flow cytometry analysis of the 14 markers of MISC_A with the other three groups (MISC_C, post-COVID-19 and controls), significant differences were identified as follows: 1. CD4+IL-17+/million CD3+: 293.0(256.4-870.9) vs. 50.7(8.4-140.5); p-value: 0.03, vs. 96.7(89.2-135.4); p-value: 0.03 and vs. 8.7(0.0-82.4); p-value: 0.03, respectively; 2. CD8+IL-17+/million CD3+: 335.2(225.8-429.9) vs. 78.0(31.9-128.9) vs. 84.1(0.0-204.6) vs. 33.2(0.0-114.6); p-value: 0.05, respectively; 3. CD8+IFNγ+/million CD3+: 162.2(91.6-273.4) vs. 41.5(0.0-77.4); p-value: 0.03 vs. 30.3(0.0-92.8); p-value: 0.08, respectively.

CONCLUSIONS

In children presenting with MIS-C one month after COVID-19 infection, T cells were found to be polarized towards IL-17 and IFNγ production compared to those with uncomplicated convalescent COVID-19, a finding that could provide possible immunological biomarkers for MIS-C detection.

One- and Two-year Multidisciplinary Follow-Up of MIS-C at a Tertiary Hospital: A Retrospective Cohort Study

BACKGROUND

Although 6-month follow-up of patients with multisystem inflammatory syndrome in children (MIS-C) was reassuring, there is scant data on long-term sequelae, including whether changing variants affect clinical severity and outcomes.

METHODS

Children (<18 years of age) admitted to Great Ormond Street Hospital between April 4, 2020, and January 2023, meeting diagnostic criteria for MIS-C were included. Admission and follow-up data were categorized by the predominant SARS-CoV-2 circulating variant in the United Kingdom.

RESULTS

One hundred and sixty children [median age, 10.1 (interquartile range, 7.9-12.6) years] were included. There was no difference in the time of symptom onset to diagnosis between waves ( P =0.23) or hospitalization days across all waves ( P =0.32). Inflammatory markers were normal for up to 2 years in all patients except one. Eleven patients (6.9%) remain in follow-up: cardiology (n=5), gastroenterology (n=5) and nephrology (n=1). The main self-reported symptoms at 2 years were abdominal pain (n=5) and myalgia (n=2). Fatigue was present in approximately a quarter of patients at admission; this reduced to 14 (9%), (2%) and 1 (2%) at 6-month, 1-year and 2-year follow-ups, respectively. Chronic fatigue or long-COVID symptomatology was rare (n=1) even with high rates of concurrent Epstein-Barr virus positivity (49/134). All patients had sustained neurological recovery with no new neurological pathology observed.

CONCLUSIONS

Patients with MIS-C have a sustained recovery, which is reassuring for positive long-term outcomes. Across waves, time from symptom onset to diagnosis and treatment, symptomatology and length of stay were similar. Sustained recovery is reassuring for clinicians and parents alike. Differentiating long-COVID symptomatology from that of MIS-C is important in formulating an individualized treatment plan.

Leukocyte activation patterns in hospitalized children: comparing SARS-CoV-2, bacterial infections, and inflammatory pathologies

In adults, monocytes and neutrophils play important roles in the hyperinflammatory responses characteristic of severe forms of SARS-CoV-2 infection. We assessed leukocyte activation in 55 children attending the emergency department for acute fever between March 2020 and September 2021. The following markers were analyzed by flow cytometry: CD169 and HLA-DR on monocytes, CD64 and CD16 on neutrophils, and CD38 on lymphocytes TCD8. Fifteen of the children had SARS-CoV-2 infection, 15 had bacterial infections, and 15 had inflammatory diseases. We observed overexpression of CD169 on monocytes and CD38 on T lymphocytes in all patients with a diagnosis of SARS-CoV-2, while overexpression of CD64 on neutrophils was observed with bacterial infections and inflammatory diseases. There was a decrease in the expression of HLA-DR on monocytes in the bacterial infection and inflammatory pathology groups. Leukocyte analysis identifies distinct activation patterns in children during SARS-CoV-2 infections, bacterial infections, and inflammatory diseases.

Shared neutrophil and T cell dysfunction is accompanied by a distinct interferon signature during severe febrile illnesses in children

Severe febrile illnesses in children encompass life-threatening organ dysfunction caused by diverse pathogens and other severe inflammatory syndromes. A comparative approach to these illnesses may identify shared and distinct features of host immune dysfunction amenable to immunomodulation. Here, using immunophenotyping with mass cytometry and cell stimulation experiments, we illustrate trajectories of immune dysfunction in 74 children with multi-system inflammatory syndrome in children (MIS-C) associated with SARS-CoV-2, 30 with bacterial infection, 16 with viral infection, 8 with Kawasaki disease, and 42 controls. We explore these findings in a secondary cohort of 500 children with these illnesses and 134 controls. We show that neutrophil activation and apoptosis are prominent in multi-system inflammatory syndrome, and that this is partially shared with bacterial infection. We show that memory T cells from patients with multi-system inflammatory syndrome and bacterial infection are exhausted. In contrast, we show viral infection to be characterized by a distinct signature of decreased interferon signaling and lower interferon receptor gene expression. Improved understanding of immune dysfunction may improve approaches to immunomodulator therapy in severe febrile illnesses in children.

Risks of Kawasaki disease and multisystem inflammatory syndrome in pediatric patients with COVID-19 infection: A TriNetX based cohort study

BACKGROUND

The associations of coronavirus disease (COVID-19) with Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) remain unclear. Few large-scale studies have estimated the cumulative incidence of MIS-C and KD after COVID-19 in children.

METHODS

Data were obtained from TriNetX. After propensity score matching was completed, data from 258 645 patients with COVID-19 (COVID-19 group) and 258 645 patients without COVID-19 (non-COVID-19 group) were analyzed using Cox regression. Hazard ratio (HR), 95% CI, and cumulative incidence of MIS-C and KD were calculated for both groups. A stratified analysis was performed to validate the results.

RESULTS

After matching for age at baseline and sex, the risks of MIS-C and KD were higher in the COVID-19 group than in the non-COVID-19 group (HR: 3.023 [95% CI, 2.323-3.933] and 1.736 [95% CI, 1.273-2.369], respectively). After matching for age at baseline, sex, race, ethnicity, and comorbidities, the risks of MIS-C and KD remained significantly higher in the COVID-19 group than in the non-COVID-19 group (HR: 2.899 [95% CI, 2.173-3.868] and 1.435 [95% CI, 1.030-2.000]). When stratified by age, the risk of MIS-C was higher in the COVID-19 group-for patients aged >5 years and ≤5 years (HR: 2.399 [95% CI, 1.683-3.418] and 2.673 [95% CI, 1.737-4.112], respectively)-than in the non-COVID-19 group. However, the risk of KD was elevated only in patients aged ≤5 years (HR: 1.808; 95% CI, 1.203-2.716). When stratified by COVID-19 vaccination status, the risks of MIS-C and KD were elevated in unvaccinated patients with COVID-19 (HR: 2.406 and 1.835, respectively).

CONCLUSION

Patients with COVID-19 who are aged <18 and ≤5 years have increased risks of MIS-C and KD, respectively. Further studies are required to confirm the role of COVID-19 in the pathogenesis of MIS-C and KD.

The Intricate Dance of Infections and Autoimmunity: An Interesting Paradox

Besides genetic susceptibility, infections due to viruses, bacteria and protozoa have been implicated in the development of autoimmune diseases (AD). AD can be triggered in a genetically susceptible individual by infections that disrupt immunological tolerance towards self-antigens. Pathogens can initiate autoimmunity by way of molecular mimicry, bystander activation, epitope spreading or persistent infection with polyclonal activation. This review covers two main topics: (i) the mechanisms by which an infectious agent can trigger or worsen autoimmunity; and (ii) the correlation between specific infectious agents and AD in humans with special emphasis on multisystem inflammatory syndrome in children (MIS-C).

The Spectrum of Postacute Sequelae of COVID-19 in Children: From MIS-C to Long COVID

The effects of SARS-CoV-2 infection on children continue to evolve following the onset of the COVID-19 pandemic. Although life-threatening multisystem inflammatory syndrome in children (MIS-C) has become rare, long-standing symptoms stemming from persistent immune activation beyond the resolution of acute SARS-CoV-2 infection contribute to major health sequelae and continue to pose an economic burden. Shared pathophysiologic mechanisms place MIS-C and long COVID within a vast spectrum of postinfectious conditions characterized by intestinal dysbiosis, increased gut permeability, and varying degrees of immune dysregulation. Insights obtained from MIS-C will help shape our understanding of the more indolent and prevalent postacute sequelae of COVID and ultimately guide efforts to improve diagnosis and management of postinfectious complications of SARS-CoV-2 infection in children.

Emergency Myelopoiesis Distinguishes Multisystem Inflammatory Syndrome in Children From Pediatric Severe Coronavirus Disease 2019

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) is a hyperinflammatory condition caused by recent infection with severe acute respiratory syndrome coronavirus 2, but the underlying immunological mechanisms driving this distinct syndrome are unknown.

METHODS

We utilized high-dimensional flow cytometry, cell-free (cf) DNA, and cytokine and chemokine profiling to identify mechanisms of critical illness distinguishing MIS-C from severe acute coronavirus disease 2019 (SAC).

RESULTS

Compared to SAC, MIS-C patients demonstrated profound innate immune cell death and features of emergency myelopoiesis (EM), an understudied phenomenon observed in severe inflammation. EM signatures were characterized by fewer mature myeloid cells in the periphery and decreased expression of HLA-DR and CD86 on antigen-presenting cells. Interleukin 27 (IL-27), a cytokine known to drive hematopoietic stem cells toward EM, was increased in MIS-C, and correlated with immature cell signatures in MIS-C. Upon recovery, EM signatures decreased and IL-27 plasma levels returned to normal levels. Despite profound lymphopenia, we report a lack of cfDNA released by adaptive immune cells and increased CCR7 expression on T cells indicative of egress out of peripheral blood.

CONCLUSIONS

Immune cell signatures of EM combined with elevated innate immune cell-derived cfDNA levels distinguish MIS-C from SAC in children and provide mechanistic insight into dysregulated immunity contributing toward MIS-C, offering potential diagnostic and therapeutic targets.

Esophageal ulcer and multisystem inflammatory syndrome after COVID-19: A case report

BACKGROUND

Multisystem inflammatory syndrome in adults (MIS-A) is a rare but severe disease occurring several weeks after severe acute respiratory syndrome coronavirus 2 infection. It develops in adults with inflammation of different organs including the gastrointestinal tract, heart, kidneys, skin and hematopoietic system.

CASE SUMMARY

We present a 58-year-old Chinese man diagnosed with MIS-A. His chief complaints were fever, generalized fatigue and anorexia, accompanied with rashes on his back. Further examination showed cardiac, renal and liver injury. He had melena and gastroscopy indicated esophageal ulcer and severe esophagitis. Repeated blood and sputum culture did not show growth of bacteria or fungi. Antibiotic treatment was stopped due to unsatisfactory performance. His condition improved after prednisone and other supportive treatment.

CONCLUSION

Gastrointestinal involvement in MIS-A is not uncommon. Intestinal involvement predominates, and esophageal involvement is rarely reported. Esophageal ulcer with bleeding could also be a manifestation of MIS-A.

Describing Elephants: An Update on the Immunopathology of Multisystem Inflammatory Syndrome in Children

First described in 2020, multi-system inflammatory syndrome in children (MIS-C) is an, initially life-threatening, disease characterised by severe inflammation and following exposure to SARS-CoV-2. The immunopathology of MIS-C involves a hyperinflammation characterised by a cytokine storm and activation of both the innate and adaptive immune system, eventually leading to multi-organ failure. Several etiological theories are described in literature. Firstly, it is suggested that the gut plays an important role in the translocation of microbial products to the systemic circulation. Additionally, the production of autoantibodies that develop after the initial infection with SARS-CoV-2 might lead to many of its broad clinical symptoms. Finally, the superantigen theory where non-specific binding of the SARS-CoV-2 spike glycoprotein to the T-cell receptor leads to a subsequent activation of T cells, generating a powerful immune response. Despite the sudden outbreak of MIS-C and alarming messages, as of 2024, cases have declined drastically and subsequently show a less severe clinical spectrum. However, subacute cases not meeting current diagnostic criteria might be overlooked even though they represent a valuable research population. In the future, research should focus on adjusting these criteria to better understand the broad pathophysiology of MIS-C, aiding early detection, therapy, and prediction.

Case report: Cytokine and miRNA profiling in multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is an imperative pediatric inflammatory condition closely linked to COVID-19, which garners substantial attention since the onset of the pandemic. Like Kawasaki illness, this condition is characterized by an overactive immune response, leading to symptoms including pyrexia, cardiac and renal complications. To elucidate the pathogenesis of MIS-C and identify potential biomarkers, we conducted an extensive examination of specific cytokines (IL-6, IL-1β, IL-6R, IL-10, and TNF-α) and microRNA (miRNA) expression profiles at various intervals (ranging from 3 to 20 days) in the peripheral blood sample of a severely affected MIS-C patient. Our investigation revealed a gradual decline in circulating levels of IL-6, IL-1β, IL-10, and TNF-α following intravenous immune globulin (IVIG) therapy. Notably, IL-6 exhibited a significant reduction from 74.30 to 1.49 pg./mL, while IL-6R levels remained consistently stable throughout the disease course. Furthermore, we observed an inverse correlation between the expression of hsa-miR-596 and hsa-miR-224-5p and the aforementioned cytokines. Our findings underscore a robust association between blood cytokine and miRNA concentrations and the severity of MIS-C. These insights enhance our understanding of the genetic regulatory mechanisms implicated in MIS-C pathogenesis, offering potential avenues for early biomarker detection and therapy monitoring through miRNA analysis.

Molecular mimicry in multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is a severe, post-infectious sequela of SARS-CoV-2 infection1,2, yet the pathophysiological mechanism connecting the infection to the broad inflammatory syndrome remains unknown. Here we leveraged a large set of samples from patients with MIS-C to identify a distinct set of host proteins targeted by patient autoantibodies including a particular autoreactive epitope within SNX8, a protein involved in regulating an antiviral pathway associated with MIS-C pathogenesis. In parallel, we also probed antibody responses from patients with MIS-C to the complete SARS-CoV-2 proteome and found enriched reactivity against a distinct domain of the SARS-CoV-2 nucleocapsid protein. The immunogenic regions of the viral nucleocapsid and host SNX8 proteins bear remarkable sequence similarity. Consequently, we found that many children with anti-SNX8 autoantibodies also have cross-reactive T cells engaging both the SNX8 and the SARS-CoV-2 nucleocapsid protein epitopes. Together, these findings suggest that patients with MIS-C develop a characteristic immune response to the SARS-CoV-2 nucleocapsid protein that is associated with cross-reactivity to the self-protein SNX8, demonstrating a mechanistic link between the infection and the inflammatory syndrome, with implications for better understanding a range of post-infectious autoinflammatory diseases.

The complex landscape of immune dysregulation in multisystem inflammatory syndrome in children with COVID-19

The immune responses following SARS-CoV-2 infection in children are still under investigation. While coronavirus disease 2019 (COVID-19) is usually mild in the paediatric population, some children develop severe clinical manifestations or multisystem inflammatory syndrome in children (MIS-C) after infection. MIS-C, typically emerging 2-6 weeks after SARS-CoV-2 exposure, is characterized by a hyperinflammatory response affecting multiple organs. This review aims to explore the complex landscape of immune dysregulation in MIS-C, focusing on innate, T cell-, and B cell-mediated immunity, and discusses the role of SARS-CoV-2 spike protein as a superantigen in MIS-C pathophysiology. Understanding these mechanisms is crucial for improving the management and outcomes for affected children.

Altered spike IgG Fc N-linked glycans are associated with hyperinflammatory state in adult COVID and Multisystem Inflammatory Syndrome in Children

Background

Severe COVID and multisystem inflammatory syndrome (MIS-C) are characterized by excessive inflammatory cytokines/chemokines. In adults, disease severity is associated with SARS-CoV-2-specific IgG Fc afucosylation, which induces pro-inflammatory cytokine secretion from innate immune cells. This study aimed to define spike IgG Fc glycosylation following SARS-CoV-2 infection in adults and children and following SARS-CoV-2 vaccination in adults and the relationships between glycan modifications and cytokine/chemokine levels.

Methods

We analyzed longitudinal (n=146) and cross-sectional (n=49) serum/plasma samples from adult and pediatric COVID patients, MIS-C patients, adult vaccinees, and adult and pediatric healthy controls. We developed methods for characterizing bulk and spike IgG Fc glycosylation by capillary electrophoresis (CE) and measured levels of ten inflammatory cytokines/chemokines by multiplexed ELISA.

Results

Spike IgG were more afucosylated than bulk IgG during acute adult COVID and MIS-C. We observed an opposite trend following vaccination, but it was not significant. Spike IgG were more galactosylated and sialylated and less bisected than bulk IgG during adult COVID, with similar trends observed during pediatric COVID/MIS-C and following SARS-CoV-2 vaccination. Spike IgG glycosylation changed with time following adult COVID or vaccination. Afucosylated spike IgG exhibited inverse and positive correlations with inflammatory markers in MIS-C and following vaccination, respectively; galactosylated and sialylated spike IgG inversely correlated with pro-inflammatory cytokines in adult COVID and MIS-C; and bisected spike IgG positively correlated with inflammatory cytokines/chemokines in multiple groups.

Conclusions

We identified previously undescribed relationships between spike IgG glycan modifications and inflammatory cytokines/chemokines that expand our understanding of IgG glycosylation changes that may impact COVID and MIS-C immunopathology.

Elevated risk for psychiatric outcomes in pediatric patients with Multisystem Inflammatory Syndrome (MIS-C): A review of neuroinflammatory and psychosocial stressors

Multisystem Inflammatory Syndrome in Children (MIS-C) is a secondary immune manifestation of COVID-19 involving multiple organ systems in the body, resulting in fever, skin rash, abdominal pain, nausea, shock, and cardiac dysfunction that often lead to hospitalization. Although many of these symptoms resolve following anti-inflammatory treatment, the long-term neurological and psychiatric sequelae of MIS-C are unknown. In this review, we will summarize two domains of the MIS-C disease course, 1) Neuroinflammation in the MIS-C brain and 2) Psychosocial disruptions resulting from stress and hospitalization. In both domains, we present existing clinical findings and hypothesize potential connections to psychiatric outcomes. This is the first review to conceptualize a holistic framework of psychiatric risk in MIS-C patients that includes neuroinflammatory and psychosocial risk factors. As cases of severe COVID-19 and MIS-C subside, it is important for clinicians to monitor outcomes in this vulnerable patient population.

IL-10 suppresses T cell expansion while promoting tissue-resident memory cell formation during SARS-CoV-2 infection in rhesus macaques

The regulation of inflammatory responses and pulmonary disease during SARS-CoV-2 infection is incompletely understood. Here we examine the roles of the prototypic pro- and anti-inflammatory cytokines IFNγ and IL-10 using the rhesus macaque model of mild COVID-19. We find that IFNγ drives the development of 18fluorodeoxyglucose (FDG)-avid lesions in the lungs as measured by PET/CT imaging but is not required for suppression of viral replication. In contrast, IL-10 limits the duration of acute pulmonary lesions, serum markers of inflammation and the magnitude of virus-specific T cell expansion but does not impair viral clearance. We also show that IL-10 induces the subsequent differentiation of virus-specific effector T cells into CD69+CD103+ tissue resident memory cells (Trm) in the airways and maintains Trm cells in nasal mucosal surfaces, highlighting an unexpected role for IL-10 in promoting airway memory T cells during SARS-CoV-2 infection of macaques.

Testing for SARS-CoV-2: lessons learned and current use cases

SUMMARYThe emergence and worldwide dissemination of SARS-CoV-2 required both urgent development of new diagnostic tests and expansion of diagnostic testing capacity on an unprecedented scale. The rapid evolution of technologies that allowed testing to move out of traditional laboratories and into point-of-care testing centers and the home transformed the diagnostic landscape. Four years later, with the end of the formal public health emergency but continued global circulation of the virus, it is important to take a fresh look at available SARS-CoV-2 testing technologies and consider how they should be used going forward. This review considers current use case scenarios for SARS-CoV-2 antigen, nucleic acid amplification, and immunologic tests, incorporating the latest evidence for analytical/clinical performance characteristics and advantages/limitations for each test type to inform current debates about how tests should or should not be used.

TAFRO Syndrome and COVID-19

TAFRO syndrome is a systemic inflammatory disease characterized by thrombocytopenia and anasarca. It results from hyperinflammation and produces severe cytokine storms. Severe acute respiratory syndrome coronavirus 2, which led to the coronavirus disease 2019 (COVID-19) pandemic, also causes cytokine storms. COVID-19 was reported to be associated with various immune-related manifestations, including multisystem inflammatory syndrome, hemophagocytic syndrome, vasculitis, and immune thrombocytopenia. Although the pathogenesis and complications of COVID-19 have not been fully elucidated, the pathogeneses of excessive immunoreaction after COVID-19 and TAFRO syndrome both involve cytokine storms. Since the COVID-19 pandemic, there have been a few case reports about the onset of TAFRO syndrome after COVID-19 or COVID-19 vaccination. Castleman disease also presents with excessive cytokine production. We reviewed the literature about the association between TAFRO syndrome or Castleman disease and COVID-19 or vaccination against it. While the similarities and differences between the pathogeneses of TAFRO syndrome and COVID-19 have not been investigated previously, the cytokines and genetic factors associated with TAFRO syndrome and COVID-19 were reviewed by examining case reports. Investigation of TAFRO-like manifestations after COVID-19 or vaccination against COVID-19 may contribute to understanding the pathogenesis of TAFRO syndrome.

Advanced nanomedicines and immunotherapeutics to treat respiratory diseases especially COVID-19 induced thrombosis

Immunotherapy and associated immune regulation strategies gained huge attraction in order to be utilized for treatment and prevention of respiratory diseases. Engineering specifically nanomedicines can be used to regulate host immunity in lungs in the case of respiratory diseases including coronavirus disease 2019 (COVID-19) infection. COVID-19 causes pulmonary embolisms, thus new therapeutic options are required to target thrombosis, as conventional treatment options are either not effective due to the complexity of the immune-thrombosis pathophysiology. In this review, we discuss regulation of immune response in respiratory diseases especially COVID-19. We further discuss thrombosis and provide an overview of some antithrombotic nanoparticles, which can be used to develop nanomedicine against thrombo-inflammation induced by COVID-19 and other respiratory infectious diseases. We also elaborate the importance of immunomodulatory nanomedicines that can block pro-inflammatory signalling pathways, and thus can be recommended to treat respiratory infectious diseases.

Integration of metalloproteome and immunoproteome reveals a tight link of iron-related proteins with COVID-19 pathogenesis and immunity

Increasing clinical data show that the imbalance of host metallome is closely associated with different kinds of disease, however, the intrinsic mechanisms of action of metals in immunity and pathogenesis of disease remain largely undefined. There is lack of multiplexed profiling system to integrate the metalloproteome-immunoproteome information at systemic level for exploring the roles of metals in immunity and disease pathogenesis. In this study, we build up a metal-coding assisted multiplexed proteome assay platform for serum metalloproteomic and immunoproteomic profiling. By taking COVID-19 as a showcase, we unbiasedly uncovered the most evident modulation of iron-related proteins, i.e., Ft and Tf, in serum of severe COVID-19 patients, and the value of Ft/Tf could work as a robust biomarker for COVID-19 severity stratification, which overtakes the well-established clinical risk factors (cytokines). We further uncovered a tight association of transferrin with inflammation mediator IL-10 in COVID-19 patients, which was proved to be mainly governed by the monocyte/macrophage of liver, shedding light on new pathophysiological and immune regulatory mechanisms of COVID-19 disease. We finally validated the beneficial effects of iron chelators as anti-viral agents in SARS-CoV-2-infected K18-hACE2 mice through modulation of iron dyshomeostasis and alleviating inflammation response. Our findings highlight the critical role of liver-mediated iron dysregulation in COVID-19 disease severity, providing solid evidence on the involvement of iron-related proteins in COVID-19 pathophysiology and immunity.

Innate and adaptive immunity in acute myocarditis

Acute myocarditis is an acute inflammatory cardiomyopathy associated with cardiac damage triggered by a virus or a pathological immune activation. It may present with a wide range of clinical presentations, ranging from mild symptoms to severe forms like fulminant myocarditis, characterized by hemodynamic compromise and cardiogenic shock. The immune system plays a central role in the pathogenesis of myocarditis. In fact, while its function is primarily protective, aberrant responses can be detrimental. In this context, both innate and adaptive immunity play pivotal roles; notably, the innate system offers a non-specific and immediate defense, while the adaptive provides specialized protection with immunological memory. However, dysregulation in these systems can misidentify cardiac tissue, triggering autoimmune reactions and possibly leading to significant cardiac tissue damage. This review highlights the importance of innate and adaptive immune responses in the progression and treatment of acute myocarditis.

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.

The gonadal niche safeguards human fetal germline cell development following maternal SARS-CoV-2 infection

During pregnancy, germline development is vital for maintaining the continuation of species. Recent studies have shown increased pregnancy risks in COVID-19 patients at the perinatal stage. However, the potential consequence of infection for reproductive quality in developing fetuses remains unclear. Here, we analyze the transcriptome and DNA methylome of the fetal germline following maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We find that infection at early gestational age, a critical period of human primordial germ cell specification and epigenetic reprogramming, trivially affects fetal germ cell (FGC) development. Additionally, FGC-niche communications are not compromised by maternal infection. Strikingly, both general and SARS-CoV-2-specific immune pathways are greatly activated in gonadal niche cells to protect FGCs from maternal infection. Notably, there occurs an "in advance" development tendency in FGCs after maternal infection. Our study provides insights into the impacts of maternal SARS-CoV-2 infection on fetal germline development and serves as potential clinical guidance for future pandemics.

Enhanced CD95 and interleukin 18 signalling accompany T cell receptor Vβ21.3+ activation in multi-inflammatory syndrome in children

Multisystem inflammatory syndrome in children is a post-infectious presentation SARS-CoV-2 associated with expansion of the T cell receptor Vβ21.3+ T-cell subgroup. Here we apply muti-single cell omics to compare the inflammatory process in children with acute respiratory COVID-19 and those presenting with non SARS-CoV-2 infections in children. Here we show that in Multi-Inflammatory Syndrome in Children (MIS-C), the natural killer cell and monocyte population demonstrate heightened CD95 (Fas) and Interleuking 18 receptor expression. Additionally, TCR Vβ21.3+ CD4+ T-cells exhibit skewed differentiation towards T helper 1, 17 and regulatory T cells, with increased expression of the co-stimulation receptors ICOS, CD28 and interleukin 18 receptor. We observe no functional evidence for NLRP3 inflammasome pathway overactivation, though MIS-C monocytes show elevated active caspase 8. This, coupled with raised IL18 mRNA expression in CD16- NK cells on single cell RNA sequencing analysis, suggests interleukin 18 and CD95 signalling may trigger activation of TCR Vβ21.3+ T-cells in MIS-C, driven by increased IL-18 production from activated monocytes and CD16- Natural Killer cells.

Treatment of multisystem inflammatory syndrome in children

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C), a relatively uncommon but severe pediatric complication, is associated with coronavirus disease 2019 (COVID-19). A variety of treatment approaches, including intravenous immunoglobulins (IVIGs), glucocorticoids (GCs) and biologic agents, such as anakinra and infliximab, have been described for the management of COVID-19-related MIS-C. Anticoagulant therapy is also important. However, a well-developed treatment system has not been established, and many issues remain controversial. Several recently published articles related to the treatment of MIS-C have been released. Hence, in this review, we identified relevant articles published recently and summarized the treatment of MIS-C more comprehensively and systematically.

DATA SOURCES

We reviewed the literature on the treatment of MIS-C through 20 September 2023. The PubMed/Medline, Web of Science, EMBASE, and Cochrane Library databases were searched with the combination of the terms "multisystem inflammatory syndrome", "MIS-C", "PIMS-TS", "therapy", "treatment", "drug", "IVIG", "GCs", "intravenous immunoglobulin", "corticosteroids", "biological agent", and "aspirin".

RESULTS

The severity of MIS-C varies, and different treatment schemes should be used according to the specific condition. Ongoing research and data collection are vital to better understand the pathophysiology and optimal management of MIS-C.

CONCLUSIONS

MIS-C is a disease involving multiple systems and has great heterogeneity. With the accumulation of additional experience, we have garnered fresh insights into its treatment strategies. However, there remains a critical need for greater standardization in treatment protocols, alongside the pressing necessity for more robust and meticulously conducted studies to deepen our understanding of these protocols. Supplementary file1 (MP4 208044 kb).

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.

Multisystem inflammatory syndrome in children associated with COVID-19: from pathophysiology to clinical management and outcomes

Multisystem inflammatory syndrome in children (MIS-C), also known as pediatric inflammatory multisystem syndrome (PIMS), is a new postinfectious illness associated with COVID-19, affecting children after SARS-CoV-2 exposure. The hallmarks of this disorder are hyperinflammation and multisystem involvement, with gastrointestinal, cardiac, mucocutaneous, and hematologic disturbances seen most commonly. Cardiovascular involvement includes cardiogenic shock, ventricular dysfunction, coronary artery abnormalities, and myocarditis. Now entering the fourth year of the pandemic, clinicians have gained some familiarity with the clinical presentation, initial diagnosis, cardiac evaluation, and treatment of MIS-C. This has led to an updated definition from the Centers for Disease Control and Prevention in the USA driven by increased experience and clinical expertise. Furthermore, the available evidence established expert consensus treatment recommendations supporting a combination of immunoglobulin and steroids. However, the pathophysiology of the disorder and answers to what causes this remain under investigation. Fortunately, long-term outcomes continue to look promising, although continued follow-up is still needed. Recently, COVID-19 mRNA vaccination is reported to be associated with reduced risk of MIS-C, while further studies are warranted to understand the impact of COVID-19 vaccines on MIS-C. We review the findings and current literature on MIS-C, including pathophysiology, clinical features, evaluation, management, and medium- to long-term follow-up outcomes.

Myeloid-derived suppressor cells and T cell populations in children with Multisystem Inflammatory Syndrome

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) represents a hyperinflammatory state that can result in multi-organ dysfunction and death. Myeloid-derived suppressor cells (MDSC) are an immunosuppressive cell population that expands under inflammatory conditions and suppresses T cell function. We hypothesized that MDSC would be increased in children with MIS-C and that MDSC expansion would be associated with T cell lymphopenia.

METHODS

We conducted a prospective, observational study. Initial blood samples were collected within 48 h of admission. Age-matched healthy controls underwent sampling once. MDSC and T cell populations were identified by flow cytometric methods.

RESULTS

We enrolled 22 children with MIS-C (12 ICU, 10 ward) and 21 healthy controls (HC). Children with MIS-C demonstrated significantly higher MDSC compared to HC, and MDSC expansion persisted for >3 weeks in the ICU group. Children with MIS-C admitted to the ICU demonstrated significantly lower absolute numbers of T cells and natural killer cells. There were no significant associations between MDSC and cardiac dysfunction, duration of hospitalization, or vasoactive inotrope score.

CONCLUSIONS

Our study suggests that children critically ill with MIS-C have expansion of MDSC and associated decreased T cell and NK cell populations. Our results did not demonstrate associations between MDSC and clinical outcomes.

IMPACT

Multisystem inflammatory syndrome in children (MIS-C) is a dysregulated immune response occurring several weeks after SARS-CoV-2 infection that can result in multi-organ dysfunction and death. Children severely ill with MIS-C demonstrated increased myeloid-derived suppressor cells and decreased absolute numbers of CD4+ and CD8 + T cells and NK cells compared to healthy controls. There was no significant association between MDSC numbers and clinical outcomes; including cardiac dysfunction, length of stay, or requirement of vasoactive support, in children with MIS-C.

Cardiac injury progression in children with multisystem inflammatory syndrome associated with SARS-CoV-2 infection: a review

The symptoms and signs of infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are milder in children than in adults. However, in April 2020, British pediatricians first reported that coronavirus disease 2019 (COVID-19) may present as multisystem inflammatory syndrome in children and adolescents (MIS-C), similar to that observed in Kawasaki disease. MIS-C can be associated with multiple systemic injuries and even death in children. In addition to digestive system involvement, cardiac injury is prominent. This article reviews the pathogenesis, clinical manifestations, and treatment of cardiac injury caused by MIS-C, which may help clinicians in early diagnosis and timely commencement of treatment.

Assessment of the Choroidal Vascular Structure in Multisystem Inflammatory Syndrome in Children

PURPOSE

To evaluate the choroidal vascular structure in cases of multisystem inflammatory syndrome in children (MIS-C).

METHODS

This prospective study included 38 eyes of 19 patients with MIS-C and 60 eyes of 30 healthy participants. Optical coherence tomography (OCT) imaging was performed at 1 month after diagnosis in the MIS-C group. Using enhanced depth imaging OCT, choroidal thickness was measured in the subfoveal, nasal, and temporal quadrants at 500 and 1,500 µm distances from the fovea (SCT, N500CT, T500CT, N1500CT, and T1500CT, respectively). The luminal, stromal, and total choroidal areas were evaluated with the binarization method in ImageJ software (National Institutes of Health). The ratio of the luminal area to the total choroidal area was determined as the choroidal vascular index (CVI).

RESULTS

The age and sex distributions of the two groups without any ophthalmologic pathology were similar (P > .05). The choroidal thickness values in all quadrants except for T1500CT were similar between the two groups (P > .05). T1500CT was significantly lower in the MIS-C group (P = .02). The luminal choroidal area was 1.04 ± 0.10 mm2 in the MIS-C group and 1.26 ± 0.24 mm2 in the healthy control group (P < .001), and the CVI values were 0.52 ± 0.04 and 0.57 ± 0.09, respectively (P = .01). The stromal and total choroidal area values did not significantly differ between the two groups (P > .05).

CONCLUSIONS

This is the first study to evaluate CVI in patients with MIS-C. It was observed that the choroidal vascular structure could be affected in the early period of MIS-C, as shown by a decrease in the CVI value and luminal vascular area. OCT can be used to monitor ocular vascular changes in these patients. [J Pediatr Ophthalmol Strabismus. 2024;61(2):120-126.].

A genetically modulated Toll-like-receptor-tolerant phenotype in peripheral blood cells of children with multisystem inflammatory syndrome

Dysregulated innate immune responses contribute to multisystem inflammatory syndrome in children (MIS-C), characterized by gastrointestinal, mucocutaneous, and/or cardiovascular injury occurring weeks after SARS-CoV-2 exposure. To investigate innate immune functions in MIS-C, we stimulated ex vivo peripheral blood cells from MIS-C patients with agonists of Toll-like receptors (TLR), key innate immune response initiators. We found severely dampened cytokine responses and elevated gene expression of negative regulators of TLR signaling. Increased plasma levels of zonulin, a gut leakage marker, were also detected. These effects were also observed in children enrolled months after MIS-C recovery. Moreover, cells from MIS-C children carrying rare genetic variants of lysosomal trafficking regulator (LYST) were less refractory to TLR stimulation and exhibited lysosomal and mitochondrial abnormalities with altered energy metabolism. Our results strongly suggest that MIS-C hyperinflammation and/or excessive or prolonged stimulation with gut-originated TLR ligands drive immune cells to a lasting refractory state. TLR hyporesponsiveness is likely beneficial, as suggested by excess lymphopenia among rare LYST variant carriers. Our findings point to cellular mechanisms underlying TLR hyporesponsiveness; identify genetic determinants that may explain the MIS-C clinical spectrum; suggest potential associations between innate refractory states and long COVID; and highlight the need to monitor long-term consequences of MIS-C.

Comparing the immune abnormalities in MIS-C to healthy children and those with inflammatory disease reveals distinct inflammatory cytokine production and a monofunctional T cell response

Multisystem inflammatory syndrome in children (MIS-C) is a severe, hyperinflammatory disease that occurs after exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The underlying immune pathology of MIS-C is incompletely understood, with limited data comparing MIS-C to clinically similar paediatric febrile diseases at presentation. SARS-CoV-2-specific T cell responses have not been compared in these groups to assess whether there is a T cell profile unique to MIS-C. In this study, we measured inflammatory cytokine concentration and SARS-CoV-2-specific humoral immunity and T cell responses in children with fever and suspected MIS-C at presentation (n = 83) where MIS-C was ultimately confirmed (n = 58) or another diagnosis was made (n = 25) and healthy children (n = 91). Children with confirmed MIS-C exhibited distinctly elevated serum IL-10, IL-6, and CRP at presentation. No differences were detected in SARS-CoV-2 spike IgG serum concentration, neutralisation capacity, antibody dependant cellular phagocytosis, antibody dependant cellular cytotoxicity or SARS-CoV-2-specific T cell frequency between the groups. Healthy SARS-CoV-2 seropositive children had a higher proportion of polyfunctional SARS-CoV-2-specific CD4+ T cells compared to children with MIS-C and those with other inflammatory or infectious diagnoses, who both presented a largely monofunctional SARS-CoV-2-specific CD4+ T cell profile. Treatment with steroids and/or intravenous immunoglobulins resulted in rapid reduction of inflammatory cytokines but did not affect the SARS-CoV-2-specific IgG or CD4+ T cell responses in MIS-C. In these data, MIS-C had a unique cytokine profile but not a unique SARS-CoV-2 specific humoral or T cell cytokine response.

Using HScore for Evaluation of Hemophagocytosis in Multisystem Inflammatory Syndrome Associated with COVID-19 in Children

Hemophagocytic syndrome is a key point in the pathogenesis of severe forms of multisystem inflammatory syndrome associated with COVID-19 in children (MIS-C). The factors associated with hemophagocytosis in patients with MIS-C were assessed in the present study of 94 boys and 64 girls ranging in age from 4 months to 17 years, each of whose HScore was calculated. In accordance with a previous analysis, patients with HScore ≤ 91 (n = 79) and HScore > 91 (n = 79) were compared. Patients with HScore > 91 had a higher frequency of symptoms such as cervical lymphadenopathy, dry cracked lips, bright mucous, erythema/swelling of hands and feet, peeling of fingers, edematous syndrome, hepatomegaly, splenomegaly, and hypotension/shock. They also had a higher erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and D-dimer levels, and a tendency to anemia, thrombocytopenia, and hypofibrinogenemia. They more often needed acetylsalicylic acid and biological treatment and were admitted to ICU in 70.9% of cases. Conclusion: The following signs of severe MIS-C were associated with HScore > 91: myocardial involvement, pericarditis, hypotension/shock, and ICU admission.

Metabolomic and Immunologic Discriminators of MIS-C at Emergency Room Presentation

Multisystem Inflammatory Syndrome in Childhood (MIS-C) follows SARS-CoV-2 infection and frequently leads to intensive care unit admission. The inability to rapidly discriminate MIS-C from similar febrile illnesses delays treatment and leads to misdiagnosis. To identify diagnostic discriminators at the time of emergency department presentation, we enrolled 104 children who met MIS-C screening criteria, 14 of whom were eventually diagnosed with MIS-C. Before treatment, we collected breath samples for volatiles and peripheral blood for measurement of plasma proteins and immune cell features. Clinical and laboratory features were used as inputs for a machine learning model to determine diagnostic importance. MIS-C was associated with significant changes in breath volatile organic compound (VOC) composition as well as increased plasma levels of secretory phospholipase A2 (PLA2G2A) and lipopolysaccharide binding protein (LBP). In an integrated model of all analytes, the proportion of TCRVβ21.3+ non-naive CD4 T cells expressing Ki-67 had a high sensitivity and specificity for MIS-C, with diagnostic accuracy further enhanced by low sodium and high PLA2G2A. We anticipate that accurate diagnosis will become increasingly difficult as MIS-C becomes less common. Clinical validation and application of this diagnostic model may improve outcomes in children presenting with multisystem febrile illnesses.

COVID-19-Related Multi-systemic Inflammatory Syndrome in Children (MIS-C)

Multisystem inflammatory syndrome in children (MIS-C) is a severe complication of SARS-CoV-2 infections in children. This syndrome manifests about a month after the initial viral infection and is characterized by fever, multiorgan dysfunction, and systemic inflammation. This chapter will review the emergence, epidemiology, clinical characteristics, diagnosis, pathophysiology, immunomodulatory treatment, prognosis, outcomes, and prevention of MIS-C. While the pathophysiology of MIS-C remains to be defined, it is a post-infection, hyperinflammatory syndrome of childhood with elevated inflammatory cytokines.

Genetics of Primary Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) constitutes a rare, potentially life-threatening hyperinflammatory immune dysregulation syndrome that can present with a variety of clinical signs and symptoms, including fever, hepatosplenomegaly, and abnormal laboratory and immunological findings such as cytopenias, hyperferritinemia, hypofibrinogenemia, hypertriglyceridemia, elevated blood levels of soluble CD25 (interleukin (IL)-2 receptor α-chain), or diminished natural killer (NK)-cell cytotoxicity (reviewed in detail in Chapter 11 of this book). While HLH can be triggered by an inciting event (e.g., infections), certain monogenic causes have been associated with a significantly elevated risk of development of HLH, or recurrence of HLH in patients who have recovered from their disease episode. These monogenic predisposition syndromes are variably referred to as "familial" (FHL) or "primary" HLH (henceforth referred to as "pHLH") and are the focus of this chapter. Conversely, secondary HLH (sHLH) often occurs in the absence of monogenic etiologies that are commonly associated with pHLH and can be triggered by infections, malignancies, or rheumatological diseases; these triggers and the genetics associated with sHLH are discussed in more detail in other chapters in this book.

Kawasaki Disease-Associated Cytokine Storm Syndrome

Kawasaki disease (KD) is a hyperinflammatory syndrome manifesting as an acute systemic vasculitis characterized by fever, nonsuppurative conjunctival injection, rash, oral mucositis, extremity changes, and cervical lymphadenopathy. KD predominantly affects young children and shares clinical features and immunobiology with other hyperinflammation syndromes including systemic juvenile idiopathic arthritis (sJIA) and multisystem inflammatory syndrome in children (MIS-C). Cytokine storm syndrome (CSS) is an acute complication in ~2% of KD patients; however, the incidence is likely underestimated as many clinical and laboratory features of both diseases overlap. CSS should be entertained when a child with KD is unresponsive to IVIG therapy with recalcitrant fever. Early recognition and prompt institution of immunomodulatory treatment can substantially reduce the mortality and morbidity of CSS in KD. Given the known pathogenetic role of IL-1β in both syndromes, the early use of IL-1 blockers in refractory KD with CSS deserves consideration.