Cytotoxic lymphocytes are dysregulated in multisystem inflammatory syndrome in children

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

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

A translational genomics approach identifies IL10RB as the top candidate gene target for COVID-19 susceptibility

Recent efforts have identified genetic loci that are associated with coronavirus disease 2019 (COVID-19) infection rates and disease outcome severity. Translating these genetic findings into druggable genes that reduce COVID-19 host susceptibility is a critical next step. Using a translational genomics approach that integrates COVID-19 genetic susceptibility variants, multi-tissue genetically regulated gene expression (GReX), and perturbagen signatures, we identified IL10RB as the top candidate gene target for COVID-19 host susceptibility. In a series of validation steps, we show that predicted GReX upregulation of IL10RB and higher IL10RB expression in COVID-19 patient blood is associated with worse COVID-19 outcomes and that in vitro IL10RB overexpression is associated with increased viral load and activation of disease-relevant molecular pathways.

Genetic and Clinical Characteristics of Patients in the Middle East With Multisystem Inflammatory Syndrome in Children

IMPORTANCE

Clinical, genetic, and laboratory characteristics of Middle Eastern patients with multisystem inflammatory syndrome in children (MIS-C) have not yet been documented.

OBJECTIVE

To assess the genetic and clinical characteristics of patients with MIS-C of primarily Arab and Asian origin.

DESIGN, SETTING, AND PARTICIPANTS

A prospective, multicenter cohort study was conducted from September 1, 2020, to August 31, 2021, in the United Arab Emirates and Jordan. Forty-five patients with MIS-C and a matched control group of 25 healthy children with a confirmed SARS-CoV-2 infection status were recruited. Whole exome sequencing in all 70 participants was performed to identify rare, likely deleterious variants in patients with MIS-C and to correlate genetic findings with the clinical course of illness.

EXPOSURES

SARS-CoV-2.

MAIN OUTCOMES AND MEASURES

Fever, organ system complications, laboratory biomarkers, whole exome sequencing findings, treatments, and clinical outcomes were measured. The Mann-Whitney U test was used to assess the association between genetic variants and MIS-C attributes. The Fisher exact test was used to compute the genetic burden in MIS-C relative to controls.

RESULTS

A total of 45 patients with MIS-C (23 [51.1%] male; 30 [66.7%] of Middle Eastern origin; mean [SD] age, 6.7 [3.6] years) and 25 controls (17 [68.0%] male; 24 [96.0%] of Middle Eastern origin; mean [SD] age 7.4 [4.0] years) participated in the study. Key inflammatory markers were significantly dysregulated in all patients with MIS-C. Mucocutaneous and gastrointestinal manifestations were each reported in 36 patients (80.0%; 95% CI, 66.1%-89.1%), cardiac findings were reported in 22 (48.9%; 95% CI, 35.0%-63.0%), and neurologic findings were reported in 14 (31.1%; 95% CI, 19.5%-45.6%). Rare, likely deleterious heterozygous variants in immune-related genes, including TLR3, TLR6, IL22RA2, IFNB1, and IFNA6, were identified in 19 patients (42.2%; 95% CI, 29.0%-56.7%), of whom 7 had multiple variants. There was higher enrichment of genetic variants in patients relative to controls (29 vs 3, P < .001). Patients with those variants tended to have earlier disease onset (7 patients [36.8%; 95% CI, 19.1%-58.9%] with genetic findings vs 2 [7.7%; 95% CI, 2.1%-24.1%] without genetic findings were younger than 3 years at onset) and resistance to treatment (8 patients [42.1%; 95% CI, 23.1%-63.7%] with genetic findings vs 3 patients [11.5%; 95% CI, 4.0%-29.0%] without genetic findings received 2 doses of intravenous immunoglobulin).

CONCLUSIONS AND RELEVANCE

The results of this cohort study suggest that rare, likely deleterious genetic variants may contribute to MIS-C disease. This finding paves the way for additional studies with larger, diverse populations to fully characterize the genetic contribution to this new disease entity.

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.