MIS-C: myths have been debunked, but mysteries remain

Coronary artery dilation in children with MIS-C: prevalence, risk factor, and progression

Cardiac injury is the critical issue in children with MIS-C, particularly coronary artery dilation. This study aimed to describe the prevalence, risk factors associated with coronary artery abnormalities, and their progression after 3 months of follow-up in MIS-C children in Vietnam. A prospective multicenter case series study was conducted on MIS-C patients diagnosed per WHO criteria from September 2021 to February 2023 at the two largest pediatric hospitals in southern Vietnam. Data on demographics, clinical features, laboratory findings, and treatments during the acute phase of MIS-C were collected. Patients were followed for 3 months post-discharge and categorized into normal and abnormal coronary artery groups for comparative analysis. Among 195 patients (mean age 6.3 years; male to female ratio 1.5:1), 33.3% exhibited coronary artery abnormalities at admission. Treatment included a combination of intravenous immunoglobulin (IVIG) and corticosteroids (53.3%), corticosteroids alone (42.6%), and IVIG alone (4.1%). After 3 months, only 3.6% of patients had persistent coronary artery abnormalities. Independent risk factors for coronary artery dilation included male sex (OR 4.59; 95% CI 1.62-12.94; p = 0.004), Kawasaki-like phenotype (OR 6.42; 95% CI 2.25-18.33; p = 0.001), and mesenteric lymphadenitis (OR 8.79; 95% CI 1.74-44.31; p = 0.008).

CONCLUSION

Coronary artery dilation in MIS-C patients shows a favorable recovery trajectory after a 3-month follow-up. Male sex, Kawasaki-like MIS-C, and mesenteric lymphadenitis are independent risk factors for coronary artery dilation in MIS-C patients.

WHAT IS KNOWN

• Multisystem inflammatory syndrome in children (MIS-C) is a severe inflammatory syndrome following SARS-CoV-2 infection, often leading to cardiac complications, particularly coronary artery dilation.

WHAT IS NEW

• Coronary artery dilation in MIS-C patients mostly resolves within three months of follow-up. Factors associated with coronary artery dilation in MIS-C patients include: male sex, Kawasaki-like phenotype and mesenteric lymphadenitis.

Severity of Pediatric Inflammatory Multisystem Syndrome Temporally Associated with SARS-CoV-2 Diminished During Successive Waves of the COVID-19 Pandemic: Data from a Nationwide German Survey

OBJECTIVE

To elucidate how the clinical presentation of Pediatric Inflammatory Multisystem Syndrome temporally associated with Severe Acute Respiratory Syndrome-related Coronavirus 2 (PIMS-TS) was influenced by the successive variants of concern (VOC) and patient age.

STUDY DESIGN

A nationwide PIMS-TS registry was established in Germany in May 2020, shortly after the first cases were described in the US and United Kingdom. The registry captured information on patient characteristics, clinical course, laboratory findings, imaging, and outcome. All pediatric hospitals in Germany, along with one in Austria, were invited to participate. Between March 18, 2020, and April 30, 2023, 920 cases were reported.

RESULTS

By examining a combination of data on clinical features, laboratory findings, treatment, imaging results, and outcomes, our analysis demonstrated disease severity to have continuously declined over the course of the Wildtype, Alpha, Delta, and Omicron waves. Based on clinical symptoms, laboratory and diagnostic findings, and intensive care unit admission rates, older children, irrespective of the related VOC, were shown to experience more severe, acute PIMS-TS; however, they had lower rates of coronary aneurysm.

CONCLUSIONS

During the course of COVID-19 pandemic, as each new VOC emerged, PIMS-TS lessened in severity. In parallel, older children came to experience more debilitating disease.

Proteomic profiling reveals diagnostic signatures and pathogenic insights in multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) is a severe disease that emerged during the COVID-19 pandemic. Although recognized as an immune-mediated condition, the pathogenesis remains unresolved. Furthermore, the absence of a diagnostic test can lead to delayed immunotherapy. Using state-of-the-art mass-spectrometry proteomics, assisted by artificial intelligence (AI), we aimed to identify a diagnostic signature for MIS-C and to gain insights into disease mechanisms. We identified a highly specific 4-protein diagnostic signature in children with MIS-C. Furthermore, we identified seven clusters that differed between MIS-C and controls, indicating an interplay between apolipoproteins, immune response proteins, coagulation factors, platelet function, and the complement cascade. These intricate protein patterns indicated MIS-C as an immunometabolic condition with global hypercoagulability. Our findings emphasize the potential of AI-assisted proteomics as a powerful and unbiased tool for assessing disease pathogenesis and suggesting avenues for future interventions and impact on pediatric disease trajectories through early diagnosis.

Exploring Factors Influencing Changes in Incidence and Severity of Multisystem Inflammatory Syndrome in Children

Multisystem inflammatory syndrome (MIS-C) is a rare condition associated with COVID-19 affecting children, characterized by severe and aberrant systemic inflammation leading to nonspecific symptoms, such as gastrointestinal, cardiac, respiratory, hematological, and neurological disorders. In the last year, we have experienced a progressive reduction in the incidence and severity of MIS-C, reflecting the worldwide trend. Thus, starting from the overall trend in the disease in different continents, we reviewed the literature, hypothesizing the potential influencing factors contributing to the reduction in cases and the severity of MIS-C, particularly the vaccination campaign, the spread of different SARS-CoV-2 variants (VOCs), and the changes in human immunological response. The decrease in the severity of MIS-C and its incidence seem to be related to a combination of different factors rather than a single cause. Maturation of an immunological memory to SARS-CoV-2 over time, the implication of mutations of key amino acids of S protein in VOCs, and the overall immune response elicited by vaccination over the loss of neutralization of vaccines to VOCs seem to play an important role in this change.

A systems approach evaluating the impact of SARS-CoV-2 variant of concern mutations on CD8+ T cell responses

T cell recognition of SARS-CoV-2 antigens after vaccination and/or natural infection has played a central role in resolving SARS-CoV-2 infections and generating adaptive immune memory. However, the clinical impact of SARS-CoV-2-specific T cell responses is variable and the mechanisms underlying T cell interaction with target antigens are not fully understood. This is especially true given the virus' rapid evolution, which leads to new variants with immune escape capacity. In this study, we used the Omicron variant as a model organism and took a systems approach to evaluate the impact of mutations on CD8+ T cell immunogenicity. We computed an immunogenicity potential score for each SARS-CoV-2 peptide antigen from the ancestral strain and Omicron, capturing both antigen presentation and T cell recognition probabilities. By comparing ancestral vs. Omicron immunogenicity scores, we reveal a divergent and heterogeneous landscape of impact for CD8+ T cell recognition of mutated targets in Omicron variants. While T cell recognition of Omicron peptides is broadly preserved, we observed mutated peptides with deteriorated immunogenicity that may assist breakthrough infection in some individuals. We then combined our scoring scheme with an in silico mutagenesis, to characterise the position- and residue-specific theoretical mutational impact on immunogenicity. While we predict many escape trajectories from the theoretical landscape of substitutions, our study suggests that Omicron mutations in T cell epitopes did not develop under cell-mediated pressure. Our study provides a generalisable platform for fostering a deeper understanding of existing and novel variant impact on antigen-specific vaccine- and/or infection-induced T cell immunity.