Backgrounds:

Multisystem Inflammatory Syndrome in Children (MIS-C) occurs several weeks after SARS-CoV-2 infection with symptoms including fever, shock and multiorgan failure. Clinical features of MIS-C overlap with Kawasaki Disease (KD), bacterial, and viral infections, making accurate diagnosis challenging. Host genes, measurable through whole blood transcriptomics, are an alternative tool for diagnosing infectious and inflammatory diseases.

Methods

Patients with MIS-C, KD, bacterial, and viral infections were recruited to the EU-funded PERFORM and DIAMONDS studies and the NIH-funded PREVAIL study. Patients were phenotyped using a standardised algorithm. Genome wide RNA sequencing of whole blood was undertaken, and feature selection was performed to identify a diagnostic signature for distinguishing between MIS-C and other infectious and inflammatory conditions. The expression levels of the genes identified were measured using RT-qPCR assays in an independent validation cohort.

Results:

Through feature selection and differential expression analysis, 11 genes with diagnostic potential were identified and taken forward into cross-platform validation using RT-qPCR. With up to 11 genes, it was possible to distinguish between MIS-C vs. KD, bacterial, and viral infections with high accuracy, with an AUC of 92.9% (95% CI: 88.2%-97.6%) in the validation cohort. The diagnostic gene signature retained its high performance when tested within the groups separately in the validation cohort: MIS-C vs. bacterial infections (AUC: 94.6%), vs. viral infections (AUC: 93.1%), and vs. KD (AUC: 89.8%).

Conclusions/Learning Points:

Despite the clinical similarities between MIS-C and other infectious and inflammatory conditions, there are key differences in gene expression profiles that can be used in diagnostic contexts. It will be necessary for the genes reported here to undergo further validation prior to their development into tests with clinical utility.

Backgrounds:

Cardiomyopathy is one of the significant features of SARS-CoV-2 induced multi-system inflammatory syndrome in children (MIS-C) and it is also a rare complication of mRNA COVID-19 vaccination in young adults. MIS-C occurs 4-6 weeks following SARS-CoV-2 infection; we therefore postulated that antibodies might play a role in the cardiac immunopathology. The mechanism of vaccine-induced myocarditis is currently being explored. We investigated the role of anti-cardiac antibodies in post SARS-CoV-2 vaccine myocarditis and MIS-C.

Methods:

Clinical cohort: Pre-treatment acute MIS-C (n=10), acute COVID-19 vaccination-induced myocarditis (n=10), Pre-COVID-19 pandemic healthy children (n=10) and healthy COVID-19 vaccinated adults (10).

Immunohistochemistry was performed on human left ventricular tissue sections from 2 donor hearts (deemed unsuitable for donation) for assessment of auto-antibody binding. Sera from patients and controls were used as primary antibodies. FITC-conjugated anti-human-IgG (1:150), IgM (1:150) and IgA (1:50) were used for detection. 10 images were taken at random from each section and immunoglobulin deposition was quantified by calculating mean fluorescent intensity using ImageJ/Fiji. This method has previously shown specific binding of IgG to cardiac tissue following treatment with serum obtained from an adult myocarditis patient.

Results:

No specific binding was seen in left ventricular tissue treated with sera from paediatric patients with either MIS-C or COVID-19 vaccine-induced myocarditis. There was no significant difference in the mean fluorescent intensity of IgG, IgM and IgA in patients compared to controls (Figure 1).

Conclusions/Learning Points:

Our study did not find evidence for a role of an anti-cardiac antibody-mediated inflammatory process in MIS-C cardiomyopathy and COVID-19 vaccine induced myocarditis.