Inflammatory responses in SARS-CoV-2 associated Multisystem Inflammatory Syndrome and Kawasaki Disease in children: An observational study

Abstract

Multisystem Inflammatory Syndrome in Children (MIS-C) is a severe inflammatory disease in children related to SARS-CoV-2 with multisystem involvement including marked cardiac dysfunction and clinical symptoms that can resemble Kawasaki Disease (KD). We hypothesized that MIS-C and KD might have commonalities as well as unique inflammatory responses and studied these responses in both diseases. In total, fourteen children with MIS-C (n=8) and KD (n=6) were included in the period of March-June 2020. Clinical and routine blood parameters, cardiac follow-up, SARS-CoV-2-specific antibodies and CD4+ T-cell responses, and cytokine-profiles were determined in both groups. In contrast to KD patients, all MIS-C patients had positive Spike protein-specific CD3+CD4+ T-cell responses. MIS-C and KD patients displayed marked hyper-inflammation with high expression of serum cytokines, including the drug-targetable interleukin (IL)-6 and IFN-γ associated chemokines CXCL9, 10 and 11, which decreased at follow-up. No statistical differences were observed between groups. Clinical outcomes were all favourable without cardiac sequelae at 6 months follow-up. In conclusion, MIS-C and KD-patients both displayed cytokine-associated hyper-inflammation with several high levels of drug-targetable cytokines.

Fig 1. CD3+ T-cell subsets and CD3+CD4+ T-cell responses to SARS-CoV-2 spike protein.

(A) C3+CD4+ and CD3+CD4+ T-cell frequencies depicted per patient, MIS-C classification, ICU stay and age. (B) CD4+/CD8+ ratios in MIS-C and KD patients (C) CD4+/CD8+ ratios in relation to ICU stay (D) Representative flow cytometry contour plots of CD3+CD4+ T-cells incubated with (SARS-CoV-2) and without (unstimulated) SARS-CoV-2 Spike peptide pool. Upon SARS-CoV-2 Spike protein stimulation CD3+CD4+ T-cells of MIS-C children were activated and expressed CD40L and IFN- γ (E) Representative flow cytometry contour plots demonstrating the phenotypic composition of CD4⁺ T cells of patient 4 (black plot), as measured by CD45RA and CD27 expression and GZMB and CD4+ T-cell when stimulated with SARS-CoV-2 Spike peptide pool (red plot). CD3+CD4+ and CD3+CD8+ T-cell subsets are per patients illustrated in the S3 Fig Depicted plots of PBMCs (D and E) belong to patient 4. Abbreviations: GZMB = Granzyme B.

Fig 2. Serum cytokine profiles in MIS-C and Kawasaki Disease patients.

Levels of serum proteins in healthy controls (HC), MIS-C and KD children, in the acute phase of the illness (AP) and at follow-up (FU). Left panel: Agglomerative hierarchical cluster analysis using average linkage (between groups), with squared Euclidean distance. Right panel: Violin plots IFN- γ related cytokines across study groups).