The Innate and Adaptive Immune Landscape of SARS-CoV-2-Associated Multisystem Inflammatory Syndrome in Children (MIS-C) From Acute Disease to Recovery (preprint)

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening disease occurring several weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Deep immune profiling showed acute MIS-C patients had highly activated neutrophils, classical monocytes and memory CD8+ T-cells; increased frequencies of B-cell plasmablasts and double-negative B-cells. Post treatment samples from the same patients, taken when symptoms were resolving, identified recovery-associated immune features including CD163+ monocytes, emergence of a new population of immature neutrophils and, in some patients, a transient increase in arginase. Plasma profiling identified multiple features shared by MIS-C, Kawasaki Disease and COVID-19 and that therapeutic inhibition of IL6 may be preferable to IL1 or TNF-a. We identified potential new mechanisms of action for IVIG, the most commonly used drug to treat MIS-C. Finally, we showed systemic complement activation with high plasma C5b-9 levels is common in MIS-C, suggesting complement inhibitors could be used to treat the disease.Funding Information: Birmingham Women’s and Children’s Hospital Charity funded the single cell RNA sequencing analysis. No other external funding was received. Declaration of Interests: None declared.Ethics Approval Statement: Reviewed and approved by South of Birmingham Research Ethics Committee (REC: 17/WM/0453, IRAS: 233593).

The Innate and Adaptive Immune Landscape of SARS-CoV-2-Associated Multisystem Inflammatory Syndrome in Children (MIS-C) from Acute Disease to Recovery (preprint)

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening disease occurring several weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. MIS-C has overlapping clinical features with Kawasaki Disease (KD), a rare childhood vasculitis, but whether these diseases share underpinning immunological perturbations is unknown. Deep immune profiling showed acute MIS-C patients had highly activated neutrophils, classical monocytes and memory CD8+ T-cells; increased frequencies of B-cell plasmablasts and double-negative B-cells; and increased cytokine levels. Post treatment samples from the same patients, taken when symptoms were resolving, identified recovery-associated immune features including CD163+ monocytes, emergence of a new population of immature neutrophils and, in some patients, a transient increase in arginase. Our data show MIS-C and KD share substantial immunopathology during the acute and recovery stages of disease and identify potential new mechanisms of action for IVIG, a widely used anti-inflammatory drug used to treat MIS-C, KD and other inflammatory diseases.

Short Term Respiratory Outcomes in Children with Antibody Positive PIMS -TS (preprint)

Paediatric multisystem inflammatory syndrome: temporally associated with SARS-COV-2 (PIMS-TS) is a well described rare but severe COVID-19 related syndrome. PIMS-TS have been reported in children from geographical areas of high COVID-19 infection. Most children with PIMS-TS require management in an intensive care unit with variable respiratory involvement. Adults recovering from COVID-19 infection have been reported to suffer from respiratory morbidity but such outcomes are unknown in children. We present the first report of normal short term respiratory outcomes as measured by spirometry in children with SARS-COV-2 antibody positive, PIMS-TS syndrome managed at a specialist children’s hospital in the UK.

Association between Treatments and Short-Term Biochemical and Clinical Outcomes in Paediatric Inflammatory Multisystem Syndrome Temporally Associated with SARS-CoV-2 (PIMS-TS) (preprint)

Background: Clinicians observed a cluster of children with unexplained inflammation requiring admission to United Kingdom (UK) paediatric intensive care units (PICUs) in April 2020. Despite multiple guidelines, which treatments are effective in Paediatric Inflammatory Multisystem Syndrome Temporally associated with SARS-CoV-2 (PIMS-TS) is unknown.Methods: Multicentre observational study of children (<18 years) admitted to UK PICUs between 1 April and 10 May 2020, fulfilling the case definition of PIMS-TS. Routinely collected, de-identified data was analysed. Linear mixed effects models were used to analyse the effect of steroids, intravenous immunoglobulin (IVIG), and biologic agents on C-reactive protein (CRP), platelet counts,and lymphocyte counts. The content of UK clinical guidelines was collated. Findings: Over the six week study period: 59/78 (76%) children received IVIG, 57/78 (73%) steroids, and 17/78 (22%) a biologic agent. We found no evidence of a difference in response in clinical markers of inflammation between patients with PIMS-TS who were treated with IVIG, steroids or biologics, compared to those who were not. Despite a progression to near universal treatment with immunomodulators, the proportion of patients with coronary artery abnormalities increased. Guidelines universally advised or considered the use of IVIG, steroids, and biologics. Interpretation: We were unable to identify any short term benefit from any of the treatments, or treatment combinations administered. Despite a lack of evidence, worldwide treatment guidelines for PIMS-TS have become very similar. Clinicians treating PIMS-TS should continue to have equipoise and participate in robust clinical trials of all treatments currently being utilised for this important condition. Funding: NoneDeclaration of Interests: All authors have completed the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest, and have no conflicts of interest to disclose.Ethics Approval Statement: The project was classified as a service evaluation by the Nottingham Research and Innovation team (Nottingham Clinical Effectiveness Team ref: 20- 235C), and ethics approval was not required. The study team analysed routinely collected de-identified data submitted by clinicians from the individual PICUs as a local service evaluation. Clinicians obtained informed parental consent if required locally.

Single-cell RNA-seq reveals profound monocyte changes in Paediatric Inflammatory Multisystem Syndrome Temporally associated with SARS-CoV-2 infection (PIMS-TS) (preprint)

Paediatric inflammatory multisystem inflammatory syndrome temporally associated with SARS-CoV-2 infection (PIMS-TS) is a new disease with overlapping features of Kawasaki disease (KD) and toxic shock syndrome. Unbiased single cell RNA sequencing analysis of peripheral blood mononuclear cells from PIMS-TS and KD patients shows monocytes are the main source of pro-inflammatory cytokines and large changes in the frequency of classical, intermediate and non-classical monocytes occur in both diseases.

Serology confirms SARS-CoV-2 infection in PCR-negative children presenting with Paediatric Inflammatory Multi-System Syndrome (preprint)

Background. During the COVID-19 outbreak, reports have surfaced of children who present with features of a multisystem inflammatory syndrome with overlapping features of Kawasaki disease and toxic shock syndrome - Paediatric Inflammatory Multisystem Syndrome- temporally associated with SARS-CoV-2 pandemic (PIMS-TS). Initial reports find that many of the children are PCR-negative for SARS-CoV-2, so it is difficult to confirm whether this syndrome is a late complication of viral infection in an age group largely spared the worst consequences of this infection, or if this syndrome reflects enhanced surveillance. Methods. Children hospitalised for symptoms consistent with PIMS-TS between 28 April and 8 May 2020, and who were PCR-negative for SARS-CoV-2, were tested for antibodies to viral spike glycoprotein using an ELISA test. Results. Eight patients (age range 7-14 years, 63% male) fulfilled case-definition for PIMS-TS during the study period. Six of the eight patients required admission to intensive care. All patients exhibited significant IgG and IgA responses to viral spike glycoprotein. Further assessment showed that the IgG isotypes detected in children with PIMS-TS were of the IgG1 and IgG3 subclasses, a distribution similar to that observed in samples from hospitalised adult COVID-19 patients. In contrast, IgG2 and IgG4 were not detected in children or adults. IgM was not detected in children, which contrasts with adult hospitalised adult COVID-19 patients of whom all had positive IgM responses. Conclusions. Strong IgG antibody responses can be detected in PCR-negative children with PIMS-TS. The low detection rate of IgM in these patients is consistent with infection having occurred weeks previously and that the syndrome onset occurs well after the control of SARS-CoV-2 viral load. This implies that the disease is largely immune-mediated. Lastly, this indicates that serology can be an appropriate diagnostic tool in select patient groups.