610 - High dimensional immune profiling of Multisystem Inflammatory Syndrome in Children (MIS-C)

Publication Number: 610.5526

Juan C. Salazar, University of Connecticut School of Medicine, Hartford, CT, United States; Katherine W. Herbst, Connecticut Children's Research Institute, Hartford, CT, United States; Courtney L. Gunter, University of Connecticut School of Medicine, West Hartford, CT, United States; Derya Unutmaz, Jackson Laboratory, Farmington, CT, United States

Background: Multisystem Inflammatory Syndrome in Children (MIS-C) is a rare but severe condition that occurs 2-6 weeks after SARS-CoV-2 infection. As of September 2024, 9,731 cases and 80 deaths have been reported in the United States. MIS-C commonly presents in school-aged children and is characterized by persistent fever, systemic hyperinflammation, and multisystem organ dysfunction. Several articles have reported that polyclonal expansion of TCR Vb21.3 expressing CD4+ and CD8+ T cells are highly specific to MIS-C and not seen in acute COVID-19.

Objective: Our study aimed to validate published findings on Vb21.3 and to further explore it’s expression in effector T cell profiles and mucosal invariant T cells (MAIT) by comparing flow cytometry results between COVID vs MIS-C vs Control cohorts.

Design/Methods: Peripheral blood mononuclear cells (PBMCs) were collected from children enrolled in a prospective cohort study (IRB #21-004) who were hospitalized for acute COVID-19 or MIS-C, or underwent outpatient surgery for a non-inflammatory condition (Control). PBMCs were counted and divided into two parts: one part for day 0 surface staining and the other part cultured in complete media with IL-7 and IL-15 for 6 days, followed by intracellular cytokine staining. Flow cytometry analysis was performed on a Cytek Aurora spectral cell analyzer and data analyzed using FlowJo. Between group comparisons were made using Mann-Whitney U test.

Results: Included were 107 subjects (32 COVID, 27 MIS-C, 48 Controls). MIS-C subjects in our population also showed highly significant increases in Vb21.3+ CD4+ T cells compared to children with COVID (p < 0.001) and Controls (p < 0.0001), primarily in memory T cells, validating previously published findings. We further delineated expression of Vb21.3 in CD4+ T cells with effector T cell profiles, and found MIS-C subjects showed significantly increased expression of Vb21.3+ in Th1 and Th2 T cells compared to COVID (p < 0.001) and Controls (p < 0.001), with overrepresentation of Vb21.3+ in Th1 vs Th2 cells (p < 0.0001). Vb21.3+ was more highly expressed in Th17+ cells of MIS-C subjects vs COVID (p < 0.05), and significantly higher in the Th17.1 subset vs the Th17.2 subset (p < 0.001). Our analysis also found that MIS-C subjects showed higher expansion of Vb21.3 in CD4- CD8- MAIT cells compared to COVID (p < 0.0005) and Controls (p < 0.0001), as well as CD161+ CD8+ memory T cells (p < 0.001) and, to a lesser extent, in children with severe COVID compared to Controls (p < 0.05).

Conclusion(s): These finding suggest there is a specific expansion of proinflammatory and gut homing T cell subsets in MIS-C.

Vb21.3+ expression in memory and naive CD8+ T cells
Vb21.3+ expression is significantly higher in memory CD8+ T cells in the MIS-C group compared to the COVID and Control groups, but there was no significant difference between the groups in naïve CD8+ T cells.

Analysis of MAIT cells in MIS-C


Vb21.3+ expression in MAIT cells
Vb21.3+ expression is increased in MAIT cells in the MIS-C group compared to COVID and Control groups.