TGFβ links EBV to multisystem inflammatory syndrome in children

In a subset of children and adolescents, SARS-CoV-2 infection leads to multisystem inflammatory syndrome in children (MIS-C), a severe hyperinflammatory shock occurring 4-8 weeks post-infection. MIS-C is characterized by a specific expansion of TCRVβ21.3+ T-cells and systemic hyperinflammation, with an unclear pathogenesis. Here, we show that acute MIS-C exhibits impaired reactivation of virus-specific memory T cells due to elevated TGF-β levels, mirroring severe COVID-19 in adults. Functionally, the impaired T-cell cytotoxicity is accompanied by TGF-β-response signatures and reduced antigen-presentation capabilities of monocytes, reversible by TGF-β blockade. MIS-C TCRVβ21.3+ T cells resemble Epstein-Barr Virus (EBV)-reactive T cells, displaying enhanced capability in eliminating EBV-infected B cells. Clinically, active MIS-C correlates with TGF-β-induced defects in T-cell cytotoxicity, elevated EBV seroprevalence, and EBV-reactivation. Our findings establish a connection between SARS-CoV-2 infection and COVID-19 sequelae in children, where reduced T-cell cytotoxicity induced by SARS-CoV-2-triggered TGF-β overproduction leads to EBV-reactivation and contributes to hyperinflammation.