T Cells in Multisystem Inflammatory Syndrome in Children (MIS-C) Have a Predominant CD4+ T Helper Response to SARS-CoV-2 Peptides and Numerous Virus-Specific CD4- CD8- Double-Negative T Cells.

We studied SARS-CoV-2-specific T cell responses in 22 subacute MIS-C children enrolled in 2021 and 2022 using peptide pools derived from SARS-CoV-2 spike or nonspike proteins. CD4+ and CD8+ SARS-CoV-2-specific T cells were detected in 5 subjects, CD4+ T helper (Th) responses alone were detected in 12 subjects, and CD8+ cytotoxic T cell (CTL) responses alone were documented in 1 subject. Notably, a sizeable subpopulation of CD4- CD8- double-negative (DN) T cells out of total CD3+ T cells was observed in MIS-C (median: 14.5%; IQR 8.65-25.3) and recognized SARS-CoV-2 peptides. T cells bearing the Vß21.3 T cell receptor (TcRs), previously reported as pathogenic in the context of MIS-C, were detected in high frequencies, namely, in 2.8% and 3.9% of the CD4+ and CD8+ T cells, respectively. However, Vß21.3 CD8+ T cells that responded to SARS-CoV-2 peptides were detected in only a single subject, suggesting recognition of nonviral antigens in the majority of subjects. Subjects studied 6-14 months after MIS-C showed T cell epitope spreading, meaning the activation of T cells that recognize more SARS-CoV-2 peptides following the initial expansion of T cells that see immunodominant epitopes. For example, subjects that did not recognize nonspike proteins in the subacute phase of MIS-C showed good Th response to nonspike peptides, and/or CD8+ T cell responses not appreciable before arose over time and could be detected in the 6-14 months' follow-up. The magnitude of the Th and CTL responses also increased over time. In summary, patients with MIS-C associated with acute lymphopenia, a classical feature of MIS-C, showed a physiological response to the virus with a prominent role for virus-specific DN T cells.

Unbalanced atrioventricular septal defect: defining the limits of biventricular repair.

Unbalanced atrioventricular septal defect (uAVSD) is a challenging lesion with suboptimal outcomes in the current era. Severe forms of uAVSD mandate univentricular repair with well-documented outcomes. Determining the feasibility of biventricular repair (BVR) in patients with moderate forms of uAVSD is difficult. Ventricular hypoplasia has traditionally formed the cornerstone of defining uAVSD. However, malalignment of the atrioventricular junction and related derangements of the anatomy and physiology of the atrioventricular inflow play a central role in establishing and sustaining a biventricular end state. Atrioventricular valve index, left ventricular inflow index, and right ventricle/left ventricle inflow angle are important recently described measures of inflow physiology. Additional patient anatomic and physiologic factors that impact BVR feasibility undoubtedly exist. A recently launched Congenital Heart Surgeons Society prospective inception cohort study will address these and other issues that impair our ability to predict BVR feasibility in uAVSD.

Long-term use of ventricular assist device as a bridge to recovery in acute fulminant myocarditis.

We report the successful long-term use of a left ventricular assist device (Berlin EXCOR) as a bridge to recovery in a patient with fulminant parvovirus B19 myocarditis. The use of this device allowed time for myocardial recovery, avoiding the need for cardiac transplantation.