Abnormal innate immune responses and associated genetic factors in Multisystem Inflammatory Syndrome in Children (MIS-C)

Abstract

Abstract Multisystem inflammatory syndrome in children (MIS-C) is a rare, severe complication of COVID-19 characterized by multi-lineage immune activation and multi-organ system involvement. While baseline immunophenotypes have been characterized, innate immune cell functionality and genetic risk factors remain poorly understood. To address these knowledge gaps, we assessed inflammatory immune responses in children with MIS-C (n = 33) relative to healthy controls (n = 5). We found that Toll like receptor (TLR) signaling is severely dampened in peripheral blood cells in the MIS-C group, with weak cytokine responses to LPS stimulation and increased baseline gene expression of TLR negative regulators, compared to controls. We also found that the cytokine response to LPS was abnormally heterogeneous in the MIS-C group. In particular, cytokine response outliers were enriched for rare and potentially deleterious variants in the lysosomal trafficking regulator (LYST) locus. These LYST variants were associated with markers of lysosomal and mitochondrial dysfunction, altered energy metabolism, and low levels of TLR negative regulator expression. Improved knowledge of immune dysfunctions associated with MIS-C and risk factors may help explain aspects of MIS-C and other manifestations of long COVID and identify targets for therapy of MIS-C and other hyperinflammatory syndromes in children.