Abstract 480: IL-33 Promotes Cardiovascular Lesions Development In A Mouse Model Of Kawasaki Disease

Kawasaki Disease (KD), a pediatric acute febrile illness and systemic vasculitis, is the leading cause of acquired heart diseases in children. Coronary artery aneurysms (CAAs) occur in up to 25% of untreated children, which is reduced to 5% with intravenous immunoglobulin (IVIG) treatment. However, up to 20% of KD patients are refractory to IVIG and at higher risk of CAAs, highlighting the need to characterize the mechanisms mediating KD vasculitis to develop more efficient therapies. IL-33 is released upon inflammation and tissue damage and exerts its effects by binding to its receptor ST2 ( IL1RL1 ). Levels of IL-33 are elevated in KD patients during the acute phase. However, how IL-33 contributes to the development of KD cardiovascular lesions remains unknown. Using the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, we observed increased Il33 mRNA expression in hearts and abdominal aortas aneurysms of LCWE-injected mice. While ST2 was detected by immunofluorescence in the abdominal aortas of both control and LCWE-injected mice, IL-33 was mainly detected in tissues from LCWE-injected mice. Single-cell RNA-sequencing of abdominal aortas from LCWE-injected mice indicated that Il33 transcripts were expressed primarily by fibroblasts, endothelial cells, B cells, and vascular smooth muscle cells. In contrast, Il1rl1 was highly expressed by tissue infiltrating regulatory T cells, macrophages, eosinophils, and neutrophils. Blocking IL-33 with either anti-IL-33 or using Il33 -/- mice significantly attenuated LCWE-induced KD vasculitis. Our results indicate that IL-33 participates in LCWE-induced KD vasculitis in mice and could therapeutically be targeted to inhibit KD cardiovascular lesions.