The SARS-CoV-2 E protein induces Toll-like receptor 2-mediated neonatal lung injury in a model of COVID-19 viremia that is rescued by the glucocorticoid ciclesonide.

ABSTRACT

SARS-CoV-2 viremia is associated with increased acute lung injury (ALI) and mortality in children and adults. The mechanisms by which viral components in the circulation mediate ALI in COVID-19 remain unclear. We tested the hypothesis that the SARS-CoV-2 envelope (E) protein induces Toll-like receptor (TLR)-mediated ALI and lung remodeling in a model of neonatal COVID-19. Neonatal C57BL6 mice given intraperitoneal E protein injections revealed a dose-dependent increase in lung cytokines [interleukin 6 (Il6), tumor necrosis factor (Tnfα), and interleukin 1 beta (Il1ß)] and canonical proinflammatory TLR signaling. Systemic E protein induced endothelial immune activation, immune cell influx, and TGFß signaling and lung matrix remodeling inhibited alveolarization in the developing lung. E protein-mediated ALI and transforming growth factor beta (TGFß) signaling was repressed in Tlr2-/-, but not Tlr4-/- mice. A single dose of intraperitoneal E protein injection induced chronic alveolar remodeling as evidenced by a decrease in radial alveolar counts and increase in mean linear intercepts. Ciclesonide, a synthetic glucocorticoid, inhibited E protein-induced proinflammatory TLR signaling and ALI. In vitro, E protein-mediated inflammation and cell death were TLR2-dependent in human primary neonatal lung endothelial cells and were rescued by ciclesonide. This study provides insight into the pathogenesis of ALI and alveolar remodeling with SARS-CoV-2 viremia in children, whereas revealing the efficacy of steroids.NEW & NOTEWORTHY We reveal that the envelope protein of SARS-CoV-2 mediates acute lung injury (ALI) and alveolar remodeling through Toll-like receptor activation, which is rescued by the glucocorticoid, ciclesonide.