A myeloid program associated with COVID-19 severity is decreased by therapeutic blockade of IL-6 signaling

Summary Altered myeloid inflammation and lymphopenia are hallmarks of severe infections, including SARS-CoV-2. Here, we identified a gene program, defined by correlation with EN-RAGE ( S100A12 ) gene expression, which was up-regulated in patient airway and blood myeloid cells. The EN-RAGE program was expressed in 7 cohorts and observed in patients with both COVID-19 and acute respiratory distress syndrome (ARDS) from other causes. This program was associated with greater clinical severity and predicted future mechanical ventilation and death. EN-RAGE + myeloid cells express features consistent with suppressor cell functionality, with low HLA-DR and high PD-L1 surface expression and higher expression of T cell-suppressive genes. Sustained EN-RAGE signature expression in airway and blood myeloid cells correlated with clinical severity and increasing expression of T cell dysfunction markers, such as PD-1. IL-6 upregulated many of the severity-associated genes in the EN-RAGE gene program in vitro , along with potential mediators of T cell suppression, such as IL-10. Blockade of IL-6 signaling by tocilizumab in a placebo-controlled clinical trial led to rapid normalization of ENRAGE and T cell gene expression. This identifies IL-6 as a key driver of myeloid dysregulation associated with worse clinical outcomes in COVID-19 patients and provides insights into shared pathophysiological mechanisms in non-COVID-19 ARDS.