Endothelial Cell Expression of a STING Gain-of-function Mutation Initiates Pulmonary Lymphocytic Infiltration

Patients afflicted with STING gain-of-function mutations frequently present with debilitating interstitial lung disease (ILD) that is recapitulated in mice expressing the STINGV154M mutation (VM). Prior radiation chimera studies revealed an unexpected and critical role for non-hematopoietic cells in initiating ILD. To identify STING-expressing non-hematopoietic cell types required for the development of ILD, we generated a conditional knock-in (CKI) model and directed expression of the VM allele to hematopoietic cells, fibroblasts, epithelial cells, or endothelial cells. Only endothelial cell-targeted VM expression resulted in enhanced recruitment of immune cells to the lung associated with chemokine expression and the formation of bronchus-associated lymphoid tissue, as seen in the parental VM strain. These findings reveal the importance of endothelial cells as instigators of STING-driven lung disease and suggest that therapeutic targeting of STING inhibitors to endothelial cells could potentially mitigate inflammation in the lungs of SAVI patients or patients afflicted with other ILD-related disorders. To investigate role of the STING gain-of-function mutation V154M (VM), in endothelial cells, we generated a conditioal knock-in (CKI) mouse model of the VM mutation in all cells (CKI x CAGG-cre ERTM) and endothelial cells (CKI x Cdh5-cre ERT2). To understand how ubiquitous and endothelial targeting of VM alters gene expression within lung stromal and parenchymal cells, we depleted hematopoietic (CD45+) and erythrocytes (Ter119+) from the lungs and performed RNA-seq.