Pi16+ adventitial fibroblasts promote monocyte recruitment via CCL2-CCR2 signaling following influenza A virus infection 4436

Abstract Description Lung fibroblasts are emerging as central regulators of immune cell recruitment into the tissue and have been associated with driving severe disease after respiratory virus infection. Fibroblasts exhibit remarkable heterogeneity across lung compartments, including adventitial, alveolar, and peribronchial regions that express specific transcriptional signatures. It is unknown whether these fibroblast lineages in specific lung compartments have unique functional responses to influenza A virus (IAV) infection that impact infection outcomes. Our data indicated that adventitial fibroblasts showed the highest inflammatory response to IAV infection. Cytokine profiling of supernatants from cultured adventitial fibroblasts demonstrated increased production of the chemokine CCL2, at baseline and after TNF stimulation. Cell-cell ligand-receptor interaction analysis from our single-cell RNASeq data predicted adventitial fibroblasts as the highest CCL2 expressing cells and monocytes as highest CCR2 expressing cells. To validate these cell interactions functionally, we performed a transwell migration assay. We found that conditioned media from adventitial fibroblasts dramatically enhanced monocyte migration, and antibody-based neutralization of CCL2 in the conditioned media significantly reduced their migration. These findings suggest that adventitial fibroblasts are a primary source of secreted CCL2, which has been shown to contribute to severe disease after IAV infections. Funding Sources Supported by National Heart, Lung, and Blood Institute (NHLBI) - R01HL170121 ; California Institute for Regenerative Medicine (CIRM) Predoctoral Fellowship - EDUC4-12759 Topic Categories Viral Immunology (VIR)