C107-13 A ‘Taste’ of Danger: Tuft Cells Trigger Th2 Inflammation Following Influenza-Induced Acute Respiratory Distress Syndrome (ARDS)

Rationale Tuft cells are rare chemosensory cells that use bitter taste transduction pathways to detect pathogens and allergens. They line mucosal surfaces, including the gastrointestinal tract, pharynx and trachea. In the upper airways, tuft cells act as sentinels that amplify type 2 (Th2) inflammation by activating type 2 innate lymphoid cells (ILC2s), leading to mucus metaplasia and eosinophilic inflammation in response to viral infections and allergens—forming the epithelial-ILC2 response circuit. Although absent from the distal lung, our lab and others have observed the emergence of ectopic tuft cells following influenza-induced acute respiratory distress syndrome (ARDS). Ectopic tuft cells form in regions of basal stem cell-driven dysplastic repair of flooded alveoli, where gas-exchanging tissue is replaced by epithelial scars which temporarily restores barrier integrity but at the cost of long-term alveolar regeneration. Here, we test the central hypothesis that ectopic tuft cells within these scars orchestrate Th2 inflammation in influenza-induced ARDS. Methods IFNγ, ILC2, POU2F3 deficient mice and littermate controls in a C57BL6/J background were intranasally infected with A/H1N1/PR/8 (PR8). Body weights and pulse oximetry were measured prior to and following PR8-infection. 22-days following infection, mice lungs were harvested for immunostaining or whole-lung cell suspensions were prepared for flow cytometry, sorting and single-cell RNA-seq. The protocol number for the ethical approval of this work is 806262. Results To determine whether ectopic tuft cells regulate the epithelial-ILC2 circuit in the lower airways, we first infected IFNγ-deficient mice with PR8. IFNγ is a known inhibitor of Th2 immunity. IFNγ deficient mice had increase ectopic tuft cell differentiation following infection, implicating tuft cells in the ILC2 response circuit (Figure 1A). Conversely, ILC2-deficient mice infected with PR8 showed reduced tuft cell expansion (Figure 1B). We also found tuft cell deficient mice infected with PR8 had significant decrease in both eosinophils and ILC2s (Figure 1C-D). Finally, single-cell RNA sequencing confirmed upregulation of Th2-associated genes, e.g. Retnla, supporting a tuft cell-ILC2 regulatory circuit in the lower-airways (Figure 1E). Conclusions Our findings suggests that ectopic tuft cells regulate the epithelial-ILC2 circuit in the lower airways. IFNγ restricts tuft cell differentiation, while ILC2s are required for tuft cell expansion and eosinophilic inflammation. Together with transcriptomic evidence of Th2 pathway activation, these results support a tuft cell-ILC2 regulatory loop in the lung and may represent a potential therapeutic target in ARDS. This abstract is funded by: T32HL160493, RO1: HL131817, RO1: HL153539