Flagellin nebulization enhances respiratory immune responses in the porcine model.

Respiratory delivery of the Toll-like receptor 5-agonist FLAMOD, a recombinant flagellin, stimulates the airway epithelium, mobilizing immune cells and effectors in mouse models to combat respiratory infections, especially bacterial pneumonia. This study represents a comprehensive assessment of FLAMOD delivered by nebulization in pigs. A single nebulized dose was well tolerated with no adverse clinical effects. FLAMOD treatment led to immune cell infiltration in the lung tissue and granulocyte recruitment in conducting airways, as shown by histology and flow cytometry. RNA sequencing established immune activation across the respiratory tract, from the nose, trachea, and bronchi to the lungs, highlighting innate immunity, bacterial defense, cytokine and chemokine signaling, and granulocyte chemotaxis as key biological pathways. These findings demonstrate that FLAMOD stimulates a robust and common respiratory immunity, as well as compartment-specific response, providing a proof-of-concept for inhalation-based therapeutic strategies to combat bacterial pneumonia in the clinical setting.