Disruption of goat airway epithelial barrier function by caprine parainfluenza virus type 3 infection in an ALI model

The respiratory epithelium acts as the airway's first physical barrier against invading pathogens, mainly relying on mucociliary clearance (MCC) and apical junctional complexes (tight junctions/TJs and adherens junctions/AJs) for barrier function. Primary airway epithelial cells cultured in the air-liquid interface (ALI) system can well mimic these characteristics in vitro. This study established and characterized well-differentiated ALI-cultured goat airway epithelial cells (ALI-GAECs), and developed a CPIV3 infection model therein, verifying the apical infection and release of CPIV3 in ALI-GAECs. CPIV3 infection impaired the barrier function of ALI-GAECs, as reflected by decreased trans-epithelial electrical resistance (TEER), increased FITC-Dextran permeability, and reorganization of the ZO-1 and F-actin meshwork. Mechanistically, RT-qPCR and Western blot analyses demonstrated that CPIV3 downregulated major TJ proteins (ZO-1, occludin, claudin-1) while upregulated the expression of proinflammatory cytokines (TNF-α, IL-1β, IL-4, IL-6). The NF-κB signaling pathway, but not the MAPK pathways, was activated upon viral infection. Treatment with the NF-κB inhibitor BAY 11-7082 partially restored the expression of TJ proteins and proinflammatory cytokines. Collectively, the activation of the NF-κB pathway and subsequent production of proinflammatory cytokines is responsible for CPIV3-induced TJ disruption. In addition, the developed ALI-GAECs model provides a valuable in vitro tool for investigating the pathogenesis of CPIV3 and other caprine respiratory pathogens.