Mucin-enriched environment shapes bacteriophage protection against Pseudomonas aeruginosa in airway epithelial cells

Mucin hypersecretion, a hallmark of chronic respiratory diseases (CRD), creates a complex microenvironment that reshapes host immunity and microbial behavior. However, its impact on bacteriophage therapy remains poorly understood. Here, we demonstrate that, despite reducing Pseudomonas aeruginosa internalization, exogenous mucin increases bacterial-induced cytotoxicity and inflammation in airway epithelial cells, while driving CRD-like transcriptional changes, including hypoxia and stress responses. Under bacterial culture, mucin selectively downregulates bacterial virulence factors without impairing growth. P. aeruginosa-infecting bacteriophage DMS3vir retains full lytic activity in mucin-rich conditions and, in synergy with mucin, enhances protection against cytotoxicity in epithelial cells. DMS3vir also reduces IL-8 gene expression without triggering antiviral responses. Furthermore, mucin supplementation shapes phage-resistant P. aeruginosa phenotypes, altering colony pigmentation, pyocyanin production, and motility, influencing virulence trade-offs. These findings uncover the dual role of mucins as modulators of infection and sensitizers to phage protection, paving the way for optimized, mucosa-adapted phage therapies in chronic lung diseases.