Mucin-enriched microenvironment shapes bacteriophage protection efficacy 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, mucin increases bacterial-induced cytotoxicity and inflammation in airway epithelial cells, while driving CRD-like transcriptional changes, including hypoxia and stress responses. Mucin selectively downregulates virulence factors without impairing bacterial growth. P. aeruginosa-infecting bacteriophage DMS3vir retained full lytic activity in mucin-rich conditions and, in synergy with mucin, enhanced epithelial cells protection against cytotoxicity. DMS3vir also reduced IL-8 gene expression without triggering antiviral responses. Furthermore, mucin shaped phage-resistant P. aeruginosa phenotypes, altering pigmentation, pigmentation, pyocyanin production, and motility. These changes influenced 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.