Fig. 6

Mechanisms of microbiota-mucosal immunity axis in antagonizing viral infection. A. Viral invasion and host-microbiota interactions in the respiratory mucosa. I. Viral particles penetrate the mucus-cilia barrier and bind to cellular adhesion molecules (e.g., ICAM-1, sialic acid receptors). II. Epithelial activation triggers PRR signaling, releasing antiviral effector molecules. III. Cross-talk between mucosal epithelium and immune cells (innate/adaptive) establishes coordinated defense. IV. Commensal microbiota competitively inhibits viral pathogenesis through direct antagonism and immune modulation, forming the microbiota-mucosal immunity axis. B. Mechanisms of microbiota-mediated antiviral protection. I. Receptor competition: Resident bacteria sequester viral attachment receptors through molecular mimicry, reducing virion shedding and transmissibility. II. Immune priming: Microbial colonization stimulates interferon responses that suppress viral replication. III. Inflammatory regulation: Commensal-derived metabolites attenuate infection-induced cytokine storms and tissue pathology.NHNE, normal human nasal epithelial; PR8 influenza, A/PR/8/34 influenza