C15-09 Vagal Nerve Transport of Gut-Derived Bacteria to the Lung Reveals a Novel Gut-Lung Axis

Abstract Rationale Increasing evidence suggests that gut microbiota play a critical role in severity of interstitial lung diseases. Dysbiosis of the intestinal microbiome has been implicated in altering inflammatory processes in distal organs, such as the lungs. However, the precise mechanism through which bacteria or bacterial products translocate from the gut to extraintestinal organs remains undefined. Independent studies implicate the vagus nerve, such as having demonstrated that protein transport from the gut to the brain via the vagus nerve, and experimental vagotomy has been shown to reduce pulmonary fibrosis severity in mice. We tested the hypothesis that gut microbiota travel to the lung via the vagus nerve. Methods To investigate this, GFP-expressing Escherichia coli (1 × 109 CFU) were administered via oral gavage to both C57BL/6J and germ-free (GF) mice. Five minutes post-gavage, animals were euthanized, and samples including stool, muscle, heart, lung lobes, trachea, esophagus, stomach, small intestine, carotid and anterior vagus nerve, were collected under sterile conditions for microbial culture and fluorescence imaging. Non-gavaged GF and C57BL/6J mice served as controls. Additionally, shotgun metagenomic sequencing was performed on tissues from non-infected C57BL/6J mice to profile resident microbial species. Results Within five minutes of gavage, E. coli colonies were detected not only in gastrointestinal tissues (stomach, small intestine, stool) but also in extraintestinal sites including the cervical and anterior vagus nerve, lungs, heart, aorta, esophagus, trachea, and skeletal muscle. Colony counts were significantly higher in lungs of gavaged compared to non-gavaged mice (p = 0.02). Immunofluorescence microscopy confirmed the presence of GFP-E. coli within the carotid and anterior vagus nerves of GF mice. To assess if microbial transfer occurs in wild type mice, we conducted Metagenomic profiling of non-infected mice. We noted three bacterial species Curtobacterium flaccumfaciens, Klebsiella pneumoniae, and Actualibacter muris consistently present in both stool and extraintestinal organs. Weighted principal coordinate analysis demonstrated overlapping microbial communities between stool and organs. Alpha diversity was significantly higher in stool compared to other organs, while Shannon diversity and evenness indices were comparable, indicating similar microbiotal in organ and stool. Conclusion These findings reveal that gut-derived bacteria can rapidly reach the lung via transneuronal transport along the vagus nerve from the gut. The shared microbial signatures between gut and lung support the existence of a functional gut-lung axis. Future studies investigate this axis that contributes to systemic inflammation, granuloma formation in sarcoidosis and interstitial lung diseases. This abstract is funded by: none