Outer Membrane Vesicles Secreted by Bacteroides fragilis Inhibit CFTR Chloride Secretion by Human Colon Organoids

Area of Science:

• Microbiology
• Immunology
• Gastroenterology

Background:

• Bacteroides fragilis resides in the colon mucus, suggesting outer membrane vesicles (OMVs) mediate host-microbe communication.
• Bacteroides fragilis toxin (BFT) is implicated in host-pathogen interactions.
• CFTR (cystic fibrosis transmembrane conductance regulator) plays a crucial role in epithelial ion transport.

Purpose of the Study:

• Develop a model for studying host-pathogen interactions in primary human colon cells.
• Investigate if BFT secreted in OMVs modulates mucosal immunity and CFTR Cl- secretion.

Main Methods:

• Utilized four strains of Bacteroides fragilis: ETBF, NTBF, ETBF Δbft, and NTBF+bft.
• Applied OMVs from these strains to primary human colon cell monolayers.
• Measured CFTR Cl- secretion, tight junction integrity, transepithelial resistance, and innate immune response.

Main Results:

• Most B. fragilis OMVs reduced forskolin-stimulated CFTR Cl- secretion.
• OMVs did not affect tight junction structure, transepithelial resistance, or innate immunity.
• BFT contributed to CFTR Cl- inhibition, but other OMV factors were also involved.

Conclusions:

• Bacteroides fragilis OMVs are significant mediators of host-pathogen interactions in the colon.
• OMVs reduce CFTR Cl- secretion, suggesting a role in colonic mucosal immune modulation.
• Further research is needed to identify other OMV components affecting CFTR.