Characterizing the Role of Extracellular Vesicles in Bacteria-Host Communication

Abstract

The gastrointestinal tract contains trillions of symbiotic microorganisms (microbiota) that are critical for normal immunity, physiology, and development. Yet the extent to which these microbes influence neurodevelopment, and the mechanisms they use to do so, are poorly characterized. Using a mouse model, we show that perturbations of the maternal microbiota by treatment with low-dose penicillin during the last week of pregnancy alters behaviour and microbiota composition in adult offspring. These changes were sex-specific; female offspring had reduced anxiety-like behaviours, while males showed abnormal social behaviours, which correlated with altered hippocampal gene expression and reduced regulatory T cells. Microbiota composition was distinct between sexes and from untreated controls, suggesting that antibiotic exposure altered microbiota, which may have mediated other changes seen. To investigate a mechanism by which gut microbes may influence distal organ systems, we focused on the bacterium Lacticaseibacillus rhamnosus JB-1. We found that membrane vesicles (MV) produced by JB-1 contain lipoteichoic acid, which activates Toll-like receptor 2 (TLR2) and induces interleukin-10 production by dendritic cells. We further showed that JB-1 MV are internalized by human and mouse intestinal epithelial cell lines in a clathrin-dependent manner in culture, and by mouse intestinal epithelial cells in vivo. We then fed JB-1 bacteria to mice and showed that within 2.5 hours there are functional nanoparticles in their blood that reproduce effects associated with the fed bacteria. Plasma nanoparticles from fed mice had a size distribution distinct from that of saline-fed mice. They also activated TLR2 and induced interleukin-10 production by dendritic cells via lipoteichoic acid. These nanoparticles are likely bacterial MV as they contained bacterial protein and DNA from a novel bacteriophage in the original fed bacteria. Altogether these experiments support a role for microbiota in neurodevelopment and demonstrate novel nanoparticulate mechanisms of bacteria-host communication that may underlie their systemic influence.