Outer Membrane Vesicle-Host Cell Interactions

Abstract

Outer membrane vesicles (OMVs) are nanosized proteoliposomes derived from the outer membrane of Gram-negative bacteria. They are ubiquitously produced both in culture and during infection and are now recognized to play crucial roles during host-microbe interactions. OMVs can transport a broad range of chemically diverse cargoes, including lipids and lipopolysaccharides, membrane-embedded and associated proteins and small molecules, peptidoglycan, and nucleic acids. Particularly, virulence factors such as adhesins and toxins are often enriched in OMVs. Here we discuss a variety of ways in which OMVs facilitate host-microbe interactions, including their contributions to biofilm formation, nutrient scavenging, and modulation of host cell function. We particularly examine recent findings regarding OMV-host cell interactions in the oral cavity and the gastrointestinal tract.

FIGURE 1

Structure and composition of bacterial OMVs. (A to C) Examples of purified OMVs isolated from Porphyromonas gingivalis (A), Treponema denticola (B), and Tannerella forsythia (C). OMVs were purified using an optiprep gradient and visualized using cryo-transmission electron microscopy as previously described (70). Scale bars, 200 nm. (D) Typical composition of bacterial OMVs.

FIGURE 2

A summary of OMV interactions within gingival tissues. Bacteria accrete on the tooth’s surface and form a bacterial (plaque) biofilm that is adjacent to the epithelial cells in the gingival (gum) tissue. OMVs secreted from bacteria in this plaque biofilm bind to and penetrate into the mucosal tissue and generate host cell interactions and responses. These responses culminate in a chronic inflammatory response resulting in osteoclast activation which, in turn, promotes bone resorption and eventual tooth loss.

FIGURE 3

Summary of OMV interactions with the gastrointestinal tract. Environmental pressures, such as low pH, mucin, or peptides or overgrowth of certain bacteria, result in the release of OMVs in the gastric lumen. These OMVs are able to penetrate the mucosal barrier and via different mechanisms adhere to and interact with the underlying epithelial cell and immune cells, inducing homeostasis or pathology.