Oral Presentation Lorne Infection and Immunity 2018

Staphylococcus aureus membrane vesicles are immunostimulatory and activate innate immune pathways (#102)

Natalie J Bitto 1 2 , Mitch Shambrook 2 3 , Andrew F Hill 2 3 , Timothy P Stinear 4 , Maria Kaparakis-Liaskos 1 2
  1. Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, Victoria, Australia
  2. Research Centre for Extracellular Vesicles, School of Molecular Sciences, La Trobe University, Bundoora, Victoria, Australia
  3. La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
  4. Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria, Australia

Extracellular vesicles are ubiquitously released by all forms of life. The roles of Gram-negative outer membrane vesicles (OMVs) in inter-bacterial communication and host-pathogen interactions are well described in the literature. In contrast, research surrounding Gram-positive membrane vesicles (MVs) is still in its infancy. There is limited knowledge regarding the pathogenic properties of Gram-positive MVs, including their contents, biological functions and role in cellular communication.

 

This study characterises MVs produced by the Gram-positive pathogen, Staphylococcus aureus, and elucidates their ability to induce an innate immune response. Transmission electron microscopy was used to visualise MVs produced by S. aureus, while NanoSight particle tracking analysis enabled quantification of the size and amount of MVs. Furthermore, we characterised the protein, DNA and RNA contents of S. aureus MVs. Investigation into the immunogenicity of S. aureus MVs revealed that, similar to Gram-negative OMVs, S. aureus MVs induced the production of pro-inflammatory cytokines by epithelial cells. Reporter cell lines were used to elucidate the specific innate immune sensors activated by S. aureus MVs.

                                                         

This study reveals that S. aureus MVs contain a range of cargo including proteins and nucleic acids, that may play a role in host immune modulation. The findings facilitate understanding of a previously unknown mechanism of S. aureus pathogenesis, suggesting that MVs may be driving inflammation at a mucosal-epithelial cell surface.