<em>Mycobacterium tuberculosis</em> Extracellular Vesicle Enrichment through Size Exclusion Chromatography

The role of extracellular vesicles (EVs) in the context of bacterial infection has emerged as a new avenue for understanding microbial physiology. Specifically, Mycobacterium tuberculosis (Mtb) EVs play a role in the host-pathogen interaction and response to environmental stress. Mtb EVs are also highly antigenic and show potential as vaccine components. The most common method for purifying Mtb EVs is density gradient ultracentrifugation. This process has several limitations, including low throughput, low yield, reliance on expensive equipment, technical challenges, and it can negatively impact the resulting preparation. Size exclusion chromatography (SEC) is a gentler alternative method that combats many of the limitations of ultracentrifugation. This protocol demonstrates that SEC is effective for Mtb EV enrichment and produces high-quality Mtb EV preparations of increased yield in a rapid and scalable manner. Additionally, a comparison to density gradient ultracentrifugation by quantification and qualification procedures demonstrates the benefits of SEC. While the evaluation of EV quantity (nanoparticle tracking analysis), phenotype (transmission electron microscopy), and content (Western blotting) is tailored to Mtb EVs, the workflow provided can be applied to other mycobacteria.