Extraction and biological evaluation of Mycobacterium kansasii extracellular vesicles as a vaccine candidate against mycobacterial pulmonary infections

Introduction: Extracellular vesicles (EVs) are bacterial products with diverse biological roles. Like many microorganisms, Mycobacterium kansasii as a nontuberculous mycobacteria (NTM), can naturally release EVs. The aim of the present study was the extraction and biological evaluation of M. kansasii as a vaccine candidate against mycobacterial pulmonary infections. Methods: After bacterial culture of the standard species of M. kansasii, the EVs extraction was done by density gradient ultra-centrifugation method and biological evaluations of EVs were performed by SDS-PAGE and electron microscopy. Endotoxin safety of the EVs was evaluated by LAL test. Results: SDS-PAGE result showed more than 5 prominent protein bands (60-180 kDa). The intactness of the vesicles was verified by electron microscopy through which the spherical configuration of EVs with diameter of 200-300 nm could be observed. The amount of lipopolysaccharide (LPS) contamination existing in EVs was in the specified application range of biological products. Conclusion: EVs were prepared with acceptable quality composition with intact conformational structure throughout the extraction procedure. The extracted EVs had the initial requirements as an immunogenic molecule, such as safety, stability, inexpensiveness and antigens possession which based on the similarities between M. kansasii and M. tuberculosis, make them a suitable candidate for future prophylactics, therapeutic, detection and adjuvants studies against mycobacterial pulmonary infections.