Glycine Induction Method: Effective Production of Immunoactive Bacterial Membrane Vesicles with Low Endotoxin Content

Bacteria are known to release nanometer scale proteoliposomes termed bacterial membrane vesicles (MVs), and it is considered that native and bioengineered MVs would be applicable for development of acellular vaccines and novel drug delivery systems in medical settings. However, important considerations for manufacturing purposes include the varied productivity of MV among bacterial species and strains, as well as endotoxicity levels due to the lipopolysaccharide component. The method for MV induction using glycine described here is simple and provides a solution to these problems. Glycine weakens bacterial peptidoglycans and significantly increases bacterial MV formation, while the relative endotoxin activity of glycine-induced MVs is extremely reduced as compared to that of noninduced MVs. Nevertheless, glycine-induced MVs elicit strong immune responses at levels nearly equivalent to those of noninduced MVs. Taken together, the present method for induction by glycine is convenient for research studies of bacterial MVs and has potential for use in medical applications including vaccine development.