Dr. Nakao, as a principal investigator, comprehensively studied bacterial membrane vesicles, looking ahead to MV vaccine development in future. The following four topics have been mainly addressed.
(i) Vaccine effect and safety assessment of MVs of Porphyromonas gingivalis
MVs of a periodontopathic bacterium, Porphyromonas gingivalis (Pg), has been investigated with regard to their vaccine effect and safety in mouse models. Our findings suggest that intranasal immunization of mice with combination of Pg-MVs and Poly(I:C) is a feasible vaccine strategy against periodontal diseases.
(ii) Novel strategies to yield many E. coli MVs and to engineer chimeric MVs
Glycine-supplemented LB media greatly increased MV production of a probiotic E. coli strain (EcN). Novel glyco-engineering strategy to generate exogenous capsular polysaccharide-tethered EcN-MVs has been also established.
(iii)Enhanced MV release by E. coli expressing a commonly occurring plasmid gene
The kil gene is widely conserved among naturally occurring colicinogenic plasmids and some cloning vectors. Our findings suggest that kil-expressing strain provokes extracellular release of aberrant MVs and enhances hyper biofilm formation.
(iv) Real-time nano-imaging of MV production
A brand-new nano-imaging system captured real-time images of membrane bleb formation and membrane rupture of bacteria following treatment with antimicrobials.