Guan, L., Mu, W., Champeimont, J., Wang, Q., Wu, H., Xiao, J., Lubitz, W., Zhang, Y., and Liu, Q. (2011) Iron-regulated lysis of recombinant Escherichia coli in host to release protective antigen and confer biological containment. Infection and Immunity. 79(7):2608-18.
Recombinant bacterial vector vaccine is an attractive vaccinationstrategy to induce immune response to a carried protective antigen.The superiorities of live bacterial vectors include mimicryof a natural infection, intrinsic adjuvant properties and thepotential for administration by mucosal routes. Escherichiacoli is a simple and efficient vector system for productionof exogenous proteins. In addition, many strains are nonpathogenicand avirulent making it a good candidate for use in recombinantvaccine design. In this study, we screened 23 different iron-regulatedpromoters in E. coli BL21(DE3) vector and found one, PviuB,with characteristics suitable for our use. We fused PviuB withlysis gene E, establishing an in vivo inducible lysis circuit.The resulting in vivo lysis circuit was introduced into a strainalso carrying an IPTG-inducible PT7-controlled protein synthesiscircuit, forming a novel E. coli-based protein delivery system.The recombinant E. coli produced a large amount of antigen invitro, and could deliver the antigen into zebrafish after vaccinationvia injection. The strain subsequently lysed in response tothe iron-limiting signal in vivo, implementing antigen releaseand biological containment. The gapA gene, encoding the protectiveantigen GAPDH from the fish pathogen Aeromonas hydrophila LSA34,was introduced into the E. coli-based protein delivery system,and the resultant recombinant vector vaccine was evaluated inturbot (Scophtalmus maximus). Over 80% of the vaccinated fishsurvived challenge with A. hydrophila LSA34, suggesting thatthe E. coli-based antigen delivery system had great potentialin bacterial vector vaccine application.