Evaluation of Immunogenicity of Chitosan Nanoparticles Containing STxB and STxB-IpaD Antigens of Shigella Dysenteriae Type 1 in Mice

Background The intestinal infection caused by Shigella and Escherichia coli is known as a bioterrorist agent. IpaD and STx proteins play an important role in the invasion and angiogenesis by Shigella. Therefore, IpaD with STxB can be appropriate candidates for a safety vaccine. In this study the immunogenicity of STxB and combined STxB-IpaD nanocapsule recombinant proteins has been examined in the form of oral and injection in mice.
Methods & Materials In this experimental study, pET28a() vectors containing stxB and stxB-ipaD genes were transformed into E. coli BL21 DE3 bacteria. These bacteria were grown on antibiotic medium and were confirmed by direct PCR, and protein expression and SDS-PAGE gel. Recombinant proteins purified by nickel column and SDS-PAGE gel and were confirmed by immunoblotting. STxB and STxB-IpaD recombinant proteins become nanoparticles by inotropic gelation method with chitosan polymer and its picture was taken by Scanning Electronic Microscope (SEM). STxB and STxB-IpaD nanocapsule antigens prescript in the form of oral and injection four time to mice and their antibodies titer and immunogenicity were monitored.
Results By performing ELISA test, IgG antibody titer was detected by injection method but not in oral method, maybe due to loss of nanoparticle structure and antigens in acidic environment and trypsin enzyme of stomach. Immunized mice’s with STxB and STxB-IpaD recombinant proteins with inotropic gel method were able to tolerance order up to 7 and 10 times the E. coli O157: H7 Shiga toxin LD50.
Conclusion STxB and STxB-IpaD protein nanoparticles can be used as safety injection adjuvant for immunogenesis against the E. coli O157: H7 Shiga toxin.