Immunogenicity of inactivated O157:H7 with Stx2B microparticle in mice.

Objectives: Vaccination using inactivated bacteria is one of the most effective ways to protect against EHEC infection. O157:H7 infections are mainly influenced by Shiga toxins (Stx) and attaching/effacing factors. Among various factors, Stx2B is gaining much attention as a vaccine candidate. Formulating an inactivated bacteria with a suitable adjuvant increases vaccine efficacy and antibody production and can lead to a lasting immune response and protection against O157:H7.

Materials And Methods: To assess vaccine efficacy, in this study, we have considered heat and formalin-inactivated bacteria along with chitosan-coated Stx2B/ Stx2B in a mouse model. Ionotropic gelation via tripolyphosphate anions was used to coat Stx2B on chitosan. Subcutaneous injection or oral gavage was used to immunize mice, which were then challenged with O157:H7.

Results: Immunity and protection against O157:H7 were achieved by all forms of the vaccine. Inactivated O157:H7 formulated with chitosan-coated Stx2B effectively evoked humoral and mucosal immune responses. However, minimum shedding appeared with the mice groups orally immunized with formalin-inactivated bacteria sublimated with chitosan-coated Stx2B and heat-inactivated bacteria plus Stx2B in subcutaneous immunization.

Conclusion: Administration of inactivated whole-cell and toxin was synergistic and increased the protection capacity with both parenteral and oral immunization routes.