Immunogenicity of inactivated Escherichia coli O157:H7 with Stx2B microparticle in mice

Vaccination using inactivated bacteria is one of the most effective ways to protect against EHEC infection. Escherichia coli 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.

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 E. coli O157:H7.

Immunity and protection against E. coli O157:H7 were achieved by all forms of the vaccine. Inactivated E. coli 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.

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