Vaccination of attenuated EIS-producing Salmonella induces protective immunity against enterohemorrhagic Escherichia coli in mice.

There is an urgent need for vaccine against enterohemorrhagic Escherichia coli (EHEC), which causes a wide range of life-threatening diseases in human and animals. E. coli secreted protein A (EspA), intimin and shiga toxin (Stx) are important pathogenic factors and protective antigens of EHEC. In our previous study, we found that recombinant trivalent protein EIS, which is composed of EspA (E), the 300 amino acids of the carboxyl terminus of intimin (I) and the B subunit of Stx2 (S), was able to efficiently elicit protective immunity against EHEC. The application of live attenuated Salmonella as a carrier for vaccine against mucosal pathogens provided unparalleled merits. Therefore, in this study we constructed live attenuated EIS-producing Salmonella vaccine and tested it as vaccine in mice model. We found that the vaccination of EIS-producing recombinant Salmonella was able to induce significant increases of EspA, intimin and Stx2 specific IgG in serum and secretory IgA in feces. Antigen specific T cell proliferation was also observed in the mice immunized with recombinant EIS-producing Salmonella. In addition, this immunity was able to protect mice from a challenge of a lethal dose of EHEC, even after a period of 70 days. Moreover, the EIS-producing Salmonella induced immunity can be boosted by a single subcutaneous injection of purified EIS protein, even after an interval of 70 days. This EIS-producing Salmonella vaccine provides an alternative approach for the prevention of EHEC infection.