Immunogenicity of a plant-derived edible chimeric vaccine candidate against two important enterotoxigenic bacteria in mice model

Diarrheal diseases have been considered as one of the most important world health problems in all ages all around the world. Among all the pathogen agents causes diarrhea two bacterial, Vibrio cholerae and entrohemorrhagic Escherichia coli (EHEC) could be referred. In EHEC group, O157:H7 serotype is the most prevalent cause of diarrhea which causes the disease by producing STX toxin. In Vibrio cholerae, the cholera toxin (CTX) is considered as the main virulence factor that leads cholera disease. Due to non-toxicity and natural immunogenic characteristic of B subunit of both toxins, it could be introduced as an appropriate immunogenic candidate against these virulence factors. Expression and subsequently administration of recombinant immunogenic protein in a specific part of a transgenic plant, such as seed, could act as effective tools for immunogene delivery. In this research, chimeric recombinant gene sc (stx2B and ctxB), was designed and synthesized as an artificial construct based on bioinformatics studies. The synthetic gene (sc) cloned into a plant expression vector adjacent to FAE sequence as canola seeds specific promoter. Transgenic canola plants were produced and the transgenicity were confirmed by PCR. The ELISA assays also demonstrated sufficient amount of SC protein (0.13% TSP). Mice were either immunized rSC protein by 3 ways: 1. Subcutaneously with rSC (expressed in E.coli) 2. Feeding by transgenic seeds, and 3. Combination of feed/injection strategy. The ELISA assay with mice immune sera showed that the rSC protein can effectively delivers the components of the epitopes to the immune system. The orally immunized mice with transgenic seeds show the mucosal immune response. In addition, immunized mice challenge test whit lethal dose of CTX, confirms the protective effect of this chimeric protein. The results show that the rSC protein has suitable capacity to minimize the lethal effect of toxin when administrated orally via transgenic plant material.

Keywords:

Diarrheal diseases , EHEC , Vibrio cholerae , stx2 , ctx , Edible immunogen