Generation And Immunogenicity Of Swine Salmonella Ghost Vaccine

Salmonella is one of the important zoonotic pathogen, which has serious threat to the breeding of livestock and health of young animals. it can cause Septicemia, Enteritis and abortion. Salmonella are important pathogens in pig industry and animal food health.Bacterial ghosts(BGs) are dead and empty bacterial cell that lack cytoplasm and nucleic acid, which is formed by physiological and biochemical methods, their cell contents were lost, so it is safe, easy preparation and convenient storage, Bacterial ghosts can be used to prepare a polyvalent vaccine. By contrast, Bacterial ghosts are better than the formalin-killed vaccines, without modifying any immunogenicity, it also has the ability to load a foreign antigen, DNA vaccines, drugs and other substances, Therefore, Bacterial ghosts are an optimize candidate inactivated vaccine.The biochemical tests, PCR and 16 SrDNA methods for identification of Salmonella, By the median lethal dose in mice and susceptibility testing, we selected non ampicillin-resistant and virulent Salmonella, which provided the foundation for subsequent experiments.In this study, a broad-host expression plasmid PBVE220, with temperature sensitive functions, was constructed and then transformed into Salmonella. It is successful to screen and get plasmid-type Salmonella ghost vaccine strain. This study analysised Salmonella ghost by bacteriolytic dynamics test. By optimizing inductive conditions, plasmid-type Salmonella ghost vaccine strain was incubated at 28℃ to an OD600 of 0.4, the temperature was subsequently raised to 42 ℃until 6 hours later to prepared BGs with lysis rate of 99.46%, which counted approximately 7.3×107/mL, Electron microscopic observation Salmonella ghosts showed that their cell contents were lost through the lysis channel and their cell envelopes retained the complete surface structure.At last, this experiment evaluated safety and immungenicity of plasmid-type Salmonella ghost vaccine strain, Salmonella inactivated vaccine, and Salmonella inactivated vaccine with adjuvant respectively. The results of IgG serum on immunized mice showed that the IgG serum of Salmonella ghosts was higher than other groups. Salmonella ghosts could effectively generate specific humoral immunity. Lymphocyte subsets analysis indicated that the plasmid-type Salmonella ghost vaccine strain group could induce Th1-type cellular immune response, and cytokines detection experiments in vitro showed that BG groups significantly secreted higher levels of IFN-γ and IL-12 than the control group did. However, the level of IL-4 secretion compared with the control group had no significant difference. Salmonella ghost group could induce Th1-type protective immune response. The results of protective immunity showed that Salmonella ghost group provide the protection rate of 70%, the pathological changes of Salmonella ghost group are lighter than other groups in mice.In summary, plasmid-type Salmonella ghost vaccine strain had good safety and immunogenicity, which provide useful evidence and had promising prospects.