Mice orally vaccinated with Edwardsiella tarda ghosts are significantly protected against infection

Bacterial ghosts may be generated by the controlled expression of the phiX174 lysis gene E in Gram-negative bacteria and they are intriguing vaccine candidates since ghosts retain functional antigenic cellular determinants often lost during traditional inactivation procedures. The Edwardsiella tarda ghost (ETG) vaccine was prepared using this technology and tested in vaccination trials. Control groups included mice immunized with formalin-killed E. tarda (FKC) or mice treated with phosphate-buffered saline (PBS), respectively. The results showed that serum IgA and IgG antibody titers were significantly higher in the ETG-vaccinated group compared to the other groups. In addition, CD8+ T cell counts in peripheral blood were elevated in the ETG groups. Most important, ETG-immunized mice were significantly protected against E. tarda challenge (86.7% survival) compared to 73.3 and 33.3% survival in the FKC-immunized and PBS-treated control, respectively, suggesting that an ETG oral vaccine could confer protection against infection in a mouse model of disease.