The immune response and protective efficacy of vaccination with oral microparticle Aeromonas sobria vaccine in mice

The effect of an oral alginate microparticle Aeromonas sobria vaccine on immune response and protection of mice was investigated. The formalin-killed cultures (FKC) of A. sobria strain Z-1 treated with three methods were incorporated into alginate microparticles, and the encapsulated vaccines were orally used for immunizing mice. Four weeks after immunization, the serum agglutinating antibody titers, bactericidal activity of leucocytes and relative percent survival (RPS) of mice immunized orally with three microparticle vaccines were significantly higher than those of control mice. Among the immune efficacy of 3 microparticle vaccines, vaccine prepared directly from FKC (MVC) was the most, vaccine from FKC treated with freeze–melt method (MVCF) secondly, and vaccine from FKC treated with ultrasonic wave (MVCU) the worst. The serum agglutinating antibody titers and phagocytic activity of the blood monocytes in mice immunized orally with MVC reached a level equivalent to those of injection with FKC, and were significantly higher than those of control group. Moreover, from the 7th to 12th weeks, the serum agglutinating antibody titers in the MVC-immunized mice was significantly higher than those of injection with FKC. The RPS of mice immunized orally with MVC was 87.5%, while 100% of mice immunized orally with FKC and also the control mice died. These results demonstrated that oral alginate microparticle of A. sobria strain Z-1 was immunogenic and conferred protective immunity in mice, and could be used as a candidate vector system of oral vaccine of Aeromonas.