Effect of alginate/chitosan nanoencapsulation on immunogenicity and efficacy of Streptococosis/lactococosis vaccine in rainbow trout (Oncorhynchus mykiss)

In this study, the effect of injection of streptococcus / lactococcosis vaccine with alginate / chitosan microparticles on immunogenicity in rainbow trout was investigated. For this purpose, first S. iniae and L. garviae were cultured in TSB medium and inactivated with formalin, then the inactivated bacteria were finely coated with alginate / chitosan particles. 600 pieces of rainbow trout (14 ± 2.1 g) divided to four Treatments: Each treatment was divided into three replications as follows: the first treatment with encapsulated vaccine, the second treatment with uncoated vaccine and the third treatment with alginate / chitosan without bacteria, and the fourth treatment was injected with sterile PBS as control. The fish were fed and maintained for two months and on days 0, 20, 40 and 60, serum samples were prepared from the fish and immunity indicators included: serum antibody titer, complement activity, bactericidal, lysozyme activity, Leukocyte phagocytosis, serum protein and immunoglobulin levels, and expression levels of IL-6 and IgM in anterior kidney were evaluated. Treatments with both bacteria were challenged separately and mortality was compared between treatments. The results showed that the immunity indices in fish vaccinated with encapsulated vaccine improved compared to other treatments. Also, the expression of IL-6 and IgM genes and survival after bacterial challenge were significantly higher in encapsulated treatment than other treatments. Therefore, the vaccine microencapsulated method with chitosan and alginate microparticles is effective and can be used to improve the efficiency of streptococcus / lactococcosis vaccine in rainbow trout.