Study on the immunogencity of poly(D,L-lactide-co-glycolide) (PLGA) microspheres-encapsulated vaccine preparation against Stenotrophomonas maltophilia infection in channel catfish (Ictalurus punctatus)

The purpose of the experiment is to study the poly(D, L-lactide-co-glycolide) (PLGA) microspheres of coated in fish vaccine formulations. In this study, we prepared Pseudomonas bacteria widowed raise PLGA microspheres vaccine by double emulsion evaporation maltophilia. It was prepared to support the completion of the Stenotrophomonas maltophilia oligonucleotide PLGA microspheres vaccine through injection as well as oral and immersion in three ways inoculated based on body weight (100 plus or minus 5 g) of channel catfish, each has five immunization groups, of which three group were different doses of the immune group, the other two groups were not coated with S. maltophilia raising vaccination with inactivated Aeromonas group and the control group. During the 0, 28 and 56th day, the immunization group were processed in same way. Collection of blood and measuring of immune-related indicators at 0, 7th, 21st, 35 super(th) and 49 super(th) day were carried out. At the 63th day, 0.2 ml of each fish at the concentration of 1 x 10 super(9) cfu/ml of Stenotrophomonas widow raising a single cell suspension of viable bacteria was injected into the Channel catfish. Continuous observation and recording of the results of each group shows that the experimental vaccine preparation of PLGA microspheres encapsulation efficiency was 88.93%, the immunization route vaccine group versus those in saline control group significantly enhance the phagocytic activity of white blood cells, serum lysozyme, complement C3, serum protein content and antibody IgM levels. Channel catfish immunized by injection were challenged with live S. maltophilia, the relative survival rates of group 3 was 9.16% higher than group 5; however group 1 was 15% lower than group 5, group 2 was 1.67%. Another five groups immunized by oral vaccination were challenged with S. maltophilia, the relative survival rates of group 1 to group 3 were 43.33, 65 and 75%, but group 5 was only 6.68%. Conclusively, injection and oral vaccination of Stenotrophomonas widow raising Aeromonas vaccine PLGA microspheres in Channel catfish has a good immune protective effect, while the immersion of the protective effect of various immunization groups was not obvious.