Evaluation of immune protection effect of a vaccine constructed using yeast display against infectious pancreatic necrosis
DONG Ying 1,2,3, HE Wenbin2, ZHAO Jingzhuang2, REN Guangming2, LU Tongyan2, SHAO Yizhi2, XU Liming2,4*
1.National Demonstration Centre for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China； 2.Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin 150070,China； 3.National Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, Shanghai 201306, China； 4.Key Laboratory of Aquatic Animal Diseases and Immune Technology of Heilongjiang Province, Harbin 150070, China
Abstract: Juvenile rainbow trout Oncorhynchusmykiss with body weight of (5±1)g were orally immunized by a previous vaccine (EBY100/pYD1-VP2) constructed by displaying VP2 protein of infectious pancreatic necrosis virus (IPNV) on yeast surface, and the optimal induction time of 60 h for the vaccine strain was determined by cell immunofluorescence assay and flow cytometry for preparation of a large amount of yeast oral vaccine to evaluate the immunoprotective efficacy of rainbow trout immunized with single or multiple oral irrigations. Single immunization was continuous immunization for 7 days, and the multiple immunization was repeated for 7 days with the same dose after 1 week of single immunization, with daily immunization dose of 100 μL of yeast(1×1010 CFU/mL). Meanwhile, the yeast carrying empty plasmid immunization group and PBS mock- immunization group were set, and the protective efficacies of this oral vaccine was analyzed by immunity-related genes quantification, neutralization antibody titration and quantitative analysis of IPNV load at different times post vaccination. There were significantly higher expression levels of IgT, IgM, CD4 and CD8 genes in the head kidney and hindgut of rainbow trout in the vaccine immunized group than those in the empty yeast immunized group(P<0.05). The expression levels of immune-related genes in the multiple immunization group were found to be significantly higher compared with the single immunization group. Neutralizing antibodies were found in the serum of rainbow trout in the vaccine immunized group, higher neutralizing antibody titer in the multiple immunized group than that in the single immunized group at each time, with the maximal neutralizing antibody titer of 39.28 on the 49 days after immunization. The viral loads analysis revealed that the expression levels of VP1 and VP2 genes in the vaccine immunization group were significantly lower than those in the empty vector yeast immunization group at each time(P<0.05) and the expression levels of VP1 and VP2 genes in the single vaccine immunized group were 2.25, 3.33 times(VP1) and 2.67, 2.80 times(VP2) of that in the multiple vaccine immunized group, respectively. The findings indicated that the oral vaccine induced rainbow trout to produce non-specific and specific immune response, and that had significant immunoprotective effects on rainbow trout, which provided the foundation with the development of a new oral live vector vaccine against IPNV.
2020, Vol. 35 
