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目的探讨用聚乳酸-羟基乙酸[poly(D,L-lactic-co-glycolic)acid,PLGA]包裹无乳链球菌制备的口服疫苗对罗非鱼的免疫保护效果。方法复乳溶剂挥发法制备包裹无乳链球菌全菌和破碎后上清的PLGA微球,通过口服给予方式免疫尼罗罗非鱼,以注射灭活全菌疫苗为阳性对照,免疫后第7、14、21、28天测定受免鱼血清的白细胞吞噬百分比与吞噬指数、血清中的溶菌酶与超氧化物歧化酶活性以及抗体水平。人工攻毒实验比较罗非鱼无乳链球菌PLGA微球的免疫保护作用。结果实验组鱼的白细胞吞噬百分比、吞噬指数、溶菌酶和超氧化物歧化酶均显著高于阴性对照组,低于阳性对照组;抗体水平也有类似结果,但第14天后阳性对照组鱼的抗体水平开始下降,而实验组鱼则仍维持在较高水平。攻毒实验显示全菌和破碎后的上清微球疫苗相对免疫保护率(RPS)分别为57.63%和34.40%,阳性对照组为94.53%。结论本研究制备的罗非鱼无乳链球菌PLGA微球口服疫苗能够增强罗非鱼对无乳链球菌的免疫反应,并可通过缓释作用使机体维持较高的抗体水平,可为罗非鱼提供一定的免疫保护,但其RPS低于全菌灭活注射疫苗。
OBJECTIVE: To investigate the immunoprotective effect of oral vaccine with Streptococcus agalactiae (poly (D, L-lactic-co-glycolic) acid, PLGA] on tilapia. Methods The PLGA microspheres encapsulating the whole bacteria and the supernatant of Streptococcus agalactiae were prepared by the double emulsion method and the whole cell vaccine was inoculated into the Nile tilapia by oral administration. After immunization, 14, 21, and 28 days. The percentage of leukocyte phagocytosis and phagocytosis index, the activity of lysozyme and superoxide dismutase in serum and the level of antibody were determined. Artificial challenge experiment comparing the immunoprotection effect of Streptococcus agalactiae PLGA microspheres from tilapia. Results The leucocyte phagocytic percentage, phagocytic index, lysozyme and superoxide dismutase of experimental group were significantly higher than those of negative control group and lower than that of positive control group. The antibody level also had similar results, but the antibody of positive control group after 14 days The level began to decline, while the experimental group of fish remained at a high level. Toxicity tests showed that the relative immunoprotection rates (RPS) of the whole bacteria and the supernatant microspheres vaccine after disruption were 57.63% and 34.40% respectively, and the positive control group was 94.53%. Conclusion The Tilapia S. agalactiae PLGA microspheres oral vaccine prepared in this study can enhance the immune response of tilapia to Streptococcus agalactiae and maintain the high antibody level through sustained release, Fish provide some immunity protection, but their RPS is lower than the whole-body inactivated vaccine.