海豚链球菌灭活疫苗对罗非鱼免疫效果的研究

用野外分离的海豚链球菌(Streptococcus iniae)海水菌株HD-1和淡水菌株TBY-1制备成含1×1010cfu/mL的灭活疫苗,以0.1 mL/尾的剂量对尼罗罗非鱼(Oreochromis niloticus)进行腹腔注射,免疫2次,测定免疫后1周、3周和5周免疫鱼血清中抗海豚链球菌的抗体滴度和相应菌株攻毒后的相对保护率,以评价海豚链球菌灭活疫苗对罗非鱼的免疫保护性.结果显示免疫鱼血清中抗体凝集效价在免疫后第3周和第5周呈显著性升高,且两种疫苗免疫血清存在明显的交叉凝集反应,说明HD-1和TBY-1抗原具有交叉免疫原性.在免疫后第4周,利用8倍半数致死量浓度(LD50)的海豚链球菌强毒菌株进行攻毒试验,结果显示:HD-1和TBY-1免疫组的死亡率分别为5%和0%,相对保护率分别为93.8%和100%;未经免疫的阴性对照组的死亡率分别为77.5%和62.5%.

Studies on Immune Protective Effect of Streptococcus iniae Inactivated Vaccine in Tilapia (Oreochromis niloticus)

In this study,80 nile tilapias(Oreochromis niloticus) were immunized intraperitoneally twice with an inactivated vaccine prepared with Streptococcus iniae HD-1 strain and TBY-1 strain isolated from seawater and freshwater fish respectively.Agglulation titer of serum antibody sampled from immunized fish at 1st week,3rd and 5th post-immunization and immune protection of immunized fish were detected.The result showed that the serum antibody titers were significantly increased at third,fifth week and obviously cross agglutination reaction between two different vaccine were observed,which indicated that antigenic determinant of HD-1 and TBY-1 is partially alike.At the fourth week,all fish challenged with virulent S.iniae at eight times medial lethal dose to detect the protective effect of the vaccine.The result showed that mortality of HD-1 control group,TBY-1 control group,HD-1 immunized group and TBY-1 immunized group were77.5%,62.5%,6.2% and 0% respectively.In conclusion,S.iniae inactivated vaccine can effectively prevent streptococcicosis of fish.