罗非鱼源无乳链球菌灭活疫苗免疫效果的研究

Immunoprotection of the inactivated vaccine against Streptococcus agalactiae infection in tilapia

将罗非鱼源无乳链球菌GD201008-001连续传50代,用API20 Strep生化鉴定试剂条和全自动生化分析仪对其各代次进行比较鉴定;将灭活疫苗以5×10~8CF U/尾分别肌肉注射和腹腔注射30 g±5 g的罗非鱼,第3次免疫后第14天,以50倍LD_(50)对其攻毒,记录死亡情况;在免疫后不同时间里用试剂盒检测罗非鱼肝的各个酶活指标,用RT-PCR检测头肾中IL-1β的表达量,分析其免疫保护效果。结果显示,GD201008-001各代次间生化特性稳定;肌肉注射免疫组和腹腔注射免疫组的免疫保护率分别为83.97%和93.33%,免疫前后多数酶活指标并没有显著差异(P>0.05),第3次免疫后第14天IL-1β的表达量均显著高于第1次免疫后第14天的数值,且肌肉注射方式显著高于腹腔注射(P<0.05),肌肉注射组超氧化物歧化酶活力、溶菌酶活力、总抗氧化能力、过氧化氢酶活力均略低于腹腔注射组,而丙二醛及IL-1β表达量则相反。结果表明,该无乳链球菌灭活疫苗对罗非鱼具有很好的免疫保护性,可以作为预防无乳链球菌感染的候选疫苗。

After the Streptococcus agalactiae GD201008-001 isolated from tilapia was continually passaged by 50 generations,the biochemical characteristics of every passage were compared by API 20 Strep and automatic biochemistry analyzer. 30 ±5 g tilapias were immunized by intramuscular （IM） injection and intraperitoneal（IP） injection with 5 × 10^8CFU of inactivated vaccine per fish.Fifty LD50 challenged the tilapias on day 14 after three immunizations and the death of tilapia was recorded. The immunological protective efficacy in tilapia was analyzed by detecting some enzyme indexes of livers with kits and the expression of IL-1β in head kidney with RT-PCR at different time points during the immune phase. In results, the biochemical characteristics were stable among different generations. The relative percent survival rates for these groups were 83.97% and 93.33% after infection,res- pectivelzThere was no significant difference among the most enzyme indexes with different injec- tions before and after immunization（P〉0. 05）. The IL-1β expressed significantly higher at 14 days after the 3rd immunization than the ist immunization（P^O. 05） and the expression of the IL-1β was signi ficant higer by IM injection than IP injection at 14 days after the 3rd immunization（P〈O. 05）. The activities of superoxide dismutase,lysozyme,catalase,total antioxidant capacity immunized by IM injection showed slightly lower than that by IP injection,which was contrary to the MDA and the expression of IL-1β.In conclusion,the inactivated vaccine was effective in protecting tilapia against S.agalactiae, so that it could be used as a vaccine candidate against S. agalactiae.