海豚链球菌simA和pgmA真核表达质粒对尼罗罗非鱼免疫保护的研究

Study on immunoprotection of eukaryotic expression plasmids of Streptococcus iniae simA and pgmA in Oreochromis niloticus

尼罗罗非鱼(Oreochromis niloticus)是世界水产养殖业中的重要经济鱼类,但在养殖生产中易受海豚链球菌(Streptococcus iniae)感染而致病致死,使用疫苗是一种相对理想的防感染措施。该研究采用海豚链球菌simA、pgmA基因构建的真核表达载体作为DNA疫苗,肌肉注射罗非鱼评估疫苗保护效果。免疫后在DNA和RNA水平上,在注射鱼体内检测到2个目的基因。首次免疫后第7至第28天,鳃、肝、肾脏、头肾中疫苗组的白介素1 (Interleukin,IL-1β)与肿瘤坏死因子(Tumor Necrosis Factor,TNF-α)表达量高于PBS对照组;疫苗组的抗体滴度、血清抗菌活性显著(P<0.05)高于PBS对照组。攻毒后,注射pcDNA3.1-pgmA、pcDNA3.1-simA、pcDNA3.1-pgmA与pcDNA3.1-simA等比例混合疫苗的相对保护率(Relative percent survival,RPS)分别为60.7%、49.9%和75.0%。结果表明所制备的疫苗具有免疫保护效果,可作为候选疫苗。

Nile tilapia(Oreochromis niloticus)is an important commercial fish in aquaculture in the world.However,it is easy to be infected by Streptococcus iniae in the breeding production.The use of vaccine is a relatively ideal anti infection measure.In this study,eukaryotic expression vectors(DNA vaccine)were constructed by taking the simA and pgmA genes of S.iniae as the target genes.Then protective efficacy was evaluated by intramuscular injection of tilapia.Two target genes were detected in the injected fish at DNA and RNA levels after immunization.Besides,7−28 d after the first immunization,the expression levels of interleukin-1(IL-1β)and Tumor Necrosis Factor(TNF-α)in the gill,liver,kidney and head kidney of the vaccinal group were higher to some extent than those in the PBS control group.The antibody titer and antibacterial activity of immunized groups were significantly higher than those of control groups(P<0.05).Two weeks after being challenged with S.iniae,the relative percent survival of mixed vaccines of pcDNA3.1-pgmA,pcDNA3.1-simA and pcDNA3.1-pgmA,with pcDNA3.1-simA were 60.7%,49.9%and 75.0%,respectively.It is revealed that the vaccine prepared in this paper has immune protection effect and can be used as a candidate vaccine.