海豚链球菌类M样蛋白基因突变株BY-1ΔsimA的免疫保护作用

Immune protection of Streptococcus iniae M-like protein mutant strain BY-1 ΔsimA

目的探讨海豚链球菌类M样蛋白基因突变株BY-1ΔsimA作为减毒活疫苗保护小鼠免受海豚链球菌感染的能力。方法通过同源重组的方法构建海豚链球菌类M样蛋白基因突变株,利用穿梭载体p VE6007温度敏感、可在链球菌中复制的特征,高效率筛选突变株BY-1ΔsimA。将鉴定正确的BY-1ΔsimA经腹腔注射免疫昆明鼠,21 d后,用3倍半数致死剂量的海豚链球菌BY-1进行攻毒,观察15 d,统计动物死亡数。结果经海豚链球菌突变株BY-1ΔsimA免疫后的昆明鼠感染海豚链球菌BY-1后的死亡率为13.3%,即相对保护率(RPS)为77.8%,与免疫海豚链球菌野生株BY-1全菌灭活疫苗获得的RPS(55.5%)之间差异无统计学意义(P>0.05)。结论海豚链球菌突变株BY-1ΔsimA可有效保护昆明鼠免受海豚链球菌感染,是一种较为理想的减毒活疫苗候选物。

Objective To investigate the immune protection of Streptococcus iniae M-like protein mutant strain BY-1ΔsimA being used as a live attenuated vaccine to protect mice from Streptococcus iniae infection.Methods Allelic exchange mutagenesis was performed to construct Streptococcus iniae M-like protein mutant strain BY-1ΔsimA.Shuttle vector pVE6007,which was sensitive to temperature,was used and could replicate in Streptococcus,to screen mutant strain BY-1ΔsimA in a high efficiency.Kunming mice were immunized by the verified mutant strain BY-1ΔsimA by intra-peritoneal injection,and infected with lethal dose Streptococcus iniae BY-1after21d.The observation lasted for15d,and the accumulated death number was counted.Results Only13.3%mice immunized with Streptococcus iniae mutant strain BY-1ΔsimA were dead,resulting in77.8%relative percentage survival(RPS),which showed no statistical significance for wild type BY-1whole-cell killed vaccine(P>0.05),which had55.5%of RPS.Conclusions Streptococcus iniae mutant strain BY-1ΔsimA could effectively protect mice from Streptococcus iniae infection,which was an ideal live attenuated vaccine candidate.