表达弓形虫棒状体蛋白1的重组乳酸乳球菌诱导小鼠免疫应答的研究

Immune response after oral immunization with recombinant Lactococcus lactis expressing ROP1 of Toxoplasma gondii in mice

目的用表达弓形虫棒状体蛋白1(ROP1)的乳酸乳球菌口服免疫小鼠,观察其所诱导的体液免疫、黏膜体液免疫和保护力。方法69只BALB/c小鼠随机分成疫苗免疫组、乳球菌对照组和生理盐水组,每次分别饲喂5×109个/鼠悬浮在缓冲液中的重组乳酸乳球菌、不含重组质粒的乳酸乳球菌及等体积的生理盐水。第27、34、48天分别从鼠尾静脉采血,分离血清,酶联免疫吸附试验(ELISA)检测IgG水平;第48天杀死3只小鼠,分离小肠黏液检测SIgA水平;第48天用弓形虫灌胃感染小鼠,观察小鼠发病情况,计算小鼠死亡率,30 d后统计小鼠肝、脑组织中的虫体数量。结果疫苗免疫组小鼠IgG水平与乳球菌对照组、生理盐水组比较,差异均有统计学意义(P均<0.01)。疫苗免疫组小鼠SIgA水平与乳球菌对照组、生理盐水组比较,差异均有统计学意义(P均<0.01)。疫苗免疫组小鼠肝、脑组织中虫体数与乳球菌对照组、生理盐水组比较,差异均无统计学意义(P均>0.05)。结论表达弓形虫ROP1蛋白的乳酸乳球菌可诱导小鼠体液免疫和黏膜体液免疫,但对弓形虫感染无保护力。

Objective To study the protective effects against Toxoplasma gondii after oral immunization with recombinant Lactococcus lactis expressing ROP1 in mice. Methods Sixty-nine BALB/c mice aged 6 -8 weeks old were randomly divided into three groups ： a vaccinated group, L. lactis control group, and normal saline control group. They were given 5 × 10^9 recombinant L. lactis cells （vaccinated group）, L. lactis cells （L. lactis control group） and normal saline （normal saline control group）, respectively. The serum samples of the immunized mice （3 mice） were collected on day 27, 34 and 48, respectively. The mucosal secretions in the lumen of the intestine of immunized mice were collected on day 48. IgG and SIgA were measured with ELISA. The mice were infected with T. gondii on day 48 and sacrificed 30 days after the infection, and the tachyzoites in the livers and brains were counted. Results Compared with the two control groups, the levels of IgG in the serum and SIgA in the mucosal secretions of the immunized mice were significantly increased. The survival proportion and tachyzoite burdens of the immunized mice were the same as those in the control groups. Conclusions Oral immunization with recombinant L. lactis expressing ROP1 can significantly induce the humoral immunity and mucosal immune responses, but can not increase the protective efficacy against T. gondii.