日本血吸虫SjIR3 DNA疫苗诱导的抗攻击感染保护力

DNA Vaccine Encoding SjIR3 Induces Partial Immune Protection against Schistosoma japonicum in Mice

目的探讨日本血吸虫SjIR3核酸疫苗诱导小鼠抗日本血吸虫攻击感染的保护效果。方法用SjIR3的特异引物构建疫苗SjIR3/pC。54只昆明小鼠随机分为3组:A组(对照组)、B组(空质粒组)和C组(实验组)分别肌注生理盐水(100μl)、pcDNA3.0和SjIR3/pC(各50μg),共免疫3次,每次间隔2周。于每次免疫前和感染前尾静脉采血,ELISA检测血清IgG抗体水平。末次免疫后2周,各组剖杀其中6只小鼠取脾细胞,分别用ConA或rSjIR3重组蛋白诱导,用四甲基偶氮唑盐微量酶反应比色法(MTT)检测脾淋巴细胞增殖情况。各组余下小鼠分别经腹部感染日本血吸虫尾蚴40±1条,45d后宰杀,观察实验组小鼠的减虫率和肝减卵率。结果ELISA结果显示,A组与B组IgG抗体水平变化不明显(P>0.05),C组于末次免疫后2周(攻击感染前)IgG抗体水平最高为0.78±0.05,且与A、B两组比较差异有统计学意义(P<0.01);末次免疫后,实验组小鼠脾淋巴细胞分别在ConA或rSjIR3重组蛋白诱导下可增殖,分别为0.57±0.02、0.68±0.01,与A、B组相比差异有统计学意义(P<0.01)。经SjIR3/pC免疫的实验组小鼠攻击感染后可产生29.4%的减虫率和36.6%的肝减卵率。结论SjIR3/pC核酸疫苗具有较好的免疫原性,可诱导小鼠产生部分免疫保护力。

Objective To detect the protection in mice induced by DNA vaccine encoding SjIR3 against Schistosoma joponicum（Sj）. Methods SjIR3 was amplified by PCR with specific primers and linked to T vector. The reconstructed plasmid was digested by Xho Ⅰ and BamH Ⅰ. The target segments were collected and inserted into PeDNA3.0 to construct DNA vaccine SjIR3/pC. Fifty-four female mice were divided into 3 groups： groups A and B received normal saline and pcDNA3.0 respectively as controls, and group C was immunized with SjIR3/pC. All the mice were injected three times with an interval of two weeks. Sera were collected before each inoculation and before challenge infection. Six mice from each group were sacrificed 2 weeks after the final inoculation and spleen cells were collected. Serum IgG was detected by ELISA and the proliferation activity of spleen T lymphocytes induced by ConA or rSjIR3 was detected by MTr assay. The remaining mice were infected by （40±1） Sj cercariae per mouse 2 weeks after the final inoculation. Forty-five days later, mice were sacrificed and perfused, numbers of adult worms and of eggs in liver tissue were counted. Results ELISA showed no significant change of serum IgG level in groups A and B, but considerable increase in group C （0.78±0.05）（P〈0.01）. The proliferation activity of spleen T lymphocytes increased with the induction of ConA or recombinant protein rSjIR3 after the final inoculation. The A570 was 0.57±0.02 and 0.68±0.01 respectively, showing a significant difference in comparison to the groups A and B （P〈0.01）. The worm reduction rate and the egg reduction rate in group C were 29.42% and 36.56% respectively. Conclusion DNA vaccine encoding SjIR3 induces humoral and cell-mediated immune response, and shows partial immune protection against Schistosoma japonicum.