重组白细胞介素-4增强日本血吸虫组织蛋白酶B核酸疫苗诱导小鼠的保护力

Boost Effect of Recombinant IL-4 on Protection of Schistosoma japonicum Cathepsin B DNA Vaccine in Mice Against the Parasite

目的探讨重组白细胞介素-4(IL-4)真核表达质粒增强日本血吸虫组织蛋白酶BDNA疫苗对小鼠的免疫保护效果。方法将小鼠IL-4基因克隆至真核表达载体pcDNA3.1以构建小鼠重组IL-4表达质粒,并联合日本血吸虫组织蛋白酶B的表达质粒DNA(VR1012-Sj31)肌注免疫小鼠,设重组IL-4表达质粒、组织蛋白酶B表达质粒和2种空载体质粒对照组。免疫组化检测IL-4和组织蛋白酶B在小鼠肌细胞内的表达,末次免疫3周后攻击感染,用减虫率及减卵率表示保护力。结果重组IL-4和组织蛋白酶BDNA均在小鼠肌细胞表达,重组IL-4和组织蛋白酶BDNA联合免疫小鼠,产生43.2%的减虫率和76.6%的减卵率,与组织蛋白酶BDNA单独免疫相比差异有显著性(P<0.01,P<0.05)。结论重组IL-4能提高日本血吸虫组织蛋白酶B核酸疫苗的抗血吸虫保护力作用,具有佐剂的免疫效应。

Objective To investigate the enhancement effect of IL-4 expression plasmid on cathepsin B DNA vaccine of Schistosoma japonicum (Sj) in mice. Methods The recombinant IL-4 plasmid constructed by cloning PCR amplified product of murine IL-4 gene into eukaryotic expression vector pcDNA3.1 was co-injected intramuscularly with Sj cathepsin B expression plasmid DNA to mice as the test group. The other three groups of mice were set up as control including IL-4 expression plasmid, Sj cathepsin B expression plasmid and two vacant vector plasmids. The expression of IL-4 and cathepsin B was visualized by immunohistochemistry. Challenge infection in mice was carried out 3 weeks after the last vaccination and immune protection was assessed by worm and egg reduction rates. Results The recombinant mIL-4 plasmid and cathepsin B DNA vaccine were expressed in muscular cells of the vaccinated mice. Immunization with cathepsin B DNA plus recombinant mIL-4 plasmid yielded a 43.2 % of worm reduction rate and a 76.6% of egg reduction rate, showing a significant difference(P<0.01, P<0.05) compared with that of cathepsin B DNA vaccine alone. Conclusion As an adjuvant, IL-4 DNA can improve the protective effect of cathepsin B DNA vaccine in mice against S. japonicum infection.