日本血吸虫雌虫抗原模拟表位的筛选及免疫保护性

SCREENING OF EPITOPES MIMICKING FEMALE SCHISTOSOMA JAPONICUM ANTIGEN AND THEIR PROTECTIVE IMMUNITY

目的 筛选日本血吸虫雌虫抗原的模拟表位 ,并探讨其抗日本血吸虫的免疫保护效果。 方法 用日本血吸虫雌虫免疫兔血清IgG作配体对噬菌体随机 12肽库进行 3轮亲和筛选 ,随机挑取 18个噬菌体克隆用Dot ELISA检测其特异性 ,并对其中的 4个阳性克隆进行测序。分别在 0、2、4周用混合噬菌体克隆免疫小鼠 3次 ,第 6周每鼠经腹部感染 40条日本血吸虫尾蚴 ,42d后剖杀冲虫 ,计数虫数和每克肝卵数。 结果 经 3轮筛选 ,特异性噬菌体富集了 2 0 0多倍 ,随机挑取的 18个克隆经Dot ELISA鉴定有 17个能与雌虫抗原免疫兔血清呈阳性反应。DNA自动测序的 4个序列与GenBank的已知序列均无同源性。与对照组相比 ,混合噬菌体克隆免疫小鼠的减虫率为 2 6.5 7% ,减卵率为 65 .3 4%。 结论 采用噬菌体随机肽库技术可获得模拟日本血吸虫雌虫特异性抗原表位的短肽分子 ,这些短肽分子能诱导一定程度的保护性免疫。

Objective To obtain peptide mimicking epitopes of female Schistosoma japonicum (Sj) worm through screening of a phage peptide library and to explore their immune protection against Sj in mice. Methods A 12-mers random peptide library was immunoscreened with purified IgG from rabbits' sera immunized with soluble female Sj antigen. After three rounds of biopanning,the pooled phages were used to immunize mice for three times at week 0,2,4. Two weeks after last immunization each mouse was challenged by 40 cercaria, then all mice were perfused after 42 days and the worms and eggs were counted. 18 randomly picked clones were detected by Dot-ELISA,of which 4 positive clones were sequenced. Results The specific phages binding to IgG were enriched 200 folds after three rounds of biopanning. 17 of the 18 randomly picked clones were shown to be antigenic and the 4 sequences of the positive clones showed no homology with other sequences in the GenBank. Compared with control group,a significant reduction in adult worms (26.57%) and a high egg reduction (65.34%) were achieved following immunization. Conclusion The specific peptides simulating antigenic epitopes of female Sj can be obtained by immunoscreening phage random peptide library and a protective immunity against Sj can be induced by these epitopes in mice.