重组弓形虫棒状体蛋白5诱导小鼠的免疫应答及其抗弓形虫感染的保护作用

为探讨重组弓形虫棒状体蛋白5诱导的免疫应答及其免疫保护效应，本研究克隆表达了弓形虫棒状体蛋白5，并分析其诱导的细胞免疫、体液免疫应答和抗弓形虫感染的保护作用。采用PCR方法从刚地弓形虫cDNA中扩增出ROP5基因片段，将该基因片段克隆至pET-28a原核表达载体表达，用重组ROP5蛋白免疫BALB／c小鼠，ELISA检测免疫后小鼠抗体和细胞因子的变化。以强毒型RH株弓形虫攻击感染免疫小鼠，统计小鼠不同时间存活率，评价重组蛋白产生的免疫保护性。结果表明ROP5重组蛋白疫苗免疫BALB／c小鼠诱导机体产生高水平的IgG、IgG1、IgG2a抗体和IFN—y、IL-2及IL-10细胞因子。与PBS及佐剂对照组相比，重组蛋白免疫组小鼠的存活时间明显延长。本实验证实了ROP5重组蛋白免疫BALB／c小鼠能够诱导其产生高水平的体液免疫和细胞免疫应答，以及一定的抗弓形虫感染保护作用。

STUDIES ON THE PROTECTIVE IMMUNITY RESPONSES INDUCED BY THE RECOMBINANT ROP5 PROTEIN OF TOXOPLASMA GONDII IN MICE

To observe the effect of recombinant Toxoplasma gondii ROP5 （Tg-ROP5） protein on BALB/c mice, the ROP5 cDNA of T. gondii was cloned and expressed in E. coli, and its protective immunity was detected. The ROP5 cDNA was amplified from T. gondii cDNA by PCR, then the cDNA fragment was cloned into the expression vector pET-28a, expressed in BL21 （DE3） E. coli and purified with Ni-NTA column. The immune response of host to the recombinant antigen was investigated by detection of cytokines and specific antibodies. Then, mice were challenged with highly virulent tachyzoites of RH strain, and their survival was monitored daily. BALB/c mice subcutaneously immunized with rROP5 induced specific high titer of IgG, IgG1, IgG2a antibodies as well as IFN--y, IL-2 and IL-10 cytokines in mice. Moreover, the survival time of immunized mice against a lethal challenge was prolonged significantly compared to that of the control groups. This experiment confirmed that immunization with rROP5 can elicit both humoral and cellular immune responses, and prolong the survival time of the mice challenged with virulent RH strain of T. gondii.