重组恶性疟原虫DNA质粒免疫小鼠及抗原表达的调控

将恶性疟原虫MSP1-31基因序列，引入四环素(Tc)控制的真核表达载体pTRE，获得重组质粒pTRE-31。将MSP1-31的原核表达载体pDS56T1转化大肠杆菌表达MSP1-31，亲和纯化后作检测用抗原。pTRE-31与辅助质粒pTet-off(tTA)肌肉注射4周龄BALB/c小鼠，观察DNA介导免疫情况。结果显示，四环素饲喂的小鼠4周时血清抗体阳转率为7.1%(1/14)，而不饲喂四环素组可达100%(14/14)，表明用pTRE-31/pTet-off重组质粒组合直接注射小鼠有效地引发了针对疟原虫MSP1-31抗原的体液免疫反应，且可受控于四环素。不饲喂四环素组小鼠在12周后仍能维持抗体阳性，倍比稀释ELISA显示血清抗体滴度在4周、8周和12周内持续上升。饲喂四环素组小鼠4周后停止饲喂Tc，第8周和第12周检测仍有部分(60%)小鼠血清抗体阳转，而继续饲喂Tc的小鼠未有抗体阳转，暗示重组质粒DNA在小鼠体内可持续存在至少4周并仍具备表达功能。

Immunization of Mice with Piasmid DNA Against Malaria and Regulation of Antigen Expression by Tetracycline-controlled Promoter

Sequence of MSP1 31 of Plasmodium falciparum was constructed into eukaryotic expression vector pTRE,which could be repressed by tetracycline (Tc) and resulted in recombinant plasmid pTRE 31.The plasmid was injected into the quadriceps muscle of BALB/c mice with Tc responsive plasmid pTet off to measure specific antibodies.The MSP1 31 prokaryotic expressed protein was used as antigen in ELISA.Result showed that mice orally administered by Tc had a seroconversion rate of 7 1% (1/14) 4 weeks after injection,whereas the contral mice had a seroconversion rate of 100% and the titers of antibody were raised continusly within 12 weeks.The study suggested that the recombinant plasmids pTRE 31/pTet off could efficiently induce humoral response against MSP1 31 of malaria.Moreover this immune response was controlled by Tc and was revesible after withdrawal of Tc dilivery.The induction of antibody by removing Tc at the fourth week after injection indicated that DNA vaccine could remain in mice and capable of expressing antigen for at least 4 weeks.