摘要目的 构建一种可表达特异性10-23脱氧核酶(deoxyribozyme,DZ)的巨噬细胞靶向性细菌载体疫苗,并鉴定其在巨噬细胞表达10-23DZ的能力以及抑制靶基因表达的效果.方法 采用亚克隆方法将分枝杆菌复制子oriM克隆入10-23DRz真核表达载体pSDE01中,获取可在分枝杆菌和真核细胞中穿梭的重组质粒pSDE02.在前期研究基础上选择一有效的针对巨噬细胞taco基因的10-23DZ--DZ1,根据DZ1序列设计并制备DZ1的双链表达序列,插入pSDE02中获取重组质粒pDZM01.将pDZM01经电穿孔方法转化入耻垢分枝杆菌Ms1-2c株构建重组耻垢分枝杆菌rMS-DZ1.分别采用Ziehl-Heelson染色法和直接荧光观测法鉴定重组耻垢分枝杆菌的巨噬细胞靶向性.用rMS-DZ1感染巨噬细胞株RAW264.7,分别于感染后的24 h和48 h采用斑点杂交方法检测rMS-DZ1在巨噬细胞中表达DZ1的情况,再分别采取RT-PCR和免疫印迹方法检测巨噬细胞TACO表达的差异.结果 限制性内切酶酶切、菌落PCR及测序结果显示pSDE02、pDZM01和rMS-DZ1构建成功.rMS-DZ1感染RAW264.7细胞后24 h和48 h,经点杂交方法均检测到了DZ1的表达.半定量RT-PCR和免疫印迹检测结果显示,与未感染组比较,rMS-DZ1感染后24 h和48 h时巨噬细胞TACOmRNA分别下降了67.90%和57.14%,TACO蛋白水平分别下降了53.85%和68.92%.同时,表达对照寡脱氧核糖核苷酸DZ1U的重组耻垢分枝杆菌rMS-DZ1U感染RAW264.7细胞后,其TACOmRNA和TACO蛋白水平与未感染组比较均无明显差异.结论 本研究成功构建了一种可表达特异性10-23DZ的巨噬细胞靶向性重组耻垢分枝杆菌的载体,可在巨噬细胞内表达并抑制相应靶基因的表达,可作为研制治疗用疫苗的基础,这也是国内外首次报道可表达10-23DZ的细菌性载体.

abstractsObjective To construct a recombinant bacterial vaccine which can express specific 10-23 deoxyribozyme(DZ) in macrophage, identify the intracellular production of specific 10-23DZ and detect the activity of this recombinant bacterial vaccine on inhibiting the expression of TACO gene in macrophage.Methods The pSDE02 was obtained by inserting the replicon of Mycobacterium into pSDE01, a plasmid which can express 10-23DZ in eukaryotic cells. The expression sequence of DZ1, a 10-23DZ targeting the TACO mRNA of macrophage designed in our previous study was synthesized and inserted into pSDE02. The resulted plasmid was named pDZM01. pDZM01 was then transferred into Mycobacterium smegmatis by electroperation. The recombinant M. smegmatis, named rMs-DZ1 was screened on low-salt LB medium containing Zeocin and identified by Colony PCR. The targeted delivery property of recombinant M. smegmatis was observed by Ziehl-Heelson stain and GFP expression observation via fluorescence microscope. rMs-DZ1 was used to infect RAW264.7 cells and the expression of DZ1 in macrophage was identified by dot-blot assay. At 24 h and 48 h after infection, total RNA and proteins were extracted and the TACO mRNA and protein expression level was assayed by RT-PCR and western-blot respectively. Results Restrictive analysis and sequencing data showed that the Mycobacterium-eukaryotic cell shuttle plasmid pSDE02 and pDZM01 was successfully constructed. rMs-DZ1 was confirmed by colony PCR. When engulfed by macrophage, rMs-DZ1 would express DZ1 in RAW264.7 cells and inhibit the expression of taco gene. When compared to uninfected macrophage, rMs-DZ1 significantly reduced the taco mRNA by 67.90% and 57.14% and down-regulated the expression of TACO protein by 53.85% and 68.92% at 24 h and 48 h respectively. Conclusion A recombinant M. smegmatis vaccine was successfully constructed which could generate specific 10-23DZ in macrophage and inhibit the expression of target gene of interest. To our knowledge, this is the first bacterial vector which can express intracellularly 10-23DRz in targeted manner. This study may further prompt the feasibility of using 10-23 DNAzyme to achieve effective and targeted gene silence.