基于狂犬病病毒G蛋白scFv介导的靶向shRNA制备与鉴定

【目的】探讨以狂犬病病毒G糖蛋白单链抗体介导的载体表达shRNA靶向制剂,靶向抑制狂犬病毒复制的可行性。【方法】应用PCR技术获得狂犬病毒G糖蛋白单链抗体scFv(G)和绿脓杆菌跨膜区-酵母DNA结合结构域ETA-GAL4基因,通过搭桥PCR法获得scFv(G)-ETA-GAL4(SEG)嵌合基因;克隆至原核表达载体pET28a(+),构建重组表达质粒pET28a(+)-scFv(G)-ETA-GAL4(pET28a-SEG);在大肠杆菌BL21(DE3)中经IPTG诱导表达,利用镍柱亲和层析法纯化包涵体,经复性、鉴定制得SEG蛋白;ELISA法检测表达蛋白与狂犬病毒特异结合活性;将SEG蛋白与含shRNA的质粒(pRNATU6.3-shRNA)连接制成靶向shRNA,接入100 TCID50狂犬病毒感染BHK-21细胞,35 h观察细胞中绿色荧光蛋白(GFP)表达情况;48 h用直接免疫荧光抗体试验测定复合物抑制病毒效果。【结果】克隆得到1557 bp的SEG蛋白编码基因,大肠杆菌中成功表达57 KDa的SEG蛋白,能与抗His的单克隆抗体发生特异性反应,SEG蛋白经镍柱纯化、复性后得率为2.8 mg/mL。ELISA试验证明SEG蛋白在一定浓度范围内与RV结合呈正相关。细胞试验表明GFP在细胞内得到表达;直接免疫荧光试验测定该复合物能抑制76%病毒复制。【结论】SEG蛋白能与携带shRNA的质粒结合,可运送该质粒至RV感染BHK-21细胞中,抑制狂犬病毒的复制。

Targeted inhibition of Rabies Virus replication in vitro by single chain antibody domain mediated vector expression shRNA delivery

Abstract: Objective] Single chain antibody-mediated delivery is a novel approach for targeting shRNA to appropriate cells. In this report, we studied whether this shRNA delivery strategy would be effective against rabies virus. Methods] Rabies virus scFv(G) gene and ETA-GAL4 gene were amplified by PCR from vector scFv(G)-T and PE40-GAL4-T respectively. Then, the chimeric gene scFv(G)-ETA-GAL4 was constructed by lapextension PCR and cloned into the prokaryotic expression vector pET28a(+). Recombinant expression plasmid of pET28a(+)-scFv(G)-ETA-GAL4 was constructed and then transformed into the competent E.coli BL21(DE3) cells for expression under the induction of IPTG. scFv(G)-ETA-GAL4 protein was purified by Ni-NTA His Bind Resin affinity chromatograph and identified by SDS-PAGE gel and Western blot assay. Binding of the fusion protein scFv(G)-ETA-GAL4 to rabies virus was determined by ELISA. Complexes which formed spontaneously by the fusion protein scFv(G)-ETA-GAL4 with plasmid pRNATU6.3-shRNA were added to BHK-21 cells culture medium that infected with RV. Green fluorescent protein (GFP) was observed after 35h and judged the transferring efficiency of the complexes. The inhibition of RV replication by shRNA was detected by direct immune fluorescence test. Results] A 1557 bp DNA encoding scFv(G)-ETA-GAL4 protein gene was cloned and successfully expressed in inclusion body with approximate molecular weight of 57.0 KDa, which could be recognized by anti-His mAb. The scFv(G)-ETA-GAL4 proteins were purified by Ni-NTA column , and after renatured with the yield of 2.8 mg/mL. The ELISA results showed that when concentration of the scFv(G)-ETA-GAL4 protein ranging from 2.8 nmol/L to 1000 nmol/L, binding affinity is directly related with RV. The GFP expressed in BHK-21 cell after transfection with the complexes and effectively inhibited RV replication in BHK-21 cell. Conclusion] scFv(G)-ETA-GAL4 fusion protein could mediated plasmid pRNATU6.3-shRNA transferred into BHK-21 cell infected with RV, and then inhibited RV replication.