Construction of retrovirus vector with HBV Pol gene and its expression in vitro

Objective: To construct retroviral vector with HBV Pol gene and study its expression in vitro. Methods:The recombinant plasmid HBV2/pBR322 containing 2 copies of HBV full-length gene was provided as the amplification template. The PCR product was cloned into pMD 18-T and subcloned into pMSCVneo and pLNCX2 to construct the recombinant retroviral vectors with HBV Pol gene named by HBV P/pMSCVneo and HBV P/pLNCX2. HBV Pol gene was detected by RTPCR after transfecting the recombinant plasmids into SMMC7721 cells with liposome and G418 selection. Results: The retroviral vector with HBV Pol gene was successfully constructed and the expression of HBV Pol gene in vitro was detected by RTPCR. Conclusion: The retroviral vector with HBV Pol gene can be obtained, which will provide a new insight on the function of HBV Pol gene.

IN VITRO STUDY ON THE CLONING AND TRANSDUCTION OF HUMAN O^6-METHYLGUANINE-DNA-METHYLTRANS cDNA INTO HUMAN UMBILICAL CORD BLOOD CD34^+ CELLS

Objective: To explore whether human umbilical cord blood hematopoietic progenitor cells transduced with human O^6-methylguanine-DNA-methyltrans (MGMT) gene could increase resistance to 1,3-Bis(2- Chloroethyl)-1-Nitrosourea (BCNU). Methods: The cDNA encoding the MGMT was isolated by using RT- PCR method from total RNA of fresh human liven the fragment was cloned into PGEM-T vector and further subcloned into GINa retrovirus vector. Then the GINaMGMT was transduced into the packaging cell lines GP+E86 and PA317 by LipofectAMINE. By using the medium containing BCNU for cloning selection and ping-ponging supernatant infection between ecotropic producer clone and amphotropic producer clone, high titer amphotropic PA317 producer clone with the highest titer up to 5.8x105 CFU/ml was obtained. Cord blood CD34+ cells were transfected repeatedly with supernatant of retrovirus containing human MGMT- cDNA under stimulation of hemopoietic growth factors. Results: The retrovirus vector construction was verified by restriction endonuclease analysis and DNA sequencing. PCR, RT-PCR, Southern Blot, Western Blot and MTT analyses showed that MGMT drug resistance gene has been integrated into the genomic DNA of cord blood CD34+ cells and expressed efficiently. The transgene cord blood CD34+ cells conferred 4-folds stronger resistance to BCNU than untransduced cells. Conclusion: The retrovirus vector-mediated transfer of MGMT drug resistance gene into human cord blood CD34+ cells and its expression provided an experimental foundation for gene therapy in clinical trial.

Retrovirus-mediated delivery of an IL-4 receptor antagonist inhibits allergic responses in a murine model of asthma

This work reports the investigation of the effect of airway IL-4RA gene transfer by a recombinant retroviral vector on airway inflammation and airway responsiveness in asthmatic mice. The retrovirus-mediated delivery of IL-4RA to the airways of mice inhibited elevations of airway responsiveness and the development of allergic inflammation in asthmatic mice, and regulated the Th1/Th2 balance in OVA-sensitized and -challenged mouse models. This suggests that gene therapy is a therapeutic option for treating and controlling chronic airway inflammation and asthma symptoms.

Selective expansion and enhanced anti-tumor effect of antigen-specific CD4^(+)T cells by retrovirus-mediated IL-15 expression

Mounting evidence has demonstrated that CD4^(+)T cells play an important role in anti-tumor immune responses.Thus,adoptive transfer of these cells may have great potential for anti-cancer therapy.However,due to the difficulty to generate sufficient tumor-specific CD4^(+)T cells,the use of CD4^(+)T cells in tumor therapy is limited.It has been found that IL-15 transfection enhances the proliferation and anti-tumor activity of tumor-specific CD8+Tcells,but the effect of IL-15 transfection on CD4^(+)T cells remains unknown.Here,the effects of retrovirusmediated IL-15 expression in Ova-specific CD4^(+)T cells from Do11.10 mice were evaluated and it was discovered that IL-15 transfected CD4^(+)T cells expressed both soluble and membrane-bound IL-15.Retrovirusmediated IL-15 expression led to a selective expansion of antigen-specific CD4^(+)T cells by inhibiting their apoptosis.In vivo IL-15 transfected CD4^(+)T cells were more effective in suppressing tumor growth than control retroviral vector transfected ones.To ensure the safety of the method,the employment of thymidine kinase gene made it possible to eliminate these transgenic CD4^(+)T cells following ganciclovir treatment.Together,we show that IL-15 transfection induced a selective expansion of antigen-specific CD4^(+)T cells ex vivo and enhanced their tumor-suppression effects in vivo.This has an important significance for improving the efficacy of adoptive T cell therapy.

人胰岛素样生长因子-1逆转录病毒载体的构建及其在骨髓基质干细胞中的表达

目的构建人胰岛素样生长因子-1的逆转录表达载体,建立逆病毒介导的IGF-1基因转移系统。方法用逆转录-多聚酶链反应(RT-PCR)从人肝细胞克隆IGF-1的基因;经DNA测序分析证实后将目的基因插入逆转录病毒载体LXSN,制备pLXSN-IGF-1表达载体;借助阳离子脂质体转染包装细胞PA317,G418筛选阳性克隆,获取病毒上清;培养人骨髓基质干细胞,用病毒上清感染骨髓基质干细胞;采用RT-PCR及Western blot法检测目的基因在靶细胞的表达。结果经酶切电泳和DNA测序表明成功构建了IGF-1逆转录病毒表达载体,转染包装细胞后可以产生IGF-1逆转录病毒,病毒感染人骨髓基质干细胞后能够表达IGF1-1重组蛋白。结论成功建立逆转录病毒载体介导的IGF-1体外表达体系,能够快速、稳定地将IGF-1基因转入骨髓基质干细胞。

A novel strategy to derive iPS cells from porcine fibroblasts

Induced pluripotent stem (iPS) cell technology demonstrates that somatic cells can be reprogrammed to a pluripotent state by over-expressing four reprogramming factors.This technology has created an interest in deriving iPS cells from domesticated animals such as pigs,sheep and cattle.Moloney murine leukemia retrovirus vectors have been widely used to generate and study mouse iPS cells.However,this retrovirus system infects only mouse and rat cells,which limits its use in establishing iPS cells from other mammals.In our study,we demonstrate a novel retrovirus strategy to efficiently generate porcine iPS cells from embryonic fibroblasts.We transfected four human reprogramming factors (Oct4,Sox2,Klf4 and Myc) into fibroblasts in one step by using a VSV-G envelope-coated pantropic retrovirus that was easily packaged by GP2-293 cells.We established six embryonic stem (ES)-like cell lines in human ES cell medium supplemented with bFGF.Colonies showed a similar morphology to human ES cells with a high nuclei-cytoplasm ratio and phase-bright flat colonies.Porcine iPS cells could form embryoid bodies in vitro and differentiate into the three germ layers in vivo by forming teratomas in immunodeficient mice.

携带抗口蹄疫病毒ScFv基因猪成纤维细胞系的建立

根据口蹄疫病毒的感染特征及其在临床发病过程中呈现的症状,筛选抗口蹄疫病毒单链抗体基因。通过EcoRⅠ/NotⅠ双酶切中间质粒pGEX-ScFv获得单链抗体基因片段,并克隆至反转录病毒载体质粒pFB-neo,构建反转录病毒穿梭载体质粒pFB-ScFv。将pFB-ScFv与辅助质粒pVPack-GP、pVPack-10A1共转染HEK293T细胞,包装重组反转录病毒MMLV-ScFv。同时,构建含增强型绿色荧光蛋白基因的重组反转录病毒MMLV-EGFP作为对照。利用所包装重组反转录病毒感染猪成纤维细胞,通过G418筛选获得携带目的基因的单克隆细胞集落。试验结果表明,本试验在成功构建反转录病毒穿梭载体pFB-ScFv和pFB-EGFP的基础上,获得了分别携带抗口蹄疫病毒单链抗体基因和增强型绿色荧光蛋白基因的反转录病毒,并最终筛选出分别携带上述基因的猪成纤维细胞克隆,为抗口蹄疫病毒转基因动物的研究奠定了基础。

逆转录病毒作为基因治疗载体的生物安全检测

目的在以逆转录病毒为载体的抗乙型肝炎病毒（ＨＢＶ）细胞内免疫基因治疗研究过程中，建立较完整的生物安全检测系统，为临床应用奠定基础。方法包括无菌，支原体和可复制性逆转录病毒的检测。支原体检测采用聚合酶链反应（ＰＣＲ）方法，可复制性逆转录病毒的检测应用Ｓ＋／Ｌ－试验，ＮＩＨ３Ｔ３细胞扩增试验和ｎｅｏ基因补救分析。结果在所建立的靶基因包装细胞系中，无菌试验均为阴性，一株包装细胞支原体呈阳性，全部包装细胞系未测到可复制性逆转录病毒。结论本研究采用的生物安全检测系统具有稳定性好，敏感染性高的优点，对基因治疗临床试验的生物安全检测具有重要的应用价值。