Production of lentiviral vectors in suspension cells using low proportion of supercoiled circular plasmid DNA

The supercoiled circular (SC) topology form of plasmid DNA has been regarded to be advantageous over open circular or linearized analogue in transfection and expression efficiency, and therefore are largely demanded in the biopharmaceutical manufacturing. However, production of high-purity SC plasmid DNA would result in high manufacturing cost. The effect of SC proportion in plasmid DNA on the quality of packaged lentiviral vectors has never been reported. In this study, we established an efficient system for production of high-titer lentiviral vectors using suspension HEK293SF cells in serum-free media, and the lentiviral titer was not associated with the proportion of SC plasmid DNA. Plasmids DNA with different proportion of SC, open-circular, and linearized forms were prepared using the thermal denaturation method, and were transfected to adherent HEK293T or suspension HEK293SF cells for packaging of lentiviral vectors. The titer of lentiviral vectors from HEK293T cells, but not from HEK293SF cells, was significantly impaired when the proportion of SC plasmid DNA decreased from 60–80% to 30–40%. Further decrease of SC plasmid proportion to 3% led to a dramatic reduction of lentiviral titer no matter the packaging cell line was. However, lentiviral vectors from HEK293SF cells still showed a high titer even when the proportion of SC plasmid DNA was 3%. This study demonstrated that extremely high proportion of SC plasmid DNA was not required for packaging of high-titer lentiviral vector in HEK293SF cells, at least under our manufacturing process.     

SCG10基因重组质粒的构建及蛋白表达和定位

目的构建SCG10真核表达载体并证实融合蛋白在细胞内表达及定位。方法以人胎脑cDNA文库为模板,PCR扩增SCG10全长编码基因,亚克隆至pEGFP-C1表达载体中。将构建的重组质粒测序并转染到人胚肾HEK293中,提取细胞蛋白进行Western blot检测。利用共聚焦激光扫描显微镜观察pEGFP-SCG10在HEK293细胞内定位。结果 SCG10全长基因序列克隆到了真核表达载体pEGFP-C1中,酶切鉴定片段大小540bp。Western blot检测到了融合蛋白表达,分子量约为48kD。pEGFP-SCG10在细胞内定位以细胞浆为主,在细胞核少量表达。结论成功构建了SCG10全长基因真核表达载体,pEGFP-SCG10蛋白主要定位于HEK293细胞浆内。     

A new vector for controllable expression of an anti-HER2/neu mini-antibody-barnase fusion protein in HEK 293T cells

Tumor-targeted vectors with controllable expression of therapeutic genes and specific antitumor antibodies are promising tools for the reduction of malignant tumors. Here we describe a new plasmid for the eukaryotic expression of an anti-HER2/neu mini-antibody-barnase fusion protein (4D5 scFv-barnase-His(5)) with an NH(2)-terminal leader peptide. The 4D5 scFv-barnase-His(5) gene was placed downstream of the tetracycline responsive-element minimal promoter in the vector using the Tet-Off gene-expression system. The Bacillus amyloliquefaciens ribonuclease barnase is toxic for the host cells. To overcome this problem, barstar gene under its own minimal cytomegalovirus promoter was used in designed vector. Barstar inhibits the background level of barnase in the cells in the presence of tetracycline in culture medium. The HEK 293T cells were transfected with the designed vector, and the 4D5 scFv-barnase-His(5) fusion protein was identified by anti-barnase antibodies in cell culture medium and after purification from cell lysates using metal-affinity chromatography. The overexpression of the anti-HER2/neu mini-antibody-barnase fusion protein decreased the intensity of fluorescence of HEK 293T cells co-transfected with the generated plasmid and a plasmid containing the gene of enhanced green fluorescent protein (pEGFP-N1), in comparison with the intensity of fluorescence of HEK 293T cells transfected with pEGFP-N1, in the absence of tetracycline in the medium. The effect of the 4D5 scFv-barnase-His(5) on EGFP fluorescence indicates that the introduced barnase functions as a ribonuclease inside the cells. The anti-HER2/neu mini-antibody could be used to deliver barnase to HER2/neu-positive cells and provide its penetration into the target cells, as HER2/neu is a ligand-internalizing receptor. This expression vector has potential applications to both gene and antibody therapies of cancer.     

猪内源性反转录病毒囊膜基因env真核表达质粒的构建及鉴定

目的:构建猪内源性反转录病毒(PERV)囊膜基因env的真核表达质粒pHCMV-env并加以鉴定,为研究PERV的细胞嗜性和宿主范围奠定基础。方法:用RT-PCR方法扩增五指山猪来源PERV的env基因,将其插入pGEM-T easy载体中,构建重组质粒pGEM-T-env,酶切鉴定正确后,将pGEM-T-env与pHCMV-VSV-G表达质粒同时经EcoRⅠ酶切消化后连接,构建重组表达质粒pHCMV-env,并进行酶切、测序鉴定;将鉴定正确的质粒pHCMV-env转染HEK293T细胞,采用PCR、RT-PCR检测转染后env基因的整合和转录情况。结果:扩增得到五指山猪来源PERV的env基因,并构建了pHCMV-env真核表达质粒,转染HEK293T细胞系后,该细胞系中有目的基因的整合和转录。结论:构建了真核表达质粒pHCMV-env,并且在HEK293T细胞中能够整合并转录,为研究PERV的细胞嗜性和宿主范围奠定了基础。     

大鼠μ型阿片受体的pIRES2-EGFP质粒构建及其在HEK293细胞中的表达

提取大鼠脑组织总RNA,通过逆转录巢式PCR,扩增μ型阿片受体全长cDNA,克隆至pMD20-T载体中,测序鉴定,纠正点突变后,经酶切连接克隆入pIRES2-EGFP中,测序及酶切结果表明μ基因正确,μ-pIRES2-EGFP质粒构建成功.用脂质体法将μ-pIRES2-EGFP转染入HEK293细胞中,在荧光显微镜下,转染细胞可以观察到绿色荧光,应用免疫组化荧光可以观察到μ基因的高强度表达.     

CD真核表达载C 体的构建及在 2KHE39 细胞中的表达

目的：构建含自杀基因胞嘧啶脱氨酶（CD）的真核表达载体pcDNA3．1／HA—myc-His（-）Z—CD,并进行哺乳动物细胞HEK293转染研究。方法：以本实验室保存的含CD基因全长的质粒为模版,用PcR方法扩增CD基因阅读框序列,并定向克隆到带有HAtag的pcDNA3．1／HA—myc-His（-）Z载体上,使目的基因与HAtag在同一阅读框。重组体质粒经EcoRI和BamHI双酶切鉴定,并对插入的CD基因片段进行测序,将鉴定好的阳性重组质粒pcDNA3．1／HA—myc-His（-）Z—CD用脂质体介导转染HEK293,提取细胞蛋白,western blot检测CD基因的表达情况.结果：阳性重组质粒pcDNA3．1／HA—myc-His（-）ZCD经Eco砌和BanHI双酶切后,获得约为5．5kb片段和1．3kb插入片段,序列分析表明插入的片段与GenBank发布的序列一致．western blot检测到CD基因的表达。结论：成功构建了含自杀基因CD的真核表达质粒。     

人P2X7真核表达载体的构建及稳定转染细胞株的建立

目的：构建人P2X7基因的真核表达载体,并通过转染获得稳定表达P2X7分子的HEK293细胞株。方法：以人脑组织P2X7cDNA为模板扩增出P2X7基因,插入到真核表达载体pEGFP-N1中,构建重组质粒pEGFP-N1/P2X7。用X-fect试剂盒将重组质粒转染HEK293细胞,通过G418辅助荧光筛选建立稳定表达P2X7-EGFP细胞株。经流式细胞仪、Western blot和激光共聚焦显微镜检测,了解人P2X7在HEK293细胞中的表达水平及细胞内定位。结果：重组质粒pEGFP-N1/P2X7构建正确,建立了稳定表达人P2X7的HEK293细胞系。Western blot和流式细胞仪检测证实,P2X7在HEK293细胞系中成功表达,激光共聚焦显微镜检测显示P2X7-EGFP定位在细胞膜上。结论：重组载体pEGFP-N1/P2X7构建成功并建立了稳定表达人P2X7的HEK293细胞系,为进一步研究P2X7离子通道结构和功能奠定基础。     

构建稳定表达RFP及嘌呤霉素抗性的K562细胞株

目的构建稳定表达红色荧光蛋白（red fluorescent protein,RFP）和嘌呤霉素（puromycin）抗性的K562．PM．RFP细胞株,便于慢性粒细胞性白血病研究中K562细胞的观察和筛选。方法采用PCR法获得RFP片段,将其插入到慢病毒pGC-FU-3FLAG-IRES—Puromycin载体中获得pGC—PM—RFP重组质粒,经脂质体转染到293T细胞中获得慢病毒LV—PM—RFP,有限稀释法检测慢病毒在293T细胞中的转染效率,用包装获得的慢病毒感染K562细胞,经嘌呤霉素筛选获得RFP阳性的K562-PM—RFP细胞株。结果PCR及测序结果证实目的基因RFP正确克隆至慢病毒质粒中,经慢病毒LV—PM-RFP感染的K562细胞能在嘌呤霉素抗性培养基中存活,并稳定表达RFP。结论成功构建了慢病毒重组质粒pGC—PM-RFP,并获得了携带RFP及嘌呤霉素抗性基因的K562-PM—RFP细胞株。     

HAX1和EGFP共表达重组腺病毒载体的构建、鉴定

目的构建和鉴定HAX1和EGFP双基因共表达重组腺病毒载体。方法采用DNA重组技术,将目的基因HAX1克隆至含有报告基因EGFP的穿梭质粒pAdTrack—CMV中,并转化于大肠埃希菌DH5a;筛选出重组质粒pAdTrack—CMV—HAX1,并在BJ5183细菌中与pAdEasy-1质粒进行同源重组,产生重组腺病毒载体;用lipofectamine将其转染HEK293细胞,包装携带全长HAX1的重组复制缺陷型腺病毒pad—HAX1-EGFP,酶切和序列测定鉴定;用制备好的Ad—HAX1-EGFP感染HEK293细胞,流式细胞术检测其感染效率,RT—PCR、Western印迹鉴定外源基因HAX1的表达。BrdU检测感染了Ad—HAX1-EGFP的HEK293细胞增殖情况。结果pAdTrack—CMV—HAX1重组质粒构建成功。pAdTrack—CMV—HAX1质粒与pAdEasy-1质粒同源重组后与预期结果相符。构建好的Ad—HAX1-EGFP能有效感染HEK293细胞;外源基因能在239细胞中有效表达。HAX1高表达的HEK293细胞其增殖率得以提高。结论成功构建了表达HAX1和EGFP共表达的重组腺病毒载体,HAX1能够促进结肠癌细胞HEK293细胞的增殖。     

肿瘤内皮标志物8同型物Ⅰ基因真核表达载体的构建及其在HEK293F细胞中的表达

目的:构建肿瘤内皮标志物8(TEM8)基因真核表达载体,实现TEM8在HEK293F细胞中的外源表达。方法:用PCR技术扩增TEM8基因,经限制性酶切、连接、转化,插入pcDNA3.1(+)-EGFP真核表达载体,并通过脂质体将TEM8表达质粒转染至HEK293F细胞中,Western印迹检测TEM8的表达。结果:PCR扩增得到TEM8基因,构建了真核表达载体pcDNA3.1(+)-TEM8-EGFP并转染HEK293F细胞,经G418加压筛选及有限稀释法得到生长性状良好、表达效率高的单克隆细胞系TEM8-EGFP/HEK293F;Western印迹证明过表达细胞系TEM8-EGFP/HEK293F显著表达TEM8蛋白。结论:构建了表达TEM8的重组HEK293F工程细胞系TEM8-EGFP/HEK293F,为进一步研究TEM8的生理功能奠定了基础。     

醛糖还原酶抑制剂细胞筛选模型的建立

目的：将糖尿病慢性并发症相关基因醛糖还原酶 (aldose reductase, AR) 基因与腺相关病毒(adeno associated virus, AAV) 表达载体pSNAV2.0重组,使其在HEK293细胞中表达,以基因工程表达的AR为靶向,建立醛糖还原酶抑制剂 (aldose reductase inhibitor, ARI) 细胞筛选模型。方法：首先采用酶切、连接等方法构建含有人AR基因序列的AAV表达载体pSNAV-hAR,将重组质粒转染HEK293细胞,通过活性测定、Western blot和免疫荧光检测目的基因转染及表达的情况。结果：PCR、酶切、DNA测序均证实表达质粒pSNAV-hAR构建正确。转染HEK293细胞后,一系列分析结果显示,腺相关病毒表达载体介导的AR真核细胞表达产物是具有功能活性的目的蛋白。应用经典醛糖还原酶抑制剂 Sobinil 和 Zopolrestat 对此模型进行了验证。结论：AR高表达细胞模型的建立,为进一步筛选ARI、探讨多元醇通路学说在糖尿病慢性并发症发病机制中的作用奠定了基础。针对先后建立的酵母细胞与真核细胞模型的特点及三种AR活性测定方法中的注意事项进行了讨论。     

G418抗性HEK293细胞的培育

目的　培育具有G418抗性的HEK2 93细胞 ,用于建立猪内源性反转录病毒感染人HEK2 93细胞的模型。方法　通过脂质体转染的方法 ,将含有neo基因的质粒pIRESneo导入HEK2 93细胞中 ,利用G418的选择特性 ,对转染细胞进行压力筛选 ,并对其进行了PCR鉴定。结果　经 6 0 0 μg ml的G418压力筛选后 ,获得了抗性细胞克隆。抗性细胞的形态和生长速度与筛选前细胞没有差异 ,特异性核苷酸引物检测抗性细胞基因组DNA ,可以扩增出对应的核苷酸片段。结论　成功地培育了G418抗性HEK2 93细胞 ,为建立猪内源性反转录病毒感染人HEK2 93细胞的模型奠定了基础。     

Detailed design and comparative analysis of protocols for optimized production of high-performance HIV-1-derived lentiviral particles

Transgenic HIV-1-derived lentiviral particles are at the forefront of current gene therapy and tissue engineering initiatives, which will require optimal protocols for large-scale production of clinical-grade therapeutic lentiviruses. Production of latest-generation self-inactivating lentiviral particles requires cotransfection of mammalian production cell lines with two helper plasmids along with the lentivector, whose transgene-encoding expression cassette is the only genetic information stably transduced into target chromosomes. Capitalizing on a recently designed lentiviral expression vector family, we conducted rigorous analysis of production-relevant parameters including transfection, cell density, media composition, temperature, relative (helper) vector concentrations and genetic configuration. Comparative analysis of lentiviral particle performance (VP) was based on the viral titer (reflecting the number of transduction-competent lentiviral particles) relative to the number of lentiviral particles produced (correlating with p24 production levels) (VP=titer/viral particle number). Optimal lentiviral production parameters, resulting in up to 132-fold greater VP compared to standard protocols, required (i) CaPO4-based transfection (ii) of helper plasmids and lentivector at a fixed concentration ratio (helper plasmid I:helper plasmid II:lentivector=1:1:2) (iii) into 1x10(5) human embryonic kidney cells/cm2 (HEK293-T) (iv) cultivated at 37 degrees C (v) in Advanced D-MEM medium supplemented with (vi) 2% fetal calf serum, (vii) and a culture additive containing 0.01 mM cholesterol, 0.01 mM egg's lecithin and 1x chemically defined lipid concentrate. (viii) Furthermore, constitutive transgene expression units placed in a forward polyadenylation site (pA)-free orientation relative to the lentivector backbone resulted in optimal transgene transduction/expression. Our studies suggest that detailed knowledge of lentivector design and the production of lentiviral particles will advance large-scale manufacturing of clinically relevant lentiviruses for future gene therapy applications.     

大鼠miR-126慢病毒表达载体的构建及其在肝星状细胞中的表达

目的：肝星状细胞（hepaticstellatecell,HSC）激活并发生表型改变是肝纤维化形成的关键,本实验期待通过构建慢病毒mo—miR．126,并体外转染Hsc,为研究miR．126在肝纤维化中的作用奠定实验基础。方法：PCR扩增miR-126的前体,构建miR．126的重组表达载体pCDH．CMV-MCS．EFl．copGFP-miR．126,脂质体法转染包装细胞293TN细胞,包装产生慢病毒,以293TN细胞绿色荧光蛋白（greenfluorescentprotein,GFP）的表达水平测定病毒滴度,构建重组慢病毒（Lentivims,LV）载体（Lv．miR．126）,体外转染活化的HSC．T6,荧光显微镜观察荧光阳性细胞百分率,real—timePCR检测miR一126转入水平。结果：经PCR扩增检测阳性菌落和测序证实,成功构建携带大鼠miR一126基因重组慢病毒载体。倒置荧光显微镜下观察可见包装细胞293TN呈绿色荧光,并测得滴度108〉ifu／ml。荧光显微镜下HSC的荧光阳性率在95％以上。Real—timePCR检测证实miR-126转染后获得了较高的表达。结论：成功构建大鼠慢病毒载体Lv—miR-126,并可在体外高效稳定表达,为本研究后续对miR-126靶点验证和功能研究奠定实验基础。     

人ANKRD49基因真核表达载体的构建及其功能的初步研究和RNA干扰靶点的鉴定

目的: 克隆人ANKRD49基因并构建其真核表达重组体,利用构建成功的ANKRD49真核表达重组体对其进行功能的初步研究,并筛选和鉴定其RNA干扰靶点. 方法: 提取人肺腺癌细胞株A549总RNA,逆转录-聚合酶链式反应(RT-PCR)对ANKRD49进行扩增,扩增产物与真核表达载体p3×Flag-CMV-14同时进行双酶切,酶切产物连接后转化入感受态细胞Top10,阳性重组质粒p3×Flag-CMV-14/ANKRD49经菌液PCR、双酶切和测序鉴定正确后,用脂质体法(Lipofectamine^TM 2000)转染人胚肾细胞(HEK 293T),免疫印迹(Immunoblotting)和免疫荧光技术检测表达产物.免疫荧光法检测ANKRD49在宿主细胞内的定位.MTT法检测ANKRD49对宿主细胞的增殖作用.设计并合成针对人ANKRD49基因的RNA干扰靶点序列,与p3×Flag-CMV-14/ANKRD49共转染HEK 293T细胞后,Immunoblotting鉴定ANKRD49的RNA干扰靶点. 结果: RT-PCR结果显示,从A549细胞中扩增出约720 bp的片段.菌液PCR、双酶切及测序结果显示重组质粒p3×Flag-CMV-14/ANKRD49构建成功且序列正确.免疫荧光和Immunoblotting结果显示,在转染p3×Flag-CMV-14/ANKRD49的细胞中有ANKRD49的表达,蛋白质相对分子质量(Mr)约为27kDa,而转染空质粒组未见表达.MTT结果显示,ANKRD49对细胞增殖没有影响.共转染实验结果显示,1号和4号RNA干扰序列可以有效降低人ANKRD49的表达. 结论: 成功构建了真核表达重组体p3×Flag-CMV-14/ANKRD49,该蛋白质位于细胞核,不参与细胞增殖;同时鉴定出该基因的2个有效干扰靶点,为进一步研究其功能奠定了基础.     

慢病毒介导的HTRA1 基因稳定过表达人脑血管平滑肌细胞株的建立

目的:构建并包装针对HTRA1基因以及其1091TC突变基因(HTRA1-Mut)的过表达慢病毒载体,以及建立稳定表达HTRA1及HTRA1-Mut基因的人脑血管平滑肌细胞(HBVSMC)株。方法:采用RT-PCR方法扩增HTRA1及HTRA1-Mut基因片段并将其连接于GV287载体质粒,采用慢病毒包装三质粒系统(GV287/p Helper 1.0/p Helper 2.0)转染293T细胞,收集富含慢病毒颗粒的细胞上清液并标定病毒滴度,慢病毒感染经培养和鉴定的HBVSMC细胞株。结果:成功构建含HTRA1及HTRA1-Mut基因的慢病毒重组载体,PCR鉴定阳性的克隆进行测序和BLAST比对分析显示与源基因序列一致,并能够有效的感染并在293T细胞中表达。表达载体包装后测定病毒滴度为:2E+8 TU/mL。过表达慢病毒感染后HBVSMC有荧光表达,并且荧光率达80%以上,细胞生长良好传后细胞几乎无死亡现象。结论:成功构建了过表达HTRA1及HTRA1-Mut基因的慢病毒表达载体,得到了较高滴度的病毒悬液,建成了稳定表达HTRA1及HTRA1-Mut基因的HBVSMC细胞株,为进一步探讨HTRA1基因及突变后细胞的功能变化提供了良好的研究工具。     

稳定表达hHCN2基因 HEK293细胞系的建立

目的：培育稳定表达hHCN2基因的细胞系,建立一种表达研究心肌离子通道的有效模型。方法：通过脂质体转染的方法,将重组pcDNA3-hHCN2真核表达载体导入人胚肾细胞（HEK293细胞）,以G418压力筛选转染细胞,并对其进行全细胞膜片钳记录。结果：经600μg／ml压力筛选后,获得抗性细胞克隆,并用全细胞膜片钳技术记录到克隆hHCN2通道编码电流。结论：本实验采用脂质体转染法成功地培育出G418抗性HEK293细胞。为进一步研究克隆离子通道结构和功能的关系奠定基础。     

反转录病毒载体介导的猪APOBEC3F在猪源细胞PK15中的表达

目的:利用反转录病毒载体构建猪载脂蛋白B mRNA编辑酶催化多肽样蛋白(APOBEC)3F重组质粒,并实现其在猪肾细胞PK15中的表达。方法:用RT-PCR方法扩增五指山猪来源的外周血淋巴细胞APOBEC3F基因,将其定点插入反转录病毒载体pMSCV neo中,同时于插入位点两侧分别添加FLAG和GFP标签,构建重组质粒pMSCV-FLAG-A3F-GFP,并进行酶切、测序鉴定;将鉴定正确的重组质粒与pVSV-G、pGag-Pol共转染包装细胞HEK293T,分别于转染后48~72 h收集细胞的培养上清以获得假型病毒粒子;用该假型病毒感染猪源细胞PK15,通过PCR、Western印迹检测目的基因的整合及表达。结果:PCR扩增到1254 bp的猪APOBEC3F基因,重组质粒pMSCV-FLAG-A3F-GFP经酶切、测序,结果无误;3质粒共转染HEK293T细胞包装出的假型病毒感染PK15细胞后观察到GFP表达;从感染假型病毒的PK15细胞基因组中扩增到1254 bp的猪APOBEC3F基因,Western印迹检测到78.1×103的猪APOBEC3F蛋白的表达。结论:实现了反转录病毒载体介导的猪APOBEC3F在猪源细胞PK15中的整合与表达,为深入研究该分子对猪内源性反转录病毒(PERV)的抑制作用奠定了基础。     

含F／2A序列的抗P185^erbB2人鼠嵌合抗体慢病毒表达载体的构建

目的构建含F／2A序列的抗P185^erbB2人鼠嵌合抗体慢病毒表达载体,观察其在293T细胞中的表达。方法用具有自我剪切能力的弗林蛋白酶（Furin）／口蹄疫病毒2A多肽（F/2A）连接人鼠嵌合抗体的重链和轻链,形成一个开放阅读框（ORF）,插入慢病毒表达载体pWPI,构建重组抗P185神睨全长人鼠嵌合抗体表达载体pWPI／H-F2A—L。以已构建的慢病毒表达载体pWPI／H-IRES-L为对照质粒。应用磷酸钙沉淀法将慢病毒载体3质粒系统共转染入293T细胞进行包装,测定病毒滴度。再感染293T细胞,荧光显微镜下观察GFP的表达和转染效率,RT—PER、ELISA方法分别检测嵌合抗体mRNA和蛋白的表达。结果经测序鉴定,pWPI／H—F2A—L与预期设计一致;pWPI／H—F2A—L组的病毒滴度为4．3×10^5TU／ml,而pWPI／H—IRES—L组的病毒滴度为3．5×10^5TU／ml;两组重组慢病毒的转染效率分别为87．68％和79．08％;两组重组慢病毒感染293T细胞后,都有嵌合重链和嵌合轻链的表达,由F／2A介导的嵌合抗体的表达水平要高于由IRES介导的嵌合抗体。结论成功构建了含F／2A序列的抗P185^erbB2人鼠嵌合抗体慢病毒表达载体,为今后抗P185^erbB2工程抗体的研究奠定了基础。