反义HLA-A2和GDNF共表达逆转录病毒载体的构建和鉴定

为构建GDNF和反义HLA -A2共表达的逆转录病毒载体,将人GDNF酶切片段(XhoI/SalI)克隆于逆转录病毒载体pLNCX2 的XhoI位点,再将HLA A2cDNA片段反向克隆于上述重组载体的HindIII/SalI位点,对其作酶切鉴定和测序后转染PA317包装细胞系进行病毒的包装。收获重组病毒感染的NIH3T3并进行病毒滴度的测定,GDNF及HLA- A2表达的RT -PCR检测,进一步感染人胚肺成纤维细胞,观察GDNF分泌情况。结果表明:GDNF和反义HLA -A2两片段的序列和插入方向完全正确,包装后获得的重组病毒的平均滴度为5×105 CFU/ml。RT PCR显示:在小鼠源性的PA317细胞中有人GDNF和HLA A2的表达,ELISA法测得病毒感染人胚肺成纤维细胞上清液中GDNF含量为450pg/ml。通过本实验,我们获得能共表达GDNF和反义HLA -A2的重组逆转录病毒,其转染的人成纤维细胞具有合成GDNF的能力。     

EXPRESSION OF HUMAN CD59 ANTIGEN ON MOUSE NIH3T3 AND EL-4 CELLS CONFERS PROTECTION AGAINST HUMAN COMPLEMENT ATTACK

CD59分子是广泛分布于各组织细胞表面的18kDa糖蛋白,通过肌醇磷脂酰聚糖(GPI)锚固于细胞膜,具有抑制同源补体攻膜复合物(MAC)形成和参与介导T细胞活化等多种功能.本文应用RT-PCR方法,从Jurkat细胞的总RNA中扩增得到396bp的cDNA片段,经测序证实该片段包括25aa信号肽在内的全部的CD59编码序列.进一步将此CD59的cDNA重组于逆转录病毒载体pLXSN,电穿孔转染PA317细胞,并用病毒上清感染小鼠成纤维母细胞NIH3T3及小鼠胸腺瘤细胞EL-4.经G418加压筛选,FACS检测获得表达CD59的阳性细胞克隆.补体杀伤实验结果表明:表达GPI-型CD59分子的NIH3T3和EL-4细胞对人血清补体溶破的抵抗作用较空载体转染的非表达细胞明显增强.证实了用逆转录病毒载体可成功地将人CD59基因导入异源细胞,使表达CD59的异源细胞获得抑制人补体溶破的功能.本研究为探讨CD59分子与细胞活化的关系及其信号转导机制建立了良好的细胞模型,并为进一步应用于异种器官移植,或对由于CD59遗传缺损所致PNH进行基因治疗奠定了基础.     

Recovery of a rare clone from a population of unstable retroviral vector-expressing mammalian cells using a new RNA extraction and slot-blot protocol

Although a useful and important method of gene transfer, retroviral vectors can be genetically unstable. In the course of experiments using DOEJS, a retroviral vector able to confer expression of a H-ras oncogene and a neomycin resistance gene (neo) on mammalian cells (Compere et al., 1989), it was found that the vast majority of infected rat embryo fibroblasts, recovered on the basis of neo activity (i.e., G418 resistance), did not express ras mRNA. It was subsequently observed that most cells in the ψ2 cell line used to propagate DOEJS failed to produce virus capable of expressing both ras and neo in primary rat embryo fibroblasts. A simplified RNA extraction and slot-blot technique was developed to screen mRNA from several hundred fibroblast clones and, in doing so, infected fibroblast clones producing both neo and ras mRNA were identified at low frequency. The DOEJS/ψ2 packaging line was subsequently subcloned and individual clones screened for their ability to confer appropriate gene expression on target cells. Subclone DOEJS/ψ2-B6 was eventually isolated after screening 24 DOEJS subclones and 240 infected rat embryo fibroblast colonies. DOEJS/ψ2-B6 was shown to induce reliably phenotypic transformation, G418 resistance, and ras and neo mRNA expression in primary rat embryo fibroblasts. The RNA extraction and screening procedure was thus useful for recovering an infrequent subclone producing a retrovirus with the original properties.     

肝癌细胞稳定转染B7.1后的免疫学特性

目的 探讨赋予肝癌细胞第二信号分子Ｂ７．１增强癌细胞与淋巴细胞之间的识别与激活作用,从而达到增强淋巴细胞对肝癌细胞的杀伤或抑制作用。方法 利用逆转录方法,转染Ｂ７．１分子至包装细胞系ＰＡ３１７。筛选获得高滴度的克隆后,以病毒上清感染肝癌细胞,使其表达Ｂ７．１分子,最后以ＬＤＨ释放法测定ＬＡＫ细胞的细胞毒活性。结果 肝癌细胞可稳定表达Ｂ７．１分子,阳性率达９４．３％,未转染的细胞无表达,其所诱发的Ｌ     

Effect of recombinant adeno-associated virus transforming growth factor-beta 1 on the infection activity of bone marrow mesenchymal stem cells

背景：目前常用基因载体具有一定缺陷性,无法直接在体内应用。应用腺相关病毒作为转化生长因子β1载体促进软骨修复的研究报道较少。 目的：构建重组转化生长因子β1腺相关病毒,测定病毒滴度,并测定重组病毒对骨髓基质干细胞的感染活性。 方法：PCR方法扩增转化生长因子β1基因,构建重组骨架质粒pAAV-转化生长因子β1-绿色荧光蛋白,与包装质粒pAAV-RC、辅助质粒pAAV-Helper共转染AAV-293细胞包装重组腺相关病毒rAAV-转化生长因子β1-绿色荧光蛋白。应用该重组病毒感染AAV-HT1080细胞测定病毒滴度并鉴定。并感染体外培养的兔骨髓基质干细胞,检测重组病毒感染骨髓基质干细胞的效率及活性。 结果与结论：转化生长因子β1扩增产物测序结果正确,重组骨架质粒pAAV-转化生长因子β1-绿色荧光蛋白双酶切后可见位于1.3 Kb附近转化生长因子β1条带。收获病毒滴度5.2×1011 v.g/mL。鉴定重组病毒rAAV-转化生长因子β1-绿色荧光蛋白包装成功。重组病毒感染骨髓基质干细胞后可于荧光显微镜下观测到绿色荧光蛋白的表达,感染效率达42%。结果证实,成功构建重组腺相关病毒rAAV-转化生长因子β1-绿色荧光蛋白,能够高效感染兔骨髓基质干细胞。     

Analysis of retroviral packaging lines for generation of replication-competent virus

Amplification of retroviral vector sequences occurs in cocultures of ecotropic and amphotropic packaging cell lines. Mixed packaging line cocultures were used to determine both the host range and time of appearance of replication-competent virus after introduction of a retroviral vector. Replication-competent virus was generated at a characteristic time for a given ecotropic and amphotropic packaging line combination. The time required to generate replication-competent virus in a packaging line varied with the number of recombination events necessary to generate replication-competent virus from the retroviral sequences present in the line. The psi 2 packaging line generated replication-competent virus within 10 days after transfection of the N2 vector into a mixture of psi 2 (ecotropic) and PA317 (amphotropic) packaging cells. Under the same conditions, it took only 3 days to develop replication-competent virus in psi 2/PA12 cocultures. The host range of replication-competent virus was used to identify the packaging line that initially generates virus. Each packaging line combination generated replication-competent virus at a characteristic time and this time period can be used as a measure of the "safety" of the packaging line and vector combination.     

Stable expression of the ecotropic retrovirus receptor in amphotropic packaging cells facilitates the transfer of recombinant vectors and enhances the yield of retroviral particles.

Retroviral vectors are used widely as gene transfer vehicles. Vector particles are generated by packaging cell lines, which supply the structural proteins gag, pol and env needed to package the retroviral vector RNA. The most efficient way to introduce the vector genome into the packaging cell line is cross-infection with a retroviral vector. Since the infection of a packaging cell line by the produced virus is blocked due to the down regulation of the retrovirus receptor by the envelope glycoprotein, the vector genome should be introduced by a virus with a host tropism different from the one of the packaging cell line. The murine ecotropic retrovirus receptor was expressed in the human amphotropic packaging cell line FLYA13 to generate a cell line which can be infected by murine ecotropic retroviruses. Vector transfer can now be facilitated by cross-infection with the appropriate ecotropic retroviral vectors and provides a simple and efficient method for the generation of amphotropic packaging lines.     

稳定表达EGFRvⅢex的NIH3T3细胞株的建立及其免疫原性分析

目的:建立表皮生长因子突变体Ⅲ胞外区(EGFRvⅡ-Iex)的NIH3T3稳定细胞系并分析其免疫原性。方法:将编码EGFRvⅢex基因的表达质粒pLNCX2-EGFRvⅢex转染NIH3T3细胞后,用G418筛选阳性克隆,得到多个细胞克隆。采用免疫组化和Western blot法鉴定这些细胞克隆。选取高表达EG-FRvⅢex的细胞株(命名为3T3-vⅢex)免疫BALB/c小鼠,制备抗血清。用ELISA、Western blot和免疫荧光分别检测抗血清的效价和特异性。结果:成功地构建了真核表达载体pLNCX2-EGFRvⅢex并获得了稳定高表达EGFRvⅢex的NIH3T3细胞系3T3-vⅢex。用3T3-vⅢex免疫小鼠所获得的抗血清效价为10-5。Western blot和免疫荧光鉴定证明抗血清可以与EGFR-vⅢex特异结合。结论:人EGFRvⅢex可在NIH3T3细胞内获得稳定表达,以其免疫小鼠可以获得高效价、高特异性的抗血清。     

表达Cre酶复制缺陷型重组腺病毒载体的构建及鉴定

目的构建Cre-loxP条件性基因敲除系统中Cre酶的重组腺病毒表达载体,作为体细胞条件性基因敲除的基础,并为传统ES细胞条件性基因敲除提供新的选择。方法用pAd-easy系统在大肠杆菌内经同源重组的方法构建Cre酶的复制缺陷型重组腺病毒载体;W estern b lot方法鉴定Cre蛋白的表达。结果在大肠杆菌内构建出重组腺病毒质粒,在包装细胞系内包装出重组病毒颗粒;测定病毒滴度为106pfu/L;重组病毒在细胞内表达Cre蛋白。结论表达Cre酶的重组腺病毒载体构建成功,阳性重组质粒的鉴定方法得以改进,为进一步的体细胞Cre-loxP条件性基因敲除提供了基础。     

含结核分枝杆菌Ag85A基因的2型重组腺相关病毒的构建和免疫原性

目的构建含结核分枝杆菌Ag85A基因的2型重组腺相关病毒并初步研究其免疫原性。方法采用PCR法从结核杆菌H37Rv株扩增Ag85A基因，将PCR扩增产物克隆于2型腺相关病毒（AAV-2）表达质粒pSNAV中，构建重组质粒pSNAV-Ag85A；用脂质体转染的方法将重组质粒转入BHK-21细胞中，G418筛选得到能表达目的基因混合细胞系BHK—Ag85A；用具有rAAV-2包装功能的辅助病毒感染BHK-Ag85A，纯化后得到rAAV-2-Ag85A：Western blotting检测重组病毒Ag85A基因在BHK-21细胞中的表达；rAAV-2-Ag85A免疫Balb／c小鼠．ELISA法检测血清中抗-Ag85A抗体，^51Cr释放分析检测细胞毒性T淋巴细胞（CTL）活性。结果PCR扩增的Ag85A基因序列与GenBank公布的序列一致，纯化后得到的rAAV-2-Ag85A滴度为1×10^12 virus particles／ml；Western blotting检测到rAAV-2-AgSSA在BHK-21细胞中能够表达出一相对分子质量为32000的多肽；rAAV-2-Ag85A免疫的Balb／c小鼠．抗-Ag85A抗体的滴度可达1：1024，同时还可激发Ag85A特异性的CTL产生。结论rAAV-2-Ag85A构建成功．rAAV-2-Ag85A免疫小鼠可以同时诱导体液和细胞免疫反应的出现。rAAV-2-Ag85A对于防止结核分枝杆菌感染．尤其是作为结核病的治疗性疫苗可能具有潜在的应用价值，值得进一步深入研究。     

逆转录病毒介导DNA修复蛋白在人骨髓细胞中的表达和抗性研究

目的增强造血细胞对化疗药物的耐药表型,探讨逆转录病毒介导的基因转移效率及耐药基因的特性和在造血细胞保护性基因治疗中的作用和意义.方法应用RT-PCR从人肝组织中获得编码六氧甲基鸟嘌呤-DNA-甲基转移酶(MGMT)cDNA,将其克隆于pGEM-T质粒载体并构建了逆转录病毒载体G1Na-MGMT,应用脂质体LipofectAMINE基因转移法将后者导入GP+E86和PA317病毒包装细胞,以BCNU加压筛选后的阳性克隆上清经乒乓效应后继而感染K562细胞和人造血细胞.应用PCR,Southernblot,RT-PCR,Westernblot及MTT法检测人MGMT基因在细胞中的转移和表达.结果酶切鉴定及DNA测序证实其MGMTcDNA克隆的正确性,脂质体介导方法成功将其导入病毒包装细胞,BCNU加压筛选和乒乓感染法使病毒效价达8.6×106CFU/ml,逆转录病毒载体介导的MGMT基因在K562细胞及人造血细胞中获得有效转移和表达.结论MGMT耐药基因的成功克隆并导入骨髓造血细胞且获高效表达对开展肿瘤基因治疗的临床研究奠定了实验基础.     

稳定表达人可溶性增殖诱导配体(sAPRIL)的CHO细胞株的建立及鉴定

目的:构建稳定表达人可溶性增殖诱导配体(soluble a proliferation-inducing ligand,sAPRIL)的CHO细胞株。方法:利用RT-PCR方法克隆出sAPRIL基因,构建表达该基因的慢病毒表达载体,与辅助质粒共转染HEK-293T细胞,以包装病毒颗粒。将病毒上清感染CHO细胞,获得稳定表达sAPRIL的细胞株。利用RT-PCR、Western blot及FACS等方法鉴定其表达。结果:成功克隆出人sAPRIL基因,RT-PCR、Western blot及FACS结果显示成功构建了稳定表达sAPRIL的CHO细胞株。结论:结论:成功获得了稳定表达sAPRIL的细胞株,为进一步研究其生物学功能奠定了基础。     

The history of the HSV amplicon: from naturally occurring defective genomes to engineered amplicon vectors

We have derived the HSV amplicon vector in 1981/1982 after elaborate experience with "defective viruses", arising spontaneously in viral stocks propagated at high multiplicities of infection (m.o.i.). The defective viruses were found to contain large concatemeric genomes with repeat units of limited complexity. We employed cloned defective genome repeats to generate the "amplicon" vectors, which in the presence of helper virus replicate to produce packaged large concatemeric genomes, transmissible to uninfected cells. The cloned amplicons were then employed to fine map and analyze the signals essential for amplicon propagation: (i) A DNA replication origin, producing concatemeric genomes by rolling circle replication. Three DNA replication origins were identified in the HSV genome. (ii) Signals termed pac-1 and pac-2, directing a measuring function for coordinate cleavage of the concatemeric genomes and their packaging as full-size (150 kb) genomes. Using amplicons, foreign genes of large sizes could be linked to less than 1 kb of the cis-acting HSV DNA sequences and become amplified in packaged defective genomes, transmissible to new cells. The transgenes are expressed efficiently, due to sequence reiterations. Large quantities of vectors can be produced in vitro. The amplicons are attractive vectors for use as non-integrating gene delivery vectors. The packaging signals pac-1 and pac-2 are well conserved in different herpesviruses and amplicons with a DNA replication origin and cleavage and packaging signals have been produced in additional herpesviruses. Depending on amplicon-host cell combination, the vectors can be employed with and without mutated helper virus(es) to obtain high gene expression, and desired effect on the target cell. In the absence of helper virus, the defective virus produced is limited for spread in the targeted cells. We expect that new vectors employing state of the art transgenes, will be developed to generate amplicon based concatemeric defective viruses capable of efficient expression of these genes.     

Immortalization of xeroderma pigmentosum cells by simian virus 40 DNA having a defective origin of DNA replication

A simian virus 40 (SV40) DNA fragment, encompassing the whole early region and having a defective origin of DNA replication, has been used to transform human fibroblast cells derived from two xeroderma pigmentosum (XP) patients. Two of the SV40-transformed XP cell lines, belonging to complementation group C, had acquired the characteristic of indefinite life-span in culture. These XP cell lines synthesize T antigen as shown by immunofluorescence and retain the high sensitivity to UV irradiation. Detailed karyotype analysis shows very few chromosomal changes, while the transfecting SV40 DNA is integrated into cellular DNA sequences. These are the first immortalized XP cell lines derived from complementation group C. In view of the extreme difficulty in obtaining immortalized human fibroblasts, we suggest a possible advantage of replication defective SV40 DNA molecules for immortalizing human fibroblast cells of any source.     

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。     

Murine xenotropic type C viruses. V. Biologic and structural differences among three cloned retroviruses isolated from kidney cells from one NZB mouse

Three xenotropic retroviruses have been biologically cloned from cells cultured from the kidney of a 3-month-old NZB female mouse. They were obtained by first cocultivating the kidney cells for several weeks with mink, dog, and human cells and then cloning them by endpoint dilution. The cloned viruses differ in their infectivity and replicative ability in a variety of heterologous cell lines. The mink cell line-derived virus (X-NZB/K-Mlc) reaches titers in culture of over 10(8) infectious viruses/ml, and is produced in high titer within 24 hr after infection of mink lung cells. The human and dog cell-derived NZB viruses (X-NZB/K-Huc and X-NZB/K-Dgc) grow to lower titers and are similar in many respects. They differ in their relative ability to replicate in dog and human cells and to transform mink S+L- cells. Peptide mapping studies indicate that the X-NZB/K-Mlc virus has a unique p15(E) protein which distinguishes it from the other two cloned NZB viruses. These results lend further support to the observation that several types of xenotropic virus are present in a mouse strain and that more than one virus can be expressed by one organ of a particular mouse.     

Comparison of guinea pig cytomegalovirus and guinea pig herpes-like virus: growth characteristics and antigentic relationship.

The growth characteristics of guinea pig cytomegalovirus (GPCMV) and guinea pig herpes-like virus (GPHLV) in cell cultures were compared. Guinea pig fibroblast cells were highly susceptible to infection with both viruses, whereas guinea pig kidney cells were sensitive only to GPHLV. No cytopathic effect was observed in the latter cell system after infection with GPCMV,nor was there an increase in virus titer, although the cirus persisted in the kidney cells for 2 to 3 weeks postinfection. Electron microscope studies showed nonvirion tubular structures in GPCMV -infected fibroblast cells, but not in GPHLV- infected cells. Large packages of enveloped nuclear virus particles were commonly seen in GPHLV -infected cells, especially kidney epithelial cells, but none were found in the GPCMV -infected fibroblasts. Complete enveloped extracellular virus particles were present in both virus-cell systems. Both viruses showed narrow host spectra and replicated well only in guinea pig cells although GPHLV multiplied to some degree in rabbit cells. No antigenic relationship could be demonstrated between the two viruses using antisera specific for each virus that was produced in rabbits and guinea pigs. Rabbits produced high neutralizing antibody titers to GPHLV, whereas guinea pigs were the animals of choice for GPCMV antiserum production.     

大鼠CD86基因RNAi慢病毒载体的构建与功能鉴定

目的 构建大鼠CD86基因的RNAi慢病毒载体并在大鼠原代培养树突状细胞(DC)上鉴定其基因沉默效率.方法 将筛选获得的大鼠CD86基因特异性siRNA靶点,合成短发卡结构shRNA序列并退火成双链DNA,与pgC-GFP慢病毒载体重组形成shRNA表达载体,利用PCR和测序鉴定获得连接正确的克隆.经由293T细胞包装shRNA慢病毒颗粒,随后将其感染原代培养的大鼠Dc细胞,采用real-time PCR和Western blot的方法检测靶基因在mRNA和蛋白水平的沉默效率.结果 构建的慢病毒载体shRNA的PcR鉴定和测序正确,shRNA慢病毒颗粒感染大鼠DC细胞后CD86基因的mRNA表达量较阴性对照载体慢病毒感染组下降了90.6%;蛋白表达显著抑制.结论 成功构建了大鼠CD86基因的shRNA慢病毒表达载体,能够在大鼠DC细胞上有效沉默靶基因.