小鼠IL—3 cDNA转化细胞移植体内表达的初步研究

随着基因治疗技术的发展和多个细胞因子基因的克隆，人们提出了供细胞因子的基因治疗的设想，以期为肿瘤、老年性痴呆、严重的造血功能障碍等这样一类难治疾病的治疗另辟蹊径。为改善放射损伤小鼠受抑制的造血功能，我们采用基因治疗的方法，将小鼠ＩＬ－３基因ｃＤＮＡ与逆转录病毒载体重组，转染包装细胞ＰＡ３１７，用其分泌的含ＩＬ－３ ｃＤＮＡ的复制缺陷逆转录病毒感染、转化ＮＩＨ３Ｔ３细胞，从中筛选可在体外分泌ＩＬ－３     

包装细胞系及其在基因治疗研究中的应用

以逆转录病毒作载体的基因转移系统是基因治疗最基本的手段之一包装细胞系的构建是这一系统的重大突破它的主要特性是能将重组逆转录病毒载体包装成具一次感染性的缺失性病毒粒子,以此感染靶细胞,即能将外源基因稳定地整合到靶细胞的基因组上。通过改良,得到了能产生具广泛宿主范围的重组病毒的包装细胞系,并杜绝了辅助病毒的产生。以重组逆转录病毒载体-包装细胞系这一系统已建立了很多体外以至整体动物内基因转移及表达的模型,有力地促进了基因治疗研究的发展。     

提高逆转录病毒介导的基因转导效率的研究

在基因治疗研究中，８０％左右采用逆转录病毒作为基因载体，由于逆转录病毒整合至靶细胞具有选择性，所以如何提高其转导效率便成为许多研究者关注的焦点，并从转导技术方面作了不少探讨。本文报告在进行细胞内免疫抗乙型肝炎病毒（ＨＢＶ）基因治疗研究中，应用４种不同转导条件，对基因转导效率进行比较的结果，以探讨既有实用价值，又能获得满意的转导效率的方法。１　材料和方法１－１　细胞培养　２株含抗ＨＢＶ核心抗原单链抗体基因（ＨＢｃＳＦＶ）的包装细胞系ｐＡ３１７，ＮＩＨ３Ｔ３和人肝癌细胞系Ｈｅｐ３Ｂ，均培养于含１０％…     

重组逆转录病毒载体携带乙型肝炎病毒载体的构建与表达

目的 探索利用逆转录病毒载体表达HBV载体的可能性及复制缺损性HBV能否被正确包装。方法 在逆转录病毒载体中插入表达显性阴性突变体的HBV基因复制单元，制备重组逆转录病毒后分别用以感染Hep G2和2．2．15细胞，免疫荧光法检测细胞内HBV核心抗原的表达，PCR检测上清液中重组HBV颗粒。结果 在包装细胞系PA317中能形成较高滴度的重组逆转录病毒，用以感染Hep G2细胞后，可检出核心抗原的表达。感染2．2．15细胞后，在培养上清液中能检测出突变型HBV颗粒。结论 重组逆转录病毒能携带HBV载体在细胞内表达，并在有野生型HBV提供结构蛋白的前提下，发挥HBV载体的功能，可望用于抗HBV基因治疗。     

逆转录病毒载体介导乙型肝炎病毒反义基因的转录表达

为了探索在真核细胞内转录表达乙型肝炎病毒（ＨＢＶ）反义核酸的方法，用基因重组技术将ＨＢＶ前Ｃ／Ｃ基因（ＰｒｅＣ／Ｃ）和前Ｓ／Ｓ基因（ＰｒｅＳ／Ｓ）片段反向插入逆转录病毒载体质粒，再将重组体分别转染ＰＡ３１７包装细胞，进而获得能够介导ＨＢＶ反义基因向小鼠ＮＩＨ３Ｔ３细胞转移表达的重组逆转录病毒。经分子杂交试验表明，含有ＨＢＶ反义基因的重组逆转录病毒序列已经整合到转染的ＰＡ３１７细胞染色体上；转导的ＮＩＨ３Ｔ３细胞内有ＨＢＶ反义ＲＮＡ转录表达。结论：逆转录病毒载体包装细胞系统能够介导ＨＢＶ反义基因在真核细胞中转录表达，因而有可能利用反义技术和基因转移方法进行抗－ＨＢＶ基因治疗     

细胞内生成的抗整合酶单链抗体阻断HIV—1复制的实验研究

通通细胞内表达抗ＨＩＶ－１整合酶单链抗体（ＩＮ－ｓＦｖ）基因,阻断病毒基因组与缩主细胞基因组的整合,进而抑制病毒复制,探讨该基因载体在ＮＩＶ－１感染基因治疗中应用的意义。方法用带有ＩＮ－ｓＦｖ基因的逆转录病毒表达载体ｐＳＬＸＣＭＶ／ＩＮｓＦＶ转染ＰＡ３１７包装细胞,并用包装后含有目的基因的逆转录病毒转导ＳｕｐＴ１细胞及外周血单个核细胞（ＰＢＭＣ）。以ＨＩＶ－１ＮＬ４－３病毒株感染表达ＩＮ－ｓＦｖ的     

Ⅱ型人多巴胺受体逆转录病毒载体的构建及表达

目的构建人全长耽R基因真核表达载体,研究D2R在帕金森病（PD）中的作用和机制。方法将D,ReDNA片段克隆于pLNCX2逆转录病毒载体,转染成纤维包装细胞系PT67,G418筛选单克隆后进行传代培养,通过原位杂交、免疫组织化学和Western blot检测其表达效果。病毒上清再感染骨髓基质细胞（MSCs）,免疫荧光检测D2R基因表达率。结果成功构建了逆转录病毒表达载体pLNCX2-D2R,原位杂交证实D2R基因在PT-67表达的阳性率为80％以上,免疫组织化学检测可见其蛋白分布在胞浆和胞膜,细胞裂解后Western blot蛋白电泳可检测到约48．84kD的蛋白。经转染D2R基因的PT67细胞能分泌病毒并感染MSCs。结论逆转录病毒介导的D2R基因经PT67细胞包装后,能够产生病毒颗粒,收集含病毒颗粒的上清可进一步感染MSCs,这种经逆转录病毒介导的D2R基因可用来作针对帕金森病进行基因治疗的研究。     

小鼠IL－3 cDNA转化细胞移植体内表达的初步研究

随着基因治疗技术的发展和多个细胞因子基因的克隆，人们提出了供细胞因子的基因治疗的设想，以期为肿瘤、老年性痴呆、严重的造血功能障碍等这样一类难治疾病的治疗另辟蹊径。为改善放射损伤小鼠受抑制的造血功能，我们采用基因治疗的方法，将小鼠ＩＬ－３基因ｃＤＮＡ与逆转录病毒载体重组，转染包装细胞ＰＡ３１７，用其分泌的含ＩＬ－３ｃＤＮＡ的复制缺陷逆转录病毒感染、转化ＮＩＨ３Ｔ３细胞，从中筛选可在体外分泌ＩＬ－３的克隆，将可分泌ＩＬ－３的细胞种植到放射损伤小鼠体内后发现：受体小鼠血清中检出了ＩＬ－３的活性；其外周血白细胞计数升至５５万／ｍｍ３，以成熟中性粒细胞为主；肝、脾脏内有大量各个分化阶段的中性粒细胞。这些结果表明：可以利用基因治疗技术，在体内表达ＩＬ－３，改善机体的造血功能。     

人IFN－γcDNA逆转录病毒载体的构建及其在Lewis肺癌细胞的稳定表达

应用分子克隆技术构建了含８４３ｂｐ的全长人ＩＦＮ－γｃＤＮＡ的逆转录病毒表达载体Ｎ２／ＩＦＮ，采用磷酸钙共沉淀方法转染包装细胞ΨＣＲＥ和ΨＣＲＩＰ，并能得到较高滴度的含病毒颗粒上清。然后应用ΨＣＲＩＰ细胞培养上清的复制缺陷性病毒颗粒感染Ｌｅｗｉｓ肺癌细胞（ＬＬＣ），经过Ｇ４１８筛选克隆得到一株能稳定分泌ＩＦＮ（６４００Ｕ／Ｍ）的克隆，Ｓｏｕｔｈｅｒｎ印迹证实ＩＦＮ－γ基因已插入ＬＬＣ基因组。结果表明，该逆转录病毒载体系统能有效地介导基因转移，并能使目的基因在靶细胞稳定表达。结果为肿瘤基因治疗及制备新型肿瘤疫苗奠定了基础。     

腺苷脱氨酶缺乏症基因异常与基因治疗

腺苷脱氨酶（ＡＤＡ）缺乏症是一种常染色体隐性遗传性疾病。目前研究证明ＡＤＡ编码基因点突变至少可在８个位点上发生，ＡＤＡ缺乏症是重度复合免疫缺陷症（ＳＣＩＤ）的主要病种。也是人类历史上首次进行基因治疗临床实验的一种遗传病，因而其研究倍受重视。研究者在应用于临床治疗前，在细胞水平，低、高等动物水平上进行了系统的基因治疗实验研究。逆转录病毒载体和包装细胞系是ＡＤＡ基因转移的有效途径。美国一４岁女孩患ＡＤＡ缺乏症，经基因治疗获得成功。从而开始了基因治疗新时代。     

Characterization of recombination events leading to the production of an ecotropic replication-competent retrovirus in a GP+envAM12-derived producer cell line

Replication-competent retrovirus (RCR) was identified in a GP+envAM12-derived producer cell, containing the MFG-S-Neo retroviral vector, using a marker rescue assay. Studies were undertaken to determine the origin and structure of this RCR. Receptor interference assays demonstrated that the virus was pseudotyped with an ecotropic envelope. Molecular analysis demonstrated the presence of a MoMLV ecotropic env recombinant where the neomycin resistance gene of the MFG-S-Neo vector was replaced by MoMLV ecotropic env. Additional recombinants linking the retroviral pol gene to neo and the neo gene to MoMLV env were also identified. A full-length MoMLV retroviral genome was detected by nested PCR in the contaminated amphotropic producer cells and in cells infected with its supernatant. Unexpectedly, this was also present in the GP+E86 packaging cells together with a previously undescribed envelope construct possessing a full 5' and 3' LTR, although these cells were consistently negative for the presence of RCR. These anomalies in the GP+E86 packaging cell line result in increased homology with the MFG-S-Neo vector, leading to an increased risk for the production of RCR. Our findings point to a need for increased vigilance when using these packaging lines to generate replication-defective retrovirus.     

逆转录病毒介导的基因治疗中的安全性检测

逆转录病毒介导的基因治疗中安全性的最大危险是产生有复制能力的逆转录病毒（RCR）。本实验对经3T3扩增的样品进行 S~+L~-分析、标记拯救分析和PCR扩增方法检测RCR。比较三种方法,标记拯救分析比S~+L~-分析结果容易判断,且PCR可以从10~5个无病毒基因的细胞中检测出一个带有病毒基因的细胞。3T3扩增可提高灵敏度约10倍。安全性是基因治疗首要考虑的问题,本方法为其提供了保证。     

Biosafety of onco-retroviral vectors

Extensive gene therapy studies in preclinical models and in clinical trials underscore the relative safety of onco-retroviral vectors. Up until recently, no adverse effects have been reported in nearly 2000 patients that were enrolled in gene therapy clinical trials involving onco-retroviral vectors. However, the main safety concern of using onco-retroviral vectors is related to the risk of malignant transformation following oncogene activation due to random onco-retroviral genomic integration. Based on primate studies, there is an apparent low risk of malignancy that is predominately associated with the occurrence of chronic retroviremia resulting from replication-competent retroviruses (RCR), particularly in immunosuppressed recipient hosts. However, in the latest packaging cell lines and vectors, the risk of RCR-generation has been drastically reduced, primarily by minimizing the homologous overlap between vector and helper sequences. Nevertheless, results from a recent preclinical study in mice and a clinical trial in patients suffering from SCID-X1 strongly suggest that onco-retroviral vectors devoid of RCR can contribute to lymphomagenesis by insertional activation of cellular oncogenes. The risk of inadvertent germline transmission of onco-retroviral vectors appears to be low, especially relative to the endogenous rate of germline insertion, which is known to occur naturally in the human population via transmission of endogenous retro-transposons. The strict dependency of onco-retroviral gene transfer on cell division is an important safety advantage that significantly limits the risks of horizontal transmission. Since improved onco-retroviral vectors or transduction protocols may result in an increased number of retroviral integrations per cell, this may concomitantly increase the risk of malignant transformation. The use of suicide genes, self-inactivating vectors and/or chromosomal insulators is, therefore, warranted to further enhance the safety features of onco-retroviral vectors. Detailed analyses of insertion sites combined with long-term clinical follow-up may contribute to a more accurate risk assessment.     

Inducible Vesicular Stomatitis Virus (VSV) L Cell Line for Packaging of Recombinant VSV

Recently, recombinant vesicular stomatitis viruses (VSV) have been developed as high-level expression vectors which serve as effective vaccine vectors in animals. An ideal approach for VSV vector production would be the development of stable packaging cell lines that can produce vector particles without transfection step. In this report, we describe generation of an inducible cell line that expresses the VSV polymerase gene (L) under the control of the reverse tetracycline-controlled transactivator (rtTA) system as a first step to make VSV-based packaging cell lines. Integrated polymerase (L) gene was controlled by an rtetR-dependent promoter in the rtTA-producing BHK cell line. When the cell lines were cultured in the presence of tet (tetracycline) or tetracycline derivative doxycycline, the recombinant VSV and wild type VSV were replicated, whereas in the absence of tet or tetracycline derivative doxycycline, the recombinant VSV was not replicated. Viral supernatants were harvested, diluted, and monitored by plaque assay for the presence of infectious VSV. Plaques of VSV containing an additional sequence encoding the EGFP protein allowed rapid detection of infection. Our results suggest wide applications of other surrogate viruses based on VSV. The availability of stable packaging cell lines represents a step toward the use of a VSV vector delivery system that can allow scale-up production of vector-stocks for gene therapy.     

人脂肪酸合成酶启动子在乳腺癌细胞中的转录活性分析

目的分析人脂肪酸合成酶（FAS）启动子在乳腺癌细胞中的转录活性,并与cerbB2启动子、midkine启动子相比较,为其乳腺癌靶向基因治疗提供依据。方法Western blot和间接免疫荧光法检测FAS蛋白在3种人乳腺癌细胞系SKBR3、MCF-7、MDA-MB-231以及正常成纤维细胞系NIH3T3中的表达。构建pGL3-FAS、pGL3-cerbB2和pGL3-midkine荧光素酶表达载体,并分析其在SKBR3、MCF-7、MDA-MB-231和NIH3T3细胞系中的相对转录活性。结果FAS蛋白在3种乳腺癌细胞系中均有表达,其中在SKBR3细胞中表达量最高,在MDA-MB-231细胞中表达量最低,而在正常成纤维细胞系NIH3T3中不表达。FAS蛋白主要定位于细胞质。FAS启动子在3种乳腺癌细胞系中均具有较强的转录活性,转录活性明显高于强启动子SV40和肿瘤特异性启动子midkine;而在正常成纤维细胞中,转录活性很低。FAS启动子在cerbB2高表达的SKBR3细胞中转录活性最高,与cerbB2启动子相当;在cerbB2表达较弱的MCF-7和MDA-MB-231细胞中的转录活性则明显高于cerbB2启动子。结论FAS启动子在乳腺癌细胞中具有强转录活性,较cerbB2启动子作用范围更广,较midkine启动子转录活性更高,而在正常细胞中转录活性很低,具有良好的乳腺癌靶向性,可作为乳腺癌广谱基因治疗的靶向工具。     

A sensitive and quantitative microassay for the detection of mycoplasma contamination: inhibition of IL-2 dependent cell line proliferation

A simple, rapid and sensitive microassay for mycoplasma detection in cell culture is reported. The assay is based on the fact that culture supernatants from contaminated cells inhibit [3H]thymidine incorporation by an IL-2 dependent mouse cytotoxic T cell line (CTLL). The mechanism of inhibition is related to the production by several mycoplasma strains of a pyrimidine-specific nucleoside phosphorylase which can degrade the radiolabelled thymidine used for the measurement of DNA synthesis. These strains were the commonest contaminants in cultures of 24 cell lines from 5 different sources. To establish the sensitivity of the test to detect mycoplasmas we have also used the inhibition assay to monitor the clearance of mycoplasma from 2 contaminated cell lines.     

Improved detection of replication-competent retrovirus

Recombinant retroviral vectors are the predominant delivery system in human gene therapy protocols. Since contaminating replication-competent retrovirus (RCR) can arise during the production of retroviral vector supernatants, sensitive assays for the screening of supernatants are necessary. In this study, we present a marker rescue assay based upon a Mus dunni cell line stably transduced with a lacZ gene. We show that detection of RCR in vector supernatants by the M. dunni lacZ marker rescue assay or PG-4 S + L — focus-forming assay is equally sensitive. By inoculating test supernatants under centrifugation (which we term spinoculation), we increased the sensitivity of detection of RCR 10 to 100-fold with the PG-4 S + L — and lacZ marker rescue assays. While the spinoculation protocol had no adverse effects on cells, spinoculation of high titer vector supernatants onto PG-4 cells resulted in some cytotoxicity, making identification of RCR positive cultures difficult. However, spinoculation of vector supernatants onto M. dunni lacZ cells resulted in no cytotoxicity, and also partially overcame inhibition of detection of low levels of RCR due to the presence of high titer replication-incompetent vector.