High-level sustained transgene expression in human embryonic stem cells using lentiviral vectors

Here we describe the sustained expression of transgenes introduced into human embryonic stem (ES) cells using self-inactivating lentiviral vectors. At low multiplicity of infection, vesicular stomatitis virus-pseudotyped vectors containing a green fluorescent protein (GFP) transgene under the control of a human elongation factor 1alpha promoter transduced human ES cells at high efficiency. The majority of the transduced ES cells, which harbored low numbers of integrated vectors, continued to express GFP after 60 days of culture. Incorporation of a scaffold attachment region (SAR) from the human interferon-beta gene into the lentiviral vector backbone increased the average level of GFP expression, and inclusion of the SAR together with a chromatin insulator from the 5' end of the chicken beta-globin locus reduced the variability in GFP expression. When the transduced ES cells were induced to differentiate into CD34(+) hematopoietic precursors in vitro, GFP expression was maintained with minimal silencing. The ability to efficiently introduce active transgenes into human ES cells will facilitate gain-of-function studies of early developmental processes in the human system. These results also have important implications for the possible future use of gene-modified human ES cells in transplantation and tissue regeneration applications.     

Sustained long-term engraftment and transgene expression of peripheral blood CD34+ cells transduced with third-generation lentiviral vectors

As mobilized peripheral blood (MPB) represents an attractive cell source for gene therapy, we investigated the ability of third-generation lentiviral vectors (LVs) to transfer the enhanced green fluorescent protein gene into MPB CD34(+) cells in culture conditions allowing expansion of transplantable human hematopoietic stem cells. To date, few studies have reported transduction of MPB cells with vesicular stomatitis virus G pseudotyped LVs. The critical issue remains whether primitive, hematopoietic repopulating cells have, indeed, been transduced. In vitro (5 weeks' culture in FLT3 ligand + thrombopoietin + stem cell factor + interleukin 6) and in vivo (serial transplantation in NOD/SCID mice) experiments show that MPB CD34(+) cells can be effectively long-term transduced by LV and maintain their proliferation, self-renewal, and multilineage differentiation potentials. We show that expansion following transduction improves the engraftment of transduced MPB CD34(+) (4.6-fold expansion of SCID repopulating cells by limiting dilution studies). We propose ex vivo expansion after transduction as an effective tool to improve gene therapy protocols with MPB. Disclosure of potential conflicts of interest is found at the end of this article.     

携人PTHLH基因慢病毒表达载体的构建

目的构建携带人甲状旁腺相关激素（PTHLH）基因的慢病毒表达载体pGC-FU/PTHLH。方法酶切载体pGC-FU,根据人PTHLH基因合成特定引物,扩增目的基因片段,将其克隆到pGC-FU质粒（含EGFP基因）上,菌落PCR鉴定及测序分析重组载体,使用Lipofectamine 2000诱导转染pGC-FU、pHelper1.0和pHelper2.0载体三质粒进入293T细胞包装慢病毒,并用带PTHLH的慢病毒感染293T细胞和鼻咽癌CEN1细胞确认慢病毒包装是否成功。结果菌液PCR产物琼脂糖凝胶电泳鉴定显示,与理论预计值阳性转化子735bp,阴性转化子198bp基本相吻合;PCR鉴定阳性的克隆进行测序和比对分析,结果完全匹配,进一步鉴定载体构建成功。分别将质粒包装系统共转染293T细胞,包装产生空白对照慢病毒（pGC-FU）和过表达PTHLH的慢病毒（pGC-FU/PTHLH）;或用携带PTHLH和EGFP基因的病毒上清感染CNE1细胞,48h后,倒置荧光显微镜下观察293T和CNE1细胞,均可见绿色荧光,转染成功。结论成功构建携人PTHLH基因慢病毒表达载体,为进一步研究PTHLH基因在鼻咽癌转移中的作用及鼻咽癌发病分子机制奠定了基础。     

Hybrid HIV/MSCV LTR enhances transgene expression of lentiviral vectors in human CD34(+) hematopoietic cells

HIV-based lentiviral vectors can transduce nondividing cells, an important advantage over murine leukemia virus (MLV)-based vectors when transducing slowly dividing hematopoietic stem cells. However, we find that in human CD34(+) hematopoietic cells, the HIV-based vectors with an internal cytomegalovirus (CMV) promoter express transgenes 100- to 1,000-fold less than the MLV-based retroviral vector murine stem cell virus (MSCV). To increase the expression of the integrated lentivirus, we replaced CMV promoter with that of the Rous sarcoma virus or MSCV and obtained a modest augmentation in expression. A more dramatic effect was seen when the CMV enhancer/promoter was removed and the HIV long-terminal repeat (LTR) was replaced by a novel HIV/MSCV hybrid LTR. This vector retains the ability to transduce nondividing cells but now expresses its transgene (enhanced green fluorescent protein) 10- to 100-fold greater than the original HIV-based vector. When compared under identical conditions, the HIV vector with the hybrid LTR transduced a higher percentage of CD34(+) cells than the MSCV-based retroviral vector (19.4% versus 2.4%). The number of transduced cells and level of transgene expression remain constant over 5-8 weeks as determined by long-term culture-initiating cells, fluoresence-activated cell sorting, and nonobese diabetic/severe combined immunodeficiency repopulation assay.     

携带人c-Myc和EGFP基因慢病毒表达载体的构建

目的构建携带人c-Myc和EGFP基因的慢病毒表达载体pFUMGW。方法 XhoI线性化pLenti-EF1a-c-Myc-IRES-EGFP,回收片段并补平XhoI,接着BamHI酶切该片段,回收2722bp片段而获连接用c-Myc-IRES-EGFP;EcoRI线性化pFUGW,回收并补平EcoRI,然后BamHI酶切该片段,回收9174bp片段获连接用载体片段,最后使用DNA连接试剂盒（TaKaRa）中的SolutionI将其与连接用c-Myc-IRES-EGFP连接,连接产物转化,次日挑选单菌落,提取质粒并行酶切鉴定。所构建载体命名为pFUMGW。获pFUMGW后,按Invitrogen公司推荐的标准程序进行慢病毒包装和确认慢病毒是否成功生产;携带c-Myc和EGFP基因的慢病毒感染人胚肾细胞株293、肿瘤细胞株CNE1和C666以建立相应的病毒感染体系。结果酶切证实成功构建了pFUMGW,按标准程序生产的携带c-Myc和EGFP基因的慢病毒上清高效率感染293、CNE1和C666。结论成功构建携带人c-Myc和EGFP基因的慢病毒表达载体pFUMGW,为相关后续研究打下了良好基础。     

Transduction of umbilical cord blood CD34+ NOD/SCID-repopulating cells by simian foamy virus type 1 (SFV-1) vector

Foamy viruses are nonpathogenic retroviruses that offer unique opportunities for gene transfer into various cell types including hematopoietic stem cells. We used a simian foamy virus type 1 vector (SFV-1) containing a LacZ reporter gene with a titer of 1-5 x 10(6) viral particles/ml that was free of replication-competent retrovirus to transduce human umbilical cord blood CD34+ cells. Transduced CD34+ cord blood cells were transplanted into NOD/SCID mice and plated in serum-free methylcellulose culture to determine the transduction efficiency of human hematopoietic progenitor cells. A transduction efficiency of about 20% was obtained. At 6-10 weeks posttransplantation, human hematopoietic cell engraftment and marking were determined. Marrow from transplanted mice demonstrated human cell engraftment by the presence of human (CD45+) cells containing both CD19+ lymphoid and CD33+ myeloid cells. Serial sampling of NOD/SCID bone marrow revealed the presence of 6.7-14.0% CD45+ cells at 6 weeks posttransplant as compared to 3.6-27.2% CD45+ cells at 9-10 weeks posttransplant. Human progenitors examined from NOD/SCID bone marrow cells 9 weeks posttransplant revealed from 7.4 to 25.9% of the colonies exhibiting X-gal staining. Our study demonstrates the ability of a simian foamy virus vector to transduce the SCID-repopulating cell and offers a promising new gene delivery system for use in hematopoietic stem cell gene therapy.     

人神经生长因子β亚基慢病毒载体的构建

背景：糖尿病神经源性膀胱的发病与神经生长因子缺乏有关,β亚基是构成神经生长因子(NGF)3种亚基中惟一具有生物活性的亚基,慢病毒载体是基因治疗的理想载体。 目的：构建过表达人神经生长因子β亚基(β-NGF)基因的慢病毒载体。 方法：通过目的基因的获得,载体质粒双酶切,载体质粒与目的基因的连接将人β-NGF基因克隆到慢病毒载体质粒pGC-FU中,构建重组慢病毒载体质粒pGC-FU-β-NGF。观察人β-NGF基因的克隆情况,并进行重组慢病毒载体质粒pGC-FU-β-NGF的PCR鉴定和测序。 结果与结论：构建的重组慢病毒载体质粒pGC-FU-β-NGF进行PCR实际获得的产物与预计PCR产物大小一致,即初步判断为构建成功的重组质粒。所获得的β-NGF基因经测序后与GenBank报道序列完全一致。说明pGC-FU-β-NGF中携带有正确的β-NGF基因。结果证实,实验成功构建了携带人β-NGF基因的重组慢病毒载体质粒。     

SPARC基因RNAi慢病毒载体的构建及其在SKM-1细胞中的表达

目的:构建SPARC基因RNAi慢病毒载体获得稳定产毒的细胞,并观察其对人MDS细胞株SKM-1细胞的转染效率及其对SPARC基因的抑制效率。方法:针对已经筛选确定的SPARC基因RNAi有效靶序列,合成靶序列的OligoDNA,退火形成双链DNA,与经AgeⅠ和EcoRⅠ双酶切后的pGCSIL-GFP载体连接产生GC-shSPARC慢病毒载体,PCR筛选阳性克隆并进行测序鉴定。用GC-shSPARC、pHelper1.0和pHelper 2.0载体共转染包装细胞293T细胞,包装产生慢病毒,以293T细胞GFP蛋白的表达水平测定病毒滴度,并将获得的重组慢病毒GC-shSPARC转染SKM-1细胞,通过荧光显微镜检测转染后GFP表达情况,测定转染效率;RT-PCR和Western blot分别验证转染后SKM-1细胞SPARC mRNA及蛋白的表达。结果:经测序证实,构建出了SPARC shRNA的慢病毒载体GC-sh SPARC。包装、浓缩病毒悬液的滴度为1×109TU/mL。荧光显微镜下能直接观察到转染组细胞的GFP表达,转染效率为70%,RT-PCR、Western blot技术分别检测到GC-shSPARC慢病毒转染SKM-1细胞SPARC mRNA、SPARC蛋白表达水平较空白组明显降低(P<0.05)。结论:成功构建SPARC基因RNAi慢病毒载体,其能高效干扰SKM-1细胞SPARC基因的表达。     

Appearance of human plasma cells following differentiation of human B cells in NOD/SCID mouse spleen

Relatively little is known for the differentiation and maturation process of human B cells to plasma cells. This is particularly important in reconstitution work involving transfer of autoantibodies. To address this issue, we transplanted human peripheral blood mononuclear cells (PBMC) directly into the spleen of irradiated NOD/SCID mice depleted of natural killer cell activity. Within 6 weeks, naive B cells differentiated into memory B cells and, importantly, the numbers of human CD138+ plasma cells in spleen increased by 100 fold after transplantation. Plasma cell numbers correlated with the detection of human IgM and IgG in serum, indicating that human B cells had differentiated into mature plasma cells in the murine spleen. In addition to CD19+ plasma cells, a distinct CD19- plasma cell population was detected, suggesting that downregulation of CD19 associated with maturation of plasma cells occurred. When purified human B cells were transplanted, those findings were not observed. Our results indicate that differentiation and maturation of human B cells and plasma cells can be investigated by transplantation of human PBMC into the spleen of NOD/SCID mice. The model will be useful for studying the differentiation of human B cells and generation of plasma cells.     

Efficient transduction of cytotoxic and anti-HIV-1 genes by a gene-regulatable lentiviral vector

Lentiviral vectors modified from human immunodeficiency virus type 1 (HIV-1) offer a promising approach for gene therapy, facilitating transduction of genes into non-dividing cells both in vitro and in vivo. When transducing cytotoxic or anti-HIV genes, however, the vector must avoid self-inhibition by the transgene that can lead to a disruption in production of infectious virions. In this study, we constructed two HIV-1-based lentiviral vectors harboring the mifepristone-inducible gene expression unit in either the forward or the reverse orientation with respect to the direction of viral genomic RNA. The ability of these vectors to transduce cytotoxic and anti-HIV genes was evaluated. When human CD14 was used as a transgene, infectious lentiviral vectors were produced by both forward and reverse vector systems. CD14 expression was efficiently induced in cells transduced by both lentiviral vectors following treatment with mifepristone. However, a higher level of basal transgene expression was observed in the forward vector system in the absence of mifepristone. In contrast, high titers of infectious lentiviral vector containing the cytotoxic vesicular stomatitis virus M gene were successfully generated using the reverse vector, but not the forward vector. In addition, when a VPS4B-dominant negative mutant against HIV-1 budding was cloned into the reverse vector, significant amounts of lentiviral vector were obtained. Subsequent transduction of cells with the VPS4B mutant resulted in approximately 50% inhibition of HIV-1 production only in the presence of mifepristone. Our study thus demonstrates that incorporation of a mifepristone-regulatable gene expression unit in the reverse orientation makes significant advances toward development of a lentiviral vector that allows transduction of harmful genes.     

Efficient lentiviral transduction and improved engraftment of human bone marrow mesenchymal cells

Human bone marrow (BM) mesenchymal stem/progenitor cells are potentially attractive targets for ex vivo gene therapy. The potential of lentiviral vectors for transducing BM mesenchymal cells was examined using a self-inactivating vector that expressed the green fluorescent protein (GFP) from an internal cytomegalovirus (CMV) promoter. This vector was compared with oncoretroviral vectors expressing GFP from the CMV promoter or a modified long-terminal repeat that had been optimized for long-term expression in stem cells. The percentage of GFP-positive cells was consistently higher following lentiviral versus oncoretroviral transduction, consistent with increased GFP mRNA levels and increased gene transfer efficiency measured by polymerase chain reaction and Southern blot analysis. In vitro GFP and FVIII expression lasted for several months post-transduction, although expression slowly declined. The transduced cells retained their stem/progenitor cell properties since they were still capable of differentiating along adipogenic and osteogenic lineages in vitro while maintaining high GFP and FVIII expression levels. Implantation of lentivirally transduced human BM mesenchymal cells using collagen scaffolds into immunodeficient mice resulted in efficient engraftment of gene-engineered cells and long-term transgene expression in vivo. These biocompatible BM mesenchymal implants represent a reversible, safe, and versatile protein delivery approach because they can be retrieved in the event of an unexpected adverse reaction or when expression of the protein of interest is no longer required. In conclusion, efficient gene delivery with lentiviral vectors in conjunction with the use of bioengineered reversible scaffolds improves the therapeutic prospects of this novel approach for gene therapy, protein delivery, or tissue engineering.     

人EGFL7基因RNA干扰慢病毒载体的构建及其在人喉癌细胞中的表达

 目的：构建人表皮生长因子样结构域7（epidermal growth factor-like domain 7, EGFL7）基因RNA干扰（RNA interference, RNAi）慢病毒表达载体,并建立稳定干扰EGFL7基因表达的喉癌细胞亚系,为研究EGFL7蛋白在喉癌发生发展中的功能奠定基础。方法：针对人EGFL7基因序列,设计特异性RNAi靶序列,与pcDNA6.2-GW/EmGFP-miR线性载体定向连接,得到的阳性重组子再与pLenti6.3-MCS/V5-DEST慢病毒载体进行重组,获得真核表达慢病毒干扰载体。在POLOdelivererTM 3000介导下将慢病毒包装质粒和EGFL7基因重组慢病毒载体导入293T细胞包装病毒,测定病毒滴度,感染人喉癌细胞HEp-2,杀稻瘟菌素筛选获得稳定干扰EGFL7基因的细胞亚系。结果：成功构建EGFL7 pLenti6.3-EGFL7-miR真核表达慢病毒干扰载体并获得相应慢病毒,经测定病毒滴度为5×1011 TU/L,实时荧光定量PCR证实pLenti6.3-EGFL7-miR慢病毒载体对喉癌细胞HEp-2 EGFL7基因的沉默效率为97%。结论：成功构建人EGFL7基因特异性的慢病毒干扰载体,并获得EGFL7基因稳定干扰的喉癌细胞亚系。     

携带人血管内皮生长因子165慢病毒表达载体的构建与表达*

背景：已有研究证实血管内皮生长因子在正常肝脏肝部分切除后余肝的再生过程中发挥着重要的作用,但关于其对肝硬化肝脏是否也有相同作用国内外鲜有报道。 目的：构建携带人血管内皮生长因子165基因的慢病毒载体,体外转染BLR 3A大鼠肝细胞并观察该细胞中人血管内皮生长因子165基因的表达。 方法：采用DNA重组技术将人血管内皮生长因子165基因克隆入pLenti6/V5-D-TOPO慢病毒表达载体中,筛选出阳性克隆与慢病毒包装系统ViraPowerTM Packaging Mix共转染293T细胞产生病毒颗粒,通过实时定量-聚合酶链反应法测定病毒滴度;携带人血管内皮生长因子165基因的慢病毒载体体外转染BLR 3A大鼠肝细胞72 h后,利用反转录-聚合酶链反应及Western blot法检测细胞中人VEGF165 mRNA及蛋白的表达。 结果与结论：成功构建了表达人VEGF165基因的慢病毒载体pLenti6/V5-D-TOPO-VEGF165,测得病毒滴度为1.18×     107 VP/mL。重组慢病毒载体转染BLR 3A大鼠肝细胞72 h后,荧光蛋白表达率超过80%,反转录-聚合酶链反应及Western blot法测得转染组人血管内皮生长因子165 mRNA及血管内皮生长因子165蛋白表达阳性。提示构建的携带人血管内皮生长因子165的慢病毒载体可有效转染BLR 3A大鼠肝细胞,并促使该细胞表达人血管内皮生长因子165 mRNA及蛋白。 关键词：人血管内皮生长因子165;慢病毒载体;BLR 3A大鼠肝细胞;转染;基因治疗 doi:10.3969/j.issn.1673-8225.2012.11.007     

Efficient multicistronic expression of a transgene in human embryonic stem cells

The applicability of human embryonic stem cells (hESCs) will be greatly enhanced by techniques that permit efficient genetic modification with multiple transgenes. We report here on single-promoter-driven foot-and-mouth disease virus segment 2A-mediated multicistronic expression of a transgene in hESCs. Efficient multicistronic expression of the transgene was permitted by 2A-mediated separation with almost the same amounts of encoded proteins in hESC. In addition, the multicistronic protein expression was successful in hESC-derived differentiated cells in in vivo and in vitro differentiation assays. This technology may be a significant advance in the genetic engineering of hESCs and hESC-derived cells for purposes that require the reliable expression of multiple transgenes. Disclosure of potential conflicts of interest is found at the end of this article.     

构建人端粒酶催化亚单位基因慢病毒表达载体转染人骨髓基质细胞

背景：骨髓基质细胞不表达端粒酶,因而在体外传代扩增过程中端粒长度逐渐缩短,导致细胞衰老,这是限制其用于细胞治疗应用的一个重要因素。 目的：构建人端粒酶催化亚单位基因慢病毒表达载体,探讨以慢病毒介导的人端粒酶催化亚单位基因修饰人骨髓基质细胞的可行性。 方法：以pReceiver-M02-hTERT质粒为模板PCR扩增获得目的基因。用BP重组系统将目的片段重组到载体pDONR221上。然后使用LR重组系统将目的序列重组到载体pLenti6.3/V5-DEST上。将重组载体与包装质粒充分混合,利用脂质体共转染293FT细胞获得慢病毒颗粒。 结果与结论：成功构建人端粒酶催化亚单位慢病毒表达载体,病毒的平均物理滴度为1.07×10¹² LP/L。以之转染人骨髓基质细胞,目的基因表达水平有显著提升,细胞正确表达人端粒酶反转录酶蛋白。说明以慢病毒介导的人端粒酶催化亚单位基因修饰人骨髓基质细胞能强化细胞表达人端粒酶催化亚单位。     

一种新型慢病毒载体制备体系的改进

目的完善已初步建立的以痘病毒为辅助病毒的慢病毒载体（LV）瞬时制备体系。方法通过同源重组质粒pZIPPY-NEO/GUS,将vTF7-3痘病毒D13L基因的ORF通过同源重组被新霉素基因（neo）以及可视性筛选基因（GUS）替代,制备D13L缺陷性痘病毒（vTF7-3-ΔD13L）。结果经RT-PCR鉴定,D13L基因被完全敲除。制备体系中将vTF7-3-ΔD13L代替vTF7-3后,制备体系培养上清经RT-PCR、Western blotting分别检测到慢病毒载体特异性RNA序列以及特征性p24蛋白的存在,提示系统可以正常制备出慢病毒载体颗粒,并进一步评价了慢病毒载体的感染性。此外,对此系统的动力学特征也进行了初步分析。结论 vTF7-3-ΔD13L制备成功,通过此系统可制备出没有复制性痘病毒污染的慢病毒载体,本研究为该系统的大规模应用奠定了客观基础。     

Lentiviral vector: a useful tool for transduction of human liver endothelial cells

Endothelial cells play multiple roles in pathophysiologic processes and are increasingly being recognized as target cells of gene therapy. Lentiviral vectors derived from human immunodeficiency virus type 1 have an ability to infect both dividing and nondividing cells and currently receive a great deal of attention as an innovative tool for transduction of target cells. The purpose of the present work was to evaluate the efficacy of a lentiviral vector for transducing human liver endothelial cells (HLECs) in vitro. For the present study, a pseudotyped lentiviral vector encoding a green fluorescent protein (GFP) gene, LtV-GFP, was generated by means of FuGENE 6 method and allowed to infect HLECs. Approximately 95% of HLECs were positive for GFP expression after LtV-GFP infection at a multiplicity of infection of 10. Notably, LtV-GFP transduced HLECs had stable and long term GFP expression, showed gene expression of endothelial markers including CD 34, factor VIII, flt-1, KDR/flk-1 and HGF, and maintained in vitro angiogenic potential in a Matrigel assay to the same extent as primarily cultured HLECs. These findings provide evidence that lentivirus based gene delivery is an efficient tool for transduction of endothelial cells that could be considered for cell and gene therapies and hybrid artificial organs.     

Quantitative analysis demonstrates expansion of SCID-repopulating cells and increased engraftment capacity in human cord blood following ex vivo culture with human brain endothelial cells

Initial clinical trials examining the transplantation of ex vivo expanded cord blood (CB) cells have failed to demonstrate an impact on hematopoietic recovery compared with historical unmanipulated CB controls. In this study, we tested whether coculture with primary human brain endothelial cells (HUBECs) could increase the engraftment capacity and repopulating cell frequency within CB CD34+ cells. Quantitative analysis demonstrated that HUBEC coculture for 7 days supported a 19-fold greater number of CD34+ cells and 3.4-fold and 2.6-fold greater severe combined immunodeficient (SCID)-repopulating cell (SRC) frequencies than fresh CB CD34+ cells and liquid suspension-cultured cells. Mice transplanted with day-14 HUBEC-cultured cells showed 4.2-fold higher levels of human engraftment than mice transplanted with day-7 HUBEC-cultured cells, indicating that SRC enrichment continued to occur through day 14. Noncontact HUBEC cultures also maintained SRCs at levels comparable with contact HUBEC cultures, demonstrating that HUBEC-secreted soluble factors critically supported SRC self-renewal. Seeding efficiency studies demonstrated that HUBEC-cultured CB CD34+ cells engrafted nonobese diabetic/SCID marrow at significantly higher levels than either fresh CB CD34+ cells or liquid suspension-cultured CD34+ cells. These studies indicate that the application of HUBEC coculture or HUBEC-conditioned media can potentially improve upon current strategies for the clinical expansion of CB stem cells.