慢病毒表达双报告基因载体系统的构建及病毒制备

本研究旨在构建萤火虫荧光素酶(firefly luciferase,FLUC)和红色荧光蛋白(red fluorescent protein,RFP)双基因表达的慢病毒载体,并转染特定细胞系(HeLa),观察双基因的表达。采用PCR技术分别扩增FLUC和RFP报告基因,再将报告基因连接到慢病毒表达载体pLenti-Bi-cistronic中,获得具有双报告基因的慢病毒重组质粒pLenti-FLUC-RFP。然后,用脂质体将该慢病毒重组质粒转染293T细胞,收集纯化慢病毒颗粒。最后,测定病毒滴度,并用所获慢病毒感染HeLa细胞,采用荧光显微镜和荧光素酶报告基因检测试剂盒检测RFP和FLUC的表达。结果表明,酶切和测序证明RFP和FLUC基因成功连入目的载体,所构建的pLenti-FLUC-RFP慢病毒重组质粒序列符合预期。经纯化获得的慢病毒滴度为1×107TU/ml。将pLenti-FLUC-RFP转染HeLa细胞系后,在荧光显微镜下可见大量细胞表达RFP,荧光发光检测仪也检测到转染细胞具有较高的荧光素酶活性。结论:本研究成功构建了具有双报告基因的慢病毒重组质粒pLenti-Ⅲ-FLUC-RFP,经纯化获得了高滴度的慢病毒颗粒,该病毒颗粒具有很好的感染活性,为研究间充质干细胞在体内的动态分布奠定了基础。     

Potent inhibition of simian immunodeficiency virus (SIV) replication by an SIV-based lentiviral vector expressing antisense Env

In light of findings demonstrating that the macaque TRIM5alpha protein inhibits infection of cells by human immunodeficiency virus (HIV)-1, simian immunodeficiency virus (SIV)-based lentiviral vectors may have distinct advantages over HIV-1 vectors for the transduction of macaque hematopoietic stem cells. We evaluated the ability of an SIV vector (VRX859) encoding an antisense SIV envelope sequence and enhanced green fluorescent protein (GFP) to inhibit viral replication and to transduce rhesus CD34(+) lymphoid progenitor cells. After infection with homologous SIV strains, CD4(+) cell lines transduced with VRX859 exhibited more than 600-fold inhibition of viral replication compared with control cells. Less inhibition was observed with the divergent SIV strain SIVsmE660. Partial inhibition of a chimeric simian-human immunodeficiency virus, which contains an HIV-1 envelope in an SIV backbone, was observed, suggesting that the SIV vector also contributes to viral inhibition independent of the antisense envelope inhibitor. Transduction of rhesus CD34(+) cells with VRX859 at various multiplicities of infection resulted in transduction efficiencies comparable to those obtained with the HIV vector VRX494. However, when we evaluated transduction of rhesus T lymphocyte progenitors by examining GFP expression in CD4(+) T cells derived from transduced CD34(+) cells, we observed more efficient transduction with the SIV-based vector. GFP(+)CD4(+) T cells derived from VRX859-transduced CD34(+) cells strongly inhibited SIVmac239 replication as compared with control CD4(+) T cells. The ability of this SIV-based vector to mediate potent inhibition of SIV replication, coupled with its efficient transduction of rhesus hematopoietic progenitor cells, make it an important candidate for proof-of-principle experiments of stem cell gene therapy in the SIV-macaque model.     

Lentiviral siRNAs targeting multiple highly conserved RNA sequences of human immunodeficiency virus type 1

The high mutation rate of the human immunodeficiency virus (HIV) makes it difficult for any therapy employing a single anti-HIV targeting mechanism to sustain prolonged effect. In an attempt to explore novel therapy for AIDS, we developed and tested lentiviral small interfering RNA (siRNA) vectors targeting multiple highly conserved regions in the HIV type 1 (HIV-1) genome. The siRNA expression cassette was cloned into an extensively deleted HIV-1-derived lentiviral self-inactivating insulator (SIN) insulator [corrected] vector. Although some of the siRNAs targeting sites were also present in the helper construct of the vector system, the production of these lentiviral siRNA vectors were not significantly affected. When tested against different HIV-1 strains including pNL4-3 (subtype B), p89.6 (subtype B) and p90CF402.1.8 (subtype A/E recombinant), the siRNAs targeting conserved gag, pol, int and vpu, but not U3, nef or U5 regions, efficiently inhibited replication of all three viral strains. These lentiviral siRNA vectors also protected host cells from syncytium-forming macrophage- and T-cell-tropic HIV-1-induced cytotoxicity. Transduction of a long-term chronically infected human lymphoma cell line with lentiviral siRNAs resulted in stable inhibition of HIV-1 replication. Northern analysis showed that both genomic and subgenomic viral RNA species were downregulated. In addition, the viral RNA was inhibited in both the nuclear and cytoplasmic compartments of [corrected] chronically infected cells after prolonged passage, suggesting that [corrected] lentiviral siRNAs have a nuclear effect [corrected] Using these lentiviral siRNA [corrected] vectors, we further demonstrated reduced replication kinetics of HIV-1 in primary human peripheral blood lymphocytes. These results suggest that lentiviral siRNAs targeting multiple conserved HIV-1 sequences holds significant promise for the treatment of HIV-1 infections.     

慢病毒载体介导红色荧光蛋白基因转染人脑胶质瘤干细胞的实验研究

目的 探讨HIV-1来源的慢病毒载体介导红色荧光蛋白(RFP)基因转染人脑胶质瘤干细胞可行性和试验方法.方法用无血清干细胞培养基培养人脑胶质瘤干细胞,然后用细胞免疫荧光染色检测其干细胞特性表面标志物CD133、Nestin表达情况.以HIV-1来源的慢病毒为载体,以RFP基因为目的 的基因转染人脑胶质瘤干细胞,荧光显微镜下观察RFP阳性细胞表达情况及其转染率.MTT法检测转染后细胞与未转染RFP细胞组细胞增殖情况.再次用细胞免疫荧光染色检测转染后脑胶质瘤干细胞表面标志物CD133、Nestin表达情况.结果 红色荧光慢病毒转染胶质瘤干细胞体外连续培养后,RFP在干细胞中稳定表达,在荧光显微镜下即发出红色荧光,并且转染效率高.RFP- lentivirus转染后干细胞与未转染RFP组比较,生长曲线无明显差异,且转染后干细胞表面标志物仍表达阳性.结论 采用HIV-1来源的慢病毒载体介导以RFP基因为生物标记物标记人脑胶质瘤干细胞是可行的,以慢病毒转染对干细胞的生长影响小,转染效率高.     

Silencing of HIV-1 with RNA interference: a multiple shRNA approach.

Double-stranded RNA can induce gene silencing via a process known as RNA interference (RNAi). Previously, we have shown that stable expression of a single shRNA targeting the HIV-1 Nef gene strongly inhibits HIV-1 replication. However, this was not sufficient to maintain inhibition. One of the hallmarks of RNAi, its sequence specificity, presented a way out for the virus, as single nucleotide substitutions in the target region abolished inhibition. For the development of a durable gene therapy that prevents viral escape, we proposed to combine multiple shRNAs against conserved HIV-1 regions. Therefore, we screened 86 different shRNAs targeting highly conserved regions. We identified multiple shRNAs that act as potent inhibitors of virus replication. We show, for the first time, that expression of three different shRNAs from a single lentiviral vector results in similar levels of inhibition per shRNA compared to single shRNA vectors. Thus, their combined expression results in a much stronger inhibition of virus production. Moreover, when we infected cells transduced with a double shRNA viral vector, virus escape was delayed. These results confirm that RNAi has great potential as an antiviral gene therapy approach and support our efforts to develop this strategy for treatment of HIV-1-infected individuals.     

NANOG基因在急性淋巴细胞白血病细胞的表达及其慢病毒干扰载体的构建

本研究探讨NANOG基因在人急性淋巴细胞白血病（ALL）细胞中的表达并构建特异性干扰NANOG表达的慢病毒载体。利用RT—PCR及Westernblot技术检测MOLT4、CCRF—HSB2、Jurkat等ALL细胞系及在我院住院治疗的15例新诊断的ALL患者骨髓细胞中NANOG的表达情况。通过构建携带NANOG特异性shRNA的慢病毒载体包装病毒颗粒,感染MOLT4细胞后经分选获得稳定表达株,并在基因及蛋白水平检测NANOG干扰效率。结果表明,MOLT-4细胞、CCRF—HSB2细胞以及33．3％的ALL患者中可见NANOG基因mRNA的扩增产物及蛋白表达。测序表明,ALL患者及MOLT-4、CCRF—HSB2细胞主要表达NANOGP8mRNA。构建隧病毒干扰质粒pLB-shNANOG-1、pLB-shNANOG-2及pLB—shcontrol,包装病毒颗粒超速离心后病毒滴度达（1．83—3．12）×10^8IU／ml。病毒感染MOLT-4细胞后经流式细胞仪分选获得GFP＋细胞。实时定量PCR及Westernblot证实,两种shRNA可有效下调NANOG基因及蛋白的表达。结论：MOLT4细胞、CCRF．HSB2细胞以及部分ALL患者骨髓细胞中存在NANOG的表达,其主要为NANOGP8mRNA的转录。成功构建了特异性干扰NANOG表达的慢病毒载体,获得可稳定下调NANOG表达的MOLT4细胞株。     

Effective transduction and stable transgene expression in human blood cells by a third-generation lentiviral vector

Difficulty in gene transduction of human blood cells, including hematopoietic stem cells, has hampered the development of gene therapy applications for hematological disorders, encouraging the development and use of new gene delivery systems. In this study, we used a third-generation self-inactivating (SIN) lentiviral vector system based on human immunodeficiency virus type 1 (HIV-1) to improve transduction efficiency and prevent vector-related toxicity. The transduction efficiency of the HIV-1-based vector was compared directly with the Moloney murine leukemia virus (MLV) SIN vector in human leukemia cell lines. Initial transduction efficiencies were almost 100% for the HIV and less than 50% for the MLV vectors. Similar results were observed in 11 types of primary cells obtained from leukemia or myeloma patients. Transgene expression persisted for 8 weeks in cells transduced with the HIV vector, but declined with the MLV vector. In addition, resting peripheral blood lymphocytes and CD34(+) hematopoietic cells were transduced successfully with the HIV vector, but not with the MLV vector. Finally, we confirmed vector gene integration in almost all colony-forming cells transduced with the HIV vector, but not with the MLV vector. In conclusion, this lentiviral vector is an excellent gene transduction system for human blood cells because of its high gene transduction and host chromosome integration efficiency.     

小鼠miR-214重组慢病毒载体的构建和鉴定

目的构建携带miR-214的重组慢病毒表达载体,为研究miR-214的功能和作用机制奠定基础。方法从小鼠基因组DNA扩增miR-214基因,测序鉴定后克隆至pCDH-CMV-MCS-EF1-copGFP慢病毒载体上,测序鉴定、病毒包装后转染HEK293细胞,测定病毒滴度。将重组慢病毒载体感染HEK293细胞,应用萤光定量PCR法检测miR-214表达。结果重组慢病毒载体pCDH-CMV-miR-214-EF1-copGFP测序完全正确,pCDH-CMV-miR-214-EF1-copGFP感染的HEK293细胞中miR-214表达显著增强。结论成功构建小鼠miR-214重组慢病毒载体,并可在HEK293细胞中稳定表达出miR-214,为进一步进行miR-214的功能和机制研究奠定了试验基础。     

The Impact of Unprotected T Cells in RNAi-based Gene Therapy for HIV-AIDS

RNA interference (RNAi) is highly effective in inhibiting human immunodeficiency virus type 1 (HIV-1) replication by the expression of antiviral short hairpin RNA (shRNA) in stably transduced T-cell lines. For the development of a durable gene therapy that prevents viral escape, we proposed to combine multiple shRNAs against highly conserved regions of the HIV-1 RNA genome. The future in vivo application of such a gene therapy protocol will reach only a fraction of the T cells, such that HIV-1 replication will continue in the unmodified T cells, thereby possibly frustrating the therapy by generation of HIV-1 variants that escape from the inhibition imposed by the protected cells. We studied virus inhibition and evolution in pure cultures of shRNA-expressing cells versus mixed cell cultures of protected and unprotected T cells. The addition of the unprotected T cells indeed seems to accelerate HIV-1 evolution and escape from a single shRNA inhibitor. However, expression of three antiviral shRNAs from a single lentiviral vector prevents virus escape even in the presence of unprotected cells. These results support the idea to validate the therapeutic potential of this anti-HIV approach in appropriate in vivo models.     

Tissue-specific restriction of cyclophilin A-independent HIV-1- and SIV-derived lentiviral vectors

The host factor alpha isoform of the tripartite motif 5 (TRIM5alpha) restricts human immunodeficiency virus type 1 (HIV-1) infection in certain non-human primate species. Restriction of HIV-1 is enhanced by binding of the viral capsid to cyclophilin A (CypA) in target cells, although CypA is not absolutely required for restriction in rhesus macaque cells. Simian immunodeficiency virus (SIV) is not restricted by rhesus macaque TRIM5alpha and its capsid does not bind to CypA. Here, the effect of lentiviral CypA dependence on restriction in different tissues was examined by engineering an HIV-1 capsid quadruple mutant (V(86)P/H(87)Q/I(91)V/M(96)I) lentiviral vector (HIV(quad)) that is CypA-independent. Whereas HIV-1 was restricted in rhesus macaque and owl monkey epithelial cells, infection with the HIV(quad) vector was efficient at high viral concentrations. In contrast, HIV(quad) was largely restricted in primary rhesus macaque CD34(+) cells. Human epithelial and primary CD34(+) cells were permissive for HIV-1, HIV(quad) and SIV, whereas transduction of human T cells by HIV(quad) or SIV was impaired. The restrictive human cells did not express increased levels of TRIM5alpha, and restriction was not relieved by abolishing CypA, consistent with HIV(quad) and SIV being CypA-independent. Pseudotyping of lentiviral vectors with the gibbon ape leukemia virus envelope altered their sensitivity to perturbations of the virus-CypA interaction compared to pseudotyping with vesicular stomatitis virus glycoproteins, suggesting that the viral entry pathway modulates restriction. Together, these studies reveal that an HIV-1 capsid quadruple mutant can partially overcome lentiviral restriction in non-human primate epithelial cells, but not in hematopoietic cells. Similarly, human cells vary in their permissiveness for CypA-independent lentiviruses, and suggest the presence of tissue-specific factor(s) that can inhibit lentiviral transduction independently of viral interaction with TRIM5alpha and CypA.     

Potent inhibition of human immunodeficiency virus type 1 replication by conditionally replicating human immunodeficiency virus-based lentiviral vectors expressing envelope antisense mRNA

We describe an HIV-based lentiviral vector that expresses a 1-kb antisense mRNA directed against the HIV-1 mRNAs containing env sequences. The expression of antisense env mRNAs (envAS) does not inhibit the synthesis of p24 expressed from the HIV-1 helper plasmid used to package the vector, as this helper has a deletion in the env gene. This allows the production of high-titer VSV-G pseudotyped lentiviral particles. In challenge experiments using unselected populations of SupT1 cells transduced with this vector, a complete inhibition of HIV-1 replication was observed for long periods of in vitro culture, even at high HIV-1 infectious doses. The potent inhibition of HIV-1 replication by this vector correlated with a low occurrence of mobilization of the vector to previously untransduced cells. The infectivity of the wild-type HIV-1 that escapes inhibition was highly inhibited, suggesting that the vector is providing HIV-1 inhibition of replication not only due to its antisense effect but also by competing for encapsidation and mobilization to noninfected cells.     

G2 cell cycle arrest and cyclophilin A in lentiviral gene transfer.

Lentiviral vectors derived from the human immunodeficiency virus-1 (HIV-1) have a higher propensity to transduce nondividing cells compared to vectors based on oncoretroviruses. We report here that genistein, a previously known protein tyrosine kinase (PTK) inhibitor and G2 cell cycle arrest inducer, significantly enhanced lentiviral transduction in a dose-dependent manner. Increased transduction, as measured by vector expression, was seen in a variety of human cell lines, murine primary lymphocytes, and primary human CD34(+) peripheral blood progenitor cells as well. Increased vector expression was also associated with an increase in vector DNA copy number, as assessed by quantitative PCR. Genistein-mediated G2 cell cycle arrest, rather than PTK inhibition, appears to be the major factor responsible for increased gene transfer. Genistein also increases cyclophilin A (CypA) protein, a cellular protein important for efficient HIV-1 infection. While we show that CypA(-/-) Jurkat cells transduce poorly with lentiviral vectors, genistein does increase gene transfer in CypA-deficient cells. CypA and G2 cell cycle arrest appear to be two independent factors important for efficient lentiviral gene transfer. The role of genistein and other G2-arresting agents may be useful for improving the efficiency of lentiviral gene therapy.     

SIVMAC Vpx improves the transduction of dendritic cells with nonintegrative HIV-1-derived vectors

Lentiviral vector (LV)-mediated gene therapy bears an intrinsic risk of insertional mutagenesis following integration into the host genome. Nonintegrative LVs may offer an alternative avenue at least in nondividing cells where episomal viral DNA persists stably. Owing to their central role in immune system functions, differentiated dendritic cells (DCs) offer an interesting cell target for these vectors. We have previously described that the transduction of DCs with wild-type HIV-1-derived vectors can be considerably improved by providing DCs with noninfectious virion-like particles (VLPs) carrying Vpx (Vpx-VLPs), a nonstructural protein coded by members of the SIV(SM)/HIV-2 lineage that removes a specific restriction to lentiviral infection in these cells. Here, we describe that the transduction efficiency of DCs with nonintegrative HIV-1 vectors can also be improved via Vpx-VLPs that promote the accumulation of complete and episomal viral DNA. In this setting, Vpx increases both the number of transduced cells and the levels of transgene expression. Thus, these results describe a simple procedure by which transduction of differentiated DCs can be achieved at low viral inputs with safer LVs to improve both the number of transduced cells and the levels of transgene expression.