慢病毒载体在RNA干扰中的应用

慢病毒载体是以人类免疫缺陷1型病毒为基础发展起来的基因治疗载体.区别一般的逆转录病毒载体,它对分裂细胞和非分裂细胞均具有感染能力.该载体可以将外源基因有效地整合到宿主染色体上,从而达到持久件表达.在感染能力方面可有效地感染神经元细胞、肝细胞、心肌细胞、肿瘤细胞、内皮细胞、干细胞等多种类型的细胞,从而达到良好的基因治疗效果.RNA干扰技术是近年来发展起来的新技术,通过产生针对特定基因的小分子干扰RNA,能高效特异地抑制特定基因的表达,在探查基因功能和治疗人类疾病方面有广阔的应用前景.     

反义及小干扰RNA对大鼠肝星状细胞金属蛋白酶组织抑制因子-1表达的抑制作用

目的观察以腺相关病毒（AAV）为载体，含有针对大鼠金属蛋白酶组织抑制因子（TIMP）-1的反义RNA及小干扰RNA（siRNA）的重组AAV（rAAV／ANTI-TIMP—1／neo及rAAV／siRNA—TIMP—1／neo）感染大鼠肝星状细胞系HSC—T6后，TIMP—1表达的受抑制情况。方法经聚合酶链反应（PCR）扩增及酶切后连接，将针对TIMP—1的反义RNA片段及甄RNA片段分别构建于AAV载体中并测序鉴定，将其包装成重组病毒后感染大鼠肝星状细胞系HSC—T6，同时设空白对照组。经G418以400ug／m1的浓度筛选30d后，分别应用荧光定量PCR技术及Westernblot检测重组病毒感染组及空白对照组HSC-T6 TIMP-1的基因转录及蛋白质表达水平。结果经PCR、酶切及序列测定证实，两种重组AAV载体质粒（pd16-95／ANTI—TIMP-1／neo和pd16—95／siRNA-TIMP-1／neo）克隆成功。将重组质粒包装成病毒感染HSC—T6细胞30d后，通过荧光定量PCR技术及Westernblot分析显示，重组病毒rAAV／siRNA-TIMP-1／neo组与对照组细胞相比，HSC—T6中的TIMP-1基因的转录被抑制（P〈0．01），且表达水平与对照组相比约下降60％。而rAAV／ANTI—TIMP—1／neo组及空载体组与对照组相比TIMP—1基因的转录及表达水平差异无统计学意义（P〉0．05）。结论通过AAV载体技术重组病毒rAAV／siRNA-TIMP—1／neo可有效地抑制TIMP-1基因的表达，而针对TIMP—1基因全长的重组病毒rAAV／ANTI—TIMP—1／neo对体外培养的HSC—T6细胞TIMP—1基因的转录与表达无明显抑制作用。     

人激肽释放酶腺相关病毒载体的构建及其在人脐静脉内皮细胞中的表达

目的研究人激肽释放酶腺相关病毒载体的构建,观察重组病毒感染人脐静脉内皮细胞株后人激肽释放酶基因的表达。方法将人激肽释放酶基因定向克隆入AAV载体质粒pAAV-MCS中,并与两种辅助质粒pAAV-RC和pHelper共转染293细胞,包装成带有人激肽释放酶基因的重组腺相关病毒(rAAV);收集病毒颗粒并测定病毒滴度。以不同滴度的病毒分别感染人脐静脉内皮细胞,逆转录聚合酶链反应定量检测人激肽释放酶在该细胞中的表达。酶联免疫吸附法测定人脐静脉内皮细胞内人激肽释放酶的含量。结果成功获得了重组人激肽释放酶基因AAV载体,重组病毒滴度为6.2×1010个/L。以滴度分别为1×109个/L、1×108个/L和1×107个/L的病毒感染人脐静脉内皮细胞,与空白对照组比较,人激肽释放酶的表达均有增加(P<0.05),但以1×109个/L组升高最明显(P<0.001)。结论带有人激肽释放酶的重组腺相关病毒滴度可以稳定地达到1010个/L以上,感染人脐静脉内皮细胞后,人激肽释放酶基因在宿主细胞中的表达明显增强。     

通过腺相关病毒载体导入树突状细胞的HBV基因可诱导CTL的活性

乙型肝炎已是一个越来越重要的全球问题，但是还很难治疗。不过免疫学治疗提供了新的有效的治疗措施。3种重组性腺相关病毒（AAV）2型载体分别将HBV基因S，C或X中的任何一个导入专职抗原提呈树突状细胞（DC），可刺激体内细胞毒性T淋巴细胞（CTL）的活性。研究发现这3种携带重组性AAV／HBV抗原病毒的DC其转导有效率为90％。更为重要的是，这3种AAV转导树突状细胞都刺激了快速的，抗原特异性的MHCCTL活性。     

分泌表达PR39重组腺相关病毒对缺氧鸡胚促血管生成的影响

目的 探讨腺相关病毒(AAV)介导的融合基因NT4-TAT-His-PR39对缺氧人脐静脉内皮细胞株ECV304内缺氧诱导因子1α(HIF-1α)表达的影响及其对缺氧环境鸡胚血管生成的影响.方法 PCR技术和T载体克降法克隆PR39基因,将编码PR39、穿膜肽TAT、6×His及NT4信号肽四个基因片段相连.磷酸钙沉淀法获得重组携带NT4-TAT-His-PR39的从V载体,然后AAV-PR39感染ECV304,免疫细胞化学检测ECV304胞内6×His表达情况.在1%O2条件培养ECV304,免疫细胞化学测定AAV-PR39组和PBS组胞内HIF-1α蛋白表达.30只鸡胚随机分为从V-PR39组、EV组和PBS组(各组n=10),分别在鸡胚尿膜囊(CAM)上加AAV-PR39、EV、PBS,然后每组各取5只鸡胚分别在低氧(5%O2)和常氧(21%O2)条件培养.图像软件Image Pro Plus(IPP)分析CAM血管密度.结果 AAV-PR39组ECV304中检测到6×His表达.低氧环境下,AAV-PR39组ECV304中HIF-1α蛋白表达明显高于PBS组,AAV-PR39组CAM血管密度明显大于其他两组.结论重组携带NT4-TAT-His-PR39的AAV载体能在ECV304中分泌表达,并提高缺氧细胞HIF-1α蛋白表达水平.重组AAV载体显著促进缺氧CAM血管生成,而对常氧CAM无此作用.     

腺相关病毒在肝脏移植应用的研究进展

腺相关病毒(AAV)载体已成为当前基因治疗中最有潜力的病毒载体,在肝移植面临的缺血再灌注损害、免疫排斥反应等问题的基因治疗中发挥其独具的优势．他安全,无致病性,低免疫原性,高效转染肝脏并且目的基因长期表达．同时AAV用于肝移植基因治疗又涉及到一些问题,如肝移植中不可避免的缺血再灌注损伤、AAV目的基因表达的峰值延迟现象以及AAV与肿瘤发生的关系等,本文就以上问题进行综述．     

腺相关病毒为载体的基因治疗在肝病应用中的进展

基因治疗是目前医学研究的热点课题。将目的基因转入细胞的方法有很多，包括脂质体包裹转染、电打孔、微注射等，最近以重组病毒为载体的基因治疗因其独特的优势受到关注。比较常用的三大病毒载体是逆转录病毒、腺病毒和腺相关病毒（adeno—associated virus，AAV）。各种病毒载体都有各自的优点和不足，在细胞和动物实验研究中均有大量的应用。但是在临床应用中，逆转录病毒为载体的基因治疗由于在法国的临床试验出现2例白血病病历，     

人肿瘤抑素Tumstatin基因慢病毒表达载体的构建及其蛋白表达

目的 构建Tumstatin基因慢病毒表达载体,进一步研究Tumstatin基因的功能及其在肿瘤治疗中的应用.方法 采用PCR技术从含有Tumstatin基因的质粒pSPORT1-Sfi扩增目的 基因Tumstatin,并将基因克隆到慢病毒载体表达质粒PGC-Fu[含增强型绿色荧光蛋白(EGFP)基因]中,构建慢病毒载体表达质粒pGC-FU-Tum,通过酶切、测序验证Tumstatin基因后,将pGC-FU-Tum质粒和包装质粒pHelper1.0、pHelpe2.0共同转染人胚胎肾上皮细胞系293T细胞,获得携带Tumstatin基因和EGFP基因的重组慢病毒GC-Fu-Tum,并转染人脐静脉血管内皮细胞HUVEC,Wstem blot检测目的 蛋白Tumstatin的表达.结果 pGC-FU-Tum中携有正确的Tumstatin基因;pGC-FUTurn共转染包装细胞293T能产生高浓度的重组慢病毒GC-FU-Tum;目的 基因Tumstatin能被重组慢病毒高效地转导入HUVEC,荧光显微镜下能直接观察到EGFP,Western blot能检测到Tumstatin蛋白在靶细胞中的表达.结论 成功构建了携带Tumstatin基因的重组慢病毒载体;其蛋白表达与EGFP-致..     

miR-133a-3p重组腺相关病毒的构建及抑制LX-2细胞α-SMA基因表达

目的构建miR-133a-3p重组腺相关病毒(recombinant adeno-associated virus, rAAV)过表达载体并转染肝星状细胞,鉴定其转染及干预作用。方法体外培养肝星状细胞株LX-2细胞,试验分为DMEM对照组,AAV8-Scrambled对照组,AAV8-miR-133a-3p组,应用qRT-PCR法检测miR-133a-3p转染表达量,检测胶原蛋白(COL1A1)、-平滑肌肌动蛋白(alpha smooth muscle actin,α-SMA)和TGF-β/Smad信号通路基因的表达量。结果重组腺相关病毒成功构建并转染LX-2细胞,AAV8-miR-133a-3p转染LX-2细胞组的miR-133a-3p相对表达量为11 000±343.10,与DMEM对照组比较差异有统计学意义(t=32.07,P0.01)。AAV8-miR-133a-3p转染组与DMEM组α-SMA mRNA的相对表达量分别为0.42±0.06 vs 1.00±0.09(t=5.72,P0.05),COL1A1 mRNA的相对表达量为0.34±0.03 vs 1.00±0.04(t=12.66,P0.01)。结论重组腺相关病毒成功转染LX-2细胞,且能抑制肝星状细胞纤维化标志物α-SMA的表达,为探讨miR-133a-3p在调控肝星状细胞所致纤维化中的作用奠定了理论基础。     

重组腺病毒载体介导HOSM 基因对胰腺癌细胞PC3体外增殖的抑制作用

目的构建了含人抑瘤素M（HOSM）基因的复制缺陷型重组腺病毒载体AD-HOSM,观察其对人胰腺癌细胞株PC3在体外生长抑制情况。方法通过同源重组方法构建含HOSM基因的缺陷型腺病毒载体AD-HOSM,报告基因AD-GFP检测腺病毒的对胰腺癌细胞系的转染效率;人胰腺癌细胞株PC3转染含HOSM基因的缺陷型腺病毒载体AD-HOSM后,用RT-PCR法检测外源HOSM基因在其中的表达;台盼兰染色、细胞计数法检测AD-HOSM对PC3的体外增殖抑制情况。结果成功构建了重组腺病毒载体AD-HOSM,AD-HOSM对胰腺癌细胞PC3有较高的转染效率,HOSM基因在转染细胞能有效的表达。体外试验示AD-HOSM明显抑制PC3的的生长。结论重组腺病毒介导HOSM表达能有效抑制PC3在体外的增殖,提示重组腺病毒介导的HOSM基因治疗可能成为胰腺癌治疗的候选方案。     

Adeno-associated virus (AAV) vectors achieve prolonged transgene expression in mouse myocardium and arteries in vivo: a comparative study with adenovirus vectors

Plasmid DNA and adenovirus vectors currently used in cardiovascular gene therapy trials are limited by low efficiency and short-lived transgene expression, respectively. Recombinant adeno-associated virus (AAV) has recently emerged as an attractive vector for cardiovascular gene therapy. In the present study, we have compared AAV and adenovirus vectors with respect to gene transfer efficiency and the duration of transgene expression in mouse hearts and arteries in vivo. AAV vectors (titer: 5×10⁸ transducing units (TU)/ml) and adenovirus vectors (1.2×10¹⁰ TU/ml) expressing a green fluorescent protein (EGFP) gene were injected either intramyocardially (n=32) or intrapericardially (n=3) in CD-1 mice. Hearts were harvested at varying time intervals (3 days to 1 year) after gene delivery. After intramyocardial injection of 5 μl virus stock solution, cardiomyocyte transduction rates with AAV vectors were 4-fold lower than with adenovirus vectors (1.5% (range: 0.5–2.6%) vs. 6.2% (range: 2.7–13.7%); P<0.05), but similar to titer-matched adenovirus vectors (0.7%; range: 0.2–1.2%). AAV-mediated EGFP expression lasted for at least 1 year. AAV vectors instilled into the pericardial space transduced epicardial myocytes. Arterial gene transfer was studied in mouse carotids (n=26). Both vectors selectively transduced endothelial cells after luminal instillation. Transduction rates with AAV vectors were 8-fold lower than with adenovirus vectors (2.0% (range: 0–3.2%) vs. 16.2% (range: 8.5–20.2%); P<0.05). Prolonged EGFP expression was observed after AAV but not adenovirus-mediated gene transfer. In conclusion, AAV vectors deliver and express genes for extended periods of time in the myocardium and arterial endothelium in vivo. AAV vectors may be useful for gene therapy approaches to chronic cardiovascular diseases.     

Persistent liver expression of murine apoA-l using vectors based on adeno-associated viral vectors serotypes 5 and 1

Plasma levels of high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein A-l (apoA-l) are inversely related to risk for coronary heart disease. Overexpression of apoA-l inhibits atherosclerosis in animal models. A method of stably expressing apoA-l using somatic gene transfer would be of interest. Pseudotyped adeno-associated virus (AAV) vectors comprised of inverted terminal repeats from AAV serotype 2 have been used for liver-directed gene transfers. We hypothesized that liver-directed gene transfer of apoA-l using vectors based on AAV serotypes 1 and 5 would result in higher-level, prolonged expression of apoA-l and increased HDL-C. To test this hypothesis we injected apoA-l-/- mice via the tail vein with either AAV2, AAV1 or AAV5 vectors encoding the murine apoA-l cDNA driven by the liver-specific thyroxine binding globulin promoter. Plasma levels of murine apoA-l and HDL-C were highest in mice injected with the AAV1-based vector and lowest in mice injected with the AAV2-based vector. Expression of apoA-l was stable up to 1 year after vector injection. These results indicate that AAV5 and AAV1 are more effective vectors for achieving higher levels of stable transgene expression of apoA-l after liver-directed gene transfer than AAV2. Furthermore, AAV1-based vectors generate higher apoA-l levels than AAV5-based vectors. It is possible that the levels of expression achieved using these vectors will be therapeutic in preventing atherosclerosis.     

Variables pertinent to the efficiency of adeno-associated virus (AAV) vectors mediated gene transfer to human vascular endothelial cells.

Factors influencing adeno-associated virus (AAV) - mediated gene transfer to endothelial cells are not fully determined. We tested the variables pertinent to the efficiency of AAV-mediated gene transfer to human vascular endothelial cells (HUVEC) including: (i) kinetics of transduction efficiency of LacZ gene to HUVEC, (ii) the concentration and volume of vector-containing medium, (iii) the period of incubation time of AAV vectors with HUVEC, (iv) the target cell density/proliferation, (v) the duration of transgene expression. There is a dose-response relationship between moi of vectors and transduction efficiency in HUVEC. The higher moi of AAV vectors achieved more than 80% of transduction efficiency in cultured HUVEC. AAV vectors showed incubation time dependent increase in transduction efficiency of LacZ gene to the HUVEC up to 24 h of vector exposure. The foreign gene of AAV vectors preferably transduces the lower density of cells being proliferated. These results indicate that AAV-vector is efficient for gene transfer to HUVEC, and higher moi of vectors or a longer period exposure of vectors to proliferating HUVEC can facilitate efficient tranduction of foreign gene into human vascular endothelial cells in vitro.     

Parvovirus-mediated gene transfer for the haemophilias

Summary.  Gene therapy may revolutionize the treatment of haemophilia. Effective gene therapy requires sustained therapeutic levels of factors IX (FIX) and VIII. Adeno-associated virus (AAV) is a member of the parvovirus family, is a nonpathogenic virus with a broad host cell range, and does not provoke a significant immune response upon infection. These favourable characteristics make AAV a suitable gene transfer vector for factor deficient patients. A new understanding of AAV biology coupled with novel AAV vector designs suggest that the goal of effective gene transfer is within reach. We review here recent advances in AAV vectors used for gene transfer of the haemophilias.     

Novel adeno-associated viruses from rhesus monkeys as vectors for human gene therapy

Tissues from rhesus monkeys were screened by PCR for the presence of sequences homologous to known adeno-associated virus (AAV) serotypes 1-6. DNA spanning entire rep-cap ORFs from two novel AAVs, called AAV7 and AAV8, were isolated. Sequence comparisons among these and previously described AAVs revealed the greatest divergence in capsid proteins. AAV7 and AAV8 were not neutralized by heterologous antisera raised to the other serotypes. Neutralizing antibodies to AAV7 and AAV8 were rare in human serum and, when present, were low in activity. Vectors formed with capsids from AAV7 and AAV8 were generated by using rep and inverted terminal repeats (ITRs) from AAV2 and were compared with similarly constructed vectors made from capsids of AAV1, AAV2, and AAV5. Murine models of skeletal muscle and liver-directed gene transfer were used to evaluate relative vector performance. AAV7 vectors demonstrated efficiencies of transgene expression in skeletal muscle equivalent to that observed with AAV1, the most efficient known serotype for this application. In liver, transgene expression was 10- to 100-fold higher with AAV8 than observed with other serotypes. This improved efficiency correlated with increased persistence of vector DNA and higher number of transduced hepatocytes. The efficiency of AAV8 vector for liver-directed gene transfer of factor IX was not impacted by preimmunization with the other AAV serotypes. Vectors based on these novel, nonhuman primate AAVs should be considered for human gene therapy because of low reactivity to antibodies directed to human AAVs and because gene transfer efficiency in muscle was similar to that obtained with the best known serotype, whereas, in liver, gene transfer was substantially higher than previously described.     

Prevention and reversal of lupus in NZB/NZW mice by costimulatory blockade with adeno-associated virus-mediated gene transfer

OBJECTIVE: To investigate the potency of costimulatory blockade with adeno-associated virus (AAV)-mediated gene transfer in the prevention and reversal of lupus in a murine model. METHODS: AAV vectors expressing CTLA-4Ig or CD40Ig were injected into NZB/NZW mice. Serum levels of transgene expression and autoantibody titers were determined by enzyme-linked immunosorbent assay. The therapeutic effects on proteinuria, renal pathologic features, and survival rate were evaluated. Splenic T cell phenotypes were analyzed by flow cytometry. The humoral immune response to a foreign antigen was also examined in treated mice. RESULTS: A single injection of AAV serotype 8 (AAV8)-CTLA-4Ig in neonatal NZB/NZW mice before the onset of lupus effectively delayed and inhibited autoantibody production, proteinuria, and kidney damage and prolonged their lifespan. In addition, coinjection of AAV8-CTLA-4Ig and AAV8-CD40Ig vectors into neonatal mice achieved a synergistic effect and the best efficacy. The preventive effects were attributed to suppression of CD4+ T cell activation and the transition from naive to memory T cells. Moreover, coinjection of these 2 vectors in adult mice reversed the existing autoantibody levels, suppressed the development of proteinuria, and prolonged their lifespan. The therapeutic effects were found to be dependent on the vector dose. In addition, AAV-mediated long-term gene expression did not severely suppress the host humoral response to foreign antigen. CONCLUSION: Our findings show that delivery of costimulatory inhibitor transgenes by AAV vectors could prevent and reverse lupus in this murine model, suggesting the potential of AAV-mediated gene transfer as an alternative treatment for lupus.     

Total correction of hemophilia A mice with canine FVIII using an AAV 8 serotype

Despite the popularity of adeno-associated virus 2 (AAV2) as a vehicle for gene transfer, its efficacy for liver-directed gene therapy in hemophilia A or B has been suboptimal. Here we evaluated AAV serotypes 2, 5, 7, and 8 in gene therapy of factor VIII (FVIII) deficiency in a hemophilia A mouse model and found that AAV8 was superior to the other 3 serotypes. We expressed canine B domain-deleted FVIII cDNA either in a single vector or in 2 separate AAV vectors containing the heavy- and light-chain cDNAs. We also evaluated AAV8 against AAV2 in intraportal and tail vein injections. AAV8 gave 100% correction of plasma FVIII activity irrespective of the vector type or route of administration.     

Assessing the potential for AAV vector genotoxicity in a murine model

Gene transfer using adeno-associated virus (AAV) vectors has great potential for treating human disease. Recently, questions have arisen about the safety of AAV vectors, specifically, whether integration of vector DNA in transduced cell genomes promotes tumor formation. This study addresses these questions with high-dose liver-directed AAV-mediated gene transfer in the adult mouse as a model (80 AAV-injected mice and 52 controls). After 18 months of follow-up, AAV-injected mice did not show a significantly higher rate of hepatocellular carcinoma compared with controls. Tumors in mice treated with AAV vectors did not have significantly different amounts of vector DNA compared with adjacent normal tissue. A novel high-throughput method for identifying AAV vector integration sites was developed and used to clone 1029 integrants. Integration patterns in tumor tissue and adjacent normal tissue were similar to each other, showing preferences for active genes, cytosine-phosphate-guanosine islands, and guanosine/cytosine-rich regions. [corrected] Gene expression data showed that genes near integration sites did not show significant changes in expression patterns compared with genes more distal to integration sites. No integration events were identified as causing increased oncogene expression. Thus, we did not find evidence that AAV vectors cause insertional activation of oncogenes and subsequent tumor formation.     

DNA synthesis and topoisomerase inhibitors increase transduction by adeno-associated virus vectors.

Viral vectors based on adeno-associated virus (AAV) preferentially transduce cells in S phase of the cell cycle. We recently found that DNA-damaging agents increased the transduction of nondividing cells. However, the optimal concentrations were toxic to cells. Here we show that the transduction of normal human fibroblasts by AAV vectors is increased by prior exposure to DNA synthesis inhibitors, such as aphidicolin or hydroxyurea, and topoisomerase inhibitors, such as etoposide or camptothecin. Transduction efficiencies could be increased > 300-fold in stationary cultures at concentrations that did not affect cell viability or proliferative potential. Both S-phase and non-S-phase cells were affected, suggesting that cellular functions other than replicative DNA synthesis may be involved. Applying these methods to gene transfer protocols should improve prospects for gene therapy by AAV vectors.     

A shortened adeno-associated virus expression cassette for CFTR gene transfer to cystic fibrosis airway epithelia

Adeno-associated viruses (AAVs) such as AAV5 that transduce airway epithelia from the apical surface are attractive vectors for gene transfer in cystic fibrosis (CF). However, their utility in CF has been limited because packaging of the insert becomes inefficient when its length exceeds approximately 4,900-5,000 bp. To partially circumvent this size constraint, we previously developed a CF transmembrane conductance regulator (CFTR) transgene that deleted a portion of the R domain (CFTRDeltaR). In this study, we focused on shortening the other elements in the AAV expression cassette. We found that portions of the CMV immediate/early (CMVie) enhancer/promoter could be deleted without abolishing activity. We also tested various intervening sequences, poly(A) signals, and an intron to develop an expression cassette that meets the size restrictions imposed by AAV. We then packaged these shortened elements with the CFTRDeltaR transgene into AAV5 and applied them to the apical surface of differentiated CF airway epithelia. Two to 4 weeks later, the AAV5 vectors partially corrected the CF Cl(-) transport defect. These results demonstrate that a single AAV vector can complement the CF defect in differentiated airway epithelia and thereby further the development of effective CF gene transfer.