pcD-awte候选疟疾DNA疫苗制备及其质量相关性分析

本实验室构建的疟疾DNA疫苗经动物试验表明具有很好的免疫原性,为申请临床试验,进行了制备工艺的研究。本研究将含pcD-awte质粒的大肠杆菌DH5α在发酵罐中发酵培养,碱裂解法粗提质粒,再依次通过Sepharose 6FF分子筛层析、Plasmidselect 亲硫吸附层析和Source 30Q离子交换层析精制获得质粒纯品,并对纯品进行质量分析。结果每升培养液可获得质粒纯品43.9mg,质量符合Ferreira等推荐的药用标准。     

CTAB选择性沉淀和纯化质粒DNA工艺的建立

通过直接在大肠杆菌碱裂解上清中加入十六烷基三甲基溴化铵(CTAB), 优化CTAB与质粒DNA量的比例、质粒DNA选择性释放溶液的选择和TritonX-114的使用, 建立了简单、易行的大规模质粒DNA纯化工艺。纯化质粒DNA的质量检测结果显示, CTAB纯化的质粒DNA无菌体RNA污染, 菌体基因组DNA、内毒素和蛋白含量分别小于 100 ng/mg、50 EU/mg和10 mg/mg质粒DNA, OD260/OD280比值介于1.75~1.85之间, 超螺旋质粒DNA的比例大于80%, 该工艺纯化的质粒DNA能达到或接近FDA规定的人用质粒DNA的各项指标, 整个过程不使用动物源性酶和苯酚、氯仿、无水乙醇等有毒或易燃、易爆试剂, 成本低廉, 工艺环保。     

临床用DNA疫苗生产工艺研究进展

DNA疫苗是继传统疫苗和基因工程蛋白亚单位疫苗之后的新一代疫苗,具有很好的市场潜力。DNA疫苗生产工艺的质粒DNA大规模制备技术对DNA疫苗的产业化具有重要意义。本文介绍了DNA疫苗生产工艺的研究进展包括提高质粒DNA产量的策略、发酵后处理工艺、有效去除杂质和分离超螺旋构象质粒DNA的纯化工艺以及DNA疫苗生产相关的质量控制体系等。     

大规模生产制备质粒DNA技术进展

质粒DNA疫苗或基因治疗剂是生物制品的新品种。鉴于质粒DNA表达效率低、持续时间短,需建立一套大规模生产制备质粒DNA的工艺,即发酵、碱性裂解、分离纯化及质量控制。目前质粒DNA大规模生产已经达到千克级水平,一些产品正在进行临床实验。     

大肠杆菌质粒DNA提取方法的优化

目的:简化操作流程,缩短提取时间,降低试验对操作者的危害。方法:该方法去除酚、氯仿等有害试剂,采用LiCl沉淀去除质粒制备物中小片段核酸(包括DNA和RNA);工程菌生长至对数期时通过加入氯霉素后不仅方便质粒DNA的提取过程中蛋白质的去除,而且可使质粒的拷贝数进一步增加,提高质粒DNA产量的目的。结果:实验改进方法所提取的质粒DNA产量高于常规方法,达到20μg/mL。结论:改进方法提取的质粒DNA,其下游的内切酶消化,PCR、重组质粒鉴定、转化大肠杆菌等实验的结果和重复性都令人满意,完全可用于一般的分子生物学研究。     

编码酵母丙氨酸tRNA两个半分子的DNA的克隆

用DNA合成仪合成寡聚脱氧核苷酸。用T4-DNA连接酶把这些寡聚脱氧核苷酸重组成双链DNA。这两个双链DNA的上游是T7-启动子,下游分别编码酵母丙氨酸tRNA的5′半分子(1-35位核苷酸)和3′半分子(35-76位核苷酸)。再把这两个双链DNA克隆到PUC 12质粒中。经点杂交筛选和DNA顺序测定证明克隆是成功的。     

应用PCR技术定向引入DNA小片段的策略

描述一种应用PCR技术定向引入DNA小片段和特异酶切位点的方法。为了获得m2/loxp66EGFPloxp71基因片段。根据EGFP基因序列,设计一对特异引物,上、下游引物分别引入m2/loxp66、loxp71序列和Xhol、Mlu1酶切位点。以pEGFPN1质粒为模板,采用PCR扩增以合成DNA双链,插入到克隆载体pMD18T。对重组子测序结果表明,实现了DNA小片段和酶切位点的定向引入。     

药用昆虫神农洁蜣螂炮制品DNA条形码序列的测定与分析

当药用昆虫被加工炮制成碎块或粉末状态时,其昆虫类别和真伪的鉴别就显得十分困难。未经准确鉴定的药用昆虫会影响临床用药安全。为寻找准确、灵敏且快速的检测方法,采用DNA条形码技术,分别以药用神农洁蜣螂(Catharsius molossus)炮制品药材的完整和破碎个体为研究材料,对其mtCOI基因进行提取、扩增及测序分析,探讨DNA条形码技术对炮制后药用蜣螂鉴定的可行性。通过对不同DNA提取方法的比较,成功从炮制后干燥药材虫体内提取出总DNA并扩增出mtCOI基因片段。测序分析结果表明mtCOI基因序列能够区分神农洁蜣螂和其形态近似种。作为药用神农洁蜣螂DNA条形码标准片段的mtCOI基因序列已投递至GenBank。研究还表明,碎块状药用蜣螂药材中混杂有一定比例的其他昆虫。该结果有助于建立适合加工炮制后药用蜣螂的DNA条形码分子鉴定标准,并为保证临床用药安全提供支持。     

高等植物细胞质雄性不育分子机理的研究进展

从线粒体DNA、叶绿体DNA和线粒体质粒DNA方面较详细地阐述了高等植物细胞质雄性不育的分子机理及最新进展;探讨了细胞核DNA和细胞质DNA之间的相互关系。     

DNA对电穿孔转染效率的影响

以外源红细胞生成素cDNA的表达产物为指标,研究了运载DNA和重组表达质粒的构象对电穿孔转染CHO细胞的效率的影响.结果250mg/L的运载DNA可使外源基因表达水平提高3倍;线性化质粒DNA比超螺旋DNA更适合于用电穿孔方法获得永久表达.这一结果提示,运载DNA的存在和质粒DNA的线性化对提高电穿孔转染CHO细胞的效率是必须的.     

Plasmid DNA production for pharmaceutical use: role of specific growth rate and impact on process design

Application of plasmid DNA as pharmaceutical to be used in gene therapy and vaccination has been investigated intensively in recent years. To be able to provide sufficient material that is in accordance with quality of pharmaceutical grade it is mandatory to gain comprehensive process knowledge which is even requested by regulatory agencies. Regarding plasmid DNA production the specific growth rate has been identified as one of the key parameters. The reduction of specific growth rate results in an increase of plasmid DNA formation. However, quantitative explanations that allow for efficient process development and design are still missing. The presented study proposes a model that clearly demonstrates the relationship between specific growth rate and plasmid formation due to identification of the specific plasmid production rate as relevant key parameter. In addition the model is proved to serve as a useful tool in process development and design.     

Processing of plasmid DNA with ColE1-like replication origin

With the increasing utilization of plasmid DNA as a biopharmaceutical drug, there is a rapidly growing need for high quality plasmid DNA for drug applications. Although there are several different kinds of replication origins, ColE1-like replication origin is the most extensively used origin in biotechnology. This review addresses problems in upstream and downstream processing of plasmid DNA with ColE1-like origin as drug applications. In upstream processing of plasmid DNA, regulation of replication of ColE1-like origin was discussed. In downstream processing of plasmid DNA, we analyzed simple, robust, and scalable methods, which can be used in the efficient production of pharmaceutical-grade plasmid DNA.     

Animal-free production of ccc-supercoiled plasmids for research and clinical applications

The topological structure of plasmid DNA can be characterized by capillary gel electrophoresis (CGE analysis)-an important tool for quality control and stability assessments in DNA storage or application. Hence, a large-scale manufacturing process was developed that allows the removal of undesired open circular (oc) or linear plasmid topologies, bacterial genomic DNA, RNA, proteins as well as lipopolysaccharides (endotoxins) and results in obtaining supercoiled (covalently closed circular, ccc) plasmid DNA in a pure form without using any animal-derived substances. Using CGE, the development and in-line monitoring for pharmaceutical plasmid production starting from fermentation control throughout the whole manufacturing process including the formulated and filled product can be performed the first time in a way conforming to good manufacturing practices (GMP). Plasmid stability data were obtained from analysis of shear effects influencing the plasmid quality in DNA drug delivery formulation and application (e.g. gene gun or jet injection). The physical stability of plasmid DNA is for the first time evaluated in DNA storage experiments on the level of different plasmid forms.     

基因治疗用质粒DNA生产面临的问题及研究进展

基因治疗已成为21世纪一些重大疾病的有效治疗策略,目前携带治疗基因的重组质粒已作为基因药物进入临床研究。对用于基因治疗的生物制品的生产与质量控制都有相当严格的要求。虽然已建立大规模符合药学规格的质粒DNA生产工艺,能满足临床需求,但在这些生产工艺中还存在一些难以克服的瓶颈,如:载体构建、细胞裂解、细菌染色体DNA去除、细菌内毒素去除、生产过程中质量控制等。就近年来大规模生产临床用质粒DNA遇到的相关问题及解决方案作一综述。     

Production of recombinant RNase Ba and its application in downstream processing of plasmid DNA for pharmaceutical use

The demand for new strategies in downstream processing of biopharmaceutical plasmid DNA has increased in response to the importance of nucleic acids as active pharmaceutical ingredients (API) in gene therapy and genetic vaccination. Led by the problematic usage of animal-derived proteins for producing reagents of clinical applications, we present an opportunity of removing RNA prior to chromatographic steps by using a recombinant RNase Ba (barnase of Bacillus amyloliquefaciens) as an alternative to bovine RNase A. An expression vector for RNase Ba production was constructed enabling periplasmic localization of the recombinant protein. Cultivation of the RNase-producing clone showed stable activity (3.6 kU mL(-1) during stationary phase) throughout the cultivation process. After purification the RNase activity was tested and compared to that of commercially available RNase A. RNase Ba showed no DNase activity even after prolonged incubation with plasmid DNA. Thus, it is a suitable substitute for bovine RNase A in pharmaceutical purification processes.     

Quantitation of supercoiled circular content in plasmid DNA solutions using a fluorescence-based method

A method for quantifying the proportion of supercoiled circular (SC) forms in DNA solutions is described. The method (SCFluo) takes advantage of the reversible denaturation property of SC forms and the high specificity of the PicoGreen fluorochrome for double-stranded (ds)DNA. Fluorescence values of forms capable of reversible denaturation after a 5 min heating, 2 min cooling step are normalised to fluorescence values of total dsDNA present in the preparation. For samples with a SC content >20–30%, good regression fits were obtained when values derived from densitometric scanning of an agarose gel and those derived from the SCFluo method were compared. The method represents an attractive alternative to currently established methods because it is simple, rapid and quantitative. During large-scale processing and long-term storage, enzymatic, chemical and shear degradation may substantially decrease the SC content of plasmid DNA preparations. Regulations for pharmaceutical grade products for use in gene therapy and DNA vaccination may require >90% of the plasmid to be in the SC form. In the present study the SC content of 6.9, 13 and 20 kb plasmid preparations that had been subjected to chemical and shear degradation was successfully quantified using the new method.     

Generation of chromosomal DNA during alkaline lysis and removal by reverse micellar extraction

The separation of structurally related impurities from pharmaceutical plasmid DNA by highly scalable purification techniques is a challenge for biochemical engineering. Next to RNA, proteins, and lipopolysaccharides, the chromosomal DNA of the plasmid replicating host has to be removed. Here, we describe the application of reverse micellar extraction for the separation of chromosomal from plasmid DNA. By applying different procedures for alkaline lysis, bacterial lysates with different amounts of chromosomal DNA were generated. A reverse micellar extraction step enabled us to deplete the concentration of this impurity below the required level of 50 mg g⁻¹ of plasmid DNA with almost complete plasmid recovery.     

Streamlined Purification of Plasmid DNA From Prokaryotic Cultures

We describe the complete process of AcroPrep Advance Filter Plates for 96 plasmid preparations, starting from prokaryotic culture and ending with high purity DNA. Based on multi-well filtration for bacterial lysate clearance and DNA purification, this method creates a streamlined process for plasmid preparation. Filter plates containing silica-based media can easily be processed by vacuum filtration or centrifuge to yield appreciable quantities of plasmid DNA. Quantitative analyses determine the purified plasmid DNA is consistently of high quality with average OD_260/280 ratios of 1.97. Overall, plasmid yields offer more pure DNA for downstream applications, such as sequencing and cloning. This streamlined method of using AcroPrep Advance Filter Plates allows for manual, semi-automated or fully-automated processing.     

Production of supercoiled multimeric plasmid DNA for biopharmaceutical application

Production of nucleic acids as an active pharmaceutical ingredient (API) in gene therapy and genetic vaccination is gaining more and more importance. Non-viral vectors like plasmid DNA are currently investigated in various clinical trials. Supercoiled multimeric plasmids are of particular interest for pharmaceutical purpose because they contain multiple copies of a therapeutic gene and can therefore be more efficient vectors. A process for the preparation of Escherichia coli strains replicating dimers, trimers, and tetramers of a 4.6 kb plasmid is presented. Cultivation of these clones on semi-defined glycerol medium in a 7 l bioreactor shows structural stability of dimers and trimers during the whole cultivation process. Plasmid concentrations and selectivities are compared to the corresponding cultivation with the plasmid monomer. Cultivation of the tetramer replicating strain shows a disintegration of the plasmid multimer and reconstitution of the monomer and smaller multimers.     

DNA assay for recombinant pharmaceutical substances using the real-time PCR technique

A real-time PCR procedure is proposed for assaying E. coli residual DNA in the pharmaceutical substance of human recombinant insulin. For the quantitative analysis of the DNA content, an amplification of fragments of the bla gene plasmid DNA and E. coli genomic DNA of the 16S RNA gene were used. The contents of plasmid and genomic DNA were detected both in intermediates at various stages of the insulin purification process and in the finished product.