阳离子脂质体在基因转染载体中的研究进展

目前基因治疗面临的首要技术问题是基因药物的载体,用于基因治疗的载体主要分为两大类:病毒载体和非病毒载体.病毒载体可能在体内发生基因的重组或互补,因此具有较大的潜在危险,限制了它在临床基因治疗上的应用[1].非病毒载体中发展最为成熟的是阳离子脂质体(cationic liposomes,CL)载体,它具有可自然降解、无免疫原性、可重复转染等优点,迄今已有数十种阳离子脂质体被用于基因转染[2].该项技术目前已成为基因治疗的研究热点之一,现就其进展综述如下.     

癌基因治疗传递系统研究的新进展

基因治疗的主要目的是开发和利用高效无毒的基因载体，包裹和传递外源性基因材料到靶细胞。病毒型基因载体包括逆转录病毒、腺病毒、单纯疱疹病毒、腺病毒相关病毒和痘病毒，基因传递效率高，但安全性差和基因载量低。非病毒载体包括阳离子聚合物、阳离子多肽和阳离子脂质体，基因传递效率比病毒载体低，但更安全、制备简单、基因包裹率高。     

慢病毒———基因转移的潜在新载体

随着对疾病分子机制认识的加深及生物技术的发展，基因治疗已成为治疗感染性疾病、遗传疾病、神经系统疾病以及肿瘤的新焦点。用于基因治疗的载体系统可分为病毒性载体和非病毒性载体两类。目前常用的病毒载体包括逆转录病毒载体、腺病毒载体、腺相关病毒载体、疱疹病毒载体、痘苗病毒载体等，但是这些载体均存在不足之处，严重影响了基因治疗的有效性及安全性。在基因治疗中广泛应用的逆转录病毒载体存在的主要问题，是无法高效转导非分裂期细胞，而腺病毒载体虽然能转导非分裂期细胞，但在体内不能实现目的基因稳定的长期表达，且反复应用容易引起免疫反应。慢病毒载体不但可以感染非分裂期细胞，还具有容纳外源性目的基因片段大、免疫反应小等优点，在基因治疗中具有广泛的应用前景。现以HIV-1为例，就慢病毒载体的生物学特征、慢病毒载体的构建、在基因治疗中的应用以及生物安全性等方面作一综述。     

卵巢癌基因治疗的新进展

卵巢癌是恶性度最高的妇科肿瘤之一，由于手术和化疗的不尽人意，基因治疗是当今肿瘤研究的热点。卵巢癌的基因治疗载体主要分为病毒载体系统和非病毒载体系统。其中，腺病毒载体转染效率较高，是目前基因治疗的主要手段和最有前途的载体。卵巢癌的基因治疗策略有分子化学治疗，基因替代和免疫系统的基因调控。由于这一领域的迅速发展，卵巢癌的基因治疗有着光明的前景。     

减毒沙门菌载体在肿瘤基因治疗中的研究进展

目前基因治疗发展迅速,肿瘤基因治疗方法已经逐步从实验及基础研究过渡到临床试用阶段,理论和技术层次上日趋成熟。然而基因治疗还没达到完全安全、高效、准确的目标,其中基因治疗的载体是最受关注问题之一。合适的载体应具备最大的有效性和最小的毒性,传统生物类载体主要是病毒载体和非病毒载体。目前低毒或无毒的且具有靶向性感染特点的细菌载体在肿瘤基因治疗得到证实,充分说明了细菌载体开辟抗肿瘤治疗的新途径。本文就减毒沙门菌作为载体在肿瘤基因治疗中的应用综述如下。     

慢病毒——基因转移的潜在新载体

随着对疾病分子机制认识的加深及生物技术的发展,基因治疗已成为治疗感染性疾病、遗传疾病、神经系统疾病以及肿瘤的新焦点。用于基因治疗的载体系统可分为病毒性载体和非病毒性载体两类。目前常用的病毒载体包括逆转录病毒载体、腺病毒载体、腺相关病毒载体、疱疹病毒载体、痘苗病毒载体等,但是这些载体均存在不足之处,严重影响了基因治疗的有效性及安全性。在基因治疗中广泛应用的逆转录病毒载体存在的主要问题,是无法高效转导非分裂期细胞,而腺病毒载体虽然能转导非分裂期细胞,但在体内不能实现目的基因稳定的长期表达,且反复应用容易引…     

阳离子聚合物在乳腺癌基因治疗中的研究进展

乳腺癌是女性最常见的恶性肿瘤之一,难以治愈且对标准治疗产生抗药性的乳腺癌常与基因的改变有关,快速发展的基因治疗为乳腺癌治疗提供了新思路。目前,基因载体分为病毒载体和非病毒载体两大类,相对于病毒载体,非病毒载体中的阳离子聚合物,由于其低免疫原性、安全性高、结构可修饰和制备简单等特点,是一类极具应用前景的基因载体。本文就阳离子聚合物作为基因载体在乳腺癌治疗中的研究进展进行综述。     

基因治疗产品及其载体的研究进展和挑战

基因治疗是一种通过改变个体的基因表达来治疗疾病的方法，为肿瘤、罕见病及其他难治性疾病提供了全新的治疗策略。基因治疗通过基因编辑技术实现对个体致病基因的改造，同时也依赖基因递送载体改善其在体内的稳定性和靶向性。本综述简述了基因治疗的方式，结合目前的基因治疗产品，介绍了病毒、非病毒基因递送载体和基因编辑技术在基因治疗中的发展概况，并总结归纳了临床实践中基因治疗的安全性问题。     

肝癌的基因治疗探讨

本研究探讨肝癌基因治疗的载体及治疗策略。根据临床实践及相关文献资料,分析肝癌的基因治疗载体及临床治疗策略。肝癌的基因治疗载体为病毒、非病毒载体,治疗方法为诱导癌细胞凋亡、抑制肿瘤血管生成及激活机体免疫系统等。肝癌为常见的癌症,探讨基因治疗载体及方法,具有重要的临床价值。     

基因治疗的载体系统及应用

目前的基因载体系统可分为病毒载体和非病毒载体。利用病毒载体介导的基因转移 ,以其高转染率和良好靶向性成为肿瘤基因治疗中应用最广泛的方法。非病毒载体由于其非免疫性和易于生产性而逐渐引起学者瞩目。基因治疗是一种用正常基因取代缺陷基因的治疗 ,目前主要用于肿瘤治疗 ,同时在基因治疗造血细胞疾病、心血管疾病、风湿性关节炎方面 ,已在动物试验中取得一定进展。1　基因载体系统本文介绍几种将外源基因引入宿主细胞的转移方法 ,这些方法可使外源基因短期 (数天 )或长期 (数星期或数年 )稳定的表达[1] 。通常可将这些方法分为病毒载…     

Prospects for cationic polymers in gene and oligonucleotide therapy against cancer

Gene and antisense/ribozyme therapy possesses tremendous potential for the successful treatment of genetically based diseases, such as cancer. Several cancer gene therapy strategies have already been realized in vitro, as well as in vivo. A few have even reached the stage of clinical trials, most of them phase I, while some antisense strategies have advanced to phase II and III studies. Despite this progress, a major problem in exploiting the full potential of cancer gene therapy is the lack of a safe and efficient delivery system for nucleic acids. As viral vectors possess toxicity and immunogenicity, non-viral strategies are becoming more and more attractive. They demonstrate adequate safety profiles, but their rather low transfection efficiency remains a major drawback. This review will introduce the most important cationic polymers used as non-viral vectors for gene and oligonucleotide delivery and will summarize strategies for the targeting of these agents to cancer tissues. Since the low efficiency of this group of vectors can be attributed to specific systemic and subcellular obstacles, these hurdles, as well as strategies to circumvent them, will be discussed. Local delivery approaches of vector/DNA complexes will be summarized and an overview of the principles of anticancer gene and antisense/ribozyme therapy as well as an outline of ongoing clinical trials will be presented.     

Chitosan-DNA nanoparticles as non-viral vectors in gene therapy: strategies to improve transfection efficacy.

Currently, the major drawback of gene therapy is the gene transfection rate. The two main types of vectors that are used in gene therapy are based on viral or non-viral gene delivery systems. The viral gene delivery system shows a high transfection yield but it has many disadvantages, such as oncogenic effects and immunogenicity. However, cationic polymers, like chitosan, have potential for DNA complexation and may be useful as non-viral vectors for gene therapy applications. Chitosan is a natural non-toxic polysaccharide, it is biodegradable and biocompatible, and protects DNA against DNase degradation and leads to its condensation. The objective of this paper was to summarize the state of the art in gene therapy and particularly the use of chitosan to improve the transfection efficiency in vivo and in vitro.     

Current status of non-viral gene therapy for CNS disorders

ABSTRACT

Introduction: Viral and non-viral vectors have been used as methods of delivery in gene therapy for many CNS diseases. Currently, viral vectors such as adeno-associated viruses (AAV), retroviruses, lentiviruses, adenoviruses and herpes simplex viruses (HHV) are being used as successful vectors in gene therapy at clinical trial levels. However, many disadvantages have risen from their usage. Non-viral vectors like cationic polymers, cationic lipids, engineered polymers, nanoparticles, and naked DNA offer a much safer option and can therefore be explored for therapeutic purposes.

Areas covered: This review discusses different types of viral and non-viral vectors for gene therapy and explores clinical trials for CNS diseases that have used these types of vectors for gene delivery. Highlights include non-viral gene delivery and its challenges, possible strategies to improve transfection, regulatory issues concerning vector usage, and future prospects for clinical applications.

Expert opinion: Transfection efficiency of cationic lipids and polymers can be improved through manipulation of molecules used. Efficacy of cationic lipids is dependent on cationic charge, saturation levels, and stability of linkers. Factors determining efficacy of cationic polymers are total charge density, molecular weights, and complexity of molecule. All of the above mentioned parameters must be taken care for efficient gene delivery.     

Development of recombinant cationic polymers for gene therapy research

Cationic polymers created through recombinant DNA technology have the potential to fill a void in the area of gene delivery. The recombinant cationic polymers to be discussed here are amino acid based polymers synthesized in E. coli with the purpose to not only address the major barriers to efficient gene delivery but offer safety, biodegradability, targetability and cost-effectiveness. This review helps the readers to get a better understanding about the evolution of recombinant cationic polymers; and the potential advantages that they could offer over viral and synthetic non-viral vectors for gene delivery. It also discusses some of the major challenges that must be addressed in future studies to turn recombinant polymers into clinically effective gene delivery systems. Recent advances with the biopolymer design suggest that this emerging new class of gene delivery systems has the potential to address some of the major barriers to efficient, safe and cost-effective gene therapy.     

Cationic lipid vectors for plasmid DNA delivery

Successful gene therapy depends on efficient gene transfer vectors. Viral vectors and non-viral vectors have been investigated extensively. Cationic lipids are non-viral vectors, which resemble traditional pharmaceuticals, display little immunogenicity, and have no potential for viral infection. However, toxicity and low transfection efficiency are two barriers limiting the clinical applications of cationic lipids. Over the last decade, hundreds of cationic lipids have been synthesized to address these problems. In this brief review, we summarized recent research results concerning the structures of DNA/liposomes complexes, some important strategies used to design different classes of cationic lipids, and use of disulfide cationic lipids in plasmid DNA delivery.     

Cationic transfection lipids in gene therapy: successes,set-backs,challenges and promises

The clinical success of gene therapy is critically dependent on the development of efficient and safe gene delivery reagents, popularly known as "Transfection Vectors". The transfection vectors commonly used in gene therapy are mainly of two types: viral and non-viral. The efficiencies of viral transfection vectors are, in general, superior to their non-viral counterparts. However, the myriads of potentially adverse immunogenic aftermaths associated with the use of viral vectors are increasingly making the non-viral gene delivery reagents as the vectors of choice. Among the existing arsenal of non-viral gene delivery reagents, the distinct advantages associated with the use of cationic transfection lipids include their: (a) robust manufacture; (b) ease in handling & preparation techniques; (c) ability to inject large lipid:DNA complexes and (d) low immunogenic response. The present review will highlight the successes, set-backs, challenges and future promises of cationic transfection lipids in non-viral gene therapy.     

Gene expression in an intact ex-vivo skin tissue model following percutaneous delivery of cationic liposome-plasmid DNA complexes

The skin represents an attractive site for the localised gene therapy of dermatological pathologies and as a potential antigen bioreactor following transdermal delivery. Potential also exists for the gene therapy of skin as a cosmetic intervention. The most exploited non-viral gene delivery system involves the complexation of cationic liposomes with plasmid DNA (pDNA) to form lipid:pDNA vectors that protect the DNA from nuclease-mediated degradation and improve transgene-cell interactions. Despite numerous studies examining the potential for these vectors in delivering genes to a variety of keratinocyte models, investigations into the topical application of such complexes to intact skin tissue is limited. This ex-vivo study, conducted with intact skin tissue derived from hairless mice, provides quantitative confirmation that topical administration of cationic lipid:pDNA complexes can mediate uptake and expression of reporter pDNA (33-fold higher compared with control) in viable epidermal tissue. The ex-vivo study design provides for intact skin tissue that has not been subjected to depilatory procedures of potential detriment to stratum corneum barrier function, and can be utilised for the quantitative and efficient examination of a potentially wide range of non-viral gene vectors designed for epidermal expression.     

Cationic lipids containing cyclen and ammonium moieties as gene delivery vectors

In this study, two novel cationic lipids containing protonated cyclen and quaternary ammonium moieties were designed and synthesized as non-viral gene delivery vectors. The structures of the two lipids differ in their hydrophobic region (cholesterol or diosgenin). Cationic liposomes were easily prepared from the lipids individually or from the mixtures of each cationic lipid and dioleoylphosphatidylethanolamine. Several studies including DLS, gel retardation assay, and ethidium bromide intercalation assay suggest that these amphiphilic molecules are able to bind and compact DNA into nanometer particles which can be used as non-viral gene delivery agents. Our results from in vitro transfection show that in association with dioleoylphosphatidylethanolamine, two cationic lipids can induce effective gene transfection in human embryonic kidney 293 cells, although the gene transfection efficiencies of two cationic lipids were found to be lower than that of lipofectamine 2000(TM) . Besides, different cytotoxicity was found for two lipoplexes. This study demonstrates that the title cationic lipids have large potential to be efficient non-viral gene vectors.     

Reducing the immunostimulatory activity of CpG-containing plasmid DNA vectors for non-viral gene therapy

The mammalian innate immune system has the ability to recognise and direct a response against incoming foreign DNA. The primary signal that triggers this response is unmethylated CpG motifs present in the DNA sequence of various disease-causing pathogens. These motifs are rare in vertebrate DNA, but abundant in bacterial and some viral DNAs. Because gene therapy generally involves the delivery of DNA from either plasmids of bacterial origin or recombinant viruses, an acute inflammatory response of variable severity inevitably results. The response is most serious for non-viral gene delivery vectors composed of cationic lipid-DNA complexes, producing adverse effects at lower doses and lethality at higher doses of complex. This review examines the role of immunostimulatory CpG motifs in the acute inflammatory response to non-viral gene therapy vectors. Strategies to neutralise or eliminate CpG motifs within plasmid DNA vectors, and the existing limitations of CpG reduction on improving the safety profile of non-viral vectors, will be discussed.