Use of attenuated bacteria as delivery vectors for DNA vaccines

Live, attenuated bacterial vaccines (LBV) are promising candidates for the induction of a broad-based immune response directed at recombinant heterologous antigens and the corresponding pathogen. LBVs allow vaccination through the mucosal surfaces and specific targeting of professional antigen-presenting cells located at the inductive sites of the immune system. A novel approach exploits attenuated intracellular bacteria as delivery vectors for eukaryotic antigen-expression plasmids (so-called DNA vaccines). Candidate carrier bacteria include attenuated strains of Gram-positive and Gram-negative bacteria. These bacteria have been shown to deliver DNA vaccines to human cells in vitro and have also proven their in vivo efficacy in several experimental animal models of infectious diseases and different cancers. The clinical assessment of the safety, immunogenicity and efficacy of these candidate strains will be the next challenging step towards live bacterial DNA vaccines.

Gene therapy on the move

The first gene therapy clinical trials were initiated more than two decades ago. In the early days, gene therapy shared the fate of many experimental medicine approaches and was impeded by the occurrence of severe side effects in a few treated patients. The understanding of the molecular and cellular mechanisms leading to treatment- and/or vector-associated setbacks has resulted in the development of highly sophisticated gene transfer tools with improved safety and therapeutic efficacy. Employing these advanced tools, a series of Phase I/II trials were started in the past few years with excellent clinical results and no side effects reported so far. Moreover, highly efficient gene targeting strategies and site-directed gene editing technologies have been developed and applied clinically. With more than 1900 clinical trials to date, gene therapy has moved from a vision to clinical reality. This review focuses on the application of gene therapy for the correction of inherited diseases, the limitations and drawbacks encountered in some of the early clinical trials and the revival of gene therapy as a powerful treatment option for the correction of monogenic disorders.

Delivery of dsRNA for RNAi in insects: an overview and future directions

RNA interference (RNAi) refers to the process of exogenous double-stranded RNA (dsRNA) silencing the complementary endogenous messenger RNA. RNAi has been widely used in entomological research for functional genomics in a variety of insects and its potential for RNAi-based pest control has been increasingly emphasized mainly because of its high specificity. This review focuses on the approaches of introducing dsRNA into insect cells or insect bodies to induce effective RNAi. The three most common delivery methods, namely, microinjection, ingestion, and soaking, are illustrated in details and their advantages and limitations are summarized for purpose of feasible RNAi research. In this review, we also briefly introduce the two possible dsRNA uptake machineries, other dsRNA delivery methods and the history of RNAi in entomology. Factors that influence the specificity and efficiency of RNAi such as transfection reagents, selection of dsRNA region, length, and stability of dsRNA in RNAi research are discussed for further studies.

Emerging RNA-based drugs: siRNAs, microRNAs and derivates

An emerging new category of therapeutic agents based on ribonucleic acid has emerged and shown very promising in vitro, animal and pre-clinical results, known as small interfering RNAs (siRNAs), microRNAs mimics (miRNA mimics) and their derivates. siRNAs are small RNA molecules that promote potent and specific silencing of mutant, exogenous or aberrant genes through a mechanism known as RNA interference. These agents have called special attention to medicine since they have been used to experimentally treat a series of neurological conditions with distinct etiologies such as prion, viral, bacterial, fungal, genetic disorders and others. siRNAs have also been tested in other scenarios such as: control of anxiety, alcohol consumption, drug-receptor blockage and inhibition of pain signaling. Although in a much earlier stage, miRNAs mimics, anti-miRs and small activating RNAs (saRNAs) also promise novel therapeutic approaches to control gene expression. In this review we intend to introduce clinicians and medical researchers to the most recent advances in the world of siRNA- and miRNA-mediated gene control, its history, applications in cells, animals and humans, delivery methods (an yet unsolved hurdle), current status and possible applications in future clinical practice.

Nucleic acid transfection and transgenesis in parasitic nematodes

Transgenesis is an essential tool for assessing gene function in any organism, and it is especially crucial for parasitic nematodes given the dwindling armamentarium of effective anthelmintics and the consequent need to validate essential molecular targets for new drugs and vaccines. Two of the major routes of gene delivery evaluated to date in parasitic nematodes, bombardment with DNA-coated microparticles and intragonadal microinjection of DNA constructs, draw upon experience with the free-living nematode Caenorhabditis elegans. Bombardment has been used to transiently transfect Ascaris suum, Brugia malayi and Litomosoides sigmodontis with both RNA and DNA. Microinjection has been used to achieve heritable transgenesis in Strongyloides stercoralis, S. ratti and Parastrongyloides trichosuri and for additional transient expression studies in B. malayi. A third route of gene delivery revisits a classic method involving DNA transfer facilitated by calcium-mediated permeabilization of recipient cells in developing B. malayi larvae and results in transgene inheritance through host and vector passage. Assembly of microinjected transgenes into multi-copy episomal arrays likely results in their transcriptional silencing in some parasitic nematodes. Methods such as transposon-mediated transgenesis that favour low-copy number chromosomal integration may remedy this impediment to establishing stable transgenic lines. In the future, stable transgenesis in parasitic nematodes could enable loss-of-function approaches by insertional mutagenesis, in situ expression of inhibitory double-stranded RNA or boosting RNAi susceptibility through heterologous expression of dsRNA processing and transport proteins.

Insect transgenesis: current applications and future prospects

The ability to manipulate the genomes of many insects has become a practical reality over the past 15 years. This has been led by the identification of several useful transposon vector systems that have allowed the identification and development of generalized, species-specific, and tissue-specific promoter systems for controlled expression of gene products upon introduction into insect genomes. Armed with these capabilities, researchers have made significant strides in both fundamental and applied transgenics in key model systems such as Bombyx mori, Tribolium casteneum, Aedes aegypti, and Anopheles stephensi. Limitations of transposon systems were identified, and alternative tools were developed, thus significantly increasing the potential for applied transgenics for control of both agricultural and medical insect pests. The next 10 years promise to be an exciting time of transitioning from the laboratory to the field, from basic research to applied control, during which the full potential of gene manipulation in insect systems will ultimately be realized.

Effects of combining electrical stimulation with BDNF gene transfer on the regeneration of crushed rat sciatic nerve

BACKGROUND AND AIMS

Various techniques have been investigated to enhance peripheral nerve regeneration including the application of low-intensity electrical stimulation (ES) and the administration of growth factors, especially brain-derived neurotrophic factor (BDNF). The purpose of this study was to investigate the effects of combining short-term (ES) and recombinant adenoviral vector-mediated BDNF (BDNF-Ad) transfer, in comparison to each sole modality, on peripheral nerve regeneration in a rat model with crush-injured sciatic nerve.

METHODS

Sixty male Sprague-Dawley rats (250-300 g) were equally distributed into four groups; the control group, the ES group, the BDNF-Ad group, and the combination group (n = 15 each). A standard crush injury was introduced to the sciatic nerve. The control group received no treatment after injury, the ES group received 30 minutes of low-intensity ES, the BDNF-Ad group received an injection of recombinant BDNF-Ad (concentration = 10(11) pfu/μl, 3 μl/rat) after injury, and the combination group received both ES and BDNF-Ad. The rats were followed-up for 3 weeks.

RESULTS

At the end of the follow-up period, the sciatic function index (ES =-39, BDNF-Ad =-38) and number of the retrogradely labeled sensory neurons were significantly increased in the ES group and the BDNF-Ad group (ES = 326, BDNF-Ad = 264), but not in the combined treatment group, compared to the control group (SFI = -53, retrogradely labeled neurons = 229). Axonal counts were highest in the ES group (7,208 axons), axonal densities in the BDNF group (10,598 axons/mm(2)), and the myelin thickness was greater in both groups as compared to the control group. The combined treatment group showed no signs of superior recovery compared to the other groups.

CONCLUSIONS

Both the ES and the BDNF-Ad treatments were effective techniques enhancing the sciatic nerve regeneration following a crush injury in rats. Nevertheless, the combined treatment with ES and BDNF-Ad produces neither a synergistic effect nor an improvement in this injury model.

Gene therapy for ocular diseases

The eye is an easily accessible, highly compartmentalised and immune-privileged organ that offers unique advantages as a gene therapy target. Significant advancements have been made in understanding the genetic pathogenesis of ocular diseases, and gene replacement and gene silencing have been implicated as potentially efficacious therapies. Recent improvements have been made in the safety and specificity of vector-based ocular gene transfer methods. Proof-of-concept for vector-based gene therapies has also been established in several experimental models of human ocular diseases. After nearly two decades of ocular gene therapy research, preliminary successes are now being reported in phase 1 clinical trials for the treatment of Leber congenital amaurosis. This review describes current developments and future prospects for ocular gene therapy. Novel methods are being developed to enhance the performance and regulation of recombinant adeno-associated virus- and lentivirus-mediated ocular gene transfer. Gene therapy prospects have advanced for a variety of retinal disorders, including retinitis pigmentosa, retinoschisis, Stargardt disease and age-related macular degeneration. Advances have also been made using experimental models for non-retinal diseases, such as uveitis and glaucoma. These methodological advancements are critical for the implementation of additional gene-based therapies for human ocular diseases in the near future.

[Gene doping--current possibilities, risks and means of prevention]

With the advances in gene therapy fears of an abuse in sports arise. The WADA's definition of the term strictly differentiates between gene doping and gene therapy. There are in vivo and ex vivo practices to manipulate the different phases of gene expression in the organism, with viral vectors being looked upon as the most efficient ones. IGF-1, PPARδ, MSTN and EPO play the most important roles in today's scientific research. Their potential was proven in various animal studies, showing a significant improvement of performances. Potential risks for human users include severe immune reactions, mutagenesis, and raised risk for cancer. Big efforts are being put into the development of ways of detection, however until now there are neither practicable methods of control nor any reported cases of manipulated humans. Still, a usage of gene doping that has already taken place cannot be ruled out and is highly likely.

[Worldwide experience and recent trends in gene therapy of ischaemic diseases]

Fifteen odd years have passed since the first application of a gene-therapeutic modality in clinical practice for treatment of lower-limb chronic ischaemia. Over this time, vast experience has been gained worldwide, with not less than one thousand patients treated by gene-based therapies, thus making it possible to generalise the published findings of these clinical trials. Resulting from such an analysis, it should be recognized that the least dangerous gene therapeutic modalities available so far are plasmid ones, with the most efficient being those containing the gene of vascular endothelial growth factor VEGF(165). The most convincing results were obtained while treating chronic ischemia of the lower extremities, whereas gene-based therapy used for treatment of coronary artery disease failed to have yielded, as of yet, clear cut positive results.

Innovations in siRNA research: a technology comes of age

Short interfering RNAs, or siRNAs, belong to a class of RNA species which play a role in both cellular defence and gene regulation. siRNAs comprise a larger portion of the RNA interference pathway that includes the degradation of RNAs which possess complementarily to specific target sequences. This property has given siRNA technology the potential to become a powerful new tool for a wide variety of disciplines, ranging from the design of novel anti-cancer agents to applications in agriculture. The following review outlines patents that have been issued over the past 6 months concerning siRNA technology. Patents are discussed which encompass improved delivery systems for cellular uptake of siRNAs, new therapeutics to combat human diseases, and unique uses of siRNAs to advance plant science. The review also provides detailed lists of the most recent patents that have been issued which cover these areas of siRNA technology, and paves the way for future innovations based on RNA interference in the life sciences.

Advances in synthetic siRNA delivery

The application of RNA interference-based gene silencing technologies has the potential to treat a variety of illness. Preclinical studies and some early clinical trials have already demonstrated the utility of small interfering RNAs (siRNAs) as a potential novel therapy for the treatment of cancer, viral infections, as well as a wide range of additional diseases. To be effective, an siRNA must be taken up by specific cells, enter the cytoplasm, and be loaded onto the Argonaute protein, the catalytic core of the RNA induced silencing complex (RISC) to direct the cleavage of the homologous transcripts. To meet this need, a variety of novel siRNA delivery strategies have been developed. As our understanding of the molecular mechanisms underlying the RNAi pathway has increased so has the ability to rationally design effective silencing and delivery strategies. This review will examine the latest advances in non-viral delivery of siRNA, with special reference to targeted siRNA delivery to specific target tissues and cell types in vivo in preclinical animal models.

Humanized mouse models to study human diseases

PURPOSE OF REVIEW

Update on humanized mouse models and their use in biomedical research.

RECENT FINDINGS

The recent description of immunodeficient mice bearing a mutated IL-2 receptor gamma chain (IL2rgamma) facilitated greatly the engraftment and function of human hematolymphoid cells and other cells and tissues. These mice permit the development of human immune systems, including functional T and B cells, following engraftment of hematopoietic stem cells (HSCs). The engrafted functional human immune systems are capable of T and B cell-dependent immune responses, antibody production, antiviral responses, and allograft rejection. Immunodeficient IL2rgamma(null) mice also support heightened engraftment of primary human cancers and malignant progenitor cells, permitting in-vivo investigation of pathogenesis and function. In addition, human-specific infectious agents for which animal models were previously unavailable can now be studied in vivo using these new-generation humanized mice.

SUMMARY

Immunodeficient mice bearing an IL2rgamma(null) mutated gene can be engrafted with functional human cells and tissues, including human immune systems, following engraftment with human hematolymphoid cells. These mice are now used as in-vivo models to study human hematopoiesis, immunity, regeneration, stem cell function, cancer, and human-specific infectious agents without putting patients at risk.

Progress in siRNA delivery using multifunctional nanoparticles

Nanoparticles made from synthetic polymers have been developed to deliver small interfering RNA (siRNA). For successful siRNA delivery, these nanoparticles need to efficiently encapsulate siRNA, actively target sites of interest, and release siRNA intracellularly. This chapter reviews recent progress using a multifunctional approach to design and engineer polymeric nanoparticles for siRNA delivery.

[Current progress in researches on the gene delivery systems based on nanoparticles technology]

Gene therapy, as a therapeutic treatment for genetic or acquired diseases, is attracting much interest in the research community, leading to noteworthy developments over the past two decades. Although this field is still dominated by viral vectors, novel nonviral gene delivery systems based on nanoparticle technology have recently received an ever increasing attention in order to overcome the safety problems of viral vectors as well as the cytotoxicity of conventional nonviral vectors. This review presented the aspects of bionanotechnology involved in the gene delivery process and explored the recent developments and achievements of inorganic nanodelivery systems for gene transfection.

Gene therapy in transplantation: Toward clinical trials

The genetic modification of organs or cells is an attractive approach to protect allogeneic transplants from acute rejection and other complications. The transplant setting offers a unique opportunity to utilize ex vivo gene therapy for the modification of allogeneic organs and tissues prior to implantation. However, significant challenges exist in the application of this concept to human organ transplantation, including the large number of potential molecular targets, the diversity and safety profile of available vector delivery systems and the merging of gene-based therapies with existing immunosuppressive regimens. Accordingly, many different therapeutic concepts and vector systems have been investigated in preclinical studies with the aim of prolonging allograft survival. However, the translation of promising gene therapy strategies to transplant clinical trials has lagged behind the progress made in other medical fields. This review describes the recent preclinical applications of gene transfer to transplantation, and critically evaluates the degree to which gene therapy has been tested clinically in organ transplant recipients.

siRNA for inflammatory diseases

Infection is generally followed by inflammation; uncontrolled inflammation often precedes multiple organ failure and cancer. In this review, recent developments on the potential use of siRNAs in the treatment of inflammatory diseases of the liver, lung, joints and colon are summarized. Although target identification and a high degree of efficacy of siRNA have been achieved in cell culture studies in vitro, the major challenge has been the identification of acceptable delivery systems for in vivo application. In addition to delivery challenges, off-target effects and interferon response are major hurdles to overcome before a suitable siRNA formulation can be developed as a therapeutic. Nevertheless, recent preclinical and clinical studies have demonstrated promise in the treatment of diseases related to inflammation of the joints, lungs and colon, where delivery of siRNAs can be achieved without systemic administration.

[Comparison of commercialization of transgenic crops in China and world-wide]

Currently, transgenic crops create huge economic, social and ecological benefits with the development of its commercial production. For China, the speed of development and commercialization of transgenic crops is a strategic issue for the sustainable agriculture development and the international competitiveness of our agricultural products. In this paper, we compared and analyzed the status of commercialization of transgenic crops in China and world-wide.

Electrotransfer of therapeutic molecules into tissues

Electroporation is a physical method for the delivery of various molecules into cells by application of controlled external electrical fields that transiently increase permeability of the cell membrane. This technique is now widely used as an alternative to viral gene delivery for transfection of therapeutic genes into different tissues. Gene electrotransfer holds great potential for clinical application due to the ease of preparation of large quantities of endotoxin-free plasmid DNA, the control and reproducibility of this method, and the development of electric pulse generators approved for clinical use. Electroporation has been utilized mainly for DNA vaccination against infectious diseases and cancer. It has also been used for the delivery of other therapeutic genes, mainly cytokines, used in the treatment of various diseases, including cancer, arthritis, multiple sclerosis and inflammation, following organ transplantation. Electroporation as a delivery system for chemotherapeutic drugs, termed antitumor electrochemotherapy, is already at the clinical stage and is being used routinely in several oncology centers in Europe. In addition, the first clinical trials for electrogene therapy of cancer are ongoing. Therefore, it can be presumed that electrotransfer of therapeutic genes into tissues will soon form a validated alternative to viral delivery systems in a clinical setting.