Plasmid DNA is superior to viral vectors for direct gene transfer into adult mouse skeletal muscle

Gene therapy for retinal diseases: From genetics to treatment

The gene therapy approach for retinal disorders has been considered largely over the last decade owing to the favorable outcomes of the US Food and Drug Administration-approved commercial gene therapy, Luxturna. Technological advances in recent years, such as next-generation sequencing, research in molecular pathogenesis of retinal disorders, and precise correlations with their clinical phenotypes, have contributed to the progress of gene therapies for various diseases worldwide, and more recently in India as well. Thus, considerable research is being conducted for the right choice of vectors, transgene engineering, and accessible and cost-effective large-scale vector production. Many retinal disease-specific clinical trials are presently being conducted, thereby necessitating the collation of such information as a ready reference for the scientific and clinical community. In this article, we present an overview of existing gene therapy research, which is derived from an extensive search across PubMed, Google Scholar, and clinicaltrials.gov sources. This contributes to prime the understanding of basic aspects of this cutting-edge technology and information regarding current clinical trials across many different conditions. This information will provide a comprehensive evaluation of therapies in existing use/research for personalized treatment approaches in retinal disorders.

Recent Advances in In Vivo Somatic Cell Gene Modification in Newborn Pups

Germline manipulation at the zygote stage using the CRISPR/Cas9 system has been extensively employed for creating genetically modified animals and maintaining established lines. However, this approach requires a long and laborious task. Recently, many researchers have attempted to overcome these limitations by generating somatic mutations in the adult stage through tail vein injection or local administration of CRISPR reagents, as a new strategy called "in vivo somatic cell genome editing". This approach does not require manipulation of early embryos or strain maintenance, and it can test the results of genome editing in a short period. The newborn is an ideal stage to perform in vivo somatic cell genome editing because it is immune-privileged, easily accessible, and only a small amount of CRISPR reagents is required to achieve somatic cell genome editing throughout the entire body, owing to its small size. In this review, we summarize in vivo genome engineering strategies that have been successfully demonstrated in newborns. We also report successful in vivo genome editing through the neonatal introduction of genome editing reagents into various sites in newborns (as exemplified by intravenous injection via the facial vein), which will be helpful for creating models for genetic diseases or treating many genetic diseases.

Establishment of an Antiplasmodial Vaccine Based on PfRH5-Encoding RNA Replicons Stabilized by Cationic Liposomes

BACKGROUND

Nucleic acid-based vaccines have been studied for the past four decades, but the approval of the first messenger RNA (mRNA) vaccines during the COVID-19 pandemic opened renewed perspectives for the development of similar vaccines against different infectious diseases. Presently available mRNA vaccines are based on non-replicative mRNA, which contains modified nucleosides encased in lipid vesicles, allowing for entry into the host cell cytoplasm, and reducing inflammatory reactions. An alternative immunization strategy employs self-amplifying mRNA (samRNA) derived from alphaviruses, but lacks viral structural genes. Once incorporated into ionizable lipid shells, these vaccines lead to enhanced gene expression, and lower mRNA doses are required to induce protective immune responses. In the present study, we tested a samRNA vaccine formulation based on the SP6 Venezuelan equine encephalitis (VEE) vector incorporated into cationic liposomes (dimethyldioctadecyl ammonium bromide and a cholesterol derivative). Three vaccines were generated that encoded two reporter genes (GFP and nanoLuc) and the Plasmodium falciparum reticulocyte binding protein homologue 5 (PfRH5).

METHODS

Transfection assays were performed using Vero and HEK293T cells, and the mice were immunized via the intradermal route using a tattooing device.

RESULTS

The liposome-replicon complexes showed high transfection efficiencies with in vitro cultured cells, whereas tattooing immunization with GFP-encoding replicons demonstrated gene expression in mouse skin up to 48 h after immunization. Mice immunized with liposomal PfRH5-encoding RNA replicons elicited antibodies that recognized the native protein expressed in P. falciparum schizont extracts, and inhibited the growth of the parasite in vitro.

CONCLUSION

Intradermal delivery of cationic lipid-encapsulated samRNA constructs is a feasible approach for developing future malaria vaccines.

CORP: Gene delivery into murine skeletal muscle using in vivo electroporation

The strategy of gene delivery into skeletal muscles has provided exciting avenues in identifying new potential therapeutics towards muscular disorders and addressing basic research questions in muscle physiology through overexpression and knockdown studies. In vivo electroporation methodology offers a simple, rapidly effective technique for the delivery of plasmid DNA into post-mitotic skeletal muscle fibers and the ability to easily explore the molecular mechanisms of skeletal muscle plasticity. The purpose of this review is to describe how to robustly electroporate plasmid DNA into different hindlimb muscles of rodent models. Further, key parameters (e.g., voltage, hyaluronidase, plasmid concentration) which contribute to the successful introduction of plasmid DNA into skeletal muscle fibers will be discussed. In addition, details on processing tissue for immunohistochemistry and fiber cross-sectional area (CSA) analysis will be outlined. The overall goal of this review is to provide the basic and necessary information needed for successful implementation of in vivo electroporation of plasmid DNA and thus open new avenues of discovery research in skeletal muscle physiology.

Immunological Mechanisms of Vaccine-Induced Protection against SARS-CoV-2 in Humans

The SARS-CoV-2 infection spread rapidly throughout the world and appears to involve in both humoral and cell-mediated immunity. SARS-CoV-2 is attached to host cells via binding to the viral spike (S) proteins and its cellular receptors angiotensin-converting enzyme 2 (ACE2). Consequently, the S protein is primed with serine proteases TMPRSS2 and TMPRSS4, which facilitate the fusion of viral and cellular membranes result in the entry of viral RNA into the host cell. Vaccines are urgently required to combat the coronavirus disease 2019 (COVID-19) outbreak and aid in the recovery to pre-pandemic levels of normality. The long-term protective immunity is provided by the vaccine antigen (or pathogen)-specific immune effectors and the activation of immune memory cells that can be efficiently and rapidly reactivated upon pathogen exposure. Research efforts aimed towards the design and development of vaccines for SARS-CoV-2 are increasing. Numerous coronavirus disease 2019 (COVID-19) vaccines have passed late-stage clinical investigations with promising outcomes. This review focuses on the present state and future prospects of COVID-19 vaccines research and development, with a particular emphasis on immunological mechanisms of various COVID-19vaccines such as adenoviral vector-based vaccines, mRNA vaccines, and DNA vaccines that elicits immunological responses against SARS-CoV-2 infections in humans.

A DNA Vaccine Encoding Plasmodium falciparum PfRH5 in Cationic Liposomes for Dermal Tattooing Immunization

Vaccines are the primary means of controlling and preventing pandemics and outbreaks of pathogens such as bacteria, viruses, and parasites. However, a major drawback of naked DNA-based vaccines is their low immunogenicity and the amount of plasmid DNA necessary to elicit a response. Nano-sized liposomes can overcome this limitation, enhancing both nucleic acid stability and targeting to cells after administration. We tested two different DNA vaccines in cationic liposomes to improve the immunogenic properties. For this, we cloned the coding sequences of the Plasmodium falciparum reticulocyte binding protein homologue 5 (PfRH5) either alone or fused with small the small hepatitis virus (HBV) envelope antigen (HBsAg) encoding sequences, potentially resulting in HBsAg particles displaying PfRH5 on their outside. Instead of invasive intraperitoneal or intramuscular immunization, we employed intradermal immunization by tattooing nano-encapsulated DNA. Mice were immunized with 10 μg encapsulated DNA encoding PfRH5 alone or in fusion with HBsAg and this elicited antibodies against schizont extracts (titer of 10⁴). Importantly, only IgG from animals immunized with PfRH5-HBs demonstrated sustained IgG-mediated inhibition in in vitro growth assays showing 58% and 39% blocking activity after 24 and 48 h, respectively. Intradermal tattoo-vaccination of encapsulated PfRH5-HBsAg coding plasmid DNA is effective and superior compared with an unfused PfRH5-DNA vaccine, suggesting that the HBsAg fusion may be advantageous with other vaccine antigens.

Sonodelivery in Skeletal Muscle: Current Approaches and Future Potential

There are currently multiple approaches to facilitate gene therapy via intramuscular gene delivery, such as electroporation, viral delivery, or direct DNA injection with or without polymeric carriers. Each of these methods has benefits, but each method also has shortcomings preventing it from being established as the ideal technique. A promising method, ultrasound-mediated gene delivery (or sonodelivery) is inexpensive, widely available, reusable, minimally invasive, and safe. Hurdles to utilizing sonodelivery include choosing from a large variety of conditions, which are often dependent on the equipment and/or research group, and moderate transfection efficiencies when compared to some other gene delivery methods. In this review, we provide a comprehensive look at the breadth of sonodelivery techniques for intramuscular gene delivery and suggest future directions for this continuously evolving field.

PGC-1α Overexpression via Local In Vivo Transfection in Mouse Skeletal Muscle

The overexpression of a specific protein is a common method for investigating the specific biological function of the substance and the mechanism of action. In vivo electrotransfer has been confirmed to be one of the most reliable, efficient and cost-effective way to overexpress a protein in a select biological tissue. Typically, this technique involves a physical injection of plasmid DNA followed by electric pulses across the injection site. Here, we introduce this method that we used to transfect green fluorescent protein (GFP)-tagged PGC-1α plasmid DNA into mouse tibialis anterior (TA) muscle, which attained high transfection efficiency with no muscle damage. To quantify the transfection efficiency, we also demonstrate the visualization of plasmid DNA transfected fibers via immunohistochemical staining on muscle cross sections.

Biomaterial-Guided Gene Delivery for Musculoskeletal Tissue Repair

Gene therapy is a promising strategy for musculoskeletal tissue repair and regeneration where local and sustained expression of proteins and/or therapeutic nucleic acids can be achieved. However, the musculoskeletal tissues present unique engineering and biological challenges as recipients of genetic vectors. Targeting specific cell populations, regulating expression in vivo, and overcoming the harsh environment of damaged tissue accompany the general concerns of safety and efficacy common to all applications of gene therapy. In this review, we will first summarize these challenges and then discuss how biomaterial carriers for genetic vectors can address these issues. Second, we will review how limitations specific to given vectors further motivate the utility of biomaterial carriers. Finally, we will discuss how these concepts have been combined with tissue engineering strategies and approaches to improve the delivery of these vectors for musculoskeletal tissue regeneration.

Long-Term Expression of a Fluorescent Reporter Gene via Direct Injection of Plasmid Vector into Mouse Skeletal Muscle: Comparison of Human Creatine Kinase and Cmv Promoter Expression Levels in Vivo

Expression of a fluorescent reporter gene has been studied using two alternate promoters to transcribe the green fluorescent protein (gfp) from Aequorea victoria. The human cytomegalovirus (CMV) enhancer/promoter or the human muscle-specific creatine kinase promoter (CKM) were inserted along with the gfp cDNA into a plasmid expression vector based on a modified adeno-associated virus genome. Naked plasmid DNA was injected into the hamstring muscle of mdx mice and gfp gene expression determined from frozen muscle sections taken at 4, 14, and 42 days postinjection. Fluorescence patterns obtained by photomicroscopy and quantitative fluorescence measurements indicated a near-linear increase in the accumulation of the gfp in skeletal muscle during the length of the study, with gfp expression at 42 days being roughly four times the values obtained at 4 days. The levels of expression of gfp from the CKM construct were consistantly higher than for the CMV construct. The CKM promoter/expression vector combination demonstrates significant potential for simple, direct delivery and long-term, high-level expression of genes in skeletal muscle.

Enhanced Immune Response Following DNA Immunization Through In Vivo Electroporation

DNA immunization offers the advantage of allowing for the initiation of animal immunogenicity studies while work to produce and purify the protein of interest is completed. In this study, we sought to evaluate in vivo electroporation (EP) as a means to enhance the antigen-specific immune response from DNA immunization. Mice were immunized thrice with DNA encoding the protein of interest through intramuscular (IM) or intradermal (ID) injections. Test animals were administered an electrical pulse into the muscle or dermis at the site of injection immediately following immunization. In addition, cardiotoxin was injected into the muscle of a subset of test animals 5 days before each DNA injection. Nine weeks following the final DNA immunization, mice were immunized with the encoded purified protein emulsified in Freund's adjuvant. Sera from EP mice taken 2 weeks following the final DNA immunization showed a significant enhancement in antibody response. Specifically, those mice treated with cardiotoxin, immunized IM and given EP showed a strong response, but this was only observed versus solid phase and not solution phase antigen, suggesting the resulting antibody was of low titer and affinity. Similar testing following the protein immunization revealed a significant improvement in relative affinity versus sera taken following DNA immunization. Our results suggest EP can enhance the immune response elicited by DNA immunization.

Horizontal gene transfer from macrophages to ischemic muscles upon delivery of naked DNA with Pluronic block copolymers

Intramuscular administration of plasmid DNA (pDNA) with non-ionic Pluronic block copolymers increases gene expression in injected muscles and lymphoid organs. We studied the role of immune cells in muscle transfection upon inflammation. Local inflammation in murine hind limb ischemia model (MHLIM) drastically increased DNA, RNA and expressed protein levels in ischemic muscles injected with pDNA/Pluronic. The systemic inflammation (MHLIM or peritonitis) also increased expression of pDNA/Pluronic in the muscles. When pDNA/Pluronic was injected in ischemic muscles the reporter gene, Green Fluorescent Protein (GFP) co-localized with desmin(+) muscle fibers and CD11b(+) macrophages (MØs), suggesting transfection of MØs along with the muscle cells. P85 enhanced (∼ 4 orders) transfection of MØs with pDNA in vitro. Moreover, adoptively transferred MØs were shown to pass the transgene to inflamed muscle cells in MHLIM. Using a co-culture of myotubes (MTs) and transfected MØs expressing a reporter gene under constitutive (cmv-luciferase) or muscle specific (desmin-luciferase) promoter we demonstrated that P85 enhances horizontal gene transfer from MØ to MTs. Therefore, MØs can play an important role in muscle transfection with pDNA/Pluronic during inflammation, with both inflammation and Pluronic contributing to the increased gene expression. pDNA/Pluronic has potential for therapeutic gene delivery in muscle pathologies that involve inflammation.

Dual gene transfer of bFGF and PDGF in a single plasmid for the treatment of myocardial infarction

Basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) have been shown to be involved in a spectrum of cellular processes. In a previous study, we constructed a novel multigenic vector that contained two separate transcription units, each consisting of a strong promoter and an efficient polyadenylation signal. The two promoters were chosen for their ability to work simultaneously. Dual gene transfer of bFGF and PDGF in a single plasmid resulted in a significant increase in collateral blood vessel formation in a rabbit model of hind limb ischemia. The aim of the present study was to investigate the effect of this dual gene transfer strategy in a rat model of acute myocardial infarction (AMI). AMI was induced in rats by ligation of the left anterior descending coronary artery. The animals were randomly divided into four groups and treated with the following therapeutic strategies: Empty plasmid (control), plasmid encoding bFGF (PL-bFGF), plasmid encoding PDGF (PL-PDGF) or plasmid encoding bFGF and PDGF (PL-F-P). Echocardiography and histological examinations were performed 28 days subsequent to gene transfer. Dual gene therapy with bFGF and PDGF resulted in a significant angiogenic effect accompanied by vessel maturation, along with a significant reduction in infarct size and improvement in cardiac function. In a rat model of AMI, single plasmid-mediated dual gene therapy with bFGF and PDGF decreased infarct size and improved cardiac function due to the formation of functionally and morphologically mature vasculature. These results are relevant to the ongoing clinical trials involving the use of single plasmid-mediated angiogenic factors for the treatment of myocardial ischemic disease.

Enhancing specific-antibody production to the ragB vaccine with GITRL that expand Tfh, IFN-γ(+) T cells and attenuates Porphyromonas gingivalis infection in mice

The outer membrane protein RagB is one of the major virulence factors of the periodontal pathogen Porphyromonas gingivalis (P. gingivalis). In order to induce protective immune response against P. gingivalis infection, an mGITRL gene-linked ragB DNA vaccine (pIRES-ragB-mGITRL ) was constructed. Six-week-old female BALB/c mice were immunized with pIRES-ragB-mGITRL through intramuscular injection and then challenged by subcutaneous injection in the abdomen with P. gingivalis. RagB-specific antibody-forming cells were evaluated by an Enzyme-linked immunosorbent spot, and specific antibody was determined by enzyme-linked immunosorbent assay. In addition, the frequencies of Tfh and IFN-γ(+) T cells in spleen were measured using flow cytometer, and the levels of IL-21 and IFN-γ mRNA or proteins were detected by real time RT-PCR or ELISA. The data showed that the mGITRL-linked ragB DNA vaccine induced higher levels of RagB-specific IgG in serum and RagB-specific antibody-forming cells in spleen. The frequencies of Tfh and IFN-γ(+) T cells were obviously expanded in mice immunized by pIRES-ragB-mGITRL compared with other groups (pIRES or pIRES-ragB ). The levels of Tfh and IFN-γ(+) T cells associated cytokines were also significantly increased in pIRES-ragB-mGITRL group. Therefore, the mice immunized with ragB plus mGITRL showed the stronger resistant to P. gingivalis infection and a significant reduction of the lesion size caused by P. gingivalis infection comparing with other groups. Taken together, our findings demonstrated that intramuscular injection of DNA vaccine ragB together with mGITRL induced protective immune response dramatically by increasing Tfh and IFN-γ(+) T cells and antibody production to P. gingivalis.

Angiogenic factor AGGF1 promotes therapeutic angiogenesis in a mouse limb ischemia model

BACKGROUND

Peripheral arterial disease (PAD) is a common disease accounting for about 12% of the adult population, and causes significant morbidity and mortality. Therapeutic angiogenesis using angiogenic factors has been considered to be a potential treatment option for PAD patients. In this study, we assessed the potential of a new angiogenic factor AGGF1 for therapeutic angiogenesis in a critical limb ischemia model in mice for PAD.

METHODS AND RESULTS

We generated a unilateral hindlimb ischemia model in mice by ligation of the right common iliac artery and femoral artery. Ischemic mice with intrasmuscular administration of DNA for an expression plasmid for human AGGF1 (AGGF1 group) resulted in increased expression of both AGGF1 mRNA and protein after the administration compared with control mice with injection of the empty vector (control group). Color PW Doppler echocardiography showed that the blood flow in ischemic hindlimbs was significantly increased in the AGGF1 group compared to control mice at time points of 7, 14, and 28 days after DNA administration (n = 9/group, P = 0.049, 0.001, and 0.001, respectively). Increased blood flow in the AGGF1 group was correlated to increased density of CD31-positive vessels and decreased necrosis in muscle tissues injected with AGGF1 DNA compared with the control tissue injected with the empty vector. Ambulatory impairment was significantly reduced in the AGGF1 group compared to the control group (P = 0.004). The effect of AGGF1 was dose-dependent. At day 28 after gene transfer, AGGF1 was significantly better in increasing blood flow than FGF-2 (P = 0.034), although no difference was found for tissue necrosis and ambulatory impairment.

CONCLUSIONS

These data establish AGGF1 as a candidate therapeutic agent for therapeutic angiogenesis to treat PAD.

Electroporation-mediated gene transfer directly to the swine heart

In vivo gene transfer to the ischemic heart via electroporation holds promise as a potential therapeutic approach for the treatment of heart disease. In the current study, we investigated the use of in vivo electroporation for gene transfer using three different penetrating electrodes and one non-penetrating electrode. The hearts of adult male swine were exposed through a sternotomy. Eight electric pulses synchronized to the rising phase of the R wave of the electrocardiogram were administered at varying pulse widths and field strengths following an injection of either a plasmid encoding luciferase or one encoding green fluorescent protein. Four sites on the anterior wall of the left ventricle were treated. Animals were killed 48 h after injection and electroporation and gene expression was determined. Results were compared with sites in the heart that received plasmid injection but no electric pulses or were not treated. Gene expression was higher in all electroporated sites when compared with injection only sites demonstrating the robustness of this approach. Our results provide evidence that in vivo electroporation can be a safe and effective non-viral method for delivering genes to the heart, in vivo.

Safety and feasibility of high-pressure transvenous limb perfusion with 0.9% saline in human muscular dystrophy

We evaluated safety and feasibility of the transvenous limb perfusion gene delivery method in muscular dystrophy. A dose escalation study of single limb perfusion with 0.9% saline starting with 5% of limb volume was carried out in adults with muscular dystrophies under intravenous analgesia/anesthesia. Cardiac, vascular, renal, muscle, and nerve functions were monitored. A tourniquet was placed above the knee with inflated pressure of 310 mm Hg. Infusion was carried out with a clinically approved infuser via an intravenous catheter inserted in the saphenous vein with a goal infusion rate of 80 ml/minute. Infusion volume was escalated stepwise to 20% limb volume in seven subjects. No subject complained of any post procedure pain other than due to needle punctures. Safety warning boundaries were exceeded only for transient depression of limb tissue oximetry and transient elevation of muscle compartment pressures; these were not associated with nerve, muscle, or vascular damage. Muscle magnetic resonant imaging (MRI) demonstrated fluid accumulation in muscles of the perfused lower extremity. High-pressure retrograde transvenous limb perfusion with saline up to 20% of limb volume at above infusion parameters is safe and feasible in adult human muscular dystrophy. This study will serve as a basis for future gene transfer clinical trials.

Review: Stem cells and gene therapy

Both stem cell and gene therapy research are currently the focus of intense research in institutions and companies around the world. Both approaches hold great promise by offering radical new and successful ways of treating debilitating and incurable diseases effectively. Gene therapy is an approach to treat, cure, or ultimately prevent disease by changing the pattern of gene expression. It is mostly experimental, but a number of clinical human trials have already been conducted. Gene therapy can be targeted to somatic or germ cells; the most common vectors are viruses. Scientists manipulate the viral genome and thus introduce therapeutic genes to the target organ. Viruses, in this context, can cause adverse events such as toxicity, immune and inflammatory responses, as well as gene control and targeting issues. Alternative modalities being considered are complexes of DNA with lipids and proteins. Stem cells are primitive cells that have the capacity to self renew as well as to differentiate into 1 or more mature cell types. Pluripotent embryonic stem cells derived from the inner cell mass can develop into more than 200 different cells and differentiate into cells of the 3 germ cell layers. Because of their capacity of unlimited expansion and pluripotency, they are useful in regenerative medicine. Tissue or adult stem cells produce cells specific to the tissue in which they are found. They are relatively unspecialized and predetermined to give rise to specific cell types when they differentiate. The current review provides a summary of our current knowledge of stem cells and gene therapy as well as their clinical implications and related therapeutic options.

Therapeutic strategies for SLE involving cytokines: mechanism-oriented therapies especially IFN-gamma targeting gene therapy

Systemic lupus erythematosus (SLE: lupus) is a chronic complicated autoimmune disease and pathogenesis is still unclear. However, key cytokines have been recognized. Interferon (IFN)-γ and also IFNalpha/beta are of particular importance. Depending on the concept that lupus is a helper T(Th)1 disease and that dendritic cells (DCs) determine the direction of lupus, balance shift of Th1/Th2 and immunogenic/tolerogenic DCs is reviewed for therapy. (IFN)-gamma- and IFN-alpha/beta-targeted (gene) therapies are introduced. These consist of Th1/Th2 balance shift and elimination of IFN-gamma and IFN-gamma-related cytokines such as (interleukin)IL-12 and IL-18. Other approaches include suppression of immunocompetent cells, normalization of abnormal T-cell function, costimulation blockade, B lymphocyte stimulator (Blys) blockade, and suppression of nephritic kidney inflammation. Moreover, balance shift of IFN-alpha/beta and tumor necrosis factor (TNF)-alpha together with regulatory T(Treg) cells are briefly introduced. Clinical application will be discussed.

Evaluation of hydrodynamic limb vein injections in nonhuman primates

The administration route is emerging as a critical aspect of nonviral and viral vector delivery to muscle, so as to enable gene therapy for disorders such as muscular dystrophy. Although direct intramuscular routes were used initially, intravascular routes are garnering interest because of their ability to target multiple muscles at once and to increase the efficiency of delivery and expression. For the delivery of naked plasmid DNA, our group has developed a hydrodynamic, limb vein procedure that entails placing a tourniquet over the proximal part of the target limb to block all blood flow and injecting the gene vector rapidly in a large volume so as to enable the gene vector to be extravasated and to access the myofibers. The present study was conducted in part to optimize the procedure in preparation for a human clinical study. Various injection parameters such as the effect of papaverine preinjection, tourniquet inflation pressure and duration, and rate of injection were evaluated in rats and nonhuman primates. In addition, the safety of the procedure was further established by determining the effect of the procedure on the neuromuscular and vascular systems. The results from these studies provide additional evidence that the procedure is well tolerated and they provide a foundation on which to formulate the procedure for a human clinical study.

Using trehalose delivered by the intramuscular injection of plasmid DNA as an adjuvant for transgene expression

BACKGROUND

Intramuscular injection is a popular and effective approach to administer naked plasmid for transgene expression. The use of an adjuvant can provide a straightforward approach for enhancing transgene expression.

METHODS

Expression plasmid was formulated with various concentrations of trehalose for injection into the skeletal muscles of C57BL/6 mice. The effects of trehalose on gene dosage and the duration of transgene expression were assessed. The levels of transgene expression were indicated by levels of luciferase expression of the homogenized whole skeletal muscle or by histological X-gal staining of beta-galactosidase expression. Trehalose was also added to serum to examine the ability of protecting the DNA from degradation.

RESULTS

It was found that an optimal trehalose concentration of 10 mM will achieve a level of transgene expression that is seven-fold higher than in the absence of trehalose. When compared with other disaccharides, only the incorporation of trehalose can effectively enhance transgene expression. Trehalose is able to improve transgene expression by intramuscular injection at a low gene dosage as well as prolong the duration of transgene expression.

CONCLUSIONS

Trehalose is an effective adjuvant for intramuscular administration of naked plasmid with respect to both enhanced levels and prolonged duration of transgene expression, most likely due to retarding plasmid degradation.

Nonviral jet-injection technology for intratumoral in vivo gene transfer of naked DNA

The main challenges for application of gene therapy to patients are poor selectivity in vector targeting, insufficient gene transfer, and great difficulties in systemic treatment in association with safety concerns for particular vector systems. For success in gene therapy, safe, applicable, and efficient transfer technologies are required. Because of the complex nature of targeted vector delivery to the tumor, our strategy for gene therapy is focused on the development of local nonviral gene transfer. This approach of local interference with tumor growth and progression could contribute to better control of the disease. Transfer of naked DNA is an important alternative to liposomal or viral systems. Different physical procedures are used for improved delivery of naked DNA into the target cells or tissues in vitro and in vivo. Among the various nonviral gene delivery technologies, jet-injection is gaining increased attractiveness, because this technique allows gene transfer into different tissues with deep penetration of naked DNA by circumventing the disadvantages associated with, e.g., viral vectors. The jet-injection technology is based on jets of high velocity for penetration of the skin and underlaying tissues, associated with efficient transfection of the affected area. The jet-injection technology has been successfully applied for in vivo gene transfer in different tumor models. More importantly, the efficacy and safety of jet-injection gene transfer have recently been investigated in a phase I clinical trial.

Polarization of protective immunity induced by replication-incompetent adenovirus expressing glycoproteins of pseudorabies virus

Replication-incompetent adenoviruses expressing three major glycoproteins (gB, gC, and gD) of pseudorabies virus (PrV) were constructed and used to examine the ability of these glycoproteins to induce protective immunity against a lethal challenge. Among three constructs, recombinant adenovirus expressing gB (rAd-gB) was found to induce the most potent immunity biased to Th1-type, as determined by the IgG isotype ratio and the profile of the Th1/Th2 cytokine production. Conversely, the gC-expressing adenovirus (rAd-gC) revealed Th2-type immunity and the gD-expressing adenovirus (rAd-gD) induced lower levels of IFN-? and IL-4 production than other constructs, except IL-2 production. Mucosal delivery of rAd-gB induced mucosal IgA and serum IgG responses and biased toward Th2-type immune responses. However, these effects were not observed in response to systemic delivery of rAd-gB. In addition, rAd-gB appeared to induce effective protective immunity against a virulent viral infection, regardless of whether it was administered via the muscular or systemic route. These results suggest that administration of replication-incompetent adenoviruses can induce different types of immunity depending on the expressed antigen and that recombinant adenoviruses expressing gB induced the most potent Th1-biased humoral and cellular immunity and provided effective protection against PrV infection.

The relative immunogenicity of DNA vaccines delivered by the intramuscular needle injection, electroporation and gene gun methods

Immunogenicity of DNA vaccines varies significantly due to many factors including the inherent immunogenicity of the protein antigen encoded in the DNA vaccine, the optimal immune responses that can be achieved in different animal models and in humans with different genetic backgrounds and, to a great degree, the delivery methods used to administer the DNA vaccines. Based on published results, only the gene gun-mediated delivery approach has been able to elicit protective levels of immune responses in healthy, adult volunteers by DNA immunization alone without the use of another vaccine modality as a boost. Recent results from animal studies suggest that electroporation is also effective in eliciting high level immune responses. However, there have been no reports to identify the similarities and differences between these two leading physical delivery methods for DNA vaccines against infectious disease targets. In the current study, we compared the relative immunogenicity of a DNA vaccine expressing a hemagglutinin (HA) antigen from an H5N1 influenza virus in two animal models (rabbit and mouse) when delivered by either intramuscular needle immunization (IM), gene gun (GG) or electroporation (EP). HA-specific antibody, T cell and B cell responses were analyzed. Our results indicate that, overall, both the GG and EP methods are more immunogenic than the IM method. However, EP and IM stimulated a Th-1 type antibody response and the antibody response to GG was Th-2 dominated. These findings provide important information for the further selection and optimization of DNA vaccine delivery methods for human applications.

Improvement of in vivo transfer of plasmid DNA in muscle: comparison of electroporation versus ultrasound

Plasmid-based gene delivery to muscle is a treatment strategy for many diseases with potential advantages above viral-based gene delivery methods, however, with a relative low transfection efficiency. We compared two physical methods - electroporation and ultrasound - that facilitate DNA uptake into cells. Mice (C57Bl/6) were injected intramuscular using plasmid DNA encoding an intracellular protein (p53) followed by electroporation or ultrasound. Then 48 hr after the injections the mice were sacrificed. The parameter for transfection efficiency was the area of muscle expressing the transgene. The p53 expression plasmid showed a 36-fold increase (p = 0.015) in transfection efficiency with electroporation compared to ultrasound. Compared with ultrasound, electroporation significantly improves transfection efficiency of naked plasmid DNA transfer into skeletal muscle.

Enhanced effect of microdystrophin gene transfection by HSV-VP22 mediated intercellular protein transport

Background

Duchenne musclar dystrophy (DMD) is an X-linked recessive disease caused by mutations of dystrophin gene, there is no effective treatment for this disorder at present. Plasmid-mediated gene therapy is a promising therapeutical approach for the treatment of DMD. One of the major issues with plasmid-mediated gene therapy for DMD is poor transfection efficiency and distribution. The herpes simplex virus protein VP22 has the capacity to spread from a primary transduced cell to surrounding cells and improve the outcome of gene transfer. To improve the efficiency of plasmid-mediated gene therapy and investigate the utility of the intercellular trafficking properties of VP22-linked protein for the treatment for DMD, expression vectors for C-terminal versions of VP22-microdystrophin fusion protein was constructed and the VP22-mediated shuttle effect was evaluated both in vitro and in vivo.

Results

Our results clearly demonstrate that the VP22-microdystrophin fusion protein could transport into C2C12 cells from 3T3 cells, moreover, the VP22-microdystrophin fusion protein enhanced greatly the amount of microdystrophin that accumulated following microdystrophin gene transfer in both transfected 3T3 cells and in the muscles of dystrophin-deficient (mdx) mice.

Conclusion

These results highlight the efficiency of the VP22-mediated intercellular protein delivery for potential therapy of DMD and suggested that protein transduction may be a potential and versatile tool to enhance the effects of gene delivery for somatic gene therapy of DMD.

In vivo expression and antitumor activity of p53 gene transfer with naked plasmid DNA in an ovarian cancer xenograft model in nude mice

INTRODUCTION

Abnormalities in the p53 and p16 tumor suppressor genes are one of the most common occurrences associated with human neoplasia. Consequently, restoration of wild-type p53 or p16 functions is seen as a particularly promising approach for cancer gene therapy. In vitro and in vivo data have demonstrated that virus-mediated p53 gene transfer can induce active cell death and ovarian tumor regression.

AIM

To evaluate the efficiency of intratumoral injection of naked DNA in tumor growth inhibition in an ovarian xenograft model. For that purpose, plasmid vectors encoding wild-type p53 (wt-p53) or p16 alone or in combination were used.

METHODS

Nude mice were injected subcutaneously with the human ovarian adenocarcinoma cell line SKOV3. Three weeks after xenograft, tumor-bearing mice were injected twice a week with plasmid vectors carrying WT-p53 and/or WT-p16 cDNA. Empty plasmids and saline buffer were used as control. Tumor growth was monitored to evaluate the inhibition potential with p53 and/or p16 restoration.

RESULTS

When compared to the control, intratumoral repeated injections of naked plasmid DNA encoding wt-p53 were inhibiting tumor growth. This inhibition was not observed with p16 and no synergy could be obtained between p53 and p16. p53 expression was restored in 84% of mice injected with plasmid encoding wt-p53. p16 expression was restored in 63% of mice injected with plasmid encoding p16.

CONCLUSIONS

In this report we demonstrated that: (i) naked DNA represents an efficient gene transfer in the SKOV3 xenograft model; (ii) restoration of wt-p53 gene allows tumor growth inhibition; and (iii) this inhibition could be correlated with p53 expression as seen in 84% of treated mice after repeated naked DNA injections. These results allow us to envisage naked DNA as a therapeutic adjuvant in ovarian cancer treatment, concomitantly with tumor resection and chemotherapy.

Targeted in vitro and in vivo gene transfer into T lymphocytes: potential of direct inhibition of allo-immune activation

Background

Successful inhibition of alloimmune activation in organ transplantation remains one of the key events in achieving a long-term graft survival. Since T lymphocytes are largely responsible for alloimmune activation, targeted gene transfer of gene of cyclin kinase inhibitor p21 into T cells might inhibit their aberrant proliferation. A number of strategies using either adenoviral or lentiviral vectors linked to mono or bispecific antibodies directed against T cell surface markers/cytokines did not yield the desired results. Therefore, this study was designed to test if a CD3promoter-p21 chimeric construct would in vitro and in vivo transfer p21 gene to T lymphocytes and result in inhibition of proliferation. CD3 promoter-p21 chimeric constructs were prepared with p21 in the sense and antisense orientation. For in vitro studies EL4-IL-2 thyoma cells were used and for in vivo studies CD3p21 sense and antisense plasmid DNA was injected intramuscularly in mice. Lymphocyte proliferation was quantified by ³H-thymidine uptake assay; IL-2 mRNA expression was studied by RT-PCR and using Real Time PCR assay, we monitored the CD3, p21, TNF-α and IFN-γ mRNA expression.

Results

Transfection of CD3p21 sense and antisense in mouse thyoma cell line (EL4-IL-2) resulted in modulation of mitogen-induced proliferation. The intramuscular injection of CD3p21 sense and antisense plasmid DNA into mice also modulated lymphocyte proliferation and mRNA expression of pro-inflammatory cytokines.

Conclusion

These results demonstrate a novel strategy of in vitro and in vivo transfer of p21 gene to T cells using CD3-promoter to achieve targeted inhibition of lymphocyte proliferation and immune activation.

Multiple strategies for gene transfer, expression, knockdown, and chromatin influence in mammalian cell lines and transgenic animals

Manipulation of the eukaryotic genome has contributed to the progress in our knowledge of multicellular organisms but has also ameliorated our experimental strategies. Biological questions can now be addressed with more efficiency and reproducibility. There are new and varied strategies for gene transfer and sequence manipulation with improved methodologies that facilitate the acquisition of results. Cellular systems and transgenic animals have demonstrated their invaluable benefits. In this review, I present an overview of the methods of gene transfer with particular attention to cultured cell lines and large-scale sequence vectors, like artificial chromosomes, with the possibility of their manipulation based on homologous recombination strategies. Alternative strategies of gene transfer, including retroviral vectors, are also described and the applications of such methods are discussed. Finally, several comments are made about the influence of chromatin structure on gene expression. Recent experimental data have shown that for convenient stable transgene expression, the influence of chromatin structure should be seriously taken into account. Novel chromatin regulatory and structural elements are proposed as an alternative for proper and sustained gene expression. These chromatin elements are facing a new era in transgenesis and we are probably beginning a new generation of gene and cancer therapy vectors.

Comparative evaluation of IGF-I gene transfer and IGF-I protein administration for enhancing skeletal muscle regeneration after injury

Developing methodologies to enhance skeletal muscle regeneration and hasten the restoration of muscle function has important implications for minimizing disability after injury and for treating muscle diseases such as Duchenne muscular dystrophy. Although delivery of various growth factors, such as insulin-like growth factor-I (IGF-I), have proved successful in promoting skeletal muscle regeneration after injury, no study has compared the efficacy of different delivery methods directly. We compared the efficacy of systemic delivery of recombinant IGF-I protein via mini-osmotic pump (approximately 1.5 mg/kg/day) with a single electrotransfer-assisted plasmid-based gene transfer, to hasten functional repair of mouse tibialis anterior muscles after myotoxic injury. The relative efficacy of each method was assessed at 7, 21 and 28 days post-injury. Our findings indicate that IGF-I hastened functional recovery, regardless of the route of IGF-I administration. However, gene transfer of IGF-I was superior to systemic protein administration because in the regenerating muscle, this delivery method increased IGF-I levels, activated intracellular signals (Akt phosphorylation), induced a greater magnitude of myofiber hypertrophy and hastened functional recovery at an earlier time point (14 days) after injury than did protein administration (21 days). Thus, the relative efficacy of different modes of delivery is an important consideration when assessing the therapeutic potential of various proteins for treating muscle injuries and skeletal muscle diseases.

Long-term persistence of hepatitis B surface antigen and antibody induced by DNA-mediated immunization results in liver and kidney lesions in mice

DNA-mediated immunization has been recognized as a new approach for prevention and treatment of hepatitis B virus (HBV) infection. However, the side effects of this approach have not been well described. Here we report that DNA-mediated immunization by intramuscular injection of plasmid DNA encoding HBV surface antigen (HBsAg) induced long-term persistence of HBsAg and HBsAg-specific antibody (anti-HBs) in the sera of the immunized BALB/c mice and resulted in liver and kidney lesions. The lesions persisted for 6 months after injection. Lesions were also found in normal mice injected with the sera from immunized mice, and in HBV-transgenic mice injected with anti-HBs antibody, or sera from immunized mice. Furthermore, lesions were accompanied by deposition of circulating immune complex (CIC) of HBsAg and anti-HBs antibody in the damaged organs. These results indicate that long-term persistence of HBsAg and anti-HBs in the immunized mice can result in deposited CIC in liver and kidney, and in development of lesions. The use of DNA containing mammalian replication origins, such as the plasmids used in this study, is not appropriate for human vaccines due to safety concerns relating to persistence of DNA; nevertheless, the safety of DNA-mediated immunization protocols still needs to be carefully evaluated before practical application.

Gene expression analysis of ectopic bone formation induced by electroporatic gene transfer of BMP4

Implantation of bone morphogenetic protein (BMP) using a carrier or by BMP gene transfer into rodent muscle can induce bone formation. Implanted BMP becomes bioactive immediately after implantation. In BMP gene transfer, there is a time-lag between the secretion of gene products and bone formation. We analyzed the gene expression of chondrogenic and osteogenic specific markers in the process of ectopic bone formation by using semi-quantitative RT-PCR. A plasmid vector containing mouse BMP4 gene (pCAGGS-BMP4) was transferred into the gastrocnemius muscles of mice using electroporation. Histological examination revealed the process of endochondral bone formation in the pCAGGS-BMP4 transferred muscles. As chondrogenic markers, aggrecan gene maximal expression was detected on day 7 and decreased by day 14, and for collagen X the gene maximal expression was on day 10. As osteogenic markers, osteocalcin (OCN), bone sialoprotein (BSP) and osteopontin (OPN) gene expressions were clearly detected from day 10 and then increased by day 14. In conclusion, the present study proved that ectopic bone formation by BMP4 gene transfer into the muscle induced endochondral ossification that corresponded well with that to that by implantation of demineralized bone matrix.

Normal myoblast fusion requires myoferlin

Muscle growth occurs during embryonic development and continues in adult life as regeneration. During embryonic muscle growth and regeneration in mature muscle, singly nucleated myoblasts fuse to each other to form myotubes. In muscle growth, singly nucleated myoblasts can also fuse to existing large, syncytial myofibers as a mechanism of increasing muscle mass without increasing myofiber number. Myoblast fusion requires the alignment and fusion of two apposed lipid bilayers. The repair of muscle plasma membrane disruptions also relies on the fusion of two apposed lipid bilayers. The protein dysferlin, the product of the Limb Girdle Muscular Dystrophy type 2 locus, has been shown to be necessary for efficient, calcium-sensitive, membrane resealing. We now show that the related protein myoferlin is highly expressed in myoblasts undergoing fusion, and is expressed at the site of myoblasts fusing to myotubes. Like dysferlin, we found that myoferlin binds phospholipids in a calcium-sensitive manner that requires the first C2A domain. We generated mice with a null allele of myoferlin. Myoferlin null myoblasts undergo initial fusion events, but they form large myotubes less efficiently in vitro, consistent with a defect in a later stage of myogenesis. In vivo, myoferlin null mice have smaller muscles than controls do, and myoferlin null muscle lacks large diameter myofibers. Additionally, myoferlin null muscle does not regenerate as well as wild-type muscle does, and instead displays a dystrophic phenotype. These data support a role for myoferlin in the maturation of myotubes and the formation of large myotubes that arise from the fusion of myoblasts to multinucleate myotubes.

The mechanism of naked DNA uptake and expression

The administration of naked nucleic acids into animals is increasingly being used as a research tool to elucidate mechanisms of gene expression and the role of genes and their cognate proteins in the pathogenesis of disease in animal models (Herweijer and Wolff, 2003; Hodges and Scheule, 2003). It is also being used in several human clinical trials for genetic vaccines, Duchenne muscular dystrophy, peripheral limb ischemia, and cardiac ischemia (Davis et al., 1996; Romero et al., 2002; Tsurumi et al., 1997). Naked DNA is an attractive non-viral vector because of its inherent simplicity and because it can easily be produced in bacteria and manipulated using standard recombinant DNA techniques. It shows very little dissemination and transfection at distant sites following delivery and can be readministered multiple times into mammals (including primates) without inducing an antibody response against itself (i.e., no anti-DNA antibodies generated) (Jiao et al., 1992). Also, contrary to common belief, long-term foreign gene expression from naked plasmid DNA (pDNA) is possible even without chromosome integration if the target cell is postmitotic (as in muscle) or slowly mitotic (as in hepatocytes) and if an immune reaction against the foreign protein is not generated (Herweijer et al., 2001; Miao et al., 2000; Wolff et al., 1992; Zhang et al., 2004). With the advent of intravascular and electroporation techniques, its major restriction--poor expression levels--is no longer limiting and levels of foreign gene expression in vivo are approaching what can be achieved with viral vectors. Direct in vivo gene transfer with naked DNA was first demonstrated when efficient transfection of myofibers was observed following injection of mRNA or pDNA into skeletal muscle (Wolff et al., 1990). It was an unanticipated finding in that the use of naked nucleic acids was the control for experiments designed to assess the ability of cationic lipids to mediate expression in vivo. Subsequent studies also found foreign gene expression after direct injection in other tissues such as heart, thyroid, skin, and liver (Acsadi et al., 1991; Hengge et al., 1996; Kitsis and Leinwand, 1992; Li et al., 1997; Sikes and O'Malley 1994; Yang and Huang, 1996). However, the efficiency of gene transfer into skeletal muscle and these other tissues by direct injection is relatively low and variable, especially in larger animals such as nonhuman primates (Jiao et al., 1992). After our laboratory had developed novel transfection complexes of pDNA and amphipathic compounds and proteins, we sought to deliver them to hepatocytes in vivo via an intravascular route into the portal vein. Our control for these experiments was naked pDNA and we were once again surprised that this control group had the highest expression levels (Budker et al., 1996; Zhang et al., 1997). High levels of expression were achieved by the rapid injection of naked pDNA in relatively large volumes via the portal vein, the hepatic vein, and the bile duct in mice and rats. The procedure also proved effective in larger animals such as dogs and nonhuman primates (Eastman et al., 2002; Zhang et al., 1997). The next major advance was the demonstration that high levels of expression could also be achieved in hepatocytes in mice by the rapid injection of naked DNA in large volumes simply into the tail vein (Liu et al., 1999; Zhang et al., 1999). This hydrodynamic tail vein (HTV) procedure is proving to be a very useful research tool not only for gene expression studies, but also more recently for the delivery of small interfering RNA (siRNA) (Lewis et al., 2002; McCaffrey et al., 2002). The intravascular delivery of naked pDNA to muscle cells is also attractive particularly since many muscle groups would have to be targeted for intrinsic muscle disorders such as Duchenne muscular dystrophy. High levels of gene expression were first achieved by the rapid injection of naked DNA in large volumes via an artery route with both blood inflow and outflow blocked surgically (Budker et al., 1998; Zhang et al., 2001). Intravenous routes have also been shown to be effective (Hagstrom et al., 2004; Liang et al., 2004; Liu et al., 2001). For limb muscles, the ability to use a peripheral limb vein for injection and a proximal, external tourniquet to block blood flow renders the procedure to be clinically viable. This review concerns itself with the mechanism by which naked DNA is taken up by cells in vivo. A greater understanding of the mechanisms involved in the uptake and expression of naked DNA, and thus connections between postulated mechanisms and expression levels, is emphasized. Inquiries into the mechanism not only aid these practical efforts, but are also interesting on their own account with relevance to viral transduction and cellular processes. The delivery to hepatocytes is first discussed given the greater information available for this process, and then uptake by myofibers is discussed.

Reciprocal role of cyclins and cyclin kinase inhibitor p21WAF1/CIP1 on lymphocyte proliferation, allo-immune activation and inflammation

Background

Immune activation that results due to the aberrant proliferation of lymphocytes leads to inflammation and graft rejection in organ transplant recipients. We hypothesize that the cell cycle control and inflammation are parallel events, inhibition of cellular proliferation by cyclin kinase inhibitor specifically p21 will limit inflammation and prevent allograft rejection.

Methods

We performed in vitro and in vivo studies using lymphocytes, and rat heart transplant model to understand the role of cyclins and p21 on mitogen and allo-induced lymphocyte activation and inflammation. Lymphocyte proliferation was studied by ³H-thymidine uptake assay and mRNA expression was studied RT-PCR.

Results

Activation of allo- and mitogen stimulated lymphocytes resulted in increased expression of cyclins, IL-2 and pro-inflammatory cytokines, which was inhibited by cyclosporine. The over-expression of p21 prolonged graft survival in a completely mismatched rat heart transplant model resulted by inhibiting circulating and intra-graft expression of proinflammatory cytokines.

Conclusion

Cyclins play a significant role in transplant-induced immune activation and p21 over-expression has potential to inhibit T cell activation and inflammation. The results from this study will permit the design of alternate strategies by controlling cell cycle progression to achieve immunosuppression in transplantation.

Lipopolysaccharide recognition protein, MD-2, facilitates cellular uptake of E. coli-derived plasmid DNA in synovium

BACKGROUND

Several cell types are susceptible to transfection in vivo using naked plasmid DNA. The mechanisms involved in mediating in vivo transfection are incompletely known, but evidence suggests that receptor-mediated endocytosis is important for specific types of cells. In this study we tested the hypothesis that residual Escherichia coli lipopolysaccharide (LPS) forms a non-covalent complex with expression plasmid DNA, and host-cell-derived soluble LPS-binding proteins bind to the DNA-LPS complexes in order to facilitate receptor-mediated endocytosis.

METHODS

Cells from the murine synovial lining were used as an in vivo model system and in vivo luciferase imaging was used to quantify levels of transgene expression. Using a series of gene-deleted mice, the roles of LPS recognition complex proteins, lipopolysaccharide-binding protein (LBP), CD14 and MD-2, in the process of in vivo transfection were determined.

RESULTS

Luciferase expression assays revealed that mice lacking LBP or CD14 had increased luciferase expression (p < 0.023 and < 0.165, respectively), while mice deleted of MD-2 had significant reductions in luciferase expression (p < 0.001). Gene deletion of hyaluronic acid binding protein CD44 was used as a control and had no statistically significant effect on transgene expression in vivo. In muscle tissue, where neither cell surface nor soluble MD-2 is expressed, no MD-2 dependence of plasmid transfection was identified, suggesting the role of MD-2 is tissue or cell type specific. Additionally, depleting mice of macrophages showed that luciferase expression is occurring within fibroblast-like synoviocytes.

CONCLUSIONS

Our data support a physical association between LPS and E. coli-derived plasmid DNA, and that in vivo transfection of fibroblast-like synoviocytes is dependent on the soluble form of the LPS-binding protein MD-2.

Enhanced Antitumor Effect of the Combination of Tumstatin Gene Therapy and Gemcitabine in Murine Models

Targeting tumor endothelium is an important strategy for cancer therapy. We evaluated the effectiveness of gene therapy, that is, intramuscular delivery of plasmid DNA encoding tumstatin (pSecTag2B-tum), combined with gemcitabine administration in vitro and in vivo, using colon carcinoma (CT26) and Lewis lung carcinoma (LLC) murine models. The in vitro growth-inhibitory and proapoptotic effects of gemcitabine and/or tumstatin on human umbilical vein endothelial cells (HUVECs) and mouse endothelial cells (SVEC4-10), respectively, were assessed. in vitro, conditioned medium from pSecTag2B-tum-transfected COS cells inhibited the growth of endothelial cells but not of CT26 or LLC cells, whereas gemcitabine inhibited the growth of both endothelial cells and CT26 and LLC cells. Mice bearing subcutaneously established CT26 or LLC tumors received pSecTag2B-tum alone or in combination with gemcitabine to assess tumor growth inhibition. in vivo, combined treatment with pSecTag2B-tum and gemcitabine significantly decreased tumor growth through increased inhibition of tumor angiogenesis and increased tumor cell apoptosis compared with either agent alone. Enhanced antiproliferative and proapoptotic activity of the combination therapy on tumor-associated endothelial cells was calculated to be significant. This study suggests that combined treatment by the intramuscular delivery of plasmid DNA encoding tumstatin and gemcitabine augments tumor growth inhibition by suppressing angiogenesis and enhancing apoptosis in murine models. A combination of these agents could be used in future studies and translated into the clinical setting.

The modulation of angiogenesis in the foreign body response by the poxviral protein M-T7

The foreign body response is characterized by enhanced recruitment of inflammatory cells. As the directional movement of cells is controlled by chemokines, disruption of the chemokine network would be an attractive approach to improve biocompatibility of an implanted material. The sequestration of chemokines by cell surface-expressed glycosaminoglycans (GAGs) is vital for in vivo chemokine activity. The myxoma virus encodes a soluble protein, M-T7, that interacts with conserved GAG-binding domains of chemokines to block chemokine-mediated leukocyte recruitment. We hypothesized that M-T7 might also affect the function of other inflammation-associated proteins in addition to chemokines that bind to GAG. In our studies, we focussed on the modulation of the GAG-binding molecules macrophage chemoattractant protein-1 (MCP-1) and vascular endothelial growth factor-164 (VEGF164) in the inflammatory reaction against subcutaneously implanted degradable cross-linked dermal sheep collagen discs in AO rats. Genetic delivery of M-T7 delays the influx of macrophages into the collagen discs. In addition, angiogenesis around the implanted material was reduced. The discs revealed reduced levels of rat MCP-1 and rat VEGF164. This was not due to down regulation of transcription of the genes that encode MCP-1 and VEGF164. Our in vivo observations suggest that, in addition to chemokines such as MCP-1, M-T7 neutralizes VEGF164.

Mechanisms of action of DNA vaccines

The field of DNA vaccines can trace its inception to two papers which demonstrated that administration of plasmid DNA vectors expressing proteins resulted in expression in situ. Thereafter, the possible application of this technique to vaccine development was demonstrated through the induction of antibody responses in mice against a foreign protein, cellular immune responses against a viral antigen and protective efficacy in an infectious disease challenge model. Subsequently, the general utility of DNA vaccines in animal models of infectious and non-infectious disease has been established (for review, see [5]). Initially, most efforts were directed toward demonstration of effectiveness in particular disease models. Recently, however, more attention has been paid to gaining a better understanding of some of the underlying mechanisms of DNA vaccines. This review will focus on this new information and discuss it in the context of how it could benefit the development of more effective DNA vaccines.

Rabies DNA vaccines for protection and therapeutic treatment

Rabies is a successful zoonotic disease that has persisted over time, achieving worldwide distribution in a variety of species. Annually, in developing countries with limited access to high-quality antirabies biologics, approximately 50,000 individuals and millions of animals die of rabies. Many of these countries continue to use vaccines produced in sheep, goat or suckling mouse brain, with ultraviolet light or phenol inactivation of the virus. Although there are several efficacious rabies vaccines derived from cultured cells, such as the human diploid cell vaccine, they are costly to produce and prohibitively expensive for developing countries. DNA vaccines offer a new and powerful approach for the generation of needed vaccines. They are stable, inexpensive to produce, easy to construct and induce a full spectrum of long-lasting humoral and cellular immune responses. This review concerns the present state of rabies DNA vaccines, and addresses the technology that may enhance their therapeutic efficacy.

Gene therapy for proliferative ocular diseases

Proliferative ocular diseases encompass a wide variety of pathological processes with adverse cellular differentiation, proliferation and migration as common features. Pathologies may involve neovascular responses associated with diabetic retinopathy, retinopathy of prematurity or age-related macular degeneration. These diseases are quite prevalent and account for substantial visual impairment and blindness worldwide. Although treatment strategies are largely surgical, advances in our understanding of the proteins crucial to cell transdifferentiation, proliferation and migration, along with better gene transfer techniques, have greatly increased the potential for biological treatment options. In this report, the most common proliferative ocular vascular diseases and existing therapeutic modalities will be reviewed and an overview of possible gene therapy options will be discussed, along with potential candidate genes.

Non‐Viral Vector as Vaccine Carrier

Over the last several years, advances in gene-based delivery technology arising from the field of gene therapy have helped revitalize the field of vaccine development. Genetic vaccination encoding antigen from bacteria, virus, and cancer has shown promise in protective humoral and cellular immunity; however, the potential disadvantages of naked DNA vaccine have reduced the value of the approach. To optimize antigen delivery efficiency as well as vaccine efficacy, the non-viral vector as vaccine carrier, for example, the cationic liposome, has shown particular benefits to circumvent the obstacles that both peptide/protein- and gene-based vaccines have encountered. Liposome-mediated vaccine delivery provides greater efficacy and safer vaccine formulation for the development of vaccine for human use. The success of the liposome-based vaccine has been demonstrated in clinical trials and further human trials are also in progress.

Mice body weight gain is prevented after naked human leptin cDNA transfer into skeletal muscle by electroporation

BACKGROUND

In this investigation, the feasibility of gene therapy for obesity by electroporational transfer of naked plasmid with leptin cDNA into skeletal muscle was tested. Both young and adult mice were studied.

METHODS

Human leptin cDNA was attached to the human insulin precursor secretion signal peptide gene. The fused gene was then inserted into the mammalian expression vector pcDNA3.1(-) and transferred into skeletal muscle of normal female mice using electroporation.

RESULTS

During the time of exogenic gene expression, daily food intake of leptin cDNA-treated mice was observed to be lower than the control. The body weight gain was prevented efficaciously regardless of if they were young or adult. At the 7th week after gene transfer, the body weight of both young and adult leptin cDNA-treated mice was about 20% lighter than the control. Although the body weight of pair fed controlled adult mice was close to the leptin cDNA-treated mice at the 8th week, they were always heavier than the leptin cDNA-treated mice before this time. The levels of retroperitoneal fats and serum TG of leptin cDNA-treated mice were markedly lower than that of the control. The relative serum hyperleptinemic level could last for about 2 months. The expression of leptin cDNA in muscle cells was also detected by RT-PCR. The levels of serum insulin and glucose of leptin cDNA-treated mice decreased slightly. Our data also showed that the hyperleptinmia resulted in uterus expansion in young mice, but not in the adults.

CONCLUSION

The present study provides evidence of successful electroporation of naked plasmid DNA transfer for prevention or treatment of mice obesity.

Nonviral DNA vectors for immunization and therapy: design and methods for their obtention

The use of plasmid DNA for vaccination and therapy is a relatively novel technology, with advantages and limitations as with other gene transfer techniques. The technology is based on DNA vectors designed for administering genes coding for relevant proteins into a given organism, fulfilling requirements of the regulatory agencies that once properly formulated and delivered the desired vaccine/therapeutic effect can be achieved. Starting from conventional plasmid DNA vectors currently tested in clinical trials, improvement resulted in bacterial element-less vectors, increasing the complexity of the developmental process. The present review focuses on systems described for generating these nonviral DNA vectors for immunization and therapy from bacterial hosts (conventional and conditionally replicating plasmids, nonreplicating minicircles, and linear dumbbell-shaped expression cassettes) in vivo or in vitro. Additionally, nontherapeutic genetic sequences with a negative or positive effect according to the specific application are described, bringing a better comprehension of the technology's state of the art.

Codon optimization and mRNA amplification effectively enhances the immunogenicity of the hepatitis C virus nonstructural 3/4A gene

We have recently shown that the NS3-based genetic immunogens should contain also hepatitis C virus (HCV) nonstructural (NS) 4A to utilize fully the immunogenicity of NS3. The next step was to try to enhance immunogenicity by modifying translation or mRNA synthesis. To enhance translation efficiency, a synthetic NS3/4A-based DNA (coNS3/4A-DNA) vaccine was generated in which the codon usage was optimized (co) for human cells. In a second approach, expression of the wild-type (wt) NS3/4A gene was enhanced by mRNA amplification using the Semliki forest virus (SFV) replicon (wtNS3/4A-SFV). Transient tranfections of human HepG2 cells showed that the coNS3/4A gene gave 11-fold higher levels of NS3 as compared to the wtNS3/4A gene when using the CMV promoter. We have previously shown that the presence of NS4A enhances the expression by SFV. Both codon optimization and mRNA amplification resulted in an improved immunogenicity as evidenced by higher levels of NS3-specific antibodies. This improved immunogenicity also resulted in a more rapid priming of cytotoxic T lymphocytes (CTLs). Since HCV is a noncytolytic virus, the functionality of the primed CTL responses was evaluated by an in vivo challenge with NS3/4A-expressing syngeneic tumor cells. The priming of a tumor protective immunity required an endogenous production of the immunogen and CD8+ CTLs, but was independent of B and CD4+ T cells. This model confirmed the more rapid in vivo activation of an NS3/4A-specific tumor-inhibiting immunity by codon optimization and mRNA amplification. Finally, therapeutic vaccination with the coNS3/4A gene using gene gun 6-12 days after injection of tumors significantly reduced the tumor growth in vivo. Codon optimization and mRNA amplification effectively enhances the overall immunogenicity of NS3/4A. Thus, either, or both, of these approaches should be utilized in an NS3/4A-based HCV genetic vaccine.