Expression of naked plasmids by cultured myotubes and entry of plasmids into T tubules and caveolae of mammalian skeletal muscle

Seeing the Future: A Review of Ocular Therapy

Ocular diseases present a unique challenge and opportunity for therapeutic development. The eye has distinct advantages as a therapy target given its accessibility, compartmentalization, immune privilege, and size. Various methodologies for therapeutic delivery in ocular diseases are under investigation that impact long-term efficacy, toxicity, invasiveness, and delivery range. While gene, cell, and antibody therapy and nanoparticle delivery directly treat regions that have been damaged by disease, they can be limited in the duration of the therapeutic delivery and have a focal effect. In contrast, contact lenses and ocular implants can more effectively achieve sustained and widespread delivery of therapies; however, they can increase dilution of therapeutics, which may result in reduced effectiveness. Current therapies either offer a sustained release or a broad therapeutic effect, and future directions should aim toward achieving both. This review discusses current ocular therapy delivery systems and their applications, mechanisms for delivering therapeutic products to ocular tissues, advantages and challenges associated with each delivery system, current approved therapies, and clinical trials. Future directions for the improvement in existing ocular therapies include combination therapies, such as combined cell and gene therapies, as well as AI-driven devices, such as cortical implants that directly transmit visual information to the cortex.

Extracellular HMGB1 augments macrophage inflammation by facilitating the endosomal accumulation of ALD-DNA via TLR2/4-mediated endocytosis

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with unclear pathogenesis. We previously reported that syngenetic, activated lymphocyte-derived DNA (ALD-DNA) could robustly elicit macrophage activation, which plays an important role in the pathogenesis of murine lupus nephritis. In addition, extracellular HMGB1 obviously facilitated the accumulation of ALD-DNA in endosomes and promoted macrophage inflammation. While the detailed mechanism was still unknown. In this study, we found that HMGB1 could obviously change the DNA uptake pathways in macrophages. ALD-DNA alone was mainly uptake by the low efficient and unselective macropinocytosis, while extracellular HMGB1 potently promoted the more efficient and specific clathrin-/caveolin-1-dependent receptor-mediated endocytosis pathways, and led to the rapid and abundant aggregation of ALD-DNA in endosomes. This effect relied on the DNA binding ability and TLR2/TLR4 of HMGB1. Our study not only helped us to understand the promotion mechanisms of extracellular HMGB1 on ALD-DNA-induced macrophage inflammation, but also provided some clues to the pathogenesis of SLE.

DNA vaccination for finfish aquaculture

In fish, DNA vaccines have been shown to give very high protection in experimental facilities against a number of viral diseases, particularly diseases caused by rhabdoviruses. However, their efficacy in generating protection against other families of fish viral pathogens is less clear. One DNA vaccine is currently in use commercially in fish farms in Canada and the commercialisation of another was authorised in Europe in 2017. The mechanism of action of DNA vaccines, including the role of the innate immune responses induced shortly after DNA vaccination in the activation of the adaptive immunity providing longer term specific protection, is still not fully understood. In Europe the procedure for the commercialisation of a veterinary DNA vaccine requires the resolution of certain concerns particularly about safety for the host vaccinated fish, the consumer and the environment. Relating to consumer acceptance and particularly environmental safety, a key question is whether a DNA vaccinated fish is considered a Genetically Modified Organism (GMO). In the present opinion paper these key aspects relating to the mechanisms of action, and to the development and the use of DNA vaccines in farmed fish are reviewed and discussed.

Magnetic Nanovectors for the Development of DNA Blood-Stage Malaria Vaccines

DNA vaccines offer cost, flexibility, and stability advantages, but administered alone have limited immunogenicity. Previously, we identified optimal configurations of magnetic vectors comprising superparamagnetic iron oxide nanoparticles (SPIONs), polyethylenimine (PEI), and hyaluronic acid (HA) to deliver malaria DNA encoding Plasmodium yoelii (Py) merozoite surface protein MSP1₁₉ (SPIONs/PEI/DNA + HA gene complex) to dendritic cells and transfect them with high efficiency in vitro. Herein, we evaluate their immunogenicity in vivo by administering these potential vaccine complexes into BALB/c mice. The complexes induced antibodies against PyMSP1₁₉, with higher responses induced intraperitoneally than intramuscularly, and antibody levels further enhanced by applying an external magnetic field. The predominant IgG subclasses induced were IgG2a followed by IgG1 and IgG2b. The complexes further elicited high levels of interferon gamma (IFN-γ), and moderate levels of interleukin (IL)-4 and IL-17 antigen-specific splenocytes, indicating induction of T helper 1 (Th1), Th2, and Th17 cell mediated immunity. The ability of such DNA/nanoparticle complexes to induce cytophilic antibodies together with broad spectrum cellular immunity may benefit malaria vaccines.

Therapeutic angiogenesis for critical limb ischemia: design of the hepatocyte growth factor therapeutic angiogenesis clinical trial

The objective of the HGF-STAT clinical trial is to determine whether perfusion can be improved by gene transfer with a plasmid DNA containing hepatocyte growth factor (HGF) in the affected limb of patients with unreconstructable critical limb ischemia (CLI). CLI results in a high rate of limb loss and impaired quality of life. The current therapeutic strategies, including bypass surgery and percutaneous interventions, are only successful in treating a subset of patients. Therapeutic angiogenesis is an investigational method that seeks to favorably impact tissue per-fusion in CLI. HGF-STAT is a double-blind, parallel-group, placebo-controlled, dose response study in 100 patients with unreconstructable CLI. Eligible subjects will be randomized 1:1:1:1 to receive saline placebo or one of three dose/regimens of HGF plasmid DNA. The selection of outcome measures, including the primary endpoint, and changes in transcutaneous oxygen pressure (TcPO2) from baseline to 3 months will be discussed. In conclusion, this study will help to determine whether therapeutic angiogenesis with HGF is a viable option in the treatment of patients with CLI.

Using Plasmids as DNA Vaccines for Infectious Diseases

DNA plasmids can be used to induce a protective (or therapeutic) immune response by delivering genes encoding vaccine antigens. That naked DNA (without the refinement of coat proteins or host evasion systems) can cross from outside the cell into the nucleus and be expressed is particularly remarkable given the sophistication of the immune system in preventing infection by pathogens. As a result of the ease, low cost, and speed of custom gene synthesis, DNA vaccines dangle a tantalizing prospect of the next wave of vaccine technology, promising individual designer vaccines for cancer or mass vaccines with a rapid response time to emerging pandemics. There is considerable enthusiasm for the use of DNA vaccination as an approach, but this enthusiasm should be tempered by the successive failures in clinical trials to induce a potent immune response. The technology is evolving with the development of improved delivery systems that increase expression levels, particularly electroporation and the incorporation of genetically encoded adjuvants. This review will introduce some key concepts in the use of DNA plasmids as vaccines, including how the DNA enters the cell and is expressed, how it induces an immune response, and a summary of clinical trials with DNA vaccines. The review also explores the advances being made in vector design, delivery, formulation, and adjuvants to try to realize the promise of this technology for new vaccines. If the immunogenicity and expression barriers can be cracked, then DNA vaccines may offer a step change in mass vaccination.

Polyethylenimine-mediated expression of transgenes in the acinar cells of rats salivary glands in vivo

Non viral-mediated transfection of plasmid DNA provides a fast and reliable way to express various transgenes in selected cell populations in live animals. Here, we show an improvement of a previously published method that is based on injecting plasmid DNA into the ductal system of the salivary glands in live rats. Specifically, using complexes between plasmid DNA and polyethyleneimine (PEI) we show that the expression of the transgenes is directed selectively to the salivary acinar cells. PEI does not affect the ability of cells to undergo regulated exocytosis, which was one of the main drawbacks of the previous methods. Moreover PEI does not affect the proper localization and targeting of transfected proteins, as shown for the apical plasma membrane water channel aquaporin 5 (AQP5). Overall, this approach, coupled with the use of intravital microscopy, permits to conduct localization and functional studies under physiological conditions, in a rapid, reliable, and affordable fashion.

Recent trends of polymer mediated liposomal gene delivery system

Advancement in the gene delivery system have resulted in clinical successes in gene therapy for patients with several genetic diseases, such as immunodeficiency diseases, X-linked adrenoleukodystrophy (X-ALD) blindness, thalassemia, and many more. Among various delivery systems, liposomal mediated gene delivery route is offering great promises for gene therapy. This review is an attempt to depict a portrait about the polymer based liposomal gene delivery systems and their future applications. Herein, we have discussed in detail the characteristics of liposome, importance of polymer for liposome formulation, gene delivery, and future direction of liposome based gene delivery as a whole.

Hydrodynamic immunization leads to poor CD8 T-cell expansion, low frequency of memory CTLs and ineffective antiviral protection

Hepatotropic pathogens, such as hepatitis B (HBV) and hepatitis C (HCV), often escape cellular immune clearance resulting in chronic infection. As HBV and HCV infections are the most common causes of hepatocellular carcinoma (HCC), prevention of these infections is believed to be key to the prevention of HCC. It is believed that an effective immune therapy must induce strong cytotonic T lymphocytes (CTLs) that can migrate into the liver, where they can clear infected hepatocytes. Here, we compared the induction of CD8 T cells by two different DNA immunization methods for T-cell differentiation, function, memory programming and their distribution within relevant tissues in a highly controlled fashion. We used hydrodynamic tail vein injection of plasmid to establish liver-specific LCMV-gp antigen (Ag) transient expression, and studied CD8 T cells induced using the P14 transgenic mouse model. CD8 T cells from this group exhibited unique and limited expansion, memory differentiation, polyfunctionality and cytotoxicity compared with T cells generated in intramuscularly immunized mice. This difference in liver-generated expansion resulted in lower memory CD8 T-cell frequency, leading to reduced protection against lethal viral challenge. These data show an unusual induction of naive CD8 T cells contributed to the lower frequency of Ag-specific CTLs observed after immunization in the liver, suggesting that limited priming in liver compared with peripheral tissues is responsible for this outcome.

The effect of cholesterol domains on PEGylated liposomal gene delivery in vitro

AIM

PEGylated components have been widely used to reduce particle aggregation in serum and extend circulation lifetime for lipid- and polymer-based gene-delivery systems. However, PEGylation is known to interfere with cell interaction and intracellular trafficking, resulting in decreased biological activity. In the present study, the effect of cholesterol domains on PEGylated liposome-mediated gene delivery was evaluated by PEGylating formulations with and without a cholesterol domain, and also by altering the location of PEG on the particle surface (i.e., within or excluded from the domain).

MATERIALS AND METHODS

Lipoplexes formulated with PEG-cholesterol or PEG-diacyl lipid were used to transfect various cell lines, including human and mouse cancer cells. Cellular uptake of lipoplexes was also quantified and compared with the transfection results.

RESULTS

Our findings are consistent with previous work demonstrating that PEGylation reduces transfection rates; however, formulations in which PEG was incorporated into the cholesterol domain did not exhibit this detrimental effect. In some cell lines, the incorporation of PEG into the domain actually increased transfection rates, despite no enhancement of cellular uptake.

DISCUSSION

These results suggest that the adverse alterations in intracellular trafficking that are a consequence of PEGylation may be avoided by utilizing delivery vehicles that allow PEG to partition into a cholesterol domain.

Therapeutic effect of recombinant plasmid-encoded human interleukin-12 in tumor-bearing mice

The aim of this study was to investigate the effects of gene therapy using a recombinant plasmid encoding human interleukin-12 (rIL-12, pcDNA6-p70) on transplanted tumors in mice. Tumor-bearing mice were transplanted with sarcoma‑180 (S-180) cells and randomly divided into three groups of 10 mice with each group receiving a separate treatment. Following this, pcDNA6-p70 (dissolved in purified water; 100 µg/mouse), cyclophosphamide (dissolved in 0.9% saline; 40 mg/kg) or 0.9% saline (100 µl/mouse) was directly injected into the tumors on the 4th, 7th, 10th, 14th and 17th days following transplantation of the S-180 cells. Mice survival time was monitored and surviving mice were sacrificed on the 21st day. In addition to survival time, tumor volume, NK cell activity, spleen lymphocyte proliferation and IFN-γ production were investigated. The mice were also monitored for any adverse effects regarding the administration of pcDNA6-p70. Our results demonstrated that pcDNA6-p70 prolongs the survival time of tumor-bearing mice, decreases tumor size (P<0.01) and increases the proliferative response of spleen cells, the activity of NK cells and the serum level of IFN-γ. There were no significant adverse effects caused by the administration of pcDNA6-p70. The results of the present study support the hypothesis that gene therapy using the rIL-12 plasmid exerts a therapeutic effect in tumor models by triggering antitumor cellular immunity.

Plasmid DNA is internalized from the apical plasma membrane of the salivary gland epithelium in live animals

Non-viral-mediated gene delivery represents an alternative way to express the gene of interest without inducing immune responses or other adverse effects. Understanding the mechanisms by which plasmid DNAs are delivered to the proper target in vivo is a fundamental issue that needs to be addressed in order to design more effective strategies for gene therapy. As a model system, we have used the submandibular salivary glands in live rats and we have recently shown that reporter transgenes can be expressed in different cell populations of the glandular epithelium, depending on the modality of administration of plasmid DNA. Here, by using a combination of immunofluorescence and intravital microscopy, we have explored the relationship between the pattern of transgenes expression and the internalization of plasmid DNA. We found that plasmid DNA is internalized: (1) by all the cells in the salivary gland epithelium, when administered alone, (2) by large ducts, when mixed with empty adenoviral particles, and (3) by acinar cells upon stimulation of compensatory endocytosis. Moreover, we showed that plasmid DNA utilizes different routes of internalization, and evades both the lysosomal degradative pathway and the retrograde pathway towards the Golgi apparatus. This study clearly shows that in vivo approaches have the potential to address fundamental questions on the cellular mechanisms regulating gene delivery.

Drug delivery trends in clinical trials and translational medicine: challenges and opportunities in the delivery of nucleic acid-based therapeutics

The ability to deliver nucleic acids (e.g., plasmid DNA, antisense oligonucleotides, siRNA) offers the potential to develop potent vaccines and novel therapeutics. However, nucleic acid-based therapeutics are still in their early stages as a new category of biologics. The efficacy of nucleic acids requires that these molecules be delivered to the interior of the target cell, which greatly complicates delivery strategies and compromises efficiency. Due to the safety concerns of viral vectors, synthetic vectors such as liposomes and polymers are preferred for the delivery of nucleic acid-based therapeutics. Yet, delivery efficiencies of synthetic vectors in the clinic are still too low to obtain therapeutic levels of gene expression. In this review, we focus on some key issues in the field of nucleic acid delivery such as PEGylation, encapsulation and targeted delivery and provide some perspectives for consideration in the development of improved synthetic vectors.

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.

TAA polyepitope DNA-based vaccines: a potential tool for cancer therapy

DNA-based cancer vaccines represent an attractive strategy for inducing immunity to tumor associated antigens (TAAs) in cancer patients. The demonstration that the delivery of a recombinant plasmid encoding epitopes can lead to epitope production, processing, and presentation to CD8+ T-lymphocytes, and the advantage of using a single DNA construct encoding multiple epitopes of one or more TAAs to elicit a broad spectrum of cytotoxic T-lymphocytes has encouraged the development of a variety of strategies aimed at increasing immunogenicity of TAA polyepitope DNA-based vaccines. The polyepitope DNA-based cancer vaccine approach can (a) circumvent the variability of peptide presentation by tumor cells, (b) allow the introduction in the plasmid construct of multiple immunogenic epitopes including heteroclitic epitope versions, and (c) permit to enroll patients with different major histocompatibility complex (MHC) haplotypes. This review will discuss the rationale for using the TAA polyepitope DNA-based vaccination strategy and recent results corroborating the usefulness of DNA encoding polyepitope vaccines as a potential tool for cancer therapy.

Quantitative real-time PCR study on persistence of pDNA vaccine pVax-Hsp60 TM814 in beef muscles

Background

Application of plasmid DNA for immunization of food-producing animals established new standards of food safety. The addition of foreign products e.g. pDNA into the food chain should be carefully examined to ensure that neither livestock animals nor consumers develop unpredicted or undesirable side-effects.

Methods

A quantitative real-time PCR (QRTPCR) methodology was developed to study the biodistribution and persistence of plasmid DNA vaccine pDNAX (pVAX-Hsp60 TM814) in mice and beef cattle. The linear quantification range and the sensitivity of the method was found to be 10 – 10⁹ copies per reaction (500 ng/gDNA) and 3 copies per reaction, respectively.

Results

Persistence of pDNAX in mice muscle tissue was restricted to injection site and the amount of pDNAX showed delivery formulation dependent (naked pDNA, electroporation, cationic liposome complexes) and mouse age-dependent clearance form injection site but pDNAX was still detectable even after 365 days. The QRTPCR analysis of various muscle tissue samples of vaccinated beef bulls performed 242–292 days after the last revaccination proved that residual pDNAX was found only in the injection site. The highest plasmid levels (up to 290 copies per reaction) were detected in the pDNAX:CDAN/DOPE group similarly to mice model. No pDNA was detected in the samples from distant muscles and draining lymph nodes.

Conclusion

Quantitative real-time PCR (QRTPCR) assay was developed to assess the residual pDNA vaccine pVAX-Hsp60 TM814 in mice and beef cattle. In beef cattle, ultra low residual level of pDNA vaccine was only found at the injection site. According to rough estimation, consumption of muscles from the injection site represents almost an undetectable intake of pDNA (400 fg/g muscle tissue) for consumers. Residual plasmid in native state will hardly be found at measurable level following further meat processing. This study brings supportive data for animal and food safety and hence for further approval of pDNA vaccine field trials.

What happens to the DNA vaccine in fish? A review of current knowledge

The primary function of DNA vaccines, a bacterial plasmid DNA containing a construct for a given protective antigen, is to establish specific and long-lasting protective immunity against diseases where conventional vaccines fail to induce protection. It is acknowledged that less effort has been made to study the fate, in terms of cellular uptake, persistence and degradation, of DNA vaccines after in vivo administration. However, during the last year some papers have given new insights into the fate of DNA vaccines in fish. By comparing the newly acquired information in fish with similar knowledge from studies in mammals, similarities with regard to transport, blood clearance, cellular uptake and degradation of DNA vaccines have been found. But the amount of DNA vaccine redistributed from the administration site after intramuscular administration seems to differ between fish and mammals. This review presents up-to-date and in-depth knowledge concerning the fate of DNA vaccines with emphasis on tissue distribution, cellular uptake and uptake mechanism(s) before finally describing the intracellular hurdles that DNA vaccines need to overcome in order to produce their gene product.

Smooth muscle-specific gene delivery in the vasculature based on restriction of DNA nuclear import

The two currently employed approaches restricting gene delivery and/or expression to desired cell types in vivo rely on cell surface targeting or cell-specific promoters. We have developed a third approach based on cell-specific nuclear transport of the delivered plasmid DNA. We have previously shown that plasmid nuclear import in non-dividing cells is sequence-specific and have identified a set of cell-specific DNA nuclear targeting sequences that can be used to limit DNA nuclear import to desired cell types. Specifically we have identified elements of the smooth muscle gamma actin (SMGA) promoter that direct plasmid nuclear import selectively in smooth muscle cells (SMCs) in vitro (Vacik et al, 1999, Gene Therapy 6:1006-1014). In the present study, we demonstrate that the SMC-specific DNA nuclear targeting sequence from the SMGA promoter drives nuclear accumulation of plasmids and subsequent gene expression exclusively in the smooth muscle cell layer of the vessel wall in the intact vasculature of rats using electroporation mediated delivery. These results demonstrate that certain DNA nuclear targeting sequences can be used to restrict DNA nuclear import to specific cell types providing a new, novel means of cell targeting for gene therapy.

Endocytosis of DNA-Hsp65 alters the pH of the late endosome/lysosome and interferes with antigen presentation

Background

Experimental models using DNA vaccine has shown that this vaccine is efficient in generating humoral and cellular immune responses to a wide variety of DNA-derived antigens. Despite the progress in DNA vaccine development, the intracellular transport and fate of naked plasmid DNA in eukaryotic cells is poorly understood, and need to be clarified in order to facilitate the development of novel vectors and vaccine strategies.

Methodology and Principal Findings

Using confocal microscopy, we have demonstrated for the first time that after plasmid DNA uptake an inhibition of the acidification of the lysosomal compartment occurs. This lack of acidification impaired antigen presentation to CD4 T cells, but did not alter the recruitment of MyD88. The recruitment of Rab 5 and Lamp I were also altered since we were not able to co-localize plasmid DNA with Rab 5 and Lamp I in early endosomes and late endosomes/lysosomes, respectively. Furthermore, we observed that the DNA capture process in macrophages was by clathrin-mediated endocytosis. In addition, we observed that plasmid DNA remains in vesicles until it is in a juxtanuclear location, suggesting that the plasmid does not escape into the cytoplasmic compartment.

Conclusions and Significance

Taken together our data suggests a novel mechanism involved in the intracellular trafficking of plasmid DNA, and opens new possibilities for the use of lower doses of plasmid DNA to regulate the immune response.

Identification of proteins released by mammalian cells that mediate DNA internalization through proteoglycan-dependent macropinocytosis

Naked DNA plasmid represents the simplest vehicle for gene therapy and DNA-based vaccination purposes; however, the molecular mechanisms of DNA uptake in mammalian cells are poorly understood. Here, we show that naked DNA uptake occurs via proteoglycan-dependent macropinocytosis, thus challenging the concept of a specific DNA-internalizing receptor. Cells genetically deficient in proteoglycans, which constitute a major source of cell-surface polyanions, exhibited substantially decreased uptake of likewise polyanionic DNA. The apparent paradox was explained by the action of DNA-transporting proteins present in conditioned medium. Complexes between these proteins and DNA require proteoglycans for cellular entry. Mass spectrometry analysis of cell medium components identified several proteins previously shown to associate with DNA and to participate in membrane transport of macromolecular cargo. The major pathway for proteoglycan-dependent DNA uptake was macropinocytosis, whereas caveolae-dependent and clathrin-dependent pathways were not involved, as determined by using caveolin-1 knock-out cells, dominant-negative constructs for dynamin and Eps15, and macropinocytosis-disruptive drugs, as well as confocal fluorescence co-localization studies. Importantly, a significant fraction of internalized DNA was translocated to the nucleus for expression. Our results provide novel insights into the mechanism of DNA uptake by mammalian cells and extend the emerging role of proteoglycans in macromolecular transport.

An ESAT-6:CFP10 DNA vaccine administered in conjunction with Mycobacterium bovis BCG confers protection to cattle challenged with virulent M. bovis

The potency of genetic immunization observed in the mouse has demonstrated the utility of DNA vaccines to induce cell-mediated and humoral immune responses. However, it has been relatively difficult to generate comparable responses in non-rodent species. The use of molecular adjuvants may increase the magnitude of these suboptimal responses. In this study, we demonstrate that the co-administration of plasmid-encoded GM-CSF and CD80/CD86 with a novel ESAT-6:CFP10 DNA vaccine against bovine tuberculosis enhances antigen-specific cell-mediated immune responses. ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA vaccinated animals exhibited significant (p<0.01) antigen-specific proliferative responses compared to other DNA vaccinates. Increased expression (p< or =0.05) of CD25 on PBMC from ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA vaccinates was associated with increased proliferation, as compared to control DNA vaccinates. Significant (p<0.05) numbers of ESAT-6:CFP10-specific IFN-gamma producing cells were evident from all ESAT-6:CFP10 DNA vaccinated animals compared to control DNA vaccinates. However, the greatest increase in IFN-gamma producing cells was from animals vaccinated with ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA. In a low-dose aerosol challenge trial, calves vaccinated as neonates with Mycobacterium bovis BCG and ESAT-6:CFP10+GM-CSF+CD80/CD86 DNA exhibited decreased lesion severity in the lung and lung-associated lymph nodes following viruluent M. bovis challenge compared to other vaccinated animals or non-vaccinated controls. These data suggest that a combined vaccine regimen of M. bovis BCG and a candidate ESAT-6:CFP10 DNA vaccine may offer greater protection against tuberculosis in cattle than vaccination with BCG alone.

Non-ionic amphiphilic biodegradable PEG-PLGA-PEG copolymer enhances gene delivery efficiency in rat skeletal muscle

Naked plasmid DNA (pDNA)-based gene therapy has low delivery efficiency, and consequently, low therapeutic effect. We present a biodegradable nonionic triblock copolymer, PEG(13)-PLGA(10)-PEG(13), to enhance gene delivery efficiency in skeletal muscle. Effects of PEG(13)-PLGA(10)-PEG(13) on physicochemical properties of pDNA were evaluated by atomic force microscopy (AFM) imaging, gel electrophoresis and zeta-potential analysis. AFM imaging suggested a slightly compacted structure of pDNA when it was mixed with the polymer, while zeta-potential measurement indicated an increased surface potential of negatively charged pDNA. PEG(13)-PLGA(10)-PEG(13) showed a relatively lower toxicity compared to Pluronic P85 in a skeletal muscle cell line. The luciferase expression of pDNA delivered in 0.25% polymer solution was up to three orders of magnitude more than branched polyethylenimine (bPEI(25 k))/pDNA and three times more than that of naked pDNA five days after intramuscular administration. This in vivo gene delivery enhancement was also observed displaying a two-fold higher expression of human vascular endothelial growth factor (VEGF). Based on fluorescence labeled pDNA distribution, it is speculated that the greater diffusivity of PEG(13)-PLGA(10)-PEG(13)/pDNA compared to bPEI(25 k)/pDNA accounts for better transfection efficiency in vivo. To summarize, combining PEG(13)-PLGA(10)-PEG(13) with pDNA possesses the potential to improve gene delivery efficiency in skeletal muscle.

Vinyl Polymers as Non-Viral Gene Delivery Carriers: Current Status and Prospects

Since the first application of polymers as non-viral gene delivery systems in 1965 by Vaheri and Pagano using functionalised dextran (A. Vaheri and J. S. Pagano, "Infectious poliovirus RNA: a sensitive method of assay", Virology 1965, 27, 434-6), a large number of different polymers have been developed, studied and compared for application as DNA carriers. Vinyl-based polymers are one type of polymers that have gained considerable interest. The interest in developing this particular type of polymer is partly related to the straightforward way in which large amounts of these polymers can be prepared by radical (co)polymerisation. This opens up a path for establishing a wide range of structure-property relations using polymer libraries. The present review aims to give an overview of past and ongoing research using vinyl-based gene delivery systems. The application of cationic, neutral and zwitterionic polymers as DNA carriers is summarised and discussed. [structure: see text] Chemical structure of DEAE-functionalised dextran.

Comparing reagents for efficient transfection of human primary myoblasts: FuGENE 6, Effectene and ExGen 500

This study compared three different synthetic reagents (FuGENE 6, Effectene and ExGen 500) for the transfection of human primary myoblasts. We examined the efficiency, cytotoxicity and size of the complexes formed in the presence of different amounts of vector and DNA and with variable amounts of serum. Transfection rates were relatively high for primary cells, especially with FuGENE 6 (20%), which appeared to be the best transfection reagent for these cells, even in the presence of 10% serum. Cultured human myoblasts are an interesting tool for studying neuromuscular diseases and are potentially useful for myoblast transfer therapy studies. Moreover, the efficiency of these transfection reagents in a medium containing 10% serum is promising for possible gene therapy protocols for muscle diseases.

Nonviral delivery of cancer genetic vaccines

The potential use of genetic vaccines to address numerous diseases including cancer is promising, but currently unrealized. Here, we review advances in the nonviral delivery of antigen-encoded plasmid DNA for the purpose of treating cancer through the human immune system, as this disease has drawn the most attention in this field to date. Brief overviews of dendritic cell immunobiology and the mechanism of immune activation through genetic vaccines set the stage for the desirability of delivery technology. Several promising nonviral delivery techniques are discussed along with a mention of targeting strategies aimed at improving the potency of vaccine formulations. Implications for the future of genetic vaccines are also presented.

Angiogenic and antiangiogenic gene therapy

Gene therapy is thought to be a promising method for the treatment of various diseases. One gene therapy strategy involves the manipulations on a process of formation of new vessels, commonly defined as angiogenesis. Angiogenic and antiangiogenic gene therapy is a new therapeutic approach to the treatment of cardiovascular and cancer patients, respectively. So far, preclinical and clinical studies are successfully focused mainly on the treatment of coronary artery and peripheral artery diseases. Plasmid vectors are often used in preparations in angiogenic gene therapy trials. The naked plasmid DNA effectively transfects the skeletal muscles or heart and successfully expresses angiogenic genes that are the result of new vessel formation and the improvement of the clinical state of patients. The clinical preliminary data, although very encouraging, need to be well discussed and further study surely continued. It is really possible that further development of molecular biology methods and advances in gene delivery systems will cause therapeutic angiogenesis as well as antiangiogenic methods to become a supplemental or alternative option to the conventional methods of treatment of angiogenic diseases.

Highly Efficient Constant-Current Electroporation IncreasesIn VivoPlasmid Expression

Electroporation has been demonstrated as an effective technique for enhancing the delivery of plasmids coding for DNA vaccines and therapeutic proteins into skeletal muscle. Nevertheless, constant-voltage techniques do not take into account the resistance of the tissue and result in tissue damage, inflammation, and loss of plasmid expression. In the present study, we have used a software-driven constant-current electroporator to deliver plasmids to mice and small and large pigs. The voltage, amperage, and resistance of the tissue during pulses were recorded and analyzed. Optimal conditions of electroporation were identified in both species, and found to be highly dependent on the individual tissue resistance. Six- to 10-week-old pigs had higher muscle resistance compared to 1- to 2-year-old pigs, but both values were four to five times lower than the resistance of the mouse muscle. In mice, optimum amperage, pulse length, and lag time between plasmid injection and electroporation were identified to be 0.1 Amps, 20 msec and 0 sec. The electroporation pulse pattern among the electrodes also affected plasmid expression. These results indicate that age- and tissue-specific resistance, pulse pattern, and other variables associated with the electroporation need to be optimized for each separate species to achieve maximum plasmid expression.

Formulation and characterization of poly (β amino ester) microparticles for genetic vaccine delivery

Microparticulate delivery systems are a promising and versatile enhancement to DNA vaccines because they can target large payloads of plasmid and immunomodulating materials to antigen presenting cells (APC). A pH sensitive poly-beta amino ester (PBAE) has been recently described which substantially increases adjuvancy and delivery efficiency of such microparticle formulations. This work describes the characterization and formulation considerations specific to these PBAE containing microparticles. PBAE increases the supercoiled content and overall effective loading of plasmid DNA. This polymer also significantly buffers the pH microenvironment created by ester bond degradation, rendering encapsulated plasmid more suitable for transfection. Release of plasmid from microparticles is controllable based on the amount of PBAE in the composition. Transfection is dependant upon phagocytosis, and is optimal for 15% and 25% PBAE microparticle formulations. However, larger quantities of PBAE may be toxic to cells indicating that the 15% PBAE formulation is a suitable candidate for delivery in future studies with disease specific, DNA vaccines.

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.

Manipulation of local disposition and gene expression characteristics of plasmid DNA following intramuscular administration by complexation with cationic macromolecule

To modulate the immune responses of DNA vaccine, it is very important to control the disposition and gene expression of plasmid DNA (pDNA) after local administration. We chose methylated bovine serum albumin (mBSA), a cationic macromolecule, as a carrier of pDNA. We examined the effects of complexation of pDNA with mBSA on the disposition and gene expression in mice after intramuscular administration. The elimination from injection site was retarded and the accumulation to lymph nodes was increased at the positively charged mBSA/pDNA complexes. As the charge ratios of mBSA/pDNA complexes were higher, the levels of gene expression were reduced. Antigen specific immune responses were evaluated using pDNA encoding ovalbumin (OVA), pCMV-OVA, as a model antigen-expressing pDNA. However, significant levels of production of anti-ovalbumin IgG antibody were obtained in mice immunized with a positively charged complex, mBSA/pCMV-OVA (8:1) (weight ratio). In vitro experiments using DC2.4 cells, a murine dendritic cell line, demonstrated that the levels of gene expression and cytokine release were increased by complexation. These results suggest that the immune responses might be manipulated by complexation presumably due to the altered disposition and gene expression of pDNA.

Pluronic Block Copolymers for Gene Delivery

Amphiphilic block copolymers of poly(ethylene oxide) and poly(propylene oxide) called Pluronic or poloxamer are commercially available pharmaceutical excipients. They recently attracted considerable attention in gene delivery applications. First, they were shown to increase the transfection with adenovirus and lentivirus vectors. Second, they were shown to increase expression of genes delivered into cells using non-viral vectors. Third, the conjugates of Pluronic with polycations, were used as DNA-condensing agents to form polyplexes. Finally, it was demonstrated that they can increase regional expression of the naked DNA after its injection in the skeletal and cardiac muscles or tumor. Therefore, there is substantial evidence that Pluronic block copolymers can improve gene expression with different delivery routes and different types of vectors, including naked DNA. These results and possible mechanisms of Pluronic effects are discussed. At least in some cases, Pluronic can act as biological adjuvants by activating selected signaling pathways, such as NF-kappaB, and upregulating the transcription of the genes.

New dimensions in vaccinology: A new insight

The development of vaccines to prevent infectious diseases has been one of the most important contributions of biomedical sciences. Increasing understanding in biochemistry, molecular biology, molecular genetics and related fields have provided an opportunity for the development of new generation vaccines that are based on rational design approaches. This is possible because of proper understanding of the microbial-genetics, biochemistry, host-pathogen interaction and recent developments in molecular immunology. Another important improvement made in the quality of vaccine production is the incorporation of immunomodulators or adjuvants with modified delivery vehicles viz liposomes, Iscoms and microspheres apart from alum being used as a gold standard. This article reviews the art of vaccination from Jenner period to present day context highlighting all the developments made at each stage of the vaccine development. Various criteria have been discussed regarding the selection of epitopes that expand B & T cells, its linkage with other accessory cells of the immune system, means to overcome MHC linked immune unresponsiveness, enhanced antigen processing and presentations that specially induce either helper or cytotoxic or mucosal immune responses were critically discussed.

Biodegradable polyphosphoester micelles for gene delivery

A new biodegradable polyphosphoester, poly[[(cholesteryl oxocarbonylamido ethyl) methyl bis(ethylene) ammonium iodide] ethyl phosphate] (PCEP) was synthesized and investigated for gene delivery. Carrying a positive charge in its backbone and a lipophilic cholesterol structure in the side chain, PCEP self-assembled into micelles in aqueous buffer at room temperature with an average size of 60-100 nm. It could bind and protect plasmid DNA from nuclease digestion. Cell proliferation assay indicated a lower cytotoxicity for PCEP than for poly-L-lysine and Lipofectamine. The IC50 determined by the WST-1 assay was 69.8, 51.6, and 12.1 microg/mL for PCEP, Lipofectamine, and poly-L-lysine, respectively. PCEP efficiently delivered DNA to several cell lines such as HEK293, Caco-2, and HeLa. The highest efficiency was achieved when PCEP/DNA complex was prepared in Opti-MEM with a +/- charge ratio of 1.5-2. The transfection efficiency did not change significantly when the complex was used 3 days after preparation. The addition of chloroquine to the formulation increased transfection efficiency 10- to 50-fold compared to the complex alone. In vivo studies showed a luciferase expression by PCEP/DNA complexes in muscle increasing with time during 3 months, although the expression level was lower than that by direct injection of naked DNA. In addition to biodegradability and lower toxicity, the PCEP micelle carrier offers structural versatility. The backbone charge density and the side chain lipophilicity are two parameters that can be varied through copolymerization and monomer variation to optimize the transfection efficiency.

Influence of routes and administration parameters on antibody response of pigs following DNA vaccination

Using the nucleoprotein of porcine reproductive and respiratory syndrome virus as model antigen, we optimised parameters for gene gun vaccination of pigs, including firing pressure and vaccination site. As criteria for optimisation, we characterised particle penetration and local tissue damage by histology. For selected combinations, vaccination efficiency in terms of antibody response was studied. Gene gun vaccination on ear alone was as efficient as a multi-site (ear, thorax, inguinal area, tongue mucosa) gene gun approach, and more efficient than combined intramuscular (i.m.)/intradermal (i.d.) injection of plasmid DNA. This indicates, that the ear is an attractive site for gene gun vaccination of pigs.

Intramuscular plasmid DNA electrotransfer: biodistribution and degradation

We have studied radiolabelled plasmid DNA biodistribution and degradation in the muscle at different times after injection, with or without electrotransfer using previously defined conditions. Radiolabelled plasmid progressively left the muscle and was degraded as soon as 5 min after plasmid injection, with or without electrotransfer. Autoradiography showed that the major part of injected radioactivity was detected in the interfibrilar space of a large proportion of the muscle. Large zones of accumulation of radioactivity, which seems to be contained in some fibres (more than 20 microm), were identified as soon as 5 min after electrotransfer. Such structures were never observed on slices of non-electrotransferred muscles. However, these structures were not frequent and probably lesional. The surprising fact is that despite the amount of intact plasmid having been greatly reduced between 5 min and 3 h after injection, the level of transfection remains unchanged whether electric pulses were delivered 20 s or 3 h after injection. Such a behavior was similarly observed when injecting 0.3, 3 or 30 microg of plasmid DNA. Moreover, the transfection level was correlated to the amount of plasmid DNA injected. These results suggest that as soon as it is injected, plasmid DNA is proportionally partitioned between at least two compartments. While a major part of plasmid DNA is rapidly cleared and degraded, the electrotransferable pool of plasmid DNA represents a very small part of the amount injected and belongs to another compartment where it is protected from endogenous DNAses.

Humoral immunoreaction induced by TCR DNA vaccine for β chain of T cell lymphoma

We exploited the humoral immunoreaction of mice induced by TCR DNA vaccine of beta chain of T cell lymphoma. The plasmids of pcDNA3.1/TCR V beta 8 was constructed. The BALB/c mice were randomly divided into four groups which were pcDNA3.1, pcDNA3.1/TCR V beta 8, pcDNA3.1/TCR V beta 8 + CpG + liposome and phosphorothioate CpG groups with six mice in each group. Vaccines were injected in bilateral musculus quadriceps femoris of mice in the 0, second, and fourth week, respectively. The antibody formation was tested by indirect immuofluorescence in the 0, second, fourth, sixth and eighth weeks, respectively, before and after immunization. Production of antibody against TCR V beta 8 antigen was observed in the groups of pcDNA3.1/TCR V beta 8 and pcDNA3.1/TCR V beta 8 + CpG + liposome. The antibody titer began to rise in the fourth week and attain the maximal value in the sixth week. The antibody titer in the group of pcDNA3.1/TCR V beta 8 + CpG + liposome was higher than that in the group of pcDNA3.1/TCR V beta 8 in the fourth and eighth weeks (both P<0.01); the antibody titer in the group of pcDNA3.1/TCR V beta 8 + CpG + liposome was markedly higher than that in the group of pcDNA3.1/TCR V beta 8 in the sixth week (P<0.001). The result indicate that TCR V beta 8 antigen can induce formation of special antibody in mice. CpG and liposome can improve the humoral immunoreaction induced by TCR V beta 8 gene vaccine.

The role of lipid charge density in the serum stability of cationic lipid/DNA complexes

To evaluate the role of lipid charge density in the serum stability of DOTAP-Chol/DNA complexes (lipoplexes), lipid-DNA interactions, extent of aggregation, supercoil content, and in vitro transfection efficiency of lipoplexes were investigated. In general, higher serum concentration destabilized, and increasing molar charge ratio of DOTAP to negatively charged phosphates in the DNA (DOTAP(+)/DNA(-)) stabilized lipoplexes in serum as assessed by the criteria used in this study. The increase of cholesterol content led to increased serum stability, and DOTAP:Chol (mol/mol 1:4)/DNA lipoplex with DOTAP(+)/DNA(-) ratio 4 was the most serum stable formulation of all the formulations examined, and maintained lipid-DNA interactions, did not aggregate and exhibited high in vitro transfection efficiency in 50% (v/v) serum. The increased stability of this formulation could not be explained by the decreased charge density of the lipid component. Furthermore, no single parameter examined in the study could be used to consistently predict the in vitro transfection efficiency of lipoplexes in serum. Surprisingly, no correlation between the maintenance of supercoiled DNA content and in vitro transfection efficiency was found in the study.

Uptake and trafficking of DNA in keratinocytes: evidence for DNA-binding proteins

The skin is an interesting organ for human gene therapy due to accessibility, immunologic potential and synthesis capabilities. In this study, we attempted to visualize and measure the uptake of naked FITC-labeled plasmid by FACS analysis detecting up to 15% internalization in a dose- and time-dependent manner. Cycloheximide treatment inhibited the uptake by >90%, suggesting a protein-mediated uptake. The inhibition of different internalization pathways demonstrated that blocking macropinocytosis (by amiloride and N,N-dimethylamylorid) reduced DNA uptake by >85%, while the inhibition of clathrin-coated pits (by chlorpromazine) and caveolae (by nystatin/filipin III) did not limit the uptake. Colocalization studies using confocal laser microscopy revealed a time-dependent accumulation of plasmid DNA in endosomes and lysosomes. When a green fluorescent protein (GFP) expression vector was used, specific GFP-RNA became detectable by reverse transcriptase-PCR, whereas measurable amounts of protein could not be identified in FACS experiments. To detect the potential DNA receptors on the keratinocyte surface, membrane proteins were extracted and subjected to South-Western blotting using digoxigenin-labeled calf thymus and lambda-phage DNA. Two DNA-binding proteins, ezrin and moesin, known as plasma membrane-actin linkers, were identified by one- and two-dimensional-South-Western blots and matrix-assisted laser desorption and ionization-mass spectrometry. Ezrin and moesin are functionally associated with a number of transmembrane receptors such as the EGF, CD44 or ICAM-1 receptor. Taken together, naked plasmid DNA seems to enter human keratinocytes through different pathways, mainly by macropinocytosis. Two DNA-binding proteins were identified that seemed to be involved in binding/trafficking of internalized DNA.

Effect of side-chain structures on gene transfer efficiency of biodegradable cationic polyphosphoesters

Cationic polyphosphoesters (PPEs) with different side-chain charge groups were designed and synthesized as biodegradable gene carriers. Poly(N-methyl-2-aminoethyl propylene phosphate) (PPE-MEA), with a secondary amino group (-CH(2)CH(2)NHCH3) side chain released DNA in several hours at N/P (amino group of polymer to phosphate group of DNA) ratios from 0.5 to 5; whereas PPE-HA, bearing -CH(2)(CH2)(4)CH(2)NH(2) groups in the side chain, did not release DNA at the same ratio range for 30 days. Hydrolytic degradation and DNA binding results suggested that side chain cleavage, besides the polymer degradation, was the predominant factor affected the DNA release and transfection efficiencies. The side chain of PPE-MEA was cleaved faster than that of PPE-HA, resulting poor cellular uptake and no transgene expression for PPE-MEA/DNA complexes in COS-7 cells at charge ratios from 4 to 12. In contrast, PPE-HA/DNA complexes were stable enough to be internalized by cells and effected gene transfection (3400 folds higher than background at a charge ratio of 12). Interestingly, gene expression levels mediated by PPE-MEA and PPE-HA in mouse muscle following intramuscular injection of complexes showed a reversed order: PPE-MEA/DNA complexes mediated a 1.5-2-fold higher luciferase expression in mouse muscle as compared with naked DNA injection, while PPE-HA/DNA complexes induced delayed and lowered luciferase expression than naked DNA. These results suggested that the side chain structure is a crucial factor determining the mechanism and kinetics of hydrolytic degradation of PPE carriers, which in turn influenced the kinetics of DNA release from PPE/DNA complexes and their transfection abilities in vitro and in vivo.