Skin permeation, biodistribution, and expression of topically applied plasmid DNA

Minicircle DNA is superior to plasmid DNA in eliciting antigen-specific CD8+ T-cell responses

Clinical trials reveal that plasmid DNA (pDNA)-based gene delivery must be improved to realize its potential to treat human disease. Current pDNA platforms suffer from brief transgene expression, primarily due to the spread of transcriptionally repressive chromatin initially deposited on plasmid bacterial backbone sequences. Minicircle (MC) DNA lacks plasmid backbone sequences and correspondingly confers higher levels of sustained transgene expression upon delivery, accounting for its success in preclinical gene therapy models. In this study, we show for the first time that MC DNA also functions as a vaccine platform. We used a luciferase reporter transgene to demonstrate that intradermal delivery of MC DNA, relative to pDNA, resulted in significantly higher and persistent levels of luciferase expression in mouse skin. Next, we immunized mice intradermally with DNA encoding a peptide that, when presented by the appropriate major histocompatibility complex class I molecule, was recognized by endogenous CD8(+) T cells. Finally, immunization with peptide-encoding MC DNA, but not the corresponding full-length (FL) pDNA, conferred significant protection in mice challenged with Listeria monocytogenes expressing the model peptide. Together, our results suggest intradermal delivery of MC DNA may prove more efficacious for prophylaxis than traditional pDNA vaccines.

Nanopolymeric micelle effect on the transdermal permeability, the bioavailability and gene expression of plasmid

This study attempts to investigate the transdermal permeability, the bioavailability and gene expression of plasmid formulated with nonionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) polymeric micelles (PM). Dynamic light scattering (DLS) and atomic force microscopy (AFM) were used to analyze the PM formulated pCMV-Lac Z (P/PM) containing the gene for β-galactosidase (β-Gal) driven by cytomegalovirus early promoter. Franz diffusion cell was used for in vitro transdermal permeability analysis. Real-time PCR was used to quantify the permeated plasmid in vitro and in vivo. β-Gal activity assay was performed to evaluate transgene expression in vivo. The size of P/PM was ~50 nm with round shape. PM significantly enhanced the in vitro transdermal permeability of plasmid in a direction- and temperature-dependent manner. Following transdermal application of P/PM, higher area under the curve (AUC(P/PM): 98.34 h·ng/mL) and longer half-life of plasmid were detected compared with that of plasmid alone (AUC(P): 10.12 h·ng/mL). Additionally, the β-Gal activity was significantly increased in skin, stomach, brain and spinal cord at both 48 and 72 h after P/PM application and in testis and spleen at 72 h postapplication. In conclusion, PM formulation enhanced the permeation of plasmid through skin into blood circulation, increasing its absorption and the transgene expression in various tissues.

Transcutaneous DNA immunization following waxing-based hair depilation

Transcutaneous DNA immunization is an attractive immunization approach. Previously, we reported that transcutaneous immunization by applying plasmid DNA onto a skin area wherein the hair follicles had been induced into growth stage by 'cold' waxing-based hair plucking significantly enhanced the resultant immune responses. In the present study, using a plasmid that encodes the Bacillus anthracis protective antigen (PA63) gene fragment, it was shown that the anti-PA63 antibody responses induced by applying the plasmid onto a skin area where the hair was plucked by 'warm' waxing were significantly stronger than by 'cold' waxing, very likely because the 'warm' waxing-based hair depilation significantly i) enhanced the uptake (or retention) of the plasmid in the application area and ii) enhanced the expression of the transfected gene in the follicular and interfollicular epidermis in the skin. The antibody response induced by transcutaneous DNA immunization was hair cycle dependent, because the plasmid needed to be applied within 5days after the hair plucking to induce a strong antibody response. The antibody responses were not affected by whether the expressed PA63 protein, as an antigen, was secreted or cell surface bound. Finally, this strategy of enhancing the immune responses induced by transcutaneous DNA immunization following 'warm' waxing-based hair depilation was not limited to the PA63 as an antigen, because immunization with a plasmid that encodes the HIV-1 env gp160 gene induced a strong anti-gp160 response as well. Transcutaneous DNA immunization by modifying the hair follicle cycle may hold a great promise in inducing strong and functional immune responses.

Biodistribution and blood clearance of plasmid DNA administered in arginine peptide complexes

Background

Peptide/DNA complexes have great potential as non-viral methods for gene delivery. Despite promising results for peptide-mediated gene delivery technology, an effective systemic peptide-based gene delivery system has not yet been developed.

Methods

This study used pCMV-Luc as a model gene to investigate the biodistribution and the in vivo efficacy of arginine peptide-mediated gene delivery by polymerase chain reaction (PCR).

Results

Plasmid DNA was detected in all organs tested 1 h after intraperitoneal administration of arginine/DNA complexes, indicating that the arginine/DNA complexes disseminated widely through the body. The plasmid was primarily detected in the spleen, kidney, and diaphragm 24 h post administration. The mRNA expression of plasmid DNA was noted in the spleen, kidney, and diaphragm for up to 2 weeks, and in the other major organs, for at least 1 week. Blood clearance studies showed that injected DNA was found in the blood as long as 6 h after injection.

Conclusions

Taken together, our results demonstrated that arginine/DNA complexes are stable in blood and are effective for in vivo gene delivery. These findings suggest that intraperitoneal administration of arginine/DNA complexes is a promising tool in gene therapy.

DNA vaccines: an historical perspective and view to the future

This review provides a detailed look at the attributes and immunologic mechanisms of plasmid DNA vaccines and their utility as laboratory tools as well as potential human vaccines. The immunogenicity and efficacy of DNA vaccines in a variety of preclinical models is used to illustrate how they differ from traditional vaccines in novel ways due to the in situ antigen production and the ease with which they are constructed. The ability to make new DNA vaccines without needing to handle a virulent pathogen or to adapt the pathogen for manufacturing purposes demonstrates the potential value of this vaccine technology for use against emerging and epidemic pathogens. Similarly, personalized anti-tumor DNA vaccines can also readily be made from a biopsy. Because DNA vaccines bias the T-helper (Th) cell response to a Th1 phenotype, DNA vaccines are also under development for vaccines against allergy and autoimmune diseases. The licensure of four animal health products, including two prophylactic vaccines against infectious diseases, one immunotherapy for cancer, and one gene therapy delivery of a hormone for a food animal, provides evidence of the efficacy of DNA vaccines in multiple species including horses and pigs. The size of these target animals provides evidence that the somewhat disappointing immunogenicity of DNA vaccines in a number of human clinical trials is not due simply to the larger mass of humans compared with most laboratory animals. The insights gained from the mechanisms of protection in the animal vaccines, the advances in the delivery and expression technologies for increasing the potency of DNA vaccines, and encouragingly potent human immune responses in certain clinical trials, provide insights for future efforts to develop DNA vaccines into a broadly useful vaccine and immunotherapy platform with applications for human and animal health.

Gene therapy for psoriasis in the K14-VEGF transgenic mouse model by topical transdermal delivery of interleukin-4 using ultradeformable cationic liposome

BACKGROUND

Topical transdermal gene delivery to the skin shows great potential for painless, non-invasive administration of vaccines and therapeutic agents. Interleukin (IL)-4 strategies have shown a good antipsoriatic effect in clinic trials. To date, no information has been acquired on the effectiveness of gene therapy for psoriasis in the K14-VEGF transgenic mouse model by topical transdermal penetration of murine IL-4 (mIL-4) using ultradeformable cationic liposome (UCL).

METHODS

In the present study, we synthesized an UCL and determined a suitable formula for transdermally delivering plasmid DNA to mouse skin. We then tested the antipsoriatic efficacy in the K14-VEGF transgenic mouse model by transdermal delivery of mIL-4 using UCL.

RESULTS

We found that plasmid DNA was transdermally delivered to vicinal sites of epidermis and hair follicles using this optimized formula. Plasmid DNA expression was detected in ear skin. Twenty-four hours after topical application, plasmid DNA was not detected in blood serum and liver, which may decrease the risk of insertion of promoter from plasmid to genomic DNA. Mice treated with UCL/mIL-4 displayed a mild psoriasis phenotype. Histological analysis of pathological score using the Baker scoring system revealed an antipsoriatic effect. Immunohistochemical analysis revealed that hyperplastic and inflamed vessels were suppressed.

CONCLUSIONS

These observations provide evidence of antipsoriatic efficacy by topical transdermal delivery of mIL-4. Therefore, topical transdermal gene transfer is attractive and offers future potential for application in human patients with other dermatogic diseases.

Skin permeation of retinol in Tween 20-based deformable liposomes: in-vitro evaluation in human skin and keratinocyte models

To develop a more effective transdermal delivery method for lipophilic functional cosmetic compounds such as retinol, we formulated various deformable liposomes and compared their transdermal delivery efficiency with those of neutral or negatively-charged conventional liposomes. We tested the deformability of liposomes containing edge activators such as bile salts, polyoxyethylene esters and polyoxyethylene ethers. As indicators of deformability, we used the passed volume and phospholipid ratios during extrusion, as well as the deformability index. We found that the type of edge activator significantly affected the extent of deformability, and that Tween 20 provided the highest level of deformability. Accordingly, we used Tween 20 to formulate deformable liposomes containing retinol in the membrane bilayers, and conducted a skin permeation study in Franz diffusion cells, using dermatomed human skin and three-dimensional human keratinocyte layers. As compared with the use of conventional neutral or negatively-charged liposomes, the use of Tween 20-based deformable liposomes significantly increased the skin permeation of retinol. These results suggested that deformable liposomes might be of potential use for the formulation of retinol and other lipophilic functional cosmetic compounds.

The hairless mouse in skin research

The hairless (Hr) gene encodes a transcriptional co-repressor highly expressed in the mammalian skin. In the mouse, several null and hypomorphic Hr alleles have been identified resulting in hairlessness in homozygous animals, characterized by alopecia developing after a single cycle of relatively normal hair growth. Mutations in the human ortholog have also been associated with congenital alopecia. Although a variety of hairless strains have been developed, outbred SKH1 mice are the most widely used in dermatologic research. These unpigmented and immunocompetent mice allow for ready manipulation of the skin, application of topical agents, and exposure to UVR, as well as easy visualization of the cutaneous response. Wound healing, acute photobiologic responses, and skin carcinogenesis have been extensively studied in SKH1 mice and are well characterized. In addition, tumors induced in these mice resemble, both at the morphologic and molecular levels, UVR-induced skin malignancies in man. Two limitations of the SKH1 mouse in dermatologic research are the relatively uncharacterized genetic background and its outbred status, which precludes inter-individual transplantation studies.

Modulation of biodistribution and expression of plasmid DNA following mesenchymal progenitor cell-based delivery

Although therapeutic applications of mesenchymal progenitor cells (MPCs) have been studied, the in vivo fate of genes delivered by the MPCs has received little attention. We report here the in vivo kinetics, tissue distribution, and duration of gene expression after systemic administration of plasmid DNA delivered by MPCs. Murine MPCs were isolated from bone marrow, cultured, and transfected with plasmid DNA using polyethylenimine. The gene-modified MPCs or naked plasmid DNA was administered intravenously to mice. Injected MPCs incorporating plasmid DNA yielded elevated serum concentrations when compared with the group treated with plasmid DNA alone, a 280-fold higher level measured at 5-min post-administration. Moreover, plasmid DNA delivered in MPCs was detected in several organs, lymph nodes, and bone marrow. The highest levels of distribution were observed in the liver, followed by lung and spleen at 4 days post-dose. Similar to the distribution of DNA, significant expression levels of the exogenous gene were observed only after delivery of the DNA in MPCs, demonstrating the sustained expression at the liver, lung, and kidney for 4 days after tail vein injection. This study provides perspectives regarding the in vivo fate and target tissue distribution of genes following MPC-based delivery.

Enhanced brain targeting efficiency of intranasally administered plasmid DNA: an alternative route for brain gene therapy

Recently, nasal administration has been studied as a noninvasive route for delivery of plasmid DNA encoding therapeutic or antigenic genes. Here, we examined the brain targeting efficiency and transport pathways of intranasally administered plasmid DNA. Quantitative polymerase chain reaction (PCR) measurements of plasmid DNA in blood and brain tissues revealed that intranasally administered pCMVbeta (7.2 kb) and pN2/CMVbeta (14.1 kb) showed systemic absorption and brain distribution. Following intranasal administration, the beta-galactosidase protein encoded by these plasmids was significantly expressed in brain tissues. Kinetic studies showed that intranasally administered plasmid DNA reached the brain with a 2,595-fold higher efficiency than intravenously administered plasmid DNA did, 10 min post-dose. Over 1 h post-dose, the brain targeting efficiencies were consistently higher for intranasally administered plasmid DNA than for intravenously administered DNA. To examine how plasmid DNA enters the brain and moves to the various regions, we examined tissues from nine brain regions, at 5 and 10 min after intranasal or intravenous administration of plasmid DNA. Intravenously administered plasmid DNA displayed similar levels of plasmid DNA in the nine different regions, whereas, intranasally administered plasmid DNA exhibited different levels of distribution among the regions, with the highest plasmid DNA levels in the olfactory bulb. Moreover, plasmid DNA was mainly detected in the endothelial cells, but not in glial cells. Our results suggest that intranasally applied plasmid DNA may reach the brain through a direct route, possibly via the olfactory bulb, and that the nasal route might be an alternative method for efficiently delivering plasmid DNA to the brain.

Epidermal cell culture model with tight stratum corneum as a tool for dermal gene delivery studies

The purpose of this study was to evaluate the feasibility of organotypic cultures of rat epidermal cells as a tool to study non-invasive dermal gene delivery. Also, a novel transfection method employing liposomal pre-treatment of stratum corneum (SC) was evaluated. Rat epidermal cells were cultured on Transwell tissue culture inserts and formation of stratum corneum barrier was evaluated in permeability studies with two model compounds. Transfections were performed with naked pCMV-SEAP2 plasmid and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)/dioleyl-phosphatidylethanolamine (DOPE)/DNA lipoplexes. Naked DNA was administered on the stratum corneum of the cell culture model with or without prior treatment of the stratum corneum with DOTAP/DOPE liposomes. Transfection was evaluated non-invasively by monitoring concentrations of secreted alkaline phosphatase (SEAP) in the culture medium of the basolateral compartment at 24-h intervals. Transfection with lipoplexes produced significant gene expression in rat epidermal keratinocyte (REK) epidermal culture model. Likewise, delivery of naked DNA on stratum corneum after DOTAP/DOPE liposome pre-treatment produced gene expression. Naked DNA alone did not result in detectable gene expression. In dermal gene delivery studies REK epidermal culture model is a suitable tool that includes tight stratum corneum and allows transgene expression in viable epidermis and non-invasive sampling of secreted gene product in the basolateral compartment. Liposomal pre-treatment of the stratum corneum augments transfection of viable epidermis.

Comparative evaluation of three different intramuscular delivery methods for DNA immunization in a nonhuman primate animal model

Although plasmid DNA vaccines induce potent cell-mediated immune responses and prime for antibody responses in experimental laboratory animals, their immunogenicity in humans has been less remarkable. A number of strategies have been proposed to improve the immunogenicity of these vaccines, including using novel means of vaccine delivery. In the present study, the immunogenicity of three different methods of intramuscular plasmid DNA administration was compared in cynomolgus monkeys: needle and syringe, Biojector 2000, and Mini-Ject. The elicited cellular and humoral immune responses were comparable in monkeys immunized using these different delivery techniques, suggesting that the needle-free approaches to vaccine administration do not significantly improve the immunogenicity of the plasmid DNA vaccine used in the study.