Electroporation-based DNA immunisation: translation to the clinic

Intranasal DNA vaccination induces potent mucosal and systemic immune responses and cross-protective immunity against influenza viruses

The induction of potent virus-specific immune responses at mucosal surfaces where virus transmission occurs is a major challenge for vaccination strategies. In the case of influenza vaccination, this has been achieved only by intranasal delivery of live-attenuated vaccines that otherwise pose safety problems. Here, we demonstrate that potent mucosal and systemic immune responses, both cellular and humoral, are induced by intranasal immunization using formulated DNA. We show that formulation with the DNA carrier polyethylenimine (PEI) improved by a 1,000-fold the efficiency of gene transfer in the respiratory track following intranasal administration of luciferase-coding DNA. Using PEI formulation, intranasal vaccination with DNA-encoding hemagglutinin (HA) from influenza A H5N1 or (H1N1)2009 viruses induced high levels of HA-specific immunoglobulin A (IgA) antibodies that were detected in bronchoalveolar lavages (BALs) and the serum. No mucosal responses could be detected after parenteral or intranasal immunization with naked-DNA. Furthermore, intranasal DNA vaccination with HA from a given H5N1 virus elicited full protection against the parental strain and partial cross-protection against a distinct highly pathogenic H5N1 strain that could be improved by adding neuraminidase (NA) DNA plasmids. Our observations warrant further investigation of intranasal DNA as an effective vaccination route.

Biodistribution, persistence and lack of integration of a multigene HIV vaccine delivered by needle-free intradermal injection and electroporation

It is likely that gene-based vaccines will enter the human vaccine area soon. A few veterinary vaccines employing this concept have already been licensed, and a multitude of clinical trials against infectious diseases or different forms of cancer are ongoing. Highly important when developing novel vaccines are the safety aspects and also new adjuvants and delivery techniques needs to be carefully investigated so that they meet all short- and long-term safety requirements. One novel in vivo delivery method for plasmid vaccines is electroporation, which is the application of short pulses of electric current immediately after, and at the site of, an injection of a genetic vaccine. This method has been shown to significantly augment the transfection efficacy and the subsequent vaccine-specific immune responses. However, the dramatic increase in delivery efficacy offered by electroporation has raised concerns of potential increase in the risk of integration of plasmid DNA into the host genome. Here, we demonstrate the safety and lack of integration after immunization with a high dose of a multigene HIV-1 vaccine delivered intradermally using the needle free device Biojector 2000 together with electroporation using Derma Vax™ DNA Vaccine Skin Delivery System. We demonstrate that plasmids persist in the skin at the site of injection for at least four months after immunization. However, no association between plasmid DNA and genomic DNA could be detected as analyzed by qPCR following field inversion gel electrophoresis separating heavy and light DNA fractions. We will shortly initiate a phase I clinical trial in which healthy volunteers will be immunized with this multiplasmid HIV-1 vaccine using a combination of the delivery methods jet-injection and intradermal electroporation.

Electroporation enhances immune responses and protection induced by a bovine viral diarrhea virus DNA vaccine in newborn calves with maternal antibodies

Bovine viral diarrhea virus (BVDV) is one of the major pathogens in cattle. In this study, newborn calves with maternal antibodies were vaccinated with a BVDV DNA vaccine, either by conventional intramuscular (IM) injection or with the TriGrid™ Delivery System for IM delivery (TDS-IM). The calves vaccinated with the TDS-IM developed more rapidly and effectively BVDV-specific humoral and cell-mediated immune responses in the presence of maternal antibodies. Overall, the immune responses induced by delivery with the TDS-IM remained stronger than those elicited by conventional IM injection of the BVDV DNA vaccine. Accordingly, electroporation-mediated delivery of the BVDV DNA vaccine resulted in close to complete protection from clinical signs of disease, while conventional IM administration did not fully prevent morbidity and mortality following challenge with BVDV-2. These results demonstrate the TDS-IM to be effective as a delivery system for a BVDV DNA vaccine in newborn calves in the presence of maternal antibodies, which supports the potential of electroporation as a delivery method for prophylactic DNA vaccines.

Abeta DNA vaccination for Alzheimer's disease: focus on disease prevention

Pre-clinical and clinical data suggest that the development of a safe and effective anti-amyloid-beta (Abeta) immunotherapy for Alzheimer's disease (AD) will require therapeutic levels of anti-Abeta antibodies, while avoiding proinflammatory adjuvants and autoreactive T cells which may increase the incidence of adverse events in the elderly population targeted to receive immunotherapy. The first active immunization clinical trial with AN1792 in AD patients was halted when a subset of patients developed meningoencephalitis. The first passive immunotherapy trial with bapineuzumab, a humanized monoclonal antibody against the end terminus of Abeta, also encountered some dose dependent adverse events during the Phase II portion of the study, vasogenic edema in 12 cases, which were significantly over represented in ApoE4 carriers. The proposed remedy is to treat future patients with lower doses, particularly in the ApoE4 carriers. Currently there are at least five ongoing anti-Abeta immunotherapy clinical trials. Three of the clinical trials use humanized monoclonal antibodies, which are expensive and require repeated dosing to maintain therapeutic levels of the antibodies in the patient. However in the event of an adverse response to the passive therapy antibody delivery can simply be halted, which may provide a resolution to the problem. Because at this point we cannot readily identify individuals in the preclinical or prodromal stages of AD pathogenesis, passive immunotherapy is reserved for those that already have clinical symptoms. Unfortunately those individuals have by that point accumulated substantial neuropathology in affected regions of the brain. Moreover, if Abeta pathology drives tau pathology as reported in several transgenic animal models, and once established if tau pathology can become self propagating, then early intervention with anti-Abeta immunotherapy may be critical for favorable clinical outcomes. On the other hand, active immunization has several significant advantages, including lower cost and the typical immunization protocol should be much less intrusive to the patient relative to passive therapy, in the advent of Abeta-antibody immune complex-induced adverse events the patients will have to receive immuno-supperssive therapy for an extended period until the anti Abeta antibody levels drop naturally as the effects of the vaccine decays over time. Obviously, improvements in vaccine design are needed to improve both the safety, as well as the efficacy of anti-Abeta immunotherapy. The focus of this review is on the advantages of DNA vaccination for anti-Abeta immunotherapy, and the major hurdles, such as immunosenescence, selection of appropriate molecular adjuvants, universal T cell epitopes, and possibly a polyepitope design based on utilizing existing memory T cells in the general population that were generated in response to childhood or seasonal vaccines, as well as various infections. Ultimately, we believe that the further refinement of our AD DNA epitope vaccines, possibly combined with a prime boost regime will facilitate translation to human clinical trials in either very early AD, or preferably in preclinical stage individuals identified by validated AD biomarkers.

Influenza virus vaccine based on the conserved hemagglutinin stalk domain

Although highly effective in the general population when well matched to circulating influenza virus strains, current influenza vaccines are limited in their utility due to the narrow breadth of protection they provide. The strain specificity of vaccines presently in use mirrors the exquisite specificity of the neutralizing antibodies that they induce, that is, antibodies which bind to the highly variable globular head domain of hemagglutinin (HA). Herein, we describe the construction of a novel immunogen comprising the conserved influenza HA stalk domain and lacking the globular head. Vaccination of mice with this headless HA construct elicited immune sera with broader reactivity than those obtained from mice immunized with a full-length HA. Furthermore, the headless HA vaccine provided full protection against death and partial protection against disease following lethal viral challenge. Our results suggest that the response induced by headless HA vaccines is sufficiently potent to warrant their further development toward a universal influenza virus vaccine.

Current influenza vaccines are effective against only a narrow range of influenza virus strains. It is for this reason that new vaccines must be generated and administered each year. We now report progress toward the goal of an influenza virus vaccine which would protect against multiple strains. Our approach is based on presentation to the host immune system of a region of the influenza virus—called a “headless hemagglutinin” (headless HA)—which is similar among a multitude of diverse strains. We show that vaccination of mice with a headless HA confers protection to these animals against a lethal influenza virus challenge, thereby demonstrating the viability of the approach. Through further development and testing, we predict that a single immunization with a headless HA vaccine will offer effective protection through several influenza epidemics.

Avian influenza pandemic preparedness: developing prepandemic and pandemic vaccines against a moving target

The unprecedented global spread of highly pathogenic avian H5N1 influenza viruses within the past ten years and their extreme lethality to poultry and humans has underscored their potential to cause an influenza pandemic. Combating the threat of an impending H5N1 influenza pandemic will require a combination of pharmaceutical and nonpharmaceutical intervention strategies. The emergence of the H1N1 pandemic in 2009 emphasised the unpredictable nature of a pandemic influenza. Undoubtedly, vaccines offer the most viable means to combat a pandemic threat. Current egg-based influenza vaccine manufacturing strategies are unlikely to be able to cater to the huge, rapid global demand because of the anticipated scarcity of embryonated eggs in an avian influenza pandemic and other factors associated with the vaccine production process. Therefore, alternative, egg-independent vaccine manufacturing strategies should be evaluated to supplement the traditional egg-derived influenza vaccine manufacturing. Furthermore, evaluation of dose-sparing strategies that offer protection with a reduced antigen dose will be critical for pandemic influenza preparedness. Development of new antiviral therapeutics and other, nonpharmaceutical intervention strategies will further supplement pandemic preparedness. This review highlights the current status of egg-dependent and egg-independent strategies against an avian influenza pandemic.

Antibodies designed as effective cancer vaccines

Antigen/antibody complexes can efficiently target antigen presenting cells to allow stimulation of the cellular immune response. Due to the difficulty of manufacture and their inherent instability complexes have proved inefficient cancer vaccines. However, anti-idiotypic antibodies mimicking antigens have been shown to stimulate both antibody and T cell responses. The latter are due to T cell mimotopes expressed within the complementarity-determining regions (CDRs) of antibodies that are efficiently presented to dendritic cells in vivo. Based on this observation we have designed a DNA vaccine platform called ImmunoBody, where cytotoxic T lymphocyte (CTL) and helper T cell epitopes replace CDR regions within the framework of a human IgG1 antibody. The ImmunoBody expression system has a number of design features which allow for rapid production of a wide range of vaccines. The CDR regions of the heavy and light chain have been engineered to contain unique restriction endonuclease sites, which can be easily opened, and oligonucleotides encoding the T cell epitopes inserted. The variable and constant regions of the ImmunoBody are also flanked by restriction sites, which permit easy exchange of other IgG subtypes. Here we show a range of T cell epitopes can be inserted into the ImmunoBody vector and upon immunization these T cell epitopes are efficiently processed and presented to stimulate high frequency helper and CTL responses capable of anti-tumor activity.

Immune response induced by a linear DNA vector: influence of dose, formulation and route of injection

Previously, minimalistic, immunogenetically defined gene expression (MIDGE) vectors were developed as effective and sophisticated carriers for DNA vaccination. Here we evaluate the influence of dose, formulation and delivery route on the immune response after vaccination with MIDGE-Th1 vectors encoding hepatitis B virus surface antigen (HBsAg). An HBsAg-specific IgG1 and IgG2a antibody response was induced in a dose-dependent manner, whereas the IgG2a/IgG1 ratio was independent of the injected DNA dose. Formulation of MIDGE-HBsAg-Th1 with the cationic pyridinium amphiphile SAINT-18 significantly increased antibody levels of IgG1 and IgG2a compared to the unformulated vector. In contrast, SAINT-18 had neither a significant effect on the IgG2a/IgG1 ratio nor on the type and strength of cellular immunity. Overall, the strongest immune response was generated after intradermal injection, followed by intramuscular and subcutaneous (s.c.) injection. The results show that the formulation of MIDGE-Th1 with SAINT-18 increased the efficacy of the MIDGE-Th1 DNA vaccine and is therefore a suitable approach to improve the efficacy of DNA vaccines also in large animals and humans.

Egg-independent vaccine strategies for highly pathogenic H5N1 influenza viruses

The emergence of a highly pathogenic H5N1 influenza virus in Hong Kong in 1997 and the subsequent appearance of other H5N1 strains and their spread to several countries in southeast Asia, Africa, the Middle East and Europe has evoked fear of a global influenza pandemic. Vaccines offer the best hope to combat the threat of an influenza pandemic. However, the global demand for a pandemic vaccine cannot be fulfilled by the current egg-based vaccine manufacturing strategies, thus creating a need to explore alternative technologies for vaccine production and delivery. Several egg-independent vaccine approaches such as cell culture-derived whole virus or subvirion vaccines, recombinant protein-based vaccines, virus-like particle (VLP) vaccines, DNA vaccines and viral vector-based vaccines are currently being investigated and appear promising both in preclinical and clinical studies. The present review will highlight the various egg-independent alternative vaccine approaches for pandemic influenza.

Electrodes for in vivo localised subcutaneous electropulsation and associated drug and nucleic acid delivery

BACKGROUND

Drug and nucleic acids can be delivered in vivo by an injection of the product followed by the application of a train of electric pulses.

OBJECTIVE

The success of the method is linked to the proper distribution of the electric field in the target tissue. This is under the control of the design of the electrodes.

METHODS

The field distribution can be obtained by computer simulation mainly by using numerical methods and simplifying hypothesis. The conclusions are validated by comparing the computed current and its experimental values on phantoms. A good agreement is obtained.

RESULTS/CONCLUSION

Targeting the delivery to the skin can be obtained by using an array of very short needle electrodes, by pinching the skin between two parallel plate electrodes, or by using contact wire electrodes.

Phase 1 safety and immunogenicity evaluation of ADMVA, a multigenic, modified vaccinia Ankara-HIV-1 B'/C candidate vaccine

Background

We conducted a Phase I dose escalation trial of ADVAX, a DNA-based candidate HIV-1 vaccine expressing Clade C/B' env, gag, pol, nef, and tat genes. Sequences were derived from a prevalent circulating recombinant form in Yunnan, China, an area of high HIV-1 incidence. The objective was to evaluate the safety and immunogenicity of ADVAX in human volunteers.

Methodology/Principal Findings

ADVAX or placebo was administered intramuscularly at months 0, 1 and 3 to 45 healthy volunteers not at high risk for HIV-1. Three dosage levels [0.2 mg (low), 1.0 mg (mid), and 4.0 mg (high)] were tested. Twelve volunteers in each dosage group were assigned to receive ADVAX and three to receive placebo in a double-blind design. Subjects were followed for local and systemic reactogenicity, adverse events, and clinical laboratory parameters. Study follow up was 18 months. Humoral immunogenicity was evaluated by anti-gp120 binding ELISA. Cellular immunogenicity was assessed by a validated IFNγ ELISpot assay and intracellular cytokine staining. ADVAX was safe and well-tolerated, with no vaccine-related serious adverse events. Local and systemic reactogenicity events were reported by 64% and 42% of vaccine recipients, respectively. The majority of events were mild. The IFNγ ELISpot response rates to any HIV antigen were 0/9 (0%) in the placebo group, 3/12 (25%) in the low-dosage group, 4/12 (33%) in the mid-dosage group, and 2/12 (17%) in the high-dosage group. Overall, responses were generally transient and occurred to each gene product, although volunteers responded to single antigens only. Binding antibodies to gp120 were not detected in any volunteers, and HIV seroconversion did not occur.

Conclusions/Significance

ADVAX delivered intramuscularly is safe, well-tolerated, and elicits modest but transient cellular immune responses.

Trial Registration

Clinicaltrials.gov NCT00249106

Intradermal DNA electroporation induces survivin-specific CTLs, suppresses angiogenesis and confers protection against mouse melanoma

Survivin is an intracellular tumor-associated antigen that is broadly expressed in a large variety of tumors and also in tumor associated endothelial cells but mostly absent in differentiated tissues. Naked DNA vaccines targeting survivin have been shown to induce T cell as well as humoral immune responses in mice. However, the lack of epitope-specific CD8+ T cell detection and modest tumor protection observed highlight the need for further improvements to develop effective survivin DNA vaccination approaches. Here, the efficacy of a human survivin DNA vaccine delivered by intradermal electroporation (EP) was tested. The CD8+ T cell epitope surv(20-28) restricted to H-2 Db was identified based on in-silico epitope prediction algorithms and binding to MHC class I molecules. Intradermal DNA EP of mice with a human survivin encoding plasmid generated CD8+ cytotoxic T lymphocyte (CTL) responses cross-reactive with the mouse epitope surv(20-28), as determined by intracellular IFN-gamma staining, suggesting that self-tolerance has been broken. Survivin-specific CTLs displayed an activated effector phenotype as determined by CD44 and CD107 up-regulation. Vaccinated mice displayed specific cytotoxic activity against B16 and peptide-pulsed RMA-S cells in vitro as well as against surv(20-28) peptide-pulsed target cells in vivo. Importantly, intradermal EP with a survivin DNA vaccine suppressed angiogenesis in vivo and elicited protection against highly aggressive syngeneic B16 melanoma tumor challenge. We conclude that intradermal EP is an attractive method for delivering a survivin DNA vaccine that should be explored also in clinical studies.

Gene electrotransfer: from biophysical mechanisms to in vivo applications : Part 2 - In vivo developments and present clinical applications

Gene electrotransfer can be obtained not just on single cells in diluted suspension. For more than 10 years, this is a quasi routine strategy in tissue on the living animal and a few clinical trials have now been approved. New problems have been brought by the close contacts of cells in tissue both on the local field distribution and on the access of DNA to target cells. They need to be solved to provide a further improvement in the efficacy and safety of protein expression. There is a competition between gene transfer and cell destruction. Nevertheless, present results are indicative that electrotransfer is a promising approach for gene therapy. High level and long-lived expression of proteins can be obtained in muscles. This is used for a successful method of electrovaccination.

Enhancing DNA vaccine potency by co-administration of xenogenic MHC class-I DNA

Intramuscular administration of DNA vaccines can lead to the generation of antigen-specific immune responses through cross-priming mechanisms. We propose a strategy that is capable of leading to local inflammation and enhancing cross-priming, thus resulting in improved antigen-specific immune responses. Therefore, in the current study, we evaluated immunologic responses elicited through electroporation mediated intramuscular administration of a DNA vaccine encoding calreticulin (CRT) linked to HPV-16 E7 (CRT/E7) in combination with DNA expressing HLA-A2 as compared to CRT/E7 DNA vaccination alone. We found that the co-administration of a DNA vaccine in conjunction with a DNA encoding an xenogenic MHC molecule could significantly enhance the E7-specific CD8+ T cell immune responses as well an antitumor effects against an E7-expressing tumor, TC-1 in C57BL/6 tumor-bearing mice. Furthermore, a similar enhancement in E7-specific immune responses was observed by co-administration of CRT/E7 DNA with DNA encoding other types of xenogenic MHC class I molecules. This strategy was also applicable to another antigenic system, ovalbumin. Further characterization of the injection site revealed that co-administration of HLA-A2 DNA led to a significant increase in the number of infiltrating CD8+ T lymphocytes as well as CD11b/c+ antigen presenting cells. Furthermore, the E7-specific immune responses generated by intramuscular co-administration of CRT/E7 with HLA-A2 DNA were reduced in HLA-A2 transgenic mice. Thus, our data suggest that intramuscular co-administration of DNA encoding xenogenic MHC class I can further improve the antigen-specific immune responses as well as antitumor effects generated by DNA vaccines through enhancement of cross-priming mechanisms.

Universal influenza DNA vaccine encoding conserved CD4+ T cell epitopes protects against lethal viral challenge in HLA-DR transgenic mice

The goal of the present study was to design a vaccine that would provide universal protection against infection of humans with diverse influenza A viruses. Accordingly, protein sequences from influenza A virus strains currently in circulation (H1N1, H3N2), agents of past pandemics (H1N1, H2N2, H3N2) and zoonotic infections of man (H1N1, H5N1, H7N2, H7N3, H7N7, H9N2) were evaluated for the presence of amino acid sequences, motifs, that are predicted to mediate peptide epitope binding with high affinity to the most frequent HLA-DR allelic products. Peptides conserved among diverse influenza strains were then synthesized, evaluated for binding to purified HLA-DR molecules and for their capacity to induce influenza-specific immune recall responses using human donor peripheral blood mononuclear cells (PBMC). Accordingly, 20 epitopes were selected for further investigation based on their conservancy among diverse influenza strains, predicted population coverage in diverse ethnic groups and capacity to recall influenza-specific responses. A DNA plasmid encoding the epitopes was constructed using amino acid spacers between epitopes to promote optimum processing and presentation. Immunogenicity of the DNA vaccine was measured using HLA-DR4 transgenic mice and the TriGrid in vivo electroporation device. Vaccination resulted in peptide-specific immune responses, augmented HA-specific antibody responses and protection of HLA-DR4 transgenic mice from lethal PR8 influenza virus challenge. These studies demonstrate the utility of this vaccine format and the contribution of CD4(+) T cell responses to protection against influenza infection.

Skin electroporation: effects on transgene expression, DNA persistence and local tissue environment

Background

Electrical pulses have been used to enhance uptake of molecules into living cells for decades. This technique, often referred to as electroporation, has become an increasingly popular method to enhance in vivo DNA delivery for both gene therapy applications as well as for delivery of vaccines against both infectious diseases and cancer. In vivo electrovaccination (gene delivery followed by electroporation) is currently being investigated in several clinical trials, including DNA delivery to healthy volunteers. However, the mode of action at molecular level is not yet fully understood.

Methodology/Principal Findings

This study investigates intradermal DNA electrovaccination in detail and describes the effects on expression of the vaccine antigen, plasmid persistence and the local tissue environment. Gene profiling of the vaccination site showed that the combination of DNA and electroporation induced a significant up-regulation of pro-inflammatory genes. In vivo imaging of luciferase activity after electrovaccination demonstrated a rapid onset (minutes) and a long duration (months) of transgene expression. However, when the more immunogenic prostate specific antigen (PSA) was co-administered, PSA-specific T cells were induced and concurrently the luciferase expression became undetectable. Electroporation did not affect the long-term persistence of the PSA-expressing plasmid.

Conclusions/Significance

This study provides important insights to how DNA delivery by intradermal electrovaccination affects the local immunological responses of the skin, transgene expression and clearance of the plasmid. As the described vaccination approach is currently being evaluated in clinical trials, the data provided will be of high significance.

Administration of HPV DNA vaccine via electroporation elicits the strongest CD8+ T cell immune responses compared to intramuscular injection and intradermal gene gun delivery

DNA vaccines are an attractive approach to eliciting antigen-specific immunity. Intracellular targeting of tumor antigens through its linkage to immunostimulatory molecules such as calreticulin (CRT) can improve antigen processing and presentation through the MHC class I pathway and increase cytotoxic CD8+ T cell production. However, even with these enhancements, the efficacy of such immunotherapeutic strategies is dependent on the identification of an effective route and method of DNA administration. Electroporation and gene gun-mediated particle delivery are leading methods of DNA vaccine delivery that can generate protective and therapeutic levels of immune responses in experimental models. In this study, we perform a head-to-head comparison of three methods of vaccination--conventional intramuscular injection, electroporation-mediated intramuscular delivery, and epidermal gene gun-mediated particle delivery--in the ability to generate antigen-specific cytotoxic CD8+ T cell responses as well as anti-tumor immune responses against an HPV-16 E7 expressing tumor cell line using the pNGVL4a-CRT/E7(detox) DNA vaccine. Vaccination via electroporation generated the highest number of E7-specific cytotoxic CD8+ T cells, which correlated to improved outcomes in the treatment of growing tumors. In addition, we demonstrate that electroporation results in significantly higher levels of circulating protein compared to gene gun or intramuscular vaccination, which likely enhances calreticulin's role as a local tumor anti-angiogenesis agent. We conclude that electroporation is a promising method for delivery of HPV DNA vaccines and should be considered for DNA vaccine delivery in human clinical trials.

Electroporation for the delivery of DNA-based vaccines and immunotherapeutics: current clinical developments

Electroporation (EP) has been used in basic research for the past 25 years to aid in the transfer of DNA into cells in vitro. EP in vivo enhances transfer of DNA vaccines and therapeutic plasmids to the skin, muscle, tumors, and other tissues resulting in high levels of expression, often with serological and clinical benefits. The recent interest in nonviral gene transfer as treatment options for a vast array of conditions has resulted in the refinement and optimization of EP technology. Current research has revealed that EP can be successfully used in many species, including humans. Clinical trials are currently under way. Herein, the transition of EP from basic science to clinical trials will be discussed.

Tolerability of two sequential electroporation treatments using MedPulser DNA delivery system (DDS) in healthy adults

Immunotherapy against infectious agents and malignant tumors requires efficient priming of effector cells through direct expression and/or efficient cross-presentation of antigens by antigen-presenting cells. Electroporation is a new procedure aimed at transiently increasing cell membrane permeability and direct delivery of antigen or antigen-encoding nucleic acids inside targeted cells. We evaluated the tolerability including compliance with repeated electroporation treatments using MedPulser DDS in 24 healthy adults. Pain severity was evaluated at time of electroporation treatment, and at 1, 5, 10, and 20 minutes, and 24 hours thereafter, using two clinically validated questionnaires: McGill Pain Questionnaire (MPQ) (Present Pain Intensity) and Brief Pain Inventory (BPI). Electroporation treatments were generally well tolerated. Twenty-two out of 24 subjects returned for the second electroporation treatment 14 days after first treatment. Only two subjects reported a treatment-related systemic adverse experience following either electroporation application. For both pain assessment tools, maximum pain and/or discomfort were mostly reported immediately (within 5 minutes) after electroporation; Furthermore, no difference was observed when comparing peak-pain scores after first and second electroporation treatments. This study supports the clinical application of MedPulser DDS for the improvement of antigen-induced immune responses for prophylactic or therapeutic vaccines, especially in gene-based therapies for cancer.

Microscale electroporation: challenges and perspectives for clinical applications

Microscale engineering plays a significant role in developing tools for biological applications by miniaturizing devices and providing controllable microenvironments for in vitro cell research. Miniaturized devices offer numerous benefits in comparison to their macroscale counterparts, such as lower use of expensive reagents, biomimetic environments, and the ability to manipulate single cells. Microscale electroporation is one of the main beneficiaries of microscale engineering as it provides spatial and temporal control of various electrical parameters. Microscale electroporation devices can be used to reduce limitations associated with the conventional electroporation approaches such as variations in the local pH, electric field distortion, sample contamination, and the difficulties in transfecting and maintaining the viability of desired cell types. Here, we present an overview of recent advances of the microscale electroporation methods and their applications in biology, as well as current challenges for its use for clinical applications. We categorize microscale electroporation into microchannel and microcapillary electroporation. Microchannel-based electroporation can be used for transfecting cells within microchannels under dynamic flow conditions in a controlled and high-throughput fashion. In contrast, microcapillary-based electroporation can be used for transfecting cells within controlled reaction chambers under static flow conditions. Using these categories we examine the use of microscale electroporation for clinical applications related to HIV-1, stem cells, cancer and other diseases and discuss the challenges in further advancing this technology for use in clinical medicine and biology.

Gene therapy by electroporation for the treatment of chronic renal failure in companion animals

Background

Growth hormone-releasing hormone (GHRH) plasmid-based therapy for the treatment of chronic renal failure and its complications was examined. Companion dogs (13.1 ± 0.8 years, 29.4 ± 5.01 kg) and cats (13.2 ± 0.9 years, 8.5 ± 0.37 kg) received a single 0.4 mg or 0.1 mg species-specific plasmid injection, respectively, intramuscularly followed by electroporation, and analyzed up to 75 days post-treatment; controls underwent electroporation without plasmid administration.

Results

Plasmid-treated animals showed an increase in body weight (dogs 22.5% and cats 3.2%) compared to control animals, and displayed improved quality of life parameters including significant increases in appetite, activity, mentation and exercise tolerance levels. Insulin-like growth factor I (IGF-I, the downstream effector of GHRH) levels were increased in the plasmid treated animals. Hematological parameters were also significantly improved. Protein metabolism changes were observed suggesting a shift from a catabolic to an anabolic state in the treated animals. Blood urea nitrogen and creatinine did not show any significant changes suggesting maintenance of kidney function whereas the control animal's renal function deteriorated. Treated animals survived longer than control animals with 70% of dogs and 80% of cats surviving until study day 75. Only 17% and 40% of the control dogs and cats, respectively, survived to day 75.

Conclusion

Improved quality of life, survival and general well-being indicate that further investigation is warranted, and show the potential of a plasmid-based therapy by electroporation in preventing and managing complications of renal insufficiency.

Targeting cytochrome P450 CYP1B1 with a therapeutic cancer vaccine

The role that the immune system plays in limiting tumor formation and growth is becoming increasingly clear and passive immunotherapeutic approaches, such as the use of monoclonal antibodies, are now being successfully applied in clinical practice. Active immunization against tumors, however, has not yet been shown to have the same level of clinical efficacy. Two important reasons for this lack of efficacy have to do with the antigens being targeted, as well as the immunization approaches that have been tested. This review will highlight some of the requirements thought to be important for the successful development of an active immunization approach, with a focus on the ongoing development efforts for a novel agent targeting the cytochrome P450 family member, CYP1B1.

A consensus-hemagglutinin-based DNA vaccine that protects mice against divergent H5N1 influenza viruses

H5N1 influenza viruses have spread extensively among wild birds and domestic poultry. Cross-species transmission of these viruses to humans has been documented in over 380 cases, with a mortality rate of approximately 60%. There is great concern that a H5N1 virus would acquire the ability to spread efficiently between humans, thereby becoming a pandemic threat. An H5N1 influenza vaccine must, therefore, be an integral part of any pandemic preparedness plan. However, traditional methods of making influenza vaccines have yet to produce a candidate that could induce potently neutralizing antibodies against divergent strains of H5N1 influenza viruses. To address this need, we generated a consensus H5N1 hemagglutinin (HA) sequence based on data available in early 2006. This sequence was then optimized for protein expression before being inserted into a DNA plasmid (pCHA5). Immunizing mice with pCHA5, delivered intramuscularly via electroporation, elicited antibodies that neutralized a panel of virions that have been pseudotyped with the HA from various H5N1 viruses (clades 1, 2.1, 2.2, 2.3.2, and 2.3.4). Moreover, immunization with pCHA5 in mice conferred complete (clades 1 and 2.2) or significant (clade 2.1) protection from H5N1 virus challenges. We conclude that this vaccine, based on a consensus HA, could induce broad protection against divergent H5N1 influenza viruses and thus warrants further study.

Immunogenicity in mice and rabbits of DNA vaccines expressing woodchuck hepatitis virus antigens

The licensed vaccine against hepatitis B virus (HBV) is an effective means to prevent infection, but is not an effective therapeutic strategy to treat established chronic infections when used alone. In an animal model of chronic HBV infection (the woodchuck experimentally infected with woodchuck hepatitis virus (WHV)), the combination of conventional vaccine and potent antiviral drugs has shown promise as a potential therapeutic intervention. This approach might be improved further through the application of newer vaccine technologies. In the present study, we evaluated electroporation (EP)-based intramuscular (i.m.) delivery of a codon-optimized DNA vaccine for the WHV surface antigen (WHsAg) in mice and rabbits. In mice, this immunization procedure compared favorably to vaccination by i.m. injection of the DNA vaccine or i.m. administration of a recombinant WHsAg-alum vaccine, exhibiting characteristics expected to be beneficial for a therapeutic vaccine strategy. These included dose efficiency, consistency, vigorous induction of antibody responses to WHsAg, as well as a Th1 bias. Following scale-up to rabbits, a species that approximates the size of the woodchuck, the EP dosing regimen was markedly more effective than conventional i.m. injection of the DNA vaccine. Taken together, these results provide the foundation for studies of EP-based DNA immunization in the woodchuck in order to further assess its potential as an immunotherapeutic approach for treatment of chronic HBV infection in humans.

Recruitment of antigen-presenting cells to the site of inoculation and augmentation of human immunodeficiency virus type 1 DNA vaccine immunogenicity by in vivo electroporation

In vivo electroporation (EP) has been shown to augment the immunogenicity of plasmid DNA vaccines, but its mechanism of action has not been fully characterized. In this study, we show that in vivo EP augmented cellular and humoral immune responses to a human immunodeficiency virus type 1 Env DNA vaccine in mice and allowed a 10-fold reduction in vaccine dose. This enhancement was durable for over 6 months, and re-exposure to antigen resulted in anamnestic effector and central memory CD8(+) T-lymphocyte responses. Interestingly, in vivo EP also recruited large mixed cellular inflammatory infiltrates to the site of inoculation. These infiltrates contained 45-fold-increased numbers of macrophages and 77-fold-increased numbers of dendritic cells as well as 2- to 6-fold-increased numbers of B and T lymphocytes compared to infiltrates following DNA vaccination alone. These data suggest that recruiting inflammatory cells, including antigen-presenting cells (APCs), to the site of antigen production substantially improves the immunogenicity of DNA vaccines. Combining in vivo EP with plasmid chemokine adjuvants that similarly recruited APCs to the injection site, however, did not result in synergy.