Peptides-Coated Oncolytic Vaccines for Cancer Personalized Medicine

Oncolytic Viruses (OVs) work through two main mechanisms of action: the direct lysis of the virus-infected cancer cells and the release of tumor antigens as a result of the viral burst. In this sc.enario, the OVs act as in situ cancer vaccines, since the immunogenicity of the virus is combined with tumor antigens, that direct the specificity of the anti-tumor adaptive immune response. However, this mechanism in some cases fails in eliciting a strong specific T cell response. One way to overcome this problem and enhance the priming efficiency is the production of genetically modified oncolytic viruses encoding one or more tumor antigens. To avoid the long and expensive process related to the engineering of the OVs, we have exploited an approach based on coating OVs (adenovirus and vaccinia virus) with tumor antigens. In this work, oncolytic viruses encoding tumor antigens and tumor antigen decorated adenoviral platform (PeptiCRAd) have been used as cancer vaccines and evaluated both for their prophylactic and therapeutic efficacy. We have first tested the oncolytic vaccines by exploiting the OVA model, moving then to TRP2, a more clinically relevant tumor antigen. Finally, both approaches have been investigated in tumor neo-antigens settings. Interestingly, both genetically modified oncolytic adenovirus and PeptiCRAd elicited T cells-specific anti-tumor responses. However, in vitro cross-representation experiments, showed an advantage of PeptiCRAd as regards the fast presentation of the model epitope SIINFEKL from OVA in an immunogenic rather than tolerogenic fashion. Here two approaches used as cancer oncolytic vaccines have been explored and characterized for their efficacy. Although the generation of specific anti-tumor T cells was elicited in both approaches, PeptiCRAd retains the advantage of being rapidly adaptable by coating the adenovirus with a different set of tumor antigens, which is crucial in personalized cancer vaccines clinical setting.

New generation of DNA-based immunotherapy induces a potent immune response and increases the survival in different tumor models

BACKGROUND

Strategies to increase nucleic acid vaccine immunogenicity are needed to move towards clinical applications in oncology. In this study, we designed a new generation of DNA vaccines, encoding an engineered vesicular stomatitis virus glycoprotein as a carrier of foreign T cell tumor epitopes (plasmid to deliver T cell epitopes, pTOP). We hypothesized that pTOP could activate a more potent response compared with the traditional DNA-based immunotherapies, due to both the innate immune properties of the viral protein and the specific induction of CD4 and CD8 T cells targeting tumor antigens. This could improve the outcome in different tumor models, especially when the DNA-based immunotherapy is combined with a rational therapeutic strategy.

METHODS

The ability of pTOP DNA vaccine to activate a specific CD4 and CD8 response and the antitumor efficacy were tested in a B16F10-OVA melanoma (subcutaneous model) and GL261 glioblastoma (subcutaneous and orthotopic models).

RESULTS

In B16F10-OVA melanoma, pTOP promoted immune recognition by adequate processing of both MHC-I and MHC-II epitopes and had a higher antigen-specific cytotoxic T cell (CTL) killing activity. In a GL261 orthotopic glioblastoma, pTOP immunization prior to tumor debulking resulted in 78% durable remission and long-term survival and induced a decrease of the number of immunosuppressive cells and an increase of immunologically active CTLs in the brain. The combination of pTOP with immune checkpoint blockade or with tumor resection improved the survival of mice bearing, a subcutaneous melanoma or an orthotopic glioblastoma, respectively.

CONCLUSIONS

In this work, we showed that pTOP plasmids encoding an engineered vesicular stomatitis virus glycoprotein, and containing various foreign T cell tumor epitopes, successfully triggered innate immunity and effectively promoted immune recognition by adequate processing of both MHC-I and MHC-II epitopes. These results highlight the potential of DNA-based immunotherapies coding for viral proteins to induce potent and specific antitumor responses.

Oncolytic adenovirus drives specific immune response generated by a poly-epitope pDNA vaccine encoding melanoma neoantigens into the tumor site

Background

DNA vaccines against cancer held great promises due to the generation of a specific and long-lasting immune response. However, when used as a single therapy, they are not able to drive the generated immune response into the tumor, because of the immunosuppressive microenvironment, thus limiting their use in humans. To enhance DNA vaccine efficacy, we combined a new poly-epitope DNA vaccine encoding melanoma tumor associated antigens and B16F1-specific neoantigens with an oncolytic virus administered intratumorally.

Methods

Genomic analysis were performed to find specific mutations in B16F1 melanoma cells. The antigen gene sequences were designed according to these mutations prior to the insertion in the plasmid vector. Mice were injected with B16F1 tumor cells (n = 7–9) and therapeutically vaccinated 2, 9 and 16 days after the tumor injection. The virus was administered intratumorally at day 10, 12 and 14. Immune cell infiltration analysis and cytokine production were performed by flow cytometry, PCR and ELISPOT in the tumor site and in the spleen of animals, 17 days after the tumor injection.

Results

The combination of DNA vaccine and oncolytic virus significantly increased the immune activity into the tumor. In particular, the local intratumoral viral therapy increased the NK infiltration, thus increasing the production of different cytokines, chemokines and enzymes involved in the adaptive immune system recruitment and cytotoxic activity. On the other side, the DNA vaccine generated antigen-specific T cells in the spleen, which migrated into the tumor when recalled by the local viral therapy. The complementarity between these strategies explains the dramatic tumor regression observed only in the combination group compared to all the other control groups.

Conclusions

This study explores the immunological mechanism of the combination between an oncolytic adenovirus and a DNA vaccine against melanoma. It demonstrates that the use of a rational combination therapy involving DNA vaccination could overcome its poor immunogenicity. In this way, it will be possible to exploit the great potential of DNA vaccination, thus allowing a larger use in the clinic.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0644-7) contains supplementary material, which is available to authorized users.

Cancer DNA vaccines: current preclinical and clinical developments and future perspectives

The recent developments in immuno-oncology have opened an unprecedented avenue for the emergence of vaccine strategies. Therapeutic DNA cancer vaccines are now considered a very promising strategy to activate the immune system against cancer. In the past, several clinical trials using plasmid DNA vaccines demonstrated a good safety profile and the activation of a broad and specific immune response. However, these vaccines often demonstrated only modest therapeutic effects in clinical trials due to the immunosuppressive mechanisms developed by the tumor. To enhance the vaccine-induced immune response and the treatment efficacy, DNA vaccines could be improved by using two different strategies. The first is to increase their immunogenicity by selecting and optimizing the best antigen(s) to be inserted into the plasmid DNA. The second strategy is to combine DNA vaccines with other complementary therapies that could improve their activity by attenuating immunosuppression in the tumor microenvironment or by increasing the activity/number of immune cells. A growing number of preclinical and clinical studies are adopting these two strategies to better exploit the potential of DNA vaccination. In this review, we analyze the last 5-year preclinical studies and 10-year clinical trials using plasmid DNA vaccines for cancer therapy. We also investigate the strategies that are being developed to overcome the limitations in cancer DNA vaccination, revisiting the rationale for different combinations of therapy and the different possibilities in antigen choice. Finally, we highlight the most promising developments and critical points that need to be addressed to move towards the approval of therapeutic cancer DNA vaccines as part of the standard of cancer care in the future.

Combination of immune checkpoint blockade with DNA cancer vaccine induces potent antitumor immunity against P815 mastocytoma

DNA vaccination against cancer has become a promising strategy for inducing a specific and long-lasting antitumor immunity. However, DNA vaccines fail to generate potent immune responses when used as a single therapy. To enhance their activity into the tumor, a DNA vaccine against murine P815 mastocytoma was combined with antibodies directed against the immune checkpoints CTLA4 and PD1. The combination of these two strategies delayed tumor growth and enhanced specific antitumor immune cell infiltration in comparison to the corresponding single therapies. The combination also promoted IFNg, IL12 and granzyme B production in the tumor microenvironment and decreased the formation of liver metastasis in a very early phase of tumor development, enabling 90% survival. These results underline the complementarity of DNA vaccination and immune checkpoint blockers in inducing a potent immune response, by exploiting the generation of antigen-specific T cells by the vaccine and the ability of immune checkpoint blockers to enhance T cell activity and infiltration in the tumor. These findings suggest how and why a rational combination therapy can overcome the limits of DNA vaccination but could also allow responses to immune checkpoint blockers in a larger proportion of subjects.

PLGA based drug delivery systems: Promising carriers for wound healing activity

Wound treatment remains one of the most prevalent and economically burdensome healthcare issues in the world. Current treatment options are limited and require repeated administrations which led to the development of new therapeutics to satisfy the unmet clinical needs. Many potent wound healing agents were discovered but most of them are fragile and/or sensitive to in vivo conditions. Poly(lactic-co-glycolic acid) (PLGA) is a widely used biodegradable polymer approved by food and drug administration and European medicines agency as an excipient for parenteral administrations. It is a well-established drug delivery system in various medical applications. The aim of the current review is to elaborate the applications of PLGA based drug delivery systems carrying different wound healing agents and also present PLGA itself as a wound healing promoter. PLGA carriers encapsulating drugs such as antibiotics, anti-inflammatory drugs, proteins/peptides, and nucleic acids targeting various phases/signaling cycles of wound healing, are discussed with examples. The combined therapeutic effects of PLGA and a loaded drug on wound healing are also mentioned.

EPR monitoring of wound oxygenation as a biomarker of response to gene therapy encoding hCAP-18/LL37 peptide

PURPOSE

To investigate the value of electron paramagnetic resonance oximetry to follow oxygenation in wounds treated by a plasmid-encoding host defense peptide hCAP-18/LL37.

METHODS

Flaps were created on diabetic mice (7- or 12-week-old db/db mice) presenting different levels of microangiopathy. The hCAP-18/LL37-encoding plasmids were administered in wounds by electroporation. Low-frequency electron paramagnetic resonance oximetry using lithium phthalocyanine as the oxygen sensor was used to monitor wound oxygenation in flaps during the healing process. Flaps were analyzed by immunohistochemistry to assess hypoxia and cell proliferation. Kinetics of closure was also assessed in excisional skin wounds.

RESULTS

A reoxygenation of the flap was observed during the healing process in the 7-week-old db/db treated mice, but not in the untreated mice and the 12-week-old mice. Histological studies demonstrated less hypoxic regions and higher proportion of proliferating cells in hCAP-18/LL37-treated flaps in the 7-week-old db/db treated mice compared with untreated mice. Consistently, the kinetics of excisional wound closure was improved by hCAP-18/LL37 treatment in the 7-week-old db/db but not in the 12-week-old mice.

CONCLUSIONS

Oxygenation measured by electron paramagnetic resonance oximetry is a promising biomarker of response to treatments designed to modulate wound oxygenation. Magn Reson Med 79:3267-3273, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Codon-Optimized P1A-Encoding DNA Vaccine: Toward a Therapeutic Vaccination against P815 Mastocytoma

DNA vaccine can be modified to increase protein production and modulate immune response. To enhance the efficiency of a P815 mastocytoma DNA vaccine, the P1A gene sequence was optimized by substituting specific codons with synonymous ones while modulating the number of CpG motifs. The P815A murine antigen production was increased with codon-optimized plasmids. The number of CpG motifs within the P1A gene sequence modulated the immunogenicity by inducing a local increase in the cytokines involved in innate immunity. After prophylactic immunization with the optimized vaccines, tumor growth was significantly delayed and mice survival was improved. Consistently, a more pronounced intratumoral recruitment of CD8⁺ T cells and a memory response were observed. Therapeutic vaccination was able to delay tumor growth when the codon-optimized DNA vaccine containing the highest number of CpG motifs was used. Our data demonstrate the therapeutic potential of optimized P1A vaccine against P815 mastocytoma, and they show the dual role played by codon optimization on both protein production and innate immune activation.

Coadministration of a Plasmid Encoding HIV-1 Gag Enhances the Efficacy of Cancer DNA Vaccines

DNA vaccination holds great promise for the prevention and treatment of cancer and infectious diseases. However, the clinical ability of DNA vaccines is still controversial due to the limited immune response initially observed in humans. We hypothesized that electroporation of a plasmid encoding the HIV-1 Gag viral capsid protein would enhance cancer DNA vaccine potency. DNA electroporation used to deliver plasmids in vivo, induced type I interferons, thereby supporting the activation of innate immunity. The coadministration of ovalbumin (OVA) and HIV-1 Gag encoding plasmids modulated the adaptive immune response. This strategy favored antigen-specific Th1 immunity, delayed B16F10-OVA tumor growth and improved mouse survival in both prophylactic and therapeutic vaccination approaches. Similarly, a prophylactic DNA immunization against the melanoma-associated antigen gp100 was enhanced by the codelivery of the HIV-1 Gag plasmid. The adjuvant effect was not driven by the formation of HIV-1 Gag virus-like particles. This work highlights the ability of both electroporation and the HIV-1 Gag plasmid to stimulate innate immunity for enhancing cancer DNA vaccine immunogenicity and demonstrates interesting tracks for the design of new translational genetic adjuvants to overcome the current limitations of DNA vaccines in humans.

Chitosan Nanoparticles for SiRNA Delivery In Vitro

RNA interference, the process in which small interfering RNAs (SiRNAs) silence a specific gene and thus inhibit the associated protein, has opened new doors for the treatment of a wide range of diseases. However, efficient delivery of SiRNAs remains a challenge, especially due to their instability in biological environments and their inability to cross cell membranes. To protect and deliver SiRNAs to mammalian cells, a variety of polymeric nanocarriers have been developed. Among them, the polysaccharide chitosan has generated great interests. This derivative of natural chitin is biodegradable and biocompatible, and can complex SiRNAs into nanoparticles on account of its positive charges. However, chitosan presents some limitations that need to be taken into account when designing chitosan/SiRNA nanoparticles. Here, we describe a method to prepare SiRNA/chitosan nanoparticles with high gene silencing efficiency and low cytotoxicity by using the ionic gelation technique.

APP-dependent glial cell line-derived neurotrophic factor gene expression drives neuromuscular junction formation

Besides its crucial role in the pathogenesis of Alzheimer's disease, the knowledge of amyloid precursor protein (APP) physiologic functions remains surprisingly scarce. Here, we show that APP regulates the transcription of the glial cell line-derived neurotrophic factor (GDNF). APP-dependent regulation of GDNF expression affects muscle strength, muscular trophy, and both neuronal and muscular differentiation fundamental for neuromuscular junction (NMJ) maturation in vivo In a nerve-muscle coculture model set up to modelize NMJ formation in vitro, silencing of muscular APP induces a 30% decrease in secreted GDNF levels and a 40% decrease in the total number of NMJs together with a significant reduction in the density of acetylcholine vesicles at the presynaptic site and in neuronal maturation. These defects are rescued by GDNF expression in muscle cells in the conditions where muscular APP has been previously silenced. Expression of GDNF in muscles of amyloid precursor protein null mice corrected the aberrant synaptic morphology of NMJs. Our findings highlight for the first time that APP-dependent GDNF expression drives the process of NMJ formation, providing new insights into the link between APP gene regulatory network and physiologic functions.-Stanga, S., Zanou, N., Audouard, E., Tasiaux, B., Contino, S., Vandermeulen, G., René, F., Loeffler, J.-P., Clotman, F., Gailly, P., Dewachter, I., Octave, J.-N., Kienlen-Campard, P. APP-dependent glial cell line-derived neurotrophic factor gene expression drives neuromuscular junction formation.

Clinical potential of electroporation for gene therapy and DNA vaccine delivery

INTRODUCTION

Electroporation allows efficient delivery of DNA into cells and tissues, thereby improving the expression of therapeutic or immunogenic proteins that are encoded by plasmid DNA. This simple and versatile method holds a great potential and could address unmet medical needs such as the prevention or treatment of many cancers or infectious diseases.

AREAS COVERED

This review explores the electroporation mechanism and the parameters affecting its efficacy. An analysis of past and current clinical trials focused on DNA electroporation is presented. The pathologies addressed, the protocol used, the treatment outcome and the tolerability are highlighted. In addition, several of the possible optimization strategies for improving patient compliance and therapeutic efficacy are discussed such as plasmid design, use of genetic adjuvants for DNA vaccines, choice of appropriate delivery site and electrodes as well as pulse parameters.

EXPERT OPINION

The growing number of clinical trials and the results already available underline the strong potential of DNA electroporation which combines both safety and efficiency. Nevertheless, it remains critical to further increase fundamental knowledge to refine future strategies, to develop concerted and common DNA electroporation protocols and to continue exploring new electroporation-based therapeutic options.

Development of functionalized nanoparticles for vaccine delivery to dendritic cells: a mechanistic approach

AIM

Produce biodegradable nanoparticles to target antigen-presenting cells (APCs) and evaluate their potential to be used as a vaccine delivery system.

MATERIALS & METHODS

Untargeted PEGylated poly(d,l-lactic-co-glycolide)-based nanoparticles and mannose-grafted nanoparticles were formulated and physicochemically characterized. Immortalized and primary APCs were used to study nanoparticle internalization patterns. The endocytic pathways and intracellular trafficking followed by nanoparticles were also investigated.

RESULTS & DISCUSSION

Nanoparticles displayed mannose residues available for binding at the nanoparticle surface. Different nanoparticle internalization patterns by immortalized and primary APCs were verified. Macropinocytosis, clathrin-mediated endocytosis, caveolin- and lipid raft-dependent endocytosis are involved in nanoparticles internalization. Nanoparticles demonstrate both endolysosomal and cytosolic localizations and a tendency to accumulate nearby the endoplasmic reticulum.

CONCLUSION

The developed nanoparticles might drive antigens to be presented through MHC class I and II molecules to both CD8(+) and CD4(+) T cells, favoring a complete and coordinated immune response.

Combined effects of PLGA and vascular endothelial growth factor promote the healing of non-diabetic and diabetic wounds

Growth factor therapies to induce angiogenesis and thereby enhance the blood perfusion, hold tremendous potential to address the shortcomings of current impaired wound care modalities. Vascular endothelial growth factor stimulates (VEGF) wound healing via multiple mechanisms. Poly(lactic-co-glycolic acid) (PLGA) supplies lactate that accelerates neovascularization and promotes wound healing. Hence, we hypothesized that the administration of VEGF encapsulated in PLGA nanoparticles (PLGA-VEGF NP) would promote fast healing due to the sustained and combined effects of VEGF and lactate. In a splinted mouse full thickness excision model, compared with untreated, VEGF and PLGA NP, PLGA-VEGF NP treated wounds showed significant granulation tissue formation with higher collagen content, re-epithelialization and angiogenesis. The cellular and molecular studies revealed that PLGA-VEGF NP enhanced the proliferation and migration of keratinocytes and upregulated the expression of VEGFR2 at mRNA level. We demonstrated the combined effects of lactate and VEGF for active healing of non-diabetic and diabetic wounds.

FROM THE CLINICAL EDITOR

The study of wound healing has been under a tremendous amount of research over recent years. In diabetic wounds, vasculopathy leading to localized ischemia would often result in delayed 
wound healing. In this article, the authors encapsulated vascular endothelial growth factor stimulates (VEGF) in PLGA nanoparticles and studies the potential pro-healing effects. It was found that the combination of these two components provided synergistic actions for healing. The encouraging results should provide a basis for combination therapy in the future.

Increased B and T Cell Responses in M. bovis Bacille Calmette-Guérin Vaccinated Pigs Co-Immunized with Plasmid DNA Encoding a Prototype Tuberculosis Antigen

The only tuberculosis vaccine currently available, bacille Calmette-Guérin (BCG) is a poor inducer of CD8(+) T cells, which are particularly important for the control of latent tuberculosis and protection against reactivation. As the induction of strong CD8(+) T cell responses is a hallmark of DNA vaccines, a combination of BCG with plasmid DNA encoding a prototype TB antigen (Ag85A) was tested. As an alternative animal model, pigs were primed with BCG mixed with empty vector or codon-optimized pAg85A by the intradermal route and boosted with plasmid delivered by intramuscular electroporation. Control pigs received unformulated BCG. The BCG-pAg85A combination stimulated robust and sustained Ag85A specific antibody, lymphoproliferative, IL-6, IL-10 and IFN-γ responses. IgG1/IgG2 antibody isotype ratio reflected the Th1 helper type biased response. T lymphocyte responses against purified protein derivative of tuberculin (PPD) were induced in all (BCG) vaccinated animals, but responses were much stronger in BCG-pAg85A vaccinated pigs. Finally, Ag85A-specific IFN-γ producing CD8(+) T cells were detected by intracellular cytokine staining and a synthetic peptide, spanning Ag85A131-150 and encompassing two regions with strong predicted SLA-1*0401/SLA-1*0801 binding affinity, was promiscuously recognized by 6/6 animals vaccinated with the BCG-pAg85A combination. Our study provides a proof of concept in a large mammalian species, for a new Th1 and CD8(+) targeting tuberculosis vaccine, based on BCG-plasmid DNA co-administration.

The site of administration influences both the type and the magnitude of the immune response induced by DNA vaccine electroporation

We investigated the influence of the site of administration of DNA vaccine on the induced immune response. DNA vaccines were administered by electroporation at three different sites: tibial cranial muscle, abdominal skin and ear pinna. Aiming to draw general conclusions about DNA vaccine delivery, we successively used several plasmids encoding either luciferase and ovalbumin as models or gp160 and P1A as vaccines against HIV and P815 mastocytoma, respectively. Low levels and duration of luciferase transgene expression were observed after electroporation of the abdominal skin, partly explaining its lower immunogenic performance as compared to the other sites of administration. Analyses of OT-I CD8+ and OT-II CD4+ T cell responses highlighted the differential impact of the delivery site on the elicited immune response. Muscle electroporation induced the strongest humoral immune response and both muscle and ear pinna sites induced cellular immunity against gp160. Ear pinna delivery generated the highest level of CTL responses against P1A but electroporation of muscle and ear pinna were equally efficient in delaying P815 growth and improving mice survival. The present study demonstrated that the site of administration is a key factor to be tested in the development of DNA vaccine.

Fibrin hydrogels to deliver dental stem cells of the apical papilla for regenerative medicine

Aim: Evaluation of survival, proliferation and neurodifferentiation of dental stem cells from the apical papilla (SCAP) in fibrin hydrogels. We hypothesized that fibrin composition will influence cell behavior. Methods: Modulus, pore and fiber size were measured. SCAP in vitro viability, proliferation and neural differentiation, as well as in vivo proliferation and angiogenesis were studied. Results: Hydrogel moduli were influenced by fibrin formulation but not hydrogel morphology, SCAP in vitro viability and proliferation. In total 60% of SCAP expressed PanNeurofilament in vitro without induction in Fibrinogen50-Thrombin10. SCAP proliferated when implanted in vivo and stimulated host endothelial cell infiltration. Conclusion: Fibrinogen30-Thrombin10 or Thrombin50 would be more favorable to in vitro SCAP viability and in vivo proliferation, while Fibrinogen 50-Thrombin50 would be more adapted to neurodifferentiation.

In vivo delivery of peptides and Toll-like receptor ligands by mannose-functionalized polymeric nanoparticles induces prophylactic and therapeutic anti-tumor immune responses in a melanoma model

We hypothesized that the co-entrapment of melanoma-associated antigens and the Toll-like receptor (TLR) ligands Poly(I:C) and CpG, known to be Th1-immunopotentiators, in mannose-functionalized aliphatic polyester-based nanoparticles (NPs) could be targeted to mannose receptors on antigen-presenting cells and induce anti-tumor immune responses. High entrapment efficiencies of antigens and immunopotentiators in 150nm NPs were obtained. The co-entrapment of the model antigen ovalbumin and the TLR ligands was crucial to induce high IgG2c/IgG1 ratios and high levels of IFN-γ and IL-2. Mannose-functionalization of NPs potentiated the Th1 immune response. The nanoparticulate vaccines decreased the growth rate of murine B16F10 melanoma tumors in therapeutic and prophylatic settings. The combination of mannose-functionalized NPs containing MHC class I- or class II-restricted melanoma antigens and the TLR ligands induced the highest tumor growth delay. Overall, we demonstrate that the multifunctional properties of NPs in terms of targeting and antigen/adjuvant delivery have high cancer immunotherapeutic potential.

Increased T and B cell responses in M. bovis BCG vaccinated pigs by co-immunization with pDNA encoding a prototype tuberculosis antigen (VAC7P.973)

The only vaccine currently available to prevent tuberculosis, M. bovis BCG, has limited efficacy. BCG is a poor inducer of CD8+ T cells, which are particularly important for the control of latent tuberculosis and protection against reactivation TB. The induction of strong CD8+ T cell responses is a hallmark of DNA vaccines. We postulated that combining the existing BCG vaccine with plasmid DNA encoding immunodominant antigens of M. tuberculosis, could improve the vaccine by generating stronger CD8+ (and CD4+) T cell responses. As a prototype tuberculosis antigen, the mycolyl-transferase Ag85A was selected. Three groups of six pigs each, were vaccinated intradermally with BCG alone, BCG combined with empty vector or BCG combined with codon-optimized V1j.ns-tPA-Ag85A vector. The BCG-pAg85A DNA combination induced strongly increased and sustained humoral and Th1 type cellular responses against Ag85A and against the purified protein derivative of tuberculin. Increased IFN-γ producing CD8 T cells were detected by intracellular cytokine staining and an Ag85A T cell epitope with predicted MHC class I motif, was promiscuously recognized by 5/6 pigs vaccinated with the combination. In summary, our study provides the first proof of concept in a large mammalian species, for a new TB vaccine, based on a BCG-pDNA combination.

Chitosan nanoparticles for siRNA delivery: optimizing formulation to increase stability and efficiency

This study aims at developing chitosan-based nanoparticles suitable for an intravenous administration of small interfering RNA (siRNA) able to achieve (i) high gene silencing without cytotoxicity and (ii) stability in biological media including blood. Therefore, the influence of chitosan/tripolyphosphate ratio, chitosan physicochemical properties, PEGylation of chitosan as well as the addition of an endosomal disrupting agent and a negatively charged polymer was assessed. The gene silencing activity and cytotoxicity were evaluated on B16 melanoma cells expressing luciferase. We monitored the integrity and the size behavior of siRNA nanoparticles in human plasma using fluorescence fluctuation spectroscopy and single particle tracking respectively. The presence of PEGylated chitosan and poly(ethylene imine) was essential for high levels of gene silencing in vitro. Chitosan nanoparticles immediately released siRNA in plasma while the inclusion of hyaluronic acid and high amount of poly(ethylene glycol) in the formulation improved the stability of the particles. The developed formulations of PEGylated chitosan-based nanoparticles that achieve high gene silencing in vitro, low cytotoxicity and high stability in plasma could be promising for intravenous delivery of siRNA.

Skin electroporation of a plasmid encoding hCAP-18/LL-37 host defense peptide promotes wound healing

Host defense peptides, in particular LL-37, are emerging as potential therapeutics for promoting wound healing and inhibiting bacterial growth. However, effective delivery of the LL-37 peptide remains limiting. We hypothesized that skin-targeted electroporation of a plasmid encoding hCAP-18/LL-37 would promote the healing of wounds. The plasmid was efficiently delivered to full-thickness skin wounds by electroporation and it induced expression of LL-37 in the epithelium. It significantly accelerated reepithelialization of nondiabetic and diabetic wounds and caused a significant VEGFa and interleukin (IL)-6 induction. IL-6 was involved in LL-37-mediated keratinocyte migration in vitro and IL-6 neutralizing antibodies delivered to mice were able to suppress the wound healing activity of the hCAP-18/LL-37 plasmid. In a hindlimb ischemia model, electroporation of the hCAP-18/LL-37 plasmid increased blood perfusion, reduced muscular atrophy, and upregulated the angiogenic chemokines VEGFa and SDF-1a, and their receptors VEGF-R and CXCR-4. These findings demonstrate that a localized gene therapy with LL-37 is a promising approach for the treatment of wounds.

Use of Staby(®) technology for development and production of DNA vaccines free of antibiotic resistance gene

The appearance of new viruses and the cost of developing certain vaccines require that new vaccination strategies now have to be developed. DNA vaccination seems to be a particularly promising method. For this application, plasmid DNA is injected into the subject (man or animal). This plasmid DNA encodes an antigen that will be expressed by the cells of the subject. In addition to the antigen, the plasmid also encodes a resistance to an antibiotic, which is used during the construction and production steps of the plasmid. However, regulatory agencies (FDA, USDA and EMA) recommend to avoid the use of antibiotics resistance genes. Delphi Genetics developed the Staby(®) technology to replace the antibiotic-resistance gene by a selection system that relies on two bacterial genes. These genes are small in size (approximately 200 to 300 bases each) and consequently encode two small proteins. They are naturally present in the genomes of bacteria and on plasmids. The technology is already used successfully for production of recombinant proteins to achieve higher yields and without the need of antibiotics. In the field of DNA vaccines, we have now the first data validating the innocuousness of this Staby(®) technology for eukaryotic cells and the feasibility of an industrial production of an antibiotic-free DNA vaccine. Moreover, as a proof of concept, mice have been successfully vaccinated with our antibiotic-free DNA vaccine against a deadly disease, pseudorabies (induced by Suid herpesvirus-1).

Chitosan-based siRNA delivery systems

Recently, chitosan has attracted significant attention in the formulation of small interfering RNA (siRNA). Because of its cationic nature, chitosan can easily complex siRNA, thus readily forming nanoparticles. Moreover, chitosan is biocompatible and biodegradable, which make it a good candidate for siRNA delivery in vivo. However, chitosan requires further development to achieve high efficiency. This review will describe the major barriers that impair the efficiency of the chitosan-based siRNA delivery systems, including the stability of the delivery system in biological fluids and endosomal escape. Several solutions to counteract these barriers have been developed and will be discussed. The parameters to consider for designing powerful delivery systems will be described, particularly the possibilities for grafting targeting ligands. Finally, optimized systems that allow in vivo therapeutic applications for both local and systemic delivery will be reviewed. This review will present recent improvements in chitosan-based siRNA delivery systems that overcome many of these system's previous pitfalls and pave the way to a new generation of siRNA delivery systems.

Kinetics of butyrate metabolism in the normal colon and in ulcerative colitis: the effects of substrate concentration and carnitine on the β-oxidation pathway

BACKGROUND

Butyrate, a colonic metabolite of carbohydrates, is considered as the major energy source for the colonic mucosa. An impaired butyrate metabolism has been reported in ulcerative colitis (UC), however, the cause still remains unknown.

AIM

In the present study, we investigated whether higher butyrate concentrations could normalise the oxidation rate in UC. Furthermore, it was investigated whether carnitine could enhance the butyrate oxidation.

METHODS

Mucosal biopsies from a total of 26 UC patients and 25 controls were incubated with (14)C-labelled Na-butyrate and the produced (14)CO(2) was measured. First, the rate of oxidative metabolism was compared at three different concentrations of Na-butyrate (0.05 mm, 1 mm and 10 mm). Then, incubations of biopsies were performed with carnitine alone or combined with ATP.

RESULTS

Overall, butyrate oxidation in UC was significantly lower than that in controls. The maximum rate of butyrate oxidation was achieved in UC and control subjects from 1 mm onwards. Increasing the butyrate concentration to a level to be present in the colonic lumen, i.e. 10 mm, did not increase the rate of butyrate oxidation in UC to the rate observed in controls. Addition of carnitine alone or combined with ATP caused no effects.

CONCLUSIONS

Saturation of butyrate kinetics was achieved from 1 mm in UC and control subjects. The rate of butyrate metabolism was significantly impaired in active ulcerative colitis. The addition of compounds interfering with the β-oxidation pathway had no effect on the butyrate metabolism in UC.

New generation of plasmid backbones devoid of antibiotic resistance marker for gene therapy trials

Since it has been established that the injection of plasmid DNA can lead to an efficient expression of a specific protein in vivo, nonviral gene therapy approaches have been considerably improved, allowing clinical trials. However, the use of antibiotic resistance genes as selection markers for plasmid production raises safety concerns which are often pointed out by the regulatory authorities. Indeed, a horizontal gene transfer to patient's bacteria cannot be excluded, and residual antibiotic in the final product could provoke allergic reactions in sensitive individuals. A new generation of plasmid backbones devoid of antibiotic resistance marker has emerged to increase the safety profile of nonviral gene therapy trials. This article reviews the existing strategies for plasmid maintenance and, in particular, those that do not require the use of antibiotic resistance genes. They are based either on the complementation of auxotrophic strain, toxin-antitoxin systems, operator-repressor titration, RNA markers, or on the overexpression of a growth essential gene. Minicircles that allow removing of the antibiotic resistance gene from the initial vector will also be discussed. Furthermore, reported use of antibiotic-free plasmids in preclinical or clinical studies will be listed to provide a comprehensive view of these innovative technologies.

Delivery of soluble VEGF receptor 1 (sFlt1) by gene electrotransfer as a new antiangiogenic cancer therapy

Since tumor growth is highly dependent on the formation of new blood vessels, angiogenesis inhibitors have become important players in anticancer treatments. Although less cytotoxic than conventional chemotherapy, most of the available antiangiogenic agents may provoke severe adverse effects which can limit their use. The design of new antiangiogenic strategies therefore requires integrating an early evaluation of possible interference with quiescent endothelial cells and nontumor angiogenesis. Here, we describe such a novel antiangiogenic approach based on the in vivo delivery by gene electrotransfer of a negative regulator of angiogenesis, namely, sFlt1. We found that this soluble variant of the vascular endothelial growth factor receptor 1 (Flt1, also known as VEGFR1), which acts as a VEGF trap, differentially influences tumor and postischemic hind limb angiogenesis in mice. sFlt1 gene electrotransfer in tibial cranial muscle leads to high sFlt1 protein expression and secretion, leading to a significant delay in the growth of syngeneic tumors but not altering the revascularization of ischemic peripheral tissue. The higher sensitivity of tumor-bearing animals toward sFlt1 trapping effects (vs ischemia-recovering animals) might be explained by a distinct pattern of VEGF release, as shown by VEGF measurements in plasma and tissue. In conclusion, our data support sFlt1 gene electrotransfer as a novel and safe modality to target VEGF-driven tumor angiogenesis and to maintain unaltered the recovery potential of ischemic tissues.

Cationic and anionic lipoplexes inhibit gene transfection by electroporation in vivo

BACKGROUND

Nonviral gene therapy still suffers from low efficiency. Methods that would lead to higher gene expression level of longer duration would be a major advance in this field. Lipidic vectors and physical methods have been investigated separately, and both induced gene expression improvement.

METHODS

We sought to combine both chemical and physical methods. Cationic or anionic lipids can potentially destabilize the cell membrane and could consequently enhance gene delivery by a physical method such as electrotransfer. A plasmid model encoding luciferase was used, either free or associated with differently-charged lipoplexes before electrotransfer.

RESULTS

Electrotransfer alone strongly enhanced gene expression after intramuscular and intradermal injection of naked DNA. On the other hand, cationic and anionic lipoplex formulations decreased gene expression after electrotransfer, whereas poorly-charged thiourea-based complexes, brought no benefit. Pre-injection of the lipids, followed by administration of naked DNA, did not modified gene expression induced by electroporation in the skin.

CONCLUSIONS

The results obtained in the present study suggest that packing of DNA plasmid in lipoplexes strongly decreases the efficiency of gene electrotransfer, independently of the lipoplex charge. Non-aggregating complexes, such as poorly-charged thiourea-based complexes, should be preferred to increase DNA release.

pFARs, plasmids free of antibiotic resistance markers, display high-level transgene expression in muscle, skin and tumour cells

BACKGROUND

Nonviral gene therapy requires a high yield and a low cost production of eukaryotic expression vectors that meet defined criteria such as biosafety and quality of pharmaceutical grade. To fulfil these objectives, we designed a novel antibiotic-free selection system.

METHODS

The proposed strategy relies on the suppression of a chromosomal amber mutation by a plasmid-borne function. We first introduced a nonsense mutation into the essential Escherichia coli thyA gene, resulting in thymidine auxotrophy. The bacterial strain was optimized for the production of small and novel plasmids free of antibiotic resistance markers (pFARs) and encoding an amber suppressor t-RNA. Finally, the potentiality of pFARs as eukaryotic expression vectors was assessed by monitoring luciferase activities after electrotransfer of LUC-encoding plasmids into various tissues.

RESULTS

The introduction of pFARs into the optimized bacterial strain restored normal growth to the auxotrophic mutant and allowed an efficient production of monomeric supercoiled plasmids. The electrotransfer of LUC-encoding pFAR into muscle led to high luciferase activities, demonstrating an efficient gene delivery. In transplanted tumours, transgene expression levels were superior after electrotransfer of the pFAR derivative compared to a plasmid carrying a kanamycin resistance gene. Finally, in skin, whereas luciferase activities decreased within 3 weeks after intradermal electrotransfer of a conventional expression vector, sustained luciferase expression was observed with the pFAR plasmid.

CONCLUSIONS

Thus, we have designed a novel strategy for the efficient production of biosafe plasmids and demonstrated their potentiality for nonviral gene delivery and high-level transgene expression in several tissues.

Hollow microneedle arrays for intradermal drug delivery and DNA electroporation

The association of microneedles with electric pulses causing electroporation could result in an efficient and less painful delivery of drugs and DNA into the skin. Hollow conductive microneedles were used for (1) needle-free intradermal injection and (2) electric pulse application in order to achieve electric field in the superficial layers of the skin sufficient for electroporation. Microneedle array was used in combination with a vibratory inserter to disrupt the stratum corneum, thus piercing the skin. Effective injection of proteins into the skin was achieved, resulting in an immune response directed to the model antigen ovalbumin. However, when used both as microneedles to inject and as electrodes to apply the electric pulses, the setup showed several limitations for DNA electrotransfer. This could be due to the distribution of the electric field in the skin as shown by numerical calculations and/or the low dose of DNA injected. Further investigation of these parameters is needed in order to optimize minimally invasive DNA electrotransfer in the skin.

Ear Pinna: A Privileged DNA Electroporation Site for Inducing Strong Th1 Immune Responses

DNA vaccination appears a very attractive approach for inducing immune responses towards the encoded antigen, but studies in large animals and in humans revealed weaknesses of such responses. In this study, we evaluated a new approach based on a new device combining DNA vaccination with electroporation (EP) at the ear pinna site. Under optimal EP conditions, the expression of the DNA encoded antigen and the induced immune responses were considerably increased. Very interestingly, DNA vaccination using EP at the ear pinna induced much stronger cellular immune responses than at the flank skin although antigen expression was similar at both sites. As compared to vaccination at the ear pinna without EP, IFN-􀀁 but not IL-4 production by splenocytes from immunized mice was significantly enhanced. In contrast, IL-4 but not IFN-􀀁 production was increased by EP at the flank skin. The vaccination site of the ear pinna combined with EP route even provided therapeutic effects in a mouse tumor model.

In conclusion, this study highlights the ear pinna as a privileged site for the induction of strong Th1 polarized cellular immunity against a defined antigen when combining DNA vaccination with EP.

Optimisation of intradermal DNA electrotransfer for immunisation

The development of DNA vaccines requires appropriate delivery technologies. Electrotransfer is one of the most efficient methods of non-viral gene transfer. In the present study, intradermal DNA electrotransfer was first optimised. Strong effects of the injection method and the dose of DNA on luciferase expression were demonstrated. Pre-treatments were evaluated to enhance DNA diffusion in the skin but neither hyaluronidase injection nor iontophoresis improved efficiency of intradermal DNA electrotransfer. Then, DNA immunisation with a weakly immunogenic model antigen, luciferase, was investigated. After intradermal injection of the plasmid encoding luciferase, electrotransfer (HV 700 V/cm 100 micros, LV 200 V/cm 400 ms) was required to induce immune response. The response was Th1-shifted compared to immunisation with the luciferase recombinant protein. Finally, DNA electrotransfer in the skin, the muscle or the ear pinna was compared. Muscle DNA electrotransfer resulted in the highest luciferase expression and the best IgG response. Nevertheless electrotransfer into the skin, the muscle and the ear pinna all resulted in IFN-gamma secretion by luciferase-stimulated splenocytes suggesting that an efficient Th1 response was induced in all case.

Encapsulation of amphotericin B in poly(ethylene glycol)-block-poly(epsilon-caprolactone-co-trimethylenecarbonate) polymeric micelles

The aim of this work was to evaluate the potential of self-assembling poly(ethyleneglycol)(750)-block-poly(epsilon-caprolactone-co-trimethylenecarbonate)(4500) 50/50 copolymers (PEG-p(CL-co-TMC)) to solubilize amphotericin B in polymeric micelles and to disaggregate the drug to the less toxic monomeric form. Amphotericin B was encapsulated in the micelles upon dilution of a mixture of the liquid polymer and the drug in water. Its solubility was increased by two orders of magnitude depending on polymer concentration. The aggregation state of amphotericin B was decreased by PEG-p(CL-co-TMC). The preparation method and the loading of the polymeric micelles influenced it. The antifungal activity of the drug was reduced by encapsulation in the polymeric micelles whereas the onset of amphotericin B-induced hemolysis was delayed. PEG-p(CL-co-TMC) micelles could be an easy method for amphotericin B encapsulation.