Development of an antigen-presenting cell-targeted DNA vaccine against melanoma by mannosylated liposomes

Mannosylated chitosan-graft-polyethylenimine as a gene carrier for Raw 264.7 cell targeting

Gene transfer using non-viral vectors is a promising approach for the safe delivery of therapeutic genes. Among non-viral vectors, chitosans have been proposed as alternative, biocompatible cationic polymers for non-viral gene delivery. However, the low transfection efficiency and low specificity of chitosan needs to be addressed prior to clinical application. In this study, mannosylated chitosan-graft-polyethylenimine (Man-CHI-g-PEI) copolymer was prepared by thiourea reaction between the isothiocyanate group of mannopyranosylphenylisothiocyanate and the amine groups of chitosan-graft-PEI (CHI-g-PEI) for targeting into antigen presenting cells (APCs) having mannose receptors. The composition and molecular weight were characterized using (1)H NMR and GPC, respectively. The copolymer was complexed with plasmid DNA in various copolymer/DNA (N/P) charge ratios, and the complexes were characterized. Man-CHI-g-PEI showed good DNA binding ability and high protection of DNA from nuclease attack and had low cytotoxicity compared with PEI 25K. The transfection efficiency of Man-CHI-g-PEI/DNA complexes into the Raw 264.7 macrophage cell line, which has mannose receptors, was higher than CHI-g-PEI itself as well as PEI 25K, indicating Man-CHI-g-PEI can be used as an APCs' targeting gene delivery carrier.

Targeting the porcine immune system--particulate vaccines in the 21st century

During the last decade, the propagation of immunological knowledge describing the critical role of dendritic cells (DC) in the induction of efficacious immune responses has promoted research and development of vaccines systematically targeting DC. Based on the promise for the rational design of vaccine platforms, the current review will provide an update on particle-based vaccines of both viral and synthetic origin, giving examples of recombinant virus carriers such as adenoviruses and biodegradable particulate carriers. The viral carriers carry pathogen-associated molecular patterns (PAMP), used by the original virus for targeting DC, and are particularly efficient and versatile gene delivery vectors. Efforts in the field of synthetic vaccine carriers are focussing on decorating the particle surface with ligands for DC receptors such as heparan sulphate glycosaminoglycan structures, integrins, Siglecs, galectins, C-type lectins and toll-like receptors. The emphasis of this review will be placed on targeting the porcine immune system, but reference will be made to advances with murine and human vaccine delivery systems where information on DC targeting is available.

Polymeric Materials for Gene Delivery and DNA Vaccination

Gene delivery holds great potential for the treatment of many different diseases. Vaccination with DNA holds particular promise, and may provide a solution to many technical challenges that hinder traditional vaccine systems including rapid development and production and induction of robust cell-mediated immune responses. However, few candidate DNA vaccines have progressed past preclinical development and none have been approved for human use. This Review focuses on the recent progress and challenges facing materials design for nonviral DNA vaccine drug delivery systems. In particular, we highlight work on new polymeric materials and their effects on protective immune activation, gene delivery, and current efforts to optimize polymeric delivery systems for DNA vaccination.

Protein/peptide and DNA vaccine delivery by targeting C-type lectin receptors

C-type lectin receptors (CLRs) are a class of pathogen-recognition receptors that are actively investigated in the field of vaccine delivery. Many of their properties have functions linked to the immune system. These receptors are expressed abundantly on antigen-presenting cells and are considered to be the sentinels of immune surveillance owing to their endocytic nature and the ability to recognize a diverse range of pathogens through recognition of pathogen-associated molecular patterns. CLRs are also involved in the processes of antigen presentation mediated through the induction of dendritic cell maturation and cytokine production. These properties engender CLRs to be ideal for vaccine targeting. Conversely, CLRs also function to recognize glycosylated self-antigens to induce homeostatic control and tolerance. In this review, we will describe the various preclinical/clinical vaccination strategies to target antigens and plasmid DNA to this diverse class of receptors.

Delivery strategies of melanoma vaccines: an overview

For many years, various cancer vaccines have been widely evaluated, however clinical responses remain rare. In this review, we attempt to address the question of which delivery strategies and platforms are feasible to produce clinical response and define the characteristics of the strategy that will induce long-lasting antitumor response. We limit our analysis and discussion to microparticles/nanoparticles, liposomes, heat-shock proteins, viral vectors and different types of adjuvants. This review aims to provide an overview of the specific characteristics, strengths and limitations of these delivery systems, focusing on their impacts on the development of melanoma vaccine. To date, only adoptive T-cell transfer has shown promising clinical outcomes compared to other treatments.

Use of mannosylated cationic liposomes/ immunostimulatory CpG DNA complex for effective inhibition of peritoneal dissemination in mice

BACKGROUND

Immunotherapy using immunostimulatory CpG DNA could be a promising new therapeutic approach to combat refractory peritoneal dissemination. In the present study, we report the use of a mannosylated cationic liposomes/immunostimulatory CpG DNA complex (Man/CpG DNA lipoplex) for effective inhibition of peritoneal dissemination in mice.

METHODS

The immune response characteristics of the Man/CpG DNA lipoplex were evaluated by measuring tumor necrosis factor (TNF)-alpha production using primary cultured mouse peritoneal macrophages. Subsequently, Man/CpG DNA lipoplex was administered intraperitoneally (i.p.) to peritoneal dissemination model mice, and the number of tumor cells (colon26/Luc) was quantitatively evaluated by measuring luciferase activity. The effect on survival time of the Man/CpG DNA lipoplex was also investigated. The serum transaminase levels of mice receiving i.p. Man/CpG DNA lipoplex treatment were measured to evaluate systemic toxicity.

RESULTS

The Man/CpG DNA lipoplex induced higher TNF-alpha production from macrophages than CpG DNA complexed with conventional cationic liposomes and galactosylated cationic liposomes (Bare/CpG DNA lipoplex and Gal/CpG DNA lipoplex), suggesting mannose receptor-mediated CpG DNA transfer. Intraperitoneal administration of Man/CpG DNA lipoplex inhibited the proliferation of tumor cells in the greater omentum and the mesentery more efficiently than Bare/CpG DNA lipoplex and Gal/CpG DNA lipoplex. Furthermore, the survival time of the peritoneal dissemination model mice was prolonged by i.p. administration of Man/CpG DNA lipoplex. The serum transaminase levels of mice receiving i.p. Man/CpG DNA lipoplex were found to be the same as those of untreated mice.

CONCLUSIONS

The results obtained suggest that i.p. administered Man/CpG DNA lipoplex can be used for efficient immunotherapy to combat peritoneal dissemination.

Protection against tuberculosis by a single intranasal administration of DNA-hsp65 vaccine complexed with cationic liposomes

Background

The greatest challenges in vaccine development include optimization of DNA vaccines for use in humans, creation of effective single-dose vaccines, development of delivery systems that do not involve live viruses, and the identification of effective new adjuvants. Herein, we describe a novel, simple technique for efficiently vaccinating mice against tuberculosis (TB). Our technique consists of a single-dose, genetic vaccine formulation of DNA-hsp65 complexed with cationic liposomes and administered intranasally.

Results

We developed a novel and non-toxic formulation of cationic liposomes, in which the DNA-hsp65 vaccine was entrapped (ENTR-hsp65) or complexed (COMP-hsp65), and used to immunize mice by intramuscular or intranasal routes. Although both liposome formulations induced a typical Th1 pattern of immune response, the intramuscular route of delivery did not reduce the number of bacilli. However, a single intranasal immunization with COMP-hsp65, carrying as few as 25 μg of plasmid DNA, leads to a remarkable reduction of the amount of bacilli in lungs. These effects were accompanied by increasing levels of IFN-γ and lung parenchyma preservation, results similar to those found in mice vaccinated intramuscularly four times with naked DNA-hsp65 (total of 400 μg).

Conclusion

Our objective was to overcome the significant obstacles currently facing DNA vaccine development. Our results in the mouse TB model showed that a single intranasal dose of COMP-hsp65 elicited a cellular immune response that was as strong as that induced by four intramuscular doses of naked-DNA. This formulation allowed a 16-fold reduction in the amount of DNA administered. Moreover, we demonstrated that this vaccine is safe, biocompatible, stable, and easily manufactured at a low cost. We believe that this strategy can be applied to human vaccines to TB in a single dose or in prime-boost protocols, leading to a tremendous impact on the control of this infectious disease.

Surface modified liposomes for nasal delivery of DNA vaccine

The aim of the present work was to investigate the potential utility of glycol chitosan coated liposomes as nasal vaccine delivery vehicle for eliciting viral specific humoral mucosal and cellular immune responses. Plasmid pRc/CMV-HBs(S) encapsulated liposomes were prepared by dehydration-rehydration method and subsequently coated with glycol chitosan by simple incubation method. Liposomes were then characterized for their size, surface charge, entrapment efficiency, and ability to protect encapsulated DNA against nuclease digestion and for their mucoadhesiveness. The liposomes were then administered to mice in order to study their feasibility as nasal vaccine carriers. The developed liposomes possessed +9.8 mV zeta potential and an average vesicle size less than 1 microm and entrapment efficiency of approximately 53%. Following intranasal administration, glycol chitosan coated liposomes elicited humoral mucosal and cellular immune responses that were significant as compared to naked DNA justifying the potential advantage of mucosal vaccination in the production of local antibodies at the sites where pathogens enters the body.

[Immunotherapy against peritoneal dissemination by immunostimulatory CpG DNA]

Peritoneal dissemination is one of the most common causes of metastasis from malignancies in the abdominal cavity. However, the treatment of peritoneal dissemination is difficult; patients receiving normal chemotherapy have a 0-1% chance of surviving for 5 years. Milky spots in the greater omentum are considered to facilitate the adhesion and invasion of abdominal free cancer cells, and subsequently lymph node metastasis occurs. Since immune cells such as macrophages and lymphocytes are present in the greater omentum and lymph nodes, the activation of immune cells would be a promising strategy for treatment. Single-stranded oligonucleotides containing CpG dinucleotides (CpG DNA) are recognized by Toll-like receptor-9 on antigen-presenting cells such as macrophages to stimulate Th-1-type immune responses. However, a delivery system for CpG DNA to immune cells is essential to develop effective therapy against peritoneal dissemination. Here we review the pathophysiologic basis of peritoneal dissemination and introduce our approach that employs cationic liposomes as a carrier for CpG DNA as a new approach in the treatment of peritoneal dissemination.