Receptor-mediated gene transfer into macrophages

Nanoplatform-Based In Vivo Gene Delivery Systems for Cancer Therapy

Gene therapy uses modern molecular biology methods to repair disease-causing genes. As a burgeoning therapeutic, it has been widely applied for cancer therapy. Since 1989, there have been numerous clinical gene therapy cases worldwide. However, a few are successful. The main challenge of clinical gene therapy is the lack of efficient and safe vectors. Although viral vectors show high transfection efficiency, their application is still limited by immune rejection and packaging capacity. Therefore, the development of non-viral vectors is overwhelming. Nanoplatform-based non-viral vectors become a hotspot in gene therapy. The reasons are mainly as follows. 1) Non-viral vectors can be engineered to be uptaken by specific types of cells or tissues, providing effective targeting capability. 2) Non-viral vectors can protect goods that need to be delivered from degradation. 3) Nanoparticles can transport large-sized cargo such as CRISPR/Cas9 plasmids and nucleoprotein complexes. 4) Nanoparticles are highly biosafe, and they are not mutagenic in themselves compared to viral vectors. 5) Nanoparticles are easy to scale preparation, which is conducive to clinical conversion and application. Here, an overview of the categories of nanoplatform-based non-viral gene vectors, the limitations on their development, and their applications in cancer therapy.

Surface functionalized nanoparticles: A boon to biomedical science

The rapid development of nanomedicine has increased the likelihood that manufactured nanoparticles will one day come into contact with people and the environment. A variety of academic fields, including engineering and the health sciences, have taken a keen interest in the development of nanotechnology. Any significant development in nanomaterial-based applications would depend on the production of functionalized nanoparticles, which are believed to have the potential to be used in fields like pharmaceutical and biomedical sciences. The functionalization of nanoparticles with particular recognition chemical moieties does result in multifunctional nanoparticles with greater efficacy while at the same time minimising adverse effects, according to early clinical studies. This is because of traits like aggressive cellular uptake and focused localization in tumours. To advance this field of inquiry, chemical procedures must be developed that reliably attach chemical moieties to nanoparticles. The structure-function relationship of these functionalized nanoparticles has been extensively studied as a result of the discovery of several chemical processes for the synthesis of functionalized nanoparticles specifically for drug delivery, cancer therapy, diagnostics, tissue engineering, and molecular biology. Because of the growing understanding of how to functionalize nanoparticles and the continued work of innovative scientists to expand this technology, it is anticipated that functionalized nanoparticles will play an important role in the aforementioned domains. As a result, the goal of this study is to familiarise readers with nanoparticles, to explain functionalization techniques that have already been developed, and to examine potential applications for nanoparticles in the biomedical sciences. This review's information is essential for the safe and broad use of functionalized nanoparticles, particularly in the biomedical sector.

Mannosylated Cationic Copolymers for Gene Delivery to Macrophages

Macrophages are desirable targets for gene therapy of cancer and other diseases. Cationic diblock copolymers of polyethylene glycol (PEG) and poly-L-lysine (PLL) or poly{N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (pAsp(DET)) are synthesized and used to form polyplexes with a plasmid DNA (pDNA) that are decorated with mannose moieties, serving as the targeting ligands for the C type lectin receptors displayed at the surface of macrophages. The PEG-b-PLL copolymers are known for its cytotoxicity, so PEG-b-PLL-based polyplexes are cross-linked using reducible reagent dithiobis(succinimidyl propionate) (DSP). The cross-linked polyplexes display low toxicity to both mouse embryonic fibroblasts NIH/3T3 cell line and mouse bone marrow-derived macrophages (BMMΦ). In macrophages mannose-decorated polyplexes demonstrate an ≈8 times higher transfection efficiency. The cross-linking of the polyplexes decrease the toxicity, but the transfection enhancement is moderate. The PEG-b-pAsp(DET) copolymers display low toxicity with respect to the IC-21 murine macrophage cell line and are used for the production of non-cross-linked pDNA-contained polyplexes. The obtained mannose modified polyplexes exhibit ca. 500-times greater transfection activity in IC-21 macrophages compared to the mannose-free polyplexes. This result greatly exceeds the targeting gene transfer effects previously described using mannose receptor targeted non-viral gene delivery systems. These results suggest that Man-PEG-b-pAsp(DET)/pDNA polyplex is a potential vector for immune cells-based gene therapy.

Self-amplifying RNA vaccines for infectious diseases

Vaccinology is shifting toward synthetic RNA platforms which allow for rapid, scalable, and cell-free manufacturing of prophylactic and therapeutic vaccines. The simple development pipeline is based on in vitro transcription of antigen-encoding sequences or immunotherapies as synthetic RNA transcripts, which are then formulated for delivery. This approach may enable a quicker response to emerging disease outbreaks, as is evident from the swift pursuit of RNA vaccine candidates for the global SARS-CoV-2 pandemic. Both conventional and self-amplifying RNAs have shown protective immunization in preclinical studies against multiple infectious diseases including influenza, RSV, Rabies, Ebola, and HIV-1. Self-amplifying RNAs have shown enhanced antigen expression at lower doses compared to conventional mRNA, suggesting this technology may improve immunization. This review will explore how self-amplifying RNAs are emerging as important vaccine candidates for infectious diseases, the advantages of synthetic manufacturing approaches, and their potential for preventing and treating chronic infections.

Biodegradable nanoparticles decorated with different carbohydrates for efficient macrophage-targeted gene therapy

Macrophages are attractive therapeutic targets due to their contributions to many pathological processes including cancers, atherosclerosis, obesity, diabetes and other inflammatory diseases. Macrophage-targeted gene therapy is an effective strategy for regulating macrophage function at the site of inflammation to treat related diseases. However, macrophages are recognized as difficult to transfect cells and non-specific delivery would inevitably cause unwanted systemic side effects. Herein, we prepared a series of macrophage-targeted nanoparticles (NPs) using cationic lipid-like compound G0-C14 and different carbohydrates-modified poly(lactide-co-glycolide) (PLGA) or poly(lactide-coglycolide)-b-poly(ethylene glycol) (PLGA-PEG) for gene delivery by a robust self-assembly method. The yielded NPs were decorated with carbohydrate-based targeting moieties including mannose, galactose, dextran, and a mixture of mannose and galactose. EGFP messenger RNA (mRNA) and GFP plasmid DNA (pDNA) were used as reporter genes to evaluate NP-mediated gene transfection in macrophages. Experimental results of macrophage phagocytosis demonstrated that more carbohydrate-decorated NPs were endocytosed by Raw 264.7 cells than the ones without carbohydrate modification. Mannose-decorated NPs showed better targeting ability to macrophages than NPs decorated with galactose only and a blended mixture of mannose and galactose. It is worth noting that polysaccharide dextran-modified NPs also exhibited evident targeting effects. CCK-8 assay revealed that no cytotoxicity was observed for all tested NP concentrations up to 2.8 mg/mL. The carbohydrate-decorated polymer/G0-C14 exhibited strong entrapment of mRNA and pDNA with an encapsulation efficiency of above 95%. The targeted NPs significantly improved cellular internalization and transfection efficiency in macrophages, depending on the type and content of the carbohydrate moieties presented on the NP surface. Interestingly, dextran-decorated NPs showing higher endocytosis at various concentrations in macrophages also demonstrated more efficient mRNA transfection, suggesting that the NP-mediated mRNA transfection efficiency was consistent with the endocytosis results.

Shikimoyl-ligand decorated gold nanoparticles for use in ex vivo engineered dendritic cell based DNA vaccination

Since mannose receptors (MRs) are expressed on the surfaces of dendritic cells (DCs), the most professional antigen presenting cells in our body, DNA vaccine carriers containing either covalently grafted mannosyl- or mannose-mimicking shikimoyl-ligands are being increasingly used in ex vivo DC-transfection based DNA vaccination. To this end, we have recently demonstrated that ex vivo immunization of mice with liposomes of shikimoylated cationic amphiphiles containing a 6-amino hexanoic acid spacer group in the head-group region in complexation with melanoma antigen (MART1) encoded DNA vaccine (pCMV-MART1) induces long lasting anti-melanoma immune responses (C. Voshavar, et al., J. Med. Chem., 2017, 60, 1605-1610). This finding prompted us to examine, in the present investigation, the efficacies of gold nanoparticles conjugated to the mannose-mimicking shikimoyl ligand (SL) via a 6-amino hexane thiol spacer (AuNPs-SL) for use in ex vivo DC-transfection based genetic immunization. Herein, we report on the design, synthesis, physico-chemical characterization and bioactivities of AuNPs-SL. Dynamic light scattering and transmission electron microscopy studies revealed the hydrodynamic diameters of theAuNPs-SL nanoconjugates to be within the range of 23-44 nm and their surface potentials within the range of 9-28 mV. MTT-assay showed the non-cytotoxic nature of AuNPs-SL and the findings in the electrophoretic gel retardation assays revealed strong DNA binding properties of the AuNPs-SL. Importantly, subcutaneous immunization of C57BL/6J mice with DCs ex vivo transfected with an electrostatic complex of AuNPs-SL & melanoma antigen (MART1) encoded DNA vaccine (p-CMV-MART1) induced a long lasting (100 days) anti-tumor immune response in immunized mice upon subsequent challenge with a lethal dose of melanoma. Notably, mice immunized with either autologous mbmDCs ex vivo pre-transfected with nanoplexes of shikimoylated AuNPs-SL & an irrelevant pCMV-SPORT-β-gal plasmid (without having encoded melanoma antigen) or untransfected DCs showed no lasting protection against subsequent tumor challenge. The presently described shikimoyl-decorated gold nanoparticles (AuNPs-SL) are expected to find future use in ex vivo DC-transfection based genetic immunization against cancer and other infectious diseases.

Targeted Gene Delivery to Macrophages by Biodegradable Star-Shaped Polymers

In this report, two biodegradable star-shaped polyasparamide derivatives and four analogues modified with either mannose or folic acid moiety for preferential targeting of a difficult-to-transfect immune cell type, i.e., macrophage, have been synthesized. Each of the prepared star polymers complexes with plasmid DNA to form nanosized particles featuring a core-shell-like morphology. Mannose or folate functionalized star polymers can greatly improve the transfection performance on a macrophage cell line RAW 264.7. As a result, a combination of targeting ligand modification and topological structures of gene carriers is a promising strategy for immune cells-based gene therapy.

Ionic α-helical polypeptides toward nonviral gene delivery

The advent of polymeric materials has significantly promoted the development and rapid growth of various technologies in biomedical applications, such as tissue engineering and controlled drug and gene delivery. Water-soluble polypeptides bearing functional side chains and adopting stable secondary structures are a new class of functional polymeric materials of potentially broad applications in medicine and biotechnology. In this article, we summarize our recent effort on the design and synthesis of the water-soluble α-helical ionic polypeptides originally developed in our laboratory and highlight their applications in cell membrane penetration and nonviral gene/small interfering RNA (siRNA) delivery.

Harmonized tuning of nucleic acid and lectin binding properties with multivalent cyclodextrins for macrophage-selective gene delivery

Polycationic amphiphilic cyclodextrins (paCDs) have been shown to behave as efficient non-viral gene carriers paralleling the efficacy of commercial vectors towards a variety of cell lines.

Development of non-viral vehicles for targeted gene transfer into microglia via the integrin receptor CD11b

Microglial activation is a central event in neurodegeneration. Novel technologies are sought for that specifically manipulate microglial function in order to delineate their role in onset and progression of neuropathologies. We investigated for the first time whether non-viral gene delivery based on polyethyleneglycol-polyethyleneimine conjugated to the monoclonal anti-CD11b antibody OX42 ("OX42-immunogene") could be used to specifically target microglia. We first conducted immunofluorescence studies with the OX42 antibody and identified its microglial integrin receptor CD11b as a potential target for receptor-mediated gene transfer based on its cellular specificity in mixed glia culture and in vivo and found that the OX42 antibody is rapidly internalized and trafficked to acidic organelles in absence of activation of the respiratory burst. We then performed transfection experiments with the OX42-immunogene in vitro and in rat brain showing that the OX42-immunogene although internalized was degraded intracellularly and did not cause substantial gene expression in microglia. Investigation of specific barriers to microglial gene transfer revealed that aggregated OX42-immunogene polyplexes stimulated the respiratory burst that likely involved Fcγ-receptors. Transfections in the presence of the endosomolytic agent chloroquine improved transfection efficiency indicating that endosomal escape may be limited. This study identifies CD11b as an entry point for antibody-mediated gene transfer into microglia and takes important steps toward the further development of OX42-immunogenes.

Mannosylated chitosan nanoparticles for delivery of antisense oligonucleotides for macrophage targeting

The therapeutic potential of antisense oligonucleotides (ASODN) is primarily dependent upon its safe and efficient delivery to specific cells overcoming degradation and maximizing cellular uptake in vivo. The present study focuses on designing mannosylated low molecular weight (LMW) chitosan nanoconstructs for safe ODNs delivery by macrophage targeting. Mannose groups were coupled with LMW chitosan and characterized spectroscopically. Mannosylated chitosan ODN nanoparticles (MCHODN NPs) were formulated by self-assembled method using various N/P ratio (moles of amine groups of MCH to phosphate moieties of ODNs) and characterized for gel retardation assay, physicochemical characteristics, cytotoxicity and transfection efficiency, and antisense assay. Complete complexation of MCH/ODN was achieved at charge ratio of 1:1 and above. On increasing the N/P ratio of MCH/ODN, particle size of the NPs decreased whereas zeta potential (ZV) increased. MCHODN NPs displayed much higher transfection efficiency into Raw 264.7 cells (bears mannose receptors) than Hela cells and no significant toxicity was observed at all MCH concentrations. Antisense assay revealed that reduction in lipopolysaccharide (LPS) induced serum TNF-α is due to antisense activity of TJU-2755 ODN (sequence complementary to 3′-UTR of TNF-α). These results suggest that MCHODN NPs are acceptable choice to improve transfection efficiency in vitro and in vivo.

Macrophage mannose receptor-specific gene delivery vehicle for macrophage engineering

Macrophages are the most plastic cells in the hematopoietic system and they exhibit great functional diversity. They have been extensively applied in anti-inflammatory, anti-fibrotic and anti-cancer therapies. However, the application of macrophages is limited by the efficiency of their engineering. The macrophage mannose receptor (MMR, CD206), a C-type lectin receptor, is ubiquitously expressed on macrophages and has a high affinity for mannose oligosaccharides. In the present study, we developed a novel non-viral vehicle with specific affinity for MMR. Mannan was cationized with spermine at a grafted ratio of ∼12% to deliver DNA and was characterized as a stable system for delivery. This spermine-mannan (SM)-based delivery system was evaluated as a biocompatible vehicle with superior transfection efficiency on murine macrophages, up to 28.5-fold higher than spermine-pullulan, 11.5-fold higher than polyethylenimine and 3.0-fold higher than Lipofectamine™ 2000. We confirmed that the SM-based delivery system for macrophages transfection was MMR-specific and we described the intracellular transport of the delivery system. To our knowledge, this is the first study using SM to demonstrate a mannose receptor-specific gene delivery system, thereby highlighting the potential of a novel specific non-viral delivery vehicle for macrophage engineering.

An agent-based model of the response to angioplasty and bare-metal stent deployment in an atherosclerotic blood vessel

PURPOSE

While animal models are widely used to investigate the development of restenosis in blood vessels following an intervention, computational models offer another means for investigating this phenomenon. A computational model of the response of a treated vessel would allow investigators to assess the effects of altering certain vessel- and stent-related variables. The authors aimed to develop a novel computational model of restenosis development following an angioplasty and bare-metal stent implantation in an atherosclerotic vessel using agent-based modeling techniques. The presented model is intended to demonstrate the body's response to the intervention and to explore how different vessel geometries or stent arrangements may affect restenosis development.

METHODS

The model was created on a two-dimensional grid space. It utilizes the post-procedural vessel lumen diameter and stent information as its input parameters. The simulation starting point of the model is an atherosclerotic vessel after an angioplasty and stent implantation procedure. The model subsequently generates the final lumen diameter, percent change in lumen cross-sectional area, time to lumen diameter stabilization, and local concentrations of inflammatory cytokines upon simulation completion. Simulation results were directly compared with the results from serial imaging studies and cytokine levels studies in atherosclerotic patients from the relevant literature.

RESULTS

The final lumen diameter results were all within one standard deviation of the mean lumen diameters reported in the comparison studies. The overlapping-stent simulations yielded results that matched published trends. The cytokine levels remained within the range of physiological levels throughout the simulations.

CONCLUSION

We developed a novel computational model that successfully simulated the development of restenosis in a blood vessel following an angioplasty and bare-metal stent deployment based on the characteristics of the vessel cross-section and stent. A further development of this model could ultimately be used as a predictive tool to depict patient outcomes and inform treatment options.

Smart adjuvants

Although vaccine adjuvants have been used for almost a century, alum is the only adjuvant licensed by the US FDA for human vaccine use. Many adjuvants studied to date have generalized inflammatory properties and lack specificity in terms of targeting immune compartments and cell populations. Indeed, such adjuvants have often been crude in formulation, their effects usually restricted to T-helper 2-type immunity and their use limited owing to inherent toxicity. However, recent advances in immunology have resulted in a number of potential adjuvant candidates that are able to modulate the immune response in a more controlled and specific manner. These novel adjuvants are attractive for inclusion in current and future vaccine strategies since they have better-defined mechanisms of action. In this article, we review several compounds that target specific immune components, such as cells, receptors or signaling pathways, and have termed such reagents 'smart adjuvants'.

Maximizing gene delivery efficiencies of cationic helical polypeptides via balanced membrane penetration and cellular targeting

The application of non-viral gene delivery vectors is often accompanied with the poor correlation between transfection efficiency and the safety profiles of vectors. Vectors with high transfection efficiencies often suffer from high toxicities, making it unlikely to improve their efficiencies by increasing the DNA dosage. In the current study, we developed a ternary complex system which consisted of a highly membrane-active cationic helical polypeptide (PVBLG-8), a low-toxic, membrane-inactive cationic helical polypeptide (PVBLG-7) capable of mediating mannose receptor targeting, and DNA. The PVBLG-7 moiety notably enhanced the cellular uptake and transfection efficiency of PVBLG-8 in a variety of mannose receptor-expressing cell types (HeLa, COS-7, and Raw 264.7), while it did not compromise the membrane permeability of PVBLG-8 or bring additional cytotoxicities. Because of the simplicity and adjustability of the self-assembly approach, optimal formulations of the ternary complexes with a proper balance between membrane activity and targeting capability were easily identified in each specific cell type. The optimal ternary complexes displayed desired cell tolerability and markedly outperformed the PVBLG-8/DNA binary complexes as well as commercial reagent Lipofectamine™ 2000 in terms of transfection efficiency. This study therefore provides an effective and facile strategy to overcome the efficiency-toxicity poor correlation of non-viral vectors, which contributes insights into the design strategy of effective and safe non-viral gene delivery vectors.

Cyclodextrin-scaffolded glycotransporters for gene delivery

Conventional drugs consist of a formulation of a bioactive species and a carrier, the former accounting for most of the sophistication of the design. In the case of biomolecular drugs, however, the role of the carrier becomes decisive in enabling the load to reach its target to carry out its designed therapeutic function. Thus, the clinical success of gene therapy, where the active principles are nucleic acids, critically depends on the use of efficient and safe delivery systems. Carbohydrates have proven particularly useful in this regard. Glycocoating, similarly to poly(ethylene)glycol (PEG)-coating (pegylation), can stabilize colloidal aggregates by improving solvation and preventing nonspecific interactions, for example, with serum proteins. Moreover, glycoconjugates can drive specific recognition and receptor-mediated internalization in target cells. Actually, the inherent flexibility of carbohydrate and glycoconjugate chemistry has greatly contributed to enlarging the range of functional materials that can be rationally conceived for gene delivery. Herein, this is illustrated with selected examples that focus on controlling the architectural parameters of the vectors to make them suitable for structure–activity relationship (SAR) and optimization studies. The members of the cyclomaltooligosaccharide (cyclodextrin, CD) family will be the central actors of the story.

Respiratory syncytial virus infection: from biology to therapy: a perspective

Respiratory syncytial virus (RSV) is responsible for significant morbidity and mortality, particularly in infants younger than 18 months and in the elderly. To date, there are few effective treatment options available to prevent or treat RSV infections. Attractive therapeutic strategies include targeting host epithelial adhesion molecules required for RSV infection, enhancing localized cell-mediated immunity, interfering with RSV viral gene expression and developing a multigene DNA vaccine. The most recent data supporting the advantages and limitations of each of these approaches are discussed in detail. Several promising strategies offer hope for safe and effective prophylaxis and treatment of RSV infection.

Cationic, helical polypeptide-based gene delivery for IMR-90 fibroblasts and human embryonic stem cells

Diblock copolymers consisting of poly(ethylene glycol)-block-poly(γ-4-(((2-(piperidin-1-yl)ethyl)amino)methyl)benzyl-L-glutamate) (PEG-b-PVBLG-8) were synthesized and evaluated for their ability to mediate gene delivery in hard-to-transfect cells like IMR-90 human fetal lung fibroblasts and human embryonic stem cells (hESCs). The PEG-b-PVBLG-8 contained a membrane-disruptive, cationic, helical polypeptide block (PVBLG-8) for complexing with DNA and a hydrophilic PEG block to improve the biocompatibility of the gene delivery vehicle. The incorporation of PEG effectively reduced the toxicity of the helical PVBLG-8 block without dramatically compromising the polymer's ability to destabilize membranes or form complexes with DNA. PEG-b-PVBLG-8 copolymers with low (n = 76) and high (n = 287) degrees of polymerization (n) of the PVBLG-8 block were synthesized and evaluated for gene delivery. PEG-b-PVBLG-8 diblock polymers with a high degree of polymerization have a greater transfection efficiency and lower toxicity in IMR-90 cells than the commercial reagent Lipofectamine 2000. The usefulness of PEG-b-PVBLG-8 was further demonstrated via the successful transfection of hESCs without a measured loss in cell pluripotency markers.

Reactive and bioactive cationic α-helical polypeptide template for nonviral gene delivery

Poly(γ-(4-vinylbenzyl)-l -glutamate) (PVBLG) served as a bioactive and reactive template for the generation of a library of cationic α-helical polypeptides for gene delivery. The top performing polymer outperformed 25-kDa polyethylenimine by 12-fold. Preliminary data indicates that helicity of these cationic polypeptides is essential for their improved performance, with enhanced membrane disruption a likely source of their transfection efficiency.

Recent developments in carbohydrate-decorated targeted drug/gene delivery

Targeted delivery of a drug or gene to its site of action has clear therapeutic advantages by maximizing its therapeutic efficiency and minimizing its systemic toxicity. Generally, targeted drug or gene delivery is performed by loading a macromolecular carrier with an appropriate drug or gene, and by targeting the drug/gene carrier to specific cell or tissue with the help of specific targeting ligand. The emergence of glycobiology, glycotechnology, and glycomics and their continual adaptation by pharmaceutical scientists have opened exciting avenue of medicinal applications of carbohydrates. Among them, the biocompatibility and specific receptor recognition ability confer the ability of carbohydrates as potential targeting ligands for targeted drug and gene delivery applications. This review summarizes recent progress of carbohydrate-decorated targeted drug/gene delivery applications.

Functional polymers for targeted delivery of nucleic acid drugs

Cationic polymers have been chemically modified with a variety of targeting molecules such as peptides, proteins, antibodies, sugars and vitamins for targeted delivery of nucleic acid drugs to specific cells. Stimuli-sensitive polymers exhibiting different size, charge and conformation in response to physiological signals from specific cells have also been utilized for targeted delivery. To achieve target-specific delivery of nucleic acids, conjugation chemistry is critical to produce stable nanosized polyplexes tethered with cell-recognizable ligands for facile cellular uptake via a receptor-mediated endocytic pathway. In this review, synthetic strategies of functional cationic polymers with various targeting ligands are presented.

Nanocarrier cross-linking density and pH sensitivity regulate intracellular gene transfer

Treatment of diseases on the molecular level by genetic material is limited by effective delivery mechanisms. We focused on the synthesis of a pH-sensitive gene delivery vehicle based on dimethylaminoethyl methacrylate (DMAEMA) with tunable swelling, cross-linking density, and DNA release kinetics within the endosomal pH range. Our strategy, which utilized a single step for DNA encapsulation, enhanced gene transfection efficiency and reduced cytotoxicity relative to polyethyleneimine (PEI) and poly-L-lysine (PLL).

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.

Molecular basis of improved immunogenicity in DNA vaccination mediated by a mannan based carrier

Receptor mediated gene delivery is an attractive non-viral method for targeting genetic material to specific cell types. We have previously utilized oxidized (OMPLL) and reduced mannan poly-L-lysine (RMPLL) to target DNA vaccines to antigen presenting cells and demonstrated that it could induce far stronger immune responses in mice compared to naked DNA immunization. In this study, we describe the immune enhancing attributes of mannan-PLL mediated DNA vaccination at the molecular level. Several attributes observed in similar gene delivery conjugates, such as entry via the endocytic pathway, low toxicity, protection from nucleases and compaction of particle size, were also evident here. In addition, OMPLL and RMPLL conjugates had profound effects on the antigen presentation functions of dendritic cells and macrophages, through the stimulation of cytokine production and maturation of dendritic cells. Interestingly, we demonstrate that OMPLL-DNA and RMPLL-DNA are able to mediate dendritic cell activation via toll-like receptor 2 as opposed to mannan alone which mediates via toll-like receptor 4. Overall, this report leads to greater understanding of how oxidized and reduced mannan mediated gene delivery could augment immune responses to DNA vaccination and provide insights into ways of further improving its immunogenicity.

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.

Non-viral gene transfection technologies for genetic engineering of stem cells

The recent rapid progress of molecular biology together with the steady progress of genome projects has given us some essential and revolutionary information about DNA and RNA to elucidate various biological phenomena at a genetic level. Under these circumstances, the technology and methodology of gene transfection have become more and more important to enhance the efficacy of gene therapy for several diseases. In addition, gene transfection is a fundamental technology indispensable to the further research development of basic biology and medicine regarding stem cells. Stem cells genetically manipulated will enhance the therapeutic efficacy of cell transplantation. In this paper, the carrier and technology of gene delivery are briefly overviewed while the applications to the basic researches of biology and medicine as well as regenerative medical therapy are introduced. A new non-viral carrier and the cell culture system are described to efficiently manipulate stem cells.

A reverse transfection technology to genetically engineer adult stem cells

A new non-viral method of gene transfection was designed to enhance the level of gene expression for rat mesenchymal stem cells (MSCs). Pullulan was cationized using chemical introduction of spermine to prepare cationized pullulan of non-viral carrier (spermine-pullulan). The spermine-pullulan was complexed with a plasmid deoxyribonucleic acid (DNA) of luciferase and coated on the surface of culture substrate together with Pronectin of artificial cell adhesion protein. MSCs were cultured and transfected on the complex-coated substrate (reverse transfection), and the level and duration of gene expression were compared with those of MSCs transfected by culturing in the medium containing the plasmid DNA-spermine-pullulan complex (conventional method). The reverse transfection method enhanced and prolonged gene expression significantly more than did the conventional method. The reverse method permitted the transfection culture of MSCs in the presence of serum, in contrast to the conventional method, which gave cells a good culture condition to lower cytotoxicity. The reverse transfection was carried out for a non-woven fabric of polyethylene terephthalate (PET) coated with the complex and Pronectin using agitation and stirring culture methods. The two methods enhanced the level and duration of gene expression for MSCs significantly more than did the static method. It is possible that medium circulation improves the culture conditions of cells in terms of oxygen and nutrition supply and waste excretion, resulting in enhanced gene expression.

Needle-like morphology of H2K4b polyplexes associated with increases in transfection in vitro

SUMMARY: Several synthetic histidine-lysine (HK) polymers have been screened for their efficacy as carriers of nucleic acids in vitro. One branched HK polymer, H2K4b (and its derivatives), has been particularly effective as an in vitro carrier of plasmids. In this study, we investigated whether various salt conditions during formation of the H2K4b/plasmid DNA polyplex affected transfection. We compared the transfection ability of H2K4b polyplexes prepared under three conditions: 1) water, 2) water and then Opti-MEM (or 300 mM NaCl), or 3) Opti-MEM (or 150 mM NaCl). The milieu in which the H2K4b polyplexes were prepared significantly affected in vitro transfection, and conditions that resulted in highest to lowest transfection levels were as follows: water and then Opti-MEM > Opti-MEM (or 150 mM NaCl)>> water. Several biophysical properties (size and shape of polyplex, surface charge, stability) were examined for their correlation with the level of transfection by the HK carrier. Strikingly, electron micrographs showed that HK polyplexes, first formed in water and then in salt, had a needle-like morphology with a mean length of 170 nm and a width of 53 nm; these needle-like polyplexes were observed intracellularly and absorbed to the cell surface, which was in marked contrast to the spherical HK polyplexes formed in water or in Opti-MEM. Notably, these needle-like HK polyplexes entered the cell through clathrin-mediated endocytosis, in contrast to spherical polyplexes, which entered primarily through non clathrin-mediated endocytosis.

Mannan-mediated gene delivery for cancer immunotherapy

Recent years have seen a resurgence in interest in the development of efficient non-viral delivery systems for DNA vaccines and gene therapy. We have previously used oxidized and reduced mannan as carriers for protein delivery to antigen-presenting cells by targeting the receptors that bind mannose, resulting in efficient induction of cellular responses. In the present study, oxidized mannan and reduced mannan were used as receptor-mediated gene transfer ligands for cancer immunotherapy. In vivo studies in C57BL/6 mice showed that injection of DNA encoding ovalbumin (OVA) complexed to oxidized or reduced mannan-poly-L-lysine induced CD8 and CD4 T-cell responses as well as antibody responses leading to protection of mice from OVA+ tumours. Both oxidized and reduced mannan delivery was superior to DNA alone or DNA-poly-L-lysine. These studies demonstrate the potential of oxidized and reduced mannan for efficient receptor-mediated gene delivery in vivo, particularly as DNA vaccines for cancer immunotherapy.

Gene Transfer by DNA/mannosylated Chitosan Complexes into Mouse Peritoneal Macrophages

Chitosan is a biodegradable and biocompatible polymer and is useful as a non-viral vector for gene delivery. In order to deliver pDNA/chitosan complex into macrophages expressing a mannose receptor, mannose-modified chitosan (man-chitosan) was employed. The cellular uptake of pDNA/man-chitosan complexes through mannose recognition was then observed. The pDNA/man-chitosan complexes showed no significant cytotoxicity in mouse peritoneal macrophages, while pDNA/man-PEI complexes showed strong cytotoxicity. The pDNA/man-chitosan complexes showed much higher transfection efficiency than pDNA/chitosan complexes in mouse peritoneal macrophages. Observation with a confocal laser microscope suggested differences in the cellular uptake mechanism between pDNA/chitosan complexes and pDNA/man-chitosan complexes. Mannose receptor-mediated gene transfer thus enhances the transfection efficiency of pDNA/chitosan complexes.

Specific interaction of mannosylated glycopolymers with macrophage cells mediated by mannose receptor

Poly[N-p-vinylbenzyl-O-beta-mannopyranosyl-(1-4)-D-gluconamide] (PV-Man) is a polystyrene derivative that contains mannose moieties and interacts with the mannose-receptor-carrying macrophage cell line. To clarify the specific interaction between the PV-Man and the macrophage cell line J774A1, PV-Man polymer labeled with fluorescent fluorescein isothiocyanate (FITC) was used to amonitor the specific interaction, which was visualized by confocal laser microscopy. We found that PV-Man strongly binds to macrophage cells, probably due to a specific interaction mediated by the presence of mannose receptors on the cell membrane. The fluorescence intensity of PV-Man and macrophage cells was up to 7-fold that of any other glycopolymers bound to macrophage cells. Moreover, cellular fluorescence intensity increased significantly with increasing incubation time and polymer concentration. Many macrophage cells strongly express mannose and mannose receptor-related receptors, and receptor-mediated gene transfer via the mannose receptor using a PV-Man glycopolymer is a versatile means of targeted gene delivery into these cells.