Potent antigen-specific immune responses stimulated by codelivery of CpG ODN and antigens in degradable microparticles

Allergen immunotherapy: progress and future outlook

INTRODUCTION

Allergy, the immunological hypersensitivity to innocuous environmental compounds, is a global health problem. The disease triggers, allergens, are mostly proteins contained in various natural sources such as plant pollen, animal dander, dust mites, foods, fungi and insect venoms. Allergies can manifest with a wide range of symptoms in various organs, and be anything from just tedious to life-threatening. A majority of all allergy patients are self-treated with symptom-relieving medicines, while allergen immunotherapy (AIT) is the only causative treatment option.

AREAS COVERED

This review will aim to give an overview of the state-of-the-art allergy management, including the use of new biologics and the application of biomarkers, and a special emphasis and discussion on current research trends in the field of AIT.

EXPERT OPINION

Conventional AIT has proven effective, but the years-long treatment compromises patient compliance. Moreover, AIT is typically not offered in food allergy. Hence, there is a need for new, effective and safe AIT methods. Novel routes of administration (e.g. oral and intralymphatic), hypoallergenic AIT products and more effective adjuvants holds great promise. Most recently, the development of allergen-specific monoclonal antibodies for passive immunotherapy may also allow treatment of patients currently not treated or treatable.

Magnetic nanoparticles enhance the cellular immune response of dendritic cell tumor vaccines by realizing the cytoplasmic delivery of tumor antigens

Dendritic cells (DCs)-based tumor vaccines have the advantages of high safety and rapid activation of T cells, and have been approved for clinical tumor treatment. However, the conventional DC vaccines have some severe problems, such as poor activation of DCs in vitro, low level of antigen presentation, reduced cell viability, and difficulty in targeting lymph nodes in vivo, resulting in poor clinical therapeutic effects. In this research, magnetic nanoparticles Fe₃O₄@Ca/MnCO₃ were prepared and used to actively and efficiently deliver antigens to the cytoplasm of DCs, promote antigen cross-presentation and DC activation, and finally enhance the cellular immune response of DC vaccines. The results show that the magnetic nanoparticles can actively and quickly deliver antigens to the cytoplasm of DCs by regulating the magnetic field, and achieve cross-presentation of antigens. At the same time, the nanoparticles degradation product Mn²⁺ enhanced immune stimulation through the interferon gene stimulating protein (STING) pathway, and another degradation product Ca²⁺ ultimately promoted cellular immune response by increasing autophagy. The DC vaccine constructed with the magnetic nanoparticles can more effectively migrate to the lymph nodes, promote the proliferation of CD8⁺ T cells, prolong the time of immune memory, and produce higher antibody levels. Compared with traditional DC vaccines, cytoplasmic antigen delivery with the magnetic nanoparticles provides a new idea for the construction of novel DC vaccines.

Lipid Microparticles Show Similar Efficacy With Lipid Nanoparticles in Delivering mRNA and Preventing Cancer

PURPOSE

Messenger RNA (mRNA) has shown great promise for vaccine against both infectious diseases and cancer. However, mRNA is unstable and requires a delivery vehicle for efficient cellular uptake and degradation protection. So far, lipid nanoparticles (LNPs) represent the most advanced delivery platform for mRNA delivery. However, no published studies have compared lipid microparticles (LMPs) with lipid nanoparticles (LNPs) in delivering mRNA systematically, therefore, we compared the impact of particle size on delivery efficacy of mRNA vaccine and subsequent immune responses.

METHODS

Herein, we prepared 3 different size lipid particles, from nano-sized to micro-sized, and they loaded similar amounts of mRNA. These lipid particles were investigated both in vitro and in vivo, followed by evaluating the impact of particle size on inducing cellular and humoral immune responses.

RESULTS

In this study, all mRNA vaccines showed a robust immune response and lipid microparticles (LMPs) show similar efficacy with lipid nanoparticles (LNPs) in delivering mRNA and preventing cancer. In addition, immune adjuvants, either toll like receptors or active molecules from traditional Chinese medicine, can improve the efficacy of mRNA vaccines.

CONCLUSIONS

Considering the efficiency of delivery and endocytosis, besides lipid nanoparticles with size smaller than 150 nm, lipid microparticles (LMPs) also have the potential to be an alternative and promising delivery system for mRNA vaccines.

Peptide loaded polymeric nanoparticles by non-aqueous nanoprecipitation

It is always a challenge to encapsulate water-soluble peptides in polymer nanoparticle (NP) systems. We establish and validate our newly developed non-aqueous nanoprecipitation method to encapsulate neuro-peptides drugs such as oxytocin and Luteinizing hormone-releasing hormone (LHRH) in poly(sebacic anhydride) (PSA) NPs. NPs were prepared by a solvent-antisolvent process under a strict anhydrous environment to obtain high drug loading and to avoid premature PSA degradation and drug release. Dynamic light scattering (DLS) and Scanning Electron Microscopy (SEM) reveal the size for both drug loaded PSA NPs to ∼ 300 nm. The drug loaded NPs were dispersible and spherical in shape with uniform morphology. The in vitro release profile of oxytocin from PSA NPs occurs with the burst release of ∼ 50% within the first hour in the aqueous release medium, whereas LHRH release is comparatively slow. Thus, looking into the fast degrading properties of PSA and drug release behavior, the developed NPs can be used for direct delivery of the neuropeptides to the olfactory epithelium using a refillable nasal atomizer that deposits mist onto the olfactory neuro-epithelium. We also applied our developed method to prepare NPs of poly(lactic-co-glycolic acid) (PLGA), polylactic acid (PLA), and poly(ε-caprolactone) (PCL). A Thyrotropin releasing hormone (TRH) was used as the sample neuropeptide drug to validate our non-aqueous method. The results reveal the formation of TRH loaded PLGA, PLA and PCL NPs with 100% drug loading. TEM analysis shows the formation of spherical NPs, having similar release properties as those of PSA NPs. Overall, we report that our developed method is suitable for co-encapsulating hydrophilic drugs in polymer NPs with high drug loading and release properties.

Encapsulating Polyethyleneimine-DNA Nanoplexes into PEGylated Biodegradable Microparticles Increases Transgene Expression In Vitro and Reduces Inflammatory Responses In Vivo

Encapsulating genetic material into biocompatible polymeric microparticles is a means to improving gene transfection while simultaneously decreasing the tendency for inflammatory responses; and can be advantageous in terms of delivering material directly to the lungs via aerosolization for applications such as vaccinations. In this study, we investigated the advantages of using polymeric microparticles carrying the luciferase reporter gene in increasing transfection efficiency in the readily transfectable HEK293 cell line and the difficult to transfect RAW264.7 cell line. The results indicated that there was a limit to the ratio of nitrogen in polyethylenimine (PEI) to phosphate in DNA (N/P ratio) beyond which further increases in transgene expression no longer, or only marginally, occurred. Microparticles encapsulating PEI:DNA nanoplexes induced cellular toxicity in a dose-dependent manner. PEGylation increased transgene expression, likely related to enhanced degradation of particles. Furthermore, intra-tracheal instillation in rats allowed us to investigate the inflammatory response in the lung as a function of PEGylation, porosity, and size. Porosity did not influence cell counts in bronchoalveolar lavage fluid in the absence of PEG, but in particles containing PEG, non-porous particles recruited fewer inflammatory cells than their porous counterparts. Finally, both 1 μm and 10 μm porous PLA-PEG particles recruited more neutrophils than 4 μm particles. Thus, we have shown that PEGylation and lack of porosity are advantageous for faster release of genetic cargo from microparticles and a reduced inflammatory response, respectively.

Oral Nanoparticles of SNX10-shRNA Plasmids Ameliorate Mouse Colitis

Background

Our previous study found that deletion of Sorting nexin 10 (SNX10) can protect against colonic inflammation and pathological damage induced by dextran sulfate sodium (DSS). This inspired us that modulation of SNX10 expression in colonic epithelial cells might represent a promising therapeutic strategy for inflammatory bowel disease (IBD).

Methods

Effective delivery of siRNA/shRNA to silence genes is a highly sought-after means in the treatment of multiple diseases. Here, we encapsulated SNX10-shRNA plasmids (SRP) with polylactide-polyglycolide (PLGA) to make oral nanoparticles (NPs), and then applied them to acute and chronic IBD mice model, respectively. The characteristics of the nanoparticles were assayed and the effects of SRP-NPs on mouse IBD were evaluated.

Results

High-efficiency SNX10-shRNA plasmids were successfully constructed and coated with PLGA to obtain nanoparticles, with a particle size of 275.2 ± 11.4mm, uniform PDI distribution, entrapment efficiency of 87.6 ± 2.5%, and drug loading of 13.11 ± 1.38%, displayed dominant efficiency of SNX10 RNA interference in the colon. In both acute and chronic IBD models, SRP-NPs could effectively reduce the loss of mice body weight, relieve the intestinal mucosal damage and inflammatory infiltration, inhibit the expression of inflammatory cytokines IL-1β, IL-23, TNF-α, and down-regulate the expression of toll-like receptors (TLRs) 2 and 4.

Conclusion

Oral nanoparticles of SNX10-shRNA plasmid displayed dominant efficiency of SNX10 RNA interference in the colon and ameliorate mouse colitis via TLR signaling pathway. SNX10 is a new target for IBD treatment and nanoparticles of SNX10-shRNA plasmid might be a promising treatment option for IBD.

Nanoparticle-based immunotherapy: state of the art and future perspectives

INTRODUCTION

For several years now, medicine has been benefiting from the contribution of nanoparticles (NPs) technology for both diagnosis and therapy. They can be used as adjuvants, being capable per se of immune-modulating activity, or as carriers for molecules to be transported to a specific target, eventually loaded with specific ligands favoring specific uptake.

AREAS COVERED

The review focuses on experimental use of NPs as adjuvants/carriers for allergen immunotherapy (AIT). Human clinical trials conducted so far are discussed.

EXPERT OPINION

Results of experimental studies and recent clinical trials support the use of NPs as carrier/adjuvant in AIT. Comparisons between NP-based and classical AIT are needed, to show the usefulness of the NP-based approach. However, there are still unsolved problems: the persistence of non-degradable NPs with possible toxicological consequences, and the formation of the protein corona around the NPs, which could alter their activity and fate. Virus-like particles seem the most promising NPs for allergy treatment, as for other vaccines. Over the next decade, NP-based AIT will be largely used to treat allergic disorders.

Nanoparticle-based vaccine development and evaluation against viral infections in pigs

Virus infections possess persistent health challenges in swine industry leading to severe economic losses worldwide. The economic burden caused by virus infections such as Porcine Reproductive and Respiratory Syndrome Virus, Swine influenza virus, Porcine Epidemic Diarrhea Virus, Porcine Circovirus 2, Foot and Mouth Disease Virus and many others are associated with severe morbidity, mortality, loss of production, trade restrictions and investments in control and prevention practices. Pigs can also have a role in zoonotic transmission of some viral infections to humans. Inactivated and modified-live virus vaccines are available against porcine viral infections with variable efficacy under field conditions. Thus, improvements over existing vaccines are necessary to: (1) Increase the breadth of protection against evolving viral strains and subtypes; (2) Control of emerging and re-emerging viruses; (3) Eradicate viruses localized in different geographic areas; and (4) Differentiate infected from vaccinated animals to improve disease control programs. Nanoparticles (NPs) generated from virus-like particles, biodegradable and biocompatible polymers and liposomes offer many advantages as vaccine delivery platform due to their unique physicochemical properties. NPs help in efficient antigen internalization and processing by antigen presenting cells and activate them to elicit innate and adaptive immunity. Some of the NPs-based vaccines could be delivered through both parenteral and mucosal routes to trigger efficient mucosal and systemic immune responses and could be used to target specific immune cells such as mucosal microfold (M) cells and dendritic cells (DCs). In conclusion, NPs-based vaccines can serve as novel candidate vaccines against several porcine viral infections with the potential to enhance the broader protective efficacy under field conditions. This review highlights the recent developments in NPs-based vaccines against porcine viral pathogens and how the NPs-based vaccine delivery system induces innate and adaptive immune responses resulting in varied level of protective efficacy.

Recent Advances in Nanovaccines Using Biomimetic Immunomodulatory Materials

The development of vaccines plays a vital role in the effective control of several fatal diseases. However, effective prophylactic and therapeutic vaccines have yet to be developed for completely curing deadly diseases, such as cancer, malaria, HIV, and serious microbial infections. Thus, suitable vaccine candidates need to be designed to elicit appropriate immune responses. Nanotechnology has been found to play a unique role in the design of vaccines, providing them with enhanced specificity and potency. Nano-scaled materials, such as virus-like particles, liposomes, polymeric nanoparticles (NPs), and protein NPs, have received considerable attention over the past decade as potential carriers for the delivery of vaccine antigens and adjuvants, due to their beneficial advantages, like improved antigen stability, targeted delivery, and long-time release, for which antigens/adjuvants are either encapsulated within, or decorated on, the NP surface. Flexibility in the design of nanomedicine allows for the programming of immune responses, thereby addressing the many challenges encountered in vaccine development. Biomimetic NPs have emerged as innovative natural mimicking biosystems that can be used for a wide range of biomedical applications. In this review, we discuss the recent advances in biomimetic nanovaccines, and their use in anti-bacterial therapy, anti-HIV therapy, anti-malarial therapy, anti-melittin therapy, and anti-tumor immunity.

Tunable Properties of Poly-DL-Lactide-Monomethoxypolyethylene Glycol Porous Microparticles for Sustained Release of Polyethylenimine-DNA Polyplexes

Direct pulmonary delivery is a promising step in developing effective gene therapies for respiratory disease. Gene therapies can be used to treat the root cause of diseases, rather than just the symptoms. However, developing effective therapies that do not cause toxicity and that successfully reach the target site at therapeutic levels is challenging. We have developed a polymer-DNA complex utilizing polyethylene imine (PEI) and DNA, which was then encapsulated into poly(lactic acid)-co-monomethoxy poly(ethylene glycol) (PLA-mPEG) microparticles via double emulsion, solvent evaporation. Then, the resultant particle size, porosity, and encapsulation efficiency were measured as a function of altering preparation parameters. Microsphere formation was confirmed from scanning electron micrographs and the aerodynamic particle diameter was measured using an aerodynamic particle sizer. Several formulations produced particles with aerodynamic diameters in the 0-5 μm range despite having larger particle diameters which is indicative of porous particles. Furthermore, these aerodynamic diameters correspond to high deposition within the airways when inhaled and the measured DNA content indicated high encapsulation efficiency. Thus, this formulation provides promise for developing inhalable gene therapies.

Acidic pH-responsive polymer nanoparticles as a TLR7/8 agonist delivery platform for cancer immunotherapy

Synthetic imidazoquinoline-based toll-like receptor (TLR) 7/8 bi-specific agonists are promising vaccine adjuvants that can induce maturation of dendritic cells (DCs) and activate them to secrete pro-inflammatory cytokines. However, in vivo efficacy of these small molecule agonists is often hampered by their fast clearance from the injection site, limiting their use to topical treatments. In this study, we investigated the use of acidic pH-responsive poly(lactide-co-glycolide) (PLGA) nanoparticles for endo-lysosome specific release of 522, a novel TLR7/8 agonist. Bicarbonate salt was incorporated into the new formulation to generate carbon dioxide (CO2) gas at acidic pH, which can disrupt the polymer shell to rapidly release the payload. Compared to conventional PLGA nanoparticles, the pH responsive formulation resulted in 33-fold higher loading of 522. The new formulation demonstrated acid-responsive CO2 gas generation and drug release. The acid-responsive formulation increased the in vitro expression of co-stimulatory molecules on DCs and improved antigen-presentation via MHC I, both of which are essential for CD8 T cell priming. In vivo studies showed that the pH-responsive formulation elicited stronger antigen-specific CD8 T cell and natural killer (NK) cell responses than conventional PLGA nanoparticles, resulting in enhanced anticancer efficacy in a murine melanoma tumor model. Our results suggest that acidic-pH responsive, gas-generating nanoparticles are an efficient TLR7/8 agonist delivery platform for cancer immunotherapy.

High adjuvant activity of layered double hydroxide nanoparticles and nanosheets in anti-tumour vaccine formulations

Effective adjuvants in anti-tumour vaccine formulations are very important in the development of new-generation vaccines. In this study, two layered double hydroxide (LDH) nanomaterial forms, i.e. nanoparticles (NPs) and nanosheets (NSs), were synthesised and examined as adjuvants to provoke the immune responses for anti-tumour purpose. Immunogen ovalbumin (OVA) delivered by both nanomaterials induced much stronger humoral and cell-medicated immune responses, together with an immune stimulant (TLR9 ligand CpG), as evidenced by higher levels of IgG1, IgG2a and interferon-γ. By comparison, LDH NSs showed higher activity to promote specific antibody responses than LDH NPs but with a similar cell-mediated immune response. The mice immunised with OVA-CpG vaccines formulated with both nanomaterials showed stronger inhibition of the inoculated tumour growth and had a longer survival. Altogether, these data indicate that LDH NPs and NSs can be used as potential nanoadjuvants for efficient protein-based anti-tumour vaccines.

Radiation-enhanced delivery of systemically administered amphiphilic-CpG oligodeoxynucleotide

Along with vaccines and checkpoint blockade, immune adjuvants may have an important role in tumor immunotherapy. Oligodeoxynucleotides containing unmethylated cytidyl guanosyl dinucleotide motifs (CpG ODN) are TLR9 ligands with attractive immunostimulatory properties, but intratumoral administration has been required to induce an effective anti-tumor immune response. Following on recent studies with radiation-targeted delivery of nanoparticles, we examined enhanced tumor-specific delivery of amphiphile-CpG, an albumin-binding analog of CpG ODN, following systemic administration 3days after tumor irradiation. The combination of radiation and CpG displayed superior tumor control over either treatment alone. Intravital imaging of fluorescently labeled amphiphilic-CpG revealed increased accumulation in irradiated tumors along with decreased off-target accumulation in visceral organs. Within 48h after amphiphile-CpG administration, immune activation could be detected by increased Granzyme B and Interferon gamma activity in the tumor as well as in circulating monocytes and activated CD8⁺ T cells. Using radiotherapy to enhance the targeting of CpG to tumors may help advance this once promising therapy to clinical relevance.

Recent advances in the use of nanoparticles for allergen-specific immunotherapy

The number of patients suffering from allergic asthma and rhinoconjunctivitis has increased dramatically within the last decades. Allergen-specific immunotherapy (AIT) is the only available cause-oriented therapy so far. AIT reduces symptoms, but has also a disease-modifying effect. Disadvantages are a long-lasting procedure, and in a few cases potential systemic adverse reactions. Encapsulation of allergens or DNA vaccines into nanostructures may provide advantages compared to the conventional AIT with noncapsulated allergen extracts: The protein/DNA molecule can be protected from degradation, higher local concentrations and targeted delivery to the site of action appear possible, and most importantly, recognition of encapsulated allergen by the immune system, especially by IgE antibodies, is prevented. AIT with nanoparticles (NPs) may offer a safer and potentially more efficient way of treatment for allergic diseases. In this review, we summarize the use of biodegradable NPs consisting of synthetic or natural polymers, liposomes, and virus-like particles as well as nonbiodegradable NPs like dendrimers, and carbon- or metal-based NPs for AIT. More or less successful applications of these NPs in prophylactic as well as therapeutic vaccination approaches in rodents or other animals as well as first human clinical trials are discussed in detail.

The effect of polyanhydride chemistry in particle-based cancer vaccines on the magnitude of the anti-tumor immune response

The goal of this research was to study the effect of polyanhydride chemistry on the immune response induced by a prophylactic cancer vaccine based on biodegradable polyanhydride particles. To achieve this goal, different compositions of polyanhydride copolymers based on 1,8-bis-(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG), 1,6-bis-(p-carboxyphenoxy)-hexane (CPH), and sebacic anhydride (SA) were synthesized by melt polycondensation, and polyanhydride copolymer particles encapsulating a model antigen, ovalbumin (OVA), were then synthesized using a double emulsion solvent evaporation technique. The ability of three different compositions of polyanhydride copolymers (50:50 CPTEG:CPH, 20:80 CPTEG:CPH, and 20:80 CPH:SA) encapsulating OVA to elicit immune responses was investigated. In addition, the impact of unmethylated oligodeoxynucleotides containing deoxycytidyl-deoxyguanosine dinucleotides (CpG ODN), an immunological adjuvant, on the immune response was also studied. The immune response to cancer vaccines was measured after treatment of C57BL/6J mice with two subcutaneous injections, seven days apart, of 50μg OVA encapsulated in particles composed of different polyanhydride copolymers with or without 25μg CpG ODN. In vivo studies showed that 20:80 CPTEG:CPH particles encapsulating OVA significantly stimulated the highest level of CD8⁺ T lymphocytes, generated the highest serum titers of OVA-specific IgG antibodies, and provided longer protection against tumor challenge with an OVA-expressing thymoma cell line in comparison to formulations made from other polyanhydride copolymers. The results also revealed that vaccination with CpG ODN along with polyanhydride particles encapsulating OVA did not enhance the immunogenicity of OVA. These results accentuate the crucial role of the copolymer composition of polyanhydrides in stimulating the immune response and provide important insights on rationally designing efficacious cancer vaccines.

STATEMENT OF SIGNIFICANCE

Compared to soluble cancer vaccine formulations, tumor antigens encapsulated in biodegradable polymeric particles have been shown to sustain antigen release and provide long-term protection against tumor challenge by improving the immune response towards the antigen. Treatment of mice with cancer vaccines based on different polyanhydride copolymers encapsulating OVA resulted in stimulation of tumor-specific immune responses with different magnitudes. This clearly indicates that polyanhydride chemistry plays a substantial role in stimulating the immune response. Vaccination with 20:80 CPTEG:CPH/OVA, the most hydrophobic formulation, stimulated the strongest cellular and humoral immune responses and provided the longest survival outcome without adding any other adjuvant. The most important finding in this study is that the copolymer composition of polyanhydride particle-based vaccines can have a direct effect on the magnitude of the antitumor immune response and should be selected carefully in order to achieve optimal cancer vaccine efficacy.

Dual stimulation of antigen presenting cells using carbon nanotube-based vaccine delivery system for cancer immunotherapy

Although anti-cancer immuno-based combinatorial therapeutic approaches have shown promising results, efficient tumour eradication demands further intensification of anti-tumour immune response. With the emerging field of nanovaccinology, multi-walled carbon nanotubes (MWNTs) have manifested prominent potentials as tumour antigen nanocarriers. Nevertheless, the utilization of MWNTs in co-delivering antigen along with different types of immunoadjuvants to antigen presenting cells (APCs) has not been investigated yet. We hypothesized that harnessing MWNT for concurrent delivery of cytosine-phosphate-guanine oligodeoxynucleotide (CpG) and anti-CD40 Ig (αCD40), as immunoadjuvants, along with the model antigen ovalbumin (OVA) could potentiate immune response induced against OVA-expressing tumour cells. We initially investigated the effective method to co-deliver OVA and CpG using MWNT to the APC. Covalent conjugation of OVA and CpG prior to loading onto MWNTs markedly augmented the CpG-mediated adjuvanticity, as demonstrated by the significantly increased OVA-specific T cell responses in vitro and in C57BL/6 mice. αCD40 was then included as a second immunoadjuvant to further intensify the immune response. Immune response elicited in vitro and in vivo by OVA, CpG and αCD40 was significantly potentiated by their co-incorporation onto the MWNTs. Furthermore, MWNT remarkably improved the ability of co-loaded OVA, CpG and αCD40 in inhibiting the growth of OVA-expressing B16F10 melanoma cells in subcutaneous or lung pseudo-metastatic tumour models. Therefore, this study suggests that the utilization of MWNTs for the co-delivery of tumour-derived antigen, CpG and αCD40 could be a competent approach for efficient tumours eradication.

Diaminosulfide based polymer microparticles as cancer vaccine delivery systems

The aim of the research presented here was to determine the characteristics and immunostimulatory capacity, in vivo, of antigen and adjuvant co-loaded into microparticles made from a novel diaminosulfide polymer, poly(4,4'-trimethylenedipiperdyl sulfide) (PNSN), and to assess their potential as cancer vaccine vectors. PNSN microparticles co-loaded with the antigen, ovalbumin (OVA), and adjuvant, CpG 1826, (PNSN(OVA + CpG)) were fabricated and characterized for size (1.64 μm diameter; PDI=0.62), charge (-23.1 ± 0.3), and loading efficiencies of antigen (7.32 μg/mg particles) and adjuvant (0.95 μg/mg particles). The ability of PNSN(OVA + CpG) to stimulate cellular and humoral immune responses in vivo was compared with other PNSN microparticle formulations as well as with poly(lactic-co-glycolic acid)(PLGA)-based microparticles, co-loaded with OVA and CpG (PLGA(OVA + CpG)), an adenovirus encoding OVA (Ad5-OVA), and OVA delivered with incomplete Freund's adjuvant (IFA(OVA)). In vivo OVA-specific IgG1 responses, after subcutaneous prime/boosts in mice, were similar when PNSN(OVA + CpG) and PLGA(OVA + CpG) were compared and the presence of CpG 1826 within the PNSN microparticles demonstrated significantly improved responses when compared to PNSN microparticles loaded with OVA alone (PNSN(OVA)), plus or minus soluble CpG 1826. Cellular immune responses to all particle-based vaccine formulations ranged from being negligible to modest with PNSN(OVA + CpG) generating the greatest responses, displaying significantly increased levels of OVA-specific CD8+ T lymphocytes compared to controls and IFA(OVA) treated mice. Finally, it was shown that of all vaccination formulations tested PNSN(OVA + CpG) was the most protective against subsequent challenge with an OVA-expressing tumor cell line, E.G7. Thus, microparticles made from poly(diaminosulfide)-based macromolecules possess promising potential as vaccine vectors and, as demonstrated here, may have impact as cancer vaccines in particular.

Applying biodegradable particles to enhance cancer vaccine efficacy

One of the primary goals of our group and our collaborators here at the University of Iowa is to develop therapeutic cancer vaccines using biodegradable and biocompatible polymer-based vectors. A major advantage of using discretely packaged immunogenic cargo over non-encapsulated vaccines is that they promote enhanced cellular immunity, a key requirement in achieving antitumor activity. We discuss the importance of co-encapsulation of tumor antigen and adjuvant, with specific focus on the synthetic oligonucleotide adjuvant, cytosine-phosphate-guanine oligodeoxynucleotides. We also discuss our research using a variety of polymers including poly(α-hydroxy acids) and polyanhydrides, with the aim of determining the effect that parameters, such as size and polymer type, can have on prophylactic and therapeutic tumor vaccine formulation efficacy. Aside from their role as vaccine vectors per se, we also address the research currently underway in our group that utilizes more novel applications of biodegradable polymer-based particles in facilitating other types of immune-based therapies.

Effects of mesenchymal stem cell therapy, in association with pharmacologically active microcarriers releasing VEGF, in an ischaemic stroke model in the rat

Few effective therapeutic interventions are available to limit brain damage and functional deficits after ischaemic stroke. Within this context, mesenchymal stem cell (MSC) therapy carries minimal risks while remaining efficacious through the secretion of trophic, protective, neurogenic and angiogenic factors. The limited survival rate of MSCs restricts their beneficial effects. The usefulness of a three-dimensional support, such as a pharmacologically active microcarrier (PAM), on the survival of MSCs during hypoxia has been shown in vitro, especially when the PAMs were loaded with vascular endothelial growth factor (VEGF). In the present study, the effect of MSCs attached to laminin-PAMs (LM-PAMs), releasing VEGF or not, was evaluated in vivo in a model of transient stroke. The parameters assessed were infarct volume, functional recovery and endogenous cellular reactions. LM-PAMs induced the expression of neuronal markers by MSCs both in vitro and in vivo. Moreover, the prolonged release of VEGF increased angiogenesis around the site of implantation of the LM-PAMs and facilitated the migration of immature neurons towards the ischaemic tissue. Nonetheless, MSCs/LM-PAMs-VEGF failed to improve sensorimotor functions. The use of LM-PAMs to convey MSCs and to deliver growth factors could be an effective strategy to repair the brain damage caused by a stroke.

Injectable, spontaneously assembling, inorganic scaffolds modulate immune cells in vivo and increase vaccine efficacy

Materials implanted in the body to program host immune cells are a promising alternative to transplantation of ex vivo–manipulated cells to direct an immune response, but required a surgical procedure. Here we demonstrate that high-aspectratio, mesoporous silica rods (MSRs) injected with a needle spontaneously assemble in vivo to form macroporous structures that provide a 3D cellular microenvironment for host immune cells. In mice, substantial numbers of DCs are recruited to the pores between the scaffold rods. The recruitment of DCs and their subsequent homing to lymph nodes can be modulated by sustained release of inflammatory signals and adjuvants from the scaffold. Moreover, injection of an MSR-based vaccine formulation enhances systemic T_H1 and T_H2 serum antibody and cytotoxic T cell levels compared to bolus controls. These findings suggest that injectable MSRs may serve as a multifunctional vaccine platform to modulate host immune cell function and provoke adaptive immune responses.

Exploiting the tumor phenotype using biodegradable submicron carriers of chemotherapeutic drugs

Tumor tissues possess characteristics that distinguish them from healthy tissues and make them attractive targets for submicron carriers of chemotherapeutic drugs (CTX). CTX are generally administered systemically in free form to cancer patients resulting in unwanted cytotoxic effects and placing limitations on the deliverable CTX dose. In an effort to raise the therapeutic index of CTX there are now liposome-based CTX formulations in clinical use that are more tumor specific than the free form of CTX. However, progression to liposome-based chemotherapy in the clinic has been slow and there have been no approved formulations introduced in the last decade. Alternative carrier systems such as those made from the biodegradable polymer poly(lactic-co-glycolic) acid (PLGA) have been investigated in preclinical settings with promising outcomes. Here we review the principle behind biodegradable submicron carriers as CTX delivery vehicles for solid tumors with a specific focUS on liposomes and PLGA-based carriers, highlighting the strengths and weaknesses of each system.

Tumor lysate-loaded biodegradable microparticles as cancer vaccines

Cancer vaccines that use tumor lysate (TL) as a source of tumor-associated antigens (TAAs) have significant potential for generating therapeutic anti-tumor immune responses. Vaccines encompassing TL bypass the limitations of single antigen vaccines by simultaneously stimulating immunity against multiple TAAs, thereby broadening the repertoire of TAA-specific T-cell clones available for activation. Administration of TL in particulate form, such as when encapsulated in biodegradable microparticles, increases its immunostimulatory capacity and produces more robust immune responses than when TL is given in soluble form. These effects can be further enhanced by co-administering TL with adjuvants. A number of recent studies using polymeric microparticle delivery of TL, with or without adjuvants, have produced promising results in preclinical studies. In this review, we will discuss current experimental approaches involving TL being pursued in the oncoimmunology field, and comment on strategies such as combining specific chemotherapeutic agents with TL microparticle delivery that may eventually lead to improved survival outcomes for cancer patients.

Polarized immune responses modulated by layered double hydroxides nanoparticle conjugated with CpG

Modulation of the immune response is an important step in the induction of protective humoral and cellular immunity against pathogens. In this study, we investigated the possibility of using a nanomaterial conjugated with the toll-like receptor (TLR) ligand CpG to modulate the immune response towards the preferred polarity. MgAl-layered double hydroxide (LDH) nanomaterial has a very similar chemical composition to Alum, an FDA approved adjuvant for human vaccination. We used a model antigen, ovalbumin (OVA) to demonstrate that MgAl-LDH had comparable adjuvant activity to Alum, but much weaker inflammation. Conjugation of TLR9 ligand CpG to LDH nanoparticles significantly enhanced the antibody response and promoted a switch from Th2 toward Th1 response, demonstrated by a change in the IgG2a:IgG1 ratio. Moreover, immunization of mice with CpG-OVA-conjugated LDH before challenge with OVA-expressing B16/F10 tumor cells retarded tumor growth. Together, these data indicate that LDH nanomaterial can be used as an immune adjuvant to promote Th1 or Th2 dominant immune responses suitable for vaccination purposes.

Development of a poly (lactic-co-glycolic acid) particle vaccine to protect against house dust mite induced allergy

Poly(lactic-co-glycolic acid) (PLGA) particles carrying antigen and adjuvant is a promising vaccine system which has been shown to stimulate systemic antigen-specific immune responses. In this study, we investigated the relationship of (i) the sizes of PLGA particle and (ii) the presence of cytosine-phosphate-guanine motifs (CpG), with the extent and type of immune response stimulated against Dermatophagoides pteronyssinus-2 (Der p2) antigen. Different sizes of PLGA particles encapsulating CpG were prepared using a double emulsion solvent evaporation method. Mice were vaccinated with Der p2 and different sizes of empty or CpG-loaded PLGA particles. Vaccinated mice were exposed to daily intranasal instillation of Der p2 for 10 days followed by euthanization to estimate leukocyte accumulation in bronchoalveolar lavage (BAL) fluids, antibody profiles, and airway hyperresponsiveness. PLGA particles showed a size-dependent decrease in the proportion of eosinophils found in BAL fluids. Mice vaccinated with the Der p2 coated on 9-μm-sized empty PLGA particles showed increased levels of IgE and IgG1 antibodies as well as increased airway hyperresponsiveness. All sizes of PLGA particles encapsulating CpG prevented airway hyperresponsiveness after Der p2 exposures. Inflammatory responses to Der p2 exposure were significantly reduced when smaller PLGA particles were used for vaccination. In addition, encapsulating CpG in PLGA particles increased IgG2a secretion. This study shows that the size of PLGA particles used for vaccination plays a major role in the prevention of house dust mite-induced allergy and that incorporation of CpG into the PLGA particles preferentially develops a Th1-type immune response.

Biodegradable particles as vaccine antigen delivery systems for stimulating cellular immune responses

There is a need for both new and improved vaccination formulations for a range of diseases for which current vaccines are either inadequate or non-existent. Biodegradable polymer-based vaccines fulfill many of the desired properties in achieving effective long-term protection in a manner that is safe, economical, and potentially more practicable on a global scale. Here we discuss some of the work performed with micro/nanoparticles made from either synthetic (poly[lactic-co-glycolic acid] [PLGA] and polyanhydrides) or natural (chitosan) biodegradable polymers. Our attention is focused on, but not limited to, the generation of antitumor immunity where we stress the importance of particle size and co-delivery of antigen and adjuvant.

Characterizing the antitumor response in mice treated with antigen-loaded polyanhydride microparticles

Delivery of vaccine antigens with an appropriate adjuvant can trigger potential immune responses against cancer leading to reduced tumor growth and improved survival. In this study, various formulations of a bioerodible amphiphilic polyanhydride copolymer based on 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) and 1,6-bis(p-carboxyphenoxy) hexane (CPH) with inherent adjuvant properties were evaluated for antigen-loading properties, immunogenicity and antitumor activity. Mice were vaccinated with 50:50 CPTEG:CPH microparticles encapsulating a model tumor antigen, ovalbumin (OVA), in combination with the Toll-like receptor-9 agonist, CpG oligonucleotide 1826 (CpG ODN). Mice treated with OVA-encapsulated CPTEG:CPH particles elicited the highest CD8(+) T cell responses on days 14 and 20 when compared to other treatment groups. This treatment group also displayed the most delayed tumor progression and the most extended survival times. Particles encapsulating OVA and CpG ODN generated the highest anti-OVA IgG(1) antibody responses in mice but these mice did not show significant tumor protection. These results suggest that antigen-loaded CPTEG:CPH microparticles can stimulate antigen-specific cellular responses and could therefore potentially be used to promote antitumor responses in cancer patients.

Alginate-coated chitosan nanogel capacity to modulate the effect of TLR ligands on blood dendritic cells

Biodegradable nanoparticles have been employed for vaccine delivery, frequently admixed with adjuvants. Surprisingly, there is little information on their modulation of immune responses, speculated to be negligible. We analyzed the immunomodulatory capacity of alginate-coated chitosan nanogels (Ng), on porcine and human blood dendritic cells (DCs), when applied with defined adjuvants targeting different DC subpopulations. DC maturation, cytokine production and cell migration were assessed. Ng differentially influenced the immunomodulatory characteristics of individual Toll-like receptor (TLR) ligands: Pam3Cys-SK4-induced IL-1β was enhanced; CpG-oligodeoxynucleotides (CpG-ODN)-induced IFN-α, IL-6 and TNFα were impaired; CpG-ODN-induced CD86 and CCR7, and cell migration, were diminished-plasmacytoid DCs (pDCs) were particularly sensitive. Therein, the Ng influence on DC endocytosis of the TLR ligands was apparently a major contributory element. This demonstrates the importance of predefining the interplay between delivery vehicles and admixed immunostimulatory moieties, for ensuring appropriate immune activation and efficacious combinations.

FROM THE CLINICAL EDITOR

Biodegradable nanoparticles have been utilized in vaccine delivery; however, there is little information available on their immunomodulatory properties, which are thought to be negligible. This study clearly demonstrates that nanogels do influence the developing immune response, which needs to be taken into consideration when utilizing these otherwise very efficacious vaccine delivery approaches.

Antigen-coated poly α-hydroxy acid based microparticles for heterologous prime-boost adenovirus based vaccinations

Adenoviruses show promising potential as vectors for cancer vaccines, however, their high immunogenicity can be problematic when it comes to homologous prime-boost strategies. In the studies presented here we show that heterologous prime-boost vaccinations involving ovalbumin (OVA)-antigen-coated microparticles as a prime, and adenovirus encoding OVA (AdOVA) as a boost, were equally as effective as homologous AdOVA prime-boosts at generating OVA-specific CD8(+) T-cell responses, which translated into effective tumor protection. OVA-coated biodegradable poly α-hydroxy acid-based microparticles of varying chemistries, when used as primes in heterologous prime-boost vaccinations, were comparable in terms of promoting OVA-specific CD8(+) T cells as well as providing protection against subsequent tumor challenge. These findings auger well for using poly α-hydroxy acid-based microparticles in prime-boost viral vaccination strategies geared toward the safer, and potentially more efficient, generation of anti-tumor immunity.

Biodegradable particles as vaccine delivery systems: size matters

Poly(lactide-co-glycolide) (PLGA) particles have strong potential as antigen delivery systems. The size of PLGA particles used to vaccinate mice can affect the magnitude of the antigen-specific immune response stimulated. In this study, we fabricated and characterized 17 μm, 7 μm, 1 μm, and 300 nm PLGA particles coloaded with a model antigen ovalbumin (OVA) and CpG oligodeoxynucleotides (CpG ODN). PLGA particles demonstrated a size-dependent burst release followed by a more sustained release of encapsulated molecules. PLGA particles that were 300 nm in size showed the highest internalization by, and maximum activation of, dendritic cells. The systemic antigen-specific immune response to vaccination was measured after administration of two intraperitoneal injections, 7 days apart, of 100 μg OVA and 50 μg CpG ODN in C57BL/6 mice. In vivo studies showed that 300 nm sized PLGA particles generated the highest antigen-specific cytotoxic T cell responses by days 14 and 21. These mice also showed the highest IgG2a:IgG1 ratio of OVA-specific antibodies on day 28. This study suggests that the smaller the PLGA particle used to deliver antigen and adjuvants the stronger the antigen-specific cytotoxic T cell response generated.

DOCK8 functions as an adaptor that links TLR-MyD88 signaling to B cell activation

The adaptors DOCK8 and MyD88 have been linked to serological memory. Here we report that DOCK8-deficient patients had impaired antibody responses and considerably fewer CD27(+) memory B cells. B cell proliferation and immunoglobulin production driven by Toll-like receptor 9 (TLR9) were considerably lower in DOCK8-deficient B cells, but those driven by the costimulatory molecule CD40 were not. In contrast, TLR9-driven expression of AICDA (which encodes the cytidine deaminase AID), the immunoglobulin receptor CD23 and the costimulatory molecule CD86 and activation of the transcription factor NF-κB, the kinase p38 and the GTPase Rac1 were intact. DOCK8 associated constitutively with MyD88 and the tyrosine kinase Pyk2 in normal B cells. After ligation of TLR9, DOCK8 became tyrosine-phosphorylated by Pyk2, bound the Src-family kinase Lyn and linked TLR9 to a Src-kinase Syk-transcription factor STAT3 cascade essential for TLR9-driven B cell proliferation and differentiation. Thus, DOCK8 functions as an adaptor in a TLR9-MyD88 signaling pathway in B cells.

Structure-dependent immunostimulatory effect of CpG oligodeoxynucleotides and their delivery system

Unmethylated cytosine-phosphate-guanosine (CpG) oligodeoxynucleotides (ODNs) are recognized by Toll-like receptor 9 (TLR9) found in antigen-presenting cells and B cells and can activate the immune system. Using CpG ODNs as an adjuvant has been found to be effective for treating infectious diseases, cancers, and allergies. Because natural ODNs with only a phosphodiester backbone are easily degraded by nuclease (deoxyribonuclease [DNase]) in serum, CpG ODNs with a phosphorothioate backbone have been studied for clinical application. CpG ODNs with a phosphorothioate backbone have raised concern regarding undesirable side effects; however, several CpG ODNs with only a phosphodiester backbone have been reported to be stable in serum and to show an immunostimulatory effect. In recent years, research has been conducted on delivery systems for CpG ODNs using nanoparticles (NPs). The advantages of NP-based delivery of CpG ODN include (1) it can protect CpG ODN from DNase, (2) it can retain CpG ODN inside the body for a long period of time, (3) it can improve the cellular uptake efficiency of CpG ODN, and (4) it can deliver CpG ODN to the target tissues. Because the target cells of CpG ODN are cells of the immune system and TLR9, the receptor of CpG ODN is localized in endolysosomes, CpG ODN delivery systems are required to have qualities different from other nucleic acid drugs such as antisense DNA and small interfering RNA. Studies until now have reported various NPs as carriers for CpG ODN delivery. This review presents DNase-resistant CpG ODNs with various structures and their immunostimulatory effects and also focuses on delivery systems of CpG ODNs that utilize NPs. Because CpG ODNs interact with TLR9 and activate both the innate and the adaptive immune system, the application of CpG ODNs for the treatment of cancers, infectious diseases, and allergies holds great promise.

Immunostimulatory CpG-DNA and PSA-peptide vaccination elicits profound cytotoxic T cell responses

OBJECTIVE

Novel strategies for the treatment of advanced prostate cancer (CaP), including immunotherapy or gene therapy, are currently under evaluation with Sipuleucel-T as first FDA-approved immunotherapeutic. Here, we examine cytosine-phosphorothioate-guanine (CpG)-DNA oligonucleotides (ODN) to boost cytokine responses and costimulatory molecule expression on murine bone marrow-derived dendritic cells (mBMDC). Furthermore, we evaluate the potency of a PSA-peptide based vaccine in combination with CpG-DNA to elicit specific cytotoxic T cell (CTL) responses.

MATERIALS AND METHODS

mBMDC were stimulated with CpG-DNA (1668: 5'-TCCATGACGTTCCTGATGCT-3') or non-stimulatory control-ODN (1720: 5'-TCCATGAGCTTCCTGATGCT-3'). Subsequently, expression of the costimulatory molecules CD40 and CD86 and induction of proinflammatory cytokines (interleukin (IL)-6 and IL-12) were analyzed. For induction of PSA-peptide specific CTL, female C57BL/6 mice were immunized with PSA-peptide 65-73 (HCIRNKSVI) alone or in combination with 1668 or 1720-ODN. In vivo cytotoxicity assay determined PSA-peptide specific cytotoxicity 1 week after vaccination.

RESULTS

Treatment of mBMDC with stimulatory CpG-DNA ODN resulted in pronounced up-regulation of costimulatory molecule expression on mBMDC in a dose-dependent manner. CpG-ODN significantly increased production of IL-6 and IL-12 in mBMDC (P < 0.001). Induction of PSA-peptide specific CTL responses in mice immunized with PSA-peptide and CpG-DNA were significantly greater than those of PSA-peptide and control-ODN immunized mice or PSA-peptide only vaccination.

CONCLUSIONS

CpG-DNA acts as potent adjuvant for vaccination therapies and elicits profound PSA-peptide specific CTL responses in combination with an immunodominant PSA-peptide. CpG-ODN mediated immunotherapy represents a potentially inexpensive, safe, easy-to-produce, and easy-to-handle treatment alternative. Therefore, further evaluation of CpG-DNA in immunization therapies against CaP is warranted.

Efficacy of polymeric encapsulated C5a peptidase-based group B streptococcus vaccines in a murine model

OBJECTIVE

The purpose was to examine in mice the efficacy of various polymeric-encapsulated C5a peptidase vaccine formulations in eliciting a long-term immune response and preventing group B streptococcus (GBS) infection.

STUDY DESIGN

C5a peptidase was encapsulated in semipermeable microspheres of poly(lactide-coglycolide) (PLGA). Female ICR mice were immunized with 0, 10, or 30 μg of encapsulated C5a peptidase within 2 different formulations of PLGA polymers. Booster doses were given at weeks 4 and 8. Antibody responses were measured by enzyme-linked immunosorbent assay at weeks 4, 8, 11, and 40. Vaginal challenges with GBS types 1a, III, and V were performed at week 12.

RESULTS

Thirty microgram doses of the 75:25 and 50:50 PLGA formulations generate the highest and most sustained C5a peptidase-specific immune responses. Mice that received encapsulated C5a peptidase were significantly protected from vaginal colonization compared with mice that received empty microspheres.

CONCLUSION

Encapsulated C5a peptidase elicited significant immune responses and protection against a GBS challenge. C5a peptidase microsphere encapsulation has potential as a GBS vaccine.

Rational design, fabrication, characterization and in vitro testing of biodegradable microparticles that generate targeted and sustained transgene expression in HepG2 liver cells

Poly(lactide-co-glycolide) (PLGA) microparticles have significant potential for sustained delivery of plasmid DNA (pDNA). However, unmodified PLGA microparticles have poor transfection efficiencies. In this study, we use several approaches to enhance the transfection efficiencies of PLGA microparticles in a HepG2 liver cell line. Polyethylenimine (PEI) is used to condense the pDNA prior to loading into the PLGA microparticles. This provides enhanced loading efficiencies and greater protection to the pDNA during the entrapment process. In addition, the pDNA used (ApoE) incorporates a hybrid liver-specific murine albumin enhancer/α1 antitrypsin promoter (AlbE/hAAT) to enhance transgene expression in human liver (HepG2) cells. The percentage of surfactant used in the preparation of the microparticles, the polymer composition of the PLGA, the ratio of the PEI to pDNA (N/P), the structure of the PEI and the potential utility of a galactose targeting ligand were then investigated to further optimize the efficacy of the cationic microparticle non-viral delivery system in transfecting HepG2 cells. For each PLGA PEI-pDNA microparticle formulation prepared, we evaluated particle size, ζ-potential, loading of pDNA, cytotoxicity, and transgene expression in HepG2 cells and control human embryonic kidney (HEK293) and monkey African green kidney fibroblast-like (COS7) cells. Loading PLGA particles with PEI-ApoE pDNA complexes resulted in a significant reduction in particle size when compared to PLGA microparticles loaded with ApoE pDNA alone. Scanning electron microscopy images showed that all the particle formulations were smooth and spherical in appearance. Incorporation of the cationic PEI in the PLGA particles changed the ζ-potential from negative to positive. Complexing PEI with ApoE pDNA increased the loading efficiency of the ApoE pDNA into the PLGA microparticles. The cytotoxicity of PLGA particles loaded with PEI-ApoE pDNA complexes was similar to PLGA particles loaded with ApoE pDNA alone. The transfection efficiency of all particle formulations prepared with ApoE pDNA was significantly higher in HepG2 cells when compared to HEK293 and COS7 cell lines. The release of PEI-pDNA complexes from particles prepared with different PLGA polymer compositions including PLGA 50-50, PLGA 75-25, and PLGA 85-15 was sustained in all cases but the release profile was dependent on the polymer composition. Transmission electron microscopy images showed that PEI-pDNA complexes remained structurally intact after release. The optimum formulation for PLGA particles loaded with PEI-ApoE pDNA complexes was prepared using 2% polyvinyl alcohol, 50-50 PLGA compositions and N/P ratios of 5-10. Strong sustained transgene expression in HepG2 cells was generated by PLGA PEI-ApoE pDNA particles up to the full 13 days tested.

Drug delivery systems for differential release in combination therapy

INTRODUCTION

Combination therapy with multiple therapeutic agents has wide applicability in medical and surgical treatment, especially in the treatment of cancer. Thus, new drug delivery systems that can differentially release two or more drugs are desired. Utilizing new techniques to engineer the established drug delivery systems and synthesizing new materials and designing carriers with new structures are feasible ways to fabricate proper multi-agent delivery systems, which are critical to meet requirements in the clinic and improve therapeutic efficacy.

AREAS COVERED

This paper aims to give an overview about the multi-agent delivery systems developed in the last decade for differential release in combination therapy. Multi-agent delivery systems from nanoscale to bulk scale, such as liposomes, micelles, polymer conjugates, nano/microparticles and hydrogels, developed over the last 10 years, have been collected and summarized. The characteristics of different delivery systems are described and discussed, including the structure of drug carriers, drug-loading techniques, release behaviors and consequent evaluation in biological assays.

EXPERT OPINION

The chemical structure of drug delivery systems is the key to controlling the release of therapeutic agents in combination therapy, and the differential release of multiple drugs could be realized by the successful design of a proper delivery system. Besides biological evaluation in vitro and in vivo, it is important to speed up practical application of the resulting delivery systems.

Immunostimulatory sutures that treat local disease recurrence following primary tumor resection

Neuroblastoma is a common childhood cancer that often results in progressive minimal residual disease after primary tumor resection. Cytosine-phosphorothioate-guanine oligonucleotides (CpG ODN) have been reported to induce potent anti-tumor immune responses. In this communication, we report on the development of a CpG ODN-loaded suture that can close up the wound following tumor excision and provide sustained localized delivery of CpG ODN to treat local disease recurrence. The suture was prepared by melt extruding a mixture of polylactic acid-co-glycolic acid (PLGA 75:25 0.47 dL g⁻¹) pellets and CpG ODN 1826. Scanning electron microscopy images showed that the sutures were free of defects and cracks. UV spectrophotometry measurements at 260 nm showed that sutures provide sustained release of CpG ODN over 35 days. Syngeneic female A/J mice were inoculated subcutaneously with 1 × 10⁶ Neuro-2a murine neuroblastoma wild-type cells and tumors were grown between 5 to 10 mm before the tumors were excised. Wounds from the tumor resection were closed using CpG ODN-loaded sutures and/or polyglycolic acid Vicryl suture. Suppression of neuroblastoma recurrence and mouse survival were significantly higher in mice where wounds were closed using the CpG ODN-loaded sutures relative to all other groups.

PCPP (poly[di(carboxylatophenoxy)-phosphazene]) microparticles co-encapsulating ovalbumin and CpG oligo-deoxynucleotides are potent enhancers of antigen specific Th1 immune responses in mice

We generated poly[di(carboxylatophenoxy)-phosphazene] (PCPP) microparticles encapsulating ovalbumin (OVA) and CpG of 0.5-2.5 μm in diameter with an encapsulation efficiency of approximately 63% and 95% respectively. In mice the microparticles generated high antigen-specific IgG, IgG1 and IgG2a titers with higher IgG2a/IgG1 ratios. Whole body in vivo imaging of mice subcutaneously injected with MPs showed several fold increase of OVA and CpG in draining inguinal lymph nodes compared to soluble formulations. We conclude that PCPP MPs are more effective in enhancing immune responses compared to soluble formulations, due to co-delivery of OVA and CpG resulting in a Th1 type of immune response.

Nanoparticle delivery systems in cancer vaccines

Therapeutic strategies that involve the manipulation of the host's immune system are gaining momentum in cancer research. Antigen-loaded nanocarriers are capable of being actively taken up by antigen-presenting cells (APCs) and have shown promising potential in cancer immunotherapy by initiating a strong immunostimulatory cascade that results in potent antigen-specific immune responses against the cancer. Such carrier systems offer versatility in that they can simultaneously co-deliver adjuvants with the antigens to enhance APC activation and maturation. Furthermore, modifying the surface properties of these nanocarriers affords active targeting properties to APCs and/or enhanced accumulation in solid tumors. Here, we review some recent advances in these colloidal and particulate nanoscale systems designed for cancer immunotherapy and the potential for these systems to translate into clinical cancer vaccines.

TLR9-targeted biodegradable nanoparticles as immunization vectors protect against West Nile encephalitis

Vaccines that activate humoral and cell-mediated immune responses are urgently needed for many infectious agents, including the flaviviruses dengue and West Nile (WN) virus. Vaccine development would be greatly facilitated by a new approach, in which nanoscale modules (Ag, adjuvant, and carrier) are assembled into units that are optimized for stimulating immune responses to a specific pathogen. Toward that goal, we formulated biodegradable nanoparticles loaded with Ag and surface modified with the pathogen-associated molecular pattern CpG oligodeoxynucleotides. We chose to evaluate our construct using a recombinant envelope protein Ag from the WN virus and tested the efficiency of this system in eliciting humoral and cellular responses and providing protection against the live virus. Animals immunized with this system showed robust humoral responses polarized toward Th1 immune responses compared with predominately Th2-biased responses with the adjuvant aluminum hydroxide. Immunization with CpG oligodeoxynucleotide-modified nanoparticles resulted in a greater number of circulating effector T cells and greater activity of Ag-specific lymphocytes than unmodified nanoparticles or aluminum hydroxide. Ultimately, compared with alum, this system offered superior protection in a mouse model of WN virus encephalitis.

Delivery of Exogenous Antigens to Induce Cytotoxic CD8+ T Lymphocyte Responses

Vaccines intended to induce a cytotoxic CD8+ T-cell response are highly sought after. However, some of these vaccines can be problematic if they replicate in the host. An alternative strategy is to exploit cross-presentation of exogenous antigens to express peptides on major histocompatibility complex (MHC) class I molecules. During cross-presentation, the delivered exogenous antigen can be taken up and processed through diverse mechanisms. Here, we will discuss the recent advances regarding the complex nature of the cross-priming process and the models that reflect its relevance in vivo. Moreover, we summarize current data that explore potential adjuvants and vaccine vectors that deliver antigens to activate CD8+ T cells relying on cross-presentation.

Cytosolic delivery mediated via electrostatic surface binding of protein, virus, or siRNA cargos to pH-responsive core-shell gel particles

We recently described a strategy for intracellular delivery of macromolecules, utilizing pH-responsive "core-shell" structured gel particles. These cross-linked hydrogel particles disrupt endosomes with low toxicity by virtue of physical sequestration of an endosome-disrupting "proton sponge" core inside a nontoxic hydrophilic shell. Here we tested the efficacy of this system for cytosolic delivery of a broad range of macromolecular cargos, and demonstrate the delivery of proteins, whole viral particles, or siRNA oligonucleotides into the cytosol of dendritic cells and epithelial cells via core-shell particles. We assessed the functional impact of particle delivery for vaccine applications and found that cytosolic delivery of protein antigens in dendritic cells via the core-shell particles promotes priming of CD8(+) T-cells at 100-fold lower doses than soluble protein. Functional gene knockdown following delivery of siRNA using the particles was demonstrated in epithelial cells. Based on these findings, these materials may be of interest for a broad range of biomedical applications.