Self-assembling CpG DNA nanoparticles for efficient antigen delivery and immunostimulation

Non-Modified CpG Oligodeoxynucleotide Forming Guanine-Quadruplex Structure Complexes with ε-Poly-L-Lysine Induce Antibody Production as Vaccine Adjuvants

Unmethylated cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODNs) induce inflammatory cytokines and type I interferons (IFNs) to activate the immune system. To apply CpG ODNs as vaccine adjuvants, the cellular uptake and stability of phosphodiester-based, non-modified ODNs require further improvement. Previously developed new CpG ODNs forming guanine-quadruplex (G4) structures showed higher nuclease resistance and cellular uptake than linear CpG ODNs; however, the complex formation of G4-CpG ODNs with antigen proteins is necessary for their application as vaccine adjuvants. In this study, we utilized a cationic polymer, ε-poly-_L-lysine (ε-PLL), as a carrier for G4-CpG ODNs and antigen. The ε-PLL/G4-CpG ODN complex exhibited enhanced stability against nucleases. Cellular uptake of the ε-PLL/G4-CpG ODN complex positively correlated with the N/P ratio. In comparison to naked G4-CpG ODNs, the ε-PLL/G4-CpG ODN complex induced extremely high levels of interleukin (IL)-6, IL-12, and IFN-β. Relative immune cytokine production was successfully tuned by N/P ratio modification. Mice with the ε-PLL/G4-CpG ODN/ovalbumin (OVA) complex showed increased OVA-specific immunoglobulin (Ig)G, IgG1, and IgG2c levels, whereas total IgE levels did not increase and weight gain rates were not affected. Therefore, ε-PLL can serve as a safe and effective phosphodiester-based, non-modified CpG ODN delivery system, and the ε-PLL/G4-CpG ODN/antigen complex is a highly promising candidate for vaccine adjuvants and can be further used in clinical research.

RNA-Cholesterol Nanoparticles Function as Potent Immune Activators via TLR7 and TLR8

The innate immune system senses viral and bacterial ribonucleic acid (RNA) via pattern recognition receptors (PRR) leading to subsequent activation of the immune system. One group of RNA sensors is formed by endosomal/lysosomal Toll-like receptors (TLR) such as TLR7 and TLR8. During viral or bacterial infection, immunostimulatory RNA is part of the pathogen reaching the endosomal/lysosomal compartment after cellular uptake. Synthetic single-stranded or double-stranded oligoribonucleotides (ORN) can mimic RNA from pathogens and are widely used as activating ligands for TLR7 and TLR8. However, one limitation in the use of synthetic ORN driven immune stimulation is the need for transfection reagents for RNA delivery into cells. Here we demonstrate that the conjugation of cholesterol to a double-stranded version of immunostimulatory RNA40 strongly enhanced RNA uptake into monocytes and plasmacytoid dendritic cells when compared to naked RNA. Cholesterol-conjugated RNA (RNA-chol) formed nanoparticles that were superior to RNA-liposomes complexes in regard to induction of type I interferon from human and murine plasmacytoid dendritic cells as well as proinflammatory cytokine production (e.g. TNF-α, IL12p70 or IL-6) in human monocytes. Furthermore, the RNA40-chol induced cytokines in human monocyte cultures supported T_H1 and T_FH cell differentiation underscoring a strong adjuvant function of RNA-chol nanoparticles for adaptive immune responses. In summary, cholesterol-conjugated immunostimulatory RNA forms nanoparticles and functions as a potent immune adjuvant in human and murine immune cells. It further simplifies the use of immunostimulatory RNA by avoiding the need for liposomal transfection reagents.

CpG incorporated DNA microparticles for elevated immune stimulation for antigen presenting cells

As emerging evidence supports the immune stimulating capability of the CpG oligodeoxynucleotides (ODN), CpG-based adjuvants have been widely used. For efficient induction of immune responses, current issues affecting the use of nucleic acid-based adjuvants, e.g. stability in physiological conditions, delivery to immune cells, and successful release within the phagolysosome, should be addressed. Here, we present CpG-based DNA microparticles (DNA-MPs) fabricated by complementary rolling circle amplification (cRCA) as adjuvants for enhancing immune response and production of selective antibody production. Using cRCA method, the sizes of CpG-based DNA-MPs were finely controlled (0.5 and 1 μm) with superior and provided mismatched single stranded form of CpG ODN region for specific cleavage site by DNase II within the phagolysosome. Fabricated CpG-based 1 μm DNA-MPs (DNA-MP-1.0) were successfully internalized into primary macrophages and macrophage cell line (RAW264.7 cells), and elicited superior cytokine production e.g. TNF-α and IL-6, compared to conventional CpG ODNs. After in vivo administration of DNA-MP-1.0 with model antigen ovalbumin (OVA), significantly elevated OVA-specific antibody production was observed. With this in mind, DNA-MP-1.0 could serve as a novel type of adjuvant for the activation of macrophages and the following production of selective antibodies without any noticeable toxicity in vitro and in vivo.

As emerging evidence supports the immune stimulating capability of the CpG oligodeoxynucleotides (ODN), CpG-based adjuvants have been widely used.

Antigen-loaded polymeric hybrid micelles elicit strong mucosal and systemic immune responses after intranasal administration

Increasing attention has been paid to nasal delivery. Subunit vaccines based on antigenic proteins or polypeptides offer good safety. However, lack of delivery efficiency, particularly for nasal immunization, is a big issue. Here we designed a highly tunable polymeric hybrid micelle (PHM) system offering good vaccine efficacy after nasal administration. PHMs are formulated from two amphiphilic diblock copolymers, polycaprolactone-polyethylenimine (PCL-PEI) and polycaprolactone-polyethyleneglycol (PCL-PEG), the ratio of which determines PHM physicochemical properties. Citraconic anhydride-modified ovalbumin (Cit-OVA), as model antigen, was incorporated into PHMs via electrostatic interaction, giving antigen-loaded micelles of around 150nm in size. Their surface characteristics which are found closely related to their in vivo kinetics can be modulated by adjusting the mass ratio of PCL-PEG and PCL-PEI. PHM/Cit-OVA complexes containing PCL-PEI and PCL-PEG in a 1:1 mass ratio induced strong immune responses in nasal mucosa and serum in vivo without causing obvious toxicity, and Cit-OVA was efficiently internalized by dendritic cells. These results demonstrate the promise of this multifunctional polymeric delivery system for nasal vaccination.

Ready-to-use colloidal adjuvant systems for intranasal immunization

Adjuvant systems based on oil-in-water (o/w) microemulsions (MEs) for vaccination via intranasal administration were prepared and evaluated. A ready-to-use blank ME system composed of mineral oil (oil), Labrasol (surfactant), Tween 80 (cosurfactant), and water was prepared and blended with antigen (Ag) solution prior to use. The o/w ME system developed exhibited nano-size droplets within the tested range of Ag concentrations and dilution factors. The maintenance of primary, secondary, and tertiary structural stability of ovalbumin (OVA) in ME, compared with OVA in solution, was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), and fluorescence intensity measurements, respectively. The uptake efficiency in RAW 264.7 cells, evaluated by flow cytometry, of OVA in the ME group was significantly higher than that of the OVA solution group (p<0.05). In an intranasal immunization study with OVA ME in mice, elevated adjuvant effects in terms of mucosal immunization and Th1-dominant cell-mediated immune responses were identified. Given the convenience of use (simply mixing with Ag solution prior to use) and the adjuvant effects after intranasal immunization, the new o/w ME may be a practical and efficient adjuvant system for intranasal vaccination.

Self-Assembled DNA Immunonanoflowers as Multivalent CpG Nanoagents

Synthetic unmethylated cytosine-guanine (CpG) oligodeoxynucleotides are immunostimulatory motifs that have shown promise as vaccines or adjuvants for diseases such as cancers and infectious diseases. In the present work, novel immuno-nanoflowers (NFs), self-assembled from long DNA integrated with tandem CpG through rolling circle replication, were developed for efficient CpG delivery and protection from nuclease degradation. In a model of macrophage-like cells, the CpG NFs proved to be potent immunostimulators by triggering the proliferation of these immune cells, which, in turn, secreted immunostimulatory cytokines, including tumor necrosis factor α, interleukin-6, and interleukin-10. These results demonstrate the ability of CpG NFs to induce cancer cell apoptosis and necrosis.

Functionalized iron oxide nanoparticles for controlling the movement of immune cells

Immunotherapy is currently being investigated for the treatment of many diseases, including cancer. The ability to control the location of immune cells during or following activation would represent a powerful new technique for this field. Targeted magnetic delivery is emerging as a technique for controlling cell movement and localization. Here we show that this technique can be extended to microglia, the primary phagocytic immune cells in the central nervous system. The magnetized microglia were generated by loading the cells with iron oxide nanoparticles functionalized with CpG oligonucleotides, serving as a proof of principle that nanoparticles can be used to both deliver an immunostimulatory cargo to cells and to control the movement of the cells. The nanoparticle-oligonucleotide conjugates are efficiently internalized, non-toxic, and immunostimulatory. We demonstrate that the in vitro migration of the adherent, loaded microglia can be controlled by an external magnetic field and that magnetically-induced migration is non-cytotoxic. In order to capture video of this magnetically-induced migration of loaded cells, a novel 3D-printed "cell box" was designed to facilitate our imaging application. Analysis of cell movement velocities clearly demonstrate increased cell velocities toward the magnet. These studies represent the initial step towards our final goal of using nanoparticles to both activate immune cells and to control their trafficking within the diseased brain.

Effective CpG DNA delivery using amphiphilic cycloamylose nanogels

Unmethylated CpG oligodeoxynucleotides induce inflammatory immune responses through cytokine production and have attracted increasing attention as an immunostimulator. However, there remains a challenging issue of the use of 'native CpG DNA'. In the present study, we prepared cationic nanometer-sized gels (nanogels) consisting of cycloamylose modified with cholesterol and diethylaminoethane to form hydrophobic cross-linking points and to add positively charged groups, respectively. The cationic nanogels and native CpG DNA formed nanometer-sized complexes. Complexes of native CpG DNA with cationic nanogels delivered native CpG DNA to macrophage-like cells and induced cytokine production. In addition, complexes of negative control oligonucleotides with cationic nanogels did not induce cytokine production, and the induction of cytokines using complexes of phosphorothioate-modified CpG with cationic nanogels was lower than that of native CpG DNA. These results suggest that the complex of native CpG DNA with cationic nanogels is a promising strategy for nucleic acid adjuvants.