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

Development of combination adjuvant for efficient T cell and antibody response induction against protein antigen

Most current clinical vaccines work primarily by inducing the production of neutralizing antibodies against pathogens. Vaccine adjuvants that efficiently induce T cell responses to protein antigens need to be developed. In this study, we developed a new combination adjuvant consisting of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP), D35, and an aluminum salt. Among the various combinations tested, the DOTAP/D35/aluminum salt adjuvant induced strong T cell and antibody responses against the model protein antigen with a single immunization. Adjuvant component and model antigen interaction studies in vitro also revealed that the strong mutual interactions among protein antigens and other components were one of the important factors for this efficient immune induction by the novel combination adjuvant. In addition, in vivo imaging of the antigen distribution suggested that the DOTAP component in the combination adjuvant formulation elicited transient antigen accumulation at the draining lymph nodes, possibly by antigen uptake DC migration. These results indicate the potential of the new combination adjuvant as a promising vaccine adjuvant candidate to treat infectious diseases and cancers.

Mesenchymal Stem Cells as a Gene Delivery Tool: Promise, Problems, and Prospects

The cell-based approach in gene therapy arises as a promising strategy to provide safe, targeted, and efficient gene delivery. Owing to their unique features, as homing and tumor-tropism, mesenchymal stem cells (MSCs) have recently been introduced as an encouraging vehicle in gene therapy. Nevertheless, non-viral transfer of nucleic acids into MSCs remains limited due to various factors related to the main stakeholders of the process (e.g., nucleic acids, carriers, or cells). In this review, we have summarized the main types of nucleic acids used to transfect MSCs, the pros and cons, and applications of each. Then, we have emphasized on the most efficient lipid-based carriers for nucleic acids to MSCs, their main features, and some of their applications. While a myriad of studies have demonstrated the therapeutic potential for engineered MSCs therapy in various illnesses, optimization for clinical use is an ongoing challenge. On the way of improvement, genetically modified MSCs have been combined with various novel techniques and tools (e.g., exosomes, spheroids, 3D-Bioprinting, etc.,) aiming for more efficient and safe applications in biomedicine.

Recent strategies for nano-based PTT combined with immunotherapy: from a biomaterial point of view

Cancer has been a great threat to humans for decades. Due to the limitations of monotherapy, combinational therapies such as photothermal therapy (PTT) and immunotherapy have gained increasing attention with expectation to overcome the shortfalls of each other and obtain satisfactory therapeutic outcomes. PTT can inhibit primary tumors by thermal ablation but usually fails to achieve complete eradication and cannot prevent metastasis and recurrence. Meanwhile, the efficacy of immunotherapy is usually attenuated by the weak immunogenicity of tumor and the immunosuppressive tumor microenvironment (ITM). Therefore, many recent studies have attempted to synergize PTT with immunotherapy in order to enhance the therapeutic efficacy. In this review, we aim to summarize the cutting-edge strategies in combining nano-based PTT with immunotherapy for cancer treatment. Herein, the combination strategies were mainly classified into four categories, including 1) nano-based PTT combined with antigens to induce host immune responses; 2) nano-based PTT in combination with immune adjuvants acting as in situ vaccines; 3) nano-based PTT synergized with immune checkpoint blockade or other regulators to relieve the ITM; 4) nano-based PTT combined with CAR-T therapy or cytokine therapy for tumor treatment. The characteristics of various photothermal agents and nanoplatforms as well as the immunological mechanisms for the synergism were also introduced in detail. Finally, we discussed the existing challenges and future prospects in combined PTT and immunotherapy.

Enhanced Immunostimulatory Activity of CpG Oligodeoxynucleotide by the Combination of Mannose Modification and Incorporation into Nanostructured DNA

The immunostimulatory activity of unmethylated cytosine-phosphate-guanine oligodeoxynucleotide (CpG ODN) could be improved via delivery to immune cells expressing Toll-like receptor 9 (TLR9). Previously, we showed that the polypod-like structured nucleic acid (polypodna), a nanostructured DNA comprised of three or more ODNs, was an efficient system for the delivery of CpG ODNs to immune cells. Because some TLR9-positive immune cells express mannose receptors (MR), the uptake of polypodna by immune cells can be further increased by its modification with mannose. In this study, we selected the phosphodiester CpG ODN, ODN1668, which has a sequence identical to CpG1668, and a hexapodna, a polypodna with six pods, to design a hexapodna that harbored ODN1668 or the mannosylated CpG ODN (Man-ODN1668) synthesized via modification of the 5'-terminal of ODN1668 with a synthesized mannose motif. By mixing ODN1668 or Man-ODN1668 with the hexapodna, ODN1668/hexapodna and Man-ODN1668/hexapodna were successfully formed with high yields. However, Man-ODN1668/hexapodna was found to induce a greater tumor necrosis factor-α release from TLR9- and MR-positive mouse peritoneal macrophages and macrophage-like J774.1 cells than Man-ODN1668 or ODN1668/hexapodna. These results indicate that the combination of mannose modification and incorporation into nanostructured DNA is a useful approach for enhancing the immunostimulatory activity of CpG ODN.

CpG Oligonucleotides as Vaccine Adjuvants

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides specifically designed to stimulate Toll-like receptor 9. TLR9 is expressed on human plasmacytoid dendritic cells and B cells and triggers an innate immune response characterized by the production of Th1 and pro-inflammatory cytokines. This chapter reviews recent progress in understanding the mechanism of action of CpG ODN and provides an overview of human clinical trial results using CpG ODN to improve vaccines for the prevention/treatment of cancer, allergy, and infectious disease.

Modulating the Tumour Microenvironment by Intratumoural Injection of Pattern Recognition Receptor Agonists

Signalling through pattern recognition receptors (PRRs) leads to strong proinflammatory responses, enhancing the activity of antigen presenting cells and shaping adaptive immune responses against tumour associated antigens. Unfortunately, toxicities associated with systemic administration of these agonists have limited their clinical use to date. Direct injection of PRR agonists into the tumour can enhance immune responses by directly modulating the cells present in the tumour microenvironment. This can improve local antitumour activity, but importantly, also facilitates systemic responses that limit tumour growth at distant sites. As such, this form of therapy could be used clinically where metastatic tumour lesions are accessible, or as neoadjuvant therapy. In this review, we summarise current preclinical data on intratumoural administration of PRR agonists, including new strategies to optimise delivery and impact, and combination studies with current and promising new cancer therapies.

Immune Responses and Antitumor Effect through Delivering to Antigen Presenting Cells by Optimized Conjugates Consisting of CpG-DNA and Antigenic Peptide

Immunotherapy using antigen-specific cytotoxic T lymphocytes (CTLs) has become one of the most attractive strategies for cancer treatment. For the induction of antigen-specific CTLs in vivo, the co-delivery of CpG-DNAs and antigens to the same antigen-presenting cells (APCs) is a promising strategy. In this study, we prepared conjugates consisting of 40mer of CpG-DNA (CpG40) and antigenic peptide (OVA_257-264), which have the following distinctive features: (1) multiple CpG motifs in a molecule; (2) cleavage in the cytosol because of the disulfide bonding via cysteine residue between peptide and CpG-DNA; (3) conjugation designed to induce antigen presentation on MHC class I molecules. Immunization with the conjugate CpG40-C-OVA_257-264 at the mouse tail base induced strong CTL activity at a very low peptide dose of 20 ng/head. It was found that the conjugates were internalized into C-type mannose receptor 1 (MRC1)-expressing cells in inguinal lymph nodes, indicating that the CpG portion in the conjugate acts as not only an adjuvant for the activation of TLR9 but also a carrier to APCs expressing MRC1. In a tumor-bearing mice model, mice immunized with CpG40-C-OVA_257-264 conjugates exhibited long delays in tumor growth compared with those treated with PBS, OVA_257-264 alone, or a mixture of CpG40 and OVA_257-264. Therefore, CpG-C-peptide conjugates could be a new and effective platform for peptide vaccine for the treatment of cancers and infectious diseases.

Toll-Like Receptor 9 Agonists in Cancer

Toll-like receptor 9 (TLR9) is a pattern recognition receptor that is predominantly located intracellularly in immune cells, including dendritic cells, macrophages, natural killer cells, and other antigen-presenting cells (APC). The primary ligands for TLR9 receptors are unmethylated cytidine phosphate guanosine (CpG) oligodinucleotides (ODN). TLR9 agonists induce inflammatory processes that result in the enhanced uptake and killing of microorganisms and cancer cells as well as the generation of adaptive immune responses. Preclinical studies of TLR9 agonists suggested efficacy both as monotherapy and in combination with several agents, which led to clinical trials in patients with advanced cancer. In these studies, intravenous, intratumoral, and subcutaneous routes of administration have been tested; with anti-tumor responses in both treated and untreated metastatic sites. TLR9 agonist monotherapy is safe, although efficacy is minimal in advanced cancer patients; conversely, combinations appear to be more promising. Several ongoing phase I and II clinical trials are evaluating TLR9 agonists in combination with a variety of agents including chemotherapy, radiotherapy, targeted therapy, and immunotherapy agents. In this review article, we describe the distribution, structure and signaling of TLR9; discuss the results of preclinical studies of TLR9 agonists; and review ongoing clinical trials of TLR9 agonists singly and in combination in patients with advanced solid tumors.

Immune profiling before treatment is predictive of TLR9-induced antitumor efficacy

TLR9 targeting has been a dynamic research field with promising potential in tumor immunotherapy. However, why most patients do not respond to TLR9 agonists remains unknown. In our attempt to resolve this issue, we observed that anti-tumor response to our TLR9-targeting cancer nanomedicines varied according to the initial immune profile of the animals. Speculating that immune profiling before treatment, including the measurement of IFN-α, IL-12, IL-6, TNF, tumor-infiltrating lymphocytes and spleen-residing lymphocytes, could be used to predictively distinguish responders from non-responders, we performed experiments in two different tumor models 4T1-BALB/c and B16-C57BL/6, to validate the hypothesis. Results confirmed that antitumor efficacy with respect to tumor growth, immune cell infiltration, and cytokines release, correlated with the different condition of individuals, as well as the categorization of the animals. This work suggests that immune profiling before treatment might be able to predict the antitumor efficacy of TLR9 agonists in vivo.

Template-Mediated Assembly of DNA into Microcapsules for Immunological Modulation

There is a need for effective vaccine delivery systems and vaccine adjuvants without extraneous excipients that can compromise or minimize their efficacy. Vaccine adjuvants cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODNs) can effectively activate immune responses to secrete cytokines. However, CpG ODNs are not stable in serum due to enzymatic cleavage and are difficult to transport through cell membranes. Herein, DNA microcapsules made of CpG ODNs arranged into 3D nanostructures are developed to improve the serum stability and immunostimulatory effect of CpG. The DNA microcapsules allow encapsulation and co-delivery of cargoes, including glycogen. The DNA capsules, with >4 million copies of CpG motifs per capsule, are internalized in cells and accumulate in endosomes, where the Toll-like receptor 9 is engaged by CpG. The capsules induce up to 10-fold and 20-fold increases in tumor necrosis factor (TNF)-α and interleukin (IL)-6 secretion, respectively, in RAW264.7 cells compared with CpG ODNs. Furthermore, the microcapsules stimulate TNF-α and IL-6 secretion in a concentration- and time-dependent manner. The immunostimulatory activity of the capsules correlates to their intracellular trafficking, endosomal confinement, and degradation, assessed by confocal and super-resolution microscopy. These DNA capsules can serve as both adjuvants to stimulate an immune reaction and vehicles to encapsulate vaccine peptides/genes to achieve synergistic immune effects.

Monomeric G-Quadruplex-Based CpG Oligodeoxynucleotides as Potent Toll-Like Receptor 9 Agonists

Synthetic oligodeoxynucleotides (ODNs) containing unmethylated cytosine-phosphate-guanine (CpG) motifs trigger the immune response by stimulating endosomal Toll-like receptor (TLR) 9. Natural linear ODNs are susceptible to nuclease degradation, thereby limiting their clinical applications. Here, we designed monomeric G-quadruplex-based CpG ODNs (G4 CpG ODNs) containing CpG motifs in the central loop region of the G4 structure. The monomeric G4 CpG ODNs were more stable in serum than the linear ODNs. The monomeric G4 CpG ODNs containing two or three CpG motifs induced the production of immunostimulatory cytokines interleukin (IL)-6, IL-12, and interferon (IFN)-β in mouse macrophage-like RAW264 cells. We also showed that the number of CpG motifs and the number of nucleotides between the CpG motif and G-tracts define the efficacy of the G4 CpG ODNs in activating TLR9. Incubating human peripheral blood mononuclear cells with G4 CpG ODNs promoted IL-6 and IFN-γ production, confirming their stimulatory effects on human immune cells. Mice given intraperitoneal injections of G4 CpG ODNs produced higher plasma IL-6 compared with injections of linear ODNs. These findings provide further understanding of the parameters governing the immunostimulatory activity of G4 CpG ODNs, thereby providing insights into the rational design of highly potent G4 CpG ODNs for vaccine adjuvants.

An overview of in silico vaccine design against different pathogens and cancer

INTRODUCTION

Due to overcome the hardness of the vaccine design, computational vaccinology is emerging widely. Prediction of T cell and B cell epitopes, antigen processing analysis, antigenicity analysis, population coverage, conservancy analysis, allergenicity assessment, toxicity prediction, and protein-peptide docking are important steps in the process of designing and developing potent vaccines against various viruses and cancers. In order to perform all of the analyses, several bioinformatics tools and online web servers have been developed. Scientists must take the decision to apply more suitable and precise servers for each part based on their accuracy.

AREAS COVERED

In this review, a wide-range list of different bioinformatics tools and online web servers has been provided. Moreover, some studies were proposed to show the importance of various bioinformatics tools for predicting and developing efficient vaccines against different pathogens including viruses, bacteria, parasites, and fungi as well as cancer.

EXPERT OPINION

Immunoinformatics is the best way to find potential vaccine candidates against different pathogens. Thus, the selection of the most accurate tools is necessary to predict and develop potent preventive and therapeutic vaccines. To further evaluation of the computational and in silico vaccine design, in vitro/in vivo analyses are required to develop vaccine candidates.

A Novel Small-Molecule Inhibitor of Endosomal TLRs Reduces Inflammation and Alleviates Autoimmune Disease Symptoms in Murine Models

Toll-like receptors (TLRs) play a fundamental role in the inflammatory response against invading pathogens. However, the dysregulation of TLR-signaling pathways is implicated in several autoimmune/inflammatory diseases. Here, we show that a novel small molecule TLR-inhibitor (TAC5) and its derivatives TAC5-a, TAC5-c, TAC5-d, and TAC5-e predominantly antagonized poly(I:C) (TLR3)-, imiquimod (TLR7)-, TL8-506 (TLR8)-, and CpG-oligodeoxynucleotide (TLR9)-induced signaling pathways. TAC5 and TAC5-a significantly hindered the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), reduced the phosphorylation of mitogen-activated protein kinases, and inhibited the secretion of tumor necrosis factor-α (TNF-α) and interleukin-6. Besides, TAC5-a prevented the progression of psoriasis and systemic lupus erythematosus (SLE) in mice. Interestingly, TAC5 and TAC5-a did not affect Pam3CSK4 (TLR1/2)-, FSL-1 (TLR2/6)-, or lipopolysaccharide (TLR4)-induced TNF-α secretion, indicating their specificity towards endosomal TLRs (TLR3/7/8/9). Collectively, our data suggest that the TAC5 series of compounds are potential candidates for treating autoimmune diseases such as psoriasis or SLE.

N-Acetyl-l-Leucine-Polyethyleneimine-Mediated Delivery of CpG Oligodeoxynucleotides 2006 Inhibits RAW264.7 Cell Osteoclastogenesis

INTRODUCTION

CpG oligodeoxynucleotides (CpG ODN) play important roles in resisting inflammation and bone resorption. However, the inherent instability and rapid degradation hinder their wider application. This study aimed to evaluate whether N-acetyl-L-leucine-modified polyethyleneimine (N-Ac-L-Leu-PEI) could effectively deliver CpG ODN 2006 to RAW264.7 cells and and if it can regulate osteoclastogenesis in vitro.

MATERIALS AND METHODS

Gel retardation assay was conducted to evaluate whether N- Ac-L-Leu-PEI and CpG ODN could form a stable complex. RAW264.7 cells were divided into four groups of control group, ODN group, phosphorothioate ODN group and N-Ac-L-Leu-PEI/ODN group. Fluorescence assay was conducted to evaluate the transfection rate of ODNs in different groups. Cell viability was determined by MTT assay. Cell apoptosis was determined by live-dead cell staining and flow cytometry assay. Relative expression levels of osteoclastic differentiation factors, including Nfatc, c-fos, receptor activator of nuclear factor κB (RANK), and matrix metalloproteinase 9 (MMP9), were determined by real-time PCR and Western blot.

RESULTS

N-Ac-L-Leu-PEI and CpG ODN could form a stable complex at a mass ratio of 1:1 (w:w). MTT assay showed that the cell viability of N-Ac-L-Leu-PEI was relatively high even at a mass ratio of 8 μg/mL. The transfection rate of N-Ac-L-Leu-PEI-ODN complex was higher than 90%. The cell proliferation and apoptosis was significantly enhanced in N-Ac-L-Leu-PEI- CpG ODN group when compared to those in phosphorothioate CpG ODN. The expression levels of Nfatc, c-fos, RANK, and MMP9 were significantly decreased in N-Ac-L-Leu-PEI/ODN complex group.

DISCUSSION

N-Ac-L-Leu-PEI could be a potential gene vehicle for the prevention of periodontitis-mediated bone resorption.

Novel Toll-Like Receptor 9 Agonist Derived from Cryptococcus neoformans Attenuates Allergic Inflammation Leading to Asthma Onset in Mice

INTRODUCTION

The enhanced type 2 helper (Th2) immune response is responsible for the pathogenesis of allergic asthma. To suppress the enhanced Th2 immune response, activation of the Th1 immune response has been an alternative strategy for anti-asthma therapy. In this context, effective Th1-inducing adjuvants that inhibit the development of allergic asthma but do not flare the side effects of the primary agent are required in clinical treatment and preventive medicine.

OBJECTIVE

In this study, we aimed to determine the regulation of the Th2 type immune response in asthma by a novel immunostimulatory oligodeoxynucleotide (ODN) derived from Cryptococcus neoformans, termed ODN112, which contains a cytosine-guanine (CG) sequence but not canonical CpG motifs.

METHODS

Using an ovalbumin-induced asthma mouse model, we assessed the effect of ODN112 on prototypical asthma-related features in the lung and on the Th1/Th2 profile in the lymph nodes and lung of mice treated with ODN112 during sensitization.

RESULTS AND CONCLUSION

ODN112 treatment attenuated asthma features in mice. In the bronchial lymph nodes of the lungs and in the spleen, ODN112 increased interferon-γ production and attenuated Th2 recall responses. In dendritic cells (DCs) after allergen sensitization, ODN112 enhanced cluster of differentiation (CD) 40 and CD80 expression but did not alter CD86 expression. Interleukin-12p40 production from DCs was also increased in a Th2-polarizing condition. Our results suggest that ODN112 is a potential Th1-inducing adjuvant during Th2 cell differentiation in the sensitization phase.

Pulmonary Delivery of Nanoparticle-Bound Toll-like Receptor 9 Agonist for the Treatment of Metastatic Lung Cancer

CpG oligodeoxynucleotides are potent toll-like receptor (TLR) 9 agonists and have shown promise as anticancer agents in preclinical studies and clinical trials. Binding of CpG to TLR9 initiates a cascade of innate and adaptive immune responses, beginning with activation of dendritic cells and resulting in a range of secondary effects that include the secretion of pro-inflammatory cytokines, activation of natural killer cells, and expansion of T cell populations. Recent literature suggests that local delivery of CpG in tumors results in superior antitumor effects as compared to systemic delivery. In this study, we utilized PRINT (particle replication in nonwetting templates) nanoparticles as a vehicle to deliver CpG into murine lungs through orotracheal instillations. In two murine orthotopic metastasis models of non-small-cell lung cancer-344SQ (lung adenocarcinoma) and KAL-LN2E1 (lung squamous carcinoma), local delivery of PRINT-CpG into the lungs effectively promoted substantial tumor regression and also limited systemic toxicities associated with soluble CpG. Furthermore, cured mice were completely resistant to tumor rechallenge. Additionally, nanodelivery showed extended retention of CpG within the lungs as well as prolonged elevation of antitumor cytokines in the lungs, but no elevated levels of proinflammatory cytokines in the serum. These results demonstrate that PRINT-CpG is a potent nanoplatform for local treatment of lung cancer that has collateral therapeutic effects on systemic disease and an encouraging toxicity profile and may have the potential to treat lung metastasis of other cancer types.

Construction of Monomeric and Dimeric G-Quadruplex-Structured CpG Oligodeoxynucleotides for Enhanced Uptake and Activation in TLR9-Positive Macrophages

The G-quadruplex (GQ) structure has potential applications in nucleic acid drug delivery because of its superior stability. In this study, we added one G-tract (five guanines) to an unmethylated phosphodiester-linked cytosine-phosphate-guanine oligodeoxynucleotide (CpG ODN), a potential immune adjuvant, to construct a GQ-structured CpG ODN with precise structural properties, increased biological stability, and efficient delivery to Toll-like receptor 9 (TLR9)-positive immune cells. A G-tract was added to phosphodiester-backboned CpG1668 at the 5'-end [1668(5'-G₅)], 3'-end [1668(3'-G₅)], or within the sequence [1668(mid-G₅)]. Circular dichroism analysis showed that all CpG ODNs with a G-tract formed parallel GQ structures, irrespective of its position. Electrophoresis showed that 1668(5'-G₅) formed a GQ dimer, whereas others remained GQ monomers. GQ-structured CpG ODNs induced greater tumor necrosis factor-α and interleukin-6 secretion from TLR9-positive mouse macrophage-like RAW264.7 cells than single-stranded CpG ODNs, with the highest for 1668(3'-G₅). GQ structuration increased CpG ODN uptake by RAW264.7 cells, and 1668(3'-G₅) decomposed more slowly in serum than 1668(5'-G₅). Thus, GQ formation with one G-tract is a simple and efficient strategy for CpG ODN delivery to TLR9-positive cells, and addition of a G-tract to the 3'-end is effective in obtaining monomeric GQ-structured CpG ODN with high biological stability and immunostimulatory activity.

Adjuvant Effect of Toll-Like Receptor 9 Activation on Cancer Immunotherapy Using Checkpoint Blockade

Immunotherapy using checkpoint blockade has revolutionized cancer treatment, improving patient survival and quality of life. Nevertheless, the clinical outcomes of such immunotherapy are highly heterogeneous between patients. Depending on the cancer type, the patient response rates to this immunotherapy are limited to 20–30%. Based on the mechanism underlying the antitumor immune response, new therapeutic strategies have been designed with the aim of increasing the effectiveness and specificity of the antitumor immune response elicited by checkpoint blockade agents. The activation of toll-like receptor 9 (TLR9) by its synthetic agonists induces the antitumor response within the innate immunity arm, generating adjuvant effects and priming the adaptive immune response elicited by checkpoint blockade during the effector phase of tumor-cell killing. This review first describes the underlying mechanisms of action and current status of monotherapy using TLR9 agonists and immune checkpoint inhibitors for cancer immunotherapy. The rationale for combining these two agents is discussed, and evidence indicating the current status of such combination therapy as a novel cancer treatment strategy is presented.

Biodegradable PLGA-b-PEG Nanoparticles Induce T Helper 2 (Th2) Immune Responses and Sustained Antibody Titers via TLR9 Stimulation

Sustained immune responses, particularly antibody responses, are key for protection against many endemic infectious diseases. Antibody responses are often accompanied by T helper (Th) cell immunity. Herein we study small biodegradable poly (ethylene glycol)-b-poly (lactic-co-glycolic acid) nanoparticles (PEG-b-PLGA NPs, 25-50 nm) as antigen- or adjuvant-carriers. The antigen carrier function of PEG-b-PLGA NPs was compared against an experimental benchmark polystyrene nanoparticles (PS NPs, 40-50 nm), both conjugated with the model antigen ovalbumin (OVA-PS NPs, and OVA-PEG-b-PLGA NPs). The OVA-PEG-b-PLGA NPs induced sustained antibody responses to Day 120 after two immunizations. The OVA-PEG-b-PLGA NPs as a self-adjuvanting vaccine further induced IL-4 producing T-helper cells (Th2), but not IFN-γ producing T-cells (Th1). The PEG-b-PLGA NPs as a carrier for CpG adjuvant (CpG-PEG-b-PLGA NPs) were also tested as mix-in vaccine adjuvants comparatively for protein antigens, or for protein-conjugated to PS NPs or to PEG-b-PLGA NPs. While the addition of this adjuvant NP did not further increase T-cell responses, it improved the consistency of antibody responses across all immunization groups. Together these data support further development of PEG-b-PLGA NPs as a vaccine carrier, particularly where it is desired to induce Th2 immunity and achieve sustained antibody titers in the absence of affecting Th1 immunity.

Synthesis of protein conjugates adsorbed on cationic liposomes surface

The well-known Toll like receptor 9 (TLR9) agonist CpG ODN has shown promising results as vaccine adjuvant in preclinical and clinical studies, however its in vivo stability and potential systemic toxicity remain a concern. In an effort to overcome these issues, different strategies have been explored including conjugation of CpG ODN with proteins or encapsulation/adsorption of CpG ODN into/onto liposomes. Although these methods have resulted in enhanced immunopotency compared to co-administration of free CpG ODN and antigen, we believe that this effect could be further improved. Here, we designed a novel delivery system of CpG ODN based on its conjugation to serve as anchor for liposomes. Thiol-maleimide chemistry was utilised to covalently ligate model protein with the CpG ODN TLR9 agonist. Due to its negative charge, the protein conjugate readily electrostatically bound cationic liposomes composed of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol and dimethyldioctadecylammonium bromide (DDA) in a very high degree. The novel cationic liposomes-protein conjugate complex shared similar vesicle characteristics (size and charge) compared to free liposomes. The conjugation of CpG ODN to protein in conjunction with adsorption on cationic liposomes, could promote co-delivery leading to the induction of immune response at low antigen and CpG ODN doses.•

The CpG ODN Toll-like receptor (TLR) 9 agonist was conjugated to protein antigens via thiol-maleimide chemistry.

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Due to their negative charge, protein conjugates readily electrostatically bound cationic liposomes composed of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol and dimethyldioctadecylammonium bromide (DDA) resulting to the design of novel cationic liposomes-protein conjugate complexes.

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The method is suited for the liposomal delivery of a variety of adjuvant-protein conjugates.

Low molecular weight chitosan nanoparticles for CpG oligodeoxynucleotides delivery: Impact of molecular weight, degree of deacetylation, and mannosylation on intracellular uptake and cytokine induction

Although synthetic CpG oligodeoxynucleotides (ODNs) have shown substantial potential as immunotherapeutic agents, their effective intracellular delivery remains challenging. In this work, nanoparticles prepared from low-molecular weight (LMW) chitosans were investigated as CpG ODN delivery systems. Chitosan samples with a molecular weight (M_w) of 5 and 15 kDa and degree of deacetylation (DDA) of 50 and 80% were prepared. Additionally, mannosylated chitosans with a substitution degree of 15% were synthesized. The impact of LMW chitosan M_w and DDA on nanoparticle physical properties and the associated immunostimulatory effect in RAW 264.7 cells was studied. Nanoparticles prepared with chitosan of higher DDA and larger M_w exhibited better CpG ODN binding ability and intracellular uptake. Nevertheless, the most efficient immunostimulatory effect was observed while using 50% acetylated and mannosylated samples. The decreased charge density on chitosan backbone resulted in the enhanced intracellular CpG ODN release, which promoted in vitro cytokine secretion. Moreover, mannose ligand grafting promoted nanoparticle uptake through receptor-mediated recognition. Overall, this research suggests that chitosan structural parameters can be modulated to prepare LMW chitosan nanoparticles that first efficiently encapsulate CpG ODN, and then release it in immune cells, thus may be used as an efficient vector for intracellular CpG ODN delivery.

Polyamide Backbone Modified Cell Targeting and Penetrating Peptides in Cancer Detection and Treatment

Cell penetrating and targeting peptides (CPPs and CTPs) encompass an important class of biochemically active peptides owning the capabilities of targeting and translocating within selected cell types. As such, they have been widely used in the delivery of imaging and therapeutic agents for the diagnosis and treatment of various diseases, especially in cancer. Despite their potential utility, first generation CTPs and CPPs based on the native peptide sequences are limited by poor biological and pharmacological properties, thereby restricting their efficacy. Therefore, medicinal chemistry approaches have been designed and developed to construct related peptidomimetics. Of specific interest herein, are the design applications which modify the polyamide backbone of lead CTPs and CPPs. These modifications aim to improve the biochemical characteristics of the native peptide sequence in order to enhance its diagnostic and therapeutic capabilities. This review will focus on a selected set of cell penetrating and targeting peptides and their related peptidomimetics whose polyamide backbone has been modified in order to improve their applications in cancer detection and treatment.

Class C CpG Oligodeoxynucleotide Immunomodulatory Response in Aged Squirrel Monkey (Saimiri Boliviensis Boliviensis)

One means of stimulating the mammalian innate immune system is via Toll-like receptor 9 (TLR9) being exposed to unmethylated cytosine-phosphate-guanine (CpG) DNA, also known as pathogen-associated molecular patterns (PAMPs) of microbial origin. Synthetic CpG oligodeoxynucleotides (ODNs) with defined CpG motifs possess broad immunostimulatory properties that make CpG ODNs suitable as therapeutic interventions in a variety of human disease conditions, including Alzheimer's disease (AD). Rodent models are often used to preclinically test the effectiveness of CpG ODN therapeutic agents for AD and other disorders. However, the translatability of findings in such models is limited due to the significant difference of the expression of TLR9 between primates and rodents. The squirrel monkey (SQM), a New World non-human primate (NHP), is known to be phylogenetically proximate to humans, and develops extensive age-dependent cerebral amyloid angiopathy (CAA), a key pathological feature of AD. Hence, this model is currently being used to test AD therapeutics. In the present study, we conducted the first examination of Class C CpG ODN's immunomodulatory role in elderly SQMs. We documented the effectiveness of CpG ODN to trigger an immune response in an aged cohort whose immune system is senescent. The specific immune response patterns detected here closely resembled CpG ODN-induced immunostimulatory patterns observed in prior human studies. Overall, our findings provide critical data regarding the immunomodulatory potential of CpG ODN in this NHP model, allowing for future translational studies of innate immunity stimulation via TLR9 agonists for diverse indications, including AD therapeutics.

Protective cellular immune response against hepatitis C virus elicited by chimeric protein formulations in BALB/c mice

The eradication of hepatitis C virus (HCV) infection is a public health priority. Despite the efficiency of treatment with direct-acting antivirals, the high cost of the therapy and the lack of accurate data about the HCV-infected population worldwide constitute important factors hampering this task. Hence, an affordable preventive vaccine is still necessary for reducing transmission and the future disease burden globally. In this work, chimeric proteins (EnvCNS3 and NS3EnvCo) encompassing conserved and immunogenic epitopes from the HCV core, E1, E2 and NS3 proteins were produced in Escherichia coli, and their immunogenicity was evaluated in BALB/c mice. The impact of recombinant HCV E2.680 protein and oligodeoxynucleotide 39M (ODN39M) on the immune response to chimeric proteins was also assessed. Immunization with chimeric proteins mixed with E2.680 enhanced the antibody and cellular response against HCV antigens and chimeric proteins. Interestingly, the combination of NS3EnvCo with E2.680 and ODN39M as adjuvant elicited a potent antibody response characterized by an increase in antibodies of the IgG2a subclass against E2.680, NS3 and chimeric proteins, suggesting the induction of a Th1-type response. Moreover, a cytotoxic T lymphocyte response and a broad response of IFN-γ-secreting cells against HCV antigens were induced with this formulation as well. This T cell response was able to protect vaccinated mice against challenge with a surrogate model based on HCV recombinant vaccinia virus. Overall, the vaccine candidate NS3EnvCo/E2.680/ODN39M might constitute an effective immunogen against HCV with potential for reducing the likelihood of viral persistence.

Lipid Nanoparticles Potentiate CpG-Oligodeoxynucleotide-Based Vaccine for Influenza Virus

Current influenza vaccines are generally effective against highly similar (homologous) strains, but their effectiveness decreases markedly against antigenically mismatched (heterologous) strains. One way of developing a universal influenza vaccine with a broader spectrum of protection is to use appropriate vaccine adjuvants to improve a vaccine's effectiveness and change its immune properties. Oligodeoxynucleotides (ODNs) with unmethylated cytosine-phosphate-guanine (CpG) motifs (CpG ODNs), which are Toll-like-receptor 9 (TLR9) agonists, are among the most promising adjuvants and are already being used in humans. However, the development of novel delivery vehicles to improve adjuvant effects in vivo is highly desirable. Here, we assessed the potential of lipid nanoparticles (LNPs) as CpG ODN delivery vehicles in mice to augment the vaccine adjuvant effects of CpG ODN and enhance the protective spectrum of conventional influenza split vaccine (SV). In vitro, compared with CpG ODN, LNPs containing CpG ODNs (LNP-CpGs) induced significantly greater production of cytokines such as IL-12 p40 and IFN-α by mouse dendritic cells (DCs) and significantly greater expression of the co-stimulatory molecules CD80 and CD86 on DCs. In addition, after subcutaneous administration in mice, compared with CpG ODN, LNP-CpGs enhanced the expression of CD80 and CD86 on plasmacytoid DCs in draining lymph nodes. LNP-CpGs given with SV from H1N1 influenza A virus improved T-cell responses and gave a stronger not only SV-specific but also heterologous-virus-strain-specific IgG2c response than CpG ODN. Furthermore, immunization with SV plus LNP-CpGs protected against not only homologous strain challenge but also heterologous and heterosubtypic strain challenge, whereas immunization with SV plus CpG ODNs protected against homologous strain challenge only. We therefore demonstrated that LNP-CpGs improved the adjuvant effects of CpG ODN and broadened the protective spectrum of SV against influenza virus. We expect that this strategy will be useful in developing adjuvant delivery vehicles and universal influenza vaccines.

Adoptive cellular immunotherapy of tumors via effective CpG delivery to dendritic cells using dendrimer-entrapped gold nanoparticles as a gene vector

PEGylated Au DENPs ({(Au⁰)₂₅-G5·NH₂-mPEG₂₀}) are synthesized and used as a novel nonviral vector to deliver CpG to mature BMDCs for the subsequent activation of T cells for adoptive tumor immunotherapy.

A cationic amphiphilic co-polymer as a carrier of nucleic acid nanoparticles (Nanps) for controlled gene silencing, immunostimulation, and biodistribution

Programmable nucleic acid nanoparticles (NANPs) provide controlled coordination of therapeutic nucleic acids (TNAs) and other biological functionalities. Beyond multivalence, recent reports demonstrate that NANP technology can also elicit a specific immune response, adding another layer of customizability to this innovative approach. While the delivery of nucleic acids remains a challenge, new carriers are introduced and tested continuously. Polymeric platforms have proven to be efficient in shielding nucleic acid cargos from nuclease degradation while promoting their delivery and intracellular release. Here, we venture beyond the delivery of conventional TNAs and combine the stable cationic poly-(lactide-co-glycolide)-graft-polyethylenimine with functionalized NANPs. Furthermore, we compare several representative NANPs to assess how their overall structures influence their delivery with the same carrier. An extensive study of various formulations both in vitro and in vivo reveals differences in their immunostimulatory activity, gene silencing efficiency, and biodistribution, with fibrous NANPs advancing for TNA delivery.

Silk Fibroin for CpG Oligodeoxynucleotide Delivery

CpG oligodeoxynucleotides (ODNs) have attracted increasing attention as immunotherapeutic agents. However, efficient transfection of CpG ODNs into the immune cells remains a big challenge. In this study, for the first time, we reported that silk fibroin (SF) could function as an efficient carrier for CpG ODNs. A novel strategy was developed to prepare SF-CpG ODNs nanoparticles (NPs) based on self-assembly of SF. The as-prepared SF-CpG NPs were spherical in shape and were uniformly dispersed. SF-CpG NPs exhibited good stability and biocompatibility. SF-CpG NPs possessed significantly enhanced (7 folds) cellular uptake compared with CpG ODNs. Release of CpG ODNs from SF-CpG NPs was accelerated in environment-mimicking TLR9-localized endo/lysosome. SF-CpG NPs stimulated about four folds higher levels of immune cytokines and nitric oxide compared with CpG ODNs. Our results suggested that SF notably improved the CpG ODNs delivery. SF-CpG NPs have strong potential in immunotherapy.

Immunostimulatory Activities of CpG-Oligodeoxynucleotides in Teleosts: Toll-Like Receptors 9 and 21

Toll-like receptors (TLRs) are pattern-recognition receptors that detect a wide variety of microbial pathogens for the initiation of host defense immunological responses. Thirteen TLRs have been identified in mammals, and teleosts contain 22 mammalian or non-mammalian TLRs. Of these, TLR9 and TLR21 are the cytosine-phosphate-guanosine-oligodeoxynucleotides (CpG-ODNs) recognition TLRs in teleosts. TLR9 is a mammalian TLR expressed in teleost but not in the avian species. TLR21 is a non-mammalian TLR expressed in both teleost and the avian species. Synthetic CpG-ODNs are potent immunostimulants that are being studied for their application against tumors, allergies, and infectious diseases, and as a vaccine adjuvant in humans. The immunostimulatory effects of CpG-ODNs as vaccine adjuvants and their antimicrobial function in domestic animals and teleosts are also being investigated. Most of our current knowledge about the molecular basis for the immunostimulatory activity of CpG-ODNs comes from earlier studies of the interaction between CpG-ODN and TLR9. More recent studies indicate that in addition to TLR9, TLR21 is another receptor for CpG-ODN recognition in teleosts to initiate immune responses. Whether these two receptors have differential functions in mediating the immunostimulatory activity of CpG-ODN in teleost has not been well-studied. Nevertheless, the existence of two recognition TLRs suggests that the molecular basis for the immunostimulatory activity of CpG-ODN in teleosts is different and more complex than in mammals. This article reviews the current knowledge of TLR9 and TLR21 activation by CpG-ODNs. The key points that need to be considered for CpG-ODNs as immunostimulants with maximum effectiveness in activation of immune responses in teleosts are discussed. This includes the structure/activity relationship of CpG-ODN activities for TLR9 and TLR21, the structure/functional relationship of these two TLRs, and differential expression levels and tissue distributions for these two TLRs.

Class-B CpG-ODN Formulated With a Nanostructure Induces Type I Interferons-Dependent and CD4+ T Cell-Independent CD8+ T-Cell Response Against Unconjugated Protein Antigen

There is a need for new vaccine adjuvant strategies that offer both vigorous antibody and T-cell mediated protection to combat difficult intracellular pathogens and cancer. To this aim, we formulated class-B synthetic oligodeoxynucleotide containing unmethylated cytosine-guanine motifs (CpG-ODN) with a nanostructure (Coa-ASC16 or coagel) formed by self-assembly of 6-0-ascorbyl palmitate ester. Our previous results demonstrated that mice immunized with ovalbumin (OVA) and CpG-ODN formulated with Coa-ASC16 (OVA/CpG-ODN/Coa-ASC16) elicited strong antibodies (IgG1 and IgG2a) and Th1/Th17 cellular responses without toxic systemic effects. These responses were superior to those induced by a solution of OVA with CpG-ODN or OVA/CpG-ODN formulated with aluminum salts. In this study, we investigated the capacity of this adjuvant strategy (CpG-ODN/Coa-ASC16) to elicit CD8+ T-cell response and some of the underlying cellular and molecular mechanisms involved in adaptive response. We also analyzed whether this adjuvant strategy allows a switch from an immunization scheme of three-doses to one of single-dose. Our results demonstrated that vaccination with OVA/CpG-ODN/Coa-ASC16 elicited an antigen-specific long-lasting humoral response and importantly-high quality CD8+ T-cell immunity with a single-dose immunization. Moreover, Coa-ASC16 promoted co-uptake of OVA and CpG-ODN by dendritic cells. The CD8+ T-cell response induced by OVA/CpG-ODN/Coa-ASC16 was dependent of type I interferons and independent of CD4+ T-cells, and showed polyfunctionality and efficiency against an intracellular pathogen. Furthermore, the cellular and humoral responses elicited by the nanostructured formulation were IL-6-independent. This system provides a simple and inexpensive adjuvant strategy with great potential for future rationally designed vaccines.

Modified Fe3O4 Magnetic Nanoparticle Delivery of CpG Inhibits Tumor Growth and Spontaneous Pulmonary Metastases to Enhance Immunotherapy

As a novel toll-like receptor 9 (TLR9) agonist, synthetic unmethylated cytosine-phosphate-guanine (CpG) oligodeoxynucleotides can stimulate a Th1 immune response and potentially be used as therapeutic agents or vaccine adjuvants for the treatment of cancer. However, some drawbacks of CpG limit their applications, such as rapid elimination by nuclease-mediated degradation and poor cellular uptake. Therefore, repeat high-dose drug administration is required for treatment. In this work, a CpG delivery system based on 3-aminopropyltriethoxysilane (APTES)-modified Fe₃O₄ nanoparticles (FeNPs) was designed and studied for the first time to achieve better bioactivity of CpG. In our results, we designed FeNP-delivered CpG particles (FeNP/CpG) with a small average size of approximately 50 nm by loading CpG into FeNPs. The FeNP/CpG particle delivery system, with enhanced cell uptake of CpG in bone marrow-derived dendritic cells (BMDCs) in vitro and through intratumoral injection, showed significant antitumor ability by stimulating better humoral and cellular immune responses in C26 colon cancer and 4T1 breast cancer xenograft models in vivo over those of free CpG. Moreover, mice treated by FeNP/CpG particles had delayed tumor growth with an inhibitory rate as high as 94.4%. In addition, approximately 50% of the tumors in the C26 model appeared to regress completely. Similarly, there were lower pulmonary metastases and a 69% tumor inhibitory rate in the 4T1 breast cancer tumor model than those in the untreated controls. In addition to their effectiveness, the easy preparation, safety, and high stability of FeNP/CpG particles also make them an attractive antitumor immunotherapy.

BN nanospheres functionalized with mesoporous silica for enhancing CpG oligodeoxynucleotide-mediated cancer immunotherapy

CpG oligodeoxynucleotides (CpG ODNs) possess strong immunostimulatory activity, which hold great promise in cancer immunotherapy. However, their therapeutic efficacy is largely limited due to nuclease degradation and poor cellular internalization. Efficiently delivering CpG ODNs into target cells is crucial to improve their therapeutic efficacy. Boron nitride nanospheres (BNNS) possess advantage as carriers for CpG ODNs. However, their poor aqueous dispersity and low CpG ODN loading capacity became a big obstacle for further applications. Herein, we develop amino group grafted, mesoporous silica (MS)-functionalized BNNS as novel nanovectors for CpG ODN delivery. Modification of BNNS with MS significantly improved the dispersity of BNNS and CpG ODN loading. BNNS@MS-NH2 exhibited no cytotoxicity and enhanced the delivery of CpG ODNs into macrophages. BNNS@MS-NH2/CpG ODN complexes triggered enhanced immunostimulation and induced higher amounts of cytokines. Most importantly, BNNS@MS-NH2/CpG ODN complexes induced bifurcated cytokines, which simultaneously simulated the secretion of IL-6, TNF-α and IFN-α. In contrast, CpG ODN and BNNS/CpG ODN complexes could not. The result of the Transwell plate assay suggested that BNNS@MS-NH2/CpG ODN complexes were more effective in inhibiting cancer cell growth. Taken together, our findings provide a promising strategy for enhancing CpG ODN-mediated cancer immunotherapy.

Nanoparticle-based CpG-oligonucleotide therapy for treating allergic asthma

Allergic asthma is becoming increasingly prevalent in the developed world, and many common allergens are capable of inducing allergic asthma responses, particularly in atopic individuals. Unmethylated CpG-oligonucleotide (ODN) therapy can shift the immune response to mitigate these allergic responses. Therapeutic and prophylactic delivery of soluble CpG-ODN in preclinical studies has shown promise in treating existing asthma and preventing allergic responses upon subsequent allergen exposure, respectively. However, when CpG-ODN is coupled with nanoparticles or self assembled into nanostructures, improved efficacy of CpG-ODN treatment for several common allergens is observed in preclinical studies and clinical trials. Here we discuss the role of CpG-ODN in treating allergic asthma and how nanoparticle-based delivery can further enhance its therapeutic properties.

Site-Specific DBCO Modification of DEC205 Antibody for Polymer Conjugation

The design of multifunctional polymer-based vectors, forming pDNA vaccines, offers great potential in cancer immune therapy. The transfection of dendritic immune cells (DCs) with tumour antigen-encoding pDNA leads to an activation of the immune system to combat tumour cells. In this work, we investigated the chemical attachment of DEC205 antibodies (aDEC205) as DC-targeting structures to polyplexes of P(Lys)-b-P(HPMA). The conjugation of a synthetic block copolymer and a biomacromolecule with various functionalities (aDEC205) requires bioorthogonal techniques to avoid side reactions. Click chemistry and in particular the strain-promoted alkyne-azide cycloaddition (SPAAC) can provide the required bioorthogonality. With regard to a SPAAC of both components, we firstly synthesized two different azide-containing block copolymers, P(Lys)-b-P(HPMA)-N₃(stat) and P(Lys)-b-P(HPMA)-N₃(end), for pDNA complexation. In addition, the site-specific incorporation of ring-strained dibenzocyclooctyne (DBCO) moieties to the DEC205 antibody was achieved by an enzymatic strategy using bacterial transglutaminase (BTG). The chemical accessibility of DBCO molecules within aDEC205 as well as the accessibility of azide-functionalities on the polyplex' surface were investigated by various SPAAC experiments and characterized by fluorescence correlation spectroscopy (FCS).

Oral administration of PLGA-encapsulated CpG ODN and Campylobacter jejuni lysate reduces cecal colonization by Campylobacter jejuni in chickens

Campylobacter jejuni (C. jejuni) is a major cause of bacterial food-borne illness in humans. It is considered a commensal organism of the chicken gut and infected chickens serve as a reservoir and shed bacteria throughout their lifespan. Contaminated poultry products are considered the major source of infection in humans. Therefore, to reduce the risk of human campylobacteriosis, it is essential to reduce the bacterial load in poultry products. The present study aimed to evaluate the protective effects of soluble and PLGA-encapsulated oligodeoxynucleotides (ODN) containing unmethylated CpG motifs (E-CpG ODN) as well as C. jejuni lysate as a multi-antigen vaccine against colonization with C. jejuni. The results revealed that oral administration of a low (5 µg) or high (50 µg) dose of CpG resulted in a significant reduction in cecal C. jejuni colonization by 1.23 and 1.32 log₁₀ (P < .05) in layer chickens, respectively, whereas E-CpG significantly reduced cecal C. jejuni colonization by 1.89 and 1.46 log₁₀ in layer and broiler chickens at day 22 post-infection (slaughter age in broilers), respectively. Similar patterns were observed for C. jejuni lysate; oral administration of C. jejuni lysate reduced the intestinal burden of C. jejuni in layer and broiler chickens by 2.24 and 2.14 log₁₀ at day 22 post-infection, respectively. Moreover, the combination of E-CpG and C. jejuni lysate reduced bacterial counts in cecal contents by 2.42 log₁₀ at day 22 post-infection in broiler chickens. Anti-C. jejuni IgG antibody (Ab) titers were significantly higher for broiler chickens receiving a low or high dose of E-CpG or a low dose of C. jejuni lysate than for chickens receiving the placebo. Furthermore, a positive correlation was observed between serum IgG Ab titers and cecal counts of C. jejuni in these groups. These findings suggest that PLGA-encapsulated CpG or C. jejuni lysate could be a promising strategy for control of C. jejuni in chickens.

Retardation of Antigen Release from DNA Hydrogel Using Cholesterol-Modified DNA for Increased Antigen-Specific Immune Response

Our previous study indicates that cationization of an antigen is effective for sustained release of both immunostimulatory DNA containing unmethylated cytosine-phosphate-guanine (CpG) dinucleotides, or CpG DNA, and antigen from a DNA hydrogel. Another approach to sustained antigen release would increase the applicability and versatility of the system. In this study, a hydrophobic interaction-based sustained release system of ovalbumin (OVA), a model antigen, from immunostimulatory CpG DNA hydrogel is developed by the use of cholesterol-modified DNA and urea-denatured OVA (udOVA). Cholesterol-modified DNA forms a hydrogel, Dgel(chol), and induces IL-6 mRNA expression in mouse skin after intradermal injection, as DNA without cholesterol does. Cholesterol-modified DNA associated with OVA and denaturation of OVA using urea increases the interaction. The release of udOVA from Dgel(chol) is significantly slower than that from DNA hydrogel with no cholesterol, Dgel. Moreover, intratumoral injections of udOVA/Dgel(chol) significantly inhibit the growth of EG7-OVA tumors in mice. These results indicate that sustained release of antigen from Dgel can be achieved by the combination of urea denaturation and cholesterol modification, and retardation of antigen release is effective to induce antigen-specific cancer immunity.

Nanoscale Zeolitic Imidazolate Framework-8 as Efficient Vehicles for Enhanced Delivery of CpG Oligodeoxynucleotides

CpG oligodeoxynucleotides (ODNs) activate the immune system and induce Th 1 responses by stimulation of Toll-like receptor 9 (TLR9). Thus, CpG ODNs have become immunotherapeutics against various diseases including cancers, allergies, and infection. However, applications of CpG ODNs are largely limited because of their easy degradation by DNase as well as inefficient cellular uptake. Development of efficient delivery systems capable of transferring CpG ODNs into immune cells is important to enhance their therapeutic efficacy. Herein, for the first time, we demonstrated the construction of a novel CpG ODNs delivery system by encapsulating CpG ODNs into zeolitic imidazolate framework-8 (ZIF-8) nanoparticles. ZIF-8 possessed high CpG ODNs loading capacity due to its porous structure. ZIF-8/CpG ODNs complexes exhibited good stability in a physiological environment but effectively released CpG ODNs in acid conditions corresponding to the TLR 9-localized endolysosomes. ZIF-8/CpG ODNs complexes had no cytotoxicity in contrast to ZIF-8. ZIF-8 significantly increased the intracellular uptake of CpG ODNs in RAW264.7 cells, which further enhanced the secretion of immune cytokines both in vitro and in vivo. Our results suggest that nanoscale metal-organic frameworks (MOFs) can serve as ideal vehicles for the delivery of CpG ODNs.

CpG loaded MoS2 nanosheets as multifunctional agents for photothermal enhanced cancer immunotherapy

Single or few-layered MoS₂ nanosheets, as a novel class of 2D nanomaterials, have received tremendous attention due to their fantastic physical and chemical properties. Here, we fabricated MoS₂-PEG-CpG with a small and uniform size as a multifunctional platform for photothermal enhanced immunotherapy. MoS₂ nanosheets were fabricated by chemical exfoliation and further probe sonication. To realize MoS₂-based adjuvant delivery, MoS₂ nanosheets were functionalized with cytosine-phosphate-guanine (CpG) and polyethylene glycol (PEG) to form MoS₂-PEG-CpG nanoconjugates. As an efficient nanocarrier with excellent near infrared-light (NIR) absorbing performance, MoS₂-PEG-CpG significantly promotes CpG intracellular accumulation and the effect can be further enhanced by photothermal treatment. In addition, the enhanced uptake can stimulate the production of proinflammatory cytokines and remarkably elevate the immune response level. Finally, we found that MoS₂-PEG-CpG could reduce the proliferative activity of cancer cells when co-cultured with a macrophage-like cell upon NIR irradiation, implying a novel strategy for multifunctional therapeutics against cancers.

Enhancing the osteogenic capacity of MG63 cells through N-isopropylacrylamide-modified polyethylenimine-mediated oligodeoxynucleotide MT01 delivery

The delivery of MT01 into MG63 cells was successfully achieved using the PEN derivative.

Development of CpG ODN Based Vaccine Adjuvant Formulations

Development of effective vaccine mediated immune responses relies on the use of vaccine adjuvants capable of enhancing and directing the adaptive immune response to the antigen. When used as vaccine adjuvants, type I interferon inducing agents can elicit potent effector/memory T cell responses and humoral immunity. Distinct sequences of single stranded synthetic oligodeoxynucleotides containing unmethylated cytosine-phosphate-guanine oligodeoxynucleotide motifs (CpG ODN) can generate type I interferon production via a TLR9-MyD88-IRF7-mediated signaling pathway. Here, we describe two different methods of preparing CpG ODN-based vaccine adjuvant formulations that can induce a robust IFNα response from human peripheral blood mononuclear cells.

Graphene oxide-chitosan nanocomposites for intracellular delivery of immunostimulatory CpG oligodeoxynucleotides

CpG oligodeoxynucleotides (ODNs) activate innate and adaptive immune responses, and show strong potential as immunotherapeutic agents against various diseases. Benefiting from their unique physicochemical properties, graphene oxide (GO) has recently attracted great attention in nanomedicine. In this study, we developed a novel CpG ODNs delivery system based on GO-chitosan (GO-CS) nanocomposites. GO-CS nanocomposites were prepared by self-assembly of both components via electrostatic interactions. Compared with GO, GO-CS nanocomposites possessed smaller size, positive surface charge and lower cytotoxicity. CpG ODNs were loaded onto GO-CS nanocomposites via electrostatic interactions. GO-CS nanocomposites greatly improved the loading capacity and cellular uptake of CpG ODNs. GO-CS/CpG ODNs complexes further resulted in an enhanced interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) production compared with that of free CpG ODNs and GO/CpG ODNs complexes. Therefore, GO-CS nanocomposites can serve as efficient nanocarriers for enhancing the delivery efficiency of CpG ODNs.

Induction of a balanced Th1/Th2 immune responses by co-delivery of PLGA/ovalbumin nanospheres and CpG ODNs/PEI-SWCNT nanoparticles as TLR9 agonist in BALB/c mice

To develop effective and safe vaccines with reduced dose of antigen and adjuvant, intelligent delivery systems are required. Many delivery systems have been developed to enhance the biological activity of cytosine-phosphorothioate-guanine oligodeoxynucleotides (CpG ODN) as both immunotherapeutic agents and vaccine adjuvants. In this study we designed a novel CpG ODN delivery system based on single-walled carbon nanotube (SWCNT) functionalized with polyethylenimine (PEI) and alkylcarboxylated PEI (AL-PEI). The physicochemical characteristics, cytotoxicity and cellular uptake studies of these carriers were performed. All carriers were conjugated with CpG ODN followed by co-delivery with ovalbumin (OVA) encapsulated into poly (lactic-co-glycolic acid) nanospheres (PLGA NSs) to enhance the induction of immune responses. The effect of these formulations on antibody (IgG1, IgG2a) and cytokine (IL-1β, IFN-γ, IL-4) production was evaluated in an in vivo experiment. The results showed that all nano-adjuvant formulations had a strong influence in up-regulation of IFN-γ and IL-4 in parallel with high IgG1-IgG2a isotype antibody titers in mice. In particular, SWCNT-AL-PEI nano-adjuvant formulation generated a balanced Th1 and Th2 immune response with more biased toward Th1 response without exhibiting any inflammatory and toxic effects. Therefore this nano-adjuvant formulation could be used as an efficient prophylactic immune responses agent.

Optimisation of one-step desolvation and scale-up of gelatine nanoparticle production

Gelatine nanoparticles (GNPs) are biodegradable and biocompatible drug delivery systems with excellent clinical performances. A two-step desolvation is commonly used for their preparation, although this methodology has several shortcomings: lack of reproducibility, small scales and low yields. A straightforward and more consistent GNP preparation approach is presented here focusing on the development of a one-step desolvation with the use of a commercially available gelatine type. Controlled stirring conditions and ultrafiltration are used to achieve large-scale production of nanoparticles of up to 2.6 g per batch. Particle size distributions are conserved and comparable to those determined for two-step desolvation on small scale. Additionally, a range of cross-linking agents is examined for their effectiveness in stabilising GNPs as an alternative to glutaraldehyde. Glyceraldehyde demonstrated outstanding properties, which led to high colloidal stability. This approach optimises the manufacturing process and the scale-up of the production capacity, providing a clear potential for future applications.

Pleiotropic action of CpG-ODN on endothelium and macrophages attenuates angiogenesis through distinct pathways

There is an integral relationship between vascular cells and leukocytes in supporting healthy tissue homeostasis. Furthermore, activation of these two cellular components is key for tissue repair following injury. Toll-like receptors (TLRs) play a role in innate immunity defending the organism against infection, but their contribution to angiogenesis remains unclear. Here we used synthetic TLR9 agonists, cytosine-phosphate-guanosine oligodeoxynucleotides (CpG-ODN), to investigate the role of TLR9 in vascular pathophysiology and identify potential therapeutic translation. We demonstrate that CpG-ODN stimulates inflammation yet inhibits angiogenesis. Regulation of angiogenesis by CpG-ODN is pervasive and tissue non-specific. Further, we noted that synthetic CpG-ODN requires backbone phosphorothioate but not TLR9 activation to render and maintain endothelial stalk cells quiescent. CpG-ODN pre-treated endothelial cells enhance macrophage migration but restrain pericyte mobilisation. CpG-ODN attenuation of angiogenesis, however, remains TLR9-dependent, as inhibition is lost in TLR9 deficient mice. Additionally, CpG-ODNs induce an M1 macrophage phenotype that restricts angiogenesis. The effects mediated by CpG-ODNs can therefore modulate both endothelial cells and macrophages through distinct pathways, providing potential therapeutic application in ocular vascular disease.

Mechanism of Mitochondrial Transcription Factor A Attenuation of CpG-Induced Antibody Production

Mitochondrial transcription factor A (TFAM) had previously been shown to act as a damage associated molecular pattern with the ability to enhance CpG-A phosphorothioate oligodeoxynucleotide (ODN)-mediated stimulation of IFNα production from human plasmacytoid dendritic cells. Examination of the mechanism by which TFAM might influence CpG ODN mediated innate immune responses revealed that TFAM binds directly, tightly and selectively to the structurally related CpG-A, -B, and -C ODN. TFAM also modulated the ability of the CpG-B or -C to stimulate the production of antibodies from human B cells. TFAM showed a dose-dependent modulation of CpG-B, and -C -induced antibody production from human B cells in vitro, with enhancement of high dose and inhibition of low doses of CpG stimulation. This effect was linked to the ability of TFAM to directly inhibit the binding of CpG ODNs to B cells, in a manner consistent with the relative binding affinities of TFAM for the ODNs. These data suggest that TFAM alters the free concentration of the CpG available to stimulate B cells by sequestering this ODN in a TFAM-CpG complex. Thus, TFAM has the potential to decrease the pathogenic consequences of exposure to natural CpG-like hypomethylated DNA in vivo, as well as such as that found in traumatic injury, infection, autoimmune disease and during pregnancy.

Effects of CpG Oligodeoxynucleotide 1826 on transforming growth factor-beta 1 and radiation-induced pulmonary fibrosis in mice

Background

Cytosine-phosphate-guanine (CpG) oligodeoxyribonucleotides (ODNs) are synthetic DNA fragments containing unmethylated cytosine-guanine motifs with potential immune modulatory effects and have recently been suggested to enhance sensitivity to traditional therapies in lung cancer. This study aimed to examine the effects of CpG ODN1826 on transforming growth factor-beta 1(TGF-β1) and radiation-induced pulmonary fibrosis in mice.

Methods

The radiation-induced pulmonary fibrosis mouse model was established by a single dose of 20 Gy, 6 MV X-rays exposure to the left lung. ICR mice were evenly randomized into four groups, comprising: a control group, a radiation group (RT group), a CpG group and a radiation combined with CpG ODN1826 group (RT + CpG group), with 40 mice in each group. CpG ODN1826 was intraperitoneally injected into mice at 1, 3, 5, 7 and 9 d post-irradiation. The mice were sacrificed at 1, 5, 15, 30 and 90 d post-irradiation. Paraffin sections of the radiated lung were subjected to H&E staining and Masson staining. The Ashcroft scale was used for quantitative histological analysis of fibrotic changes induced by irradiation. Concentrations of serum TGF-β1 were determined by ELISA, and concentrations of Hydroxyproline(Hyp) in the lung were determined with the alkaline hydrolysis method. Relative gene expression of FoxP3 was determined by real-time PCR.

Results

The radiation-induced pulmonary fibrosis mouse model was successfully established. The serum concentrations of TGF -β1 of RT group were higher than those of the RT + CpG group (t = 5.212, 7.126, 7.972 and 3.785, P < 0.05). The Hyp in the lung of RT group was higher than that of RT + CpG group (t = 4.606, P < 0.05). The relative expressions of FoxP3 gene in the lung of the RT group were higher than those of RT + CpG group (t = 8.395, 5.099 and 6.147, P < 0.05).

Conclusions

CpG ODN1826 could reduce the serum concentrations of TGF-β1 and the lung content of Hyp in radiation-induced pulmonary fibrosis, which might be related to the possibility that CpG ODN1826 can reduce expression of the FoxP3 gene.