Immunomodulatory oligonucleotides containing a cytosine-phosphate-2'-deoxy-7-deazaguanosine motif as potent toll-like receptor 9 agonists

Reversing immune evasion using a DNA nano-orchestrator for pancreatic cancer immunotherapy

Immune evasion caused by the paucity of MHCI is a prominent characteristic of pancreatic adenocarcinoma (PAAD), which is thought to underlie dysfunctional even absent adaptive T cell immunity and is responsible for ineffective immunotherapy. Here, we report a ROS-responsive DNA nano-orchestrator to cascade reverse MHC I-associated immune evasion and boost anti-tumor T cell stimulation, stimulating the activation of tumoricidal immunity against PAAD. Chloroquine phosphate (CQP) as an autophagy inhibitor was first encapsulated with ferritin, and via DNA modular self-assembly technology, the generated ferritin nanocores (FNC) were then caged into ROS-responsive CpG-DNA nanoframe. After systemic injection, the FNC-laden DNA nanoframe (FNC@NF) was passively enriched in tumor tissues in which the DNA nanoframe was cleaved upon the ROS stimulation. Oligodeoxynucleotide (ODN) with CpG motifs was detached and functioned as a TLR9 agonist. The liberated FNC was then endocytosed in an actively targeted manner by binding to transferrin receptor 1. In the lysosome, CQP was burst released from FNC due to acid-triggering. Through CQP-mediated autophagy abrogation, MHC-I molecules were preserved. We demonstrated that cascade inhibiting autophagy and boosting TLR9 stimulation via our proposed DNA-based hybrid nanosystem restored MHC I on the tumor cell surface and reshaped the antigen presentation of DCs, and ultimately reversed immune evasion and synergistically reinforced the activation of cytotoxic T cells against PAAD cells. In sum, our work provides an alternative strategy for cascade reversing immune evasion and boosting anti-tumor T cell stimulation and holds great potential for pancreatic cancer immunotherapy. STATEMENT OF SIGNIFICANCE: A DNA nano-orchestrator was created by sequentially assembling chloroquine phosphate-laden ferritin nanocores with ROS-responsive CpG-DNA nanoframe. Through cascade inhibiting autophagy and boosting TLR9 stimulation, the nano-orchestrator efficiently reversed MHC I-associated immune evasion and augmented anti-tumor T cell stimulation, which ultimately activated tumoricidal immunity against pancreatic adenocarcinoma.

Effect of oligonucleotide MT01 delivered by N-isopropylacrylamide modified polyethyleneimine for bone regeneration

Objective: This study aimed to investigate the regulatory effect of N-isopropylacrylamide-modified polyethyleneimine (PEN)-delivered oligodeoxynucleotide (ODN) MT01 on bone regeneration in vitro and in vivo. Methods: A polyethylenimine (PEI) derivative, PEN, was constructed through Michael addition and employed as a carrier for ODN MT01 transfection. PEN/MT01 nanocomposites were characterized using agarose gel retardation assay, size distribution, zeta potential and transmission electron microscopy. The Cell Counting Kit-8 (CCK-8) assay was used to detect the effect of PEN on cell viability. Alkaline phosphatase (ALP) staining was used to detect the osteogenic differentiation ability of PEN/MT01 nanocomposite. Real-time quantitative PCR (q RT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used to detect the regulatory effects of PEN/MT01 nanocomposite on osteogenic differentiation gene expression. Rat model was observed using the skull defect method and verified using micro-computed tomography (CT), serum biochemical indices, hematoxylin and eosin (H&E) staining and Immunohistochemistry (IHC). Results: PEN had good biological properties and could deliver MT01 well to achieve efficient transmission of MT01. PEN/MT01 nanocomposites were effectively transfected into MC3T3-E1 cells at a ratio of 6.0. CCK-8 assay displayed that PEN had no cytotoxicity to MC3T3-E1 cells. Additionally, PEN/MT01 nanocomposites could promote the expression of osteogenic genes. In vivo results revealed that PEN/MT01 nanocomposites could promote bone regeneration more effectively than the other groups. Conclusion: PEN has good biocompatibility and low toxicity, which is a good carrier for ODN MT01. PEN-delivered MT01 can be potentially employed as a useful approach to achieving bone regeneration.

TLR9 in the Human Papilloma Virus Infections: Friend or Foe?

Immune system plays dual roles during human papilloma virus (HPV) infections, from defense against the virus to induction or stimulation of the HPV-related cancers. It appears that various differences within the immune-related genes and the functions of the immunological parameters of the patients are the main factors responsible for the roles played by immune system during HPV infections. Toll-like receptors (TLRs) play key roles in the recognition of viruses and activation of immune responses. The molecules also can alter the target cell intracellular signaling and may participate in the transformation of the infected cells. TLR9 is the unique intracellular member of TLRs that recognize foreign DNA, including viral DNA. Thus, TLR9 may play significant roles in the defense against HPV and its related cancers. This review article discusses TLR9 antiviral and pathological roles during HPV infection.

Delivery of therapeutic oligonucleotides in nanoscale

Therapeutic oligonucleotides (TOs) represent one of the most promising drug candidates in the targeted cancer treatment due to their high specificity and capability of modulating cellular pathways that are not readily druggable. However, efficiently delivering of TOs to cancer cellular targets is still the biggest challenge in promoting their clinical translations. Emerging as a significant drug delivery vector, nanoparticles (NPs) can not only protect TOs from nuclease degradation and enhance their tumor accumulation, but also can improve the cell uptake efficiency of TOs as well as the following endosomal escape to increase the therapeutic index. Furthermore, targeted and on-demand drug release of TOs can also be approached to minimize the risk of toxicity towards normal tissues using stimuli-responsive NPs. In the past decades, remarkable progresses have been made on the TOs delivery based on various NPs with specific purposes. In this review, we will first give a brief introduction on the basis of TOs as well as the action mechanisms of several typical TOs, and then describe the obstacles that prevent the clinical translation of TOs, followed by a comprehensive overview of the recent progresses on TOs delivery based on several various types of nanocarriers containing lipid-based nanoparticles, polymeric nanoparticles, gold nanoparticles, porous nanoparticles, DNA/RNA nanoassembly, extracellular vesicles, and imaging-guided drug delivery nanoparticles.

Intratumoural administration and tumour tissue targeting of cancer immunotherapies

Immune-checkpoint inhibitors and chimeric antigen receptor (CAR) T cells are revolutionizing oncology and haematology practice. With these and other immunotherapies, however, systemic biodistribution raises safety issues, potentially requiring the use of suboptimal doses or even precluding their clinical development. Delivering or attracting immune cells or immunomodulatory factors directly to the tumour and/or draining lymph nodes might overcome these problems. Hence, intratumoural delivery and tumour tissue-targeted compounds are attractive options to increase the in situ bioavailability and, thus, the efficacy of immunotherapies. In mouse models, intratumoural administration of immunostimulatory monoclonal antibodies, pattern recognition receptor agonists, genetically engineered viruses, bacteria, cytokines or immune cells can exert powerful effects not only against the injected tumours but also often against uninjected lesions (abscopal or anenestic effects). Alternatively, or additionally, biotechnology strategies are being used to achieve higher functional concentrations of immune mediators in tumour tissues, either by targeting locally overexpressed moieties or engineering 'unmaskable' agents to be activated by elements enriched within tumour tissues. Clinical trials evaluating these strategies are ongoing, but their development faces issues relating to the administration methodology, pharmacokinetic parameters, pharmacodynamic end points, and immunobiological and clinical response assessments. Herein, we discuss these approaches in the context of their historical development and describe the current landscape of intratumoural or tumour tissue-targeted immunotherapies.

Tilsotolimod with Ipilimumab Drives Tumor Responses in Anti-PD-1 Refractory Melanoma

Many patients with advanced melanoma are resistant to immune checkpoint inhibition. In the ILLUMINATE-204 phase I/II trial, we assessed intratumoral tilsotolimod, an investigational Toll-like receptor 9 agonist, with systemic ipilimumab in patients with anti-PD-1- resistant advanced melanoma. In all patients, 48.4% experienced grade 3/4 treatment-emergent adverse events. The overall response rate at the recommended phase II dose of 8 mg was 22.4%, and an additional 49% of patients had stable disease. Responses in noninjected lesions and in patients expected to be resistant to ipilimumab monotherapy were observed. Rapid induction of a local IFNα gene signature, dendritic cell maturation and enhanced markers of antigen presentation, and T-cell clonal expansion correlated with clinical response. A phase III clinical trial with this combination (NCT03445533) is ongoing. SIGNIFICANCE: Despite recent developments in advanced melanoma therapies, most patients do not experience durable responses. Intratumoral tilsotolimod injection elicits a rapid, local type 1 IFN response and, in combination with ipilimumab, activates T cells to promote clinical activity, including in distant lesions and patients not expected to respond to ipilimumab alone.This article is highlighted in the In This Issue feature, p. 1861.

The Evolution of Antisense Oligonucleotide Chemistry-A Personal Journey

Over the last four decades, tremendous progress has been made in use of synthetic oligonucleotides as therapeutics. This has been possible largely by introducing chemical modifications to provide drug like properties to oligonucleotides. In this article I have summarized twists and turns on use of chemical modifications and their road to success and highlight areas of future directions.

Trial Watch: Experimental Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) are prototypic pattern recognition receptors (PRRs) best known for their ability to activate the innate immune system in response to conserved microbial components such as lipopolysaccharide and double-stranded RNA. Accumulating evidence indicates that the function of TLRs is not restricted to the elicitation of innate immune responses against invading pathogens. TLRs have indeed been shown to participate in tissue repair and injury-induced regeneration as well as in adaptive immune responses against cancer. In particular, TLR4 signaling appears to be required for the efficient processing and cross-presentation of cell-associated tumor antigens by dendritic cells, which de facto underlie optimal therapeutic responses to some anticancer drugs. Thus, TLRs constitute prominent therapeutic targets for the activation/intensification of anticancer immune responses. In line with this notion, long-used preparations such as the Coley toxin (a mixture of killed Streptococcus pyogenes and Serratia marcescens bacteria) and the bacillus Calmette-Guérin (BCG, an attenuated strain of Mycobacterium bovis originally developed as a vaccine against tuberculosis), both of which have been associated with consistent anticancer responses, potently activate TLR2 and TLR4 signaling. Today, besides BCG, only one TLR agonist is FDA-approved for therapeutic use in cancer patients: imiquimod. In this Trial Watch, we will briefly present the role of TLRs in innate and cognate immunity and discuss the progress of clinical studies evaluating the safety and efficacy of experimental TLR agonists as immunostimulatory agents for oncological indications.

Intratumoural immunotherapy: activation of nucleic acid sensing pattern recognition receptors

Recently, it has become clear that the tumour microenvironment (TME) is important in cancer immunotherapy. While immune checkpoint inhibitors are effective for some patients, the heterogeneous nature and status of the TME (‘cold’ tumours) play a critical role in suppressing antitumour immunity in non-responding patients. Converting ‘cold’ to ‘hot’ tumours through modulation of the TME may enable expansion of the therapeutic efficacy of immunotherapy to a broader patient population. This paper describes advances in intratumoural immunotherapy, specifically activation of nucleic acid sensing pattern recognition receptors to modulate the TME.

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Intratumoural immunotherapy to modulate the tumour microenvironment.

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Use of novel immunostimulatory agents which activate nucleic acid sensing pattern recognition receptors.

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Harnessing innate and adaptive immunity induced by receptor-mediated immune cascade.

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Intratumoural therapy leads to local and anenestic tumour responses.

Pharmacological modulation of nucleic acid sensors - therapeutic potential and persisting obstacles

Nucleic acid sensors, primarily TLR and RLR family members, as well as cGAS-STING signalling, play a critical role in the preservation of cellular and organismal homeostasis. Accordingly, deregulated nucleic acid sensing contributes to the origin of a diverse range of disorders, including infectious diseases, as well as cardiovascular, autoimmune and neoplastic conditions. Accumulating evidence indicates that normalizing aberrant nucleic acid sensing can mediate robust therapeutic effects. However, targeting nucleic acid sensors with pharmacological agents, such as STING agonists, presents multiple obstacles, including drug-, target-, disease- and host-related issues. Here, we discuss preclinical and clinical data supporting the potential of this therapeutic paradigm and highlight key limitations and possible strategies to overcome them.

Endogenous Nur77 Is a Specific Indicator of Antigen Receptor Signaling in Human T and B Cells

Distinguishing true Ag-stimulated lymphocytes from bystanders activated by the inflammatory milieu has been difficult. Nur77 is an immediate early gene whose expression is rapidly upregulated by TCR signaling in murine T cells and human thymocytes. Nur77-GFP transgenes serve as specific TCR and BCR signaling reporters in murine transgenic models. In this study, we demonstrate that endogenous Nur77 protein expression can serve as a reporter of TCR and BCR specific signaling in human PBMCs. Nur77 protein amounts were assessed by immunofluorescence and flow cytometry in T and B cells isolated from human PBMCs obtained from healthy donors that had been stimulated by their respective Ag receptors. We demonstrate that endogenous Nur77 is a more specific reporter of Ag-specific signaling events than the commonly used CD69 activation marker in both human T and B cells. This is reflective of the disparity in signaling pathways that regulate the expression of Nur77 and CD69. Assessing endogenous Nur77 protein expression has great potential to identify Ag-activated lymphocytes in human disease.

Trial Watch: Immunostimulation with Toll-like receptor agonists in cancer therapy

Accumulating preclinical evidence indicates that Toll-like receptor (TLR) agonists efficiently boost tumor-targeting immune responses (re)initiated by most, if not all, paradigms of anticancer immunotherapy. Moreover, TLR agonists have been successfully employed to ameliorate the efficacy of various chemotherapeutics and targeted anticancer agents, at least in rodent tumor models. So far, only three TLR agonists have been approved by regulatory agencies for use in cancer patients. Moreover, over the past decade, the interest of scientists and clinicians in these immunostimulatory agents has been fluctuating. Here, we summarize recent advances in the preclinical and clinical development of TLR agonists for cancer therapy.

Immunological and hematological toxicities challenging clinical translation of nucleic acid-based therapeutics

INTRODUCTION

Nucleic acid-based therapeutics (NATs) are proven agents in correcting disorders caused by gene mutations, as treatments against cancer, microbes and viruses, and as vaccine adjuvants. Although many traditional small molecule NATs have been approved for clinical use, commercialization of macromolecular NATs has been considerably slower, and only a few have successfully reached the market. Preclinical and clinical evaluation of macromolecular NATs has revealed many assorted challenges in immunotoxicity, hematotoxicity, pharmacokinetics (PKs), toxicology and formulation. Extensive review has been given to the PK and toxicological concerns of NATs including approaches designed to overcome these issues. Immunological and hematological issues are a commonly reported side effect of NAT treatment; however, literature exploring the mechanistic background of these effects is sparse.

AREAS COVERED

This review focuses on the immunomodulatory properties of various types of therapeutic nucleic acid concepts. The most commonly observed immunological and hematological toxicities are described for various NAT classes, with citations of how to circumvent these toxicities.

EXPERT OPINION

Although some success with overcoming immunological and hematological toxicities of NATs has been achieved in recent years, immunostimulation remains the main dose-limiting factor challenging clinical translation of these promising therapies. Novel delivery vehicles should be considered to overcome this challenge.

Strategy for selecting nanotechnology carriers to overcome immunological and hematological toxicities challenging clinical translation of nucleic acid-based therapeutics

INTRODUCTION

Clinical translation of nucleic acid-based therapeutics (NATs) is hampered by assorted challenges in immunotoxicity, hematotoxicity, pharmacokinetics, toxicology and formulation. Nanotechnology-based platforms are being considered to help address some of these challenges due to the nanoparticles' ability to change drug biodistribution, stability, circulation half-life, route of administration and dosage. Addressing toxicology and pharmacology concerns by various means including NATs reformulation using nanotechnology-based carriers has been reviewed before. However, little attention was given to the immunological and hematological issues associated with nanotechnology reformulation.

AREAS COVERED

This review focuses on application of nanotechnology carriers for delivery of various types of NATs, and how reformulation using nanoparticles affects immunological and hematological toxicities of this promising class of therapeutic agents.

EXPERT OPINION

NATs share several immunological and hematological toxicities with common nanotechnology carriers. In order to avoid synergy or exaggeration of undesirable immunological and hematological effects of NATs by a nanocarrier, it is critical to consider the immunological compatibility of the nanotechnology platform and its components. Since receptors sensing nucleic acids are located essentially in all cellular compartments, a strategy for developing a nanoformulation with reduced immunotoxicity should first focus on precise delivery to the target site/cells and then on optimizing intracellular distribution.

TLR9: an important molecule in the fight against hepatitis B virus

Hepatitis B virus (HBV) is the most prevalent infectious agent that can induce severe liver disease. Patients infected with long-term HBV, including chronic, asymptomatic and occult forms, cannot clear HBV from infected hepatocytes completely. It is not clear why some people can clear the infection while others cannot. Furthermore, the main mechanisms responsible for progression of the infections are not fully understood. It has been hypothesised that differences in genetic and immunological parameters between patients and subjects who successfully clear HBV infections are responsible for inducing the long-term forms of the infection. Previous investigations showed that Toll-like receptors (TLRs) play important roles in immune responses, especially innate immunity, against viral infections, including hepatitis B. TLR9 detects intracellular viral dsDNA, which results in the activation of an immune response against HBV. However, defects in this system may result in an attenuated response ultimately leading to long-term HBV infections. Targeting the defects in TLR9 or reactivating the downstream pathways that are normally switched on by TLR9 in response to HBV infection is a new approach to the treatment of long-term HBV infection. However, the pathways and defects seen in patients with long-term HBV need to be thoroughly explored before therapeutics can be applied in the clinical setting. Furthermore, the apparently multigenic nature of long-term HBV infection suggests that treatment of patients may need to be personalised.

Open-label phase 1b study of FOLFIRI plus cetuximab plus IMO-2055 in patients with colorectal cancer who have progressed following chemotherapy for advanced or metastatic disease

PURPOSE

The immune modulatory oligonucleotide IMO-2055 (EMD 1201081) is a phosphorothioate oligodeoxynucleotide agonist of Toll-like receptor 9. In preclinical studies, IMO-2055 was shown to activate natural killer cells and to support the antitumor activity of monoclonal antibodies. This phase 1b, open-label, 3 + 3 dose-escalation trial was performed to determine the recommended phase 2 dose of IMO-2055 combined with FOLFIRI/cetuximab in patients with previously treated, advanced/metastatic colorectal cancer (NCT00719199).

METHODS

Patients received 14-day cycles of cetuximab (days 1/8; 400 mg/m(2) day 1 cycle 1, 250 mg/m(2) for subsequent days/cycles), irinotecan (day 1; 180 mg/m(2)), folinic acid (day 1; 400 mg/m(2) racemic or 200 mg/m(2) L-form), 5-fluorouracil (day 1; 400 mg/m(2) intravenous bolus, followed by 2,400 mg/m(2) as 46-h infusion), and escalating IMO-2055 doses (days 1/8; 0.16, 0.32, 0.48 mg/kg). Fifteen patients received IMO-2055, including six, three, and six patients who were treated at the dose levels 0.16, 0.32, and 0.48 mg/kg, respectively.

RESULTS

One dose-limiting toxicity was observed (grade 3 fatigue; at dose level 0.16 mg/kg). The most common adverse events were injection site reactions, diarrhea, fatigue, hypomagnesemia, and stomatitis. One patient achieved a confirmed partial response; 12 had stable disease, including five with stable disease ≥4.0 months.

CONCLUSIONS

IMO-2055 combined with FOLFIRI/cetuximab was well tolerated at all dose levels tested. IMO-2055 0.48 mg/kg was considered as the recommended phase 2 dose.

Novel drugs targeting Toll-like receptors for antiviral therapy

Toll-like receptors (TLRs) are sentinel receptors of the host innate immune system that recognize conserved 'pathogen-associated molecular patterns' of invading microbes, including viruses. The activation of TLRs establishes antiviral innate immune responses and coordinates the development of long-lasting adaptive immunity in order to control viral pathogenesis. However, microbe-induced damage to host tissues may release 'danger-associated molecular patterns' that also activate TLRs, leading to an overexuberant inflammatory response and, ultimately, to tissue damage. Thus, TLRs have proven to be promising targets as therapeutics for the treatment of viral infections that result in inflammatory damage or as adjuvants in order to enhance the efficacy of vaccines. Here, we explore recent advances in TLR biology with a focus on novel drugs that target TLRs (agonists and antagonists) for antiviral therapy.

Toll-Like Receptor 9 Agonists for Cancer Therapy

The immune system has acquired increasing importance as a key player in cancer maintenance and growth. Thus, modulating anti-tumor immune mediators has become an attractive strategy for cancer treatment. Toll-like receptors (TLRs) have gradually emerged as potential targets of newer immunotherapies. TLR-9 is preferentially expressed on endosome membranes of B-cells and plasmacytoid dendritic cells (pDC) and is known for its ability to stimulate specific immune reactions through the activation of inflammation-like innate responses. Several synthetic CpG oligonucleotides (ODNs) have been developed as TLR-9 agonists with the aim of enhancing cancer immune surveillance. In many preclinical models, CpG ODNs were found to suppress tumor growth and proliferation both in monotherapy and in addition to chemotherapies or target therapies. TLR-9 agonists have been also tested in several clinical trials in patients with solid tumors. These agents showed good tolerability and usually met activity endpoints in early phase trials. However, they have not yet been demonstrated to significantly impact survival, neither as single agent treatments, nor in combination with chemotherapies or cancer vaccines. Further investigations in larger prospective studies are required.

Trial Watch: Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) have long been known for their ability to initiate innate immune responses upon exposure to conserved microbial components such as lipopolysaccharide (LPS) and double-stranded RNA. More recently, this family of pattern recognition receptors has been attributed a critical role in the elicitation of anticancer immune responses, raising interest in the development of immunochemotherapeutic regimens based on natural or synthetic TLR agonists. In spite of such an intense wave of preclinical and clinical investigation, only three TLR agonists are currently licensed by FDA for use in cancer patients: bacillus Calmette–Guérin (BCG), an attenuated strain of Mycobacterium bovis that operates as a mixed TLR2/TLR4 agonist; monophosphoryl lipid A (MPL), a derivative of Salmonella minnesota that functions as a potent agonist of TLR4; and imiquimod, a synthetic imidazoquinoline that activates TLR7. One year ago, in the August and September issues of OncoImmunology, we described the main biological features of TLRs and discussed the progress of clinical studies evaluating the safety and therapeutic potential of TLR agonists in cancer patients. Here, we summarize the latest developments in this exciting area of research, focusing on preclinical studies that have been published during the last 13 mo and clinical trials launched in the same period to investigate the antineoplastic activity of TLR agonists.

Selectively targeting the toll-like receptor 9 (TLR9)--IRF 7 signaling pathway by polymer blend particles

Signaling through toll-like receptor 9 (TLR9) has been exploited for cancer therapy. The stimulation of TLR9 leads to two bifurcating signaling pathways - NF-κB-dependent pro-inflammatory cytokines pathway and IRF-7-dependent type I interferons (IFNs) pathway. In this study, we employ polymer blend particles to present the synthetic ligand, CpG oligonucleotides (CpG ODNs), to TLR9. The polymer blend particles are made from the blend of pH-insensitive and pH-sensitive copolymer. By tailoring the composition of the pH-sensitive polymer, CpG ODNs are presented to TLR9 in a way that only activates the IRF-7 signaling pathway. CpG ODNs have been used for cancer therapy in both preclinical and clinical studies. The selective activation of IRF-7 could potentially enhance the apoptosis of tumor cells and immunological control of tumor progression without inadvertently activating NF-κB-dependent oncogenesis.

Sequential induction of type I and II interferons mediates a long-lasting gene induction in the liver in response to a novel toll-like receptor 9 agonist

BACKGROUND & AIMS

The toll-like receptor 9 (TLR9) agonist IMO-2125 is currently evaluated in clinical trials for chronic hepatitis C therapy. The aim of this study was to investigate the in vivo mode of action of a closely related compound, referred to as immunomodulatory oligonucleotide (IMO).

METHODS

We analyzed the Jak-STAT pathway activation and induction of interferon-stimulated genes in the liver of wild type, interferon-α/β receptor-deficient and interferon-γ-deficient mice, after administration of IMO.

RESULTS

IMO induced a prolonged activation of the Jak-STAT pathway and upregulation of interferon-stimulated genes in the mouse liver. Contrary to the response observed after interferon-α injection, the signalling induced by IMO was not abrogated following repeated administration. At early time points after IMO injection, STAT1 phosphorylation and interferon-stimulated gene induction required a functional interferon-α/β receptor, whereas at the later time points, the activation was type I interferon-independent. Microarray analysis revealed that IMO induced a broad transcriptional response in the mouse liver. This included upregulation of cytokine and chemokine genes responsible for recruitment of IFN-γ producers, such as T cells and natural killer cells. Interferon-γ-deficient mice showed a transient response to IMO, demonstrating the central role of interferon-γ in sustained activation of Jak-STAT pathway by IMO.

CONCLUSIONS

The bimodal kinetics of response to IMO in the mouse liver are driven by the sequential endogenous production of type I and II interferons. The lack of refractoriness to IMO, combined with the long-lasting induction of interferon-stimulated genes, reveals a favourable pharmacodynamics profile of this novel TLR9 agonist for the treatment of chronic viral hepatitis.

Immune-Stimulatory Dinucleotide at the 5'-End of Oligodeoxynucleotides Is Critical for TLR9-Mediated Immune Responses

Oligodeoxynucleotides (ODNs) containing a CpG or certain synthetic dinucleotides, referred to as immune-stimulatory dinucleotides, induce Toll-like receptor 9 (TLR9)-mediated immune responses. Chemical modifications such as 2'-O-methylribonucleotides incorporated adjacent to the immune-stimulatory dinucleotide on the 5'-side abrogate TLR9-mediated immune responses. In this study, we evaluated the effect of the location of immune-stimulatory dinucleotides in ODNs on TLR9-mediated immune responses. We designed and synthesized ODNs with two immune-stimulatory dinucleotides, one placed toward the 5'-end region and the other toward the 3'-end region, incorporated 2'-O-methylribonucleotides selectively preceding the 5'- or 3'-immune-stimulatory dinucleotide or both, and studied TLR9-mediated immune responses of these compounds in cell-based assays and in vivo in mice. These studies showed that an immune-stimulatory dinucleotide located closer to the 5'-end is critical for and dictates TLR9-mediated immune responses. These studies provide insights for the use of ODNs when employed as TLR9 agonists and antagonists or antisense agents.

Alkynyl phosphonate DNA: a versatile "click"able backbone for DNA-based biological applications

Major hurdles associated with DNA-based biological applications include, among others, targeted cell delivery, undesirable nonspecific effects, toxicity associated with various analogues or the reagents used to deliver oligonucleotides to cells, and stability toward intracellular enzymes. Although a plethora of diverse analogues have been investigated, a versatile methodology that can systematically address these challenges has not been developed. In this contribution, we present a new, Clickable, and versatile chemistry that can be used to rapidly introduce diverse functionality for studying these various problems. As a demonstration of the approach, we synthesized the core analogue, which is useful for introducing additional functionality, the triazolylphosphonate, and present preliminary data on its biological properties. We have developed a new phosphoramidite synthon--the alkynyl phosphinoamidite, which is compatible with conventional solid-phase oligonucleotide synthesis. Postsynthesis, the alkynylphosphonate can be functionalized via "Click" chemistry to generate the 1,2,3-triazolyl or substituted 1,2,3-triazolyl phosphonate-2'-deoxyribonucleotide internucleotide linkage. This manuscript describes the automated, solid-phase synthesis of mixed backbone oligodeoxyribonucleotides (ODNs) having 1,2,3-triazolylphosphonate (TP) as well as phosphate or thiophosphate internucleotide linkages and also 2'-OMe ribonucleotides and locked nucleic acids (LNAs) at selected sites. Nuclease stability assays demonstrate that the TP linkage is highly resistant toward 5'- and 3'-exonucleases, whereas melting studies indicate a slight destabilization when a TP-modified ODN is hybridized to its complementary RNA. A fluorescently labeled 16-mer ODN modified with two TP linkages shows efficient cellular uptake during passive transfection. Of particular interest, the subcellular distribution of TP-modified ODNs is highly dependent on cell type; a significant nuclear uptake is observed in HeLa cells, whereas diffuse cytoplasmic fluorescence is found in the WM-239A cell line. Cytoplasmic distribution is also present in human neuroblastoma cells (SK-N-F1), but Jurkat cells show both diffuse and punctate cytoplasmic uptake. Our results demonstrate that triazolylphosphonate ODNs are versatile additions to the oligonucleotide chemist's toolbox relative to designing new biological research reagents.

An in situ autologous tumor vaccination with combined radiation therapy and TLR9 agonist therapy

PURPOSE

Recent studies have shown that a new generation of synthetic agonist of Toll-like receptor (TLR) 9 consisting a 3'-3'-attached structure and a dCp7-deaza-dG dinucultodie shows more potent immunostimulatory effects in both mouse and human than conventional CpG oligonucleotides. Radiation therapy (RT) provides a source of tumor antigens that are released from dying, irradiated, tumor cells without causing systemic immunosuppression. We, therefore, examined effect of combining RT with a designer synthetic agonist of TLR9 on anti-tumoral immunity, primary tumor growth retardation and metastases in a murine model of lung cancer.

METHODS

Grouped C57BL/6 and congenic B cell deficient mice (B(-/-)) bearing footpad 3LL tumors were treated with PBS, TLR9 agonist, control oligonucelotide, RT or the combination of RT and TLR9 agonist. Immune phenotype of splenocytes and serum IFN-γ and IL-10 levels were analyzed by FACS and ELISA, 24 h after treatment. Tumor growth, lung metastases and survival rate were monitored and tumor specific antibodies in serum and deposition in tumor tissue were measured by ELISA and immunofluorescence.

RESULTS

TLR9 agonist expanded and activated B cells and plasmacytoid dendritic cells in wild-type mice and natural killer DCs (NKDCs) in B cell-deficient (B(-/-)) mice bearing ectopic Lewis lung adenocarcinoma (3LL). Combined RT with TLR9 agonist treatment inhibited 3LL tumor growth in both wild type and B(-/-) mice. A strong tumor-specific humoral immune response (titer: 1/3200) with deposition of mouse IgG auto-antibodies in tumor tissue were found in wildtype mice, whereas the number of tumor infiltrating NKDCs increased in B(-/-) mice following RT+ TLR9 agonist therapy. Furthermore, mice receiving combination therapy had fewer lung metastases and a higher survival than single treatment cohorts.

CONCLUSIONS

Combination therapy with TLR9 agonist and RT induces systemic anti-tumoral humoral response, augments tumoral infiltration of NKDCs, reduces pulmonary metastases and improves survival in a murine model of 3LL cancer.

Targeting pattern recognition receptors in cancer immunotherapy

Pattern recognition receptors (PRRs) are known for many years for their role in the recognition of microbial products and the subsequent activation of the immune system. The 2011 Nobel Prize for medicine indeed rewarded J. Hoffmann/B. Beutler and R. Steinman for their revolutionary findings concerning the activation of the immune system, thus stressing the significance of understanding the mechanisms of activation of the innate immunity. Such immunostimulatory activities are of major interest in the context of cancer to induce long-term antitumoral responses. Ligands for the toll-like receptors (TLRs), a well-known family of PRR, have been shown to have antitumoral activities in several cancers. Those ligands are now undergoing extensive clinical investigations both as immunostimulant molecules and as adjuvant along with vaccines. However, when considering the use of these ligands in tumor therapy, one shall consider the potential effect on the tumor cells themselves as well as on the entire organism. Recent data indeed demonstrate that TLR activation in tumor cells could trigger both pro- or antitumoral effect depending on the context. This review discusses this balance between the intrinsic activation of PRR in tumor cells and the extrinsic microenvironment activation in term of overall effect of PRR ligands on tumor development. We review recent advances in the field and underline appealing prospects for clinical development of PRR agonists in the light of our current knowledge on their expression and activation.

Antiviral applications of Toll-like receptor agonists

In the past, antiviral research has focused mainly on viral targets. As the search for effective and differentiated antiviral therapies continues, cellular targets are becoming more common, bringing with them a variety of challenges and concerns. Toll-like receptors (TLRs) provide a unique mechanism to induce an antiviral state in the host. In this review we introduce TLRs as targets for the pharmaceutical industry, including how they signal and thereby induce an antiviral state through the production of type I interferons. We examine how TLRs are being therapeutically targeted and discuss several clinically precedented agents for which efficacy and safety data are available. We describe some of the chemistries that have been applied to both small molecule and large molecule leads to tune agonist potency, and offer a differentiated safety profile through targeting certain compartments such as the gut or the lung, thereby limiting systemic drug exposure and affecting systemic cytokine levels. The application of low-dose agonists of TLRs as vaccine adjuvants or immunoprotective agents is also presented. Some of the challenges presented by this approach are then discussed, including viral evasion strategies and mechanism-linked inflammatory cytokine induction.

TLR9 agonist protects mice from radiation-induced gastrointestinal syndrome

Purpose

Radiation-induced gastrointestinal syndrome (RIGS) is due to the clonogenic loss of crypt cells and villi depopulation, resulting in disruption of mucosal barrier, bacterial invasion, inflammation and sepsis. Intestinal macrophages could recognize invading bacterial DNA via TLR9 receptors and transmit regenerative signals to the neighboring crypt. We therefore investigated whether systemic administration of designer TLR9 agonist could ameliorate RIGS by activating TLR9.

Methods and Materials

Male C57Bl6 mice were distributed in four experimental cohorts, whole body irradiation (WBI) (8.4–10.4 Gy), TLR9 agonist (1 mg/kg s.c.), 1 h pre- or post-WBI and TLR9 agonist+WBI+iMyd88 (pretreatment with inhibitory peptide against Myd88). Animals were observed for survival and intestine was harvested for histological analysis. BALB/c mice with CT26 colon tumors in abdominal wall were irradiated with 14 Gy single dose of whole abdominal irradiation (AIR) for tumor growth study.

Results

Mice receiving pre-WBI TLR9 agonist demonstrated improvement of survival after 10.4 Gy (p<0.03), 9.4 Gy (p<0.008) and 8.4 Gy (p<0.002) of WBI, compared to untreated or iMyd88-treated controls. Post-WBI TLR9 agonist mitigates up to 8.4 Gy WBI (p<0.01). Histological analysis and xylose absorption test demonstrated significant structural and functional restitution of the intestine in WBI+TLR9 agonist cohorts. Although, AIR reduced tumor growth, all animals died within 12 days from RIGS. TLR9 agonist improved the survival of mice beyond 28 days post-AIR (p<0.008) with significant reduction of tumor growth (p<0.0001).

Conclusions

TLR9 agonist treatment could serve both as a prophylactic or mitigating agent against acute radiation syndrome and also as an adjuvant therapy to increase the therapeutic ratio of abdominal Radiation Therapy for Gastro Intestinal malignancies.

Synthesis, purification, and characterization of immune-modulatory oligodeoxynucleotides that act as agonists of Toll-like receptor 9

Methods and protocols for automated synthesis and purification of immune modulatory oligonucleotides (IMOs), a novel class of Toll-like receptor 9 (TLR9) agonists, are described. IMOs containing two short identical sequences of 11-mers with phosphorothioate linkages can be synthesized in parallel synthetic strategy. A C3-linker that mimics the natural inter-nucleotide distance was commonly used for joining the two segments of IMOs. NittoPhase solid support bearing a symmetrical C3-linker (glycerol) and nucleoside-β-cyanoethyl-N,N-diisopropylphosphoramidites were used for IMO synthesis. The parallel synthesis was carried out in a 3'→ 5' direction with removal of the final dimethoxytrityl (DMT) protecting group. After synthesis, the IMO was cleaved and deprotected by treating with aqueous ammonia. The product was purified on anion-exchange HPLC, desalted, lyophilized, and characterized by anion-exchange HPLC, capillary gel electrophoresis, polyacrylamide gel electrophoresis, and MALDI-TOF mass spectral analysis.

B cells from HIV-infected patients with primary central nervous system lymphoma display an activated phenotype and have a blunted TNF-α response to TLR9 triggering

Each cell in HIV-associated primary central nervous system lymphoma (PCNSL) harbors latent EBV. Notably, the triggering of TLR9, a key event in HIV pathogenesis, also promotes EBV latency and transformation. We hypothesized that because only a minority of HIV-infected patients develops PCNSL, their B cells exhibit aberrant signaling responses to TLR9 triggering. We found higher levels of IL-6, CD80, and CD86 expression at baseline in B cells of those patients than in B cells of matched controls, whereas TNF-a expression was lower. Notably, on TLR9 triggering with CpG 2006, CD80 and TNF-α were up-regulated to a lesser extent in B cells of the former than in those of matched controls. The reduced up-regulation of CD80 might be explained by its higher baseline expression resulting in a more blunted response rather than a specific deficit of the signaling response to TLR9 triggering. However, this cannot explain the blunted TNF-α response, which warrants further investigation. Finally, since increased IL-6 expression is linked to EBV-associated Hodgkin’s lymphoma, the enhanced baseline expression of IL-6 might be important in the pathogenesis of PCNSL in HIV-infected patients.

In vitro analysis of the factors contributing to the antiviral state induced by a plasmid encoding the viral haemorrhagic septicaemia virus glycoprotein G in transfected trout cells

We have found out that transfection of the RTG-2 cell line with the viral haemorrhagic septicaemia virus (VHSV) glycoprotein G (G(VHSV))-coding plasmid induces an anti-VHSV state, similar to that induced by poly I:C. Taking the advantage of the constitutive expression of toll-like receptor 9 gene (tlr9) in RTG-2 cells, we have investigated whether this antiviral state was induced by the cytosine-phosphodiester-guanine (CpG) motifs present in the plasmid DNA, by the endogenous expression of G(VHSV) protein or by both elements. For that, we have analysed the expression profile of the rainbow trout tlr9 and several genes related to TLR9-mediated immune response in the absence or presence of a lysosomotropic drug that specifically blocks TLR9-CpG DNA interaction. The results suggested that the high levels of cell protection conferred by a plasmid encoding G(VHSV) gene are due to G(VHSV) rather than to the CpG motifs within plasmid DNA. Therefore, plasmid DNA might not play a key role in the immune response elicited by DNA vaccines or perhaps other receptors instead TLR9 could be implicated in CpG motifs recognition and signalling. In addition, since RTG-2 cells express tlr9 gene, this cell line could be a good tool for screening TLR9 agonists, such as the immunomodulatory oligonucleotides (IMOs), as fish DNA vaccine adjuvants.

Targeting the TLR9-MyD88 pathway in the regulation of adaptive immune responses

IMPORTANCE OF THE FIELD

Toll-like receptors (TLRs) are innate immune receptors critical in the innate immune defense against invading pathogens. Recent advances also reveal a crucial role for TLRs in shaping adaptive immune responses, conferring a potential therapeutic value to their modulation in the treatment of diseases.

AREAS COVERED IN THIS REVIEW

The aim of this review is to discuss TLR9, the TLR9-MyD88 signaling pathway and its role in regulation of adaptive immune responses, as well as potential therapeutic implications by targeting this pathway.

WHAT THE READER WILL GAIN

This review shows that the TLR9-MyD88 signaling pathway plays a critical role in promoting adaptive immune responses and that modulation of this pathway may have enormous therapeutic potential in enhancing vaccine potency, controlling autoimmunity, as well as improving the outcome of viral-vector-mediated gene therapy.

TAKE HOME MESSAGE

Although TLR9 agonists have been used as adjuvants for enhancing vaccine potency, further exploitation of the TLR9-MyD88 pathway and its dynamic interaction with the immune system in vivo is needed to provide more effective therapeutic inventions in the design of vaccines for infectious diseases, allergies and cancer, in the control of autoimmunity, as well as in the improvement of viral-vector-mediated gene therapy.

Impact of nature and length of linker incorporated in agonists on toll-like receptor 9-mediated immune responses

Oligodeoxynucleotides containing unmethylated CpG motifs act as ligands of Toll-like receptor 9 (TLR9). We previously reported a novel class of TLR9 agonists, referred to as immune-modulatory oligonucleotides (IMOs), in which two 11-mers of the same sequence are attached via their 3'-ends through a 1,2,3-propanetriol linker and contain a synthetic immune-stimulatory motif, Cp7-deaza-dG. In the present study, we have examined the impact of length, nature, and stereochemistry of the linker incorporated in agonists for TLR9 activation. The new linkers studied include (S)-(-)-1,2,4-butanetriol, 1,3,5-pentanetriol, cis,cis-1,3,5-cyclohexanetriol, cis,trans-1,3,5-cyclohexanetriol, 1,3,5-tris(2-hydroxyethyl)isocyanurate, tetraethyleneglycol, and hexaethyleneglycol in place of 1,2,3-propanetriol linker. Agonists with various linkers are studied for TLR9-mediated immune responses in HEK293 cells, human cell-based assays, and in vivo in mice. Results of these studies suggest that C3-C5 linkers, 1,2,3-propanetriol, (S)-(-)-1,2,4-butanetriol, or 1,3,5-pentanetriol, are optimal for stimulation of TLR9-mediated immune responses. Rigid C3 linkers with different stereochemistry have little effect on immune stimulation, while linkers longer than C5 reduced TLR9-mediated immune stimulation.

Immunomodulatory Agents with Antivascular Activity in the Treatment of Non-Small Cell Lung Cancer: Focus on TLR9 Agonists, IMiDs and NGR-TNF

Standard treatments for nonsmall cell lung cancer (NSCLC), such as surgery, chemotherapy, and radiotherapy, often lead to disappointing results. Unfortunately, also the various immunotherapeutic approaches so far tested have not produced satisfactory results to be widely applied in the clinical practice. However, the recent development of new immunomodulatory agents may open promising therapeutic options. This paper focuses on PF3512676, lenalidomide, and NGR-TNF, that is, drugs belonging to three different classes of immunomodulatory agents, that are also capable to affect tumor blood vessels with different mechanisms, and discusses the potential role of such agents in NSCLC treatment strategy.

A TLR9 agonist enhances therapeutic effects of telomerase genetic vaccine

The telomerase reverse transcriptase (TERT) is an attractive target for cancer vaccination because its expression is reactivated in most tumors. In this study, we have evaluated the ability of a genetic vaccine targeting murine TERT (mTERT) based on DNA electroporation (DNA-EP) and adenovirus serotype 6 (Ad6) to exert therapeutic effects in combination with a novel TLR9 agonist, referred to as immune modulatory oligonucleotide (IMO), as an adjuvant. IMO was administered to mice at the same time as vaccine. IMO induced dose-dependent cytokine secretion and activation of NK cells. Most importantly, vaccination of mice with IMO in combination with mTERT vaccine conferred therapeutic benefit in tumor bearing animals and this effect was associated with increased NK, DC and T cell tumor infiltration. These data show that appropriate combination of a DNA-EP/Ad6-based cancer vaccine against TERT with IMO induces multiple effects on innate and adaptive immune responses resulting in a significant antitumor efficacy.

Synthesis and immunological activities of novel agonists of toll-like receptor 9

Novel agonists of TLR9 with two 5'-ends and synthetic immune stimulatory motifs, referred to as immune modulatory oligonucleotides (IMOs) are potent agonists of TLR9. In the present study, we have designed and synthesized 15 novel IMOs by incorporating specific chemical modifications and studied their immune response profiles both in vitro and in vivo. Analysis of the immunostimulatory profiles of these IMOs in human and NHP cell-based assays suggest that changes in the number of synthetic immunostimulatory motifs gave only a subtle change in immune stimulation of pDCs as indicated by IFN-alpha production and pDC maturation while the addition of self-complementary sequences produced more dramatic changes in both pDC and B cell stimulation. All IMOs induced cytokine production in vivo immediately after administration in mice. Representative compounds were also compared for the ability to stimulate cytokine production in vivo (IFN-alpha and IP-10) in rhesus macaques after intra-muscular administration.

Coadministration of telomerase genetic vaccine and a novel TLR9 agonist in nonhuman primates

The human telomerase reverse transcriptase (hTERT) is an attractive target for human cancer vaccination because its expression is reactivated in most human tumors. We have evaluated the ability of DNA electroporation (DNA-EP) and adenovirus serotype 6 (Ad6) to induce immune responses against hTERT in nonhuman primates (NHPs) (Macaca mulatta). Vaccination was effective in all treated animals, and the adaptive immune response remained detectable and long lasting without side effects. To further enhance the efficacy of the hTERT vaccine, we evaluated the combination of hTERT vaccine and a novel TLR9 agonist, referred to as immunomodulatory oligonucleotide (IMO). Monkeys were dosed weekly with IMO concurrently with the vaccine regimen and showed increases in cytokine secretion and activation of natural killer (NK) cells compared with the group that received vaccine alone. Using a peptide array, a specific profile of B-cell reactive epitopes was identified when hTERT vaccine was combined with IMO. The combination of IMO with hTERT genetic vaccine did not impact vaccine-induced TERT-specific cell-mediated immunity. Our results show that appropriate combination of a DNA-EP/Ad6-based cancer vaccine against hTERT with IMO induces multiple effects on innate and adaptive immune responses in NHPs.

Toll-like receptor 9-dependent activation of myeloid dendritic cells by Deoxynucleic acids from Candida albicans

The innate immune system of humans recognizes the human pathogenic fungus Candida albicans via sugar polymers present in the cell wall, such as mannan and beta-glucan. Here, we examined whether nucleic acids from C. albicans activate dendritic cells. C. albicans DNA induced interleukin-12p40 (IL-12p40) production and CD40 expression by murine bone marrow-derived myeloid dendritic cells (BM-DCs) in a dose-dependent manner. BM-DCs that lacked Toll-like receptor 4 (TLR4), TLR2, and dectin-1, which are pattern recognition receptors for fungal cell wall components, produced IL-12p40 at levels comparable to the levels produced by BM-DCs from wild-type mice, and DNA from a C. albicans pmr1Delta null mutant, which has a gross defect in mannosylation, retained the ability to activate BM-DCs. This stimulatory effect disappeared completely after DNase treatment. In contrast, RNase treatment increased production of the cytokine. A similar reduction in cytokine production was observed when BM-DCs from TLR9(-/-) and MyD88(-/-) mice were used. In a luciferase reporter assay, NF-kappaB activation was detected in TLR9-expressing HEK293T cells stimulated with C. albicans DNA. Confocal microscopic analysis showed similar localization of C. albicans DNA and CpG-oligodeoxynucleotide (CpG-ODN) in BM-DCs. Treatment of C. albicans DNA with methylase did not affect its ability to induce IL-12p40 synthesis, whereas the same treatment completely eliminated the ability of CpG-ODN to induce IL-12p40 synthesis. Finally, impaired clearance of this fungal pathogen was not found in the kidneys of TLR9(-/-) mice. These results suggested that C. albicans DNA activated BM-DCs through a TLR9-mediated signaling pathway using a mechanism independent of the unmethylated CpG motif.

Current status and challenges of cytokine pharmacology

The major concern of pharmacology about cytokines has originated from plentiful data showing association between gross changes in their production and pathophysiological processes. Despite the enigmatic role of cytokines in diseases, a number of them have become a subject of cytokine and anti-cytokine immunotherapies. Production of cytokines can be influenced by many endogenous and exogenous stimuli including drugs. Cells of the immune system, such as macrophages and lymphocytes, are richly endowed with receptors for the mediators of physiological functions, such as biogenic amines, adenosine, prostanoids, steroids, etc. Drugs, agonists or antagonists of these receptors can directly or indirectly up- and down-regulate secretion of cytokines and expression of cytokine receptors. Vice versa, cytokines interfere with drug pharmacokinetics and pharmacodynamics through the interactions with cytochrome P450 and multiple drug resistance proteins. The aim of the review is to encourage more intensive studies in these fields of cytokine pharmacology. It also outlines major areas of searching promising candidates for immunotherapeutic interventions.

Treatment of mammary carcinomas in HER-2 transgenic mice through combination of genetic vaccine and an agonist of Toll-like receptor 9

PURPOSE

Oligodeoxynucleotides containing unmethylated CpG dinucleotides induce innate and adaptive immunity through Toll-like receptor 9 (TLR9). In the present study, we have examined the ability of a novel agonist of TLR9, called immunomodulatory oligonucleotide (IMO), to enhance effects of a HER-2/neu plasmid DNA electroporation/adenovirus (DNA-EP/Ad) vaccine.

EXPERIMENTAL DESIGN

BALB/NeuT mice were treated with DNA-EP vaccine alone, IMO alone, or the combination of two agents starting at week 13, when all mice showed mammary neoplasia. Tumor growth and survival were documented. Antibody and CD8+ T-cell responses were determined. Peptide microarray analysis of sera was carried out to identify immunoreactive epitopes. Additionally, microCT and microPET imaging was carried out in an advanced-stage tumor model starting treatment at week 17 in BALB/NeuT mice.

RESULTS

The combination of DNA-EP and IMO resulted in significant tumor regression or delay to tumor progression. 2-Deoxy-2-[18F]fluoro-D-glucose microPET and microCT imaging of mice showed reduced tumor size in the DNA-EP/IMO combination treatment group. Mice treated with the combination produced greater antibody titers with IgG2a isotype switch and antibody-dependent cellular cytotoxicity activity than did mice treated with DNA-EP vaccine. An immunogenic B-cell linear epitope, r70, within the HER-2 dimerization domain was identified through microarray analysis. Heterologous DNA-EP/Ad vaccination combined with IMO increased mice survival.

CONCLUSION

The combination of HER-2/neu genetic vaccine and novel agonist of TLR9 had potent antitumor activity associated with antibody isotype switch and antibody-dependent cellular cytotoxicity activities. These results support possible clinical trials of the combination of DNA-EP/Ad-based cancer vaccines and IMO.

Immune interventions of human diseases through toll-like receptors

Toll-like receptors (TLRs) are the immune sensors for infections, triggering robust innate immune activation followed by protective adaptive immunity against various infectious diseases. Recent evidence, however, has suggested that TLRs are involved in the pathogenesis of many diseases, including not only infectious diseases but also autoimmune diseases, allergy and atherosclerosis. Therefore, prophylactic or therapeutic application of TLR-based immune interventions should be potent, but their safety must be demonstrated using experimental animal models as well as human resources, including analysis of single nucleotide polymorphisms. Here, we focus on recent advances in understanding of the protective and pathogenic roles of TLRs in human diseases.

Impact of secondary structure of toll-like receptor 9 agonists on interferon alpha induction

Oligodeoxynucleotides containing a CpG motif and double- or multistranded structure-forming sequences act as agonists of Toll-like receptor 9 (TLR9) and induce high levels of interferon alpha (IFN-alpha) in addition to other Th1-type cytokines. In the present study, we evaluated three highly effective IFN-alpha-inducing agonists of TLR9 to determine the type of duplex structures formed and the agonist's ability to induce immune responses, including IFN-alpha induction, in human cell-based assays and in vivo in mice and nonhuman primates. Thermal melting studies showed that two of the agonists evaluated had a single melting transition with similar hyperchromicity in both heating and cooling cycles, suggesting the formation of intermolecular duplexes. A third agonist showed a biphasic melting transition in the heating cycle and a monophasic melting transition with lower hyperchromicity during the cooling cycle, suggesting the formation of both intra- and intermolecular duplexes. All three agonists induced the production of Th1-type cytokines and chemokines, including high levels of IFN-alpha, in human peripheral blood mononuclear cell and plasmacytoid dendritic cell cultures. Subcutaneous administration of the two intermolecular duplex-forming agonists, but not the intramolecular duplex-forming agonist, induced cytokine secretion in mice. In nonhuman primates, the two agonists that formed intermolecular duplexes induced IFN-alpha and IP-10 secretion. On the contrary, the agonist that formed an intramolecular duplex induced only low levels of cytokines in nonhuman primates, suggesting that this type of structure formation is less immunostimulatory in vivo than the other structure. Taken together, the present results suggest that oligonucleotide-based agonists of TLR9 that form intermolecular duplexes induce potent immune responses in vivo.

Immunostimulatory CpG oligonucleotides form defined three-dimensional structures: results from an NMR study

The DNA eicosamer 5'-TCCATGACGTTCCTGATGCT-3' is known to stimulate the innate immune system of vertebrae. The immunostimulatory activity is based on the activation of Toll-like receptor 9 (TLR9). While it is known that the CG dinucleotide of the eicosamer has to be unmethylated, the structural basis of the recognition of the DNA through the receptor remains unclear. Oligodeoxynucleotides containing the sequence of the eicosamer, or a portion thereof, ranging in length from hexamer to pentaeicosamer were studied by (1)H NMR spectroscopy. Based on two-dimensional NMR spectra, a number of resonances could be unambiguously assigned. For all oligonucleotides, structural transitions were detected upon heating, as monitored by the line width and chemical shift of low-field resonances. This includes the TC dinucleotide of the 5'-terminal portion, which does not have any clear base-pairing partners. The melting transitions, together with the NOESY cross-peaks, demonstrate that structure formation occurs well beyond the core hexamer 5'-GACGTT-3', a fact that may be important for understanding the molecular recognition by the Toll-like receptors of the innate immune system.