CpG still rocks! Update on an accidental drug

Clinical applications of oligonucleotides for cancer therapy

Oligonucleotide therapeutics (ONTs) represent a rapidly evolving modality for cancer treatment, capitalizing on their ability to modulate gene expression with high specificity. With more than 20 nucleic acid-based therapies that gained regulatory approval, advances in chemical modifications, sequence optimization, and novel delivery systems have propelled ONTs from research tools to clinical realities. ONTs, including siRNAs, antisense oligonucleotides, saRNA, miRNA, aptamers, and decoys, offer promising solutions for targeting previously "undruggable" molecules, such as transcription factors, and enhancing cancer immunotherapy by overcoming tumor immune evasion. The promise of ONT application in cancer treatment is exemplified by the recent FDA approval of the first oligonucleotide-based treatment to myeloproliferative disease. At the same time, there are challenges in delivering ONTs to specific tissues, mitigating off-target effects, and improving cellular uptake and endosomal release. This review provides a comprehensive overview of ONTs in clinical trials, emerging delivery strategies, and innovative therapeutic approaches, emphasizing the role of ONTs in immunotherapy and addressing hurdles that hinder their clinical translation. By examining advances and remaining challenges, we highlight opportunities for ONTs to revolutionize oncology and enhance patient outcomes.

Local CpG-Stat3 siRNA treatment improves antitumor effects of immune checkpoint inhibitors

Immune checkpoint blockade (ICB) therapy has significantly benefited patients with several types of solid tumors and some lymphomas. However, many of the treated patients do not have a durable clinical response. It has been demonstrated that rescuing exhausted CD8+ T cells is required for ICB-mediated antitumor effects. We recently developed an immunostimulatory strategy based on silencing STAT3 while stimulating immune responses by CpG, a ligand for Toll-like receptor 9 (TLR9). The CpG-small interfering RNA (siRNA) conjugates efficiently enter immune cells, silencing STAT3 and activating innate immunity to enhance T cell-mediated antitumor immune responses. In the present study, we demonstrate that blocking STAT3 through locally delivered CpG-Stat3 siRNA enhances the efficacies of the systemic PD-1 and CTLA4 blockade against mouse A20 B cell lymphoma. In addition, locally delivered CpG-Stat3 siRNA combined with systemic administration of PD-1 antibody significantly augmented both local and systemic antitumor effects against mouse B16 melanoma tumors, with enhanced tumor-associated T cell activation. Furthermore, locally delivered CpG-Stat3 siRNA enhanced CD8+ T cell tumor infiltration and antitumor activity in a xenograft tumor model. Overall, our studies in both B cell lymphoma and melanoma mouse models demonstrate the potential of combinatory immunotherapy with CpG-Stat3 siRNA and checkpoint inhibitors as a therapeutic strategy for B cell lymphoma and melanoma.

Screening Splice-Switching Antisense Oligonucleotides in Pancreas-Cancer Organoids

Aberrant alternative splicing is emerging as a cancer hallmark and a potential therapeutic target. It is the result of dysregulated or mutated splicing factors, or genetic alterations in splicing-regulatory cis-elements. Targeting individual altered splicing events associated with cancer-cell dependencies is a potential therapeutic strategy, but several technical limitations need to be addressed. Patient-derived organoids are a promising platform to recapitulate key aspects of disease states, and to facilitate drug development for precision medicine. Here, we report an efficient antisense-oligonucleotide (ASO) lipofection method to systematically evaluate and screen individual splicing events as therapeutic targets in pancreatic ductal adenocarcinoma organoids. This optimized delivery method allows fast and efficient screening of ASOs, e.g., those that reverse oncogenic alternative splicing. In combination with advances in chemical modifications of oligonucleotides and ASO-delivery strategies, this method has the potential to accelerate the discovery of antitumor ASO drugs that target pathological alternative splicing.

Schlafen 11 triggers innate immune responses through its ribonuclease activity upon detection of single-stranded DNA

Nucleic acids are major structures detected by the innate immune system. Although intracellular single-stranded DNA (ssDNA) accumulates during pathogen infection or disease, it remains unclear whether and how intracellular ssDNA stimulates the innate immune system. Here, we report that intracellular ssDNA triggers cytokine expression and cell death in a CGT motif-dependent manner. We identified Schlafen 11 (SLFN11) as an ssDNA-activated RNase, which is essential for the innate immune responses induced by intracellular ssDNA and adeno-associated virus infection. We found that SLFN11 directly binds ssDNA containing CGT motifs through its carboxyl-terminal domain, translocates to the cytoplasm upon ssDNA recognition, and triggers innate immune responses through its amino-terminal ribonuclease activity that cleaves transfer RNA (tRNA). Mice deficient in Slfn9, a mouse homolog of SLFN11, exhibited resistance to CGT ssDNA-induced inflammation, acute hepatitis, and septic shock. This study identifies CGT ssDNA and SLFN11/9 as a class of immunostimulatory nucleic acids and pattern recognition receptors, respectively, and conceptually couples DNA immune sensing to controlled RNase activation and tRNA cleavage.

Nanoparticle-Conjugated Toll-Like Receptor 9 Agonists Improve the Potency, Durability, and Breadth of COVID-19 Vaccines

Development of effective vaccines for infectious diseases has been one of the most successful global health interventions in history. Though, while ideal subunit vaccines strongly rely on antigen and adjuvant(s) selection, the mode and time scale of exposure to the immune system has often been overlooked. Unfortunately, poor control over the delivery of many adjuvants, which play a key role in enhancing the quality and potency of immune responses, can limit their efficacy and cause off-target toxicities. There is a critical need for improved adjuvant delivery technologies to enhance their efficacy and boost vaccine performance. Nanoparticles have been shown to be ideal carriers for improving antigen delivery due to their shape and size, which mimic viral structures but have been generally less explored for adjuvant delivery. Here, we describe the design of self-assembled poly(ethylene glycol)-b-poly(lactic acid) nanoparticles decorated with CpG, a potent TLR9 agonist, to increase adjuvanticity in COVID-19 vaccines. By controlling the surface density of CpG, we show that intermediate valency is a key factor for TLR9 activation of immune cells. When delivered with the SARS-CoV-2 spike protein, CpG nanoparticle (CpG-NP) adjuvant greatly improves the magnitude and duration of antibody responses when compared to soluble CpG, and results in overall greater breadth of immunity against variants of concern. Moreover, encapsulation of CpG-NP into injectable polymeric-nanoparticle (PNP) hydrogels enhances the spatiotemporal control over codelivery of CpG-NP adjuvant and spike protein antigen such that a single immunization of hydrogel-based vaccines generates humoral responses comparable to those of a typical prime-boost regimen of soluble vaccines. These delivery technologies can potentially reduce the costs and burden of clinical vaccination, both of which are key elements in fighting a pandemic.

Targeting RNA with synthetic oligonucleotides: Clinical success invites new challenges

Synthetic antisense oligonucleotides (ASOs) and duplex RNAs (dsRNAs) are an increasingly successful strategy for drug development. After a slow start, the pace of success has accelerated since the approval of Spinraza (nusinersen) in 2016 with several drug approvals. These accomplishments have been achieved even though oligonucleotides are large, negatively charged, and have little resemblance to traditional small-molecule drugs-a remarkable achievement of basic and applied science. The goal of this review is to summarize the foundation underlying recent progress and describe ongoing research programs that may increase the scope and impact of oligonucleotide therapeutics.

Local CpG- Stat3 siRNA treatment improves antitumor effects of immune checkpoint inhibitors

Immune checkpoint blockade (ICB) therapy has significantly benefited patients with several types of solid tumors and some lymphomas. However, many of the treated patients do not have durable clinical response. It has been demonstrated that rescuing exhausted CD8 + T cells is required for ICB-mediated antitumor effects. We recently developed an immunostimulatory strategy based on silencing STAT3 while stimulating immune responses by CpG, ligand for Toll-like receptor 9 (TLR9). The CpG-small interfering RNA (siRNA) conjugates efficiently enter immune cells, silencing STAT3 and activating innate immunity to enhance T-cell mediated antitumor immune responses. In the present study, we demonstrate that blocking STAT3 through locally delivered CpG- Stat3 siRNA enhances the efficacies of the systemic PD-1 and CTLA4 blockade against mouse A20 B cell lymphoma. In addition, locally delivered CpG- Stat3 siRNA combined with systemic administration of PD-1 antibody significantly augmented both local and systemic antitumor effects against mouse B16 melanoma tumors, with enhanced tumor-associated T cell activation. Overall, our studies in both B cell lymphoma and melanoma mouse models demonstrate the potential of combinatory immunotherapy with CpG- Stat3 siRNA and checkpoint inhibitors as a therapeutic strategy for B cell lymphoma and melanoma.

Enhancing the Effectiveness of Oligonucleotide Therapeutics Using Cell-Penetrating Peptide Conjugation, Chemical Modification, and Carrier-Based Delivery Strategies

Oligonucleotide-based therapies are a promising approach for treating a wide range of hard-to-treat diseases, particularly genetic and rare diseases. These therapies involve the use of short synthetic sequences of DNA or RNA that can modulate gene expression or inhibit proteins through various mechanisms. Despite the potential of these therapies, a significant barrier to their widespread use is the difficulty in ensuring their uptake by target cells/tissues. Strategies to overcome this challenge include cell-penetrating peptide conjugation, chemical modification, nanoparticle formulation, and the use of endogenous vesicles, spherical nucleic acids, and smart material-based delivery vehicles. This article provides an overview of these strategies and their potential for the efficient delivery of oligonucleotide drugs, as well as the safety and toxicity considerations, regulatory requirements, and challenges in translating these therapies from the laboratory to the clinic.

A first-in-human phase 1 study of cavrotolimod, a TLR9 agonist spherical nucleic acid, in healthy participants: Evidence of immune activation

Introduction

Tumor immunotherapy is designed to control malignancies through the host immune response but requires circumventing tumor-dysregulated immunomodulation through immunostimulation, relieving immunorepression, or a combination of both approaches. Here we designed and characterized cavrotolimod (formerly AST-008), an immunostimulatory spherical nucleic acid (SNA) compound targeting Toll-like receptor 9 (TLR9). We assessed the safety and pharmacodynamic (PD) properties of cavrotolimod in healthy participants in a first-in-human Phase 1 study under protocol AST-008-101 (NCT03086278; https://clinicaltrials.gov/ct2/show/NCT03086278).

Methods

Healthy participants aged 18 to 40 years were enrolled to evaluate four dose levels of cavrotolimod across four cohorts. Each cohort included four participants, and all received a single subcutaneous dose of cavrotolimod. The dose levels were 5, 10, 12.5 and 18.8 µg/kg.

Results and discussion

Cavrotolimod was well tolerated and elicited no serious adverse events or dose limiting toxicities at the doses tested. The results demonstrated that cavrotolimod is a potent innate immune activator, specifically stimulating Th1-type immune responses, and exhibits PD properties that may result in anti-tumor effects in patients with cancer. This study suggests that cavrotolimod is a promising clinical immunotherapy agent.

G-rich motifs within phosphorothioate-based antisense oligonucleotides (ASOs) drive activation of FXN expression through indirect effects

Friedreich's ataxia is an incurable disease caused by frataxin (FXN) protein deficiency, which is mostly induced by GAA repeat expansion in intron 1 of the FXN gene. Here, we identified antisense oligonucleotides (ASOs), complementary to two regions within the first intron of FXN pre-mRNA, which could increase FXN mRNA by ∼2-fold in patient fibroblasts. The increase in FXN mRNA was confirmed by the identification of multiple overlapping FXN-activating ASOs at each region, two independent RNA quantification assays, and normalization by multiple housekeeping genes. Experiments on cells with the ASO-binding sites deleted indicate that the ASO-induced FXN activation was driven by indirect effects. RNA sequencing analyses showed that the two ASOs induced similar transcriptome-wide changes, which did not resemble the transcriptome of wild-type cells. This RNA-seq analysis did not identify directly base-paired off-target genes shared across ASOs. Mismatch studies identified two guanosine-rich motifs (CCGG and G4) within the ASOs that were required for FXN activation. The phosphorodiamidate morpholino oligomer analogs of our ASOs did not activate FXN, pointing to a PS-backbone-mediated effect. Our study demonstrates the importance of multiple, detailed control experiments and target validation in oligonucleotide studies employing novel mechanisms such as gene activation.

Assessment of the Immunogenicity Potential for Oligonucleotide-Based Drugs

Therapeutic oligonucleotides (ONs) have characteristics of both small molecules and biologics. Although safety assessment of ONs largely follows guidelines established for small molecules, the unique characteristics of ONs often require incorporation of concepts from the safety assessment of biologics. The assessment of immunogenicity for ON therapeutics is one area where the approach is distinct from either established small molecule or biologic platforms. Information regarding immunogenicity of ONs is limited, but indicates that administration of ONs can result in antidrug antibody formation. In this study, we summarize the collective experience of the Oligonucleotide Safety Working Group in designing the immunogenicity assessment appropriate for this class of therapeutic, including advice on assay development, clinical monitoring, and evaluation of the impact of immunogenicity on exposure, efficacy, and safety of therapeutic ONs.

Vaccine adjuvants to engage the cross-presentation pathway

Adjuvants are indispensable components of vaccines for stimulating optimal immune responses to non-replicating, inactivated and subunit antigens. Eliciting balanced humoral and T cell-mediated immunity is paramount to defend against diseases caused by complex intracellular pathogens, such as tuberculosis, malaria, and AIDS. However, currently used vaccines elicit strong antibody responses, but poorly stimulate CD8 cytotoxic T lymphocyte (CTL) responses. To elicit potent CTL memory, vaccines need to engage the cross-presentation pathway, and this requirement has been a crucial bottleneck in the development of subunit vaccines that engender effective T cell immunity. In this review, we focus on recent insights into DC cross-presentation and the extent to which clinically relevant vaccine adjuvants, such as aluminum-based nanoparticles, water-in oil emulsion (MF59) adjuvants, saponin-based adjuvants, and Toll-like receptor (TLR) ligands modulate DC cross-presentation efficiency. Further, we discuss the feasibility of using carbomer-based adjuvants as next generation of adjuvant platforms to elicit balanced antibody- and T-cell based immunity. Understanding of the molecular mechanism of DC cross-presentation and the mode of action of adjuvants will pave the way for rational design of vaccines for infectious diseases and cancer that require balanced antibody- and T cell-based immunity.

Intranasal Delivery of Thermostable Subunit Vaccine for Cross-Reactive Mucosal and Systemic Antibody Responses Against SARS-CoV-2

Despite the remarkable efficacy of currently approved COVID-19 vaccines, there are several opportunities for continued vaccine development against SARS-CoV-2 and future lethal respiratory viruses. In particular, restricted vaccine access and hesitancy have limited immunization rates. In addition, current vaccines are unable to prevent breakthrough infections, leading to prolonged virus circulation. To improve access, a subunit vaccine with enhanced thermostability was designed to eliminate the need for an ultra-cold chain. The exclusion of infectious and genetic materials from this vaccine may also help reduce vaccine hesitancy. In an effort to prevent breakthrough infections, intranasal immunization to induce mucosal immunity was explored. A prototype vaccine comprised of receptor-binding domain (RBD) polypeptides formulated with additional immunoadjuvants in a chitosan (CS) solution induced high levels of RBD-specific antibodies in laboratory mice after 1 or 2 immunizations. Antibody responses were durable with high titers persisting for at least five months following subcutaneous vaccination. Serum anti-RBD antibodies contained both IgG1 and IgG2a isotypes suggesting that the vaccine induced a mixed Th1/Th2 response. RBD vaccination without CS formulation resulted in minimal anti-RBD responses. The addition of CpG oligonucleotides to the CS plus RBD vaccine formulation increased antibody titers more effectively than interleukin-12 (IL-12). Importantly, generated antibodies were cross-reactive against RBD mutants associated with SARS-CoV-2 variants of concern, including alpha, beta and delta variants, and inhibited binding of RBD to its cognate receptor angiotensin converting enzyme 2 (ACE2). With respect to stability, vaccines did not lose activity when stored at either room temperature (21-22°C) or 4°C for at least one month. When delivered intranasally, vaccines induced RBD-specific mucosal IgA antibodies, which may protect against breakthrough infections in the upper respiratory tract. Altogether, data indicate that the designed vaccine platform is versatile, adaptable and capable of overcoming key constraints of current COVID-19 vaccines.

Systemic delivery of a targeted synthetic immunostimulant transforms the immune landscape for effective tumor regression

Promoting immune activation within the tumor microenvironment (TME) is a promising therapeutic strategy to reverse tumor immunosuppression and elicit anti-tumor immunity. To enable tumor-localized immunotherapy following intravenous administration, we chemically conjugated a polyspecific integrin-binding peptide (PIP) to an immunostimulant (Toll-like receptor 9 [TLR9] agonist: CpG) to generate a tumor-targeted immunomodulatory agent, referred to as PIP-CpG. We demonstrate that systemic delivery of PIP-CpG induces tumor regression and enhances therapeutic efficacy compared with untargeted CpG in aggressive murine breast and pancreatic cancer models. Furthermore, PIP-CpG transforms the immune-suppressive TME dominated by myeloid-derived suppressor cells into a lymphocyte-rich TME infiltrated with activated CD8+ T cells, CD4+ T cells, and B cells. Finally, we show that T cells are required for therapeutic efficacy and that PIP-CpG treatment generates tumor-specific CD8+ T cells. These data demonstrate that conjugation to a synthetic tumor-targeted peptide can improve the efficacy of systemically administered immunostimulants and lead to durable anti-tumor immune responses.

AMD Genomics: Non-Coding RNAs as Biomarkers and Therapeutic Targets

Age-related macular degeneration (AMD) is a progressive neurodegenerative disease that is the world’s leading cause of blindness in the aging population. Although the clinical stages and forms of AMD have been elucidated, more specific prognostic tools are required to determine when patients with early and intermediate AMD will progress into the advanced stages of AMD. Another challenge in the field has been the appropriate development of therapies for intermediate AMD and advanced atrophic AMD. After numerous negative clinical trials, an anti-C5 agent and anti-C3 agent have recently shown promising results in phase 3 clinical trials, in terms of slowing the growth of geographic atrophy, an advanced form of AMD. Interestingly, both drugs appear to be associated with an increased incidence of wet AMD, another advanced form of the disease, and will require frequent intravitreal injections. Certainly, there remains a need for other therapeutic agents with the potential to prevent progression to advanced stages of the disease. Investigation of the role and clinical utility of non-coding RNAs (ncRNAs) is a major advancement in biology that has only been minimally applied to AMD. In the following review, we discuss the clinical relevance of ncRNAs in AMD as both biomarkers and therapeutic targets.

DNA Damage Repair in Brain Tumor Immunotherapy

With the gradual understanding of tumor development, many tumor therapies have been invented and applied in clinical work, and immunotherapy has been widely concerned as an emerging hot topic in the last decade. It is worth noting that immunotherapy is nowadays applied under too harsh conditions, and many tumors are defined as “cold tumors” that are not sensitive to immunotherapy, and brain tumors are typical of them. However, there is much evidence that suggests a link between DNA damage repair mechanisms and immunotherapy. This may be a breakthrough for the application of immunotherapy in brain tumors. Therefore, in this review, first, we will describe the common pathways of DNA damage repair. Second, we will focus on immunotherapy and analyze the mechanisms of DNA damage repair involved in the immune process. Third, we will review biomarkers that have been or may be used to evaluate immunotherapy for brain tumors, such as TAMs, RPA, and other molecules that may provide a precursor assessment for the rational implementation of immunotherapy for brain tumors. Finally, we will discuss the rational combination of immunotherapy with other therapeutic approaches that have an impact on the DNA damage repair process in order to open new pathways for the application of immunotherapy in brain tumors, to maximize the effect of immunotherapy on DNA damage repair mechanisms, and to provide ideas and guidance for immunotherapy in brain tumors.

Cutaneous CpG adjuvant conditioning to enhance vaccine responses

Adjuvant activity of the Toll receptor 9 agonist CpG 1826 was compared when given subcutaneously (s.c.) together with ovalbumin (s.c.[CpG + Ova]), or when given by either s.c. or intradermally (i.d.) routes two days prior to s.c. ovalbumin. Frequencies of CD8 + effector (T_EFF) and central memory (T_CM) T cells along with total IgG, IgG2c, and IgG1 titres were measured to ascertain how timing and location of CpG conditioning influenced vaccination outcome. Prior treatment with CpG enhanced T_EFF, T_CM, as well as total IgG responses. T_EFF and T_CM responses were greatest when CpG was given intradermally and prior to s.c. ovalbumin, conditions that eliminated the fraction of T_CM 'non-responders' observed after s.c.[CpG + Ova] vaccination. IgG responses were polarized toward IgG2c after early s.c. CpG but toward IgG1 after early i.d. CpG. Separating CpG adjuvant and antigen application in time and space can improve vaccination outcome.

Engineering Optimal Vaccination Strategies: Effects of Physical Properties of the Delivery System on Functions

With rapid developments in medical science and technology, vaccinations have become the key to solving public health problems. Various diseases can be prevented by vaccinations, which mimic a disease by...

Overcoming PD-1 Blockade Resistance with CpG-A Toll-Like Receptor 9 Agonist Vidutolimod in Patients with Metastatic Melanoma

Patients with advanced melanoma that is resistant to PD-1 blockade therapy have limited treatment options. Vidutolimod (formerly CMP-001), a virus-like particle containing a CpG-A Toll-like receptor 9 (TLR9) agonist, may reverse PD-1 blockade resistance by triggering a strong IFN response to induce and attract antitumor T cells. In the dose-escalation part of this phase Ib study, vidutolimod was administered intratumorally at escalating doses with intravenous pembrolizumab to 44 patients with advanced melanoma who had progressive disease or stable disease on prior anti-PD-1 therapy. The combination of vidutolimod and pembrolizumab had a manageable safety profile, and durable responses were observed in 25% of patients, with tumor regression in both injected and noninjected lesions, including visceral lesions. Patients who responded to vidutolimod and pembrolizumab had noninflamed tumors at baseline and induction of an IFNγ gene signature following treatment, as well as increased systemic expression of the IFN-inducible chemokine CXCL10.

SIGNIFICANCE

In this phase Ib study in patients with advanced melanoma, intratumoral TLR9 agonist vidutolimod in combination with pembrolizumab had a manageable safety profile and showed promising clinical activity, supporting the further clinical development of vidutolimod to overcome PD-1 blockade resistance through induction of an IFN response. See related commentary by Sullivan, p. 2960. This article is highlighted in the In This Issue feature, p. 2945.

From bench side to clinic: Potential and challenges of RNA vaccines and therapeutics in infectious diseases

The functional and structural versatility of Ribonucleic acids (RNAs) makes them ideal candidates for overcoming the limitations imposed by small molecule-based drugs. Hence, RNA-based biopharmaceuticals such as messenger RNA (mRNA) vaccines, antisense oligonucleotides (ASOs), small interfering RNAs (siRNAs), microRNA mimics, anti-miRNA oligonucleotides (AMOs), aptamers, riboswitches, and CRISPR-Cas9 are emerging as vital tools for the treatment and prophylaxis of many infectious diseases. Some of the major challenges to overcome in the area of RNA-based therapeutics have been the instability of single-stranded RNAs, delivery to the diseased cell, and immunogenicity. However, recent advancements in the delivery systems of in vitro transcribed mRNA and chemical modifications for protection against nucleases and reducing the toxicity of RNA have facilitated the entry of several exogenous RNAs into clinical trials. In this review, we provide an overview of RNA-based vaccines and therapeutics, their production, delivery, current advancements, and future translational potential in treating infectious diseases.

Elucidating the Motif for CpG Oligonucleotide Binding to the Dendritic Cell Receptor DEC-205 Leads to Improved Adjuvants for Liver-Resident Memory

DEC-205 is a cell-surface receptor that transports bound ligands into the endocytic pathway for degradation or release within lysosomal endosomes. This receptor has been reported to bind a number of ligands, including keratin, and some classes of CpG oligodeoxynucleotides (ODN). In this study, we explore in detail the requirements for binding ODNs, revealing that DEC-205 efficiently binds single-stranded, phosphorothioated ODN of ≥14 bases, with preference for the DNA base thymidine, but with no requirement for a CpG motif. DEC-205 fails to bind double-stranded phosphodiester ODN, and thus does not bind the natural type of DNA found in mammals. The ODN binding preferences of DEC-205 result in strong binding of B class ODN, moderate binding to C class ODN, minimal binding to P class ODN, and no binding to A class ODN. Consistent with DEC-205 binding capacity, induction of serum IL-12p70 or activation of B cells by each class of ODN correlated with DEC-205 dependence in mice. Thus, the greater the DEC-205 binding capacity, the greater the dependence on DEC-205 for optimal responses. Finally, by covalently linking a B class ODN that efficiently binds DEC-205, to a P class ODN that shows poor binding, we improved DEC-205 binding and increased adjuvancy of the hybrid ODN. The hybrid ODN efficiently enhanced induction of effector CD8 T cells in a DEC-205-dependent manner. Furthermore, the hybrid ODN induced robust memory responses, and was particularly effective at promoting the development of liver tissue-resident memory T cells.

Delivery of Oligonucleotide Therapeutics: Chemical Modifications, Lipid Nanoparticles, and Extracellular Vesicles

Oligonucleotides (ONs) comprise a rapidly growing class of therapeutics. In recent years, the list of FDA-approved ON therapies has rapidly expanded. ONs are small (15-30 bp) nucleotide-based therapeutics which are capable of targeting DNA and RNA as well as other biomolecules. ONs can be subdivided into several classes based on their chemical modifications and on the mechanisms of their target interactions. Historically, the largest hindrance to the widespread usage of ON therapeutics has been their inability to effectively internalize into cells and escape from endosomes to reach their molecular targets in the cytosol or nucleus. While cell uptake has been improved, "endosomal escape" remains a significant problem. There are a range of approaches to overcome this, and in this review, we focus on three: altering the chemical structure of the ONs, formulating synthetic, lipid-based nanoparticles to encapsulate the ONs, or biologically loading the ONs into extracellular vesicles. This review provides a background to the design and mode of action of existing FDA-approved ONs. It presents the most common ON classifications and chemical modifications from a fundamental scientific perspective and provides a roadmap of the cellular uptake pathways by which ONs are trafficked. Finally, this review delves into each of the above-mentioned approaches to ON delivery, highlighting the scientific principles behind each and covering recent advances.

Myeloid cell-targeted STAT3 inhibition sensitizes head and neck cancers to radiotherapy and T cell-mediated immunity

The tumor microenvironment affects the outcome of radiotherapy against head and neck squamous cell carcinoma (HNSCC). We recently found that tolerogenic myeloid cells accumulate in the circulation of HNSCC patients undergoing radiotherapy. Here, we analyzed tumor-containing lymph node biopsies collected from these patients. After 2 weeks of radiotherapy, we found an increase in tumor-associated macrophages (TAMs) with activated STAT3, while CD8+ T cells were reduced as detected using multiplex IHC. Gene expression profiling indicated upregulation of M2 macrophage-related genes (CD163, CD206), immunosuppressive mediators (ARG1, LIF, TGFB1), and Th2 cytokines (IL4, IL5) in irradiated tumors. We next validated STAT3 as a potential target in human HNSCC-associated TAMs, using UM-SCC1 xenotransplants in humanized mice. Local injections of myeloid cell-targeted STAT3 antisense oligonucleotide (CpG-STAT3ASO) activated human DCs/macrophages and promoted CD8+ T cell recruitment, thereby arresting UM-SCC1 tumor growth. Furthermore, CpG-STAT3ASO synergized with tumor irradiation against syngeneic HPV+ mEERL and HPV- MOC2 HNSCC tumors in mice, triggering tumor regression and/or extending animal survival. The antitumor immune responses were CD8+ and CD4+ T cell dependent and associated with the activation of antigen-presenting cells (DCs/M1 macrophages) and increased CD8+ to regulatory T cell ratio. Our observations suggest that targeted inhibition of STAT3 in tumor-associated myeloid cells augments the efficacy of radiotherapy against HNSCC.

Innate immunity stimulation via CpG oligodeoxynucleotides ameliorates Alzheimer's disease pathology in aged squirrel monkeys

Alzheimer's disease is the most common cause of dementia and the only illness among the top 10 causes of death for which there is no disease-modifying therapy. The failure rate of clinical trials is very high, in part due to the premature translation of successful results in transgenic mouse models to patients. Extensive evidence suggests that dysregulation of innate immunity and microglia/macrophages plays a key role in Alzheimer's disease pathogenesis. Activated resident microglia and peripheral macrophages can display protective or detrimental phenotypes depending on the stimulus and environment. Toll-like receptors (TLRs) are a family of innate immune regulators known to play an important role in governing the phenotypic status of microglia. We have shown in multiple transgenic Alzheimer's disease mouse models that harnessing innate immunity via TLR9 agonist CpG oligodeoxynucleotides (ODNs) modulates age-related defects associated with immune cells and safely reduces amyloid plaques, oligomeric amyloid-β, tau pathology, and cerebral amyloid angiopathy (CAA) while promoting cognitive benefits. In the current study we have used a non-human primate model of sporadic Alzheimer's disease pathology that develops extensive CAA-elderly squirrel monkeys. The major complications in current immunotherapeutic trials for Alzheimer's disease are amyloid-related imaging abnormalities, which are linked to the presence and extent of CAA; hence, the prominence of CAA in elderly squirrel monkeys makes them a valuable model for studying the safety of the CpG ODN-based concept of immunomodulation. We demonstrate that long-term use of Class B CpG ODN 2006 induces a favourable degree of innate immunity stimulation without producing excessive or sustained inflammation, resulting in efficient amelioration of both CAA and tau Alzheimer's disease-related pathologies in association with behavioural improvements and in the absence of microhaemorrhages in aged elderly squirrel monkeys. CpG ODN 2006 has been well established in numerous human trials for a variety of diseases. The present evidence together with our earlier, extensive preclinical research, validates the beneficial therapeutic outcomes and safety of this innovative immunomodulatory approach, increasing the likelihood of CpG ODN therapeutic efficacy in future clinical trials.

CpG immunostimulatory oligodeoxynucleotide 1826 as a novel nasal ODN adjuvant enhanced the protective efficacy of the periodontitis gene vaccine in a periodontitis model in SD rats

BACKGROUND

We previously demonstrated that nasal administration of periodontitis gene vaccine (pVAX1-HA2-fimA) or pVAX1-HA2-fimA plus IL-15 as adjuvant provoked protective immunity in the periodontal tissue of SD rats. This study evaluated the immune effect of pVAX1-HA2-fimA plus CpG-ODN 1826 as an adjuvant in the SD rat periodontitis models to improve the efficacy of the previously used vaccine.

METHODS

Periodontitis was induced in maxillary second molars in SD rats receiving a ligature and infected with Porphyromonas gingivalis. Forty-two SD rats were randomly assigned to six groups: A, control without P. gingivalis; B, P. gingivalis with saline; C, P. gingivalis with pVAX1; D, P. gingivalis with pVAX1-HA2-fimA; E, P. gingivalis with pVAX1-HA2-fimA/IL-15; F, P. gingivalis with pVAX1-HA2-fimA+CpG ODN 1826 (30 µg). The levels of FimA-specific and HA2-specific secretory IgA antibodies in the saliva of rats were measured by ELISA. The levels of COX-2 and RANKL were detected by immunohistochemical assay. Morphometric analysis was used to evaluate alveolar bone loss. Major organs were observed by HE staining.

RESULTS

30 μg could be the optimal immunization dose for CpG-ODN 1826 and the levels of SIgA antibody were consistently higher in the pVAX1-HA2-fimA+CpG-ODN 1826 (30 µg) group than in the other groups during weeks 1-8 (P < 0.05, except week 1 or 2). Morphometric analysis demonstrated that pVAX1-HA2-fimA+CpG-ODN 1826 (30 µg) significantly reduced alveolar bone loss in ligated maxillary molars in group F compared with groups B-E (P < 0.05). Immunohistochemical assays revealed that the levels of COX-2 and RANKL were significantly lower in group F compared with groups B-E (P < 0.05). HE staining results of the major organs indicated that pVAX1-HA2-fimA with or without CpG-ODN 1826 was not toxic for in vivo use.

CONCLUSIONS

These results indicated that CpG-ODN 1826 (30 µg) could be used as an effective and safe mucosal adjuvant for pVAX1-HA2-fimA in SD rats since it could elicit mucosal SIgA responses and modulate COX-2 and RANKL production during weeks 1-8, thereby inhibiting inflammation and decreasing bone loss.

Irreversible Electroporation and Nivolumab Combined with Intratumoral Administration of a Toll-Like Receptor Ligand, as a Means of In Vivo Vaccination for Metastatic Pancreatic Ductal Adenocarcinoma (PANFIRE-III). A Phase-I Study Protocol

Simple Summary

Metastatic pancreatic ductal adenocarcinoma has a dismal prognosis, and to date no curative treatment options exist. The image guided tumor ablation technique irreversible electroporation (IRE) employs high-voltage electrical pulses through the application of several needle electrodes in and around the tumor in order to induce cell death. IRE ablation of the primary tumor has the ability to reduce pancreatic tumor induced immune suppression while allowing the expansion of tumor specific effector T cells, hereby possibly shifting the pancreatic tumor microenvironment into a more immune permissive state. The addition of immune enhancing therapies to IRE might work synergistically and could potentially induce a clinically significant treatment effect. This study protocol describes the rationale and design of the PANFIRE-III trial that aims to assess the safety of the combination of IRE with IMO-2125 (toll-like receptor 9 ligand) and/or nivolumab in patients with metastatic pancreatic ductal adenocarcinoma.

Abstract

Irreversible electroporation (IRE) is a novel image-guided tumor ablation technique with the ability to generate a window for the establishment of systemic antitumor immunity. IRE transiently alters the tumor’s immunosuppressive microenvironment while simultaneously generating antigen release, thereby instigating an adaptive immune response. Combining IRE with immunotherapeutic drugs, i.e., electroimmunotherapy, has synergistic potential and might induce a durable antitumor response. The primary objective of this study is to assess the safety of the combination of IRE with IMO-2125 (a toll-like receptor 9 ligand) and/or nivolumab in patients with metastatic pancreatic ductal adenocarcinoma (mPDAC). In this randomized controlled phase I clinical trial, 18 patients with mPDAC pretreated with chemotherapy will be enrolled in one of three study arms: A (control): nivolumab monotherapy; B: percutaneous IRE of the primary tumor followed by nivolumab; or C: intratumoral injection of IMO-2125 followed by percutaneous IRE of the primary tumor and nivolumab. Assessments include contrast enhanced computed tomography (ceCT), ¹⁸F-FDG and ¹⁸F-BMS-986192 (PD-L1) positron emission tomography (PET)-CT, biopsies of the primary tumor and metastases, peripheral blood samples, and quality of life and pain questionnaires. There is no curative treatment option for patients with mPDAC, and palliative chemotherapy regimens only moderately improve survival. Consequently, there is an urgent need for innovative and radically different treatment approaches. Should electroimmunotherapy establish an effective and durable anti-tumor response, it may ultimately improve PDAC’s dismal prognosis.

The Role of Regulatory T Cells in Epicutaneous Immunotherapy for Food Allergy

In recent decades, a rapid increase in the prevalence of food allergies has led to extensive research on novel treatment strategies and their mechanisms. Mouse models have provided preliminary insights into the mechanism of epicutaneous immunotherapy (EPIT)-induced immune tolerance. In EPIT, antigen applied on the skin surface can be captured, processed, and presented in the lymph nodes (LNs) by Antigen-presenting cells (APCs). In the LNs, induction of regulatory T cells (Treg cells) requires both direct contact during antigen presentation and indirect mechanisms such as cytokines. Foxp3+CD62L+ Treg cells can exhibit the characteristics of hypomethylation of Foxp3 TSDR and Foxp3-LAP+ Treg cells, which increase the expression of surface tissue-specific homing molecules to exert further sustained systemic immune tolerance. Studies have shown that EPIT is a potential treatment for food allergies and can effectively induce immune tolerance, but its mechanism needs further exploration. Here, we review Treg cells' role in immune tolerance induced by EPIT and provide a theoretical basis for future research directions, such as the mechanism of EPIT and the development of more effective EPIT treatments.

Diffuse Large B-Cell Lymphoma: Recognition of Markers for Targeted Therapy

Diffuse large B-cell lymphomas (DLBCL)s, the most common type of Non-Hodgkin’s Lymphoma, constitute a heterogeneous group of disorders including different disease sites, strikingly diverse molecular features and a profound variability in the clinical behavior. Molecular studies and clinical trials have partially revealed the underlying causes for this variability and have made possible the recognition of some molecular variants susceptible of specific therapeutic approaches. The main histogenetic groups include the germinal center, activated B cells, thymic B cells and terminally differentiated B cells, a basic scheme where the large majority of DLBCL cases can be ascribed. The nodal/extranodal origin, specific mutational changes and microenvironment peculiarities provide additional layers of complexity. Here, we summarize the status of the knowledge and make some specific proposals for addressing the future development of targeted therapy for DLBC cases.

Development of CpG oligodeoxynucleotide TLR9 agonists in anti-cancer therapy

INTRODUCTION

Toll-like receptor-9(TLR9) can recognize the foreign unmethylated CpG DNA, and thus intrigue a strong Th1 response which plays a crucial role in the innate and adaptive immune responses. To date, CpG oligodeoxynucleotide (ODN)-based TLR9 agonists have undergone four generations. Each generations' breakthroughs in immune activation, safety profiles and pharmacokinetic properties were confirmed by both preclinical and clinical studies.

AREAS COVERED

We reviewed the development and major clinical trials of TLR9 agonists and summarized the optimization strategies of each generation. The applications, limitations and prospects of TLR9 agonists in cancer immunotherapy are also discussed.

EXPERT OPINION

Clinical trials of CpG ODN TLR9 agonists as a single agent demonstrated insufficient efficacy to reverse the immunosuppressive status of majority of patients with high tumor burden. Therefore, more efforts are now been carried out in combination with chemotherapy, radiotherapy and immunotherapy maintenance therapy as well as vaccine adjuvant. Importantly, the synergistic and complementary effect of TLR9 agonists and tumor immune checkpoint inhibitor therapy is expected to exert greater potential. On the other hand, the double-edged sword effect of TLR9 activation in tumor and toxic effect reported in combination therapies should be noted and further studies required.

Generation of αCD11b-CpG antibody conjugates for the targeted stimulation of myeloid cells

CpG oligonucleotides are short single-stranded synthetic DNA molecules. Upon binding to Toll-like receptor 9 (TLR9), CpG activates immune cells in humans and mice. This results in robust Th1 type immunity potentially resulting in clearance of pathogens, reduction of allergy and anti-tumor immunity. However, the effectiveness of CpG as an adjuvant depends on its administration route, with only strong effects seen when CpG is administered locally. As local administration is not always feasible, we generated conjugates to specifically deliver CpG to myeloid cells often abundantly present in tumors. For this we coupled CpG (3'-Thiol-modified phosphorothioate (PTO) CpG-ODN1826 type B (5'-tccatgacgttcctgacgtt-3')) to monoclonal antibodies (mAbs) directed against the myeloid cell marker CD11b using maleimide-thiol coupling. The CD11b-CpG mAb (αCD11b-CpG) conjugates contained about four CpG molecules/conjugate and displayed binding and internalization characteristics similar to unconjugated CD11b mAbs (αCD11b). The αCD11b-CpG conjugates readily induced maturation of murine dendritic cells (DCs) in a TLR9-dependent manner in vitro. Following intravenous injection, αCD11b-CpG conjugates efficiently targeted CD11b⁺ immune cells in the blood, lymph nodes and spleen. Finally, injection of αCD11b-CpG conjugates, but not untargeted conjugates, induced maturation of CD11b⁺ cell subsets in vivo. In conclusion, conjugating CpG to αCD11b enabled specific targeting and activation of myeloid cells in vivo.

Discrepant antitumor efficacies of three CpG oligodeoxynucleotide classes in monotherapy and co-therapy with PD-1 blockade

Unmethylated CpG oligodeoxynucleotides (ODNs) activate plasmacytoid dendritic cells (pDCs) and B cells to induce humoral and cellular immunity, and are under development for the treatment of multiple cancers. However, the specific differences in antitumor effects among the three CpG ODN classes when administered as a monotherapy or in co-therapy with the anti-PD-1 antibody are unclear. We compared the immunostimulatory effects in vitro and antitumor effects in a CT26 subcutaneous mouse tumor model among the three CpG ODN classes. We found that CpG-A slightly suppressed tumor growth but possessed no synergistic antitumor effects with the anti-PD-1 antibody. CpG-B at low doses significantly inhibited tumor growth and possessed synergistic antitumor effects with the anti-PD-1 antibody. A high dose of CpG-C was required to achieve antitumor effects comparable to those of CpG-B, which was consistent with the immunostimulatory effects in B-cell proliferation and TLR9-NF-κB activation. Importantly, CpG-C in combination with anti-PD-1 antibody inhibited tumor growth more quickly and effectively than CpG-B because CpG-B significantly upregulated PD-L1 expression on multiple host immune cells to promote tumor immune escape. Moreover, co-therapy increased the infiltration of effector memory T cells. In summary, CpG-B and CpG-C with different optimal concentrations possessed strong antitumor effects, while CpG-C was more rapid and effective for co-therapy with the anti-PD-1 antibody.

Dual-adjuvant effect of pH-sensitive liposomes loaded with STING and TLR9 agonists regress tumor development by enhancing Th1 immune response

Nucleic acid-based pattern recognition receptor agonists are effective adjuvants and immunotherapeutic agents. Rather than single applications, ligand combinations could synergistically potentiate immune responses by elevating cytokine and chemokine production via triggering multiple signaling pathways. However, short half-lives of such labile ligands due to nuclease attack and limited cellular uptake due to their structure significantly hamper their in vivo performances. More importantly, simultaneous delivery and activity presentation of protein antigen and nucleic acid ligands critically limit the clinical development of these constructs. In this work, we approached this problem by co-encapsulating a model antigen ovalbumin along with TLR9 and STING ligands within liposomes, a well-established drug delivery system that enables payload stability and enhanced cellular activity upon internalization. Moreover, by loading dual ligands we postulated to achieve heightened Th-1 immune response that would yield pronounced protective vaccine efficacy. We show that, pH-sensitive liposomes co-encapsulating CpG ODN and cGAMP induced synergistic innate immune response by elevating type I and type II interferon levels. Most importantly, this vaccine formulation led to ~70% regression of established melanoma tumor. pH-sensitive liposomal vaccine administration elevated IgG2c/IgG1 antibody ratio, indicative of augmented OVA-specific Th1-biased immunity. Importantly, while the frequency of tumor-specific IFN-γ producing CD8⁺ T-cells was significantly increased, the M2-type anti-inflammatory macrophage levels were decreased in the tumor bed. In conclusion, our strategy induces reversal of immunosuppressive tumor microenvironment, while enhancing effective anti-tumor immune-response. We propose that this could be coupled with standard therapies during combating tumor eradication.

Chemical Strategies to Boost Cancer Vaccines

Personalized cancer vaccines (PCVs) are reinvigorating vaccine strategies in cancer immunotherapy. In contrast to adoptive T-cell therapy and checkpoint blockade, the PCV strategy modulates the innate and adaptive immune systems with broader activation to redeploy antitumor immunity with individualized tumor-specific antigens (neoantigens). Following a sequential scheme of tumor biopsy, mutation analysis, and epitope prediction, the administration of neoantigens with synthetic long peptide (SLP) or mRNA formulations dramatically improves the population and activity of antigen-specific CD4+ and CD8+ T cells. Despite the promising prospect of PCVs, there is still great potential for optimizing prevaccination procedures and vaccine potency. In particular, the arduous development of tumor-associated antigen (TAA)-based vaccines provides valuable experience and rational principles for augmenting vaccine potency which is expected to advance PCV through the design of adjuvants, delivery systems, and immunosuppressive tumor microenvironment (TME) reversion since current personalized vaccination simply admixes antigens with adjuvants. Considering the broader application of TAA-based vaccine design, these two strategies complement each other and can lead to both personalized and universal therapeutic methods. Chemical strategies provide vast opportunities for (1) exploring novel adjuvants, including synthetic molecules and materials with optimizable activity, (2) constructing efficient and precise delivery systems to avoid systemic diffusion, improve biosafety, target secondary lymphoid organs, and enhance antigen presentation, and (3) combining bioengineering methods to innovate improvements in conventional vaccination, "smartly" re-educate the TME, and modulate antitumor immunity. As chemical strategies have proven versatility, reliability, and universality in the design of T cell- and B cell-based antitumor vaccines, the union of such numerous chemical methods in vaccine construction is expected to provide new vigor and vitality in cancer treatment.

Therapeutic Targeting of Signaling Pathways Related to Cancer Stemness

The theory of cancer stem cells (CSCs) proposes that the different cells within a tumor, as well as metastasis deriving from it, are originated from a single subpopulation of cells with self-renewal and differentiation capacities. These cancer stem cells are supposed to be critical for tumor expansion and metastasis, tumor relapse and resistance to conventional therapies, such as chemo- and radiotherapy. The acquisition of these abilities has been attributed to the activation of alternative pathways, for instance, WNT, NOTCH, SHH, PI3K, Hippo, or NF-κB pathways, that regulate detoxification mechanisms; increase the metabolic rate; induce resistance to apoptotic, autophagic, and senescence pathways; promote the overexpression of drug transporter proteins; and activate specific stem cell transcription factors. The elimination of CSCs is an important goal in cancer therapeutic approaches because it could decrease relapses and metastatic dissemination, which are main causes of mortality in oncology patients. In this work, we discuss the role of these signaling pathways in CSCs along with their therapeutic potential.

Intraperitoneal CMP-001: A Novel Immunotherapy for Treating Peritoneal Carcinomatosis of Gastrointestinal and Pancreaticobiliary Cancer

BACKGROUND

The treatment options for patients with peritoneal carcinomatosis (PC) of gastrointestinal and pancreaticobiliary origins are limited. The virus-like particle, CMP-001, composed of the Qβ bacteriophage capsid protein encapsulating a CpG-A oligodeoxynucleotide, activates plasmacytoid dendritic cells (pDCs) and triggers interferon alpha (IFNα) release, leading to a cascade of anti-tumor immune effects.

METHODS

To evaluate the ability of CMP-001 to trigger an immune response in patients with PC, peritoneal cells were isolated and stimulated ex vivo with CMP-001. Both IFNα release and percentage of pDC were quantified using enzyme-linked immunosorbent assay (ELISA) and flow cytometry, respectively. To evaluate the anti-tumor response in vivo, murine PC models were generated using mouse cancer cell lines (Panc02 and MC38) in immunocompetent mice treated with intraperitoneal CMP-001 or saline control. Survival was followed, and the immunophenotype of cells in the peritoneal tumor microenvironment was evaluated.

RESULTS

The pDCs accounted for 1% (range 0.1-3.9%; n = 17) of the isolated peritoneal cells. Ex vivo CMP-001 stimulation of the peritoneal cells released an average of 0.77 ng/ml of IFNα (range, 0-4700 pg/ml; n = 14). The IFNα concentration was proportional to the percentage of pDCs present in the peritoneal cell mixture (r = 0.6; p = 0.037). In murine PC models, intraperitoneal CMP-001 treatment elicited an anti-tumor immune response including an increase in chemokines (RANTES and MIP-1β), pro-inflammatory cytokines (IFNγ, interleukin 6 [IL-6], and IL-12), and peritoneal/tumor immune infiltration (CD4⁺/CD8⁺ T and natural killer [NK] cells). The CMP-001 treatment improved survival in both the Panc02 (median, 35 vs 28 days) and the MC38 (median: 57 vs 35 days) PC models (p < 0.05).

CONCLUSIONS

As a novel immunotherapeutic agent, CMP-001 may be effective for treating patients with PC.

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.

CpG-Oligodeoxynucleotides Alleviate Tert-Butyl Hydroperoxide-Induced Macrophage Apoptosis by Regulating Mitochondrial Function and Suppressing ROS Production

Oxidative stress and mitochondrial dysfunction are related to disease pathogenesis. Oligodeoxynucleotide containing CpG motifs (CpG ODN) demonstrate possibilities for immunotherapy applications. The aim of the present work is to explore the underlying mechanism of the cytoprotective function of CpG ODN by employing the oxidative stress modulation in immune cells. We used the imaging flow cytometry to demonstrate that tert-butyl hydroperoxide (t-BHP) induces mitochondrial-mediated apoptosis and ROS production in RAW264.7 cells. After pretreatment with CpG ODN, the percentage of apoptotic cells and ROS production was both markedly reduced. The decrease in mitochondrial membrane potential (MMP) induced by t-BHP was partially reversed by CpG ODN. The t-BHP induced upregulation of the expression of apoptosis-related proteins (cleaved-caspase 3, cleaved-caspase 9, cleaved-PARP, and bax) was notably decreased in the presence of CpG ODN. Furthermore, we found that CpG ODN enhanced phosphorylation of ERK1/2 and Akt to inhibit ROS production. In conclusion, the protective effect of CpG ODN in mitigation of t-BHP-induced apoptosis is dependent on the reduction of ROS.

The Antitumor Efficacy of CpG Oligonucleotides is Improved by Encapsulation in Plant Virus-Like Particles

Oligodeoxynucleotides (ODNs) with CpG motifs have potent immunostimulatory effects on many subsets of immune cells. For example, Class B CpG-ODNs, such as ODN1826 induce the phagocytic activity of macrophages by activating the Toll-like receptor 9 signaling pathway. Systemic ODN delivery results in unfavorable pharmacokinetic profiles and can trigger adverse effects. To address this issue, plant virus-like particles (VLPs) are developed for the targeted delivery of ODN1826 to tumor-associated macrophages (TAMs). ODN1826 is encapsulated by the in vitro disassembly and reassembly of Cowpea chlorotic mottle virus (CCMV), producing VLPs that are structurally analogous to the native virus. The encapsulation of ODN1826 in CCMV-derived VLPs promotes ODN uptake by TAMs ex vivo and significantly enhance their phagocytic activity. The antitumor activity of the VLPs in vivo is also evaluated, revealing that the direct injection of ODN1826 VLPs into established tumors induces a robust antitumor response by increasing the phagocytic activity of TAMs in the tumor microenvironment. CCMV encapsulation significantly enhances the efficacy of ODN1826 compared to the free drug, slowing tumor growth and prolonging survival in mouse models of colon cancer and melanoma.

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.

Harnessing cancer immunotherapy during the unexploited immediate perioperative period

The immediate perioperative period (days before and after surgery) is hypothesized to be crucial in determining long-term cancer outcomes: during this short period, numerous factors, including excess stress and inflammatory responses, tumour-cell shedding and pro-angiogenic and/or growth factors, might facilitate the progression of pre-existing micrometastases and the initiation of new metastases, while simultaneously jeopardizing immune control over residual malignant cells. Thus, application of anticancer immunotherapy during this critical time frame could potentially improve patient outcomes. Nevertheless, this strategy has rarely been implemented to date. In this Perspective, we discuss apparent contraindications for the perioperative use of cancer immunotherapy, suggest safe immunotherapeutic and other anti-metastatic approaches during this important time frame and specify desired characteristics of such interventions. These characteristics include a rapid onset of immune activation, avoidance of tumour-promoting effects, no or minimal increase in surgical risk, resilience to stress-related factors and minimal induction of stress responses. Pharmacological control of excess perioperative stress-inflammatory responses has been shown to be clinically feasible and could potentially be combined with immune stimulation to overcome the direct pro-metastatic effects of surgery, prevent immune suppression and enhance immunostimulatory responses. Accordingly, we believe that certain types of immunotherapy, together with interventions to abrogate stress-inflammatory responses, should be evaluated in conjunction with surgery and, for maximal effectiveness, could be initiated before administration of adjuvant therapies. Such strategies might improve the overall success of cancer treatment.

A Novel C Type CpG Oligodeoxynucleotide Exhibits Immunostimulatory Activity In Vitro and Enhances Antitumor Effect In Vivo

Background

C type CpG oligodeoxynucleotides (CpG-C ODNs), possessing the features of both A type and B type CpG ODNs, exert a variety of immunostimulatory activities and have been demonstrated as an effective antitumor immunotherapy. Based on the structural characteristics, we designed 20 potential ODNs with the aim of synthesizing an optimal, novel CpG-C ODN specific to human and murine Toll-like receptor 9 (TLR9). We also sought to investigate the in vitro immunostimulatory and in vivo antitumor effects of the novel CpG-C ODN.

Methods

Twenty potential CpG-C ODNs were screened for their ability to secrete interferon (IFN)-α, and interleukin (IL)-6 and tumor necrosis factor (TNF)-α production for the three most promising sequences were assayed in human peripheral blood mononuclear cells (PBMCs) by enzyme-linked immunosorbent assay (ELISA) or cytometric bead array assay. The functions of human and mouse B cells, and cytokine production in mice induced by the most promising sequence, HP06T07, were determined by flow cytometry and ELISA. Growth and morphology of tumor tissues in in vivo murine models inoculated with CT26 cells were analyzed by a growth inhibition assay and immunohistochemistry, respectively.

Results

Among the 20 designed ODNs, HP06T07 significantly induced IFN-α, IL-6, and TNF-α secretion, and promoted B-cell activation and proliferation in a dose-dependent manner in human PBMCs and mouse splenocytes in vitro. Intratumoral injection of HP06T07 notably suppressed tumor growth and prolonged survival in the CT26 subcutaneous mouse model in a dose-dependent manner. HP06T07 administered nine times at 2-day intervals (I2) eradicated tumor growth at both primary and distant sites of CT26 tumors. HP06T07 restrained tumor growth by increasing the infiltration of T cells, NK cells, and plasmacytoid dendritic cells (pDCs).

Conclusions

HP06T07, a novel CpG-C ODN, shows potent immunostimulatory activity in vitro and suppresses tumor growth in the CT26 subcutaneous mouse model.

Adjuvant-free immunization with infective filarial larvae as lymphatic homing antigen carriers

Controlled infection with intestinal nematodes has therapeutic potential for preventing the symptoms of allergic and autoimmune diseases. Here, we engineered larvae of the filarial nematode Litomosoides sigmodontis as a vaccine strategy to induce adaptive immunity against a foreign, crosslinked protein, chicken egg ovalbumin (OVA), in the absence of an external adjuvant. The acylation of filarial proteins with fluorescent probes or biotin was not immediately detrimental to larval movement and survival, which died 3 to 5 days later. At least some of the labeled and skin-inoculated filariae migrated through lymphatic vessels to draining lymph nodes. The immunization potential of OVA-biotin-filariae was compared to that of an OVA-bound nanoparticulate carrier co-delivered with a CpG adjuvant in a typical vaccination scheme. Production of IFNγ and TNFα by restimulated CD4+ cells but not CD8+ confirmed the specific ability of filariae to stimulate CD4+ T cells. This alternative method of immunization exploits the intrinsic adjuvancy of the attenuated nematode carrier and has the potential to shift the vaccination immune response towards cellular immunity.

Antibody Opsonization of a TLR9 Agonist-Containing Virus-like Particle Enhances In Situ Immunization

The immunologic and therapeutic effects of intratumoral (IT) delivery of a novel virus-like particle as a lymphoma immunotherapy were evaluated in preclinical studies with human cells and a murine model. CMP-001 is a virus-like particle composed of the Qβ bacteriophage capsid protein encapsulating an immunostimulatory CpG-A oligodeoxynucleotide TLR9 agonist. In vitro, CMP-001 induced cytokine production, including IFN-α from plasmacytoid dendritic cells, but only in the presence of anti-Qβ Ab. In vivo, IT CMP-001 treatment of murine A20 lymphoma enhanced survival and reduced growth of both injected and contralateral noninjected tumors in a manner dependent on both the ability of mice to generate anti-Qβ Ab and the presence of T cells. The combination of IT CMP-001 with systemic anti-PD-1 enhanced antitumor responses in both injected and noninjected tumors. IT CMP-001 alone or combined with anti-PD-1 augmented T cell infiltration in tumor-draining lymph nodes. We conclude IT CMP-001 induces a robust antitumor T cell response in an anti-Qβ Ab-dependent manner and results in systemic antitumor T cell effects that are enhanced by anti-PD-1 in a mouse model of B cell lymphoma. Early-phase clinical evaluation of CMP-001 and anti-PD-1 combination therapy in lymphoma will begin shortly, based in part on these results.

Synthesis and properties of DNA oligomers containing stereopure phosphorothioate linkages and C-5 modified deoxyuridine derivatives

Phosphorothioate (PS) modification, where a non-bridging oxygen atom in a phosphodiester linkage is replaced by a sulfur atom, is widely used to improve the properties of nucleic acid drugs. Each PS linkage can be found in two stereoisomers, Rp and Sp. Since one non-bridging oxygen or sulfur atom in Sp-PS or Rp-PS, respectively, is located close to the C-5 substituent of uracil in a DNA/RNA hybrid duplex, the combination of the stereochemistry of the PS linkages and the type of the C-5 modification of uracil bases is expected to affect the properties of the hybrid duplexes. Herein, DNA oligomers containing both stereopure phosphorohioate linkages and C-5 modified deoxyuridine derivatives were synthesized. The thermodynamic stability of the DNA/RNA and DNA/DNA duplexes and RNase H activity of the DNA/RNA duplexes were evaluated. The combination of 5-propynyluracil and (Rp)-PS linkages in a DNA strand could significantly increase the thermal stability of a DNA/RNA hybrid duplex without reducing its RNase H activity.

The combination of 5-propynyluracil and (Rp)-PS linkages in a DNA strand could significantly increase the thermal stability of a DNA/RNA hybrid duplex.

NMR solution structure of tricyclo-DNA containing duplexes: insight into enhanced thermal stability and nuclease resistance

Tc-DNA is a conformationally constrained oligonucleotide analogue which shows significant increase in thermal stability when hybridized with RNA, DNA or tc-DNA. Remarkably, recent studies revealed that tc-DNA antisense oligonucleotides (AO) hold great promise for the treatment of Duchenne muscular dystrophy and spinal muscular atrophy. To date, no high-resolution structural data is available for fully modified tc-DNA duplexes and little is known about the origins of their enhanced thermal stability. Here, we report the structures of a fully modified tc-DNA oligonucleotide paired with either complementary RNA, DNA or tc-DNA. All three investigated duplexes maintain a right-handed helical structure with Watson-Crick base pairing and overall geometry intermediate between A- and B-type, but closer to A-type structures. All sugars of the tc-DNA and RNA residues adopt a North conformation whereas the DNA deoxyribose are found in a South-East-North conformation equilibrium. The conformation of the tc-DNA strand in the three determined structures is nearly identical and despite the different nature and local geometry of the complementary strand, the overall structures of the examined duplexes are very similar suggesting that the tc-DNA strand dominates the duplex structure.

Targeted silencing of genes related to acute monocytic leukaemia by CpG(B)-MLAA-34 siRNA conjugates

Acute monocytic leukaemia (AML-M5) associated antigen-34 (MLAA-34) is a novel antigen overexpressed in patients with acute monocytic leukaemia. RNA interference is a promising therapy in oncology, especially for refractory acute leukaemia. In this study, we delivered MLAA-34 siRNA into AML-M5 THP-1 cells using CpG(B)-MLAA-34 siRNA conjugates, in the absence of any other transfection reagent. The uptake efficiency and the rate of apoptosis were measured by using flow cytometry. The level of relevant mRNAs was measured by quantitative PCR. THP-1 cell invasion was assessed by transwell assay. Protein expression was analysed by western blotting. The spleen and liver of AML-M5 nude mice were measured and weighted after euthanisation. Spleen sections were analysed by immunohistochemistry. We found that MLAA-34 siRNA was successfully delivered into THP-1 cells and induced MLAA-34 gene silencing via the blockade of JAK2/STAT3 and Wnt/-catenin signalling pathways. In addition, CpG(B)-MLAA-34 siRNA upregulated Gsk3β protein expression, resulting in retraining of the JAK2/STAT3 and Wnt/β-catenin signalling pathways. Importantly, CpG(B)-MLAA-34 siRNA reduced the survival and invasiveness of THP-1 cells. We further demonstrated that CAB39L was effectively downregulated by CpG(B)-MLAA-34 siRNA in vivo. These findings suggested CpG(B)-MLAA-34 siRNA conjugates may provide a novel therapeutic strategy for acute monocytic leukaemia.

The versatile plasmacytoid dendritic cell: Function, heterogeneity, and plasticity

Since their identification as the natural interferon-producing cell two decades ago, plasmacytoid dendritic cells (pDCs) have been attributed diverse functions in the immune response. Their most well characterized function is innate, i.e., their rapid and robust production of type-I interferon (IFN-I) in response to viruses. However, pDCs have also been implicated in antigen presentation, activation of adaptive immune responses and immunoregulation. The mechanisms by which pDCs enact these diverse functions are poorly understood. One central debate is whether these functions are carried out by different pDC subpopulations or by plasticity in the pDC compartment. This chapter summarizes the latest reports regarding pDC function, heterogeneity, cell conversion and environmentally influenced plasticity, as well as the role of pDCs in infection, autoimmunity and cancer.

The Pharmacokinetics of 2'-O-Methyl Phosphorothioate Antisense Oligonucleotides: Experiences from Developing Exon Skipping Therapies for Duchenne Muscular Dystrophy

Delivery to the target site and adversities related to off-target exposure have made the road to clinical success and approval of antisense oligonucleotide (AON) therapies challenging. Various classes of AONs have distinct chemical features and pharmacological properties. Understanding the similarities and differences in pharmacokinetics (PKs) among AON classes is important to make future development more efficient and may facilitate regulatory guidance of AON development programs. For the class of 2'-O-methyl phosphorothioate (2OMe PS) RNA AONs, most nonclinical and clinical PK data available today are derived from development of exon skipping therapies for Duchenne muscular dystrophy (DMD). While some publications have featured PK aspects of these AONs, no comprehensive overview is available to date. This article presents a detailed review of absorption, distribution, metabolism, and excretion of 2OMe PS AONs, compiled from publicly available data and previously unpublished internal data on drisapersen and related exon skipping candidates in preclinical species and DMD patients. Considerations regarding drug-drug interactions, toxicokinetics, and pharmacodynamics are also discussed. From the data presented, the picture emerges of consistent PK properties within the 2OMe PS class, predictable behavior across species, and a considerable overlap with other single-stranded PS AONs. A level of detail on muscle as a target tissue is provided, which was not previously available. Furthermore, muscle biopsy samples taken in DMD clinical trials allowed confirmation of the applicability of interspecies scaling approaches commonly applied in the absence of clinical target tissue data.

Deleterious synergistic effects of distress and surgery on cancer metastasis: Abolishment through an integrated perioperative immune-stimulating stress-inflammatory-reducing intervention

The perioperative period holds disproportionate impact on long-term cancer outcomes. Nevertheless, perioperative interventions to improve long-term cancer outcomes are not clinical routines, including perioperative stress-reducing or immune-stimulating approaches. Here, mimicking the clinical setting of pre-operative distress, followed by surgery, we examined the separate and combined effects of these events on the efficacy of pre-operative immune stimulation in rats and mice, and on post-operative resistance to tumor metastasis of the syngeneic mammary adenocarcinoma MADB106 in F344 rats and the CT26 colon carcinoma in Balb/C mice. The novel immune stimulating agents, GLA-SE or CpG-C (TLR-4 and TLR-9 agonists, respectively), were employed pre-operatively. Sixteen hours of pre-operative behavioral stressors (i) lowered CpG-C induced plasma IL-12 levels, and reduced resistance to MADB106 and CT-26 experimental metastases, and (ii) worsened the deleterious effects of laparotomy on metastasis in both tumor models. In rats, these effects of pre-operative stress were further studied and successfully abolished by the glucocorticoid receptor antagonist RU-486. Additionally, in vitro studies indicated the dampening effect of corticosterone on immune stimulation. Last, we tested a perioperative integrated intervention in the context of pre-operative stress and laparotomy, based on (i) antagonizing the impact of glucocorticoids before surgery, (ii) activating anti-metastatic immunity perioperatively, and (iii) blocking excessive operative and post-operative adrenergic and prostanoid responses. This integrated intervention successfully and completely abolished the deleterious effects of stress and of surgery on post-operative resistance to experimental metastasis. Such and similar integrated approaches can be studied clinically in cancer patients.

Potential Novel Approaches to Understand the Pathogenesis and Treat Alzheimer's Disease

There is growing genetic and proteomic data highlighting the complexity of Alzheimer's disease (AD) pathogenesis. Greater use of unbiased "omics" approaches is being increasingly recognized as essential for the future development of effective AD research, that need to better reflect the multiple distinct pathway abnormalities that can drive AD pathology. The track record of success in AD clinical trials thus far has been very poor. In part, this high failure rate has been related to the premature translation of highly successful results in animal models that mirror only limited aspects of AD pathology to humans. We highlight our recent efforts to increase use of human tissue to gain a better understanding of the AD pathogenesis subtype variety and to develop several distinct therapeutic approaches tailored to address this diversity. These therapeutic approaches include the blocking of the Aβ/apoE interaction, stimulation of innate immunity, and the simultaneous blocking of Aβ/tau oligomer toxicity. We believe that future successful therapeutic approaches will need to be combined to better reflect the complexity of the abnormal pathways triggered in AD pathogenesis.