Phase 1 trial of a CpG oligodeoxynucleotide for patients with recurrent glioblastoma

Brain microglia activation induced by intracranial administration of oligonucleotides and its pharmacological modulation

Oligonucleotide overloading results in type I interferonopathies such as the Aicardi-Goutiéres Syndrome, a progressive encephalopathy determined by an immune response against endogenous DNA/RNA molecules. No therapy targeting pathogenic mechanisms is available for affected patients. Accordingly, we set up an in vitro/in vivo experimental model aimed at reproducing the pathogenic mechanisms of type I interferonopathies, in order to develop an effective pharmacological modulation and toxicological alterations caused by intracranial delivery of encapsulated CpG. The in vitro model used Aicardi-Goutiéres Syndrome immortalized lymphocytes activated by interferon I and co-cultured with human astrocytes; lymphocyte neurotoxicity was attenuated by the calcineurin-inhibitor Tacrolimus and by the anti-interferon monoclonal antibody Sifalimumab. The in vivo model was set up in mice by subcutaneous injection of encapsulated CpG oligonucleotides; the immune-stimulating activity was demonstrated by cytometric analysis in the spleen. To mime pathogenesis of type I interferonopathies in the central nervous system, CpG oligonucleotides were administered intracranially in mice. In the brain, CpG overload induced a rapid activation of macrophage-like microglial cells and focal accumulation mononuclear cells. The subcutaneous administration of Tacrolimus and, more potently, Sifalimumab attenuated CpG-induced brain alterations. These findings shed light on molecular mechanisms triggered by oligonucleotides to induce brain damage. Monoclonal antibodies inhibiting interferon seem a promising therapeutic strategy to protect brain in type I interferonopathies.

Virus-like particles (VLP) in prophylaxis and immunotherapy of allergic diseases

BACKGROUND

Apart from active allergen avoidance, immunotherapy is regarded as the most effective form of treatment available for type I allergies. Such treatments involve the administration of allergen preparations in various forms and by various routes. Virus-like particles (VLPs) offer a very effective platform for immunization with the allergen and are characterized by high immunogenicity, low allergenicity and high clinical efficacy. Formulations that include Toll-like receptor ligands, T cell stimulatory epitopes and/or depot-forming adjuvants appear to enhance activation of the relevant immune cells. Short nucleotide sequences including CpG motifs have also been intensively explored as potent stimulators of dendritic cells and B cells.

METHODS

The present paper is based on a systematic literature search in PubMed and MEDLINE, and focuses on the pertinent immunological processes and on clinical data relating to use of VLPs and CpG motifs for the treatment of allergic rhinitis (AR).

RESULTS

Many published studies have reported positive clinical results following administration of VLPs, either alone or in combination with CpG motifs and, in some cases, even in the absence of the allergen-specific allergen.

CONCLUSIONS

These results indicate that VLPs modulate immune responses in ways which underline their exceptional promise as a platform for the immunotherapy of allergic disorders. However, clinical evaluations remain limited, and further large-scale and longer-term studies will be necessary to substantiate the efficacy and safety of these novel therapies.

Immunostimulatory CpG on Carbon Nanotubes Selectively Inhibits Migration of Brain Tumor Cells

Even when treated with aggressive current therapies, patients with glioblastoma usually survive less than two years and exhibit a high rate of recurrence. CpG is an oligonucleotide that activates the innate immune system via Toll-like receptor 9 (TLR9) activation. Injection of CpG into glioblastoma tumors showed promise as an immunotherapy in mouse models but proved disappointing in human trials. One aspect of glioma that is not addressed by CpG therapy alone is the highly invasive nature of glioma cells, which is associated with resistance to radiation and chemotherapy. Here, we demonstrate that single-walled carbon nanotubes noncovalently functionalized with CpG (SWNT/CpG), which retain the immunostimulatory property of the CpG, selectively inhibit the migration of glioma cells and not macrophages without affecting cell viability or proliferation. SWNT/CpG also selectively decreased NF-κB activation in glioma cells, while activating macrophages by induction of the TLR9/NF-κB pathway, as we have previously reported. The migration inhibition of glioma cells was correlated with selective reduction of intracellular levels of reactive oxygen species (ROS), suggesting that an antioxidant-based mechanism mediates the observed effects. To the best of our knowledge, SWNT/CpG is the first nanomaterial that inhibits the migration of cancer cells while stimulating the immune system.

Neoplastic meningitis in solid tumors: from diagnosis to personalized treatments

Neoplastic meningitis (NM) is a devastating complication of solid tumors with poor outcome. Some randomized clinical trials have been conducted with heterogeneous inclusion criteria, diagnostic parameters, response evaluation and primary endpoints. Recently, the Leptomeningeal Assessment in Neuro-Oncology (LANO) Group and the European Society for Medical Oncology/European Association for Neuro-Oncology have proposed some recommendations in order to provide diagnostic criteria and response evaluation scores for NM. The aim of these guidelines is to integrate the neurological examination with magnetic resonance imaging and cerebrospinal fluid findings as well as to provide a framework for use in clinical trials. However, this composite assessment needs further validation. Since intrathecal therapy represents a treatment with limited efficacy in NM, many studies have been conducted on systemic therapies, including target therapies, with some encouraging results in terms of disease control. In this review, we have analyzed the clinical aspects and the most recent diagnostic tools and therapeutic options in NM.

Radiation and Anti-Cancer Vaccines: A Winning Combination

The emerging combination of radiation therapy with vaccines is a promising new treatment plan in the fight against cancer. While many cancer vaccines such as MUC1, p53 CpG oligodeoxynucleotide, and SOX2 may be great candidates for antitumor vaccination, there still remain many investigations to be done into possible vaccine combinations. One fruitful partnership that has emerged are anti-tumor vaccines in combination with radiation. Radiation therapy was previously thought to be only a tool for directly or indirectly damaging DNA and therefore causing cancer cell death. Now, with much preclinical and clinical data, radiation has taken on the role of an in situ vaccine. With both cancer vaccines and radiation at our disposal, more and more studies are looking to combining vaccine types such as toll-like receptors, viral components, dendritic-cell-based, and subunit vaccines with radiation. While the outcomes of these combinatory efforts are promising, there is still much work to be covered. This review sheds light on the current state of affairs in cancer vaccines and how radiation will bring its story into the future.

RNA interference for glioblastoma therapy: Innovation ladder from the bench to clinical trials

Glioblastoma multiforme (GBM) is the most common and deadliest type of primary brain tumor with a prognosis of 14months after diagnosis. Current treatment for GBM patients includes "total" tumor resection, temozolomide-based chemotherapy, radiotherapy or a combination of these options. Although, several targeted therapies, gene therapy, and immunotherapy are currently in the clinic and/or in clinical trials, the overall survival of GBM patients has hardly improved over the last two decades. Therefore, novel multitarget modalities are urgently needed. Recently, RNA interference (RNAi) has emerged as a novel strategy for the treatment of most cancers, including GBM. RNAi-based therapies consist of using small RNA oligonucleotides to regulate protein expression at the post-transcriptional level. Despite the therapeutic potential of RNAi molecules, systemic limitations including short circulatory stability and low release into the tumor tissue have halted their progress to the clinic. The effective delivery of RNAi molecules through the blood-brain barrier (BBB) represents an additional challenge. This review focuses on connecting the translational process of RNAi-based therapies from in vitro evidence to pre-clinical studies. We delineate the effect of RNAi in GBM cell lines, describe their effectiveness in glioma mouse models, and compare the proposed drug carriers for the effective transport of RNAi molecules through the BBB to reach the tumor in the brain. Furthermore, we summarize the most important obstacles to overcome before RNAi-based therapy becomes a reality for GBM treatment.

A bifunctional nanomodulator for boosting CpG-mediated cancer immunotherapy

Unmethylated cytosine-phosphate-guanine (CpG) oligonucleotides (ODNs) possess high immunostimulatory activity and represent attractive tools for cancer treatment. However, their success in eliminating large solid tumors was hampered by the immunosuppressive tumor microenvironment. Herein, we report that the design of a novel MnO₂-CpG-silver nanoclusters (AgNCs)-doxorubicin (DOX) conjugate for enhanced cancer immunotherapy, in which MnO₂ nanosheets function as unique supports to integrate the chemotherapy drug DOX and the immunotherapeutic agent CpG-AgNCs. Importantly, DOX could be conjugated with MnO₂ nanosheets through π-π interactions to serve as a bifunctional modulator of the tumor microenvironment to activate a tumor-specific immune response by inducing immunogenic cell death, and reverse the immunosuppressive tumor microenvironment via abrogating the immune-suppressive activity of regulatory T cells, both of which would greatly improve the immune response of CpG-AgNCs. In this way, the T-cell immune responses of CpG-AgNCs which are linked to MnO₂ nanosheets were significantly enhanced and could exhibit remarkable antitumor activity against large solid tumors. Our study may guide the rational design of immunotherapeutic boosters for improving cancer treatment.

Microglia in Cancer: For Good or for Bad?

Glioblastoma is a malignant tumor of astrocytic origin that is highly invasive, proliferative and angiogenic. Despite current advances in multimodal therapies, such as surgery, radio- and chemotherapy, the outcome for patients with glioblastoma is nearly always fatal. The glioblastoma microenvironment has a tremendous influence over the tumor growth and spread. Microglia and macrophages are abundant cells in the tumor mass. Increasing evidence indicates that glioblastoma recruits these cell populations and signals in a way that microglia and macrophages are subverted to promote tumor progression. In this chapter, we discuss some aspects of the interaction between microglia and glioblastoma, consequences of this interaction for tumor progression and the possibility of microglial cells being used as therapeutic vectors, which opens up new alternatives for the development of GBM therapies targeting microglia.

LPS alters the immuno-phenotype of glioma and glioma stem-like cells and induces in vivo antitumor immunity via TLR4

BACKGROUND

This study examined the ability of lipopolysaccharide (LPS) to affect glioma and glioma stem-like cells (GSCs) in vitro and to induce antitumor immunity in vivo and the role of TLR4 in these processes.

METHODS

Using RT-PCR and immunohistochemistry, we examined the expression of TLR4 in 34 glioblastoma clinical samples. Using real time-PCR, western blot and ELISA analyses, the effect of LPS stimulation on the expression of immune related molecules was evaluated in RG2 and U87 GSCs. Control or LPS-pretreated RG2 GSCs were intracranially or subcutaneously implanted into wild-type or nude Fisher 344 rats. Histopathological examinations were used to assess tumor progression and immune infiltration and Kaplan-Meier analyses to compare survival times of the animal models.

RESULTS

TLR4 was highly expressed in glioblastoma clinical samples. In vitro LPS stimulation for 6 h significantly altered expression of immune related molecules in RG2 and U87 GSCs. However, prolonged LPS stimulation diminished this effect. Rats inoculated intracranially with LPS-pretreated RG2 GSCs survived significantly longer than rats inoculated with control RG2 GSCs. In vivo, LPS-pretreated RG2 GSCs expressed higher levels of MHC molecules, CXCL10 and TNF-α and recruited more CD8⁺ lymphocytes. However, intratumoral LPS treatment was not equally beneficial. Furthermore, the in vitro and in vivo effects of LPS stimulation appeared to be largely TLR4-dependent.

CONCLUSION

LPS pretreatment promotes the recognition and eradication of tumor GSCs in vivo when the immune function of the tumor-bearing host is intact. In addition, our data indicate a complex relationship between bacterial infection and glioma prognosis.

Intracerebral injection of CpG oligonucleotide for patients with de novo glioblastoma-A phase II multicentric, randomised study

BACKGROUND

Immunostimulating oligodeoxynucleotides containing unmethylated cytosine-guanosine motifs (CpG-ODN) have shown a promising efficacy in several cancer models when injected locally. A previous phase II study of CpG-ODN in patients with recurrent glioblastoma (GBM) has suggested some activity and has shown a limited toxicity. This multicentre single-blinded randomised phase II trial was designed to study the efficacy of a local treatment by CpG-ODN in patients with de novo glioblastomas.

PATIENTS AND METHODS

Patients with a newly diagnosed glioblastoma underwent large surgical resection and CpG-ODN was randomly administrated locally around the surgical cavity. The patients were then treated according to standard of care (SOC) with radiotherapy and temozolomide. The primary objective was 2-year survival. Secondary outcomes were progression free survival (PFS), and tolerance.

RESULTS

Eighty-one (81) patients were randomly assigned to receive CpG-ODN plus SOC (39 patients) or SOC (42 patients). The 2-year overall survival was 31% (19%; 49%) in the CpG-ODN arm and 26% (16%; 44%) in the SOC arm. The median PFS was 9 months in the CpG-ODN arm and 8.5 months in the SOC arm. The incidence of adverse events was similar in both arms; although fever and post-operative haematoma were more frequent in the CpG-ODN arm.

CONCLUSIONS

Local immunotherapy with CpG-ODN injected into the surgical cavity after tumour removal and followed by SOC, although well tolerated, does not improve survival of patients with newly diagnosed GBM.

CpG and transfer factor assembled on nanoparticles reduce tumor burden in mice glioma model

This work describes the use of a transfer factor, a low molecular protein that can transfer cell mediated immunity from donor to recipient, and CpG, a clinically relevant toll-like receptor agonist, for treating glioma.

Chimeric peptide containing both B and T cells epitope of tumor-associated antigen L6 enhances anti-tumor effects in HLA-A2 transgenic mice

Synthetic peptides are attractive for cancer immunotherapy because of their safety and flexibility. In this report, we identified a new B cell epitope of tumor-associated antigen L6 (TAL6) that could induce antibody-dependent cellular cytotoxicity (ADCC) in vivo. We incorporated the B cell epitope with a cytotoxic T lymphocyte (CTL) and a helper T (Th) epitope to form a chimeric long peptide. We formulated the chimeric peptide with different adjuvants to immunize HLA-A2 transgenic mice and evaluate their immunogenicity. The chimeric peptide formulated with an emulsion type nanoparticle (PELC) adjuvant and a toll-like receptor 9 agonist (CpG ODN) (PELC/CpG) induced the greatest ADCC and CTL responses. The induced anti-tumor immunity inhibited the growth of TAL6-positive cancer cells. Moreover, we observed that immunization with the chimeric peptide inhibited cancer cell migration in vitro and metastasis in vivo. These data suggest that a chimeric peptide containing both B and T cell epitopes of TAL6 formulated with PELC/CpG adjuvant is feasible for cancer immunotherapy.

One-Shot Immunomodulatory Nanodiamond Agents for Cancer Immunotherapy

The use of functional nanodiamonds (fNDs) to deliver CpG oligonucleotides (ODNs) for sustained immunostimulation is reported. It is demonstrated that monotherapy using this immunostimulatory agent significantly suppresses the tumor growth in two murine tumor models. This fND-based nanoagent opens new opportunities for immunotherapy, as well as clinical applications of various types of therapeutic nucleic acids.

Metronomic Doses of Temozolomide Enhance the Efficacy of Carbon Nanotube CpG Immunotherapy in an Invasive Glioma Model

Even when treated with aggressive current therapies, most patients with glioblastoma survive less than two years. Rapid tumor growth, an invasive nature, and the blood-brain barrier, which limits the penetration of large molecules into the brain, all contribute to the poor tumor response associated with conventional therapies. Immunotherapy has emerged as a therapeutic approach that may overcome these challenges. We recently reported that single-walled carbon nanotubes (SWCNTs) can be used to dramatically increase the immunotherapeutic efficacy of CpG oligonucleotides in a mouse model of glioma. Following implantation in the mouse brain, the tumor cell line used in these previous studies (GL261) tends to form a spherical tumor with limited invasion into healthy brain. In order to evaluate SWCNT/CpG therapy under more clinically-relevant conditions, here we report the treatment of a more invasive mouse glioma model (K-Luc) that better recapitulates human disease. In addition, a CpG sequence previously tested in humans was used to formulate the SWCNT/CpG which was combined with temozolomide, the standard of care chemotherapy for glioblastoma patients. We found that, following two intracranial administrations, SWCNT/CpG is well-tolerated and improves the survival of mice bearing invasive gliomas. Interestingly, the efficacy of SWCNT/CpG was enhanced when combined with temozolomide. This enhanced anti-tumor efficacy was correlated to an increase of tumor-specific cytotoxic activity in splenocytes. These results reinforce the emerging understanding that immunotherapy can be enhanced by combining it with chemotherapy and support the continued development of SWCNT/CpG.

Evolving Drug Delivery Strategies to Overcome the Blood Brain Barrier

The blood-brain barrier (BBB) poses a unique challenge for drug delivery to the central nervous system (CNS). The BBB consists of a continuous layer of specialized endothelial cells linked together by tight junctions, pericytes, nonfenestrated basal lamina, and astrocytic foot processes. This complex barrier controls and limits the systemic delivery of therapeutics to the CNS. Several innovative strategies have been explored to enhance the transport of therapeutics across the BBB, each with individual advantages and disadvantages. Ongoing advances in delivery approaches that overcome the BBB are enabling more effective therapies for CNS diseases. In this review, we discuss: (1) the physiological properties of the BBB, (2) conventional strategies to enhance paracellular and transcellular transport through the BBB, (3) emerging concepts to overcome the BBB, and (4) alternative CNS drug delivery strategies that bypass the BBB entirely. Based on these exciting advances, we anticipate that in the near future, drug delivery research efforts will lead to more effective therapeutic interventions for diseases of the CNS.

Novel delivery methods bypassing the blood-brain and blood-tumor barriers

Glioblastoma (GBM) is the most common primary brain tumor and carries a grave prognosis. Despite years of research investigating potentially new therapies for GBM, the median survival rate of individuals with this disease has remained fairly stagnant. Delivery of drugs to the tumor site is hampered by various barriers posed by the GBM pathological process and by the complex physiology of the blood-brain and blood-cerebrospinal fluid barriers. These anatomical and physiological barriers serve as a natural protection for the brain and preserve brain homeostasis, but they also have significantly limited the reach of intraparenchymal treatments in patients with GBM. In this article, the authors review the functional capabilities of the physical and physiological barriers that impede chemotherapy for GBM, with a specific focus on the pathological alterations of the blood-brain barrier (BBB) in this disease. They also provide an overview of current and future methods for circumventing these barriers in therapeutic interventions. Although ongoing research has yielded some potential options for future GBM therapies, delivery of chemotherapy medications across the BBB remains elusive and has limited the efficacy of these medications.

New therapeutic strategies regarding endovascular treatment of glioblastoma, the role of the blood-brain barrier and new ways to bypass it

The treatment protocols for glioblastoma multiforme (GBM) involve a combination of surgery, radiotherapy and adjuvant chemotherapy. Despite this multimodal approach, the prognosis of patients with GBM remains poor and there is an urgent need to develop novel strategies to improve quality of life and survival in this population. In an effort to improve outcomes, intra-arterial drug delivery has been used in many recent clinical trials; however, their results have been conflicting. The blood-brain barrier (BBB) is the major obstacle preventing adequate concentrations of chemotherapy agents being reached in tumor tissue, regardless of the method of delivering the drugs. Therapeutic failures have often been attributed to an inability of drugs to cross the BBB. However, during the last decade, a better understanding of BBB physiology along with the development of new technologies has led to innovative methods to circumvent this barrier. This paper focuses on strategies and techniques used to bypass the BBB already tested in clinical trials in humans and also those in their preclinical stage. We also discuss future therapeutic scenarios, including endovascular treatment combined with BBB disruption techniques, for patients with GBM.

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.

Immunotherapy with CpG-ODN in neoplastic meningitis: A phase I trial

TLR-9 agonists are immunostimulating agents that have antitumor effects in animal models. A phase I trial was conducted to define the safety profile of subcutaneous injections, combined with intrathecally administration of CpG-28, a TRL 9 agonist, in patients with neoplastic meningitis (NM). Cohorts of 3–6 patients with NM were treated for 5 weeks with escalating doses of CpG-28. The primary endpoint was tolerance. Secondary endpoints were progression free survival (PFS) and overall survival (OS). Twenty-nine patients were treated with CpG-28. The primary cancers were malignant glioma, lung carcinoma, breast cancer, melanoma or melanocytoma, ependymoma, and colorectal cancer. The median age was 56 years and median Karnovsky Performance status (KPS) was 70%. The treatment was well tolerated. Adverse effects that were possibly or probably related to the studied drug were grade 2 lymphopenia, anemia and neutropenia, local erythema at injection sites, fever and seizure. There were five serious adverse events: two confusions, two infections of ventricular devices and one grade 4 thrombopenia and neutropenia. The median PFS was 7 weeks and median OS was 15 weeks. Interestingly, the median survival was slightly (but not significantly) higher in the eight patients who were concomitantly treated with bevacizumab (19 weeks vs 15 weeks; P = 0.11). CpG-28 was well tolerated at doses up to 0.3 mg/kg subcutaneously and 18 mg intrathecally. Additional trials are warranted.

Enhancement of anti-tumor effect of particulate vaccine delivery system by 'bacteriomimetic' CpG functionalization of poly-lactic-co-glycolic acid nanoparticles

AIM

Low immunogenicity remains a major obstacle in realizing the full potential of cancer vaccines. In this study, we evaluated CpG-coated tumor antigen (Tag)-encapsulating 'bacteriomimetic' nanoparticles (CpG-nanoparticle [NP]-Tag NPs) as an approach to enhance anti-tumor immunity.

MATERIALS & METHODS

CpG-NP-Tag NPs were synthesized, characterized for their physicochemical properties and tested in vivo.

RESULTS

We found CpG predosing followed by intraperitoneal (IP) immunization with CpG-NP-Tag NPs significantly attenuated tumor growth in female BALB/c mice compared with respective controls. Histopathological and Immunofluorescence data revealed CpG-NP-Tag tumors had lower proliferation, higher apoptotic activity, greater CD4(+) and CD8(+) T cell infiltration as well as higher IFN-γ levels as compared with control groups.

CONCLUSION

Our findings suggest CpG-NP-Tag NPs can enhance anti-tumor effect of nanoparticulate tumor vaccination system.

Antisense oligonucleotides in therapy for neurodegenerative disorders

Antisense oligonucleotides are synthetic single stranded strings of nucleic acids that bind to RNA and thereby alter or reduce expression of the target RNA. They can not only reduce expression of mutant proteins by breakdown of the targeted transcript, but also restore protein expression or modify proteins through interference with pre-mRNA splicing. There has been a recent revival of interest in the use of antisense oligonucleotides to treat several neurodegenerative disorders using different approaches to prevent disease onset or halt disease progression and the first clinical trials for spinal muscular atrophy and amyotrophic lateral sclerosis showing promising results. For these trials, intrathecal delivery is being used but direct infusion into the brain ventricles and several methods of passing the blood brain barrier after peripheral administration are also under investigation.

Whole Tumor Antigen Vaccines: Where Are We?

With its vast amount of uncharacterized and characterized T cell epitopes available for activating CD4⁺ T helper and CD8⁺ cytotoxic lymphocytes simultaneously, whole tumor antigen represents an attractive alternative source of antigens as compared to tumor-derived peptides and full-length recombinant tumor proteins for dendritic cell (DC)-based immunotherapy. Unlike defined tumor-derived peptides and proteins, whole tumor lysate therapy is applicable to all patients regardless of their HLA type. DCs are essentially the master regulators of immune response, and are the most potent antigen-presenting cell population for priming and activating naïve T cells to target tumors. Because of these unique properties, numerous DC-based immunotherapies have been initiated in the clinics. In this review, we describe the different types of whole tumor antigens that we could use to pulse DCs ex vivo and in vivo. We also discuss the different routes of delivering whole tumor antigens to DCs in vivo and activating them with toll-like receptor agonists.

In ovo delivery of CpG DNA reduces avian infectious laryngotracheitis virus induced mortality and morbidity

Endosomal toll-like receptor-21 and -9 sense CpG DNA activating production of pro-inflammatory mediators with antimicrobial effects. Here, we investigated the induction of antiviral response of in ovo delivered CpG DNA against infectious laryngotracheitis virus (ILTV) infection. We found that in ovo delivered CpG DNA significantly reduces ILTV infection pre-hatch correlating with the expression of IL-1β and increase of macrophages in lungs. As assessed in vitro, CpG DNA stimulated avian macrophages could be a potential source of IL-1β and other pro-inflammatory mediators. Since we also found that in ovo CpG DNA delivery maintains increased macrophages in the lungs post-hatch, we infected the chickens on the day of hatch with ILTV. We found that in ovo delivered CpG DNA significantly reduces mortality and morbidity resulting from ILTV infection encountered post-hatch. Thus, CpG DNA can be a candidate innate immune stimulant worthy of further investigation for the control of ILTV infection in chickens.

Convection-enhanced delivery to the central nervous system

Convection-enhanced delivery (CED) is a bulk flow–driven process. Its properties permit direct, homogeneous, targeted perfusion of CNS regions with putative therapeutics while bypassing the blood-brain barrier. Development of surrogate imaging tracers that are co-infused during drug delivery now permit accurate, noninvasive real-time tracking of convective infusate flow in nervous system tissues. The potential advantages of CED in the CNS over other currently available drug delivery techniques, including systemic delivery, intrathecal and/or intraventricular distribution, and polymer implantation, have led to its application in research studies and clinical trials. The authors review the biophysical principles of convective flow and the technology, properties, and clinical applications of convective delivery in the CNS.

Maintenance treatment with the immunomodulator MGN1703, a Toll-like receptor 9 (TLR9) agonist, in patients with metastatic colorectal carcinoma and disease control after chemotherapy: a randomised, double-blind, placebo-controlled trial

PURPOSE

This phase II study evaluated the synthetic DNA-based immunomodulator and Toll-like receptor 9 agonist MGN1703 as maintenance treatment in metastatic colorectal carcinoma (mCRC).

METHODS

Fifty-nine patients with mCRC and disease control after standard first-line chemotherapy were randomised to MGN1703 60 mg (N = 43) or placebo (N = 16).

RESULTS

The hazard ratio (HR) for the primary endpoint [progression-free survival (PFS) from the start of maintenance] was 0.56 (95 % CI 0.29-1.08; P = 0.07) and 0.55 (95 % CI 0.3-1.0; P = 0.04) by independent and investigator review, respectively. MGN1703 significantly improved PFS measured from the start of induction therapy versus placebo on independent (HR 0.49; 95 % CI 0.26-0.94; P = 0.03) and investigator review (HR 0.50; 95 % CI 0.31-1.02; P = 0.02). Overall survival (OS) data remain immature (HR 95 %; 95 % CI 0.3-1.5; P = 0.29) with 28/43 patients alive after a medium follow-up of >17 months. Retrospective subgroup analysis showed a significant effect of MGN1703 on PFS versus placebo in patients with greater than median tumour size reduction and normalised carcinoembryonic antigen concentrations following induction therapy, and in patients with elevated activated NKT cells ≥3.08 %. Adverse events were mild to moderate and limited to injection-site reactions or linked to general immune system activation.

CONCLUSIONS

MGN1703 maintenance treatment was well tolerated and appears to induce durable and prolonged PFS and disease control in a subgroup of patients with mCRC following induction therapy. Activated NKT cells may be a predictive biomarker for selecting patients likely to benefit more from MGN1703.

Clinical evaluation of CpG oligonucleotides as adjuvants for vaccines targeting infectious diseases and cancer

Synthetic oligonucleotides (ODN) that express unmethylated "CpG motifs" trigger cells that express Toll-like receptor 9. In humans this includes plasmacytoid dendritic cells and B cells. CpG ODN induce an innate immune response characterized by the production of Th1 and pro-inflammatory cytokines. Their utility as vaccine adjuvants was evaluated in a number of clinical trials. Results indicate that CpG ODN improve antigen presentation and the generation of vaccine-specific cellular and humoral responses. This work provides an up-to-date overview of the utility of CpG ODN as adjuvants for vaccines targeting infectious agents and cancer.

Immunotherapy of type-1 allergies with virus-like particles and CpG-motifs

Immunotherapy of type-I-allergies is regarded as the most efficient treatment option besides allergen avoidance. Different forms of allergen preparations are used as well as different routes of application. Virus-like particles represent a potent vaccine platform with proven immunogenicity and clinical efficacy. The addition of toll-like receptor ligands and/or depot-forming adjuvants further enhances immune cell activation. This article will focus on the function of virus-like particles loaded with DNA rich in CpG-motifs and discuss clinical experience in treatment of allergic rhinitis. Evidence will be presented that clinically effective treatment can be obtained even in the absence of allergens. Results encourage further investigation of virus-like particles and CpG-motifs in immunotherapy, either as a stand alone product, or as adjuvants for allergen-specific immunotherapy.

Combination therapy targeting toll like receptors 7, 8 and 9 eliminates large established tumors

Background

The TLR7/8 agonist 3M-052 and the TLR9 agonist CpG ODN both trigger innate immune responses that support the induction of tumor-specific immunity. Previous studies showed that these agonists used individually could improve the survival of mice challenged with small tumors but were of limited therapeutic benefit against large/advanced tumors.

Methods

Normal mice were challenged with syngeneic tumors. Once these tumors reached clinically detectable size (500–800 mm³) they were treated by intra-tumoral injection with 3M-052 and/or CpG ODN. Anti-tumor immunity and tumor growth were evaluated.

Results

The co-delivery of agonists targeting TLRs 7, 8 and 9 increased the number and tumoricidal activity of tumor infiltrating CTL and NK cells while reducing the frequency of immunosuppressive MDSC. The combination of 3M-052 plus CpG ODN (but not each agent alone) eradicated large primary tumors and established long-term protective immunity.

Conclusion

The combination of agonists targeting TLRs 7/8 and 9 represents a significant improvement in cancer immunotherapy.

Phosphorothioate-modified CpG oligodeoxynucleotide (CpG ODN) induces apoptosis of human hepatocellular carcinoma cells independent of TLR9

Toll-like receptors (TLRs) expressed on cancer cells are closely associated with tumor development. In this study, we investigated the biological functions of the TLR9 ligand, CpG oligodeoxynucleotide (CpG ODN), on TLR9 expressed in the cytoplasm of hepatocellular carcinoma (HCC) cells. In vitro, human HCC cell lines were transfected with phosphorothioate-modified oligodeoxynucleotides TLR9 agonist OND M362 and its negative control ODN M362 ctrl, which inhibited the proliferation of HCC cells by inducing apoptosis without altering the cell cycle. Interestingly, ODN M362 and ODN M362 Ctrl displayed a similar proapoptotic effect on HCC, possibly related to phosphorothioate modification of the structure of CpG ODN. Although both of them resulted in the upregulation of the TLR9 receptor, their effect on HCC apoptosis was independent of TLR9. They also upregulated inflammatory cytokines, but did not activate the NF-κB signaling pathway. Finally, the activities of ODN M362 and ODN M362 Ctrl were demonstrated in nude mice inoculated with HCC cells. These findings suggest that the phosphorothioate-modified TLR9 agonist ODN M362, and its control, elicit antitumor activity in HCC cells and may serve as a novel therapeutic target for HCC therapy.

Adjuvant-carrying synthetic vaccine particles augment the immune response to encapsulated antigen and exhibit strong local immune activation without inducing systemic cytokine release

Augmentation of immunogenicity can be achieved by particulate delivery of an antigen and by its co-administration with an adjuvant. However, many adjuvants initiate strong systemic inflammatory reactions in vivo, leading to potential adverse events and safety concerns. We have developed a synthetic vaccine particle (SVP) technology that enables co-encapsulation of antigen with potent adjuvants. We demonstrate that co-delivery of an antigen with a TLR7/8 or TLR9 agonist in synthetic polymer nanoparticles results in a strong augmentation of humoral and cellular immune responses with minimal systemic production of inflammatory cytokines. In contrast, antigen encapsulated into nanoparticles and admixed with free TLR7/8 agonist leads to lower immunogenicity and rapid induction of high levels of inflammatory cytokines in the serum (e.g., TNF-α and IL-6 levels are 50- to 200-fold higher upon injection of free resiquimod (R848) than of nanoparticle-encapsulated R848). Conversely, local immune stimulation as evidenced by cellular infiltration of draining lymph nodes and by intranodal cytokine production was more pronounced and persisted longer when SVP-encapsulated TLR agonists were used. The strong local immune activation achieved using a modular self-assembling nanoparticle platform markedly enhanced immunogenicity and was equally effective whether antigen and adjuvant were co-encapsulated in a single nanoparticle formulation or co-delivered in two separate nanoparticles. Moreover, particle encapsulation enabled the utilization of CpG oligonucleotides with the natural phosphodiester backbone, which are otherwise rapidly hydrolyzed by nucleases in vivo. The use of SVP may enable clinical use of potent TLR agonists as vaccine adjuvants for indications where cellular immunity or robust humoral responses are required.

Intraperitoneal prophylaxis with CpG oligodeoxynucleotides protects neutropenic mice against intracerebral Escherichia coli K1 infection

Background

Prophylaxis with unmethylated cytosine phosphate guanidine (CpG) oligodeoxynucleotides (ODN) protects against several systemic experimental infections. Escherichia coli is a major cause of Gram-negative neonatal bacterial meningitis and also causes meningitis and meningoencephalitis in older and immunocompromised patients.

Methods

Wild-type (wt) and Toll-like receptor 9 (TLR9)-deficient mice were rendered neutropenic by intraperitoneal administration of the anti-Ly-6G monoclonal antibody. Immunocompetent and neutropenic mice received intraperitoneal CpG ODN or vehicle 72 h prior to induction of E. coli K1 meningoencephalitis.

Results

Pre-treatment with CpG ODN significantly increased survival of neutropenic wt mice from 33% to 75% (P = 0.0003) but did not protect neutropenic TLR9^-/- mice. The protective effect of CpG ODN was associated with an enhanced production of interleukin (IL)-12/IL-23p40 with sustained increased levels in serum and spleen at least for 17 days after conditioning compared to buffer-treated animals. CpG-treated neutropenic wt mice showed reduced bacterial concentrations and increased recruitment of Ly6C^highCCR2⁺ monocytes in brain and spleen 42 h after infection. The levels of macrophage inflammatory protein 1α (MIP-1α) and interferon gamma (IFN-γ) in spleen were higher 42 h after infection in CpG-treated compared to buffer-treated neutropenic animals. In immunocompetent mice, prophylaxis with CpG ODN did not significantly increase survival compared to the buffer group (60% vs. 45%, P = 0.2).

Conclusions

These findings suggest that systemic administration of CpG ODN may help to prevent bacterial CNS infections in immunocompromised individuals.

Victory and defeat in the induction of a therapeutic response through vaccine therapy for human and canine brain tumors: a review of the state of the art

Anti-tumor immunotherapy using tumor lysate-based vaccines has made great advances over recent decades. Cancer vaccines aim to elicit adaptive immune responses through various pathways by providing tumor and tumor-associated antigens with an immune stimulant or adjuvant. These anti-tumor vaccines are therefore developed as personalized treatments. Utilizing tumors as a source of vaccine antigens in immunotherapy has demonstrated promising results with minimal toxicity. However, to date, researchers have failed to overcome the overpowering immune suppressive effects within the tumor microenvironment. Immune suppression occurs naturally via multiple mechanisms. These mechanisms serve an important homeostatic role restoring a normal tissue microenvironment following an inflammatory response. Due to these suppressive mechanisms and the inherent heterogeneity of tumors, it is imperative to then elicit and maintain a specific tumoricidal response if vaccine therapy or some other combination of reagents is chosen. In this review, we focus on the historical use of tumors as a source of antigens to elicit a tumoricidal response and the limitations encountered that prevent greater success in immunotherapy. We describe the advantages and disadvantages of various vaccines and their ineffectiveness due to tumor-induced immune suppression.

Immunotherapy of allergic rhinitis: new therapeutic opportunities with virus-like particles filled with CpG motifs

BACKGROUND

The incidence of allergic rhinitis (AR) has increased constantly over the last decades. The disease can significantly lower quality of life and subsequently might progress to allergic asthma. Allergen-specific immunotherapy is mostly used to cope with the cause of the disease. However, incidence of systemic reactions or limited compliance hampers the widespread use of this therapeutic approach. Therefore, new candidates are examined to improve immunotherapy of allergies. Recently, a new technology was developed with the aim to positively influence the immune system of allergic patients. Virus-like particles (VLPs) represent a potent vaccine platform that has been proven to be immunogenic and clinically effective. To enhance immune cell activation, addition of Toll-like receptor ligands and/or depot-forming adjuvants seems to be helpful. In this context, CpG motifs represent intensive investigated and potent stimulators of T cells. This article focuses on the function of VLPs and CpG motifs and their clinical experience for treatment of AR.

METHODS

A literature review was performed.

RESULTS

Several published studies showed a beneficial impact of the treatment on allergic symptoms. They tested VLPs filled with or without CpG motifs in combination with or without allergen.

CONCLUSION

Results encourage further investigations of VLPs and CpG motifs as adjuncts to or even alternative candidates for immunotherapy of allergic disorders.

Treg depletion followed by intracerebral CpG-ODN injection induce brain tumor rejection

Using brain lymphoma model, we demonstrate that immunotherapy combining Treg depletion (using anti-CD25 mAb PC61) followed by intracranial CpG-ODN administration induced tumor rejection in all treated mice and led to the establishment of a memory antitumor immune response in 60% of them. This protective effect was associated with a recruitment of NK cells and, to a lesser extent, of dendritic cells, B cells and T lymphocytes. NK cell depletion abolished the protective effect of the treatment, confirming a major role of NK cells in brain tumor elimination. Each treatment used alone failed to protect brain tumor bearing mice, revealing the therapeutic benefit of combining Treg depletion and local CpG-ODN injection.

Recent progress concerning CpG DNA and its use as a vaccine adjuvant

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides designed to specifically agonize Toll-like receptor 9. Here, we review recent progress in understanding the mechanism of action of CpG ODN and provide an overview of human clinical trial results using CpG ODN to improve the vaccines for cancer, allergy and infectious disease.

A novel emulsion-type adjuvant containing CpG oligodeoxynucleotides enhances CD8+ T-cell-mediated anti-tumor immunity

PELC is a novel emulsion-type adjuvant that contains the bioresorbable polymer poly (ethylene glycol)-block-poly (lactide-co-ε-caprolactone) (PEG-b-PLACL), Span®85 and squalene. To investigate whether PELC is able to enhance CTL responses of antigens for treating tumor, peptides or protein antigens derived from HPV16 E7 were formulated with PELC nanoparticles and CpG oligodeoxynucleotide. We identified that PELC formulation could delay the release of antigens in vitro and in vivo. We assessed the immunogenicity of an H-2D(b)-restricted CTL epitope RAHYNIVTF (RAH) formulated with PELC or PELC/CpG and investigated the ability of these formulations to promote tumor regression. Following a single-dose subcutaneous injection in mice, we found that the RAH peptide formulated with PELC/CpG (RAH/PELC/CpG) resulted in increased numbers of IFN-γ-secreting cells and RAH-specific CD8(+) T cells and an enhanced cytotoxic T cell response compared with RAH formulated with PELC or CpG alone. The tumor-bearing mice received a single-dose injection of RAH/PELC/CpG, which induced complete tumor regression. These results demonstrated that peptide antigen formulated with PELC/CpG nanoparticles is feasible for cancer immunotherapy.

Synthetic immunostimulatory oligonucleotides in experimental and clinical practice

BACKGROUND

Oligonucleotides belong to a class of macromolecules with great potential for research and various therapeutic applications. Their mechanisms of action are extremely diverse, although they are rather homogeneous in composition. Single-stranded oligodeoxynucleotides are not only inhibitors of gene expression, but their CpG sequence motifs may activate the innate immune response. Recent progress made in preclinical and clinical testing, as well as the case of the most recently discovered RNA interference technology, will help to overcome efficacy problems of the previous approaches of the 'standard therapy' of such diseases as tumors and various infections.

METHODS

The aim of this article is to present various therapeutic aspects of oligonucleotides, and to review the most significant therapeutic applications of synthetic oligonucleotides. This paper presents a comprehensive review of current literature on various therapeutic properties of synthetic oligonucleotides.

CONCLUSIONS

The available results gathered from preclinical and clinical studies suggest that TLR9-targeted therapy of oligonucleotides can stimulate both innate and adaptive immunity. It also appears that CpG ODNs are generally safe, although moderate adverse effects, based on a backbone-related mechanism have been reported. The presented studies demonstrate that adjuvant CpG ODN can unify an immune response that leads to enhanced antigen-specific Ab formation. CpG ODN may therefore provide a unique approach to enhancing the efficacy of immunization, including the strengthening of antitumor immunity.

Immune system targeting by biodegradable nanoparticles for cancer vaccines

The concept of therapeutic cancer vaccines is based on the activation of the immune system against tumor cells after the presentation of tumor antigens. Nanoparticles (NPs) have shown great potential as delivery systems for cancer vaccines as they potentiate the co-delivery of tumor-associated antigens and adjuvants to dendritic cells (DCs), insuring effective activation of the immune system against tumor cells. In this review, the immunological mechanisms behind cancer vaccines, including the role of DCs in the stimulation of T lymphocytes and the use of Toll-like receptor (TLR) ligands as adjuvants will be discussed. An overview of each of the three essential components of a therapeutic cancer vaccine - antigen, adjuvant and delivery system - will be provided with special emphasis on the potential of particulate delivery systems for cancer vaccines, in particular those made of biodegradable aliphatic polyesters, such as poly(lactic-co-glycolic acid) (PLGA) and poly-ε-caprolactone (PCL). Some of the factors that can influence NP uptake by DCs, including size, surface charge, surface functionalization and route of administration, will also be considered.

Therapeutic applications of nucleic acids and their analogues in Toll-like receptor signaling

Toll-like receptors (TLRs) belong to a family of innate immune receptors that detect and clear invading microbial pathogens. Specifically intracellular TLRs such as TLR3, TLR7, TLR8 and TLR9 recognize nucleic acids such as double-stranded RNA, single-stranded RNA and CpG DNA respectively derived from microbial components. Upon infection, nucleic acid sensing TLRs signal within endosomal compartment triggering the induction of essential proinflammatory cytokines and type I interferons to initiate innate immune responses thereby leading to a critical role in the development of adaptive immune responses. Thus, stimulation of TLRs by nucleic acids is a promising area of research for the development of novel therapeutic strategies against pathogenic infection, allergies, malignant neoplasms and autoimmunity. This review summarizes the therapeutic applications of nucleic acids or nucleic acid analogues through the modulation of TLR signaling pathways.

The pharmacokinetics of Toll-like receptor agonists and the impact on the immune system

Toll-like receptor (TLR) ligation activates both the innate and adaptive immune systems, and plays an important role in antiviral and anti-tumor immunity. Therefore, a significant amount of effort has been devoted to exploit the therapeutic potential of TLR agonists. Depending on the therapeutic purpose, either as adjuvants to vaccine, chemotherapy or standalone therapy, TLR agonists have been administered via different routes. Both preclinical and clinical studies have suggested that the route of administration has significant effects on pharmacokinetics, and that understanding these effects is critical to the success of TLR agonist drug development. This article will summarize the pharmacokinetics of TLR agonists with different administration routes, with an emphasis on clinical studies of TLR ligands in oncologic applications.

Intracerebral CpG immunotherapy with carbon nanotubes abrogates growth of subcutaneous melanomas in mice

PURPOSE

Recently, we showed that intratumoral delivery of low-dose, immunostimulatory CpG oligodeoxynucleotides conjugated with carbon nanotubes (CNT-CpG) was more effective than free CpG and not only eradicated intracranial (i.c.) gliomas but also induced antitumor immunity that protected mice from subsequent i.c. or systemic tumor rechallenge. Here, we examined whether the same "intracerebral immunotherapy" strategy could be applied to the treatment of metastatic brain tumors.

EXPERIMENTAL DESIGN

Mice with both i.c. and s.c. melanomas were injected intratumorally with CNT-CpG into either location. Antitumor responses were assessed by flow cytometry, bioluminescent imaging, and animal survival.

RESULTS

When given s.c., CNT-CpG response was mostly local, and it only modestly inhibited the growth of i.c. melanomas. However, i.c. CNT-CpG abrogated the growth of not only brain but also s.c. tumors. Furthermore, compared with s.c. injections, i.c. CNT-CpG elicited a stronger inflammatory response that resulted in more potent antitumor cytotoxicity and improved in vivo trafficking of effector cells into both i.c. and s.c. tumors. To investigate factors that accounted for these observations, CNT-CpG biodistribution and cellular inflammatory responses were examined in both tumor locations. Intracranial melanomas retained the CNT-CpG particles longer and were infiltrated by Toll-like receptor (TLR-9)-positive microglia. In contrast, myeloid-derived suppressive cells were more abundant in s.c. tumors. Although depletion of these cells before s.c. CNT-CpG therapy enhanced its cytotoxic responses, antitumor responses to brain melanomas were unchanged.

CONCLUSIONS

These findings suggest that intracerebral CNT-CpG immunotherapy is more effective than systemic therapy in generating antitumor responses that target both brain and systemic melanomas.

CpG ODN107 potentiates radiosensitivity of human glioma cells via TLR9-mediated NF-κB activation and NO production

Radiotherapy is a standard treatment for glioma patient with or without surgery; radiosensitizer can increase tumor sensitivity for radiotherapy. Herein, a synthetic oligodeoxynucleotide containing unmethylated CpG dinucleotides (CpG ODN107) as a radiosensitizer was investigated in vitro and in vivo, and the possible mechanisms were studied in vitro. In the present experiments, the human glioma U87 cell line used herein was resistant to 5 Gy of β-ray irradiation. The results showed that 10 μg/ml of CpG ODN107 in combination with irradiation significantly inhibited cell proliferation both in MTT assay and colony formation experiments. Tumor growth was inhibited by CpG ODN107 in combination with local irradiation but not by local irradiation or CpG ODN107 alone in human glioma xenograft model in nude mice. The inhibition ratio of tumor growth produced by CpG ODN107 (1.7, 5, and 15 mg/kg) in combination with irradiation was 27.3, 67.0, and 65.5 %, respectively. Further molecular mechanisms were studied in vitro. The results showed that the expressions of iNOS, NO, TLR9 mRNA, and NF-κB p50/p65 increased in the cells treated with CpG ODN107 in combination with irradiation. CpG ODN107 in combination with irradiation did not induce apoptosis but induced cell cycle arrest at G(1) phase. The said results demonstrated that CpG ODN107 possessed a radiosensitizing effect via TLR9-mediated NF-κB activation and NO production in the tumor cells, leading to cell cycle arrest. Therefore, CpG ODN107 is a potential candidate as radiosensitizer for human glioma.

Glioblastoma multiforme: overview of current treatment and future perspectives

Glioblastoma multiforme is the most common primary malignant tumor of the central nervous system. Despite new insights into glioblastoma pathophysiology, the prognosis for patients diagnosed with this highly aggressive tumor remains bleak. Current treatment regimens combine surgical resection and chemoradiotherapy, providing an increase in median overall survival from 12.1 to 14.6 months. Ongoing preclinical and clinical studies evaluating the efficacy of novel therapies provide hope for increasing survival benefit. This article reviews the advancements in glioblastoma treatment in newly diagnosed and recurrent glioblastoma, including novel therapies such as antiangiogenic agents, mammalian target of rapamycin inhibitors, poly(ADP-ribose) polymerase-1 inhibitors, and immunotherapies.

Effects of human exogenous DNA on production of perforin-containing CD8+ cytotoxic lymphocytes in laboratory setting and clinical practice

We investigated the influence of Panagen DNA preparations on laboratory animals and IFN-induced human dendritic cells, as well as analyzed the data from a phase II clinical trial in the therapy of breast cancer. It was shown that this treatment resulted in increased number of CD8+/perforin+ T cells in peripheral lymphoid organs of experimental animals, in mixed lymphocyte culture population and in peripheral blood of breast cancer patients. Moreover, we demonstrated that when Panagen DNA preparations are used in combination with the standard FAC-based breast cancer therapies, non-specific immune response activity remains at the same levels as observed prior to therapy, whereas in FAC-placebo patients, non-specific immunity is greatly diminished.

CpG still rocks! Update on an accidental drug

The discovery of the CpG motif in 1995 led to a change in the perception of the immune stimulatory effects of oligodeoxynucleotides (ODN) from an unwanted nonspecific effect to a highly evolved immune defense that can be selectively triggered for a wide range of therapeutic applications. Over the last decade dozens of human clinical trials have been conducted with different CpG ODN in thousands of humans for applications ranging from vaccine adjuvant to immunotherapies for allergy, cancer, and infectious diseases. Along with many positive results have come some failures showing the limitations of several therapeutic approaches. This review summarizes these results to provide an overview of the clinical development of CpG ODN.