Improving the therapeutic index of CpG oligodeoxynucleotides by intralymphatic administration

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.

Advanced subunit vaccine delivery technologies: From vaccine cascade obstacles to design strategies

Designing and manufacturing safe and effective vaccines is a crucial challenge for human health worldwide. Research on adjuvant-based subunit vaccines is increasingly being explored to meet clinical needs. Nevertheless, the adaptive immune responses of subunit vaccines are still unfavorable, which may partially be attributed to the immune cascade obstacles and unsatisfactory vaccine design. An extended understanding of the crosstalk between vaccine delivery strategies and immunological mechanisms could provide scientific insight to optimize antigen delivery and improve vaccination efficacy. In this review, we summarized the advanced subunit vaccine delivery technologies from the perspective of vaccine cascade obstacles after administration. The engineered subunit vaccines with lymph node and specific cell targeting ability, antigen cross-presentation, T cell activation properties, and tailorable antigen release patterns may achieve effective immune protection with high precision, efficiency, and stability. We hope this review can provide rational design principles and inspire the exploitation of future subunit vaccines.

Application of Nano-Delivery Systems in Lymph Nodes for Tumor Immunotherapy

Immunotherapy has become a promising research "hotspot" in cancer treatment. "Soldier" immune cells are not uniform throughout the body; they accumulate mostly in the immune organs such as the spleen and lymph nodes (LNs), etc. The unique structure of LNs provides the microenvironment suitable for the survival, activation, and proliferation of multiple types of immune cells. LNs play an important role in both the initiation of adaptive immunity and the generation of durable anti-tumor responses. Antigens taken up by antigen-presenting cells in peripheral tissues need to migrate with lymphatic fluid to LNs to activate the lymphocytes therein. Meanwhile, the accumulation and retaining of many immune functional compounds in LNs enhance their efficacy significantly. Therefore, LNs have become a key target for tumor immunotherapy. Unfortunately, the nonspecific distribution of the immune drugs in vivo greatly limits the activation and proliferation of immune cells, which leads to unsatisfactory anti-tumor effects. The efficient nano-delivery system to LNs is an effective strategy to maximize the efficacy of immune drugs. Nano-delivery systems have shown beneficial in improving biodistribution and enhancing accumulation in lymphoid tissues, exhibiting powerful and promising prospects for achieving effective delivery to LNs. Herein, the physiological structure and the delivery barriers of LNs were summarized and the factors affecting LNs accumulation were discussed thoroughly. Moreover, developments in nano-delivery systems were reviewed and the transformation prospects of LNs targeting nanocarriers were summarized and discussed.

Inhalative Nanoparticulate CpG Immunotherapy in Severe Equine Asthma: An Innovative Therapeutic Concept and Potential Animal Model for Human Asthma Treatment

Simple Summary

Severe equine asthma is the most common globally widespread non-infectious equine respiratory disease (together with its mild and moderate form), which is associated with exposure to hay dust and mold spores, has certain similarities to human asthma, and continues to represent a therapeutic problem. Immunomodulatory DNA sequences (CpG) bound to nanoparticles were successfully administered by inhalation to severe asthmatic horses in several studies. It was possible to demonstrate a significant, sustained, one-to-eight-week improvement in important clinical parameters: partial oxygen pressure in the blood, quantity and viscosity of tracheal mucus secretion in the airways, and the amount of inflammatory cells in the respiratory tracts of severe asthmatic horses. The immunotherapy with CpG is performed independent of specific allergens. At an immunological level, the treatment leads to decreases in allergic and inflammatory parameters. This innovative therapeutic concept thus opens new perspectives in severe equine asthma treatment and possibly also in human asthma treatment.

Abstract

Severe equine asthma is the most common globally widespread non-infectious equine respiratory disease (together with its mild and moderate form), which is associated with exposure to hay dust and mold spores, has certain similarities to human asthma, and continues to represent a therapeutic problem. Immunomodulatory CpG-ODN, bound to gelatin nanoparticles as a drug delivery system, were successfully administered by inhalation to severe equine asthmatic patients in several studies. It was possible to demonstrate a significant, sustained, and allergen-independent one-to-eight-week improvement in key clinical parameters: the arterial partial pressure of oxygen, the quantity and viscosity of tracheal mucus, and neutrophilic inflammatory cells in the respiratory tracts of the severe equine asthmatic subjects. At the immunological level, an upregulation of the regulatory antiallergic and anti-inflammatory cytokine IL-10 as well as a downregulation of the proallergic IL-4 and proinflammatory IFN-γ in the respiratory tracts of the severe equine asthmatic patients were identified in the treatment groups. CD4⁺ T lymphocytes in the respiratory tracts of the asthmatic horses were demonstrated to downregulate the mRNA expression of Tbet and IL-8. Concentrations of matrix metalloproteinase-2 and -9 and tissue inhibitors of metalloproteinase-2 were significantly decreased directly after the treatment as well as six weeks post-treatment. This innovative therapeutic concept thus opens new perspectives in the treatment of severe equine asthma and possibly also that of human asthma.

Glutamic acid decarboxylase immunotherapy for type 1 diabetes

PURPOSE OF REVIEW

To describe recent development of an autoantigen (GAD) treatment towards well tolerated and efficacious precision medicine in type 1 diabetes.

RECENT FINDINGS

Although subcutaneous GAD-alum treatment failed to reach primary endpoint in a phase III trial, metanalyses showed a 97% probability of efficacy, and clear efficacy in patients carrying Hyman Leucoycte Antigen (HLA) DR3DQ2. Efforts have been made to improve efficacy by trying combination therapies with vitamin D + Ibuprofen resp vitamin D + Etanercept (TNF-α inhibition), without any breakthrough until the administration of GAD-alum was changed from subcutaneous to intralymphatic. With a very small dose of GAD-alum (4 μg) given into an inguinal lymph three times with 1 month interval, the efficacy in patients with HLADR3DQ2 has been impressive, with significantly better beta cell preservation than patients who got placebo in a double-blind randomized trial, and clinical efficacy with more patients in partial remission (IDAA1c < 9) and larger proportion of patients with CGM-measured blood glucose Time In Range (TIR), significantly correlated to the C-peptide values. The treatment has been easy for patients and healthcare without treatment-related risk or adverse events.

SUMMARY

Intralymphatic GAD-alum treatment in type 1 diabetes patients carrying HLA DR3DQ2 seems to be an attractive immune intervention.

Free Feeding of CpG-Oligodeoxynucleotide Particles Prophylactically Attenuates Allergic Airway Inflammation and Hyperresponsiveness in Mice

CpG-oligodeoxynucleotides (CpG-ODNs) constitute an attractive alternative for asthma treatment. However, very little evidence is available from studies on the oral administration of CpG-ODNs in animals. Previously, we developed acid-resistant particles (named ODNcap) as an oral delivery device for ODNs. Here, we showed that free feeding of an ODNcap-containing feed prophylactically attenuates allergic airway inflammation, hyperresponsiveness, and goblet cell hyperplasia in an ovalbumin-induced asthma model. Using transcriptomics-driven approaches, we demonstrated that injury of pulmonary vein cardiomyocytes accompanies allergen inhalation challenge, but is inhibited by ODNcap feeding. We also showed the participation of an airway antimicrobial peptide (Reg3γ) and fecal microbiota in the ODNcap-mediated effects. Collectively, our findings suggest that daily oral ingestion of ODNcap may provide preventive effects on allergic bronchopulmonary insults via regulation of mechanisms involved in the gut-lung connection.

Engineering Strategies for Lymph Node Targeted Immune Activation

Development of vaccine technology that induces long lasting and potent adaptive immune responses is of vital importance to combat emerging pathogens and to design the next generation of cancer immunotherapies. Advanced biomaterials such as nanoparticle carriers are intensively explored to increase the efficacy and safety of vaccines and immunotherapies, based on their intrinsic potential to focus the therapeutic payload onto the relevant immune cells and to limit systemic distribution. With adaptive immune responses being primarily initiated in lymph nodes, the potency of nanoparticle vaccines in turn is tightly linked to their capacity to reach and accumulate in the lymph nodes draining the immunization site. Here, we discuss the main strategies applied to increase nanoparticle delivery to lymph nodes: (1) direct lymph node injection, (2) active cell-mediated transport through targeting of peripheral dendritic cells, and (3) exploiting passive transport through the afferent lymphatics.The intralymph nodal injection is obviously the most direct way for nanoparticles to reach lymph nodes, and multiple studies have demonstrated its capability in enhancing immunostimulant drugs' immune activation and increasing the therapeutic window. However, the requirement of using ultrasound guidance for mapping lymph nodes in patients renders intranodal administration unsuited for mass vaccination campaigns. As lymph nodes are fine structured organs with lymphocytes and chemokine gradients arrayed in a highly ordered fashion, the breakdown of such formats by the intralymph nodal injection is another concern. The exploitation of dendritic cells as live vectors for transporting nanoparticles to lymph nodes has intensively been studied both ex vivo and in vivo. While ex vivo engineering of dendritic cells in theory can achieve 100% dendritic cell-specific selectivity, a scenario impossible to be achieved in vivo, this procedure is usually laborious and complicated and entails the participation of professional staff and equipment. In addition, the poor efficiency of dendritic cell migration to the draining lymph node is another significant limitation following the injection of ex vivo cultured dendritic cells. Thus, in vivo targeting of surface receptors, particularly C-type lectin receptors, on dendritic cells by conjugating nanoparticles with antibodies or ligands is intensively studied by both academia and industry. Although such nanoparticles in vivo still face nonspecific engulfment by various phagocytes, multiple studies have shown its feasibility in targeting dendritic cells with high selectivity. Moreover, through optimizing the physicochemical properties of nanoparticles, nanoparticles can passively drain to lymph nodes carried by the interstitial flow. Compared to dendritic cell-mediated transport, passive draining is much faster and of higher efficiency. Of all such properties, size is the most important parameter as large particles (>500 nm) can only reach lymph nodes by an active cell-mediated transport. Other surface properties, such as the charge and the balance of hydrophobicity-vs-hydrophilicity, strongly influence the mobility of nanoparticles in the extracellular space. In addition, albumin, a natural fatty acid transporter, has recently been demonstrated capable of binding the amphiphiles through their lipid moiety and subsequent transporting them to lymph nodes.

Multifactorial Design of a Supramolecular Peptide Anti-IL-17 Vaccine Toward the Treatment of Psoriasis

Current treatments for chronic immune-mediated diseases such as psoriasis, rheumatoid arthritis, or Crohn's disease commonly rely on cytokine neutralization using monoclonal antibodies; however, such approaches have drawbacks. Frequent repeated dosing can lead to the formation of anti-drug antibodies and patient compliance issues, and it is difficult to identify a single antibody that is broadly efficacious across diverse patient populations. As an alternative to monoclonal antibody therapy, anti-cytokine immunization is a potential means for long-term therapeutic control of chronic inflammatory diseases. Here we report a supramolecular peptide-based approach for raising antibodies against IL-17 and demonstrate its efficacy in a murine model of psoriasis. B-cell epitopes from IL-17 were co-assembled with the universal T-cell epitope PADRE using the Q11 self-assembling peptide nanofiber system. These materials, with or without adjuvants, raised antibody responses against IL-17. Exploiting the modularity of the system, multifactorial experimental designs were used to select formulations maximizing titer and avidity. In a mouse model of psoriasis induced by imiquimod, unadjuvanted nanofibers had therapeutic efficacy, which could be enhanced with alum adjuvant but reversed with CpG adjuvant. Measurements of antibody subclass induced by adjuvanted and unadjuvanted formulations revealed strong correlations between therapeutic efficacy and titers of IgG1 (improved efficacy) or IgG2b (worsened efficacy). These findings have important implications for the development of anti-cytokine active immunotherapies and suggest that immune phenotype is an important metric for eliciting therapeutic anti-cytokine antibody responses.

Synthesis of protein conjugates adsorbed on cationic liposomes surface

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

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

•

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

•

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

Autoantigen Treatment in Type 1 Diabetes: Unsolved Questions on How to Select Autoantigen and Administration Route

Autoantigen treatment has been tried for the prevention of type 1 diabetes (T1D) and to preserve residual beta-cell function in patients with a recent onset of the disease. In experimental animal models, efficacy was good, but was insufficient in human subjects. Besides the possible minor efficacy of peroral insulin in high-risk individuals to prevent T1D, autoantigen prevention trials have failed. Other studies on autoantigen prevention and intervention at diagnosis are ongoing. One problem is to select autoantigen/s; others are dose and route. Oral administration may be improved by using different vehicles. Proinsulin peptide therapy in patients with T1D has shown possible minor efficacy. In patients with newly diagnosed T1D, subcutaneous injection of glutamic acid decarboxylase (GAD) bound to alum hydroxide (GAD-alum) can likely preserve beta-cell function, but the therapeutic effect needs to be improved. Intra-lymphatic administration may be a better alternative than subcutaneous administration, and combination therapy might improve efficacy. This review elucidates some actual problems of autoantigen therapy in the prevention and/or early intervention of type 1 diabetes.

The challenge and prospect of mRNA therapeutics landscape

Messenger RNA (mRNA)-based therapeutics hold the potential to cause a major revolution in the pharmaceutical industry because they can be used for precise and individualized therapy, and enable patients to produce therapeutic proteins in their own bodies without struggling with the comprehensive manufacturing issues associated with recombinant proteins. Compared with the current therapeutics, the production of mRNA is much cost-effective, faster and more flexible because it can be easily produced by in vitro transcription, and the process is independent of mRNA sequence. Moreover, mRNA vaccines allow people to develop personalized medications based on sequencing results and/or personalized conditions rapidly. Along with the great potential from bench to bedside, technical obstacles facing mRNA pharmaceuticals are also obvious. The stability, immunogenicity, translation efficiency, and delivery are all pivotal issues need to be addressed. In the recently published research results, these issues are gradually being overcome by state-of-the-art development technologies. In this review, we describe the structural properties and modification technologies of mRNA, summarize the latest advances in developing mRNA delivery systems, review the preclinical and clinical applications, and put forward our views on the prospect and challenges of developing mRNA into a new class of drug.

Engineering drug delivery systems to overcome mucosal barriers for immunotherapy and vaccination

Mucosal surfaces protect our bodies from pathogens and external irritants using a system of biological barriers. Overcoming these barriers is a significant drug delivery challenge, particularly for immunotherapies that aim to modulate the local immune response. Reaching local lymphoid tissues and draining lymph nodes (LNs) requires crossing the mucus mesh, mucosal epithelium, and either targeting M cells covering lymphoid tissues or utilizing lymphatic transport that shuttles molecules and particulates from the periphery to the LN. We first highlight the barrier properties of mucus and mucosal epithelium, and the function of the mucosal immune system. We then dive into existing drug delivery technologies that have been engineered to overcome each of these barriers. We particularly focus on novel strategies for targeting lymphoid tissues, which has been shown to enhance immunotherapies and vaccinations, via directly targeting LNs, lymphatic vessels, and M cells that transport samples of mucosal content to the lymphoid tissues.

NIR-light-mediated spatially selective triggering of anti-tumor immunity via upconversion nanoparticle-based immunodevices

Immunomodulatory therapies are becoming a paradigm-shifting treatment modality for cancer. Despite promising clinical results, cancer immunotherapy is accompanied with off-tumor toxicity and autoimmune adverse effects. Thus, the development of smarter systems to regulate immune responses with superior spatiotemporal precision and enhanced safety is urgently needed. Here we report an activatable engineered immunodevice that enables remote control over the antitumor immunity in vitro and in vivo with near-infrared (NIR) light. The immunodevice is composed of a rationally designed UV light-activatable immunostimulatory agent and upconversion nanoparticle, which acts as a transducer to shift the light sensitivity of the device to the NIR window. The controlled immune regulation allows the generation of effective immune response within tumor without disturbing immunity elsewhere in the body, thereby maintaining the antitumor efficacy while mitigating systemic toxicity. The present work illustrates the potential of the remote-controlled immunodevice for triggering of immunoactivity at the right time and site.

Oligonucleotide therapy: An emerging focus area for drug delivery in chronic inflammatory respiratory diseases

Oligonucleotide-based therapies are advanced novel interventions used in the management of various respiratory diseases such as asthma and Chronic Obstructive Pulmonary Disease (COPD). These agents primarily act by gene silencing or RNA interference. Better methodologies and techniques are the need of the hour that can deliver these agents to tissues and cells in a target specific manner by which their maximum potential can be reached in the management of chronic inflammatory diseases. Nanoparticles play an important role in the target-specific delivery of drugs. In addition, oligonucleotides also are extensively used for gene transfer in the form of polymeric, liposomal and inorganic carrier materials. Therefore, the current review focuses on various novel dosage forms like nanoparticles, liposomes that can be used efficiently for the delivery of various oligonucleotides such as siRNA and miRNA. We also discuss the future perspectives and targets for oligonucleotides in the management of respiratory diseases.

Nanoparticle-based CpG-oligonucleotide therapy for treating allergic asthma

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

New Routes of Allergen Immunotherapy

Objectives

Allergen immunotherapy is the only cure for immunoglobulin E mediated type I respiratory allergies. Subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) are the most common treatments. In this article, we reviewed new routes of allergen immunotherapy.

Methods

Data on alternative routes to allow intralymphatic immunotherapy (ILIT), epicutaneous immunotherapy (EPIT), local nasal immunotherapy (LNIT), oral immunotherapy (OIT), and oral mucosal immunotherapy (OMIT) were gathered from the literature and were discussed.

Results

ILIT features direct injection of allergens into lymph nodes. ILIT may be clinically effective after only a few injections and induces allergen-specific immunoglobulin G, similarly to SCIT. A limitation of ILIT is that intralymphatic injections are required. EPIT features allergen administration by using patches mounted on the skin. EPIT seeks to target epidermal antigen–presenting Langerhans cells rather than mast cells or the vasculature; this should reduce both local and systemic adverse effects. LNIT involves the spraying of allergen extracts into the nasal cavity. Natural or chemically modified allergens (the latter, termed allergoids, lack immunoglobulin E reactivity) are prepared in a soluble form. OIT involves the regular administration of small amounts of a food allergen by mouth and commences with low oral doses, which are then increased as tolerance develops. OMIT seeks to deliver allergenic proteins to an expanded population of Langerhans cells in the mucosa of the oral cavity.

Conclusions

ILIT, EPIT, LNIT, OIT, and OMIT are new routes for allergen immunotherapy. They are safe and effective.

Allergen immunotherapy, routes of administration and cytokine networks: an update

Allergen immunotherapy is a disease-modifying therapy, effective for the treatment of allergic rhinitis, allergic asthma, conjunctivitis or stinging insect allergy. Allergen immunotherapy involves the administration of increasing doses of allergens with the aim of ameliorating the allergic response. Although precise underlying mechanisms of the induction of immune tolerance remain unclear, immunotherapy has been associated with the induction of distinct subsets of Tregs that eventually lead to peripheral tolerance by inducing a deviation from Th2 to Th1 immune responses. This review focuses on the current knowledge of the mechanisms of immunotherapy in relationship to different routes of administration and also provides a unifying view.

Intralymphatic immunotherapy

Gold Standard allergen-specific immunotherapy is associated with low efficacy because it requires either many subcutaneous injections of allergen or even more numerous sublingual allergen administrations to achieve amelioration of symptoms. Intralymphatic vaccination can maximize immunogenicity and hence efficacy. We and others have demonstrated that as few as three low dose intralymphatic allergen administrations are sufficient to effectively alleviate symptoms. Results of recent prospective and controlled trials suggest that this strategy may be an effective form of allergen immunotherapy.

Liposome-encapsulated CpG enhances antitumor activity accompanying the changing of lymphocyte populations in tumor via intratumoral administration

Although oligodeoxynucleotides containing CpG motifs (CpG-ODN) are potent immune stimulators, the use of natural CpG-ODN--phosphodiester-backbone CpG--has been limited due to its instability by nuclease in vivo. The aim of this study is to investigate the anticancer efficiency of CpG-ODN capsulated using liposome, which enhances the stability of CpG-ODN. We formulated lipoplex, encapsulated natural CpG-ODN from Mycobacterium bovis with liposome, and tested its immune stimulatory activity in vitro and in vivo. The lipoplex induced a systemic innate immune response in vivo and stimulated dendritic cells, but not macrophages, to stimulate proinflammatory cytokines such as tumor necrosis factor alpha and interleukin-6 in vitro. As expected, the lipoplex effectively mediated the prolonged cancer-therapeutic activity against B16 melanoma, which was dependent on natural killer and CD8(+) T cells. The therapeutic activity was observed after only intratumoral administration of lipoplex among several treatment routes. Intratumoral treatment of lipoplex significantly increased the populations of natural killer and CD8(+) T cells and reduced regulatory CD4(+) T cell recruitment, which was correlated with expression profiles of chemokines (CCL1, CCL3, CXCL1, CXCL10, and CCL22). The antitumor therapeutic effect of lipoplex was dependent on the altered lymphocyte population that might be developed by the profile of intratumoral chemokine expression.

The ReNAissanCe of mRNA-based cancer therapy

About 25 years ago, mRNA became a tool of interest in anticancer vaccination approaches. However, due to its rapid degradation in situ, direct application of mRNA was confronted with considerable skepticism during its early use. Consequently, mRNA was for a long time mainly used for the ex vivo transfection of dendritic cells, professional antigen-presenting cells known to stimulate immunity. The interest in direct application of mRNA experienced a revival, as researchers became aware of the many advantages mRNA offers. Today, mRNA is considered to be an ideal vehicle for the induction of strong immune responses against cancer. The growing numbers of preclinical trials and as a consequence the increasing clinical application of mRNA as an off-the-shelf anticancer vaccine signifies a renaissance for transcript-based antitumor therapy. In this review, we highlight this renaissance using a timeline providing all milestones in the application of mRNA for anticancer vaccination.

Routes of delivery for CpG and anti-CD137 for the treatment of orthotopic kidney tumors in mice

We have found previously that the tumor cell lines, Renca (a renal cancer) and MC38 (a colon tumor) which had been injected subcutaneously in mice, could be successfully treated with a combination therapy of an oligodeoxynucleotide (CpG1826) (injected intratumorally) and anti-CD137 antibody (injected intraperitoneally). Thus the combination treatment was expected to initiate a “danger” signal via TLR9 on immune cells, and the anti-CD137 was expected to further activate T cells. In the present study, we found that several other tumor types injected subcutaneously could also be successfully treated with this combination therapy. In addition, we wished to determine if the treatment could work as effectively in an orthotopic metastatic model, which is more physiologically relevant to cancer in humans. Renca was selected as we were familiar with injecting this orthotopically into the outer cortex of the kidney in mice, and it spontaneously metastasizes to lung and abdominal sites. We tested various routes of delivery of CpG combined with intraperitoneal delivery of anti-CD137. Orthotopic tumors were injected with CpG intratumorally, using ultrasound-guided delivery on multiple occasions, combined with anti-CD137 intraperitoneally. A reduction in primary tumor size was observed following intratumoral injection of CpG compared to other treatments. We found that there was a statistically significant increase in survival of mice with orthotopic Renca tumor following intratumoral injection of CpG. However, we determined that the most effective route of delivery of CpG was intravenous, which led to further significantly enhanced survival of mice when combined with anti-CD137 intraperitoneally, likely due to inhibition of metastatic disease. Our data supports future development of this combination therapy for cancer.

Intralymphatic immunotherapy and vaccination in mice

Vaccines are typically injected subcutaneously or intramuscularly for stimulation of immune responses. The success of this requires efficient drainage of vaccine to lymph nodes where antigen presenting cells can interact with lymphocytes for generation of the wanted immune responses. The strength and the type of immune responses induced also depend on the density or frequency of interactions as well as the microenvironment, especially the content of cytokines. As only a minute fraction of peripherally injected vaccines reaches the lymph nodes, vaccinations of mice and humans were performed by direct injection of vaccine into inguinal lymph nodes, i.e. intralymphatic injection. In man, the procedure is guided by ultrasound. In mice, a small (5-10 mm) incision is made in the inguinal region of anesthetized animals, the lymph node is localized and immobilized with forceps, and a volume of 10-20 μl of the vaccine is injected under visual control. The incision is closed with a single stitch using surgical sutures. Mice were vaccinated with plasmid DNA, RNA, peptide, protein, particles, and bacteria as well as adjuvants, and strong improvement of immune responses against all type of vaccines was observed. The intralymphatic method of vaccination is especially appropriate in situations where conventional vaccination produces insufficient immunity or where the amount of available vaccine is limited.

Allergen immunotherapy: routes, safety, efficacy, and mode of action

Allergic rhinitis, allergic conjunctivitis, and allergic asthma have been steadily increasing in prevalence in recent years. These allergic diseases have a major impact on quality of life and are a major economic burden in the US. Although allergen avoidance and pharmacotherapy are currently the mainstays of therapy, they are not always successful in treating patients' symptoms effectively. If a patient fails allergen avoidance and medical therapy, immunotherapy may be indicated. Furthermore, immunotherapy is the only therapy that may change the course of the disease and induce long-term remission. Though subcutaneous administration has been the standard route for immunotherapy for many decades, there are several other routes of administration that have been and are currently being studied. The goal of utilizing alternative routes of immunotherapy is to improve safety without decreasing the efficacy of treatment. This paper will review the novel routes of immunotherapy, including sublingual, oral, local nasal, epicutaneous, and intralymphatic.

Novel routes for allergen immunotherapy: safety, efficacy and mode of action

Allergen immunotherapy is the only curative treatment of IgE-mediated type I respiratory allergies. Subcutaneous immunotherapy (SCIT) is used as a reference therapy and has transformed allergic treatments; it improves symptoms (asthma and rhinitis) as well as the quality of life of patients. SCIT requires repetitive administration and carries the risk of severe systemic adverse effects, including anaphylaxis. Sublingual immunotherapy is now a valid noninvasive alternative to SCIT, as a safe and efficacious treatment for respiratory allergies. In this article, we compare various routes of allergen immunotherapy, including SCIT and sublingual immunotherapy, as well as more exploratory routes currently under investigation (i.e., intralymphatic, epicutaneous, intranasal and oral). We discuss their respective advantages, as well as their foreseen modes of action.

Intralymphatic immunotherapy for cat allergy induces tolerance after only 3 injections

BACKGROUND

Subcutaneous allergen-specific immunotherapy frequently causes allergic side effects and requires 30 to 80 injections over 3 to 5 years.

OBJECTIVE

We sought to improve immunotherapy by using intralymphatic allergen administration (intralymphatic immunotherapy [ILIT]) and by targeting allergen to the MHC class II pathway.

METHODS

Recombinant major cat dander allergen Fel d 1 was fused to a translocation sequence (TAT) and to part of the human invariant chain, generating a modular antigen transporter (MAT) vaccine (MAT-Fel d 1). In a randomized double-blind trial ILIT with MAT-Fel d 1 in alum was compared with ILIT with placebo (saline in alum) in allergic patients (ClinicalTrials.govNCT00718679).

RESULTS

ILIT with MAT-Fel d 1 elicited no adverse events. After 3 placebo injections within 2 months, nasal tolerance increased less than 3-fold, whereas 3 intralymphatic injections with MAT-Fel d 1 increased nasal tolerance 74-fold (P < .001 vs placebo). ILIT with MAT-Fel d 1 stimulated regulatory T-cell responses (P = .026 vs placebo) and increased cat dander-specific IgG(4) levels by 5.66-fold (P = .003). The IgG(4) response positively correlated with IL-10 production (P < .001).

CONCLUSION

In a first-in-human clinical study ILIT with MAT-Fel d 1 was safe and induced allergen tolerance after 3 injections.

In situ engineering of the lymph node microenvironment via intranodal injection of adjuvant-releasing polymer particles

Recent studies have demonstrated a simple, potentially universal strategy to enhance vaccine potency, via intralymph node (i.LN) injection. To date, intranodal immunization studies have focused on the delivery of unadjuvanted vaccines (e.g., naked DNA, peptide, or protein). We hypothesized that combining i.LN vaccination with controlled release biomaterials permitting sustained dosing of molecular adjuvants to the local tissue microenvironment would further enhance this promising vaccination strategy. To test this idea, we encapsulated the Toll-like receptor-3 ligand poly(inosinic:cytidylic acid) (polyIC) in biodegradable poly(lactide-co-glycolide) microparticles (MPs) designed to remain extracellular and release polyIC in the LN over several days. Intranodal injection of MPs increased persistence of polyIC in LNs compared to the same dose of soluble polyIC or polyIC formulated in nanoparticles, leading to increased accumulation of Toll-like receptor agonist in LN-resident antigen presenting cells and more enduring dendritic cell activation. Intralymph node injection of ovalbumin mixed with polyIC-releasing MPs enhanced the humoral response and expanded ovalbumin-specific T cells to frequencies as high as 18% among all CD8(+) cells following a single injection (8.2-fold greater than the same vaccine given i.m.), a response that could not be matched by antigen mixed with polyIC-loaded nanoparticles or a 10-fold greater dose of soluble polyIC. Thus, i.LN immunization with slow release-formulated adjuvants may be a broadly applicable strategy to enhance therapeutic or prophylactic vaccines.

A novel, broad spectrum therapeutic HPV vaccine targeting the E7 proteins of HPV16, 18, 31, 45 and 52 that elicits potent E7-specific CD8T cell immunity and regression of large, established, E7-expressing TC-1 tumors

Persistent infection by high risk genotypes of human papillomavirus (HPV) is the cause of cervical cancer, which remains one of the most common cancers among women worldwide. In addition, there is a growing appreciation that high risk HPVs are associated with a number of other cancers including anogenital cancers as well as a subset of head and neck cancers. Recently, prophylactic HPV vaccines targeting the two most prevalent high risk HPVs (HPV16 and HPV18) have been deployed in large-scale vaccination campaigns. However, the extent to which these prophylactic vaccines confer protection against other high risk HPV genotypes is largely unknown and prophylactic vaccines have been shown to be ineffective against pre-existing infection. Thus there continues to be an urgent need for effective therapeutic vaccines against HPV. The E7 protein of HPV16 has been widely studied as a target for therapeutic vaccines in HPV-associated cancer settings because HPV16 is the most prevalent of the high risk HPV genotypes. However, HPV16 accounts for only about 50% of cervical cancers and there are at least 15 other high risk HPVs that are known to be oncogenic. We have developed a novel, broad-spectrum, therapeutic vaccine (Pentarix) directed at the E7 proteins from five of the most prevalent high-risk genotypes of HPV worldwide (HPV16, 18, 31, 45 and 52) that together account for more than 80% of all HPV-associated cancers. Pentarix is a recombinant protein-based vaccine that elicits strong, multi-genotype specific CD8 T cell immunity when administered to mice in combination with adjuvants comprised of agonists of the TLR3 or TLR9 family of innate immune receptors. Furthermore, large, established E7-expressing TC-1 tumors undergo rapid and complete regression after therapeutic vaccination of mice with Pentarix. Together, these data suggest that Pentarix may be of clinical value for patients with E7-positive, HPV-associated precancerous lesions or malignant disease.

Antitumor activity mediated by CpG: the route of administration is critical

Unmethylated CpG oligodeoxynucleotides (CpG) are synthetic toll-like receptor 9 agonists that activate innate immune cells and which have been tested as an immune therapy in a number of cancer clinical trials. Although some antitumor immune responses have been reported, so far the majority of studies have failed to show significant clinical responses to CpG. Here we showed that the route of administration is critical to the antitumor activity of CpG. Although intravenous (i.v.) injection of CpG was capable of inducing the activation and expansion of tumor antigen-specific T cells, most of these activated T cells failed to migrate to tumor sites. By contrast, intratumoral (i.t.) injection of CpG led to extensive tumor infiltration of antigen-specific T cells and subsequent tumor suppression. We further showed that very high levels of inflammatory chemokines [regulated upon activation, normal T-cell expressed, and secreted (RANTES), interferon-inducible protein-10 (IP-10), monocyte chemoattractant protein-1, monocyte chemotactic protein (MCP5), macrophage inflammatory proteins (MIP1α, and MIP1β)] were induced in the tumor microenvironment after i.t. CpG injection, compared with administration by the i.v. route. It is interesting to note that, in vivo depletion of plasmacytoid dendritic cells greatly reduced the levels of chemokines induced; also, T-cell accumulation and antitumor effect were impaired. We also showed that i.t. but not i.v. CpG injection induced a broad antigen-specific T-cell response against tumor-derived antigens. Collectively, our data provides evidence that the route of CpG administration is a critical factor in mediating antitumor activity. By inducing localized inflammatory signals at tumor sites, i.t. CpG effectively promotes the migration, activation and function of immune cells, ultimately leading to improved tumor control.

Intralymphatic immunotherapy: from the rationale to human applications

Allergen specific immunotherapy (SIT) is the only treatment of IgE mediated allergies that is causative and has a long-term effect. Classically, SIT requires numerous subcutaneous injections of the allergen during 3-5 years. Over the last decade sublingual allergen applications have established as an alternative, but treatment duration could not be shortened. This review focuses on direct administration of vaccines in general and of allergens in particular into lymph nodes with the aim to enhance immunotherapy. Several studies have found that direct injection of antigens into lymph nodes enhanced immune responses. Recently we have focused on intralymphatic allergen administration in order to enhance SIT. Data in mouse models and in clinical trials showed that intralymphatic allergen administration strongly enhanced SIT, so that the number of allergen injections could be reduced to three, and the allergen dose could be reduced 10-100 fold. Intralymphatic injections proved easy, practically painless and safe. In mice and men, intralymphatic immunotherapy injecting allergens into a subcutaneous lymph node markedly enhances the protective immune response, so that both the dose and number of allergen injections can be reduced, making SIT safer and faster, which enhances patient convenience and compliance.

Programmed cell death-1 (PD-1) at the heart of heterologous prime-boost vaccines and regulation of CD8+ T cell immunity

Developing new vaccination strategies and optimizing current vaccines through heterologous prime-boost carries the promise of integrating the benefits of different yet synergistic vectors. It has been widely thought that the increased immunity afforded by heterologous prime-boost vaccination is mainly due to the minimization of immune responses to the carrier vectors, which allows a progressive build up of immunity against defined epitopes and the subsequent induction of broader immune responses against pathogens. Focusing on CD8⁺ T cells, we put forward a different yet complementary hypothesis based primarily on the systematic analysis of DNA vaccines as priming agents. This hypothesis relies on the finding that during the initiation of immune response, acquisition of co-inhibitory receptors such as programmed cell death-1 (PD-1) is determined by the pattern of antigen exposure in conjunction with Toll-like receptor (TLR)-dependent stimulation, critically affecting the magnitude and profile of secondary immunity. This hypothesis, based upon the acquisition and co-regulation of pivotal inhibitory receptors by CD8⁺ T cells, offers a rationale for gene-based immunization as an effective priming strategy and, in addition, outlines a new dimension to immune homeostasis during immune reaction to pathogens. Finally, this model implies that new and optimized immunization approaches for cancer and certain viral infections must induce highly efficacious T cells, refractory to a broad range of immune-inhibiting mechanisms, rather than solely or primarily focusing on the generation of large pools of vaccine-specific lymphocytes.

Optimized systemic dosing with CpG DNA enhances dendritic cell-mediated rejection of a poorly immunogenic mammary tumor in BALB/c mice

To model a clinical trial of dendritic cell (DC) therapy of a poorly immunogenic mammary tumor, we treated BALB/c mice bearing an established TS/A mammary tumor with lysate-pulsed DCs and CpG DNA. We observed that the dose of CpG DNA required to activate DCs in vitro was insufficient to mediate tumor rejection in vivo. We therefore undertook in vivo studies to identify an optimized dose of CpG DNA for tumor therapy, defined as the lowest and least frequently administered dose of CpG DNA that mediated complete tumor rejection. We show that one priming dose of 15 nanomoles and one booster dose of 10 nanomoles of CpG DNA given 7 days apart, respectively, with lysate-loaded DCs were sufficient to mediate complete tumor rejection in vivo. This dose of CpG DNA was 42-fold higher than that required to activate DCs in vitro but was not associated with any toxicity in mice. Also, the cured mice rejected a subsequent challenge with fresh TS/A tumor, and both CD4(+) and CD8(+) T cells were required for tumor rejection. We conclude that effective DC-based therapy of a poorly immunogenic TS/A tumor is enhanced by optimized dosing of CpG DNA. Our data have important implications for DC-based clinical trials of breast cancer immunotherapy.

Intralymphatic immunotherapy

PURPOSE OF REVIEW

IgE-mediated allergy can be treated by subcutaneous allergen-specific immunotherapy (SCIT). However, the percentage of allergic patients undergoing SCIT is low, mainly due to the long duration of the therapy and the risk of severe systemic allergic reactions associated with the allergen administration. Typically, SCIT requires dozens of subcutaneous allergen injections that stretch over 3-5 years. Over the last decade, sublingual immunotherapy has been established as an alternative to SCIT, but treatment duration and dosing frequencies could not be reduced. Recently, immunotherapy by direct administration of the allergen into lymph nodes [intralymphatic immunotherapy (ILIT)] has proven a promising alternative and this method is the focus of the present review.

RECENT FINDINGS

Several studies on animals and on humans have shown that direct injection into lymph nodes enhanced immune responses to protein, peptide, and naked DNA vaccines. Moreover, ILIT strongly improved allergen immunotherapy, so that the number of allergen administrations as well as the allergen dose could be reduced. As ILIT was also well tolerated, practically painless, and easy to perform, patient compliance was improved as compared with SCIT.

SUMMARY

Direct ILIT into a subcutaneous lymph node markedly enhances protective immune responses, so that both the dose and the number of allergen injections can be reduced, making ILIT safer and faster than other forms of immunotherapy, and most importantly, this enhances patient convenience and compliance.

Route of administration of the TLR9 agonist CpG critically determines the efficacy of cancer immunotherapy in mice

Background

The TLR9 agonist CpG is increasingly applied in preclinical and clinical studies as a therapeutic modality to enhance tumor immunity. The clinical application of CpG appears, however, less successful than would be predicted from animal studies. One reason might be the different administration routes applied in most mouse studies and clinical trials. We studied whether the efficacy of CpG as an adjuvant in cancer immunotherapy is dependent on the route of CpG administration, in particular when the tumor is destructed in situ.

Methodology/Principal Findings

In situ tumor destruction techniques are minimally invasive therapeutic alternatives for the treatment of (nonresectable) solid tumors. In contrast to surgical resection, tumor destruction leads to the induction of weak but tumor-specific immunity that can be enhanced by coapplication of CpG. As in situ tumor destruction by cryosurgery creates an instant local release of antigens, we applied this model to study the efficacy of CpG to enhance antitumor immunity when administrated via different routes: peritumoral, intravenous, and subcutaneous but distant from the tumor. We show that peritumoral administration is superior in the activation of dendritic cells, induction of tumor-specific CTL, and long-lasting tumor protection. Although the intravenous and subcutaneous (at distant site) exposures are commonly used in clinical trials, they only provided partial protection or even failed to enhance antitumor responses as induced by cryosurgery alone.

Conclusions/Significance

CpG administration greatly enhances the efficacy of in situ tumor destruction techniques, provided that CpG is administered in close proximity of the released antigens. Hence, this study helps to provide directions to fully benefit from CpG as immune stimulant in a clinical setting.

All three classes of CpG ODNs up-regulate IP-10 gene in pigs

The analysis of CpG ODN induced innate immune responses in different animal species has shown substantial similarities and differences in levels and types of induced cytokines profile. The objectives of these studies were to identify innate immune biomarkers activated by three classes of CpG ODNs in pigs. For this purpose, we investigated the kinetics of innate immune responses in immune cells from pigs following in vitro and in vivo stimulation with CpG ODNs. The mRNA expression of cytokine and chemokine genes were assayed by SYBR green based quantitative real time PCR. A-class CpG ODN induced significant but transient levels of IFN-gamma, IL-12 (P40), IL-6, IL-4 and TNF-alpha mRNA, C-class CpG ODN induced significant level of IFN-gamma, IFN-alpha and IL-12 mRNA and the lowest level of IL-4 (Th-2 type) mRNA. A very low level of some cytokines stimulation was observed by GC ODNs. It is noteworthy, that IL-12 (P35) mRNA was significantly stimulated by B-class GpC ODN 7909. Interestingly, all classes of CpG ODNs induced significant level of IP-10 at 12h post stimulation. These in vitro and in vivo observations suggest that interferon-gamma inducible protein 10 (IP-10) may be a reliable biomarker for immune activity induced by CpG ODNs in pigs.

Lymph node-targeted immunotherapy mediates potent immunity resulting in regression of isolated or metastatic human papillomavirus-transformed tumors

PURPOSE

The goal of this study was to investigate the therapeutic potential of a novel immunotherapy strategy resulting in immunity to localized or metastatic human papillomavirus 16-transformed murine tumors.

EXPERIMENTAL DESIGN

Animals bearing E7-expressing tumors were coimmunized by lymph node injection with E7 49-57 antigen and TLR3-ligand (synthetic dsRNA). Immune responses were measured by flow cytometry and antitumor efficacy was evaluated by tumor size and survival. In situ cytotoxicity assays and identification of tumor-infiltrating lymphocytes and T regulatory cells were used to assess the mechanisms of treatment resistance in bulky disease. Chemotherapy with cyclophosphamide was explored to augment immunotherapy in late-stage disease.

RESULTS

In therapeutic and prophylactic settings, immunization resulted in a considerable expansion of E7 49-57 antigen-specific T lymphocytes in the range of 1/10 CD8(+) T cells. The resulting immunity was effective in suppressing disease progression and mortality in a pulmonary metastatic disease model. Therapeutic immunization resulted in control of isolated tumors up to a certain volume, and correlated with antitumor immune responses measured in blood. In situ analysis showed that within bulky tumors, T-cell function was affected by negative regulatory mechanisms linked to an increase in T regulatory cells and could be overcome by cyclophosphamide treatment in conjunction with immunization.

CONCLUSIONS

This study highlights a novel cancer immunotherapy platform with potential for translatability to the clinic and suggests its potential usefulness for controlling metastatic disease, solid tumors of limited size, or larger tumors when combined with cytotoxic agents that reduce the number of tumor-infiltrating T regulatory cells.

Enhancing DNA vaccination by sequential injection of lymph nodes with plasmid vectors and peptides

DNA vaccines or peptides are capable of inducing specific immunity; however, their translation to the clinic has generally been problematic, primarily due to the reduced magnitude of immune response and poor pharmacokinetics. Herein, we demonstrate that a novel immunization strategy, encompassing sequential exposure of the lymph node milieu to plasmid and peptide in a heterologous prime-boost fashion, results in considerable MHC class I-restricted immunity in mice. Plasmid-primed antigen expression was essential for the generation of a population of central memory T cells, expressing CD62L and low in PD-1, with substantial capability to expand and differentiate to peripheral memory and effector cells, following subsequent exposure to peptide. These vaccine-induced T cells dominated the T cell repertoire, were able to produce large amounts of chemokines and pro-inflammatory cytokines, and recognized tumor cells effectively. In addition to outlining a feasible and effective method to transform plasmid DNA vaccination into a potentially viable immunotherapeutic approach for cancer, this study sheds light on the mechanism of heterologous prime-boost and the considerable heterogeneity of MHC class I-restricted T cell responses.

Intralymphatic allergen administration renders specific immunotherapy faster and safer: a randomized controlled trial

The only causative treatment for IgE-mediated allergies is allergen-specific immunotherapy. However, fewer than 5% of allergy patients receive immunotherapy because of its long duration and risk of allergic side effects. We aimed at enhancing s.c. immunotherapy by direct administration of allergen into s.c. lymph nodes. The objective was to evaluate safety and efficacy compared with conventional s.c. immunotherapy. In a monocentric open-label trial, 165 patients with grass pollen-induced rhinoconjunctivitis were randomized to receive either 54 s.c. injections with pollen extract over 3 years [cumulative allergen dose 4,031,540 standardized quality units (SQ-U)] or 3 intralymphatic injections over 2 months (cumulative allergen dose 3,000 SQ-U). Patients were evaluated after 4 months, 1 year, and 3 years by nasal provocation, skin prick testing, IgE measurements, and symptom scores. Three low-dose intralymphatic allergen administrations increased tolerance to nasal provocation with pollen already within 4 months (P < 0.001). Tolerance was long lasting and equivalent to that achievable after standard s.c. immunotherapy (P = 0.291 after 3 years). Intralymphatic immunotherapy ameliorated hay fever symptoms (P < 0.001), reduced skin prick test reactivity (P < 0.001), decreased specific serum IgE (P < 0.001), caused fewer adverse events than s.c. immunotherapy (P = 0.001), enhanced compliance (P < 0.001), and was less painful than venous puncture (P = 0.018). In conclusion, intralymphatic allergen administration enhanced safety and efficacy of immunotherapy and reduced treatment time from 3 years to 8 weeks.

Targeting CpG oligonucleotides to the lymph node by nanoparticles elicits efficient antitumoral immunity

Viral nucleic acids are recognized by specific pattern-recognition receptors of the Toll-like and RIG-I-like receptor families. Synthetic DNA and RNA oligonucleotides can activate the immune system through these receptors and potentiate Ab and CD8 cytotoxic responses to Ags. Systemic application of immunostimulatory oligonucleotides however also results in a generalized, non-Ag-specific stimulation of the immune system. In this study, we have dissociated the induction of an Ag-specific response from the systemic immune activation generally associated with immunostimulatory oligonucleotides. Delivery of CpG oligodeoxynucleotides that bind TLR9 by cationized gelatin-based nanoparticles potentiates the in vivo generation of an Ag-specific cytotoxic T cell and Ab response. Furthermore, immunization with CpG-loaded nanoparticles induces a protective antitumoral response in a murine model of melanoma. The systemic release of proinflammatory cytokines and widespread immunostimulation associated with free CpG is however completely abolished. In addition, we show that gelatin nanoparticle formulation prevents the destruction of lymphoid follicles mediated by CpG. Nanoparticle-delivered CpG, in contrast to free CpG, are selectively targeted to APCs in the lymph nodes where they mediate local immune stimulation. We describe a novel strategy to target immunostimulatory oligonucleotides to the initiation site of the immune response while at the same time protecting from an indiscriminate and generalized activation of the immune system.

In vivo colocalization of antigen and CpG [corrected] within dendritic cells is associated with the efficacy of cancer immunotherapy

Immunostimulatory cytidyl guanosyl (CpG) motifs are of great interest as cancer vaccine adjuvants. They act as potent inducers of Th1 responses, including the activation of cytotoxic CD8(+) T lymphocytes (CTL). Whereas animal models have provided clear evidence that CpG enhances antitumor immunity, clinical trials in humans have thus far been less successful. Applying cryosurgery as an instant in situ tumor destruction technique, we now show that timing of CpG administration crucially affects colocalization of antigen and CpG within EEA-1(+) and LAMP-1(+) compartments within dendritic cells in vivo. Moreover, antigen/CpG colocalization is directly correlated with antigen cross-presentation, the presence of CTL, and protective antitumor immunity. Thus, failure or success of CpG as a vaccine adjuvant may depend on colocalization of antigen/CpG inside DCs and hence on the timing of CpG administration. These data might aid in the design of future immunotherapeutic strategies for cancer patients.

Phase 1 trial of intranodal injection of a Melan-A/MART-1 DNA plasmid vaccine in patients with stage IV melanoma

Nineteen patients with stage IV melanoma were treated in an escalating dose, phase 1 trial of a DNA plasmid vaccine pSEM. The plasmid encoded T-cell epitopes from differentiation antigens Melan-A/melanoma antigen recognized by T cells (MART)-1 and tyrosinase, encompassing amino acids 26-35 and 31-70 from Melan-A/MART-1, and 1-9 as well as 369-377 from tyrosinase. End points of the trial were safety, tolerability, and melanoma antigen-specific immunity by tetramer assay. Intralymph nodal infusions of the vaccine were given 4 times, every 2 weeks over 96 hours each to groin lymph nodes. Vaccine doses were 500, 1000, and 1500 microg of DNA per infusion. Disease evaluation was performed 8 weeks after treatment initiation. The vaccine was well tolerated, with only grade I/II toxicity observed and no dose limiting toxicity at the highest dose of 1500 microg per infusion. Immune response defined prospectively was seen in 4/19 patients, and 5/19 had evidence of preexisting immunity to Melan-A/MART-1. No immune responses to tyrosinase was seen. There was a correlation between time to progression (TTP) and Melan-A/MART-1 immunity (preexisting or induced) for all patients. There was no association between TTP and immune competence assayed by ex vivo polyclonal stimulation of peripheral blood mononuclear cells. No clinical responses were seen. DNA plasmid pSEM vaccine was well tolerated when administered intranodally by 96-hour infusion to patients with stage IV melanoma, and was immunogenic, but did not induce regression of established disease. The association of TTP with preexisting or induced Melan-A immunity supports future attempts to induce potent immunity to this antigen.

The pharmacology of endosomal TLR agonists in viral disease

The discovery of endosomal TLRs (Toll-like receptors) and their natural ligands has accelerated efforts to exploit them for therapeutic benefit. Importantly, this was preceded by clinical exploration of agents now known to be endosomal TLR agonists. Clinical effects in viral disease have been reported with agonists of TLR3, TLR7, TLR7/8 and TLR9, and the TLR7 agonist imiquimod is marketed for topical use against warts, a papillomavirus disease. The observed pre-clinical and clinical profiles of agonists of each of these TLRs suggest induction of a multifaceted innate immune response, with biomarker signatures indicative of type 1 interferon induction. However, these agents differ in both their pharmaceutical characteristics and the cellular distribution of their target TLRs, suggesting that drugs directed to these targets will display differences in their overall pharmacological profiles.

Topical TLR9 agonists induce more efficient cross-presentation of injected protein antigen than parenteral TLR9 agonists do

Topical application of adjuvant to the skin promotes the generation of immune responses to co-administered peptide or protein antigen. We demonstrate that topical administration of CpG adjuvant (a TLR9 agonist) induces the cross-presentation of, and antigen-specific CTL induction to, locally injected soluble protein antigen. C57BL/6 mice were immunized by subcutaneous or intramuscular injection with ovalbumin (OVA) protein as model antigen. Application of CpG to the local skin induced more efficient cross-presentation of the injected antigen than co-injected adjuvant. Robust antigen-specific CTL responses were generated, as determined by antigen-specific CTL enumeration using tetramers, IFN-gamma ELISPOT analysis and cytotoxicity assays. Long-term memory CTL responses were induced. Topical administration of adjuvant induced Langerhans cell migration, local type 1 IFN-dependent myxovirus-resistance protein A expression and bystander dendritic cell (DC) activation. Soluble antigen-bearing DC within the skin draining lymph nodes were mainly CD11chiCD11bhilangerinloDEC205lo. Topical administration did not result in the splenomegaly or systemic cytokine induction (including TNF-alpha, IL-12, IFN-gamma and MCP-1) noted with parenteral administration. Topical TLR9 family agonists may be used to modulate the immune response to soluble protein vaccines administered by standard percutaneous route. Topical adjuvant administration increases efficacy of CTL induction and reduces toxicity when compared to parenteral adjuvant administration.

Posttranscriptional gene expression regulation in CpG-activated macrophages depends on FXR1P RNA-binding protein

An RNA-binding protein (RBP) was recently identified, FXR1P, which regulates tumour necrosis factor (TNF) gene expression at the posttranscriptional level in response to lipopolysaccharide, was recently identified resulting in higher TNF production in macrophages from FXR1 knockout (KO) mice compared with wild-type (WT) macrophages. In this study, the importance of FXR1P in the induction of TNF by toll-like receptor 7 (TLR7) ligand S28463 and TLR9 ligand CpG is evaluated. The results clearly reveal a much higher level of TNF protein expression in FXR1-KO than in WT macrophages following stimulation with CpG but not with S28463. To better understand the molecular mechanism, both the steady-state levels and the stability of TNF mRNA were assessed. It was found that the TNF mRNA steady-state level was more elevated in CpG-stimulated FXR1-KO macrophages, while the stability of TNF mRNA was not affected in CpG-stimulated FXR1-KO macrophages. It was also established that FXR1P is involved in regulating the expression of several other inflammatory cytokines and chemokines. Together, the data clearly demonstrate the importance of FXR1P RBP in the regulation of a wide spectrum of inflammatory genes and suggest an important role of MAP signalling in the response of macrophages to selected TLR ligands, including CpG.