Systemic cancer immunotherapy with Toll-like receptor 7 agonists: Timing is everything

Toll-like receptor (TLR) 7 agonists represent a promising strategy for the immunotherapy of cancer. We have recently investigated the influence of TLR tolerance on the efficacy of systemic tumor treatment with TLR7 ligands. We propose that considering the kinetics of receptor sensitivity highly improves the outcome of cancer immunotherapy

Vaccination with DNA encoding a myelin autoantigen exacerbates experimental autoimmune encephalitis

The ultimate goal in the treatment of autoimmune diseases is to reestablish tolerance to self antigens. One strategy to induce tolerance is to express the target autoantigen by DNA vaccination. In this work, the potential of vaccination with a DNA construct encoding the myelin oligodendrocyte glycoprotein (MOG), an important candidate autoantigen in multiple sclerosis, to induce tolerance and protect against experimental autoimmune encephalomyelitis (EAE) was assessed. Unexpectedly, mice vaccinated with MOG-DNA develop an exacerbated form of EAE when challenged with either MOG or an unrelated encephalitogen, myelin proteolipid protein. Disease exacerbation is due to the inability of DNA vaccination to tolerise the MOG specific T cell response and to the concomitant induction of a MOG-specific autoantibody response which is pathogenic, enhancing demyelination, inflammation and disease severity. These results suggest that tolerogenic strategies for autoimmune diseases based on DNA vaccination should be approached with caution

NAB2 is a novel immune stimulator of MDA-5 that promotes a strong type I interferon response

Novel adjuvants are needed to increase the efficacy of vaccine formulations and immune therapies for cancer and chronic infections. In particular, adjuvants that promote a strong type I IFN response are required, since this cytokine is crucial for the development of efficient anti-tumoral and anti-viral immunity. Nucleic acid band 2 (NAB2) is a double- stranded RNA molecule isolated from yeast and identified as an agonist of the pattern- recognition receptors TLR3 and MDA-5. We compared the ability of NAB2 to activate innate immunity with that of poly(I:C), a well-characterized TLR3 and MDA-5 agonist known for the induction of type I IFN. NAB2 promoted stronger IFN-α production and induced a higher activation state of both murine and human innate immune cells compared to poly(I:C). This correlated with a stronger activation of the signalling pathway downstream of MDA-5, and IFN-α induction was dependent on MDA-5. Upon injection, NAB2 induced higher levels of serum IFN-α in mice than poly(I:C). These results suggest that NAB2 has the potential to become an efficient adjuvant for the induction of type-I IFN responses in therapeutic immunization against cancer or infections

Neonatal immune tolerance induction to allow long-term studies with an immunogenic therapeutic monoclonal antibody in mice

The purpose of this study is to test the feasibility of neonatal immune tolerance induction in mice to enable long-term pharmacokinetic studies with immunogenic therapeutic monoclonal antibodies (mAb). Neonatal immune tolerance was induced by transfer of a mAb to neonatal mice via colostrum from nursing mother mice treated with two subcutaneous doses of a tolerogen starting within the first 24 h after delivery. Adalimumab and efalizumab were administered as tolerogens at various dose levels. Tolerance induction was evaluated in the offspring after reaching adulthood at 8 weeks of age. After a single intravenous injection of the same mAb as used for tolerance induction, the pharmacokinetics of the mAb and formation of anti-drug antibodies (ADA) in plasma were assessed using ELISA. Tolerance induction to adalimumab was achieved in a maternal dose-dependent manner. Adalimumab immune-tolerant offspring showed a slower adalimumab clearance (4.24 ± 0.32 mL/day/kg) as compared to the control group (12.09 ± 3.81 mL/day/kg). In the control group, accelerated clearance started 7 days after adalimumab dosing, whereas immune- tolerant offspring showed a log-linear terminal concentration-time course. In the offspring, the absence of predose ADA levels was indicative of successful tolerance induction. The second test compound efalizumab was not immunogenic in mice under our experimental conditions. Overall, the present study demonstrated the suitability of neonatal immune tolerance induction for a 4-week single dose study in adult mice with a human therapeutic mAb that is otherwise immunogenic in laboratory animals

Immune response to functionalized mesoporous silica nanoparticles for targeted drug delivery

Multifunctional mesoporous silica nanoparticles (MSN) have attracted substantial attention with regard to their high potential for targeted drug delivery. For future clinical applications it is crucial to address safety concerns and understand the potential immunotoxicity of these nanoparticles. In this study, we assess the biocompatibility and functionality of multifunctional MSN in freshly isolated, primary murine immune cells. We show that the functionalized silica nanoparticles are rapidly and efficiently taken up into the endosomal compartment by specialized antigen-presenting cells such as dendritic cells. The silica nanoparticles showed a favorable toxicity profile and did not affect the viability of primary immune cells from the spleen in relevant concentrations. Cargo-free MSN induced only very low immune responses in primary cells as determined by surface expression of activation markers and release of pro-inflammatory cytokines such as Interleukin-6, -12 and -1β. In contrast, when surface-functionalized MSN with a pH-responsive polymer capping were loaded with an immune-activating drug, the synthetic Toll-like receptor 7 agonist R848, a strong immune response was provoked. We thus demonstrate that MSN represent an efficient drug delivery vehicle to primary immune cells that is both non-toxic and non-inflammagenic, which is a prerequisite for the use of these particles in biomedical applications

Amphiphilic nanoparticle delivery enhances the anticancer efficacy of a TLR7 ligand via local immune activation

Although immunotherapy shows great promise for the long-term control of cancer, many tumors still fail to respond to treatment. To improve the outcome, the delivery of immunostimulants to the lymph nodes draining the tumor, where the antitumor immune response is initiated, is key. Efforts to use nanoparticles as carriers for cancer immunotherapy have generally required targeting agents and chemical modification of the drug, and have unfortunately resulted in low delivery and therapeutic efficiency. Here, we report on the efficacy of gold nanoparticles with approximately 5 nm hydrodynamic diameter coated with a mixture of 1-octanethiol and 11- mercaptoundecanesulfonic acid for the delivery of an immunostimulatory TLR7 ligand to tumor-draining lymph nodes. The drug was loaded without modification through nonspecific adsorption into the ligand shell of the nanoparticles, taking advantage of their amphiphilic nature. After loading, nanoparticles retained their stability in solution without significant premature release of the drug, and the drug cargo was immunologically active. Upon subcutaneous injection into tumor-bearing mice, the drug-loaded particles were rapidly transported to the tumor-draining lymph nodes. There, they induced a local immune activation and fostered a cytotoxic T-cell response that was specific for the tumor. Importantly, the particle-delivered TLR7 ligand blocked the growth of large established tumors and significantly prolonged survival compared to the free form of the drug. Thus, we demonstrate for the first time that nanoparticle delivery of a TLR7 immunostimulant to the tumor-draining lymph nodes enhances antitumor immunity and improves the outcome of cancer immunotherapy

Antimicrobial silver-filled silica nanorattles with low immunotoxicity in dendritic cells

The progression in the use of orthopedic implants has led to an increase in the absolute number of implant infections, triggering a search for more effective antibacterial coatings. Nanorattles have recently gained interest in biomedical applications such as drug delivery, as encapsulation of the cargo inside the hollow structure provides a physical protection from the surrounding environment. Here, silver-containing silica nanorattles (Ag@SiO2) were evaluated for their antimicrobial potential and for their impact on cells of the immune system. We show that Ag@SiO2 nanorattles exhibited a clear antibacterial effect against Escherichia coli as well as Staphylococcus aureus found in post-operative infections. Immunotoxicological analyses showed that the particles were taken up through an active phagocytic process by dendritic cells of the immune system and did not affect their viability nor induce unwanted immunological effects. Silver-containing silica nanorattles thus fulfill several prerequisites for an antibacterial coating on surgical implants

Polymer-Coated Gold Nanospheres Do Not Impair the Innate Immune Function of Human B Lymphocytes in Vitro

Gold nanoparticles (GNPs) are intended for use within a variety of biomedical applications due to their physicochemical properties. Although, in general, biocompatibility of GNPs with immune cells such as macrophages and dendritic cells is well established, the impact of GNPs on B lymphocyte immune function remains to be determined. Since B lymphocytes play an important role in health and disease, the suitability of GNPs as a B cell-targeting tool is of high relevance. Thus, we provide information on the interactions of GNPs with B lymphocytes. Herein, we exposed freshly isolated human B lymphocytes to a set of well-characterized and biomedically relevant GNPs with distinct surface (polyethylene glycol (PEG), PEG/poly(vinyl alcohol) (PEG/PVA)) and shape (spheres, rods) characteristics. Polymer-coated GNPs poorly interacted with B lymphocytes, in contrast to uncoated GNPs. Importantly, none of the GNPs significantly affected cell viability, even at the highest concentration of 20 μg/mL over a 24 h suspension exposure period. Furthermore, none of the nanosphere formulations affected the expression of activation markers (CD69, CD86, MHC II) of the naive B lymphocytes, nor did they cause an increase in the secretion of pro-inflammatory cytokines ( i.e. , IL-6, IL-1β). However, the absence of polymer coating on the sphere GNPs and the rod shape caused a decrease in IL-6 cytokine production by activated B lymphocytes, suggesting a functional impairment. With these findings, the present study contributes imperative knowledge toward the safe-by-design approaches being conducted to benefit the development of nanomaterials, specifically those as theranostic tools

Polymer-based nanoparticles loaded with a TLR7 ligand to target the lymph node for immunostimulation

Small-molecule agonists for the Toll-like receptors (TLR) 7 and 8 are effective for the immunotherapy of skin cancer when used as topical agents. Their systemic use has however been largely unsuccessful due to dose-limiting toxicity. We propose a polymer-based nanodelivery system to target resiquimod, a TLR7 ligand, to the lymph node in order to focus the immunostimulatory activity and to prevent a generalized inflammatory response. We demonstrate successful encapsulation of resiquimod in methoxypoly(ethylene glycol)-b-poly(DL-lactic acid) (mPEG-PLA) and mixed poly(DL- lactic-co-glycolic acid) (PLGA)/mPEG-PLA nanoparticles. We show that these particles are taken up mainly by dendritic cells and macrophages, which are the prime initiators of anticancer immune responses. Nanoparticles loaded with resiquimod activate these cells, demonstrating the availability of the immune-stimulating cargo. The unloaded particles are non-inflammatory and do not have cytotoxic activity on immune cells. Following subcutaneous injection in mice, mPEG-PLA and PLGA/mPEG-PLA nanoparticles are detected in dendritic cells and macrophages in the draining lymph nodes, demonstrating the targeting potential of these particles. Thus, polymer-based nanoparticles represent a promising delivery system that allows lymph node targeting for small-molecule TLR7 agonists in the context of systemic cancer immunotherapy