A Chromatin-Mimetic Nanomedicine for Therapeutic Tolerance Induction

Liver-Targeting Nanoplatforms for the Induction of Immune Tolerance

Liver-targeting nanoparticles have emerged as a promising platform for the induction of immune tolerance by taking advantage of the liver's unique tolerogenic properties and nanoparticles' physicochemical flexibility. Such an approach provides a versatile solution to the treatment of a diversity of immunologic diseases. In this review, we begin by assessing the design parameters integral to cell-specific targeting and the tolerogenic induction of nanoplatforms engineered to target the four critical immunogenic hepatic cells, including liver sinusoidal epithelial cells (LSECs), Kupffer cells (KCs), hepatic stellate cells (HSCs), and hepatocytes. We also include an overview of multiple therapeutic strategies in which nanoparticles are being studied to treat many allergies and autoimmune disorders. Finally, we explore the challenges of using nanoparticles in this field while highlighting future avenues to expand the therapeutic utility of liver-targeting nanoparticles in autoimmune processes.

Nanomaterials for antigen-specific immune tolerance therapy

Impairment of immune tolerance might cause autologous tissue damage or overactive immune response against non-pathogenic molecules. Although autoimmune disease and allergy have complicated pathologies, the current strategies have mainly focused on symptom amelioration or systemic immunosuppression which can lead to fatal adverse events. The induction of antigen-specific immune tolerance may provide therapeutic benefits to autoimmune disease and allergic response, while reducing nonspecific immune adverse responses. Diverse nanomaterials have been studied to induce antigen-specific immune tolerance therapy. This review will cover the immunological background of antigen-specific tolerance, clinical importance of antigen-specific immune tolerance, and nanomaterials designed for autoimmune and allergic diseases. As nanomaterials for modulating immune tolerances, lipid-based nanoparticles, polymeric nanoparticles, and biological carriers have been covered. Strategies to provide antigen-specific immune tolerance have been addressed. Finally, current challenges and perspectives of nanomaterials for antigen-specific immune tolerance therapy will be discussed.

Immunomodulatory and immunoregulatory nanomedicines for autoimmunity

Autoimmune diseases, caused by cellularly and molecularly complex immune responses against self-antigens, are largely treated with broad-acting, non-disease-specific anti-inflammatory drugs. These compounds can attenuate autoimmune inflammation, but tend to impair normal immunity against infection and cancer, cannot restore normal immune homeostasis and are not curative. Nanoparticle (NP)- and microparticle (MP)-based delivery of immunotherapeutic agents affords a unique opportunity to not only increase the specificity and potency of broad-acting immunomodulators, but also to elicit the formation of organ-specific immunoregulatory cell networks capable of inducing bystander immunoregulation. Here, we review the various NP/MP-based strategies that have so far been tested in models of experimental and/or spontaneous autoimmunity, with a focus on mechanisms of action.

Pre-treatment with high molecular weight free PEG effectively suppresses anti-PEG antibody induction by PEG-liposomes in mice

Immune responses against polyethylene glycol (PEG) can lead to the rapid clearance of PEGylated drugs and are associated with increased risk of serious adverse events such as infusion reactions and anaphylaxis. Although select PEGylated therapeutics can induce anti-PEG antibodies (APA), there is currently no readily deployable strategy to mitigate their negative effects. Given the large number of PEGylated therapeutics that are either FDA-approved or in clinical development, methods that suppress APA induction to ensure the safety and efficacy of PEGylated drugs in patients would be a valuable clinical tool. We previously showed that infusion of high molecular weight (MW) free PEG can safely and effectively restore the circulation of PEG liposomes in animals with high pre-existing titers of APA, without stimulating additional APA production. Here, we explored the effectiveness of prophylaxis with free PEG or tolerogenic PEGylated liposomes as a strategy to reduce the amount of APA induced by subsequently administered PEGylated liposomes. Surprisingly, we found that a single administration of free PEG alone was capable of markedly reducing the APA response to PEG-liposomes for ~2 months; the effectiveness was comparable to, and frequently exceeded, interventions with different tolerogenic PEG-liposomes. These results support further investigations of free PEG prophylaxis as a potential strategy to ameliorate the APA response to sensitizing PEGylated therapeutics.

Synthesis of surfactant-modified ZIF-8 with controllable microstructures and their drug loading and sustained release behaviour

Metal-organic frameworks (MOFs) as drug carriers have many advantages than traditional drug carriers and have received extensive attention from researchers. However, how to regulate the microstructure of MOFs to improve the efficiency of drug delivery and sustained release behaviour is still a big problem for the clinical application. Herein, the authors synthesise surfactant-modified ZIF-8 nanoparticles with different microstructures by using different types of surfactants to modify ZIF-8. The surfactant-modified ZIF-8 nanoparticles have the larger specific surface area and total micropore volumes than the original ZIF-8, which enables doxorubicin (DOX) to be more effectively loaded on the drug carriers and achieve controlled drug sustained release. Excellent degradation performance of ZIF-8 nanoparticles facilitates the metabolism of drug carriers. The formulation was evaluated for cytotoxicity, cellular uptake and intracellular location in the A549 human non-small-cell lung cancer cell line. ZIF-8/DOX nano drugs exhibit higher cytotoxicity towards cells in comparison with free DOX, suggesting the potential application in nano drugs to cancer chemotherapy.

Nanoparticle Platforms for Antigen-Specific Immune Tolerance

Innovative approaches in nanoparticle design have facilitated the creation of new formulations of nanoparticles that are capable of selectively calibrating the immune response. These nanomaterials may be engineered to interact with specific cellular and molecular targets. Recent advancements in nanoparticle synthesis have enabled surface functionalization of particles that mimic the diversity of ligands on the cell surface. Platforms synthesized using these design principles, called "biomimetic" nanoparticles, have achieved increasingly sophisticated targeting specificity and cellular trafficking capabilities. This holds great promise for next generation therapies that seek to achieve immune tolerance. In this review, we discuss the importance of physical design parameters including size, shape, and biomimetic surface functionalization, on the biodistribution, safety and efficacy of biologic nanoparticles. We will also explore potential applications for immune tolerance for organ or stem cell transplantation.

De novo design of functional zwitterionic biomimetic material for immunomodulation

Superhydrophilic zwitterionic polymers are a class of nonfouling materials capable of effectively resisting any nonspecific interactions with biological systems. We designed here a functional zwitterionic polymer that achieves a trade-off between nonspecific interactions providing the nonfouling property and a specific interaction for bioactive functionality. Built from phosphoserine, an immune-signaling molecule in nature, this zwitterionic polymer exhibits both nonfouling and immunomodulatory properties. Its conjugation to uricase is shown to proactively eradicate all unwanted immune response, outperforming the zwitterionic polymers. On the other hand, this polymer could significantly prolong the half-life of protein drugs in vivo, overcoming the innate drawback of phosphoserine in inducing accelerated clearance. Our demonstration of a nonfouling zwitterionic material with built-in immunomodulatory functionality provides new insights into the fundamental design of biomaterials, as well as far-reaching implications for broad applications such as drug delivery, implants, and cell therapy.

[Induction of Anti-PEG Immune Responses by PEGylation of Proteins]

Modification of proteins with polyethylene glycol (PEG) (PEGylation) is a gold standard technique that improves the solubility, pharmacokinetics, and immunogenicity of modified proteins. To date more than 10 PEGylated protein formulations have been approved, and more than 20 PEGylated drugs are entering clinical trials. PEG has been considered non-immunogenic and non-toxic, but several studies have shown that PEG acquires immunogenicity following attachment to nanoparticles. The administration of PEGylated liposomes, micelles and proteins induces the production of antibodies against PEG (anti-PEG antibodies) in animals and human subjects. Indeed, approximately 20% of healthy human subjects possess pre-existing anti-PEG antibodies prior to treatment with PEGylated therapeutics. The induced and pre-existing anti-PEG antibodies cause not only the elimination of PEGylated proteins from blood circulation, but also allergic responses via the release of anaphylatoxins. Consequently, therapeutic outcomes for PEGylated proteins are impaired. The utility of PEGylated proteins could be improved by attenuating the PEG-related immune response. On the other hand, anti-PEG immune responses might be exploited for vaccine applications. Our recent studies demonstrated that anti-PEG antibodies mediate the delivery of antigens encapsulated in PEGylated liposomes, and enhance antigen-specific immune responses. In this review, we summarize anti-PEG antibody induction by PEGylated proteins and alterations in anti-PEG IgM-mediated pharmacokinetics and pharmacodynamics. These findings extend our knowledge of PEG-related immune responses.