Targeting proinsulin to local immune cells using an intradermal microneedle delivery system; a potential antigen-specific immunotherapy for type 1 diabetes

The role of regulatory T cells in vitiligo and therapeutic advances: a mini-review

BACKGROUND

Regulatory T cells (Tregs) play vital roles in controlling immune reactions and maintaining immune tolerance in the body. The targeted destruction of epidermal melanocytes by activated CD8+T cells is a key event in the development of vitiligo. However, Tregs may exert immunosuppressive effects on CD8+T cells, which could be beneficial in treating vitiligo.

METHODS

A comprehensive search of PubMed and Web of Science was conducted to gather information on Tregs and vitiligo.

RESULTS

In vitiligo, there is a decrease in Treg numbers and impaired Treg functions, along with potential damage to Treg-related signaling pathways. Increasing Treg numbers and enhancing Treg function could lead to immunosuppressive effects on CD8+T cells. Recent research progress on Tregs in vitiligo has been summarized, highlighting various Treg-related therapies being investigated for clinical use. The current status of Treg-related therapeutic strategies and potential future directions for vitiligo treatment are also discussed.

CONCLUSIONS

A deeper understanding of Tregs will be crucial for advancing Treg-related drug discovery and treatment development in vitiligo.

Advancing immunotherapy using biomaterials to control tissue, cellular, and molecular level immune signaling in skin

Immunotherapies have been transformative in many areas, including cancer treatments, allergies, and autoimmune diseases. However, significant challenges persist in extending the reach of these technologies to new indications and patients. Some of the major hurdles include narrow applicability to patient groups, transient efficacy, high cost burdens, poor immunogenicity, and side effects or off-target toxicity that results from lack of disease-specificity and inefficient delivery. Thus, there is a significant need for strategies that control immune responses generated by immunotherapies while targeting infection, cancer, allergy, and autoimmunity. Being the outermost barrier of the body and the first line of host defense, the skin presents a unique immunological interface to achieve these goals. The skin contains a high concentration of specialized immune cells, such as antigen-presenting cells and tissue-resident memory T cells. These cells feature diverse and potent combinations of immune receptors, providing access to cellular and molecular level control to modulate immune responses. Thus, skin provides accessible tissue, cellular, and molecular level controls that can be harnessed to improve immunotherapies. Biomaterial platforms - microneedles, nano- and micro-particles, scaffolds, and other technologies - are uniquely capable of modulating the specialized immunological niche in skin by targeting these distinct biological levels of control. This review highlights recent pre-clinical and clinical advances in biomaterial-based approaches to target and modulate immune signaling in the skin at the tissue, cellular, and molecular levels for immunotherapeutic applications. We begin by discussing skin cytoarchitecture and resident immune cells to establish the biological rationale for skin-targeting immunotherapies. This is followed by a critical presentation of biomaterial-based pre-clinical and clinical studies aimed at controlling the immune response in the skin for immunotherapy and therapeutic vaccine applications in cancer, allergy, and autoimmunity.

Exploiting Unique Features of Microneedles to Modulate Immunity

Microneedle arrays (MNAs) are small patches containing hundreds of short projections that deliver signals directly to dermal layers without causing pain. These technologies are of special interest for immunotherapy and vaccine delivery because they directly target immune cells concentrated in the skin. The targeting abilities of MNAs result in efficient immune responses-often more protective or therapeutic-compared to conventional needle delivery. MNAs also offer logistical benefits, such as self-administration and transportation without refrigeration. Thus, numerous preclinical and clinical studies are exploring these technologies. Here the unique advantages of MNA, as well as critical challenges-such as manufacturing and sterility issues-the field faces to enable widespread deployment are discussed. How MNA design parameters can be exploited for controlled release of vaccines and immunotherapies, and the application to preclinical models of infection, cancer, autoimmunity, and allergies are explained. Specific strategies are also discussed to reduce off-target effects compared to conventional vaccine delivery routes, and novel chemical and manufacturing controls that enable cargo stability in MNAs across flexible intervals and temperatures. Clinical research using MNAs is then examined. Drawbacks of MNAs and the implications, and emerging opportunities to exploit MNAs for immune engineering and clinical use are concluded.

Vaccines for immune tolerance against autoimmune disease

The high prevalence and rising incidence of autoimmune diseases have become a prominent public health issue. Autoimmune disorders result from the immune system erroneously attacking the body's own healthy cells and tissues, causing persistent inflammation, tissue injury, and impaired organ function. Existing treatments primarily rely on broad immunosuppression, leaving patients vulnerable to infections and necessitating lifelong treatments. To address these unmet needs, an emerging frontier of vaccine development aims to restore immune equilibrium by inducing immune tolerance to autoantigens, offering a potential avenue for a cure rather than mere symptom management. We discuss this burgeoning field of vaccine development against inflammation and autoimmune diseases, with a focus on common autoimmune disorders, including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, inflammatory bowel disease, and systemic lupus erythematosus. Vaccine-based strategies provide a new pathway for the future of autoimmune disease therapeutics, heralding a new era in the battle against inflammation and autoimmunity.

Current Status of Microneedle Array Technology for Therapeutic Delivery: From Bench to Clinic

In recent years, microneedle (MN) patches have emerged as an alternative technology for transdermal delivery of various drugs, therapeutics proteins, and vaccines. Therefore, there is an urgent need to understand the status of MN-based therapeutics. The article aims to illustrate the current status of microneedle array technology for therapeutic delivery through a comprehensive review. However, the PubMed search was performed to understand the MN's therapeutics delivery status. At the same time, the search shows the number no of publications on MN is increasing (63). The search was performed with the keywords "Coated microneedle," "Hollow microneedle," "Dissolvable microneedle," and "Hydrogel microneedle," which also shows increasing trend. Similarly, the article highlighted the application of different microneedle arrays for treating different diseases. The article also illustrated the current status of different phases of MN-based therapeutics clinical trials. It discusses the delivery of different therapeutic molecules, such as drug molecule delivery, using microneedle array technology. The approach mainly discusses the delivery of different therapeutic molecules. The leading pharmaceutical companies that produce the microneedle array for therapeutic purposes have also been discussed. Finally, we discussed the limitations and future prospects of this technology.

Single-cell RNAseq identifies clonally expanded antigen-specific T-cells following intradermal injection of gold nanoparticles loaded with diabetes autoantigen in humans

Gold nanoparticles (GNPs) have been used in the development of novel therapies as a way of delivery of both stimulatory and tolerogenic peptide cargoes. Here we report that intradermal injection of GNPs loaded with the proinsulin peptide C19-A3, in patients with type 1 diabetes, results in recruitment and retention of immune cells in the skin. These include large numbers of clonally expanded T-cells sharing the same paired T-cell receptors (TCRs) with activated phenotypes, half of which, when the TCRs were re-expressed in a cell-based system, were confirmed to be specific for either GNP or proinsulin. All the identified gold-specific clones were CD8+, whilst proinsulin-specific clones were both CD8+ and CD4+. Proinsulin-specific CD8+ clones had a distinctive cytotoxic phenotype with overexpression of granulysin (GNLY) and KIR receptors. Clonally expanded antigen-specific T cells remained in situ for months to years, with a spectrum of tissue resident memory and effector memory phenotypes. As the T-cell response is divided between targeting the gold core and the antigenic cargo, this offers a route to improving resident memory T-cells formation in response to vaccines. In addition, our scRNAseq data indicate that focusing on clonally expanded skin infiltrating T-cells recruited to intradermally injected antigen is a highly efficient method to enrich and identify antigen-specific cells. This approach has the potential to be used to monitor the intradermal delivery of antigens and nanoparticles for immune modulation in humans.

Biomaterial-based delivery platforms for transdermal immunotherapy

Nowadays, immunotherapy is one of the most essential treatments for various diseases and a broad spectrum of disorders are assumed to be treated by altering the function of the immune system. For this reason, immunotherapy has attracted a great deal of attention and numerous studies on different approaches for immunotherapies have been investigated, using multiple biomaterials and carriers, from nanoparticles (NPs) to microneedles (MNs). In this review, the immunotherapy strategies, biomaterials, devices, and diseases supposed to be treated by immunotherapeutic strategies are reviewed. Several transdermal therapeutic methods, including semisolids, skin patches, chemical, and physical skin penetration enhancers, are discussed. MNs are the most frequent devices implemented in transdermal immunotherapy of cancers (e.g., melanoma, squamous cell carcinoma, cervical, and breast cancer), infectious (e.g., COVID-19), allergic and autoimmune disorders (e.g., Duchenne's muscular dystrophy and Pollinosis). The biomaterials used in transdermal immunotherapy vary in shape, size, and sensitivity to external stimuli (e.g., magnetic field, photo, redox, pH, thermal, and even multi-stimuli-responsive) were reported. Correspondingly, vesicle-based NPs, including niosomes, transferosomes, ethosomes, microemulsions, transfersomes, and exosomes, are also discussed. In addition, transdermal immunotherapy using vaccines has been reviewed for Ebola, Neisseria gonorrhoeae, Hepatitis B virus, Influenza virus, respiratory syncytial virus, Hand-foot-and-mouth disease, and Tetanus.

Tuning innate immune function using microneedles containing multiple classes of toll-like receptor agonists

Microneedle arrays (MNAs) are patches displaying hundreds of micron-scale needles that can penetrate skin. As a result, these arrays efficiently and painlessly access this immune cell-rich niche, motivating significant clinical interest in MNA-based vaccines. Our lab has developed immune polyelectrolyte multilayers (iPEMs), nanostructures built entirely from immune signals employing electrostatic self-assembly. iPEMs consist of positively charged peptide antigen and negatively charged toll-like receptor agonists (TLRas) to assemble these components at ultra-high density since no carrier is needed. Here we used this technology to deliver MNAs with antigen and defined ratios of multiple classes of TLRa. Notably, this approach resulted in facile assembly and corresponding signal transduction through each respective TLR pathway. This control ultimately activated primary antigen presenting cells and drove proliferation of antigen-specific T cells. In related in vivo vaccine studies, application of MNAs resulted in distinct T cells response depending on the number of TLRa classes delivered with MNAs. These MNAs technologies create an opportunity to deliver nanostructured vaccine components at high density, and to probe integration of multiple TLRas in skin to tune immunity.

Advanced Delivery Strategies for Immunotherapy in Type I Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) has been defined as an autoimmune disease characterised by immune-mediated destruction of the pancreatic β cells, leading to absolute insulin deficiency and hyperglycaemia. Current research has increasingly focused on immunotherapy based on immunosuppression and regulation to rescue T-cell-mediated β-cell destruction. Although T1DM immunotherapeutic drugs are constantly under clinical and preclinical development, several key challenges remain, including low response rates and difficulty in maintaining therapeutic effects. Advanced drug delivery strategies can effectively harness immunotherapies and improve their potency while reducing their adverse effects. In this review, we briefly introduce the mechanisms of T1DM immunotherapy and focus on the current research status of the integration of the delivery techniques in T1DM immunotherapy. Furthermore, we critically analyse the challenges and future directions of T1DM immunotherapy.

Delivery route considerations for designing antigen-specific biomaterial strategies to combat autoimmunity

Disease modifying drugs and biologics used to treat autoimmune diseases, although promising, are non-curative. As the field moves towards development of new approaches to treat autoimmune disease, antigen-specific therapies immunotherapies (ASITs) have emerged. Despite clinical approval of ASITs for allergies, clinical trials using soluble ASITs for autoimmunity have been largely unsuccessful. A major effort to address this shortcoming is the use of biomaterials to harness the features unique to specific delivery routes. This review focuses on biomaterials being developed for delivery route-specific strategies to induce antigen-specific responses in autoimmune diseases such as multiple sclerosis, type 1 diabetes, rheumatoid arthritis, and celiac disease. We first discuss the delivery strategies used in ongoing and completed clinical trials in autoimmune ASITs. Next, we highlight pre-clinical biomaterial approaches from the most recent 3 years in the context of these same delivery route considerations. Lastly, we provide discussion on the gaps remaining in biomaterials development and comment on the need to consider delivery routes in the process of designing biomaterials for ASITs.

Biomaterial Strategies for Selective Immune Tolerance: Advances and Gaps

Autoimmunity and allergies affect a large number of people across the globe. Current approaches to these diseases target cell types and pathways that drive disease, but these approaches are not cures and cannot differentiate between healthy cells and disease-causing cells. New immunotherapies that induce potent and selective antigen-specific tolerance is a transformative goal of emerging treatments for autoimmunity and serious allergies. These approaches offer the potential of halting-or even reversing-disease, without immunosuppressive side effects. However, translating successful induction of tolerance to patients is unsuccessful. Biomaterials offer strategies to direct and maximize immunological mechanisms of tolerance through unique capabilities such as codelivery of small molecules or signaling molecules, controlling signal density in key immune tissues, and targeting. While a growing body of work in this area demonstrates success in preclinical animal models, these therapies are only recently being evaluated in human trials. This review will highlight the most recent advances in the use of materials to achieve antigen-specific tolerance and provide commentary on the current state of the clinical development of these technologies.

A wearable, minimally-invasive, fully electrochemically-controlled feedback minisystem for diabetes management

Diabetes is a chronic disease affecting 10% of the population globally, and can lead to serious damage in the heart, kidneys, eyes, blood vessels or nerves. Commercial artificial closed-loop feedback systems can significantly improve diabetes management and save lives. However, they are large and expensive for users. Here, we demonstrate for the first time a wearable, minimally-invasive, fully electrochemically-controlled feedback minisystem for diabetes management. Both the working principles of the sensor and pump in the feedback system are based on electrochemical reactions. The smart minisystem was constructed based on integrating the thermoplastic polyurethane hollow microneedles with an electrochemical biosensing device on its outer layer and an electrochemical micropump facing the inner layer of the microneedles. The sensing device was constructed based on sputtering thin metal films through a shadow mask and electroplating Prussian blue on the surface of the microneedles, followed by the immobilization of glucose oxidase on the working electrode. The electrochemical micropump was constructed by sputtering the interdigital electrodes, followed by sealing with a thin elastic film, which was further integrated with the inner channels of the microneedles. Both the sensor and the pump were electrically powered. Via being controlled by a printed circuit board, the biosensing device monitored the levels of interstitial glucose continuously to drive the electrochemical pump to deliver insulin intelligently, in order to control blood glucose within the normal range. The closed-loop feedback system was studied for its capability in maintaining the blood glucose levels of diabetic rats under various physiological conditions. The utility of the intelligent feedback system was successfully demonstrated on diabetic rats for controlling the blood glucose levels within the normal range. The minisystem is wearable, small, cost-effective, precise, stable and painless. It is anticipated that this approach opens a new paradigm for the development of closed-loop diabetes minisystems and may lead to a compelling future for diabetes management.

Emergence of microneedles as a potential therapeutics in diabetes mellitus

Diabetes mellitus is a severe condition in which the pancreas produces inadequate insulin or the insulin generated is ineffective for utilisation by the body; as a result, insulin therapy is required for control blood sugar levels in patients having type 1 diabetes and is widely recommended in advanced type 2 diabetes patients with uncontrolled diabetes despite dual oral therapy, while subcutaneous insulin administration using hypodermic injection or pump-mediated infusion is the traditional route of insulin delivery and causes discomfort, needle phobia, reduced adherence, and risk of infection. Therefore, transdermal insulin delivery has been extensively explored as an appealing alternative to subcutaneous approaches for diabetes management which not only is non-invasive and easy, but also avoids first-pass metabolism and prevents gastrointestinal degradation. Microneedles have been commonly investigated in human subjects for transdermal insulin administration because they are minimally invasive and painless. The different types of microneedles developed for the transdermal delivery of anti-diabetic drugs are discussed in this review, including solid, dissolving, hydrogel, coated, and hollow microneedles. Numerous microneedle products have entered the market in recent years. But, before the microneedles can be effectively launched into the market, a significant amount of investigation is required to address the numerous challenges. In conclusion, the use of microneedles in the transdermal system is an area worth investigating because of its significant benefits over the oral route in the delivery of anti-diabetic medications and biosensing of blood sugar levels to assure improved clinical outcomes in diabetes management.

Microneedles for drug delivery: recent advances in materials and geometry for preclinical and clinical studies

INTRODUCTION

A microneedle array patch (MAP) has been studied as a means for delivering drugs or vaccines and has shown superior delivery efficiency compared to the conventional transdermal drug delivery system (TDD). This paper reviews recent advancements in the development of MAPs, with a focus on their size, shapes, and materials in preclinical and clinical studies for pharmaceutics.

AREA COVERED

We classified MAPs for drug delivery into four types: coated, dissolving, separable, and swellable. We covered their recent developments in materials and geometry in preclinical and clinical studies.

EXPERT OPINION

The design of MAPs needs to be determined based on what properties would be effective for the target diseases and purposes. In addition, in preclinical studies, it is necessary to consider not only the novelty of the formulations but also the feasibility of clinical application. Currently, clinical studies of microneedles loaded with various drugs and vaccines are in progress. When the regulation of pharmaceutical microneedles is established and more clinical studies are published, more drugs will be developed as microneedle products and clinical research will proceed. With these considerations, the microneedle array patch will be a better option for drug delivery.

Novel delivery mechanisms for antigen-specific immunotherapy

PURPOSE OF REVIEW

Current therapies for autoimmune disorders often employ broad suppression of the immune system. Antigen-specific immunotherapy (ASI) seeks to overcome the side-effects of immunosuppressive therapy by specifically targeting only disease-related autoreactive T and B cells. Although it has been in development for several decades, ASI still is not in use clinically to treat autoimmunity. Novel ways to deliver antigen may be effective in inducing ASI. Here we review recent innovations in antigen delivery.

RECENT FINDINGS

New ways to deliver antigen include particle and nonparticle approaches. One main focus has been the targeting of antigen-presenting cells in a tolerogenic context. This technique often results in the induction and/or expansion of regulatory T cells, which has the potential to be effective against a complex, polyclonal immune response.

SUMMARY

Whether novel delivery approaches can help bring ASI into general clinical use for therapy of autoimmune diseases remains to be seen. However, preclinical work and early results from clinical trials using these new techniques show promising signs.

Recent advances in mechanical force-assisted transdermal delivery of macromolecular drugs

The transdermal delivery of macromolecular drugs has become one of the focused topics in pharmaceutical research since it enables highly specific and effective delivery, while avoiding the pain and needle phobia associated with injection, or incidences like drug degradation and low bioavailability of oral administration. However, the passive absorption of macromolecular drugs via skin is highly restricted by the stratum corneum owing to high molecular weight. Therefore, various strategies have been extensively developed and conducted to facilitate the transdermal delivery of macromolecular drugs, among which, mechanical force-assisted techniques occupy dominant positions. Such techniques include ultrasound, needle-free jet injection, temporary pressure and microneedles. In this review, we focus on recent transdermal enhancing strategies utilizing mechanical force, and summarize their mechanisms, advantages, limitations and clinical applications respectively.

Microneedles for painless transdermal immunotherapeutic applications

Immunotherapy has recently garnered plenty of attention to improve the clinical outcomes in the treatment of various diseases. However, owing to the dynamic nature of the immune system, this approach has often been challenged by concerns regarding the lack of adequate long-term responses in patients. The development of microneedles (MNs) has resulted in the improvement and expansion of immuno-reprogramming strategies due to the housing of high accumulation of dendritic cells, macrophages, lymphocytes, and mast cells in the dermis layer of the skin. In addition, MNs possess many outstanding properties, such as the ability for the painless traverse of the stratum corneum, minimal invasiveness, facile fabrication, excellent biocompatibility, convenient administration, and bypassing the first pass metabolism that allows direct translocation of therapeutics into the systematic circulation. These advantages make MNs excellent candidates for the delivery of immunological biomolecules to the dermal antigen-presenting cells in the skin with the aim of vaccinating or treating different diseases, such as cancer and autoimmune disorders, with minimal invasiveness and side effects. This review discusses the recent advances in engineered MNs and tackles limitations relevant to traditional immunotherapy of various hard-to-treat diseases.

A Question of Tolerance-Antigen-Specific Immunotherapy for Type 1 Diabetes

PURPOSE OF REVIEW

Antigen-specific immunotherapy (ASI) is a long sought-after goal for type 1 diabetes (T1D), with the potential of greater long-term safety than non-specific immunotherapy. We review the most recent advances in identification of target islet epitopes, delivery platforms and the ongoing challenges.

RECENT FINDINGS

It is now recognised that human proinsulin contains a hotspot of epitopes targeted in people with T1D. Beta-cell neoantigens are also under investigation as ASI target epitopes. Consideration of the predicted HLA-specificity of the target antigen for subject selection is now being incorporated into trial design. Cell-free ASI approaches delivering antigen with or without additional immunomodulatory agents can induce antigen-specific regulatory T cell responses, including in patients and many novel nanoparticle-based platforms are under development. ASI for T1D is rapidly advancing with a number of modalities currently being trialled in patients and many more under development in preclinical models.