Oral delivery of single-chain insulin (SCI-59) analog by bacterium-like particles (BLPs) induces oral tolerance and prevents autoimmune diabetes in NOD mice

Engineering Probiotics for Diabetes Management: Advances, Challenges, and Future Directions in Translational Microbiology

Background

Diabetes Mellitus (DM) is a substantial health concern worldwide, and its incidence is progressively escalating. Conventional pharmacological interventions frequently entail undesirable side effects, and while probiotics offer benefits, they are hindered by constraints such as diminished stability and effectiveness within the gastrointestinal milieu. Given these complications, the advent of bioengineered probiotics is a promising alternative for DM management.

Aim of Review

The objective of this review is to provide an exhaustive synthesis of the most recent studies on the use of engineered probiotics in the management of DM. This study aimed to clarify the mechanisms through which these probiotics function, evaluate their clinical effectiveness, and enhance public awareness of their prospective advantages in the treatment of DM.

Key Scientific Concepts of Review

Scholarly critiques have explored diverse methodologies of probiotic engineering, including physical alteration, bioenrichment, and genetic manipulation. These techniques augment the therapeutic potency of probiotics by ameliorating gut microbiota, fortifying the intestinal barrier, modulating metabolic pathways, and regulating immune responses. Such advancements have established engineered probiotics as a credible therapeutic strategy for DM, potentially providing enhanced results compared to conventional treatments.

Oral delivery of bi-autoantigens by bacterium-like particles (BLPs) against autoimmune diabetes in NOD mice

Induction of oral tolerance by vaccination with type 1 diabetes mellitus (T1DM)-associated autoantigens exhibits great potential in preventing and treating this autoimmune disease. However, antigen degradation in the gastrointestinal tract (GIT) limits the delivery efficiency of oral antigens. Previously, bacterium-like particles (BLPs) have been used to deliver a single-chain insulin (SCI-59) analog (BLPs-SCI-59) or the intracellular domain of insulinoma-associated protein 2 (IA-2ic) (BLPs-IA-2ic). Both monovalent BLPs vaccines can suppress T1DM in NOD mice by stimulating the corresponding antigen-specific oral tolerance, respectively. Here, we constructed two bivalent BLPs vaccines which simultaneously deliver SCI-59 and IA-2ic (Bivalent vaccine-mix or Bivalent vaccine-SA), and evaluated whether there is an additive beneficial effect on tolerance induction and suppression of T1DM by treatment with BLPs-delivered bi-autoantigens. Compared to the monovalent BLPs vaccines, oral administration of the Bivalent vaccine-mix could significantly reduce morbidity and mortality in T1DM. Treatment with the bivalent BLPs vaccines (especially Bivalent vaccine-mix) endowed the mice with a stronger ability to regulate blood glucose and protect the integrity and function of pancreatic islets than the monovalent BLPs vaccines treatment. This additive effect of BLPs-delivered bi-autoantigens on T1DM prevention may be related to that SCI-59- and IA-2-specific Th2-like immune responses could be induced, which was more beneficial for the correction of Th1/Th2 imbalance. In addition, more CD4+CD25+Foxp3+ regulatory T cells (Tregs) were induced by treatment with the bivalent BLPs vaccines than did the monovalent BLPs vaccines. Therefore, multiple autoantigens delivered by BLPs maybe a promising strategy to prevent T1DM by efficiently inducing antigen-specific immune tolerance.

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.

Bacterium-like particles derived from probiotics: progress, challenges and prospects

Bacterium-like particles (BLPs) are hollow peptidoglycan particles obtained from food-grade Lactococcus lactis inactivated by hot acid. With the advantage of easy preparation, high safety, great stability, high loading capacity, and high mucosal delivery efficiency, BLPs can load and display proteins on the surface with the help of protein anchor (PA), making BLPs a proper delivery system. Owning to these features, BLPs are widely used in the development of adjuvants, vaccine carriers, virus/antigens purification, and enzyme immobilization. This review has attempted to gather a full understanding of the technical composition, characteristics, applications. The mechanism by which BLPs induces superior adaptive immune responses is also discussed. Besides, this review tracked the latest developments in the field of BLPs, including Lactobacillus-derived BLPs and novel anchors. Finally, the main limitations and proposed breakthrough points to further enhance the immunogenicity of BLPs vaccines were discussed, providing directions for future research. We hope that further developments in the field of antigen delivery of subunit vaccines or others will benefit from BLPs.

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.

Suppression of anti-drug antibody formation against coagulation factor VIII by oral delivery of anti-CD3 monoclonal antibody in hemophilia A mice

Active tolerance to ingested dietary antigens forms the basis for oral immunotherapy to food allergens or autoimmune self-antigens. Alternatively, oral administration of anti-CD3 monoclonal antibody can be effective in modulating systemic immune responses without T cell depletion. Here we assessed the efficacy of full length and the F(ab')2 fragment of oral anti-CD3 to prevent anti-drug antibody (ADA) formation to clotting factor VIII (FVIII) protein replacement therapy in hemophilia A mice. A short course of low dose oral anti-CD3 F(ab')2 reduced the production of neutralizing ADAs, and suppression was significantly enhanced when oral anti-CD3 was timed concurrently with FVIII administration. Tolerance was accompanied by the early induction of FoxP3+LAP-, FoxP3+LAP+, and FoxP3-LAP+ populations of CD4+ T cells in the spleen and mesenteric lymph nodes. FoxP3+LAP+ Tregs expressing CD69, CTLA-4, and PD1 persisted in spleens of treated mice, but did not produce IL-10. Finally, we attempted to combine the anti-CD3 approach with oral intake of FVIII antigen (using our previously established method of using lettuce plant cells transgenic for FVIII antigen fused to cholera toxin B (CTB) subunit, which suppresses ADAs in part through induction of IL-10 producing FoxP3-LAP+ Treg). However, combining these two approaches failed to improve suppression of ADAs. We conclude that oral anti-CD3 treatment is a promising approach to prevention of ADA formation in systemic protein replacement therapy, albeit via mechanisms distinct from and not synergistic with oral intake of bioencapsulated antigen.

Therapeutic potential of tolerance-based peptide vaccines in autoimmune diseases

Autoimmune diseases are caused by the dysfunction of the body's immune regulatory system, which leads to the recognition of self-antigens and the destruction of self-tissues and is mediated by immune cells such as T and B cells, and affects 5-10% of the population worldwide. Current treatments such as non-steroidal anti-inflammatory drugs and glucocorticoids can only relieve symptoms of the disease and are accompanied by serious side effects that affect patient quality of life. The recent rise in antigen-specific therapies, especially vaccines carrying autoantigenic peptides, promises to change this disadvantage, where research has increased dramatically in the last decade. This therapy established specific immune tolerance by delivering peptide fragments containing disease-specific self-antigen epitopes to suppress excessive immune responses, thereby exerting a therapeutic effect, with high safety and specificity. This article presents the latest progress on the treatment of autoimmune diseases with autoantigen peptide vaccines. It includes the construction of peptide vaccine delivery system, the mechanism of inducing immune tolerance and its application.

Oral delivery of the intracellular domain of the insulinoma-associated protein 2 (IA-2ic) by bacterium-like particles (BLPs) prevents type 1 diabetes mellitus in NOD mice

Antigen-specific immune tolerance, which possesses great potential in preventing or curing type 1 diabetes mellitus (T1DM), can be induced by oral vaccination with T1DM-related autoantigens. However, direct administration of autoantigens via oral route exhibits a low tolerance-inducing effect as a result of the digestion of protein antigens in the gastrointestinal tract (GIT) and therefore, a large dosage of autoantigens may be needed. In this study, bacterium-like particles (BLPs) made from food-grade lactic acid bacteria were used to deliver the intracellular domain of the insulinoma-associated protein 2 (IA-2ic). For this purpose, BLPs-IA-2ic vaccine in which IA-2ic bound to the surface of BLPs was constructed. BLPs enhanced the stability of the delivered IA-2ic based on the stability analysis in vitro. Oral administration of BLPs-IA-2ic significantly reduced T1DM incidence in NOD mice. The mice fed BLPs-IA-2ic exhibited a significant reduction in insulitis and preserved the ability to secrete insulin. Immunologic analysis showed that oral vaccination with BLPs-IA-2ic induced antigen-specific T cell tolerance. The results revealed that the successful induction of immune tolerance was dependent on the immune deviation (in favor of T helper 2 responses) and CD4+CD25+FoxP3+ regulatory T cells. Hence, oral vaccination with BLPs-IA-2ic shows potential for application in preventing T1DM.

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.

Evolution of nanomedicines for the treatment of autoimmune disease: From vehicles for drug delivery to inducers of bystander immunoregulation

Over the last two decades, the nanomedicine field has witnessed an explosive growth of research on the development of nanoparticle/microparticle (NP/MP)-based compounds for the treatment of autoimmune diseases. Studies have evaluated compounds generated with a broad range of materials with different shapes, sizes, surface chemistries and structures. A number of active pharmaceutical ingredients, including immunosuppressants, cytokines, nucleotides, peptides, proteins and immunomodulators of various types have been encapsulated into or incorporated onto the surface of these compounds, either individually or in combination, and delivered to animal models of autoimmune inflammation via different administration routes. These NP/MP-based compounds can be categorized into four different groups based on their intended mechanisms of action. Here, we review the engineering designs, the pharmacodynamic and therapeutic correlates and the disease specificity of nanomedicines belonging to each of these groups.

Demystifying particle-based oral vaccines

Introduction: The oral route of vaccination is pain- and needle-free and can induce systemic and mucosal immunity. However, gastrointestinal barriers and antigen degradation impose significant hurdles in the development of oral vaccines. Live attenuated viruses and bacteria can overcome these barriers but at the risk of introducing safety concerns. As an alternative, particles have been investigated for antigen protection and delivery, yet there are no FDA-approved oral vaccines based on particle-based delivery systems. Our objective was to discover underlying determinants that can explain the current inadequacies and identify paradigms that can be implemented in future for successful development of oral vaccines relying on particle-based delivery systems.Areas covered: We reviewed literature related to the use of particles for oral vaccination and placed special emphasis on formulation characteristics and administration schedules to gain an insight into how these parameters impact production of antigen-specific antibodies in systemic and mucosal compartments.Expert opinion: Despite the long history of vaccines, particle-based oral vaccination is a relative new field with the first study published in 1989. Substantial variability exists between different studies with respect to dosing schedules, number of doses, and the amount of vaccine per dose. Most studies have not used adjuvants in the formulations. Better standardization in vaccination parameters is required to improve comparison between experiments, and adjuvants should be used to enhance the systemic and mucosal immune responses and to reduce the number of doses, which will make oral vaccines more attractive.

Insulin's other life: an autoantigen in type 1 diabetes

One hundred years ago, Frederick Banting, John Macleod, Charles Best and James Collip, and their collaborators, discovered insulin. This discovery paved the way to saving countless lives and ushered in the "Insulin Era." Since the discovery of insulin, we have made enormous strides in understanding its role in metabolism and diabetes. Insulin has played a dramatic role in the treatment of people with diabetes; particularly type 1 diabetes (T1D). Insulin replacement is a life-saving therapy for people with T1D and some with type 2 diabetes. T1D is an autoimmune disease caused by the T-cell-mediated destruction of the pancreatic insulin-producing beta cells that leads to a primary insulin deficiency. It has become increasingly clear that insulin, and its precursors preproinsulin (PPI) and proinsulin (PI), can play another role-not as a hormone but as an autoantigen in T1D. Here we review the role played by the products of the INS gene as autoantigens in people with T1D. From many elegant animal studies, it is clear that T-cell responses to insulin, PPI and PI are essential for T1D to develop. Here we review the evidence that autoimmune responses to insulin and PPI arise in people with T1D and discuss the recently described neoepitopes derived from the products of the insulin gene. Finally, we look forward to new approaches to deliver epitopes derived from PPI, PI and insulin that may allow immune tolerance to pancreatic beta cells to be restored in people with, or at risk of, T1D.

Type 1 diabetes mellitus and its oral tolerance therapy

As a T cell-mediated autoimmune disease, type 1 diabetes mellitus (T1DM) is marked by insulin defect resulting from the destruction of pancreatic β-cells. The understanding of various aspects of T1DM, such as its epidemiology, pathobiology, pathogenesis, clinical manifestations, and complications, has been greatly promoted by valuable research performed during the past decades. However, these findings have not been translated into an effective treatment. The ideal treatment should safely repair the destroyed immune balance in a long-lasting manner, preventing or stopping the destruction of β-cells. As a type of immune hypo-responsiveness to the orally administrated antigen, oral tolerance may be induced by enhancement of regulatory T cells (Tregs) or by anergy/deletion of T cells, depending on the dosage of orally administrated antigen. Acting as an antigen-specific immunotherapy, oral tolerance therapy for T1DM has been mainly performed using animal models and some clinical trials have been completed or are still ongoing. Based on the review of the proposed mechanism of the development of T1DM and oral tolerance, we give a current overview of oral tolerance therapy for T1DM conducted in both animal models and clinical trials.

Insulin and its single-chain analogue

Insulin therapy remains the most effective method to treat diabetes mellitus (DM), and the demand for this valuable hormone has exceeded that of any other protein-based medicine as a result of the dramatic increase in the number of diabetic patients worldwide. Understanding the structure of insulin and the interaction with its receptor is important for developing proper formulations. As a result of the relatively low thermal stability of native insulin and its two-chain analogues, the application of single-chain insulin (SCI) analogues, which can be obtained relatively easily by recombinant DNA technology or chemical synthetic methods, represents a promising alternative approach. In this review, the basic knowledge of insulin (discovery, biosynthesis, and structure) and the current model of the interaction with its receptor are outlined. Furthermore, we outline the strategies for the design and production of various SCI analogues and their reported applications.