Immunotherapy for Type 1 Diabetes: Why Do Current Protocols Not Halt the Underlying Disease Process?

Vitamin D Supplementation as a Therapeutic Strategy in Autoimmune Diabetes: Insights and Implications for LADA Management

Latent autoimmune diabetes of adults (LADA) is the most prevalent form of autoimmune diabetes (AI-D) in adulthood; however, its accurate diagnosis and optimal treatment remain challenging. Vitamin D deficiency (VDD) is commonly observed in LADA patients, while increased vitamin D exposure through supplementation and dietary intake is associated with a reduced incidence of LADA. Although limited, case reports, case-control studies, and randomized clinical trials have examined the effects of vitamin D supplementation-alone or combined with dipeptidyl peptidase-4 inhibitors (DPP4-is)-on glucose regulation, residual β-cell function, and glutamic acid decarboxylase antibody (GADA65) levels. Findings, while preliminary, indicate that vitamin D supplementation may enhance glycemic control, preserve β-cell function, and reduce autoimmune activity. Given its accessibility, affordability, and relative safety, vitamin D supplementation presents an attractive adjunct treatment option for LADA patients. This narrative review discusses current evidence on the potential therapeutic benefits of vitamin D supplementation in patients with AI-D, including LADA, who are also vitamin D deficient. Beginning with an exploration of the epidemiological patterns, clinical presentation, and diagnostic framework essential for understanding and identifying LADA, this review then examines the proposed mechanisms through which vitamin D may influence autoimmune modulation of pancreatic β-cells, integrating recent data pertinent to LADA pathology. By distilling and consolidating existing research, we aim to provide a platform for advancing targeted investigations within this distinct patient population.

Gamma-aminobutyric acid for delaying type 1 diabetes mellitus: an update

The current gold-standard management of hyperglycemia in individuals with type 1 diabetes mellitus (T1DM) is insulin therapy. However, this therapy is associated with a high incidence of complications, and delaying the onset of this disease produces a substantially positive impact on quality of life for individuals with a predisposition to T1DM, especially children. This review aimed to assess the use of gamma-aminobutyric acid (GABA) to delay the onset of T1DM in children. GABA produces protective and proliferative effects in 2 ways, β cell and immune cell modulation. Various in vitro and in vivo studies have shown that GABA induces proliferation of β cells, increases insulin levels, inhibits β-cell apoptosis, and suppresses T helper 1 cell activity against islet antigens. Oral GABA is safe as no serious adverse effects were reported in any of the studies included in this review. These findings demonstrate promising results for the use of GABA treatment to delay T1DM, specifically in genetically predisposed children, through immunoregulatory effects and the ability to induce β-cell proliferation.

How do parasitic worms prevent diabetes? An exploration of their influence on macrophage and β-cell crosstalk

Diabetes is the fastest growing chronic disease globally, with prevalence increasing at a faster rate than heart disease and cancer. While the disease presents clinically as chronic hyperglycaemia, two distinct subtypes have been recognised. Type 1 diabetes (T1D) is characterised as an autoimmune disease in which the insulin-producing pancreatic β-cells are destroyed, and type 2 diabetes (T2D) arises due to metabolic insufficiency, in which inadequate amounts of insulin are produced, and/or the actions of insulin are diminished. It is now apparent that pro-inflammatory responses cause a loss of functional β-cell mass, and this is the common underlying mechanism of both T1D and T2D. Macrophages are the central immune cells in the pathogenesis of both diseases and play a major role in the initiation and perpetuation of the proinflammatory responses that compromise β-cell function. Furthermore, it is the crosstalk between macrophages and β-cells that orchestrates the inflammatory response and ensuing β-cell dysfunction/destruction. Conversely, this crosstalk can induce immune tolerance and preservation of β-cell mass and function. Thus, specifically targeting the intercellular communication between macrophages and β-cells offers a unique strategy to prevent/halt the islet inflammatory events underpinning T1D and T2D. Due to their potent ability to regulate mammalian immune responses, parasitic worms (helminths), and their excretory/secretory products, have been examined for their potential as therapeutic agents for both T1D and T2D. This research has yielded positive results in disease prevention, both clinically and in animal models. However, the focus of research has been on the modulation of immune cells and their effectors. This approach has ignored the direct effects of helminths and their products on β-cells, and the modulation of signal exchange between macrophages and β-cells. This review explores how the alterations to macrophages induced by helminths, and their products, influence the crosstalk with β-cells to promote their function and survival. In addition, the evidence that parasite-derived products interact directly with endocrine cells to influence their communication with macrophages to prevent β-cell death and enhance function is discussed. This new paradigm of two-way metabolic conversations between endocrine cells and macrophages opens new avenues for the treatment of immune-mediated metabolic disease.

Liraglutide protects β-cells in novel human islet spheroid models of type 1 diabetes

To enable accurate, high-throughput and longer-term studies of the immunopathogenesis of type 1 diabetes (T1D), we established three in-vitro islet-immune injury models by culturing spheroids derived from primary human islets with proinflammatory cytokines, activated peripheral blood mononuclear cells or HLA-A2-restricted preproinsulin-specific cytotoxic T lymphocytes. In all models, β-cell function declined as manifested by increased basal and decreased glucose-stimulated insulin release (GSIS), and decreased intracellular insulin content. Additional hallmarks of T1D progression such as loss of the first-phase insulin response (FFIR), increased proinsulin-to-insulin ratios, HLA-class I expression, and inflammatory cytokine release were also observed. Using these models, we show that liraglutide, a glucagon-like peptide 1 receptor agonist, prevented loss of GSIS under T1D-relevant stress, by preserving the FFIR and decreasing immune cell infiltration and cytokine secretion. Our results corroborate that liraglutide mediates an anti-inflammatory effect that aids in protecting β-cells from the immune-mediated attack that leads to T1D.

INNODIA Master Protocol for the evaluation of investigational medicinal products in children, adolescents and adults with newly diagnosed type 1 diabetes

BACKGROUND

The INNODIA consortium has established a pan-European infrastructure using validated centres to prospectively evaluate clinical data from individuals with newly diagnosed type 1 diabetes combined with centralised collection of clinical samples to determine rates of decline in beta-cell function and identify novel biomarkers, which could be used for future stratification of phase 2 clinical trials.

METHODS

In this context, we have developed a Master Protocol, based on the "backbone" of the INNODIA natural history study, which we believe could improve the delivery of phase 2 studies exploring the use of single or combinations of Investigational Medicinal Products (IMPs), designed to prevent or reverse declines in beta-cell function in individuals with newly diagnosed type 1 diabetes. Although many IMPs have demonstrated potential efficacy in phase 2 studies, few subsequent phase 3 studies have confirmed these benefits. Currently, phase 2 drug development for this indication is limited by poor evaluation of drug dosage and lack of mechanistic data to understand variable responses to the IMPs. Identification of biomarkers which might permit more robust stratification of participants at baseline has been slow.

DISCUSSION

The Master Protocol provides (1) standardised assessment of efficacy and safety, (2) comparable collection of mechanistic data, (3) the opportunity to include adaptive designs and the use of shared control groups in the evaluation of combination therapies, and (4) benefits of greater understanding of endpoint variation to ensure more robust sample size calculations and future baseline stratification using existing and novel biomarkers.

Interactions between islets and regulatory immune cells in health and type 1 diabetes

Type 1 diabetes results from defects in immune self-tolerance that lead to inflammatory infiltrate in pancreatic islets, beta cell dysfunction and T cell-mediated killing of beta cells. Although therapies that broadly inhibit immunity show promise to mitigate autoinflammatory damage caused by effector T cells, these are unlikely to permanently reset tolerance or promote regeneration of the already diminished pool of beta cells. An emerging concept is that certain populations of immune cells may have the capacity to both promote tolerance and support the restoration of beta cells by supporting proliferation, differentiation and/or regeneration. Here we will highlight three immune cell types-macrophages, regulatory T cells and innate lymphoid cells-for which there is evidence of dual roles of immune regulation and tissue regeneration. We explore how findings in this area from other fields might be extrapolated to type 1 diabetes and highlight recent discoveries in the context of type 1 diabetes. We also discuss technological advances that are supporting this area of research and contextualise new therapeutic avenues to consider for type 1 diabetes.

Increased spontaneous CCL2 (MCP-1) and CCL5 (RANTES) secretion in vitro in LADA compared to type 1 diabetes and type 2 diabetes: Action LADA 14

AIMS

Immune-mediated type 1 diabetes (T1D) in adulthood and latent autoimmune diabetes in adults (LADA) share similar pathological mechanisms but differ clinically in disease progression. The aim of this study was to acquire insights into spontaneous and stimulated chemokine secretion of immune cells in different diabetes types.

MATERIALS AND METHODS

We investigated in vitro spontaneous, mitogen (PI) and antigen (HSP60, p277, pGAD, pIA2) stimulated chemokine secretion of leucocytes from patients with T1D (n = 32), LADA (n = 22), type 2 diabetes (T2D; n = 49), and glucose-tolerant individuals (n = 13). Chemokine concentration in supernatants was measured for CCL2 (MCP-1), CXCL10 (IP10) and CCL5 (RANTES) using a multiplex bead array assay.

RESULTS

Spontaneous secretion of CCL2 and CCL5 were higher in LADA compared to T1D and T2D (all p < 0.05) while CXCL10 was similar in the groups. Mitogen-stimulated secretion of CCL2 in LADA was lower compared to T1D and T2D (all p < 0.05) while CXCL10 and CCL5 were similar in all groups. Upon stimulation with pIA2 the secretion of CCL2 in LADA was lower compared to T2D (p < 0.05). Spontaneous CXCL10 secretion in LADA was positively associated with body mass index (r²  = 0.35; p = 0.0035) and C-peptide (r²  = 0.30; p = 0.009).

CONCLUSIONS

Chemokine secretion is altered between different diabetes types. Increased spontaneous secretion of CCL2 and CCL5 and decreased secretion of CCL2, upon stimulation with PI and pIA2, in LADA compared to T1D and T2D could reflect altered immune responsiveness in LADA patients in association with their slower clinical progression compared to insulin dependence.

Tolerogenic Dendritic Cell-Based Approaches in Autoimmunity

Dendritic cells (DCs) dictate the outcomes of tissue-specific immune responses. In the context of autoimmune diseases, DCs instruct T cells to respond to antigens (Ags), including self-Ags, leading to organ damage, or to becoming regulatory T cells (Tregs) promoting and perpetuating immune tolerance. DCs can acquire tolerogenic properties in vitro and in vivo in response to several stimuli, a feature that opens the possibility to generate or to target DCs to restore tolerance in autoimmune settings. We present an overview of the different subsets of human DCs and of the regulatory mechanisms associated with tolerogenic (tol)DC functions. We review the role of DCs in the induction of tissue-specific autoimmunity and the current approaches exploiting tolDC-based therapies or targeting DCs in vivo for the treatment of autoimmune diseases. Finally, we discuss limitations and propose future investigations for improving the knowledge on tolDCs for future clinical assessment to revert and prevent autoimmunity. The continuous expansion of tolDC research areas will lead to improving the understanding of the role that DCs play in the development and treatment of autoimmunity.

Current state of antigen-specific immunotherapy for type 1 diabetes

PURPOSE OF REVIEW

Update on antigen-specific immunotherapy (ASIT) in type 1 diabetes (T1D) with focus on deoxyribonucleic acid (DNA)-induced immunization and the current obstacles to further research and clinical realization.

RECENT FINDINGS

In T1D, immune system imbalances together with malfunctioning islet-specific processes cause autoreactive immune cells to destroy beta cells in the islets. ASIT may restore self-tolerance; however, the approach has yet to fully meet its promise and may require co-administration of antigen (preproinsulin) and suitable immune response modifiers.

SUMMARY

A self-tolerant immune system may be regained using ASIT where T effector cells are repressed and/or T regulatory cells are induced. Administration of exogenous antigens has been safe in T1D. Conversely, adequate and lasting beta cell preservation has yet to be tested in sufficiently large clinical trials in suitable patients and may require targeting of multiple parts of the immunopathophysiology using combination therapies. DNA-based induction of native antigen expression to ensure important posttranscriptional modifications and presentation to the immune system together with tolerance-enhancing immune response modifiers (i.e., cytokines) may be more efficacious than exogenous antigens given alone. Progress is limited mainly by the scarcity of validated biomarkers to track the effects of ASIT in T1D.

Mitochondrial-encoded MOTS-c prevents pancreatic islet destruction in autoimmune diabetes

Mitochondria are principal metabolic organelles that are increasingly unveiled as immune regulators. However, it is currently not known whether mitochondrial-encoded peptides modulate T cells to induce changes in phenotype and function. In this study, we found that MOTS-c (mitochondrial open reading frame of the 12S rRNA type-c) prevented autoimmune β cell destruction by targeting T cells in non-obese diabetic (NOD) mice. MOTS-c ameliorated the development of hyperglycemia and reduced islet-infiltrating immune cells. Furthermore, adoptive transfer of T cells from MOTS-c-treated NOD mice significantly decreased the incidence of diabetes in NOD-severe combined immunodeficiency (SCID) mice. Metabolic and genomic analyses revealed that MOTS-c modulated T cell phenotype and function by regulating T cell receptor (TCR)/mTOR complex 1 (mTORC1) signaling. Type 1 diabetes (T1D) patients had a lower serum MOTS-c level than did healthy controls. Furthermore, MOTS-c reduced T cell activation by alleviating T cells from the glycolytic stress in T1D patients, suggesting therapeutic potential. Our findings indicate that MOTS-c regulates the T cell phenotype and suppresses autoimmune diabetes.

Prevention of type 1 diabetes: where we are and where we are going

T1D (T1D) is one of the most frequent chronic disease in children and is associated to the risk of severe acute and chronic complications. There are about 550000 children with T1D in the world and about 86000 children are diagnosed with T1D every year and its incidence is ever increasing. In this narrative review we will discuss current and future perspectives in T1D prevention strategies as well as their pitfalls. It is important to remember that for the first time one drug, in particular Teplizumab (antibody anti CD3) is going to be accepted for treatment in stage 2 of type 1 diabetes mellitus: this represent the onset of a new era.

Current and future therapies for type 1 diabetes

In type 1 diabetes, insulin remains the mature therapeutic cornerstone; yet, the increasing number of individuals developing type 1 diabetes (predominantly children and adolescents) still face severe complications. Fortunately, our understanding of type 1 diabetes is continuously being refined, allowing for refocused development of novel prevention and management strategies. Hitherto, attempts based on immune suppression and modulation have been only partly successful in preventing the key pathophysiological feature in type 1 diabetes: the immune-mediated derangement or destruction of beta cells in the pancreatic islets of Langerhans, leading to low or absent insulin secretion and chronic hyperglycaemia. Evidence now warrants a focus on the beta cell itself and how to avoid its dysfunction, which is putatively caused by cytokine-driven inflammation and other stress factors, leading to low insulin-secretory capacity, autoantigen presentation and immune-mediated destruction. Correspondingly, beta cell rescue strategies are being pursued, which include antigen vaccination using, for example, oral insulin or peptides, as well as agents with suggested benefits on beta cell stress, such as verapamil and glucagon-like peptide-1 receptor agonists. Whilst autoimmune-focused prevention approaches are central in type 1 diabetes and will be a requirement in the advent of stem cell-based replacement therapies, managing the primarily cardiometabolic complications of established type 1 diabetes is equally essential. In this review, we outline selected recent and suggested future attempts to address the evolving profile of the person with type 1 diabetes.

Anti-interleukin-21 antibody and liraglutide for the preservation of β-cell function in adults with recent-onset type 1 diabetes: a randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Type 1 diabetes is characterised by progressive loss of functional β-cell mass, necessitating insulin treatment. We aimed to investigate the hypothesis that combining anti-interleukin (IL)-21 antibody (for low-grade and transient immunomodulation) with liraglutide (to improve β-cell function) could enable β-cell survival with a reduced risk of complications compared with traditional immunomodulation.

METHODS

This randomised, parallel-group, placebo-controlled, double-dummy, double-blind, phase 2 trial was done at 94 sites (university hospitals and medical centres) in 17 countries. Eligible participants were adults aged 18-45 years with recently diagnosed type 1 diabetes and residual β-cell function. Individuals with unstable type 1 diabetes (defined by an episode of severe diabetic ketoacidosis within 2 weeks of enrolment) or active or latent chronic infections were excluded. Participants were randomly assigned (1:1:1:1), with stratification by baseline stimulated peak C-peptide concentration (mixed-meal tolerance test [MMTT]), to the combination of anti-IL-21 and liraglutide, anti-IL-21 alone, liraglutide alone, or placebo, all as an adjunct to insulin. Investigators, participants, and funder personnel were masked throughout the treatment period. The primary outcome was the change in MMTT-stimulated C-peptide concentration at week 54 (end of treatment) relative to baseline, measured via the area under the concentration-time curve (AUC) over a 4 h period for the full analysis set (intention-to-treat population consisting of all participants who were randomly assigned). After treatment cessation, participants were followed up for an additional 26-week off-treatment observation period. This trial is registered with ClinicalTrials.gov, NCT02443155.

FINDINGS

Between Nov 10, 2015, and Feb 27, 2019, 553 adults were assessed for eligibility, of whom 308 were randomly assigned to receive either anti-IL-21 plus liraglutide, anti-IL-21, liraglutide, or placebo (77 assigned to each group). Compared with placebo (ratio to baseline 0·61, 39% decrease), the decrease in MMTT-stimulated C-peptide concentration from baseline to week 54 was significantly smaller with combination treatment (0·90, 10% decrease; estimated treatment ratio 1·48, 95% CI 1·16-1·89; p=0·0017), but not with anti-IL-21 alone (1·23, 0·97-1·57; p=0·093) or liraglutide alone (1·12, 0·87-1·42; p=0·38). Despite greater insulin use in the placebo group, the decrease in HbA_1c (a key secondary outcome) at week 54 was greater with all active treatments (-0·50 percentage points) than with placebo (-0·10 percentage points), although the differences versus placebo were not significant. The effects diminished upon treatment cessation. Changes in immune cell subsets across groups were transient and mild (<10% change over time). The most frequently reported adverse events included gastrointestinal disorders, in keeping with the known side-effect profile of liraglutide. The rate of hypoglycaemic events did not differ significantly between active treatment groups and placebo, with an exception of a lower rate in the liraglutide group than in the placebo group during the treatment period. No events of diabetic ketoacidosis were observed. One participant died while on liraglutide (considered unlikely to be related to trial treatment) in connection with three reported adverse events (hypoglycaemic coma, pneumonia, and brain oedema).

INTERPRETATION

The combination of anti-IL-21 and liraglutide could preserve β-cell function in recently diagnosed type 1 diabetes. The efficacy of this combination appears to be similar to that seen in trials of other disease-modifying interventions in type 1 diabetes, but with a seemingly better safety profile. Efficacy and safety should be further evaluated in a phase 3 trial programme.

FUNDING

Novo Nordisk.

Arrest in the Progression of Type 1 Diabetes at the Mid-Stage of Insulitic Autoimmunity Using an Autoantigen-Decorated All-trans Retinoic Acid and Transforming Growth Factor Beta-1 Single Microparticle Formulation

Type 1 diabetes (T1D) is a disorder of impaired glucoregulation due to lymphocyte-driven pancreatic autoimmunity. Mobilizing dendritic cells (DC) in vivo to acquire tolerogenic activity is an attractive therapeutic approach as it results in multiple and overlapping immunosuppressive mechanisms. Delivery of agents that can achieve this, in the form of micro/nanoparticles, has successfully prevented a number of autoimmune conditions in vivo. Most of these formulations, however, do not establish multiple layers of immunoregulation. all-trans retinoic acid (RA) together with transforming growth factor beta 1 (TGFβ1), in contrast, has been shown to promote such mechanisms. When delivered in separate nanoparticle vehicles, they successfully prevent the progression of early-onset T1D autoimmunity in vivo. Herein, we show that the approach can be simplified into a single microparticle formulation of RA + TGFβ1 with surface decoration with the T1D-relevant insulin autoantigen. We show that the onset of hyperglycemia is prevented when administered into non-obese diabetic mice that are at the mid-stage of active islet-selective autoimmunity. Unexpectedly, the preventive effects do not seem to be mediated by increased numbers of regulatory T-lymphocytes inside the pancreatic lymph nodes, at least following acute administration of microparticles. Instead, we observed a mild increase in the frequency of regulatory B-lymphocytes inside the mesenteric lymph nodes. These data suggest additional and potentially-novel mechanisms that RA and TGFβ1 could be modulating to prevent progression of mid-stage autoimmunity to overt T1D. Our data further strengthen the rationale to develop RA+TGFβ1-based micro/nanoparticle “vaccines” as possible treatments of pre-symptomatic and new-onset T1D autoimmunity.

A mutant α1antitrypsin in complex with heat shock proteins as the primary antigen in type 1 diabetes in silico investigation

Based on previous results demonstrating that complexes of a mutant α1-antitrypsin with the heat shock proteins (HSP)70 and glucose-regulated protein94 (Grp94) circulate in the blood of patients with type 1 diabetes, we raised the hypothesis that these complexes could represent the primary antigen capable of triggering the autoimmune reactions leading to overt diabetes. As a first approach to this issue, we searched whether A1AT and HSPs had a sequence similarity to major islet antigen proteins so as to identify among the similar sequences those with potential relevance for the pathogenesis of diabetes. A thorough in silico analysis was performed to establish the score of similarity of the human proteins: A1AT, pro-insulin (INS), GAD65, IAPP, IA-2, ICA69, Grp94, HSP70 and HSP60. The sequences of A1AT and HSPs with the highest score of similarity to the islet peptides reported in the literature as the main autoantigens in human diabetes were recorded. At variance with other HSPs, also including HSP90 and Grp78, Grp94 contained the highest number and the longest sequences with structural similarity to A1AT and to well-known immunogenic peptides/epitopes of INS, GAD65, and IA-2. The similarity of A1AT with Grp94 and that of Grp94 with INS also suggested a functional relationship among the proteins. Specific sequences were identified in A1AT, Grp94 and HSP70, with the highest score of cross-similarity to a pattern of eight different islet protein epitopes. The similarity also involved recently discovered autoantigens in type 1 diabetes such as a hybrid peptides of insulin and the defective ribosomal insulin gene product. The significant similarity displayed by specific sequences of Grp94 and A1AT to the islet peptides considered main antigens in human diabetes, is a strong indication for testing these sequences as new peptides of immunogenic relevance in diabetes.

Immunomodulatory Dual-Sized Microparticle System Conditions Human Antigen Presenting Cells Into a Tolerogenic Phenotype In Vitro and Inhibits Type 1 Diabetes-Specific Autoreactive T Cell Responses

Current monotherapeutic agents fail to restore tolerance to self-antigens in autoimmune individuals without systemic immunosuppression. We hypothesized that a combinatorial drug formulation delivered by a poly-lactic-co-glycolic acid (PLGA) dual-sized microparticle (dMP) system would facilitate tunable drug delivery to elicit immune tolerance. Specifically, we utilized 30 µm MPs to provide local sustained release of granulocyte-macrophage colony-stimulating factor (GM-CSF) and transforming growth factor β1 (TGF-β1) along with 1 µm MPs to facilitate phagocytic uptake of encapsulated antigen and 1α,25(OH)2 Vitamin D3 (VD3) followed by tolerogenic antigen presentation. We previously demonstrated the dMP system ameliorated type 1 diabetes (T1D) and experimental autoimmune encephalomyelitis (EAE) in murine models. Here, we investigated the system's capacity to impact human cell activity in vitro to advance clinical translation. dMP treatment directly reduced T cell proliferation and inflammatory cytokine production. dMP delivery to monocytes and monocyte-derived dendritic cells (DCs) increased their expression of surface and intracellular anti-inflammatory mediators. In co-culture, dMP-treated DCs (dMP-DCs) reduced allogeneic T cell receptor (TCR) signaling and proliferation, while increasing PD-1 expression, IL-10 production, and regulatory T cell (Treg) frequency. To model antigen-specific activation and downstream function, we co-cultured TCR-engineered autoreactive T cell "avatars," with dMP-DCs or control DCs followed by β-cell line (ßlox5) target cells. For G6PC2-specific CD8+ avatars (clone 32), dMP-DC exposure reduced Granzyme B and dampened cytotoxicity. GAD65-reactive CD4+ avatars (clone 4.13) exhibited an anergic/exhausted phenotype with dMP-DC presence. Collectively, these data suggest this dMP formulation conditions human antigen presenting cells toward a tolerogenic phenotype, inducing regulatory and suppressive T cell responses.

Glucose-dependent partitioning of arginine to the urea cycle protects β-cells from inflammation

Chronic inflammation is linked to diverse disease processes, but the intrinsic mechanisms that determine cellular sensitivity to inflammation are incompletely understood. Here, we show the contribution of glucose metabolism to inflammation-induced changes in the survival of pancreatic islet β-cells. Using metabolomic, biochemical and functional analyses, we investigate the protective versus non-protective effects of glucose in the presence of pro-inflammatory cytokines. When protective, glucose metabolism augments anaplerotic input into the TCA cycle via pyruvate carboxylase (PC) activity, leading to increased aspartate levels. This metabolic mechanism supports the argininosuccinate shunt, which fuels ureagenesis from arginine and conversely diminishes arginine utilization for production of nitric oxide (NO), a chief mediator of inflammatory cytotoxicity. Activation of the PC-urea cycle axis is sufficient to suppress NO synthesis and shield cells from death in the context of inflammation and other stress paradigms. Overall, these studies uncover a previously unappreciated link between glucose metabolism and arginine-utilizing pathways via PC-directed ureagenesis as a protective mechanism.

Toll-like Receptors as a Potential Drug Target for Diabetes Mellitus and Diabetes-associated Complications

Diabetes mellitus (DM) is a chronic endocrine disease distinguished by hyperglycemia due to disturbance in carbohydrate or lipid metabolism or insulin function. To date, diabetes, and its complications, is established as a global cause of morbidity and mortality. The intended aim during the management of diabetes is to maintain blood glucose close to normal because the majority of patients have poor control of their elevated blood glucose and are highly prone to severe macrovascular and microvascular complications. To decrease the burden of the disease and its complications, scientists from various disciplines are working intensively to identify novel and promising drug targets for diabetes and its complications. Increased and ongoing investigations on mechanisms relating to diabetes and associated complications could potentially consider inflammatory cascades as a promising component of the strategy in the prevention and control of diabetes and its complications. The potential of targeting mediators of inflammation like toll-like receptors (TLRs) are part of current investigation by the scientific community. Hence, the aim of the present review is to discuss the role of TLRs as a potential drug target for diabetes and diabetes associated complications.

Nomenclature for the Phases of the Development of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a common immune-mediated inflammatory disease. Research on RA is increasingly focused on the earliest stages of the disease, and has provided strong evidence that clinical signs and symptoms may be preceded by a preclinical phase during which evidence of systemic autoimmunity may be present. To facilitate research in this area, a number of international initiatives have proposed definitions of the phases of disease leading up to RA. The first of these initiatives was the European League Against Rheumatism's (EULAR) set of recommendations on terminology in persons at risk for RA, which suggested that the "at-risk phases" be described in terms of patients variably having: (A) genetic risk factors for RA; (B) environmental risk factors for RA; (C) systemic autoimmunity associated with RA; (D) symptoms without clinical arthritis; and (E) unclassified arthritis. The phrase clinically suspect arthralgia (CSA) is now widely used and can be regarded as describing a subgroup of patients in phase D. A definition of CSA was recently proposed by a EULAR taskforce, and primary research has begun to explore the full range of symptoms, as well as their sensitivity and specificity alone and in combination with other factors, that characterize this phase. Similarly, immune abnormalities at mucosal and others sites that precede and/or are associated with the onset of musculoskeletal symptoms are being increasingly studied and understood. Whether some of these at-risk phases, in particular CSA, represent entities meriting their own classification criteria is an essential area for consensus and will be discussed.

Elevated T cell levels in peripheral blood predict poor clinical response following rituximab treatment in new-onset type 1 diabetes

Biologic treatment of type 1 diabetes (T1D) with agents including anti-CD3 (otelixizumab and teplizumab), anti-CD20 (rituximab), LFA3Ig (alafacept), and CTLA4Ig (abatacept) results in transient stabilization of insulin C-peptide, a surrogate for endogenous insulin secretion. With the goal of inducing more robust immune tolerance, we used systems biology approaches to elucidate mechanisms associated with C-peptide stabilization in clinical trial blood samples from new-onset T1D subjects treated with the B cell-depleting drug, rituximab. RNA sequencing (RNA-seq) analysis of whole-blood samples from this trial revealed a transient increase in heterogeneous T cell populations, which were associated with decreased pharmacodynamic activity of rituximab, increased proliferative responses to islet antigens, and more rapid C-peptide loss. Our findings illustrate complexity in hematopoietic remodeling that accompanies B cell depletion by rituximab, which impacts and predicts therapeutic efficacy in T1D. Our data also suggest that a combination of rituximab with therapy targeting CD4 + T cells may be beneficial for T1D subjects.

B lymphocyte alterations accompany abatacept resistance in new-onset type 1 diabetes

Costimulatory interactions control T cell activation at sites of activated antigen-presenting cells, including B cells. Blockade of the CD28/CD80/CD86 costimulatory axis with CTLA4Ig (abatacept) is widely used to treat certain autoimmune diseases. While transiently effective in subjects with new-onset type 1 diabetes (T1D), abatacept did not induce long-lasting immune tolerance. To elucidate mechanisms limiting immune tolerance in T1D, we performed unbiased analysis of whole blood transcriptomes and targeted measurements of cell subset levels in subjects from a clinical trial of abatacept in new-onset T1D. We showed that individual subjects displayed age-related immune phenotypes ("immunotypes") at baseline, characterized by elevated levels of B cells or neutrophils, that accompanied rapid or slow progression, respectively, in both abatacept- and placebo-treated groups. A more pronounced immunotype was exhibited by a subset of subjects showing poor response (resistance) to abatacept. This resistance immunotype was characterized by a transient increase in activated B cells (one of the cell types that binds abatacept), reprogrammed costimulatory ligand gene expression, and reduced inhibition of anti-insulin antibodies. Our findings identify immunotypes in T1D subjects that are linked to the rate of disease progression, both in placebo- and abatacept-treated subjects. Furthermore, our results suggest therapeutic approaches to restore immune tolerance in T1D.

Lymphocyte-Derived Exosomal MicroRNAs Promote Pancreatic β Cell Death and May Contribute to Type 1 Diabetes Development

Type 1 diabetes is an autoimmune disease initiated by the invasion of pancreatic islets by immune cells that selectively kill the β cells. We found that rodent and human T lymphocytes release exosomes containing the microRNAs (miRNAs) miR-142-3p, miR-142-5p, and miR-155, which can be transferred in active form to β cells favoring apoptosis. Inactivation of these miRNAs in recipient β cells prevents exosome-mediated apoptosis and protects non-obese diabetic (NOD) mice from diabetes development. Islets from protected NOD mice display higher insulin levels, lower insulitis scores, and reduced inflammation. Looking at the mechanisms underlying exosome action, we found that T lymphocyte exosomes trigger apoptosis and the expression of genes involved in chemokine signaling, including Ccl2, Ccl7, and Cxcl10, exclusively in β cells. The induction of these genes may promote the recruitment of immune cells and exacerbate β cell death during the autoimmune attack. Our data point to exosomal-miRNA transfer as a communication mode between immune and insulin-secreting cells.

Effects of B-cell directed therapy on the preclinical stage of rheumatoid arthritis: the PRAIRI study

Objectives

We explored the effects of B-cell directed therapy in subjects at risk of developing autoantibodypositive rheumatoid arthritis (RA), who never experienced inflammatory arthritis before, and explored biomarkers predictive of arthritis development.

Methods

Individuals positive for both anti-citrullinated peptide antibodies and rheumatoid factor but without arthritis were included in a randomised, double-blind, placebo-controlled study to receive a single infusion of 1000 mg rituximab or placebo.

Results

Eighty-one individuals received treatment and were followed up for a mean of 29.0 (0–54) months, during which 30/81 (37%) individuals developed arthritis. The observed risk of developing arthritis in the placebo-treated group was 40%, which was decreased by 55% (HR 0.45, 95% CI 0.154 to 1.322) in the rituximab-treated group at 12 months. Rituximab treatment caused a delay in arthritis development of 12 months compared with placebo treatment at the point when 25% of the subjects had developed arthritis (p<0.0001). Erythrocyte sedimentation rate and the presence of anti-citrullinated α-enolase peptide 1 at baseline were significant predictors of arthritis development.

Conclusions

A single infusion of 1000 mg rituximab significantly delays the development of arthritis in subjects at risk of developing RA, providing evidence for the pathogenetic role of B cells in the earliest, prearthritis stage of autoantibody positive RA.

A long-lived IL-2 mutein that selectively activates and expands regulatory T cells as a therapy for autoimmune disease

Susceptibility to multiple autoimmune diseases is associated with common gene polymorphisms influencing IL-2 signaling and T_reg function, making T_reg-specific expansion by IL-2 a compelling therapeutic approach to treatment. As an in vivo IL-2 half-life enhancer we used a non-targeted, effector-function-silent human IgG1 as a fusion protein. An IL-2 mutein (N88D) with reduced binding to the intermediate affinity IL-2Rβγ receptor was engineered with a stoichiometry of two IL-2N88D molecules per IgG, i.e. IgG-(IL-2N88D)₂. The reduced affinity of IgG-(IL-2N88D)₂ for the IL-2Rβγ receptor resulted in a T_reg-selective molecule in human whole blood pSTAT5 assays. Treatment of cynomolgus monkeys with single low doses of IgG-(IL-2N88D)₂ induced sustained preferential activation of T_regs accompanied by a corresponding 10–14-fold increase in CD4⁺ and CD8⁺ CD25⁺FOXP3⁺ T_regs; conditions that had no effect on CD4⁺ or CD8⁺ memory effector T cells. The expanded cynomolgus T_regs had demethylated FOXP3 and CTLA4 epigenetic signatures characteristic of functionally suppressive cells. Humanized mice had similar selective in vivo responses; IgG-(IL-2N88D)₂ increased T_regs while wild-type IgG-IL-2 increased NK cells in addition to T_regs. The expanded human T_regs had demethylated FOXP3 and CTLA4 signatures and were immunosuppressive. These results describe a next-generation immunotherapy using a long-lived and T_reg-selective IL-2 that activates and expands functional T_regsin vivo. Patients should benefit from restored immune homeostasis in a personalized fashion to the extent that their autoimmune disease condition dictates opening up the possibility for remissions and cures.

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A human IL-2 molecule mutated to decrease binding to the intermediate affinity IL-2 receptor preferentially activates Tregs.

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Two IL-2 muteins fused to human IgG1 allow for sustained, preferential expansion of Tregs in cynomolgus and humanized mice.

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As compared to the wild type IL-2 fusion protein, humanized mice expand fewer NK cells in response to the mutein.

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The dynamic range of Treg increase based on dose suggests the ability to individualize dosing for particular diseases.

Immune Checkpoint Molecules, Personalized Immunotherapy, and Autoimmune Diabetes

Although significant progress has been made in understanding autoimmunity, no immunotherapy to effectively halt immune-mediated destruction of β cells in type 1 diabetes (T1D) is currently available. For successful immunotherapy it will be necessary to identify novel drug targets as well as robust immunologic biomarkers to predict disease heterogeneity and patient responsiveness. Inhibition of immune checkpoint mechanisms represents a novel and effective strategy in tumor immunotherapy. Because they are fundamental to rewiring immune circuits, the underlying mechanisms could be therapeutically enhanced and used as biomarkers in T1D. We examine here current knowledge of immune checkpoint molecules in T1D. One specific immune checkpoint mechanism, namely tryptophan metabolism, may meet the need for a valid drug target and robust biomarker in the quest for effective and personalized immunotherapy in T1D.

Effects of proinsulin misfolding on β-cell dynamics, differentiation and function in diabetes

ER stress due to proinsulin misfolding has an important role in the pathophysiology of rare forms of permanent neonatal diabetes (PNDM) and probably also of common type 1 (T1D) and type 2 diabetes (T2D). Accumulation of misfolded proinsulin in the ER stimulates the unfolded protein response (UPR) that may eventually lead to apoptosis through a process called the terminal UPR. However, the β-cell ER has an incredible ability to cope with accumulation of misfolded proteins; therefore, it is not clear whether in common forms of diabetes the accumulation of misfolded proinsulin exceeds the point of no return in which terminal UPR is activated. Many studies showed that the UPR is altered in both T1D and T2D; however, the observed changes in the expression of different UPR markers are inconsistent and it is not clear whether they reflect an adaptive response to stress or indeed mediate the β-cell dysfunction of diabetes. Herein, we critically review the literature on the effects of proinsulin misfolding and ER stress on β-cell dysfunction and loss in diabetes with emphasis on β-cell dynamics, and discuss the gaps in understanding the role of proinsulin misfolding in the pathophysiology of diabetes.

The Autoantigenic Proinsulin B-Chain Peptide B11-23 Synergises with the 70 kDa Heat Shock Protein DnaK in Macrophage Stimulation

BACKGROUND

Heat shock proteins (Hsp) act as intracellular chaperones and in addition are used as adjuvant in vaccines of peptides complexed with recombinant Hsp. By interacting with autologous peptides, Hsp may promote the induction of autoimmune reactivity.

OBJECTIVE

Here, we analysed whether the effect of Hsp on macrophages is modulated by insulin peptides known to interact with Hsp.

RESULTS

Combinations of the 70 kDa Hsp DnaK with peptide B11-23 from the core region of the proinsulin B-chain induced the release of the inflammatory mediators interleukin-6, tumor necrosis factor α, and interleukin-1β from cells of human and murine macrophage lines. In parallel, there was high-affinity binding of B11-23 to DnaK. DnaK mixed with peptides from other regions of the insulin molecule did not stimulate cytokine secretion. DnaK alone induced little cytokine production, and peptides alone induced none.

CONCLUSION

The macrophage-stimulating potential of Hsp70 family proteins when combined with the proinsulin B-chain peptide B11-23 may contribute to the immunodominance of this peptide in the development of beta cell-directed autoimmunity in type 1 diabetes.

Proteomic Landscape of Patient-Derived CD4+ T Cells in Recent-Onset Type 1 Diabetes

The pathophysiology underlying the autoimmune disease type 1 diabetes (T1D) is poorly understood. Obtaining an accurate proteomic profile of the T helper cell population is essential for understanding the pathogenesis of T1D. Here, we performed in-depth proteomic profiling of peripheral CD4+ T cells in a pediatric cohort to identify cellular signatures associated with the onset of T1D. Using only 250 000 CD4+ T cells per patient, isolated from biobanked PBMC samples, we identified nearly 6000 proteins using deep-proteome profiling with LC-MS/MS data-independent acquisition. Our analysis revealed an inflammatory signature in patients with T1D; this signature is characterized by circulating mediators of neutrophils, platelets, and the complement system. This signature likely reflects the inflammatory extracellular milieu, which suggests that activation of the innate immune system plays an important role in disease onset. Our results emphasize the potential value of using high-resolution LC-MS/MS to investigate limited quantities of biobanked samples to identify disease-relevant proteomic patterns. Proteomic profiles of 114 individuals have been deposited in a comprehensive portable repository serving as a unique resource for CD4+ T cell expression in the context of both health and T1D disease.

Reply to "Tolerogenic insulin peptide therapy precipitates type 1 diabetes"

In this issue of JEM, Bergman et al. (https://doi.org/10.1084/jem.20160471) challenge the data published in our previous JEM paper on the preventive effect of tolerogenic vaccination with a strong agonist insulin mimetope in type 1 diabetes. Here, we provide a response to these data and suggest that appropriate subimmunogenic conditions are required to induce Foxp3⁺ regulatory T cell conversion.

Targeting innate immunity to downmodulate adaptive immunity and reverse type 1 diabetes

Type 1 diabetes (T1D) is characterized by specific destruction of pancreatic insulin-producing beta cells accompanied by evidence of beta-cell-directed autoimmunity such as autoreactive T cells and islet autoantibodies (IAAs). Currently, T1D cannot be prevented or reversed in humans. T1D is easy to prevent in the nonobese diabetic (NOD) spontaneous mouse model but reversing new-onset T1D in mice is more difficult. Since the discovery of the T-cell receptor in the 1980s and the subsequent identification of autoreactive T cells directed toward beta-cell antigens (eg, insulin, glutamic acid decarboxylase), the dream of antigen-specific immunotherapy has dominated the field with its promise of specificity and limited side effects. While such approaches have worked in the NOD mouse, however, dozens of human trials have failed. Broader immunosuppressive approaches (originally cyclosporine, subsequently anti-CD3 antibody) have shown partial successes (e.g., prolonged C peptide preservation) but no major therapeutic efficacy or disease reversal. Human prevention trials have failed, despite the ease of such approaches in the NOD mouse. In the past 50 years, the incidence of T1D has increased dramatically, and one explanation is the “hygiene hypothesis”, which suggests that decreased exposure of the innate immune system to environmental immune stimulants (e.g., bacterial products such as Toll-like receptor (TLR) 4-stimulating lipopolysaccharide [LPS]) dramatically affects the adaptive immune system and increases subsequent autoimmunity. We have tested the role of innate immunity in autoimmune T1D by treating acute-onset T1D in NOD mice with anti-TLR4/MD-2 agonistic antibodies and have shown a high rate of disease reversal. The TLR4 antibodies do not directly stimulate T cells but induce tolerogenic antigen-presenting cells (APCs) that mediate decreased adaptive T-cell responses. Here, we review our current knowledge and suggest future prospects for targeting innate immunity in T1D immunotherapy.

Antibiotics, gut microbiota, environment in early life and type 1 diabetes

The gut microbiota interact with innate immune cells and play an important role in shaping the immune system. Many factors may influence the composition of the microbiota such as mode of birth, diet, infections and medication including antibiotics. In diseases with a multifactorial etiology, like type 1 diabetes, manipulation and alterations of the microbiota in animal models have been shown to influence the incidence and onset of disease. The microbiota are an important part of the internal environment and understanding how these bacteria interact with the innate immune cells to generate immune tolerance may open up opportunities for development of new therapeutic strategies. In this review, we discuss recent findings in relation to the microbiota, particularly in the context of type 1 diabetes.