PD-L1-driven tolerance protects neurogenin3-induced islet neogenesis to reverse established type 1 diabetes in NOD mice

From Edmonton to Lantidra and beyond: immunoengineering islet transplantation to cure type 1 diabetes

Type 1 diabetes (T1D) is characterized by the autoimmune destruction of insulin-producing β cells within pancreatic islets, the specialized endocrine cell clusters of the pancreas. Islet transplantation has emerged as a β cell replacement therapy, involving the infusion of cadaveric islets into a patient's liver through the portal vein. This procedure offers individuals with T1D the potential to restore glucose control, reducing or even eliminating the need for exogenous insulin therapy. However, it does not address the underlying autoimmune condition responsible for T1D. The need for systemic immunosuppression remains the primary barrier to making islet transplantation a more widespread therapy for patients with T1D. Here, we review recent progress in addressing the key limitations of islet transplantation as a viable treatment for T1D. Concerns over systemic immunosuppression arise from its potential to cause severe side effects, including opportunistic infections, malignancies, and toxicity to transplanted islets. Recognizing the risks, the Edmonton protocol (2000) marked a shift away from glucocorticoids to prevent β cell damage specifically. This transition led to the development of combination immunosuppressive therapies and the emergence of less toxic immunosuppressive and anti-inflammatory drugs. More recent advances in islet transplantation derive from islet encapsulation devices, biomaterial platforms releasing immunomodulatory compounds or surface-modified with immune regulating ligands, islet engineering and co-transplantation with accessory cells. While most of the highlighted studies in this review remain at the preclinical stage using mouse and non-human primate models, they hold significant potential for clinical translation if a transdisciplinary research approach is prioritized.

Islet allografts expressing a PD-L1 and IDO fusion protein evade immune rejection and reverse preexisting diabetes in immunocompetent mice without systemic immunosuppression

Allogeneic islet transplantation is a promising experimental therapy for poorly controlled diabetes. Despite pharmacological immunosuppression, long-term islet engraftment remains elusive. Here, we designed a synthetic fusion transgene coupling PD-L1 and indoleamine dioxygenase [hereafter PIDO] whose constitutive expression prevents immune destruction of genetically engineered islet allograft transplanted in immunocompetent mice. PIDO expressing murine islets maintain robust dynamic insulin secretion in vitro and when transplanted in allogeneic hyperglycemic murine recipients reverse pre-existing streptozotocin-induced and autoimmune diabetes in the absence of pharmacological immunosuppression for more than 50 and 8 weeks, respectively, and is dependent on host CD4 competence. Additionally, PIDO expression in allografts preserves endocrine functional viability of islets and promotes a localized tolerogenic milieu characterized by the suppression of host CD8 T cell and phagocyte recruitment and accumulation of FOXP3⁺ Tregs. Furthermore, in the canine model of xenogeneic islet transplantation, muscle implanted PIDO-expressing porcine islets displayed physiological glucose-responsive insulin secretion competency in euglycemic recipient for up to 20 weeks. In conclusion, the PIDO transgenic technology enables host CD4⁺ T cell-modulated immune evasiveness and long-term functional viability of islet allo- and xenografts in immune-competent recipients without the need for pharmacological immune suppression and would allow for improved outcomes for tissue transplantation.

Changes of macrophage and CD4+ T cell in inflammatory response in type 1 diabetic mice

Immune cells play an important role in the development of inflammation in type 1 diabetes mellitus, so we want to explore the changes of CD4+ T cells and macrophages in vivo, which can provide an experimental basis for immunotherapy based on CD4+ T cells and macrophages. The intraperitoneal injection of streptozocin was used to induce a type 1 diabetes mellitus mouse model; the blood glucose, body weight, and the expression of inflammatory factors in the kidney were measured. Immunohistochemistry was applied to determine and analyze the infiltration of CD4+ T cells and macrophages in the spleen, pancreas, and kidney. The subtypes of macrophages in the kidney and CD4+ T cells in the spleen were analyzed by flow cytometry. Our study suggests that CD4+ T cells and macrophages increase, while the inflammatory immune response system is activated in the development of T1DM. CD4+ T cells positively correlated with macrophages in the pancreas and kidney of T1DM. CD4+ T cells turn to pro-inflammatory subtypes in the spleen of T1DM, while macrophages turn to pro-inflammatory subtypes in the kidney of T1DM. Therefore, regulation of CD4+ T cells and macrophages may be a potential target for T1DM and kidney complications.

Engineered immunomodulatory accessory cells improve experimental allogeneic islet transplantation without immunosuppression

Islet transplantation has been established as a viable treatment modality for type 1 diabetes. However, the side effects of the systemic immunosuppression required for patients often outweigh its benefits. Here, we engineer programmed death ligand-1 and cytotoxic T lymphocyte antigen 4 immunoglobulin fusion protein-modified mesenchymal stromal cells (MSCs) as accessory cells for islet cotransplantation. The engineered MSCs (eMSCs) improved the outcome of both syngeneic and allogeneic islet transplantation in diabetic mice and resulted in allograft survival for up to 100 days without any systemic immunosuppression. Immunophenotyping revealed reduced infiltration of CD4+ or CD8+ T effector cells and increased infiltration of T regulatory cells within the allografts cotransplanted with eMSCs compared to controls. The results suggest that the eMSCs can induce local immunomodulation and may be applicable in clinical islet transplantation to reduce or minimize the need of systemic immunosuppression and ameliorate its negative impact.

Syngeneically transplanted insulin producing cells differentiated from adipose derived stem cells undergo delayed damage by autoimmune responses in NOD mice

Insulin-producing cells (IPCs) generated by our established protocol have reached the non-clinical ‘proof of concept’ stage. Our strategy for their clinical application is the autotransplantation of IPCs into patients with type 1 diabetes mellitus (T1DM). In this context, the autoimmunity that characterized T1DM is important, rather than allorejection. We aimed to determine how these IPCs respond to T1DM autoimmunity. IPCs were generated from the subcutaneous fat tissue of non-obese diabetic (NOD) mice using our protocol. IPCs derived from NOD mice were transplanted under the kidney capsules of NOD mice at the onset of diabetes and the subsequent changes in blood glucose concentration were characterized. Blood glucose decreased within 30 days of transplantation, but increased again after 40–60 days in three of four recipient NOD mice. In tissue samples, the numbers of CD4⁺ and CD8⁺ T cells were significantly higher 60 days after transplantation than 30 days after transplantation. In conclusion, IPCs significantly ameliorate the diabetes of mice in the short term, but are damaged by autoimmunity in the longer term, as evidenced by local T cells accumulation. This study provides new insights into potential stem cell therapies for T1DM.

Current Topics of Relevance to the Xenotransplantation of Free Pig Islets

Pig islet xenotransplantation is a potential treatment for patients with type 1 diabetes. Current efforts are focused on identifying the optimal pig islet source and overcoming the immunological barrier. The optimal age of the pig donors remains controversial since both adult and neonatal pig islets have advantages. Isolation of adult islets using GMP grade collagenase has significantly improved the quantity and quality of adult islets, but neonatal islets can be isolated at a much lower cost. Certain culture media and coculture with mesenchymal stromal cells facilitate neonatal islet maturation and function. Genetic modification in pigs affords a promising strategy to prevent rejection. Deletion of expression of the three known carbohydrate xenoantigens (Gal, Neu5Gc, Sda) will certainly be beneficial in pig organ transplantation in humans, but this is not yet proven in islet transplantation, though the challenge of the '4th xenoantigen' may prove problematic in nonhuman primate models. Blockade of the CD40/CD154 costimulation pathway leads to long-term islet graft survival (of up to 965 days). Anti-CD40mAbs have already been applied in phase II clinical trials of islet allotransplantation. Fc region-modified anti-CD154mAbs successfully prevent the thrombotic complications reported previously. In this review, we discuss (I) the optimal age of the islet-source pig, (ii) progress in genetic modification of pigs, (iii) the immunosuppressive regimen for pig islet xenotransplantation, and (iv) the reduction in the instant blood-mediated inflammatory reaction.

A Patient with Atezolizumab-Induced Autoimmune Diabetes Mellitus Presenting with Diabetic Ketoacidosis

Background: Atezolizumab, an immune checkpoint inhibitor, is a humanized monoclonal, anti-programmed death ligand 1 (PD-L1) antibody used for the treatment of metastatic urothelial carcinoma that has progressed after chemotherapy.Case Presentation: We describe a patient with a known history of urothelial carcinoma who presented with diabetic ketoacidosis 6 weeks following his second cycle of atezolizumab. His serum lactate level was slightly elevated (2 mM) and his β-hydroxybutyrate level was elevated (3.9 mM). High anion gap metabolic acidosis secondary to diabetic ketoacidosis was diagnosed. Subsequent testing demonstrated hemoglobin A1c level of 9.9%, positivity for anti-glutamic acid decarboxylase antibody (0.03 nM, reference range <0.02 nM), and suppressed C-peptide level (0.1 μg/L, reference range 0.9‐7.1 μg/L) in the absence of detectable anti-islet antigen 2 (IA-2) or anti-insulin antibodies. His initial management included cessation of atezolizumab treatment, intravenous sodium chloride administration, and insulin pump infusion, after which metabolic acidosis gradually resolved. The insulin pump was subsequently switched to Protaphane at 18 units before breakfast and 8 units before dinner, together with metformin at 1000 mg twice daily. Four weeks later his medication was changed to human isophane insulin plus neutral insulin (70%/30%; Mixtard 30 HM; 26 units/4 units). Linagliptin at 5 mg was added 1 month later. His hemoglobin A1c level declined to 8.1% 1 year later.Conclusions: PD-L1 inhibitors can induce type 1 diabetes, and patients can present with diabetic ketoacidosis. Blood glucose levels should be regularly monitored in patients who are prescribed these medications.

The Role of Programmed Death-1 in Type 1 Diabetes

PURPOSE OF REVIEW

Programmed death-1 (PD-1) is an inhibitory receptor that controls T and B cell proliferation and function through interacting with its ligand PD-L1 or PD-L2. PD-1/PD-L1 blockade reboots anti-tumor immunity and is currently used to treat > 15 different types of cancer. However, the response rate is not at 100% and some patients relapse. Importantly, up to 37% of patients treated with PD-1/PD-L1 blocking antibodies develop immune-related adverse events, including overt autoimmunity, such as type 1 diabetes (T1D). Herein, we discuss the role of PD-1, PD-L1, and PD-L2 signaling in pre-clinical models of T1D, including recent work from our laboratory.

RECENT FINDINGS

We highlight ongoing efforts to harness PD-1/PD-L1 signaling and treat autoimmunity. We also evaluate studies aimed at defining biomarkers that could reliably predict the development of immune-related adverse events after clinical PD-1/PD-L1 blockade. With increasing use of PD-1 blockade in the clinic, onset of autoimmunity is a growing health concern. In this review, we discuss what is known about the role of PD-1 pathway signaling in T1D and comment on ongoing efforts to identify patients at risk of T1D development after PD-1 pathway blockade.

A Stem Cell Approach to Cure Type 1 Diabetes

Treatment of type 1 diabetes with insulin injection is expensive, complicated, and insufficient. While cadaveric islet transplantations coupled with immunosuppressants can cure diabetes, the scarcity of acceptable islets is problematic. Developmental research on pancreas formation has informed in vitro differentiation of human pluripotent stem cells into functional islets. Although generating β cells from stem cells offers a potential cure for type 1 diabetes, several challenges remain, including protecting the cells from the immune system.

Novel human immunomodulatory T cell receptors and their double-edged potential in autoimmunity, cardiovascular disease and cancer

In the last decade, approaches based on T cells and their immunomodulatory receptors have emerged as a solid improvement in treatments for various types of cancer. However, the roles of these molecules in the therapeutic context of autoimmune and cardiovascular diseases are still relatively unexplored. Here, we review the best known and most commonly used immunomodulatory T cell receptors in clinical practice (PD-1 and CTLA-4), along with the rest of the receptors with known functions in animal models, which have great potential as modulators in human pathologies in the medium term. Among these other receptors is the receptor CD69, which has recently been described to be expressed in mouse and human T cells in autoimmune and cardiovascular diseases and cancer. However, inhibition of these receptors individually or in combination by drugs or monoclonal antibodies generates a loss of immunological tolerance and can trigger multiple autoimmune disorders in different organs and immune-related adverse effects. In the coming decades, knowledge on the functions of different immunomodulatory receptors will be pivotal for the development of new and better therapies with less harmful side effects. In this review, we discuss the roles of these receptors in the control of immunity from a perspective focused on therapeutic potential in not only cancer but also autoimmune diseases, such as systemic lupus erythematosus, autoimmune diabetes and rheumatoid arthritis, and cardiovascular diseases, such as atherosclerosis, acute myocardial infarction, and myocarditis.

Immunotherapy via PD-L1-presenting biomaterials leads to long-term islet graft survival

Antibody-mediated immune checkpoint blockade is a transformative immunotherapy for cancer. These same mechanisms can be repurposed for the control of destructive alloreactive immune responses in the transplantation setting. Here, we implement a synthetic biomaterial platform for the local delivery of a chimeric streptavidin/programmed cell death-1 (SA-PD-L1) protein to direct "reprogramming" of local immune responses to transplanted pancreatic islets. Controlled presentation of SA-PD-L1 on the surface of poly(ethylene glycol) microgels improves local retention of the immunomodulatory agent over 3 weeks in vivo. Furthermore, local induction of allograft acceptance is achieved in a murine model of diabetes only when receiving the SA-PD-L1-presenting biomaterial in combination with a brief rapamycin treatment. Immune characterization revealed an increase in T regulatory and anergic cells after SA-PD-L1-microgel delivery, which was distinct from naïve and biomaterial alone microenvironments. Engineering the local microenvironment via biomaterial delivery of checkpoint proteins has the potential to advance cell-based therapies, avoiding the need for systemic chronic immunosuppression.

Type 1 diabetes pathogenesis and the role of inhibitory receptors in islet tolerance

Type 1 diabetes (T1D) affects over a million Americans, and disease incidence is on the rise. Despite decades of research, there is still no cure for this disease. Exciting beta cell replacement strategies are being developed, but in order for such approaches to work, targeted immunotherapies must be designed. To selectively halt the autoimmune response, researchers must first understand how this response is regulated and which tolerance checkpoints fail during T1D development. Herein, we discuss the current understanding of T1D pathogenesis in humans, genetic and environmental risk factors, presumed roles of CD4+ and CD8+ T cells as well as B cells, and implicated autoantigens. We also highlight studies in non-obese diabetic mice that have demonstrated the requirement for CD4+ and CD8+ T cells and B cells in driving T1D pathology. We present an overview of central and peripheral tolerance mechanisms and comment on existing controversies in the field regarding central tolerance. Finally, we discuss T cell- and B cell-intrinsic tolerance mechanisms, with an emphasis on the roles of inhibitory receptors in maintaining islet tolerance in humans and in diabetes-prone mice, and strategies employed to date to harness inhibitory receptor signaling to prevent or reverse T1D.

Navigating Two Roads to Glucose Normalization in Diabetes: Automated Insulin Delivery Devices and Cell Therapy

Incredible strides have been made since the discovery of insulin almost 100 years ago. Insulin formulations have improved dramatically, glucose levels can be measured continuously, and recently first-generation biomechanical "artificial pancreas" systems have been approved by regulators around the globe. However, still only a small fraction of patients with diabetes achieve glycemic goals. Replacement of insulin-producing cells via transplantation shows significant promise, but is limited in application due to supply constraints (cadaver-based) and the need for chronic immunosuppression. Over the past decade, significant progress has been made to address these barriers to widespread implementation of a cell therapy. Can glucose levels in people with diabetes be normalized with artificial pancreas systems or via cell replacement approaches? Here we review the road ahead, including the challenges and opportunities of both approaches.

PDL1 is expressed in the islets of people with type 1 diabetes and is up-regulated by interferons-α and-γ via IRF1 induction

Background

Antibodies targeting PD-1 and its ligand PDL1 are used in cancer immunotherapy but may lead to autoimmune diseases, including type 1 diabetes (T1D). It remains unclear whether PDL1 is expressed in pancreatic islets of people with T1D and how is it regulated.

Methods

The expression of PDL1, IRF1, insulin and glucagon was evaluated in samples of T1D donors by immunofluorescence. Cytokine-induced PDL1 expression in the human beta cell line, EndoC-βH1, and in primary human pancreatic islets was determined by real-time RT-PCR, flow cytometry and Western blot. Specific and previously validated small interference RNAs were used to inhibit STAT1, STAT2, IRF1 and JAK1 signaling. Key results were validated using the JAK inhibitor Ruxolitinib.

Findings

PDL1 was present in insulin-positive cells from twelve T1D individuals (6 living and 6 deceased donors) but absent from insulin-deficient islets or from the islets of six non-diabetic controls. Interferons-α and -γ, but not interleukin-1β, induced PDL1 expression in vitro in human islet cells and EndoC-βH1 cells. Silencing of STAT1 or STAT2 individually did not prevent interferon-α-induced PDL1, while blocking of JAKs – a proposed therapeutic strategy for T1D – or IRF1 prevented PDL1 induction.

Interpretation

These findings indicate that PDL1 is expressed in beta cells from people with T1D, possibly to attenuate the autoimmune assault, and that it is induced by both type I and II interferons via IRF1.

CD4 T Cells Reactive to Hybrid Insulin Peptides Are Indicators of Disease Activity in the NOD Mouse

We recently established that hybrid insulin peptides (HIPs), formed in islet β-cells by fusion of insulin C-peptide fragments to peptides of chromogranin A or islet amyloid polypeptide, are ligands for diabetogenic CD4 T-cell clones. The goal of this study was to investigate whether HIP-reactive T cells were indicative of ongoing autoimmunity. MHC class II tetramers were used to investigate the presence, phenotype, and function of HIP-reactive and insulin-reactive T cells in NOD mice. Insulin-reactive T cells encounter their antigen early in disease, but they express FoxP3 and therefore may contribute to immune regulation. In contrast, HIP-reactive T cells are proinflammatory and highly diabetogenic in an adoptive transfer model. Because the frequency of antigen-experienced HIP-reactive T cells increases over progression of disease, they may serve as biomarkers of autoimmune diabetes.

Anti-TCRβ mAb in Combination With Neurogenin3 Gene Therapy Reverses Established Overt Type 1 Diabetes in Female NOD Mice

Insulin-producing β cells in patients with type 1 diabetes (T1D) are destroyed by T lymphocytes. We investigated whether targeting the T-cell receptor (TCR) with a monoclonal antibody (mAb) abrogates T-cell response against residual and newly formed islets in overtly diabetic nonobese diabetic (NOD) mice. NOD mice with blood glucose levels of 250 to 350 mg/dL or 350 to 450 mg/dL were considered as new-onset or established overt diabetes, respectively. These diabetic NOD mice were transiently treated with an anti-TCR β chain (TCRβ) mAb, H57-597, for 5 days. Two weeks later, some NOD mice with established overt diabetes further received hepatic gene therapy using the islet-lineage determining gene Neurogenin3 (Ngn3), in combination with the islet growth factor gene betacellulin (Btc). We found that anti-TCRβ mAb (50 µg/d) reversed >80% new-onset diabetes in NOD mice for >14 weeks by reducing the number of effector T cells in the pancreas. However, anti-TCRβ mAb therapy alone reversed only ∼20% established overt diabetes in these mice. Among those overtly diabetic NOD mice whose diabetes was resistant to anti-TCRβ mAb treatment, ∼60% no longer had diabetes when they also received Ngn3-Btc hepatic gene transfer 2 weeks after initial anti-TCRβ mAb treatment. This combination of Ngn3-Btc gene therapy and anti-TCRβ mAb treatment induced the sustained formation of periportal insulin-producing cells in the liver of overtly diabetic mice. Therefore, directly targeting TCRβ with a mAb potently reverses new-onset T1D in NOD mice and protects residual and newly formed gene therapy-induced hepatic neo-islets from T-cell‒mediated destruction in mice with established overt diabetes.

Targeting memory T cells in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease that leads to progressive destruction of pancreatic beta cells. Compared to healthy controls, a characteristic feature of patients with T1D is the presence of self-reactive T cells with a memory phenotype. These autoreactive memory T cells in both the CD4(+) and CD8(+) compartments are likely to be long-lived, strongly responsive to antigenic stimulation with less dependence on costimulation for activation and clonal expansion, and comparatively resistant to suppression by regulatory T cells (Tregs) or downregulation by immune-modulating agents. Persistence of autoreactive memory T cells likely contributes to the difficulty in preventing disease progression in new-onset T1D and maintaining allogeneic islet transplants by regular immunosuppressive regimens. The majority of immune interventions that have demonstrated some success in preserving beta cell function in the new-onset period have been shown to deplete or modulate memory T cells. Based on these and other considerations, preservation of residual beta cells early after diagnosis or restoration of beta cell mass by use of stem cell or transplantation technology will require a successful strategy to control the autoreactive memory T cell compartment, which could include depletion, inhibition of homeostatic cytokines, induction of hyporesponsiveness, or a combination of these approaches.

Alefacept provides sustained clinical and immunological effects in new-onset type 1 diabetes patients

BACKGROUND

Type 1 diabetes (T1D) results from destruction of pancreatic β cells by autoreactive effector T cells. We hypothesized that the immunomodulatory drug alefacept would result in targeted quantitative and qualitative changes in effector T cells and prolonged preservation of endogenous insulin secretion by the remaining β cells in patients with newly diagnosed T1D.

METHODS

In a multicenter, randomized, double-blind, placebo-controlled trial, we compared alefacept (two 12-week courses of 15 mg/wk i.m., separated by a 12-week pause) with placebo in patients with recent onset of T1D. Endpoints were assessed at 24 months and included meal-stimulated C-peptide AUC, insulin use, hypoglycemic events, and immunologic responses.

RESULTS

A total of 49 patients were enrolled. At 24 months, or 15 months after the last dose of alefacept, both the 4-hour and the 2-hour C-peptide AUCs were significantly greater in the treatment group than in the control group (P = 0.002 and 0.015, respectively). Exogenous insulin requirements were lower (P = 0.002) and rates of major hypoglycemic events were about 50% reduced (P < 0.001) in the alefacept group compared with placebo at 24 months. There was no apparent between-group difference in glycemic control or adverse events. Alefacept treatment depleted CD4+ and CD8+ central memory T cells (Tcm) and effector memory T cells (Tem) (P < 0.01), preserved Tregs, increased the ratios of Treg to Tem and Tcm (P < 0.01), and increased the percentage of PD-1+CD4+ Tem and Tcm (P < 0.01).

CONCLUSIONS

In patients with newly diagnosed T1D, two 12-week courses of alefacept preserved C-peptide secretion, reduced insulin use and hypoglycemic events, and induced favorable immunologic profiles at 24 months, well over 1 year after cessation of therapy.

TRIAL REGISTRATION

https://clinicaltrials.gov/ NCT00965458.

FUNDING

NIH and Astellas.