Neoantigens and Microenvironment in Type 1 Diabetes: Lessons from Antitumor Immunity

Induction of islet autoimmunity to defective ribosomal product of the insulin gene as neoantigen after anti-cancer immunotherapy leading to autoimmune diabetes

Introduction

The autoimmune response in type 1 diabetes (T1D), in which the beta cells expressing aberrant or modified proteins are killed, resembles an effective antitumor response. Defective ribosomal protein products in tumors are targets of the anti-tumor immune response that is unleashed by immune checkpoint inhibitor (ICI) treatment in cancer patients. We recently described a defective ribosomal product of the insulin gene (INS-DRiP) that is expressed in stressed beta cells and targeted by diabetogenic T cells. T1D patient-derived INS-DRiP specific T cells can kill beta cells and are present in the insulitic lesion. T cells reactive to INS-DRiP epitopes are part of the normal T cell repertoire and are believed to be kept in check by immune regulation without causing autoimmunity.

Method

T cell autoreactivity was tested using a combinatorial HLA multimer technology measuring a range of epitopes of islet autoantigens and neoantigen INS-DRiP. INS-DRiP expression in human pancreas and insulinoma sections was tested by immunohistochemistry.

Results

Here we report the induction of islet autoimmunity to INS-DRiP and diabetes after ICI treatment and successful tumor remission. Following ICI treatment, T cells of the cancer patient were primed against INS-DRiP among other diabetogenic antigens, while there was no sign of autoimmunity to this neoantigen before ICI treatment. Next, we demonstrated the expression of INS-DRiP as neoantigen in both pancreatic islets and insulinoma by staining with a monoclonal antibody to INS-DRiP.

Discussion

These results bridge cancer and T1D as two sides of the same coin and point to neoantigen expression in normal islets and insulinoma that may serve as target of both islet autoimmunity and tumor-related autoimmunity.

Oral gavage delivery of Cornus officinalis extract delays type 1 diabetes onset and hyperglycemia in non-obese diabetic (NOD) mice

Type 1 diabetes (T1D) is an autoimmune disease initiated by genetic predisposition and environmental influences, which result in the specific destruction of insulin-producing pancreatic β-cells. Currently, there are over 1.6 million cases of T1D in the United States with a worldwide incidence rate that has been increasing since 1990. Here, we examined the effect of Cornus officinalis (CO), a well-known ethnopharmacological agent, on a T1D model of the non-obese diabetic (NOD) mouse. A measured dose of CO extract was delivered into 10-week-old NOD mice by oral gavage for 15 weeks. T1D incidence and hyperglycemia were significantly lower in the CO-treated group as compared to the water gavage (WT) and a no handling or treatment control group (NHT) following treatment. T1D onset per group was 30%, 60% and 86% for the CO, WT and NHT groups, respectively. Circulating C-peptide was higher, and pancreatic insulitis was decreased in non-T1D CO-treated mice. Our findings suggest that CO may have therapeutic potential as both a safe and effective interventional agent to slow early stage T1D progression.

Shedding new light on the role of ERAP1 in Type 1 diabetes: A perspective on disease management

Type 1 diabetes mellitus (T1D) is a multifactorial organ specific autoimmune disease which originates from the destruction of insulin-producing beta cells within the pancreatic islets by autoreactive CD8⁺ T lymphocytes. The autoimmune responses are raised against autoantigenic peptides presented in the context of the Major Histocompatibility Complex (MHC) class I molecules. Peptides are generated in the cytoplasm of the beta cell by degradation through the proteasome activity and other proteases. Proteolytic intermediate protein fragments are then vehicled into the endoplasmic reticulum (ER) by transporters associated with antigen processing TAP1 and TAP2. In the ER, Endoplasmic Reticulum Aminopeptidase 1 (ERAP1) and 2 (ERAP2) shape the intermediate proteins to produce the optimal peptide size for loading into the MHC class I molecules. Subsequently complexes are shuttled to the cell surface for antigen presentation. Genome Wide Association Studies (GWAS) have identified different SNPs of ERAP1 associated to several autoimmune diseases and in particular the T1D-related ERAP1 SNP rs30187 encoding for K528R ERAP1. An association between the ER stress and the increased exposure of beta cells to the immune system has been hypothesized to further contribute to the etiopathogenesis. In particular in a recent study by Thomaidou et al. 2020 (doi: https://doi.org/10.2337/db19-0984) the posttranscriptional regulation of ERAP1 is shown to shaping the recognition of the preproinsulin (PPI) signal peptide by cytotoxic T lymphocytes. In the light of foregoing ERAP1 inhibitors could potentially prevent the activation of epitope-specific autoimmune-promoting T cells and their cytokine production; further regulating ERAP1 expression at posttranscriptional level under stress conditions of the beta cells could help to reverse autoimmune process through limiting epitope-presentation to autoreactive T cells. In this article we provide a perspective on the role of ERAP1 as implicated in the pathogenesis of insulin-dependent diabetes mellitus by reviewing studies reported in literature and discussing our own experimental evidence.

Single-cell RNA sequencing highlights the roles of C1QB and NKG7 in the pancreatic islet immune microenvironment in type 1 diabetes mellitus

Single-cell RNA sequencing (scRNA-seq) technology is a powerful tool for characterizing individual cells and elucidating biological mechanisms at the cellular level. Using this technology, this study focuses on the mechanism of C1QB and NKG7 in pancreatic islet immune microenvironment in type 1 diabetes mellitus (T1DM). T1DM-related scRNA-seq data were downloaded from GEO database, followed by batch effect removal, cluster analysis, cell annotation and enrichment analysis. Thereafter, T1DM-related Bulk RNA-seq data were downloaded from GEO database. The infiltrating immune cell abundance was estimated and its correlation with the expression of immune cell marker genes was determined. Functional assays were performed in a constructed rat model of T1DM and cultured monocytes and lymphocytes for further validation. A large number of highly variable genes were found in pancreatic islet samples in T1DM. T1DM islet-derived cells may consist of 14 cell types. Macrophages and T lymphocytes were the major cells in pancreatic islet immune microenvironment. C1QB and NKG7 may be the key genes affecting macrophages and T lymphocytes, respectively. Silencing C1QB inhibited the differentiation of monocytes into macrophages and reduced the number of macrophages. Silencing NKG7 prevented T lymphocyte activation and proliferation. In vivo data confirmed that silencing C1QB and NKG7 reduced the number of macrophages and T lymphocytes in the pancreatic islet of T1DM rats, respectively, and alleviated pancreatic islet β-cell damage. Overall, C1QB and NKG7 can increase the number of macrophages and T lymphocytes, respectively, causing pancreatic islet β-cell damage and promoting T1DM in rats.

From Disease and Patient Heterogeneity to Precision Medicine in Type 1 Diabetes

Type 1 diabetes (T1D) remains a devastating disease that requires much effort to control. Life-long daily insulin injections or an insulin pump are required to avoid severe complications. With many factors contributing to disease onset, T1D is a complex disease to cure. In this review, the risk factors, pathophysiology and defect pathways are discussed. Results from (pre)clinical studies are highlighted that explore restoration of insulin production and reduction of autoimmunity. It has become clear that treatment responsiveness depends on certain pathophysiological or genetic characteristics that differ between patients. For instance, age at disease manifestation associated with efficacy of immune intervention therapies, such as depleting islet-specific effector T cells or memory B cells and increasing immune regulation. The new challenge is to determine in whom to apply which intervention strategy. Within patients with high rates of insulitis in early T1D onset, therapy depleting T cells or targeting B lymphocytes may have a benefit, whereas slow progressing T1D in adults may be better served with more sophisticated, precise and specific disease modifying therapies. Genetic barcoding and immune profiling may help determining from which new T1D endotypes patients suffer. Furthermore, progressed T1D needs replenishment of insulin production besides autoimmunity reversal, as too many beta cells are already lost or defect. Recurrent islet autoimmunity and allograft rejection or necrosis seem to be the most challenging obstacles. Since beta cells are highly immunogenic under stress, treatment might be more effective with stress reducing agents such as glucagon-like peptide 1 (GLP-1) analogs. Moreover, genetic editing by CRISPR-Cas9 allows to create hypoimmunogenic beta cells with modified human leukocyte antigen (HLA) expression that secrete immune regulating molecules. Given the differences in T1D between patients, stratification of endotypes in clinical trials seems essential for precision medicines and clinical decision making.

Long RNA Sequencing and Ribosome Profiling of Inflamed β-Cells Reveal an Extensive Translatome Landscape

Type 1 diabetes (T1D) is an autoimmune disease characterized by autoreactive T cell-mediated destruction of the insulin-producing pancreatic β-cells. Increasing evidence suggest that the β-cells themselves contribute to their own destruction by generating neoantigens through the production of aberrant or modified proteins that escape central tolerance. We recently demonstrated that ribosomal infidelity amplified by stress could lead to the generation of neoantigens in human β-cells, emphasizing the participation of nonconventional translation events in autoimmunity, as occurring in cancer or virus-infected tissues. Using a transcriptome-wide profiling approach to map translation initiation start sites in human β-cells under standard and inflammatory conditions, we identify a completely new set of polypeptides derived from noncanonical start sites and translation initiation within long noncoding RNA. Our data underline the extreme diversity of the β-cell translatome and may reveal new functional biomarkers for β-cell distress, disease prediction and progression, and therapeutic intervention in T1D.

Endoplasmic Reticulum-Mitochondria Crosstalk and Beta-Cell Destruction in Type 1 Diabetes

Beta-cell destruction in type 1 diabetes (T1D) results from the combined effect of inflammation and recurrent autoimmunity. In response to inflammatory signals, beta-cells engage adaptive mechanisms where the endoplasmic reticulum (ER) and mitochondria act in concert to restore cellular homeostasis. In the recent years it has become clear that this adaptive phase may trigger the development of autoimmunity by the generation of autoantigens recognized by autoreactive CD8 T cells. The participation of the ER stress and the unfolded protein response to the increased visibility of beta-cells to the immune system has been largely described. However, the role of the other cellular organelles, and in particular the mitochondria that are central mediator for beta-cell survival and function, remains poorly investigated. In this review we will dissect the crosstalk between the ER and mitochondria in the context of T1D, highlighting the key role played by this interaction in beta-cell dysfunctions and immune activation, especially through regulation of calcium homeostasis, oxidative stress and generation of mitochondrial-derived factors.

Endocrine Autoimmune Disease as a Fragility of Immune Surveillance against Hypersecreting Mutants

Some endocrine organs are frequent targets of autoimmune attack. Here, we addressed the origin of autoimmune disease from the viewpoint of feedback control. Endocrine tissues maintain mass through feedback loops that balance cell proliferation and removal according to hormone-driven regulatory signals. We hypothesized the existence of a dedicated mechanism that detects and removes mutant cells that missense the signal and therefore hyperproliferate and hypersecrete with potential to disrupt organismal homeostasis. In this mechanism, hypersecreting cells are preferentially eliminated by autoreactive T cells at the cost of a fragility to autoimmune disease. The "autoimmune surveillance of hypersecreting mutants" (ASHM) hypothesis predicts the presence of autoreactive T cells in healthy individuals and the nature of self-antigens as peptides from hormone secretion pathway. It explains why some tissues get prevalent autoimmune disease, whereas others do not and instead show prevalent mutant-expansion disease (e.g., hyperparathyroidism). The ASHM hypothesis is testable, and we discuss experimental follow-up.

β-Cell Stress Shapes CTL Immune Recognition of Preproinsulin Signal Peptide by Posttranscriptional Regulation of Endoplasmic Reticulum Aminopeptidase 1

The signal peptide of preproinsulin is a major source for HLA class I autoantigen epitopes implicated in CD8 T cell (CTL)-mediated β-cell destruction in type 1 diabetes (T1D). Among them, the 10-mer epitope located at the C-terminal end of the signal peptide was found to be the most prevalent in patients with recent-onset T1D. While the combined action of signal peptide peptidase and endoplasmic reticulum (ER) aminopeptidase 1 (ERAP1) is required for processing of the signal peptide, the mechanisms controlling signal peptide trimming and the contribution of the T1D inflammatory milieu on these mechanisms are unknown. Here, we show in human β-cells that ER stress regulates ERAP1 gene expression at posttranscriptional level via the IRE1α/miR-17-5p axis and demonstrate that inhibition of the IRE1α activity impairs processing of preproinsulin signal peptide antigen and its recognition by specific autoreactive CTLs during inflammation. These results underscore the impact of ER stress in the increased visibility of β-cells to the immune system and position the IRE1α/miR-17 pathway as a central component in β-cell destruction processes and as a potential target for the treatment of autoimmune T1D.

Setting the Stage for Islet Autoimmunity in Type 2 Diabetes: Obesity-Associated Chronic Systemic Inflammation and Endoplasmic Reticulum (ER) Stress

Islet autoimmunity has been identified as a component of both type 1 (T1D) and type 2 (T2D) diabetes, but the pathway through which islet autoimmunity develops in T1D and T2D may be different. Acknowledging the presence of islet autoimmunity in the pathophysiology of T2D, a historically nonautoimmune metabolic disease, would pave the way for important changes in classifications of and therapeutic options for T2D. In order to fully appreciate the importance of islet autoimmunity in T2D, the underlying mechanisms for immune system activation need to be explored. In this review, we focus on the potential origin of immune system activation (innate and adaptive) leading to the development of islet autoimmunity in T2D.

β-Cell Maturation and Identity in Health and Disease

The exponential increase of patients with diabetes mellitus urges for novel therapeutic strategies to reduce the socioeconomic burden of this disease. The loss or dysfunction of insulin-producing β-cells, in patients with type 1 and type 2 diabetes respectively, put these cells at the center of the disease initiation and progression. Therefore, major efforts have been taken to restore the β-cell mass by cell-replacement or regeneration approaches. Implementing novel therapies requires deciphering the developmental mechanisms that generate β-cells and determine the acquisition of their physiological phenotype. In this review, we summarize the current understanding of the mechanisms that coordinate the postnatal maturation of β-cells and define their functional identity. Furthermore, we discuss different routes by which β-cells lose their features and functionality in type 1 and 2 diabetic conditions. We then focus on potential mechanisms to restore the functionality of those β-cell populations that have lost their functional phenotype. Finally, we discuss the recent progress and remaining challenges facing the generation of functional mature β-cells from stem cells for cell-replacement therapy for diabetes treatment.

Fulminant type 1 diabetes associated with Isolated ACTH deficiency induced by anti-programmed cell death 1 antibody-insight into the pathogenesis of autoimmune endocrinopathy

Therapeutic blocking antibodies against programmed death 1 (PD1) and cytotoxic T-lymphocyte antigen 4 (CTLA4) are applied for advanced cancer therapy, but induce a wide range of immune-related adverse events. In our recent case of a 52-year-old female doctor suffering from breast cancer having metastasized to the lung and liver, it was decided to use nivolumab to prevent the disease progressing after excisional surgeries and multiple chemotherapies. One month after completing the nivolumab course, fatigue, hypoglycemia and hypotension developed and isolated ACTH deficiency (IAD) was diagnosed. A further month later, under steroid supplementation, hyperglycemia emerged alongside thirst and polydipsia, prompting a diagnosis of fulminant type 1 diabetes (FT1D). Her susceptibility to type 1 diabetes was examined by HLA haplotype and CTLA4 gene polymorphism analyses. Polymorphisms CT60G>A and +49G>A in CTLA4 both generated a GG genotype. Our patient manifested one of the rarest combinations of autoimmune disease induced by nivolumab. Whereas the HLA haplotype was unsusceptible to autoimmune type 1 diabetes, polymorphisms of CTLA4, the antibody of which frequently causes hypophysitis, were susceptible to FT1D. Peripheral modulation of activated T cells, mainly by PD-1 antibodies, induced FT1D associated with IAD in patients with CTLA4 polymorphism. This case reveals hints of the T-cell etiology in T1D and evidence of CTLA4 involvement in IAD.

Antigen-based immune modulation therapy for type 1 diabetes: the era of precision medicine

Precision medicine has emerged as a mantra for therapeutic approaches to complex diseases. The defining concept relies on a detailed insight into disease pathogenesis and therapeutic mechanism. Although the type 1 diabetes field has gained new insights into disease endotypes and indications of efficacy for several therapies, none of these is yet licensed, partly because of immune suppressive side-effects beyond control of islet autoimmunity. New strategies designed to regulate the immune system continue to emerge as basic science discoveries are made, including the use of antigen-based immunotherapies. A single agent or approach seems unlikely to halt disease progression in all people with or at risk of type 1 diabetes; as such, tailored methods relying on patient subgroups and knowledge of disease endotypes are gaining attention. Recent insights into disease mechanisms and emerging trial data are being translated into opportunities for tissue-specific prevention of progressive loss of β-cell function and survival. Results so far point to feasibility, safety, and tolerability of administration of islet autoantigens and peptides thereof into recipients with or at risk of type 1 diabetes. Findings from mechanistic studies suggest favourable changes in islet autoimmunity, with signs of immune regulation. Major challenges remain, including those related to dose and dosing frequency, route of administration, and use of adjuvants. However, the first steps towards tissue-specific and personalised medicine in type 1 diabetes have been made, which will guide future studies into induction of immune tolerance to intervene in the initiation and progression of islet autoimmunity and disease.

CD33+ HLA-DR- Myeloid-Derived Suppressor Cells Are Increased in Frequency in the Peripheral Blood of Type1 Diabetes Patients with Predominance of CD14+ Subset

INTRODUCTION:

Type 1 Diabetes Mellitus (T1D) is an autoimmune disease that results from the destruction of insulin-producing beta cells of the pancreas by autoreactive T cells. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that can potently suppress T cell responses.

AIM:

To detect the presence of MDSCs in T1D and compare their percentage in T1D versus healthy individuals.

METHOD:

Thirty T1D patients were included in the study. Diabetic patients with nephropathy (n = 18) and diabetic patients without nephropathy (n = 12). A control group of healthy individuals (n = 30) were also included. CD33⁺ and HLA-DR– markers were used to identify MDSCs by flow cytometry. CD14 positive and negative MDSCs subsets were also identified.

RESULTS:

MDSCs was significantly increased in T1D than the control group and diabetic patient with nephropathy compared to diabetic patients without nephropathy. M-MDSCs (CD14⁺ CD33⁺ HLA–DR⁻) were the most abundant MDSCs subpopulation in all groups, however their percentage decrease in T1D than the control group.

CONCLUSION:

MDSCs are increased in the peripheral blood of T1D with a predominance of the CD14⁺ MDSCs subset. Future studies are needed to test the immune suppression function of MDSCs in T1D.

Optimizing Multiplexed Detections of Diabetes Antibodies via Quantitative Microfluidic Droplet Array

Sensitive, single volume detections of multiple diabetes antibodies can provide immunoprofiling and early screening of at-risk patients. To advance the state-of-the-art suspension assays for diabetes antibodies, porous hydrogel droplets are leveraged in microfluidic serpentine arrays to enhance reagent transport. This spatially multiplexed assay is applied to the detection of antibodies against insulin, glutamic acid decarboxylase, and insulinoma-associated protein 2. Optimization of assay protocol results in a shortened assay time of 2 h, with better than 20 pg mL Supporting Information detection limits across all three antibodies. Specificity and cross-reactivity tests show negligible background, nonspecific antibody-antigen, and nonspecific antibody-antibody bindings. Multiplexed detections are able to measure within 15% of target concentrations from low to high ranges. The technique enables quantifications of as little as 8000 molecules in each 500 µm droplet in a single volume, multiplexed assay format, a breakthrough necessary for the adoption of diabetes panels for clinical screening and monitoring in the future.

Combination Immunotherapy for Type 1 Diabetes

PURPOSE OF REVIEW

Type 1 diabetes (T1D) is an autoimmune disease marked by β-cell destruction. Immunotherapies for T1D have been investigated since the 1980s and have focused on restoration of tolerance, T cell or B cell inhibition, regulatory T cell (Treg) induction, suppression of innate immunity and inflammation, immune system reset, and islet transplantation. The purpose of this review is to provide an overview and lessons learned from single immunotherapy trials, describe recent and ongoing combination immunotherapy trials, and provide perspectives on strategies for future combination clinical interventions aimed at preserving insulin secretion in T1D.

RECENT FINDINGS

Combination immunotherapies have had mixed results in improving short-term glycemic control and insulin secretion in recent-onset T1D. A handful of studies have successfully reached their primary end-point of improved insulin secretion in recent-onset T1D. However, long-term improvements glycemic control and the restoration of insulin independence remain elusive. Future interventions should focus on strategies that combine immunomodulation with efforts to alleviate β-cell stress and address the formation of antigens that activate autoimmunity.

The Clinical Course of Patients with Preschool Manifestation of Type 1 Diabetes Is Independent of the HLA DR-DQ Genotype

Introduction: Major histocompatibility complex class II genes are considered major genetic risk factors for autoimmune diabetes. We analysed Human Leukocyte Antigen (HLA) DR and DQ haplotypes in a cohort with early-onset (age < 5 years), long term type 1 diabetes (T1D) and explored their influence on clinical and laboratory parameters. Methods: Intermediate resolution HLA-DRB1, DQA1 and DQB1 typing was performed in 233 samples from the German Paediatric Diabetes Biobank and compared with a local control cohort of 19,544 cases. Clinical follow-up data of 195 patients (diabetes duration 14.2 ± 2.9 years) and residual C-peptide levels were compared between three HLA risk groups using multiple linear regression analysis. Results: Genetic variability was low, 44.6% (104/233) of early-onset T1D patients carried the highest-risk genotype HLA-DRB1*03:01-DQA1*05:01-DQB1*02:01/DRB1*04-DQA1*03:01-DQB1*03:02 (HLA-DRB1*04 denoting 04:01/02/04/05), and 231 of 233 individuals carried at least one of six risk haplotypes. Comparing clinical data between the highest (n = 83), moderate (n = 106) and low risk (n = 6) genotypes, we found no difference in age at diagnosis (mean age 2.8 ± 1.1 vs. 2.8 ± 1.2 vs. 3.2 ± 1.5 years), metabolic control, or frequency of associated autoimmune diseases between HLA risk groups (each p > 0.05). Residual C-peptide was detectable in 23.5% and C-peptide levels in the highest-risk group were comparable to levels in moderate to high risk genotypes. Conclusion: In this study, we saw no evidence for a different clinical course of early-onset T1D based on the HLA genotype within the first ten years after manifestation.

Autoimmunity against a defective ribosomal insulin gene product in type 1 diabetes

Identification of epitopes that are recognized by diabetogenic T cells and cause selective beta cell destruction in type 1 diabetes (T1D) has focused on peptides originating from native beta cell proteins. Translational errors represent a major potential source of antigenic peptides to which central immune tolerance is lacking. Here, we describe an alternative open reading frame within human insulin mRNA encoding a highly immunogenic polypeptide that is targeted by T cells in T1D patients. We show that cytotoxic T cells directed against the N-terminal peptide of this nonconventional product are present in the circulation of individuals diagnosed with T1D, and we provide direct evidence that such CD8⁺ T cells are capable of killing human beta cells and thereby may be diabetogenic. This study reveals a new source of nonconventional polypeptides that act as self-epitopes in clinical autoimmune disease.

A roadmap of the generation of neoantigens as targets of the immune system in type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease characterized by the selective destruction of the insulin-producing beta cells. Beta cell dysfunction caused by an inflammatory microenvironment is believed to trigger the peripheral activation of CD4 and CD8 autoreactive T cells. This review will compile post-transcriptional and post-translational modifications (PTM) involved in the generation of beta cell neoantigens and proposes a reconstruction of the sequence of events connecting environmental changes and autoimmunity.

Prohibitin in Adipose and Immune Functions

Prohibitin (PHB) was discovered in a quest to find genes with antiproliferative functions. However, the attribute of PHB that is responsible for its antiproliferative function remains elusive. Meanwhile, recent studies have established PHB as a pleiotropic protein with roles in metabolism, immunity, and senescence. PHB has cell compartment-specific functions, acting as a scaffolding protein in mitochondria, an adaptor molecule in membrane signaling, and a transcriptional coregulator in the nucleus. However, it remains unclear whether different functions and locations of PHB are interrelated or independent from each other, or if PHB works in a tissue-specific manner. Here, we discuss new findings on the role of PHB in adipose-immune interaction and an unexpected role in sex differences in adipose and immune functions.