Who let the dogs out? The ever-present threat of autoreactive T cells

Cell-Surface ZnT8 Antibody Prevents and Reverses Autoimmune Diabetes in Mice

Type 1 diabetes (T1D) is an autoimmune disease in which pathogenic lymphocytes target autoantigens expressed in pancreatic islets, leading to the destruction of insulin-producing β-cells. Zinc transporter 8 (ZnT8) is a major autoantigen abundantly present on the β-cell surface. This unique molecular target offers the potential to shield β-cells against autoimmune attacks in T1D. Our previous work showed that a monoclonal antibody (mAb43) against cell-surface ZnT8 could home in on pancreatic islets and prevent autoantibodies from recognizing β-cells. This study demonstrates that mAb43 binds to exocytotic sites on the β-cell surface, masking the antigenic exposure of ZnT8 and insulin after glucose-stimulated insulin secretion. In vivo administration of mAb43 to NOD mice selectively increased the proportion of regulatory T cells in the islet, resulting in complete and sustained protection against T1D onset as well as reversal of new-onset diabetes. The mAb43-induced self-tolerance was reversible after treatment cessation, and no adverse effects were exhibited during long-term monitoring. Our findings suggest that mAb43 masking of the antigenic exposure of β-cells suppresses the immunological cascade from B-cell antigen presentation to T cell-mediated β-cell destruction, providing a novel islet-targeted and antigen-specific immunotherapy to prevent and reverse clinical T1D.

ARTICLE HIGHLIGHTS

Antigen-specific immunotherapies in type 1 diabetes

Type 1 diabetes mellitus (T1DM) is an autoimmune disease caused by the destruction of pancreatic beta cells, in which immune system disorder plays an important role. Finding a cure for T1DM and restoring beta cell function has been a long-standing goal. Research has shown that immune regulation with pancreatic islet auto-antigens may be the most specific and safe treatment for T1DM. Immunological intervention using diabetogenic auto-antigens as a target can help identify T1DM in high-risk individuals by early screening of autoantibodies (AAbs) before the loss of pancreatic islet function and thus achieve primary prevention of T1DM. However, induction of self-tolerance in patients with pre-diabetes can also slow down the attack of autoimmunity, and achieve secondary prevention. Antigen-based immune therapy opens up new avenues for the prevention and treatment of T1DM. The zinc transporter 8 (ZnT8) protein, presents in the serum of pre-diabetic and diabetic patients, is immunogenic and can cause T1D autoimmune responses. ZnT8 has become a potential target of humoral autoimmunity; it is of great significance for the early diagnosis of T1D. ZnT8-specific CD8⁺ T cells can be detected in most T1DM patients, and play a key role in the progression of T1D. As an immunotherapy target, it can improve the dysfunction of beta cells in T1DM and provide new ideas for the treatment of T1D. In this review, we summarize research surrounding antigen-specific immunotherapies (ASI) over the past 10 years and the ZnT8 antigen as an autoimmune target to induce self-tolerance for T1DM.

Mechanisms underlying immune-related adverse events during checkpoint immunotherapy

Immune checkpoint (IC) proteins are some of the most important factors that tumor cells hijack to escape immune surveillance, and inhibiting ICs to enhance or relieve antitumor immunity has been proven efficient in tumor treatment. Immune checkpoint blockade (ICB) agents such as antibodies blocking programmed death (PD) 1, PD-1 ligand (PD-L) 1, and cytotoxic T lymphocyte-associated antigen (CTLA)-4 have been approved by the U.S. Food and Drug Administration (FDA) to treat several types of cancers. Although ICB agents have shown outstanding clinical success, and their application has continued to expand to additional tumor types in the past decade, immune-related adverse events (irAEs) have been observed in a wide range of patients who receive ICB treatment. Numerous studies have focused on the clinical manifestations and pathology of ICB-related irAEs, but the detailed mechanisms underlying irAEs remain largely unknown. Owing to the wide expression of IC molecules on distinct immune cell subpopulations and the fact that ICB agents generally affect IC-expressing cells, the influences of ICB agents on immune cells in irAEs need to be determined. Here, we discuss the expression and functions of IC proteins on distinct immune cells and the potential mechanism(s) related to ICB-targeted immune cell subsets in irAEs.

Immunoregulated insulitis and slow-progressing type 1 diabetes after duodenopancreatectomy

AIMS/HYPOTHESIS

We report the case of a woman who underwent a partial pancreatectomy for a serous cystadenoma when aged 56 years. She had been diagnosed with diabetes 6 years before and had Hashimoto's thyroiditis. Despite positive anti-GAD autoantibodies (GADA) and previous surgery, she was transiently weaned off long-acting insulin. Blood glucose levels remained well controlled with low-dose long-acting insulin. Insulin needs eventually increased 8 years after surgery, in conjunction with anti-zinc transporter 8 (ZnT8) seroconversion and decreasing residual C-peptide. We hypothesised that the surgical pancreas specimens and blood autoimmune T cell responses may provide correlates of this indolent clinical course.

METHODS

Beta and alpha cell area and insulitis were quantified on pancreas head tissue sections obtained at surgery. Blood T cell responses against beta cell antigens were analysed by enzyme-linked immunospot.

RESULTS

Pancreas sections displayed reduced beta cell and normal alpha cell area (0.27% and 0.85% of section area, respectively). High-grade insulitis was observed, mostly in insulin-containing islets, with a peri-insulitis pattern enriched in T cells positive for regulatory forkhead box protein 3 (FOXP3). In vitro challenge with beta cell antigens of circulating T cells collected 4 and 9 years after surgery revealed dominant and persistent IL-10 responses; IFN-γ responses increasing at 9 years, after anti-ZnT8 seroconversion, was observed.

CONCLUSIONS/INTERPRETATION

Despite persistent GADA and the histopathological finding of insulitis and decreased beta cell area 6 years after diabetes diagnosis, glycaemic control was maintained with low-dose insulin up to 8 years after surgery. Regulated T cell responses towards beta cell antigens and FOXP3-positive peri-insulitis suggest spontaneous long-term regulation of islet autoimmunity after substantial beta cell loss, and eventual autoimmune progression upon anti-ZnT8 seroconversion.

Presumption of innocence for beta cells: why are they vulnerable autoimmune targets in type 1 diabetes?

It is increasingly appreciated that the pathogenic mechanisms of type 1 diabetes involve both the autoimmune aggressors and their beta cell targets, which engage in a conflicting dialogue within and possibly outside the pancreas. Indeed, autoimmune CD8⁺ T cells, which are the final mediators of beta cell destruction, circulate at similar frequencies in type 1 diabetic and healthy individuals. Hence a universal state of 'benign' islet autoimmunity exists, and we hypothesise that its progression to type 1 diabetes may at least partially rely on a higher vulnerability of beta cells, which play a key, active role in disease development and/or amplification. We posit that this autoimmune vulnerability is rooted in some features of beta cell biology: the stress imposed by the high rate of production of insulin and other granule proteins, their dense vascularisation and the secretion of their products directly into the bloodstream. Gene variants that may predispose individuals to this vulnerability have been identified, e.g. MDA5, TYK2, PTPN2. They interact with environmental cues, such as viral infections, that may drive this genetic potential towards exacerbated local inflammation and progressive beta cell loss. On top of this, beta cells set up compensatory responses, such as the unfolded protein response, that become deleterious in the long term. The relative contribution of immune and beta cell drivers may vary and phenotypic subtypes (endotypes) are likely to exist. This dual view argues for the use of circulating biomarkers of both autoimmunity and beta cell stress for disease staging, and for the implementation of both immunomodulatory and beta cell-protective therapeutic strategies. Graphical abstract.

Gut Microbiota in T1DM-Onset Pediatric Patients: Machine-Learning Algorithms to Classify Microorganisms as Disease Linked

AIMS

The purpose of this work is to find the gut microbial fingerprinting of pediatric patients with type 1 diabetes.

METHODS

The microbiome of 31 children with type 1 diabetes at onset and of 25 healthy children was determined using multiple polymorphic regions of the 16S ribosomal RNA. We performed machine-learning analyses and metagenome functional analysis to identify significant taxa and their metabolic pathways content.

RESULTS

Compared with healthy controls, patients showed a significantly higher relative abundance of the following most important taxa: Bacteroides stercoris, Bacteroides fragilis, Bacteroides intestinalis, Bifidobacterium bifidum, Gammaproteobacteria and its descendants, Holdemania, and Synergistetes and its descendants. On the contrary, the relative abundance of Bacteroides vulgatus, Deltaproteobacteria and its descendants, Parasutterella and the Lactobacillus, Turicibacter genera were significantly lower in patients with respect to healthy controls. The predicted metabolic pathway more associated with type 1 diabetes patients concerns "carbon metabolism," sugar and iron metabolisms in particular. Among the clinical variables considered, standardized body mass index, anti-insulin autoantibodies, glycemia, hemoglobin A1c, Tanner stage, and age at onset emerged as most significant positively or negatively correlated with specific clusters of taxa.

CONCLUSIONS

The relative abundance and supervised analyses confirmed the importance of B stercoris in type 1 diabetes patients at onset and showed a relevant role of Synergistetes and its descendants in patients with respect to healthy controls. In general the robustness and coherence of the showed results underline the relevance of studying the microbioma using multiple polymorphic regions, different types of analysis, and different approaches within each analysis.

Peptide-Based Vaccination Therapy for Rheumatic Diseases

Rheumatic diseases are extremely heterogeneous diseases with substantial risks of morbidity and mortality, and there is a pressing need in developing more safe and cost-effective treatment strategies. Peptide-based vaccination is a highly desirable strategy in treating noninfection diseases, such as cancer and autoimmune diseases, and has gained increasing attentions. This review is aimed at providing a brief overview of the recent advances in peptide-based vaccination therapy for rheumatic diseases. Tremendous efforts have been made to develop effective peptide-based vaccinations against rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), while studies in other rheumatic diseases are still limited. Peptide-based active vaccination against pathogenic cytokines such as TNF-α and interferon-α (IFN-α) is shown to be promising in treating RA or SLE. Moreover, peptide-based tolerogenic vaccinations also have encouraging results in treating RA or SLE. However, most studies available now have been mainly based on animal models, while evidence from clinical studies is still lacking. The translation of these advances from experimental studies into clinical therapy remains impeded by some obstacles such as species difference in immunity, disease heterogeneity, and lack of safe delivery carriers or adjuvants. Nevertheless, advances in high-throughput technology, bioinformatics, and nanotechnology may help overcome these impediments and facilitate the successful development of peptide-based vaccination therapy for rheumatic diseases.

Vaccination against autoimmune diseases moves closer to the clinic

Biologicals, e.g. TNF inhibitors, have improved dramatically the efficacy of medical interventions in autoimmune diseases, such as in rheumatoid arthritis (RA). However, although progressive inflammation can be halted in this way, no drug-free remissions or lasting cures are reached. For this to become real, therapies based on induction antigen-specific immune tolerance are sought. This review describes mechanisms of tolerance and the current possibilities for induction of therapeutic tolerance through antigen-specific vaccination approaches. And despite the fact that for various diseases the search for appropriate autoantigens is ongoing, pioneering studies are now already developed that use more broadly inflammation associated antigens. Through their capacity to preferentially induce regulatory T cells, heat shock proteins are an attractive source of such broadly inflammation associated antigens.

CD8+ T cells from patients with narcolepsy and healthy controls recognize hypocretin neuron-specific antigens

Narcolepsy Type 1 (NT1) is a neurological sleep disorder, characterized by the loss of hypocretin/orexin signaling in the brain. Genetic, epidemiological and experimental data support the hypothesis that NT1 is a T-cell-mediated autoimmune disease targeting the hypocretin producing neurons. While autoreactive CD4+ T cells have been detected in patients, CD8+ T cells have only been examined to a minor extent. Here we detect CD8+ T cells specific toward narcolepsy-relevant peptides presented primarily by NT1-associated HLA types in the blood of 20 patients with NT1 as well as in 52 healthy controls, using peptide-MHC-I multimers labeled with DNA barcodes. In healthy controls carrying the disease-predisposing HLA-DQB1*06:02 allele, the frequency of autoreactive CD8+ T cells was lower as compared with both NT1 patients and HLA-DQB1*06:02-negative healthy individuals. These findings suggest that a certain level of CD8+ T-cell reactivity combined with HLA-DQB1*06:02 expression is important for NT1 development.