Preexisting insulin autoantibodies predict efficacy of otelixizumab in preserving residual β-cell function in recent-onset type 1 diabetes

Islet autoantibodies as precision diagnostic tools to characterize heterogeneity in type 1 diabetes: a systematic review

BACKGROUND

Islet autoantibodies form the foundation for type 1 diabetes (T1D) diagnosis and staging, but heterogeneity exists in T1D development and presentation. We hypothesized that autoantibodies can identify heterogeneity before, at, and after T1D diagnosis, and in response to disease-modifying therapies.

METHODS

We systematically reviewed PubMed and EMBASE databases (6/14/2022) assessing 10 years of original research examining relationships between autoantibodies and heterogeneity before, at, after diagnosis, and in response to disease-modifying therapies in individuals at-risk or within 1 year of T1D diagnosis. A critical appraisal checklist tool for cohort studies was modified and used for risk of bias assessment.

RESULTS

Here we show that 152 studies that met extraction criteria most commonly characterized heterogeneity before diagnosis (91/152). Autoantibody type/target was most frequently examined, followed by autoantibody number. Recurring themes included correlations of autoantibody number, type, and titers with progression, differing phenotypes based on order of autoantibody seroconversion, and interactions with age and genetics. Only 44% specifically described autoantibody assay standardization program participation.

CONCLUSIONS

Current evidence most strongly supports the application of autoantibody features to more precisely define T1D before diagnosis. Our findings support continued use of pre-clinical staging paradigms based on autoantibody number and suggest that additional autoantibody features, particularly in relation to age and genetic risk, could offer more precise stratification. To improve reproducibility and applicability of autoantibody-based precision medicine in T1D, we propose a methods checklist for islet autoantibody-based manuscripts which includes use of precision medicine MeSH terms and participation in autoantibody standardization workshops.

Effect of Immunotherapy on C-peptide Levels in Patients With Type I Diabetes Mellitus: A Systematic Review of Randomized Controlled Trials

Type 1 diabetes mellitus is an autoimmune condition characterized by insulin deficiency resulting from loss of function of beta cells in the pancreas, leading to hyperglycemia and associated long-term systemic complications and even death. Immunotherapy demonstrates beta cell function-preserving potential; however, its impact on C-peptide levels, a definitive biomarker of beta cell function, and endogenous insulin secretion remain unclear. A systematic review of various immunotherapeutic interventions is hence needed for a comprehensive assessment of their effectiveness as well as identifying research gaps and influencing future research and clinical decisions. An extensive literature search was done in PubMed, Scopus, and Cochrane Library databases using precise keywords and filters to identify relevant studies. Three independent reviewers assessed eligibility according to predetermined eligibility criteria, and data was extracted. The Cochrane risk of bias assessment tool (RoB 2.0) was used to evaluate the quality and validity of the included studies. A senior reviewer resolved discrepancies and differences of opinion between independent reviewers. A total of 11 studies were included, with 1464 study participants. Both Phase II and III trials were included. Within the included studies, four studies assessed the anti-CD3 monoclonal antibody otelixizumab as an intervention. Another anti-CD3 monoclonal antibody, teplizumab, was assessed as an intervention in four studies, whereas two studies assessed the anti-CD20 antibody rituximab and one study assessed abatacept as its interventional drug. Otelixizumab demonstrated benefits at higher doses but was associated with adverse effects like Ebstein-Barr virus reactivation and cytomegalovirus infection, while at lower doses it failed to show a significant difference in C-peptide levels or glycosylated hemoglobin (HbA1c). Teplizumab, on the other hand, showed promise in reducing C-peptide loss and exogenous insulin requirements and was associated with adverse events such as rash, lymphopenia, urinary tract infection, and cytokine release syndrome. However, these reactions were only associated with therapy initiation, and they subsided on their own. Rituximab improved C-peptide responses, and abatacept therapy demonstrated reduced loss of C-peptide, improved C-peptide levels, and lowered HbA1c. Teplizumab, rituximab, otelixizumab, and abatacept show potential for preserving beta cell function by reducing C-peptide loss in patients with type I diabetes mellitus. However, careful monitoring of adverse reactions, particularly viral infections and cytokine release syndrome, is necessary for the safe implementation of these therapies.

Baseline plasma proinsulin response to glucose for predicting therapeutic response to otelixizumab in recent-onset type 1 diabetes

AIMS

In recent-onset type 1 diabetes, clamp-derived C-peptide predicts good response to anti-CD3. Elevated proinsulin and proinsulin/C-peptide ratio (PI/CP) suggest increased metabolic/inflammatory beta cell burden. We reanalyzed trial data to compare the ability of baseline acutely glucose-stimulated proinsulin, C-peptide and PI/CP to predict functional outcome.

METHODS

Eighty recent-onset type 1 diabetes patients participated in the placebo-controlled otelixizumab (GSK; NCT00627146) trial. Hyperglycemic clamps were performed at baseline, 6, 12 and 18 months, involving 3 h of induced euglycemia, followed by acutely raising and maintaining glycemia to ≥ 10 mmol/l for 140 min. Plasma proinsulin, C-peptide and PI/CP were determined after acute (minute 0 at 10 mmol/l; PI0, CP0, PI/CP0) and sustained glucose stimulation (AUC between minutes 60-140). Outcome was assessed as change in AUC60-140 C-peptide from baseline.

RESULTS

In multiple linear regression, higher baseline (≥median [P50]) PI0 independently predicted preservation of beta cell function in response to anti-CD3 and interacted significantly with IAA. During follow-up, anti-CD3 tempered a further increase in PI/CP0, but not in PI0. CP0 outperformed PI0 and PI/CP0 for post-treatment monitoring.

CONCLUSIONS

In recent-onset type 1 diabetes, elevated acutely glucose-stimulated proinsulin may complement or replace acutely or sustainedly stimulated C-peptide release for identifying good responders to anti-CD3, but not as outcome measure.

Disease-modifying therapies and features linked to treatment response in type 1 diabetes prevention: a systematic review

BACKGROUND

Type 1 diabetes (T1D) results from immune-mediated destruction of insulin-producing beta cells. Prevention efforts have focused on immune modulation and supporting beta cell health before or around diagnosis; however, heterogeneity in disease progression and therapy response has limited translation to clinical practice, highlighting the need for precision medicine approaches to T1D disease modification.

METHODS

To understand the state of knowledge in this area, we performed a systematic review of randomized-controlled trials with ≥50 participants cataloged in PubMed or Embase from the past 25 years testing T1D disease-modifying therapies and/or identifying features linked to treatment response, analyzing bias using a Cochrane-risk-of-bias instrument.

RESULTS

We identify and summarize 75 manuscripts, 15 describing 11 prevention trials for individuals with increased risk for T1D, and 60 describing treatments aimed at preventing beta cell loss at disease onset. Seventeen interventions, mostly immunotherapies, show benefit compared to placebo (only two prior to T1D onset). Fifty-seven studies employ precision analyses to assess features linked to treatment response. Age, beta cell function measures, and immune phenotypes are most frequently tested. However, analyses are typically not prespecified, with inconsistent methods of reporting, and tend to report positive findings.

CONCLUSIONS

While the quality of prevention and intervention trials is overall high, the low quality of precision analyses makes it difficult to draw meaningful conclusions that inform clinical practice. To facilitate precision medicine approaches to T1D prevention, considerations for future precision studies include the incorporation of uniform outcome measures, reproducible biomarkers, and prespecified, fully powered precision analyses into future trial design.

Type 1 Diabetes Prevention: a systematic review of studies testing disease-modifying therapies and features linked to treatment response

Background

Type 1 diabetes (T1D) results from immune-mediated destruction of insulin-producing beta cells. Efforts to prevent T1D have focused on modulating immune responses and supporting beta cell health; however, heterogeneity in disease progression and responses to therapies have made these efforts difficult to translate to clinical practice, highlighting the need for precision medicine approaches to T1D prevention.

Methods

To understand the current state of knowledge regarding precision approaches to T1D prevention, we performed a systematic review of randomized-controlled trials from the past 25 years testing disease-modifying therapies in T1D and/or identifying features linked to treatment response, analyzing bias using a Cochrane-risk-of-bias instrument.

Results

We identified 75 manuscripts, 15 describing 11 prevention trials for individuals with increased risk for T1D, and 60 describing treatments aimed at preventing beta cell loss in individuals at disease onset. Seventeen agents tested, mostly immunotherapies, showed benefit compared to placebo (only two prior to T1D onset). Fifty-seven studies employed precision analyses to assess features linked to treatment response. Age, measures of beta cell function and immune phenotypes were most frequently tested. However, analyses were typically not prespecified, with inconsistent methods reporting, and tended to report positive findings.

Conclusions

While the quality of prevention and intervention trials was overall high, low quality of precision analyses made it difficult to draw meaningful conclusions that inform clinical practice. Thus, prespecified precision analyses should be incorporated into the design of future studies and reported in full to facilitate precision medicine approaches to T1D prevention.

Plain Language Summary

Type 1 diabetes (T1D) results from the destruction of insulin-producing cells in the pancreas, necessitating lifelong insulin dependence. T1D prevention remains an elusive goal, largely due to immense variability in disease progression. Agents tested to date in clinical trials work in a subset of individuals, highlighting the need for precision medicine approaches to prevention. We systematically reviewed clinical trials of disease-modifying therapy in T1D. While age, measures of beta cell function, and immune phenotypes were most commonly identified as factors that influenced treatment response, the overall quality of these studies was low. This review reveals an important need to proactively design clinical trials with well-defined analyses to ensure that results can be interpreted and applied to clinical practice.

New therapeutic approaches for type 1 diabetes: Disease-modifying therapies

It has been 100 years since the first successful clinical use of insulin, yet it remains the only treatment option for type 1 diabetes mellitus (T1DM) patients. Advances in diabetes care, such as insulin analogue therapies and new devices, including continuous glucose monitoring with continuous subcutaneous insulin infusion have improved the quality of life of patients but have no impact on the pathogenesis of the disease. They do not eliminate long-term complications and require several lifestyle sacrifices. A more ideal future therapy for T1DM, instead of supplementing the insufficient hormone production (a consequence of β-cell destruction), would also aim to stop or slow down the destructive autoimmune process. The discovery of the autoimmune nature of type 1 diabetes mellitus has presented several targets by which disease progression may be altered. The goal of disease-modifying therapies is to target autoimmune mechanisms and prevent β-cell destruction. T1DM patients with better β-cell function have better glycemic control, reduced incidence of long-term complications and hypoglycemic episodes. Unfortunately, at the time symptomatic T1DM is diagnosed, most of the insulin secreting β cells are usually lost. Therefore, to maximize the salvageable β-cell mass by disease-modifying therapies, detecting autoimmune markers in an early, optimally presymptomatic phase of T1DM is of great importance. Disease-modifying therapies, such as immuno- and regenerative therapies are expected to take a relevant place in diabetology. The aim of this article was to provide a brief insight into the pathogenesis and course of T1DM and present the current state of disease-modifying therapeutic interventions that may impact future diabetes treatment.

Anti-CD3 monoclonal antibodies for the prevention and treatment of type 1 diabetes: A literature review

DISCLAIMER

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

Type 1 diabetes (T1D) is an autoimmune disease characterized by the destruction of beta cells, resulting in a loss of insulin production. Patients with T1D carry a substantial disease burden as well as substantial short-term and long-term risks associated with inadequate glycemic control. Currently, treatment mainly consists of insulin, which only treats the symptoms of T1D and not the root cause. Thus, disease-modifying agents such as anti-CD3 monoclonal antibodies (mAbs) that target the autoimmune destruction of beta cells in T1D would provide significant relief and health benefits for patients with T1D. This review summarizes the clinical evidence regarding the safety and efficacy of anti-CD3 mAbs in the prevention and treatment of T1D.

SUMMARY

A total of 27 studies reporting or evaluating data from clinical trials involving otelixizumab and teplizumab were included in the review. Anti-CD3 mAbs have shown significant benefits in both patients at high risk for T1D and those with recent-onset T1D. In high-risk populations, anti-CD3 mAbs delayed time to diagnosis, preserved C-peptide levels, and improved metabolic parameters. In recent-onset T1D, anti-CD3 mAbs preserved C-peptide levels and reduced insulin needs for extended periods. Anti-CD3 mAb therapy appears to be safe, with primarily transient and self-limiting adverse effects and no negative long-term effects.

CONCLUSION

Anti-CD3 mAbs are promising disease-modifying treatments for T1D. Their role in T1D may introduce short-term and long-term benefits with the potential to mitigate the significant disease burden; however, more evidence is required for an accurate assessment.

Function and composition of pancreatic islet cell implants in omentum of type 1 diabetes patients

Intraportal (IP) islet cell transplants can restore metabolic control in type 1 diabetes patients, but limitations raise the need for establishing a functional beta cell mass (FBM) in a confined extrahepatic site. This study reports on function and composition of omental (OM) implants after placement of islet cell grafts with similar beta cell mass as in our IP-protocol (2-5.10⁶ beta cells/kg body weight) on a scaffold. Four of seven C-peptide-negative recipients achieved low beta cell function (hyperglycemic clamp [HGC] 2-8 percent of controls) until laparoscopy, 2-6 months later, for OM-biopsy and concomitant IP-transplant with similar beta cell dose. This IP-transplant increased HGC-values to 15-40 percent. OM-biopsies reflected the composition of initial grafts, exhibiting varying proportions of endocrine-cell-enriched clusters with more beta than alpha cells and leucocyte pole, non-endocrine cytokeratin-positive clusters surrounded by leucocytes, and scaffold remnants with foreign body reaction. OM-implants on a polyglactin-thrombin-fibrinogen-scaffold presented larger endocrine clusters with infiltrating endothelial cells and corresponded to the higher HGC-values. No activation of cellular immunity to GAD/IA2 was measured post-OM-transplant. Establishment of a metabolically adequate FBM in omentum may require a higher beta cell number in grafts but also elimination of their immunogenic non-endocrine components as well as local conditioning that favors endocrine cell engraftment and function.

β-Cell Death in Diabetes: Past Discoveries, Present Understanding, and Potential Future Advances

β-cell death is regarded as a major event driving loss of insulin secretion and hyperglycemia in both type 1 and type 2 diabetes mellitus. In this review, we explore past, present, and potential future advances in our understanding of the mechanisms that promote β-cell death in diabetes, with a focus on the primary literature. We first review discoveries of insulin insufficiency, β-cell loss, and β-cell death in human diabetes. We discuss findings in humans and mouse models of diabetes related to autoimmune-associated β-cell loss and the roles of autoreactive T cells, B cells, and the β cell itself in this process. We review discoveries of the molecular mechanisms that underlie β-cell death-inducing stimuli, including proinflammatory cytokines, islet amyloid formation, ER stress, oxidative stress, glucotoxicity, and lipotoxicity. Finally, we explore recent perspectives on β-cell death in diabetes, including: (1) the role of the β cell in its own demise, (2) methods and terminology for identifying diverse mechanisms of β-cell death, and (3) whether non-canonical forms of β-cell death, such as regulated necrosis, contribute to islet inflammation and β-cell loss in diabetes. We believe new perspectives on the mechanisms of β-cell death in diabetes will provide a better understanding of this pathological process and may lead to new therapeutic strategies to protect β cells in the setting of diabetes.

A randomised, single-blind, placebo-controlled, dose-finding safety and tolerability study of the anti-CD3 monoclonal antibody otelixizumab in new-onset type 1 diabetes

AIMS/HYPOTHESIS

Numerous clinical studies have investigated the anti-CD3ɛ monoclonal antibody otelixizumab in individuals with type 1 diabetes, but limited progress has been made in identifying the optimal clinical dose with acceptable tolerability and safety. The aim of this study was to evaluate the association between dose-response, safety and tolerability, beta cell function preservation and the immunological effects of otelixizumab in new-onset type 1 diabetes.

METHODS

In this randomised, single-blind, placebo-controlled, 24 month study, conducted in five centres in Belgium via the Belgian Diabetes Registry, participants (16-27 years old, <32 days from diagnosis of type 1 diabetes) were scheduled to receive placebo or otelixizumab in one of four dose cohorts (cumulative i.v. dose 9, 18, 27 or 36 mg over 6 days; planned n = 40). Randomisation to treatment was by a central computer system; only participants and bedside study personnel were blinded to study treatment. The co-primary endpoints were the incidence of adverse events, the rate of Epstein-Barr virus (EBV) reactivation, and laboratory measures and vital signs. A mixed-meal tolerance test was used to assess beta cell function; exploratory biomarkers were used to measure T cell responses.

RESULTS

Thirty participants were randomised/28 were analysed (placebo, n = 6/5; otelixizumab 9 mg, n = 9/8; otelixizumab 18 mg, n = 8/8; otelixizumab 27 mg, n = 7/7; otelixizumab 36 mg, n = 0). Dosing was stopped at otelixizumab 27 mg as the predefined EBV reactivation stopping criteria were met. Adverse event frequency and severity were dose dependent; all participants on otelixizumab experienced at least one adverse event related to cytokine release syndrome during the dosing period. EBV reactivation (otelixizumab 9 mg, n = 2/9; 18 mg, n = 4/8: 27 mg, n = 5/7) and clinical manifestations (otelixizumab 9 mg, n = 0/9; 18 mg, n = 1/8; 27 mg, n = 3/7) were rapid, dose dependent and transient, and were associated with increased productive T cell clonality that diminished over time. Change from baseline mixed-meal tolerance test C-peptide weighted mean AUC_0-120 min following otelixizumab 9 mg was above baseline for up to 18 months (difference from placebo 0.39 [95% CI 0.06, 0.72]; p = 0.023); no beta cell function preservation was observed at otelixizumab 18 and 27 mg.

CONCLUSIONS/INTERPRETATION

A metabolic response was observed with otelixizumab 9 mg, while doses higher than 18 mg increased the risk of unwanted clinical EBV reactivation. Although otelixizumab can temporarily compromise immunocompetence, allowing EBV to reactivate, the effect is dose dependent and transient, as evidenced by a rapid emergence of EBV-specific T cells preceding long-term control over EBV reactivation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02000817.

FUNDING

The study was funded by GlaxoSmithKline. Graphical abstract.

miR-409-3p is reduced in plasma and islet immune infiltrates of NOD diabetic mice and is differentially expressed in people with type 1 diabetes

AIMS/HYPOTHESIS

MicroRNAs (miRNAs) are a novel class of potential biomarkers emerging in many diseases, including type 1 diabetes. Here, we aim to analyse a panel of circulating miRNAs in non-obese diabetic (NOD) mice and individuals with type 1 diabetes.

METHODS

We adopted standardised methodologies for extracting miRNAs from small sample volumes to evaluate a profiling panel of mature miRNAs in paired plasma and laser-captured microdissected immune-infiltrated islets of recently diabetic and normoglycaemic NOD mice. Moreover, we validated the findings during disease progression and remission after anti-CD3 therapy in NOD mice, as well as in individuals with type 1 diabetes.

RESULTS

Plasma levels of five miRNAs were downregulated in diabetic vs normoglycaemic mice. Of those, miR-409-3p was also downregulated in situ in the immune islet infiltrates of diabetic mice, suggesting an association with disease pathogenesis. Target-prediction tools linked miR-409-3p to immune- and metabolism-related signalling molecules. In situ miR-409-3p expression correlated with insulitis severity, and CD8⁺ central memory T cells were found to be enriched in miR-409-3p. Plasma miR-409-3p levels gradually decreased during diabetes development and improved with disease remission after anti-CD3 antibody therapy. Finally, plasma miR-409-3p levels were lower in people recently diagnosed with type 1 diabetes compared with a non-diabetic control group, and levels were inversely correlated with HbA_1c levels.

CONCLUSIONS/INTERPRETATION

We propose that miR-409-3p may represent a new circulating biomarker of islet inflammation and type 1 diabetes severity.

SLC30A8 polymorphism and BMI complement HLA-A*24 as risk factors for poor graft function in islet allograft recipients

AIMS/HYPOTHESIS

HLA-A*24 carriership hampers achievement of insulin independence in islet allograft recipients. However, less than half of those who fail to achieve insulin independence carry the allele. We investigated whether genetic polymorphism at the recipients' zinc transporter 8-encoding SLC30A8 gene (rs13266634) could complement their HLA-A*24 status in predicting functional graft outcome.

METHODS

We retrospectively analysed data of a hospital-based patient cohort followed for 18 months post transplantation. Forty C-peptide-negative type 1 diabetic individuals who received >2 million beta cells (>4000 islet equivalents) per kg body weight in one or two intraportal implantations under similar immunosuppression were genotyped for SLC30A8. Outcome measurements included achievement and maintenance of graft function. Metabolic benefit was defined as <25% CV of fasting glycaemia in the presence of >331 pmol/l C-peptide, in addition to achievement of insulin independence and maintenance of C-peptide positivity.

RESULTS

In multivariate analysis, HLA-A*24 positivity, presence of SLC30A8 CT or TT genotypes and BMI more than or equal to the group median (23.9 kg/m²) were independently associated with failure to achieve insulin independence (p = 0.015-0.046). The risk increased with the number of factors present (p < 0.001). High BMI interacted with SLC30A8 T allele carriership to independently predict difficulty in achieving graft function with metabolic benefit (p = 0.015). Maintenance of C-peptide positivity was mainly associated with older age at the time of implantation. Only HLA-A*24 carriership independently predicted failure to maintain acceptable graft function once achieved (p = 0.012).

CONCLUSIONS/INTERPRETATION

HLA-A*24, the SLC30A8 T allele and high BMI are associated with poor graft outcome and should be considered in the interpretation of future transplantation trials.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00798785 and NCT00623610.

The elusive role of B lymphocytes and islet autoantibodies in (human) type 1 diabetes

The role of B lymphocytes in the pathogenesis of type 1 diabetes in humans is not entirely evident. These cells are presumed to be important, but this assumption is largely based on animal models of autoimmune diabetes, where compelling evidence for the contribution of both B lymphocytes and insulin-specific autoantibodies to this disease is in place. For humans, this is much less the case; the exact way in which B lymphocytes and/or autoantibodies may contribute to type 1 diabetes is not yet known but the possibilities include a pathogenic function ('fire'), or they may represent a surrogate of loss of immune tolerance to beta cells ('smoke') or, indeed, they could be a marker of an attempt at immune regulation ('ice water'). In this issue of Diabetologia, a study by Willcox et al (DOI: 10.1007/s00125-017-4221-7 ) adds new information but no greater clarity on the relevance of B lymphocytes in type 1 diabetes, showing a decrease in germinal centre frequencies in donors with recent-onset type 1 diabetes compared with control donors and donors with longstanding type 1 diabetes. These new findings may guide the research community to design experiments to unambiguously define whether B lymphocytes or their products function as fire, smoke or perhaps ice water in the immunopathogenesis of type 1 diabetes.

Reversal of Diabetes in NOD Mice by Clinical-Grade Proinsulin and IL-10-Secreting Lactococcus lactis in Combination With Low-Dose Anti-CD3 Depends on the Induction of Foxp3-Positive T Cells

The introduction of β-cell autoantigens via the gut through Lactococcus lactis (L. lactis) has been demonstrated to be a promising approach for diabetes reversal in NOD mice. Here we show that a combination therapy of low-dose anti-CD3 with a clinical-grade self-containing L. lactis, appropriate for human application, secreting human proinsulin and interleukin-10, cured 66% of mice with new-onset diabetes, which is comparable to therapy results with plasmid-driven L. lactis Initial blood glucose concentrations (<350 mg/dL) and insulin autoantibody positivity were predictors of the stable reversal of hyperglycemia, and decline in insulin autoantibody positivity was an immune biomarker of therapeutic outcome. The assessment of the immune changes induced by the L. lactis-based therapy revealed elevated frequencies of CD4⁺Foxp3⁺ T cells in the pancreas-draining lymph nodes, pancreas, and peripheral blood of all treated mice, independent of metabolic outcome. Neutralization of cytotoxic T-lymphocyte antigen 4 and transforming growth factor-β partially abrogated the suppressive function of therapy-induced regulatory T cells (Tregs). Ablation or functional impairment of Foxp3⁺ Tregs in vivo at the start or stop of therapy impaired immune tolerance, highlighting the dependence of the therapy-induced tolerance in mice with new-onset diabetes on the presence and functionality of CD4⁺Foxp3⁺ T cells. Biomarkers identified in this study can potentially be used in the future to tailor the L. lactis-based combination therapy for individual patients.

T Cell-Mediated Beta Cell Destruction: Autoimmunity and Alloimmunity in the Context of Type 1 Diabetes

Type 1 diabetes (T1D) results from destruction of pancreatic beta cells by T cells of the immune system. Despite improvements in insulin analogs and continuous blood glucose level monitoring, there is no cure for T1D, and some individuals develop life-threatening complications. Pancreas and islet transplantation have been attractive therapeutic approaches; however, transplants containing insulin-producing cells are vulnerable to both recurrent autoimmunity and conventional allograft rejection. Current immune suppression treatments subdue the immune system, but not without complications. Ideally a successful approach would target only the destructive immune cells and leave the remaining immune system intact to fight foreign pathogens. This review discusses the autoimmune diabetes disease process, diabetic complications that warrant a transplant, and alloimmunity. First, we describe the current understanding of autoimmune destruction of beta cells including the roles of CD4 and CD8 T cells and several possibilities for antigen-specific tolerance induction. Second, we outline diabetic complications necessitating beta cell replacement. Third, we discuss transplant recognition, potential sources for beta cell replacement, and tolerance-promoting therapies under development. We hypothesize that a better understanding of autoreactive T cell targets during disease pathogenesis and alloimmunity following transplant destruction could enhance attempts to re-establish tolerance to beta cells.

Beta-cell Specific Autoantibodies: Are they Just an Indicator of Type 1 Diabetes?

BACKGROUND

Autoantibodies (AAbs) against islet autoantigens (AAgs) are used for type 1 diabetes (T1D) diagnosis and prediction. Islet-specific AAbs usually appear early in life and may fluctuate in terms of number and titer sometimes for over 20 years before T1D develops. Whereas their predictive power is high for pediatric subjects with high genetic risk who rapidly progress to multiple AAb positivity, they are less reliable for children with low genetic risk, single AAb positivity and slow disease progression.

OBJECTIVE

It is unknown how AAbs develop and whether they are involved in T1D pathogenesis. So far an increase in AAb number seems to only indicate AAg spreading and progression towards clinical T1D. The goal of this review is to shed light on the possible involvement of AAbs in T1D development.

METHOD

We thoroughly review the current literature and discuss possible mechanisms of AAb development and the roles they may play in disease pathogenesis.

RESULTS

Genetic and environmental factors instigate changes at the molecular and cellular levels that promote AAb development. Although direct involvement of AAbs in T1D is less clear, autoreactive B cells are clearly involved in various immune and autoimmune responses via antigen presentation, immunoregulation and cytokine production.

CONCLUSION

Our analysis suggests that understanding the mechanisms that lead to islet-specific AAb development and the diabetogenic processes that autoreactive B cells promote may uncover additional biomarkers and therapeutic targets.

HLA-A*24 Carrier Status and Autoantibody Surges Posttransplantation Associate With Poor Functional Outcome in Recipients of an Islet Allograft

OBJECTIVE

We investigated whether changes in islet autoantibody profile and presence of HLA risk markers, reported to predict rapid β-cell loss in pre-type 1 diabetes, associate with poor functional outcome in islet allograft recipients.

RESEARCH DESIGN AND METHODS

Forty-one patients received ≥2.3 million β-cells/kg body wt in one to two intraportal implantations. Outcome after 6-18 months was assessed by C-peptide (random and stimulated), insulin dose, and HbA1c.

RESULTS

Patients carrying HLA-A*24-positive or experiencing a significant autoantibody surge within 6 months after the first transplantation (n = 19) had lower C-peptide levels (P ≤ 0.003) and higher insulin needs (P < 0.001) despite higher HbA1c levels (P ≤ 0.018). They became less often insulin independent (16% vs. 68%, P = 0.002) and remained less often C-peptide positive (47% vs. 100%, P < 0.001) than recipients lacking both risk factors. HLA-A*24 positivity or an autoantibody surge predicted insulin dependence (P = 0.007).

CONCLUSIONS

HLA-A*24 and early autoantibody surge after islet implantation associate with poor functional graft outcome.

Islet Autoantibodies

Islet autoantibodies are the main markers of pancreatic autoimmunity in type 1 diabetes (T1D). Islet autoantibodies recognize insulin (IAA), glutamic acid decarboxylase (GADA), protein phosphatase-like IA-2 (IA-2A), and ZnT8 (ZnT8A), all antigens that are found on secretory granules within pancreatic beta cells. Islet antibodies, measured by sensitive and specific liquid phase assays, are the key parameters of the autoimmune response monitored for diagnostics or prognostics in patients with T1D or for disease prediction in at-risk individuals before T1D onset. Islet autoantibodies have been the main tool used to explore the natural history of T1D; this review summarizes the current knowledge about the autoantigens and the phenotype of islets autoantibodies acquired in large prospective studies from birth in children at risk of developing T1D.

TNF-α Antibody Therapy in Combination With the T-Cell-Specific Antibody Anti-TCR Reverses the Diabetic Metabolic State in the LEW.1AR1-iddm Rat

Anti-tumor necrosis factor-α (TNF-α) therapy (5 mg/kg body weight), alone or combined with the T-cell-specific antibody anti-T-cell receptor (TCR) (0.5 mg/kg body weight), was performed over 5 days immediately after disease manifestation to reverse the diabetic metabolic state in the LEW.1AR1-iddm rat, an animal model of human type 1 diabetes. Only combination therapy starting at blood glucose concentrations below 15 mmol/L restored normoglycemia and normalized C-peptide. Increased β-cell proliferation and reduced apoptosis led to a restoration of β-cell mass along with an immune cell infiltration-free pancreas 60 days after the end of therapy. This combination of two antibodies, anti-TCR/CD3, as a cornerstone compound in anti-T-cell therapy, and anti-TNF-α, as the most prominent and effective therapeutic antibody in suppressing TNF-α action in many autoimmune diseases, was able to reverse the diabetic metabolic state. With increasing blood glucose concentrations during the disease progression, however, the proapoptotic pressure on the residual β-cell mass increased, ultimately reaching a point where the reservoir of the surviving β-cells was insufficient to allow a restoration of normal β-cell mass through regeneration. The present results may open a therapeutic window for reversal of diabetic hyperglycemia in patients, worthwhile of being tested in clinical trials.