Early induction of GAD(65)-reactive Th2 response in type 1 diabetic children treated with alum-formulated GAD(65)

Redosing with Intralymphatic GAD-Alum in the Treatment of Type 1 Diabetes: The DIAGNODE-B Pilot Trial

Immunotherapies aimed at preserving residual beta cell function in type 1 diabetes have been successful, although the effect has been limited, or raised safety concerns. Transient effects often observed may necessitate redosing to prolong the effect, although this is not always feasible or safe. Treatment with intralymphatic GAD-alum has been shown to be tolerable and safe in persons with type 1 diabetes and has shown significant efficacy to preserve C-peptide with associated clinical benefit in individuals with the human leukocyte antigen DR3DQ2 haplotype. To further explore the feasibility and advantages of redosing with intralymphatic GAD-alum, six participants who had previously received active treatment with intralymphatic GAD-alum and carried HLA DR3-DQ2 received one additional intralymphatic dose of 4 μg GAD-alum in the pilot trial DIAGNODE-B. The participants also received 2000 U/day vitamin D (Calciferol) supplementation for two months, starting one month prior to the GAD-alum injection. During the 12-month follow-up, residual beta cell function was estimated with Mixed-Meal Tolerance Tests, and clinical and immune responses were observed. C-peptide decreased minimally, and most patients showed stable HbA1c and IDAA1c. The mean % TIR increased while the mean daily insulin dose decreased at month 12 compared to the baseline. Redosing with GAD-alum seems to be safe and tolerable, and may prolong the disease modification elicited by the original GAD-alum treatment.

Intralymphatic glutamic acid decarboxylase administration in type 1 diabetes patients induced a distinctive early immune response in patients with DR3DQ2 haplotype

GAD-alum given into lymph nodes to Type 1 diabetes (T1D) patients participating in a multicenter, randomized, placebo-controlled double-blind study seemed to have a positive effect for patients with DR3DQ2 haplotype, who showed better preservation of C-peptide than the placebo group. Here we compared the immunomodulatory effect of GAD-alum administered into lymph nodes of patients with T1D versus placebo with focus on patients with DR3DQ2 haplotype.

Methods

GAD autoantibodies, GADA subclasses, GAD₆₅-induced cytokine secretion (Luminex panel) and proliferation of peripheral mononuclear cells were analyzed in T1D patients (n=109) who received either three intra-lymphatic injections (one month apart) with 4 µg GAD-alum and oral vitamin D supplementation (2000 IE daily for 120 days), or placebo.

Results

Higher GADA, GADA subclasses, GAD₆₅-induced proliferation and cytokine secretion was observed in actively treated patients after the second injection of GAD-alum compared to the placebo group. Following the second injection of GAD-alum, actively treated subjects with DR3DQ2 haplotype had higher GAD₆₅-induced secretion of several cytokine (IL4, IL5, IL7, IL10, IL13, IFNγ, GM-CSF and MIP1β) and proliferation compared to treated individuals without DR3DQ2. Stratification of samples from GAD-alum treated patients according to C-peptide preservation at 15 months revealed that "good responder" individuals with better preservation of C-peptide secretion, independently of the HLA haplotype, had increased GAD₆₅-induced proliferation and IL13 secretion at 3 months, and a 2,5-fold increase of IL5 and IL10 as compared to "poor responders". The second dose of GAD-alum also induced a more pronounced cytokine secretion in "good responders" with DR3DQ2, compared to few "good responders" without DR3DQ2 haplotype.

Conclusion

Patients with DR3DQ2 haplotype had a distinct early cellular immune response to GAD-alum injections into the lymph node, and predominant GAD₆₅-induced IL13 secretion and proliferation that seems to be associated with a better clinical outcome. If confirmed in the ongoing larger randomized double-blind placebo-controlled clinical trial (DIAGNODE-3), including only patients carrying DR3DQ2 haplotype, these results might be used as early surrogate markers for clinical efficacy.

Long-Term GAD-alum Treatment Effect on Different T-Cell Subpopulations in Healthy Children Positive for Multiple Beta Cell Autoantibodies

Objective

The objective of this study was to explore whether recombinant GAD65 conjugated hydroxide (GAD-alum) treatment affected peripheral blood T-cell subpopulations in healthy children with multiple beta cell autoantibodies.

Method

The Diabetes Prevention–Immune Tolerance 2 (DiAPREV-IT 2) clinical trial enrolled 26 children between 4 and 13 years of age, positive for glutamic acid decarboxylase autoantibody (GADA) and at least one other autoantibody (insulin, insulinoma antigen-2, or zinc transporter 8 autoantibody (IAA, IA-2A, or ZnT8A)) at baseline. The children were randomized to two doses of subcutaneously administered GAD-alum treatment or placebo, 30 days apart. Complete blood count (CBC) and immunophenotyping of T-cell subpopulations by flow cytometry were performed regularly during the 24 months of follow-up posttreatment. Cross-sectional analyses were performed comparing lymphocyte and T-cell subpopulations between GAD-alum and placebo-treated subjects.

Results

GAD-alum-treated children had lower levels of lymphocytes (10⁹ cells/L) (p = 0.006), T-cells (10³ cells/μL) (p = 0.008), T-helper cells (10³ cells/μL) (p = 0.014), and cytotoxic T-cells (10³ cells/μL) (p = 0.023) compared to the placebo-treated children 18 months from first GAD-alum injection. This difference remained 24 months after the first treatment for lymphocytes (p = 0.027), T-cells (p = 0.022), T-helper cells (p = 0.048), and cytotoxic T-cells (p = 0.018).

Conclusion

Our findings suggest that levels of total T-cells and T-cell subpopulations declined 18 and 24 months after GAD-alum treatment in healthy children with multiple beta-cell autoantibodies including GADA.

Combining anti-IL-7Rα antibodies with autoantigen-specific immunotherapy enhances non-specific cytokine production but fails to prevent Type 1 Diabetes

Autoantigen-specific methods to prevent and treat Type 1 Diabetes (T1D) carry high hopes to permanently cure this disease, but have largely failed in clinical trials. One suggested approach to increase the efficacy of islet antigen-specific vaccination is to combine it with a modulator of the T cell response, with the goal of reducing effector differentiation and promoting regulatory T cells (Tregs). Here we asked if addition of antibodies that block the IL-7/IL-7Rα pathway altered the T cell response to islet antigen vaccination and prevented T1D in non-obese diabetic (NOD) mice. Anti-IL-7Rα monoclonal antibodies (mAbs) reduced the numbers of islet antigen-specific T cells generated after vaccination with islet peptides and alum. However, addition of anti-IL-7Rα antibodies to peptide/alum vaccination unexpectedly increased non-specific IFN-γ, IL-2 and IL-10 cytokine production and did not result in improved prevention of T1D onset. In a second approach, we used a conjugate vaccine to deliver islet autoantigens, using Keyhole Limpet Hemocyanin (KLH) as a carrier. Islet antigen-KLH vaccination led to a significant expansion of antigen-specific Tregs and delayed diabetes onset in NOD mice. These outcomes were not further improved by addition of anti-IL-7Rα antibodies. To the contrary, blocking IL-7Rα during vaccination led to non-specific cytokine production and reduced the efficacy of a KLH-conjugated vaccine to prevent T1D. Our study thus revealed that adding anti-IL-7Rα antibodies during autoantigen immunization did not improve the efficacy of such vaccinations to prevent T1D, despite altering some aspects of the T cell response in a potentially advantageous way. Further refinement of this approach will be required to separate the beneficial from the adverse effects of anti-IL-7Rα antibodies to treat autoimmune disease.

Immune Mechanisms and Pathways Targeted in Type 1 Diabetes

PURPOSE OF REVIEW

The immunosuppressive agent cyclosporine was first reported to lower daily insulin dose and improve glycemic control in patients with new-onset type 1 diabetes (T1D) in 1984. While renal toxicity limited cyclosporine's extended use, this observation ignited collaborative efforts to identify immunotherapeutic agents capable of safely preserving β cells in patients with or at risk for T1D.

RECENT FINDINGS

Advances in T1D prediction and early diagnosis, together with expanded knowledge of the disease mechanisms, have facilitated trials targeting specific immune cell subsets, autoantigens, and pathways. In addition, clinical responder and non-responder subsets have been defined through the use of metabolic and immunological readouts. Herein, we review emerging T1D biomarkers within the context of recent and ongoing T1D immunotherapy trials. We also discuss responder/non-responder analyses in an effort to identify therapeutic mechanisms, define actionable pathways, and guide subject selection, drug dosing, and tailored combination drug therapy for future T1D trials.

Therapies to Suppress β Cell Autoimmunity in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that is generally considered to be T cell-driven. Accordingly, most strategies of immunotherapy for T1D prevention and treatment in the clinic have targeted the T cell compartment. To date, however, immunotherapy has had only limited clinical success. Although certain immunotherapies have promoted a protective effect, efficacy is often short-term and acquired immunity may be impacted. This has led to the consideration of combining different approaches with the goal of achieving a synergistic therapeutic response. In this review, we will discuss the status of various T1D therapeutic strategies tested in the clinic, as well as possible combinatorial approaches to restore β cell tolerance.

Antigen-Specific Regulatory T Cells and Low Dose of IL-2 in Treatment of Type 1 Diabetes

Regulatory T cells (Tregs) play an important role in preventing effector T-cell (Teff) targeting of self-antigens that can lead to tissue destruction in autoimmune settings, including type 1 diabetes (T1D). Autoimmunity is caused in part by an imbalance between Teff and Tregs. Early attempts to treat with immunosuppressive agents have led to serious side effects, thus requiring a more targeted approach. Low-dose IL-2 (LD IL-2) can provide immunoregulation with few side effects by preferentially acting on Tregs to drive tolerance. The concept of LD IL-2 as a therapeutic approach is supported by data in mouse models where autoimmunity is cured and further strengthened by success in human clinical studies in hepatitis C virus-induced vasculitis, chronic graft-versus-host disease, and Alopecia areata. Treatment will require identification of a safe therapeutic window, which is a difficult task given that patients are reported to have deficient or defective IL-2 production or signaling and have experienced mild activation of NK cells and eosinophils with LD IL-2 therapy. In T1D, an LD IL-2 clinical trial concluded that Tregs can be safely expanded in humans; however, the study was not designed to address efficacy. Antigen-specific therapies have also aimed at regulation of the autoimmune response but have been filled with disappointment despite an extensive list of diverse islet antigens tested in humans. This approach could be enhanced through the addition of LD IL-2 to the antigenic treatment regimen to improve the frequency and function of antigen-specific Tregs, without global immunosuppression. Here, we will discuss the use of LD IL-2 and islet antigen to enhance antigen-specific Tregs in T1D and focus on what is known about their immunological impact, their safety, and potential efficacy, and need for better methods to identify therapeutic effectiveness.

Targeted immune interventions for type 1 diabetes: not as easy as it looks!

PURPOSE OF REVIEW

Although insulin is lifesaving and sustaining for those with type 1 diabetes (T1D), curing the disease will be much more complex than simple replacement of this hormone. T1D is an autoimmune disease orchestrated by T cells, and includes many arms of the immune response. Tremendous effort has gone into understanding its underlying immune, genetic, and environmental causes, and this progress has led to immunologically based clinical trials in T1D. This review will focus primarily on the clinical trials of the past decade that have attempted to translate these fundamental findings.

RECENT FINDINGS

It is known that powerful, nonspecific immune suppressants can temporarily slow the course of newly diagnosed T1D, yet are too toxic for long-term use, especially in children. Recent clinical trials to reverse T1D have used newly developed therapies that target specific components of the immune process believed to be involved with T1D. Although well justified and designed, no recent approach has resulted in clinical remission and few have had any effect on disease course.

SUMMARY

Advances in our fundamental understanding of how the human diabetes immune response is activated and regulated coupled with lessons that have been learnt from the most recent era of completed trials are guiding us toward the development of more effective, multipronged therapies to ablate diabetes autoimmunity, restore immune tolerance, preserve β cells, and, ultimately, improve the lives of patients with T1D.

GAD-treatment of children and adolescents with recent-onset type 1 diabetes preserves residual insulin secretion after 30 months

BACKGROUND

This study aimed to analyse data from two different studies (phase II and phase III) regarding the safety and efficacy of treatment with alum formulated glutamic acid decarboxylase GAD65 (GAD-alum) at 30 months after administration to children and adolescents with type 1 diabetes.

METHODS

The phase II trial was a double-blind, randomised placebo-controlled study, including 70 children and adolescents who were followed for 30  months. Participants received a subcutaneous injection of either 20 µg of GAD-alum or placebo at baseline and 1 month later. During a subsequent larger European phase III trial including three treatment arms, participants received two or four subcutaneous injections of either 20 µg of GAD-alum and/or placebo at baseline, 1, 3 and 9  months. The phase III trial was prematurely interrupted at 15 months, but of the 148 Swedish patients, a majority completed the 21 months follow-up, and 45 patients completed the trial at 30 months. Both studies included GAD65 auto-antibodies-positive patients with fasting C-peptide ≥ 0.10 nmol/l. We have now combined the results of these two trials.

RESULTS

There were no treatment related adverse events. In patients treated with 2 GAD-alum doses, stimulated C-peptide area under the curve had decreased significantly less (9  m: p  <  0.037; 15 m: p  <  0.032; 21 m: p  <  0.003 and 30  m: p <  0.004), and a larger proportion of these patients were also able to achieve a peak stimulated C-peptide > 0.2  nmol/L (p  <  0.05), as compared with placebo.

CONCLUSION

Treatment with two doses of GAD-alum in children and adolescents with recent-onset type 1 diabetes shows no adverse events and preserves residual insulin secretion.

MAS-1 adjuvant immunotherapy generates robust Th2 type and regulatory immune responses providing long-term protection from diabetes in late-stage pre-diabetic NOD mice

MAS-1, a nanoparticular, emulsion-based adjuvant, was evaluated for its ability to promote Th2 and regulatory immune responses and prevent type 1 diabetes progression when given alone or as antigen-specific immunotherapy (ASI) using insulin B chain (IBC; MER3101) and its analog B:9-23(19Ala) (MER3102). MAS-1 formulations were administered to NOD mice at age 9 and 13 weeks and followed through 52 weeks. MER3101 and MER3102 provided long-term protection with 60% and 73% of mice remaining diabetes-free at week 35, and 60% and 47% at week 52. MAS-1 adjuvant emulsion by itself also provided protection with 60% and 40% of mice diabetes-free at 35 and 52 weeks, respectively. Higher levels of interleukin (IL)-10 and IL-2 positive T cells were detected among splenocytes by week 15 in MER3101 and MER3102 immunized mice, whereas MAS-1 alone induced higher levels of IL-10-positive T cells. Diabetes-free 52-week-old mice expressed significant levels of antigen-specific IL-10-positive type 1 regulatory T cells and FoxP3-positive T cells when stimulated ex vivo with IBC. Antibodies targeting IBC and B:9-23(19Ala) induced by MER3101 and MER3102 were overwhelmingly Th2 type IgG1 and IgG2b isotypes. Splenocyte cultures from 52 week diabetes-free, MER3101-treated mice secreted significantly increased levels of IL-4 and IL-5 Th2 cytokines. Based on these pre-clinical results and its clinical safety profile, MAS-1 has the requisite qualities to be considered for use in prophylactic or early stage disease settings to augment ASI to prevent disease progression in type 1 diabetes.

Cellular and humoral immune responses in type 1 diabetic patients participating in a phase III GAD-alum intervention trial

OBJECTIVE

GAD formulated in aluminum hydroxide (GAD-alum) has previously been shown to induce preservation of residual insulin secretion in recent-onset type 1 diabetes, but recent phase II and III GAD-alum trials failed to reach primary outcomes. The European phase III study was therefore closed after 15 months, and only a minority of patients completed the 30 months of follow-up.

RESEARCH DESIGN AND METHODS

This study aimed to characterize cellular and humoral responses in the Swedish patients (n = 148) participating in the phase III trial, receiving four (4D) or two (2D) GAD-alum doses or placebo. Serum GAD65 antibody (GADA) levels, GADA IgG1-4 subclass distribution, cytokine secretion, and proliferative responses in peripheral blood mononuclear cells (PBMCs) were analyzed.

RESULTS

The GAD65-induced cytokine profile tended to switch toward a predominant Th2-associated profile over time both in the 2D and 4D group. The groups also displayed increased GADA levels and PBMC proliferation compared with placebo, whereas GADA IgG subclass distribution changed in 4D patients.

CONCLUSIONS

Both 2D and 4D patients displayed GAD65-specifc cellular and humoral effects after GAD-alum treatment, but at different time points and magnitudes. No specific immune markers could be associated with treatment efficacy.

Cellular and humoral immune responses in type 1 diabetic patients participating in a phase III GAD-alum intervention trial

OBJECTIVE

GAD formulated in aluminum hydroxide (GAD-alum) has previously been shown to induce preservation of residual insulin secretion in recent-onset type 1 diabetes, but recent phase II and III GAD-alum trials failed to reach primary outcomes. The European phase III study was therefore closed after 15 months, and only a minority of patients completed the 30 months of follow-up.

RESEARCH DESIGN AND METHODS

This study aimed to characterize cellular and humoral responses in the Swedish patients (n = 148) participating in the phase III trial, receiving four (4D) or two (2D) GAD-alum doses or placebo. Serum GAD65 antibody (GADA) levels, GADA IgG1-4 subclass distribution, cytokine secretion, and proliferative responses in peripheral blood mononuclear cells (PBMCs) were analyzed.

RESULTS

The GAD65-induced cytokine profile tended to switch toward a predominant Th2-associated profile over time both in the 2D and 4D group. The groups also displayed increased GADA levels and PBMC proliferation compared with placebo, whereas GADA IgG subclass distribution changed in 4D patients.

CONCLUSIONS

Both 2D and 4D patients displayed GAD65-specifc cellular and humoral effects after GAD-alum treatment, but at different time points and magnitudes. No specific immune markers could be associated with treatment efficacy.

Antigen-specific therapeutic approaches in Type 1 diabetes

Development of strategies capable of specifically curbing pathogenic autoimmune responses in a disease- and organ-specific manner without impairing foreign or tumor antigen-specific immune responses represents a long sought-after goal in autoimmune disease research. Unfortunately, our current understanding of the intricate details of the different autoimmune diseases that affect mankind, including type 1 diabetes, is rudimentary. As a result, progress in the development of the so-called "antigen-specific" therapies for autoimmunity has been slow and fraught with limitations that interfere with bench-to-bedside translation. Absent or incomplete understanding of mechanisms of action and lack of adequate immunological biomarkers, for example, preclude the rational design of effective drug development programs. Here, we provide an overview of antigen-specific approaches that have been tested in preclinical models of T1D and, in some cases, human subjects. The evidence suggests that effective translation of these approaches through clinical trials and into patients will continue to meet with failure unless detailed mechanisms of action at the level of the organism are defined.

The clinical and immunological significance of GAD-specific autoantibody and T-cell responses in type 1 diabetes

Antigen-specific interventions are desirable approaches in Type 1 Diabetes (T1D) as they can alter islet-specific autoimmunity without systemic side effects. Glutamic acid decarboxylase of 65 kDa (GAD65) is a major autoantigen in type 1 diabetes (T1D) and GAD-specific autoimmunity is a common feature of T1D in humans but also in mouse models of the disease. In humans, administration of the GAD65 protein in an alum formulation has been shown to reduce C-peptide decline in recently diagnosed patients, however, these observations were not confirmed in subsequent phase II/III clinical trials. As GAD-based immune interventions in different formulations have successfully been employed to prevent the establishment of T1D in mouse models of T1D, we sought to analyze the efficacy of GAD-alum treatment and the effects on the GAD-specific immune response in two different mouse models of T1D. Consistent with the latest clinical trials, mice treated with GAD-alum were not protected from diabetes, although GAD-alum induced a GAD-specific Th2-deviated immune response in transgenic rat insulin promoter-glycoprotein (RIP-GP) mice. These observations underline the importance of a thorough, preclinical evaluation of potential drugs before the initiation of clinical trials.

Regulatory T cell phenotype and function 4 years after GAD-alum treatment in children with type 1 diabetes

Glutamic acid decarboxylase (GAD)(65) formulated with aluminium hydroxide (GAD-alum) was effective in preserving insulin secretion in a Phase II clinical trial in children and adolescents with recent-onset type 1 diabetes. In addition, GAD-alum treated patients increased CD4(+) CD25(hi) forkhead box protein 3(+) (FoxP3(+)) cell numbers in response to in-vitro GAD(65) stimulation. We have carried out a 4-year follow-up study of 59 of the original 70 patients to investigate long-term effects on the frequency and function of regulatory T cells after GAD-alum treatment. Peripheral blood mononuclear cells were stimulated in vitro with GAD65 for 7 days and expression of regulatory T cell markers was measured by flow cytometry. Regulatory T cells (CD4(+) CD25(hi) CD127(lo)) and effector T cells (CD4(+) CD25(-) CD127(+)) were further sorted, expanded and used in suppression assays to assess regulatory T cell function after GAD-alum treatment. GAD-alum-treated patients displayed higher frequencies of in-vitro GAD(65) -induced CD4(+) CD25(+) CD127(+) as well as CD4(+) CD25(hi) CD127(lo) and CD4(+) FoxP3(+) cells compared to placebo. Moreover, GAD(65) stimulation induced a population of CD4(hi) cells consisting mainly of CD25(+) CD127(+) , which was specific of GAD-alum-treated patients (16 of 25 versus one of 25 in placebo). Assessment of suppressive function in expanded regulatory T cells revealed no difference between GAD-alum- and placebo-treated individuals. Regulatory T cell frequency did not correlate with C-peptide secretion throughout the study. In conclusion, GAD-alum treatment induced both GAD(65) -reactive CD25(+) CD127(+) and CD25(hi) CD127(lo) cells, but no difference in regulatory T cell function 4 years after GAD-alum treatment.

Vaccine against autoimmune disease: antigen-specific immunotherapy

Recent interest in testing whether the success of antigen-specific immunotherapy (ASIT) for autoimmune diseases in mice can be translated to humans has highlighted the need for better tools to study and understand human autoimmunity. Clinical development of ASIT for allergy has been instructive, but limited understanding of CD4 T cell epitope/determinant hierarchies hampers the rational design and monitoring of ASIT. Definitive identification of pathogenic T cell epitopes as is now known in celiac disease and recent initiatives to optimize immune monitoring will facilitate rational design, monitoring and mechanistic understanding of ASIT for human autoimmune diseases.

Decreased GAD(65)-specific Th1/Tc1 phenotype in children with Type 1 diabetes treated with GAD-alum

AIM

The balance between T helper cell subsets is an important regulator of the immune system and is often examined after immune therapies. We aimed to study the immunomodulatory effect of glutamic acid decarboxylase (GAD) 65 formulated with aluminium hydroxide (GAD-alum) in children with Type 1 diabetes, focusing on chemokines and their receptors.

METHODS

Blood samples were collected from 70 children with Type 1 diabetes included in a phase II clinical trial with GAD-alum. Expression of CC chemokine receptor 5 (CCR5) and CCR4 was analysed on CD4+ and CD8+ lymphocytes after in vitro stimulation with GAD(65) using flow cytometry, and secretion of the chemokines CCL2, CCL3 and CCL4 was detected in peripheral blood mononuclear cell supernatants with Luminex.

RESULTS

Expression of Th1-associated CCR5 was down-regulated following antigen challenge, together with an increased CCR4/CCR5 ratio and CCL2 secretion in GAD-alum-treated patients, but not in the placebo group.

CONCLUSION

Our results suggest that GAD-alum treatment has induced a favourable immune modulation associated with decreased Th1/Tc1 phenotypes upon antigen re-challenge, which may be of importance for regulating GAD(65) immunity.

GAD autoantibody epitope pattern after GAD-alum treatment in children and adolescents with type 1 diabetes

AIMS

We have previously shown that two injections of glutamic acid decarboxylase formulated in alum (GAD-alum) preserved residual insulin secretion in children and adolescents with recent onset type 1 diabetes (T1D), and was accompanied by increased GAD autoantibody (GADA) titers. The aim of this study was to investigate whether GAD-alum treatment affected the GADA epitope pattern.

METHODS

Serum samples from patients treated with GAD-alum (n = 33) or placebo (n = 27), at baseline, 1, 3, 9, and 15 months after the initial injection, were tested for their binding capacity to specific GADA epitopes in an epitope-specific radioligand binding assay with six recombinant Fab (rFab) (b96.11, DPA, DPD, MICA3, b78, and N-GAD(65) mAb).

RESULTS

No significant differences in variability of binding to any of the tested rFab were observed from baseline to 15 months. There was a sustained low binding of GADA to the b78- and N-GAD(65) mAb-defined epitopes, often recognized by GADA in patients with stiff person syndrome (SPS) and seldom in T1D patients. However, binding of GADA to the T1D-associated b96.11-defined epitope increased between baseline and 3 months in GAD-alum (-8.1%, min -72.4%, max 39.6%) compared to placebo patients (1.5%, min -28.3%, max 28.6%) (p = 0.02). Subsequently, the b96.11-defined epitope recognition returned to levels similar to that observed at baseline.

CONCLUSIONS

GAD-alum injections did not affect binding of GADA to SPS-related epitopes, further supporting the safety of the treatment. There were no changes in GADA epitope specificity to the T1D-related epitopes, except for a temporarily increased binding to one of the tested epitopes.

Long-lasting immune responses 4 years after GAD-alum treatment in children with type 1 diabetes

A phase II clinical trial with glutamic acid decarboxylase (GAD) 65 formulated with aluminium hydroxide (GAD-alum) has shown efficacy in preserving residual insulin secretion in children and adolescents with recent-onset type 1 diabetes (T1D). We have performed a 4-year follow-up study of 59 of the original 70 patients to investigate long-term cellular and humoral immune responses after GAD-alum-treatment. Peripheral blood mononuclear cells (PBMC) were stimulated in vitro with GAD₆₅. Frequencies of naïve, central and effector memory CD4+ and CD8+ T cells were measured, together with cytokine secretion, proliferation, gene expression and serum GAD₆₅ autoantibody (GADA) levels. We here show that GAD-alum-treated patients display increased memory T-cell frequencies and prompt T-cell activation upon in vitro stimulation with GAD₆₅, but not with control antigens, compared with placebo subjects. GAD₆₅-induced T-cell activation was accompanied by secretion of T helper (Th) 1, Th2 and T regulatory cytokines and by induction of T-cell inhibitory pathways. Moreover, post-treatment serum GADA titres remained persistently increased in the GAD-alum arm, but did not inhibit GAD₆₅ enzymatic activity. In conclusion, memory T- and B-cell responses persist 4 years after GAD-alum-treatment. In parallel to a GAD₆₅-induced T-cell activation, our results show induction of T-cell inhibitory pathways important for regulating the GAD₆₅ immunity.

GAD-alum immunotherapy in Type 1 diabetes mellitus

Glutamic acid decarboxylase (GAD)-alum (Diamyd®, Diamyd Medical, Stockholm, Sweden) is an adjuvant-formulated vaccine incorporating recombinant human GAD65, the specific isoform of GAD expressed in human pancreatic β-cells and a major antigen targeted by autoreactive T lymphocytes in Type 1 diabetes mellitus. Intermittent vaccination with this protein is theorized to induce immune tolerance to GAD65, thereby potentially interrupting further β-cell destruction. Hence, clinical trials are ongoing to examine the efficacy and safety of GAD-alum immunotherapy in patients with autoimmune-mediated forms of diabetes, including Type 1 diabetes and latent autoimmune diabetes in adults.