Parameters influencing antigen-specific immunotherapy for type 1 diabetes

Oral delivery of the intracellular domain of the insulinoma-associated protein 2 (IA-2ic) by bacterium-like particles (BLPs) prevents type 1 diabetes mellitus in NOD mice

Antigen-specific immune tolerance, which possesses great potential in preventing or curing type 1 diabetes mellitus (T1DM), can be induced by oral vaccination with T1DM-related autoantigens. However, direct administration of autoantigens via oral route exhibits a low tolerance-inducing effect as a result of the digestion of protein antigens in the gastrointestinal tract (GIT) and therefore, a large dosage of autoantigens may be needed. In this study, bacterium-like particles (BLPs) made from food-grade lactic acid bacteria were used to deliver the intracellular domain of the insulinoma-associated protein 2 (IA-2ic). For this purpose, BLPs-IA-2ic vaccine in which IA-2ic bound to the surface of BLPs was constructed. BLPs enhanced the stability of the delivered IA-2ic based on the stability analysis in vitro. Oral administration of BLPs-IA-2ic significantly reduced T1DM incidence in NOD mice. The mice fed BLPs-IA-2ic exhibited a significant reduction in insulitis and preserved the ability to secrete insulin. Immunologic analysis showed that oral vaccination with BLPs-IA-2ic induced antigen-specific T cell tolerance. The results revealed that the successful induction of immune tolerance was dependent on the immune deviation (in favor of T helper 2 responses) and CD4⁺CD25⁺FoxP3⁺ regulatory T cells. Hence, oral vaccination with BLPs-IA-2ic shows potential for application in preventing T1DM.

Tolerogenic vaccination reduced effector memory CD4 T cells and induced effector memory Treg cells for type I diabetes treatment

Background

Vaccination could induce immune tolerance and protected NOD mice from the development of type I diabetes (T1D). We previously demonstrated that insulin peptide (B9-23) combined with dexamethasone (DEX) stimulated the expansion of antigen specific regulatory T (Treg) cells which in turn effectively prevented T1D in NOD mice. Here, we aimed to investigate the therapeutic effect of tolerogenic vaccination for T1D treatment.

Methodology/Principal Findings

The diabetic NOD mice (Blood glucose level ≧250 mg/dl) were treated with B9-23 and DEX twice. The tolerance was restored by blocking maturation of dendritic cells (DCs) and inducing Treg cells in treated NOD mice. Remarkably, the reduction of autoreactive effector memory CD4 T (Tm) cells and the induction of functional effector memory Treg (mTreg) cells contributed to the improvement of T1D in treated NOD mice.

Conclusions/Significance

Tolerogenic vaccination restored tolerance and ameliorated T1D by suppressing effector CD4 Tm cells and inducing effector mTreg cells. Our findings implicate the potential of tolerogenic vaccination for T1D treatment.

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.

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

BACKGROUND

We have previously shown that two injections of 20 µg alum-formulated glutamic acid decarboxylase 65 (GAD(65)) (GAD-alum; Diamyd(®)) in children with recent-onset type 1 diabetes lead to preservation of residual insulin secretion. In vitro cytokine production at the 15 months' follow-up indicated immunomodulation. In the present study, we took advantage of peripheral blood mononuclear cells, cryopreserved during early follow-ups, to investigate whether the immunomodulatory effect of GAD-alum was apparent earlier after treatment, preceding the changes previously reported at 15 months.

METHODS

Peripheral blood mononuclear cells from 70 type 1 diabetic children, randomly assigned GAD-alum (n = 35) or placebo (n = 35), that had been frozen at baseline (n = 27) and after 1 (n = 58), 3 (n = 67) and 9 (n = 66) months, were stimulated in vitro with GAD(65), tyrosine phosphatase-like protein IA-2 peptide, insulin peptide, GAD-alum, alum formulation or phytohaemagglutinin. Interleukin (IL)-5, -6, -10, -12, -13, -17, tumour necrosis factor and interferon-γ were measured in cell supernatants and serum samples using Luminex. Expression of FOXP3 and transforming growth factor-β was determined by real-time reverse transcription polymerase chain reaction.

RESULTS

Already 1 month after the first injection, GAD(65)-induced IL-5 and IL-13 together with FOXP3 were enhanced in GAD-alum-treated patients compared to those with placebo. The in vitro response at 3 and 9 months was characterized by a broader range of cytokines in the treated group. Notably, only the T-helper 2-associated cytokines IL-5 and IL-13 together with FOXP3 increased continuously over time.

CONCLUSIONS

Treatment with GAD-alum in type 1 diabetic children induced an early T-helper 2 immune enhanced response to GAD(65), followed by a wider spectrum of cytokines at 3 and 9 months.