Nasal administration of glutamate decarboxylase (GAD65) peptides induces Th2 responses and prevents murine insulin-dependent diabetes.

Abstract

SummaryWe previously demonstrated that a spontaneous Thl response against glutamate decarboxylase (GAD65) arises in NOD mice at four weeks in age and subsequently T cell autoimmunity spreads both intramolecularly and intermolecularly. Induction of passive tolerance to GAD65, through the inactivation of reactive T cells before the onset of autoimmunity, prevented determinant spreading and the development of insulin-dependent diabetes mellitus (IDDM). Here, we examined whether an alternative strategy, designed to induce active tolerance via the engagement of Th2 immune responses to GAD65, before the spontaneous onset of autoimmunity, could inhibit the cascade of Thl responses that lead to IDDM. We observed that a single intranasal administration of GAD65 peptides to 2-3-wk-old NOD mice induced high levels of IgGl antibodies to GAD65. GAD65 peptide treated mice displayed greatly reduced IFN~/responses and increased IL-5 responses to GAD65, confirming the diversion of the spontaneous GAD65 Thl response toward a Th2 phenotype. Consistent with the induction of an active tolerance mechanism, splenic CD4 + (but not CD8 +) T cells from GAD65 peptide-treated mice, inhibited the adoptive transfer of IDDM to NOD-scid/scid mice. This active mechanism not only inhibited the development of proliferative T cell responses to GAD65, it also limited the expansion ofautoreactive T cell responses to other [3 cell antigens (i.e., determinant spreading). Finally, GAD65 peptide treatment reduced insulitis and long-term IDDM incidence. Collectively, these data suggest that the nasal administration of GAD65 peptides induces a Th2 cell response that inhibits the spontaneous development of autoreactive Thl responses and the progression of ~ cell autoimmunity in NOD mice.

Prevention of autoimmune diabetes by immunogene therapy using recombinant vaccinia virus expressing glutamic acid decarboxylase

“…We found that the production of IL-4 increased, whereas the production of IFN-γ decreased, indicating that the immunisation of NOD mice with rVV-GAD65 induced a Th2 immune response in an antigenspecific manner. Our finding is consistent with the results of previous reports on NOD mice treated with GAD protein systemically, nasally or orally [28,29,33,34,35] or vaccinated with GAD encoding plasmid DNA [41]. Th2 immune responses induced by rVV-GAD immunisation could play an important role in the prevention of autoimmune diabetes in this animal model.…”

“…In Type I diabetes, GAD and insulin have been identified as major autoantigens and tolerisation against these autoantigens has been attempted as a method for the prevention of the disease [14,32]. It has been reported that administration of purified GAD protein or peptide or insulin protein or peptide to NOD mice by a variety of routes can tolerise the T cell-mediated immune response against pancreatic beta cells, resulting in the prevention or delay of the development of insulitis and diabetes [28,29,33,34,35,36,37,38,39]. In many cases, the preventive effect was found to be associated with a Th2 shift [14,32].…”

Pancreatic NOD beta cells express MHC class II protein and the frequency of I-Ag7 mRNA-expressing beta cells strongly increases during progression to autoimmune diabetes

“…T cells from diabetic but not from pre-diabetic young NOD mice proliferated in response to this peptide. Moreover, immunisation with this peptide protects NOD mice from diabetes (as immunisation with other autoantigens does [25,26]) by inducing regulatory T cells of the TH2 phenotype which are capable of preventing adoptively transferred diabetes [16]. These findings conflict with the idea that NOD beta cells are MHC class II-negative.…”

“…With the onset of periinsulitis, beta-cell-antigenspecific T cells become detectable [25,32,33]. These islet-specific T cells are of TH1 phenotype and show signs of activation [33,34].…”

Attenuation of Th1 response through galectin‐9 and T‐cell Ig mucin 3 interaction inhibits autoimmune diabetes in NOD mice

“…Intervention of this cytokine imbalance by autoantigen-specific tolerance induction, by costimulation blockade or by overexpression of IL-4 could prevent diabetic progression. However, those treatments are most effective when administrated to NOD mice beginning at 2-3 wk of age [26][27][28]. In pre-diabetic NOD mice that undergo late peri-insulitis, inhibition of the Th1 cell is crucial but not sufficient to completely inhibit the disease progression.…”