Check GAD antibody positivity with the Diamyd anti-GAD RIA plate*

Vaccination with GAD PlasmidSuppresses Diabetes in the NOD MouseEven After Development of InsulitisNora Sarvetnick is Professor of Immunologyat The Scripps Research Institute (TSRI) in LaJolla. Sarvetnick is focusing on new therapiesfor the prevention of autoimmune diabetes.TNora SarvetnickThe NOD mouse developsspontaneous T cell dependentautoimmune diabetes and isused as an experimental modelto explore many features sharedwith Type 1 diabetes patients.Much research has focused on pancreaticautoantigens and GAD65 is one of the bestknown targets of autoreactive T cells during theearly phase of disease development. GAD expresssionin the pancreatic islets increases with age inthe NOD mouse and when its expression is suppressed,diabetogenic T cells are not generated,resulting in protection from diabetes. The importanceof GAD in Type 1 diabetes has also beenconfirmed by adoptive transfer experiments, thatis, a GAD-specific CD4 T cell clone from a NODmice that normally develops diabetes transferreddiabetes into NOD-scid/scid mice that normallydo not develops diabetes.Autoimmune diabetes has been successfullysuppressed at the prediabetic stage via Th2 immunedeviation. For example, young NOD mice injectedwith GAD protein (intravenously or intraperitoneally)or its peptides (intranasally) respondedwith a reduction of T cell proliferation to GAD65and their insulitis and diabetes decreased. Likewise,induction of a GAD-reactive Th2 response prolongedthe survival of syngeneic islets grafted indiabetic NOD mice and inhibited disease progresssionin animals with early signs of Type 1 diabetes.Additionally, the transgenic expression of IL-4 inthe pancreas of NOD mice completely protectedthem from the disease due to the inhibition ofdiabetogenic Th1 lymphocytes by islet-reactiveTh2 cells.Recently it was shown that vaccination of micewith plasmids encoding foreign (viral) antigensinduced effective T cell responses and circumventedthe requirement for conventional immunizationwith proteins in complete Freunds adjuvant.We therefore hypothezised that genetic vaccinationwith plasmids encoding GAD may interferewith development of autoimmune diabetes.Indeed, GAD-plasmid vaccination effectively preventeddiabetes in NOD female mice when theywere treated at 4 to 5 weeks of age (before insulitis)and even at 10 to 11 weeks of age (after insulitis).This protection, however, did not stem frominduction of the classical Th2 shift as reported inseveral other GAD-vaccination protocols. On thecontrary, the mechanism of GAD-plasmid mediateddiabetes protection was due to insufficientcostimulation of GAD-specific T cells at the siteof antigen presentation. In fact when costimulationwas provided in vivo at the time of GAD-plasmidvaccination, the protective effect was abrogated.With these results our lab was first to report(Clinical Immunology, May, 2001) that GAD65-plasmid vaccination is effective in suppressing diabetesin the NOD mouse even after developmentof insulitis and that that this protection is notdependent on a systemic or pancreatic Th2 immuneresponse.page 26 dmccad june 2003