Poster Presentation The 13th International Congress of the Immunology of Diabetes Society 2013

Short Course Oral Therapy with Plant-Derived Autoantigens Delays Type 1 Diabetes Onset in NOD Mice. (#176)

Amanda Posgai 1 , Clive Wasserfall 1 , Mark Atkinson 1 , Desmond Schatz 1 , Kwang-chul Kwon , Henry Daniell 2
  1. University of Florida, Gainesville, FL, United States
  2. University of Pennsylvania, Philadelphia, Pennsylvania, United States

Insulin and glutamic acid decarboxylase (GAD) are key autoantigens in the pathogenesis of Type 1 Diabetes (T1D).  Oral autoantigen therapy has been shown to delay T1D onset in NOD mice by inducing mucosal tolerance. In a dose optimization study, we tested the hypothesis that the administration of GAD or pro-insulin (INS), bioencapsulated in plant cells, would prevent T1D in NOD mice. INS was expressed in chloroplasts as a fusion protein with cholera toxin’s non-toxic B subunit (CTB), which serves as a trans-mucosal carrier for efficient delivery and antigen presentation.  Transformed plant cells were delivered to NOD mice via oral gavage once per week for 10 weeks, beginning at 5 weeks of age. Three doses—25µg, 250µg, and 500µg—of each autoantigen were tested. Interim analysis revealed that mice treated with 500µg GAD (n=7) demonstrated 100% survival at 21 weeks of age compared to 57.1% in the WT group (n=14, p=0.0542). Those that received 250µg CTB-INS (n=15) demonstrated 73.3% survival at 24 weeks of age compared to 42.9% in the WT group (p=0.0685).  Following withdrawal of treatment, survival fell to 14% (p=0.5833) and 40% (p=0.1598) in the 500µg GAD and 250µg CTB-INS groups, respectively, compared to 21.4% in the WT group.  These data suggest that a short course therapy with GAD or CTB-INS bioencapsulated in plant cells delays T1D onset. Compared to the WT group, treatment with 250µg CTB-INS was associated with increased serum titers of IgG2b (a marker for oral tolerance) and IgM at 16 weeks of age (p=0.0088).  We expect that ongoing studies with optimized regimen – combinations of autoantigens (500µg GAD + 250µg CTB-INS) together with incretin therapy (bioencapsulated CTB-Exendin-4) and extended duration of treatment – will induce immunological tolerance, preclude loss of beta cell mass, and enhance safe efforts aimed at preventing T1D in NOD mice.