Cutting edge: vasostatin-1-derived peptide ChgA29-42 is an antigenic epitope of diabetogenic BDC2.5 T cells in nonobese diabetic mice.

Mechanistic and therapeutic insights in autoimmune diabetes would benefit from a more complete identification of relevant autoantigens. BDC2.5 TCR transgenic NOD mice express transgenes for TCR Vα1 and Vβ4 chains from the highly diabetogenic BDC2.5 CD4(+) T cell clone, which recognizes pancreatic β cell membrane Ags presented by NOD I-A(g7) MHC class II molecules. The antigenic epitope of BDC2.5 TCR is absent in β cells that do not express chromogranin A (ChgA) protein. However, characterization of the BDC2.5 epitope in ChgA has given inconclusive results. We have now identified a ChgA29-42 peptide within vasostatin-1, an N-terminal natural derivative of ChgA as the BDC2.5 TCR epitope. Having the necessary motif for binding to I-A(g7), it activates BDC2.5 T cells and induces an IFN-γ response. More importantly, adoptive transfer of naive BDC2.5 splenocytes activated with ChgA29-42 peptide transferred diabetes into NOD/SCID mice.