Vasostatin‐1 antigenic epitope mapping for induction of cellular and humoral immune responses to chromogranin A autoantigen in NOD mice

The chromogranin A (ChgA) 29–42 sequence is the antigenic epitope for the BDC2.5 CD4+ T-cell receptor in NOD mice (H-2g7). We have now characterized the binding register of the ChgA 29–42 peptide for the I-Ag7 molecule. Truncation of the peptide demonstrated that the KCVLEVISD sequence 34–42 is the binding register and extension of this sequence by flanking residues increased its binding affinity and antigenic capacity. We employed anti-ChgA peptide antibodies generated against different fragments of ChgA for immunostaining of pancreatic islet sections from NOD mice. A strong immuno-staining pattern was observed for the ChgA 17–38 peptide antibodies that overlap with the ChgA 29–42 sequence. Moreover, sera from diabetic NOD mice showed elevated titers of autoantibodies to the ChgA 29–42 peptide. These findings indicate that peptides from the N-terminal region of ChgA are able to induce cellular and humoral immune responses in NOD mice.