Mapping of antigenic epitopes within the recombinant human preproinsulin related to insulin-dependent diabetes mellitus.

The human insulin domains, signal peptide, B-chain, C-peptide, and A-chain, were highly expressed in Escherichia coli as recombinant proteins N-terminally fused to glutathione-S-transferase and a histidine-hexapeptide. The recombinant proteins were purified from insoluble cell fraction by affinity chromatography using metal chelating matrix, which was charged with Ni+2 ions. ELISA screening for autoantibodies directed to preproinsulin were performed with sera from patients with recently diagnosed insulin-dependent diabetes mellitus in order to localize the antigenic epitopes within the human preproinsulin. Of the patients, 14% had developed autoantibodies that recognized either the recombinant C-peptide or the signal peptide. No reaction was observed with the A-chain or B-chain.