Peptides for use in the therapy or prevention of Type 1 Diabetes mellitus (T1DM) are those having sequences containing QPLALEGSLQK (SEQ ID NO: 9). Examples are those having a sequence selected from the group consisting essentially of GGGPGAGSLQPLALEGSLQK (SEQ ID NO: 4), GSLQPLALEGSLQKRGIV (SEQ ID NO: 5), and QPLALEGSLQKRGIVEQ (SEQ ID NO: 6). One or more of the above peptides may be combined with one or more peptides having a sequence or sequences consisting essentially of sequences selected from LAKEWQALCAYQAEPNTCATAQGEGNIK (SEQ ID NO: 11), KLKVESSPSRSDYINASPIIEHDP (SEQ ID NO: 12), and SFYLKNVQTQETRTLTQFHF (SEQ ID NO: 13). Also disclosed is a method of assessing the potential of a peptide for T1DM therapy or prevention which comprises subjecting the candidate peptide to a first assay indicative of a pathogenic T cell response in blood or other biological sample, such as an ELISPOT assay for IFN-gamma. In the case of a positive response to the first assay, the candidate peptide is subjected to a second assay indicative of a regulatory T cell response to the peptide, such as an ELISPOT assay for IL-10).
