To assess responses

to GAD65 epitopes that could be processed and presented from intact protein, CD4+ T cells were primed by stimulation with GAD65 protein and then screened using tetramers loaded with each of the antigenic peptides identified by tetramer-guided epitope mapping. Briefly, 2·5 × 106 ‘no-touch’ Microbead-enriched CD4+ T cells were stimulated with 1·2 × 105 GAD65 protein loaded monocytes in one well of a 48-well plate. CD14+ monocytes were isolated and pulsed with recombinant GAD65 protein as in the protein-stimulated proliferation assays. At least four replicate wells (of a 48-well plate) were set up for each subject. The T cells were cultured for 14 days, adding fresh media and interleukin-2

as needed starting on day 7. Expanded cells were stained www.selleckchem.com/products/Fulvestrant.html with HLA-DR0401 tetramers loaded with each antigenic NVP-LDE225 supplier GAD65 peptide. Again, tetramer responses were considered positive when distinct staining that was more than twofold above background (this was set to 0·2% and subtracted) was observed. As described in the Materials and methods section, the tetramer-guided epitope mapping approach was used to comprehensively investigate DR0401-restricted epitopes within GAD65. Peptide pools spanning the entire GAD65 sequence were used to stimulate CD25-depleted T cells from multiple donors with DR0401 haplotypes. Consistent with the representative results shown in Fig. 1(a), a total of 17 different peptides (from 11 peptide pools) elicited a positive response from at least one of the subjects tested. With the exception of pool #6, the antigenic peptides

within each of these peptide pools could be identified using tetramers loaded with individual peptides. The antigenic peptide from pool #6 could not be identified using this approach. However, peptide p26 (GAD201–220) from pool #6 was identified as the antigenic peptide by means of a proliferation assay (Fig. 1b) and was further confirmed by stimulating C-X-C chemokine receptor type 7 (CXCR-7) of CD4+ T cells with the individual GAD201–220 peptide and staining with the DR0401/GAD#6 pooled tetramer (data not shown). The peptide sequences containing these epitopes are summarized in Table 1. The 17 antigenic peptides identified included five pairs of adjacent, overlapping peptides. It seemed likely that some of these adjacent overlapping peptides contain a single, shared antigenic sequence. To delineate the antigenic sequences within these adjacent overlapping peptides, we generated tetramer-positive T-cell lines for at least one peptide from each pair. As shown in Fig. 2, we assessed the proliferation of these lines in response to each of the adjacent peptides. These results suggested that three pairs of overlapping peptides (GAD105–124 and GAD113–132, GAD265–284 and GAD273–292, GAD545–564 and GAD553–572) appear to contain distinct antigenic sequences, because T-cell lines only proliferated in response to one of the peptides.