HLA-DQ8-Associated T Cell Responses to the Diabetes Autoantigen Phogrin (IA-2β) in Human Prediabetes

Abstract

Susceptibility to type 1A autoimmune diabetes is linked to expression of particular MHC class II molecules, notably HLA-DQ8 in man and the orthologous I-Ag7 in the nonobese diabetic mouse. In the present study, we analyzed two peptide epitopes (peptides 2 and 7) from the diabetes autoantigen phogrin (IA-2β), in the context of their presentation by the I-Ag7 and HLA-DQ8 molecules and their role as potential T cell antigenic epitopes in human diabetes. Both of these peptides are targets of diabetogenic CD4+ T cell clones in the nonobese diabetic mouse. Transgenic mice expressing HLA-DQ8 as the sole class II molecule generated a robust T cell-proliferative response when primed with peptide 2 or peptide 7 in CFA. Analysis of the IL-2 secretion from peptide 2-reactive T cell hybridomas stimulated with alanine-substituted peptides identified three residues that were crucial to the response. Among 41 islet cell Ag-positive prediabetic human subjects, 36.5% showed PBMC-proliferative responses to peptide 7, 17.1% to peptide 2, and 17.1% to both peptides; no response was seen among 20 matched healthy controls. Stratification of the data based upon HLA haplotype suggested that peptide 7 could be presented by at least one HLA-DR molecule in addition to HLA-DQ8, a finding that was supported by blocking studies with monomorphic mAbs. The results indicate that common phogrin peptides are targeted by autoreactive T cells in human and murine type 1A diabetes, and that the responses may in part be associated with the similar peptide-binding specificities of I-Ag7 and HLA-DQ8.

Natural peptides selected by diabetogenic DQ8 and murine I-Ag7 molecules show common sequence specificity

“…1, 36). In addition, previous reports analyzing T cell responses have indirectly alluded to common epitopes that may be displayed by I-A g7 and DQ8 (37)(38)(39). Our data supports the hypothesis that the NOD mouse is highly valid for identification of putative pathogenic T cell epitopes and for testing such peptides for their ability to establish disease-preventive protocols.…”

Islet-Specific Glucose-6-Phosphatase Catalytic Subunit-Related Protein-Reactive CD4+ T Cells in Human Subjects

“…Proliferation assays also confirmed the specificities of these T cell clones (data not shown). T cells that were specific for p3 were not isolated, but a p3-stimulated T cell line could be easily stained with IGRP [23][24][25][26][27][28][29][30][31][32][33][34][35] -loaded tetramers, confirming that peptide IGRP [23][24][25][26][27][28][29][30][31][32][33][34][35] encompassed the p3 epitopes (Fig. 3D).…”

“…Peptides that were 13 aas in length containing the putative binding motifs from p2, p29, p3, and p31 were then synthesized. These peptides were IGRP [13][14][15][16][17][18][19][20][21][22][23][24][25] , IGRP 226 -238 , IGRP [23][24][25][26][27][28][29][30][31][32][33][34][35] , and IGRP 247-259 , respectively (Table II). DR0301/IGRP [13][14][15][16][17][18][19][20][21][22][23][24][25] , DR0301/IGRP 226 -238 , DR0401/IGRP [23][24][25][26][27][28][29][30][31][32]…”

“…There was also one subject in which the responses toward both epitopes were minimal (subject number 15). Similarly, the prevalence of IGRP 247-259 and IGRP [23][24][25][26][27][28][29][30][31][32][33][34][35] -specific T cells in DR0401 subjects was evaluated with IGRP peptide-specific DR0401 tetramers. The results from five T1D and five healthy DR0401 subjects are shown in Fig.…”

“…8 -27 ) and p29 (IGRP 225-244 ) have a DR0301 binding motif, and peptides p3 (IGRP [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] ) and p31 (IGRP 241-260 ) have a DR0401 binding motif.…”