An insulin-IAPP hybrid peptide is an endogenous antigen for CD4 T cells in the non-obese diabetic mouse.
BDC-6.9, a diabetogenic CD4 T cell clone isolated from a non-obese diabetic (NOD) mouse, responds to pancreatic islet cells from NOD but not BALB/c mice. We recently reported that a hybrid insulin peptide (HIP), 6.9HIP, formed by linkage of an insulin C-peptide fragment and a fragment of islet amyloid polypeptide (IAPP), is the antigen for BDC-6.9. We report here that the core 12-mer peptide from 6.9HIP, centered on the hybrid peptide junction, is also highly antigenic for BDC-6.9. In agreement with the observation that BALB/c islet cells fail to stimulate the T cell clone, a single amino acid difference in the BALB/c IAPP sequence renders the BALB/c version of the HIP only weakly antigenic. Mutant peptide analysis indicates that each parent molecule-insulin C-peptide and IAPP-donates residues critical for antigenicity. Through mass spectrometric analysis, we determine the distribution of naturally occurring 6.9HIP across chromatographic fractions of proteins from pancreatic beta cells. This distribution closely matches the profile of the T cell response to the fractions, confirming that 6.9HIP is the endogenous islet antigen for the clone. Using a new MHC II tetramer reagent, 6.9HIP-tet, we show that T cells specific for the 6.9HIP peptide are prevalent in the pancreas of diabetic NOD mice. Further study of HIPs and HIP-reactive T cells could yield valuable insight into key factors driving progression to diabetes and thereby inform efforts to prevent or reverse this disease.
Department of Immunology and Microbiology, University of Colorado School of Medicine, Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
Timothy A
TA
Wiles
Department of Immunology and Microbiology, University of Colorado School of Medicine, Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
Thomas
T
Delong
Department of Immunology and Microbiology, University of Colorado School of Medicine, Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
Rocky L
RL
Baker
Department of Immunology and Microbiology, University of Colorado School of Medicine, Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
Brenda
B
Bradley
Department of Immunology and Microbiology, University of Colorado School of Medicine, Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
Gene
G
Barbour
Pharmaceutical Science, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Roger L
RL
Powell
Pharmaceutical Science, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Nichole
N
Reisdorph
Department of Immunology and Microbiology, University of Colorado School of Medicine, Denver, Anschutz Medical Campus, Aurora, CO 80045, USA. Electronic address: katie.haskins@ucdenver.edu.
Kathryn
K
Haskins
D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens / Q000737:chemistry / Q000276:immunology*; D002096:C-Peptide / Q000737:chemistry / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002478:Cells, Cultured; D018984:Epitopes, T-Lymphocyte / Q000737:chemistry / Q000276:immunology*; D007328:Insulin / Q000737:chemistry / Q000276:immunology*; D058228:Islet Amyloid Polypeptide / Q000737:chemistry / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D016688:Mice, Inbred NOD; D018345:Mice, Knockout
D001324:Autoantigens; D002096:C-Peptide; D018984:Epitopes, T-Lymphocyte; D007328:Insulin; D058228:Islet Amyloid Polypeptide
Autoimmune type 1 diabetes; Hybrid insulin peptides (HIPs); Non-obese diabetic (NOD) mouse; Peptide fusion; Tetramer