Importance of GAD65 peptides and I-Ag7 in the development of insulitis in nonobese diabetic mice.
Insulin-dependent diabetes mellitus (IDDM) develops in nonobese diabetic (NOD) mice through the destruction of the B cells in pancreatic Langerhans islets by islet autoantigen-specific T cells. The islet autoantigen glutamic acid decarboxylase 65 (GAD65) is thought to be a major target autoantigen in IDDM. In the present report, we established GAD65-specific T-cell clones using overlapping peptides that cover the amino acid sequences of mouse GAD65. T-cell epitopes of GAD65 were characterized by proliferation and binding assays using various analogue peptides and wild-type or mutant I-Ag7 transfectants. The efficacy of the peptide vaccine in IDDM was determined by administering T-cell epitope peptides to NOD mice and evaluating the histopathology of their insulitis. We obtained two types of T-cell clone, one specific for peptide p316-335 and another specific for p531-545 of GAD65. The p531-545 site has already been identified, but we report the p316-335 site for the first time. T-cell clones recognized those peptides in the wild-type I-Ag7 but not in the mutant I-Ag7 in which the serine at position 57 of the beta-chain was replaced by an aspartic acid. Both the p316-335 and p531-545 peptides bound weakly to I-Ag7. Some peptides with amino acid substitutions had antagonistic activity, and administration of a large amount of wild-type peptide reduced the severity of insulitis in NOD mice. Our results suggest that peptide vaccine therapy may be useful in autoimmune diseases, including IDDM.
Ogino
T
T
Department of Pathology, Asahikawa Medical College, Japan. ogino@asahikawa-med.ac.jp
Sato
K
K
Miyokawa
N
N
Kimura
S
S
Katagiri
M
M
D000595:Amino Acid Sequence; D000818:Animals; D003922:Diabetes Mellitus, Type 1 / Q000473:pathology / Q000628:therapy*; D018984:Epitopes, T-Lymphocyte; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000737:chemistry / Q000502:physiology*; D007515:Islets of Langerhans / Q000473:pathology*; D008213:Lymphocyte Activation; D051379:Mice; D016688:Mice, Inbred NOD; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D013329:Structure-Activity Relationship; D014612:Vaccines / Q000627:therapeutic use*
D018984:Epitopes, T-Lymphocyte; D000949:Histocompatibility Antigens Class II; C407099:I-A g7 antigen; D010446:Peptide Fragments; D014612:Vaccines; D005968:Glutamate Decarboxylase