CD4+ and CD8+ T-cell clones from congenital rubella syndrome patients with IDDM recognize overlapping GAD65 protein epitopes -: Implications for HLA class I and II allelic linkage to disease susceptibility

To fully characterize human glutamic acid decarboxylase (GAD)65 protein T-cell epitopes associated with insulin-dependent diabetes mellitus (IDDM), CTL clones specific to GAD65 protein antigens were isolated from two congenital rubella syndrome (CRS)-associated IDDM patients. Overlapping nonamer T-cell epitopes recognized by both CD4(+) or CD8(+) Cn clones within peptides GAD65(252-266) and GAD65(274-286) were identified as sequences bounded by GAD65(255-266) with 6/9 overlapping residues, and GAD65(276-285) with 8/9 overlapping residues, respectively, using two panels of overlapping peptide analogs in cytotoxicity assays. KLA restrictive elements of the T-cell clones were also identified using a panel of B cell lines with different HLA phenotypes as targets in cytotoxicity assays. The antigenic GAD65 peptides elicited cytotoxic responses of peptide-specific CD4(+) T-cell clones in the context of HLA DRB1*0404. The CD8(+) T-cell clone specific to GAD65(255-263) was found to be restricted by HLA A3 and All. Similarly, the CD8(+) T-cell clone specific to GAD65(277-285) killed peptide-sensitized target cells expressing HLA B35 and D15, The observed HLA restriction of these overlapping epitopes implies that a tandem of [DRB1*040-A11(3)] and/or a tandem of [DRB1*0404-B35(15)] might predispose CRS patients to development of IDDM. (C) American Society for Histocompatibility and Immunogenetics, 1999, published by Elsevier Science Inc.