THE IDENTIFICATION OF CD4-CELL EPITOPES WITH DEDICATED SYNTHETIC PEPTIDE LIBRARIES( T)

For a large number of T cell-mediated immunopathologies, the disease-r elated antigens are not yet identified. Identification of T cell epito pes is of crucial importance for the development of immune-interventio n strategies. We show that CD4(+) T cell epitopes can be defined by us ing a new system for synthesis and screening of synthetic peptide libr aries. These Libraries are designed to bind to the HLA class II restri ction molecule of the CD4(+) T cell clone of interest. The screening i s based on three selection rounds using partial release of 14-mer pept ides from synthesis beads and subsequent sequencing of the remaining p eptide attached to the bead. With this approach, two peptides were ide ntified that stimulate the beta cell-reactive CD4(+) T cell clone 1c10 , which was isolated from a newly diagnosed insulin-dependent diabetes mellitus patient. After performing amino acid-substitution studies an d protein database searches, a Haemophilus influenzae TonB-derived pep tide was identified that stimulates clone 1c10. The relevance of this finding for the pathogenesis of insulin-dependent diabetes mellitus is currently under investigation. We conclude that this system is capabl e of determining epitopes for (autoreactive) CD4(+) T fell clones with previously unknown peptide specificity, This offers the possibility t o define (auto)antigens by searching protein databases and/or to induc e tolerance by using the peptide sequences identified. In addition the peptides might be used as leads to develop T cell receptor antagonist s or anergy-inducing compounds.