A strategy for the synthesis and screening of thiol-modified peptide variants recognized by T cells

In this study we present a strategy for the identification of novel peptide conjugates which may be used to understand the molecular details of the recognition process or to potentially regulate T cell-mediated responses. The approach involves the incorporation of cysteine into a known peptide at a position of interest and subsequent chemical conjugation using thiol-specific agents. Conjugates derived from the nonapeptide QL9 that is recognized by CTL 2C had either enhanced or reduced activity compared to the original cys-peptides. Different classes of thiol-reactive agents (alkyl halides, alkylthiolsulfonates, and disulfides) were tested with increases in activity of over 100-fold. As with standard peptide analogs, the activity depended on the position of the cysteine within the peptide and the nature of the chemically linked functional group. Use of this approach in a cysteine 'scan' of all positions of the original peptide is cost effective and with the availability of many different thiol-specific functional groups will allow the screening of considerably larger libraries of chemically modified peptides than have been used to date. Additionally, these findings may provide insight into the pathogenesis of thiol agents involved in contact sensitivity reactions.