(158c) Screening and Identification of a High-Affinity Peptide Ligand Specific to Human CD3e

CD3 molecules are expressed on T lymphocytes as parts of T cell receptor complex are responsible for antigen recognition and activation of T cells. The present study aims to identify a novel peptide ligand which binds to human CD3ε in a specific manner, and to evaluate its effects on the functions of T lymphocytes. We had screened a phage-display peptide library against human CD3ε molecule using an improved subtractive biopanning method. After 5 rounds of biopanning, we had identified 13 phage clones displaying unique peptide sequences. One dominant phage clone, which was selected by occupying 90 % of tested plaques (18 out of 20), demonstrated enhanced bindings in a flow cytometry analysis after incubation with Jurkat cells. The peptide displayed by this most enriched phage clone binds to Jurkat cells in a dose-dependent manner but not to the 2PK3 B-cell lymphoma line. We employed molecular modeling and docking simulation to predict the structure of the peptide and it’s binding poses on the surface of CD3ε. By conjugating the synthesized peptide to magnetic beads, we confirm that the peptide-modified beads can induce T cell receptor signaling (calcium flux) which can be used for T cell expansion. The novel peptide has a great potential in applications related to T cell immunotherapy.