Tandem-epitope peptide: A novel stimulator for γδT cells in tumor immunotherapy

T cells bearing the γδTCR have become the new candidate effectors in tumor immunotherapy because of their potent cytotoxicity toward various tumor cells. However, a crucial issue in using γδT cells as effectors is how to effectively expand tumor-reactive γδT cells and enhance their functions. In previously studies, we used synthesized CDR3-peptide derived from ovarian epithelial carcinoma (OEC) infiltrating γδT cells (γδTILs) as specific probe to screen a phage display peptide library and identified seven putative epitopes named EP1–EP7. All seven putative epitopes could not only bind to γδT cells, but also activate them in vitro. To enhance the activating capability of these identified γδT cell ligands, we have constructed four types of GST epitope fusion proteins containing single epitope or tandem epitopes. These GST epitope fusion proteins could not only promote the secretion of cytokines, but also enhance the proliferation and cytotoxicity of γδT cells in vitro. Significant difference between GST tandem-epitope groups and GST single-epitope group in their activating capability was observed (P < 0.05). Furthermore, GST epitope fusion proteins could suppress the growth of tumor and prolong the survival of BALB/c nude mice inoculated with human OEC cell line (P < 0.05). In conclusion, these results provide a novel approach for tumor immunotherapy based on γδT cells.