Identification of HLA-A0201-restricted Cytotoxic T Lymphocyte Epitope from TRAG-3 Antigen

Purpose: Identification of tumor antigen and subsequent identification of T-cell epitope from these antigens make specific immunotherapy for malignant tumor applicable. Because TRAG-3 antigen is expressed in most melanomas and 54% of non-small cell lung carcinomas and HLA-A2.1-expressing individuals cover >50% in the population of China, we aim at identifying TRAG-3-encoded peptide presented by HLA-A2.1. Experimental Design: In our study, a HLA-A2.1-restricted CTL epitope was identified by using the following four-step procedure: ( a ) computer-based epitope prediction from the amino acid sequence of TRAG-3 antigen; ( b ) peptide-binding assay to determine the affinity of the predicted peptide with HLA-A2.1 molecule; ( c ) stimulation of primary T-cell response against the predicted peptides in vitro ; and ( d ) testing of the induced CTLs toward LB373-MEL cells expressing TRAG-3 antigen and HLA-A2.1. Results: Of the four tested peptides, effectors induced by a peptide of TRAG-3 at residue position 58–66 lysed LB373-MEL cells expressing both TRAG-3 and HLA-A2.1. Our results indicate that peptide TRAG-3 (58∼66) (ILLRDAGLV) is a new HLA-A2.1-restricted CTL epitope capable of inducing TRAG-3 specific CTLs in vitro . Conclusions: Because TRAG-3 is a cancer/testis antigen expressed in most melanomas and half of non-small cell lung carcinomas, identification of the TRAG-3/HLA-A2.1 peptide ILLRDAGLV may facilitate peptide-based specific immunotherapy for various histological tumors.