Identification of HLA-A3-restricted cytotoxic T lymphocyte epitopes from carcinoembryonic antigen and HER-2/neu by primary in vitro immunization withpeptide-pulsed dendritic cells

The human carcinoembryonic antigen (CEA) and HER-2/neu are potential target antigens for CTL specific immunotherapy for common malignancies such as br east, lung, colon, and gastric carcinomas. Several CTL epitopes restricted by HLA-AZ, the mast common human histocompatibility molecule, have been pre viously reported. However, to develop CTL-based immunotherapies for the gen eral population, it is necessary to identify epitopes restricted by other c ommon histocompatibility alleles. Here, we describe two HLA-A3-restricted C TL epitopes from the CEA and HER-2/neu antigens. HLA-A3 binding synthetic p eptides from CEA and HER-2/neu were tested for immunogenicity by in vitro p rimary CTL induction protocol using peripheral blood mononuclear cells from normal healthy volunteers. One peptide from CEA (CEA[9(61)]: HLFGYSWYK) an d one peptide from HER-2/neu (HER2[9(754)]: VLRENTSPK) were shown to induce CTL that was capable of killing a tumor cell line expressing HLA-A3 and th e corresponding tumor-associated antigen. Additional NMC binding studies wi th the most common HLA molecules belonging to the HLA-A3 superfamily (HLA-A *1101, -A*3101, -A*3301, and -A*6801), demonstrated that CEA[9(61)] binds f ive of five A3 supertype molecules with high affinity, and the HER2[9(754)] epitope was able to bind to four of the same five alleles. These results i ndicate that these two new CTL epitopes should be inmunogenic in individual s expressing either HLA-A3, or other members of the HLA-A3 superfamily.