Identification and characterization of a HER-2/ neu epitope as a potential target for cancer immunotherapy.

Our aim is to develop peptide vaccines that stimulate tumor antigen-specific T-lymphocyte responses against frequently detected cancers. We describe herein a novel HLA-A*0201-restricted epitope, encompassing amino acids 828–836 (residues QIAKGMSYL), which is naturally presented by various HER-2/ neu+ tumor cell lines. HER-2/ neu(828-836), [HER-2(9828)], possesses two anchor residues and stabilized HLA-A*0201 on T2 cells in a concentration-dependent Class I binding assay. This peptide was stable for 3.5 h in an off-kinetic assay. HER-2(9828) was found to be immunogenic in HLA-A*0201 transgenic (HHD) mice inducing peptide-specific and functionally potent CTL and long-lasting anti-tumor immunity. Most important, using HLA-A*0201 pentamer analysis we could detect increased ex vivo frequencies of CD8+ T-lymphocytes specifically recognizing HER-2(9828) in 8 out of 20 HLA-A*0201+ HER-2/ neu+ breast cancer patients. Moreover, HER-2(9828)-specific human CTL recognized the tumor cell line SKOV3.A2 as well as the primary RS.A2.1.DR1 tumor cell line both expressing HER-2/ neu and HLA-A*0201. Finally, therapeutic vaccination with HER-2(9828) in HHD mice was proven effective against established transplantable ALC.A2.1.HER tumors, inducing complete tumor regression in 50% of mice. Our data encourage further exploitation of HER-2(9828) as a promising candidate for peptide-based cancer vaccines. [ABSTRACT FROM AUTHOR]