T cell responses to HLA-A*0201-restricted peptides derived from human alpha fetoprotein

alpha fetoprotein (AFP)-derived peptide epitopes can be recognized by human T cells in the context of MHC class 1. We determined the identity of AFP-d erived peptides, presented in the context of HLA-A*0201, that could be reco gnized by the human (h) T cell repertoire. We screened 74 peptides and iden tified 3 new AFP epitopes, hAFP(137-145), hAFP(158-166), and hAFP(325-334), in addition to the previously reported hAFP(542-550). Each possesses two a nchor residues and stabilized HLA-A*0201 on T2 cells in a concentration-dep endent class I binding assay. The peptides were stable for 2-4 h in an off- kinetics assay. Each peptide induced peptide-specific T cells in vitro from several normal HLA-A*0201 donors. Importantly, these hAFP peptide-specific T cells also were capable of recognizing HLA-A*0201(+)/AFP(+) tumor cells in both cytotoxicity assays and IFN-gamma enzyme-linked immunospot assays. The immunogenicity of each peptide was tested in vivo with HLA-A*0201/K-b - transgenic mice. After immunization with each peptide emulsified in CFA, dr aining lymph node cells produced IFN-gamma on recognition of cells stably t ransfected with hAFP. Furthermore, AFP peptide-specific T cells could be id entified in the spleens of mice immunized with dendritic cells transduced w ith an AFP-expressing adenovirus (AdVhAFP). Three of four AFP peptides coul d be identified by mass spectrometric analysis of surface peptides from an HLA-A*0201 human hepatocellular carcinoma (HCC) cell line. Thus, compelling immunological and physiochemical evidence is presented that at least four hAFP-derived epitopes are naturally processed and presented in the context of class 1, are immunogenic, and represent potential targets for hepatocell ular carcinoma immunotherapy.