GENERATION OF HUMAN CYTOTOXIC T-CELLS SPECIFIC FOR HUMAN CARCINOEMBRYONIC ANTIGEN EPITOPES FROM PATIENTS IMMUNIZED WITH RECOMBINANT VACCINIA-CEA VACCINE

Background: The human carcinoembryonic antigen (CEA), which is express ed in several cancer types, is a potential target for specific immunot herapy using recombinant vaccines, Previous studies have shown that wh en the CEA gene is placed into vaccinia virus, the recombinant vaccine (rV-CEA) can elicit T-cell responses in both rodents and nonhuman pri mates, Purpose: Our objective was to determine if rV-CEA could elicit CEA-specific T-cell responses in humans with appropriate human leukocy te antigen (HLA) motifs, Methods: Peripheral blood lymphocytes (PBLs) obtained from patients with metastatic carcinoma, both before and afte r vaccination with rV-CEA, were analyzed for T-cell response to specif ic 9- to 11-mer CEA peptides selected to conform to human HLA class I- A2 motifs, Results: While little or no T-cell growth was seen from pre immunization PBLs of patients pulsed with CEA peptides and interleukin 2 (IL-2), T-cell lines were obtained from PBLs of patients after vacc ination with one to three cycles of stimulation, Cytolytic T-cell line s from three HLA-A2 patients were established with a 9-amino acid pept ide (CAP-1), and the CD8(+)/CD4(+) double-positive T-cell line (V24T) was chosen for detailed analysis, When autologous Epstein-Barr virus ( EBV)-transformed B cells were either incubated with CAP-1 peptide or t ransduced with the CEA gene using a retroviral vector, they were lysed by the V24T cell line, but allogeneic non-A2 EBV-transformed B cells were not, The SW403 human colon carcinoma cell line, which is CEA posi tive and HLA-A2 positive, was also lysed by the V24T cell line, while two non-HLA-AZ CEA-positive colon carcinoma cell lines were not, To fu rther confirm the class I HLA-A2 restricted nature of the V24T cytotox icity, the non-HLA-A2 SW837 CEA-expressing colon carcinoma cell line w as infected with a recombinant vaccinia virus expressing the HLA class I-A2 gene, and it became susceptible to V24T lysis, Cells infected wi th vector alone were not lysed, Conclusions: This study demonstrates f or the first time (a) the ability to generate a human cytolytic T-cell response to specific epitopes of CEA, (b) the class I HLA-AZ restrict ed nature of the T-cell mediated lysis, and (c) the ability of human t umor cells to endogenously process CEA to present a specific CEA pepti de in the context of major histocompatibility complex for T-cell-media ted lysis, Implications: These findings have implications in the devel opment of specific second-generation cancer immunotherapy protocols.