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 expressed in several cancer types, is a potential target for specific immunotherapy using recombinant vaccines. Previous studies have shown that when the CEA gene is placed into vaccinia virus, the recombinant vaccine (rV-CEA) can elicit T-cell responses in both rodents and non-human primates.


OBJECTIVE
Our objective was to determine if rVCEA could elicit CEA-specific T-cell responses in humans with appropriate human leukocyte antigen (HLA) motifs.


METHODS
Peripheral blood lymphocytes (PBLs) obtained from patients with metastatic carcinoma, both before and after vaccination with rV-CEA, were analyzed for T-cell response to specific 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 preimmunization PBLs of patients pulsed with CEA peptides and interleukin 2 (IL-2), T-cell lines were obtained from PBLs of patients after vaccination with one to three cycles of stimulation. Cytolytic T-cell lines from three HLA-A2 patients were established with a 9-amino acid peptide (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 transduced 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 positive and HLA-A2 positive, was also lysed by the V24T cell line, while two non-HLA-A2 CEA-positive colon carcinoma cell lines were not. To further confirm the class I HLA-A2 restricted nature of the V24T cytotoxicity, the non-HLA-A2 SW837 CEA-expressing colon carcinoma cell line was infected with a recombinant vaccinia virus expressing the HLA class I-A2 gene, and it became susceptible to V24T lysis. Cells infected with vector alone were not lysed.


CONCLUSIONS
This study demonstrates for the first time (a) the ability to generate a human cytolytic T-cell response to specific epitopes of CEA, (b) the class I HLA-A2 restricted nature of the T-cell mediated lysis, and (c) the ability of human tumor cells to endogenously process CEA to present a specific CEA peptide in the context of major histocompatibility complex for T-cell-mediated lysis.


CONCLUSIONS
These findings have implications in the development of specific second-generation cancer immunotherapy protocols.
Tsang
K Y
KY
Laboratory of Tumor Immunology and Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Zaremba
S
S
Nieroda
C A
CA
Zhu
M Z
MZ
Hamilton
J M
JM
Schlom
J
J
D000595:Amino Acid Sequence; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D002277:Carcinoma / Q000276:immunology; D015179:Colorectal Neoplasms / Q000276:immunology; D005434:Flow Cytometry; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D016056:Immunodominant Epitopes / Q000276:immunology*; D008969:Molecular Sequence Data; D013601:T-Lymphocytes / Q000276:immunology*; D014614:Vaccines, Synthetic / Q000276:immunology; D014616:Vaccinia virus / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*
D002272:Carcinoembryonic Antigen; D015395:Histocompatibility Antigens Class I; D016056:Immunodominant Epitopes; D014614:Vaccines, Synthetic; D014765:Viral Vaccines