MAGE-1-SPECIFIC PRECURSOR CYTOTOXIC T-LYMPHOCYTES PRESENT AMONG TUMOR-INFILTRATING LYMPHOCYTES FROM A PATIENT WITH BREAST-CANCER - CHARACTERIZATION AND ANTIGEN-SPECIFIC ACTIVATION

A potential target for development of tumor-specific immunotherapeutic strategies is the MAGE-1 gene. We have utilized a recently developed recombinant canarypox (ALVAC) virus vector containing the MAGE-1 gene (vCP235) to activate CTLs from a breast cancer patient bearing a MAGE- 1(+) tumor. Tumor-infiltrating lymphocytes (TILs) obtained from the tu mor of a patient were stimulated ill vitro with irradiated autologous peripheral blood mononuclear cells acutely infected with the vCP235 co nstruct. These TILs preferentially expanded approximately 6-fold over a 16-day culture period and specifically recognized an allogeneic tran sformed B-cell line acutely infected with a vaccinia-MAGE-1 recombinan t targeting vector (vP1188) in the context of HLA-A2 and/or B7. TCR VP analysis of in vitro expanded T cells by a quantitative multiprobe RN ase protection assay revealed preferential expansion of TCR V beta 6.3 and V beta 6.4. In addition, homologous T-cell receptor beta CDR3 joi ning sequences sere found in the in vitro stimulated cultures. These r esults suggest that tumor antigen-specific, MHC-restricted CTLs may be derived from precursor CTLs present in TILs obtained from patients wi th MAGE-1(+) tumors by in vitro stimulation with recombinant avipox MA GE-1 virus-infected autologous cells. Collectively, these findings pro vide a rationale for tumor-associated antigen-based immunization as a means of activating precursor CTLs residing in patients with tumors ex pressing defined tumor-associated antigens such as MAGE-1.