CTLs stimulated with lv-hTERT vector kill TERT-expressing tumor cells in vitro. (A) Flow cytometric analysis of HLA-A2.1 and TERT expressions on the B16/A2 cell line. (B-D) Splenocytes from lentiviral vector (lv)–hTERT–immunized HHD mice were restimulated twice in vitro with the indicated hTERT peptide. The peptide-specific cytotoxic T lymphocytes (CTLs), CTL_pY572 (B), CTL_pY988 (C), and CTL_p540 (D), were then tested against IFN-γ–treated tumor cells. Peptide recognition of CTLs was confirmed using RMAS/HHD cells pulsed with respective peptides (B-D). Results represent the percentage of lysis at various CTL/target ratios. The summarized data from 2 independent experiments are shown.