Induction of cell-mediated immune response to hTERT in rhesus monkeys by DNA-EP and Ad regimen. (a) Schematic representation of the vaccination schedule. (b) Enzyme-linked immunosorbent spot (ELISPOT) was performed on PBMCs from hTERT-immunized rhesus monkeys after the second DNA-EP. Three pools of 15-mer peptides covering hTERT (pool 1, 2, and 3) and one pool covering LTB were utilized. (c) Analysis was performed after the fifth DNA-EP. (d) ELISPOT was performed at the end of the immunization program based on five DNA-EP and two Ad (Ad6-hTERT) injections. The assay was run in duplicate and the average value from the replicates is shown. Ad6, adenovirus serotype 6; DMSO, dimethyl sulfoxide; DNA-EP, DNA electroporation; hTERT, human telomerase reverse transcriptase; LTB, β-subunit of Escherichia coli heat labile enterotoxin; PBMC, peripheral blood mononuclear cell; SFC, spot-forming cell; Vax, vaccination.