FIG. 1.

Immunization with DNA vaccine encoding a single dominant or subdominant epitope induces different levels of CTL activity. (A) BALB/c mice were immunized by gene gun with p91m (■, □), p60 217m (▴, ▵), or p60 449m (⧫, ◊) three times. Spleen cells from immunized animals were harvested 2 weeks after the last immunization and stimulated in vitro with LLO 91-99-, p60 217-225-, or p60 449-457-peptide pulsed spleen cells for 5 days. The percentage of specific lysis was determined using J774 cells (H-2^d) pulsed with LLO 91-99-peptide (solid symbols) or control medium (open symbols) as target cells. Results are expressed as the mean ± the standard deviation (SD) for six mice. (B) Translational efficiencies of the three plasmid DNA vaccines. Relative luciferase activities were assayed by transient transfections of p91m-Luc, p60 217m-Luc, and p60 449m-Luc in BALB/3T3 mouse fibroblast cells. The relative luciferase activities are normalized to Renilla remiformis luciferase activities by the cotransfected pRL-CMV (Promega, Madison, Wis.). The data are expressed as the mean ± the SD for six samples.