PR2-specific T cells expanded from PADRE-PR2 fusion peptide immunized mice are functional CTL. PR2-specific murine T cells are cytotoxic to human HLA-A2 LCL infected with rVV expressing PR3 Ag though not HLA-A2 LCL infected with rVV expressing irrelevant EGFP Ag (left panel). PR2 effectors also killed HLA-A2 LCL target cells loaded with PR2 peptide but not an irrelevant peptide (right panel). PR2 effectors were cytotoxic to K562-A2PR3 cells that endogenously express PR3, though not K562-A2 cells (central panel). Each line corresponds to the mean values of 3 individual mice. Error bars indicate the SEM. The specificities of the effector cells for rVV-EGFP-PR3–infected targets versus rVV-EGFP–infected targets, for K562-A2PR3 versus K562-A2 targets, and for PR2 peptide-pulsed targets versus gag peptide-pulsed targets were statistically significant (P < .01) as determined by 1-way ANOVA tests.