Fig. 2.

Detection of CTL-epitope-specific IFN-γ-producing cells in vaccinia–H5- (a) or pcDNA3.0–H5- (b) immunized HLA-A2.1/K^b Tg mice (hatched bars) by ELISPOT assay. Empty bars represent negative controls [PBS (a); pcDNA3.0 (b)]. Female HLA-A2.1/K^b Tg mice, 6–8 weeks old, were immunized with 3–10⁶ p.f.u. vaccinia–H5 in 20 μl PBS or PBS alone at weeks 0, 4 and 8. Ten days after the final boosting, splenocytes were isolated and CTL epitope-specific IFN-γ-producing cells were evaluated by ELISPOT assay. In the ELISPOT assay, splenocytes were stimulated in vitro in the presence of 20 U interleukin-2 (IL-2) ml⁻¹ and 20 μM of the designated peptide for 24 h. ns represents cells that were cultured in the absence of any peptide. * (P<0.05) and ** (P<0.01) indicate significant differences between peptides and ns, using Student's t test.