Figure 3.

Specific lysis of target cells and secretion of IFN-γ by induced CTLs in immunizing HLA-A2.1/K^b transgenic mice immunized with the indicated peptides. Peptide (100 μg) and the IA^b-restricted HBV-core₁₂₈ T helper epitope (140 μg) emulsified in IFA were used to immunize HLA-A2.1/K^b transgenic mice on days 0, 5, and 10. PBS only or T helper peptide emulsified in IFA was used as the negative control. On day 11, we isolated splenocytes from the mice and restimulated the cells with 10 μg/ml peptide and 10 U/ml rmIL-2 to repriming these splenocytes in vitro for additional 6 days. An LDH assay was performed to assess the lysis activity of the induced CTLs toward (a) SW620 cells (HLA-A2⁺, MTA1⁺), (b) T2 cells pulsed with each peptide, and (c) SW620 cells incubated with an anti-human HLA-A2 antibody (HLA-A2⁻, MTA1⁺). IFN-γ secretion was detected by the ELISPOT assay. (d) T2 cells incubated with each peptide and an irrelevant peptide (50 μg/ml) for 4 h were used as the stimulating cells. Each sample was measured in triplicate. Data represent means ± SD (n = 5). ^∗ P < 0.05, ^∗∗ P < 0.05, and ^∗∗∗ P < 0.001 vs. the T helper epitope group.