Fig. 3

In vitro specific lysis activity of CTL by 9-mer UC peptides. Human PBMCs treated with 9 nM and 27 nM UC-100 (a) and UC-152 (b) peptides were cocultured with SARS-CoV-2 spike-expressing HEK 293 cells at ratios of 27:1, 9:1, 3:1 and 1:1 for 5 days. The lytic activity was measured by LDH release, total target cell death was set as 100% cytotoxicity, and no peptide treatment was used as the negative control. The assay was performed in duplicate and is represented as the mean ± S.E. Significant differences are indicated by asterisks (unpaired one-tailed Student’s t test; *p < 0.05, **p < 0.01, ***p < 0.001).