A graph showing the results of the T2-cell binding assay. The binding affinity of the NP peptides to HLA-A2 in the presence of additional β2-microglobulin was detected by a T2-cell binding assay. T2 cells were pulsed with the target NP peptides, respectively, in serum-free medium supplemented with the β2-microglobulin for 2 h. The peptide-HLA-A2 complex was probed by an FITC-conjugated anti-human HLA-A2 antibody and the fluorescent signals were detected via flow cytometry. The binding affinity was presented as the fluorescent index that was calculated by the following formula: FI = [MFI (T2 + peptide)/MFI (T2 only)] − 1. The flu peptide (GILGFVFTL) was used as a positive control. The results represent the mean ± SE (n = 3).