Peptides synthesis
The predicted SARS-CoV-2 nine-mer epitopes were synthesized at least 90% purity as assessed by high-performance liquid chromatography and mass spectrometry (ChinaPeptides, Shanghai, China). Peptides from HLA-Cw*033-11 or HLA-A*023-11 leading sequences VMAPRTLIL or VMAPRTLVL, which have been confirmed to be the HLA-E-restricted epitopes, were synthesized and used as positive control. The peptide melanoma antigen-encoding gene (MAGE-1) with sequence EADPTGHSY, which couldn’t bind to HLA-E molecules, was synthesized and used as the negative control. All the peptides were stored at 1 mM concentration at −70°C and repeated freeze-thawing was avoided.