Binding of peptide variants and Mtb-VL9 hybrids to HLA-E*01:03. All peptides were evaluated for peptide binding affinity using the previously developed UV-mediated peptide exchange coupled to ELISA assay for HLA-E.⁷ (A) Affinity of the VMAPRTLIL variants for HLA-E*01:03. (B) Affinity of the VLAPRTLLL variants for HLA-E*01:03. (C) Affinity of the Mtb-VL9 hybrid peptides for HLA-E*01:03. The sequences of the hybrid peptides are shown on the X-axis and the residues that are changed relative to the wildtype sequence are shown in italics. The residue substitutions at each position are shown on the X-axis in (A) and (B). The Y-axis shows the affinity for HLA-E*01:03, displayed as a signal to positive ratio (S/P) in (A–C). The S/P ratio is a relative measure of the affinity of the peptide variant relative to the positive control peptide (VMAPRTLIL in A and VLAPRTLLL in B). Dotted lines indicate the threshold for defining peptides as binders (>0.08) or good binders (>0.18). These values were defined previously.⁷ Peptides were tested at least two times and bars represent the median S/P ratio with 95% confidence interval. Peptide sequences are provided in Table S1.