Modification of MHC Anchor Residues Generates Heteroclitic Peptides That Alter TCR Binding and T Cell Recognition

Abstract

Improving T-cell antigens by altering MHC anchor residues is a common strategy used to enhance peptide vaccines but there has been little assessment of how such modifications affect TCR binding and T-cell recognition. Here, we use surface plasmon resonance and peptide-MHC tetramer binding at the cell surface to demonstrate that changes in primary peptide anchor residues can substantially and unpredictably alter TCR binding. We also demonstrate that the ability of TCRs to differentiate between natural and anchor-modified heteroclitic peptides distinguishes T-cells that exhibit a strong preference for either type of antigen. Furthermore, we show that anchor-modified heteroclitic peptides prime T-cells with different TCRs compared to those primed with natural antigen. Thus, vaccination with heteroclitic peptides may elicit T-cells that exhibit suboptimal recognition of the intended natural antigen and, consequently, impaired functional attributes in vivo. Heteroclitic peptide-based immune interventions therefore require careful evaluation to ensure efficacy in the clinic.

Peptide Modulation of Class I Major Histocompatibility Complex Protein Molecular Flexibility and the Implications for Immune Recognition*

“…Although TCR cross-reactivity is well appreciated (44), in many cases, TCRs have been shown to be highly sensitive to changes in peptide structure or composition, sometimes with no clear structural explanation. Such fine specificity has been implicated in T cell antagonism as well as the poor performance of modified peptides as vaccine candidates (45,46). Our findings suggest that in some cases, TCR specificity could arise from dynamical changes resulting from peptide modification.…”

Vaccination‐induced functional competence of circulating human tumor‐specific CD8 T‐cells

“…43 The natural and analog peptides represent very highly cross-reactive epitopes compatible with the similar configuration of the two peptide/MHC complexes. 44 We generated >1,000 T-cell clones, and did not find a single clone binding tetramers constructed with one but not the other peptide/ MHC complex. 43,45 Similarly, cross-reactivity was always observed in functional assays, despite the quantitative differences found in peptide titration studies, with enhanced recognition of target cells labeled with natural peptide by T-cells from patients after vaccination with natural peptide.…”

Peptide length determines the outcome of TCR/peptide-MHCI engagement

“…21 In addition, the following HLA B*3508-restricted CD8 ϩ T-cell clones were used: SB14, specific for the EBV-derived EBNA-1 epitope HPVGEADYFEY (residues 407-417) 22 ; SB10, specific for the HCMV-derived pp65 epitope CPSQEPMSIYVY (residues 103-114) 23 ; and SB27, specific for the EBV-derived BZLF1 epitope LPEPLPQGQLTAY (residues 52-64). 24 The recognition parameters of these CD8 ϩ T-cell clones are detailed in Table 1.…”

“…7 pMHCI staining and flow cytometry Soluble biotinylated pMHCI monomers were produced as described previously. 21 Tetrameric pMHCI reagents (tetramers) were constructed by the addition of PE-conjugated streptavidin (Life Technologies) at a pMHCI:streptavidin molar ratio of 4:1. A total of 5 ϫ 10 4 MEL5 CD8 ϩ T cells were stained with PE-conjugated tetramer (25 g/mL) folded around the indicated peptides for 15 minutes at 37°C (for review, see Wooldridge et al 27 ) before staining with 5 L of 7-aminoactinomycin D (Viaprobe; BD Biosciences) for 30 minutes at 4°C.…”