Single Molecule Force Spectroscopy Reveals Distinctions in Key Biophysical Parameters of αβ T-Cell Receptors Compared
Debasis Banik1, Maryam Hamidinia2,3,4, Joanna Brzostek2,3,4
1Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States.
Abstract:
Chimeric antigen receptor (CAR) T-cell therapies exploit facile antibody-mediated targeting to elicit useful immune responses in patients. This work directly compares binding profiles of CAR and αβ T-cell receptors (TCR) with single cell and single molecule optical trap measurements against a shared ligand. DNA-tethered measurements of peptide-major histocompatibility complex (pMHC) ligand interaction in both CAR and TCR exhibit catch bonds with specific peptide agonist peaking at 25 and 14 pN, respectively. While a conformational transition is regularly seen in TCR-pMHC systems, that of CAR-pMHC systems is dissimilar, being infrequent, of lower magnitude, and irreversible. Slip bonds are observed with CD19-specific CAR T-cells and with a monoclonal antibody mapping to the MHC α2 helix but indifferent to the bound peptide. Collectively, these findings suggest that the CAR-pMHC interface underpins the CAR catch bond response to pMHC ligands in contradistinction to slip bonds for CARs targeting canonical ligands.
Insights
This study compares chimeric antigen receptor (CAR) and T-cell receptor (TCR) binding to ligands. CARs exhibit unique catch bonds with peptide-MHC ligands, differing from TCR interactions.
Area of Science:
- Immunology
- Biophysics
Background:
- Chimeric antigen receptor (CAR) T-cell therapies utilize antibody-mediated targeting for immune responses.
- Understanding the biophysical interactions of CARs with ligands is crucial for optimizing CAR T-cell therapy.
Purpose of the Study:
- To directly compare the binding profiles of CARs and αβ T-cell receptors (TCRs) against a shared ligand.
- To investigate the mechanical properties of CAR-TCR-ligand interactions at the single-molecule level.
Main Methods:
- Employed single-cell and single-molecule optical trap measurements.
- Utilized DNA-tethered measurements of peptide-major histocompatibility complex (pMHC) ligand interactions.
- Compared CAR and TCR binding dynamics against specific peptide agonists and CD19-specific CARs.
Main Results:
- Both CAR and TCR interactions with peptide-MHC ligands exhibited catch bonds, with peak forces of 25 pN for CAR and 14 pN for TCR.
- CAR-pMHC interactions showed infrequent, lower-magnitude, and irreversible conformational transitions, unlike TCR-pMHC systems.
- CD19-specific CAR T-cells and a monoclonal antibody displayed slip bonds, independent of the bound peptide.
Conclusions:
- The CAR-pMHC interface dictates the CAR's catch bond response to pMHC ligands.
- CAR interactions with pMHC ligands differ significantly from TCR interactions.
- Findings provide insights into the distinct mechanical behaviors of CARs and TCRs, informing CAR T-cell therapy design.
