Interdisciplinary Initiatives Program Round 10 - 2020

K. Christopher Garcia, Molecular & Cellular Physiology and Structural Biology
Polly Fordyce, Bioengineering and Genetics

Fighting infections and cancer depends critically on the ability to identify ‘foreign’ cells and mount a killing immune response without inadvertently damaging ‘self’ cells in the process. Identifying, controlling, and eradicating nascent tumor cells presents a particularly difficult challenge, as very few molecular differences exist between healthy and cancerous cells. The ability to discriminate ‘self’ from ‘foreign’ peptides relies primarily on T cell receptors (TCRs) on T cells that recognize peptide antigens presented by MHC molecules on target cells (pMHCs), which act as sentinels to alter the T cell if the cell is infected with a pathogen or is cancerous. The act of T cells crawling over antigen-presenting cells during immunosurveillance applies shearing forces to these pMHC/TCR interactions, and this force is essential for accurate discrimination. While ‘self’ peptide-TCR interactions form ‘slip’ bonds that break under increasing shear loads, ‘foreign’ peptide-TCR interactions form ‘catch’ bonds that actually strengthen under load, providing clues used by T cells to decide whether or not to activate. This property makes it very difficult to prospectively identify activating versus non-activating ligands for TCRs that could, for example, be useful for vaccines and cancer immunotherapy, as there are currently no methods available to rapidly test different TCR/pMHC interactions under applied loads in a relatively high-throughput mode to screen for ligands.

In this Bio-X seed grant, Chris Garcia, whose lab has made discoveries in the structural basis of TCR activation and developed a new technology for peptide ligand identification, will collaborate with Polly Fordyce, who brings expertise in physics, assay development, and microfluidics, to develop an entirely new platform for the rapid screening of TCR ligands. This technology, called BATTLES (Biomechanically Assisted TCR Triggering for Large-scale Exogenous-pMHC Screening), builds upon a bead-based multiplexing technology recently developed in the Fordyce lab to allow high-throughput screening of T cell activation by different pMHC complexes in the presence of physiologic applied loads. By merging the Garcia lab’s expertise in T cell biology and ligand screening with the Fordyce lab’s expertise in highthroughput assay development and biophysics, we will realize a unique platform that incorporates most of the physicochemical aspects of T cell activation (e.g. force and ultra-low pMHC density) and allows multiplexed screening of many potential TCR/pMHC pairs at high throughput and at low cost.