Overcoming T cell tolerance to tumor self-antigens through catch-bond engineering

T cells are often weakly responsive to tumor self-antigens because of central tolerance, which constrains their ability to eliminate tumors. Affinity-matured T cell receptors can exhibit enhanced tumor killing properties but in therapeutic settings have been accompanied by off-target cross-reactivity and toxicity, because high-affinity TCRs antigen specificity is altered compared to naturally selected TCRs. Here, we exploited the physiological biophysical mechanism of TCR activation through mechanical force, by engineering to a weakly reactive TCR specific for a non-mutated human prostate tumor associated antigen (TAA), Prostatic Acid Phosphatase (PAP). We isolated a catch bonding “hotspot” whose mutation enhanced T cell activity by increasing TCR-pMHC bond lifetime, whilst maintaining physiological affinities and antigen fine-specificities. T cells expressing these engineered TCRs showed vastly superior expansion and tumor killing properties in vitro and in vivo, as well as enhanced effector phenotypes and proliferation in the tumor, as measured by single-cell RNA-seq. High resolution structures and molecular dynamics simulations of the TCR-pMHC complexes reveal the structural hotspot in TCR CDR1 is primed for peptide interaction in the catch bond engineered TCR. These studies establish catch bond engineering as a viable biophysically-based strategy to convert tolerized anti-tumor T cells into potent TCR-T killers.