Engineered yeast cells simulating CD19+ cancers to control CAR T cell activation

Abstract Chimeric antigen receptor (CAR) T cells have become an established immunotherapy and show promising results for the treatment of hematological cancers in most patients. However, modulation of the surface levels of the targeted antigen in cancer cells affects the quality and safety of CAR T cell therapy. Here we present the successful engineering of yeast to simulate cancer cells with controllable surface antigen-densities for synthetic cell-cell communication with CAR T cells. Hence, we establish a novel tool for controlled activation of CAR T cell responses and the assessment of antigen-density thresholds. Specifically, we demonstrate i) controllable antigen-densities of CD19 on yeast using G protein-coupled receptors (GPCRs), ii) a customizable system applying heterologous GPCRs that define signal input types and signal pathway engineering for tuning the output intensity, and iii) efficient and robust activational control of clinically-derived CAR T cells using CD19-displaying yeast cells compared to the activation elicited by a NALM6 cancer cell line. Based on this yeast-based antigen-presenting cell system, we envision efficient assessment of how varying antigen densities in cancer cells affect CAR T cell responses and ultimately support development of safer and better quality of personalized cancer therapies.