Abstract 3563: Impact of the affinity of chimeric antigen receptor on immune activation profiles of T cells
Authors: Han Chungyong , Kim Seon-Hee , Choi Beom K. , Kwon Byoung S. 
Published: August 2018

Abstract
Background: Chimeric antigen receptor (CAR) generally uses a single chain antibody fragment (scFv) of high affinity as an antigen-binding domain. Recent studies implied that T cells engineered with CAR (CAR T cells) of an extremely low affinity have the potential to reduce on-target off-tumor toxicity that is a serious side effect in CAR T cell therapy. Defining the relation of CAR affinity to immune activation profiles is important for understanding the nature of CAR T cells.
Methods: We examined the functional variation of CAR T cells when stimulated with target antigens of various affinities. HLA-DR-specific MVR CAR T cells that were previously developed in our group were used in this study. Since MVR CAR recognizes HLA-DR, Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV LCLs) which stably express HLA-DR, stimulated MVR CAR T cells. Importantly, owing to the broad spectrum of MVR CAR affinity against polymorphic epitope of HLA-DR, six different EBV LCLs each of which express unique HLA-DRs, stimulated MVR CAR T cells with different magnitude based on the binding affinities. Using the combination of MVR CAR T cells and six different EBV LCLs, we assessed the extent of effector functions and gene expression induced by different CAR affinity.
Results: The cytolytic activity of MVR CAR T cells was correlated with the affinity between MVR CAR and HLA-DR. The induced polyfunctionality was highest in intermediate MVR CAR-target affinity and was decreased in weak and strong affinities. Gene expression analysis of the stimulated MVR CAR T cells identified a panel of genes of which the expression levels were correlated with CAR-target affinity. Gene ontology analysis revealed that the genes are mainly involved in a T cell activation pathway. Interestingly, we found that the genes involved in type I interferon signaling were upregulated following the stimulation with strong affinity antigens, while those expression levels were unchanged following the stimulation with weak and intermediate affinity antigens.
Conclusions: Here we describe the affinity-associate functional variation of CAR T cells defined by the use of the combination of MVR CAR T cells and EBV LCLs of various affinities. Using those effector/target cell combinations, we investigated the relation between CAR-antigen affinity and the effector functions which include cytolytic activity and polyfunctionality. Furthermore, we identified that type I interferon signaling is a distinct characteristics of strong affinity-induced activation of CAR T cells. These effector/target cell combinations and the observations will help to understand the nature of CAR T cells.
Citation Format: Chungyong Han, Seon-Hee Kim, Beom K. Choi, Byoung S. Kwon. Impact of the affinity of chimeric antigen receptor on immune activation profiles of T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3563.