High-affinity human PD-L1 variants attenuate the suppression of T cell activation

// Zhaoduan Liang 1 , Ye Tian 1 , Wenxuan Cai 1 , Zhiming Weng 3 , Yanyan Li 1 , Huanling Zhang 1,2 , Yifeng Bao 1 and Yi Li 1,3 1 State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China 2 School of Life Sciences, University of Science and Technology of China, Hefei, China 3 XiangXue Life Sciences Research Center, XiangXue Pharmaceutical Co. Ltd., Guangzhou, China Correspondence to: Yi Li, email: // Keywords : high affinity, programmed cell death protein 1 (PD-1), PD-ligand 1 (PD-L1), soluble PD-L1, T cell, Immunology and Microbiology Section, Immune response, Immunity Received : August 15, 2017 Accepted : September 03, 2017 Published : October 10, 2017 Abstract The activated T cells can be suppressed by programed death-1 (PD-1) axis through low affinity interaction between PD-1 and PD-ligand 1 (PD-L1) in solution or on antigen presenting cells. In clinic, the concentration of soluble PD-L1 in peripheral blood negatively correlates with cancer prognosis. However, there is little information about the relation between the affinity of PD-1/PD-L1 interaction and the suppressive capacity of PD-1 axis. In this study, we analyzed inhibitory roles of high affinity soluble human PD-L1 (hPD-L1) variants, which were generated with directed molecular evolution. Resultant two clones L3C7-hPD-L1 and L3B3-hPD-L1 showed over 20 folds greater affinity than that of native hPD-L1. We found that L3B3-hPD-L1 and L3C7-hPD-L1 could compete with an anti-PD-1 antibody (EH12.1) for binding to hPD-1. More importantly, although native soluble hPD-L1 can induce suppressive effects on activated T cells, we found L3B3-hPD-L1 and L3C7-hPD-L1 attenuated the strength of PD-1 axis for suppressing the proliferation and interferon γ (IFN-γ) secretion of PBMC. In conclusion, our data provide direct evidence in which immune checkpoint receptor-ligand interactive strength can alter the the suppressive function, in particular, the suppressive capacity of PD-1 axis could be decreased with enhanced affinity of soluble PD-L1 and PD-1 interaction. Our study might provide a new direction for manipulating immune checkpoints.