Abstract 6688: Peripheral CCR6+ T-cell profile in healthy volunteers after ingestion of Lactobacillus-derived exopolysaccharide which was reported as an ICI-efficacy enhancer in vivo
Authors: Kawanabe-Matsuda Hirotaka , Yokoo Takehiro , Tou Shogi , Ishii Shoko , Nakamura Marie , Watanabe Reiko , Ogawa Miho , Takeda Kazuyoshi , Sashihara Toshihiro , Shimizu Hiroyuki 
Published: March 2024

Abstract
Introduction: Exopolysaccharides (EPS) are high-molecular-weight polymers composed of sugar residues secreted by bacteria into the surrounding environment. We (Juntendo University and Meiji Holdings) recently reported that oral administration of EPS derived from Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1 (R-1EPS) enhanced therapeutic efficacies of immune-checkpoint inhibitors (ICIs) in vivo (Kawanabe-Matsuda et al. Cancer Discov. 2022.). Briefly, R-1EPS increased CCR6+ CD8+ T cells in the small intestine, and these T cells migrated into the tumor tissue to improve the immune microenvironment via a high IFN-γ productivity. As an early step for a medicine, we tested the R-1EPS on healthy volunteers, focusing on the peripheral immune profiling, especially for CCR6-expressing T cells.
Methods: This trial was randomized, placebo-controlled, double-blinded, and parallel-grouped. Japanese healthy adults were divided into R-1EPS and placebo groups and ingested daily test substance for four weeks. We collected PBMCs from all subjects before and after the ingestion to analyze by mass-cytometry based on Maxpar DirectTM Immune Profiling Assay with T Cell Expansion Panel 2 [Standard BioTools, N = 44 (R-1EPS) and N = 43 (placebo)].
Results: By manual gating strategy, we found that MAIT/NKT cells (CD45+CD66b−CD19−CD20−CD14−CD11c−CD3+TCRγδ−CD4−CD28+CD161high) were increased in the R-1EPS group. Most MAIT/NKT (about 60 - 90 %) were CCR6+ CD8+ cells. Moreover, we characterized three distinct CCR6+ CD4+ T-cell clusters by analyzing the CITRUS (cluster identification, characterization, and regression) algorithm, and found that CCR6+ Th1-like CD4+ T cells were also increased in the R-1EPS group. Notably, these CCR6+ Th1-like CD4+ T cells are phenotypically similar to Th7R cells, that was previously reported as a peripheral correlative biomarker of ICI response (Kagamu et al. Cancer Immunol Res. 2020., Kagamu et al. Cancer Res. 2022.).
Conclusion: These results suggested that oral administration of R-1EPS for humans specifically increased some CCR6+ CD8+ T cells, as previously reported in vivo, and CCR6+ Th1-like CD4+ T cells. Therefore, we (Meiji Holdings Co., Ltd.) consider a clinical trial for the drug development using R-1EPS to treat cancer patients with ICIs.
Citation Format: Hirotaka Kawanabe-Matsuda, Takehiro Yokoo, Shogi Tou, Shoko Ishii, Marie Nakamura, Reiko Watanabe, Miho Ogawa, Kazuyoshi Takeda, Toshihiro Sashihara, Hiroyuki Shimizu. Peripheral CCR6+ T-cell profile in healthy volunteers after ingestion of Lactobacillus-derived exopolysaccharide which was reported as an ICI-efficacy enhancer in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6688.