Bulk TCRseq analysis on CD8+ T cells in wild type mice following anti-CD4 and anti-PDL1 mAb treatment

The repertoire of tumor-infiltrating T cells is a novel perspective to characterize effective anti-tumor T cell responses. Previous studies reported that the oligoclonal expansion in tumor T-cell repertoire is associated with anti-tumor effects. However, the contribution of the expansion of diverse T-cell clones remained unclear. We demonstrated that the polyclonal fraction of tumor-reactive T-cell repertoire consisting of relatively minor clones, increased in tumor-bearing mice treated with anti-PD-L1 or anti-CD4 monoclonal antibodies (mAbs), while the oligoclonal fraction consisting of major clones was unchanged. Moreover, the polyclonal fraction was enriched with progenitor exhausted T cells, essential for a durable anti-tumor response, and more dependent on CCR7+ migratory dendritic cells, responsible for priming tumor-reactive T cells in the tumor-draining lymph node (dLN). These results proposed that the expansion of diverse tumor-reactive clones, “clonal spreading,” is an important mechanism by which anti-PD-L1 and anti-CD4 treatments exert robust and durable anti-tumor T-cell responses. CD8+, CD8+ PD1-, CD8+ PD1+ Ly108+ Tim3-, CD8+ PD1+ Ly108+ Tim3+, and CD8+ PD1+ Ly108- Tim3+ T cells from tumor, and CD8+ CD44high T cells from dLN were collected from B16F10 or Lewis lung carcinoma (LLC) tumor-bearing mouse treated with anti-CD4 mAb, anti-PD-L1 mAb or combination of anti-CD4 and anti-PD-L1 mAbs. Bulk TCR sequencing was performed, and T cell clones that overlap between tumor and dLN were identified.

肿瘤浸润T细胞库（tumor-infiltrating T cell repertoire）是表征有效抗肿瘤T细胞应答的全新研究视角。既往研究表明，肿瘤T细胞库中的寡克隆扩增与抗肿瘤效应相关，但多样化T细胞克隆扩增的具体作用仍尚不明确。本研究证实，经抗PD-L1或抗CD4单克隆抗体（monoclonal antibodies, mAbs）治疗的荷瘤小鼠体内，由相对次要克隆组成的肿瘤反应性T细胞库的多克隆组分显著升高，而由优势克隆组成的寡克隆组分则无明显变化。此外，该多克隆组分富含祖细胞耗竭T细胞——这类细胞对于持久的抗肿瘤应答至关重要——且更依赖于CCR7+迁移性树突状细胞；后者负责在肿瘤引流淋巴结（dLN）中启动肿瘤反应性T细胞的活化。本研究结果表明，多样化肿瘤反应性克隆的扩增即“克隆扩散（clonal spreading）”，是抗PD-L1与抗CD4治疗实现强效且持久的抗肿瘤T细胞应答的重要机制。研究人员从经抗CD4单克隆抗体、抗PD-L1单克隆抗体或二者联合治疗的B16F10或路易斯肺癌（Lewis lung carcinoma, LLC）荷瘤小鼠中，分别采集肿瘤组织中的CD8+、CD8+ PD1-、CD8+ PD1+ Ly108+ Tim3-、CD8+ PD1+ Ly108+ Tim3+、CD8+ PD1+ Ly108- Tim3+ T细胞，以及肿瘤引流淋巴结中的CD8+ CD44high T细胞；随后对样本开展批量T细胞受体（TCR）测序，并鉴定出肿瘤与肿瘤引流淋巴结之间共有的T细胞克隆。