Longitudinal profiling of tumor specific CD8 T cells using single cell RNA-Seq in mouse lung adenocarcinoma

T cell dysfunction is a critical obstacle to productive anti-tumor immunity. Previous work has demonstrated that a subset of dysfunctional CD8+ T cells expresses TCF-1, and that this population sustains the T cell response over time. However, the mechanisms that contribute to the generation and maintenance of TCF-1+ CD8+ T cells remain poorly understood. Here, using a model of lung adenocarcinoma, we demonstrate that TCF-1+ CD8+ T cells are found within both tumor and tumor draining LN (dLN), but phenotypically and functionally differ based on location. In tumors, TCF-1+ CD8+ T cells become dysfunctional with time, are heterogeneous, and decline over the course of progression, while TCF-1+ CD8+ T cells in the dLN remain stable. Blocking egress from the dLN decreased SlamF6+ TCF-1+ CD8+ T cells in tumors, demonstrating that the dLN is a critical reservoir of functional CD8+ T cells. Concomitant with the decline in CD8+ T cells in the tumor, migratory conventional dendritic cell type I (cDC1) numbers decreased in the dLN. Therapeutically, boosting cDC1 numbers and function using Flt3L/anti-CD40 antibody resulted in T cell proliferation within the dLN, an increased SlamF6+ TCF-1+ CD8+ T cells in tumors, and a decreased tumor burden. These data demonstrate the importance of migratory cDC1 cells in boosting TCF-1+ CD8+ T cells in the dLN, and provide rationale for targeting DCs in immunotherapy. Overall design: 10X 5' and SmartSeq2 single cell RNA-Seq and paired TCR sequencing was performed on sorted lung infiltrating H-2Kb/SIINFEKL specific and polyclonal CD8+ T cells from KrasG12D+/- Trp53-/- lung adenocarcinoma bearing lungs. Using topic modeling, we identified multiple discrete cell states occupied by Tcf7+ H-2Kb/SIINFEKL specific CD8+ T cells that varied over tumor progression.