Rath and Bajwa et al. redirected human T cells by transgenic expression of TCR8, which encodes the co-receptor CD8αβ, and an MHC-I-restricted tumor-associated antigen (TAA)-specific TCR, or only the TCR. TCR8+CD4+, TCR8+CD8+ and TCR+CD8+ (but not TCR+CD4+) T cells acted comparably upon bulk coculture with TAA+ cells. Yet, single-cell analyses showed that TCR8+CD4+ T cells best sustained upregulated expression of the most numerous and diverse sets of genes underlying proliferative, cytolytic, costimulatory, cell cycle, and metabolic pathways, representing a less differentiated and less exhausted profile, and better controlled a leukemia xenograft in vivo.
Contributed by Paula Hochman
ABSTRACT: Transgenic coexpression of a class I–restricted tumor antigen–specific T cell receptor (TCR) and CD8 (TCR8) redirects antigen specificity of CD4+ T cells. Reinforcement of biophysical properties and early TCR signaling explain how redirected CD4+ T cells recognize target cells, but the transcriptional basis for their acquired antitumor function remains elusive. We, therefore, interrogated redirected human CD4+ and CD8+ T cells by single-cell RNA sequencing and characterized them experimentally in bulk and single-cell assays and a mouse xenograft model. TCR8 expression enhanced CD8+ T cell function and preserved less differentiated CD4+ and CD8+ T cells after tumor challenge. TCR8+ CD4+ T cells were most potent by activating multiple transcriptional programs associated with enhanced antitumor function. We found sustained activation of cytotoxicity, costimulation, oxidative phosphorylation– and proliferation-related genes, and simultaneously reduced differentiation and exhaustion. Our study identifies molecular features of TCR8 expression that can guide the development of enhanced immunotherapies.