Project description:In response to acute infection, naive CD8+ T cells expand, differentiate into effector cells and then contract to a long-lived pool of memory cells after pathogen clearance. During chronic infections or in tumors, CD8+ T cells acquire an “exhausted” phenotype. Here we present genome-wide comparisons of chromatin accessibility and gene expression from endogenous CD8+ T cells responding to acute and chronic viral infection using ATAC-seq and RNA-seq. Acquisition of effector, memory or exhausted phenotypes was associated with stable changes in chromatin accessibility away from the naive T cell state. Regions differentially accessible between functional subsets in vivo were enriched for binding sites of transcription factors known to regulate these subsets, including E2A, BATF, IRF4, T-bet and TCF1. Exhaustion-specific accessible regions were enriched for consensus binding sites for NFAT and Nr4a family members, indicating that chronic stimulation confers a unique accessibility profile on exhausted cells.
Project description:Coordination of cellular metabolism is essential for optimal T cell responses. Here, we identify cytosolic acetyl-CoA production as an essential metabolic node for CD8 T cell function in vivo. We show that acetyl-CoA derived from mitochondrial citrate via the enzyme ATP citrate lyase (Acly) is required for CD8 T cell responses to infection. However, ablation of Acly triggers an alternative, acetate-dependent pathway for acetyl-CoA production in T cells mediated by acyl-CoA synthetase short chain family member 2 (Acss2). Mechanistically, acetate fuels both the TCA cycle and cytosolic acetyl-CoA production, impacting T cell effector responses, acetate-dependent histone acetylation, and effector gene expression by altering chromatin accessibility. When Acly is functional, Acss2 is not required, suggesting acetate is not an obligate metabolic substrate for CD8 T cell function. However, deletion of Acly renders CD8 T cells dependent on acetate (via Acss2) to maintain acetyl-CoA production and effector function. Thus, together Acly and Acss2 coordinate cytosolic acetyl-CoA production in CD8 T cells to maintain chromatin accessibility and T cell effector function.
Project description:Coordination of cellular metabolism is essential for optimal T cell responses. Here, we identify cytosolic acetyl-CoA production as an essential metabolic node for CD8 T cell function in vivo. We show that CD8 T cell responses to infection depend on acetyl-CoA derived from citrate via the enzyme Acly (ATP citrate lyase). However, ablation of Acly triggers an alternative, acetate-dependent pathway for acetyl-CoA production mediated by Acss2 (acyl-CoA synthetase short chain family member 2). Mechanistically, acetate fuels both the TCA cycle and cytosolic acetyl-CoA production, impacting T cell effector responses, acetate-dependent histone acetylation, and chromatin accessibility at effector gene loci. When Acly is functional, Acss2 is not required, suggesting acetate is not an obligate metabolic substrate for CD8 T cell function. However, deletion of Acly renders CD8 T cells dependent on acetate (via Acss2) to maintain acetyl-CoA production and effector function. Thus, together Acly and Acss2 coordinate cytosolic acetyl-CoA production in CD8 T cells to maintain chromatin accessibility and T cell effector function.
Project description:Transforming growth factor-β (TGF-β) is an immunosuppressive cytokine that regulates both innate and adaptive immune responses. Earlier studies have shown that TGF-β plays a role in promoting T cell exhaustion during the later stages of chronic viral infection. In this dataset we examined the global chromatin accessibility changes in CD8 T cells that are dependent on SMAD4. Our findings documenting the striking requirement for Smad4-SKI-SKIL mediated restraint of TGF-β-associated program during the effector phase of the CD8 T cell response have implications for developing immunotherapeutic approaches against chronic viral infections and cancer.
Project description:During chronic viral infection, pathogen-specifc CD8+ T cells develop into three main phenotypically and functionally distinct subsets: TCF1hi progenitor, PD-1hi exhausted, and recently identied CX3CR1+ cytotoxic effector cells. Although genetic programs governing progenitor and exhausted subset formation have been well-studied, how CX3CR1+ effector CD8+ T cell differentiation is transcriptionally and epigentically regulated remains elusive. In this study, our single cell transcriptomics and epigenetic assays revealed that three subsets of virus-specific cells were governed by distinct gene regulatory networks (GRNs) and epigenetic landscapes. Computational analyses demonstrated a striking similarity between the CX3CR1+ subset and short-live effector cells (SLECs) from acute LCMV infection. Consistently, genetic deletion of T-bet (Tbx21) significantly diminished the formation and function of the CX3CR1+ subset. Importantly, we identify that the transcription factor (TF) BATF is required to maintain a permissive chromatin structure that allows differentiation transition from TCF1+ progenitor to CX3CR1+ effector cells. Intriguingly, haplodificiency of BATF in CD8+ T cells abolished CX3CR1+ effector subset formation. Lastly, we found that BATF directly bound to key genetic regions such as Tbx21 and modulated their enhancer accessibility to facilitate progenitor to CX3CR1+ effector cell transition. These mechanistic insights can be harnessed to overcome T cell exhaustion in treating chronic infections and cancer.
