Naive CD8+ T cells differentiating into effector T cells increase glucose uptake and shift from quiescent to anabolic metabolism. Although much is known about the metabolism of cultured T cells, how ...T cells use nutrients during immune responses in vivo is less well defined. Here, we combined bioenergetic profiling and 13C-glucose infusion techniques to investigate the metabolism of CD8+ T cells responding to Listeria infection. In contrast to in vitro-activated T cells, which display hallmarks of Warburg metabolism, physiologically activated CD8+ T cells displayed greater rates of oxidative metabolism, higher bioenergetic capacity, differential use of pyruvate, and prominent flow of 13C-glucose carbon to anabolic pathways, including nucleotide and serine biosynthesis. Glucose-dependent serine biosynthesis mediated by the enzyme Phgdh was essential for CD8+ T cell expansion in vivo. Our data highlight fundamental differences in glucose use by pathogen-specific T cells in vivo, illustrating the impact of environment on T cell metabolic phenotypes.
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•Developed 13C-infusion method for studying T cell metabolism in vivo•T cell glucose use and bioenergetics differ between cell culture and mouse models•Glucose metabolism in T cells changes dynamically over an immune response•Glucose-dependent serine biosynthesis supports T cell proliferation in vivo
Although much is known about the metabolism of cultured T cells, how T cells use nutrients during immune responses in vivo is not well defined. Using 13C-glucose isotope tracing in mice, Ma et al. demonstrate prominent use of glucose for anabolic metabolism by T cells in vivo. This work highlights the importance of studying T cell metabolism in a physiological environment.
Epigenetic modifications on DNA and histones regulate gene expression by modulating chromatin accessibility to transcription machinery. Here we identify methionine as a key nutrient affecting ...epigenetic reprogramming in CD4+ T helper (Th) cells. Using metabolomics, we showed that methionine is rapidly taken up by activated T cells and serves as the major substrate for biosynthesis of the universal methyl donor S-adenosyl-L-methionine (SAM). Methionine was required to maintain intracellular SAM pools in T cells. Methionine restriction reduced histone H3K4 methylation (H3K4me3) at the promoter regions of key genes involved in Th17 cell proliferation and cytokine production. Applied to the mouse model of multiple sclerosis (experimental autoimmune encephalomyelitis), dietary methionine restriction reduced the expansion of pathogenic Th17 cells in vivo, leading to reduced T cell-mediated neuroinflammation and disease onset. Our data identify methionine as a key nutritional factor shaping Th cell proliferation and function in part through regulation of histone methylation.
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•Activated T cells use exogenous methionine to synthesize the methyl donor SAM•Methionine restriction reduces intracellular SAM and H3K4me3 levels in T cells•Methionine restriction limits the expansion of inflammatory Th17 cells•EAE onset and severity are reduced by dietary methionine restriction
CD4+ T helper (Th) cells are central drivers of autoimmune pathology in diseases such as multiple sclerosis. Roy and Chen et al. identify methionine as an essential nutrient for Th cell epigenetic programming and demonstrate that dietary methionine restriction impacts T cell-mediated autoimmunity through effects on Th17 cell proliferation and cytokine production.
T cell subsets including effector (Teff), regulatory (Treg), and memory (Tmem) cells are characterized by distinct metabolic profiles that influence their differentiation and function. Previous ...research suggests that engagement of long-chain fatty acid oxidation (LC-FAO) supports Foxp3+ Treg cell and Tmem cell survival. However, evidence for this is mostly based on inhibition of Cpt1a, the rate-limiting enzyme for LC-FAO, with the drug etomoxir. Using genetic models to target Cpt1a specifically in T cells, we dissected the role of LC-FAO in primary, memory, and regulatory T cell responses. Here we show that the ACC2/Cpt1a axis is largely dispensable for Teff, Tmem, or Treg cell formation, and that the effects of etomoxir on T cell differentiation and function are independent of Cpt1a expression. Together our data argue that metabolic pathways other than LC-FAO fuel Tmem or Treg differentiation and suggest alternative mechanisms for the effects of etomoxir that involve mitochondrial respiration.
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•Cpt1a mediates long-chain fatty acid oxidation (LC-FAO) in T cells•Cpt1a is not required for T effector (Teff) or T memory (Tmem) cell responses•Cpt1a is not required for CD4+ Treg homeostasis/differentiation/suppressive function•Etomoxir induces Cpt1a-independent off-target effects at concentrations >100 μM
Using genetic models of Cpt1a deficiency, Raud et al. demonstrate that long-chain fatty acid oxidation is largely dispensable for T cell activation and generation of CD8+ T memory (Tmem) cells and CD4+ Treg cells, and observe that, at high concentrations, the Cpt1 inhibitor etomoxir presents off-target effects on cell metabolism.
Upon immune recognition of viruses, the mammalian innate immune response activates a complex signal transduction network to combat infection. This activation requires phosphorylation of key ...transcription factors regulating IFN production and signaling, including IFN regulatory factor 3 (IRF3) and STAT1. The mechanisms regulating these STAT1 and IRF3 phosphorylation events remain unclear. Here, using human and mouse cell lines along with gene microarrays, quantitative RT-PCR, viral infection and plaque assays, and reporter gene assays, we demonstrate that a microRNA cluster conserved among bilaterian animals, encoding miR-96, miR-182, and miR-183, regulates IFN signaling. In particular, we observed that the miR-183 cluster promotes IFN production and signaling, mediated by enhancing IRF3 and STAT1 phosphorylation. We also found that the miR-183 cluster activates the IFN pathway and inhibits vesicular stomatitis virus infection by directly targeting several negative regulators of IRF3 and STAT1 activities, including protein phosphatase 2A (PPP2CA) and tripartite motif–containing 27 (TRIM27). Overall, our work reveals an important role of the evolutionarily conserved miR-183 cluster in the regulation of mammalian innate immunity.
The factors that promote T cell expansion are not fully known. Creatine is an abundant circulating metabolite that has recently been implicated in T cell function; however, its cell-autonomous role ...in immune-cell function is unknown. Here, we show that creatine supports cell-intrinsic CD8+ T cell homeostasis. We further identify creatine kinase B (CKB) as the creatine kinase isoenzyme that supports these T cell properties. Loss of the creatine transporter (Slc6a8) or Ckb results in compromised CD8+ T cell expansion in response to infection without influencing adenylate energy charge. Rather, loss of Slc6a8 or Ckb disrupts naive T cell homeostasis and weakens TCR-mediated activation of mechanistic target of rapamycin complex 1 (mTORC1) signaling required for CD8+ T cell expansion. These data demonstrate a cell-intrinsic role for creatine transport and creatine transphosphorylation, independent of their effects on global cellular energy charge, in supporting CD8+ T cell homeostasis and effector function.
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•Inactivation of the creatine transporter (SLC6A8) impairs CD8+ T cell survival•Creatine kinase B (CKB) is the predominant creatine kinase isoenzyme in CD8+ T cells•Slc6a8 or Ckb ablation compromises CD8+ T cell expansion in response to infection•Slc6a8 or Ckb deletion weakens TCR-mediated activation of mTORC1 signaling
Samborska et al. reveal a cell-intrinsic role for creatine transport and creatine transphosphorylation, independent of their effects on global cellular energy charge, in supporting CD8+ T cell homeostasis and effector function.
Triple-negative breast cancer (TNBC) is an aggressive disease for which treatment options are limited and associated with severe toxicities. Immunotherapeutic approaches like immune checkpoint ...inhibitors (ICIs) are a potential strategy, but clinical trials have demonstrated limited success in this patient cohort. Clinical studies using ICIs have revealed that patients with preexisting anticancer immunity are the most responsive. Given that oncolytic viruses (OVs) induce antitumor immunity, we investigated their use as an ICI-sensitizing approach. Using a therapeutic model that mimics the course of treatment for women with newly diagnosed TNBC, we demonstrate that early OV treatment coupled with surgical resection provides long-term benefits. OV therapy sensitizes otherwise refractory TNBC to immune checkpoint blockade, preventing relapse in most of the treated animals. We suggest that OV therapy in combination with immune checkpoint blockade warrants testing as a neoadjuvant treatment option in the window of opportunity between TNBC diagnosis and surgical resection.
The optimal route for clinical delivery of oncolytic viruses is thought to be systemic intravenous injection; however, the immune system is armed with several highly efficient mechanisms to remove ...pathogens from the circulatory system. To overcome the challenges faced in trying to delivery oncolytic viruses specifically to tumors via the bloodstream, carrier cells have been investigated to determine their suitability as delivery vehicles for systemic administration of oncolytic viruses. Cell carriers protect viruses from neutralization, one of the most limiting aspects of oncolytic virus interaction with the immune system. Cell carriers can also possess inherent tumor tropism, thus directing the delivery of the virus more specifically to a tumor. With preclinical studies already demonstrating the success and feasibility of this approach with multiple oncolytic viruses, clinical evaluation of cell-mediated delivery of viruses is on the horizon. Meanwhile, ongoing preclinical studies are aimed at identifying new cellular vehicles for oncolytic viruses and improving current promising cell carrier platforms.
Advances in immunotherapy have underscored the importance of antitumor immune responses in controlling cancer. However, the tumor microenvironment (TME) imposes several obstacles to the proper ...function of immune cells, including a metabolically challenging and immunosuppressive microenvironment. The increased metabolic activity of tumor cells can lead to the depletion of key nutrients required by immune cells and the accumulation of byproducts that hamper antitumor immunity. Furthermore, the presence of suppressive immune cells, such as regulatory T cells and myeloid-derived suppressor cells, and the expression of immune inhibitory receptors can negatively impact immune cell metabolism and function. This review summarizes the metabolic reprogramming that is characteristic of various immune cell subsets, discusses how the metabolism and function of immune cells are shaped by the TME, and highlights how therapeutic interventions aimed at improving the metabolic fitness of immune cells and alleviating the metabolic constraints in the TME can boost antitumor immunity.
Oncolytic viruses (OVs) and bacteria share the property of tumor-selective replication following systemic administration. In the case of nonpathogenic bacteria, tumor selectivity relates to their ...ability to grow extracellularly within tumor stroma and is therefore ideally suited to restricting the production of bacterially produced therapeutic agents to tumors. We have previously shown the ability of the type 1 interferon antagonist B18R to enhance the replication and spread of vesicular stomatitis virus (VSV) by overcoming related cellular innate immunity. In this study, we utilized nonpathogenic bacteria (E. coli) expressing B18R to facilitate tumor-specific production of B18R, resulting in a microenvironment depleted of bioactive antiviral cytokine, thus “preconditioning” the tumor to enhance subsequent tumor destruction by the OV. Both in vitro and in vivo infection by VSVΔ51 was greatly enhanced by B18R produced from E. coli. Moreover, a significant increase in therapeutic efficacy resulted from intravenous (IV) injection of bacteria to tumor-bearing mice 5 days prior to IV VSVΔ51 administration, as evidenced by a significant reduction in tumor growth and increased survival in mice. Our strategy is the first example where two such diverse microorganisms are rationally combined and demonstrates the feasibility of combining complementary microorganisms to improve therapeutic outcome.
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