Epigenetic tuning of PD-1 expression improves exhausted T cell function and viral control.

PD-1 is a key negative regulator of CD8 T cell activation and is highly expressed by exhausted T cells in cancer and chronic viral infection. Although PD-1 blockade can improve viral and tumor control, physiological PD-1 expression prevents immunopathology and improves memory formation. The mechanisms driving high PD-1 expression in exhaustion are not well understood and could be critical to disentangling its beneficial and detrimental effects.

Hyperactive Dendritc Cells Redirect Aged Antitumor Immunity.

Aging is one of the biggest risk factors for cancer development. More than 85% of all cancers occur in individuals above 55 years old, often accompanied by age-associated immune defects. Previous studies on the tumor microenvironment during aging have identified several factors, such as the roles of fibroblasts, immunosuppression, and metastasis.

The aged tumor microenvironment limits T cell control of cancer.

The etiology and effect of age-related immune dysfunction in cancer is not completely understood. Here we show that limited priming of CD8 T cells in the aged tumor microenvironment (TME) outweighs cell-intrinsic defects in limiting tumor control. Increased tumor growth in aging is associated with reduced CD8 T cell infiltration and function.

Disrupting CD38-driven T cell dysfunction restores sensitivity to cancer immunotherapy.

A central problem in cancer immunotherapy with immune checkpoint blockade (ICB) is the development of resistance, which affects 50% of patients with metastatic melanoma. T cell exhaustion, resulting from chronic antigen exposure in the tumour microenvironment, is a major driver of ICB resistance. Here, we show that CD38, an ecto-enzyme involved in nicotinamide adenine dinucleotide (NAD) catabolism, is highly expressed in exhausted CD8 T cells in melanoma and is associated with ICB resistance.

Stepwise differentiation of follicular helper T cells reveals distinct developmental and functional states.

Follicular helper T (Tfh) cells are essential for the formation of high affinity antibodies after vaccination or infection. Although the signals responsible for initiating Tfh differentiation from naïve T cells have been studied, the signals controlling sequential developmental stages culminating in optimal effector function are not well understood. Here we use fate mapping strategies for the cytokine IL-21 to uncover sequential developmental stages of Tfh differentiation including a progenitor-like stage, a fully developed effector stage and a post-effector Tfh stage that maintains transcriptional and epigenetic features without IL-21 production.

The PTPN2/PTPN1 inhibitor ABBV-CLS-484 unleashes potent anti-tumour immunity.

Immune checkpoint blockade is effective for some patients with cancer, but most are refractory to current immunotherapies and new approaches are needed to overcome resistance. The protein tyrosine phosphatases PTPN2 and PTPN1 are central regulators of inflammation, and their genetic deletion in either tumour cells or immune cells promotes anti-tumour immunity. However, phosphatases are challenging drug targets; in particular, the active site has been considered undruggable.

Downregulation of KEAP1 in melanoma promotes resistance to immune checkpoint blockade.

Immune checkpoint blockade (ICB) has demonstrated efficacy in patients with melanoma, but many exhibit poor responses. Using single cell RNA sequencing of melanoma patient-derived circulating tumor cells (CTCs) and functional characterization using mouse melanoma models, we show that the KEAP1/NRF2 pathway modulates sensitivity to ICB, independently of tumorigenesis. The NRF2 negative regulator, KEAP1, shows intrinsic variation in expression, leading to tumor heterogeneity and subclonal resistance.

Supporting the Next Generation of Scientists to Lead Cancer Immunology Research.

Recent success in the use of immunotherapy for a broad range of cancers has propelled the field of cancer immunology to the forefront of cancer research. As more and more young investigators join the community of cancer immunologists, the Arthur L. Irving Family Foundation Cancer Immunology Symposium provided a platform to bring this expanding and vibrant community together and support the development of the future leaders in the field.

Epigenetic scars of CD8 T cell exhaustion persist after cure of chronic infection in humans.

T cell exhaustion is an induced state of dysfunction that arises in response to chronic infection and cancer. Exhausted CD8 T cells acquire a distinct epigenetic state, but it is not known whether that chromatin landscape is fixed or plastic following the resolution of a chronic infection. Here we show that the epigenetic state of exhaustion is largely irreversible, even after curative therapy.

Differentiation of exhausted CD8 T cells after termination of chronic antigen stimulation stops short of achieving functional T cell memory.

T cell exhaustion is associated with failure to clear chronic infections and malignant cells. Defining the molecular mechanisms of T cell exhaustion and reinvigoration is essential to improving immunotherapeutic modalities. Here we confirmed pervasive phenotypic, functional and transcriptional differences between memory and exhausted antigen-specific CD8 T cells in human hepatitis C virus (HCV) infection before and after treatment.

Epigenetic Features of HIV-Induced T-Cell Exhaustion Persist Despite Early Antiretroviral Therapy.

T cell dysfunction occurs early following HIV infection, impacting the emergence of non-AIDS morbidities and limiting curative efforts. ART initiated during primary HIV infection (PHI) can reverse this dysfunction, but the extent of recovery is unknown. We studied 66 HIV-infected individuals treated from early PHI with up to three years of ART.

Not-so-opposite ends of the spectrum: CD8 T cell dysfunction across chronic infection, cancer and autoimmunity.

CD8 T cells are critical mediators of cytotoxic effector function in infection, cancer and autoimmunity. In cancer and chronic viral infection, CD8 T cells undergo a progressive loss of cytokine production and cytotoxicity, a state termed T cell exhaustion. In autoimmunity, autoreactive CD8 T cells retain the capacity to effectively mediate the destruction of host tissues.

A bilateral tumor model identifies transcriptional programs associated with patient response to immune checkpoint blockade.

Immune checkpoint blockade (ICB) is efficacious in many diverse cancer types, but not all patients respond. It is important to understand the mechanisms driving resistance to these treatments and to identify predictive biomarkers of response to provide best treatment options for all patients. Here we introduce a resection and response-assessment approach for studying the tumor microenvironment before or shortly after treatment initiation to identify predictive biomarkers differentiating responders from nonresponders.

Fibroblastic reticular cells enhance T cell metabolism and survival via epigenetic remodeling.

Lymph node fibroblastic reticular cells (FRCs) respond to signals from activated T cells by releasing nitric oxide, which inhibits T cell proliferation and restricts the size of the expanding T cell pool. Whether interactions with FRCs also support the function or differentiation of activated CD8 T cells is not known. Here we report that encounters with FRCs enhanced cytokine production and remodeled chromatin accessibility in newly activated CD8 T cells via interleukin-6.

Migratory DCs activate TGF-β to precondition naïve CD8 T cells for tissue-resident memory fate.

Epithelial resident memory T (eT) cells serve as sentinels in barrier tissues to guard against previously encountered pathogens. How eT cells are generated has important implications for efforts to elicit their formation through vaccination or prevent it in autoimmune disease. Here, we show that during immune homeostasis, the cytokine transforming growth factor β (TGF-β) epigenetically conditions resting naïve CD8 T cells and prepares them for the formation of eT cells in a mouse model of skin vaccination.

Author Correction: Subsets of exhausted CD8 T cells differentially mediate tumor control and respond to checkpoint blockade.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Subsets of exhausted CD8 T cells differentially mediate tumor control and respond to checkpoint blockade.

T cell dysfunction is a hallmark of many cancers, but the basis for T cell dysfunction and the mechanisms by which antibody blockade of the inhibitory receptor PD-1 (anti-PD-1) reinvigorates T cells are not fully understood. Here we show that such therapy acts on a specific subpopulation of exhausted CD8 tumor-infiltrating lymphocytes (TILs). Dysfunctional CD8 TILs possess canonical epigenetic and transcriptional features of exhaustion that mirror those seen in chronic viral infection.

Loss of ADAR1 in tumours overcomes resistance to immune checkpoint blockade.

Most patients with cancer either do not respond to immune checkpoint blockade or develop resistance to it, often because of acquired mutations that impair antigen presentation. Here we show that loss of function of the RNA-editing enzyme ADAR1 in tumour cells profoundly sensitizes tumours to immunotherapy and overcomes resistance to checkpoint blockade. In the absence of ADAR1, A-to-I editing of interferon-inducible RNA species is reduced, leading to double-stranded RNA ligand sensing by PKR and MDA5; this results in growth inhibition and tumour inflammation, respectively.

Tumor innate immunity primed by specific interferon-stimulated endogenous retroviruses.

Mesenchymal tumor subpopulations secrete pro-tumorigenic cytokines and promote treatment resistance. This phenomenon has been implicated in chemorefractory small cell lung cancer and resistance to targeted therapies, but remains incompletely defined. Here, we identify a subclass of endogenous retroviruses (ERVs) that engages innate immune signaling in these cells.

IgH isotype-specific B cell receptor expression influences B cell fate.

Ig heavy chain (IgH) isotypes (e.g., IgM, IgG, and IgE) are generated as secreted/soluble antibodies (sIg) or as membrane-bound (mIg) B cell receptors (BCRs) through alternative RNA splicing.

Suppression by T cells leads to durable and selective inhibition of B cell effector function.

Follicular regulatory T cells (T cells) inhibit follicular helper T cell (T cell)-mediated antibody production. The mechanisms by which T cells exert their key immunoregulatory functions are largely unknown. Here we found that T cells induced a distinct suppressive state in T cells and B cells, in which effector transcriptional signatures were maintained but key effector molecules and metabolic pathways were suppressed.

The epigenetic landscape of T cell exhaustion.

Exhausted T cells in cancer and chronic viral infection express distinctive patterns of genes, including sustained expression of programmed cell death protein 1 (PD-1). However, the regulation of gene expression in exhausted T cells is poorly understood. Here, we define the accessible chromatin landscape in exhausted CD8 T cells and show that it is distinct from functional memory CD8 T cells.

Epigenetic stability of exhausted T cells limits durability of reinvigoration by PD-1 blockade.

Blocking Programmed Death-1 (PD-1) can reinvigorate exhausted CD8 T cells (T) and improve control of chronic infections and cancer. However, whether blocking PD-1 can reprogram T into durable memory T cells (T) is unclear. We found that reinvigoration of T in mice by PD-L1 blockade caused minimal memory development.