Cancer cells subvert immune surveillance through inhibition of T cell effector function. Elucidation of the mechanism of T cell dysfunction is therefore central to cancer immunotherapy. Here, we report that dual specificity phosphatase 2 (DUSP2; also known as phosphatase of activated cells 1, PAC1) acts as an immune checkpoint in T cell antitumor immunity. PAC1 is selectively upregulated in exhausted tumor-infiltrating lymphocytes and is associated with poor prognosis of patients with cancer. PAC1(hi) effector T cells lose their proliferative and effector capacities and convert into exhausted T cells. Deletion of PAC1 enhances immune responses and reduces cancer susceptibility in mice. Through activation of EGR1, excessive reactive oxygen species in the tumor microenvironment induce expression of PAC1, which recruits the Mi-2 beta nucleosome-remodeling and histone-deacetylase complex, eventually leading to chromatin remodeling of effector T cells. Our study demonstrates that PAC1 is an epigenetic immune regulator and highlights the importance of targeting PAC1 in cancer immunotherapy. Yin and colleagues show that the phosphatase PAC1 (DUSP2) acts as a checkpoint in cytotoxic T cells to restrain their antitumor function.
T cell homeostasis and functional responsiveness require signals from self-peptide-major histocompatibility complex (self-pMHC) and cytokines, but the mechanisms controlling this signal integration are unknown. Using a conditional deletion of the T cell lineage-specific protein Themis, we show that Themis is required for the maintenance of peripheral CD8(+) T cells and for proliferative CD8(+) T cell responses to low-affinity pMHC aided by cytokines. Themis-deficient peripheral T cells show a phenotype indicative of reduced tonic signaling from self-pMHC, strongly suggesting that Themis is a positive regulator of T cell receptor signal strength in response to low-affinity self-pMHC in peripheral T cells. Signals from low-affinity pMHC and cytokines synergistically induce phosphorylation of the kinase Akt, metabolic changes and c-Myc transcription factor induction in CD8(+) T cells only in the presence of Themis. This function of Themis is mediated through Shp1 phosphatase, as peripheral Themis and Shp1 double deletion rescues the peripheral CD8(+) T cell maintenance. T cell homeostasis requires integration of signals from antigen and cytokine receptors. Gascoigne and colleagues demonstrate that the protein Themis supports signals from low-affinity TCR ligands to maintain normal CD8(+) cell function.
As a female faculty member with experience at academic institutions in the United States and in China, I reflect on the challenges encountered along the way.
Disulfiram is an FDA-approved drug for treating alcoholism. Wu and colleagues show that disulfiram can be repurposed to efficiently inhibit pyroptosis by specifically blocking gasdermin-mediated pore formation. Cytosolic sensing of pathogens and damage by myeloid and barrier epithelial cells assembles large complexes called inflammasomes, which activate inflammatory caspases to process cytokines (IL-1 beta) and gasdermin D (GSDMD). Cleaved GSDMD forms membrane pores, leading to cytokine release and inflammatory cell death (pyroptosis). Inhibiting GSDMD is an attractive strategy to curb inflammation. Here we identify disulfiram, a drug for treating alcohol addiction, as an inhibitor of pore formation by GSDMD but not other members of the GSDM family. Disulfiram blocks pyroptosis and cytokine release in cells and lipopolysaccharide-induced septic death in mice. At nanomolar concentration, disulfiram covalently modifies human/mouse Cys191/Cys192 in GSDMD to block pore formation. Disulfiram still allows IL-1 beta and GSDMD processing, but abrogates pore formation, thereby preventing IL-1 beta release and pyroptosis. The role of disulfiram in inhibiting GSDMD provides new therapeutic indications for repurposing this safe drug to counteract inflammation, which contributes to many human diseases.
Plasmodium parasite-specific antibodies are critical for protection against malaria, yet the development of long-lived and effective humoral immunity against Plasmodium takes many years and multiple rounds of infection and cure. Here, we report that the rapid development of short-lived plasmablasts during experimental malaria unexpectedly hindered parasite control by impeding germinal center responses. Metabolic hyperactivity of plasmablasts resulted in nutrient deprivation of the germinal center reaction, limiting the generation of memory B cell and long-lived plasma cell responses. Therapeutic administration of a single amino acid to experimentally infected mice was sufficient to overcome the metabolic constraints imposed by plasmablasts and enhanced parasite clearance and the formation of protective humoral immune memory responses. Thus, our studies not only challenge the current model describing the role and function of blood-stage Plasmodium-induced plasmablasts but they also reveal new targets and strategies to improve anti-Plasmodium humoral immunity. Early humoral responses to malaria fail to induce durable protective antibodies. Butler and colleagues report that low-affinity, short-lived plasmablasts become nutrient sinks for glutamine and starve germinal center B and T cells, thereby reducing the generation of high-affinity B cells and long-lived plasma cells and memory B cells.
Plasma membranes of animal cells are enriched for cholesterol. Cholesterol-dependent cytolysins (CDCs) are pore-forming toxins secreted by bacteria that target membrane cholesterol for their effector function. Phagocytes are essential for clearance of CDC-producing bacteria; however, the mechanisms by which these cells evade the deleterious effects of CDCs are largely unknown. Here, we report that interferon (IFN) signals convey resistance to CDC-induced pores on macrophages and neutrophils. We traced IFN-mediated resistance to CDCs to the rapid modulation of a specific pool of cholesterol in the plasma membrane of macrophages without changes to total cholesterol levels. Resistance to CDC-induced pore formation requires the production of the oxysterol 25-hydroxycholesterol (25HC), inhibition of cholesterol synthesis and redistribution of cholesterol to an esterified cholesterol pool. Accordingly, blocking the ability of IFN to reprogram cholesterol metabolism abrogates cellular protection and renders mice more susceptible to CDC-induced tissue damage. These studies illuminate targeted regulation of membrane cholesterol content as a host defense strategy. Bensinger and colleagues show that interferons promote host cell resistance to bacterial cytolysins by decreasing cholesterol synthesis and promoting the esterification of cholesterol, which alters the availability of this pool of 'free' cholesterol needed for pore formation.
Stimulator-of-interferon genes (STING) is vital for sensing cytosolic DNA and initiating innate immune responses against microbial infection and tumors. Redox homeostasis is the balance of oxidative and reducing reactions present in all living systems. Yet, how the intracellular redox state controls STING activation is unclear. Here, we show that cellular redox homeostasis maintained by glutathione peroxidase 4 (GPX4) is required for STING activation. GPX4 deficiency enhanced cellular lipid peroxidation and thus specifically inhibited the cGAS-STING pathway. Concordantly, GPX4 deficiency inhibited herpes simplex virus-1 (HSV-1)-induced innate antiviral immune responses and promoted HSV-1 replication in vivo. Mechanistically, GPX4 inactivation increased production of lipid peroxidation, which led to STING carbonylation at C88 and inhibited its trafficking from the endoplasmic reticulum (ER) to the Golgi complex. Thus, cellular stress-induced lipid peroxidation specifically attenuates the STING DNA-sensing pathway, suggesting that GPX4 facilitates STING activation by maintaining redox homeostasis of lipids. Zhao and colleagues show that STING activation is sensitive to membrane lipid peroxidation that occurs upon reactive oxygen species (ROS) production. The lipid hydroperoxidase glutathione peroxidase 4 (GPX4) reduces such oxidized lipids. Lack of GPX4 leads to STING protein carbonylation, which impedes its trafficking from the ER to the Golgi.
Familial Mediterranean fever is an autoinflammatory disease caused by gain-of-function mutations in the pyrin inflammasome. Kastner and colleagues show that mutant pyrin better resists suppression by the plague bacteriumYersinia pestisand may have been positively selected in human Middle Eastern populations. Familial Mediterranean fever (FMF) is an autoinflammatory disease caused by homozygous or compound heterozygous gain-of-function mutations inMEFV, which encodes pyrin, an inflammasome protein. Heterozygous carrier frequencies for multipleMEFVmutations are high in several Mediterranean populations, suggesting that they confer selective advantage. Among 2,313 Turkish people, we found extended haplotype homozygosity flanking FMF-associated mutations, indicating evolutionarily recent positive selection of FMF-associated mutations. Two pathogenic pyrin variants independently arose >1,800 years ago. Mutant pyrin interacts less avidly withYersinia pestisvirulence factor YopM than with wild-type human pyrin, thereby attenuating YopM-induced interleukin (IL)-1 beta suppression. Relative to healthy controls, leukocytes from patients with FMF harboring homozygous or compound heterozygous mutations and from asymptomatic heterozygous carriers released heightened IL-1 beta specifically in response toY. pestis.Y. pestis-infectedMefv(M680I/M680I)FMF knock-in mice exhibited IL-1-dependent increased survival relative to wild-type knock-in mice. Thus, FMF mutations that were positively selected in Mediterranean populations confer heightened resistance toY. pestis.
Group 2 innate lymphoid cells (ILC2s) closely intersect with antitumor immunity. A new study describes how activation of lung-resident ILC2s orchestrates the suppression of natural killer cell-mediated innate antitumor immunity via an eosinophil-mediated metabolic mechanism.
Chronic inflammation is a common feature of obesity, with elevated cytokines such as interleukin-1 (IL-1) in the circulation and tissues. Here, we report an unconventional IL-1R-MyD88-IRAK2-PHB/OPA1 signaling axis that reprograms mitochondrial metabolism in adipocytes to exacerbate obesity. IL-1 induced recruitment of IRAK2 Myddosome to mitochondria outer membranes via recognition by TOM20, followed by TIMM50-guided translocation of IRAK2 into mitochondria inner membranes, to suppress oxidative phosphorylation and fatty acid oxidation, thereby attenuating energy expenditure. Adipocyte-specific MyD88 or IRAK2 deficiency reduced high-fat-diet-induced weight gain, increased energy expenditure and ameliorated insulin resistance, associated with a smaller adipocyte size and increased cristae formation. IRAK2 kinase inactivation also reduced high-fat diet-induced metabolic diseases. Mechanistically, IRAK2 suppressed respiratory super-complex formation via interaction with PHB1 and OPA1 upon stimulation of IL-1. Taken together, our results suggest that the IRAK2 Myddosome functions as a critical link between inflammation and metabolism, representing a novel therapeutic target for patients with obesity. Obesity is often accompanied by chronic inflammation. Li and colleagues show that, in mice fed high-fat diets, IL-1 signaling in adipocytes induces an unconventional IRAK2 translocation to mitochondria and suppresses respiratory super-complex formation to alter mitochondrial function, and exacerbates obesity.
In coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the relationship between disease severity and the host immune response is not fully understood. Here we performed single-cell RNA sequencing in peripheral blood samples of 5 healthy donors and 13 patients with COVID-19, including moderate, severe and convalescent cases. Through determining the transcriptional profiles of immune cells, coupled with assembled T cell receptor and B cell receptor sequences, we analyzed the functional properties of immune cells. Most cell types in patients with COVID-19 showed a strong interferon-alpha response and an overall acute inflammatory response. Moreover, intensive expansion of highly cytotoxic effector T cell subsets, such as CD4(+)effector-GNLY (granulysin), CD8(+)effector-GNLY and NKT CD160, was associated with convalescence in moderate patients. In severe patients, the immune landscape featured a deranged interferon response, profound immune exhaustion with skewed T cell receptor repertoire and broad T cell expansion. These findings illustrate the dynamic nature of immune responses during disease progression. Severe COVID-19 is characterized-among other things-by a hyperinflammatory state. Wang and colleagues describe the single-cell transcriptional landscape of moderate, severe and convalescent cases of patients with COVID-19.
Accurate serology testing is urgently needed to help diagnose SARS-CoV-2 infection. Here Valkenburg and colleagues use a luciferase immunoprecipitation system to assess the antibody responses to 15 different SARS-CoV-2 antigens in patients with COVID-19 and find ORF8 and ORF3b antibodies, taken together as a cluster of points, identified 96.5% of COVID-19 samples at early and late time points of disease with 99.5% specificity The SARS-CoV-2 virus emerged in December 2019 and has caused a worldwide pandemic due to the lack of any pre-existing immunity. Accurate serology testing is urgently needed to help diagnose infection, determine past exposure of populations and assess the response to a future vaccine. The landscape of antibody responses to SARS-CoV-2 is unknown. In this study, we utilized the luciferase immunoprecipitation system to assess the antibody responses to 15 different SARS-CoV-2 antigens in patients with COVID-19. We identified new targets of the immune response to SARS-CoV-2 and show that nucleocapsid, open reading frame (ORF)8 and ORF3b elicit the strongest specific antibody responses. ORF8 and ORF3b antibodies, taken together as a cluster of points, identified 96.5% of COVID-19 samples at early and late time points of disease with 99.5% specificity. Our findings could be used to develop second-generation diagnostic tests to improve serological assays for COVID-19 and are important in understanding pathogenicity.
Immune-modulating therapies have revolutionized the treatment of chronic diseases, particularly cancer. However, their success is restricted and there is a need to identify new therapeutic targets. Here, we show that natural killer cell granule protein 7 (NKG7) is a regulator of lymphocyte granule exocytosis and downstream inflammation in a broad range of diseases. NKG7 expressed by CD4(+)and CD8(+)T cells played key roles in promoting inflammation during visceral leishmaniasis and malaria-two important parasitic diseases. Additionally, NKG7 expressed by natural killer cells was critical for controlling cancer initiation, growth and metastasis. NKG7 function in natural killer and CD8(+)T cells was linked with their ability to regulate the translocation of CD107a to the cell surface and kill cellular targets, while NKG7 also had a major impact on CD4(+)T cell activation following infection. Thus, we report a novel therapeutic target expressed on a range of immune cells with functions in different immune responses. NKG7 is a molecule well associated with NK cells but of unknown function. Engwerda and colleagues demonstrate that NKG7 is also associated with T(H)1 cells and is essential for type I and cytotoxic responses.