Exogenous non-coding dsDNA-dependent trans-activation of phagocytes augments anti-tumor immunity.

Stimulator of interferon genes (STING)-dependent signaling is requisite for effective anti-microbial and anti-tumor activity. STING signaling is commonly defective in cancer cells, which enables tumor cells to evade the immunosurveillance system. We evaluate here whether intrinsic STING signaling in such tumor cells could be reconstituted by creating recombinant herpes simplex viruses (rHSVs) that express components of the STING signaling pathway. We observe that rHSVs expressing STING and/or cGAS replicate inefficiently yet retain in vivo anti-tumor activity, independent of oncolytic activity requisite on the trans-activation of extrinsic STING signaling in phagocytes by engulfed microbial dsDNA species. Accordingly, the in vivo effects of virotherapy could be simulated by nanoparticles incorporating non-coding dsDNA species, which comparably elicit the trans-activation of phagocytes and augment the efficacy of established cancer treatments including checkpoint inhibition and radiation therapy. Our results help elucidate mechanisms of virotherapeutic anti-tumor activity as well as provide alternate strategies to treat cancer.

Innate Immune System Regulated by Stimulator of Interferon Genes, a Cytosolic DNA Sensor, Regulates Endothelial Function.

Background Sterile inflammation caused by metabolic disorders impairs endothelial function; however, the underlying mechanism by which hyperglycemia induces inflammation remains obscure. Recent studies have suggested that stimulator of interferon genes (STING), a key cytosolic DNA sensor in the innate immune system, contributes to the pathogenesis of inflammatory diseases. This study examines the role of the STING in endothelial dysfunction in streptozotocin-induced diabetic mice. Methods and Results Injection of streptozotocin promoted the expression of STING and DNA damage markers in the aorta of wild-type mice. Streptozotocin elevated blood glucose and lipid levels in both wild-type and STING-deficient mice, which showed no statistical differences. Genetic deletion of STING ameliorated endothelial dysfunction as determined by the vascular relaxation in response to acetylcholine (P<0.001) and increased endothelial nitric oxide synthase phosphorylation in the aorta (P<0.05) in STZ-injected mice. Endothelium-independent vascular response to sodium nitroprusside did not differ. Treatment with a direct STING agonist, cyclic GMP-AMP, or mitochondrial DNA increased inflammatory molecule expression (eg, VCAM1 and IFNB) and decreased endothelial nitric oxide synthase phosphorylation in human umbilical vein endothelial cells, partially through the STING pathway. Cyclic GMP-AMP significantly impaired endothelial function of aortic segments obtained from wild-type mice, which was ameliorated in the presence of C-176, a STING inhibitor, or a neutralizing interferon-ß antibody. Furthermore, the administration of C-176 ameliorated endothelial dysfunction in STZ-induced diabetic mice (P<0.01). Conclusions The DNA damage response regulated by STING impairs endothelial function. STING signaling may be a potential therapeutic target of endothelial dysfunction caused by hyperglycemia.

Evaluation of the immunogenicity and efficacy of an rVSV vaccine against Zika virus infection in macaca nemestrina.

Zika virus (ZIKV) is a mosquito-borne flavivirus that causes an acute febrile illness. ZIKV can be transmitted between sexual partners and from mother to fetus. Infection is strongly associated with neurologic complications in adults, including Guillain-Barré syndrome and myelitis, and congenital ZIKV infection can result in fetal injury and congenital Zika syndrome (CZS). Development of an effective vaccine is imperative to protect against ZIKV vertical transmission and CZS. Recombinant Vesicular Stomatitis virus (rVSV) is a highly effective and safe vector for the delivery of foreign immunogens for vaccine purposes. Here, we evaluate an rVSV vaccine expressing the full length pre-membrane (prM) and ZIKV envelope (E) proteins (VSV-ZprME), shown to be immunogenic in murine models of ZIKV infection, for its capacity to induce immune responses in nonhuman primates. Moreover, we assess the efficacy of the rVSVΔM-ZprME vaccine in the protection of pigtail macaques against ZIKV infection. Administration of the rVSVΔM-ZprME vaccine was safe, but it did not induce robust anti-ZIKV T-cell responses, IgM or IgG antibodies, or neutralizing antibodies in most animals. Post ZIKV challenge, animals that received the rVSVΔM control vaccine lacking ZIKV antigen had higher levels of plasma viremia compared to animals that received the rVSVΔM-ZprME vaccine. Anti-ZIKV neutralizing Ab titers were detected in a single animal that received the rVSVΔM-ZprME vaccine that was associated with reduced plasma viremia. The overall suboptimal ZIKV-specific cellular and humoral responses post-immunization indicates the rVSVΔM-ZprME vaccine did not elicit an immune response in this pilot study. However, recall antibody response to the rVSVΔM-ZprME vaccine indicates it may be immunogenic and further developments to the vaccine construct could enhance its potential as a vaccine candidate in a nonhuman primate pre-clinical model.

STING signalling is terminated through ESCRT-dependent microautophagy of vesicles originating from recycling endosomes.

Stimulator of interferon genes (STING) is essential for the type I interferon response against a variety of DNA pathogens. Upon emergence of cytosolic DNA, STING translocates from the endoplasmic reticulum to the Golgi where STING activates the downstream kinase TBK1, then to lysosome through recycling endosomes (REs) for its degradation. Although the molecular machinery of STING activation is extensively studied and defined, the one underlying STING degradation and inactivation has not yet been fully elucidated. Here we show that STING is degraded by the endosomal sorting complexes required for transport (ESCRT)-driven microautophagy. Airyscan super-resolution microscopy and correlative light/electron microscopy suggest that STING-positive vesicles of an RE origin are directly encapsulated into Lamp1-positive compartments. Screening of mammalian Vps genes, the yeast homologues of which regulate Golgi-to-vacuole transport, shows that ESCRT proteins are essential for the STING encapsulation into Lamp1-positive compartments. Knockdown of Tsg101 and Vps4, components of ESCRT, results in the accumulation of STING vesicles in the cytosol, leading to the sustained type I interferon response. Knockdown of Tsg101 in human primary T cells leads to an increase the expression of interferon-stimulated genes. STING undergoes K63-linked ubiquitination at lysine 288 during its transit through the Golgi/REs, and this ubiquitination is required for STING degradation. Our results reveal a molecular mechanism that prevents hyperactivation of innate immune signalling, which operates at REs.

Epigenetic state determines the in vivo efficacy of STING agonist therapy.

While STING-activating agents have shown limited efficacy in early-phase clinical trials, multiple lines of evidence suggest the importance of tumor cell-intrinsic STING function in mediating antitumor immune responses. Although STING signaling is impaired in human melanoma, its restoration through epigenetic reprogramming can augment its antigenicity and T cell recognition. In this study, we show that reversal of methylation silencing of STING in murine melanoma cell lines using a clinically available DNA methylation inhibitor can improve agonist-induced STING activation and type-I IFN induction, which, in tumor-bearing mice, can induce tumor regression through a CD8+ T cell-dependent immune response. These findings not only provide mechanistic insight into how STING signaling dysfunction in tumor cells can contribute to impaired responses to STING agonist therapy, but also suggest that pharmacological restoration of STING signaling through epigenetic reprogramming might improve the therapeutic efficacy of STING agonists.

Dectin-1/IL-15 Pathway Affords Protection against Extrapulmonary Aspergillus fumigatus Infection by Regulating Natural Killer Cell Survival.

Aspergillus fumigatus is a ubiquitous, yet potentially pathogenic, mold. The immune system employs innate receptors, such as dectin-1, to recognize fungal pathogens, but the immunological networks that afford protection are poorly explored. Here, we investigated the role of dectin-1 in anti-A. fumigatus response in an experimental model of acute invasive aspergillosis. Mice lacking dectin-1 presented enhanced signs of inflammation, with increased production of inflammatory cytokines and neutrophil infiltration, quickly succumbing to the infection. Curiously, resistance did not require T/B lymphocytes or IL-17. Instead, the main effector function of dectin-1 was the preservation of the NK cell population in the kidneys by the provision of the cytokine IL-15. While the depletion of NK cells impaired host defense in wild-type mice, IL-15 administration restored antifungal responses in dectin-1-deficient mice. Our results uncover a new effector mechanism for dectin-1 in anti-Aspergillus defense, adding an alternative approach to understand the pathophysiology of this infection.

STING, a cytosolic DNA sensor, plays a critical role in atherogenesis: a link between innate immunity and chronic inflammation caused by lifestyle-related diseases.

AIMS: Lifestyle-related diseases promote atherosclerosis, a chronic inflammatory disease; however, the molecular mechanism remains largely unknown. Endogenous DNA fragments released under over-nutrient condition provoke sterile inflammation through the recognition by DNA sensors. Here, we investigated the role of stimulator of interferon genes (STING), a cytosolic DNA sensor, in atherogenesis. METHODS AND RESULTS: Apolipoprotein E-deficient (Apoe-/-) mice fed a western-type diet (WTD), a hypercholesterolaemic mouse model, showed higher STING expression and markers for DNA damage such as γH2AX, p53, and single-stranded DNA (ssDNA) accumulation in macrophages in the aorta compared with wild-type (WT) mice. The level of cGAMP, a STING agonist, in the aorta was higher in Apoe-/- mice. Genetic deletion of Sting in Apoe-/- mice reduced atherosclerotic lesions in the aortic arch, lipid, and macrophage accumulation in plaques, and inflammatory molecule expression in the aorta compared with the control. Pharmacological blockade of STING using a specific inhibitor, C-176, ameliorated atherogenesis in Apoe-/- mice. In contrast, bone marrow-specific STING expression in Apoe-/- mice stimulated atherogenesis. Expression or deletion of STING did not affect metabolic parameters and blood pressure. In vitro studies revealed that STING activation by cGAMP or mitochondrial DNA accelerated inflammatory molecule expression (e.g. TNF-α or IFN-ß) in mouse and human macrophages. Activation of nuclear factor-κB and TANK binding kinase 1 was involved in STING-associated vascular inflammation and macrophage activation. Furthermore, human atherosclerotic lesions in the carotid arteries expressed STING and cGAMP. CONCLUSION: Stimulator of interferon genes stimulates pro-inflammatory activation of macrophages, leading to the development of atherosclerosis. Stimulator of interferon genes signalling may serve as a potential therapeutic target for atherosclerosis.

STING regulates metabolic reprogramming in macrophages via HIF-1α during Brucella infection.

Macrophages metabolic reprogramming in response to microbial insults is a major determinant of pathogen growth or containment. Here, we reveal a distinct mechanism by which stimulator of interferon genes (STING), a cytosolic sensor that regulates innate immune responses, contributes to an inflammatory M1-like macrophage profile upon Brucella abortus infection. This metabolic reprogramming is induced by STING-dependent stabilization of hypoxia-inducible factor-1 alpha (HIF-1α), a global regulator of cellular metabolism and innate immune cell functions. HIF-1α stabilization reduces oxidative phosphorylation and increases glycolysis during infection with B. abortus and, likewise, enhances nitric oxide production, inflammasome activation and IL-1ß release in infected macrophages. Furthermore, the induction of this inflammatory profile participates in the control of bacterial replication since absence of HIF-1α renders mice more susceptible to B. abortus infection. Mechanistically, activation of STING by B. abortus infection drives the production of mitochondrial reactive oxygen species (mROS) that ultimately influences HIF-1α stabilization. Moreover, STING increases the intracellular succinate concentration in infected macrophages, and succinate pretreatment induces HIF-1α stabilization and IL-1ß release independently of its cognate receptor GPR91. Collectively, these data demonstrate a pivotal mechanism in the immunometabolic regulation of macrophages during B. abortus infection that is orchestrated by STING via HIF-1α pathway and highlight the metabolic reprogramming of macrophages as a potential treatment strategy for bacterial infections.

Epigenetic reprogramming of tumor cell-intrinsic STING function sculpts antigenicity and T cell recognition of melanoma.

Lack or loss of tumor antigenicity represents one of the key mechanisms of immune escape and resistance to T cell-based immunotherapies. Evidence suggests that activation of stimulator of interferon genes (STING) signaling in tumor cells can augment their antigenicity by triggering a type I IFN-mediated sequence of autocrine and paracrine events. Although suppression of this pathway in melanoma and other tumor types has been consistently reported, the mechanistic basis remains unclear. In this study, we asked whether this suppression is, in part, epigenetically regulated and whether it is indeed a driver of melanoma resistance to T cell-based immunotherapies. Using genome-wide DNA methylation profiling, we show that promoter hypermethylation of cGAS and STING genes mediates their coordinated transcriptional silencing and contributes to the widespread impairment of the STING signaling function in clinically-relevant human melanomas and melanoma cell lines. This suppression is reversible through pharmacologic inhibition of DNA methylation, which can reinstate functional STING signaling in at least half of the examined cell lines. Using a series of T cell recognition assays with HLA-matched human melanoma tumor-infiltrating lymphocytes (TIL), we further show that demethylation-mediated restoration of STING signaling in STING-defective melanoma cell lines can improve their antigenicity through the up-regulation of MHC class I molecules and thereby enhance their recognition and killing by cytotoxic T cells. These findings not only elucidate the contribution of epigenetic processes and specifically DNA methylation in melanoma-intrinsic STING signaling impairment but also highlight their functional significance in mediating tumor-immune evasion and resistance to T cell-based immunotherapies.

STING Signaling Drives Production of Innate Cytokines, Generation of CD8+ T Cells and Enhanced Protection Against Trypanosoma cruzi Infection.

A variety of signaling pathways are involved in the induction of innate cytokines and CD8+ T cells, which are major players in protection against acute Trypanosoma cruzi infection. Previous data have demonstrated that a TBK-1/IRF3-dependent signaling pathway promotes IFN-ß production in response to Trypanosoma cruzi, but the role for STING, a main interactor of these proteins, remained to be addressed. Here, we demonstrated that STING signaling is required for production of IFN-ß, IL-6, and IL-12 in response to Trypanosoma cruzi infection and that STING absence negatively impacts activation of IRF-dependent pathways in response to the parasite. We reported no significant activation of IRF-dependent pathways and cytokine expression in RAW264.7 macrophages in response to heat-killed trypomastigotes. In addition, we showed that STING is essential for T. cruzi DNA-mediated induction of IFN-ß, IL-6, and IL-12 gene expression in RAW264.7 macrophages. We demonstrated that STING-knockout mice have significantly higher parasitemia from days 5 to 8 of infection and higher heart parasitism at day 13 after infection. Although we observed similar heart inflammatory infiltrates at day 13 after infection, IFN-ß, IL-12, CXCL9, IFN-γ, and perforin gene expression were lower in the absence of STING. We also showed an inverse correlation between parasite DNA and the expression of CXCL9, IFN-γ, and perforin genes in the hearts of infected animals at day 13 after infection. Finally, we reported that STING signaling is required for splenic IFN-ß and IL-6 expression early after infection and that STING deficiency results in lower numbers of splenic parasite-specific IFN-γ and IFN-γ/perforin-producing CD8+ T cells, indicating a pivotal role for STING signaling in immunity to Trypanosoma cruzi.

Brucella suppress STING expression via miR-24 to enhance infection.

Brucellosis, caused by a number of Brucella species, remains the most prevalent zoonotic disease worldwide. Brucella establish chronic infections within host macrophages despite triggering cytosolic innate immune sensors, including Stimulator of Interferon Genes (STING), which potentially limit infection. In this study, STING was required for control of chronic Brucella infection in vivo. However, early during infection, Brucella down-regulated STING mRNA and protein. Down-regulation occurred post-transcriptionally, required live bacteria, the Brucella type IV secretion system, and was independent of host IRE1-RNase activity. STING suppression occurred in MyD88-/- macrophages and was not induced by Toll-like receptor agonists or purified Brucella lipopolysaccharide (LPS). Rather, Brucella induced a STING-targeting microRNA, miR-24-2, in a type IV secretion system-dependent manner. Furthermore, STING downregulation was inhibited by miR-24 anti-miRs and in Mirn23a locus-deficient macrophages. Failure to suppress STING expression in Mirn23a-/- macrophages correlated with diminished Brucella replication, and was rescued by exogenous miR-24. Mirn23a-/- mice were also more resistant to splenic colonization one week post infection. Anti-miR-24 potently suppressed replication in wild type, but much less in STING-/- macrophages, suggesting most of the impact of miR-24 induction on replication occurred via STING suppression. In summary, Brucella sabotages cytosolic surveillance by miR-24-dependent suppression of STING expression; post-STING activation "damage control" via targeted STING destruction may enable establishment of chronic infection.

Virus infection is controlled by hematopoietic and stromal cell sensing of murine cytomegalovirus through STING.

Recognition of DNA viruses, such as cytomegaloviruses (CMVs), through pattern-recognition receptor (PRR) pathways involving MyD88 or STING constitute a first-line defense against infections mainly through production of type I interferon (IFN-I). However, the role of these pathways in different tissues is incompletely understood, an issue particularly relevant to the CMVs which have broad tissue tropisms. Herein, we contrasted anti-viral effects of MyD88 versus STING in distinct cell types that are infected with murine CMV (MCMV). Bone marrow chimeras revealed STING-mediated MCMV control in hematological cells, similar to MyD88. However, unlike MyD88, STING also contributed to viral control in non-hematological, stromal cells. Infected splenic stromal cells produced IFN-I in a cGAS-STING-dependent and MyD88-independent manner, while we confirmed plasmacytoid dendritic cell IFN-I had inverse requirements. MCMV-induced natural killer cytotoxicity was dependent on MyD88 and STING. Thus, MyD88 and STING contribute to MCMV control in distinct cell types that initiate downstream immune responses.

STING differentially regulates experimental GVHD mediated by CD8 versus CD4 T cell subsets.

The stimulator of interferon genes (STING) pathway has been proposed as a key regulator of gastrointestinal homeostasis and inflammatory responses. Although STING reportedly protects against gut barrier damage and graft-versus-host disease (GVHD) after major histocompatibility complex (MHC)-mismatched allogeneic hematopoietic stem cell transplantation (aHSCT), its effect in clinically relevant MHC-matched aHSCT is unknown. Studies here demonstrate that STING signaling in nonhematopoietic cells promoted MHC-matched aHSCT-induced GVHD and that STING agonists increased type I interferon and MHC I expression in nonhematopoietic mouse intestinal organoid cultures. Moreover, mice expressing a human STING allele containing three single-nucleotide polymorphisms associated with decreased STING activity also developed reduced MHC-matched GVHD, demonstrating STING's potential clinical importance. STING-/- recipients experienced reduced GVHD with transplant of purified donor CD8+ T cells in both MHC-matched and MHC-mismatched models, reconciling the seemingly disparate results. Further examination revealed that STING deficiency reduced the activation of donor CD8+ T cells early after transplant and promoted recipient MHC class II+ antigen-presenting cell (APC) survival. Therefore, APC persistence in STING pathway absence may account for the increased GVHD mediated by CD4+ T cells in completely mismatched recipients. In total, our findings have important implications for regulating clinical GVHD by targeting STING early after aHSCT and demonstrate that an innate immune pathway has opposing effects on the outcome of aHSCT, depending on the donor/recipient MHC disparity.

STING signaling and host defense against microbial infection.

The first line of host defense against infectious agents involves activation of innate immune signaling pathways that recognize specific pathogen-associated molecular patterns (PAMPs). Key triggers of innate immune signaling are now known to include microbial-specific nucleic acid, which is rapidly detected in the cytosol of the cell. For example, RIG-I-like receptors (RLRs) have evolved to detect viral RNA species and to activate the production of host defense molecules and cytokines that stimulate adaptive immune responses. In addition, host defense countermeasures, including the production of type I interferons (IFNs), can also be triggered by microbial DNA from bacteria, viruses and perhaps parasites and are regulated by the cytosolic sensor, stimulator of interferon genes (STING). STING-dependent signaling is initiated by cyclic dinucleotides (CDNs) generated by intracellular bacteria following infection. CDNs can also be synthesized by a cellular synthase, cGAS, following interaction with invasive cytosolic self-DNA or microbial DNA species. The importance of STING signaling in host defense is evident since numerous pathogens have developed strategies to prevent STING function. Here, we review the relevance of STING-controlled innate immune signaling in host defense against pathogen invasion, including microbial endeavors to subvert this critical process.

STING Signaling in Melanoma Cells Shapes Antigenicity and Can Promote Antitumor T-cell Activity.

STING (stimulator of IFN genes) signaling is an innate immune pathway for induction of a spontaneous antitumor T-cell response against certain immunogenic tumors. Although antigen-presenting cells are known to be involved in this process, insight into the participation of tumor cell-intrinsic STING signaling remains weak. In this study, we find diversity in the regulation of STING signaling across a panel of human melanoma cell lines. We show that intact activation of STING signaling in a subset of human melanoma cell lines enhances both their antigenicity and susceptibility to lysis by human melanoma tumor-infiltrating lymphocytes (TIL) through the augmentation of MHC class I expression. Conversely, defects in the STING signaling pathway protect melanoma cells from increased immune recognition by TILs and limit their sensitivity to TIL lysis. Based on these findings, we propose that defects in tumor cell-intrinsic STING signaling can mediate not only tumor immune evasion but also resistance to TIL-based immunotherapies.

Brucella abortus Cyclic Dinucleotides Trigger STING-Dependent Unfolded Protein Response That Favors Bacterial Replication.

Brucella abortus is a facultative intracellular bacterium that causes brucellosis, a prevalent zoonosis that leads to abortion and infertility in cattle, and undulant fever, debilitating arthritis, endocarditis, and meningitis in humans. Signaling pathways triggered by B. abortus involves stimulator of IFN genes (STING), which leads to production of type I IFNs. In this study, we evaluated the pathway linking the unfolded protein response (UPR) and the endoplasmic reticulum-resident transmembrane molecule STING, during B. abortus infection. We demonstrated that B. abortus infection induces the expression of the UPR target gene BiP and XBP1 in murine macrophages through a STING-dependent pathway. Additionally, we also observed that STING activation was dependent on the bacterial second messenger cyclic dimeric GMP. Furthermore, the Brucella-induced UPR is crucial for induction of multiple molecules linked to type I IFN signaling pathway, such as IFN-ß, IFN regulatory factor 1, and guanylate-binding proteins. Furthermore, IFN-ß is also important for the UPR induction during B. abortus infection. Indeed, IFN-ß shows a synergistic effect in inducing the IRE1 axis of the UPR. In addition, priming cells with IFN-ß favors B. abortus survival in macrophages. Moreover, Brucella-induced UPR facilitates bacterial replication in vitro and in vivo. Finally, these results suggest that B. abortus-induced UPR is triggered by bacterial cyclic dimeric GMP, in a STING-dependent manner, and that this response supports bacterial replication. In summary, association of STING and IFN-ß signaling pathways with Brucella-induced UPR unravels a novel link between innate immunity and endoplasmic reticulum stress that is crucial for bacterial infection outcome.

Reciprocal regulation of STING and TCR signaling by mTORC1 for T-cell activation and function.

Stimulator of interferon genes (STING) plays a key role in detecting cytosolic DNA and induces type I interferon (IFN-I) responses for host defense against pathogens. Although T cells highly express STING, its physiological role remains unknown. Here, we show that costimulation of T cells with the STING ligand cGAMP and TCR leads to IFN-I production and strongly inhibits T-cell growth. TCR-mediated mTORC1 activation and sustained activation of IRF3 are required for cGAMP-induced IFN-I production, and the mTORC1 activity is partially counteracted by cGAMP, thereby blocking proliferation. This mTORC1 inhibition in response to costimulation depends on IRF3 and IRF7. Effector T cells produce much higher IFN-I levels than innate cells in response to cGAMP. Finally, we demonstrated that STING stimulation in T cells is effective in inducing antitumor responses in vivo. Our studies demonstrate that the outputs of STING and TCR signaling pathways are mutually regulated through mTORC1 to modulate T-cell functions.

Ovarian Cancer Cells Commonly Exhibit Defective STING Signaling Which Affects Sensitivity to Viral Oncolysis.

Ovarian cancer is the sixth most prevalent cancer in women and the most lethal of the gynecologic malignancies. Treatments have comprised the use of immunotherapeutic agents as well as oncolytic viruses, with varying results for reasons that remain to be clarified. To better understand the mechanisms that may help predict treatment outcome, we have evaluated innate immune signaling in select ovarian cancer cell lines, governed by the Stimulator of Interferon Genes (STING), which controls self or viral DNA-triggered cytokine production. Our results indicate that STING-dependent signaling is habitually defective in majority of ovarian cancer cells examined, frequently through the suppression of STING and/or the cyclic dinucleotide (CDN) enzyme Cyclic GMP-AMP synthase (cGAS) expression, by epigenetic processes. However, STING-independent, dsRNA-activated innate immune cytokine production, which require RIG-I/MDA5, were largely unaffected. Such defects enabled ovarian cancer cells to avoid DNA damage-mediated cytokine production, which would alert the immunosurveillance system. Loss of STING signaling also rendered ovarian cancer cells highly susceptible to viral oncolytic γ34.5 deleted-HSV1 (Herpes simplex virus) infection in vitro and in vivo. IMPLICATIONS: STING signaling evaluation in tumors may help predict disease outcome and possibly dictate the efficacy of oncoviral and other types of cancer therapies.

Combating herpesvirus encephalitis by potentiating a TLR3-mTORC2 axis.

TLR3 is a sensor of double-stranded RNA that is indispensable for defense against infection with herpes simplex virus type 1 (HSV-1) in the brain. We found here that TLR3 was required for innate immune responses to HSV-1 in neurons and astrocytes. During infection with HSV-1, TLR3 recruited the metabolic checkpoint kinase complex mTORC2, which led to the induction of chemokines and trafficking of TLR3 to the cell periphery. Such trafficking enabled the activation of molecules (including mTORC1) required for the induction of type I interferons. Intracranial infection of mice with HSV-1 was exacerbated by impairment of TLR3 responses with an inhibitor of mTOR and was significantly 'rescued' by potentiation of TLR3 responses with an agonistic antibody to TLR3. These results suggest that the TLR3-mTORC2 axis might be a therapeutic target through which to combat herpes simplex encephalitis.