Herpes simplex encephalitis (HSE) is the most common form of acute viral encephalitis in industrialized countries. Type I interferon (IFN) is important for control of herpes simplex virus (HSV-1) in the central nervous system (CNS). Here we show that microglia are the main source of HSV-induced type I IFN expression in CNS cells and these cytokines are induced in a cGAS–STING-dependent manner. Consistently, mice defective in cGAS or STING are highly susceptible to acute HSE. Although STING is redundant for cell-autonomous antiviral resistance in astrocytes and neurons, viral replication is strongly increased in neurons in STING-deficient mice. Interestingly, HSV-infected microglia confer STING-dependent antiviral activities in neurons and prime type I IFN production in astrocytes through the TLR3 pathway. Thus, sensing of HSV-1 infection in the CNS by microglia through the cGAS–STING pathway orchestrates an antiviral program that includes type I IFNs and immune-priming of other cell types.

Stimulator of interferon genes (STING) is known be involved in control of DNA viruses but has an unexplored role in control of RNA viruses. During infection with DNA viruses STING is activated downstream of cGAMP synthase (cGAS) to induce type I interferon. Here we identify a STING-dependent, cGAS-independent pathway important for full interferon production and antiviral control of enveloped RNA viruses, including influenza A virus (IAV). Further, IAV interacts with STING through its conserved hemagglutinin fusion peptide (FP). Interestingly, FP antagonizes interferon production induced by membrane fusion or IAV but not by cGAMP or DNA. Similar to the enveloped RNA viruses, membrane fusion stimulates interferon production in a STING-dependent but cGAS-independent manner. Abolishment of this pathway led to reduced interferon production and impaired control of enveloped RNA viruses. Thus, enveloped RNA viruses stimulate a cGAS-independent STING pathway, which is targeted by IAV.

Hepatitis B virus (HBV) is a major human pathogen, and about one third of the global population will be exposed to the virus in their lifetime. HBV infects hepatocytes, where it replicates its DNA and infection can lead to acute and chronic hepatitis with a high risk of liver cirrhosis and hepatocellular carcinoma. Despite this, there is limited understanding of how HBV establishes chronic infections. In recent years it has emerged that foreign DNA potently stimulates the innate immune response, particularly type 1 interferon (IFN) production; and this occurs through a pathway dependent on the DNA sensor cyclic guanosine monophosphate-adenosine monophosphate synthase and the downstream adaptor protein stimulator of IFN genes (STING). In this work we describe that human and murine hepatocytes do not express STING. Consequently, hepatocytes do not produce type 1 IFN in response to foreign DNA or HBV infection and mice lacking STING or cyclic guanosine monophosphate-adenosine monophosphate synthase exhibit unaltered ability to control infection in an adenovirus-HBV model. Stimulation of IFN production in the murine liver by administration of synthetic RNA decreases virus infection, thus demonstrating that IFN possesses anti-HBV activity in the liver. Importantly, introduction of STING expression specifically in hepatocytes reconstitutes the DNA sensing pathway, which leads to improved control of HBV in vivo. Conclusion: The lack of a functional innate DNA-sensing pathway in hepatocytes hampers efficient innate control of HBV infection; this may explain why HBV has adapted to specifically replicate in hepatocytes and could contribute to the weak capacity of this cell type to clear HBV infection. (HEPATOLOGY 2016;64:746-759) H epatitis B virus (HBV) is a human pathogenic virus that specifically infects hepatocytes, causes chronic hepatitis, and is a major cause of hepatocellular carcinoma. HBV is a DNA virus, and it is estimated that more than 2 billion people are or have been infected worldwide (1) and that 240 million are chronic carriers. Immune responses are detectable only weeks after HBV infection when adaptive immune responses become activated, (2,3) but there are data to support that an earlier response would benefit virus clearance by the host. (4) Chronic HBV infection is a strong risk factor for development of liver

Developmental pathways have been shown to be important in the initiation and progression of cancer in various tissues. We showed that the transcription factor SOX9 is expressed in the epithelia of the mouse embryonic prostate and is required for proper prostate development. We have performed an in vivo investigation into the role of SOX9 in prostate cancer in mouse and human. Studies on Pten and Nkx3.1 mutant mice show that cells with an increased level of SOX9 appear within the epithelia at the early stages of prostate neoplasia and this high expression correlates with all stages of neoplastic progression. Using genetically modified mice we show that overexpression of SOX9 in prostate epithelia leads to an increase in cell proliferation without inducing hyperplasia. In mice that were heterozygous for the conditional mutant allele of Pten, overexpression of SOX9 gave rise to an earlier induction of high-grade prostate intraepithelial neoplasia. Consistent with this role, loss of Sox9 in prostate epithelia led to a decrease in proliferating cells in normal and in homozygous Pten mutant mice with prostate neoplasia. Analysis of a cohort of 880 human prostate cancer samples showed that SOX9 expression is associated with increasing Gleason grades and higher Ki67 staining. These studies identify SOX9 as part of a developmental pathway that is reactivated in prostate neoplasia where it is involved in regulating proliferation and suggests it can contribute to carcinogenesis in specific genetic contexts.

Prostate cancer is a major cause of male death in the Western world, but few frequent genetic alterations that drive prostate cancer initiation and progression have been identified. β-Catenin is essential for many developmental processes and has been implicated in tumorigenesis in many tissues, including prostate cancer. However, expression studies on human prostate cancer samples are unclear on the role this protein plays in this disease. We have used in vivo genetic studies in the embryo and adult to extend our understanding of the role of β-Catenin in the normal and neoplastic prostate. Our gene deletion analysis revealed that prostate epithelial β-Catenin is required for embryonic prostate growth and branching but is dispensable in the normal adult organ. During development, β-Catenin controls the number of progenitors in the epithelial buds and regulates a discrete network of genes, including c-Myc and Nkx3.1. Deletion of β-Catenin in a Pten deleted model of castration-resistant prostate cancer demonstrated it is dispensable for disease progression in this setting. Complementary overexpression experiments, through in vivo protein stabilization, showed that β-Catenin promotes the formation of squamous epithelia during prostate development, even in the absence of androgens. β-Catenin overexpression in combination with Pten loss was able to drive progression to invasive carcinoma together with squamous metaplasia. These studies demonstrate that β-Catenin is essential for prostate development and that an inherent property of high levels of this protein in prostate epithelia is to drive squamous fate differentiation. In addition, they show that β-Catenin overexpression can promote invasive prostate cancer in a clinically relevant model of this disease. These data provide novel information on cancer progression pathways that give rise to lethal prostate disease in humans.