Lack of immunological DNA sensing in hepatocytes facilitates hepatitis B virus infection

Abstract

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

The Smc5/6 Complex Restricts HBV when Localized to ND10 without Inducing an Innate Immune Response and Is Counteracted by the HBV X Protein Shortly after Infection

“…Notably, all PHH samples had very low sequence counts (range: 0–30 counts from ~30 million total reads per sample) of STING ( TMEM173 ), an adaptor protein of an innate immune receptor (cGAS) that senses intracellular DNA. This is consistent with a recent study which reported that neither murine or human hepatocytes express STING [33]. …”

“…While our data does not directly address these two possibilities, it is striking that we were not able to detect an innate immune response in PHH at any time post-infection with HBV or HBVΔX. Moreover, we detected little to no STING expression in PHH, consistent with a recent study which reported that deficiency of this adaptor protein prevents functional DNA sensing in hepatocytes, thereby facilitating HBV infection [33]. …”

Sensing of Bacterial Cyclic Dinucleotides by the Oxidoreductase RECON Promotes NF-κB Activation and Shapes a Proinflammatory Antibacterial State

“…We used the embryonically-derived murine hepatocyte cell line, TIB73, because RECON is highly expressed in hepatocytes, and mice with obstructed NF-κB activation specifically in hepatocytes are unable to clear Lm , even in the presence of NF-κB-competent immune cells (Lavon et al, 2000). Additionally, a recent study has shown that primary human and murine hepatocytes do not express STING (Thomsen et al, 2016), therefore the use of this cell type would allow us to study NF-κB activation without complications from IFN feedback.…”

MITA/STING and Its Alternative Splicing Isoform MRP Restrict Hepatitis B Virus Replication

“…also showed that overexpression of MITA/STING in mice hepatocytes could reduce HBV replication. However, they found that MITA/STING deficiency has no influence on HBV replication in a adenovirus-HBV model [55]. The discrepancy may attribute to the different mechanisms of host recognition and responses to systemic infected adenovirus vector and naked plasmid DNA delivered by HI.…”

“…demonstrated that cGAS/STING pathway was essential in MyD88-independent pathway for type I IFN induction and antiviral response to recombinant adenovirus (rAdV). Although the rAdV could trigger robust type I IFN production through STING-IRF3 pathway as well as Ad-HBV proved by Thomsen [55], loss of cGAS/STING minimally impacted viral clearance and persistence of transgene expression delivered by rAdV [57], which indicated that cGAS/STING was dispensable to the induction of adaptive immune response to rAdV. The minimal impact of MTIA/STING-mediated type I IFN pathway on adaptive immune response to rAdV was also previously confirmed in STAT2 knockout Syrian hamster model and IFNRI and STING knock out mouse [58, 59].…”