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Induction of interferon and proinflammatory cytokines is a hallmark of the infection of many different viruses. However, hepatitis B virus (HBV) does not elicit a detectable cytokine response in infected hepatocytes. In order to investigate the molecular mechanism underlying the innate immune evasion, a functional cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway was reconstituted in a human hepatoma cell line supporting tetracycline-inducible HBV replication. It was demonstrated that induction of HBV replication neither activated nor inhibited this cytosolic DNA sensing pathway. However, human hepatoma cells, as well as immortalized mouse hepatocytes, express low levels of STING, which upon activation by cGAMP, the natural ligand of STING, led to induction of a proinflammatory cytokine response. Treatment of immortalized mouse hepatocytes supporting HBV replication with either cGAMP or a small molecule pharmacologic STING agonist significantly reduced viral DNA in a STING- and Janus kinase 1-dependent manner. Moreover, cGAMP treatment was able to induce inflammatory cytokine gene expression and inhibit the transcription of covalently closed circular DNA in HBV-infected human hepatoma cells expressing sodium taurocholate cotransporting polypeptide, an essential receptor for HBV infection of hepatocytes. The studies reported here and previously (F. Guo et al., Antimicrob Agents Chemother 59:1273-1281, 2015, https://doi.org/10.1128/AAC.04321-14) thus support the notion that pharmacological activation of STING in macrophages and hepatocytes induces host innate responses that can efficiently control HBV replication. Hence, despite not playing a significant role in host innate immune response to HBV infection of hepatocytes, STING is potentially a valuable target for immunotherapy of chronic hepatitis B.

BackgroundWe aimed to develop a real-time nosocomial infection surveillance system (RT-NISS) to monitor all nosocomial infections (NIs) and outbreaks in a Chinese comprehensive hospital to better prevent and control NIs.MethodsThe screening algorithm used in RT-NISS included microbiological reports, antibiotic usage, serological and molecular testing, imaging reports, and fever history. The system could, in real-time, identify new NIs, record data, and produce time-series reports to align NI cases.ResultsCompared with a manual survey of NIs (the gold standard), the sensitivity and specificity of RT-NISS was 98.8% (84/85) and 93.0% (827/889), with time-saving efficiencies of about 200 times. RT-NISS obtained the highest hospital-wide monthly NI rate of 2.62%, while physician and medical record reviews reported rates of 1.52% and 2.35% respectively. It took about two hours for one infection control practitioner (ICP) to deal with 70 new suspicious NI cases; there were 3,500 inpatients each day in the study hospital. The system could also provide various updated data (i.e. the daily NI rate, surgical site infection (SSI) rate) for each ward, or the entire hospital. Within 3 years of implementing RT-NISS, the ICPs monitored and successfully controlled about 30 NI clusters and 4 outbreaks at the study hospital.ConclusionsJust like the “ICPs’ eyes”, RT-NISS was an essential and efficient tool for the day-to-day monitoring of all NIs and outbreak within the hospital; a task that would not have been accomplished through manual process.

Stimulator of interferon genes (STING) is an endoplasmic reticulum transmembrane protein that serves as a molecular hub for activation of interferon and inflammatory cytokine response by multiple cellular DNA sensors. Not surprisingly, STING has been demonstrated to play an important role in host defense against microorganisms and pharmacologic activation of STING is considered as an attractive strategy to treat viral diseases and boost antitumor immunity. In light of this we established a HepAD38-derived reporter cell line that expresses firefly luciferase in response to the activation of cyclic GMP-AMP synthase (cGAS)-STING pathway for high throughput screening (HTS) of small molecular human STING agonists. This cell-based reporter assay required only 4 h treatment with a reference STING agonist to induce a robust luciferase signal and was demonstrated to have an excellent performance in HTS format. By screening 16,000 compounds, a dispiro diketopiperzine (DSDP) compound was identified to induce proinflammatory cytokine response in a manner dependent on the expression of functional human STING, but not mouse STING. Moreover, we showed that DSDP induced an interferon-dominant cytokine response in human skin fibroblasts and peripheral blood mononuclear cells, which in turn potently suppressed the replication of yellow fever virus, dengue virus and Zika virus. We have thus established a robust cell-based assay system suitable for rapid discovery and mechanistic analyses of cGAS-STING pathway agonists. Identification of DSDP as a human STING agonist enriches the pipelines of STING-targeting drug development for treatment of viral infections and cancers.

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Intrinsic and acquired resistance of cancer to radio-and chemotherapy is one of the major challenges in the treatment of esophageal squamous cell carcinoma (ESCC). Elevated reactive oxygen species (ROS) play an important role in the resistance to cisplatin in ESCCs. Super dismutase [Mn], mitochondrial (SOD-2), an important primary antioxidant enzyme located in mitochondria, could regulate ROS production. Our previous study showed that tumor necrosis factor-α (TNF-α)-mediated SOD-2 through NF-κB was involved in epithelial-mesenchymal transition and migration in A549 cells. Therefore, the present study aimed to identify if TNF-α mediated SOD-2 upregulation is involved in cisplatin resistance in ESCC. It was identified that a higher expression of SOD-2 in human ESCC samples was associated with TNF-α expression and poor overall survival in patients with ESCC, suggesting that SOD-2 may act as an oncogene in ESCC. To further confirm if TNF-α could upregulate SOD-2 to contribute to cell proliferation, the human ESCC cell line Eca-109 was treated with TNF-α in vitro. TNF-α could upregulate SOD-2 and induce cell proliferation in Eca109 cells, while blocking SOD-2 using small interfering RNA (siRNA) inhibited TNF-α-induced cell proliferation. Upregulation of SOD-2 by TNF-α was inhibited by blocking the NF-κB pathway, which suggested that SOD-2 by TNF-α/NF-κB contributes to cell proliferation in Eca109 cells. Furthermore, it was observed that TNF-α could induce cisplatin resistance in Eca109 cells, while transfection with SOD-2 siRNA could significantly increase the chemosensitivity of ESCC to cisplatin. Therefore, the present results suggested that SOD-2 may serve as an oncogene, and the upregulation of SOD-2 by TNF-α/NF-κB may contribute to cisplatin resistance in ESCC.

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