Reversal of hepatitis B virus-induced immune tolerance by an immunostimulatory 3p-HBx-siRNAs in a retinoic acid inducible gene I-dependent manner

HBx protein as a therapeutic target for functional cure of hepatitis B virus infection

Hepatitis B virus (HBV) is a major cause of acute and chronic liver disease and represents a major public health problem worldwide. Current antiviral therapies with nucleos(t)ide analogues can effectively suppressing viremia but are not curative, and have little or no impact upon the HBV cccDNA minichromosome or the portions of integrated HBV DNA. Several alternative therapeutic strategies targeted at viral components and life cycle are under intense investigation. This article highlights the reasons for considering HBx as a therapeutic target as this may allow targeting of both virus and disease. Recent studies focused at HBx have led to the identification of several new pharmacological agents and development of some novel therapeutic approaches that now deserve to be taken to the next level for better management of hepatitis B. Besides, new therapies could be combined with other established therapies, to provide a functional cure from hepatitis B infection.

Antiviral activity of HuaganJiedu decoction (HGJDD) against hepatitis B virus (HBV) through FOXO4/ERK/HNF4α signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic hepatitis B virus (HBV) infection is still a widespread global health issue. HuaganJiedu Decoction (HGJDD) is a common prescription for treating HBV in China, which has the effect of enhancing antiviral efficacy and improving clinical efficacy. However, its precise mechanism of action remains unclear, warranting further investigation to elucidate its therapeutic potential and integration into standard medical practices.

AIM OF THE STUDY

This study aims to explore the therapeutic mechanism of HuaganJiedu Decoction (HGJDD) in HBV.

MATERIALS AND METHODS

We investigated the therapeutic potential of HGJDD, and LC-MS analysis characterized the chemical profile of HGJDD. In vitro, we utilized HepG2.2.15 cell line to assess cytotoxicity and treatment efficacy of HGJDD compared to Entecavir controls. In vivo, assessments included monitoring HBV-related biomarkers and viral load. Network pharmacology and RNA-seq analyses identified molecular pathways and targets influenced by HGJDD treatment. Immunofluorescence and Western blotting provided further insights into the therapeutic mechanisms underlying HGJDD for HBV.

RESULTS

HGJDD showed no toxicity on HepG2.2.15 cells at 10%, 20%, 40%, and 80% serum concentrations. In vitro, HGJDD reduced HBsAg, HBeAg, and HBV DNA levels by dose-dependently and time-dependently. HGJDD can decrease the levels of HBsAg, HBeAg, and HBV DNA in serum and liver levels, meanwhile the therapeutic effect of high-dose HGJDD approach to EVT's in HBV Tg mice. According to intersection of network pharmacology and transcriptome, FOXO signal pathway was highlighted as potential targets and Immunofluorescence find that FOXO4D protein expression lever was increased in three HGJDD group, especially in high-dose HGJDD group. Western blotting confirmed increased level of FOXO4, ERK, and p-ERK and decreased levels of HNF4α, which reflected that the therapeutic effect was closely to FOXO4/ERK/HNF4α signal pathway.

CONCLUSIONS

Traditional Chinese medicine (TCM) offers diverse herbal treatments for HBV, with HGJDD showing efficacy in reducing HBsAg, HBeAg, and HBV DNA levels at cellular and animal levels. This study identified that FOXO4/ERK/HNF4α signal pathway played an important role in HGJDD's therapeutic effects. These findings support HGJDD's potential in HBV treatment, providing a scientific basis for clinical use.

LDHB Mediates Histone Lactylation to Activate PD-L1 and Promote Ovarian Cancer Immune Escape

BACKGROUND

To investigate the effects of LDHB on lactylation of programmed cell death 1 ligand (PD-L1) and immune evasion of ovarian cancer.

METHODS

Ovarian cancer cells were transfected with LDHB siRNA and cultured with primed T cells. Cell proliferation and viability were measured by cell counting kit 8 (CCK-8) and colony formation assay. The production of immune factors was detected by enzyme-linked immunosorbent assay (ELISA). The histone lactylation and activity of PD-L1 promoter were measured by chromatin immunoprecipitation (ChIP)-qPCR assay and luciferase reporter gene assay, respectively.

RESULTS

Knockdown of LDHB notably inhibited the growth, glucose uptake, lactate production, and ATP production of ovarian cancer cells. Knockdown of LDHB enhanced the killing effects of T cells, led to increased production of immune activation factors IL-2, TNF-α, and IFN-γ, as well as elevated the levels of granzyme B and perforin. Mechanical study identified that LDHB regulated the H3K18 lactylation (H3K18la) modification on PD-L1 promoter region to promote its expression. Overexpression of PD-L1 abolished the immune activation effects that induced by siLDHB.

CONCLUSION

The LDHB modulated lactate production and the histone lactylation on PD-L1 promoter, which ultimately regulated its expression and participated in the immune evasion of ovarian cancer cells.

Combining RNA Interference and RIG-I Activation to Inhibit Hepatitis E Virus Replication

Hepatitis E virus (HEV) poses a significant global health threat, with an estimated 20 million infections occurring annually. Despite being a self-limiting illness, in most cases, HEV infection can lead to severe outcomes, particularly in pregnant women and individuals with pre-existing liver disease. In the absence of specific antiviral treatments, the exploration of RNAi interference (RNAi) as a targeted strategy provides valuable insights for urgently needed therapeutic interventions against Hepatitis E. We designed small interfering RNAs (siRNAs) against HEV, which target the helicase domain and the open reading frame 3 (ORF3). These target regions will reduce the risk of viral escape through mutations, as they belong to the most conserved regions in the HEV genome. The siRNAs targeting the ORF3 efficiently inhibited viral replication in A549 cells after HEV infection. Importantly, the siRNA was also highly effective at inhibiting HEV in the persistently infected A549 cell line, which provides a suitable model for chronic infection in patients. Furthermore, we showed that a 5' triphosphate modification on the siRNA sense strand activates the RIG-I receptor, a cytoplasmic pattern recognition receptor that recognizes viral RNA. Upon activation, RIG-I triggers a signaling cascade, effectively suppressing HEV replication. This dual-action strategy, combining the activation of the adaptive immune response and the inherent RNAi pathway, inhibits HEV replication successfully and may lead to the development of new therapies.

Identification of a potent and specific retinoic acid-inducible gene 1 pathway activator as a Hepatitis B Virus antiviral through a novel cell-based reporter assay

Chronic Hepatitis B Virus (HBV) infection remains a global burden. To identify small molecule RIG-I agonists as antivirals against HBV, we developed an HBV-pgRNA-based interferon-β (IFN-β) luciferase reporter assay with high level of assay sensitivity, specificity and robustness. Through HTS screening, lead compound (JJ#1) was identified to activate RIG-I signaling pathway by inducing TBK1 phosphorylation. Knockdown experiments demonstrated that JJ#1-induced retinoic acid-inducible gene 1 (RIG-I) signaling pathway activation was MAVS-dependent. Furthermore, JJ#1 exhibited HBV antiviral potency in HBV-infected cell models by reducing HBV DNA and antigens (HBsAg and HBeAg).

Innate immune regulations and various siRNA modalities

RNAi therapeutics are designed to produce the precise silencing effects against the gene-linked diseases which were known to be untreatable in the past. The highly immunostimulatory nature of siRNA enhances the off-target effects and easily get attacked by nucleases; hence, their modulation is essentially required for accurate alterations to be made in the structures to intensify the pharmacological attributes. The phosphonate modifications act as shield against undue phosphorylation effects, and the molecular changes in ribose sugar lowers the level of immunogenicity and increases the binding efficacy. When bases are substituted with virtual/or pseudo bases, they eventually reduce the off-target effects. These changes modulate the nucleic acid sensors and control the hyper-activation of innate immune response. Various modification designs based on STC (universal pattern), ESC, ESC + (advanced patterns) and disubstrate have been explored to silence the gene expression of various diseases e.g., hepatitis, HIV, influenza, RSV, CNV and acute kidney injury. This review describes the various innovative siRNA therapeutics and their implications on the developed immune regulations to silence the disease effects. siRNA causes the silencing effects through RISC processing. The innate immune signalling is induced by both TLR-dependent and TLR-independent pathways. Modification chemistries are utilized to modulate the immune response.

The emerging role of DEAD/H-box helicases in hepatitis B virus infection

DEAD/H-box helicases are an essential protein family with a conserved motif containing unique amino acid sequences (Asp-Glu-Ala-Asp/His). Current evidence indicates that DEAD/H-box helicases regulate RNA metabolism and innate immune responses. In recent years, DEAD/H-box helicases have been reported to participate in the development of a variety of diseases, including hepatitis B virus (HBV) infection, which is a significant risk factor for hepatic fibrosis, cirrhosis, and liver cancer. Furthermore, emerging evidence suggests that different DEAD/H-box helicases play vital roles in the regulation of viral replication, based on the interaction of DEAD/H-box helicases with HBV and the modulation of innate signaling pathways mediated by DEAD/H-box helicases. Besides these, HBV can alter the expression and activity of DEAD/H-box helicases to facilitate its biosynthesis. More importantly, current investigation suggests that targeting DEAD/H-box helicases with appropriate compounds is an attractive treatment strategy for the virus infection. In this review, we delineate recent advances in molecular mechanisms relevant to the interplay of DEAD/H-box helicase and HBV and the potential of targeting DEAD/H-box helicase to eliminate HBV infection.

Codelivery of HBx-siRNA and Plasmid Encoding IL-12 for Inhibition of Hepatitis B Virus and Reactivation of Antiviral Immunity

Chronic hepatitis B is a critical cause of many serious liver diseases such as hepatocellular carcinoma (HCC). The main challenges in hepatitis B treatment include the rebound of hepatitis B virus (HBV)-related antigen levels after drug withdrawal and the immunosuppression caused by the virus. Herein, we demonstrate that the HBV-related antigen can be effectively inhibited and antiviral immunity can be successfully reactivated through codelivery of the small interfering RNA (siRNA) targeting HBV X protein (HBx) and the plasmid encoding interleukin 12 (pIL-12) to hepatocytes and immune cells. After being treated by the siRNA/pIL-12 codelivery system, HBx mRNA and hepatitis B surface antigen (HBsAg) are dramatically reduced in HepG2.215 cells. More importantly, the downregulated CD47 and programmed death ligand 1 (PD-L1) and the upregulated interferon-β promoter stimulator-1 (IPS-1), retinoic acid-inducible gene-1 (RIG-1), CD80, and human leukocyte antigen-1 (HLA-1) in treated HepG2.215 cells indicate that the immunosuppression is reversed by the codelivery system. Furthermore, the codelivery system results in inhibition of extracellular regulated protein kinases (ERK) and phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) pathways, as well as downregulation of B-cell lymphoma-2 (Bcl-2) and upregulation of p53, implying its potential in preventing the progression of HBV-induced HCC. In addition, J774A.1 macrophages treated by the codelivery system were successfully differentiated into the M1 phenotype and expressed enhanced cytokines with anti-hepatitis B effects such as interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α). Therefore, we believe that codelivery of siRNA and pIL-12 can effectively inhibit hepatitis B virus, reverse virus-induced immunosuppression, reactivate antiviral immunity, and hinder the progression of HBV-induced hepatocellular carcinoma. This investigation provides a promising approach for the synergistic treatment of HBV infection.

miR-1258 Enhances the Anti-Tumor Effect of Liver Cancer Natural Killer (NK) Cells by Stimulating Toll-Liker Receptor (TLR)7/8 to Promote Natural Killer (NK)-Dendritic Cell (DC) Interaction

TLR7/8 agonists are immunomodulators for treating skin cancer or virus infections. miR-1258 can activate TLR7/8. This study aims to explore the role of TLR7/8 agonists and miR-1258 in activating liver cancer NK cells. NK cells and DC cells were treated with TLR7/8 agonists R837, ssRNA40 and miR-1258 followed by analysis of hepatocellular carcinoma (HCC) cell behaviors in vivo and in vitro. TLR7/8 agonist miR-1258 activated NKs and promoted DCs maturation. In addition, DCs also assisted NKs to function and enhance the anti-HCC immune responses. The interaction of DCs with NK cells stimulated by TLR7/8 agonist miR-1258 can significantly inhibit tumor development and metastasis in mice HCC model. TLR7 or TLR8 agonists, especially miR-1258, promoted DCs-NKs interaction by promoting the secretion of related cytokines and cell/cell contact, which increased anti-tumor activity of NKs and promoted DC-NK cells to inhibit the growth of HCC cells. In conclusion, miR-1258 simultaneously stimulates the expression of TLR7/8, and promotes NK-DC cells to inhibit the growth of HCC cells, providing a theoretical basis for the treatment of liver cancer.

PreS/2-21-Guided siRNA Nanoparticles Target to Inhibit Hepatitis B Virus Infection and Replication

A viable therapy is needed to overcome the deadlock of the incurable chronic hepatitis B (CHB). The prolonged existence of covalently closed circular DNA (cccDNA) and integrated HBV DNA in the nucleus of hepatocytes is the root cause of CHB. As a result, it is critical to successfully suppress HBV DNA replication and eliminate cccDNA. RNA interference has been proven in recent research to silence the expression of target genes and thereby decrease HBV replication. However, siRNA is susceptible to be degraded by RNA enzymes in vivo, making it difficult to deliver successfully and lacking of tissue targeting. To exploit the advantages of siRNA technology while also overcoming its limitations, we designed a new strategy and prepared biomimetic nanoparticles that were directed by PreS/2-21 peptides and precisely loaded HBV siRNA. Experiments on these nanoparticles in vitro and in vivo revealed that they are tiny, stable, safe and highly targetable, with high inhibitory effects on HBV DNA, pgRNA, cccDNA, HBeAg and HBsAg. PreS/2-21-directed nanoparticles loaded with HBV gene therapy drugs are expected to be promising for the treatment of CHB.

Regulation of Pattern-Recognition Receptor Signaling by HBX During Hepatitis B Virus Infection

As a small DNA virus, hepatitis B virus (HBV) plays a pivotal role in the development of various liver diseases, including hepatitis, cirrhosis, and liver cancer. Among the molecules encoded by this virus, the HBV X protein (HBX) is a viral transactivator that plays a vital role in HBV replication and virus-associated diseases. Accumulating evidence so far indicates that pattern recognition receptors (PRRs) are at the front-line of the host defense responses to restrict the virus by inducing the expression of interferons and various inflammatory factors. However, depending on HBX, the virus can control PRR signaling by modulating the expression and activity of essential molecules involved in the toll-like receptor (TLR), retinoic acid inducible gene I (RIG-I)-like receptor (RLR), and NOD-like receptor (NLR) signaling pathways, to not only facilitate HBV replication, but also promote the development of viral diseases. In this review, we provide an overview of the mechanisms that are linked to the regulation of PRR signaling mediated by HBX to inhibit innate immunity, regulation of viral propagation, virus-induced inflammation, and hepatocarcinogenesis. Given the importance of PRRs in the control of HBV replication, we propose that a comprehensive understanding of the modulation of cellular factors involved in PRR signaling induced by the viral protein may open new avenues for the treatment of HBV infection.

Enhancing anti-tumor efficacy and immune memory by combining 3p-GPC-3 siRNA treatment with PD-1 blockade in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is associated with a high mortality rate and presents a major challenge for human health. Activation of multiple oncogenes has been reported to be strongly associated with the progression of HCC. Moreover, the immunosuppressive tumor microenvironment (TME) and the host immune system are also implicated in the development of malignant HCC tumors. Glypican-3 (GPC-3), a proteoglycan involved in the regulation of cell proliferation and apoptosis, is aberrantly expressed in HCC. We synthesized a short 5'-triphosphate (3p) RNA targeting GPC-3, 3p-GPC-3 siRNA, and found that it effectively inhibited subcutaneous HCC growth by raising type I IFN levels in tumor cells and serum and promoting tumor cell apoptosis. Moreover, 3p-GPC-3 siRNA was able to enhance the activation of CD4⁺ T cells, CD8⁺ T cells, and natural killer (NK) cells while reducing the proportion of regulatory T cells (Tregs) in the TME. Most intriguingly, a blocking anti-PD-1 antibody improved the anti-tumor effect of 3p-GPC-3 siRNA, predominantly by activating the immune response, reversing immune exhaustion, and improving immune memory. Our study suggests that the combination of 3p-GPC-3 siRNA administration and PD-1 blockade may represent a promising therapeutic strategy for HCC.

Combination of natural killer cell-based immunotherapy and irreversible electroporation for the treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is among the most lethal cancer types despite great advancement in overall survival of the patients over the last decades. Surgical resection or partial hepatectomy has been approved as the curative treatment for early-stage HCC patients however only up to 30% of them are eligible for the procedures. Natural killer (NK) cells are cytotoxic lymphocytes recognized for killing virally infected cells and improving immune functions for defending the body against malignant cells. Although autologous NK cells failed to demonstrate significant clinical benefit, transfer of allogeneic adoptive NK cells arises as a promising approach for the treatment of solid tumors. The immunosuppressive tumor microenvironment and inadequate homing efficiency of NK cells to tumors can inhibit adoptive transfer immunotherapy (ATI) efficacy. However, potential of the NK cells is challenged by the transfection efficiency. The local ablation techniques that employ thermal or chemical energy have been investigated for the destruction of solid tumors for three decades and demonstrated promising benefits for individuals not eligible for surgical resection or partial hepatectomy. Irreversible electroporation (IRE) is one of the most recent minimally invasive ablation methods that destruct the cell within the targeted region through non-thermal energy. IRE destroys the tumor cell membrane by delivering high-frequency electrical energy in short pulses and overcomes tumor immunosuppression. The previous studies demonstrated that IRE can induce immune changes which can facilitate activation of specific immune responses and improve transfection efficiency. In this review paper, we have discussed the mechanism of NK cell immunotherapy and IRE ablation methods for the treatment of HCC patients and the combinatorial benefits of NK cell immunotherapy and IRE ablation.

A putative amphipathic alpha helix in hepatitis B virus small envelope protein plays a critical role in the morphogenesis of subviral particles

Hepatitis B virus (HBV) small (S) envelope protein has the intrinsic ability to direct the formation of small spherical subviral particles (SVPs) in eukaryotic cells. However, the molecular mechanism underlying the morphogenesis of SVPs from the monomeric S protein initially synthesized at the endoplasmic reticulum (ER) membrane remains largely elusive. Structure prediction and extensive mutagenesis analysis suggested that the amino acid residues spanning W156 to R169 of S protein form an amphipathic alpha helix and play essential roles in SVP production and S protein metabolic stability. Further biochemical analyses showed that the putative amphipathic alpha helix was not required for the disulfide-linked S protein oligomerization, but was essential for SVP morphogenesis. Pharmacological disruption of vesicle trafficking between the ER and Golgi complex in SVP producing cells supported the hypothesis that S protein-directed SVP morphogenesis takes place at the ER-Golgi intermediate compartment (ERGIC). Moreover, it was demonstrated that S protein is degraded in hepatocytes via a 20S proteasome-dependent, but ubiquitination-independent non-classic ER-associated degradation (ERAD) pathway. Taken together, the results reported herein favor a model in which the amphipathic alpha helix at the antigenic loop of S protein attaches to the lumen leaflet to facilitate SVP budding from the ERGIC compartment, whereas the failure of budding process may result in S protein degradation by 20S proteasome in an ubiquitination-independent manner.Importance Subviral particles are the predominant viral product produced by HBV-infected hepatocytes. Their levels exceed the virion particles by 10,000 to 100,000-fold in the blood of HBV infected individuals. The high levels of SVPs, or HBV surface antigen (HBsAg), in the circulation induces immune tolerance and contributes to the establishment of persistent HBV infection. The loss of HBsAg, often accompanied by appearance of anti-HBs antibodies, is the hallmark of durable immune control of HBV infection. Therapeutic induction of HBsAg loss is, therefore, considered to be essential for the restoration of host antiviral immune response and functional cure of chronic hepatitis B. Our findings on the mechanism of SVP morphogenesis and S protein metabolism will facilitate the rational discovery and development of antiviral drugs to achieve this therapeutic goal.

Antiviral activity of a polysaccharide from Radix Isatidis (Isatis indigotica Fortune) against hepatitis B virus (HBV) in vitro via activation of JAK/STAT signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatitis B virus (HBV) infection frequently results in both acute and chronic hepatitis and poses serious threats to human health worldwide. Despite the availability of effective HBV vaccine and anti-HBV drugs, apparently inevitable side effects and resistance have limited its efficiency, thus prompt the search for new anti-HBV agents. The traditional Chinese medicine Radix Isatidis has been used for thousands of years, mainly for the treatment of viral and bacterial infection diseases including hepatitis.

AIM OF THE STUDY

In this study, antiviral activities of a Radix Isatidis (Isatis indigotica Fortune) polysaccharide (RIP) were evaluated in vitro model using the HepG2.2.15 cell line and the underlying mechanism was elucidated with the aim of developing a novel anti-HBV therapeutic agent.

MATERIALS AND METHODS

Structure features of the purified polysaccharide RIP were investigated by a combination of chemical and instrumental analysis. Drug cytotoxicity was assessed using the MTT assay. The contents of HBsAg, HBeAg, intracellular and extracellular IFN-α level were measured using respective commercially available ELISA kit. The HBV DNA expression was evaluated by real-time quantitative polymerase chain reaction (PCR) and the relevant proteins involved in TFN/JAK/STAT signaling pathways were examined by western blot assay.

RESULTS

MTT assay showed that RIP had no toxicity on HepG2.2.15 cell line below the concentration 400 μg/ml at Day 3, 6 and 9. Furthermore, RIP at the concentration of 50, 100 and 200 μg/ml significantly reduced extracellular and intracellular level of HBsAg, HBeAg and HBV DNA in HepG2.2.15 cells in a time and dose-dependent manner. Moreover, RIP also enhanced the production of IFN-α in HepG2.2.15 cell via activation of JAK/STAT signal pathway and induction of antiviral proteins, as evidenced by the increased protein expression of p-STAT-1, p-STAT-2, p-JAK1, p-TYK2, OAS1, and Mx in HepG2.2.15 cells. In addition, the over expression of SOCS-1 and SOCS-3 was significantly abolished under same conditions.

CONCLUSIONS

These results suggested that the HBV inhibitory effect of RIP was possibly due to the activation of IFN-α-dependent JAK/STAT signal pathway and induction of the anti-HBV protein expression.

Hepatitis B Virus Infection: Overview

Hepatitis B virus (HBV) is a DNA virus, belonging to the Hepadnaviridae family. It is a partially double-stranded DNA virus with a small viral genome (3.2 kb). Chronic HBV infection remains a global public health problem. If left untreated, chronic HBV infection can progress to end-stage liver disease, such as liver cirrhosis and hepatocellular carcinoma (HCC). In recent years, tremendous advances in the field of HBV basic and clinical research have been achieved, ranging from the HBV biological characteristics, immunopathogenesis, and animal models to the development of new therapeutic strategies and new drugs against HBV. In this overview, we begin with a brief history of HBV discovery and treatment milestones. We then briefly summarize the HBV research advances, which will be detailed in the following chapters.

MiR-3613-3p impairs IFN-induced immune response by targeting CMPK1 in chronic hepatitis B

BACKGROUND

This study aims to investigate the effects of miR-3613-3p and its underlying mechanisms on chronic hepatitis B.

METHODS

Expressions of miR-3613-3p were determined in clinical samples from chronic hepatitis B patients and healthy volunteers. HBV-transfected hepatoma cell lines were constructed for in vitro study. HBV-infected animal model was established in vivo study. Quantitative real-time reverse transcription PCR (qRT-PCR) was used to determine mRNA expressions. Western blotting and ELISA were used to determine protein expressions. Luciferase reporter and biotin pull-down assays were used to analyze RNA-RNA interactions. siRNA silencing was used to knockdown miR-3613-3p and CMPK1.

RESULTS

MiR-3613-3p was upregulated in the chronic hepatitis B patients, as compared with healthy volunteers. Inhibition of miR-3613-3p decreased relative expressions of IFN-α and IFN-β, HBV DNA copies, and increased the hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) levels, whereas miR-3613-3p overexpression reversed these changes in vitro and in vivo. MiR-3613-3p directly targeted CMPK1 and interactions between CMPK1 and miR-3613-3p regulated the anti-HBV efficiency of IFN.

CONCLUSION

MiR-3613-3p impaired IFN-induced immune response by targeting CMPK1 in chronic hepatitis B.

GADD45α alleviates acetaminophen-induced hepatotoxicity by promoting AMPK activation

As an analgesic and antipyretic drug, acetaminophen (APAP) is commonly used and known to be safe at therapeutic doses. In many countries, the overuse of APAP provokes acute liver injury and even liver failure. APAP-induced liver injury (AILI) is the most used experimental model of drug-induced liver injury (DILI). Here, we have demonstrated elevated levels of growth arrest and DNA damage-inducible 45α (GADD45α) in the livers of patients with DILI/AILI, in APAP-injured mouse livers and in APAP-treated hepatocytes. GADD45α exhibited a protective effect against APAP-induced liver injury and alleviated the accumulation of small lipid droplets in vitro and in vivo. We found that GADD45α promoted the activation of AMP-activated protein kinase α and induced fatty acid beta-oxidation, tricarboxylic acid cycle (TCA) and glycogenolysis-related gene expression after APAP exposure. Liquid chromatography-mass spectrometry (LC-MS) analysis showed that GADD45α increased the levels of TCA cycle metabolites. Co-immunoprecipitation analysis showed that Ppp2cb, a catalytic subunit of protein phosphatase 2A, could interact directly with GADD45α. Our results indicate that hepatocyte GADD45α might represent a therapeutic target to prevent and rescue liver injury caused by APAP.

5'-triphosphate siRNA targeting HBx elicits a potent anti-HBV immune response in pAAV-HBV transfected mice

RNA with 5'-triphosphate (3p-RNA) is recognized by RNA sensor RIG-I (retinoic acid-inducible gene I protein). Previously, we reported that small interfering RNA targeting HBx (3p-siHBx) could confer potent anti-hepatitis B virus (HBV) efficacy via HBx silencing and RIG-I activation. However, the characteristics of innate and adaptive immunity especially exhaustion profiles in the liver microenvironment in response to 3p-siHBx therapy have not been fully elucidated. Here, we observed that 3p-siHBx more significantly inhibited HBV replication in vivo. 3p-siHBx enhanced natural killer (NK) cell activation with KLRG1 and CD69 upregulation and interferon (IFN)-γ secretion. 3p-siHBx significantly reversed the exhaustion phenotype of CD8⁺ T cells, and augmented CD8⁺ T cell activation and function. Importantly, 3p-siHBx disrupted the differentiation of myeloid-derived suppressor cells (MDSC) and regulatory T cells (Treg), accompanied by the reduction of the immunosuppressive cytokines interleukin (IL)-10 and transforming growth factor (TGF)-β. 3p-siHBx also enhanced dendritic cell maturation. Further investigation showed that RIG-I was involved in 3p-siHBx-induced IFN-α, IFN-β, and IFN-λ production. Moreover, RIG-I activation in HBV⁺ hepatocytes would improve the recruitment of CD8⁺ T cells and NK cells. These results reveal that 3p-siHBx therapy can improve the immune microenvironment in HBV-carrier liver and inhibit HBV replication, indicating the potential utility of RIG-I ligands as molecular adjuvants for viral vaccines or candidate drugs.

Combinational immune-cell therapy of natural killer cells and sorafenib for advanced hepatocellular carcinoma: a review

Background

High prevalence of hepatocellular carcinoma (HCC) and typically poor prognosis of this disease that lead to late stage diagnosis when potentially curative therapies are least effective; therefore, development of an effective and systematic treatment is an urgent requirement.

Main body

In this review, several current treatments for HCC patients and their advantages or disadvantages were summarized. Moreover, various recent preclinical and clinical studies about the performances of "two efficient agents, sorafenib or natural killer (NK) cells", against HCC cells were investigated. In addition, the focus this review was on the chemo-immunotherapy approach, correlation between sorafenib and NK cells and their effects on the performance of each other for better suppression of HCC.

Conclusion

It was concluded that combinational therapy with sorafenib and NK cells might improve the outcome of applied therapeutic approaches for HCC patients. Finally, it was also concluded that interaction between sorafenib and NK cells is dose and time dependent, therefore, a careful dose and time optimizing is necessary for development of a combinational immune-cell therapy.

RNA Interference-Induced Innate Immunity, Off-Target Effect, or Immune Adjuvant?

RNA interference (RNAi) is a natural cellular mechanism that inhibits gene expression in a sequence-specific manner. In the last decade, RNAi has become a cornerstone in basic biological systems research and drug development efforts. The RNAi-based manipulation of mammalian cells facilitates target identification and validation; assists in identifying human disease etiologies; and expedites the development of treatments for infectious diseases, cancer, and other conditions. Several RNAi-based approaches are currently undergoing assessment in phase I and II clinical trials. However, RNAi-associated immune stimulation might act as a hurdle to safe and effective RNAi, particularly in clinical applications. The induction of innate immunity may originate from small interfering RNA (siRNA) sequence-dependent delivery vehicles and even the RNAi process itself. However, in the case of antagonistic cancers and viral infection, immune activation is beneficial; thus, immunostimulatory small interfering RNAs were designed to create bifunctional small molecules with RNAi and immunostimulatory activities. This review summarizes the research studies of RNAi-associated immune stimulation and the approaches for manipulating immunostimulatory activities.

RNA interference-based technology: what role in animal agriculture?

Animal agriculture faces a broad array of challenges, ranging from disease threats to adverse environmental conditions, while attempting to increase productivity using fewer resources. RNA interference (RNAi) is a biological phenomenon with the potential to provide novel solutions to some of these challenges. Discovered just 20 years ago, the mechanisms underlying RNAi are now well described in plants and animals. Intracellular double-stranded RNA triggers a conserved response that leads to cleavage and degradation of complementary mRNA strands, thereby preventing production of the corresponding protein product. RNAi can be naturally induced by expression of endogenous microRNA, which are critical in the regulation of protein synthesis, providing a mechanism for rapid adaptation of physiological function. This endogenous pathway can be co-opted for targeted RNAi either through delivery of exogenous small interfering RNA (siRNA) into target cells or by transgenic expression of short hairpin RNA (shRNA). Potentially valuable RNAi targets for livestock include endogenous genes such as developmental regulators, transcripts involved in adaptations to new physiological states, immune response mediators, and also exogenous genes such as those encoded by viruses. RNAi approaches have shown promise in cell culture and rodent models as well as some livestock studies, but technical and market barriers still need to be addressed before commercial applications of RNAi in animal agriculture can be realised. Key challenges for exogenous delivery of siRNA include appropriate formulation for physical delivery, internal transport and eventual cellular uptake of the siRNA; additionally, rigorous safety and residue studies in target species will be necessary for siRNA delivery nanoparticles currently under evaluation. However, genomic incorporation of shRNA can overcome these issues, but optimal promoters to drive shRNA expression are needed, and genetic engineering may attract more resistance from consumers than the use of exogenous siRNA. Despite these hurdles, the convergence of greater understanding of RNAi mechanisms, detailed descriptions of regulatory processes in animal development and disease, and breakthroughs in synthetic chemistry and genome engineering has created exciting possibilities for using RNAi to enhance the sustainability of animal agriculture.

Genome-wide association study identifies 8p21.3 associated with persistent hepatitis B virus infection among Chinese

Hepatitis B virus (HBV) infection is a common infectious disease. Here we perform a genome-wide association study (GWAS) among Chinese populations to identify novel genetic loci involved in persistent HBV infection. GWAS scan is performed in 1,251 persistently HBV infected subjects (PIs, cases) and 1,057 spontaneously recovered subjects (SRs, controls), followed by replications in four independent populations totally consisting of 3,905 PIs and 3,356 SRs. We identify a novel locus at 8p21.3 (index rs7000921, odds ratio=0.78, P=3.2 × 10(-12)). Furthermore, we identify significant expression quantitative trait locus associations for INTS10 gene at 8p21.3. We demonstrate that INST10 suppresses HBV replication via IRF3 in liver cells. In clinical plasma samples, we confirm that INST10 levels are significantly decreased in PIs compared with SRs, and negatively correlated with the HBV load. These findings highlight a novel antiviral gene INTS10 at 8p21.3 in the clearance of HBV infection.

Hepatitis B virus inhibits intrinsic RIG-I and RIG-G immune signaling via inducing miR146a

Previous studies showed that hepatitis B virus (HBV), as a latency invader, attenuated host anti-viral immune responses. miRNAs were shown to be involved in HBV infection and HBV-related diseases, however, the precise role of miRNAs in HBV-mediated immunosuppression remains unclear. Here, we observed that down-regulated RIG-I like receptors might be one critical mechanism of HBV-induced suppression of type I IFN transcription in both HBV(+) hepatoma cell lines and liver cancer tissues. Then, miR146a was demonstrated to negatively regulate the expression of RIG-I-like receptors by directly targeting both RIG-I and RIG-G. Further investigation showed that antagonizing miR146a by anti-sense inhibitors or sponge approach accelerated HBV clearance and reduced HBV load both in vitro and in a HBV-carrying mouse model. Therefore, our findings indicated that HBV-induced miR146a attenuates cell-intrinsic anti-viral innate immunity through targeting RIG-I and RIG-G, and silencing miR146a might be an effective target to reverse HBV-induced immune suppression.

siRNA and RNAi optimization

The discovery and examination of the posttranscriptional gene regulatory mechanism known as RNA interference (RNAi) contributed to the identification of small interfering RNA (siRNA) and the comprehension of its enormous potential for clinical purposes. Theoretically, the ability of specific target gene downregulation makes the RNAi pathway an appealing solution for several diseases. Despite numerous hurdles resulting from the inherent properties of siRNA molecule and proper delivery to the target tissue, more than 50 RNA-based drugs are currently under clinical testing. In this work, we analyze the recent literature in the optimization of siRNA molecules. In detail, we focused on describing the most recent advances of siRNA field aimed at optimize siRNA pharmacokinetic properties. Special attention has been given in describing the impact of RNA modifications in the potential off-target effects (OTEs) such as saturation of the RNAi machinery, passenger strand-mediated silencing, immunostimulation, and miRNA-like OTEs as well as to recent developments on the delivery issue. The novel delivery systems and modified siRNA provide significant steps toward the development of reliable siRNA molecules for therapeutic use. WIREs RNA 2016, 7:316-329. doi: 10.1002/wrna.1337 For further resources related to this article, please visit the WIREs website.

TLR7/8 agonists promote NK-DC cross-talk to enhance NK cell anti-tumor effects in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common cancer worldwide and the third leading cause of cancer death. Immunotherapy is considered a promising treatment with the aim to boost or arouse HCC-specific immune responses. TLR7 and TLR8 agonists are effective immunomodulators and have been applied topically for the treatment of certain skin tumors and viral infections. Here, we explored the role of TLR7 and TLR8 agonists on the activation of dendritic cells (DCs) and natural killer (NK) cells. We demonstrated that these agonists could directly activate NK cells, promoting the maturation of immature DCs. Meanwhile, DCs also assisted in the function of NK cells, resulting in enhanced anti-tumor immune responses to HCC. Importantly, the combination therapy with NK cells stimulated with DCs and TLR7/8 agonist Gardiquimod (GDQ) significantly suppresses the growth of human HepG2 liver carcinoma xenografts. This study provides a new immunotherapeutic approach for human HCC based on DC-NK cross-talk and also suggests that TLR7 and/or TLR8 agonists, particularly GDQ, may serve as potent innate and adaptive immune response immunomodulators in tumor therapy.

Natural killer cell dysfunction in hepatocellular carcinoma and NK cell-based immunotherapy

The mechanisms linking hepatitis B virus (HBV) and hepatitis C virus (HCV) infection to hepatocellular carcinoma (HCC) remain largely unknown. Natural killer (NK) cells account for 25%–50% of the total number of liver lymphocytes, suggesting that NK cells play an important role in liver immunity. The number of NK cells in the blood and tumor tissues of HCC patients is positively correlated with their survival and prognosis. Furthermore, a group of NK cell-associated genes in HCC tissues is positively associated with the prolonged survival. These facts suggest that NK cells and HCC progression are strongly associated. In this review, we describe the abnormal NK cells and their functional impairment in patients with chronic HBV and HCV infection, which contribute to the progression of HCC. Then, we summarize the association of NK cells with HCC based on the abnormalities in the numbers and phenotypes of blood and liver NK cells in HCC patients. In particular, the exhaustion of NK cells that represents lower cytotoxicity and impaired cytokine production may serve as a predictor for the occurrence of HCC. Finally, we present the current achievements in NK cell immunotherapy conducted in mouse models of liver cancer and in clinical trials, highlighting how chemoimmunotherapy, NK cell transfer, gene therapy, cytokine therapy and mAb therapy improve NK cell function in HCC treatment. It is conceivable that NK cell-based anti-HCC therapeutic strategies alone or in combination with other therapies will be great promise for HCC treatment.

New insights into hepatitis B virus biology and implications for novel antiviral strategies

Hepatitis B virus (HBV), a small DNA virus with a unique replication mode, can cause chronic hepatitis (CHB), which is characterized by the persistence of the viral covalently closed circular DNA that serves as the template for HBV replication and the production of large amounts of secreted HBV surface antigen (HBsAg) that is present in excess of the levels of infectious virus. Despite the success of currently approved antiviral treatments for CHB patients, including interferon and nucleotide analogs, which suppress HBV replication and reduce the risk of CHB-related liver diseases, these therapies fail to eradicate the virus in most of the patients. With the development of the cell and animal models for HBV study, a better understanding of the HBV life cycle has been achieved and a series of novel antiviral strategies that target different stages of HBV replication have been designed to overcome the viral factors that contribute to HBV persistence. Such basic HBV research advancements and therapeutic developments are the subject of this review.

Modeling hepatitis B virus infection, immunopathology and therapy in mice

Despite the availability of a preventive vaccine, chronic hepatitis B virus (HBV) infection-induced liver diseases continue to be a major global public health problem. HBV naturally infects only humans and chimpanzees. This narrow host range has hindered our ability to study the characteristics of the virus and how it interacts with its host. It is thus important to establish small animal models to study HBV infection, persistence, clearance and the immunopathogenesis of chronic hepatitis B. In this review, we briefly summarize currently available animal models for HBV research, then focus on mouse models, especially the recently developed humanized mice that can support HBV infection and immunopathogenesis in vivo. This article is part of a symposium in Antiviral Research on "From the discovery of the Australia antigen to the development of new curative therapies for hepatitis B: an unfinished story."

RIG-I in RNA virus recognition

Antiviral immunity is initiated upon host recognition of viral products via non-self molecular patterns known as pathogen-associated molecular patterns (PAMPs). Such recognition initiates signaling cascades that induce intracellular innate immune defenses and an inflammatory response that facilitates development of the acquired immune response. The retinoic acid-inducible gene I (RIG-I) and the RIG-I-like receptor (RLR) protein family are key cytoplasmic pathogen recognition receptors that are implicated in the recognition of viruses across genera and virus families, including functioning as major sensors of RNA viruses, and promoting recognition of some DNA viruses. RIG-I, the charter member of the RLR family, is activated upon binding to PAMP RNA. Activated RIG-I signals by interacting with the adapter protein MAVS leading to a signaling cascade that activates the transcription factors IRF3 and NF-κB. These actions induce the expression of antiviral gene products and the production of type I and III interferons that lead to an antiviral state in the infected cell and surrounding tissue. RIG-I signaling is essential for the control of infection by many RNA viruses. Recently, RIG-I crosstalk with other pathogen recognition receptors and components of the inflammasome has been described. In this review, we discuss the current knowledge regarding the role of RIG-I in recognition of a variety of virus families and its role in programming the adaptive immune response through cross-talk with parallel arms of the innate immune system, including how RIG-I can be leveraged for antiviral therapy.

Hepatitis B virus polymerase disrupts K63-linked ubiquitination of STING to block innate cytosolic DNA-sensing pathways

The cellular innate immune system recognizing pathogen infection is essential for host defense against viruses. In parallel, viruses have developed a variety of strategies to evade the innate immunity. The hepatitis B virus (HBV), a DNA virus that causes chronic hepatitis, has been shown to inhibit RNA helicase RIG-I-mediated interferon (IFN) induction. However, it is still unknown whether HBV could affect the host DNA-sensing pathways. Here we report that in transiently HBV-transfected Huh7 cells, the stably HBV-producing cell line HepAD38, and HBV-infected HepaRG cells and primary human hepatocytes, HBV markedly interfered with IFN-β induction and antiviral immunity mediated by the stimulator of interferon genes (STING), which has been identified as a central factor in foreign DNA recognition and antiviral innate immunity. Screening analysis demonstrated that the viral polymerase (Pol), but not other HBV-encoded proteins, was able to inhibit STING-stimulated interferon regulatory factor 3 (IRF3) activation and IFN-β induction. Moreover, the reverse transcriptase (RT) and the RNase H (RH) domains of Pol were identified to be responsible for the inhibitory effects. Furthermore, Pol was shown to physically associate with STING and dramatically decrease the K63-linked polyubiquitination of STING via its RT domain without altering the expression level of STING. Taken together, these observations suggest that besides its inherent catalytic function, Pol has a role in suppression of IFN-β production by direct interaction with STING and subsequent disruption of its K63-linked ubiquitination, providing a new mechanism for HBV to counteract the innate DNA-sensing pathways.

IMPORTANCE

Although whether and how HBV infection induces the innate immune responses are still controversial, it has become increasingly clear that HBV has developed strategies to counteract the pattern recognition receptor-mediated signaling pathways. Previous studies have shown that type I IFN induction activated by the host RNA sensors could be inhibited by HBV. However, it remains unknown whether HBV as a DNA virus utilizes evasion mechanisms against foreign DNA-elicited antiviral signaling. In recent years, the cytosolic DNA sensor and key adaptor STING has been demonstrated to be essential in multiple foreign DNA-elicited innate immune signalings. Here, for the first time, we report STING as a new target of HBV to antagonize IFN induction and identify the viral polymerase responsible for the inhibitory effect, thus providing an additional molecular mechanism by which HBV evades the innate immunity; this implies that in addition to its inherent catalytic function, HBV polymerase is a multifunctional immunomodulatory protein.

Phosphorothioate modification of the TLR9 ligand CpG ODN inhibits poly(I:C)-induced apoptosis of hepatocellular carcinoma by entry blockade

Toll-like receptors (TLRs) play a crucial role in the innate immune response and subsequent induction of adaptive immune responses. Recently, it has been noted that TLRs on tumor cells are involved in tumor development, and several TLR agonists, such as the TLR3 agonist poly(I:C) and the TLR9 agonist CpG ODN, are being developed as vaccine adjuvants and cancer immunotherapeutics. In this study, we investigated whether combining poly(I:C) with a TLR9 agonist CpG ODN would result in a stronger anti-tumor effect on hepatocellular carcinoma cells (HCCs). Surprisingly, we found that simultaneous transfection of poly(I:C) and ODN M362 exhibited a lower pro-apoptotic effect on HCCs than transfection with poly(I:C) alone. Simultaneous co-transfection was accompanied by down-regulation of poly(I:C)-related innate receptors, pro-inflammatory cytokines and apoptotic genes induced by poly(I:C), indicating that ODN M362 blocked the activation of poly(I:C)-triggered intrinsic immune responses and cellular apoptosis. Further studies indicated that these effects were partly due to the phosphorothioate-modification of CpG ODN, which blocked the entry of poly(I:C) into tumor cells. This entry blockade was avoided by administering poly(I:C) after CpG ODN. Moreover, poly(I:C)-mediated pro-apoptotic effects were enhanced in vitro and in vivo by pre-treating HCC cells with CpG ODN. Our findings thus suggest that when combining poly(I:C) and CpG ODN for cancer therapy, these agents should be used in an alternating rather than simultaneous manner to avoid the blocking effect of phosphorothioate-modified TLR9 ligands.

Therapeutic strategies for a functional cure of chronic hepatitis B virus infection

Treatment of chronic hepatitis B virus (HBV) infection with the viral DNA polymerase inhibitors or pegylated alpha-interferon has led to a significant retardation in HBV-related disease progression and reduction in mortality related to chronic hepatitis B associated liver decompensation and hepatocellular carcinoma. However, chronic HBV infection remains not cured. The reasons for the failure to eradicate HBV infection by long-term antiviral therapy are not completely understood. However, clinical studies suggest that the intrinsic stability of the nuclear form of viral genome, the covalently closed circular (ccc) DNA, sustained low level viral replication under antiviral therapy and homeostatic proliferation of hepatocytes are the critical virological and pathophysiological factors that affect the persistence and therapeutic outcomes of HBV infection. More importantly, despite potent suppression of HBV replication in livers of the treated patients, the dysfunction of HBV-specific antiviral immunity persists. The inability of the immune system to recognize cells harboring HBV infection and to cure or eliminate cells actively producing virus is the biggest challenge to finding a cure. Unraveling the complex virus–host interactions that lead to persistent infection should facilitate the rational design of antivirals and immunotherapeutics to cure chronic HBV infection.

Phosphorothioate-modified CpG oligodeoxynucleotide (CpG ODN) induces apoptosis of human hepatocellular carcinoma cells independent of TLR9

Toll-like receptors (TLRs) expressed on cancer cells are closely associated with tumor development. In this study, we investigated the biological functions of the TLR9 ligand, CpG oligodeoxynucleotide (CpG ODN), on TLR9 expressed in the cytoplasm of hepatocellular carcinoma (HCC) cells. In vitro, human HCC cell lines were transfected with phosphorothioate-modified oligodeoxynucleotides TLR9 agonist OND M362 and its negative control ODN M362 ctrl, which inhibited the proliferation of HCC cells by inducing apoptosis without altering the cell cycle. Interestingly, ODN M362 and ODN M362 Ctrl displayed a similar proapoptotic effect on HCC, possibly related to phosphorothioate modification of the structure of CpG ODN. Although both of them resulted in the upregulation of the TLR9 receptor, their effect on HCC apoptosis was independent of TLR9. They also upregulated inflammatory cytokines, but did not activate the NF-κB signaling pathway. Finally, the activities of ODN M362 and ODN M362 Ctrl were demonstrated in nude mice inoculated with HCC cells. These findings suggest that the phosphorothioate-modified TLR9 agonist ODN M362, and its control, elicit antitumor activity in HCC cells and may serve as a novel therapeutic target for HCC therapy.

Interplay between hepatitis B virus and the innate immune responses: implications for new therapeutic strategies

Hepatitis B virus (HBV) infection is still a worldwide health problem; however, the current antiviral therapies for chronic hepatitis B are limited in efficacy. The outcome of HBV infection is thought to be the result of complex interactions between the HBV and the host immune system. While the role of the adaptive immune responses in the resolution of HBV infection has been well characterized, the contribution of innate immune mechanisms remains elusive until recent evidence implicates that HBV appears to activate the innate immune response and this response is important for controlling HBV infection. Here, we review our current understanding of innate immune responses to HBV infection and the multifaceted evasion by the virus and discuss the potential strategies to combat chronic HBV infection via induction and restoration of host innate antiviral responses.

miR146a impairs the IFN-induced anti-HBV immune response by downregulating STAT1 in hepatocytes

BACKGROUND & AIMS

Previous studies have shown that hepatitis B virus (HBV) interferes with host antiviral immunity via multiple pathways. In clinical practice, interferon resistance is a serious issue for treatment of HBV infection. Now, miRNAs have been reported to be widely involved in antiviral immunity and have become a novel tool to study virus-host interaction. We question whether miRNAs play a role in HBV-induced interferon resistance in hepatocytes.

METHODS

MiRNAs levels in HepG2 and HepG2.2.15 cells were compared by qRT-PCR. The effects of miR146a on HBV infection were characterized by interference miR146a level, followed by the quantification of HBV mRNA, DNA and antigens. We employed qRT-PCR and western blot to study the effects of miR146a on the IFN-α signalling pathway. The miR146a promoter activity was validated by a luciferase reporter assay.

RESULTS

HBV infection impaired IFN-α signalling pathway in hepatocytes. MiR146a was upregulated in HBV+ HepG2.2.15 cells, and the transcriptional activity of miR146a in HepG2.2.15 cells was increased compared with HepG2 cells. HBV infection, especially the introduction of HBx, induced miR146a expression in vitro. Moreover, miR146a attenuated the production of type I interferon-induced antiviral factors. Low STAT1 levels were noticed in HBV+ HCC cells, and the luciferase reporter assay showed that STAT1 was post-transcriptionally downregulated by miR146a. Furthermore, the silencing of miR146a by antisense inhibitors enhanced IFN-α-mediated anti-HBV efficiency.

CONCLUSIONS

Our findings demonstrate that HBV infection promotes miR146a transcription, which represses STAT1 and results in interferon resistance. These observations reveal a novel role for miR146a in HBV immunopathogenesis, and provide a potential target for the therapeutic recovery of IFN-α-induced anti-HBV effects.

5'-triphosphate-siRNA activates RIG-I-dependent type I interferon production and enhances inhibition of hepatitis B virus replication in HepG2.2.15 cells

Hepatitis B virus (HBV) infection often results in acute or chronic viral hepatitis and other liver diseases including cirrhosis and hepatocellular carcinoma. Current therapies for HBV usually have severe side effects and can cause development of drug-resistant mutants. An alternative and safe immunotherapeutic approach for HBV infection is urgently needed for effective anti-HBV therapy. In this study, we propose a new strategy for anti-HBV therapy that activates type-I interferon (IFN) antiviral innate immunity through stimulating pattern-recognition receptors with RNA interference (RNAi) using a 5'-end triphosphate-modified small interfering RNA (3p-siRNA). We designed and generated a 3p-siRNA targeting overlapping region of S gene and P gene of the HBV genome at the 5'-end of pregenomic HBV RNA. Our results demonstrated that 3p-siRNA induced a RIG-I-dependent antiviral type-I IFN response when transfected into HepG2.2.15 cells that support HBV replication. The 3p-siRNA significantly inhibited HBsAg and HBeAg secretion from HepG2.2.15 cells in a RIG-I-dependent manner, and the antiviral effect of 3p-siRNA was superior to that of siRNA. Furthermore, 3p-siRNA had more pronounced inhibition effects on the replication of HBV DNA and the transcription of mRNA than that of siRNA. Finally, 3p-siRNA displayed antiviral activity with long-term suppression of HBV replication. In conclusion, our findings suggest that 3p-siRNA could act as a powerful bifunctional antiviral molecule with potential for developing a promising therapeutic against chronic HBV infection.

Isolation and identification of an anti-hepatitis B virus compound from Hydrocotyle sibthorpioides Lam

ETHNOPHARMACOLOGICAL RELEVANCE

Hydrocotyle sibthorpioides (Apiaceae) have been used as a folk remedy for the treatment of fever, edema, detoxication, throat pain, psoriasis and hepatitis B virus infections in China. The aim of this study is to isolate and identify an anti-HBV compound from this herb.

MATERIALS AND METHODS

A compound (saponin) was isolated from the active ethanol extract using bioassay-guided screening. The structure of the saponin was elucidated by spectroscopic methods and compared with published data. The anti-HBV activity of the saponin was evaluated by detecting the levels of HBV antigens, extracellular HBV DNA, nuclear covalent closed circular DNA (cccDNA) and five HBV promoters in HepG2.2.15 cells. In addition, the levels of serum HBsAg/HBeAg, DHBV DNA, ALT/AST and hepatic pathological changes were analyzed in DHBV-infected ducks.

RESULTS

The chemical analysis indicated that the saponin isolated from Hydrocotyle sibthorpioides is asiaticoside. The pharmacodynamics experimental studies showed that asiaticoside effectively suppressed the levels of HBsAg/HBeAg, extracellular HBV DNA and intracellular cccDNA in a dose-dependent manner. Furthermore, experiments demonstrated that asiaticoside markedly reduced viral DNA transcription and replication by inhibiting the activities of core, s1, s2, and X gene promoters. In addition, asiaticoside markedly reduced DHBV replication without any obvious signs of toxicity. The levels of serum DHBV DNA, HBsAg/HBeAg were increased 3 days after drug withdrawal, but the levels rebounded slightly in the asiaticoside treatment groups compared with the 3TC treatment group. Moreover, analysis of the serum ALT/AST levels and the liver pathological changes indicated that asiaticoside could alleviate liver damage.

CONCLUSIONS

Our results show that asiaticoside could efficiently inhibit HBV replication both in vitro and in vivo, and asiaticoside may be a major bioactive ingredient in Hydrocotyle sibthorpioides.

Suppression of interferon-mediated antiviral immunity by hepatitis B virus: an overview of research progress

Interferon (IFN)-α is an indispensable drug for hepatitis B treatment in clinical settings. However, hepatitis B virus (HBV) can attenuate IFN-mediated antiviral responses to avoid being inhibited or cleared. Much progress has been made in exploring how the IFN-induced anti-HBV effect is inhibited. This review examines and summarizes new advances regarding the molecular mechanism underlying the HBV-induced suppression of type I IFN-mediated antiviral immunity.

Chemical modifications on siRNAs avoid Toll-like-receptor-mediated activation of the hepatic immune system in vivo and in vitro

OBJECTIVES

The therapeutic application of small interfering RNAs (siRNAs) is limited by the induction of severe off-target effects, especially in the liver. Therefore, we assessed the potential of differently modified siRNAs to induce the hepatic innate immune system in vitro and in vivo.

METHODS

Primary isolated liver cells were transfected with siRNAs against apolipoprotein B1 (APOB1), luciferase (LUC) or galactosidase (GAL). For in vivo use, siRNAs were formulated in lipid nanoparticles (LNPs) and administered intravenously to C57BL/6 mice. Liver tissue was collected 6-48 h after injection and knock-down efficiency or immune responses were determined by quantitative reverse-transcription-linked PCR.

RESULTS

Unmodified GAL siRNA transiently induced the expression of TNF-α, IL-6, IL-10, IFN-β and IFN-sensitive gene 15 in vivo, whereas a formulation of 2'-O-methylated-LUC siRNA had no such effects. Formulation of unmodified APOB1-specific siRNA suppressed APOB1 mRNA levels by ~80% in the liver 48h after application. The results were paralleled in vitro, where transfection of liver cells with unmodified siRNAs, but not with chemically modified siRNAs, led to cell-type-specific induction of immune genes. These immune responses were not observed in MYD88-deficient mice or in chloroquine-treated cells in vitro.

CONCLUSIONS

Our data indicate that siRNAs activate endosomal Toll-like receptors in different liver-derived cell types to various degrees, in vitro. LNP-formulated siRNA selectively leads to hepatic knock-down of target genes in vivo. Here, off-target immune responses are restricted to non-parenchymal liver cells. However, 2'-O-methyl modifications of siRNA largely avoid immune-stimulatory effects, which is a crucial prerequisite for the development of safe and efficient RNA-interference-based therapeutics.

Antiviral activity of methyl helicterate isolated from Helicteres angustifolia (Sterculiaceae) against hepatitis B virus

The anti-HBV effect of methyl helicterate (MH), a triterpenoid isolated from the Chinese herb Helicteres angustifolia, was explored both in vitro and in vivo. In the HBV-transfected cell line HepG2.2.15, the secretion of HBsAg/HBeAg, the levels of HBV DNA and cccDNA, and the amount of viral RNA were significantly decreased after treatment with MH for 144h. In addition, MH had no inhibitory effect on the mitochondrial DNA content. In DHBV-infected ducklings, MH significantly reduced the serum DHBV DNA, liver total viral DNA, and cccDNA levels. Furthermore, analysis of the liver pathological changes confirmed the hepatoprotective effect of MH. These results indicate that MH efficiently inhibits HBV replication both in vitro and in vivo and that MH may be a major bioactive ingredient in H. angustifolia.

Intracellular poly(I:C) initiated gastric adenocarcinoma cell apoptosis and subsequently ameliorated NK cell functions

Natural killer (NK) cells are granular lymphocytic cells that exert essential functions in viral infection defense and tumor immune surveillance. However, the functions of NK cells were impaired in cancer patients. Polycytidylic acid [poly(I:C)] has been used as an immune adjuvant to improve innate and adaptive immune responses. In this study, intracellular poly(I:C) could trigger gastric adenocarcinoma cells apoptosis quickly. Meanwhile, the sensitivity of poly(I:C)-treated gastric adenocarcinoma cells to NK cell cytolysis was increased, concomitant with the elevated expression of MICA/B and Fas. Furthermore, the cytolytic activity of NK cells against tumor cells was augmented significantly by the supernatant from poly(I:C)-transfected tumor cells compared with NK cells treated by the supernatant from untreated tumor cells, as well as the proliferation and migration abilities of NK cells. In this process, the activating receptors and cytolysis-associated molecules of NK cells were up-regulated. Further investigation showed that type I interferon (IFN) produced by poly(I:C)-transfected gastric adenocarcinoma cells played an important role in this process. Our findings demonstrated that intracellular poly(I:C) not only triggered gastric adenocarcinoma cell apoptosis, but also enhanced NK responses via inducing type I IFN production by gastric adenocarcinoma cells. These functions make poly(I:C) a promising therapeutic medicine for gastric adenocarcinoma.

Reversal of hepatitis B virus-induced systemic immune tolerance by intrinsic innate immune stimulation

Systemic immune tolerance induced by chronic hepatitis B virus (HBV) infection is a significant question, but the mechanism of which remains unclear. In this mini-review, we summarize the impaired innate and adaptive immune responses involved in immune tolerance in chronic HBV infection. Furthermore, we delineate a novel dual functional small RNA to inhibit HBV replication and stimulate innate immunity against HBV, which proposed a promising immunotherapeutic intervention to interrupt HBV-induced immunotolerance. A mouse model of HBV persistence was established and used to observe the immune tolerant to HBV vaccination, the cell-intrinsic immune tolerance of which might be reversed by chemically synthesized dual functional small RNA (3p-hepatitis B Virus X gene [HBx]-small interfering RNA) in vitro experiments and by biologically constructed dual functional vector (single-stranded RNA-HBx- short hairpin RNA) in vivo experiment using HBV-carrier mice.

Immunocompetent nontransgenic mouse models for studying hepatitis B virus immune responses

Although the chronicity of hepatitis B virus (HBV) infection is the result of impaired HBV-specific immune responses that cannot eliminate or clear the infected hepatocytes efficiently, many issues remained unsettled. It is thus crucial to have a suitable laboratory animal to study the immunopathogenesis of HBV infection and the mechanisms of HBV persistence. To meet the requirement of a mouse model resembling natural chronic HBV infection in human, there are several approaches in the development of mouse animal model by using hydrodynamic-based transfection of HBV DNA, delivery of adenovirus or adeno-associated viral vectors containing HBV DNA for studying HBV immune responses. These immunocompetent nontransgenic mouse animal models will provide new approaches to investigate the mechanisms of immune pathogenesis in HBV infection.

Therapeutic recovery of hepatitis B virus (HBV)-induced hepatocyte-intrinsic immune defect reverses systemic adaptive immune tolerance

Hepatitis B virus (HBV) persistence aggravates hepatic immunotolerance, leading to the failure of cell-intrinsic type I interferon and antiviral response, but whether and how HBV-induced hepatocyte-intrinsic tolerance influences systemic adaptive immunity has never been reported, which is becoming the major obstacle for chronic HBV therapy. In this study, an HBV-persistent mouse, established by hydrodynamic injection of an HBV-genome-containing plasmid, exhibited not only hepatocyte-intrinsic but also systemic immunotolerance to HBV rechallenge. HBV-specific CD8(+) T-cell and anti-HBs antibody generation were systemically impaired by HBV persistence in hepatocytes. Interestingly, HBV-induced hepatocyte-intrinsic immune tolerance was reversed when a dually functional vector containing both an immunostimulating single-stranded RNA (ssRNA) and an HBx-silencing short hairpin RNA (shRNA) was administered, and the systemic anti-HBV adaptive immune responses, including CD8(+) T-cell and anti-HBs antibody responses, were efficiently recovered. During this process, CD8(+) T cells and interferon-gamma (IFN-γ) secreted play a critical role in clearance of HBV. However, when IFN-α/β receptor was blocked or the Toll-like receptor (TLR)7 signaling pathway was inhibited, the activation of CD8(+) T cells and clearance of HBV was significantly impaired.

CONCLUSION

These results suggest that recovery of HBV-impaired hepatocyte-intrinsic innate immunity by the dually functional vector might overcome systemic adaptive immunotolerance in an IFN-α- and TLR7-dependent manner. The strategy holds promise for therapeutic intervention of chronic persistent virus infection and associated cancers.

Inhibition of hepatitis B virus (HBV) gene expression and replication by HBx gene silencing in a hydrodynamic injection mouse model with a new clone of HBV genotype B

BACKGROUND

It has been suggested that different hepatitis B virus (HBV) genotypes may have distinct virological characteristics that correlate with clinical outcomes during antiviral therapy and the natural course of infection. Hydrodynamic injection (HI) of HBV in the mouse model is a useful tool for study of HBV replication in vivo. However, only HBV genotype A has been used for studies with HI.

METHODS

We constructed 3 replication-competent clones containing 1.1, 1.2 and 1.3 fold overlength of a HBV genotype B genome and tested them both in vitro and in vivo. Moreover, A HBV genotype B clone based on the pAAV-MCS vector was constructed with the 1.3 fold HBV genome, resulting in the plasmid pAAV-HBV1.3B and tested by HI in C57BL/6 mice. Application of siRNA against HBx gene was tested in HBV genotype B HI mouse model.

RESULTS

The 1.3 fold HBV clone showed higher replication and gene expression than the 1.1 and 1.2 fold HBV clones. Compared with pAAV-HBV1.2 (genotype A), the mice HI with pAAV-HBV1.3B showed higher HBsAg and HBeAg expression as well as HBV DNA replication level but a higher clearance rate. Application of two plasmids pSB-HBxi285 and pSR-HBxi285 expressing a small/short interfering RNA (siRNA) to the HBx gene in HBV genotype B HI mouse model, leading to an inhibition of HBV gene expression and replication. However, HBV gene expression may resume in some mice despite an initial delay, suggesting that transient suppression of HBV replication by siRNA may be insufficient to prevent viral spread, particularly if the gene silencing is not highly effective.

CONCLUSIONS

Taken together, the HI mouse model with a HBV genotype B genome was successfully established and showed different characteristics in vivo compared with the genotype A genome. The effectiveness of gene silencing against HBx gene determines whether HBV replication may be sustainably inhibited by siRNA in vivo.

Hepatocystin/80K-H inhibits replication of hepatitis B virus through interaction with HBx protein in hepatoma cell

Hepatitis B virus (HBV) X protein (HBx) is a key player in HBV replication as well as HBV-induced hepatocellular carcinoma (HCC). However, the pathogenesis of HBV infection and the mechanisms of host-virus interactions are still elusive. In this study, a combination of affinity purification and mass spectrometry was applied to identify the host factors interacting with HBx in hepatoma cells. Thirteen proteins were identified as HBx binding partners. Among them, we first focused on determining the functional significance of the interaction between HBx and hepatocystin. A physical interaction between HBx and hepatocystin was confirmed by co-immunoprecipitation and Western blotting. Immunocytochemistry demonstrated that HBx and hepatocystin colocalized in the hepatoma cells. Domain mapping of both proteins revealed that the HBx C-terminus (amino acids 110-154) was responsible for binding to the mannose 6-phosphate receptor homology domain (amino acids, 419-525) of hepatocystin. Using translation and proteasome inhibitors, we found that hepatocystin overexpression accelerated HBx degradation via a ubiquitin-independent proteasome pathway. We demonstrated that this effect was mediated by an interaction between both proteins using a HBx deletion mutant. Hepatocystin overexpression significantly inhibited HBV DNA replication and expression of HBs antigen concomitant with HBx degradation. Using the hepatocystin mutant constructs that bind HBx, we also confirmed that hepatocystin inhibited HBx-dependent HBV replication. In conclusion, we demonstrated for the first time that hepatocystin functions as a chaperon-like molecule by accelerating HBx degradation, and thereby inhibits HBV replication. Our results suggest that inducing hepatocystin may provide a novel therapeutic approach to control HBV infection.

The liver works as a school to educate regulatory immune cells

Because of its unique blood supply, the liver maintains a special local immune tolerogenic microenvironment. Moreover, the liver can impart this immune tolerogenic effect on other organs, thus inducing systemic immune tolerance. The network of hepatic regulatory cells is an important mechanism underlying liver tolerance. Many types of liver-resident antigen-presenting cells (APCs) have immune regulatory function, and more importantly, they can also induce the differentiation of circulating immune cells into regulatory cells to further extend systemic tolerance. Thus, the liver can be seen as a type of 'school', where liver APCs function as 'teachers' and circulating immune cells function as 'students.'