Rongjuan Pei

Hepatitis B virus suppresses toll-like receptor–mediated innate immune responses in murine parenchymal and nonparenchymal liver cells†

We have previously shown that Toll‐like receptor (TLR)‐activated murine nonparenchymal liver cells [(NPC); Kupffer cells (KC), liver sinusoidal endothelial cells (LSEC)] can suppress hepatitis B virus (HBV) replication. Therefore, the aim of this study was to investigate whether HBV has the ability to counteract the TLR‐mediated control of its replication. Freshly purified murine hepatocytes and NPCs obtained from C57BL6 mice were stimulated by TLR 1‐9 ligands in the presence or absence of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), HBV virions, or supernatants from HBV‐producing HBV‐Met cells, and HBV replication was suppressed by anti‐ hepatitis B virus X protein (HBx) small interfering RNA (siRNA) in HBV‐Met cells. Supernatants were collected and tested for antiviral cytokines by viral protection assay. HBV gene expression and replication was analyzed by southern blot. RNA and proteins were analyzed by quantitative reverse transcription polymerase chain reaction (RT‐PCR) or western blot and enzyme‐linked immunosorbent assay, respectively. Pretreatment of hepatocytes and NPCs with HBV‐Met cells supernatants, HBsAg, HBeAg, or HBV virions almost completely abrogated TLR‐induced antiviral activity, which correlated with suppression of interferon beta (IFN‐β) production and subsequent interferon‐stimulated gene induction as well as suppressed activation of interferon regulatory factor 3 (IRF‐3), nuclear factor kappa B (NF‐κB), and extracellular signal‐regulated kinase (ERK) 1/2. In HBV‐infected HBV‐Met cells, TLR stimulation did not induce antiviral cytokines in contrast to primary hepatocytes. TLR‐stimulated expression of proinflammatory cytokines [tumor necrosis factor alpha (TNF‐α), interleukin‐6 (IL‐6)], and activation of IRF‐3 was suppressed after up‐regulation of HBV replication in HBV‐Met cells. Accordingly, suppression of HBV replication by siRNA led to activation or expression of proinflammatory transcription factors and cytokines. Conclusion: Our data indicate that HBV can suppress the TLR‐induced antiviral activity of liver cells. This has major implications for the interaction between HBV and the immune system. (HEPATOLOGY 2009.)

Modulation of Hepatitis B Virus Replication and Hepatocyte Differentiation by MicroRNA-1

MicroRNAs (miRNAs) are highly conserved small noncoding RNAs participating in regulation of various cellular processes. Viruses have been shown to utilize cellular miRNAs to increase their replication in host cells. Until now, the role of miRNAs in hepatitis B virus (HBV) replication has remained largely unknown. In this study, a number of miRNA mimics were transfected into hepatoma cell lines with HBV replication. It was noted that microRNA‐1 (miR‐1) transfection resulted in a marked increase of HBV replication, accompanied with up‐regulated HBV transcription, antigen expression, and progeny secretion. However, bioinformatics and luciferase reporter analysis suggested that miR‐1 may not target the HBV genome directly but regulate the expression of host genes to enhance HBV replication. Further studies showed that miR‐1 was able to enhance the HBV core promoter transcription activity by augmenting farnesoid X receptor α expression. In addition, miR‐1 arrested the cell cycle at the G1 phase and inhibited cell proliferation by targeting histone deacetylase 4 and E2F transcription factor 5. Analysis of the cellular gene expression profile indicated that miR‐1 transfected hepatoma cells developed a differentiated phenotype of hepatocytes. Conclusion: MiR‐1 regulates the expression of several host genes to enhance HBV replication and reverse cancer cell phenotype, which is apparently beneficial for HBV replication. Our findings provide a novel perspective on the role of miRNAs in host‐virus interactions in HBV infection. (HEPATOLOGY 2011;)

Toll-like receptor activated human and murine hepatic stellate cells are potent regulators of hepatitis C virus replication.

BACKGROUND/AIMS While hepatic stellate cells (HSC) are known to be key mediators of liver fibrosis, only little is known about their functional role in the innate immune system of the liver. METHODS To address this question, murine HSC were isolated from livers of C57BL/6J mice and human HSC were isolated from liver samples obtained from resections and liver explants. HSC were stimulated with Toll-like receptor (TLR) 1-9 ligands for 20 h. Supernatants were harvested and used in virus protection assays (encephalomyocarditis virus, EMCV) as well as in human and murine hepatitis C virus (HCV) replicon systems. Expression of interferon (IFN), retinoic acid-inducible gene-I (RIG-I), and interferon-stimulated genes (ISGs) was assessed by quantitative reverse transcription polymerase chain reaction. RESULTS While all TLRs were detectable in HSC, in murine HSC only TLR 3 and -4 agonists could induce cytokines that had an antiviral effect upon EMCV and HCV replication. IFN-beta was the main cytokine mediating the antiviral activity of TLR 3-stimulated HSC whereas other cytokines of undefined nature were involved in TLR 4-mediated antiviral effects. In human HSC, only TLR 3 stimulation led to production of antiviral cytokines. The antiviral effect was related to the up-regulation of ISGs and RIG-I in target cells. CONCLUSIONS These data demonstrate that murine and human HSC have as yet unrecognized antiviral properties when activated through the TLR-system and TLR 3/HCV in particular. This sheds new light on their role in the innate immune system of the liver and their participation in the control of HCV replication.

Amino Acid Substitutions at Positions 122 and 145 of Hepatitis B Virus Surface Antigen (HBsAg) Determine the Antigenicity and Immunogenicity of HBsAg and Influence In Vivo HBsAg Clearance

ABSTRACT A variety of amino acid substitutions, such as K122I and G145R, have been identified around or within the a determinant of hepatitis B surface antigen (HBsAg), impair HBsAg secretion and antibody binding, and may be responsible for immune escape in patients. In this study, we examined how different substitutions at amino acid positions 122 and 145 of HBsAg influence HBsAg expression, secretion, and recognition by anti-HBs antibodies. The results showed that the hydrophobicity, the presence of the phenyl group, and the charges in the side chain of the amino acid residues at position 145 reduced HBsAg secretion and impaired reactivity with anti-HBs antibodies. Only the substitution K122I at position 122 affected HBsAg secretion and recognition by anti-HBs antibodies. Genetic immunization in mice demonstrated that the priming of anti-HBs antibody response was strongly impaired by the substitutions K122I, G145R, and others, like G145I, G145W, and G145E. Mice preimmunized with wild-type HBsAg (wtHBsAg) or variant HBsAg (vtHBsAg) were challenged by hydrodynamic injection (HI) with a replication-competent hepatitis B virus (HBV) clone. HBsAg persisted in peripheral blood for at least 3 days after HI in mice preimmunized with vtHBsAg but was undetectable in mice preimmunized with wtHBsAg, indicating that vtHBsAgs fail to induce proper immune responses for efficient HBsAg clearance. In conclusion, the biochemical properties of amino acid residues at positions 122 and 145 of HBsAg have a major effect on antigenicity and immunogenicity. In addition, the presence of proper anti-HBs antibodies is indispensable for the neutralization and clearance of HBsAg during HBV infection.

Persistent hepatitis C virus infections and hepatopathological manifestations in immune-competent humanized mice

The majority of hepatitis C virus (HCV) infection develops chronic infection, which causes steatosis, cirrhosis and hepatocellular carcinoma. However, understanding HCV chronicity and pathogenesis is hampered by its narrow host range, mostly restricted to human and chimpanzee. Recent endeavour to infect a variety of humanized mice has not been able to achieve persistent HCV infection unless the essential innate immune responsive genes are knocked out. Nevertheless, such immune-compromised humanized mice still lacked HCV infection-induced hepatopathogenesis. Here we report that transgenic mice in ICR background harboring both human CD81 and occludin genes (C/OTg) are permissive to HCV infection at a chronicity rate comparable to humans. In this mouse model, HCV accomplishes its replication cycle, leading to sustained viremia and infectivity for more than 12 months post infection with expected fibrotic and cirrhotic progression. Host factors favorable for HCV replication, and inadequate innate immune-response may contribute to the persistence. Lastly, NS3/4 protease inhibitor telaprevir can effectively inhibit de novo RNA synthesis and acute HCV infection of C/OTg mice. Thus, chronic HCV infection with complete replication cycle and hepatopathologic manifestations is recapitulated, for the first time, in immune-competent mice. This model will open a new venue to study the mechanisms of chronic hepatitis C and develop better treatments.

Coexistence of Hepatitis B Virus Quasispecies Enhances Viral Replication and the Ability To Induce Host Antibody and Cellular Immune Responses

ABSTRACT Hepatitis B virus (HBV) quasispecies contain a large number of variants that serve as a reservoir for viral selection under antiviral treatment and the immune response, leading to the acute exacerbation and subsequent development of liver failure. However, there is no clear experimental evidence for a significant role of HBV quasispecies in viral pathogenesis. In the present study, HBV sequences were amplified from a patient with severe liver disease and used for construction of HBV replication-competent plasmids. Western blotting, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence staining were performed to analyze the expression, secretion, and subcellular localization of viral proteins in vitro. Viral replication intermediates were detected by Southern blotting. HBV gene expression and replication and the induction of specific immune responses in an HBV hydrodynamic injection (HI) mouse model were investigated. The results demonstrated that two naturally occurring HBV variants, SH and SH-DPS, were identified. The variant SH-DPS expressed only a nonexportable hepatitis B virus surface antigen (HBsAg) with abnormal intracellular accumulation. The coexistence of the HBV variants at a ratio of 1 to 4 (SH to SH-DPS) increased HBV replication. Significantly stronger intrahepatic cytotoxic T lymphocyte (CTL) responses and antibody responses specific to HBsAg were induced in mice by the HBV variants when coapplied by HI. These findings uncovered an unexpected aspect of HBV quasispecies: the coexistence of different variants can significantly modulate specific host immune responses, representing a novel mechanism for the immunopathogenesis of HBV infection. IMPORTANCE Hepatitis B virus (HBV) is an important human pathogen. HBV quasispecies with genetically heterogenous variants are thought to play a role in the progression of HBV-associated liver diseases. So far, direct evidence is available in only a few cases to confirm the proposed role of HBV variants in the pathogenesis. We report here that the coexistence of two naturally occurring HBV variants at a ratio of 1 to 4 increased HBV replication and induced significantly stronger intrahepatic cytotoxic T lymphocyte responses and antibody responses specific to HBV surface antigen (HBsAg) in mice. Our discovery uncovered an unexpected aspect of HBV quasispecies: the coexistence of different variants can significantly modulate specific host immune responses and may enhance immune-mediated liver damage under some circumstances, representing a novel mechanism for the immunopathogenesis of HBV infection.

Cytosolic Phospholipase A2 Gamma Is Involved in Hepatitis C Virus Replication and Assembly

ABSTRACT Similar to other positive-sense, single-stranded RNA viruses, hepatitis C virus (HCV) replicates its genome in a remodeled intracellular membranous structure known as the membranous web (MW). To date, the process of MW formation remains unclear. It is generally acknowledged that HCV nonstructural protein 4B (NS4B) can induce MW formation through interaction with the cytosolic endoplasmic reticulum (ER) membrane. Many host proteins, such as phosphatidylinositol 4-kinase IIIα (PI4KIIIα), have been identified as critical factors required for this process. We now report a new factor, the cytosolic phospholipase A2 gamma (PLA2G4C), which contributes to MW formation, HCV replication, and assembly. The PLA2G4C gene was identified as a host gene with upregulated expression upon HCV infection. Knockdown of PLA2G4C in HCV-infected cells or HCV replicon-containing cells by small interfering RNA (siRNA) significantly suppressed HCV replication and assembly. In addition, the chemical inhibitor methyl arachidonyl fluorophosphonate (MAFP), which specifically inhibits PLA2, reduced HCV replication and assembly. Electron microscopy demonstrated that MW structure formation was defective after PLA2G4C knockdown in HCV replicon-containing cells. Further analysis by immunostaining and immunoprecipitation assays indicated that PLA2G4C colocalized with the HCV proteins NS4B and NS5A in cells infected with JFH-1 and interacted with NS4B. In addition, PLA2G4C was able to transport the HCV nonstructural proteins from replication sites to lipid droplets, the site for HCV assembly. These data suggest that PLA2G4C plays an important role in the HCV life cycle and might represent a potential target for anti-HCV therapy.

Hepatitis C virus infection induces the expression of amphiregulin, a factor related to the activation of cellular survival pathways and required for efficient viral assembly

Amphiregulin (AREG) is a ligand of the epidermal growth factor (EGF) receptor and may play a role in the development of cirrhosis and hepatocellular carcinoma in patients infected with hepatitis C virus (HCV). AREG showed an enhanced expression in HCV-infected human hepatoma cells according to gene array analysis. Therefore, we addressed the question about the role of AREG in HCV infection. AREG expression level was elevated in hepatoma cells containing a subgenomic HCV replicon or infected by HCV. Using a reporter assay, AREG promoter activity was found to be upregulated upon HCV infection. The enhanced AREG expression in hepatoma cells was partly caused by dsRNAs, HCV NS3 protein and autocrine stimulation. AREG was able to activate cellular signalling pathways including ERK, Akt and p38, promote cell proliferation, and protect cells from HCV-induced cell death. Further, knockdown of AREG expression increased the efficiency of HCV entry, as proven by HCV pseudoparticles reporter assay. However, the formation and release of infectious HCV particles were reduced by AREG silencing with a concomitant accumulation of intracellular HCV RNA pool, indicating that the assembly and release of HCV progeny may require AREG expression. Blocking the MAPK-ERK pathway by U0126 in Huh7.5.1 cells had a similar effect on HCV replication. In conclusion, HCV infection leads to an increase in AREG expression in hepatocytes. AREG expression is essential for efficient HCV assembly and virion release. Due to the activation of the cellular survival pathways, AREG may counteract HCV-induced apoptosis of infected hepatocytes and facilitate the development of liver cirrhosis and hepatocellular carcinoma.

Regulation of Hepatitis C Virus Replication and Gene Expression by the MAPK-ERK Pathway

The mitogen activated protein kinases-extracellular signal regulated kinases (MAPK-ERK) pathway is involved in regulation of multiple cellular processes including the cell cycle. In the present study using a Huh7 cell line Con1 with an HCV replicon, we have shown that the MAPK-ERK pathway plays a significant role in the modulation of HCV replication and protein expression and might influence IFN-α signalling. Epithelial growth factor (EGF) was able to stimulate ERK activation and decreased HCV RNA load while a MAPK-ERK pathway inhibitor U0126 led to an elevated HCV RNA load and higher NS5A protein amounts in Con1 cells. It could be further demonstrated that the inhibition of the MAPK-ERK pathway facilitated the translation directed by the HCV internal ribosome entry site. Consistently, a U0126 treatment enhanced activity of the HCV reporter replicon in transient transfection assays. Thus, the MAPK-ERK pathway plays an important role in the regulation of HCV gene expression and replication. In addition, cyclin-dependent kinases (CDKs) downstream of ERK may also be involved in the modulation of HCV replication since roscovitine, an inhibitor of CDKs had a similar effect to that of U0126. Modulation of the cell cycle progression by cell cycle inhibitor or RNAi resulted consistently in changes of HCV RNA levels. Further, the replication of HCV replicon in Con1 cells was inhibited by IFN-α. The inhibitory effect of IFN-α could be partly reversed by pre-incubation of Con-1 cells with inhibitors of the MAPK-ERK pathway and CDKs. It could be shown that the MAPK-ERK inhibitors are able to partially modulate the expression of interferon-stimulated genes.

Spontaneous reactivation of hepatitis B virus replication in an HIV coinfected patient with isolated anti-Hepatitis B core antibodies

Co-infections with HBV (hepatitis B virus) occur in HIV (human immunodeficiency virus) patients frequently. It has been reported that an effective treatment of HIV can also lead to a suppression of HBV and to anti-HBs seroconversion in HBV-infected patients. Here, we report a spontaneous reactivation of HBV replication in an HIV-infected patient with anti-HBc as the only marker of chronic HBV infection. The patient was known to be coinfected with HIV and HBV for years and the HBV DNA was measured repeatedly at low levels. A significant increase of HBV DNA up to 1.7x107 IU/ml was found accompanied with clinical symptoms of hepatitis. Multiple mutations occurred in the S gene during the flare-up of HBV as shown by sequencing, including I103T, K122R, M133I, F134V, D144E, V164E and L175S. Anti-HIV/HBV treatment led to a resolution of symptoms and to a decrease in the HIV RNA and HBV DNA viral load. It is possible that the accumulated mutations during HBV replication were selected and responsible for the reactivation.