Interaction of interferon-alpha with interleukin-1 beta or tumor necrosis factor-alpha on hepatitis B virus enhancer activity

Insulin Resistance Predicts Virological Response to Interferon-α in Chronic Hepatitis B Patients

GOALS

To elucidate impact of insulin resistance (IR) on the response to interferon-α (IFN-α) therapy in chronic hepatitis B (CHB) patients.

BACKGROUND

Metabolic factors influencing the virological response of CHB patients on IFN-α treatment are still unexplored.

STUDY

Eighty CHB patients were treated with IFN-α for 48 weeks. The IR was evaluated by homeostasis model assessment of IR (HOMA-IR) before treatment. Viral load and biochemical parameters were measured at 12, 24, and 48 weeks after starting treatment, and then 24 weeks after the end of treatment. IFN-γ and tumor necrosis factor-α were tested at baseline and 12 weeks of treatment.

RESULTS

Pretreatment HOMA-IR proved to be the only independent predictor of primary nonresponse, as well as the pretreatment HOMA-IR, viral load and primary nonresponse were independently associated with virological response at 24, 48 weeks of treatment and at the follow-up endpoint. The significant higher virological relapse rate in patients with IR was observed in patients with virological response at 48 weeks of treatment. The mean HOMA-IR was significantly lower in virological responders than in virological nonresponders. The secretion of IFN-γ and tumor necrosis factor-α was not induced in patients with IR at 12 weeks after IFN-α treatment.

CONCLUSIONS

Our data suggest that IR is strongly associated with virological response, thus reflecting the important role played by metabolic factors in the viral kinetics during IFN-α treatment. These findings suggested clinical application of pretreatment HOMA-IR could enable treatment outcome to be predicted and treatment regimens to be determined.

Antiviral activity of various interferons and pro-inflammatory cytokines in non-transformed cultured hepatocytes infected with hepatitis B virus

In HBV-infected patients, therapies with nucleoside analogues or IFNα remain ineffective in eradicating the infection. Our aim was to re-analyze the anti-HBV activity of a large panel of IFNs and cytokines in vitro using non-transformed cultured hepatocytes infected with HBV, to identify new immune-therapeutic options. HepaRG cells and primary human hepatocytes were infected with HBV and, when infection was established, treated with various concentrations of different IFNs or inflammatory cytokines. Viral parameters were evaluated by quantifying HBV nucleic acids by qPCR and Southern Blot, and secreted HBV antigens were evaluated using ELISA. The cytokines tested were type-I IFNs, IFNγ, type-III IFNs, TNFα, IL-6, IL-1β, IL-18 as well as nucleos(t)ide analogues tenofovir and ribavirin. Cytokines and drugs, with the exception of IL-18 and ribavirin, exhibited a suppressive effect on HBV replication at least as strong as, but often stronger than, IFNα. The cytokine presenting the highest effect on HBV DNA was IL-1β, which exerted its inhibition within picomolar range. Importantly, we noticed differential effects on other parameters (HBV RNA, HBeAg, HBsAg) between both IFNs and inflammatory cytokines, thus suggesting different mechanisms of action. The combination of IL-1β and already used therapies, i.e. IFNα or tenofovir, demonstrated a stronger or similar anti-HBV activity. IL-1β was found to have a very potent antiviral effect against HBV in vitro. HBV was previously shown to promptly inhibit IL-1β production in Kupffer cells. Strategies aiming at unlocking this inhibition and restoring local production of IL-1β may help to further inhibit HBV replication in vivo.

In vitro resistance to interferon-alpha of hepatitis B virus with basic core promoter double mutation

The hepatitis B virus (HBV) genome basic core promoter (BCP) modulates HBeAg secretion at the transcriptional level. In addition to pre-core mutations, variations in the BCP are related to hepatitis B e antigen (HBeAg)-negative chronic hepatitis B. HBeAg-negative chronic hepatitis B patients show a lower sustained response to interferon (IFN). The aim of this study was to determine if there is a relationship between HBV BCP mutation and sensitivity of HBV to IFN-alpha in vitro. BCP mutations were introduced by site-directed mutagenesis and the entire genomes of wild-type and mutant HBV were transiently transferred into Huh7 cells by calcium phosphate transfection. With or without IFN-alpha, viral products in the culture medium and viral replication intermediates in the cytoplasm were detected 3 days after transfection. The amount of hepatitis B surface antigen (HBsAg) secreted by wild-type HBV and the BCP mutant was similar, while HBeAg secreted by the mutant was decreased by 35.4%. HBV particles and replication intermediates of the BCP mutant were increased. After IFN-alpha was added, HBeAg, HBV DNA and HBV replication intermediates decreased for both the wild-type HBV (by 25.7%, 31.8%, 29.8%, respectively) and the BCP mutant (by 8.4%, 27.4%, 10.1%, respectively). These data indicate that HBV harboring the BCP double mutation has stronger replication competence and lower sensitivity to IFN-alpha than wild-type.

In vitro resistance to interferon of hepatitis B virus with precore mutation

AIM: Chronic hepatitis B virus (HBV) infection is predominantly treated with interferon alpha (IFN-α), which results in an efficient reduction of the viral load only in 20-40% of treated patients. Mutations at HBV precore prevail in different clinical status of HBV infection. The roles of precore mutation in the progression of chronic hepatitis and interferon sensitivity are still unknown. The aim of this study was to explore if there was any relationship between HBV precore mutation and sensitivity to interferon in vitro.

METHODS: HBV replication-competent recombinant constructs with different patterns of precore mutations were developed. Then the recombinants were transiently transfected into hepatoma cell line (Huh7) by calcium phosphate transfection method. With or without IFN, viral products in culture medium were collected and quantified 3 d after transfection.

RESULTS: We obtained 4 recombinant constructs by orientation-cloning 1.2-fold-overlength HBV genome into pUC18 vector via the EcoRI and Hind III and PCR mediated site-directed mutagenesis method. All the recombinants contained mutations within precore region. Huh7 cells transfected with recombinants secreted HBsAg and HBV particles into the cell culture medium, indicating that all the recombinants were replication-competent. By comparing the amount of HBV DNA in the medium, we found that HBV DNA in medium reflecting HBV replication efficiency was different in different recombinants. Recombinants containing precore mutation had fewer HBV DNAs in culture medium than wild type. This result showed that recombinants containing precore mutation had lower replication efficiency than wild type. HBV DNA was decreased in pUC18-HBV1.2-WT recombinants after IFN was added while others with precore mutations were not, indicating that HBV harboring precore mutation was less sensitive to IFN in cell culture system.

CONCLUSION: These data indicate that HBV harboring precore mutation may be resistant to IFN in vitro.

AM3 inhibits HBV replication through activation of peripheral blood mononuclear cells

In this report, we have analyzed the effect of AM3, a glycoconjugate of natural origin with immunomodulatory properties, which is available under the commercial name of Inmunoferon, on hepatitis B virus (HBV) replication in HBV-transfected cells. We found that AM3 inhibited HBV RNA expression as well as DNA synthesis and viral antigen expression by an indirect mechanism. We found that AM3 lacked intrinsic antiviral properties, and that the antiviral effect of the glycoconjugate was due to stimulation of secretion of molecules with antiviral properties by peripheral blood mononuclear cells. Our data indicate that the employment of AM3 as an adjuvant administered simultaneously with conventional antiviral drugs may potentiate the endogenous response against viral infection.

Involvement of IL-1beta and IL-10 in IFN-alpha-mediated antiviral gene induction in human hepatoma cells

Crosstalk between interferons (IFNs) and several cytokines is likely to play an important role in viral clearance in chronic hepatitides B and C. We investigated the influence of this phenomenon on IFN-inducible antiviral gene expression in HuH-7 human hepatoma cells. HuH-7 cells were treated with IFN-alpha in the absence or presence of interleukin-1beta (IL-1beta) or IL-10 and the expression of antiviral genes such as 2(')5(')-oligoadenylate synthetase (2(')5(')-OAS) and double-stranded RNA-dependent protein kinase (PKR), as well as activation of signal transducer and activator of transcription 1 (STAT1), a key step for relaying the IFN-alpha signals, was analyzed by Northern blotting, Western blotting, and the reporter gene transfection assay. IL-1beta potentiated IFN-alpha-induced 2(')5(')-OAS and PKR gene expression, similar to expression of the transfected reporter genes containing the IFN-stimulated regulatory elements, while IL-10 suppressed IFN-alpha-stimulated gene expression. With regard to IFN-alpha signaling, IL-1beta enhanced both tyrosine and serine phosphorylation of STAT1 through p38 mitogen-activated protein kinase activation. In contrast, IL-10 inhibited IFN-alpha-mediated tyrosine phosphorylation of STAT1 by induction of a Janus kinase inhibitor, JAB. IL-1beta and IL-10 interact with IFN-alpha to up- and down-regulate antiviral gene expression, respectively, by modulating STAT1 activation induced by IFN-alpha.

Different activities of type I interferons on hepatitis B virus core promoter regulated transcription

The type I interferons (IFNs) are a group of closely related cytokines which have different signal transduction pathways and different biological activities. Using transient transfection of human hepatoma cells with reporter plasmids containing the firefly/renilla luciferase genes under the control of the HBV-Enhancer (Enh) I, Enh II and core promoter we have investigated the biological activities of 10 recombinant (r) type I IFNs on transcription. Low concentrations of IFN (0.025 ng/ml) had a significant and specific inhibitory effect but the potencies of the different recombinant type I IFNs differed markedly with IFNalpha8 and IFNbeta being six-fold more potent than the least effective subtype (IFNalpha1). However, the addition of IFNalpha5-the subtype produced predominantly in the human liver-did not cause any synergistic effects.The non-natural consensus IFN displayed a more pronounced inhibition of HBV-regulated transcription than IFNalpha8 or IFNalpha2 but not IFNbeta. The INF-induced inhibitory effect was not dependent on the presence of the HBV-Enh1 and in particular of an interferon stimulated response element (ISRE)-like sequence. The characterization of different effects among type I interferons on HBV-regulatory elements may implicate an IFN-subtype-specific role for the pathogenesis and treatment of HBV-infection.

Lack of a role of the interferon-stimulated response element-like region in interferon alpha -induced suppression of Hepatitis B virus in vitro

The antiviral effect of interferon-alpha (IFNalpha) on hepatitis B virus (HBV) is well documented in vitro and in vivo, but the mechanisms involved are elusive. Recently, an interferon-stimulated response like element (ISRE) competent for binding of interferon-stimulated gene factor-3gamma (p48) has been identified in the HBV enhancer I region. Mutation of this element was shown to abrogate IFNalpha-mediated reduction of HBV X-gene promoter-driven reporter gene expression. This suggested a role of the ISRE and of p48 in IFNalpha-induced antiviral activity against productive HBV infection. Here, we analyzed the antiviral effect of both IFNalpha and enhanced p48 expression on complete HBV genomes containing the wild-type or mutated ISRE. In human hepatoma cells transfected with both genomes, viral RNA and replicative intermediates were reduced by IFNalpha treatment to a similar degree. Enhanced p48 expression increased IFNalpha-induced suppression of HBV RNA significantly from 75 +/- 22.5% to 46 +/- 9.8%, but this was independent of the integrity of the ISRE-like region. These data imply that p48 neither mediates the antiviral activity of IFNalpha against HBV nor down-regulates enhancer I activity by binding directly to the HBV ISRE-like region, but rather argue for an indirect role of p48.

Effect of interferon alpha on hepatitis B virus replication and gene expression in transiently transfected human hepatoma cells

BACKGROUND/AIMS

Chronic hepatitis B virus (HBV) infection is predominantly treated with interferon alpha (IFNalpha), which results in efficient reduction of the viral load only in 10-20% of treated patients. The mechanisms induced by IFNalpha resulting in reduction of viremia in responding patients are unknown. The aim of this study was to characterize HBV-specific IFNalpha-induced intracellular inhibitory mechanisms and IFNalpha-sensitive HBV targets.

METHODS

To determine the antiviral activity, cells transiently transfected with HBV DNA were treated with IFNalpha and thereafter, viral products were quantified at different time points.

RESULTS

Time-dependent reduction of RNA, replicative DNA-intermediates, core protein and secreted HBsAg/HBeAg levels was observed in IFNalpha-treated cells. Viral RNA levels were reduced most effectively early post-treatment whereas those of core protein and replicative intermediates decreased later. By expression of subgenomic HBV sequences, an RNA target region mediating IFNalpha-induced RNA degradation was mapped.

CONCLUSIONS

These data indicate that HuH7 cells transiently transfected with HBV-DNA represent a system well suited for detailed analysis of IFNa-induced antiviral mechanisms and HBV targets. At least two IFNalpha-induced HBV-specific antiviral activities are active in this system: one reduces the levels of core protein and replicative intermediates, the other leads to posttranscriptional degradation of HBV-RNA. Based on the established in vitro system a detailed characterization of the IFNalpha-sensitive RNA-region and of factors mediating this intracellular antiviral effect is feasible. This may lead to the development of novel strategies for therapy of chronic hepatitis.

p48 (ISGF-3gamma) is involved in interferon-alpha-induced suppression of hepatitis B virus enhancer-1 activity

Interferon-alpha (IFN-alpha) suppresses hepatitis B virus (HBV) gene expression by reducing its enhancer-1 activity. IFN-alpha induces transcription factors, interferon-stimulated gene factor 3 (ISGF3), and interferon regulatory factor-1 (IRF-1), which activate interferon-inducible gene expression through binding to the interferon-stimulated regulatory element (ISRE) "AGTTTCNNTTTCNC" in the gene promoters. We found the ISRE-like sequence "AGGCTTTCACTTTCTC" in the HBV enhancer-1 region and elucidated the role of this sequence. Gel mobility shift assay showed binding of in vitro translated IRF-1 and in vitro translated p48 (ISGF3-gamma), which is a component of ISGF3 to this sequence. However, nuclear extracts binding to this sequence from human hepatoma cells (HuH-7) treated with IFN-alpha contained only the protein consisted of p48. In transfection experiments, IFN-alpha suppressed the HBV enhancer-1 activity, and overexpression of p48 enhanced this inhibitory effect. Both mutation and deletion of the ISRE-like sequence in the HBV enhancer-1 region reduced the suppressive effect of IFN-alpha. Our results suggest that the ISRE-like sequence in the HBV enhancer-1 can interact with the protein containing p48 and mediate the IFN-alpha-induced suppression of the enhancer activity.

The hepatitis B virus X protein up-regulates tumor necrosis factor alpha gene expression in hepatocytes

Human hepatocytes infected by hepatitis B virus (HBV) produce the proinflammatory cytokine, tumor necrosis factor (TNF-). In this study, we explored the mechanism of induction of TNF- synthesis by HBV. We found that the stable HBV-transfected hepatoma cell line, 2. 2.15, expressed high-molecular-weight (HMW) TNF- mRNAs, which were absent in the parent HepG2 cells. Treatment of 2.2.15 cells with interferon alfa (IFN-) and/or interleukin-1beta (IL-1beta) reduced both viral gene transcription and TNF- mRNA expression. Transient or stable transfection of hepatocyte-derived cell lines with HBV X protein (HBx) expression vectors induced the production of biologically active TNF-. In these cells, the HBx-induced TNF- was detected both as cell-associated and soluble forms. Luciferase gene-expression assays showed that the TNF- gene promoter contained target sequences for HBx trans-activation within the proximal region of the promoter. These results indicate that the hepatocyte TNF- synthesis induced by HBV is transcriptionally up-regulated by HBx. Thus, HBx may have a role in the induction of the intrahepatic inflammatory processes that take place during acute and chronic hepatitis B.

Evidence for a deficiency of interferon response in mononuclear cells from hepatitis C viremic patients

BACKGROUND/AIMS

The pathophysiology of chronic hepatitis C and the mechanisms of resistance to interferon alpha are poorly understood. The aim of this work was to assess the influence of HCV infection and the viral genotype on lymphocyte production of 2',5' oligo-adenylate synthetase activity and monocyte production of TNF alpha and IL1 beta.

METHODS

Mononuclear cells from 50 consecutive patients were studied after 6 months of interferon treatment. Patients with persistent viremia (PCR-positive, elevated ALT, n = 39) were compared with the PCR-negative patients with normal ALT activity (n = 11) of similar age and sex ratio.

RESULTS

Cells from the viremic patients showed lower basal and stimulated 2',5' oligo-adenylate synthetase activity, and a lower in vitro response capacity to human recombinant interferon. In contrast, no difference was observed in basal and stimulated TNF alpha or IL1 beta production between the two groups. In the PCR-positive patients the viral genotype had no significant influence on the response of mononuclear cells to interferon or endotoxin.

CONCLUSIONS

These results show that the presence of HCV in blood is associated with an elective defect in interferon system activation, independently of the viral genotype.

Posttranscriptional clearance of hepatitis B virus RNA by cytotoxic T lymphocyte-activated hepatocytes

Using transgenic mice that replicate the hepatitis B virus (HBV) genome, we recently demonstrated that class I-restricted, hepatitis B surface antigen-specific cytotoxic T lymphocytes (CTLs) can noncytolytically eliminate HBV pregenomic and envelope RNA transcripts from the hepatocyte. We now demonstrate that the steady-state content of these viral transcripts is profoundly reduced in the nucleus and cytoplasm of CTL-activated hepatocytes, but their transcription rates are only slightly reduced. Additionally, we demonstrate that transcripts covering the HBV X coding region are resistant to downregulation by the CTL. These results imply the existence of CTL-inducible hepatocellular factors that interact with a discrete element(s) between nucleotides 3157 and 1239 within the viral pregenomic and envelope transcripts and mediate their degradation, thus converting the hepatocyte from a passive victim to an active participant in the host response to HBV infection.

Tumor necrosis factor-alpha and interferon-gamma inhibit synergistically viral replication in hepatitis B virus-replicating cells

The effects of tumor necrosis factor-alpha and/or interferon-gamma on the replication of hepatitis B virus were examined using HB611 cells. These cells were derived from human hepatoblastoma cells, Huh6, by integrating hepatitis B virus DNA, and produce hepatitis B virus continuously. Each of the cytokines inhibited hepatitis B virus replication in the cells assessed as the amount of episomal hepatitis B virus DNA, without a decrease in cell viability. When the two cytokines were administered together, the inhibitory effect became greater. Incubation of the cells with 1,000 U/ml tumor necrosis factor-alpha decreased HBV DNA replicative intermediates by 55%, and that with 1,000 U/ml interferon-gamma decreased these by 51%. Furthermore, incubation with 1,000 U/ml tumor necrosis factor-alpha and 1,000 U/ml interferon-gamma in combination decreased HBV DNA replicative intermediates by 71%. In contrast, the amount of hepatitis B virus RNA and secretion of hepatitis B e antigen were not apparently reduced by the cytokines, and 2',5'-oligoadenylate synthetase activity was not detected in the supernatant. These results suggest that tumor necrosis factor-alpha and interferon-gamma inhibit hepatitis B virus replication by blocking some step in reverse transcription and that the 2',5'-oligoadenylate synthetase is not involved in the mechanism underlying the inhibition by these two cytokines.

Treatment of small hepatocellular carcinomas

There is growing interest in screening to detect symptomless hepatocellular carcinoma (HCC), which should be easier to treat than symptomatic tumours. Combined alpha-fetoprotein and ultrasound monitoring can detect HCCs of 1 cm, and Lipiodol retention can be detected in tumours smaller than 1 cm. A number of treatment options are available. Surgical resection may be curative in selected patients with a single small tumour, but the cirrhotic patient is left with a diseased liver and the risk of tumour recurrence or death from underlying liver dysfunction. Orthotopic liver transplantation is a rational treatment for patients with decompensating cirrhosis and a small HCC, but it is expensive and necessitates immunosuppression. A variety of targeted or local therapies, either individually or in combination, can be used to treat HCC. These include percutaneous alcohol injection into an HCC, which may be an alternative to surgical resection. Tumour necrosis can be seen after targeted Lipiodol chemotherapy or radiotherapy. Transcatheter arterial embolisation selectively embolises the feeding artery, and can be combined with Lipiodol chemotherapy. Small tumours are thus amenable to treatment, even in patients who cannot have surgery. Screening and treatment for symptomless HCC seems justified, unless controlled trials teach us differently.