Alpha- and gamma-interferon versus alpha-interferon alone in chronic hepatitis B. A randomized controlled study

Early application of IFNγ mediated the persistence of HBV in an HBV mouse model

The antiviral activity of interferon gamma (IFNγ) against hepatitis B virus (HBV) was demonstrated both in vivo and in vitro in a previous study. IFNγ can suppress HBV replication by accelerating the decay of replication-competent nucleocapsids of HBV. However, in this study, we found that the direct application of the mouse IFNγ (mIFNγ) expression plasmid to the liver of an HBV hydrodynamic injection (HI) mouse model led to the persistence of HBV, as indicated by sustained HBsAg and HBeAg levels in the serum as well as an increased percentage of the HBsAg positive mice, whereas the level of HBV DNA in the serum and the expression of HBcAg in the liver were inhibited at the early stage after HI. Meanwhile, we found that the productions of both HBcAb and HBsAb were suppressed after the application of mIFNγ. In addition, we found that HBV could be effectively inhibited in mice immunized with HBsAg expression plasmid before the application of mIFNγ. Furthermore, mIFNγ showed antiviral effect and promoted the production of HBsAb when the mice subjected to the core-null HBV plasmid. These results indicate that the application of mIFNγ in the HBV HI mouse model, the mice showed defective HBcAg-specific immunity that impeded the production of HBcAb and HBsAb, finally allowing the persistence of the virus. Moreover, IFNγ-induced negative immune regulatory factors also play an important role in virus persistence.

IFN-γ: A Crucial Player in the Fight Against HBV Infection?

About 0.8 million people die because of hepatitis B virus (HBV) infection each year. In around 5% of infected adults, the immune system is ineffective in countering HBV infection, leading to chronic hepatitis B (CHB). CHB is associated with hepatocellular carcinoma, which can lead to patient death. Unfortunately, although current treatments against CHB allow control of HBV infection, they are unable to achieve complete eradication of the virus. Cytokines of the IFN family represent part of the innate immune system and are key players in virus elimination. IFN secretion induces the expression of interferon stimulated genes, producing proteins that have antiviral properties and that are essential to cell-autonomous immunity. IFN-α is commonly used as a therapeutic approach for CHB. In addition, IFN-γ has been identified as the main IFN family member responsible for HBV eradication during acute infection. In this review, we summarize the key evidence gained from cellular or animal models of HBV replication or infection concerning the potential anti-HBV roles of IFN-γ with a particular focus on some IFN-γ-inducible genes.

Emerging pipeline drugs for hepatitis B infection

INTRODUCTION

Chronic hepatitis B virus (HBV) infection continues to represent a global health concern with an estimated 350 - 400 million people infected worldwide. Current treatment options are either of two IFN-based therapies or either of five oral nucleos(t)ide analogs which are used as monotherapy or in combination. Control of viral replication can be achieved basically in all patients today. However, despite the clinical efficacy of antivirals, long-term management remains a clinical challenge mainly due to the slow kinetics of HBsAg clearance. Emergence of viral resistance has been a challenge in the past with some but not all oral therapies. The development of novel therapeutic agents with different mechanisms of action might provide new opportunities to clear HBsAg and achieve HBsAg seroconversion which could be maintained off therapy. The long-term efficacy of combinations of IFN and/or nucleos(t)ide analogs might achieve antiviral synergy, preventing drug resistance and clearing viral covalently close circular DNA and infected cells.

AREAS COVERED

This article provides a review of recent data on the safety and efficacy of existing and emerging agents for the treatment of chronic hepatitis B infection.

EXPERT OPINION

Currently, entecavir and tenofovir offer a safe and effective treatment option for patients with chronic HBV with minimal to no resistance. Although entecavir and tenofovir are able to suppress replication in essentially all patients, achieving HBsAg seroconversion remains suboptimal among all antiviral therapy. There are a number of new therapies in the pipeline for the treatment of chronic HBV infection as well as revisiting IFN combined or sequential to antiviral therapy.

Inhibition of hepatitis B virus DNA replication by a thermostable interferon-γ variant

BACKGROUND

Treatment of HBV chronic carriers using interferon (IFN)-α or nucleoside/nucleotide analogues fails to suppress viral infection. Type-II IFN-γ has been shown to inhibit HBV replication. The goal of the present work was to evaluate the antiviral efficacy against HBV of a thermostable IFN-γ variant isolated using Massive Mutagenesis and thermoresistant selection (THR) technologies.

METHODS

The thermostability of wild-type (wt) and S63C IFN-γ was determined in vitro and in vivo. Activation of the IFN-γ responsive element by wt and S63C IFN-γ was tested using a luciferase assay. HepG2.2.15 cells constitutively expressing HBV were used to analyse the antiviral activity of wt and S63C IFN-γ against HBV replication. Intracellular HBV DNA was detected by Southern blot and quantified by real-time PCR analyses.

RESULTS

S63C IFN-γ was shown to be more thermostable and had a longer half-life than wt IFN-γ. Both wt and S63C IFN-γ displayed a similar capacity to activate the IFN pathway. The treatment of HepG2.2.15 cells with wt or S63C IFN-γ induced the inhibition of HBV viral replication. After heating, S63C IFN-γ displayed better conservation of its antiviral activity against HBV when compared with wt IFN-γ.

CONCLUSIONS

These results confirm that the THR method can be used to isolate mutants with enhanced thermostability and demonstrate that a thermostable IFN-γ variant presents antiviral properties against HBV replication. This molecule could provide a new strategy to treat patients who do not respond to antiviral therapy.

Novel approaches towards conquering hepatitis B virus infection

Currently approved treatments for hepatitis B virus (HBV) infection include the immunomodulatory agent, IFN-α, and nucleos(t)ide analogues. Their efficacy is limited by their side effects, as well as the induction of viral mutations that render them less potent. It is thus necessary to develop drugs that target additional viral antigens. Chemicals and biomaterials by unique methods of preventing HBV replication are currently being developed, including novel nucleosides and newly synthesized compounds such as capsid assembling and mRNA transcription inhibitors. Molecular therapies that target different stages of the HBV life cycle will aid current methods to manage chronic hepatitis B (CHB) infection. The use of immunomodulators and gene therapy are also under consideration. This report summarizes the most recent treatment possibilities for CHB infection. Emerging therapies and their potential mechanisms, efficacy, and pitfalls are discussed.

Inhibition of hepatitis B virus DNA replicative intermediate forms by recombinant interferon-γ

AIM: To evaluate the in vitro anti-HBV activity of recombinant human IFN-γ, alone and in combination with lamivudine.

METHODS: A recombinant baculovirus-HBV/HepG2 culture system was developed which could support productive HBV infection in vitro. Expression of HBsAg and HBeAg in infected HepG2 culture medium was detected by commercial enzyme immunoassays. HBV DNA replication intermediates were detected in infected cells by Southern hybridization and viral DNA load was determined by dot hybridization.

RESULTS: IFN-γ at 0.1 to 5 μg/L efficiently down regulated HBsAg expression in transduced HepG2 cells. At 5 μg/L, IFN-γ also suppressed HBV DNA replication in these cells. While treatment with a combination of lamivudine and IFN-γ showed no additive effect, sequential treatment first with lamivudine and then IFN-γ was found to be promising. In this culture system the best HBV suppression was observed with a pulse of 2 μmol/L lamivudine for two days, followed by 1 μg/L IFN-γ for another four days. Compared to treatment with lamivudine alone, the sequential use of 0.2 μmol/L lamivudine for two days, followed by 5 μg/L IFN-γ for six days showed a 72% reduction in HBV cccDNA pool.

CONCLUSION: This in vitro study warrants further evaluation of a combination of IFN-γ and lamivudine, especially in IFN-α non-responder chronic hepatitis B patients. A reduced duration of lamivudine treatment would also restrict the emergence of drug-resistant HBV mutants.

Successful treatment with novel triple drug combination consisting of interferon-gamma, interferon alfacon-1, and ribavirin in a nonresponder HCV patient to pegylated interferon therapy

Despite major advances in therapy of hepatitis C over the past decade, nearly half of the patients treated with the currently available regimens do not clear the virus. Therefore, there is a large unmet need for more effective therapy for patients who have failed pegylated interferon plus ribavirin therapy. We describe a case of a HCV genotype 1b patient who had failed previous combination therapies of interferon plus ribavirin and pegylated interferon plus ribavirin and was subsequently successfully treated with a novel triple drug combination consisting of interferon-gamma plus interferon alfacon plus ribavirin with the outcome of a sustained virologic response. This triple drug therapy combination could be an option for patients who have failed therapies with currently available pegylated interferons plus ribavirin. Prospective randomized studies are required to evaluate the effectiveness and tolerability of this regimen in this patient population.

Interferon gamma-1b for the treatment of fibrosis in chronic hepatitis C infection

Given that the complications of hepatitis C are due to fibrosis, we hypothesized that the antifibrotic effects of interferon gamma on stellate cells would lead to beneficial effects in patients with hepatitis C. Thus, we evaluated the safety and efficacy of interferon gamma-1b in patients with hepatitis C. A cohort of 20 patients with chronic hepatitis C who failed or were intolerant to previous interferon-alpha-based regimens received 200 mug of interferon gamma-1b subcutaneously three times weekly for 24 weeks. Liver biopsy was performed prior to and at the end of treatment. Biopsies were evaluated by a single blinded pathologist using the Knodell system modified by Ishak, and fibrosis was also quantitated by morphometric analysis. The study population was 75% male and 70% Caucasian. Mean age was 47.9 +/- 7.5 years. Eighteen of 20 patients completed therapy. One patient discontinued therapy because of constitutional symptoms. One patient discontinued therapy because of elevated aminotransferases greater than twice baseline. No serious adverse events occurred. Morphometric analysis revealed that six patients (30%) had >1% absolute reduction in fibrosis score. Four of 20 (20%) patients had improvement in Ishak fibrosis scores after treatment. In conclusion, interferon gamma therapy is safe and well tolerated in patients with chronic hepatitis C. Although we did not detect an overall reduction in fibrosis, interferon gamma-1b treatment led to a reduction in fibrosis in selected patients. These data provide a basis for further study of interferon gamma-1b in patients with chronic fibrosing liver disease.

Novel Approaches to New Therapies for Hepatitis B Virus Infection

Hepatitis B is one of the most prevalent viral diseases in the world. It leads to chronic liver disease in 10% of infected individuals, putting them at an increased risk for liver-related morbidity and mortality from complications of cirrhosis and hepatocellular carcinoma. Despite the success of universal hepatitis B vaccination in many countries, this disease remains a major public health problem, resulting in more than 500,000 deaths per year. Although the current therapy for chronic hepatitis B (CHB) is effective, it is not optimal; novel approaches to the management of CHB are needed. An improved understanding of virus-host interactions, advances in gene therapy, the development of molecular therapies targeted at different stages of the hepatitis B virus life cycle, and new insights into various approaches of immune modulation will lead to the development of better therapeutic agents for the management of CHB. These advances herald a new era of combination therapy. In this review, we will discuss emerging therapies and potential mechanisms, and highlight the promises and pitfalls of these new treatment strategies.

Host factors and failure of interferon-alpha treatment in hepatitis C virus

Failure of interferon-alpha (IFN-alpha) treatment in patients with chronic hepatitis C virus (HCV) infection is a challenging obstacle for clinical and experimental hepatology. Both viral and host factors have been implicated in reducing responsiveness to IFN-alpha therapy. The role of viral factors has been studied extensively and has been summarized in several review articles; however, much less attention has been paid to host factors. In this paper, we review evidence of host factor involvement in IFN-alpha treatment failure. We discuss possible underlying mechanisms responsible for these effects. Potential therapeutic strategies to enhance the effectiveness of IFN-alpha therapy for HCV are also proposed.

Non-cytolytic inhibition of hepatitis B virus replication in human hepatocytes

BACKGROUND/AIMS

Interferon-gamma (IFN-gamma) has been shown to abolish hepatitis B virus (HBV) gene expression and replication in HBV transgenic mice without destroying infected hepatocytes. We investigated the characteristics of IFN-gamma induced non-cytolytic inhibition of viral replication in human HBV infection.

METHODS

We used an in vitro model where lymphocytes from 15 HBsAg positive patients were co-cultured with transfected hepatocytes supporting HBV replication. The effector and target cells were separated by a membrane, which allowed transfer of soluble factors only, to determine whether IFN-gamma produced from antigen-specific CD4+ T cells or mitogen stimulated lymphocytes inhibits HBV replication.

RESULTS

IFN-gamma produced following lymphocyte stimulation reduced cytoplasmic HBV DNA in the target cells. The degree of HBV DNA reduction correlated with the level of IFN-gamma in the supernatants. Further investigations using naturally infected human hepatocytes confirmed that recombinant IFN-gamma reduces HBV DNA and HBV RNA in these cells as well, in parallel with the induction of cellular interferon-responsive genes. This antiviral effect was without significant cytotoxicity and was more pronounced in hepatocytes from patients with low HBV replication.

CONCLUSIONS

These results provide direct evidence that IFN-gamma can inhibit both HBV transcription and replication in human hepatocytes without cell lysis.

Combination chemotherapy for hepatitis B virus: the path forward?

Hepatitis B virus (HBV) was identified as a cause of viral hepatitis more than 30 years ago and hepatitis B vaccines have been available for almost 20 years, but HBV infection continues to be a global health problem, responsible for about 1.2 million deaths annually. By the end of this year, almost 400 million people--about 5% of the world's population and more than ten times the number infected with human immunodeficiency virus (HIV)--will be infected with HBV. Chemotherapy remains the only treatment option for controlling chronic HBV infection once acquired, but none of the many different chemotherapeutic strategies used in the past has proven consistently successful. Prospects for successful treatment of HBV have improved dramatically during the past decade due to the development of new, well tolerated and efficacious anti-HBV drugs, and to advances in our understanding of HBV replication and pathogenesis. The newer anti-HBV drugs are capable of reducing viral loads very rapidly, but the initial response is invariably followed by very much slower elimination of residual virus. As more effective anti-HBV drugs become available, the emergence of drug resistance during the slower phase of HBV elimination will probably become the most significant obstacle in the way of eventual control of HBV infection. Experience with HIV indicates that combination chemotherapy may suppress or eliminate drug resistance and methods for pre-clinical and clinical assessment of anti-HBV drug combinations are being developed. Basic research into mechanisms of drug action and interaction should assist in the design and optimisation of combination chemotherapy for HBV infection, for which additional new anti-HBV drugs will undoubtedly be required in future.

Review: Present and future directions in the treatment of chronic hepatitis B infection

The last decade has witnessed substantial progress in the development of chemotherapeutic agents for chronic hepatitis B. However, the only currently licensed treatment in Australia, interferon-alpha, has low initial response rates and the adverse effects are often unacceptable. Of the newer agents in the class of nucleoside analogues, famciclovir and lamivudine are in phase III clinical trials with encouraging preliminary results, while other agents, such as bis-POM PMEA (Adefovir), are at phase I/II development. Future approaches to therapy will be governed by an understanding of the effects of nucleoside analogues on the natural history of the disease as well as on the hepatitis B virus hepatocyte interaction. Combination antiviral therapy should theoretically offer improved response rates, decrease the development of viral resistance, and provide the greatest reduction in viral load, but it has not yet been widely examined in the clinical setting. In this article, we review the currently available strategies, discuss potential problem areas, and speculate on promising approaches with combination chemotherapy and the features of agents soon to be trialed.

Interferon gamma production in whole peripheral blood culture in acute hepatitis B

Interferon gamma (IFNg) production in whole peripheral blood (WPB) and mononuclear (MN) cell culture in acute hepatitis B (AHB) was compared. IFNg production was induced by phytogem agglutinin and measured in the cell supernatants of 14 AHB patients in the course of the disease. There were some up-regulating factors of IFNg production that probably operated in WPB culture: the presence of autoerythrocytes as well as the low content of monocytes. Autoserum regulated IFNg production in a stage-dependent way: it decreased IFNg activity at the bilirubin peak in hepatitis B infection, but not in convalescence. In contrast, we did not find a serum blocking effect in the corresponding stage of acute hepatitis A. The nature of this serum blocking factor in AHB is unclear.

Treatment of chronic hepatitis B

Chronic infection with the hepatitis B virus (HBV) is a major cause of worldwide morbidity and mortality. A large number of therapeutic approaches has been tried, including interferon (IFN), nucleoside analogues and immunomodulators. To date controlled clinical trials have shown that only IFN is of long-term value but many patients fail to respond to treatment. New approaches to treating patients with IFN-resistant hepatitis B are currently undergoing clinical and experimental evaluation, and it seems likely that new therapeutic agents will be available in the near future.