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

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.

Development of a tag-free plant-made interferon gamma production system with improved therapeutic efficacy against viruses

Plants offer a promising platform for cost-effective production of biologically active therapeutic glycoproteins. In previous studies, we have developed a plant expression system based on Bamboo mosaic virus (BaMV) by incorporating secretory signals and an affinity tag, which resulted in notably enhanced yields of soluble and secreted fusion glycoproteins (FGs) in Nicotiana benthamiana. However, the presence of fusion tags on recombinant glycoproteins is undesirable for biomedical applications. This study aimed to develop a refined expression system that can efficiently produce tag-free glycoproteins in plants, with enhanced efficacy of mature interferon gamma (mIFNγ) against viruses. To accommodate the specific requirement of different target proteins, three enzymatically or chemically cleavable linkers were provided in this renovated BaMV-based expression system. We demonstrated that Tobacco etch virus (TEV) protease could process the specific cleavage site (LTEV) of the fusion protein, designated as SSExtHis(SP)10LTEV-mIFNγ, with optimal efficiency under biocompatible conditions to generate tag-free mIFNγ glycoproteins. The TEV protease and secretory-affinity tag could be effectively removed from the target mIFNγ glycoproteins through Ni2+-NTA chromatography. In addition, the result of an antiviral assay showed that the tag-free mIFNγ glycoproteins exhibited enhanced biological properties against Sindbis virus, with comparable antiviral activity of the commercialized HEK293-expressed hIFNγ. Thus, the improved BaMV-based expression system developed in this study may provide an alternative strategy for producing tag-free therapeutic glycoproteins intended for biomedical applications.

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.

The anti-hepatitis B virus and anti-hepatotoxic efficacies of solanopubamine, a rare alkaloid from Solanum schimperianum

Chronic liver disease caused by hepatitis B virus (HBV) remains an important health issue. Though there are effective HBV-polymerase inhibitors (e.g., lamivudine), their prolonged use leads to emergence of drug-resistant (polymerase mutant) strains. Several herbal formulations and phytochemicals have been therefore, reported as potential anti-HBV agents with no sign of resistance in experimental and clinical settings. In this study, we assessed the anti-HBV as well as hepatoprotective salutations of solanopubamine, a rare alkaloid isolated from S. schimperianum. In cultured HepG2.2.15 cells, solanopubamine showed marked anti-HBV activity in a time and dose-dependent manner. Solanopubamine (30 μM) efficiently inhibited HBsAg and HBeAg expressions by 66.5%, 70.5%, respectively as compared to 82.5% and 86.5% respective inhibition by lamivudine (2 μM) at day 5. Molecular docking analyses of solanopubamine revealed formations of stable complexes with lamivudine-sensitive as well as lamivudine-resistant polymerase through interactions of catalytic ‘YMDD/YIDD’ motif residues. Moreover, solanopubamine attenuated DCFH-induced oxidative and apoptotic damage and restored HepG2 cell viability by 28.5%, and downregulated caspase-3/7 activations by 33%. Further docking analyses of solanopubamine showed formation of stable complexes with caspase-3/7. Taken together, our data demonstrates promising anti-HBV and anti-hepatotoxic therapeutic potential of solanopubamine, and warrants further molecular and pharmacological studies.

Novel Anti-Hepatitis B Virus Activity of Euphorbia schimperi and Its Quercetin and Kaempferol Derivatives

Natural or plant products, because of their structural diversity, are a potential source for identifying new anti-hepatitis B virus (HBV) agents. Here, we report the anti-HBV activity of Euphorbia schimperi and its quercetin (QRC) and kaempferol derivatives. The anti-HBV-active methanol fraction of E. schimperi was subjected to chromatographic techniques, leading to isolation of three flavonols, following their structure determination by ¹H and ¹³C NMR spectroscopies. Their cytotoxicity and anti-HBV potential were assessed using HBV reporter HepG2.2.15 cells, and their modes of action were delineated by molecular docking. The isolated compounds identified as quercetin-3-O-glucuronide (Q3G), quercetin-3-O-rhamnoside (Q3R), and kaempferol-3-O-glucuronide (K3G) were non-cytotoxic to HepG2.2.15 cells. The viral HBsAg/HBeAg production on day 5 was significantly inhibited by K3G (∼70.2/∼73.4%), Q3G (∼67.8/∼72.1%), and Q3R (∼63.2%/∼68.2%) as compared to QRC (∼70.3/∼74.8%) and lamivudine (∼76.5/∼84.5%) used as standards. The observed in vitro anti-HBV potential was strongly supported by in silico analysis, which suggested their structure-based activity via interfering with viral Pol/RT and core proteins. In conclusion, this is the first report on the anti-HBV activity of E. schimperi-derived quercitrin-3-O-glucuronide, quercitrin-3-O-rhamnoside, and kaempferol-3-O-glucuronide, most likely through interfering with HBV proteins.

Fusion of a Novel Native Signal Peptide Enhanced the Secretion and Solubility of Bioactive Human Interferon Gamma Glycoproteins in Nicotiana benthamiana Using the Bamboo Mosaic Virus-Based Expression System

Plant viruses may serve as expression vectors for the efficient production of pharmaceutical proteins in plants. However, the downstream processing and post-translational modifications of the target proteins remain the major challenges. We have previously developed an expression system derived from Bamboo mosaic virus (BaMV), designated pKB19, and demonstrated its applicability for the production of human mature interferon gamma (mIFNγ) in Nicotiana benthamiana. In this study, we aimed to enhance the yields of soluble and secreted mIFNγ through the incorporation of various plant-derived signal peptides. Furthermore, we analyzed the glycosylation patterns and the biological activity of the mIFNγ expressed by the improved pKB19 expression system in N. benthamiana. The results revealed that the fusion of a native N. benthamiana extensin secretory signal (SS^Ext) to the N-terminal of mIFNγ (designated SS^Ext mIFNγ) led to the highest accumulation level of protein in intracellular (IC) or apoplast washing fluid (AWF) fractions of N. benthamiana leaf tissues. The addition of 10 units of 'Ser-Pro' motifs of hydroxyproline-O-glycosylated peptides (HypGPs) at the C-terminal end of SS^Ext mIFNγ (designated SS^Ext mIFNγ(SP)₁₀) increased the solubility to nearly 2.7- and 1.5-fold higher than those of mIFNγ and SS^Ext mIFNγ, respectively. The purified soluble SS^Ext mIFNγ(SP)₁₀ protein was glycosylated with abundant complex-type N-glycan attached to residues N⁵⁶ and N¹²⁸, and exhibited biological activity against Sindbis virus and Influenza virus replication in human cell culture systems. In addition, suspension cell cultures were established from transgenic N. benthamiana, which produced secreted SS^Ext mIFNγ(SP)₁₀ protein feasible for downstream processing. These results demonstrate the applicability of the BaMV-based vector systems as a useful alternative for the production of therapeutic proteins, through the incorporation of appropriate fusion tags.

The anti-hepatitis B virus therapeutic potential of anthraquinones derived from Aloe vera

Although the approved hepatitis B virus (HBV)-polymerase inhibitors (e.g., lamivudine) often lead to drug-resistance, several natural products have shown promising efficacies. Though Aloe vera (AV) gel and its constituents are shown inhibitors of many viruses, their anti-HBV activity still remains elusive. We therefore, tested the anti-HBV potential of AV extract and its anthraquinones in hepatoma cells, including molecular docking, high-performance thin layer chromatography (HPTLC), and cytochrome P450 (CYP3A4) activation analyses. Our anti-HBV assays (HBsAg/HBeAg Elisa) showed maximal inhibition of viral antigens production by aloe-emodin (~83%) > chrysophanol (~62%) > aloin B (~61%) > AV extract (~37%) in HepG2.2.15 cells. Interestingly, the effect of aloe-emodin was comparable with lamivudine (~86%). Moreover, sequential treatment with lamivudine (pulse) followed by aloe-emodin (chase) enhanced the efficacy of monotherapy by ~12%. Docking (AutoDock Vina) of the anthraquinones indicated strong interactions with HBV-polymerase residues that formed stable complexes with high Gibbs's free energy. Further, identification of aloe-emodin and aloin B by validated HPTLC in AV extract strongly endorsed its anti-HBV potential. In addition, our luciferase-reporter gene assay of transfected HepG2 cells showed moderate induction of CYP3A4 by aloe-emodin. In conclusion, this is the first report on anti-HBV potential of AV-derived anthraquinones, possibly via HBV-polymerase inhibition. Of these, although aloin B exhibits novel antiviral effect, aloe-emodin appears as the most promising anti-HBV natural drug with CYP3A4 activating property towards its enhanced therapeutic efficacy.

Plant-derived antiviral drugs as novel hepatitis B virus inhibitors: Cell culture and molecular docking study

Despite high anti-HBV efficacies, while the nucleoside analogs (e.g., lamivudine) lead to the emergence of drug-resistance, interferons (e.g., IFN-α causes adverse side-effects. Comparatively, various natural or plant products have shown similar or even better efficacy. Hence, new antiviral strategies must focus not only on synthetic molecules but also on potential natural compounds. In this report, we have combined the in vitro cell culture and in silico molecular docking methods to assess the novel anti-HBV activity and delineate the inhibitory mechanism of selected plant-derived pure compounds of different classes. Of the tested (2.5-50 μg/ml) twelve non-cytotoxic compounds, ten (10 μg/ml) were found to maximally inhibit HBsAg production at day 5. Compared to quercetin (73%), baccatin III (71%), psoralen (67%), embelin (65%), menisdaurin (64%) and azadirachtin (62%) that showed high inhibition of HBeAg synthesis, lupeol (52%), rutin (47%), β-sitosterol (43%) and hesperidin (41%) had moderate efficacies against HBV replication. Further assessment of quercetin in combination with the highly active compounds, enhanced its anti-HBV activity up to 10%. Being the most important drug target, a 3-D structure of HBV polymerase (Pol/RT) was modeled and docked with the active compounds, including lamivudine as standard. Docking of lamivudine indicated strong interaction with the modeled HBV Pol active-site residues that formed stable complex (∆G = -5.2 kcal/mol). Similarly, all the docked antiviral compounds formed very stable complexes with HBV Pol (∆G = -6.1 to -9.3 kcal/mol). Taken together, our data suggest the anti-HBV potential of the tested natural compounds as novel viral Pol/RT inhibitors.

Recent advance of the hepatitis B virus inhibitors: a medicinal chemistry overview

Hepatitis B Virus (HBV) is one of the most prevalent viral infections of human worldwide. The therapies are limited in the clinical context because of negative side effects of interferons and the development of viral resistance to the nucleoside/nucleotide inhibitors. In this review, we summarize the recent advances in design and development of potent anti-HBV inhibitors from natural sources and synthetic compounds, targeting different steps in the life cycle of HBV. We attempt to emphasize the major structural modifications, mechanisms of action and computer-aided docking analysis of novel potent inhibitors that need to be addressed in the future to design potent anti-HBV molecules.

Beneficial therapeutic effect of Chinese herbal Bushen formula on CHB patients with mildly elevated alanine aminotransferase by down-regulating CD4+CD25+T cells

ETHNOPHARMACOLOGICAL RELEVANCE

To investigate the clinical effects of the Bushen formula on chronic hepatitis B (CHB) patients with mildly elevated alanine aminotransferase (ALT) (1-2 times ULN) and its relevant immune mechanism.

MATERIALS AND METHODS

Fifty CHB patients were enrolled, and they were categorized into two groups according to infection state, including CHB carrier group(24 patients) and mildly elevated ALT (1-2 times ULN) group (26 patients), and 12 healthy volunteers were collected as normal control group. In addition, patients with mildly elevated ALT were taking the Bushen formula for 6 months. Biochemical assessment, viral load quantitation and HBV markers were examined at the Department of Clinical Laboratory, Shanghai Shuguang Hospital. Peripheral blood mononuclear cells were separated from patients and healthy volunteers. T cells were separated from healthy blood, and Hepatitis B core antigen (HBcAg) was added to the culture media. The percentage of CD4+CD25+T cells and the expression levels of IFN-γ and IL-4 were examined by flow cytometry and the expression level of FoxP3 was examined by real-time PCR and flow cytometry. The Chinese medicine symptom complex score was calculated.

RESULTS

The percentage of CD4+CD25+T cells and the expression level of Foxp3 in two CHB patient groups were higher than that in the normal control group, and the percentage of CD4+CD25+T cells and the expression level of Foxp3 in the CHB carrier group were highest. The experiment in vitro showed that both the percentage of CD4+CD25+T cells and the expression of Foxp3 were elevated by HBcAg in CD4+T cells separated from normal peripheral blood. In patients with mildly elevated ALT, the serum ALT level was significantly decreased from 81.77±18.24U/L to 64.92±20.60U/L and the serum HBV DNA level was significantly decreased from 6.54±0.95 (log) to 5.15±2.22 (log), and symptom scores were significantly decreased from 6.19±3.99 to 2.77±1.66 after administration of the Bushen formula. In addition, we found that the frequency of CD4+CD25+T cells correlated negatively with the expression level of IFN-γ in CD4+T cells from CHB patients with mildly elevated ALT, and the percentage of CD4+CD25+T cells was decreased from 11.07±4.30% to 8.70±3.49% and the expression level of IFN-γ in CD4+T cells was increased from 13.98±3.25% to 15.85±3.43% after administration of the Bushen formula.

CONCLUSION

In CHB patients, the percentage of CD4+CD25+T cells and the expression of Foxp3 in peripheral blood were increased, which can be repeated in HBcAg-stimulated healthy CD4+T cells. The Bushen formula has positive effects on CHB patients with mildly elevated ALT (1-2 times ULN) by reducing serum ALT and HBV DNA levels, which is relevant with the decreasing of the percentage of CD4+CD25+T cells and the increasing of the expression level of IFN-γ in CD4+T cells.

Antiviral treatment alters the frequency of activating and inhibitory receptor-expressing natural killer cells in chronic hepatitis B virus infected patients

Natural killer (NK) cells play a critical role in innate antiviral immunity, but little is known about the impact of antiviral therapy on the frequency of NK cell subsets. To this aim, we performed this longitudinal study to examine the dynamic changes of the frequency of different subsets of NK cells in CHB patients after initiation of tenofovir or adefovir therapy. We found that NK cell numbers and subset distribution differ between CHB patients and normal subjects; furthermore, the association was found between ALT level and CD158b(+) NK cell in HBV patients. In tenofovir group, the frequency of NK cells increased during the treatment accompanied by downregulated expression of NKG2A and KIR2DL3. In adefovir group, NK cell numbers did not differ during the treatment, but also accompanied by downregulated expression of NKG2A and KIR2DL3. Our results demonstrate that treatment with tenofovir leads to viral load reduction, and correlated with NK cell frequencies in peripheral blood of chronic hepatitis B virus infection. In addition, treatments with both tenofovir and adefovir in chronic HBV infected patients induce a decrease of the frequency of inhibitory receptor(+) NK cells, which may account for the partial restoration of the function of NK cells in peripheral blood following treatment.

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.

Relationship between HBV cccDNA expression in the human ovary and vertical transmission of HBV

This study aimed to investigate the relationship between hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) in the ovary and vertical transmission of HBV. HBV DNA and HBV cccDNA were assayed in the ovaries of 33 pregnant women who were positive for HBV DNA. The HBVM (HBV markers, including HBsAg, HBsAb, HBeAg, HBeAb, HBcAb) level and the HBV DNA content in peripheral blood of infants were measured. The overall positive rate of HBV DNA and HBV cccDNA in samples was 51·52% (17/33). The intrauterine infection rate of the infants was 12·12% (4/33). When HBV DNA and HBV cccDNA were both positive, the intrauterine infection rate of infants was significantly higher than when they were both negative (P<0·05). Levels of HBV cccDNA and the rate of positive samples were significantly higher in mothers with infants with intrauterine infection than in those without (P<0·01 and P<0·05, respectively). HBV can infect the human ovary and may transmit to the filial generation via the ovum.

Hepatitis E virus ORF2 protein over-expressed by baculovirus in hepatoma cells, efficiently encapsidates and transmits the viral RNA to naïve cells

A recombinant baculovirus(vBacORF2) that expressed the full-length ORF2 capsid protein of a genotype 1 strain of hepatitis E virus(HEV) was constructed. Transduction of S10-3 human hepatoma cells with this baculovirus led to large amounts of ORF2 protein production in ~50% of the cells as determined by immune fluorescence microscopy. The majority of the ORF2 protein detected by Western blot was 72 kDa, the size expected for the full-length protein. To determine if the exogenously-supplied ORF2 protein could transencapsidate viral genomes, S10-3 cell cultures that had been transfected the previous day with an HEV replicon of genotype 1 that contained the gene for green fluorescent protein(GFP), in place of that for ORF2 protein, were transduced with the vBacORF2 virus. Cell lysates were prepared 5 days later and tested for the ability to deliver the GFP gene to HepG2/C3A cells, another human hepatoma cell line. FACS analysis indicated that lysates from cell cultures receiving only the GFP replicon were incapable of introducing the replicon into the HepG2/C3A cells whereas ~2% of the HepG2/C3A cells that received lysate from cultures that had received both the replicon and the baculovirus produced GFP. Therefore, the baculovirus-expressed ORF2 protein was able to trans-encapsidate the viral replicon and form a particle that could infect naïve HepG2/C3A cells. This ex vivo RNA packaging system should be useful for studying many aspects of HEV molecular biology.

Circulating Tregs correlate with viral load reduction in chronic HBV-treated patients with tenofovir disoproxil fumarate

Limited response to current hepatitis B virus (HBV) drugs is possibly due to inadequate host cytotoxic cellular responses. Circulating Tregs have been shown to be associated with chronicity of HBV infection, but their profile during antiviral therapy has not been studied. We analyzed the frequency and effect of Tregs on cellular immune responses against HBV in 35 chronic hepatitis B eAg-ve and eAg+ve patients treated with tenofovir 300 mg/day. Frequency of Tregs and their modulatory role in cytokine-secreting cells were determined after stimulation with HBsAg or HBcAg in the absence or presence of Tregs and after blockage of PD-1/PDL-1 in peripheral blood mononuclear cells (PBMCs). Prior to therapy, eAg-ve patients had lower HBV DNA levels, reduced CD8 T cells, increased Tregs, and T cells expressing PD1. After 12 weeks of therapy, >2 log HBV viral reduction was observed in both groups, along with an increase frequencies of CD8 T cells in eAg-ve patients and increased expression of chemokine receptors/Toll-like receptors in both groups. PD-1 expression on CD8 cells in PBMCs was decreased in both groups during therapy but not on Tregs. In eAg-ve group, sustained increase of Tregs was observed till week 12, which declined at week 24. In both groups, after 24 weeks, depletion of CD4(+)CD25(+) Tregs from PBMCs enhanced HBV-specific T cell responses, and blockage of PD-1/PDL1 pathway did enhance pro-inflammatory cytokine production in eAg+ve patients but not in eAg-ve. We conclude that Tregs induced by HBV replication in vivo are expanded in eAg-ve patients more. Reduction in HBV DNA by tenofovir partially restored adaptive immune responses and also reduced the Tregs. Blockage of PD-1/PDL1, enhanced cytokine production in eAg+ve patients but not in eAg-ve, suggests that distinctly different immunologic mechanisms are involved in eAg+ve and eAg-ve patients.

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.

Lipopolysaccharide-induced innate immune responses in primary hepatocytes downregulates woodchuck hepatitis virus replication via interferon-independent pathways

Our previous studies have shown that Toll-like receptor (TLR) ligands, Poly I:C and lipopolysaccharide (LPS), are able to activate non-parenchymal liver cells and trigger the production of interferon (IFN) to inhibit hepatitis B virus replication in vivo and in vitro. However, little is known about TLR-mediated cellular responses in primary hepatocytes. By the model of woodchuck hepatitis virus (WHV) infected primary woodchuck hepatocytes (PWHs), Poly I:C and LPS stimulation resulted in upregulation of cellular antiviral genes and relevant TLRs mRNA expression respectively. LPS stimulation led to a pronounced reduction of WHV replicative intermediates without a significant IFN induction. Poly I:C transfection resulted in the production of IFN and a highly increased expression of antiviral genes in PWHs and slight inhibitory effect on WHV replication. LPS could activate nuclear factor kappa B, MAPK and PI-3k/Akt pathways in PWHs. Further, inhibitors of MAPK-ERK and PI-3k/Akt pathways, but not that of IFN signalling pathway, were able to block the antiviral effect of LPS. These results indicate that IFN- independent pathways which activated by LPS are able to downregulate hepadnaviral replication in hepatocytes.

Interferons and their use in persistent viral infections

In 2007, the world celebrated the 50th anniversary of the discovery of interferon (IFN) by Isaacs and Lindenmann. Subsequently, the IFN-alpha gene was cloned, fully sequenced and IFN-alpha was produced in recombinant form. Recombinant IFN-alpha is now used as the basis for treatment of chronic hepatitis C virus infection and can also be used to treat certain forms of chronic hepatitis B virus infections. IFNs have also been used in other viral infections, although with less success. The antiviral mechanisms of IFNs are reviewed in this chapter as well as the utility of IFNs in the treatment of persistent viral infections.

Increased yield of high purity recombinant human interferon-gamma utilizing reversed phase column chromatography

Increasing therapeutic applications for recombinant human interferon-gamma (rhIFN-gamma), an antiviral proinflammatory cytokine, has broadened interest in optimizing methods for its production and purification. We describe a reversed phase chromatography (RPC) procedure using Source-30 matrix in the purification of rhIFN-gamma from Escherichia coli that results in a higher yield than previously reported. The purified rhIFN-gamma monomer from the RPC column is refolded in Tris buffer. Optimal refolding occurs at protein concentrations between 50 and 100 microg/ml. This method yields greater than 90% of the dimer form with a yield of 40 mg/g cell mass. Greater than 99% purity is achieved with further purification over a Superdex G-75 column to obtain specific activities of from 2 x 10(7) to 4 x 10(7)IU/mg protein as determined via cytopathic antiviral assay. The improved yield of rhIFN-gamma in a simple chromatographic purification procedure promises to enhance the development and therapeutic application of this biologically potent molecule.