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

HBV PreC interacts with SUV39H1 to induce viral replication by blocking the proteasomal degradation of viral polymerase

Hepatitis B e antigen (HBeAg) seropositivity during the natural history of chronic hepatitis B (CHB) is known to coincide with significant increases in serum and intrahepatic HBV DNA levels. However, the precise underlying mechanism remains unclear. In this study, we found that PreC (HBeAg precursor) genetic ablation leads to reduced viral replication both in vitro and in vivo. Furthermore, PreC impedes the proteasomal degradation of HBV polymerase, promoting viral replication. We discovered that PreC interacts with SUV39H1, a histone methyltransferase, resulting in a reduction in the expression of Cdt2, an adaptor protein of CRL4 E3 ligase targeting HBV polymerase. SUV39H1 induces H3K9 trimethylation of the Cdt2 promoter in a PreC-induced manner. CRISPR-mediated knockout of endogenous SUV39H1 or pharmaceutical inhibition of SUV39H1 decreases HBV loads in the mouse liver. Additionally, genetic depletion of Cdt2 in the mouse liver abrogates PreC-related HBV replication. Interestingly, a negative correlation of intrahepatic Cdt2 with serum HBeAg and HBV DNA load was observed in CHB patient samples. Our study thus sheds light on the mechanistic role of PreC in inducing HBV replication and identifies potential therapeutic targets for HBV treatment.

Manganese Breaks the Immune Tolerance of HBs-Ag

Background

Manganese (Mn²⁺⁾ has been shown to promote type I interferon (IFN) production and activate the cyclic GMP-AMP synthase (cGAS)/Stimulator of Interferon Genes (STING) signaling pathway, suggesting that Mn²⁺ could be used as an adjuvant for vaccination.

Methods

In present study, the effects of Mn²⁺ on vaccination against hepatitis B virus (HBV) were evaluated. We treated mouse hepatocytes and kuppfer cells with Mn²⁺ with or without adeno-associated virus (AAV)–HBV infection. Expression of IFN-α and IFN-β and activation of TBK1 and IRF3 were monitored. Wild-type and STING^-/- mice were treated with Mn²⁺ and then infected with AAV-HBV. Serum levels of HBV surface antigen (HBsAg), alanine aminotransferase (ALT) activity, IFN-α, and IFN-β were detected. Lymphocyte infiltration in the liver was evaluated. HBsAg-Tg mice were vaccinated with Mn²⁺ and HBsAg. The serum levels of HBsAg antibody, alanine transaminase activity, and IFN-β were monitored after vaccination.

Results

Mn²⁺ promoted IFN-α and IFN-β production in mouse hepatocytes and kuppfer cells. Mn²⁺ failed to promote IFN-α and IFN-β production in kuppfer cells deficient in STING. Mn²⁺ promoted activation/phosphorylation of TBK1 and IRF3 during AAV-HBV infection. Mn²⁺ decreased serum levels of HBsAG, increased serum levels of alanine aminotransferase (ALT), IFN-α and IFN-β, and enhanced lymphocyte infiltration and the percentage of IFN-γ-producing CD8⁺ T cells in the liver of AAV-HBV-infected mice. In contrast, Mn²⁺ treatment did not affect serum levels of HBsAG, ALT, IFN-α, or IFN-β in STING-deficient mice.

Conclusions

Mn²⁺ promoted HBsAG antibody, ALT, and IFN-β production after HBsAG immunization. Mn²⁺ promoted type I IFN production in AAV-HBV infection and HBsAG immunization and could be used as an adjuvant for vaccination.

Hepatitis B virus precore/core region mutations and genotypes among hepatitis B virus chronic carriers in South-Eastern, Nigeria

OBJECTIVES

The study aimed at detecting the prevailing hepatitis B virus (HBV) genotypes and the presence of clinically relevant mutations in the precore/core gene of the HBV DNA, among patients with chronic infection in South-eastern, Nigeria.

METHODS

A total of 72 participants with chronic HBV infection were enrolled into the study. Plasma samples from those with detectable HBV DNA were subjected to nested Polymerase Chain Reaction amplification using the precore/core specific primers. This resulted to the successful amplification and sequencing of the HBV precore/core region DNA from 16 participants. Mutation analysis on the precore/core region detected the presence of certain HBV precore/core gene mutations. Genotyping was carried out by phylogenetic analysis.

RESULTS

The precore region mutation at nucleotide position 1896, which is a G to A change resulting to a nonsense mutation, was detected in 6.25% of the participants. Other HBV precore region mutations that were detected include: G1899A, T1846A, G1862C, G1888A, T1821C, C1826T, A1827C, A1850T, C1858T, precore start codon Kozak sequence mutations and some novel core region mutations such as G/A1951T and G1957A. Genotyping revealed the existence of HBV genotype/subgenotype A1 (87.5%) and D (12.5%) among the participants. There was no significant difference in the occurrence of specific precore/core mutations among the HBV/hepatitis C virus dually infected and HBV mono-infected participants.

CONCLUSION

The data suggest the likelihood of a more severe outcome of hepatitis caused by HBV in South-eastern Nigeria due to the occurrence of a variety of precore/core mutation, which resulted to HBeAg-negative chronic HBV infection among the participants.

The response of hepatitis B virus genotype to interferon is associated with a mutation in the interferon-stimulated response element

Genetic variation and genotype of Hepatitis B virus (HBV) are related to the efficiency of interferon alpha (IFN-α)-based antiviral therapy. However, the correlation of variation in interferon-stimulated response element (ISRE) and HBV genotype response to IFN-α therapy remains elusive.Differences of ISRE between genotype B and C HBV were explored using the HBV sequences retrieved from GenBank, and further investigated by ISRE region cloning and sequencing from 60 clinical samples post-IFN-α therapy. Additionally, ISRE mutants were constructed and their relation to responsiveness of IFN-α was evaluated by real-time PCR and Southern blot analysis.ISRE pattern between genotype B and C were found based on both clinical sample sequencing and full-length sequence alignment. The primary difference is the fourth base within the ISRE region, with T and C for genotype B and C, respectively. HBV with genotype C-type ISRE had a higher replicative capability as compared to HBV with genotype B-type ISRE after IFN-α treatment in huh7 cells. CONCLUSION:: Preference of ISRE between genotype B and C HBV are distinct. Single nucleotide difference (C to T) within the HBV ISRE region may link to the efficacy of IFN-α therapy to genotype B and C HBV. Therefore, this study provides a clue for the determination of IFN-α therapy response to HBV treatment.

Serum protein expression patterns in detecting a new viral protein in HBeAg-negative chronic hepatitis B

We analysed the changes in viral protein expression in HBeAg-negative chronic hepatitis B (CHB). In total, 160 samples were obtained from individuals infected by hepatitis B virus (HBV) and divided into four groups. Group A included 71 cases of hepatitis B e antigen (HBeAg)-negative CHB, Group B included 58 cases of inactive seroconverters and Group C included 31 cases of HBeAg-positive CHB. Group D included 22 normal healthy individuals as a control. All serum samples were examined using surface enhance laser desorption/ionization time of flight-mass spectrometry (SELDI-TOF-MS). The results indicated that a peak with 4140 m/z increased markedly in Group A at 1295.55 ± 745.87, which was significantly different from that in Group B at 896.99 ± 534.86 (P = 0.013). This peak indicated a close relationship with HBV DNA replication and may contribute to pathogenesis of HBeAg-negative chronic hepatitis.

Elevated serum β2-microglobulin in individuals coinfected with hepatitis B and hepatitis D virus in a rural settings in Southwest Nigeria

OBJECTIVE

Coinfection of hepatitis B virus (HBV) with hepatitis D virus (HDV) has being reported to increase severity of progression to hepatocellular carcinoma (HCC) and liver cirrhosis (LC). Beta microglobulin (2βM) which is present on the surfaces of blood cells in acceptable levels is a tumor marker which may become elevated in disease conditions. This study hence observed the prevalence of HBV and HDV coinfection in a rural population and their 2βM concentration.

RESULTS

Of the 368 samples, 66 (17.9%) were positive to hepatitis B surface antigen (HBsAg) and 33 (50%) were coinfected with HDV, 8 (2.1%) were monoinfected with HDV. 2βM concentration increased beyond the normal level in individuals coinfected with HBV and HDV as compared with the monoinfected individuals. Coinfection resulted in the increased concentration of 2βM in HBV and HDV coinfection and the likelihood of progression to HCC and LC may not be ruled out. Monoinfection with HDV also had high 2βM concentration but this is due to having being infected with a non-detected HBV or chronic infection in which HBV is clearing.

Influences on viral replication and sensitivity to GLS4, a HAP compound, of naturally occurring T109/V124 mutations in hepatitis B virus core protein

Heteroaryldihydropyrimidine (HAP) compounds inhibit HBV replication by binding to a hydrophobic pocket at the interface between hepatitis B virus core protein (HBcAg) dimer, which interrupts capsid assembly by changing the kinetics and thermodynamics during this process. Structure biological studies have identified several amino acids in HBcAg crucial for compound binding. Here, we investigated the polymorphisms of T109 and V124 amino acids in HBV sequences submitted to GenBank database. Naturally occurring T109 and V124 and/or possible compensatory mutations in neighbored amino acids were introduced into HBV-expressing plasmids. Viral replication competence and sensitivity to GLS4, a HAP compound, were evaluated using transient transfection and in vitro infection cell models. All tested mutations in these amino acids led to decreasing viral DNA replication at different levels. Specially, T109N and all V124 mutants caused severe deficiencies in viral plus-strand DNA synthesis. T109I single mutation and all T109S/M/C/N mutations impaired HBeAg secretion. T109I showed modestly decreased sensitivities with IC50 3.3- to 6.8-folds higher than wild-type virus. In vitro infection assay showed T109N and all V124 mutants failed to synthesize cccDNA and following viral proteins. The other mutants, however, produced functional cccDNA pools as wild-type virus did. Taken together, we profiled the competences of viral replication and sensitivities to capsid inhibitor of naturally existing mutations in T109 and V124. This will help to understand the possible antiviral resistance issues in future clinical applications of capsid inhibitors.

2',3'-cyclic nucleotide 3'-phosphodiesterases inhibit hepatitis B virus replication

2’,3’-cyclic nucleotide 3’-phosphodiesterase (CNP) is a member of the interferon-stimulated genes, which includes isoforms CNP1 and CNP2. CNP1 is locally expressed in the myelin sheath but CNP2 is additionally expressed at low levels outside the nervous system. CNPs regulate multiple cellular functions and suppress protein production by association with polyadenylation of mRNA. Polyadenylation of Hepatitis B virus (HBV) RNAs is crucial for HBV replication. Whether CNPs interact with polyadenylation signal of HBV RNAs and interfere HBV replication is unknown. In this study, we evaluated expressions of CNP isoforms in hepatoma cell lines and their effects on HBV replication. We found that CNP2 is moderately expressed and gently responded to interferon treatment in HepG2, but not in Huh7 cells. The CNP1 and CNP2 potently inhibited HBV production by blocking viral proteins synthesis and reducing viral RNAs, respectively. In chronic hepatitis B patients, CNP was expressed in most of HBV-infected hepatocytes of liver specimens. Knockdown of CNP expression moderately improved viral production in the HepG2.2.15 cells treated with IFN-α. In conclusion, CNP might be a mediator of interferon-induced response against HBV.

In vitro inhibition of HBV replication by a novel compound, GLS4, and its efficacy against adefovir-dipivoxil-resistant HBV mutations

BACKGROUND

HBV infection continues to be an important worldwide cause of morbidity and mortality. Patients with chronic hepatitis B can be successfully treated using nucleoside/nucleotide analogues. However, drug-resistant HBV mutants frequently arise, leading to treatment failure and progression to liver disease. Here, we report the effects of GLS4, a non-nucleosidic inhibitor that exhibits a novel and highly specific anti-HBV activity.

METHODS

The median inhibitory concentrations (IC(50)s) of GLS4 on HBV were measured by Southern blotting. HBV capsid and core protein levels were detected by immunoblotting. To determine the antiviral activity of GLS4 against adefovir dipivoxil (ADV)-resistant HBV mutants, HepG2 cells transiently transfected with PUC-HBV1.2 plasmids that contained one of three major ADV-resistant mutations (rtA181T, rtA181V and rtN236T) were treated with GLS4. Intracellular HBV replicative intermediates were detected by Southern blotting. The effect on the in vitro assembly of HBV capsid protein was examined using dynamic light scattering and electron microscopy.

RESULTS

The IC(50) of GLS4 was 0.012 μM, which is significantly lower than that of lamivudine (0.325 μM). Immunoblot analysis of HepG2.2.15 cells and transiently transfected HepG2 cells indicated that GLS4 treatment interfered with the formation of core particles (assembly). The ADV-resistant HBV mutant strains were also sensitive to GLS4. Upon examining the in vitro assembly of HBV core protein 149 by electron microscopy, increased aberrant particles were observed after GLS4 treatment.

CONCLUSIONS

GLS4 is a new and unique potential anti-HBV agent that possesses a different mechanism of action than existing therapeutic drugs.

A mutation in the interferon regulatory element of HBV may influence the response of interferon treatment in chronic hepatitis B patients

Background

A functional interferon regulatory element (IRE) has been found in the EnhI/X promoter region of hepatitis B virus (HBV) genome. The purpose of this study is to compare the gene order of responder and non-responder to interferon therapy in patients with chronic hepatitis B (CHB), so as to evaluate the relationship between IRE mutation and the response to interferon treatment for CHB patients.

Results

Synthetic therapeutic effect is divided into complete response (CR), partial response (PR) and non-response (NR). Among the 62 cases included in this study, 40 cases (64.5%) were in the response group (CR and PR) and 22 (35.5%) cases were in the NR group. Wild type sequence of HBV IRE TTTCACTTTC were found in 35 cases (56.5%), and five different IRE gene sequences. included TTTtACTTTC, TTTCAtTTTC, TTTtAtTTTC, TTTtACTTTt and cTTtACcTTC, were found in 22 cases (35.5%), 1 case (1.6%), 1 case (1.6%), 2 cases (3.2%) and 1 case (1.6%) respectively. There were 41.9%cases (26/62) with forth base C→T mutation, consisted of 32.5% (13/40) cases in response group and 59.1% (13/22) cases in NR group. Among the 35 cases with IRE sequences, there were 67.5% (27/40) cases in response group and 36.4% (8/22) in NR group, and the difference in IRE sequences between two groups was statistic significantly (P = 0.027). The result suggested that there is likely relationship between the forth base mutation (C→T) of IRE region and the response of HBV to Interferon therapy, and this mutation may partially decrease the inhibition effect of interferon on HBV.

Conclusion

The forth base C→T mutation in IRE element of HBV may partially influence the response of Interferon treatment in CHB patients.

rtE218G, a novel hepatitis B virus mutation with resistance to adefovir dipivoxil in patients with chronic hepatitis B

Antiviral therapy is a potentially successful approach for the treatment of patients with Hepatitis B virus (HBV) infection. One antiviral agent is the nucleoside analogue adefovir dipivoxil (ADV). Its efficiency is compromised by the emergence of drug-resistant HBV mutants. Although three major ADV-resistant mutations of HBV are known, rtA181T/V and rtN236T, HBV mutations associated with ADV resistance have not been fully identified. We analyzed DNA sequences that covered a 244 base pair region of the HBV polymerase gene from patients with clinical manifestations of ADV resistance. A novel pattern of amino acid substitutions in HBV polymerase was detected in 26 out of 86 patients. This mutant exhibited a substitution of glycine for glutamic acid at residue 218 (rtE218G). Transient transfection of the HBV replication-competent construct including the rtE218G mutation was performed in HepG2 cells in order to determine the relevance of this mutation to ADV resistance. Phenotypic analyses demonstrated that the rtE218G mutation could independently confer resistance to ADV in vitro, with a 50% inhibitory concentration (IC(50)) 5.5-fold higher than wild-type HBV. RtE218G-mutated HBV also showed a decreased replication capacity in vitro, equal to 87% of wild-type HBV. The present study showed that the rtE218G mutation may be a novel ADV-resistant mutation. Further work will focus on resistance surveillance and cross-resistance analyses, and the molecular mechanisms involved.

Role of ISGF3 in modulating the anti-hepatitis B virus activity of interferon-alpha in vitro

BACKGROUND AND AIM

Although interferon-alpha (IFN-alpha) is an effective treatment for hepatitis B virus (HBV) infection, its precise mechanism of action has not been identified. In this study, we investigated the role of signal transduction pathways in the activation of anti-HBV responses mediated by IFN-alpha.

METHODS

Using an oligo microarray, we found that four genes in the IFN-alpha signal pathway were markedly upregulated by IFN-alpha in human hepatoma cells regardless of whether they had been transfected with a plasmid containing the HBV genome: signal transducers and activators of transcription 1 (STAT1), interferon regulatory factor-9 (IRF-9, also called ISGF3gamma or P48), IFN-alpha-inducible protein 15 (IFI-15) and IFN-alpha-inducible protein 6-16 (IFI-6-16). We also investigated the role of IFN-stimulated gene factor3 (ISGF3) complex in IFN-alpha-mediated anti-HBV responses in human hepatoma cells by measuring the mRNA of the three genes within ISGF3 (STAT1, STAT2 and IRF-9) using semiquantitative reverse-transcription PCR (RT-PCR), and expression of the three proteins by western blot, and the mRNA and protein of dsRNA-dependent protein kinase (PKR).

RESULTS

STAT1, STAT2, IRF-9 and PKR mRNA as well as protein levels were upregulated by IFN-alpha treatment. When cells were pretreated with genistein, STAT1, STAT2 and IRF-9 mRNA levels remained unchanged after IFN-alpha stimulation, but PKR mRNA levels decreased, and the expression of the STAT1, P-STAT2, IRF-9 and PKR proteins decreased. Levels of HBV DNA decreased in the supernatants of cells treated with IFN-alpha, while ISGF3 levels increased. The quantity of HBV DNA remained unchanged by pretreating with genistein.

CONCLUSIONS

These observations suggested that the Janus tyrosine kinase-STAT (JAK-STAT) pathway may play a major role in mediating the effects of IFN-alpha against HBV, and that ISGF3 might be a key factor.

Identification of hepatitis B virus core mutants by PCR-RFLP in chronic hepatitis B patients from Punjab, Pakistan

Chronic hepatitis B virus (HBV) infection remains a major health issue worldwide. Several factors including core gene variation are responsible for the development of chronicity of HBV infection. The present study was designed to identify the variations in the core region of the HBV genome in a local population of chronic hepatitis B patients (n = 57) using a PCR-based restriction fragment length polymorphism (PCR-RFLP) method. Fifty subjects were found to be positive for the presence of HBV DNA. For the core region genotyping, the Ava II and Msp I restriction enzymes were used. Mutations at nucleotide (nt) 2147 and nt 2362 in the HBV genome in the core region for Ava II (A4 type, 74%) and nt 2331 for Msp I (M1 type, 66%) were observed as the most common pattern. These results are different from those of previously reported studies on other populations and thus appear to be unique to the Pakistani population. This type of characterization of core mutants may be useful for the design of vaccines based on viral epitopes that are effective for the Pakistani population. Moreover, these unique genotypic patterns for the HBV core gene might be some of the main factors responsible for understanding the underlying mechanism by which HBV chronicity is developed in the Pakistani population.

Liver-derived cell lines QSG-7701 and HepG2 support different HBV replication patterns

Hepatitis B virus (HBV) infection is currently still a worldwide heath concern. In our study, we compared HBV replication patterns in two liver-derived cell lines, QSG-7701 and HepG2. Viral markers of HBV replication in culture medium and cells were analyzed after transfection of these cells with plasmid pUC18-HBV1.2 into. We showed that QSG-7701 cells could support more stable and a higher level of HBV replication than HepG2 cells. Gene expression profiles of QSG-7701 and HepG2 cells by microarray analysis showed that many genes were differentially expressed between these two cell lines, including those that are related to the HBV life cycle. The global gene expression profile of these two cell types provides some clues to explain how different HBV replication is achieved. QSG-7701 cells offer a new opportunity for basic research on HBV virus-host interactions.