Covalently closed-circular hepatitis B virus DNA reduction with entecavir or lamivudine

Modeling of hepatitis B virus kinetics and accumulation of cccDNA in primary human hepatocytes

Background & Aims

Knowledge about early HBV covalently closed circular DNA (cccDNA) accumulation post infection is lacking. We characterized and mathematically modeled HBV infection kinetics during early infection and treatment in primary human hepatocytes (PHHs).

Methods

PHHs were inoculated with HBV, and infection was monitored with and without treatment with the nucleoside analog entecavir (ETV), the HBV-entry inhibitor Myr-preS1, or both ETV + Myr-preS1. Extracellular HBV DNA (exHBV), total intracellular HBV DNA (inHBV), and cccDNA were frequently measured during the 12 days post inoculation. A multicompartmental mathematical model was developed to explain HBV infection dynamics.

Results

Multiphasic exHBV and inHBV kinetics were overall similar in untreated and Myr-preS1-treated PHHs. In ETV-treated PHHs (either alone or with Myr-preS1), exHBV and inHBV initially declined and did not resurge. ETV-treated cultures had significantly (p=0.002) lower mean cccDNA levels at Day 2 post inoculation (4.3 ± 0.1 vs. 4.7 ± 0.1) and reached plateau slower (5 vs. 2 days) than untreated and Myr-preS1-treated cultures, respectively. Modeling predicts that the recycling of inHBV into cccDNA stops when cccDNA reaches a maximum and HBV secretion changes depending on the concentration of inHBV. Even when initiated at the time of inoculation, ETV did not prevent or eradicate infection but rather blocked inHBV accumulation gradually, reaching 97% efficacy by the end of the 12-day experiment and resulting in an average 44% slower cccDNA accumulation.

Conclusions

The study provides insight into the interrelationships and dynamics of cccDNA accumulation, inHBV accumulation, and secretion of exHBV containing particles. Although kinetics and modeling support the conclusion that the level of cccDNA in the cell is regulated, the mechanisms that determine HBV capsid secretion vs. recycling to the nucleus for cccDNA accumulation require further investigation.

Impact and implications

Using primary human hepatocytes (PHHs), we characterize early HBV kinetics post infection. HBV-infected PHH were treated with an entry inhibitor to characterize the accumulation of intracellular and extracellular HBV DNA and the nuclear episomal viral genome called covalently closed circular DNA (cccDNA) in the absence of HBV spread. Kinetic and mathematical modeling in PHHs confirms that the replication inhibitor, entecavir, strongly blocks intracellular HBV DNA accumulation, which also slowed the accumulation of cccDNA. However, modeling indicates that effects on cccDNA accumulation are not directly determined by intracellular HBV DNA levels, supporting the conclusion that cccDNA levels within the cell are regulated in some yet-to-be-elucidated manner.

AAV-based vectors for human diseases modeling in laboratory animals

The development of therapeutic drugs and vaccines requires the availability of appropriate model animals that replicate the pathogenesis of human diseases. Both native and transgenic animals can be utilized as models. The advantage of transgenic animals lies in their ability to simulate specific properties desired by researchers. However, there is often a need for the rapid production of transgenic animal models, especially in situations like a pandemic, as was evident during COVID-19. An important tool for transgenesis is the adeno-associated virus. The genome of adeno-associated virus serves as a convenient expression cassette for delivering various DNA constructs into cells, and this method has proven effective in practice. This review analyzes the features of the adeno-associated virus genome that make it an advantageous vector for transgenesis. Additionally, examples of utilizing adeno-associated viral vectors to create animal models for hereditary, oncological, and viral human diseases are provided.

Characterization of Hepatitis B Virus Transcripts in Chronically HBV-Infected Chimpanzees and Patients Treated with ARC-520 siRNA Demonstrates Transcriptional Silencing of cccDNA

Full-length hepatitis B virus (HBV) transcripts of chimpanzees and patients treated with multidose (MD) HBV siRNA ARC-520 and entecavir (ETV) were characterized by single-molecule real-time (SMRT) sequencing, identifying multiple types of transcripts with the potential to encode HBx, HBsAg, HBeAg, core, and polymerase, as well as transcripts likely to be derived from dimers of dslDNA, and these differed between HBeAg-positive (HBeAg+) and HBeAg-negative (HBeAg-) individuals. HBV transcripts from the last follow-up ~30 months post-ARC-520 treatment were categorized from one HBeAg+ (one of two previously highly viremic patients that became HBeAg- upon treatment and had greatly reduced cccDNA products) and four HBeAg- patients. The previously HBeAg+ patient received a biopsy that revealed that he had 3.4 copies/cell cccDNA (two to three orders of magnitude more cccDNA than HBeAg- chimpanzees) but expressed primarily truncated X and HBsAg from iDNA, like two patients that were HBeAg- at the start of the study and had one copy/cell cccDNA. No HBV transcripts were detected in two other HBeAg- patients that had ~0.3 copies/cell cccDNA, one of which had seroconverted for HBsAg. The paucity of cccDNA-derived transcripts in the presence of high cccDNA demonstrates the transcriptional silencing of HBV following MD siRNA treatment with ETV.

Perioperative remedial antiviral therapy in hepatitis B virus-related hepatocellular carcinoma resection: How to achieve a better outcome

BACKGROUND

Although the benefits of antiviral therapy for hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) have been proven, researchers have not confirmed the differences in patient outcomes between patients who received preoperative antiviral therapy for a period of time (at least 24 wk) and patients who received remedial antiviral therapy just before radical resection for HBV-related HCC.

AIM

To investigate the efficacy of perioperative remedial antiviral therapy in patients with HBV-related HCC.

METHODS

A retrospective study of patients who underwent radical resection for HBV-related HCC at the First Affiliated Hospital of Xi'an Jiaotong University from January 2016 to June 2019 was conducted. Considering the history of antiviral therapy, patients were assigned to remedial antiviral therapy and preoperative antiviral therapy groups.

RESULTS

Kaplan-Meier analysis revealed significant differences in overall survival (P < 0.0001) and disease-free survival (P = 0.035) between the two groups. Multivariate analysis demonstrated that a history of preoperative antiviral treatment was independently related to improved survival (hazard ratio = 0.27; 95% confidence interval: 0.08-0.88; P = 0.030).

CONCLUSION

In patients with HBV-related HCC, it is ideal to receive preoperative long-term antiviral therapy, which helps patients tolerate more extensive hepatectomy; however, remedial antiviral therapy, which reduces preoperative HBV-DNA levels to less than 4 Log10 copies DNA/mL, can also result in improved outcomes.

Classifying hepatitis B therapies with insights from covalently closed circular DNA dynamics

The achievement of a functional cure for chronic hepatitis B (CHB) remains limited to a minority of patients treated with currently approved drugs. The primary objective in developing new anti-HBV drugs is to enhance the functional cure rates for CHB. A critical prerequisite for the functional cure of CHB is a substantial reduction, or even eradication of covalently closed circular DNA (cccDNA). Within this context, the changes in cccDNA levels during treatment become as a pivotal concern. We have previously analyzed the factors influencing cccDNA dynamics and introduced a preliminary classification of hepatitis B treatment strategies based on these dynamics. In this review, we employ a systems thinking perspective to elucidate the fundamental aspects of the HBV replication cycle and to rationalize the classification of treatment strategies according to their impact on the dynamic equilibrium of cccDNA. Building upon this foundation, we categorize current anti-HBV strategies into two distinct groups and advocate for their combined use to significantly reduce cccDNA levels within a well-defined timeframe.

Rapid and Reliable Protein-Free HBV DNA Extraction and Sensitive Branched DNA Southern Blot Assay

HBV covalently closed circular DNA (cccDNA) plays an important role in the persistence of hepatitis B virus (HBV) infection by serving as the template for transcription of viral RNAs. To cure HBV infection, it is expected that cccDNA needs either to be eliminated or silenced. Hence, precise cccDNA quantification is essential. Sample preparation is crucial to specifically detect cccDNA. Southern blot is regarded as the "gold standard" for specific cccDNA detection but lacks sensitivity. Here, we describe a rapid and reliable modified kit-based, HBV protein-free DNA extraction method as well as a novel enhanced sensitivity Southern blot that uses branched DNA technology to detect HBV DNA in cell culture and liver tissue samples. It is useful for both HBV molecular biology and antiviral research.

Novel Approaches to Inhibition of HBsAg Expression from cccDNA and Chromosomal Integrants: A Review

Hepatitis B virus (HBV) is a widely prevalent liver infection that can cause acute or chronic hepatitis. Although current treatment modalities are highly effective in the suppression of viral levels, they cannot eliminate the virus or achieve definitive cure. This is a consequence of the complex nature of HBV-host interactions. Major challenges to achieving sustained viral suppression include the presence of a high viral burden from the HBV DNA and hepatitis B surface antigen (HBsAg), the presence of reservoirs for HBV replication and antigen production, and the HBV-impaired innate and adaptive immune response of the host. Those therapeutic methods include cell entry inhibitors, HBsAg inhibitors, gene editing approaches, immune-targeting therapies and direct inhibitors of covalently closed circular DNA (cccDNA). Novel approaches that target these key mechanisms are now being studied in preclinical and clinical phases. In this review article, we provide a comprehensive review on mechanisms by which HBV escapes elimination from current treatments, and highlight new agents to achieve a definitive HBV cure.

Hepatocellular Carcinoma and Hepatitis: Advanced Diagnosis and Management with a Focus on the Prevention of Hepatitis B-Related Hepatocellular Carcinoma

Though the world-wide hepatitis B virus (HBV) vaccination program has been well completed for almost thirty years in many nations, almost HBV-related hepatocellular carcinoma (HCC) occurs in unvaccinated middle-aged and elderly adults. Apparently, treating 80% of qualified subjects could decrease HBV-related mortality by 65% in a short period. Nevertheless, globally, only 2.2% of CHB patients undergo antiviral therapy. The HBV markers related to HCC occurrence and prevention are as follows: the HCC risk is the highest at a baseline of HBV DNA of 6-7 log copies/mL, and it is the lowest at a baseline of an HBV DNA level of >8 log copies/mL and ≤4 log copies/mL (parabolic, and not linear pattern). The titer of an HBV core-related antigen (HBcrAg) reflecting the amount of HBV covalently closed circular DNA (ccc DNA) in the liver is related to HCC occurrence. The seroclearance of HBs antigen (HBsAg) is more crucial than HBV DNA negativity for the prevention of HCC. In terms of the secondary prevention of hepatitis B-related HCC involving antiviral therapies with nucleos(t)ide analogues (NAs), unsolved issues include the definition of the immune-tolerant phase; the optimal time for starting antiviral therapies with NAs; the limits of increased aminotransferase (ALT) levels as criteria for therapy in CHB patients; the normalization of ALT levels with NAs and the relation to the risk of HCC; and the relation between serum HBV levels and the risk of HCC. Moreover, the first-line therapy with NAs including entecavir (ETV), tenofovir disoproxil fumarate (TDF), and tenofovir alafenamide (TAF) remains to be clarified. Discussed here, therefore, are the recent findings of HBV markers related to HCC occurrence and prevention, unsolved issues, and the current secondary antiviral therapy for the prevention of HBV-related HCC.

Early intrahepatic recurrence of HBV infection in liver transplant recipients despite antiviral prophylaxis

Background & Aims

Prophylaxis with nucleos(t)ide analogues (NUCs) and hepatitis B immunoglobulin (HBIG) has decreased the rate of HBV recurrence after orthotopic liver transplantation (OLT), but the duration of this prophylaxis remains debated. Our aim was to investigate the recurrence of both intrahepatic and serum HBV markers after OLT in patients receiving long-term NUC and HBIG prophylaxis.

Methods

A total of 31 HBV-positive patients benefiting from OLT were prospectively enrolled in five French centres between 2012 and 2015. Tissue samples from the native liver, liver reperfusion biopsy, and 12-month post-OLT (M12) biopsy were collected. Intrahepatic HBV markers were quantified using Droplet Digital PCR. Serum hepatitis B core-related antigen (HBcrAg) and HBsAg were quantified using the Lumipulse platform.

Results

Among the 31 patients, 26 were HBeAg negative and 28 had undetectable serum HBV DNA at OLT. All patients received HBIG and NUC after OLT, and serum HBV DNA was undetectable at M12. Of the 27 available native livers, 26 had detectable total HBV DNA (median, 0.045 copies/cell), 21 were positive for cccDNA (0.001 copies/cell), and 19 were positive for 3.5-kb HBV RNA (0.0004 copies/cell). Among the 14 sequential reperfusion and M12 biopsies, seven were positive for HBV markers on the reperfusion sampling, and six of them were also positive at M12. Of the 27 patients with available serum samples at M12, eight were positive for HBcrAg and five were positive for HBsAg by ultrasensitive quantification, although they were negative by conventional techniques. Overall, among the 17 patients having a matched biopsy and serum sample at M12, only one had undetectable HBV markers in both the liver and serum.

Conclusions

Our results demonstrate a very early detection of viral genome in the graft and intrahepatic viral recurrence despite NUC and HBIG prophylaxis.

Clinical Trials Registration

This study is registered at ClinicalTrials.gov (NCT02602847).

Impact and Implications

In this work, we show that, despite the recommended prophylaxis based on NUC and HBIG, HBV can infect the new liver very rapidly after transplantation. Twelve months after transplantation, the majority of patients had at least one HBV marker detected in either serum or the liver. Therefore, our results demonstrate early intrahepatic viral recurrence despite NUC and HBIG therapy and underline the importance of an optimal patient compliance to the antiviral prophylaxis to prevent viral rebound.

Drug Discovery Study Aimed at a Functional Cure for HBV

Hepatitis B virus (HBV) causes acute and, most importantly, chronic hepatitis B worldwide. Antiviral treatments have been developed to reduce viral loads but few patients with chronic hepatitis B (CHB) achieve a functional cure. The development of new therapeutic agents is desirable. Recently, many novel agents have been developed, including drugs targeting HBV-DNA and HBV-RNA. This review provides an overview of the developmental status of these drugs, especially direct acting antiviral agents (DAAs). Serological biomarkers of HBV infection are essential for predicting the clinical course of CHB. It is also important to determine the amount and activity of covalently closed circular DNA (cccDNA) in the nuclei of infected hepatocytes. Hepatitis B core-associated antigen (HBcrAg) is a new HBV marker that has an important role in reflecting cccDNA in CHB, because it is associated with hepatic cccDNA, as well as serum HBV DNA. The highly sensitive HBcrAg (iTACT-HBcrAg) assay could be a very sensitive HBV activation marker and an alternative to HBV DNA testing for monitoring reactivation. Many of the drugs currently in clinical trials have shown efficacy in reducing hepatitis B surface antigen (HBsAg) levels. Combination therapies with DAAs and boost immune response are also under development; finding the best combinations will be important for therapeutic development.

DNA Repair Factor Poly(ADP-Ribose) Polymerase 1 Is a Proviral Factor in Hepatitis B Virus Covalently Closed Circular DNA Formation

The biogenesis and eradication of HBV cccDNA have been a research priority in recent years. In this study, we identified the DNA repair factor PARP1 as a host factor required for the HBV de novo cccDNA formation.

Prediction for HBsAg seroconversion in children with chronic hepatitis B

Background

To establish a prediction of HBsAg seroconversion in children with chronic hepatitis B (CHB), so as to help clinicians to choose therapeutic strategy.

Methods

A total of 63 children with HBeAg-positive CHB aged 1 to 17 years, who admitted to the fifth medical center of Chinese PLA general hospital and treated with interferon α (IFNα) 48 weeks were enrolled, the clinical data were measured. Based on the results of HBsAg seroconversion (HBsAg < 0.05 IU/mL and anti-HBsAg > 10 IU/L) at week 48, the patients were divided into HBsAg seroconversion (S) group and non-HBsAg seroconversion (NS) group. Multivariate COX regression was used to identify the impact factors associated with HBsAg seroconversion. A novel prediction index was established and the area under the receiver operating characteristic curve (AUROC) was used to assess the prediction for HBsAg seroconversion.

Results

The 63 patients were divided into S group (20.6%, 13/63) and NS group (79.4%, 50/63). Univariate and multivariate analysis identified age, baseline intrahepatic cccDNA and serum HBsAg levels were independent impact factors for HBsAg seroconversion. Intrahepatic cccDNA was positively correlated with serum HBsAg (r = 0.464, p = 0.000). AUROC of HBV cccDNA was 0.83 (95% CI 0.71 to 0.95) and AUROC of baseline HBsAg was 0.77 (95% CI 0.61 to 0.92). Intrahepatic cccDNA ≤ 0.08 log₁₀ copies/10⁶ cell is regarded as cutoff value, the positive predictive value(PPV) and negative predictive value(NPV) for HBsAg seroconversion were 86.8% and 60.0%, respectively, with a sensitivity of 92.0% and specificity of 56.2%. HBsAg ≤ 3.68 log₁₀ IU/mL is used as cut off value, the PPV and NPV for HBsAg seroconversion were 91.2% and 56.3%, respectively; the sensitivity and specificity was 86.0% of 69.2%, respectively. There was no statistical difference between them for predicting HBsAg seroconversion (p = 0.146).

Conclusions

HBsAg seroconversion can be predicted by the baseline serum HBsAg or intrahepatic cccDNA in children with CHB. Using the index, clinicians can choose more reasonable therapeutic strategy and reduce the waste of medical resources.

Serum HBV RNA correlated with intrahepatic cccDNA more strongly than other HBV markers during peg-interferon treatment

BACKGROUND

Serum hepatitis B virus RNA (HBV RNA) has been reported to be a surrogate marker of intrahepatic cccDNA during nucleos(t)ide analogs therapy. However, in HBeAg-positive patients treated with peg-interferon (peg-IFN), whether HBV RNA is superior to other HBV markers in reflecting cccDNA profile is still unclear.

METHODS

Serum HBV RNA, HBcrAg, HBV DNA, and HBsAg were longitudinally assessed among 30 HBeAg-positive patients during 48-week peg-IFN treatment. Besides, intrahepatic cccDNA was detected at baseline and week 48 respectively. Then, the individual correlations between HBV RNA, HBcrAg, HBV DNA, HBsAg, and cccDNA were statistically analyzed.

RESULTS

HBV RNA levels decreased more rapidly in patients with HBeAg seroconversion than those without HBeAg seroconversion. Among all patients, cccDNA correlated better with HBV RNA than with HBcrAg, HBV DNA, and HBsAg at baseline. After 48 weeks peg-IFN treatment, cccDNA still correlated more strongly with HBV RNA than other HBV markers. Further analysis indicated that in patients with HBeAg seroconversion cccDNA strongly correlated with HBV RNA and HBcrAg, whereas not correlate with HBV DNA and HBsAg. While in patients without HBeAg seroconversion, cccDNA highly correlated with HBV RNA and HBV DNA, moderately correlated with HBcrAg, and not correlated with HBsAg.

CONCLUSION

Compared to HBcrAg, HBV DNA, and HBsAg, serum HBV RNA correlated more strongly with intrahepatic cccDNA levels before and after 48-week peg-IFN treatment. The level of serum HBV RNA may be a superior surrogate marker in reflecting the intrahepatic cccDNA profile in HBeAg-positive patients during peg-IFN treatment. Trial registration ClinicalTrials, NCT03546530. Registered 1 January 2015. https://clinicaltrials.gov/ct2/results?cond=&term=NCT03546530 .

cccDNA Maintenance in Chronic Hepatitis B - Targeting the Matrix of Viral Replication

Chronic hepatitis B is a numerically important cause of cirrhosis and hepatocellular carcinoma, despite an effective prophylactic vaccine and well-tolerated and effective oral antivirals. Both the incapacity of the immune system to clear hepatitis B virus (HBV) infection and the unique replication strategies adopted by HBV are considered key determinants of HBV chronicity. In this regard, the formation of the HBV DNA minichromosome, the covalently closed circular DNA (cccDNA), in the nucleus of infected hepatocytes, is essential not only for the production of all viral proteins but also for HBV persistence even after long-term antiviral therapy. Licensed polymerase inhibitors target the HBV reverse transcriptase activity, control the disease with long-term therapy but fail to eliminate the cccDNA. Consequently, the production of viral RNAs and proteins, including the hepatitis B surface antigen (HBsAg), is not abolished. Novel therapeutic efforts that are in the pipeline for early clinical trials explore novel targets and molecules. Such therapeutic efforts focus on achieving a functional cure, which is defined by the loss of HBsAg and undetectable HBV DNA levels in serum. Since a true cure of HBV infection requires the elimination of the cccDNA from infected cells, comprehension of the mechanisms implicated in cccDNA biogenesis, regulation and stability appears necessary to achieve HBV eradication. In this review, we will summarize the state of knowledge on cccDNA metabolism, focusing on insights suggesting potential weak points of the cccDNA that may be key for the development of therapeutic approaches and design of clinical trials aiming at lowering cccDNA loads and activity.

Efficacy of a combination of HBV RNA and HBeAg in predicting HBeAg seroconversion in patients treated with entecavir for 144 weeks

BACKGROUND

In some previous studies, serum hepatitis B virus RNA (HBV RNA) was proposed as an HBV viral marker during therapy. However, the dynamic change of HBV RNA, the correlation of HBV RNA with cccDNA, and the combination of HBV RNA with known HBV markers in predicting entecavir (ETV) treatment outcome in the same cohort are rarely reported.

METHODS

A total of 111 HBeAg-positive patients were enrolled in our study. The dynamic changes of serum HBV RNA and the correlation of HBV RNA with other HBV markers were investigated in the early treatment period of 144-week ETV treatment. Intrahepatic cccDNA was detected at baseline and week 48. Receiver operating characteristic analyses were used to identify HBV RNA levels associated with HBeAg seroconversion.

RESULTS

The serum HBV RNA levels decreased more rapidly in patients with HBeAg seroconversion than those without HBeAg seroconversion. The levels of HBV RNA decreased slower compared with the serum HBV DNA, irrespective of whether the patients achieved HBeAg seroconversion or not. Although the serum HBV RNA was positively correlated with cccDNA at baseline among all patients, no significant correlation was observed in the patients with HBeAg seroconversion at week 48 (r=0.094, P=0.588). The area under the receiver operating characteristic (AUROC) of HBV RNA and HBeAg at week 24 was 0.754 and 0.800, respectively. The AUROC of the HBV RNA and HBeAg combination had a higher value (AUROC=0.821).

CONCLUSIONS

The level of HBV RNA at week 24 was a powerful predictor of HBeAg seroconversion in HBeAg-positive patients after 144-week ETV treatment, while the combination of HBV RNA and HBeAg was superior to HBV RNA alone in predicting HBeAg seroconversion.

Conservation and variability of hepatitis B core at different chronic hepatitis stages

BACKGROUND

Since it is currently not possible to eradicate hepatitis B virus (HBV) infection with existing treatments, research continues to uncover new therapeutic strategies. HBV core protein, encoded by the HBV core gene (HBC), intervenes in both structural and functional processes, and is a key protein in the HBV life cycle. For this reason, both the protein and the gene could be valuable targets for new therapeutic and diagnostic strategies. Moreover, alterations in the protein sequence could serve as potential markers of disease progression.

AIM

To detect, by next-generation sequencing, HBC hyper-conserved regions that could potentially be prognostic factors and targets for new therapies.

METHODS

Thirty-eight of 45 patients with chronic HBV initially selected were included and grouped according to liver disease stage [chronic hepatitis B infection without liver damage (CHB, n = 16), liver cirrhosis (LC, n = 5), and hepatocellular carcinoma (HCC, n = 17)]. HBV DNA was extracted from patients' plasma. A region between nucleotide (nt) 1863 and 2483, which includes HBC, was amplified and analyzed by next-generation sequencing (Illumina MiSeq platform). Sequences were genotyped by distance-based discriminant analysis. General and intergroup nt and amino acid (aa) conservation was determined by sliding window analysis. The presence of nt insertion and deletions and/or aa substitutions in the different groups was determined by aligning the sequences with genotype-specific consensus sequences.

RESULTS

Three nt (nt 1900-1929, 2249-2284, 2364-2398) and 2 aa (aa 117-120, 159-167) hyper-conserved regions were shared by all the clinical groups. All groups showed a similar pattern of conservation, except for five nt regions (nt 1946-1992, 2060-2095, 2145-2175, 2230-2250, 2270-2293) and one aa region (aa 140-160), where CHB and LC, respectively, were less conserved (P < 0.05). Some group-specific conserved regions were also observed at both nt (2306-2334 in CHB and 1935-1976 and 2402-2435 in LC) and aa (between aa 98-103 in CHB and 28-30 and 51-54 in LC) levels. No differences in insertion and deletions frequencies were observed. An aa substitution (P79Q) was observed in the HCC group with a median (interquartile range) frequency of 15.82 (0-78.88) vs 0 (0-0) in the other groups (P < 0.05 vs CHB group).

CONCLUSION

The differentially conserved HBC and HBV core protein regions and the P79Q substitution could be involved in disease progression. The hyper-conserved regions detected could be targets for future therapeutic and diagnostic strategies.

Host-Directed Antiviral Therapy

Antiviral drugs have traditionally been developed by directly targeting essential viral components. However, this strategy often fails due to the rapid generation of drug-resistant viruses. Recent genome-wide approaches, such as those employing small interfering RNA (siRNA) or clustered regularly interspaced short palindromic repeats (CRISPR) or those using small molecule chemical inhibitors targeting the cellular "kinome," have been used successfully to identify cellular factors that can support virus replication. Since some of these cellular factors are critical for virus replication, but are dispensable for the host, they can serve as novel targets for antiviral drug development. In addition, potentiation of immune responses, regulation of cytokine storms, and modulation of epigenetic changes upon virus infections are also feasible approaches to control infections. Because it is less likely that viruses will mutate to replace missing cellular functions, the chance of generating drug-resistant mutants with host-targeted inhibitor approaches is minimized. However, drug resistance against some host-directed agents can, in fact, occur under certain circumstances, such as long-term selection pressure of a host-directed antiviral agent that can allow the virus the opportunity to adapt to use an alternate host factor or to alter its affinity toward the target that confers resistance. This review describes novel approaches for antiviral drug development with a focus on host-directed therapies and the potential mechanisms that may account for the acquisition of antiviral drug resistance against host-directed agents.

Isolated Anti-HBc: Significance and Management

Hepatitis B virus (HBV) infection is prevalent worldwide and is associated with dramatic levels of morbidity and mortality. Isolated anti-HBc (IAHBc) is a particular serological pattern that is commonly found in immunocompromised patients. There is ongoing debate regarding the management of patients with IAHBc. Herein, we summarize the current guidelines and the newest evidence. The frequency of IAHBc is variable, with a higher prevalence in some populations, such as persons living with HIV and others immunocompromised patients. The risk of HBV reactivation depends on host factors (including immunosuppression) and viral factors. It is now well established that immunocompromised patients can be classified into three groups for risk according to the type of immunosuppression and/or treatment. In patients at high risk, HBV therapy has to be considered systematically. In patients at moderate risk, the decision is based on the level of HBV DNA (preemptive treatment or monitoring and vaccination). In patients with low risk, HBV vaccination is another possible approach, although further studies are needed to assess the type of preemptive strategy.

Significance and Management of Isolated Hepatitis B Core Antibody (Anti-HBc) in HIV and HCV: Strategies in the DAA Era

PURPOSE OF REVIEW

The purpose of this review is to summarize the prevalence and clinical implications of the isolated anti-HBc serologic profile in HIV-infected individuals. We highlight the rare but important issue of HBV reactivation in the setting of HCV therapy and describe an approach to management.

RECENT FINDINGS

The isolated anti-HBc pattern, a profile that most often indicates past exposure to HBV with waning anti-HBs immunity, is found commonly in HIV-infected individuals, particularly those with HCV. Some large cohort studies demonstrate an association with advanced liver disease, while others do not. Conversely, meta-analyses have found an association between occult HBV infection (a component of the isolated anti-HBc pattern) and advanced liver disease and hepatocellular carcinoma in HIV-uninfected individuals. In HIV-uninfected individuals with anti-HBc positivity, HBV reactivation has been reported in patients receiving HCV therapy. This phenomenon is likely the result of disinhibition of HBV with HCV eradication. In HIV-infected patients, the long-term liver outcomes associated with the isolated anti-HBc pattern remain to be fully elucidated, supporting the need for large cohort studies with longitudinal follow-up. HBV reactivation during HCV DAA therapy has been well-described in HIV-uninfected cohorts and can inform algorithms for the screening and management of the isolated anti-HBc pattern in this population.

Distinct notch signaling expression patterns between nucleoside and nucleotide analogues treatment for hepatitis B virus infection

Nucleos(t)ide analogues therapies are currently approved for the treatment of chronic hepatitis B virus (HBV) infection, which effectively suppress HBV replication and correlate with the anti-HBV-specific immune response. Notch signaling serves pleiotropic roles in the immune system that also contribute to virus-specific immunity. In this study, we assessed Notch signal-related gene expression after administrating nucleoside or nucleotide analogues to HBV-replicating cells and clinical liver tissues. We found distinct Notch signaling expression patterns under nucleos(t)ide analogues therapies, with high expression for nucleotide analogues (adefovir pivoxil or tenofovir disoproxil fumarate) and low expression for nucleoside analogues (lamivudine or entecavir) in the presence of HBV infection. Furthermore, activation of mammalian target of rapamycin (mTOR)-Akt (Ser473) phosphorylation was also observed after nucleotide analogue treatment. In conclusion, nucleoside and nucleotide analogues displayed different patterns of Notch signaling activity under HBV infection, and the induction of mTORC2-Akt (Ser473) phosphorylation may contribute to nucleotide analogues-mediated Notch signaling activation.

Hepatitis B virus (HBV)-infected patients with low hepatitis B surface antigen and high hepatitis B core-related antigen titers have a high risk of HBV-related hepatocellular carcinoma

AIM

Although the viral markers hepatitis B surface antigen (HBsAg) and hepatitis B core-related antigen (HbcrAg) could reflect intrahepatic hepatitis B virus (HBV) replication activity and constitute important biomarkers for hepatocellular carcinoma (HCC), the value of using these two markers in combination for assessing HCC risk has not been clarified in detail.

METHODS

Four hundred and forty-nine consecutive patients with chronic HBV infection were included in the study and the association of HBsAg and HBcrAg with HCC risk was investigated cross-sectionally, as well as longitudinally.

RESULTS

When the high value cut-offs of HBsAg and HBcrAg were defined as 3.0 log IU/mL and 3.0 log U/mL, respectively, patients with a history of HCC were found frequently in the low HBsAg group (P = 0.002) and high HBcrAg group (P < 0.001). When HBsAg and HBcrAg were combined, an HCC history was most frequent in the subset with low HBsAg and high HBcrAg, among the HBeAg-negative patients (odds ratio [OR], 7.83; P < 0.001), irrespective of nucleos(t) ide analogue (NA) therapy (NA: OR, 4.76; P < 0.001; non-NA: OR, 9.60; P < 0.001). In a longitudinal analysis of the subsequent development of HCC, carried out on the 338 patients without an HCC history at enrollment, HCC developed significantly more frequently in the low HBsAg/high HBcrAg group (P = 0.005).

CONCLUSIONS

Patients with low HBsAg/high HBcrAg values are at high risk of developing HBV-related HCC, according to this cross-sectional and longitudinal analysis, indicating that the combination of HBsAg and HBcrAg values is an excellent biomarker for assessing HCC risk.

Very slow decline of hepatitis B virus surface antigen and core related antigen in chronic hepatitis B patients successfully treated with nucleos(t)ide analogues

We investigated the decline of hepatitis B virus surface antigen (HBsAg) and core related antigen (HBcrAg) in chronic hepatitis B patients sussessfully treated with nucleos(t)ide analogues. In patients with plasma viral suppression, the baseline median levels of HBsAg and HBcrAg were 3.1 and 3.0 log U/mL, respectively. The levels in naïve patients were 4.2 and 3.6 log U/mL for HBsAg and HBcrAg, respectively. No significant decline was observed in patients with viral suppression within a year period. A low reduction was observed during the first months after treatment initiation, especially regarding HBcrAg. The dynamics of these antigens after viral suppression should be further investigated.

Peretinoin, an Acyclic Retinoid, Inhibits Hepatitis B Virus Replication by Suppressing Sphingosine Metabolic Pathway In Vitro

Hepatocellular carcinoma (HCC) frequently develops from hepatitis C virus (HCV) and hepatitis B virus (HBV) infection. We previously reported that peretinoin, an acyclic retinoid, inhibits HCV replication. This study aimed to examine the influence of peretinoin on the HBV lifecycle. HBV-DNA and covalently closed circular DNA (cccDNA) were evaluated by a qPCR method in HepG2.2.15 cells. Peretinoin significantly reduced the levels of intracellular HBV-DNA, nuclear cccDNA, and HBV transcript at a concentration that did not induce cytotoxicity. Conversely, other retinoids, such as 9-cis, 13-cis retinoic acid (RA), and all-trans-retinoic acid (ATRA), had no effect or rather increased HBV replication. Mechanistically, although peretinoin increased the expression of HBV-related transcription factors, as observed for other retinoids, peretinoin enhanced the binding of histone deacetylase 1 (HDAC1) to cccDNA in the nucleus and negatively regulated HBV transcription. Moreover, peretinoin significantly inhibited the expression of SPHK1, a potential inhibitor of HDAC activity, and might be involved in hepatic inflammation, fibrosis, and HCC. SPHK1 overexpression in cells cancelled the inhibition of HBV replication induced by peretinoin. This indicates that peretinoin activates HDAC1 and thereby suppresses HBV replication by inhibiting the sphingosine metabolic pathway. Therefore, peretinoin may be a novel therapeutic agent for HBV replication and chemoprevention against HCC.

Mechanism of Hepatitis B Virus Persistence in Hepatocytes and Its Carcinogenic Potential

Liver disease associated with persistent infection with hepatitis B virus (HBV) continues to be a major health problem of global impact. Despite the existence of an effective vaccine, at least 240 million people are chronically infected worldwide, and are at risk of developing liver cirrhosis and hepatocellular carcinoma. Although chronic HBV infection is considered the main risk factor for liver cancer development, the molecular mechanisms determining persistence of infection and long-term pathogenesis are not fully elucidated but appear to be multifactorial. Current therapeutic regimens based on the use of polymerase inhibitors can efficiently suppress viral replication but are unable to eradicate the infection. This is due both to the persistence of the HBV genome, which forms a stable minichromosome, the covalently closed circular DNA (cccDNA), in the nucleus of infected hepatocytes, as well as to the inability of the immune system to efficiently counteract chronic HBV infection. In this regard, the unique replication strategies adopted by HBV and viral protein production also appear to contribute to infection persistence by limiting the effectiveness of innate responses. The availability of improved experimental systems and molecular techniques have started to provide new information about the complex network of interactions that HBV establishes within the hepatocyte and that may contribute to disease progression and tumor development. Thus, this review will mostly focus on events involving the hepatocyte: the only target cell where HBV infection and replication take place.

The Role of cccDNA in HBV Maintenance

Chronic hepatitis B virus (HBV) infection continues to be a major health burden worldwide; it can cause various degrees of liver damage and is strongly associated with the development of liver cirrhosis and hepatocellular carcinoma. The molecular mechanisms determining HBV persistence are not fully understood, but these appear to be multifactorial and the unique replication strategy employed by HBV enables its maintenance in infected hepatocytes. Both the stability of the HBV genome, which forms a stable minichromosome, the covalently closed circular DNA (cccDNA) in the hepatocyte nucleus, and the inability of the immune system to resolve chronic HBV infection are believed to be key mechanisms of HBV chronicity. Since a true cure of HBV requires clearance of intranuclear cccDNA from infected hepatocytes, understanding the mechanisms involved in cccDNA biogenesis, regulation and stability is mandatory to achieve HBV eradication. This review will summarize the state of knowledge on these mechanisms including the impact of current treatments on the cccDNA stability and activity. We will focus on events challenging cccDNA persistence in dividing hepatocytes.

Reduction of covalently closed circular DNA with long-term nucleos(t)ide analogue treatment in chronic hepatitis B

BACKGROUND AND AIMS

Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA), a mini-chromosome essential for HBV replication, is supposed to be resistant to nucleos(t)ide analogue treatment. We investigated the effect of long-term nucleos(t)ide analogue treatment on cccDNA.

METHODS

Among 129 patients who had been enrolled in previous international nucleos(t)ide analogue clinical trials and had liver biopsies at baseline and one year after treatment, we recruited 43 patients on long-term continuous treatment for 72 to 145months for a third liver biopsy. Serum HBV DNA, hepatitis B surface antigen (HBsAg) levels, total intrahepatic HBV DNA (ihHBV DNA), cccDNA, HBV pregenomic RNA (pgRNA) as well as histologic changes were examined.

RESULTS

At the time of the third biopsy, serum HBV DNA levels were undetectable in all but one patient. The median levels of HBsAg, ihHBV DNA, and cccDNA were 2.88logIU/ml, 0.03copies/cell, and 0.01copies/cell, respectively. Compared to baseline levels, there was reduction of HBsAg levels by 0.54log (71.46%), ihHBV DNA levels by 2.81log (99.84%), and cccDNA levels by 2.94log (99.89%), with 49% having cccDNA levels below the detection limit. One patient had undetectable HBsAg. The median pgRNA level, measured only in the third biopsy, was 0.021copies/cell, with 40% of patients having undetectable pgRNA.

CONCLUSIONS

Long-term nucleos(t)ide analogue treatment induced marked depletion of cccDNA in the majority of patients while serum HBsAg levels, though reduced, were detectable in all but one patient. Whether cccDNA depletion is sustained and associated with better patient outcome requires further study.

LAY SUMMARY

It is generally presumed that a form of hepatitis B virus DNA, called covalently closed circular DNA (cccDNA), which hides inside the nuclei of liver cells of patients with chronic hepatitis B, cannot be reduced by antiviral treatment. The present study showed that with prolonged treatment (median period 126months), cccDNA can be markedly reduced, with 49% of liver biopsies having undetectable cccDNA. This suggests that viral replication capacity would be very low after prolonged antiviral treatment.

Metabolism and function of hepatitis B virus cccDNA: Implications for the development of cccDNA-targeting antiviral therapeutics

Persistent hepatitis B virus (HBV) infection relies on the stable maintenance and proper functioning of a nuclear episomal form of the viral genome called covalently closed circular (ccc) DNA. One of the major reasons for the failure of currently available antiviral therapeutics to achieve a cure of chronic HBV infection is their inability to eradicate or inactivate cccDNA. In this review article, we summarize our current understanding of cccDNA metabolism in hepatocytes and the modulation of cccDNA by host pathophysiological and immunological cues. Perspectives on the future investigation of cccDNA biology, as well as strategies and progress in therapeutic elimination and/or transcriptional silencing of cccDNA through rational design and phenotypic screenings, are also discussed. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."