Revisiting the Natural History of Chronic HBV Infection

Recent Progress and Future Prospective in HBV Cure by CRISPR/Cas

Hepatitis B virus (HBV) infection remains an important issue of global public health. Although current antiviral therapy has dramatically reduced the mortality and morbidity of chronic hepatitis B (CHB), it fails to cure it. Rebound viremia often occurs after stopping antiviral therapy. Persistent HBV covalently closed circular DNA (cccDNA) and integrated DNA under antiviral therapy form the major barrier to eradication of HBV infection. CRISPR-mediated genome editing has emerged as a promising therapeutic approach to specifically destroy persistent HBV genomes, both cccDNA and integrated DNA, for HBV cure. However, the cleavage of integrated HBV DNA by CRISPR-Cas9 will cause double-strand break (DSB) of host genome, raising a serious safety concern about genome instability and carcinogenesis. The newly developed CRISPR-derived base editors (BEs), which fuse a catalytically disabled nuclease with a nucleobase deaminase enzyme, can be used to permanently inactivate HBV genome by introducing irreversible point mutations for generation of premature stop codons without DSBs of host genome. Although promising, CRISPR-mediated base editing still faces daunting challenges before its clinical application, including the base-editing efficacy, the off-target effect, the difficulty in finding conserved target HBV sequences, and in vivo delivery efficiency. Several strategies have been adopted to optimize the efficiency and specificity of CRISPR-BEs and to improve in vivo delivery efficacy through novel viral and non-viral delivery approaches. Particularly, the non-viral delivery of Cas9 mRNA and ribonucleoprotein by lipid nanoparticles exhibits attractive potential for liver-targeted delivery in clinical. Along with all progress above, the CRISPR-mediated gene therapy will ultimately achieve HBV cure.

Combined viral quasispecies diversity and hepatitis B core-related antigen predict off-nucleos(t)ide analog durability in HBeAg-negative patients

BACKGROUND

Viral quasispecies dynamics between pre- and post-nucleos(t)ide analog (NA) therapy remains unclear.

AIM

This study aimed to investigate the HBV quasispecies evolution and its relationship with durability of off-therapy responses in HBeAg-negative chronic hepatitis B (CHB) patients who stopped NA therapy.

METHODS

Fifty-four HBeAg-negative CHB patients who stopped NAs, including 19 virological controllers (VC) who maintained serum HBV DNA < 2000 IU/mL beyond 1-year off-therapy, and 35 virological relapsers (VR) experiencing virological relapse within 1-year off-therapy were recruited. Viral quasispecies was analyzed by deep sequencing. Hepatitis B core-related antigen (HBcrAg) and HBsAg were also measured.

RESULTS

VC had significantly higher baseline viral quasispecies diversity of the precore/core gene, measured by nucleotide diversity, than VR. Low baseline viral nucleotide diversity (< 0.01) and high HBcrAg (≧ 2.0 KU/mL), but not HBsAg, at end of treatment (EOT) were significantly associated with higher risk of 1-year virological relapse (hazard ratio [HR] 6.09 and 3.31, respectively). Combination of low baseline viral nucleotide diversity and high HBcrAg at EOT could identify patients at high risk (HR 15.82). Further analysis of the evolution of HBV whole genome showed that HBV nucleotide diversity negatively correlated with serum HBV DNA levels. Notably, the viral quasispecies diversity between pre- and post-NA treatment remained relatively unchanged.

CONCLUSION

Higher baseline HBV quasispecies diversity associates with more durable off-therapy viral suppression in HBeAg-negative CHB patients. Combination of baseline viral nucleotide diversity and HBcrAg at EOT can identify patients at high risk for virological relapse after stopping NAs.

The Characteristics of Natural Killer Cells in Chronic Hepatitis B Patients Who Received PEGylated-Interferon versus Entecavir Therapy

Background

To explore the role of natural killer (NK) cells in the process of hepatitis B virus (HBV) clearance and whether their phenotype is related to antiviral treatment outcome in chronic hepatitis B (CHB) patients.

Method

We performed a single-center prospective cohort study to analyze changes of NK cells at weeks 12 and 24 from baseline in CHB patients who received PEGylated-interferon- (PEG-IFN-) α-2a versus entecavir. The frequencies of NK, CD56^bright, CD56^dim, IFNAR2⁺, NKp46⁺, NKp46^bright, and NKp46^dim NK cells and mean fluorescence intensity (MFI) of receptors NKp46 and IFNAR2 on the surface of NK cells were measured. Subgroup analyses were performed by comparing treatment responders versus nonresponders with aforementioned parameters in each group.

Results

In PEG-IFN-α-treated patients, posttreatment CD56^bright NK cell frequency increased, but CD56^dim NK cell frequency decreased. Additionally, receptor NKp46 and IFNAR2 expression enhanced. In entecavir-treated patients, although NK cell frequency increased, CD56^bright and CD56^dim NK cell frequencies and IFNAR2 expression did not differ between baseline and posttreatment. In subgroup analyses, posttreatment CD56^bright NK cell frequency and IFNAR2 expression significantly increased in PEG-IFN-α responders from baseline, while changes were absent in PEG-IFN-α nonresponders and entecavir treatment responders. Among patients with HBV viremia after entecavir therapy, NK cell frequency significantly increased, whereas NKp46^bright and IFNAR2⁺ NK frequency and IFNAR2 MFI significantly decreased at 12 and 24 weeks from baseline.

Conclusions

In CHB patients, PEG-IFN-α treatment significantly enhanced NK cell frequency and function when compared to entacavir. Positive treatment responses to either interferon or entecavir were associated with NK cell function improvement. This trial is registered with clinical trial registration no. NCT03208998.

Hepatitis B reactivation: diagnosis and management

INTRODUCTION

Hepatitis B virus (HBV) reactivation can be induced by treatments that attenuate the immunological control over HBV, leading to increased morbidity and mortality. The risk of HBV reactivation is determined by host immunity, viral factors, and the type and dose of treatments. Nevertheless, the risk of HBV reactivation for a growing number of novel therapies remains uncertain and needs to be carefully examined. Identification of patients at risk and administration of prophylactic antiviral agents are critical to prevent HBV reactivation. Early diagnosis and initiation of antiviral treatment are the keys to avoid devastating outcomes.

AREA COVERED

We summarized the latest evidence and recommendations for risk stratification, early diagnosis, prophylaxis, and management of HBV reactivation.

EXPERT OPINION

Universal screening, adequate prophylaxis, and close monitoring are essential for the prevention of HBV reactivation. Risk stratification of patients at risk with appropriate antiviral prophylaxis can prevent HBV reactivation effectively. Several emerging biomarkers have been proved to help determine the risk precisely. Early detection and timely administration of antiviral agents are crucial for management. Further studies on the precision of risk stratification as well as the optimal duration of prophylaxis and treatment are needed to establish an individualized strategy.

Permanent Inactivation of HBV Genomes by CRISPR/Cas9-Mediated Non-cleavage Base Editing

Current antiviral therapy fails to cure chronic hepatitis B virus (HBV) infection because of persistent covalently closed circular DNA (cccDNA). CRISPR/Cas9-mediated specific cleavage of cccDNA is a potentially curative strategy for chronic hepatitis B (CHB). However, the CRISPR/Cas system inevitably targets integrated HBV DNA and induces double-strand breaks (DSBs) of host genome, bearing the risk of genomic rearrangement and damage. Herein, we examined the utility of recently developed CRISPR/Cas-mediated "base editors" (BEs) in inactivating HBV gene expression without cleavage of DNA. Candidate target sites of the SpCas9-derived BE and its variants in HBV genomes were screened for generating nonsense mutations of viral genes with individual guide RNAs (gRNAs). SpCas9-BE with certain gRNAs effectively base-edited polymerase and surface genes and reduced HBV gene expression in cells harboring integrated HBV genomes, but induced very few insertions or deletions (indels). Interestingly, some point mutations introduced by base editing resulted in simultaneous suppression of both polymerase and surface genes. Finally, the episomal cccDNA was successfully edited by SpCas9-BE for suppression of viral gene expression in an in vitro HBV infection system. In conclusion, Cas9-mediated base editing is a potential strategy to cure CHB by permanent inactivation of integrated HBV DNA and cccDNA without DSBs of the host genome.

Quantitation of Plasmacytoid Dendritic Cells in Chronic Hepatitis B Patients with HBeAg Positivity During PEG-IFN and Entecavir Therapy

Plasmacytoid dendritic cells (pDCs) are crucial for control of chronic hepatitis B (CHB) virus infection. In this study, we evaluated the frequencies of pDCs and expression of functional molecules on pDCs in patients treated with PEG-IFN-α-2a or entecavir (ETV) and investigated changes during treatment. The mean fluorescence intensity of CD86 (CD86MFI) on the surface of pDCs and frequencies of pDCs and CD86⁺ pDCs in peripheral blood were measured. Compared with baseline, CD86⁺ pDC% and CD86MFI increased obviously after PEG-IFN-α-2a treatment for 12 and 24 weeks. For patients treated with ETV, only pDC% increased observably after treatment weeks 12 and 24 (P < 0.001) compared with baseline. Hepatitis B surface antigen (HBsAg) decline was significantly associated with elevated CD86⁺ pDC% (r = 0.348, P = 0.015) during PEG-IFN-α-2a treatment. In the HBsAg response group, CD86⁺ pDC% and CD86MFI (P < 0.001) increased observably after PEG-IFN-α-2a therapy, whereas only CD86MFI had a statistically significant difference after therapy compared with baseline (12 weeks versus 0 weeks, P = 0.022; 24 weeks versus 0 weeks, P = 0.015) in the HBsAg nonresponse group. CD86⁺ pDC% between the 2 groups had statistically significant differences at baseline (P = 0.001) and at the treatment time points of 12 and 24 weeks (P < 0.001), respectively. For patients receiving ETV therapy, pDC% increased observably, but CD86⁺ pDC% decreased significantly (P < 0.001) in the HBV DNA nonresponse group during early treatment with ETV. In CHB patients, HBsAg response in PEG-IFN-α-2a therapy correlated with the increase of CD86⁺ pDC% and HBV DNA nonresponse in ETV treatment correlated with the decrease of CD86⁺ pDC%.

Quantification of HBV core antibodies may help predict HBV reactivation in patients with lymphoma and resolved HBV infection

BACKGROUND & AIMS

Absence or low anti-HBV surface antibody (anti-HBs) is associated with an increased risk of HBV reactivation in patients with lymphoma and resolved HBV infection receiving rituximab-containing chemotherapy. Quantification of anti-HBV core antibody (anti-HBc) is a new marker associated with the natural history and treatment response of chronic HBV infection. This study investigated whether baseline anti-HBc and anti-HBs levels may better predict HBV reactivation.

METHODS

We prospectively measured the HBV DNA levels of patients with lymphoma and resolved HBV infection receiving rituximab-cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisolone-based chemotherapy and started an antiviral therapy upon HBV reactivation, defined as a greater than 10-fold increase in HBV DNA compared with previous nadir levels. Anti-HBs and anti-HBc were quantified by a double-sandwich assay. Receiver-operating-characteristic-curve analysis was used to determine the optimal baseline anti-HBc/anti-HBs levels for predicting HBV reactivation.

RESULTS

HBV reactivation occurred in 24 of the 197 patients enrolled, with an incidence of 11.6/100 person-years. For the 192 patients with enough serum samples for analysis, low anti-HBs (<56.48 mIU/ml) and high anti-HBc (≥6.41 IU/ml) at baseline were significantly associated with high risk of HBV reactivation (hazard ratio [HR] 8.48 and 4.52, respectively; p <0.01). The multivariate analysis indicated that (1) patients with both high anti-HBc and low anti-HBs at baseline (36 of 192 patients) had an HR of 17.29 for HBV reactivation (95% CI 3.92-76.30; p <0.001), and (2) HBV reactivation may be associated with inferior overall survival (HR 2.41; 95% CI 1.15-5.05; p = 0.02).

CONCLUSIONS

Baseline anti-HBc/anti-HBs levels may predict HBV reactivation in these patients with lymphoma and help optimize prophylactic antiviral therapy for high-risk patients.

LAY SUMMARY

In this study, we identified a subgroup of patients with lymphoma and resolved hepatitis B virus infection that had a high risk of hepatitis B virus reactivation after receiving rituximab-containing chemotherapy. These findings will help optimize a preventive strategy, especially in hepatitis B virus endemic regions with limited healthcare resources. Clinical trial number: NCT 00931229.

Viral Factors Affecting the Clinical Outcomes of Chronic Hepatitis B

Chronic hepatitis B (CHB) exhibits a variety of clinical outcomes, ranging from spontaneous resolution of hepatitis B to severe adverse consequences, including the development of cirrhosis, hepatic failure, and hepatocellular carcinoma. The heterogeneous clinical courses of chronic hepatitis B virus (HBV) infection reflect the complex host-virus interactions, and point to the difficulty and necessity of identifying the patients at risk. With the advance of HBV virology, several viral factors have been found to be associated with the long-term clinical outcomes of CHB patients. Different viral factors probe different aspects of CHB. Integration of these viral factors may help to determine the disease state of patients more accurately, and identify the patients who require timely antiviral therapy to prevent the development of detrimental clinical outcomes. In this article, we will introduce the conventional and emerging viral factors that are associated with clinical outcomes and discuss their utility in a clinical setting.