Loss of intrahepatic HBsAg expression predicts sustained response to peginterferon and is reflected by pronounced serum HBsAg decline

Low Level of Serum Immunoglobulin G Is Beneficial to Clinical Cure Obtained With Pegylated Interferon Therapy in Inactive Surface Antigen Carriers

Purpose

Our recent study showed a high rate of HBsAg clearance in inactive HBsAg carriers (IHCs) treated with pegylated IFN (PEG-IFN). To better understand the immune-mediated component of HBsAg clearance, this study investigated the role of serum immunoglobulin G (IgG) and its subclasses in predicting HBsAg clearance in IHCs with PEG-IFN therapy.

Methods

In this study, IHCs received PEG-IFN for 96 weeks. Subjects who achieved clearance of HBsAg were considered responders (R group), and those in whom HBsAg was not cleared were considered non-responders (NR group). The HBsAg, ALT, and serum lgG subtypes (lgG1, IgG2, IgG3, lgG4) were tested at baseline, and at 12 and 24 weeks of treatment. To evaluate the factors in predicting HBsAg clearance, univariate and multivariate logistic regression analyses were performed. The receiver operator characteristic curves and the area under the receiver operator characteristic curve (AUROC) were used to evaluate prognostic values.

Results

Our results showed that 39 cases obtained HBsAg clearance (group R), while 21 cases did not (group NR). There was no significant difference in age, ALT, and AST levels between the two groups. The serum levels of IgG1, lgG2, lgG3 and lgG4 at baseline, and at 12 and 24 weeks were significantly lower in IHC with HBsAg clearance than in the NR group. Univariate logistic regression analysis showed that serum IgG1, IgG2, IgG3, and IgG4 levels at baseline, and at 12, and 24 weeks were all strong predictors of HBsAg clearance. In all indicators, lgG2 had the highest AUROC at baseline and lgG3 the highest AUROC at week 12. A multifactor logistic analysis was performed with y=33.933-0.001*BaselinelgG1-0.002*BaselinelgG2. The area under the curve was 0.941 with 100% sensitivity and 76.19% specificity.

Conclusion

Together, our findings suggest that serum IgG has a higher predictive value compared to the convention predictors of HBsAg and ALT for HBsAg clearance and thus may be a better clinical predictor of HBsAg clearance in IHCs.

In Vitro Systems for Studying Different Genotypes/Sub-Genotypes of Hepatitis B Virus: Strengths and Limitations

Hepatitis B virus (HBV) infects the liver resulting in end stage liver disease, cirrhosis, and hepatocellular carcinoma. Despite an effective vaccine, HBV poses a serious health problem globally, accounting for 257 million chronic carriers. Unique features of HBV, including its narrow virus-host range and its hepatocyte tropism, have led to major challenges in the development of suitable in vivo and in vitro model systems to recapitulate the HBV replication cycle and to test various antiviral strategies. Moreover, HBV is classified into at least nine genotypes and 35 sub-genotypes with distinct geographical distributions and prevalence, which have different natural histories of infection, clinical manifestation, and response to current antiviral agents. Here, we review various in vitro systems used to study the molecular biology of the different (sub)genotypes of HBV and their response to antiviral agents, and we discuss their strengths and limitations. Despite the advances made, no system is ideal for pan-genotypic HBV research or drug development and therefore further improvement is required. It is necessary to establish a centralized repository of HBV-related generated materials, which are readily accessible to HBV researchers, with international collaboration toward advancement and development of in vitro model systems for testing new HBV antivirals to ensure their pan-genotypic and/or customized activity.

Drugs in the Pipeline for HBV

Chronic hepatitis B remains a significant cause of morbidity and mortality worldwide. Most hepatitis B virus (HBV)-infected individuals are neither diagnosed nor treated. In those treated, nucleos(t)ide polymerase inhibitors persistently suppress viremia to the limits of quantitation; however, few achieve a "functional cure," defined as sustained off-treatment loss of detectable serum HBV DNA with or without loss of hepatitis B surface antigen. The low cure rate has been attributed to an inability to eliminate the viral reservoir of covalently closed circular DNA from hepatocytes. This review focuses on the diverse therapeutic approaches currently under development that may contribute to the goal of HBV cure.

Serum hepatitis B surface antigen correlates with fibrosis and necroinflammation: A multicentre perspective in China

The kinetics of serum hepatitis B surface antigen (HBsAg) during the natural history of hepatitis B virus (HBV) infection has been studied, but the factors affecting them remain unclear. We aimed to investigate the factors affecting HBsAg titres, using data from multicentre, large-sized clinical trials in China. The baseline data of 1795 patients in 3 multicentre trials were studied, and the patients were classified into 3 groups: hepatitis B early antigen (HBeAg)-positive chronic HBV infection (n = 588), HBeAg-positive chronic hepatitis B (n = 596), and HBeAg-negative chronic hepatitis B (n = 611). HBsAg titres in the different phases were compared, and multiple linear progression analyses were performed to investigate the implicated factors. HBsAg titres varied significantly in different phases (P = .000), with the highest (4.60 log10 IU/mL [10%-90% confidence interval: 3.52 log10 IU/mL-4.99 log10 IU/mL]) in patients with HBeAg-positive chronic HBV infection. In all phases, age and HBV DNA were correlated with serum HBsAg level. In HBeAg-positive chronic hepatitis B patients, a negative correlation between HBsAg titres and fibrosis stage was observed. Alanine amonitransferase or necroinflammatory activity was also correlated with HBsAg titres in HBeAg-negative chronic hepatitis B patients. In conclusion, decreased HBsAg titres may be associated with advancing fibrosis in HBeAg-positive chronic hepatitis B patients or increased necroinflammation in those with HBeAg-negative chronic hepatitis B. Our findings may help clinicians better understand the kinetics of HBsAg and provide useful insights into the management of this disease.

Tenofovir alafenamide in the treatment of chronic hepatitis B virus infection: rationale and clinical trial evidence

Tenofovir alafenamide (TAF), a novel prodrug of tenofovir was developed to deliver enhanced antiviral potency and reduced systemic toxicities by more efficient intracellular delivery of the active metabolite tenofovir disphosphate than tenofovir disoproxil fumarate (TDF). In two randomized, double-blind, multinational phase III trials in patients with hepatitis B e antigen (HBeAg)-positive or -negative infection, TAF 25 mg was non-inferior to TDF 300 mg in achieving the primary efficacy outcome of a hepatitis B virus (HBV) DNA level < 29 IU/ml at week 48 and was associated with higher rates of alanine aminotransferase (ALT) normalization based on AASLD (American Association for the Study of Liver Diseases) criteria. TAF was well tolerated with low rates of adverse events, comparable to TDF. A significantly lower decline in the estimated glomerular filtration rate (eGFR) was observed in patients receiving TAF compared with patients receiving TDF and loss of bone mineral density at the hip and spine was significantly lower in the TAF groups. These trends continued to week 96. The requirement for long-term therapy in chronic HBV highlights the importance of these efficacy and safety trends, however their true clinical relevance is yet to be established and further studies with long-term follow up and real-world clinical data are needed.

The role of quantitative hepatitis B surface antigen revisited

In the past 10years, there has been a lot of enthusiasm surrounding the use of serum hepatitis B surface antigen (HBsAg) quantification to predict disease activity and monitor treatment response in chronic hepatitis B. The measurement of HBsAg levels have been standardized in IU/ml, and nowadays it is almost a mandatory measurement due to the development of new antiviral treatments aiming at HBsAg seroclearance, i.e., functional cure of hepatitis B. Recently, there has been an improved understanding of the molecular virology of HBsAg, and particularly the relative roles of covalently closed circular DNA and integrated hepatitis B virus (HBV) DNA. This has shed new light on the interpretation of HBsAg levels in different phases of chronic hepatitis B. HBsAg level can assist the differentiation of immune tolerance and immune clearance in hepatitis B e antigen (HBeAg)-positive patients, and it can predict inactive disease and spontaneous HBsAg seroclearance in HBeAg-negative patients. The determination of HBsAg level is pivotal to individualize pegylated interferon (PegIFN) treatment; it is the key investigation to decide early termination of PegIFN among non-responders. Among patients treated by nucleos(t)ide analogues, responders tend to have dramatic reduction of HBsAg to low levels, which may be followed by HBsAg seroclearance. With newer data on combination treatment of PegIFN and nucleos(t)ide analogues as well as emerging new antiviral agents, HBsAg quantification is expected to become increasingly important to monitor and guide antiviral therapy for chronic hepatitis B.