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Updated: Jul 11, 2025
Development of a Hepatitis B Virus Reporter System to Monitor the Early Stages of the Replication Cycle
Published on: February 1, 2017
Chimeric antigen receptors of HBV envelope proteins inhibit hepatitis B surface antigen secretion
Yang Wang1, Qiqi Li1, Cheng Li1
1Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Shanghai Frontier Science Center of Pathogenic Microorganisms and Infection, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China.
Insights
New chimeric antigen receptors (CARs) targeting hepatitis B virus (HBV) envelope proteins effectively reduce HBsAg. These novel CARs offer a promising strategy for achieving sustained HBsAg loss in chronic hepatitis B patients.
Area of Science:
- Hepatology
- Virology
- Immunotherapy
Background:
- Chronic hepatitis B (CHB) poses a significant risk for liver cirrhosis and cancer.
- Hepatitis B surface antigen (HBsAg) is crucial in CHB pathogenesis, and its loss signifies a cure.
- Current drugs rarely achieve sustained HBsAg loss, necessitating novel therapeutic strategies.
Purpose of the Study:
- To develop and evaluate chimeric antigen receptors (CARs) targeting HBV envelope proteins for HBsAg reduction.
- To investigate the impact of CARs on HBsAg secretion, HBV infection, and underlying mechanisms.
Main Methods:
- Development of CARs using single-chain variable fragments (scFvs) targeting HBV large and small envelope proteins.
- In vitro studies using cell culture models to assess CARs' effects on HBV infection and HBsAg secretion.
- In vivo studies using HBV mouse models to evaluate the efficacy of CARs in reducing serum HBsAg.
Main Results:
- CARs, particularly G12-scFv-Fc and G12-CAR-Fc, significantly suppressed serum HBsAg in HBV mouse models (up to 130-fold).
- The inhibitory effect of CARs on HBsAg lasted for at least 8 weeks post-delivery via adeno-associated virus vector.
- CARs demonstrated direct antiviral activity by blocking HBV infection, virion secretion, and HBsAg release, primarily by arresting HBV envelope proteins in the endoplasmic reticulum.
Conclusions:
- Chimeric antigen receptors (CARs) exhibit direct antiviral activity against HBV.
- Fc-fused G12-scFv and G12-CARs represent a novel therapeutic approach for reducing circulating HBsAg in CHB.
- These findings pave the way for new strategies aimed at achieving sustained HBsAg loss and potentially curing CHB.
Objectives:
Chronic hepatitis B (CHB) caused by HBV infection greatly increases the risk of liver cirrhosis and hepatocellular carcinoma. Hepatitis B surface antigen (HBsAg) plays critical roles in the pathogenesis of CHB. HBsAg loss is the key indicator for cure of CHB, but is rarely achieved by current approved anti-HBV drugs. Therefore, novel anti-HBV strategies are urgently needed to achieve sustained HBsAg loss.
Design:
We developed multiple chimeric antigen receptors (CARs) based on single-chain variable fragments (scFvs, namely MA18/7-scFv and G12-scFv), respectively, targeting HBV large and small envelope proteins. Their impacts on HBsAg secretion and HBV infection, and the underlying mechanisms, were extensively investigated using various cell culture models and HBV mouse models.
Results:
After secretory signal peptide mediated translocation into endoplasmic reticulum (ER) and secretory pathway, MA18/7-scFv and CARs blocked HBV infection and virion secretion. G12-scFv preferentially inhibited virion secretion, while both its CAR formats and crystallisable fragment (Fc)-attached versions blocked HBsAg secretion. G12-scFv and G12-CAR arrested HBV envelope proteins mainly in ER and potently inhibited HBV budding. Furthermore, G12-scFv-Fc and G12-CAR-Fc strongly suppressed serum HBsAg up to 130-fold in HBV mouse models. The inhibitory effect lasted for at least 8 weeks when delivered by an adeno-associated virus vector.
Conclusion:
CARs possess direct antiviral activity, besides the well-known application in T-cell therapy. Fc attached G12-scFv and G12-CARs could provide a novel approach for reducing circulating HBsAg.
