Effects of interferon-α/β on HBV replication determined by viral load

Viral-load-dependent effects of liver injury and regeneration on hepatitis B virus replication in mice

Hepatitis B virus (HBV) is a hepatotropic virus that can cause severe liver diseases. By conducting studies using four different transgenic mouse lines that carry either the wild-type HBV genome or the HBV genome incapable of expressing the X gene, we found that liver injury and regeneration induced by a partial hepatectomy (PHx) could have different effects on HBV replication depending on the mouse lines. Further studies using hydrodynamic injection to introduce different amounts of the HBV genomic DNA into the mouse liver revealed that liver injury and regeneration induced by PHx enhanced HBV replication when viral load was low and suppressed HBV replication when viral load was high. These effects of liver injury and regeneration on HBV were independent of the HBV X protein and apparently due to alpha and beta interferons (IFN-α/β), as the effects could be abolished by the injection of anti-IFN-α/β antibodies. Further analysis indicated that PHx could induce the expression of hepatocyte nuclear factor 3 gamma (HNF3γ) when viral load was low and activate the signal transducer and activator of transcription 3 (Stat3) and suppress the expression of the suppressor of cytokine signaling 3 (SOCS3) irrespective of viral load. As both HNF3γ and Stat3 are required to activate the HBV enhancer I to stimulate HBV gene expression and replication, these results provided an explanation to the viral-load-dependent effect of liver injury and regeneration on HBV replication. Our studies thus revealed a novel interaction between HBV and its host and provided important information for understanding HBV replication and pathogenesis during liver injury.

Hepatitis B Virus Genotype B and High Expression of Interferon Alpha Receptor β Subunit are Associated With Better Response to Pegylated Interferon Alpha 2a in Chinese Patients With Chronic Hepatitis B Infection

BACKGROUND

Hepatitis B virus (HBV) is one of leading causes of various hepatic diseases including acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Hundreds of million people worldwide are infected by HBV, chronically.

OBJECTIVES

This study in conducted to investigate the influence of Hepatitis B virus (HBV) genotypes and type I IFN-αreceptor β subunit (IFNAR2) expression in liver on response to treatment with pegylated IFN-α-2a (Peg-IFN-α-2a) for chronic hepatitis B infection.

PATIENTS AND METHODS

In this study, 65 eligible patients with chronic hepatitis B disease were enrolled. HBV genotypes of these patients were analyzed by using PCR-RFLP of the surface gene of HBV. The expression of IFNAR2 in the liver was immune histochemically investigated using anti-IFNAR2 antibody. All immune histochemical slides were read semi-quantitatively by image analysis. Chronic hepatitis B patients were treated with Peg-IFN-α2a therapy for a 48-week period and followed up for 24 weeks. Baseline characteristics and sustained viral response (SVR) to Peg-IFN-α-2a therapy were evaluated.

RESULTS

55 % of patients exhibited HBV genotype B and 31.7 % patients exhibited HBV genotypes C infections. After treatment with Peg-IFN-α-2a, SVR was achieved in 66.7 % of patients with HBV genotype B and in 26.3 % of patients with HBV genotype C (P = 0.009). Semiquantitative and the image analysis indicated by gray level values revealed a higher IFNAR2 expression in the group with severe inflammation (P < 0.001). Patients' high IFNAR2 protein expression had a significant impact on SVR to Peg-IFN-α-2a therapy (P = 0.028).

CONCLUSIONS

HBV genotype B and high expression of IFNAR2 in the liver of chronic hepatitis B patients are closely associated with better response to Peg-IFN-α-2a therapy in chronic hepatitis B disease.

Enhancement of hepatitis B virus replication by androgen and its receptor in mice

Hepatitis B virus (HBV) is an important pathogen that chronically infects more men than women. To understand the molecular mechanism of this gender disparity, we analyzed HBV replication in transgenic mice that carried the HBV genome with or without the ability to express the HBV X protein (HBx). We found that gender had no effect on HBV surface antigen (HBsAg), DNA, and RNA levels in mice before puberty, but its effect on HBV after puberty was apparent, with HBV replicating approximately twice more efficiently in male mice than in female mice whether or not HBx was expressed. The castration of male mice resulted in a reduction of HBV HBsAg, DNA, and RNA levels, which could be partially restored by the injection of the androgen agonist R1881, indicating a positive role of androgen in HBV replication. The introduction of HBV genomic DNA and androgen receptor (AR) short hairpin RNA (shRNA) into the liver of naïve mice by hydrodynamic injection revealed that the effect of androgen on HBV was dependent on its receptor, which apparently could also stimulate HBV replication via an androgen-independent pathway. Further studies indicated that the two previously identified androgen response elements (AREs) in the HBV genome could indeed mediate the effect of androgen on HBV RNA transcription and DNA replication in vivo. These effects of androgen and its receptor on HBV thus provide an explanation for why men have a higher risk of HBV infection than women.

Autophagy required for hepatitis B virus replication in transgenic mice

Recent studies indicate that hepatitis B virus (HBV) may induce autophagy to enhance its replication in cell cultures. To understand whether autophagy can indeed enhance HBV replication in vivo, we generated HBV transgenic mice with liver-specific knockout of the Atg5 gene, a gene critical for the initiation of autophagy. Immunoblot analyses confirmed the inhibition of autophagy in the livers of Atg5 knockout mice. This inhibition of autophagy slightly reduced HBV gene expression and affected nuclear localization of the HBV core protein. It also reduced the HBV DNA level in sera by more than 90% and the level of the HBV DNA replicative intermediate in the mouse liver to an almost undetectable level. Our results thus demonstrate that autophagy is important for HBV replication in vivo and raise the possibility of targeting this pathway to treat HBV patients.