Novel targets for hepatitis B virus therapy.

Treatment with either pegylated interferon-alpha (pegIFN-α) or last generation nucleos(t)ide analogues (NAs) successfully leads to serum viral load suppression in most chronically infected hepatitis B (CHB) patients, but HBsAg loss is only achieved in 10% of the cases after a 5-year follow-up. Thus, therapy must be administered long-term and it will not completely eliminate infection because of the persistent hepatitis B virus (HBV) minichromosome in infected cells, and cannot completely abolish the risk of developing severe sequelae such as cirrhosis and hepatocellular carcinoma. Recent progress in the development of in vitro and in vivo models of HBV infection have helped renew interest in the investigation of the viral life cycle, as well as specific virus-host cell interactions to identify new targets for the development of new antiviral drugs. This includes either direct inhibition of viral replication by targeting fundamental steps such as entry, cccDNA formation/stability, viral transcripts, capsid assembly and secretion or the manipulation of the host immune system for better defence against infection. Multiple strategies are currently under investigation, including boosting endogenous innate responses and/or restoring adaptive immunity via engineering of HBV-specific T cells or via the use of inhibitors of negative regulators, as well as therapeutic vaccines. It is increasingly clear that multiple therapeutic strategies must be combined to reach a cure of HBV and that the definition of clinical, virological and immunological correlates for the management of treatment are urgently needed.