Project Summary Hepatitis B virus (HBV) infections affect the lives of more than 296 million people who are chronically infected with HBV and are at risk of developing liver cirrhosis and hepatocellular carcinoma. Every year approximately 820,000 people die due to HBV-related complications and currently there is no effective cure. The available treatments include nucleoside analogs and interferon alpha (IFNα). In the case of IFNα treatment there is a 10% cure. Even though this number is not satisfactory it proves that HBV cure is possible. The mechanisms by which IFNα leads to a cure are still not well understood. HBV genotypes and mutations in the pre-core region that result in HBV e antigen (HBeAg) negative serology, have been associated with different health risks in chronic HBV and sensitivity to IFNα treatment. Chronicity of HBV infections is linked to the stability and maintenance of the covalently closed circular DNA (cccDNA), which is the nuclear form of the HBV genome. The goal for a functional HBV cure relies on strategies that will either eliminate or inactivate the cccDNA. Therapies that are based on nucleoside analogs do not target the cccDNA while the mechanisms by which IFNα blocks HBV replication are not entirely understood in respect to the direct or indirect effects on the cccDNA. Several investigational direct acting antivirals (DAAs) including capsid assembly modulators (CAMs) and antisense oligonucleotides (ASOs) have emerged as possible components in future combination therapies with the hope that a finite treatment will be sufficient by activating the immune system and targeting the cccDNA. Host factors are being also investigated both for understanding the basic biology of HBV but also as possible therapeutic interventions. Our recent advances in cell culture and animal models that are based on the use of primary human hepatocytes can now be exploited and combined with multiomics approaches and novel CRISPR validation tools to discover host restriction and host dependency factors in the context of chronic HBV infection. The impact of HBV genotypes and mutants provides a great tool to determine differences in chronic HBV and in the context of treatment with IFNα. Moreover, DAAs that lead to activation of innate immunity may be part of future combination therapies. In all, these studies combine expertise from multiple fields with the goal of advancing our knowledge in virus-host interactions and leading to curative therapies against chronic HBV.