Consequences of Hepatitis B virus DNA integrations for the host and the virus using a new mouse model

• Applicant: Dr. Lena Allweiss
• Subject Area: Virology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 532850572

Chronic hepatitis B affects almost 300 million people worldwide and puts them at risk of developing liver cirrhosis and hepatocellular carcinoma (HCC). The mechanisms of hepatitis B virus (HBV)-induced tumorigenesis are multifactorial and include liver inflammation leading to increased cell proliferation, high levels of viral proteins and occurrence of viral integrations into the host genome. The integration of HBV DNA sequences is believed to play a major role in HCC development through multiple, yet not entirely defined mechanisms, such as the expression of viral proteins, the induction of genomic instability and disruption of cancer-associated genes. Although HBV DNA integrations are not needed for viral replication - HBV replicates via an episomal circular DNA genome, the cccDNA - they are detectable in all phases of chronic infection and even after recovery of acute infection. We hypothesise that viral RNAs and proteins produced from HBV DNA integrations impact both hepatocyte function and HBV infection dynamics. Integrations may provide advantages for the virus by affecting infection establishment, and at the same time, integration-derived products will lead to pro-carcinogenic changes in the hepatocytes, initiating or contributing to their transformation into tumour cells. To date, there is no experimental model allowing the study of HBV DNA integrations in a controlled manner with and without the interference of a parallel cccDNA-driven HBV infection. Within this project, we will establish such a model where the role of HBV integrations and their response to antiviral therapies can be assessed in primary human hepatocytes in vivo. The model is based on human liver chimeric mice and the introduction of a specific prototypic HBV DNA integration through lentiviral gene transfer in primary human hepatocytes used to repopulate the livers of these mice. Using this model, we will characterize all viral products derived from these integrations in mouse serum and liver in comparison to their counterparts derived from an active cccDNA-driven infection. We will assess their influence on the host by analysing the hepatocyte´s intrinsic innate immunity, stress response and metabolism as well as their influence on chromosomal stability. By super-infecting integration carrying mice, we will address the question whether the presence of integration-derived viral products influences HBV spreading kinetics and cccDNA activity. We will dissect the impact of the HBV therapeutic interferon alpha on integration-derived products and cccDNA-based replication in comparison. In the future, this model can be used to address additional research questions such as the role of other distinct HBV DNA integrations or the role of immune cells in recognizing integration carrying hepatocytes. This knowledge will contribute to our understanding of the biology of HBV DNA integrations and virus-host interactions and will eventually help diagnose, monitor and treat this disease.

• DFG Programme: Research Grants