Characterization of host restriction factors interfering with replication and persistency of hepatitis B and D viruses

• Applicant: Professor Dr. Dieter Glebe
• Subject Area: Virology
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 430621923

Infections with Hepatitis B virus (HBV), and coinfections with Hepatitis D virus (HDV) are still a major global health threat. Both viruses can lead to acute and chronic (co-)infections of the liver. Over 250 million people are chronically infected with HBV and at least 11 million people are chronically (co-)infected with HDV, causing ca. 1 million casualties annually due to fatal clinical outcomes. While a protective vaccine is available that can prevent infection with both viruses, there is currently no cure for chronically HBV-infected patients, and direct anti-HDV therapies are not yet fully developed. One of the greatest obstacles to a cure for chronic HBV infection is the covalently closed circular DNA (cccDNA) that HBV uses as a stable and persistent reservoir in the nucleus of infected hepatocytes. HDV, as a defective RNA-virus, requires constant support from HBV in the form of surface proteins (HBsAg) for envelopment and secretion of virions. While HBV has developed elaborate, but not yet sufficiently studied mechanisms to remain a “stealth virus”, HDV activates innate immune responses in HDV/HBV infected cells that leads to suppression of HBV replication. Since cellular sensing mechanisms and pathways of innate immunity in chronic HBV/HDV infections still remain elusive, the proposed project aims to elicit the role of individual, downstream effector host proteins that can interfere with viral replicative cycles during HBV/HDV persistence. To pursue this goal, we will directly activate transcription of selected host target genes using a smart gain-of-function technique (CRISPRa) to systematically study the effects of activated cellular genes on replication and persistency of HBV and HDV in vitro. In detail, we will (1) investigate effects of host effector proteins on HBV and HDV infection and replication and (2) analyze persistence of HDV genomes in infected cells with 88 relevant predefined host-genes; (3) distinguish direct vs. indirect (regulatory) effect of activated host genes on HBV/HDV replication; and (4) compare effects of the host-cell response on replicating HBV cccDNA and its methylation profiles of most relevant HBV genotypes.Overall, the proposed project will provide important basic insights into the intracellular interaction of HBV and HDV with their host cells; determine the potential resistance of viral genomes to antiviral factors, and improve our understanding of the innate immune response to chronic viral hepatitis.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research
• Cooperation Partner: Professor Dr. Vladimir Chulanov