Viral Antigens

Key Biological Properties: HDV is a small, spherical, enveloped particle with a diameter of approximately 36 nm. Its viral envelope contains host phospholipids and three proteins from HBV: the large, medium, and small Hepatitis B surface antigens .

Expression Patterns and Tissue Distribution: HDV primarily infects liver cells (hepatocytes). The virus relies on the presence of HBV surface antigens to enter and replicate within these cells .

Primary Biological Functions: HDV’s primary function is to replicate within hepatocytes, causing liver inflammation and damage. It plays a significant role in the progression of liver diseases, including cirrhosis and hepatocellular carcinoma .

Role in Immune Responses and Pathogen Recognition: HDV infection triggers an immune response, leading to liver inflammation. The immune system recognizes and attacks infected hepatocytes, contributing to liver damage .

Mechanisms with Other Molecules and Cells: HDV binds to hepatocytes through interactions between HBV surface antigens and the sodium taurocholate cotransporting polypeptide (NTCP) receptor on liver cells .

Binding Partners and Downstream Signaling Cascades: Once inside the hepatocyte, HDV relies on HBV proteins for replication and assembly. The virus hijacks the host cell’s machinery to produce viral RNA and proteins, leading to the formation of new viral particles .

Regulatory Mechanisms Controlling Expression and Activity: HDV replication is tightly regulated by the availability of HBV surface antigens. The virus also undergoes RNA editing, which regulates the balance between viral replication and virion assembly .

Transcriptional Regulation and Post-Translational Modifications: HDV RNA undergoes editing by cellular enzymes, which is critical for the virus’s life cycle. This editing process influences the production of different forms of the Hepatitis Delta antigen (HDAg), essential for viral replication and assembly .

Diagnostic Tools: HDV infection is diagnosed through the detection of HDV antibodies and RNA in blood samples. These diagnostic tools are crucial for identifying and managing HDV infections .

Therapeutic Strategies: Current treatments for HDV include antiviral drugs and pegylated interferon-alpha. New therapeutic approaches, such as entry inhibitors and prenylation inhibitors, are under investigation to improve treatment outcomes .

Role Throughout the Life Cycle: HDV plays a critical role in the progression of liver diseases. It accelerates the progression of liver cirrhosis and increases the risk of hepatocellular carcinoma. Understanding the HDV life cycle is essential for developing effective treatments and preventive measures .