An update on HDV: virology, pathogenesis and treatment

Hepatitis delta virus (HDV) remains a poorly classified pathogen despite its clinical significance. Prior research has shown that HDV is a defective RNA virus requiring hepatitis B surface antigen (HBsAg) for replication. While satellite RNA and viroid-like properties are established, the full replication and transmission mechanisms remain unclear. No prior work had resolved the exact role of the two forms of the hepatitis delta antigen (HDAg) in the viral life cycle. The geographic variability of HDV genotypes has been documented, but their clinical implications remain uncertain. The severity of liver disease in HDV-infected individuals compared to HBV monoinfection is well known, but the reasons for accelerated fibrosis and higher hepatocellular carcinoma risk remain unexplained. Current treatment options are limited to interferon and liver transplantation, but gaps in therapeutic efficacy persist. This gap motivated further investigation into HDV's virology, pathogenesis, and treatment strategies.

This review aims to synthesize current knowledge on HDV virology, pathogenesis, and treatment. The specific problem addressed is the lack of a comprehensive summary of HDV characteristics and management. The motivation stems from the need to clarify HDV's unique replication mechanism and its dependence on HBV. The study also seeks to highlight geographic variability in HDV genotypes and their clinical relevance. Understanding the dual forms of HDAg is central to grasping HDV's replication cycle. The review also aims to evaluate current treatment options and identify areas for future research. By summarizing virological and clinical findings, the authors aim to guide clinical practice and research priorities. The review focuses on HDV's interaction with HBV and its impact on liver disease progression. This synthesis is intended to inform both clinical and research communities.

The authors conducted a literature review to compile information on HDV virology, pathogenesis, and treatment. They analyzed published studies on HDV's RNA genome structure and replication mechanisms. The review included data on the two forms of HDAg and their roles in viral replication and assembly. Geographic distribution of HDV genotypes was synthesized from global epidemiological reports. Clinical outcomes of HDV infection were compared with those of HBV monoinfection. The review also examined the role of HBsAg in HDV replication and transmission. Current treatment strategies were evaluated based on clinical trial data and case reports. The synthesis of findings was structured around virological, clinical, and therapeutic aspects of HDV.

HDV is a single-stranded circular RNA virus with a diameter of 36 nm. The virus replicates via the 'double rolling circle' mechanism and contains a ribozyme for self-cleavage. HDV encodes only one structural protein, the hepatitis delta antigen (HDAg). Two forms of HDAg exist: a shorter S form (22 kDa) and a longer L form (24 kDa). The S form is essential for genomic replication, while the L form aids in viral assembly. HDV requires HBsAg for replication and transmission, limiting infection to HBV-positive individuals. Eight genotypes of HDV have been identified, with HDV-1 being the most widespread. HDV viraemia levels are higher in early chronic hepatitis than in cirrhosis.

The authors propose that HDV's unique replication mechanism and dependence on HBV are central to its pathogenesis. They suggest that the two forms of HDAg play distinct roles in the viral life cycle. The synthesis indicates that HDV infection leads to more severe liver disease than HBV monoinfection. The authors propose that geographic variability in HDV genotypes influences clinical outcomes. They suggest that current treatments, including interferon and liver transplantation, remain limited in efficacy. The authors propose that further research is needed to develop better treatment strategies. The synthesis highlights the need for improved understanding of HDV's virology and pathogenesis. The authors propose that ongoing studies should focus on HDV's interaction with HBV and its impact on liver disease progression.