Which virus is dependent on co-infection with hepatitis B virus for replication?

• A. Hepatitis A virus
• B. Hepatitis B virus
• C. Hepatitis C virus
• D. Hepatitis D virus

Answer: (D)

Hepatitis D virus is a defective satellite virus that cannot form infectious particles without the hepatitis B surface antigen provided by hepatitis B virus. It relies on HBV to coat its genome-containing particle and to supply the machinery needed to enter hepatocytes. Therefore, HDV replication and spread occur only in the presence of HBV, either concurrently (coinfection) or in a person already infected with HBV who acquires HDV (superinfection). This dependence on HBV for encapsidation and entry is why it is the virus that requires co-infection with hepatitis B for replication. The remaining hepatitis viruses do not require HBV for replication: hepatitis A is nonenveloped and self-sufficient; hepatitis B replicates on its own; hepatitis C also replicates independently.