Hepatitis B virus (HBV) infection is a global public health problem. The spectrum of clinical manifestations of HBV infection varies in both acute and chronic disease. During the acute phase, manifestations range from subclinical hepatitis to anicteric hepatitis, icteric hepatitis, and fulminant hepatitis; during the chronic phase, manifestations range from an asymptomatic carrier state to chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The clinical outcome of HBV infection depends upon the age at infection, the level of HBV replication, and the immune status of the host. (See "Clinical manifestations and natural history of hepatitis B virus infection".)
This topic review will discuss the characteristics of the hepatitis B virus and the pathogenesis of HBV-related liver disease. The immune response to HBV contributes to the hepatic injury, helps control the infection, and provides the means for establishing the serologic diagnosis of HBV infection. (See "Diagnosis of hepatitis B virus infection".)
CHARACTERISTICS OF THE VIRUS
Hepatitis B virus belongs to the family of hepadnaviruses, which include duck hepatitis virus, woodchuck hepatitis virus, and ground squirrel hepatitis virus. The complete virion or Dane particle is 42 nm in diameter. It consists of:
- An envelope composed of viral-encoded proteins and host-derived lipid components
- A core particle made up of the nucleocapsid protein, the viral genome, and the polymerase protein
HBV also produces 22 nm subviral particles in the form of filaments and spheres that are composed of envelope proteins only. These subviral particles do not contain the HBV genome and are therefore noninfectious .