8 Hepatitis B

8.1 Virology

The hepatitis B virus (HBV) is a partially double-stranded DNA virus belonging to the Hepadnaviridae family. Three major subunits make up the structural components:

The genome has four genes (S, C, X and P). Both the core nucleocapsid protein (HBcAg) and the ‘early’ protein (which makes HBeAg) are translated from the C gene. HBcAg is essential for viral packaging and is an integral part of the nucleocapsid. HBeAg is a soluble protein that is not part of the virus particle. Detection of HBeAg in the serum is correlated with viral replication, and is most commonly found in those with acute hepatitis B and those with chronic HBV infection with high viral load.1