The hepatitis B virus is an important cause of acute and chronic liver disease. It is also the most common form of parenterally transmitted viral hepatitis. The HBV surface protein antigens (HBsAg) are comprised of three carboxyl co terminal HBs proteins termed large (LHBs), middle (MHBs) and small (SHBs, also called major) protein. LHBs and MHBs also share the highly hydrophobic, repetitive, membrane spanning S domain. In addition, MHBs has a 55 amino acid region called preS2. The virus is estimated to affect some 350 million people worldwide. Immunization against hepatitis B is an important component of preventative medicine and is offered to all children in approximately 30 countries. Hepatitis B virus (HBV) belongs to the Hepadnaviridae family and infection with HBV is usually more serious than infection with hepatitis A virus. In some individuals the infection is not cleared and followed by persistent intracellular viral carriage that can lead to the development of hepatocelular carcinomas. There are currently 400 million HBV carriers worldwide making HBV one of the most common human pathogens.