Description
The surface antigen of the Hepatitis B Virus (HBsAg) is a glycoprotein embedded in the viral envelope. As an envelope protein, HBsAg is recognized as an antigen by the viral host. HBsAg is involved in the infection of and release from host cells. The virus has historically been characterized by serotyping, and divided into four subtypes (adw, adr, ayw and ayr), which have been further subdivided by genotypic variations