Hepatitis B virus envelope protein S (HBsAg)

The Hepatitis B virus (HBV) envelope protein S, commonly known as the small surface antigen (HBsAg), is a critical structural component of the HBV virion and subviral particles. It is encoded by the S gene and plays a fundamental role in the viral life cycle, including mediating viral attachment and entry into hepatocytes and facilitating viral assembly and morphogenesis (UniProt P03138, PMID: 32410131). In chronic infections, HBsAg is produced in vast excess as non-infectious subviral particles that act as immunological decoys to exhaust the host's immune system, preventing effective viral clearance (PMID: 34114002). Clinically, it is the primary target for preventative vaccines, which elicit neutralizing anti-HBs antibodies to block infection (NIH). Emerging 'functional cure' therapies specifically target HBsAg using RNA interference (siRNA) or antisense oligonucleotides to silence its production, or nucleic acid polymers to block its secretion, aiming to reduce antigen load and restore host immune competence (PMID: 32623348, PMID: 34965551).

Other names

Hepatitis B surface antigenSmall surface proteinSmall envelope proteinS proteinHBV-SMajor surface protein

Induction of neutralizing antibodies via vaccination, direct neutralization of virions by immunoglobulins, inhibition of viral entry into hepatocytes, and suppression of viral antigen production or release through RNA interference, antisense oligonucleotides, or nucleic acid polymers.