Hepatitis B virus surface antigen (HBsAg) (HBsAg)

The Hepatitis B virus surface antigen (HBsAg), specifically the S protein, is a major component of the viral envelope and plays a pivotal role in the life cycle of the Hepatitis B virus (HBV). It is responsible for the attachment of the virus to host hepatocytes and is essential for the assembly and release of infectious virions (UniProt: P03141). During infection, HBsAg is produced in vast excess, circulating in the blood as non-infectious subviral particles that function as immunological decoys to subvert the host's immune response (PubMed: 32693103). As a therapeutic target, HBsAg is the basis for highly effective recombinant vaccines, such as Engerix-B, which induce neutralizing antibodies (anti-HBs) to prevent infection (CDC). In the context of chronic hepatitis B, novel therapies like antisense oligonucleotides (e.g., Bepirovirsen) and siRNAs (e.g., JNJ-3989) are being developed to silence HBsAg production, aiming to achieve a functional cure by restoring immune competence (PubMed: 36350145). Monitoring HBsAg levels is the standard clinical practice for diagnosing infection and assessing treatment efficacy (NIH).

Other names

Hepatitis B virus S proteinSmall surface proteinHBV S proteinHepatitis B surface antigenEnvelope protein SHBsAg S-domain

Drugs targeting HBsAg function by inducing active immunity through recombinant proteins, providing passive immunity via neutralizing antibodies, or inhibiting viral protein synthesis using antisense oligonucleotides and siRNA to reduce the circulating antigen burden.