HBcAg explained

Uniprot:Q9QAB9
Capsid protein
Organism:Hepatitis B virus genotype B2 (isolate Vietnam/9873/1997)
Symbol:C

HBcAg (core antigen) is a hepatitis B viral protein.[1] [2] It is an indicator of active viral replication; this means the person infected with Hepatitis B can likely transmit the virus on to another person (i.e. the person is infectious).

Structure and function

HBcAg is an antigen that can be found on the surface of the nucleocapsid core (the inner most layer of the hepatitis B virus). While both HBcAg and HBeAg are made from the same open reading frame, HBcAg is not secreted as a monomer.[3] HBcAg is considered "particulate" and it does not circulate in the blood, but recent study show it can be detected in serum by Radioimmunoassay. However, it is readily detected in hepatocytes after biopsy.[4] When both HBcAg and HBeAg proteins are present, it acts as a marker of viral replication.[5]

HBcAg, also called core protein (Cp), is a 21 kDa protein of 183–185 amino acids, depending on the genotype, and is the result of the second start codon in the open reading frame.[6] Once a threshold of HBcAg proteins are translated in the cytoplasm, the viral capsid will spontaneously into a T=3 or T=4 icosahedral capsid.[7] The capsid will usually package the hepatitis B genomic RNA, but some capsids will have cellular RNA or be empty.[8] HBcAg is the target of antiviral compounds, termed capsid assembly modulators (CAMs), that are under clinical investigation for treating chronic hepatitis B.[9]

Interactions

Tapasin can interact with HBcAg18-27 and enhance cytotoxic T-lymphocyte response against HBV.[10]

See also

Notes and References

  1. Kimura T, Rokuhara A, Matsumoto A, etal . New enzyme immunoassay for detection of hepatitis B virus core antigen (HBcAg) and relation between levels of HBcAg and HBV DNA . J. Clin. Microbiol. . 41 . 5 . 1901–6 . May 2003 . 12734224 . 154683 . 10.1128/JCM.41.5.1901-1906.2003.
  2. Cao T, Meuleman P, Desombere I, Sällberg M, Leroux-Roels G . In vivo inhibition of anti-hepatitis B virus core antigen (HBcAg) immunoglobulin G production by HBcAg-specific CD4(+) Th1-type T-cell clones in a hu-PBL-NOD/SCID mouse model . J. Virol. . 75 . 23 . 11449–56 . December 2001 . 11689626 . 114731 . 10.1128/JVI.75.23.11449-11456.2001 .
  3. Biology of the hepatitis B virus (HBV) core and capsid assembly modulators (CAMs) for chronic hepatitis B (CHB) cure . 10.35772/ghm.2023.01065 . 2023 . McFadden . William M. . Sarafianos . Stefan G. . Global Health & Medicine . 5 . 4 . 199–207 . 37655181 . 10461335 .
  4. 10.1016/j.jhep.2016.05.029 . Serum hepatitis B virus RNA is encapsidated pregenome RNA that may be associated with persistence of viral infection and rebound . 2016 . Wang . Jie . Shen . Tao . Huang . Xiangbo . Kumar . G. Renuka . Chen . Xiangmei . Zeng . Zhenzhen . Zhang . Ruiyang . Chen . Ran . Li . Tong . Zhang . Tianying . Yuan . Quan . Li . Pao-Chen . Huang . Qi . Colonno . Richard . Jia . Jidong . Hou . Jinlin . McCrae . Malcolm A. . Gao . Zhiliang . Ren . Hong . Xia . Ningshao . Zhuang . Hui . Lu . Fengmin . Journal of Hepatology . 65 . 4 . 700–710 . 27245431 . free .
  5. Hepatitis B Virus Core-Related Antigens as Markers for Monitoring Chronic Hepatitis B Infection . 10.1128/jcm.00366-07 . 2007 . Wong . Danny Ka-Ho . Tanaka . Yasuhito . Lai . Ching-Lung . Mizokami . Masashi . Fung . James . Yuen . Man-Fung . Journal of Clinical Microbiology . 45 . 12 . 3942–3947 . 17942661 . 2168562 .
  6. Assembly and Release of Hepatitis B Virus . 10.1101/cshperspect.a021394 . 2015 . Selzer . Lisa . Zlotnick . Adam . Cold Spring Harbor Perspectives in Medicine . 5 . 12 . a021394 . 26552701 . 4665036 .
  7. Theoretical aspects of virus capsid assembly . 10.1002/jmr.754 . 2005 . Zlotnick . Adam . Journal of Molecular Recognition . 18 . 6 . 479–490 . 16193532 .
  8. Secretion of Empty or Complete Hepatitis B Virions: Envelopment of Empty Capsids Versus Mature Nucleocapsids . 10.2217/fvl-2018-0128 . 2019 . Liu . Kuancheng . Hu . Jianming . Future Virology . 14 . 2 . 95–105 .
  9. Biology of the hepatitis B virus (HBV) core and capsid assembly modulators (CAMs) for chronic hepatitis B (CHB) cure . 10.35772/ghm.2023.01065 . 2023 . McFadden . William M. . Sarafianos . Stefan G. . Global Health & Medicine . 5 . 4 . 199–207 . 37655181 . 10461335 .
  10. Chen X . Tapasin modification on the intracellular epitope HBcAg18-27 enhances HBV-specific CTL immune response and inhibits hepatitis B virus replication in vivo. . Lab. Invest. . 94 . 5 . May 2014 . 24614195 . 478–90 . 10.1038/labinvest.2014.6. free .

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