HBcAg (core antigen) is a

hepatitis B Hepatitis B is an infectious disease caused by the ''Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection. Many people have no symptoms during an initial infection. Fo ...

viral protein A viral protein is both a component and a product of a virus. Viral proteins are grouped according to their functions, and groups of viral proteins include structural proteins, nonstructural proteins, regulatory proteins, and accessory proteins. Vi ...

. 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 In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

that can be found on the surface of the

nucleocapsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...

core (the inner most layer of the

hepatitis B virus ''Hepatitis B virus'' (HBV) is a partially double-stranded DNA virus, a species of the genus ''Orthohepadnavirus'' and a member of the ''Hepadnaviridae'' family of viruses. This virus causes the disease hepatitis B. Disease Despite there bein ...

). While both HBcAg and

HBeAg HBeAg is a hepatitis B viral protein, produced by the HBcAg reading frame. 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 infe ...

are made from the same

open reading frame In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible readin ...

, HBcAg is not secreted. HBcAg is considered "particulate" and it does not circulate in the blood but recent study show it can be detected in serum by

Radioimmunoassay A radioimmunoassay (RIA) is an immunoassay that uses radiolabeled molecules in a stepwise formation of immune complexes. A RIA is a very sensitive in vitro assay technique used to measure concentrations of substances, usually measuring antigen conc ...

. However, it is readily detected in

hepatocyte A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in: * Protein synthesis * Protein storage * Transformation of carbohydrates * Synthesis of cholesterol, ...

s after

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...

. The presence of both HBcAg and HBeAg proteins together act as a marker of

viral replication Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome an ...

, and antibodies to these antigens are a marker of declining replication.

Interactions

Tapasin TAP-associated glycoprotein, also known as tapasin or TAPBP, is a protein that in humans is encoded by the ''TAPBP'' gene. Function The ''TAPBP'' gene encodes a transmembrane glycoprotein that mediates interaction between newly assembled majo ...

can interact with HBcAg18-27 and enhance cytotoxic

T-lymphocyte A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell rec ...

response against HBV.

References

{{Viral proteins Viral structural proteins Hepatitis B virus

Structure and function

Interactions

See also

References