HBeAg 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. ...

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. ...

, produced by the

HBcAg HBcAg (core antigen) is a hepatitis B viral protein. 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 ...

reading frame. It is an indicator of active

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 ...

; this means the person infected with Hepatitis B can likely transmit the virus on to another person (i.e. the person is infectious). HBeAg is considered a marker for

cccDNA cccDNA (covalently closed circular DNA) is a special DNA structure that arises during the propagation of some viruses in the cell nucleus and may remain permanently there. It is a double-stranded DNA that originates in a linear form that is lig ...

replication.

Structure

HBeAg is an antigen that can be found between the

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...

nucleocapsid core and the lipid

envelope An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter or card. Traditional envelopes are made from sheets of paper cut to one of three shapes: a rhombus, a sh ...

(the outer 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 b ...

). However, HBeAg is considered "nonparticulate" or "secretory". While both HBeAg and

are made from the same

reading frame In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid ( DNA or RNA) molecule into a set of consecutive, non-overlapping triplets. Where these triplets equate to amino acids or stop signals during ...

(multiple protein products can be produced from the same DNA sequence and when the genes "ORF Core" and "Pre C" are translated together, the result is HBeAg), HBeAg is secreted and accumulates in serum as an

immunological Immunology is a branch of medicineImmunology for Medical Students, Roderick Nairn, Matthew Helbert, Mosby, 2007 and biology that covers the medical study of immune systems in humans, animals, plants and sapient species. In such we can see there ...

ly distinct soluble

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 respons ...

. Hence the reason why the presence of both proteins together acts as a marker of viral replication, and why antibodies to these antigens are a marker of declining replication. The presence of HBeAg in the serum of patients can serve as a marker of active replication in chronic hepatitis.

Function

Although the function of HBeAg was not clearly understood, one study demonstrated that it downregulated

Toll-like receptor Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single-pass membrane-spanning receptors usually expressed on sentinel cells such as macrophages and dendritic cells, that recognize ...

2 expression on hepatocytes and monocytes leading to a decrease in cytokine expression. HBeAg is dispensable for replication, as mutant viruses with defects in the pre-C region are both infectious and pathogenic.Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 7th ed. page 2062

References

{{Viral proteins Viral structural proteins Hepatitis B virus

Structure

Function

See also

References