| Large envelope protein | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Organism | |||||||
| Symbol | S | ||||||
| UniProt | Q9QAB7 | ||||||
| |||||||
HBsAg (also known as the Australia antigen) is the surface antigen of the hepatitis B virus (HBV). Its presence in blood indicates existing hepatitis B infection.
| Large envelope protein | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Organism | |||||||
| Symbol | S | ||||||
| UniProt | Q9QAB7 | ||||||
| |||||||
HBsAg (also known as the Australia antigen) is the surface antigen of the hepatitis B virus (HBV). Its presence in blood indicates existing hepatitis B infection.
The viral envelope of an enveloped virus has different surface proteins from the rest of the virus which act as antigens. These antigens are recognized by antibody proteins that bind specifically to one of these surface proteins.
The full-length HBsAg is called the L (for "large") form. It consists of a preS loop, a first transmembrane helix (TM1), a cytosolic loop (CYL), another TM helix (TM2), an antigenic loop (AGL), followed by two TM helices (TM3 and TM4). The preS loop can either be on the outside (lumen), or be located in the cytosol with the TM1 helix not actually penetrating the membrane. The M ("medium") form has a truncated preS; the part of preS1 unique to L is called preS1, while the part shared by L and M is called preS2. preS2 is always located in the lumen. The S ("small") form has no preS2. [1]
HBsAg forms the shell of the virus. Furthermore, it contains parts that are recognized by the cellular receptor of the virus NTCP in preS1, which causes the causes the virus to tightly bind to the cell. How the virus convinces the cell to take the virus in after binding via endocytosis is unknown. [2] It also serves to release the contents of the virion into the cell through membrane fusion. The part responsible for fusion is also located in preS1. [3]
HBsAg self-assembles into viral shells even when no contents are present. Such an empty shell is called a virus-like particle or a small spherical subviral particle. [1]
Today, these antigen-proteins can be genetically manufactured (e.g. transgene E. coli ) to produce material for a simple antigen test, which detects the presence of HBV.
It is present in the sera of patients with viral hepatitis B (with or without clinical symptoms). Patients who developed antibodies against HBsAg (anti-HBsAg seroconversion) are usually considered non-infectious. HBsAg detection by immunoassay is used in blood screening, to establish a diagnosis of hepatitis B infection in the clinical setting (in combination with other disease markers) and to monitor antiviral treatment.
In histopathology, the presence of HBsAg is more commonly demonstrated by the use of the Shikata orcein technique, which uses a natural dye to bind to the antigen in infected liver cells. [4]
Positive HBsAg tests can be due to recent vaccination against Hepatitis B virus but this positivity is unlikely to persist beyond 14 days post-vaccination. [5]
HBsAg made through recombinant DNA is used to make the hepatitis B vaccine. It has a very good efficacy of about 95%, [6] with protection lasting for more than 30 years, even after the anti-HbsAg antigen titers have fallen. [7]
The RTS,S also makes use of HBsAg. It is a mixture of a version of malaria surface antigen grafted to HBsAg (RTS) and ordinary HBsAg (S), both made through recombinant DNA. Much like ordinary HBsAg, these two are able to assemble into virus-like particles that are soluble in water. [8]
It is commonly referred to as the Australia Antigen. This is because it was first isolated by the American research physician and Nobel Prize winner Baruch S. Blumberg in the serum of an Australian Aboriginal person. [9] It was discovered to be part of the virus that caused serum hepatitis by virologist Alfred Prince in 1968.
Heptavax, a "first-generation" hepatitis B vaccine in the 1980s, was made from HBsAg extracted from the blood plasma of hepatitis patients. More modern vaccines are made from recombinant HBsAg grown in yeast.
A DNA vaccine is a type of vaccine that transfects a specific antigen-coding DNA sequence into the cells of an organism as a mechanism to induce an immune response.
Hepatitis D is a type of viral hepatitis caused by the hepatitis delta virus (HDV). HDV is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a satellite because it can propagate only in the presence of the hepatitis B virus (HBV). Transmission of HDV can occur either via simultaneous infection with HBV (coinfection) or superimposed on chronic hepatitis B or hepatitis B carrier state (superinfection).
Hepadnaviridae is a family of viruses. Humans, apes, and birds serve as natural hosts. There are currently 18 species in this family, divided among 5 genera. Its best-known member is hepatitis B virus. Diseases associated with this family include: liver infections, such as hepatitis, hepatocellular carcinomas, and cirrhosis. It is the sole accepted family in the order Blubervirales.
In immunology, seroconversion is the development of specific antibodies in the blood serum as a result of infection or immunization, including vaccination. During infection or immunization, antigens enter the blood, and the immune system begins to produce antibodies in response. Before seroconversion, the antigen itself may or may not be detectable, but the antibody is absent. During seroconversion, the antibody is present but not yet detectable. After seroconversion, the antibody is detectable by standard techniques and remains detectable unless the individual seroreverts, in a phenomenon called seroreversion, or loss of antibody detectability, which can occur due to weakening of the immune system or decreasing antibody concentrations over time. Seroconversion refers the production of specific antibodies against specific antigens, meaning that a single infection could cause multiple waves of seroconversion against different antigens. Similarly, a single antigen could cause multiple waves of seroconversion with different classes of antibodies. For example, most antigens prompt seroconversion for the IgM class of antibodies first, and subsequently the IgG class.
Virus-like particles (VLPs) are molecules that closely resemble viruses, but are non-infectious because they contain no viral genetic material. They can be naturally occurring or synthesized through the individual expression of viral structural proteins, which can then self assemble into the virus-like structure. Combinations of structural capsid proteins from different viruses can be used to create recombinant VLPs. Both in-vivo assembly and in-vitro assembly have been successfully shown to form virus-like particles. VLPs derived from the Hepatitis B virus (HBV) and composed of the small HBV derived surface antigen (HBsAg) were described in 1968 from patient sera. VLPs have been produced from components of a wide variety of virus families including Parvoviridae, Retroviridae, Flaviviridae, Paramyxoviridae and bacteriophages. VLPs can be produced in multiple cell culture systems including bacteria, mammalian cell lines, insect cell lines, yeast and plant cells.
Duck hepatitis B virus, abbreviated DHBV, is part of the genus Avihepadnavirus of the Hepadnaviridae, and is the causal agent of duck hepatitis B.
Hepatitis B vaccine is a vaccine that prevents hepatitis B. The first dose is recommended within 24 hours of birth with either two or three more doses given after that. This includes those with poor immune function such as from HIV/AIDS and those born premature. It is also recommended that health-care workers be vaccinated. In healthy people, routine immunization results in more than 95% of people being protected.
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.
E1 is one of two subunits of the envelope glycoprotein found in the hepatitis C virus. The other subunit is E2. This protein is a type 1 transmembrane protein with a highly glycosylated N-terminal ectodomain and a C-terminal hydrophobic anchor. After being synthesized the E1 glycoproteins associates with the E2 glycoprotein as a noncovalent heterodimer.
A subunit vaccine is a vaccine that contains purified parts of the pathogen that are antigenic, or necessary to elicit a protective immune response. Subunit vaccine can be made from dissembled viral particles in cell culture or recombinant DNA expression, in which case it is a recombinant subunit vaccine.
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.
A neutralizing antibody (NAb) is an antibody that defends a cell from a pathogen or infectious particle by neutralizing any effect it has biologically. Neutralization renders the particle no longer infectious or pathogenic. Neutralizing antibodies are part of the humoral response of the adaptive immune system against viruses, bacteria and microbial toxin. By binding specifically to surface structures (antigen) on an infectious particle, neutralizing antibodies prevent the particle from interacting with its host cells it might infect and destroy.
The transmission of hepadnaviruses between their natural hosts, humans, non-human primates, and birds, including intra-species host transmission and cross-species transmission, is a topic of study in virology.
RTS,S/AS01 is a recombinant protein-based malaria vaccine. It is one of two malaria vaccines approved. As of April 2022, the vaccine has been given to 1 million children living in areas with moderate-to-high malaria transmission, with millions more doses to be provided as the vaccine's production expands. 18 million doses have been allocated for 2023-2025. It requires at least three doses in infants by age 2, with a fourth dose extending the protection for another 1–2 years. The vaccine reduces hospital admissions from severe malaria by around 30% and reduces toddler deaths by 15%.
Raccoonpox virus (RCN) is a double-stranded DNA virus and a member of the orthopoxviruses in the family Poxviridae and subfamily Chordopoxvirinae. Vertebrates are the natural host of Chordopoxvirinae subfamily viruses. More specifically, raccoons are the natural hosts of RCN. RCN was isolated in 1961 from the upper respiratory tissues of 2 raccoons in a group of 92 observably healthy raccoons trapped close to Aberdeen, Maryland.
David Maurice Surrey Dane, MRCS CRCP MB Bchir MRCP MRCPath FRCPath FRCP was a pre-eminent British pathologist and clinical virologist known for his pioneering work in infectious diseases including poliomyelitis and the early investigations into the efficacy of a number of vaccines. He is particularly remembered for his strategic foresight in the field of blood transfusion microbiology, particularly in relation to diseases that are spread through blood transfusion.
An edible vaccine is a food, typically plants, that contain vitamins, proteins or other nourishment that act as a vaccine against a certain disease. Once the plant, fruit, or plant derived product is ingested orally, it stimulates the immune system. Specifically, it stimulates both the mucosal and humoral immune systems. Edible vaccines are genetically modified crops that contain antigens for specific diseases. Edible vaccines offer many benefits over traditional vaccines, due to their lower manufacturing cost and a lack of negative side effects. However, there are limitations as edible vaccines are still new and developing. Further research will need to be done before they are ready for widespread human consumption. Edible vaccines are currently being developed for measles, cholera, foot and mouth disease, Hepatitis B and Hepatitis C.
Ground squirrel hepatitis virus, abbreviated GSHV, is a partially double-stranded DNA virus that is closely related to human Hepatitis B virus (HBV) and Woodchuck hepatitis virus (WHV). It is a member of the family of viruses Hepadnaviridae and the genus Orthohepadnavirus. Like the other members of its family, GSHV has high degree of species and tissue specificity. It was discovered in Beechey ground squirrels, Spermophilus beecheyi, but also infects Arctic ground squirrels, Spermophilus parryi. Commonalities between GSHV and HBV include morphology, DNA polymerase activity in genome repair, cross-reacting viral antigens, and the resulting persistent infection with viral antigen in the blood (antigenemia). As a result, GSHV is used as an experimental model for HBV.
Spike (S) glycoprotein is the largest of the four major structural proteins found in coronaviruses. The spike protein assembles into trimers that form large structures, called spikes or peplomers, that project from the surface of the virion. The distinctive appearance of these spikes when visualized using negative stain transmission electron microscopy, "recalling the solar corona", gives the virus family its main name.
A genetic vaccine is a vaccine that contains nucleic acids such as DNA or RNA that lead to protein biosynthesis of antigens within a cell. Genetic vaccines thus include DNA vaccines, RNA vaccines and viral vector vaccines.
