The Structure of Hepatitis B Virus
The hepatitis B virus is a small DNA virus with unusual features similar to retroviruses, which is a prototype virus of the Hepadnaviridae family. HBV causes acute and chronic hepatitis in humans. The hepatitis B virus consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein. The virus is one of the smallest enveloped animal viruses with a virion diameter of 42 nm, and also named Dane particles. Dane particles contains both “envelope” and “core”.
The outer envelope contains embedded proteins which are involved in viral binding of susceptible cells. There are three types of proteins: small hepatitis surface proteins, middle hepatitis surface proteins and large hepatitis surface proteins, they are totally composed of hepatitis B surface proteins. The nucleocapsid encloses the viral DNA and a DNA polymerase that has reverse transcriptase activity.
There are three types of Hepatitis B Virus particles in infectious serum by electron microscopy, Dane particles, filamentous particles and spherical particles. Except for Dane particles (42 nm in diameter), there also exist pleomorphic forms, as filamentous particles (22 nm in diameter) and spherical particles (20 nm diameter).
Hepatitis B Virus Antigens
Hepatitis B surface antigen– HBsAg
Hepatitis B Virus Antigens, the presence of surface antigen in a lab report indicates a hepatitis B infection. Filamentous particles and spherical particles are totally composed of hepatitis B surface proteins. The sphere contains both middle and small hepatitis surface proteins whereas the filament also includes large hepatitis B surface protein. The absence of the hepatitis B core, polymerase, and genome causes these particles to have a non-infectious nature.
Hepatitis B core antigen-HBcAg
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. HBcAg is considered “particulate” and it does not circulate in the blood, this antigen can only be isolated by analyzing an infected hepatocyte.
Hepatitis B e antigen-HBeAg
HBeAg is an antigen that can be found between the icosahedral nucleocapsid core and the lipid envelope. It is the antigenic determinant that is closely associated with the nucleocapsid of HBV. It also circulates as a soluble protein in serum. The presence of both HBcAg and HBeAg proteins together act as a marker of Hepatitis virus replication.
The X gene codes for HBxAg. The product of the X gene is hepatitis B x antigen (HBxAg). It may be involved in carcinogenesis.
Hepatitis B Virus Antibodies
In an acute infection, the immune system is able to combat the “foreign” surface antigen by creating enough surface antibodies, to destroy this antigen within a few weeks of when symptoms first appear.
Hepatitis B core antibodies are the first detectable HBV antibodies to appear, usually within a few weeks after infection. They are present in anyone who has had either acute or chronic HBV infection.
Hepatitis B “e” antibodies usually persist for one or more years after resolution of an acute infection. Seroconversion, or production of “e” antibodies, is one of the goals of most medical treatments for hepatitis B. Once “e” antibodies are produced, there are usually fewer HBV infecting and damaging the liver. Hepatitis antibody is a marker of declining replication.
Hepatitis B x antibody and hepatitis B x antigen specific binding showed the specificity of the recombinant HBx protein.
Hepatitis B Virus Detection
Hepatitis B virus infection is a serious health problem worldwide: about 350 million people are suffering from chronic HBV infection. Hepatitis B virus is considered as one of the most common viruses spreading through blood transfusion and organ transplants. This usually results in more considerable cases of disease such as cirrhosis, chronic liver disease, hepatic failure, or hepatocellular carcinoma (HCC); so it is necessary to perform tests for viral infection in all blood donors. Since Hepatitis B virus (HBV) is known as one of the major causes of blood transmitted hepatitis infections, blood screening using the HBV ELISA test is one of the most effective ways of preventing the spread of Hepatitis B virus.
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