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The structure of the hepatitis B virus
Last reviewed: 20.11.2021
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Hepatitis B virus is a spherical formation with a diameter of 42-45 nm, has an external lipoprotein envelope and the inner part is nucleocapsid or the core of the virus.
The outer envelope of the virus is located in the cytoplasm of the infected hepatocyte and contains antigen proteins: superficialis HBsAg and pre-Sl, pre-S2 antigens. HBsAg is often found in the blood plasma of patients with chronic hepatitis in the form of spherical particles with a diameter of 22 nm, and also in the form of filamentous structures measuring 16-25 nm in size.
According to the antigenic characteristic, 4 main subtypes of HBsAg are distinguished: adw, adr, ayw, ayr, depending on the content of one common group-specific determinant a and two of the four subtype determinants d, y, w, r.
On the external envelope of the hepatitis B virus in the zone preceding the HBsAg region, pre-Sl pre-S2 antigen proteins are located. These antigens play a huge role in the mechanism of interaction of the hepatitis B virus with hepatocytes.
The internal part of the hepatitis B virus (nucleocapsid) penetrates into the nucleus of the hepatocyte and contains the following components:
- HBcAg (HBcoreAg) - the core antigen, is localized exclusively in the nuclei of hepatocytes and is not found in the blood;
- HBprecoreAg (HBeAg) - localized in the nucleocapsid of the virus next to HBcAg, representing the secreted soluble part of it; the existence of two variants of HBeAg -HBeAgl and HBeAg2, differing in the degree of association with HBcAg, HBeAg circulates in the blood;
- HBxAg - information about its significance is not sufficient yet; It is assumed that it can be an inducer of the body's tolerance to the hepatitis B virus;
- HBpol is a marker of DNA polymerase synthesis;
- genome of hepatitis B virus HBV-DNA - annular double-stranded DNA molecule; one thread (chain) is 30% shorter than the other. The missing part of DNA is completed from the nucleotides of the host by means of DNA polymerase;
- enzyme DNA polymerase.
The genome of the hepatitis B virus (DNA) contains the following genes that code for the synthesis of antigens:
- gene pre-S / S - codes for the synthesis of HBsAg, as well as pre-Sl andpre-S2;
- gene C - codes for the synthesis of HBcAg and HBeAg;
- gene X - codes for the synthesis of HBxAg, regulates the expression of viral genes and the process of replication of HBV;
- the P gene gene polymerase gene, mainly encodes the HBpol marker, and also participates in the HBcAg coding.
In the body of a patient with viral hepatitis B, antibodies: anti-HBc, anti-HBe, anti-HBs, anti-pre-Sl, anti-HBs, anti-HBs, anti-HBs, anti-HBs, anti-HBs, anti-HBs, anti-HBs, anti-HBsAg, HBeAg, HBsAg, pre-Sl, pre-S2, HBxAg, Hbpol) aHTH-pre-S2, anti-HBx, anti-HBpol. These antigens and antibodies to them are a complex of specific HBV markers. The definition of these markers has diagnostic, prognostic and epidemiological significance. The value of the determination in the blood of anti-HBx and anti-HBpol is not yet known enough.