What is hepatitis B virus?
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| What is hepatitis B virus? |
It is a DNA virus belonging to the Hepadnavividae family and is a spherical particle with a diameter of 42 nm. Also known as Dane particles, there are two parts of the outer shell and the core. The outer shell is 7-8 nm thick, has a surface antigen (HBsAg), has a core diameter of 27 nm, and contains partially double-stranded, partially single-stranded circular DNA, DNA polymerase, core antigen and e antigen. The genome of HBV DNA contains approximately 3200 base pairs. The length of the long chain is fixed, and there is a nick here where DAN polymerase; the length of the short chain is variable. When HVB replicates, the endogenous DNA polymerase repairs the short strand, making it a complete double-stranded structure, and then transcribed. The long chain of HBV DNA has four open reading frames (ORFs), namely S region, C region, P region and X region. The S region includes the pre-S1 pre-S2 and S region genes, encoding the pre-S1, pre-S2 and S coat proteins; the C region includes the pre-C region, the C region gene encodes the HBcAg protein, and the pre-C region encodes a signal peptide, which is assembled. It plays an important role in secreting viral particles and in the secretion of HBeAg; the P gene encodes a DNA polymerase; the product of the X gene is an X protein, the function of which is unclear. The short chain of HBV DNA does not contain an open reading frame and therefore cannot encode a protein.
In the serum of patients with hepatitis B, three kinds of particles can be found under the microscope observation:
- Small spherical particles having a diameter of 22 nm;
- Tubular particles, about 100 ~ 700nm long, about 22nm wide;
- Large spherical particles having a diameter of 42 nm.
Small spherical particles. The small spherical particles and the tubular particles are all excess viral outer shells, containing surface antigens, large spherical particles, ie, viral particles, both solid and hollow, and the hollow particles lack nucleic acids.
