Hepatitis D Virus
Author: mzPOTTER
Structure of hepatitis D (Delta) Virus
Hepatitis D virus, also called delta virus or agent is a defective virus that requires the presence of hepatitis B virus to replicate. We can distinguish the following components in its structure:
Outline of the structure of hepatitis D virus The virus has a single circular strand of RNA associated with a protein antigen (HDV). There are 70 HDV antigen molecules per viral particle. This structure is surrounded by a housing that includes lipoprotein surface antigen of hepatitis B virus (HBsAg).
RNA: The genome of hepatitis D virus is composed of a single strand of small circular RNA from nucleotides 1676 to 1683. Its sequence has a high degree of heterogeneity, which have been grouped into 3 genotypes (I, II and III).
Antigen: The only described the virus D antigen is a structural component of the virion, which corresponds to a phosphoprotein encoded by the complementary strand of genomic RNA.
There are 2 forms of HDAg, 24 and 27 kilodaltons, which differ in the last 19 amino acids. The synthesis of these proteins is regulated by RNA editing process during replication. Approximately 70 of these molecules bind to one molecule of viral RNA to form the core.
Lipoprotein envelope: The envelope is similar to hepatitis B virus, and 3 proteins comprising the surface antigen of hepatitis B (small, medium and large).
Replication of hepatitis D virus
The virus enters the hepatocyte in a manner similar to hepatitis B virus, since they share the same cover and receivers. Once in the hepatocyte, the viral RNA is directed to the nucleus, where it is transcribed into a complementary RNA or antigenomic. There are 2 forms of this RNA: A small, 0.8 kb, which is the messenger that HDAg is translated with the help of host polymerase II. The second way is a complete RNA (1.7 kb) that serves as a model for the transcription of more genomic RNA.
These processes are regulated by small and large antigen of hepatitis D virus The small HDAg active viral replication by binding directly to RNA. In turn, the large HDAg inhibits viral replication, leading to virion packaging because it has a binding site with the small HBsAg protein. The output of virus assembly and depends on the presence of hepatitis B virus.