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Hepatitis D virus

Hepatitis D
Classification and external resources
Specialty infectious disease
ICD-10 B17.0, B18.0
ICD-9-CM 070.31
DiseasesDB 5792
MeSH D003699
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Hepatitis D
Hepatitis-d-virion-Pathogens-04-00046-g001-1024.png
Schematic representation of the hepatitis delta virus virion.
Virus classification
Group: Group V ((-)ssRNA)
Order: Unassigned
Family: Unassigned
Genus: Deltavirus
Species: Hepatitis delta virus
Hepatitis delta virus delta antigen
PDB 1a92 EBI.jpg
oligomerization domain of hepatitis delta antigen
Identifiers
Symbol HDV_ag
Pfam PF01517
InterPro IPR002506
SCOP 1a92
SUPERFAMILY 1a92

Hepatitis D (hepatitis delta) is a disease caused by the hepatitis D virus (HDV), a small spherical enveloped viroid. This is one of five known hepatitis viruses: A, B, C, D, and E. HDV is considered to be a subviral 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).

Both superinfection and coinfection with HDV results in more severe complications compared to infection with HBV alone. These complications include a greater likelihood of experiencing liver failure in acute infections and a rapid progression to liver cirrhosis, with an increased risk of developing liver cancer in chronic infections. In combination with hepatitis B virus, hepatitis D has the highest fatality rate of all the hepatitis infections, at 20%.

The HDV is a small, spherical virus with a 36 nm diameter. It has an outer coat containing three kinds of HBV envelope protein - large, medium, and small hepatitis B surface antigens - and host lipids surrounding an inner nucleocapsid. The nucleocapsid contains single-stranded, circular RNA of 1679 nucleotides and about 200 molecules of hepatitis D antigen (HDAg) for each genome. The central region of HDAg has been shown to bind RNA. Several interactions are also mediated by a coiled-coil region at the N terminus of HDAg. The hepatitis D circular genome is unique to animal viruses because of its high GC nucleotide content. The HDV genome exists as an enveloped, negative sense, single-stranded, closed circular RNA. Its nucleotide sequence is 70% self-complementary, allowing the genome to form a partially double-stranded, rod-like RNA structure. With a genome of approximately 1700 nucleotides, HDV is the smallest "virus" known to infect animals. It has been proposed that HDV may have originated from a class of plant pathogens called viroids, which are much smaller than viruses.


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