Notes on Genus: Deltavirus
Type member: Hepatitis delta virus
The genus Deltavirus
contains a single virus that is distinctive in being the only known negative sense single stranded RNA genome that is circular. A single protein is encoded and it requires the presence of a helper virus (Hepatitis B virus
, family Hepadnaviridae
) for its replication and packaging. It is named from the delta antigen identified in infected tissue.
Virions spherical, enveloped, 36-43 nm in diameter.
Monopartite circular single-stranded RNA of about 1.7 kb.
Genus Genomic Organization
There is a single ORF expressed in two forms as a result of RNA editing. The longer form is involved in packaging and the smaller form in replication, although both functions also require proteins of the helper virus.
Type Member Genomic Organization
There is a single ORF expressed in two forms as a result of RNA editing. Both forms are multifunctional and contain dimerisation, nuclear localisation and RNA-binding domains:
- Small delta antigen (21.9 kDa) essential for replication
- Large delta antigen (24.0 kDa) essential for packaging but inhibiting replication