Notes on Genus: Deltavirus

enveloped spheres
enveloped spheres

Type member: Hepatitis delta virus

Contents

General Description

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.

Morphology

Virions spherical, enveloped, 36-43 nm in diameter.

Genome

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