Notes on Family: Pseudoviridae

variable ovoid or spheroid
variable ovoid or spheroid


General Description

This family contains retroelements that produce virus-like particles (VLPs). They do not share the infectivity of 'true' viruses (hence the name) but the VLP stage appears to be an essential stage in their 'life cycle'. VLPs contain the RNA intermediate and the corresponding DNA is integrated into the host genome. These properties are shared by members of the family Metaviridae but the genomic oranisation is different, with the integrase gene located betwen the protease and reverse transcriptase.


Virus-like particles (VLPs) are poorly studied but seem to be non-enveloped, ovoid or spheroid in shape and 60-80 nm in diameter.


The major molecule is a positive sense ssRNA transcript of 5-6 kb flanked by Long Terminal Repeats (LTRs).

Genera in the Family

The genera are based on distinct lineages in phylogenetic analyses of their reverse transcriptase domains:
  • Hemivirus: Minus strand DNA synthesis primed by a half t-RNA molecule
  • Pseudovirus: Minus strand DNA synthesis primed by a complete t-RNA molecule
  • Sirevirus: Distantly related to the other genera