Circovirus


Circovirus is a genus of viruses, in the family Circoviridae. Birds and pigs serve as natural hosts, though dogs have been shown to be infected as well. Circoviruses are single stranded DNA viruses. There are 70 species in this genus. Some members of this genus cause disease: PCV-1 is non pathogenic, while PCV-2 causes postweaning multisystemic wasting syndrome.

Structure

Viruses in Circovirus are non-enveloped, with icosahedrals capsids that have T=1 symmetry. The diameter is around 17 nm. Genomes are circular and non-segmented.
The virions of Circoviruses are surprisingly small, with diameters ranging from 17 up to 22 nm.
GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
CircovirusIcosahedralT=1Non-envelopedCircularMonopartite

Genome

Circovirus has a monopartite, circular, and ssDNA genome of between 1759 and 2319nt, making it possibly the virus of shortest genome size in mammal viruses. The virus replicates through an dsDNA intermediate initiated by the Rep protein. Two major genes are transcribed from open reading frame 1 and 2. ORF1 encodes Rep and Rep' for initiation of rolling-circle replication; ORF2 encodes Cap, the only structural and most immunogenic protein forming the viral capsid.

Life cycle

Viral replication is nuclear. Entry into the host cell is achieved by penetration. Replication follows the ssDNA rolling circle model. DNA templated transcription, with some alternative splicing mechanism is the method of transcription. The virus exits the host cell by nuclear egress, and nuclear pore export. Birds and pigs serve as the natural host. The virus is known to cause "immunosuppressive conditions" in animals that are infected; as well as having the ability to jump between species, creating difficulty in identifying the origin of infection. Transmission routes are fecal-oral and parental.
GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
CircovirusBirds; pigs-Cell receptor endocytosisBuddingNucleusNucleusHorizontal; oral-fecal

Taxonomy

The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species:Circovirus baizhenhe, White-naped crane circovirus 1Circovirus ban, Banfec circovirus 2Circovirus barbel, Barbel circovirusCircovirus bastao, Bat associated circovirus 4, also called Tadarida brasiliensis circovirus 1Circovirus bear, Ursus americanus circovirusCircovirus bianfu, Bat associated circovirus 3, also called Rhinolophus ferrumequinum circovirus 1Circovirus canary, Canary circovirusCircovirus canine, Canine circovirusCircovirus catfish, European catfish circovirus, also called Silurus glanis circovirusCircovirus chauvesouris, Bat associated circovirus 1Circovirus cia, Bat circovirus Circovirus civet, Paguma larvata circovirusCircovirus daga, Rodent circovirus Circovirus dever, Bream circovirus 1Circovirus duck, Duck circovirusCircovirus elk, Elk circovirusCircovirus eniyan, Human faeces associated circovirusCircovirus finch, Finch circovirusCircovirus gloton, Wolvfec circoviusCircovirus gnaver, Rodent circovirus Circovirus goose, Goose circovirusCircovirus gryzon, Bamboo rat circovirusCircovirus gull, Gull circovirusCircovirus gyurgyalag, Bee-eater circovirusCircovirus hirat, Dipodfec virus UA04Rod_4537Circovirus human, Human circovirus 1Circovirus ialtag, Bat circovirus Circovirus impundu, Chimpanzee faeces associated circovirusCircovirus kelawar, Bat associated circovirus 9Circovirus kiore, Rodent circovirusCircovirus kukwuria, Banfec circovirus 1Circovirus lepakko, Bat associated circovirus 7Circovirus lin, Equine circovirus 1Circovirus magu, Mongoose-associated circovirus Mon-1Circovirus mink, Mink circovirusCircovirus miztli, Sonfela circovirus 1Circovirus miztontli, Sonfela circovirus 2Circovirus morcego, Bat associated circovirus 8Circovirus mossi, Culex circovirus-like virusCircovirus naaleeli, Wigfec circovirus 1Circovirus parrot, Beak and feather disease virusCircovirus patkany, Brown rat circovirus 1Circovirus pato, Wigfec circovirus 2Circovirus penguin, Penguin circovirusCircovirus pichong, Tick circovirusCircovirus pigeon, Pigeon circovirus, also called Columbid circovirusCircovirus pipistrello, Bat circovirus Circovirus porcine1, Porcine circovirus 1Circovirus porcine2, Porcine circovirus 2Circovirus porcine3, Porcine circovirus 3Circovirus porcine4, Porcine circovirus 4Circovirus python, Black-headed python circovirus 1Circovirus ratpenat, Bat associated circovirus 6Circovirus raven, Raven circovirusCircovirus razbora, Pseudorasbora circovirus 1Circovirus roditore, Rodent circovirus Circovirus rongeur, Rodent circovirus Circovirus rosegador, Rodent circovirus Circovirus saguzarra, Bat associated circovirus 5Circovirus siksparnis, Bat circovirus Circovirus starling, Starling circovirusCircovirus swan, Swan circovirusCircovirus tetning, Werosea circovirusCircovirus torpegem, Little bittern circovirusCircovirus tzinaka, Eumops bonariensis associated circovirus 1Circovirus vleermuis, Bat associated circovirus 2Circovirus wesa, Calfel virus LSF45_cir359Circovirus whale, Beaked whale circovirusCircovirus yaa, Avian-like circovirusCircovirus zebrafinch, Zebra finch circovirus