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Circoviridae is a family of viruses. Birds and mammals serve as natural hosts. There are currently 12 species in this family, divided among 2 genera. Diseases associated with this family include: PCV-2: postweaning multisystemic wasting syndrome; CAV: chicken infectious anemia.^[1]^[2]

Structure

Viruses in Circoviridae are non-enveloped, with icosahedral and round geometries, and T=1 symmetry. The diameter is around 20 nm. Genomes are circular and non-segmented, around 3.8kb in length. The capsid consists of 12 pentagonal trumpet shaped pentamers.^[1] There are two main open reading frames arranged in opposite directions that encode the replication (Rep) and capsid (Cap) proteins. Alternative start codons are common in the avian species.

Genus	Structure	Symmetry	Capsid	Genomic arrangement	Genomic segmentation
Gyrovirus	Icosahedral	T=1	Non-enveloped	Circular	Monopartite
Circovirus	Icosahedral	T=1	Non-enveloped	Circular	Monopartite

Life cycle

Viral replication is nuclear. Entry into the host cell is achieved by penetration into the host cell. 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.^[1] A stem loop structure with a conserved nonanucleotide motif is located at the 5' intergenic region of circovirus genomes and is thought to initiate rolling-cycle replication. Birds and mammals serve as the natural host. Transmission routes are fecal-oral.^[1]

Genus	Host	Tissue tropism	Entry	Release	Replication site	Assembly site	Transmission
Gyrovirus	Birds	Chicken: Thymocytes, erythrobalstoid cells; Egg: embryonal tissues and eggshell membrane	Cell receptor endocytosis	Budding	Nucleus	Nucleus	Horizontal: oral-fecal; vertical: bird to egg
Circovirus	Birds; pigs	None	Cell receptor endocytosis	Budding	Nucleus	Nucleus	Horizontal; oral-fecal

Taxonomy

Group: ssDNA

Order: Unassigned

Family: Circoviridae
- Genus: Circovirus
  Beak and feather disease virus
  
  Canary circovirus
  
  Duck circovirus
  
  Finch circovirus
  
  Goose circovirus
  
  Gull circovirus
  
  Pigeon circovirus
  
  Porcine circovirus-1
  
  Porcine circovirus-2
  
  Starling circovirus
  
  Swan circovirus
- Genus: Gyrovirus
  Chicken anemia virus

^[2]

The family Circoviridae contains two genera, Circovirus and Gyrovirus, and one proposed genus: Cyclovirus.

Two yet-uncategorized circovirus-like viruses have been identified in fish—Barbel circovirus (BaCV) 1 and 2.^[3] Their genomes are similar in length and contain two major open reading frames similar to the capsid and replication associated protein genes found in other circoviruses.

Genus Circovirus: type species: Porcine circovirus type 1^[4]
Genus Gyrovirus: type species: Chicken anaemia virus
Proposed genus Cyclovirus : Dragonfly cyclovirus, Florida woods cockroach-associated cyclovirus^[5]

Clinical

A cyclovirus — cyclovirus-Vietnam — has been isolated from the cerebrospinal fluid of 25 Vietnamese patients with CNS infections of unknown aetiology.^[6] The same virus has been isolated from the faeces of healthy children and also from pigs and chickens. This suggests an orofaecal route of transmission with a possible animal reservoir.

References

^ ^a ^b ^c ^d "Viral Zone". ExPASy. Retrieved 15 June 2015.
^ ^a ^b ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
^ Lorincz M, Csagola A, Farkas SL, Szekely C, Tuboly T (2011) First detection and analysis of a fish circovirus. J Gen Virol
^ Mankertz P (2008). "Molecular Biology of Porcine Circoviruses". Animal Viruses: Molecular Biology. Caister Academic Press. ISBN 978-1-904455-22-6.
^ Dayaram A, Potter KA, Moline AB, Rosenstein DD, Marinov M, Thomas JE, Beitbart M, Rosario K, Argüello-Astorga GR, Varsani A (2013) High global diversity of cycloviruses amongst dragonflies. J Gen Virol
^ Tan le V, van Doorn HR, Nghia HD, Chau TT, Tu le TP, de Vries M, Canuti M, Deijs M, Jebbink MF, Baker S, Bryant JE, Tham NT, Bkrong NT, Boni MF, Loi TQ, Phuong le T, Verhoeven JT, Crusat M, Jeeninga RE, Schultsz C, Chau NV, Hien TT, van der Hoek L, Farrar J, de Jong MD (2013) Identification of a new cyclovirus in cerebrospinal fluid of patients with acute central nervous system infections. MBio 4(3). pii: e00231–13. doi: 10.1128/mBio.00231-13

External links

ICTVdB Entry for Circoviridae
Viralzone: Circoviridae
ICTV

English Journal

Gut DNA viromes of Malawian twins discordant for severe acute malnutrition.

Reyes A1, Blanton LV2, Cao S3, Zhao G3, Manary M4, Trehan I5, Smith MI6, Wang D7, Virgin HW3, Rohwer F8, Gordon JI9.
Proceedings of the National Academy of Sciences of the United States of America.Proc Natl Acad Sci U S A.2015 Sep 22;112(38):11941-6. doi: 10.1073/pnas.1514285112. Epub 2015 Sep 8.
The bacterial component of the human gut microbiota undergoes a definable program of postnatal development. Evidence is accumulating that this program is disrupted in children with severe acute malnutrition (SAM) and that their persistent gut microbiota immaturity, which is not durably repaired with
PMID 26351661

Discovery of a novel circular DNA virus in the Forbes sea star, Asterias forbesi.

Fahsbender E1, Hewson I, Rosario K, Tuttle AD, Varsani A, Breitbart M.
Archives of virology.Arch Virol.2015 Sep;160(9):2349-51. doi: 10.1007/s00705-015-2503-2. Epub 2015 Jun 26.
A single-stranded DNA (ssDNA) virus, Asterias forbesi-associated circular virus (AfaCV), was discovered in a Forbes sea star displaying symptoms of sea star wasting disease (SSWD). The AfaCV genome organization is typical of circular Rep-encoding ssDNA (CRESS-DNA) viruses and is similar to that of m
PMID 26112764

Small circular single stranded DNA viral genomes in unexplained cases of human encephalitis, diarrhea, and in untreated sewage.

Phan TG1, Mori D2, Deng X3, Rajindrajith S4, Ranawaka U5, Fan Ng TF1, Bucardo-Rivera F6, Orlandi P7, Ahmed K8, Delwart E9.
Virology.Virology.2015 Aug;482:98-104. doi: 10.1016/j.virol.2015.03.011. Epub 2015 Apr 1.
Viruses with small circular ssDNA genomes encoding a replication initiator protein can infect a wide range of eukaryotic organisms ranging from mammals to fungi. The genomes of two such viruses, a cyclovirus (CyCV-SL) and gemycircularvirus (GemyCV-SL) were detected by deep sequencing of the cerebros
PMID 25839169

Japanese Journal

A Review of DNA Viral Infections in Psittacine Birds

Katoh Hiroshi,Ogawa Hirohito,Ohya Kenji [他],FUKUSHI Hideto
Journal of Veterinary Medical Science 72(9), 1099-1106, 2010
… PBFD is caused by beak and feather virus, which belongs to the Circoviridae, and is the most important infection in psittacine birds worldwide. …
NAID 130000264240

Family Circoviridae

TODD D.
Virus Taxonomy. Classification and Nomenclature of Viruses, Seventh Report of the International Committee on Taxonomy of Viruses, 299-303, 2000
NAID 10007310848

Partial〜2.4-kb sequences of TT virus (TTV) genome from eight Japanese isolates:diagnostic and phylogenetic implications^1

TAKAHASHI Kazuaki,OHATA Yasuhiko,MISHIRO Shunji
Hepatology research : the official journal of the Japan Society of Hepatology 12(2), 111-120, 1998-09
NAID 10005911786