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  • -Circoviridae
    • Genus: Circovirus
    • Genus: Cyclovirus
    • Authors: Circoviridae
    • Resources: Circoviridae
    • References: Circoviridae
    • Citation: Circoviridae

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Genus: Cyclovirus

Distinguishing features

Cyclovirus genomes contain two major ORFs encoding the Rep and Cp. In contrast to members of the genus Circovirus, cycloviruses have the putative ori on the Cp-encoding strand [{Rosario et al., 2012:22760663RJOHTXRosario et al., 2012, A field guide to eukaryotic circular single-stranded DNA viruses: insights gained from metagenomics, Archives of Virology, 157, 10, 1851-71}]. In addition, cyclovirus genomes have an IR between the 5' end of major ORFs; however, the IR between the 3' ends of these ORFs is smaller than that of genomes representing the genus Circovirus or may be absent [{Li et al., 2010:20007276RJOHTXLi et al., 2010, Multiple diverse circoviruses infect farm animals and are commonly found in human and chimpanzee ***, Journal of Virology, 84, 4, 1674-82RJOMREFDelwart and Li 2012:22155583RJOHTXDelwart and Li 2012, Rapidly expanding genetic diversity and host range of the Circoviridae viral family and other Rep encoding small circular ssDNA genomes, Virus Research, 164, 1-2, 114-21}]. Introns have been identified within the ORFs of several cyclovirus genomes, while none have been reported for circoviruses.

Virion

Morphology

Unknown.

Physicochemical and physical properties

Unknown.

Nucleic acid

Cycloviruses exhibit small, circular ssDNA genomes ranging approximately from 1.7 to 1.9 kb.

Proteins

Unknown.

Lipids

Unknown.

Carbohydrates

Unknown.

Genome organization and replication

Cyclovirus genomes contain two major ORFs encoding the Rep and Cp [{Rosario et al., 2017:28155197RJOHTXRosario et al., 2017, Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus, Archives of Virology, 162, 5, 1447-63}]. Although the virion strand has not be experimentally demonstrated for cycloviruses, knowledge from other eukaryotic Rep-encoding ssDNA viruses suggests that the strand containing the nonanucleotide motif is encapsidated [{Rosario et al., 2012:22760663RJOHTXRosario et al., 2012, A field guide to eukaryotic circular single-stranded DNA viruses: insights gained from metagenomics, Archives of Virology, 157, 10, 1851-71}]. Since the putative cyclovirus ori and predicted Rep share conserved features with members of the genus Circovirus, cycloviruses are also thought to replicate through RCR.  Similar to circoviruses, the putative cyclovirus ori contains the canonical nonanucleotide motif ‘NAGTATTAC’ located at the apex of a potential stem-loop structure found between the 5’ ends of major ORFs. In addition, the Rep contains endonuclease and helicase domains with RCR and SF3 motifs similar to those identified in circovirus Reps. These conserved motifs include RCR motifs I [FT(L/W)NN], II [(P/x)HLQG] and III [Y(C/l)(S/x)K] and SF3 helicase motifs Walker-A [G(P/x)(P/t)(G/x)xGKS], Walker-B [uuDDF], and motif C [uTS(N/e)], where ‘‘x’’ represents any type of residue and ‘‘u’’ represents a hydrophobic amino acid (i.e., F, I, L, V, M). Moreover, putative Rep-binding domains characterized by iterative sequences near the stem-loop structure have been identified for some cyclovirus genomes [{Dayaram et al., 2013:23596268RJOHTXDayaram et al., 2013, High global diversity of cycloviruses amongst dragonflies, Journal of General Virology, 94, Pt 8, 1827-40}].

Antigenicity

Unknown.

Biology

Cyclovirus genomes were originally discovered in primate stool samples and meat products from diverse animals (camels, chickens, cows, goats, sheep) [{Li et al., 2010:20007276RJOHTXLi et al., 2010, Multiple diverse circoviruses infect farm animals and are commonly found in human and chimpanzee ***, Journal of Virology, 84, 4, 1674-82RJOMREFDelwart and Li 2012:22155583RJOHTXDelwart and Li 2012, Rapidly expanding genetic diversity and host range of the Circoviridae viral family and other Rep encoding small circular ssDNA genomes, Virus Research, 164, 1-2, 114-21}]. However, cyclovirus genomes have now been reported from various types of human samples other than faeces, including cerebrospinal fluid, blood serum, and respiratory secretions [{Smits et al., 2013:23968557RJOHTXSmits et al., 2013, Novel cyclovirus in human cerebrospinal fluid, Malawi, 2010-2011, Emerging Infectious Diseases, 19, 9RJOMREFTan le et al., 2013:23781068RJOHTXTan le et al., 2013, Identification of a new cyclovirus in cerebrospinal fluid of patients with acute central nervous system infections, MBio, 4, 3, e00231-13RJOMREFPhan et al., 2014:24421114RJOHTXPhan et al., 2014, Cyclovirus in nasopharyngeal aspirates of Chilean children with respiratory infections, Journal of General Virology, 95, Pt 4, 922-7RJOMREFPhan et al., 2015:25839169RJOHTXPhan et al., 2015, Small circular single stranded DNA viral genomes in unexplained cases of human encephalitis, diarrhea, and in untreated sewage, Virology, 482, 98-104}]. Additionally, cycloviruses have been detected in sampled from a wide range of mammalian and insect species [{Rosario et al., 2017:28155197RJOHTXRosario et al., 2017, Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus, Archives of Virology, 162, 5, 1447-63}]. Since genomes belonging to the genus Cyclovirus have only been identified through sequence-based analyses (i.e., degenerate PCR and metagenomic sequencing), definitive hosts and biology are largely unknown.

Species demarcation criteria

The species demarcation threshold is 80% genome-wide nucleotide sequence identity based on pairwise identity distribution analysis (Figure 3.Circovirus) [{Rosario et al., 2017:28155197RJOHTXRosario et al., 2017, Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus, Archives of Virology, 162, 5, 1447-63}].

Member Species

SpeciesVirus name(s)Exemplar isolateExemplar accession numberExemplar RefSeq numberAvailable sequenceOther isolatesOther isolate accession numbersVirus abbreviationIsolate abbreviation
Bat associated cyclovirus 1bat faeces associated cyclovirus 1GF-4cHM228874NC_034547Complete genomeBatACyV1
Bat associated cyclovirus 2bat faeces associated cyclovirus 2YN-BtCV-2JF938079NC_038393Complete genomeBatACyV2
Bat associated cyclovirus 3bat faeces associated cyclovirus 3YN-BtCV-4JF938081NC_038394Complete genomeBatACyV3
Bat associated cyclovirus 4bat faeces associated cyclovirus 4YN-BtCV-5JF938082NC_038395Complete genomeBatACyV4
Bat associated cyclovirus 5bat associated cyclovirus 5CyCV-TBHQ738637NC_014929Complete genomeBatACyV5
Bat associated cyclovirus 6bat associated cyclovirus 6BtRp-CV-3/GD2012KJ641712NC_038396Complete genomeBatACyV6
Bat associated cyclovirus 7bat associated cyclovirus 7BtRf-CV-24/YN2010KJ641740NC_038397Complete genomeBatACyV7
Bat associated cyclovirus 8bat associated cyclovirus 8BtRp-CV-52/GD2012KJ641715NC_038398Complete genomeBatACyV8
Bat associated cyclovirus 9bat associated cyclovirus 9BtTp-CV-2/GX2012KJ641720NC_038399Complete genomeBatACyV9
Bat associated cyclovirus 10bat associated cyclovirus 10POA/2012/VIKM382270NC_025792Complete genomeBatACyV10
Bat associated cyclovirus 11bat associated cyclovirus 11BtMspp.-CV/GD2012KJ641717NC_038400Complete genomeBatACyV11
Bat associated cyclovirus 12bat associated cyclovirus 12POA/2012/IIKM382269NC_025791Complete genomeBatACyV12
Bat associated cyclovirus 13bat associated cyclovirus 13BtPa-CV-2/NX2013KJ641728NC_038401Complete genomeBatACyV13
Bat associated cyclovirus 14bat associated cyclovirus 14Tbat_H_103699KT732785NC_038402Complete genomeBatACyV14
Bat associated cyclovirus 15bat associated cyclovirus 15Tbat_H_88317KT732786NC_038403Complete genomeBatACyV15
Bat associated cyclovirus 16bat associated cyclovirus 16Tbat_K_103923KT732787NC_038404Complete genomeBatACyV16
Bovine associated cyclovirus 1bovine cyclovirusPKbeef23HQ738634NC_038405Complete genomeBoACyV1
Chicken associated cyclovirus 1chicken associated cyclovirus 1NGchicken8HQ738643NC_038406Complete genomeChickACyV1
Chimpanzee associated cyclovirus 1chimpanzee faeces associated cyclovirusChimp11GQ404849NC_038407Complete genomeChimpACyV1
Cockroach associated cyclovirus 1Florida woods cockroach cyclovirusGS140JX569794NC_020206Complete genomeCroACyV1
Dragonfly associated cyclovirus 1dragonfly cyclovirus 1TO-DFpB1-2010JX185419Complete genomeDfACyV1
Dragonfly associated cyclovirus 2dragonfly cyclovirus 2FL1-NZ38-2010JX185422NC_023869Complete genomeDfACyV2
Dragonfly associated cyclovirus 3dragonfly cyclovirus 3FL2-5E-2010JX185424NC_023868Complete genomeDfACyV3
Dragonfly associated cyclovirus 4dragonfly cyclovirus 4US-DFKWGX-2012KC512916NC_039214Complete genomeDfACyV4
Dragonfly associated cyclovirus 5dragonfly cyclovirus 5PR-6E-2010JX185426NC_023866Complete genomeDfACyV5
Dragonfly associated cyclovirus 6dragonfly cyclovirus 6US-DFKWGX-2012KC512918NC_038408Complete genomeDfACyV6
Dragonfly associated cyclovirus 7dragonfly cyclovirus 7NZ-DFNZ3-2011KC512919NC_038409Complete genomeDfACyV7
Dragonfly associated cyclovirus 8dragonfly cyclovirus 8AU-DFB007B-2012KC512920NC_038410Complete genomeDfACyV8
Duck associated cyclovirus 1duck associated cyclovirus 1DuACyV-1/1KY851116NC_034977Complete genomeDuACyV1
Feline associated cyclovirus 1feline cyclovirusKM017740NC_024700Complete genomeFeACyV1
Goat associated cyclovirus 1goat cyclovirusPKgoat11HQ738636NC_014928Complete genomeGoACyV1
Horse associated cyclovirus 1horse cyclovirusEqu1KR902499NC_038411Complete genomeHoACyV1
Human associated cyclovirus 1human associated cyclovirus 1PK5510GQ404847NC_038412Complete genomeHuACyV1
Human associated cyclovirus 2human associated cyclovirus 2PK5006GQ404844NC_036877Complete genomeHuACyV2
Human associated cyclovirus 3human associated cyclovirus 3PK5222GQ404846NC_038413Complete genomeHuACyV3
Human associated cyclovirus 4human associated cyclovirus 4TN25GQ404857NC_038414Complete genomeHuACyV4
Human associated cyclovirus 5human associated cyclovirus 5PK5034GQ404845NC_038415Complete genomeHuACyV5
Human associated cyclovirus 6human associated cyclovirus 6NG12GQ404854NC_038416Complete genomeHuACyV6
Human associated cyclovirus 7human associated cyclovirus 7NG14GQ404855NC_038417Complete genomeHuACyV7
Human associated cyclovirus 8human associated cyclovirus 8hcf2KF031466NC_039215Complete genomeHuACyV8
Human associated cyclovirus 9human associated cyclovirus 9VS5700009KC771281NC_021568Complete genomeHuACyV9
Human associated cyclovirus 10human associated cyclovirus 107078AKF726984NC_023874Complete genomeHuACyV10
Human associated cyclovirus 11human associated cyclovirus 11SL-108277KJ831064NC_038418Complete genomeHuACyV11
Human associated cyclovirus 12human associated cyclovirus 12IECSF08KU053483NC_032682Complete genomeHuCyC12
Mouse associated cyclovirus 1mouse associated cyclovirus 1Cyclo-sf1KT878836NC_031755Complete genomeMoACyV1
Rodent associated cyclovirus 1rodent circovirusRtRf-CV-2/YN2013KY370028Complete genomeRoACyV1
Rodent associated cyclovirus 2rodent circovirusRtRs-CV/YN2013KY370026Complete genomeRoACyV2
Squirrel associated cyclovirus 1squirrel cyclovirusJP-NUBS-2014LC018134NC_027530Complete genomeSqACyV1

Virus names, the choice of exemplar isolates, and virus abbreviations, are not official ICTV designations.
Download GenBank/EMBL query for sequences listed in the table here.

Derivation of names

Cyclo: indicates circle or ring in Greek.

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