Alloherpesviridae

Alloherpesviridae is a family of viruses within the order Herpesvirales. This family includes the species that infect fish and amphibians. Phylogenetic studies have confirmed the validity of this family and suggest that it may be divided into two clades: one consisting of viruses from cyprinid and anguillid hosts and the other of viruses from ictalurid, salmonid, acipenserid and ranid hosts.[1] There are currently 12 species in this family, divided among 4 genera. Diseases associated with this family include: channel catfish disease.[2][3]

Alloherpesviridae
TEM micrograph on an alloherpesvirus, 'Pilchard herpesvirus'
Virus classification
(unranked): Virus
Phylum: incertae sedis
Class: incertae sedis
Order: Herpesvirales
Family: Alloherpesviridae
Genera

See text

Taxonomy

Alloherpesviridae was established as a family in 2005.

Genera

The family contains the following four genera:[3]

Structure

Viruses in Alloherpesviridae are enveloped, with icosahedral and spherical to pleomorphic geometries, and T=16 symmetry. The diameter is around 150-200 nm. Genomes are linear and non-segmented, around 134-248kb in length. [2]

GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
IctalurivirusSpherical pleomorphicT=16EnvelopedCircularMonopartite
CyprinivirusSpherical pleomorphicT=16EnvelopedLinearMonopartite
BatrachovirusSpherical pleomorphicT=16EnvelopedLinearMonopartite
SalmonivirusSpherical pleomorphicT=16EnvelopedLinearMonopartite

Life cycle

Viral replication is nuclear, and is lysogenic. Entry into the host cell is achieved by attachment of the viral glycoproteins to host receptors, which mediates endocytosis. DNA-templated transcription is the method of transcription. Fish serve as the natural host. Transmission routes are passive diffusion.[2]

GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
IctalurivirusFishNoneGlycoprotiensBuddingNucleusNucleusPassive diffusion
CyprinivirusFresh water eelNoneGlycoprotiensBuddingCytoplasmCytoplasmPassive diffusion
BatrachovirusFrogsNoneGlycoprotiensBuddingCytoplasmCytoplasmPassive diffusion
SalmonivirusSalmonidaeNoneGlycoprotiensBuddingNucleusNucleusPassive diffusion

Genomics

Several genomes have been sequenced.[4] Cyprinid herpesviruses 1, 2 and 3 (CyHV1, CyHV2 and CyHV3) cause disease in common carp, goldfish and koi respectively. Their genomes are respectively 291144, 290304 and 295146 base pairs in size. The overall organisation common to all three and consists of a unique central region flanked by a direct repeat at each end. 137, 150, and 155 unique, functional protein coding genes are present in the unique regions respectively: of these six, four, and eight respectively are duplicated in the terminal repeat. The genomes share 120 orthologous genes in a largely colinear arrangement. Up to 55 of these latter genes are also conserved in the other member of the genus Cyprinivirus, Anguillid herpesvirus 1. CyHV1, CyHV2, and CyHV3 have five, six and five families of paralogous genes, respectively.

References
  1. Waltzek TB, Kelley GO, Alfaro ME, Kurobe T, Davison AJ, Hedrick RP (2009). "Phylogenetic relationships in the family Alloherpesviridae". Dis. Aquat. Org. 84 (3): 179–94. doi:10.3354/dao02023. PMID 19565695.
  2. "Viral Zone". ExPASy. Retrieved 12 June 2015.
  3. ICTV. "Virus Taxonomy: 2014 Release". Retrieved 12 June 2015.
  4. Davison AJ, Kurobe T, Gatherer D, Cunningham C, Korf I, Fukuda H, Hedrick RP, Waltzek TB (2013). "Comparative genomics of carp herpesviruses". J. Virol. 87 (5): 2908–22. doi:10.1128/JVI.03206-12. PMC 3571366. PMID 23269803.

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