''Chordopoxvirinae'' is a

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almo ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Poxviridae ''Poxviridae'' is a family of double-stranded DNA viruses. Vertebrates and arthropods serve as natural hosts. The family contains 22 genera that are assigned to two subfamilies: ''Chordopoxvirinae'' and ''Entomopoxvirinae''. ''Entomopoxvirinae'' ...

''.

Vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

and

arthropods Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

serve as natural hosts. The subfamily contains 18

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

. Diseases associated with this subfamily include

smallpox Smallpox was an infectious disease caused by Variola virus (often called Smallpox virus), which belongs to the genus '' Orthopoxvirus''. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (W ...

. Four genera in this subfamily contain species that infect humans: '' Molluscipoxvirus, Orthopoxvirus, Parapoxvirus'', and ''

Yatapoxvirus ''Yatapoxvirus'' is a genus of viruses, in the family ''Poxviridae'', in the subfamily ''Chordopoxvirinae''. Monkeys and Baboon, baboons serve as natural hosts. There are two species in this genus. Diseases associated with this genus can cause H ...

''.

Virology

The virions are generally enveloped though the intracellular mature virion form of the virus, which contains a different envelope and is also infectious. They vary in their shape depending upon the species but are generally shaped like a brick or as an oval form similar to a rounded brick because they are wrapped by the

endoplasmic reticulum The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryote, eukaryotic cell, and has many other important functions such as protein folding. The word endoplasmic means "within the cytoplasm", and reticulum is Latin for ...

. The virion is exceptionally large, around 200 nm in diameter and 300 nm in length, and carries its

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

in a single, double-stranded segment of DNA. Genomes are linear, around 130–375 kb in length.

Lifecycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral proteins to host glycosaminoglycans (GAGs), which mediate endocytosis of the virus into the host cell. Fusion with the plasma membrane releases the core into the host cytoplasm. In the early phase, early genes are transcribed in the cytoplasm by viral RNA polymerase. Early expression begins at 30 minutes postinfection. The core is completely uncoated as early expression ends, the viral genome is then free in the cytoplasm. In the intermediate phase, intermediate genes are expressed, triggering genomic DNA replication about 100 minutes after infection. In the late phase, late genes are expressed from 140 min to 48 hours postinfection, producing all structural proteins. Assembly of progeny virions starts in cytoplasmic viral factories, producing a spherical, immature particle. This virus particle matures into brick-shaped intracellular mature virion, which can be released upon cell lysis, or can acquire a second double membrane from trans-Golgi and bud as external enveloped virion host receptors, which mediates endocytosis. Replication follows the DNA strand displacement model. DNA-templated transcription is the method of transcription. The virus exits the host cell by microtubular outwards viral transport, and exists in occlusion bodies after cell death and remains infectious until finding another host. Humans, vertebrates, and arthropods serve as the natural host. Transmission routes are fomite, contact, and airborne particles.

Taxonomy

The classification in this subfamily is based on the morphology, nucleic acid type, mode of replication, host organisms, and type of disease caused. Nine genera in this subfamily are recognized; also, a number of species have not yet been assigned to a genus. The species in the genus ''Avipoxvirus'' infect

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s; those in the genera ''Caiman poxvirus'' and ''Crocodylipoxvirus'' both infect crocodilians. The other genera in this subfamily infect

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s. The following genera are recognized: * '' Avipoxvirus'' * '' Capripoxvirus'' * '' Centapoxvirus'' * '' Cervidpoxvirus'' * '' Crocodylidpoxvirus'' * '' Leporipoxvirus'' * '' Macropopoxvirus'' * '' Molluscipoxvirus'' * '' Mustelpoxvirus'' * '' Orthopoxvirus'' * '' Oryzopoxvirus'' * '' Parapoxvirus'' * '' Pteropopoxvirus'' * '' Salmonpoxvirus'' * '' Sciuripoxvirus'' * '' Suipoxvirus'' * '' Vespertilionpoxvirus'' * ''

Evolution

The last common ancestor of the extant poxviruses that infect vertebrates existed . The genus ''Avipoxvirus'' diverged from the ancestor 249 ± 69 thousand years ago. The ancestor of the genus ''Orthopoxvirus'' was next to diverge from the other clades at . A second estimate of this divergence time places this event at 166 ± 43,000 years ago.Babkin IV, Babkina IN (2011) Molecular dating in the evolution of vertebrate poxviruses. Intervirology 54(5):253-260. . The division of the ''Orthopox'' into the extant species occurred about 14,000 years ago. The genus ''Leporipoxvirus'' diverged around 137 ± 35,000 years ago. This was followed by the ancestor of the genus ''Yatapoxvirus''. The last common ancestor of the ''Capripoxvirus'' and ''Suipoxvirus'' diverged 111 ± 29,000 years ago. A Bayesian study of orthopox genomes suggests that the unclassified ''Yoka poxvirus'' diverged from the lineage that gave rise to the orthopoxviruses roughly 90,000 years ago.Babkin IV, Babkina IN (2012) A retrospective study of the orthopoxvirus molecular evolution. Infect Genet Evol The orthopox viruses diverged from the other pox viruses about 10,000 years ago. Camelpox, taterapox, and variola viruses arose 3,500 years ago and horsepox virus 3,000 years ago. These viruses may have arisen in the Horn of Africa. Another Bayesian study suggests that variola arose about 3500 years ago.Babkin IV, Shelkunov SN (2008) Molecular evolution of poxviruses. Genetika 44(8):1029-1044

References

External links

Viralzone: ChordopoxvirinaeICTV
*

Electron micrograph A micrograph is an image, captured photographically or digitally, taken through a microscope or similar device to show a magnify, magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken ...

s

{{Taxonbar, from=Q1076382 Chordopoxvirinae, * Virus subfamilies