Parvoviridae
| Parvoviridae | |
|---|---|
| Virus classification | |
| Group: | Group II (ssDNA) |
| Order: | Unassigned |
| Family: | Parvoviridae |
| Genera | |
|
Subfamily: Densovirinae Subfamily: Parvovirinae |
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Subfamily: Densovirinae
Subfamily: Parvovirinae
The Parvoviridae are a family of small, rugged, genetically-compact DNA viruses, known collectively as parvoviruses. There are currently 56 species in the family, divided among 26 genera and two subfamilies. Members of this family infect a wide array of hosts and have been divided into two subfamilies, which infect either vertebrates (the Parvovirinae) or invertebrates (Densovirinae).
Parvovirus B19 was the first pathogenic human parvovirus to be discovered and is best known for causing a childhood exanthem called "fifth disease" (erythema infectiosum), although it is also associated with other diseases including arthritis.
Parvovirus particles (virions) have a durable non-enveloped protein capsid ~20–30 nm in diameter that contains a single copy of the linear single-stranded ~ 5kb DNA genome, which terminates in small imperfect palindromes that fold into dynamic hairpin telomeres. These terminal hairpins are hallmarks of the family, giving rise to the viral origins of DNA replication and mediating multiple steps in the viral life cycle including genome amplification, packaging, and the establishment of transcription complexes. However, they are often refractory to detection by PCR amplification strategies since they tend to induce polymerase strand-switching. Many parvoviruses are exceptionally resistant to inactivation, remaining infectious for months or years after release into the environment.
Viruses in this family have small protein virions that exhibit T=1 icosahedral symmetry. Their capsid shells are assembled from 60 icosahedrally-ordered copies of a single core protein (VP) sequence, but some of these VP proteins also have N-terminal extensions that are not visible in X-ray structures. Biochemical and serological studies indicate that these extensions become successively exposed at the particle surface during virus maturation and cell entry, where they contribute to virion stability and mediate specific steps in cell trafficking. Parvoviruses appear to be unique in encoding a broad spectrum phospholipase A2 (PLA2) activity, typically in the N-terminus of the longest (VP1) subset of their capsid proteins, which is deployed to mediate virion transfer across the lipid bilayer of host cells
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