Parvoviridae

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The Parvoviridae family includes the smallest known viruses, and some of the most environmentally resistant. They were discovered during the 1960s and affect vertebrates and insects. Parvoviruses have a genome consisting of single-stranded DNA and an icosahedral capsid. It is non-enveloped.

Parvovirus B19 was the first 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 RA-1 had originally also been associated with rheumatoid arthritis, but this is now thought to have been an error due to laboratory contamination.

Virology

The viruses in this family are small (18–26 nanometers in diameter) and non enveloped. The viron is icosahedral with triangulation number (T) = 1. There are 60 copies of the coat protein in the viron.

The genome is 4–6 kilobases in length and usually encodes two open reading frames. The 5' open reading frame encodes two nonstructural proteins (NS-1 and NS-2) and the 3' open reading frame encodes two or three capsid proteins (VP1, VP2, VP3). Both the 5' and 3' termini have hairpin loops. In the genus Bocaparvovirus there is a third open reading frame between the non structural and structural open reading frames.

The NS-1 protein has a superfamily 3 DNA helicase motif. These motifs are common in DNA viruses. The proteins that contain these motifs bind to the origin of replication and unwind the viral genome allowing access by the host's proteins to the viral genome for replication and transcription.

The genome is replicated by a unique rolling hairpin mechanism.

Notes

Members of the Amdoparvovirus and Protoparvovirus genera both possess a small open reading frame (ORF) within the major coat protein (VP2) gene. The function of this gene (SAT) is not known.

A Protein X, predicted to contain two transmembrane helices, is found in all members of the Erythrovirus genus.

A large genus specific ORF can be found to overlap the coat protein ORF of all members of the Dependovirus genus.

Taxonomy

The family is divided into two subfamilies: Parvovirinae, which infect vertebrates and Densovirinae, which infect invertebrates. Each subfamily has been subdivided into several genera.1 The Amdoparvovirus and Protoparvovirus genera are probably more closely related to one another than to the other genera in this family.

Subfamily Densovirinae:

Subfamily Parvovirinae:

References

  1. ^ Lukashov VV, Goudsmit J (2001) Evolutionary relationships among parvoviruses: virus-host coevolution among autonomous primate parvoviruses and links between adeno-associated and avian parvoviruses. J Virol 75: 2729–2740

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