Papillomaviridae
The virus family Papillomaviridae includes 16 genera of non-enveloped viruses with a double-stranded, circular DNA as a genome. By 2002 the family Papillomaviridae formed as a genus Papillomavirus, together with the now own family Polyomaviridae the family Papovaviridae. 1964 Joseph Melnick had proposed this now obsolete virus family due to the morphological and genetic similarities. However, the reproductive strategy, the spectrum of the disease and the arrangement of the genes are so different that they are divided into two different families.
Papillomaviruses cause at very many different vertebrate skin growths within the meaning of warts ( papillomas ). The first recognized as a virus agent from this group was by Richard Shope in 1932 from diseased rabbit isolated ( shopes Kaninchenpapillomvirus ). The development of malignant tumors from benign growths that has been observed at that time. Today, the development of various cancers in humans and animals is connected with representatives of Papillomaviridae. In humans, this is mainly the cervical cancer caused by infection with human papillomavirus. The propagation of papillomaviruses is strictly limited to epithelial cells, and they need to multiply cells that are in a phase of dedifferentiation. Due to this strict tissue tropism is not yet possible a complete reproduction of the Papillomaviridae in cell cultures.
Morphology
About 55 nm in size, non-enveloped virions consist of an icosahedral capsid papillomaviruses (T = 7), which is composed of 72 capsomeres. Of the 60 capsomeres in a five-rayed symmetry ( pentamers ) and these in turn into 12 six-pointed ( hexamers ) are arranged. Disulfide bridges exist between the pentamers. In case of defective maturation and assembly also filamentous capsids can be observed. The capsomeres are formed by two structural proteins (L1 and L2). The L1 ( 55 to 60 kDa) is dominant with about 80 % by weight. It has outwardly directed, species -specific epitopes. The L2 ( 50 to 53 kDa) has group-specific epitopes. The virions have a high environmental stability; mild detergents ( soap), acidic pH values and fat-dissolving substances commonly used for virus inactivation (eg, 2 -propanol) do not inactivate papillomavirus. They are stable to heat for 1 hour at 50 ° C.
Inside the capsid, the circular DNA genome of the virus is located. This is repeatedly twisted ( " supercoiled " ) and, together with cellular histones a nucleoprotein complex, the structurally very similar to eukaryotic nucleosomes. Of the five known histones are found the histones H2A, H2B, H3 and H4.
Genome organization
The genome of papillomaviruses is about 6800-8400 bp in size and encoded with 9 to 10 open reading frame ( ORF ) for the early viral proteins (early: E1 -E8 ) and the late structural proteins (late L1 and L2). In some species lacking E3 or E8 - reading frame. In contrast to the Polyomaviridae the reading direction for all ORFs are the same. Before the genes for the early viral proteins is a regulatory region (LCR, long control region ), the control sequences (promoters, enhancers and replication origins ) included. The reading frame overlap partially and are in different reading frames. Transcribed by cellular RNA polymerase in the nucleus of the viral mRNAs are further modifications such as capping, polyadenylation, and an RNA splicing. For the propagation of the genomic DNA of the Papillomaviridae viruses do not own DNA polymerase. They are dependent on it in virus replication that sufficient quantities of cellular DNA polymerases are present and active. Since this is particularly the case during cell division, the Papillomaviridae have developed various mechanisms, in order to stimulate said host cell to continuous division. These mechanisms are the cause of the typical tissue growths in infections with papillomaviruses and possible degeneration of the cells.
System
- Family Papillomaviridae
- Genus Alphapapillomavirus
- Genus Betapapillomavirus
- Genus Gammapapillomavirus
- Genus Deltapapillomavirus
- Genus Epsilonpapillomavirus
- Genus Zetapapillomavirus
- Genus Etapapillomavirus
- Genus Thetapapillomavirus
- Genus Iotapapillomavirus
- Genus Kappapapillomavirus
- Genus Lambdapapillomavirus
- Genus Mupapillomavirus
- Genus Nupapillomavirus
- Genus Xipapillomavirus
- Genus Omikronpapillomavirus
- Genus Pipapillomavirus
Not classified species within the family Papillomaviridae:
- Species Trichosurus vulpecula papilloma -
- Species Possum papillomavirus
Swell
- E.-M. de Villiers et al.: Family Papillomaviridae. In: CM Fauquet, MA Mayo et al.: Eighth Report of the International Committee on Taxonomy of Viruses. London, San Diego, 2005 p 239ff ISBN 0-12-249951-4
- Peter M. Howley, Douglas R. Lowy: Papillomaviruses. In: David M. Knipe, Peter M. Howley ( ed. -in- chief): Fields' Virology. 5th Edition, Volume 2, Philadelphia 2007, pp. 2299ff ISBN 0-7817-6060-7