Flavivirus

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Flavivirus
West Nile virus EM PHIL 2290 lores.jpg

TEM image of the West Nile Virus

Systematics
Classification : Viruses
Area : Riboviria
Empire : Orthornavirae
Phylum : Kitrinoviricota
Class : Flasuviricetes
Order : Amarillovirales
Family : Flaviviridae
Genre : Flavivirus
Taxonomic characteristics
Genome : (+) ssRNA linear
Baltimore : Group 4
Symmetry : icosahedral
Cover : available
Scientific name
Flavivirus
Left
NCBI  Taxonomy: 11051
ViralZone ( ExPASy , SIB): 24
ICTVdB Virus Code : 00.026.0.01

The genus Flavivirus comprises enveloped viruses with a positive-stranded RNA single strand as genome , which are transmitted to birds and mammals as vectors by arthropods ( ticks and mosquitoes ) . The name of the genus and the entire virus family Flaviviridae is derived from the yellow fever virus in humans (from Latin flavus , "yellow"), which Walter Reed recognized in 1904 as being transmitted by mosquitoes.

Viruses of the genus Flavivirus cause important diseases in animals and humans. These include diseases that correspond to a viral hemorrhagic fever or are characterized by an infection of the central nervous system in the sense of encephalitis , meningoencephalitis or leukoencephalitis . In addition to yellow fever , these include, for example, early summer meningoencephalitis (TBE), Japanese encephalitis , dengue fever and West Nile fever .

morphology

The virus particles (virions) of the flaviviruses are about 50 nm in diameter and, in the electron microscopic representation, of spherical, irregular shape. Analyzes by means of cryoelectron microscopy showed an icosahedral symmetry of the virus envelope in the dengue virus , which suggests an interaction of the envelope proteins with the capsid proteins. The capsid is made up of only one capsid protein (C, 11  kDa ). 90 dimers of the E protein (50 kDa) are embedded in the virus envelope of the virion. Another, smaller envelope protein ( M protein , 26 kDa) is found between this network of E dimers .

Genome organization

The positive-stranded RNA is about 11,000 nucleotides long and comprises only one open reading frame that codes for a polyprotein . The viral protease (N-terminal part of NS3) and the host's own proteases cut this polyprotein into 3 structural (C, prM, E) and 7 non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5 ); the list corresponds to the arrangement of the genes coding for the proteins on the genome. In contrast to the other genera of the Flaviviridae family , viruses of the Flavivirus genus have a 5 'cap structure of type 1 (m-7GpppAmp) followed by a conserved dinucleotide A G at the 5' end of the RNA . In contrast to the other genera, flaviviruses do not have a poly (A) tail at the 3 'end .

Replication

The viruses attack monocytes , macrophages and dendritic cells, among others . They attach to the cell surface via specific receptors and are taken up by a developing endosome vesicle . Inside the endosome, the acidic pH induces the fusion of the endosome membrane and the virus envelope. This causes the capsid to enter the cytosol , disintegrate, and release the genome. Both receptor binding and membrane fusion are catalyzed by protein E, which undergoes a conformational change at acidic pH, which leads to the 90 homodimers reorganizing into 60 homotrimers.

After entering the host cell, the viral genome is replicated in the rough endoplasmic reticulum and in so-called vesicle packets . Within the ER, an immature form of the virus particles is first produced, in which the M protein has not yet been cleaved by a maturation step and is present as prM ( precursor M ) in a complex with E. The immature particles are processed in the Golgi apparatus by the host protein furin , which cuts prM into M. This releases E from the complex and can take its place in the mature, infectious virion.

transmission

Flaviviruses can be transmitted indirectly by blood-sucking insects or in rare cases (for example with the Rio Bravo virus ) directly from one vertebrate to another. Some flaviviruses circulate between rodents and bats with no other vector known.

Systematics

The viruses of the genus Flavivirus were previously distinguished as arbovirus group B from arbovirus group A because of their transmission by arthropods ; the genus Alphavirus of the Togaviridae family later emerged from the latter .

The genus Flavivirus contains 89 virus species (as of 2018; in 2009 there were 53 species with 73 serotypes). The species are classified into (non-taxonomic) groups according to the type of vector (mosquito, tick), unknown vector (NKV group: no known vector ) and on the basis of phylogenetic studies. The English names are the official species names according to ICTV (International Committee on Taxonomy of Viruses), as of November 2018.

1. Flaviviruses transmitted by ticks

2. Flaviviruses transmitted by mosquitoes ( Mosquito Borne Encephalitis Complex , MBE)

  • Aroa virus group
    • Species Aroa virus ( en.Aroa virus , AROAV) with subtypes Bussuquara virus (BSQV), Iguape virus (IGUV), Naranjal virus (NJLV)
  • Dengue virus group
  • Japanese encephalitis virus group
  • Kokobera virus group
    • Species Kokobera virus (en. Kokobera virus , KOKV) with subtypes New Mapoon virus (NMV) and Stratford virus (STRV)
  • Ntaya virus group
  • Spondweni virus group
    • Species " Spondweni virus " (en " Spondweni virus ", SPONV), not confirmed by ICTV
    • Species Zika virus ( en.Zika virus , ZIKV)
  • Yellow fever virus group
  • Species " Bamaga virus " (en. " Bamage virus ", BgV), not confirmed by ICTV

3. Flaviviruses with unknown vector

4. Non-vertebrate virus group ( English Non vertebrate viruses )

5. Other unclassified candidates for this genus

literature

  • H.-J. Thiel, MS Collett, et al. : Genus Flavivirus . In: CM Fauquet, MA Mayo et al. : Eighth Report of the International Committee on Taxonomy of Viruses . London / San Diego, 2005, ISBN 0-12-249951-4
  • D. Gubler, G. Kuno, L. Markoff: Flaviviruses . In: David M. Knipe, Peter M. Howley (eds.-in-chief): Fields' Virology . 5th edition. Philadelphia 2007, Volume 1, ISBN 0-7817-6060-7 , pp. 1153 ff.
  • EA Gould, T. Solomon: Pathogenic flaviviruses . Seminar. In: Lancet 2008, 371, pp. 500-509

Web links

Individual evidence

  1. ↑ ICTV Master Species List 2018b.v2 . MSL # 34, March 2019
  2. ↑ a b c d ICTV: ICTV Taxonomy history: Yellow fever virus , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
  3. ^ EA Gould, T Solomon: Pathogenic flaviviruses . In: The Lancet . 371, No. 9611, February 2008, pp. 500-9. doi : 10.1016 / S0140-6736 (08) 60238-X . PMID 18262042 .
  4. ↑ RJ Kuhn, W Zhang, MG Rossmann et al .: Structure of dengue virus: implications for flavivirus organization, maturation, and fusion . In: Cell . 108, No. 5, March 2002, pp. 717-25. PMID 11893341 .
  5. ↑ a b c d A Sampath, R Padmanabhan: Molecular targets for flavivirus drug discovery . In: Antiviral Research . 81, No. 1, January 2009, pp. 6-15. doi : 10.1016 / j.antiviral.2008.08.004 . PMID 18796313 .
  6. ↑ Master Species List (# 33) 2018a v1. ICTV , autumn 2018
  7. ↑ H. Weissenböck, Z. Hubálek, T. Bakonyi, N. Nowotny: Zoonotic mosquito-borne flaviviruses: worldwide presence of agents with proven pathogenicity and potential candidates of future emerging diseases . In: Veterinary Microbiology, Elsevier, 2010, 140 (3-4), pp. 271 ff, doi: 0.1016 / j.vetmic.2009.08.025
  8. ^ NCBI: Tick-borne encephalitis virus group
  9. ^ Anne Piantadosi, Daniel B Rubin, Daniel P McQuillen, Liangge Hsu, Philip A Lederer: Emerging Cases of Powassan Virus Encephalitis in New England: Clinical Presentation, Imaging, and Review of the Literature . In: Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America . tape 62 , no. 6 , March 15, 2016, ISSN  1537-6591 , p. 707-713 , doi : 10.1093 / cid / civ1005 , PMID 26668338 , PMC 4850925 (free full text).
  10. Jump up ↑ Powassan Basics: About Powassan Virus Disease , Minnesota Department of Health, April 11, 2019
  11. ^ NCBI: Karshi virus
  12. ^ NCBI: Seaborne tick-borne virus group
  13. ^ NCBI: Dengue virus group
  14. ↑ NCBI: Japanese encephalitis virus group
  15. ↑ NCBI: Kokobera virus group
  16. ↑ NCBI: Ntaya virus group
  17. ↑ Joel H. Ellwanger et al. : Rocio Virus: An Overview , on: ResearchGate, July 2017
  18. ↑ NCBI: T'Ho virus (species)
  19. ↑ PMC 5469153 (free full text)
  20. ↑ Peipei Liu et al : Genomic and antigenic characterization of the newly emerging Chinese duck egg-drop syndrome flavivirus: genomic comparison with Tembusu and Sitiawan viruses , in: Journal of General Virology, Volume 93, No. 10, October 1, 2012, doi : 10.1099 / vir.0.043554-0
  21. ^ NCBI: Yellow fever virus group
  22. ^ Andrew F. van den Hurk, Willy W. Suen, Roy A. Hall, Caitlin A. O'Brien, Helle Bielefeldt-Ohmann, Jody Hobson-Peters, Agathe MG Colmant: A newly discovered flavivirus in the yellow fever virus group displays restricted replication in vertebrates . In: Journal of General Virology . 97, No. 5, 2016, pp. 1087-1093. doi : 10.1099 / jgv.0.000430 . PMID 26878841 . PDF
  23. ↑ NCBI: Fitzroy river virus (species)
  24. ↑ Cheryl A. Johansen et al : Characterization of Fitzroy River Virus and Serologic Evidence of Human and Animal Infection , in: Emerging Infectious Diseases, Volume 23, No. 8, August 2017
  25. ↑ NCBI: Nanay virus (species)
  26. ^ NCBI: Modoc virus group
  27. ↑ S Bekal, LL Domier, B Gonfa, NK McCoppin, KN Lambert, K ​​Bhalerao: A novel flavivirus in the soybean cyst nematode . In: Journal of General Virology . 95, No. Pt 6, 2014, pp. 1272-1280. doi : 10.1099 / vir.0.060889-0 . PMID 24643877 .
  28. ^ NCBI: unclassified flavivirus