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Flaviviridae

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Flaviviridae
Zika virus virion structure and genome
Virus classification Edit this classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Kitrinoviricota
Class: Flasuviricetes
Order: Amarillovirales
Family: Flaviviridae
Genera

Flaviviridae is a family of enveloped positive-strand RNA viruses which mainly infect mammals and birds.[1] They are primarily spread through arthropod vectors (mainly ticks and mosquitoes).[2] The family gets its name from the yellow fever virus; flavus is Latin for "yellow", and yellow fever in turn was named because of its propensity to cause jaundice in victims.[3] There are 89 species in the family divided among four genera.[2] Diseases associated with the group include: hepatitis (hepaciviruses), hemorrhagic syndromes, fatal mucosal disease (pestiviruses), hemorrhagic fever, encephalitis, and the birth defect microcephaly (flaviviruses).[4]

Structure[edit]

Virus particles are enveloped and spherical with icosahedral-like geometries that have pseudo T=3 symmetry. They are about 40–60 nm in diameter.[2][4]

Genome[edit]

Members of the family Flaviviridae have monopartite, linear, single-stranded RNA genomes of positive polarity, and 9.6 to 12.3 kilobase in total length. The 5'-termini of flaviviruses carry a methylated nucleotide cap, while other members of this family are uncapped and encode an internal ribosome entry site.

The genome encodes a single polyprotein with multiple transmembrane domains that is cleaved, by both host and viral proteases, into structural and non-structural proteins. Among the non-structural protein products (NS), the locations and sequences of NS3 and NS5, which contain motifs essential for polyprotein processing and RNA replication respectively, are relatively well conserved across the family and may be useful for phylogenetic analysis.

Life cycle[edit]

Life cycle of Japanese encephalitis virus (JEV)

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral envelope protein E to host receptors, which mediates clathrin-mediated endocytosis. Replication follows the positive-stranded RNA virus replication model. Positive-stranded RNA virus transcription is the method of transcription. Translation takes place by viral initiation. The virion assembles by budding through intracellular membranes and exits the host cell by exocytosis.[2][4][5]

Host range and evolutionary history[edit]

A wide variety of natural hosts are used by different members of the Flaviviridae, including fish, mammals including humans and various invertebrates, such as those specific to mollusks and crustaceans.[6] The genomes of these flaviviruses show close synteny with that of the flavivirus type species, yellow fever virus.[7] One flavivirus, the Wenzhou shark flavivirus, infects both Pacific spadenose sharks (Scoliodon macrorhynchos) and Gazami crabs (Portunus trituberculatus) with overlapping ranges, raising the possibility of a two-host marine lifecycle.[6] However, another clade of flavivirus, the insect-specific flaviviruses, have genomes that do not demonstrate strong synteny with any of these groups, suggesting a complex evolutionary history.[2][8]

Flavivirus endogenous viral elements, traces of flavivirus genomes integrated into the host's DNA, are found in many species, including a tadpole shrimp Lepidurus articus, the water flea Daphnia magna and a freshwater jellyfish Craspedacusta sowerbii,[7] suggesting ancient coevolution between animal and flavivirus lineages.[6][7] Many of the well-known members of the family causing disease in vertebrates are transmitted via arthropod vectors (ticks and mosquitoes).[2][4][7]

Taxonomy[edit]

Phylogenetic tree of Flaviviridae using the NS3 protein sequences

The Flaviviridae are part of RNA virus supergroup II, which includes certain plant viruses and bacterial viruses.[2]

The family has four genera:[1][2]

Unclassified

Other Orthoflaviviruses are known that have yet to be classified. These include Wenling shark virus.

Jingmenvirus is a group of unclassified viruses in the family which includes Alongshan virus, Guaico Culex virus, Jingmen tick virus and Mogiana tick virus. These viruses have a segmented genome of four or five pieces. Two of these segments are derived from flaviviruses.[citation needed]

A number of viruses may be related to the flaviviruses, but have features that are atypical of the flaviviruses. These include citrus Jingmen-like virus, soybean cyst nematode virus 5, Toxocara canis larva agent, Wuhan cricket virus, and possibly Gentian Kobu-sho-associated virus.[citation needed]

Clinical importance[edit]

Major diseases caused by members of the family Flaviviridae include:

References[edit]

  1. ^ a b Simmonds, P; Becher, P; Bukh, J; Gould, E; Meyers, G; Monath, T; Muerhoff, S; Pletnev, A; Rico-Hesse, R; Smith, D; Stapleton, J; ICTV Report Consortium (2017). "ICTV Virus Taxonomy Profile: Flaviviridae". Journal of General Virology. 98 (1): 2–3. doi:10.1099/jgv.0.000672. PMC 5370391. PMID 28218572.
  2. ^ a b c d e f g h Ricco-Hesse, Rebecca (2023). Knowles, Nick J.; Siddell, Stuart G. (eds.). "Flaviviridae". ICTV Online Report. Retrieved 11 July 2024.
  3. ^ "Flaviviridae". Microbe Wiki. Retrieved July 22, 2008.
  4. ^ a b c d "Viral Zone". ExPASy. Retrieved 11 July 2024.
  5. ^ Simmonds P, Becher P, Bukh J, Gould EA, Meyers G, Monath T, Muerhoff S, Pletnet A, Rico-Hesse R, Smith DB, Stapleton JT, ICTV Report Consortium (2017). "ICTV Virus Taxonomy Profile: Flaviviridae". Journal of General Virology. 98 (1): 2–3. doi:10.1099/jgv.0.000672. PMC 5370391. PMID 28218572.
  6. ^ a b c Lensink MJ, Li Y, Lequime S (2022). "Aquatic Flaviviruses". Journal of Virology. 96 (17). doi:10.1128/jvi.00439-22. PMC 9472621. PMID 35975997. Art. No. e00439-22.
  7. ^ a b c d Parry R, Asgari S (2019). "Discovery of Novel Crustacean and Cephalopod Flaviviruses: Insights into the Evolution and Circulation of Flaviviruses between Marine Invertebrate and Vertebrate Hosts". Journal of Virology. 93 (14). doi:10.1128/JVI.00432-19. PMC 6600200. PMID 31068424. Art. No. e00432-19.
  8. ^ Shi M, Lin XD, Vasilakis N, Tian JH, Li CX, Chen LJ, et al. (2015). "Divergent Viruses Discovered in Arthropods and Vertebrates Revise the Evolutionary History of the Flaviviridae and Related Viruses". Journal of Virology. 90 (2): 659–669. doi:10.1128/JVI.02036-15. PMC 4702705. PMID 26491167.

External links[edit]

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