Thogotovirus

Source: Wikipedia, the free encyclopedia.

Thogotovirus
Electron micrograph of Bourbon virus (scale bar: 100 nm)
Electron micrograph of Bourbon virus
(scale bar: 100 nm)
Virus classification Edit this classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum:
Negarnaviricota
Class: Insthoviricetes
Order: Articulavirales
Family: Orthomyxoviridae
Genus: Thogotovirus
Species
Synonyms[1]

Thogoto-like viruses

Thogotovirus is a

influenza viruses, which are transmitted by respiratory droplets and are usually confined to the respiratory system.[4]

The genus contains the species Thogoto thogotovirus and Dhori virus (DHOV), and the latter's subtype Batken virus, as well as the species or strains Araguari virus, Aransas Bay virus (ABV), Bourbon virus, Jos virus (JOSV) and Upolu virus (UPOV), which have yet to be confirmed by the International Committee on Taxonomy of Viruses (ICTV). A wide range of mammals are infected by members of the genus; some types also infect birds. THOV causes disease in livestock. THOV, DHOV and Bourbon virus can infect humans, and have occasionally been associated with human disease.

History

next-generation sequencing in 2014.[7]

Virology

Schematic drawing of a virion (genera Thogotovirus and Quaranjavirus, cross section)
Thogotovirus genome map
Predicted structure of THOV glycoprotein (left) compared with GP64 of the baculovirus, Autographa californica multicapsid nucleopolyhedrovirus (right)

The virus particle is

single-stranded, –RNA genome is linear and segmented, with six or seven segments of 0.9–2.3 kb and a total size of around 10 kb.[16][18] Reassortment of segments between strains has been observed in both ticks and mammals experimentally infected with more than one thogotovirus, but its significance in natural infections is unknown.[19]

Viral proteins

The genome encodes 7–9 proteins, including the trimeric

matrix protein (M1), which lines the envelope; and an envelope glycoprotein (GP), which acts as the virus receptor.[15][16]

The thogotovirus glycoprotein is not similar to the influenza virus glycoproteins (

Quaranfil virus of the related genus of tick-transmitted orthomyxoviruses Quaranjavirus.[21] The mechanism by which thogotoviruses gained a baculovirus-like glycoprotein is unknown. Pat Nuttall and colleagues have speculated that the acquisition enabled these viruses to infect ticks.[22] This apparent receptor specificity for arthropod cells does not prevent most thogotoviruses from infecting vertebrates.[15] The thogotovirus glycoprotein is classified as a class III or γ penetrene, lacking the fusion peptide present in influenza haemagglutinin (a class I or α penetrene).[23]

THOV and JOSV

influenza viruses (NS1).[15][16][24][25]

As in all orthomyxoviruses, the largest three segments (1–3) encode the three subunits of the RNA polymerase. In thogotoviruses, segment 4 encodes the glycoprotein and segment 5 the nucleoprotein. The messenger RNA (mRNA) from segment 6 can be spliced to encode the matrix protein or unspliced to encode ML, which has 38 additional amino acids at its C-terminus.[4][15][16][18] No product has yet been identified for the seventh segment, observed in DHOV.[18]

Life cycle

Electron micrograph showing endocytosis (arrows) of Bourbon virus (scale bar: 100 nm)

The receptor on the vertebrate host cell is

transcription and replication both occur in the cell nucleus.[15][16] In some members of the genus, replication has been shown to be sensitive to the Mx1/MxA protein, which is induced in mice and humans in response to interferon.[9][26] In one study, this inhibitory effect was shown to be caused by MxA preventing the transport of the THOV genome into the nucleus.[27]

As orthomyxoviruses do not encode a capping enzyme, initiation of transcription involves the virus cutting the cap off the 5′-end of host mRNAs, so that the mRNA is recognised by the host translation machinery. A similar "cap snatching" process is used by other orthomyxoviruses, but a much longer host RNA sequence is cleaved along with the cap and incorporated into the viral mRNA.[28][29]

The virus assembles by the cell membrane and leaves the cell by budding.[16] For THOV grown in baby hamster kidney cells, virus particles start to be released 6–8 hours after infection, with substantial quantities still being produced 24 hours after infection. This growth rate is slower than that of influenza viruses, and is more similar to Quaranfil virus.[17][21]

Epidemiology

Most thogotoviruses have been shown to infect arthropods, generally

THOV, DHOV and Bourbon virus – have been shown to infect humans.[7] They have a wide geographical range.[7]

Transmission to vertebrates usually occurs via a tick

vesicular stomatitis virus and West Nile virus viruses.[26] Transmission of DHOV by respiratory aerosol has also been observed.[6]

Host interaction and disease

Ticks

No major pathological changes are observed in Rhipicephalus appendiculatus ticks infected with THOV.[17] The virus is concentrated in the synganglion (the tick brain) early on in the blood-feeding process, with the proportion of virus located in the salivary glands increasing during the late phase of blood-feeding.[17][33] Lower levels of virus are found in the trachea, digestive tract and female sex organs, but not in the male sex organs or the excretory system. The high level of virus present in the synganglion has been proposed to help the virus persist through the metamorphosis of the tick, as the nervous system undergoes less remodeling than other systems.[17]

Vertebrates

In the laboratory setting, several members of the genus cause severe disease in mice and hamsters.[5][6] Systemic spread of the virus occurs, with pathological effects present in multiple organs and systems, including the brain, liver, lymphatic system, and sometimes the lungs and small intestine.[5][6] Lymphocytes are a major target cell for DHOV.[6] DHOV infection in mice resembles experimental influenza infection in mice and ferrets as well as fatal H5N1 influenza infection of humans, and has been proposed as a model for this disease.[6]

Natural infections with thogotoviruses in mammals generally do not appear to result in symptoms. THOV is a significant veterinary pathogen, for example, causing a febrile illness and

neuromyelitis optica in the case of THOV; encephalitis in the case of DHOV.[7][8][13][39] Hepatitis has been observed with THOV.[39] The single case of disease in a person infected with Bourbon virus was associated with decreases in blood platelets and white cells; no neurological symptoms were observed.[7] Influenza-like respiratory symptoms have not been reported.[7][8]

Treatment and prevention

No specific treatment or vaccine is available for thogotoviruses, as of February 2015. The antiviral drug ribavirin, which has a broad spectrum of activity that includes some other orthomyxoviruses,[40] has been shown to inhibit DHOV replication in vitro in a single study.[41] Supportive therapy is used for THOV disease,[39] and has been recommended by the US Centers for Disease Control and Prevention for infection with Bourbon virus. As with other arboviruses, avoidance of contact with the vector is central to prevention.[42]

Species and strains

Two species have been confirmed by the ICTV, THOV and DHOV.[43] The two viruses have a low degree of sequence identity (37% for the nucleoprotein; 31% for the envelope glycoprotein), and their antibodies do not crossreact.[13] Batken virus is a subtype of DHOV.[13] As of February 2015, a further five species or strains have been suggested as belonging to the genus.[7]

Species/strain RNA segments Diameter (nm) Vectors Vertebrate hosts Distribution
Araguari 6 105 Unknown Gray four-eyed opossum, mouse S. America
Aransas Bay 6 75–140 Ornithodoros ticks Mouse N. America
Batken 50–100 Hyalomma ticks, Aedes and Culex mosquitoes Chicken, hamster, mouse Asia
Bourbon ≥6 ~100–130 Unknown Human N. America
Dhori 7 Hyalomma ticks Birds, hare, horse, human, mouse, ruminants Africa, Asia, Europe
Jos ≥6 85–120 Amblyomma and Rhipicephalus ticks Mouse, zebu Africa
Thogoto 6 100 Amblyomma, Hyalomma and Rhipicephalus ticks Banded mongoose, donkey, human, rodents, ruminants Africa, Asia, Europe
Upolu 6 75–120 Ornithodoros ticks Mouse Australia

THOV-like viruses

Phylogeny of selected orthomyxoviruses, based on the nucleocapsid protein (scale bar: amino acid substitutions per site)

Thogoto virus (THOV)

THOV was first isolated from ticks gathered from cattle in the Thogoto Forest region of Kenya, near Nairobi, in 1960,[5] it is now known to be distributed across the African continent, and has also been found in Italy and Portugal in Europe, and Iran in the Middle East.[19][31][44] Despite this wide geographical range, the virus shows only limited variation.[44] Its vectors include various hard-bodied ticks, including Amblyomma, Hyalomma and Rhipicephalus species.[5][13][19][31][45]

Antibodies have been found to THOV in rats and many domestic animals, including goats, sheep, donkeys, camels, cattle and buffaloes, and the virus has been isolated from the wild banded mongoose (Mongos mungo).[13][32] It causes significant livestock disease, including a febrile illness and abortion in sheep.[5][36][37][38] In artificial laboratory infections, it is highly pathogenic in hamsters and also infects mice.[5] The virus is known to infect humans in natural settings.[7][31]

The virus particle is generally spherical with some filamentous forms; the diameter is around 100 nm.[17] The genome has six RNA segments.[4]

Araguari virus

The Araguari virus was first isolated from a Gray four-eyed opossum (Philander opossum) in Serra do Navio, Amapá, Brazil in 1969.[14] Its method of transmission is unknown.[6] In laboratory infections, it is pathogenic to mice. The virion is around 105 nm in diameter. The genome has six RNA segments. Based on partial sequence data the virus was found to be most closely related to THOV.[14]

Aransas Bay virus (ABV)

ABV was found in the soft-bodied tick genus Ornithodoros in seabird nests in southern Texas, USA, in 1975; it was the first member of the genus to be found in North America.[7][15] No natural vertebrate host has been identified, but the virus is highly pathogenic to mice in laboratory infections. The virus particle is spherical or ovoid, with a range of sizes, from 75 nm × 85 nm to 120 nm × 140 nm. The genome has six RNA segments. It is most similar to UPOV, with some similarity to THOV and JOSV.[15]

Jos virus (JOSV)

Hyalomma marginatum is one of the vectors of DHOV

JOSV was first isolated from the zebu (Bos indicus) in Jos, Nigeria in 1967. It has since been found infecting Amblyomma and Rhipicephalus hard-bodied ticks in several countries across Africa. In the laboratory it causes severe pathology in mice. The virus particle has a variable, usually ovoid, morphology with a diameter of 85–120 nm. The genome contains at least six RNA segments.[2] It has some sequence similarities with UPOV and ABV.[15]

Upolu virus (UPOV)

UPOV was first isolated on

Upolu Cay in the Great Barrier Reef, Australia in 1966, from soft-bodied ticks of the species Ornithodoros capensis associated with the sooty tern (Onychoprion fuscatus). No natural vertebrate host has been identified, but the virus is highly pathogenic to mice in laboratory infections. The virion can either be spherical, with a diameter in the range 75–95 nm, or slightly ovoid, with a range of dimensions from 75 nm × 85 nm to 105 nm × 120 nm. The genome has six RNA segments. It is most similar to ABV, with some similarity to THOV and JOSV.[15]

DHOV-like viruses

Dhori virus (DHOV)

DHOV was first isolated from Hyalomma dromedarii hard-bodied ticks infesting camels in Gujarat, India, in 1961.[6] It has since been observed in eastern Russia, Pakistan, Egypt, Saudi Arabia, Kenya and southern Portugal. The vector is usually a species of Hyalomma, such as H. marginatum.[6][13][31][46][47]

Where DHOV is prevalent, antibodies to the virus have been documented in camels, goats, horses, cattle and humans.

waterfowl.[13][15]

DHOV has seven RNA segments.[13]

Electron micrograph of a filamentous form of Bourbon virus (scale bar: 100 nm)

Batken virus

Transcaucasia and the area to the north of the Caspian Sea.[50] In the laboratory it is highly pathogenic for mice, hamsters and chickens.[30] The virion is variable in shape, with spherical and filamentous forms being observed; it has a diameter of 50–100 nm.[9] Batken is considered a DHOV subtype; the viruses have a high degree of sequence identity (90% in the envelope glycoprotein; 96–98% in other proteins), and their antibodies crossreact.[13][50]

Bourbon virus

Western hemisphere. As of February 2015, Bourbon virus has not been isolated from ticks, insects or non-human vertebrates. The virus is variable in shape, with filamentous as well as spherical forms; it has a diameter broadly in the range 100–130 nm. The genome contains at least six RNA segments. It is most similar to DHOV and Batken virus.[7]

Oz virus

Oz virus was first characterised in 2018 after isolation from the hard tick Amblyomma testudinarium in Ehime, Japan. [DOI: 10.1016/j.virusres.2018.03.004]. The first human case, a 70 year old female patient who died of myocarditis with isolation of Oz virus on autopsy, was reported on 23.6.2023 by the Japanese Ministry of Heath.

Notes and references

  1. PMID 8992952
    . Retrieved 4 June 2019.
  2. ^
    PMID 21994326
  3. ^ Members of the recently ratified genus Quaranjavirus are also transmitted by ticks.[2]
  4. ^
    PMID 20861272
  5. ^
    PMID 14329965
  6. ^
    PMID 17426188
  7. ^
    PMID 25899080
    .
  8. ^
    PMID 3445590
  9. ^
    PMID 9349464
  10. PMID 6858001
    .
  11. ^ ICTV 6th report (PDF), International Committee on Taxonomy of Viruses, retrieved 9 March 2015
  12. ^ Pringle CR, Virus Taxonomy 1996 - A Bulletin from the Xth International Congress of Virology in Jerusalem (PDF), International Committee on Taxonomy of Viruses, retrieved 9 March 2015
  13. ^ a b c d e f g h i j k Büchen-Osmond C, ed. (2006), "Index of Viruses - Orthomyxoviridae", ICTVdB - The Universal Virus Database, version 4, Columbia University, archived from the original on 2 April 2015, retrieved 3 July 2020
  14. ^
    PMID 16354811
    .
  15. ^
    PMID 24574415
  16. ^ a b c d e f g "Thogotovirus", ViralZone, Swiss Institute of Bioinformatics, retrieved 6 March 2015
  17. ^
    PMID 2543769
    .
  18. ^ a b c King AM, Adams MJ, Carstens EB, Lefkowitz EJ, eds. (2011), Virus Taxonomy: Ninth Report of the International Committee on Taxonomy of Viruses, Academic Press, p. 757
  19. ^
    PMID 3655743
  20. PMID 1733105
  21. ^
    PMID 19726499
  22. PMID 25392223
    .
  23. PMID 18282283
  24. PMID 16364743
  25. ^ Thogoto virus: Molecular biology of a tick-transmitted Orthomyxovirus, Universitäts Klinikum Freiburg, retrieved 7 March 2015
  26. ^
    PMID 16223950
  27. PMID 10051598
  28. PMID 9343188
  29. PMID 24454773
  30. ^
    S2CID 33344597
  31. ^ a b c d e f g Gratz N (2006), Vector- and Rodent-Borne Diseases in Europe and North America: Distribution, Public Health Burden, and Control, Cambridge University Press, pp. 108–9
  32. ^
    PMID 10466973
  33. ^
    PMID 12932755
  34. PMID 3616608
    .
  35. PMID 2617637
    .
  36. ^
    CABI
    , p. 110
  37. ^ a b Maramorosch K, McIntosh AH (1994), Arthropod Cell Culture Systems, CRC Press, p. 165
  38. ^
    PMID 7745744
  39. ^ a b c d e Berger SA, Calisher CH, Keystone JS (2003), Exotic Viral Diseases: A Global Guide, BC Decker, pp. 179–80
  40. S2CID 43106875
  41. PMID 18318134
  42. ^ "Bourbon virus", CDC website, Division of Vector-Borne Diseases, CDC, retrieved 4 March 2015
  43. ^ ICTV Master Species List 2014 v2, International Committee on Taxonomy of Viruses, 2014, archived from the original on 9 March 2015, retrieved 7 March 2015
  44. ^
    PMID 3688319
  45. PMID 16836823
  46. PMID 6415873
  47. PMID 18060218
  48. ^ L'vov DN, Dzharkenov AF, Aristova VA, Kovtunov AI, Gromashevskiĭ VL (2002), "[The isolation of Dhori viruses (Orthomyxoviridae, Thogotovirus) and Crimean-Congo hemorrhagic fever virus (Bunyaviridae, Nairovirus) from the hare (Lepus europaeus) and its ticks Hyalomma marginatum in the middle zone of the Volga delta, Astrakhan region, 2001]", Voprosy virusologii (in Russian), 47: 32–36
  49. PMID 18590134
  50. ^
    PMID 25069283

External links

Wikispecies has information related to Thogotovirus.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Thogotovirus&oldid=1187463481"