Orthonairovirus

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Orthonairovirus
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Crimean-Congo hemorrhagic fever orthonairovirus virion and genome
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(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Negarnaviricota
Class: Ellioviricetes
Order: Bunyavirales
Family: Nairoviridae
Genus:Orthonairovirus

Orthonairovirus is a genus of viruses in the family Nairoviridae of the order Bunyavirales that include viruses with circular, negative-sense single stranded RNA. [1] It got its name from the Nairobi sheep disease that affects the gastrointestinal tracts of sheep and goats. [1] The vast majority, and perhaps all viruses in this genus are tick-borne viruses that can have human or other vertebrate hosts. [2]

Contents

Structure

The virions for viruses in this genus have a spherical shape. [3] They range in size from about 80–120 nm in diameter, with 50% of their weight attributed to proteins and 20–30% of their weight attributed to lipids. [1] The ribonucleocapsid is filamentous, having a length of about 200-300 nm and a width of about 2–2.5 nm. [1] These nucleocapsids are surrounded by a single envelope that has projections made of glycoproteins protruding from its surface. These projections evenly cover the surface of the virion, and are about 5–10 nm long. [1] They aid in attachment to the host receptor in replication.

Genome

Crimean-Congo hemorrhagic fever virus (CCHFV) genome Viruses-08-00106-g002.png
Crimean-Congo hemorrhagic fever virus (CCHFV) genome

Nairovirus genomes are negative sense, single-stranded RNA. The complete genome is about 17,100–22,800 nucleotides long, and is divided into three segments: large, medium, and small. [2] The large segment is about 11000–14400 nucleotides long (11–14.4 kb), and it encodes the viral polymerase. [1] [3] The medium segment is about 4,400–6,300 nucleotides long (4.4–6.3 kb), and it encodes for glycoproteins G¬n and Gc. [1] [3] The small segment is about 1,700–2,100 nucleotides long (1.7–2.1 kb), and it encodes the nucleocapsid protein. [2] < [1] [3]

The genome has terminally redundant sequences, with the sequences being repeated at both ends. The terminal nucleotides are base-paired forming, non-covalently closed, circular RNA. [1] Both the 5’ and 3’ ends have conserved regions, 9 nucleotides in length. The sequences are, 5’end: UCUCAAAGA, and 3’end: AGAGUUUCU. [1]

Replication

Nairovirus life cycle ONSR.Nairo.Fig3.v2 WEB.png
Nairovirus life cycle

Nairoviruses attach to the host receptor by their Gn-Gc glycoprotein dimer. [3] The virus is then endocytosed into the host cell via a vesicle. The ribonucleocapsid segments are released into the cytoplasm, commencing transcription. [3] Transcription and replication occur within the cell, and the newly synthesized virions are released by budding.

Transmission and distribution

Members of this viral genus infect many different vertebrate hosts, and are transmitted via ticks. [1]

Members of the genus Nairovirus may be found the world over, wherever their arthropod vectors and vertebrate hosts are found together. [3]

Clinical importance

Only four viruses in this genus have, to date, been recognised as human pathogens:

A fifth— Erve virus —may also be pathogenic for humans.

Evolution

Phylogenetic analysis has shown that these viruses fall into two major monophyletic groups, the hard ( Ixodidae ) and soft ( Argasidae ) tick-vectored groups. [4] Fossil and phylogenetic data places the hard tick-soft tick divergence between 120  million years ago and 92  million years ago. This suggests that the Nairoviruses have been associated with these ticks for over 100 million years.

Additionally, nairoviruses vectored by ticks of the genera Argas , Carios and Ornithodoros form three separate monophyletic lineages, again supporting the suggestion of host-virus cospeciation.

The hard bodied tick serogroups are

The soft bodied tick serogroups are

The tick vectors for the Kasokero and Thiafora serogroups are not currently known.

Taxonomy

The genus includes 41 species: [5]

See also

Related Research Articles

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<i>Argentinian mammarenavirus</i> Species of virus

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<i>Orthobunyavirus</i> Genus of viruses

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<i>Lagovirus</i> Genus of viruses

Lagovirus is a genus of viruses, in the family Caliciviridae. Lagomorphs serve as natural hosts. There are two species in this genus. Diseases associated with this genus include: necrotizing hepatitis leading to fatal hemorrhages.

Kupe orthonairovirus, also called Kupe virus, is a species of virus in the genus Orthonairovirus.

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In 1954 the Hazara orthonairovirus, one of the 34 tick-borne viruses of the genus Orthonairovirus, was discovered in Pakistan in the Ixodes tick native to that region. Today this virus is studied in mice in an attempt to develop treatments for the highly pathogenic Crimean-Congo Hemorrhagic Fever virus.

Batai orthobunyavirus (BATV) is a RNA virus belonging to order Bunyavirales, genus Orthobunyavirus.

Cache Valley orthobunyavirus (CVV) is a member of the order Bunyavirales, genus Orthobunyavirus, and serogroup Bunyamwera, which was first isolated in 1956 from Culiseta inornata mosquitos collected in Utah's Cache Valley. CVV is an enveloped arbovirus, nominally 80–120 nm in diameter, whose genome is composed of three single-stranded, negative-sense RNA segments. The large segment of related bunyaviruses is approximately 6800 bases in length and encodes a probable viral polymerase. The middle CVV segment has a 4463-nucleotide sequence and the smallest segment encodes for the nucleocapsid, and a second non-structural protein. CVV has been known to cause outbreaks of spontaneous abortion and congenital malformations in ruminants such as sheep and cattle. CVV rarely infects humans, but when they are infected it has caused encephalitis and multiorgan failure.

<i>Quaranjavirus</i> Genus of viruses

Quaranjavirus is a genus of enveloped RNA viruses, one of seven genera in the virus family Orthomyxoviridae. The genome is single-stranded, negative-sense segmented RNA, generally with six segments. The genus contains two species: Johnston Atoll virus and Quaranfil virus; it has been proposed to contain species or strains including Cygnet River virus, Lake Chad virus, Tyulek virus and Wellfleet Bay virus. Quaranjaviruses predominantly infect arthropods and birds; As of March 2015, Quaranfil quaranjavirus is the only member of the genus to have been shown to infect humans. The Quaranfil and Johnston Atoll viruses are transmitted between vertebrates by ticks, resembling members of Thogotovirus, another genus of Orthomyxoviridae.

<i>Nairoviridae</i> Family of viruses

Nairoviridae is a family of viruses in the order Bunyavirales. Its name derives from Nairobi sheep disease, caused by the member Nairobi sheep disease orthonairovirus.

The Nairobi sheep disease orthonairovirus (NSDV), also known as Ganjam virus is a species in the genus Orthonairovirus belonging to the Nairobi sheep disease serogroup. NSDV's known hosts belong to the hard tick family Ixodidae, including Rhipicephalus appendiculatus, and Amblyomma variegatum, and afflict sheep and goats naturally. The virus is in the family Nairoviridae and order Bunyavirales.

The Tofla virus is a strain of Hazara orthonairovirus in the genus Orthonairovirus belonging to the Crimean-Congo hemorrhagic fever serogroup. It was isolated from Ixodid in Japan in 2016.

Farallon virus is a strain of Hughes orthonairovirus in the genus Orthonairovirus belonging to the Hughes serogroup. A known host of the virus is Ornithodoros. The virus is named after the Farallon Islands.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 "ICTV Report Nairoviridae".
  2. 1 2 3 Crabtree, Mary B., Rosemary Sang, and Barry R. Miller. "Kupe Virus, a New Virus in the Family Bunyaviridae, Genus Nairovirus, Kenya." Emerging Infectious Diseases 15 (2009): 147–54.
  3. 1 2 3 4 5 6 7 "Nairovirus." Nairovirus. Viral Zone. <http://www.expasy.ch/viralzone/all_by_species/251.html>.
  4. Honig JE, Osborne JC, Nichol ST (2004) The high genetic variation of viruses of the genus Nairovirus reflects the diversity of their predominant tick hosts. Virology 318(1):10-16
  5. "Virus Taxonomy: 2020 Release". International Committee on Taxonomy of Viruses (ICTV). March 2021. Retrieved 19 May 2021.