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Pestivirus

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Pestivirus
virions of "Pestivirus" sp.
Virions of Pestivirus sp.
Virus classification Edit this classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Kitrinoviricota
Class: Flasuviricetes
Order: Amarillovirales
Family: Flaviviridae
Genus: Pestivirus
Species

Pestivirus is a genus of viruses, in the family Flaviviridae. Viruses in the genus Pestivirus infect mammals, including members of the family Bovidae (which includes cattle, sheep, and goats) and the family Suidae (which includes various species of swine). There are 11 species in this genus. Diseases associated with this genus include: hemorrhagic syndromes, abortion, and fatal mucosal disease.[1][2]

Structure

Viruses in Pestivirus are enveloped, with spherical geometries. Their diameter is around 50 nm. Genomes are linear and not segmented, around 12kb in length.[1]

Genus Structure Symmetry Capsid Genomic arrangement Genomic segmentation
Pestivirus Icosahedral-like Pseudo T=3 Enveloped Linear Monopartite

Lifecycle

Entry into the host cell is achieved by attachment of the viral envelope protein E2 to host receptors, which mediates clathrin-mediated endocytosis. The main viral replication process happens in host cytoplasm. Replication follows the positive strand RNA virus replication model. An IRES RNA element at the 5'-nontranslated region (NTR) of the viral genome recruits viral and cellular translation factors to initiate viral protein translation.[3] Viral proteins are first translated as polyprotein, and then processed into individual structure and non-structure proteins by both viral and host proteases.[3] The virus exits the host cell by budding. Mammals serve as the natural hosts.When infected, the host sheds viruses in almost all body secretions including saliva, nasal discharge, milk, and feaces.[3] Vertical transmission (viruses crossing the placenta and infecting the fetus) are also common.[1]

Genus Host details Tissue tropism Entry details Release details Replication site Assembly site Transmission
Pestivirus Mammals None Clathrin-mediated endocytosis Secretion Cytoplasm Cytoplasm Horizontal and Vertical


Genome

Pestivirus viruses have a single strand of positive-sense RNA (i.e. RNA which can be directly translated into viral proteins) that is around 12.5 kilobases (kb) long (equal to the length of 12,500 nucleotides), but due to recombination events has been observed up to 16.5 kilobases in length.[4] Sometimes, virions (individual virus particles) contain sections of an animal's genome that have been duplicated, though this is not normally the case. Although lacking Poly-A tail at the 3' end of the genome, it contains stem-loop regions that might be involved in viral translation and replication.[5] The genome contains RNA to encode both structural and nonstructural proteins. The molecular biology of pestiviruses shares many similarities and peculiarities with the human hepaciviruses. Genome organisation and translation strategy are highly similar for the members of both genera. For BVDV, frequently nonhomologous RNA recombination events lead to the appearance of genetically distinct viruses that are lethal to the host.[6]

Transmission and prevention

Pestivirus A is widespread in Australia, mainly in cattle. Some adult cattle are immune to the disease, while others are lifelong carriers. If a foetus becomes infected within the first three to four months of gestation, then it will fail to develop antibodies towards the virus. In these cases, the animals often die before birth or shortly after. It is spread very easily among feedlot cattle as nasal secretions and close contact spread the disease, and animals with infected mucous membranes give off millions of particles of BVDV a day.[citation needed]

Symptoms of Pestivirus infection include diarrhoea, respiratory problems, and bleeding disorders.[citation needed]

Pestivirus A vaccines exist and the correct vaccine strain should be given, depending on the herd's location and the endemic strain in that region. This vaccination must be given regularly to maintain immunity.[citation needed]

Vaccines

There are 120 registered BVD vaccine products currently used around the world, mainly in North and South America.[7] These are conventional modified live virus (MLV) or inactivated/killed virus vaccines.[7] In pregnant animals live vaccines pose significant risk of vertical transmission of vaccine virus that can occasionally result in complications for calves. [8] Most of the harm done by BVDV is to unborn calves and depends on the timing of infection. [9]Vaccination has not proved to be effective for Bovine Viral Diarrhea (BVD), as the presence of BVD has not lessened since the vaccine has been developed. [10]Animals who are affected by the virus during early fetal development may become persistently infected (PI) and lack an immune response to BVD. These animal’s presence in herds and them shedding virus can infect other animals in the herd before vaccination is possible. [11] PI animals do not produce antibodies and are the main source of infection for herds, so culling is necessary to eradicate infection sources.[3] Vaccines are not able to prevent fetal infections, so this poses a huge source of infection for cattle herds.[10]  Another reason for the inefficiency of the BVD vaccine is because of failure to vaccinate whole areas, rather than just individual herds.[12] Border Disease, which affects lambs, is also caused by Pestivirus, but has no vaccine at this time. [13] Marker vaccines are beneficial tools for the eradication of animal diseases in regions with a high prevalence of the designated disease. The chimeric CP7_E2alf used to see how altered cell tropism affects pigs may not only serve as a tool for a better understanding of Pestivirus attachment, entry, and assembly, but also represent modified live CSFV "marker vaccines."[14]

Species

See also

References

  1. ^ a b c "Viral Zone". ExPASy. Retrieved 15 June 2015.
  2. ^ "Virus Taxonomy: 2020 Release". International Committee on Taxonomy of Viruses (ICTV). March 2021. Retrieved 16 May 2021.
  3. ^ a b c d Tautz N, Tews BA, Meyers G (2015). "The Molecular Biology of Pestiviruses". Advances in Virus Research. 93. Academic Press: 47–160. doi:10.1016/bs.aivir.2015.03.002. ISBN 9780128021798. PMID 26111586.
  4. ^ Meyers G, Tautz N, Stark R, Brownlie J, Dubovi EJ, Collett MS, Thiel HJ (November 1992). "Rearrangement of viral sequences in cytopathogenic pestiviruses". Virology. 191 (1): 368–386. doi:10.1016/0042-6822(92)90199-Y. PMC 7131167. PMID 1329326.
  5. ^ Pankraz A, Thiel HJ, Becher P (July 2005). "Essential and nonessential elements in the 3' nontranslated region of Bovine viral diarrhea virus". Journal of Virology. 79 (14): 9119–9127. doi:10.1128/JVI.79.14.9119-9127.2005. PMC 1168729. PMID 15994806.
  6. ^ Rümenapf T, Thiel HJ (2008). "Molecular Biology of Pestiviruses". In Mettenleiter TC, Sobrino F (eds.). Animal Viruses: Molecular Biology. Caister Academic Press. ISBN 978-1-904455-22-6.
  7. ^ a b Riitho V, Strong R, Larska M, Graham SP, Steinbach F (October 2020). "Bovine Pestivirus Heterogeneity and Its Potential Impact on Vaccination and Diagnosis". Viruses. 12 (10): 1134. doi:10.3390/v12101134. PMC 7601184. PMID 33036281.
  8. ^ Harasawa R (January 1995). "Adventitious pestivirus RNA in live virus vaccines against bovine and swine diseases". Vaccine. 13 (1): 100–103. doi:10.1016/0264-410X(95)80018-9. PMID 7762264.
  9. ^ Laven, Richard (30 September 2010). "Diagnosis of bovine viral diarrhoea virus (BVDV)-associated problems". Livestock. 13 (3): 37–41. doi:10.1111/j.2044-3870.2008.tb00163.x.
  10. ^ a b Moennig V, Becher P (June 2015). "Pestivirus control programs: how far have we come and where are we going?". Animal Health Research Reviews. 16 (1): 83–87. doi:10.1017/S1466252315000092. PMID 26050577. S2CID 21890278.
  11. ^ Hamers C, Dehan P, Couvreur B, Letellier C, Kerkhofs P, Pastoret PP (March 2001). "Diversity among bovine pestiviruses". Veterinary Journal. 161 (2): 112–122. doi:10.1053/tvjl.2000.0504. PMID 11243683.
  12. ^ Hamers C, Dehan P, Couvreur B, Letellier C, Kerkhofs P, Pastoret PP (March 2001). "Diversity among bovine pestiviruses". Veterinary Journal. 161 (2): 112–122. doi:10.1053/tvjl.2000.0504. PMID 11243683.
  13. ^ Nettleton (1990). "Pestivirus infections in ruminants other than cattle". Revue Scientifique et Technique. 9 (1).
  14. ^ Tautz N, Tews BA, Meyers G (2015). "The Molecular Biology of Pestiviruses". Advances in Virus Research. 93. Academic Press: 47–160. doi:10.1016/bs.aivir.2015.03.002. ISBN 9780128021798. PMID 26111586.
  15. ^ Loeffelholz MJ, Fenwick BW (January 2021). "Taxonomic Changes for Human and Animal Viruses, 2018 to 2020". Journal of Clinical Microbiology. 59 (2): e01932-20. doi:10.1128/JCM.01932-20. PMC 8111125. PMID 32848040.
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