Lyssavirus

Lyssavirus
Colored transmission electron micrograph of "Australian bat lyssavirus". The bullet-like objects are the virions, and some of them are budding off from a cell.
Colored transmission electron micrograph of Australian bat lyssavirus. The bullet-like objects are the virions, and some of them are budding off from a cell.
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Negarnaviricota
Class: Monjiviricetes
Order: Mononegavirales
Family: Rhabdoviridae
Genus: Lyssavirus
Species

Lyssavirus (from the Greek λύσσα lyssa "rage, fury, rabies" and the Latin vīrus)[1][2] is a genus of RNA viruses in the family Rhabdoviridae, order Mononegavirales. Mammals, including humans, can serve as natural hosts.[3][4] The genus Lyssavirus includes the rabies virus traditionally associated with the disease of the same name.

Taxonomy

Genus Lyssavirus: species and their viruses[5][6]
Genus Phylogroup Species Virus (Abbreviation)
Lyssavirus I Aravan lyssavirus Aravan virus (ARAV)
Australian bat lyssavirus Australian bat lyssavirus (ABLV)
Bokeloh bat lyssavirus Bokeloh bat lyssavirus (BBLV)
Duvenhage lyssavirus Duvenhage virus (DUVV)
European bat 1 lyssavirus European bat lyssavirus 1 (EBLV-1)
European bat 2 lyssavirus European bat lyssavirus 2 (EBLV-2)
Gannoruwa bat lyssavirus Gannoruwa bat lyssavirus (GBLV)
Irkut lyssavirus Irkut virus (IRKV)
Khujand lyssavirus Khujand virus (KHUV)
Madagascar bat lyssavirus Madagascar bat lyssavirus (MABV)
Rabies lyssavirus Rabies virus (RABV)
II Lagos bat lyssavirus Lagos bat virus (LBV)
Mokola lyssavirus Mokola virus (MOKV)
Shimoni bat lyssavirus Shimoni bat virus (SHIBV)
III West Caucasian bat lyssavirus West Caucasian bat virus (WCBV)
IV Ikoma lyssavirus Ikoma lyssavirus (IKOV)
Lleida bat lyssavirus Lleida bat lyssavirus (LLEBV)

Virology

Structure

Lyssavirions are enveloped, with bullet shaped geometries. These virions are about 75 nm wide and 180 nm long.[3] Lyssavirions have helical symmetry, so their infectious particles are approximately cylindrical in shape. This is typical of plant-infecting viruses. Virions of human-infecting viruses more commonly have cubic symmetry and take shapes approximating regular polyhedra.

The structure consists of a spiked outer envelope, a middle region consisting of matrix protein M, and an inner ribonucleocapsid complex region, consisting of the genome associated with other proteins.

Genome

Lyssavirus genomes consist of a negative-sense, single-stranded RNA molecule that encodes five viral proteins: polymerase L, matrix protein M, phosphoprotein P, nucleoprotein N, and glycoprotein G. Genomes are linear, around 11kb in length.[3]

Based on recent phylogenetic evidence, lyssaviruses have been categorized into seven major species. In addition, five more species have recently been discovered: West Caucasian bat virus, Aravan virus, Khujand virus, Irkut virus and Shimoni bat virus.[7][8] The lyssavirus genus can be divided into four phylogroups based upon DNA sequence homology. Phylogroup I includes viruses, such as Rabies virus, Duvenhage virus, European bat lyssavirus types 1 and 2, Australian bat lyssavirus, Khujand virus, Bokeloh bat lyssavirus, Irkut virus, and Aravan virus. Phylogroup II contains Lagos bat virus, Mokola virus, and Shimoni bat virus. West Caucasian bat lyssavirus is the only virus that is a part of phylogroup III. Ikoma lyssavirus and Lleida bat lyssavirus are examples in phylogroup IV. West Caucasian bat lyssavirus was classified within its own phylogroup because it is the most divergent lyssavirus that has been discovered.[9]

GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
LyssavirusBullet-shapedEnvelopedLinearMonopartite

Evolution

Phyogenetic studies suggest that the original hosts of these viruses were bats.[10] The greater antigenic diversity of lyssaviruses from Africa has led to the assumption that Africa was the origin of these viruses. An examination of 153 viruses collected between 1956 and 2015 from various geographic locations has instead suggested a Palearctic origin (85% likelihood) for these viruses.[11] Date estimates (95% likelihood) for the most recent common ancestor were very broad - between 3,995 and 166,820 years before present - which suggests there is further work to be done in this area. Although bats evolved in the Palearctic,[12] their origins antedate that of the lyassaviruses by millions of years, which argues against their co-speciation. The evolution rate in the N gene in the Africa 2 lineage has been estimated to be 3.75×10−3 substitutions per site per year.[13] This rate is similar to that of other RNA viruses.

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral G glycoproteins to host receptors, which mediates clathrin-mediated endocytosis. Replication follows the negative stranded RNA virus replication model. Negative stranded RNA virus transcription, using polymerase stuttering, is the method of transcription. The virus exits the host cell by budding and by tubule-guided viral movement. Wild mammals, especially bats and certain carnivores, serve as natural hosts. Transmission routes are typically via bite wounds.[3]

GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
Lyssavirusbats, Crocidura shrews and certain carnivoresNeuronsClathrin-mediated endocytosisBuddingCytoplasmCytoplasmBite wounds

Testing

As of 2018 the direct fluorescent antibody (DFA) test is still the gold standard to detect lyssavirus infection. Since the new millennium reverse transcription PCR (RT-PCR) tests have been developed for rabies but only been used as a confirmatory test. Real-time PCR-based tests which have higher sensitivity and objective diagnostic thresholds and allow samples to be stored at room temperature have been promising since 2005, but require a real-time PCR machine and skilled workers with experience in molecular diagnostics. In an international evaluation a single TaqMan LN34 assay could detect Lyssavirus with high sensitivity (99.90%) across the genus and high specificity (99.68%) when compared to the DFA test. It will become the primary post-mortem rabies diagnostic test where possible.[14]

Epidemiology

Classic rabies virus is prevalent throughout most of the world and can be carried by any warm blooded mammal. The other lyssaviruses have much less diversity in carriers. Only select hosts can carry each of these viral species. Also, these other species are particular only to a specific geographic area. Bats are known to be an animal vector for all identified lyssaviruses except the Mokola virus.[15]

See also

  • Bat-borne virus

References

  1. ↑ λύσσα. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
  2. ↑ vīrus. Charlton T. Lewis and Charles Short. A Latin Dictionary on Perseus Project.
  3. 1 2 3 4 "Viral Zone". ExPASy. Retrieved 15 June 2015.
  4. ↑ ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
  5. ↑ Afonso CL, Amarasinghe GK, Bányai K, Bào Y, Basler CF, Bavari S, et al. (August 2016). "Taxonomy of the order Mononegavirales: update 2016". Archives of Virology. 161 (8): 2351–2360. doi:10.1007/s00705-016-2880-1. PMC 4947412. PMID 27216929.
  6. ↑ "Genus: Lyssavirus". International Committee on Taxonomy of Viruses (ICTV). Retrieved 18 December 2018.
  7. ↑ Virus Taxonomy: 2013 Release. ictvonline.org
  8. ↑ Kuzmin IV, Hughes GJ, Botvinkin AD, Orciari LA, Rupprecht CE (July 2005). "Phylogenetic relationships of Irkut and West Caucasian bat viruses within the Lyssavirus genus and suggested quantitative criteria based on the N gene sequence for lyssavirus genotype definition". Virus Research. 111 (1): 28–43. doi:10.1016/j.virusres.2005.03.008. PMID 15896400.
  9. ↑ Gould AR, Kattenbelt JA, Gumley SG, Lunt RA (October 2002). "Characterisation of an Australian bat lyssavirus variant isolated from an insectivorous bat". Virus Research. 89 (1): 1–28. doi:10.1016/s0168-1702(02)00056-4. PMID 12367747.
  10. ↑ Banyard AC, Hayman D, Johnson N, McElhinney L, Fooks AR (2011). "Bats and lyssaviruses". Advances in Virus Research. 79: 239–289. doi:10.1016/B978-0-12-387040-7.00012-3. ISBN 978-0-12-387040-7. PMID 21601050.
  11. ↑ Hayman DT, Fooks AR, Marston DA, Garcia-R JC (December 2016). "The Global Phylogeography of Lyssaviruses - Challenging the 'Out of Africa' Hypothesis". PLOS Neglected Tropical Diseases. 10 (12): e0005266. doi:10.1371/journal.pntd.0005266. PMC 5231386. PMID 28036390.
  12. ↑ Teeling EC, Springer MS, Madsen O, Bates P, O'brien SJ, Murphy WJ (January 2005). "A molecular phylogeny for bats illuminates biogeography and the fossil record". Science. 307 (5709): 580–584. Bibcode:2005Sci...307..580T. doi:10.1126/science.1105113. PMID 15681385. S2CID 25912333.
  13. ↑ He W, Zhang H, Zhang Y, Wang R, Lu S, Ji Y, et al. (October 2017). "Codon usage bias in the N gene of rabies virus". Infection, Genetics and Evolution. 54: 458–465. doi:10.1016/j.meegid.2017.08.012. PMID 28818621.
  14. ↑ Gigante CM, Dettinger L, Powell JW, Seiders M, Condori RE, Griesser R, et al. (16 May 2018). "Multi-site evaluation of the LN34 pan-lyssavirus real-time RT-PCR assay for post-mortem rabies diagnostics". PLOS ONE. 13 (5): e0197074. Bibcode:2018PLoSO..1397074G. doi:10.1371/journal.pone.0197074. PMC 5955534. PMID 29768505.
  15. ↑ WHO Rabnet/CDC Map Production (2008). "Rabies, countries or areas at risk". World Health Organization. Archived from the original on 9 October 2010.

Further reading

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