Erbovirus

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Erbovirus
Virus classification
Group: Group IV ((+)ssRNA)
Family: Picornaviridae
Genus: Erbovirus
Species

Equine rhinitis B virus

Erbovirus is a viral genus of the Picornaviridae family.[1] Viruses belonging to the Erbovirus genus have been isolated in horses with acute upper febrile respiratory disease.[2] The structure of the erbovirus virion is icosahedral,[1] having a diameter of 27-30nm.[3]

[edit] Physical characteristics

The virion essentially is a nucleocapsid that is visible under an electron microscope and is able to infect cultured cells from a broad range of mammals including rabbit kidney (RK13), African green monkey kidney (Vero), equine foetal kidney (EFK), and is able to infect humans.[4]

The RNA genome of the virion is inside the capsid that is composed by twelve capsomers, which are cup-shaped pentamers.

The erbovirus particles are non-enveloped and the molecular mass of the virions is around 8-9 x 106 Daltons.[3] They are resistant to inactivation by non-ionic detergent treatment.[3]

Erbovirus, as a typical picornavirus, has a single-stranded positive-sense RNA genome. A feature of the picornavirus genome is the virus protein that is linked at the 5’ end of the genome, known as "VPg" (Virus-Protein-attached-to-the-Genome).[1] In addition, the 3’ end of the genome has a poly-A tail.[1] The transcription of the erbovirus genome gives rise to a polyprotein which is further more processed and cleaved to give the mature viral proteins, in order from 5' to 3' : L ("Leader"), VP4, VP2, VP3, VP1, 2A, 2B, 2C, 3A (Vpg), 3B, 3Cpro, 3Dpol.[5]

The type (and only) species of the Erbovirus genus is Equine rhinitis B virus which was recently found to have three phylogenetically distinct types, equine rhinitis B virus (ERBV)-1, ERBV-2 and ERBV-3.[6] One such phylogenetic group was found to mostly comprise of "acid stable" virus isolates, surviving pH 3.6 for 1 hour at room temperature.[7]

[edit] Epidemiology

ERBV's appear to infect most foals and weanlings, eliciting a low serum antibody response in stark contrast to equine rhinitis A virus (ERAV), which is the only species of the genus Aphthovirus that is not a foot-and-mouth disease virus (FMDV), and appears to only infect horses once they begin training for racing (approx. 2 years old). ERAV enters the blood and elicits a very high serum antibody response that seems to then limit the spread of the virus by herd-immunity, given that only approximately 40% of horses have detectable ERAV antibody.[8] The low serum antibody response of ERBV appears to allow the continual, seasonal re-infection of horses. Horses are also known to shed ERBV for up to two years, possibly more.

[edit] References

  1. ^ a b c d Notes on Genus: Erbovirus. dpvweb. Retrieved on 2007-03-16.
  2. ^ Dynon K, Black W, Ficorilli N, Hartley C, Studdert M (2007). "Detection of viruses in nasal swab samples from horses with acute, febrile, respiratory disease using virus isolation, polymerase chain reaction and serology". Aust Vet J 85 (1-2): 46–50. doi:10.1111/j.1751-0813.2006.00096.x. PMID 17300454. 
  3. ^ a b c 'Erbovirus'. ICTVdb. Retrieved on 2007-03-16.
  4. ^ Kriegshäuser G, Deutz A, Kuechler E, Skern T, Lussy H, Nowotny N (2005). "Prevalence of neutralizing antibodies to Equine rhinitis A and B virus in horses and man". Vet Microbiol 106 (3-4): 293–6. doi:10.1016/j.vetmic.2004.12.029. PMID 15778036. 
  5. ^ Wutz G, Auer H, Nowotny N, Grosse B, Skern T, Kuechler E (1996). "Equine rhinovirus serotypes 1 and 2: relationship to each other and to aphthoviruses and cardioviruses". J Gen Virol 77 ( Pt 8): 1719–30. doi:10.1099/0022-1317-77-8-1719. PMID 8760418. 
  6. ^ Black W, Studdert M (2006). "Formerly unclassified, acid-stable equine picornaviruses are a third equine rhinitis B virus serotype in the genus Erbovirus". J Gen Virol 87 (Pt 10): 3023–7. doi:10.1099/vir.0.81937-0. PMID 16963761. 
  7. ^ Black W, Hartley C, Ficorilli N, Studdert M (2005). "Sequence variation divides Equine rhinitis B virus into three distinct phylogenetic groups that correlate with serotype and acid stability". J Gen Virol 86 (Pt 8): 2323–32. doi:10.1099/vir.0.80778-0. PMID 16033980. 
  8. ^ Black W, Wilcox R, Stevenson R, Hartley C, Ficorilli N, Gilkerson J, Studdert M (2007). "Prevalence of serum neutralising antibody to equine rhinitis A virus (ERAV), equine rhinitis B virus 1 (ERBV1) and ERBV2". Vet Microbiol 119 (1): 65–71. doi:10.1016/j.vetmic.2006.08.031. PMID 17046179.