Erbovirus

Taxobox
name = "Erbovirus"
virus_group = iv
familia = "Picornaviridae"
genus = "Erbovirus"
subdivision_ranks = Species
subdivision = "Equine rhinitis B virus"

"Erbovirus" is a viral genus of the "Picornaviridae" family.cite web | title = Notes on Genus: Erbovirus | work = dpvweb| url = http://www.dpvweb.net/notes/showgenus.php?genus=Erbovirus | accessdate = 2007-03-16] Viruses belonging to the "Erbovirus" genus have been isolated in horses with acute upper febrile respiratory disease.cite journal |author=Dynon K, Black W, Ficorilli N, Hartley C, Studdert M |title=Detection of viruses in nasal swab samples from horses with acute, febrile, respiratory disease using virus isolation, polymerase chain reaction and serology |journal=Aust Vet J |volume=85 |issue=1-2 |pages=46–50 |year=2007 |pmid=17300454 |doi=10.1111/j.1751-0813.2006.00096.x] The structure of the erbovirus virion is icosahedral, having a diameter of 27-30nm.cite web | title = 'Erbovirus' | work = ICTVdb | url = http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.052.0.07.htm | accessdate = 2007-03-16 ]

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.cite journal |author=Kriegshäuser G, Deutz A, Kuechler E, Skern T, Lussy H, Nowotny N |title=Prevalence of neutralizing antibodies to Equine rhinitis A and B virus in horses and man |journal=Vet Microbiol |volume=106 |issue=3-4 |pages=293–6 |year=2005 |pmid=15778036 |doi=10.1016/j.vetmic.2004.12.029]

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. They are resistant to inactivation by non-ionic detergent treatment.

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). In addition, the 3’ end of the genome has a poly-A tail. 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, 3C^pro, 3D^pol.cite journal |author=Wutz G, Auer H, Nowotny N, Grosse B, Skern T, Kuechler E |title=Equine rhinovirus serotypes 1 and 2: relationship to each other and to aphthoviruses and cardioviruses |journal=J Gen Virol |volume=77 ( Pt 8) |issue= |pages=1719–30 |year=1996 |pmid=8760418 |doi=10.1099/0022-1317-77-8-1719]

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.cite journal |author=Black W, Studdert M |title=Formerly unclassified, acid-stable equine picornaviruses are a third equine rhinitis B virus serotype in the genus Erbovirus |journal=J Gen Virol |volume=87 |issue=Pt 10 |pages=3023–7 |year=2006 |pmid=16963761 |doi=10.1099/vir.0.81937-0] One such phylogenetic group was found to mostly comprise of "acid stable" virus isolates, surviving pH 3.6 for 1 hour at room temperature.cite journal |author=Black W, Hartley C, Ficorilli N, Studdert M |title=Sequence variation divides Equine rhinitis B virus into three distinct phylogenetic groups that correlate with serotype and acid stability |journal=J Gen Virol |volume=86 |issue=Pt 8 |pages=2323–32 |year=2005 |pmid=16033980 |doi=10.1099/vir.0.80778-0]

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.cite journal |author=Black W, Wilcox R, Stevenson R, Hartley C, Ficorilli N, Gilkerson J, Studdert M |title=Prevalence of serum neutralising antibody to equine rhinitis A virus (ERAV), equine rhinitis B virus 1 (ERBV1) and ERBV2 |journal=Vet Microbiol |volume=119 |issue=1 |pages=65–71 |year=2007 |pmid=17046179 |doi=10.1016/j.vetmic.2006.08.031] 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.

References