Genus: Erbovirus


Genus: Erbovirus

Distinguishing features

The genus is distinguished on the basis of genetic characters. The 2B and 3C proteins of erboviruses have exceptionally large chain lengths (283 and 251 aa, respectively).

Virion

Morphology

No surface morphology is visible by EM.

Physicochemical and physical properties

Equine rhinitis B virus (ERBV) has a buoyant density in CsCl of 1.41–1.45 g cm-3. pH stability is variable; ERBV-1 and ERBV-2 are labile below pH 5.0 while ERBV-3 is stable over a wide pH range (2.2-8.0). ERBV is rapidly inactivated by heating at 50°C but divalent cations stabilize against thermal inactivation.

Nucleic acid

Genome (Wutz et al., 1996): c. 8,828 nt (5′-UTR: up to 905 nt; ORF: 7,752–7,770 nt; 3′-UTR: 164 nt). The IRES is of type II. No pseudoknots have yet been identified within the 5′-UTR. The location of the cre has not been identified.

Genome organization and replication

Genome layout:

VPg+5′-UTRIRES-II-[Lpro/1A-1B-1C-1D-2Anpgp/2B-2C/3A-3B-3C-3D]-3′-UTR-poly(A)

The deduced polyprotein is of 2,583–2,589 amino acid. No evidence for alternative sites of initiation of protein synthesis is available as is found in the aphthoviruses. The L protein appears to be a proteinase, but has only 23% and 18% aa sequence identity to the L proteins of foot-and-mouth disease virus (FMDV, genus Aphthovirus) and equine rhinitis A virus (ERAV, genus Aphthovirus) respectively. 2A is a short FMDV-like polypeptide (NPG¯P).

Antigenicity

ERBV consists of three serotypes, ERBV-1, -2 and -3 (Black and Studdert 2006, Black et al., 2005, Huang et al., 2001).

Biology

ERBV causes upper respiratory tract disease in horses, with a viraemia and faecal shedding. Infections may be persistent. 

Species demarcation criteria

There is only a single species in the genus. 

Member species

SpeciesVirus name(s)Exemplar isolateExemplar accession numberExemplar RefSeq numberAvailable sequenceOther isolatesOther isolate accession numbersVirus abbreviationIsolate abbreviation
Erbovirus Aequine rhinitis B virus 1P1436 /71X96871NC_003983Complete genomeERBV-1
Erbovirus Aequine rhinitis B virus 2P313/75 (Switzerland/1975)AF361253ERBV-2
Erbovirus Aequine rhinitis B virus 34442/75 (UK/1975)DQ108383ERBV-3

Virus names, the choice of exemplar isolates, and virus abbreviations, are not official ICTV designations.

Derivation of names

Erbo-: from equine rhinitis B virus