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Type Species |
(FMDV) |
The capsid of FMDV is thin-walled (mean thickness = 33 Å), and has an unusually smooth surface. A long (17-23 aa), mobile loop, the G-H loop, projects from the surface of 1D. There is a pore at the 5-fold axis, where part of underlying 1C is exposed. Some serotypes of FMDV accumulate empty capsids.
Physicochemical and Physical Properties
Virions are acid labile; FMDV particles are unstable below pH 6.8; Equine rhinitis A virus (ERAV) particles are unstable below pH 5.5. The buoyant density in CsCl is 1.43-1.45g/cm3. Virions of FMDV sediment at 146S, empty capsids at 75S.
There is a poly(C) tract close to the 5
-terminus of the genome. In FMDV it is located about 360 nts from the end, and varies in length from 100 to more than 400 nts. Current data suggests that the poly(C) tract in ERAV is shorter ( ± 40 nts) and closer to the 5-end. In FMDV RNA there is a series of pseudoknots on the 3-side of the poly(C); the total 5-NTR is thus extremely long (1.1-1.5 kb). ERAV and FMDV differ by approximately 50% in nucleotide sequence across the entire genome.
The major CPs of FMDV have the shortest chain lengths of any picornavirus (208-220 aa); those of ERAV are only slightly longer. At the tip of the 1D G-H loop of FMDV is the conserved integrin recognition motif, RGD.
Genome Organization and Replication
Translation starts at two alternative in-frame initiation sites, resulting in two forms of the L protein (Lab and Lb). Unlike the cardioviruses, L is a papain-like cysteine proteinase which cleaves itself from the virus polyprotein. The 2A polypeptide is very short (chain length = 18 in FMDV; unpublished data), and is involved in NPGP-dependent polypeptide chain interruption at its C-terminus as in cardioviruses. The genome of FMDV encodes 3 species of VPg while ERAV only encodes one.
Five independent antigenic sites have been reported in FMDV type O, two of which have determinants in the G-H loop of 1D. There is no evidence of N-D conversion, nor ‘A’ particles.
FMDV infects mainly cloven-hooved animals, but has been isolated from at least 70 species of mammals. Clinical manifestations of FMDV infections include foot-and-mouth disease (vesicular lesions), sometimes with associated acute fatal myocarditis in young animals; of ERAV, upper respiratory tract infections of horses. Both species may produce persistent upper respiratory tract infections. FMDV infects cells by binding to integral membrane proteins of the integrin family through its 1D G-H loop; heparan sulfate proteoglycans may also serve as receptors. Cap-dependent translation of host mRNA is inhibited by Lpro, which cleaves the host eIF-4G.
List of Species Parameters in the Genus
Members of an aphthovirus species:
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share greater than 50% amino acid identity in the P1, |
|
share greater than 70% amino acid identity in the 2C + 3CD, |
|
share a natural host range, |
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have a genome base composition which varies by no more than 1%, |
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share a comm genome layout. |
Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:
|
Equine rhinitis A virus (1 serotype) |
(ERAV) | |
|
(formerly Equine rhinovirus 1) |
[L43052, X96870] |
|
|
Foot-and-mouth disease virus (7 serotypes) |
(FMDV) | |
|
FMDV type A |
[L11360, M10975] |
(FMDV-A) |
|
FMDV type Asia 1 |
[U01207] |
(FMDV-Asia1) |
|
FMDV type C |
[X00130, J02191] |
(FMDV-C) |
|
FMDV type O |
[M35873, X00871] |
(FMDV-O) |
|
FMDV type SAT 1 |
[Z98203] |
(FMDV-SAT1) |
|
FMDV type SAT 2 |
(FMDV-SAT2) | |
|
FMDV type SAT 3 |
[M28719] |
(FMDV-SAT3) |
Tentative Species in the Genus
None reported.
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