Notes on Genus: Aphthovirus


Type member: Foot-and-mouth disease virus


General Description

The genus Aphthovirus (from the greek aphtha = vesicles in the mouth) is one of the genera in the family Picornaviridae. Genome organisation is fairly conserved within the family but members of this genus have a very long (>1kb) 5'-UTR which contains a polyC tract, a leader protease and a very short 2A protein. The type member is unusual in having three VPg proteins.


Virions isometric (icosahedral), not enveloped 30 nm in diameter, made of 60 units (protomers) each consisting of one molecule of each of three surface coat proteins and with a fourth internal capsid protein.


Monopartite positive sense single-stranded RNA 7.5-8.2 kb in length. There is a genome-linked protein (VPg) at the 5'-terminus and a 3'-polyA tail.

Genus Genomic Organization

The RNA encodes a single polyprotein that is subsequently processed into the functional products. The major structural proteins are encoded near the N-terminus, following the self-cleaving leader protease.

Type Member Genomic Organization

The genome of about 8,100 nucleotides is translated into a single polyprotein, which is subsequently processed into fourteen products:
L 22.8 kDaLeader protein (protease)
1A  8.8 kDaCoat protein VP4 (internal capsid protein)
1B  24.3 kDaCoat protein VP2 (surface capsid protein)
1C 24.0 kDaCoat protein VP3 (surface capsid protein)
1D 22.9 kDaCoat protein VP1 (surface capsid protein)
2A 1.7 kDanon-structural protein
2B 16.9 kDanon-structural protein
2C 35.9 kDanon-structural protein
3A 17.4 kDanon-structural protein
3B 2.7 kDaGenome-linked protein (VPg1)
3B 2.7 kDaGenome-linked protein (VPg2)
3B 2.6 kDaGenome-linked protein (VPg3)
3C 23.0 kDaprotease
3D 52.8 kDapolymerase