Genus Cardiovirus

Type Species	Encephalomyocarditis virus	(EMCV)

Virion Properties

Morphology

Empty capsids are only seen rarely, if ever. When compared by mean wall thickness, surface unevenness, and chain length of the major proteins, the cardiovirus capsid is intermediate between the enteroviruses and aphthoviruses. In place of a continuous, circular canyon, seen in enteroviruses, is a five-fold repeated pit. There is no pocket factor.

Physicochemical and Physical Properties

Virion buoyant density in CsCl is 1.33-1.34  g/cm³. Virions are moderately stable to acidic pH.

Nucleic Acid

EMCV has a poly(C) tract of variable length (usually 80-250  nts) about 150  nts from the 5-terminus of the viral RNA, while Theilovirus lack this feature. The IRES is of type 2. The nucleotide sequence identity over the entire genome for different species of the genus Cardiovirus is more than 50% (e.g., Theiler’s murine encephalomyelitis virus, TMEV, 54% identity to EMCV)

Genome Organization and Replication

The viral genome encodes a leader (L) protein which lacks proteolytic activity, unlike the L of aphthoviruses; thus L is cleaved from P1 by the virus encoded protease 3C. The 1D/2A junction is also cleaved by 3C^pro, rather than by 2A. The 2A protein causes cleavage, or polypeptide chain interruption, between P1-2A and downstream sequences at an essential sequence, --NPGP--.

Antigenic Properties

Four independent antigenic sites have been described. There is no evidence of an N-D conversion, nor of ‘A’ particles.

Biological Properties

Encephalomyocarditis viruses have been isolated from over 30 host species including mammals, birds and insects. Clinical manifestations include encephalitis and myocarditis in mice and many other animals. TMEV can be divided into two biological subgroups which both infect mice; one causes an acute and fatal polioencephalomyelitis and the other causes a chronic persistent demyelinating infection of the white matter. Vilyuisk human encephalomyelitis virus (VHEV) is thought to be the cause of a degenerative neurological disease in man which has been reported in the Vilyuy valley in Siberia. Cardiovirus infection does not cause cleavage of the host eIF-4G. The cellular receptor used by EMCV to attach to murine vascular endothelial cells has been identified as VCAM-1. However, in human cell lines an as yet unidentified sialoglycoprotein(s) has been found. EMCV binds to human erythrocytes via glycophorin A.

List of Species Demarcation Criteria in the Genus

Members of a cardiovirus species:

	share greater than 70% amino acid identity in the P1,
	share greater than 70% amino acid identity in 2C + 3CD,
	share a natural host range,
	share a common genome layout.

Mengovirus, Columbia SK virus and Maus Elberfeld virus are strains of EMCV, based on serological cross-reaction and sequence identity.

List of Species in the Genus

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:

Species in the Genus

Encephalomyocarditis virus (1 serotype)	[M81861]	(EMCV)
Mengovirus
Columbia SK virus
Maus Elberfeld virus
Theilovirus (3 strains)		(ThV)
Theiler’s murine encephalomyelitis virus	[M20562]	(TMEV)
Vilyuisk Human encephalomyelitis virus	[M80888, M94868]	(VHEV)
Rat encephalomyelitis virus	[M80884]	(REV)

Tentative Species in the Genus

None reported.