Family: Caliciviridae

Genus: Vesivirus

Distinguishing features

Viruses in this genus form a distinct clade within the family Caliciviridae (Figure 4. Caliciviridae).  ORF2 encodes the major capsid protein that is translated as a larger precursor protein before cleavage into the mature VP1, a feature that appears unique to this genus. 

Virion

See discussion under family description. 

Genome organization and replication

The genome of vesiviruses is 8.4 kb for vesicular exanthema of swine virus (VESV) or 7.6 kb for feline calicivirus (FCV) and is organized into three major ORFs. ORF1 encodes a polyprotein that is posttranslationally cleaved into six non-structural polyproteins. ORF2 encodes the major capsid protein that is translated as a larger precursor protein before cleavage into the mature VP1. ORF1 and ORF2 are separated by either 2 nt (GC for FCV strains) or 5 nt (CCACT/C for marine vesiviruses). A third ORF (ORF3) encodes VP2 a small, basic protein and overlaps by one nt with ORF2 in a −1 frameshift. The ORF3 product has been detected in FCV-infected cells and is essential for infectious virus production. 

Biology

Most members of this genus can be readily propagated in cell culture. FCV grows most efficiently in cells of feline origin; in vivo, the primary site of replication is the upper respiratory tract. Primary isolation of most marine vesiviruses is possible in African green monkey kidney or porcine kidney cells. Approximately half of marine vesiviruses have been documented to produce skin vesicles in swine, horses and sometimes cattle and vesicles have occurred naturally in dogs, pinnipeds, cetaceans and primates (including man).  

Species demarcation criteria

Membership of a Vesivirus species is based on phylogenetic differences, subtle variation in genome structure and host range, with VESV A₄₈ and feline calicivirus as exemplar isolates of the species Vesicular exanthema of swine virus and Feline calicivirus, respectively. VESV A₄₈ and viruses isolated from marine animals are phylogenetically grouped together and colloquially referred to as “marine vesiviruses”. Both San Miguel sea lion virus types 8 and 12 have recently been shown to be phylogenetically distinct from each other and from members of the species Vesicular exanthema of swine virus (Neill 2014), (N.J. Knowles, unpublished data). Unlike other members of the genus, San Miguel sea lion virus 12 appears to have only two ORFs, ORF1 (encoding the non-structural and capsid-coding regions) and ORF3 (VP2) (N.J. Knowles, unpublished data).  

Related, unclassified viruses 

Virus names and virus abbreviations are not official ICTV designations.