ICTV Report

Book: Picornaviridae

Family: Picornaviridae

Genus: Sapelovirus

 

Distinguishing features

The genus is distinguished on the basis of genetic characters. Sapeloviruses are related to enteroviruses, but possess leader polypeptides of unknown function. The 2A polypeptide may be a cysteine protease, but it is distinct from that of the enteroviruses. The 2B and 3A proteins are also very different from the enteroviruses. In both sapelovirus species the IRES is type IV, whereas in all enterovirus species it is type I. 

Virion

Morphology

No surface morphology is visible by EM. 

Physicochemical and physical properties

Viruses are very stable, resistant to acid pH and elevated temperatures (60°C for 10 min). Buoyant density in CsCl is 1.32–1.34 g cm-3. 

Nucleic acid

Genome (Krumbholz et al., 2002, Oberste et al., 2003, Tseng and Tsai 2007): c. 7,491–8,226 nt (5′-UTR: up to 741 nt; ORF: 6,969–7,566 nt; 3′-UTR: 82–235 nt). The IRES of members of both sapelovirus species is type IV. The location of the cre has not been identified. 

Genome organization and replication

Genome layout:

VPg+5′-UTRIRES-IV-[L-1A-1B-1C-1D/2Apro-2B-2C/3A-3B-3C-3D]-3′-UTR-poly(A)

The deduced polyproteins of sapaloviruses are of 2,322–2,521 aa. There is a leader polypeptide with unknown function. The 2A protein is suspected to be a protease. The precise L/VP0 cleavage for porcine sapelovirus (PSV) or simian sapelovirus (SSV) is not clear. The sequences in this region are quite well conserved between both viruses but it would require unusual cleavages in PSV (qL/GqvhS) and SSV (qC/GqvqS) to generate a myristoylation signal. VP0 is cleaved to VP4 and VP2 as shown by N-terminal sequencing of the VP2 polypeptide for SSV. 

Biology

Sapeloviruses have been isolated from pigs and monkeys. Sapelovirus-like-specific RNA has also been detected in bats (several species), various rodents, cats, cattle, dogs, pigeons, quails, and sea lions. Four genetic types are distinguished by means of phylogenetic analysis [Sapelovirus A: 1 type (PSV-1), Sapelovirus B: 3 types (SSV-1 to -3)]. 

Derivation of names

Sapelovirus: from simian, avian and porcine entero-like viruses

Species demarcation criteria

Members of a species of the genus Sapelovirus:

  • are less than 30% divergent in polyprotein aa sequence
  • are less than 36% divergent in P1 aa sequence
  • are less than 30% divergent in 2C + 3CD aa sequence
  • have a similar genome base composition which varies by no more than 1%
  • have a common genome organization

The divergence (number of differences per site between sequences) between members of different Sapelovirus species ranges from 0.39–0.63 for P1 and 0.35–0.51 for 3CD.