Vesivirus

Vesivirus is a genus of viruses, in the family Caliciviridae. Swine, sea mammals, and felines serve as natural hosts. There are currently only two species in this genus including the type species Vesicular exanthema of swine virus. Diseases associated with this genus include: respiratory disease; FCV: conjunctivitis, respiratory disease.^[1][2]

Taxonomy

Group: ssRNA(+)

^[2]

Other, unofficial Vesi-like viruses include canine calicivirus, San Miguel sealion virus, vesivirus Cro1 and walrus calicivirus.^[3]

Virion properties

Morphology

Virions consist of a capsid. Virus capsid is non-enveloped, and are round with icosahedral symmetry and triangulation number T=3. The isometric capsid has a diameter of 35–39 nm. Empty virions have diameter of 23 nm, with triangulation number T=1.^[1] The capsid surface structure reveals a regular pattern with distinctive features, including 32 cup-shaped depressions. The capsomer arrangement is clearly visible.

Life Cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment to host receptors, which mediates endocytosis. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription is the method of transcription. Translation takes place by RNA termination-reinitiation. Swine, sea mammals, and felines serve as the natural host. Transmission routes are air borne particles.^[1]

Physical and chemical properties

The molecular mass (Mr) of virions is 15 x 106. Virions have a buoyant density in Caesium chloride (CsCl) of 1.33–1.41 g/cm³. The density gradient of virions in Potassium Tartrate-Glycerol is 1.29 g/cm³. The sedimentation coefficient is 170–187 svedberg (s_20,w), of the other(s) peak at 160–170 svedberg (s_20,w). Under in vitro conditions virions are inactivated in acid environment of pH 3–5. Virions are not stable at raised temperature in presence of high concentration of Mg⁺⁺. Virions are sensitive to treatment with trypsin (in some strains, not sensitive to treatment with mild detergents, or ether, or chloroform. The infectivity is enhanced after treatment with trypsin (in some strains).

Genome

The genome is not segmented and contains a single molecule of linear positive-sense, single-stranded RNA. Minor species of non-genomic nucleic acid are some times also found in virions. The complete genome is 7700 nucleotides long. The genome has a guanine + cytosine content of 45–49%. The 5' end of the genome has a genome-linked protein (VPg). The 3' terminus has a poly (A) tract. Each virion contains a full length copy, or defective interfering copies.

Proteins

The viral genome encodes viral structural protein. Virions consist of 1 viral structural protein (major species), or 2 Viral structural proteins (detected in Norwalk virus, amyelosis chronic stunt virus and porcine enteric calicivirus located in the capsid.

Viral structural protein: Capsid protein has a molar mass of 58000–60000 Da; is the coat protein. Capsid protein has a molecular mass of minor 'soluble' 28–30 kDa.

Antigenicity

Serological relationships between different members are found (among Feline calicivirus). Cross-reactivity is found. Cross-reactivity between species of the same serotype, but not with species of another serotype and some species of the same serotype, but not with all. Although the degree of antigenic specificity varies with the degree of relatedness, the antigenicity is distinct from canine caliciviruses, Norwalk virus serogroups of the same genus.

Impact on Biotech and Health

In June 2009, Genzyme's Allston, Massachusetts plant was shut down to correct a viral contamination (Vesivirus 2117). A similar event had occurred in 2008 at the Geel, Belgium facilities. By April 2010 it had restarted operation at diminished capacity. Vesivirus is not known to cause human disease, but can inhibit growth of Chinese Hamster Ovary cells (CHO) used extensively in biotech production or mammalian proteins.^[4]

References

External links

• ICTVdB—The Universal Virus Database, version 4.
• Viralzone: Vesivirus
• ICTV