Description of Caliciviridae
adapted from
ICTVdb
Virion Properties
Morphology
Virions consist of a
capsid. Virus capsid is not enveloped, round with icosahedral
symmetry. The isometric capsid has a diameter of 35-39 nm.
Capsids appear round to hexagonal in outline. The capsid surface
structure reveals a regular pattern with distinctive features.
The capsomer arrangement is clearly visible. Capsid with 32
cup-shaped depressions.
Physicochemical and Physical Properties
The molecular mass (Mr) of
virions is 15 x 10
6. Virions have a buoyant density in
CsCl of 1.33-1.4 g cm
-3. The density of virions is in
glycerol-potassium tartrate gradients 1.29 g cm
-3. The
sedimentation coefficient is 170-187
S20w; of
the other(s) are peak 160-170
S20w (believed to
consist of defective interfering particles). Under
in
vitro conditions virions are stable in acid environment of pH
4-5. 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).
Nucleic Acid
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 encapsidated nucleic acid is mainly of genomic
origin, but virions may also contain subgenomic RNA (in some
members). The complete genome is 7400-8300 nucleotides long. The
genome has a guanine + cytosine content of 45-56 %. The 5'-end of
the genome has a usually genome-linked protein (VPg), or
methylated nucleotide cap (in the case of hepatitis E virus). The
3'-terminus has a poly (A) tract. Each virion contains a full
length copy, or defective interfering copies.
Proteins
The viral genome encodes structural
proteins. Virions consist of 1 structural protein (major
species), or 2 structural proteins detected in Norwalk virus,
amyelosis chronic stunt virus and porcine enteric calicivirus
located in the capsid.
Structural Proteins: Capsid protein has a
molecular mass of 58000-60000 Da; is the coat protein. Capsid
protein has a molecular mass of minor 'soluble' 28-30 kDa.
Lipids
Lipids are not reported.
Genome Organization and Replication
By itself, genomic nucleic acid is infectious.
Transcription:
Sub-genomic RNA is present in infected cells (after infection
with e.g., rabbit hemorrhagic disease virus (RHDV)).