Herpesviridae. Herpesviridae

Description of Herpesviridae adapted from ICTVdb Virion Properties Morphology Virions consist of an envelope, a tegument, a nucleocapsid, and a core. Virus capsid is enveloped. Virions are spherical to pleomorphic. Virions measure 120-200 nm in diameter. Surface projections are distinctive, densely dispersed spikes that cover evenly the surface. Teguments do not display a structure and proteins in variable amounts are arranged sometimes in an asymmetric layer located between envelope and capsid. Capsid/nucleocapsid is round and exhibits icosahedral symmetry (T=16). The capsid is isometric and has a diameter of 100-110 nm. Capsids appear hexagonal in outline. The capsomer arrangement is clearly visible. The capsid consists of 162 capsomers with a hexagonal base and a hole running half-way down the long axis. The core consists of a fibrillar spool on which the DNA is wrapped. The end of the fibers are anchored to the underside of the capsid shell. Physicochemical and Physical Properties Virions have a buoyant density in CsCl of 1.15-1.29 g cm-3. Nucleic Acid The genome is not segmented and contains a single molecule of linear double-stranded DNA. The complete genome is 120000-220000 nucleotides long. The genome has a guanine + cytosine content of 35-75 %. Proteins The viral genome encodes structural proteins and non-structural proteins located in the envelope, capsid, and tegument. Structural Proteins: Internal lipid membrane consists of several proteins. Lipids Lipids are present and located in the envelope. The composition of viral lipids is not exactly known. The lipids are of host origin and are derived from nuclear or host cell membranes.