Rhabdoviridae. Rhabdoviridae

Description of Rhabdoviridae adapted from ICTVdb Virion Properties Morphology Virions consist of an envelope and a nucleocapsid. Virus capsid is enveloped. Virions are in unfixed preparations bullet-shaped, or bacilliform (in cases of plant viruses when fixed prior to negative staining), or pleomorphic. Virions measure 45-100 nm in diameter; 100-430 nm in length. Surface projections are densely dispersed, distinctive spikes. They consist of trimers of the virus glycoprotein that cover the whole surface except for the quasi-planar end. Surface projections form ring-like subunits. Surface projections are 5-10 nm long; spaced 3 nm apart. Capsid/nucleocapsid is elongated with helical symmetry. The nucleocapsid is uncoiled filamentous, or cylindrical (coiled, is cross-banded (spaced 4.5-5 nm, in negatively stained preparations and thin sections) with a length of uncoiled about 700 nm and a width of uncoiled 20 nm, or 30-70 nm. Capsid consists of an RNA and N protein complex together with an NS (M1) proteins and is surrounded by a lipid envelope containing M (M2) protein. The nucleocapsid contains transcriptase activity and is infectious. Only one species is recovered in preparations (that is a virus with defective genome, usually significantly shorter than the full length). Incomplete particles are found (defective particles proportionally shorter). Physicochemical and Physical Properties Virions have a buoyant density in sucrose of 1.14-1.2 g cm-3. Nucleic Acid The Mr of the genome constitutes 1-2% of the virion by weight. The genome is not segmented and contains a single molecule of linear; usually negative-sense, single-stranded RNA, or positive-sense full length single-stranded RNA. Up to 5% in a viral RNA population are p;ositive stranded; hairpin RNA forms are also found. The complete genome is 11000-15000 nucleotides long. Nucleotide sequences at the 3'-terminus are are inverted and complementary to similar regions on the 5' end. The 5'-end of the genome has a triphosphate cap. Each virion contains a full length copy, or shorter copies. Proteins Proteins constitute about 65-75% of the particle weight (structural). The viral genome encodes structural proteins and non-structural proteins. Lipids Lipids are present and located in the envelope and protein (G that has a covalently associated fatty acid proximal to the lipid envelope). Virions are composed of 15-25% lipids by weight (their composition depends on the host cell membrane. Generally phospholipids represent about 50-60%, sterols and glycolipids about 35-40% of the total lipids. G protein has a covalently associated fatty acid proximal to the lipid envelope). The composition of viral lipids and host cell membranes are similar. The lipids are of host origin and are derived from host cell membranes. Viral membranes include 55-60% phospholipids, sterols, and glycolipids. PolyaminesOther compounds that have been detected in the virus particles are 3% carbohydrates. The carbohydrates are present as N-linked glycan chains on G protein and as glycolipids. Genome Organization and Replication Translation: Virions are associated with helper virus, but independent from its functions during replication; defectives only replicate in the presence of homologous rhabdoviruses. Virion acts as helper for occasionally another virus; a helper for certain heterologous helper rhabdoviruses.