Rhabdoviridae

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Rhabdoviruses are viruses belonging to the family Rhabdoviridae, which is in the order Mononegavirales. The name is derived from the Greek rhabdos meaning rod referring to the shape of the viral particles. Rhabdoviruses infect a broad range of hosts throughout the animal and plant kingdom. Animal rhabdoviruses infect insects, fish, and mammals, including humans.

Virology

Classification

Rhabdoviruses carry their genetic material in the form of negative-sense single-stranded RNA. They typically carry genes for five proteins: large protein (L), glycoprotein (G), nucleoprotein (N), phosphoprotein (P), and matrix protein (M). Rhabdoviruses that infect vertebrates are bullet-shaped.

The following genera are included here:

• Genus Cytorhabdovirus; type species: Lettuce necrotic yellows virus
• Genus Dichorhabdovirus; type species: Orchid fleck virus
• Genus Ephemerovirus; type species: Bovine ephemeral fever virus
• Genus Lyssavirus; type species: Rabies virus
• Genus Novirhabdovirus; type species: Infectious hematopoietic necrosis virus
• Genus Nucleorhabdovirus; type species: Potato yellow dwarf virus
• Genus Vesiculovirus; type species: Vesicular stomatitis Indiana virus

In addition to the above, there are a large number of rhabdoviruses that have not yet been assigned to a genus.

Replication

Replication of many rhabdoviruses occurs in the cytoplasm, although several of the plant infecting viruses replicate in the nucleus. In order for replication, both the L and P protein must be expressed to regulate transcription. Transcription results in five monocistronic mRNAs being produced because the intergenic sequences act as both termination and promoter sequences for adjacent genes. During their synthesis the mRNAs are processed to introduce a 5’ cap and a 3’ polyadenylated tail to each of the molecules. This structure is homologous to cellular mRNAs and can thus be translated by cellular ribosomes to produce both structural and non-structural proteins.

Genomic replication requires a source of newly synthesized N protein to encapsidate the RNA. This occurs during its synthesis and results in the production of a full length anti-genomic copy. This in turn is used to produce more negative-sense genomic RNA. The viral polymerase is required for this process, but how the polymerase engages in both mRNA synthesis and genomic replication is not well understood.

Replication characteristically occurs in an inclusion body within the cytoplasm, from where they bud through various cytoplasmic membranes and the outer membrane of the cell. This process results in the acquisition of the M + G proteins, responsible for the characteristic bullet- shaped morphology of the virus.

Prototypical Rhabdoviruses

The prototypical and best studied rhabdovirus is vesicular stomatitis virus. Since it is easy to grow in the laboratory, it is a preferred model system to study the biology of Rhabdoviruses, and Mononegavirales in general.

The mammalian disease Rabies is caused by Lyssavirus, of which several strains have been identified.

Rhabdoviruses are important pathogens of animals and plants. Rhabdoviruses include RaV (Rabies virus), VSV (Vesicular stomatitis virus). Rhabdoviruses are transmitted to hosts by arthropods, such as aphids, planthoppers, leafhoppers, black flies, sandflies, and mosquitoes.

See also

• Rabies

References

Notes

Bibliography

Further reading

External links

• ViralZone: Rhabdoviridae
• MicrobiologyBytes: Rhabdoviruses
• Rhabdovirus overview
• RNA virus replication strategies