Rhabdoviridae

Rhabdoviridae
Vesicular stomatitis virus (VSV), the prototypical rhabdovirus
Virus classification
Group: Group V ((-)ssRNA)
Order: Mononegavirales
Family: Rhabdoviridae
Genera

Rhabdoviridae is a family of viruses in the order Mononegavirales. Vertebrates (including mammals and humans), invertebrates, and plants serve as natural hosts. There are currently 71 species in this family, divided among 11 genera. Diseases associated with this family include rabies fatal encephalitis from rabies virus, and vesicular diseases and encephalitis flu-like symptoms in humans from vesiculovirus.[1][2] The name is derived from the Greek rhabdos meaning rod referring to the shape of the viral particles.

Structure

Viruses in Rhabdoviridae are enveloped, with bullet shaped and bacilliform geometries. These viruses are about 75 nm wide and 180 nm long.[1] Genomes are linear, around 11-15kb in length.[1] 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 usually bullet-shaped.

Genus Structure Symmetry Capsid Genomic Arrangement Genomic Segmentation
LyssavirusBullet-shapedEnvelopedLinearMonopartite
NovirhabdovirusBullet-shapedEnvelopedLinearMonopartite
EphemerovirusBullet-shapedEnvelopedLinearMonopartite
PerhabdovirusBullet-shapedEnvelopedLinear
TibrovirusBullet-shapedEnvelopedLinear
NucleorhabdovirusBullet-shapedEnvelopedLinearMonopartite
TupavirusBullet-shapedEnvelopedLinear
VesiculovirusBullet-shapedEnvelopedLinearMonopartite
SprivivirusBullet-shapedEnvelopedLinear
CytorhabdovirusBullet-shapedEnvelopedLinearMonopartite
SigmavirusBullet-shapedEnvelopedLinear

Replication

Electron micrograph of two plant rhabdovirus particles

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral G glycoproteins to host receptors, which mediates clathrin-mediated endocytosis. Replication follows the negative stranded RNA virus replication model. Negative stranded RNA virus transcription, using polymerase stuttering is the method of transcription. The virus exits the host cell by budding, and tubule-guided viral movement. Transmission routes are zoonosis and bite.[1]

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.

Genus Host Details Tissue Tropism Entry Details Release Details Replication Site Assembly Site Transmission
LyssavirusHumans; mammalsNeuronsClathrin-mediated endocytosisBuddingCytoplasmCytoplasmZoonosis; animal bite
NovirhabdovirusFishNoneClathrin-mediated endocytosisBuddingCytoplasmCytoplasmPassive diffusion
EphemerovirusCattle; mosquitoesNoneClathrin-mediated endocytosisBuddingCytoplasmCytoplasmArthropod bite
PerhabdovirusFishNoneClathrin-mediated endocytosisBuddingCytoplasmCytoplasmWaterborne
TibrovirusBovineNoneClathrin-mediated endocytosisBuddingCytoplasmCytoplasmZoonosis; arthropod bite: midges
NucleorhabdovirusPlantsNoneViral movement; mechanical inoculationViral movementNucleusNucleusArthropod bite
TupavirusBirdsNoneClathrin-mediated endocytosisBuddingCytoplasmCytoplasmUnknown
VesiculovirusHuman; cattle; horse; swine; sandflies; blackfliesNeuronsClathrin-mediated endocytosisBuddingCytoplasmCytoplasmZoonosis; arthropod bite: sandflies
SprivivirusFishNoneClathrin-mediated endocytosisBuddingCytoplasmCytoplasmUnknown
CytorhabdovirusHumans; cattle; rodentsNoneClathrin-mediated endocytosis; viral movement; mechanical inoculationBudding; viral movementCytoplasmCytoplasmMechanical inoculation: aphid; mechanical inoculation: leafhopper; mechanical inoculation: planthopper
SigmavirusDrosophilaNoneClathrin-mediated endocytosisBuddingCytoplasmCytoplasmUnknown

Classification

Taxonomy

Group: ssRNA(-)

[2]

In addition to the above, there are a large number of rhabdo-like viruses (~130) that have not yet been officially classified by the ICTV.

Clades

These viruses fall into four groups based on the RNA polymerase gene.[3] The basal clade appears to be the Novirhabdoviruses, which infect fish. The Cytorhabdoviruses and the Nucleorhabdoviruses, which infect plants, are sister clades. The Lyssaviruses form a clade of their own which is more closely related to the land vertebrate and insect clades than to the plant viruses. The remaining viruses form a number of highly branched clades and infect arthropods and land vertebrates.

A 2015 analysis of 99 species of animal rhabdoviruses found that they fell into 17 taxonomic groupings, eight - Lyssavirus, Vesiculovirus, Perhabdovirus, Sigmavirus, Ephemerovirus, Tibrovirus, Tupavirus and Sprivivirus - which were previously recognized.[4] The authors proposed seven new taxa on the basis of their findings: Almendravirus, Bahiavirus, Curiovirus, Hapavirus, Ledantevirus, Sawgravirus and Sripuvirus. Seven species did not group with the others suggesting the need for additional taxa.

Proposed Classifications

The Curiovirus are a group of four viruses that were isolated from biting midges (Culicoides), sandflies (Lutzomyia ) and mosquitoes (Coqillettidia and Trichoprosopon) which were captured in the forests of South America and the Caribbean.

The taxon Bracorhabdovirus is derived from the acronym Brazilian Amazonian Culicoides rhabdoviruses.[5]

A supergroup - Dimarhabdovirus - has been created for the genera Ephemerovirus and Vesiculovirus.[6] A number of other viruses that have not been classified into genera also belong to this taxon. This supergroup contains the genera with species that replicate in both vertebrate and invertebrate hosts and have biological cycles that involve transmission by haematophagous dipterans.

Prototypical Rhabdoviruses

The prototypical and best studied rhabdovirus is vesicular stomatitis virus. 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 are transmitted to hosts by arthropods, such as aphids, planthoppers, leafhoppers, black flies, sandflies, and mosquitoes.

In September 2012, researchers writing in the journal PLOS Pathogens described a species of rhabdovirus, called Bas-Congo Virus or BASV, responsible for 4 cases of viral hemorrhagic fever in the Bas-Congo district in 2009. The 2 non-fatal cases occurred in healthcare workers treating the other 2, suggesting the possibility of person-to-person transmission.[3]

See also

Further reading

  • Rose, J.K.; Whitt, M.A. (2001). "Rhabdoviridae: The viruses and their replication". In Knipe, D.M.; Howley, P.M. Field's Virology 1 (4th ed.). Philadelphia: Lippincott Williams & Wilkins. pp. 1221–44. ISBN 0781718325. 
  • Wagner, Robert R., ed. (1987). The Rhabdoviruses. Plenum Press. ISBN 978-0-306-42453-3. 

References

  1. 1 2 3 4 "Viral Zone". ExPASy. Retrieved 15 June 2015.
  2. 1 2 ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
  3. 1 2 Grard G, Fair JN, Lee D, et al. (September 2012). "A novel rhabdovirus associated with acute hemorrhagic fever in central Africa". PLoS Pathog. 8 (9): e1002924. doi:10.1371/journal.ppat.1002924. PMC 3460624. PMID 23028323.
  4. ↑ Walker PJ, Firth C, Widen SG, Blasdell KR, Guzman H, Wood TG, Paradkar PN, Holmes EC, Tesh RB, Vasilakis N (2015) Evolution of genome size and complexity in the Rhabdoviridae. PLoS Pathog. 2015 Feb 13;11(2):e1004664. doi: 10.1371/journal.ppat.1004664
  5. ↑ Diniz JA, Nunes MR, Travassos da Rosa AP, Cruz AC, de Souza W, et al (2006) Characterization of two new rhabdoviruses isolated from midges (Culicoides spp) in the Brazilian Amazon: proposed members of a new genus, Bracorhabdovirus. Archives of Virology 151: 2519–2527. pmid 16835701 doi:10.1007/s00705-006-0812-1
  6. ↑ Bourhy H, Cowley JA, Larrous F, Holmes EC, Walker PJ (2005) Phylogenetic relationships among rhabdoviruses inferred using the L polymerase gene. J Gen Virol 86(10):2849-2858

External links

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