| Togaviruses |
| Virus classification |
| Group: |
Group IV ((+)ssRNA) |
| Family: |
Togaviridae |
| Genera |
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Togaviridae is a family of viruses. Humans, mammals, birds, and mosquitoes serve as natural hosts. There are currently 32 species in this family, divided among 2 genera. Diseases associated with this family include: Alphaviruses: arthritis, encephalitis; Rubiviruses: rubella.[1][2]
Contents
- 1 Taxonomy
- 2 Structure
- 3 Life Cycle
- 4 Replication
- 5 History
- 6 References
- 7 External links
TaxonomyEdit
Group: ssRNA(+)
Order: Unassigned
-
Family: Togaviridae
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Genus: Alphavirus
- Aura virus
- Barmah Forest virus
- Bebaru virus
- Cabassou virus
- Chikungunya virus
- Eastern equine encephalitis virus
- Eilat virus
- Everglades virus
- Fort Morgan virus
- Getah virus
- Highlands J virus
- Madariaga virus
- Mayaro virus
- Middelburg virus
- Mosso das Pedras virus
- Mucambo virus
- Ndumu virus
- O'nyong-nyong virus
- Pixuna virus
- Rio Negro virus
- Ross River virus
- Salmon pancreas disease virus
- Semliki Forest virus
- Sindbis virus
- Southern elephant seal virus
- Tonate virus
- Trocara virus
- Una virus
- Venezuelan equine encephalitis virus
- Western equine encephalitis virus
- Whataroa virus
-
[2]
StructureEdit
The Togaviridae family belong to group IV of the Baltimore classification of viruses. The genome is linear, non-segmented, single-stranded, positive sense RNA that is 10,000–12,000 nucleotides long. The 5'-terminus carries a methylated nucleotide cap and the 3'-terminus has a polyadenylated tail, therefore resembling cellular mRNA. The virus is enveloped and forms spherical particles (65–70 nm diameter), the capsid within is icosahedral, constructed of 240 monomers, having a triangulation number of 4.[1][3][4]
| Genus |
Structure |
Symmetry |
Capsid |
Genomic Arrangement |
Genomic Segmentation |
| Alphavirus |
Icosahedral |
T=4 |
Enveloped |
Linear |
Segmented |
| Rubivirus |
Icosahedral |
T=4 |
Enveloped |
Linear |
Monopartite |
Life CycleEdit
Entry into the host cell is achieved by attachment of the viral E glycoprotein to host receptors, which mediates clathrin-mediated endocytosis.[1] The receptors for binding are unknown, however the tropism is varied and it is known that the glycoprotein petal-like spikes act as attachment proteins. After virus attachment and entry into the cell, gene expression and replication takes place within the cytoplasm.[3][4]
Replication follows the positive stranded RNA virus replication model. Positive-stranded RNA-virus-transcription is the method of transcription. Translation takes place by viral initiation, and suppression of termination. The vector for Togaviridae is primarily the mosquito, where replication of the virus occurs. The Togaviridae family is classified into Old World and New World viruses based on geographical distribution, although it’s likely that a few transoceanic crossings have occurred.[3][4] Human, mammals, marsupials, birds, and mosquitoes serve as the natural host. Transmission routes are zoonosis, bite, and respiratory.[1]
| Genus |
Host Details |
Tissue Tropism |
Entry Details |
Release Details |
Replication Site |
Assembly Site |
Transmission |
| Alphavirus |
Humans; mammals; marsupials; birds; mosquitoes |
None |
Clathrin-mediated endocytosis |
Secretion |
Cytoplasm |
Cytoplasm |
Zoonosis: arthropod bite |
| Rubivirus |
Humans |
None |
Clathrin-mediated endocytosis |
Secretion |
Cytoplasm |
Cytoplasm |
Aerosol |
ReplicationEdit
The non-structural proteins are encoded at the 5’ end, formed during the first of two characteristic rounds of translation. These proteins are originally translated as a polyprotein, which consequently undergo self cleavage, forming four non-structural proteins responsible for gene expression and replication. The formation of a sub-genomic fragment, encoding the structural proteins and a negative sense fragment, a template for further synthesis of positive sense RNA are the characteristic second phase of translation. Assembly takes place at the cell surface, where the virus buds from the cell, acquiring the envelope. The replication cycle is very fast, taking around 4 hours.[3][4]
HistoryEdit
Initially the Togavirus family included what are now called the Flaviviruses, within the Alphavirus genus. The Flaviviruses were formed into their own family when sufficient differences with the Alphaviruses were noted thanks to the development of sequencing.[3]
- Early 19th century—Rubella is identified as a distinct disease
- 1930—Western Equine Encephalitis virus is first isolated in the United States (the first alphavirus ever isolated)
- 1933—Eastern Equine Encephalitis virus is first isolated in the United States.
- 1938—Venezuelan Equine Encephalitis is isolated.
- 1941—Western Equine Encephalitis epidemic is seen in the United States. It affects 300,000 horses and 3,336 humans.
- 1941—Norman Gregg notices large number of children with cataracts following a rubella outbreak. This and other defects are then categorized under the congenital rubella syndrome.
- 1942—Semliki Forest virus is isolated in Buliyama, Bwamba County, Uganda.
- 1952—Sindbis virus is isolated in the Sindbis health district, 40 miles north of Cairo, Egypt.
- 1959—Ross River virus is isolated from Aedes vigilax mosquitoes (now known as Ochlerotatus vigilax[5]) which were trapped at the Ross River in Australia.
- 1962—Rubella virus is isolated in culture.
- 1963—Ross River virus, which causes epidemic polyarthritis (mostly seen in Australia), is isolated by Doherty and colleagues.[6]
- 1964—The last major epidemic of Rubella in the United States is seen. Approximately 20,000 infants are left with permanent damage following in-utero rubella exposure.[7]
- 1969—Rubella vaccine is licensed
- 1971—Last epidemic of Venezuelan equine encephalitis is seen in horses in southern Texas.[8]
- 1972—The rubella vaccine is combined with the measles and mumps vaccines to form the Measles, Mumps and Rubella (MMR) vaccine.
- 1986—Barmah Forest virus is identified as causing human disease in Australia.[9]
- 1991–92—Most recent worldwide epidemic of rubella. Probably due to vaccine failures and missed vaccinations.
- 2001—Scientists solved the crystal structure of the glycoprotein shell of the Semliki Forest virus.
- 2005–2006—Large epidemic of the chikungunya virus on the island of La Réunion and the surrounding islands in the Indian Ocean.[10]
- 2006—Major epidemic of the chikungunya virus in India with over 1.5 million cases reported.[11]
ReferencesEdit
- ^ a b c d "Viral Zone". ExPASy. Retrieved 15 June 2015.
- ^ a b ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
- ^ a b c d e "Togaviridae". stanford.edu.
- ^ a b c d Murray; et al. (2005). Medical Microbiology (5 ed.). Philadelphia: Elsevier Mosby. ISBN 0-323-03325-3.
- ^ "Aedes vigilax". NSW Arbovirus Surveillance & Vector Monitoring Program. The New South Wales Arbovirus Surveillance and Mosquito Monitoring Program. Retrieved 2010-06-05.
Note that 'Ochlerotatus vigilax' prior to 2000, was known as 'Aedes vigilax'
- ^ Doherty, R. L.; Carley, J. G.; Best, J. C. (1972). "Isolation of Ross River virus from man". The Medical journal of Australia 1 (21): 1083–1084. PMID 5040017.
- ^ Meissner, H. C.; Reef, S. E.; Cochi, S. (2006). "Elimination of Rubella from the United States: A Milestone on the Road to Global Elimination". Pediatrics 117 (3): 933–935. doi:10.1542/peds.2005-1760. PMID 16510677.
- ^ Calisher, C. H. (1994). "Medically important arboviruses of the United States and Canada". Clinical Microbiology Reviews 7 (1): 89–116. PMC 358307. PMID 8118792.
- ^ Boughton, C. R.; Hawkes, R. A.; Naim, H. M. (1988). "Illness caused by a Barmah Forest-like virus in New South Wales". The Medical journal of Australia 148 (3): 146–147. PMID 2828896.
- ^ Tsetsarkin, K.; Higgs, S.; McGee, C. E.; Lamballerie, X. D.; Charrel, R. N.; Vanlandingham, D. L. (2006). "Infectious Clones of Chikungunya Virus (La Réunion Isolate) for Vector Competence Studies". Vector-Borne and Zoonotic Diseases 6 (4): 325–337. doi:10.1089/vbz.2006.6.325. PMID 17187566.
- ^ Lahariya, C.; Pradhan, S. K. (2006). "Emergence of chikungunya virus in Indian subcontinent after 32 years: A review". Journal of vector borne diseases 43 (4): 151–160. PMID 17175699.
External linksEdit
- Togaviridae Genomes database search results from the Viral Bioinformatics Resource Center
- Viralzone: Togaviridae
- ICTV
- Virus Pathogen Database and Analysis Resource (ViPR): Togaviridae
- "Togaviridae". NCBI Taxonomy Browser. 11018.
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Zoonotic viral diseases (A80–B34, 042–079)
|
|
| Arthropod-borne |
| Mosquito-borne |
| Bunyaviridae |
- Arbovirus encephalitides: La Crosse encephalitis
- Batai virus (BATV)
- Bwamba Fever (BWAV)
- California encephalitis
- Jamestown Canyon virus
- Tete virus
- Tahyna virus (TAHV)
- Viral hemorrhagic fevers: Rift Valley fever
- Bunyamwera fever (BUNV)
- Ngari virus (NRIV)
|
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| Flaviviridae |
- Arbovirus encephalitides: Japanese encephalitis
- Australian encephalitis
- Saint Louis encephalitis
- West Nile fever
- Viral hemorrhagic fevers: Dengue fever
- Yellow fever
- Zika fever
|
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| Togaviridae |
- Arbovirus encephalitides: Eastern equine encephalomyelitis
- Western equine encephalomyelitis
- Venezuelan equine encephalomyelitis
- Chikungunya
- O'Nyong-nyong fever
- Ross River fever
- Semliki Forest virus
- Sindbis fever
|
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| Reoviridae |
|
|
|
| Tick-borne |
| Bunyaviridae |
- Viral hemorrhagic fevers: Crimean–Congo hemorrhagic fever
- Heartland virus
- Bhanja virus
- Sandfly fever Naples virus
- Lone Star virus
- Tete virus
|
|
| Flaviviridae |
- Arbovirus encephalitides: Tick-borne encephalitis
- Powassan encephalitis
- Viral hemorrhagic fevers: Omsk hemorrhagic fever
- Kyasanur forest disease
- Langat virus (LGTV)
|
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| Reoviridae |
- Colorado tick fever
- Kemerovo tickborne viral fever
|
|
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| Sandfly-borne |
| Bunyaviridae |
- Adria virus (ADRV)
- Pappataci fever
- Sandfly fever Naples virus
- Oropouche fever
- SFTS virus
|
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| Rhabdoviridae |
|
|
|
|
| Mammal-borne |
| Rodent-borne |
| Arenaviridae |
- Viral hemorrhagic fevers: Lassa fever
- Venezuelan hemorrhagic fever
- Argentine hemorrhagic fever
- Brazilian hemorrhagic fever
- Bolivian hemorrhagic fever
- LUJV
- CHPV
|
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| Bunyaviridae |
- Hemorrhagic fever with renal syndrome
- Hantavirus pulmonary syndrome
|
|
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| Bat-borne |
| Filoviridae |
- Viral hemorrhagic fevers: Ebola virus disease
- BDBV
- EBOV
- SUDV
- TAFV
- Marburg virus disease
- MARV
- RAVV
|
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| Rhabdoviridae |
|
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| Paramyxoviridae |
|
|
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| Primate-borne |
| Herpesviridae |
|
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| Retroviridae |
- Simian foamy virus
- HTLV-1
- HTLV-2
|
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| Poxviridae |
- Tanapox
- Yaba monkey tumor virus
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| Multiple vectors |
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