Togaviruses
| Togaviruses | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Family: | Togaviridae |
| Genera | |
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.
Group: ssRNA(+)
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.
Entry into the host cell is achieved by attachment of the viral E glycoprotein to host receptors, which mediates clathrin-mediated endocytosis. 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.
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. Human, mammals, marsupials, birds, and mosquitoes serve as the natural host. Transmission routes are zoonosis, bite, and respiratory.
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