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Abstract:
The family Togaviridae comprises four genera: Alphavirus (with 26 species), Rubivirus (one species), Pestivirus (three species), and Arterivirus (one species). The main characteristics of the member viruses are: (i) the virus particles are spherical, 50-70 nm in diameter, including an envelope with surface projections that incorporate two or three polypeptides, usually glycosylated; (ii) the nucleocapsid comprises a core protein and a single strand of positive-sense RNA, molecular weight about 4 X 10(6); where characterized, the RNA has an m7G 'cap' at the 5' end and is polyadenylated at the 3' end; (iii) maturation occurs by budding of spherical nucleocapsids 30-35 nm in diameter, with proven or presumed icosahedral symmetry, through cytoplasmic membranes. Where characterized, translation of structural proteins occurs on subgenomic messenger RNA(s); these appear to represent the 3' end of the genome. Nearly all alphavirus species are transmitted by mosquitoes. Transmission also occurs transovarially (Alphavirus) or transplacentally (Rubivirus and Pestivirus). Members of a genus are serologically related, but are not related to members of other genera.
Insights
The Togaviridae family includes Alphavirus, Rubivirus, Pestivirus, and Arterivirus genera. These viruses share structural and genomic features, with varied transmission methods like mosquito or transplacental routes.
Area of Science:
- Virology
- Molecular Biology
Background:
- The Togaviridae family is a significant group of RNA viruses.
- It comprises four distinct genera: Alphavirus, Rubivirus, Pestivirus, and Arterivirus.
Purpose of the Study:
- To outline the key characteristics of Togaviridae family members.
- To detail their structure, genome, replication, and transmission.
Main Methods:
- Characterization of virus particle morphology and size.
- Analysis of the viral RNA genome structure and translation mechanisms.
- Description of viral maturation and assembly processes.
Main Results:
- Togaviridae viruses are enveloped, spherical particles (50-70 nm) with surface glycoproteins.
- The genome is a single-stranded, positive-sense RNA (approx. 4x10^6 Da) with a 5' cap and 3' polyadenylation.
- Maturation involves budding of nucleocapsids through cytoplasmic membranes, with structural protein translation occurring on subgenomic RNAs.
Conclusions:
- Togaviridae genera share fundamental biological and structural properties.
- Transmission routes vary, including arthropod vectors and vertical transmission.
- Intra-genus serological relatedness is observed, but not between genera.