Togaviridae

Abstract

The family Togaviridaecomprises 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 10⁶; 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.

Equine Arteritis Virus-induced Polypeptide Synthesis

“…It has a diameter of 60 + 13 nm and consists of an isometric core of about 35 nm which is surrounded by an envelope carrying ring-like structures (Horzinek, 1981). On the basis of morphology, size of the virion and properties of the RNA genome, EAV has been classified as a non-arthropodborne member of the family Togaviridae (Porterfield et al, 1978), the only member of the recently established genus arterivirus (Westaway et al, 1985). In horses, EAV may cause necrosis of the muscle cells surrounding small arteries (Jones et al, 1957) and abortion in pregnant mares .…”

A 29K envelope glycoprotein of equine arteritis virus expresses neutralization determinants recognized by murine monoclonal antibodies

“…Serological surveys indicate that EAV is widely distributed throughout the world (Timoney & McCollum, 1988). EAV is an enveloped, positive-stranded RNA virus and until recently it was classified as the sole member of the genus Arterivirus in the family Togaviridae (Westaway et al, 1985). This classification was based on the morphological, physical and chemical properties of EAV.…”

Nucleotide sequence of the bovine viral diarrhoea virus Osloss strain: comparison with related viruses and identification of specific DNA probes in the 5' untranslated region

“…Previously classified in the Togaviridae family (Horzinek, 1981;Westaway et al, 1985), pestiviruses were later grouped within the Flaviviridae (Francki et al, 1991) because of their genomic sequence and organization (Renard et al, 1987a;Collett et al, 1988c). To date, three pestiviral sequences have been reported in the literature, one from a BVDV strain, NADL (Collett et al, 1988 a) and two from the HCV strains Alfort (Meyers et al, 1989) and Brescia (Moorman et al, 1990).…”