ICTV Virus Taxonomy Profile: Togaviridae

Abstract

The Togaviridae is a family of small, enveloped viruses with single-stranded, positive-sense RNA genomes of 10-12 kb. Within the family, the genus Alphavirus includes a large number of diverse species, while the genus Rubivirus includes the single species Rubella virus. Most alphaviruses are mosquito-borne and are pathogenic in their vertebrate hosts. Many are important human and veterinary pathogens (e.g. chikungunya virus and eastern equine encephalitis virus). Rubella virus is transmitted by respiratory routes among humans. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Togaviridae, which is available at www.ictv.global/report/togaviridae.

Keywords: ICTV Report; Togaviridae: taxonomy; chikungunya virus; eastern equine encephalitis virus; rubella virus.

Fig. 1.

Structure of togavirus particles. (a) Three-dimensional cryo-electron reconstruction of chikungunya virus at 10.2 Å resolution (courtesy of J.  C. Y. Wang). The triangle outlines one icosahedral unit with the symmetry axes labelled. (b–d) Representation of three different rubella virions, each determined using cryo-electron tomography and no averaging procedures. The resolution of the reconstructions is not absolute, but is estimated to be better than 50 Å. All scale bars represent 10 nm. Modified from [2].

Fig. 2.

Alphavirus and rubivirus genome organisation. Black lines – non-coding regions; open boxes – ORFs (NS-ORF, non structural protein ORF; S-ORF, structural protein ORF) with processed products indicated beneath. An asterisk indicates the stop codon present in some alphaviruses that must be translationally read through to produce a precursor containing nsP4. Mtr, methyl transferase; Pro. protease; Hel, helicase; X, unknown function; RdRP, RNA-dependent RNA polymerase (courtesy of T. K. Frey).