Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/10/2012
Publication Date: 7/1/2013
Citation: Mcvey, D.S., Wilson, W.C., Drolet, B.S. 2013. Reoviridae. McVey, D.S., Kennedy, M., Chengappa, M.M., Editors. Veterinary Microbiology, 3rd Edition. New Jersey: Wiley-Blackwell. p. 491-500.
Technical Abstract: Reoviruses (genus Orthoreovirus) have been isolated from the respiratory and/or gastrointestinal tract of many animal species, including nonhuman primates, rodents, horses, cattle, sheep, swine, cats, and dogs. Reoviruses are usually isolated from healthy animals, thus their designation as “respiratory enteric orphan” viruses because they typically are not associated with any disease. However, reoviruses are sometimes isolated from animals with mild respiratory and/or enteric disease. There are three serotypes (1, 2, and 3) and many strains of mammalian reoviruses. Strains of reovirus that vary in virulence have been identified by sequence analysis of individual viral genes and proteins. Mammalian reoviruses all possess a genome of ten distinct segments of dsRNA. The genome segments are of different sizes (grouped as large, medium, and small). Each encodes a single protein except the S1 gene, which includes two distinct open reading frames. The complete reovirus particle has no envelope and exhibits icosahedral morphology with a diameter of approximately 85 nm. The reovirus particle consists of eight structural proteins arranged into inner and outer protein capsids (coats). The inner protein core contains the viral RNA-dependent RNA polymerase (transcriptase), as well as other enzymes that mediate mRNA synthesis and capping, helicase activity, and other functions that are necessary for virus replication. The predominant outer coat protein, sigma 1, is the primary determinant of virus serotype and hemagglutination and also is the cell attachment protein. Enzymatic digestion of the outer capsid protein sigma 3 from intact reovirus particles generates infectious subviral particles, and removal of the outer capsid proteins sigma 1, sigma 3, and mu 1 generates core particles. All three particles are important in the lifecycle of reovirus replication. Genetic diversity of strains of reovirus occurs through accumulation of mutations within individual viral genes (genetic drift) and by the exchange of entire genes (reassortment) between viruses during mixed infections with more than one reovirus strain or serotype.