Index >> Animal Viruses >> Reoviruses

Reoviruses - Reovirus is representative of a large group of dsRNA viruses found in bacteria, fungi, plants and animals. The word 'reo' is an acronym for 'respiratory enteric orphan'. Since the viruses are not associated with, any pathological processes in man the have been caned 'orphans' viruses in search of a disease.

Reo like viruses containing dsRNA have, however, been identified as the causative agents of a form of infantile diarrhoea and of Colorado tick fever. The particle mass of reovirus is 1.3x106 daltons, of which 15% is RNA and 85% protein. The viruses lack lipid. The reovirus particle is composed of two concentric icosahedral protein shells. The outer shell is dissolved by chymotrypsin, while the inner shell proteins (core proteins) are resistant to chymotrypsin. The core contains the dsRNA genome

Each dsRNA segment transcribes a (+) ssRNA strand which acts as messenger RNA and translates a single polypeptide chain. 'The ssRNA transcripts are of three classes, three large (l1, l2, l3), three medium (ml, ms, ms) and four small (s1, s2, s3, s4).

The core thus synthesizes 10 unique species of ssRNA that contain the entire information encoded in genomic dsRNA. The molecular weight of each is half that of the corresponding genome segment. The proteins are of three classes, lambda (λ), mu (µ) and sigma (σ).