Reoviridae
From Wikipedia, the free encyclopedia
| Reoviridae | ||||
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Orthoreovirus |
The Reoviridae (Respiratory Enteritic Orphan virus) are a family of viruses that includes some viruses that affect the gastrointestinal system (such as Rotavirus), and some that cause respiratory infections. The genetic material of viruses in this family is double-stranded RNA. The name Reoviridae is derived from respiratory enteric orphan viruses. The term "orphan virus" means a virus that is not associated with any known disease. Even though Reoviridae have been identified with various diseases, the original name is still used.
Reovirus infection occurs often in humans, but most cases are mild or subclinical. The virus can be readily detected in faeces, and many also be recovered from pharyngeal or nasal secretions, urine, cerebrospinal fluid, and blood. Despite the ease of finding Reovirus in clinical specimens, their role in human disease or treatment is still uncertain.
Reoviruses are non-enveloped and have an iscohedral capsid (T-13). It is composed of an outer and inner shell- a double protein shell.
The genome consists of three segments, which are, L, M and S corresponding to their size. S segments being the smallest and L being the largest. Segments range from ~ 3.9 kbp – 1kbp [1]. The L segment encodes for λ proteins, the M segment encodes for μ proteins and the S segment encodes for σ proteins. The different segments are transcribed and translated at different rates.
Replication occurs in the cytoplasm. The virus encodes all the enzymes it needs for transcription. The virus enters the host cell via a receptor on the cell surface. The receptor is not known but is thought to inlcude sialic acid. The virus is partially uncoated in endolysosomes, it’s double protein shell helps it survive in the endolysosome. The host cell then degrades the capsid and the core particle is released into the cytoplasm. The genome is transcribed conservatively causing an excess of (+) sense strands, which are used as mRNA templates to synthesis (-) sense strands. As well as replication occurring in the cytoplasm the viral particles assemble in the cytoplasm 6-7 hours after infection.
Work is also being done using the reovirus in approaches for combative cancer research. Oncolytics Biotech Inc in Canada has various Type I & II trials going forward using their compounded REOLYSIN® designed to focused on the development of oncolytic viruses as potential cancer therapeutics. Oncolytics’ clinical program includes a variety of Phase I and Phase I/II human trials.
The following genera are included here:
- Genus Orthoreovirus; type species: Mammalian orthoreovirus
- Genus Orbivirus; type species: Bluetongue virus
- Genus Rotavirus; type species: Rotavirus A (causes diarrhea)
- Genus Coltivirus; type species: Colorado tick fever virus
- Genus Aquareovirus; type species: Aquareovirus A
- Genus Cypovirus; type species: Cypovirus 1
- Genus Fijivirus; type species: Fiji disease virus
- Genus Phytoreovirus; type species: Rice dwarf virus
- Genus Oryzavirus; type species: Rice ragged stunt virus
- Genus Idnoreovirus; type species: Idnoreovirus 1
- Genus Mycoreovirus; type species: Mycoreovirus 1
[edit] References
MicrobiologyBytes: Reoviruses [link accessed 2007-02-21]
