Седореовирустар отбасы: құрылымы, түрлері және қызметі

Family of viruses

Sedoreoviridae (formerly Reoviridae) is a family of double stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi layered capsids. Lack of a lipid envelope has allowed three dimensional structures of these large complex viruses (diameter ~60–100 nm) to be obtained, revealing a structural and likely evolutionary relationship to the cystovirus family of bacteriophage. There are currently 97 species in this family, divided among 15 genera in two subfamilies. Reoviruses can affect the gastrointestinal system (such as rotaviruses) and respiratory tract. The name "reo " is an acronym for "respiratory enteric orphan" viruses. The term "orphan virus" refers to the fact that some of these viruses have been observed not associated with any known disease. Even though viruses in the family Reoviridae have more recently been identified with various diseases, the original name is still used. Reovirus infections occur often in humans, but most cases are mild or subclinical. Rotaviruses, however, can cause severe diarrhea and intestinal distress in children, and lab studies in mice have implicated orthoreoviruses in the expression of coeliac disease in pre disposed individuals. The virus can be readily detected in feces, and may also be recovered from pharyngeal or nasal secretions, urine, cerebrospinal fluid, and blood. Despite the ease of finding reoviruses in clinical specimens, their role in human disease or treatment is still uncertain. Some viruses of this family, such as phytoreoviruses and oryzaviruses, infect plants. Most of the plant infecting reoviruses are transmitted between plants by insect vectors. The viruses replicate in both the plant and the insect, generally causing disease in the plant, but little or no harm to the infected insect.

Reoviruses are non enveloped and have an icosahedral capsid composed of an outer (T=13) and inner (T=2) protein shell. Ultrastructure studies show that virion capsids are composed of two or three separate layers which depends on species type. The innermost layer (core) has T=1 icosahedral symmetry and is composed of 60 different types of structural proteins. The core contains the genome segments, each of them encode a variety enzyme structure which is required for transcription. The core is covered by capsid layer T=13 icosahedral symmetry. Reoviruses have a unique structure which is contains a glycolisated spike protein on the surface.

The genomes of viruses in family Reoviridae contain 9–12 segments which are grouped into three categories corresponding to their size: L (large), M (medium) and S (small). Segments range from about 0.2 to 3 kbp and each segment encodes 1–3 proteins (10–14 proteins in total The virus is partially uncoated by proteases in the endolysosome, where the capsid is partially digested to allow further cell entry. The core particle then enters the cytoplasm by a yet unknown process where the genome is transcribed conservatively causing an excess of positive sense strands, which are used as messenger RNA templates to synthesize negative sense strands. demonstrated MR for three types of reovirus after exposure to ultraviolet irradiation. In their experiments, reovirus particles were exposed to doses of UV light that would be lethal in single infections. However, when two or more inactivated viruses were allowed to infect individual host cells MR occurred and viable progeny were produced. As they stated, multiplicity reactivation by definition involves some type of repair. Michod et al. reviewed numerous examples of MR in different viruses, and suggested that MR is a common form of sexual interaction in viruses that provides the benefit of recombinational repair of genome damages.

Although reoviruses are mostly nonpathogenic in humans, these viruses have served as very productive experimental models for studies of viral pathogenesis. Newborn mice are extremely sensitive to reovirus infections and have been used as the preferred experimental system for studies of reovirus pathogenesis. Reolysin is a formulation of reovirus (Mammalian orthoreovirus serotype 3 dearing strain) that is currently in clinical trials for the treatment of various cancers, including studies currently developed to investigate the role of Reolysin combined with other immunotherapies.