Reovirales

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Reovirales
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Order:	Reovirales
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Reovirales is an order of double-stranded RNA viruses that infect a wide range of hosts, including humans, animals, plants, and fungi. The name "Reovirales" is derived from "Respiratory Enteric Orphan viruses," reflecting the initial discovery of these viruses in respiratory and enteric tracts without an associated disease. However, some members of this order are now known to cause significant diseases in humans and animals.

Characteristics

Reovirales are characterized by their double-stranded RNA genome, which is segmented. The genome is enclosed within a non-enveloped, icosahedral capsid. The capsid is typically composed of multiple protein layers, providing protection to the viral genome and facilitating entry into host cells.

Genome

The genome of Reovirales viruses is segmented, with each segment encoding one or more proteins. This segmentation allows for genetic reassortment, which can lead to the emergence of new viral strains with novel properties. The number of segments can vary among different families within the order.

Replication

Replication of Reovirales occurs in the cytoplasm of the host cell. The virus attaches to the host cell surface and is internalized, where the outer capsid is removed. The viral core, containing the RNA genome, is released into the cytoplasm. Transcription of the viral RNA occurs within the core, producing mRNA that is translated into viral proteins. New viral particles are assembled in the cytoplasm and released from the cell, often causing cell lysis.

Families

The order Reovirales is divided into several families, each with distinct characteristics and host ranges:

• Reoviridae: This family includes important human and animal pathogens such as rotavirus, which is a leading cause of severe diarrhea in infants and young children worldwide.
• Spinareoviridae: Members of this family are known to infect insects and plants, playing roles in plant disease and insect ecology.
• Sedoreoviridae: This family includes viruses that infect a variety of hosts, including humans and animals, and are often associated with respiratory and gastrointestinal diseases.

Pathogenesis

While many Reovirales viruses are asymptomatic in their hosts, some can cause significant disease. For example, rotaviruses are a major cause of gastroenteritis in children, leading to severe dehydration and potentially death if untreated. Other reoviruses can cause respiratory illnesses or contribute to the pathogenesis of diseases in animals and plants.

Diagnosis and Treatment

Diagnosis of Reovirales infections typically involves detection of viral RNA or antigens in clinical samples using techniques such as RT-PCR or ELISA. Treatment is generally supportive, focusing on managing symptoms such as dehydration in the case of rotavirus infection. Vaccines are available for some Reovirales viruses, such as rotavirus, which have significantly reduced the incidence of severe disease.

Research and Applications

Reovirales viruses are studied not only for their role in disease but also for their potential use in oncolytic virotherapy, where viruses are used to selectively infect and kill cancer cells. Their ability to undergo genetic reassortment also makes them a model for studying viral evolution and host-virus interactions.

Also see

• Virus classification
• RNA virus
• Viral replication
• Viral pathogenesis