Orthoreovirus

Orthoreovirus

Orthoreoviruses are a genus of viruses belonging to the family Reoviridae. These viruses are non-enveloped and possess a double-stranded RNA genome. They are known to infect a wide range of hosts, including mammals, birds, and reptiles. Orthoreoviruses are of particular interest in the study of viral pathogenesis and immune response due to their ability to cause mild respiratory and gastrointestinal infections in humans and animals.

Structure

Orthoreoviruses are characterized by their icosahedral capsid structure, which is composed of two concentric protein shells. The outer shell is responsible for the virus's stability and its ability to withstand environmental conditions. The inner shell encases the segmented RNA genome, which typically consists of 10 segments. Each segment encodes one or more proteins, including structural proteins and enzymes necessary for viral replication.

Genome

The orthoreovirus genome is composed of double-stranded RNA, which is segmented into 10 parts. These segments are classified into three size classes: large (L), medium (M), and small (S). The L segments encode the lambda proteins, the M segments encode the mu proteins, and the S segments encode the sigma proteins. The segmented nature of the genome allows for reassortment, which can lead to genetic diversity and the emergence of new viral strains.

Replication Cycle

The replication cycle of orthoreoviruses begins with the attachment of the virus to the host cell surface receptors. This is followed by endocytosis and the release of the viral core into the cytoplasm. The viral RNA-dependent RNA polymerase, which is packaged within the core, transcribes the viral RNA segments into mRNA. These mRNAs are then translated into viral proteins, which assemble into new viral particles. The newly formed virions are released from the host cell, often causing cell lysis.

Pathogenesis

Orthoreoviruses are generally associated with mild infections in humans, often presenting as upper respiratory tract infections or gastroenteritis. In animals, they can cause more severe diseases, such as encephalitis in birds or arthritis in mammals. The pathogenesis of orthoreovirus infections involves the virus's ability to evade the host immune response and its capacity to induce cell death through apoptosis.

Immune Response

The host immune response to orthoreovirus infection involves both innate and adaptive immunity. The innate immune response is triggered by the recognition of viral RNA by pattern recognition receptors, leading to the production of interferons and other cytokines. The adaptive immune response involves the activation of T cells and the production of neutralizing antibodies, which help to clear the infection and provide immunity against future infections.

Research and Applications

Orthoreoviruses have been studied extensively as model systems for understanding viral replication and host-virus interactions. They are also being explored as potential oncolytic agents due to their ability to selectively replicate in and kill cancer cells. This has led to the development of reovirus-based therapies for certain types of cancer.

Also see

• Reoviridae
• Viral replication
• RNA virus
• Oncolytic virus

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