''Rhadinovirus'' (synonyms: ''Rhadinoviridae'' and gamma-2 herpesviruses) is a genus of

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...

in the order ''

Herpesvirales The ''Herpesvirales'' is an order of dsDNA viruses (Baltimore group I) with animal hosts, characterised by a common morphology consisting of an icosahedral capsid enclosed in a glycoprotein-containing lipid envelope. Common infections in humans ...

'', in the family ''

Herpesviridae ''Herpesviridae'' is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word ''ἕρπει� ...

'', in the subfamily ''

Gammaherpesvirinae ''Gammaherpesvirinae'' is a subfamily of viruses in the order ''Herpesvirales'' and in the family ''Herpesviridae''. Viruses in ''Gammaherpesvirinae'' are distinguished by reproducing at a more variable rate than other subfamilies of ''Herpesvir ...

''. Humans and other mammals serve as natural hosts. There are 12 species in this genus. Diseases associated with this genus include:

Kaposi's sarcoma Kaposi's sarcoma (KS) is a type of cancer that can form masses in the skin, in lymph nodes, in the mouth, or in other organs. The skin lesions are usually painless, purple and may be flat or raised. Lesions can occur singly, multiply in a limit ...

primary effusion lymphoma Primary effusion lymphoma (PEL) is classified as a diffuse large B cell lymphoma. It is a rare malignancy of plasmablastic cells that occurs in individuals that are infected with the Kaposi's sarcoma-associated herpesvirus (i.e. KSHV/HHV8). Plasmab ...

and multicentric

Castleman's disease Castleman disease (CD) describes a group of rare lymphoproliferative disorders that involve enlarged lymph nodes, and a broad range of inflammatory symptoms and laboratory abnormalities. Whether Castleman disease should be considered an autoimmu ...

, caused by '' Human gammaherpesvirus 8'' (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV). The term rhadino comes from the Latin fragile, referring to the tendency of the viral genome to break apart when it is isolated.

Species

The genus consists of the following 12 species: * '' Ateline gammaherpesvirus 2'' * '' Ateline gammaherpesvirus 3'' * '' Bovine gammaherpesvirus 4'' * '' Cricetid gammaherpesvirus 2'' * '' Human gammaherpesvirus 8'' * '' Macacine gammaherpesvirus 5'' * '' Macacine gammaherpesvirus 8'' * '' Macacine gammaherpesvirus 11'' * '' Macacine gammaherpesvirus 12'' * '' Murid gammaherpesvirus 4'' * '' Murid gammaherpesvirus 7'' * '' Saimiriine gammaherpesvirus 2''

Hosts

In general, rhadinoviruses infect lymphocytes and adherent cells, such as fibroblasts, epithelial cells, and endothelial cells and once infection occurs, it is, in general, lifelong. Rhandinoviruses infect a wide range of mammals, include humans. Rhadinoviruses have been found in

New World monkey New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboidea ...

s such as the

squirrel monkey Squirrel monkeys are New World monkeys of the genus ''Saimiri''. ''Saimiri'' is the only genus in the subfamily Saimirinae. The name of the genus is of Tupi origin (''sai-mirím'' or ''çai-mbirín'', with ''sai'' meaning 'monkey' and ''mirím'' ...

s (herpesvirus saimiri) and in mice (''Murid gammaherpesvirus 68''). More recently, both KSHV-like viruses and a new form of rhadinovirus called rhesus rhadinovirus have been discovered in

Old World monkey Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons ...

s. These findings suggest that an additional human tumor virus related to KSHV may be found in humans.

Structure

Viruses in ''Rhadinovirus'' are enveloped, with icosahedral, spherical to pleomorphic, and round geometries, and T=16 symmetry. The diameter is around 150-200 nm. Genomes are linear and non-segmented, around 180kb in length. They are large double-stranded viruses that possess up to 100 genes in a single long chromosome, which is flanked by repetitive DNA sequences called terminal repeats.

Life cycle

Viral replication is nuclear, and is lysogenic. Entry into the host cell is achieved by attachment of the viral glycoproteins to host receptors, which mediates endocytosis. Replication follows the dsDNA bidirectional replication model. DNA-templated transcription, with some alternative splicing mechanism is the method of transcription. Translation takes place by leaky scanning. The virus exits the host cell by nuclear egress, and budding. Humans and other mammals serve as natural hosts. Transmission routes are sexual, contact, and through saliva.

Notes

Rhadinoviruses are unique because they have mastered the ability to pirate cellular genes from their host cells and incorporate them into their genomes. For example, most rhadinoviruses have a copy of the cyclin gene, which regulates the ability of the cell to divide. These viruses tend to cause tumors when infection occurs outside of their native hosts or in the case of KSHV, in humans when the host is immunosuppressed due to AIDS, old age, or in the setting of organ transplantation.

References

External links

Virus Pathogen Database and Analysis Resource (ViPR): ''Herpesviridae''

ICTV
{{Taxonbar, from=Q1427492 Gammaherpesvirinae Virus genera