''Betaherpesvirinae'' is a subfamily 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. Viruses are found in almo ...

in the order '' Herpesvirales'' and in the family ''

Herpesviridae ''Orthoherpesviridae'', previously named and more widely known as ''Herpesviridae'', is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are commonly known as herp ...

''. Mammals serve as natural hosts. There are 26 species in this subfamily, divided among 5 genera. Diseases associated with this subfamily include:

human cytomegalovirus Human cytomegalovirus (HCMV), also called human herpesvirus 5 (HHV-5), is a species of virus in the genus ''Cytomegalovirus'', which in turn is a member of the viral family known as ''Herpesviridae'' or herpesviruses. It is also commonly call ...

(HHV-5): congenital CMV infection; HHV-6: ' sixth disease' (also known as ''roseola infantum'' or ''exanthem subitum''); HHV-7: symptoms analogous to the 'sixth disease'.

Genera

''Betaherpesvirinae'' consists of the following five genera: * ''

Cytomegalovirus ''Cytomegalovirus'' (CMV) (from ''cyto-'' 'cell' via Greek - 'container' + 'big, megalo-' + -''virus'' via Latin 'poison') is a genus of viruses in the order '' Herpesvirales'', in the family '' Herpesviridae'', in the subfamily '' Betaherp ...

'' * '' Muromegalovirus'' * '' Proboscivirus'' * '' Quwivirus'' * '' Roseolovirus''

Structure

Viruses in ''Betaherpesvirinae'' 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 140-240kb in length.

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. Betaherpesviruses typically have highly restricted host ranges, although essentially all mammals, reptiles, and birds are infected with at least one betaherpesvirus species. Transmission routes are transplacental, transplantation, blood transfusion, body fluids, urine, and saliva. ''Betaherpesvirinae'' establish latency (site where virus lies dormant until reactivated) in CD34+

myeloid progenitor cells Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the ...

and CD14+

monocytes Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and monocyte-derived dendritic cells. As a part of the vertebrate innate immune system monocytes also i ...

. This is different from '' Alphaherpesvirinae'', which establish latency in

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

s, and '' Gammaherpesvirinae'', which establish latency in memory B cells.

Human health

There are four known member species of the ''Betaherpesvirinae'' subfamily that are infectious for humans: *

Human cytomegalovirus Human cytomegalovirus (HCMV), also called human herpesvirus 5 (HHV-5), is a species of virus in the genus ''Cytomegalovirus'', which in turn is a member of the viral family known as ''Herpesviridae'' or herpesviruses. It is also commonly call ...

(HCMV), also known as ''Human herpesvirus 5'' (HHV-5), * ''Human herpesvirus 6A'' and ''6B'' (HHV-6A and HHV-6B), which were classified as distinct species in 2012, * '' Human herpesvirus 7'' (HHV-7) Human cytomegalovirus (HCMV, HHV-5) "seems to have a large impact on immune parameters in later life and may contribute to increased morbidity and eventual mortality." Human herpesvirus 6A (HHV-6A) has been described as more neurovirulent, and as such is more frequently found in patients with neuroinflammatory diseases such as

multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

. Both human herpesvirus 6B (HHV-6B) and human herpesvirus 7 (HHV-7), as well as other viruses, can cause a skin condition in infants known as exanthema subitum, roseola infantum (rose rash of infants) or the sixth disease.

References

External links

*
Viralzone: ''Betaherpesvirinae''

ICTV
{{Taxonbar, from=Q747711 Herpesviridae Virus subfamilies