coinfection
Coinfection is the simultaneous infection of a host by multiple pathogen species. In virology, coinfection includes simultaneous infection of a single cell by two or more virus particles. An example is the coinfection of liver cells with he ...
of a host cell with a helper virus for its replication. Satellites can be divided into two major classes: satellite viruses and satellite nucleic acids. Satellite
virus
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 Ivanovsk ...
es, which are most commonly associated with plants, are also found in mammals, arthropods, and bacteria. They encode structural proteins to enclose their genetic material, which are therefore distinct from the structural proteins of their helper viruses. Satellite nucleic acids, in contrast, do not encode their own structural proteins, but instead are encapsulated by proteins encoded by their helper viruses. The genomes of satellites range upward from 359 nucleotides in length for satellite tobacco ringspot virus RNA (STobRV).
Most viruses have the capability to use host enzymes or their own replication machinery to independently replicate their own viral RNA. Satellites, in contrast, are completely dependent on a helper virus for replication. The symbiotic relationship between a satellite and a helper virus to catalyze the replication of a satellite genome is also dependent on the host to provide components like replicases to carry out replication.
A satellite virus of mamavirus that inhibits the replication of its host has been termed a
virophage
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for th ...
. However, the usage of this term remains controversial due to the lack of fundamental differences between virophages and classical satellite viruses.
History and discovery
The
tobacco necrosis virus
''Tobacco necrosis virus A'' is a plant pathogenic virus of the family ''Tombusviridae''.
Hosts and symptoms
Tobacco necrosis virus (TNV) can thrive on a handful of viable hosts. These hosts include tobacco, zucchini, cucumbers, carrots, French ...
was the virus that led to the discovery of the first satellite virus in 1962. Scientists discovered that the first satellite had the components to make its own protein shell. A few years later in 1969, scientists discovered another symbiotic relationship with the tobacco ringspot neopvirus (TobRV) and another satellite virus. The emergence of satellite RNA is said to have come from either the genome of the host or its co-infecting agents, and any vectors leading to transmission.
A satellite virus important to human health that demonstrates the need for co-infection to replicate and infect within a host is the virus that causes hepatitis D. Hepatitis D or delta virus (HDV) was discovered in 1977 by
Mario Rizzetto
Mario Rizzetto (born 4 June 1945) is an Italian virologist who in 1977 first reported the Hepatitis D virus as a nuclear antigen in patients infected with HBV who had severe liver disease.
He graduated in Medicine and Surgery at the University ...
and is differentiated from hepatitis A, B, and C because it requires viral particles from hepatitis B virus (HBV) to replicate and infect liver cells. HBV provides a surface antigen, HBsAg, which is utilized by HDV to create a super-infection resulting in liver failure. HDV is found all over the globe but is most prevalent in Africa, the Middle East and southern Italy.
Satellite compared to a virus
Classification
The classification of subviral agents is ongoing. The following uses an outline for subviral agents in a 2011 ICTV report. newer version; does not mention satellites A lot of the taxa have since been assigned more formal names in 2019, so these are included when possible.
Satellite viruses
Some satellite viruses have been assigned a taxon. The following reflects the results of a 2015 proposal that has since been accepted (Taxoprop 2015.009a).
*Single-stranded RNA satellite viruses
**(unassigned to a family)
***''
Albetovirus
''Albetovirus'' is a plant satellite virus genus. As a member of realm ''Riboviria'' without assigned family or order it contains just three species, ''Tobacco albetovirus 1'', ''2'', and ''3'' (alias Satellite tobacco necrosis virus 1, 2, respec ...
Aumaivirus
Maize white line mosaic satellite virus (syn. Satellite maize white line mosaic virus, Satellite virus of maize white line mosaic virus, SMWLMV, SV-MWLMV) is a plant satellite virus. It is the only species in genus ''Aumaivirus'', which is a mem ...
Papanivirus
Panicum mosaic satellite virus (SPMV) is a plant satellite virus in genus ''Papanivirus'', which is a member of realm ''Riboviria'' without assigned family or order. It only infects grasses which are infected by ''Panicum mosaic virus''. One st ...
Organic Lake virophage
Organic Lake virophage (OLV) is a double-stranded DNA virophage (a virus that requires the presence of another virus to replicate itself and in so doing limits the ability of the other virus to replicate). It was detected metagenomically in sampl ...
Adeno-associated virus
Adeno-associated viruses (AAV) are small viruses that infect humans and some other primate species. They belong to the genus ''Dependoparvovirus'', which in turn belongs to the family '' Parvoviridae''. They are small (approximately 26 nm i ...
group
Satellite nucleic acids
The following may not be comprehensive in its ICTV coverage. The nomenclature for satellite RNAs is to prefix the host virus name with "sat".
Satellite-like nucleic acids resemble satellite nucleic acids, in that they replicate with the aid of helper viruses. However they differ in that they can encode functions that can contribute to the success of their helper viruses; while they are sometimes considered to be genomic elements of their helper viruses, they are not always found within their helper viruses.
*Single-stranded satellite DNAs
**Family Alphasatellitidae (encoding a replication initiator protein)
**Family
Tolecusatellitidae
''Tolecusatellitidae'' is a family of biological satellites that is not assigned to any higher taxonomic ranks. The family contains two genera and 131 species. This family of viruses depend on the presence of another virus ( helper viruses) to ...
Tomato bushy stunt virus satellite RNA, B10
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish wor ...
''
***''
Tomato bushy stunt virus satellite RNA, B1
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish wor ...
Arabis mosaic virus small satellite RNA
''Arabis'' ,''Sunset Western Garden Book,'' 1995:606–607 or rockcress, is a genus of flowering plants, within the family Brassicaceae.
Description
The species are herbaceous, annual plant, annual or perennial plants, growing to 10–80 ...
Polerovirus
''Polerovirus'' is a genus of viruses, in the family ''Solemoviridae''. Plants serve as natural hosts. There are 26 species in this genus. Diseases associated with this genus include: PLRV causes prominent rolling of the leaves of potato and a s ...
-associated RNAs
See also
*
Virus
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 Ivanovsk ...
Virophage
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for th ...