Group Group V ((-)ssRNA) | Genus Ebolavirus | |
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The genus Ebolavirus is a virological taxon included in the family Filoviridae, order Mononegavirales. The members of this genus are called ebolaviruses. The five known virus species are named for the region where each was originally identified: Bundibugyo ebolavirus, Reston ebolavirus, Sudan ebolavirus, Taï Forest ebolavirus (originally Côte d'Ivoire ebolavirus), and Zaire ebolavirus. The Ebola virus (EBOV) protein VP24 inhibits type I and II interferon (IFN) signaling by binding to NPI-1 subfamily karyopherin α (KPNA) nuclear import proteins, preventing their interaction with tyrosine-phosphorylated STAT1 (phospho-STAT1). This inhibits phospho-STAT1 nuclear import. A biochemical screen now identifies heterogeneous nuclear ribonuclear protein complex C1/C2 (hnRNP C1/C2) nuclear import as an additional target of VP24. Co-immunoprecipitation studies demonstrate that hnRNP C1/C2 interacts with multiple KPNA family members, including KPNA1. Interaction with hnRNP C1/C2 occurs through the same KPNA1 C-terminal region (amino acids 424–457) that binds VP24 and phospho-STAT1. The ability of hnRNP C1/C2 to bind KPNA1 is diminished in the presence of VP24, and cells transiently expressing VP24 redistribute hnRNP C1/C2 from the nucleus to the cytoplasm. These data further define the mechanism of hnRNP C1/C2 nuclear import and demonstrate that the impact of EBOV VP24 on nuclear import extends beyond STAT1.[1]
Contents
- Hosts of the Ebolavirus
- Genus inclusion criteria
- Classification
- Evolution
- Genus organization and common names
- Research
- References
Each species of the genus Ebolavirus has one member virus, and four of these cause Ebola virus disease (EVD) in humans, a type of hemorrhagic fever having a very high case fatality rate; the fifth, Reston virus, has caused EVD in other primates. Zaire ebolavirus is the type species (reference or example species) for Ebolavirus, and has the highest mortality rate of the ebolaviruses, and is also responsible for the largest number of outbreaks of the five known members of the genus, including the 1976 Zaire outbreak and the outbreak with the most deaths (2014).
Ebolaviruses were first described after outbreaks of EVD in southern Sudan in June 1976 and in Zaire in August 1976. The name Ebolavirus is derived from the Ebola River in Zaire (now the Democratic Republic of the Congo), the location of the 1976 outbreak, and the taxonomic suffix -virus (denoting a viral genus). This genus was introduced in 1998 as the "Ebola-like viruses". In 2002 the name was changed to Ebolavirus and in 2010, the genus was emended. Ebolaviruses are closely related to marburgviruses.
Hosts of the Ebolavirus
Researchers have now found evidence of Ebola infection in three species of fruit bat. The bats show no symptoms of the disease, indicating that they may be the main natural reservoirs of the Ebolavirus. It is possible that there are other reservoirs and vectors.
Understanding where the virus incubates between outbreaks and how it is transmitted between species will help protect humans and other primates from the virus.
The researchers found that bats of three species—Hypsignathus monstrosus, Epomops franqueti, and Myonycteris torquata—had either genetic material from the Ebola virus, known as RNA sequences, or evidence of an immune response to the disease. The bats showed no symptoms themselves.[2]
Genus inclusion criteria
A virus of the family Filoviridae is a member of the genus Ebolavirus if
Classification
The genera Ebolavirus and Marburgvirus were originally classified as the species of the now-obsolete Filovirus genus. In March 1998, the Vertebrate Virus Subcommittee proposed in the International Committee on Taxonomy of Viruses (ICTV) to change the Filovirus genus to the Filoviridae family with two specific genera: Ebola-like viruses and Marburg-like viruses. This proposal was implemented in Washington, D.C., as of April 2001 and in Paris as of July 2002. In 2000, another proposal was made in Washington, D.C., to change the "-like viruses" to "-virus" resulting in today's Ebolavirus and Marburgvirus.
The five characterised species of the Ebolavirus genus are:
Evolution
Rates of genetic change are 8*10−4 per site per year and are thus one fourth as fast as influenza A in humans. Extrapolating backwards, Ebolavirus and Marburgvirus probably diverged several thousand years ago. A study done in 1995 and 1996 found that the genes of Ebolavirus and Marburgvirus differed by about 55% at the nucleotide level, and at least 67% at the amino acid level. The same study found that the strains of Ebolavirus differed by about 37-41% across the nucleotide level and 34-43% across the amino acid level. The EBOV strain was found to have an almost 2% change in the nucleotide level from the original 1976 strain from the Yambuki outbreak and the strain from the 1995 Kikwit outbreak. However, paleoviruses of filoviruses found in mammals indicate that the family itself is at least tens of millions of years old.
Genus organization and common names
The Ebolavirus genus has been organized into five species; however, the nomenclature has proven somewhat controversial, with many authors continuing to use common names rather than species names when referring to these viruses. In particular, the generic term "Ebola virus" is widely used to refer specifically to members of the species Zaire ebolavirus. Consequently, in 2010, a group of researchers recommended that the name "Ebola virus" be adopted for a subclassification within the species Zaire ebolavirus and that similar common names be formally adopted for other Ebolavirus species. In 2011, the International Committee on Taxonomy of Viruses (ICTV) rejected a proposal (2010.010bV) to formally recognize these names, as they do not designate names for subtypes, variants, strains, or other subspecies level groupings. As such, the widely used common names are not formally recognized as part of the taxonomic nomenclature. In particular, "Ebola virus" does not have an official meaning recognized by ICTV, and rather they continue to use and recommend only the species designation Zaire ebolavirus.
Research
A 2013 study isolated antibodies from fruit bats in Bangladesh, against Ebola Zaire and Reston viruses, thus identifying potential virus hosts and signs of the filoviruses in Asia.
A recent alignment-free analysis of Ebola virus genomes from the current outbreak reveals the presence of three short DNA sequences that appear nowhere in the human genome, suggesting that the identification of specific species sequences may prove to be useful for the development of both diagnosis and therapeutics.