Vaccinia
From Free net encyclopedia
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| Vaccinia virus
Template:Taxobox begin placement virus Template:Taxobox group i entry | |
|---|---|
| Family: | Poxviridae |
| Genus: | Orthopoxvirus |
| Species: | Vaccinia virus |
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Introduction
Vaccinia is a group one, double-stranded DNA virus, in the baltimore virus classification scheme. The family to which the virus belongs is known as the poxviridae family (also includes smallpox). The genome is approximately 190,000 base pairs in length (containing approximately 250 genes). The large genome is due to a portion devoted to synthesizing replication enzymes. These proteins are essential for the virus to be able replicate in the cytoplasm of a host cell. The virus is able to replicate with little hindrance as nuclear factors are not required for its replication.
Vaccinia virus is closely related to the virus that causes cowpox. The precise origin of Vaccinia virus is unknown the current suggestion is that the virus formed as the result of a hybrid between cowpox and variola viruses.
Vaccinia is so mild that it is typically asymptomatic in healthy individuals, but may cause a mild rash and fever, with an extremely low rate of fatality.
The body's immune response to vaccinia also immunizes against smallpox, and for this reason, vaccinia is used as a live-virus innoculator against smallpox. Vaccinia smallpox vaccine does not contain and cannot cause smallpox, but approximately one in one million individuals will develop a fatal response to the vaccination.
Vaccinia vaccination was the first example of vaccination. Prior to the use of vaccinia, smallpox epidemics were controlled somewhat through the use of inoculation -- a deliberate, minor exposure to the disease. Vaccination derives its name from Vaccinia.
Host Resistance
Vaccinia contains within its genome several proteins that give the virus resistance to interferons. K3L is a protein with homology towards the protein eIF-2alpha. K3L protein inhibits the action of PKR, an activator of interferons. E3L is another protein encoded by vaccinia. E3L also inhibits PKR activation; and is also able to bind to double stranded RNA.
External links
- Emedicine's Vaccinia information document
- Smallpox and Vaccinia
- Vaccinia virus, complete genome
- Cowpox virus strain GRI-90 is the closest known match to vaccinia.fr:Vaccine