B13R (virus protein)
| B13R (virus protein) | |||||||
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UniProt | P15059 | ||||||
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B13R (sometimes called SPI-2) is a
Vaccinia virus is member of Orthopoxvirus family. These viruses contain approximately 200 genes in their genome. About one third of the genome is not necessary for the viral replication itself. These viral products interfere with the host immune response. SPI-2 is one of these immunomodulatory factors.
SPI-2 is a nonglycosylated
SPI-2 belongs in superfamily of the inhibitors of
SPI-2 inhibits processing of an inactive precursor of
Deletion of SPI-2 leads to virus attenuation in vivo (observed in mice model after intranasal infection) but without any remarkable influence on the host immune response. That was one of the reasons this gene was targeted during search for more safe and efficient vaccine against smallpox. It was shown that immunization with vaccinia virus with deleted SPI-2 and 1 and coexpressing IFNγ leads to strong attenuation but without decreasing host immune response. Host reaction was comparable to that on MVA virus (modified virus Ankara) which serves as a smallpox vaccine nowadays.[5] The Copenhagen strain of vaccinia virus only has a truncated version of this protein.
Vaccinia virus encodes two more serpin - SPI-1 and SPI-3. SPI-1 influences the host range and SPI-3 stops infected cells from fusing together.[6]