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Mutations in modified virus Ankara protein 183 render it a non-functional counterpart of B14, an inhibitor of nuclear factor kappaB activation.

ABSTRACT: Vaccinia virus (VACV) encodes multiple proteins to evade host innate immunity, including B14, a virulence factor that binds to the inhibitor of kappaB kinase beta (IKKbeta) and blocks nuclear factor kappaB (NF-kappaB) activation. B14 shares 95 % amino acid identity with the 183 protein encoded by modified virus Ankara (MVA), an attenuated VACV strain being developed as a vaccine vector. To evaluate whether the immunogenicity of MVA might be increased by manipulation of MVA immunomodulatory proteins, the MVA counterpart of B14, protein 183, was characterized. Unlike B14, protein 183 was unstable in eukaryotic cells unless proteasome-mediated protein degradation was inhibited. Furthermore, 183 did not inhibit NF-kappaB activation in response to cytokine stimulation, and did not restore the virulence of VACV strain Western Reserve lacking gene B14R. The instability and non-functionality of 183 are probably explained by a deletion of 6 aa within alpha-helix 6 of the B14 crystal structure.

SUBMITTER: McCoy LE

PROVIDER: S-EPMC3052518 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Mutations in modified virus Ankara protein 183 render it a non-functional counterpart of B14, an inhibitor of nuclear factor kappaB activation.

McCoy Laura E LE Fahy Aodhnait S AS Chen Ron A-J RA Smith Geoffrey L GL

The Journal of general virology 20100505 Pt 9

Vaccinia virus (VACV) encodes multiple proteins to evade host innate immunity, including B14, a virulence factor that binds to the inhibitor of kappaB kinase beta (IKKbeta) and blocks nuclear factor kappaB (NF-kappaB) activation. B14 shares 95 % amino acid identity with the 183 protein encoded by modified virus Ankara (MVA), an attenuated VACV strain being developed as a vaccine vector. To evaluate whether the immunogenicity of MVA might be increased by manipulation of MVA immunomodulatory prote ...[more]

PMID: 20444990

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Project description:Modified vaccinia virus Ankara (MVA) was derived by repeated passaging in chick fibroblasts, during which deletions and mutations rendered the virus unable to replicate in most mammalian cells. Marker rescue experiments demonstrated that the host range defect could be overcome by replacing DNA that had been deleted from near the left end of the genome. One virus isolate, however, recovered the ability to replicate in monkey BS-C-1 cells but not human cells without added DNA, suggesting that it arose from a spontaneous mutation. Here, we showed that variants with enhanced ability to replicate in BS-C-1 cells could be isolated by blind passaging of MVA and that in each there was a point mutation leading to an amino acid substitution in the D10 decapping enzyme. The sufficiency of these single mutations to enhance host range was confirmed by constructing recombinant viruses. The D10 mutations occurred at N- or C-terminal locations distal to the active site, suggesting an indirect effect on decapping or on another previously unknown role of D10. Although increased amounts of viral mRNA and proteins were found in BS-C-1 cells infected with the mutants compared to those with parental MVA, the increases were much less than the 1- to 2-log-higher virus yields. Nevertheless, a contributing role for diminished decapping in overcoming the host range defect was consistent with increased replication and viral protein synthesis in BS-C-1 cells infected with an MVA engineered to have active-site mutations that abrogate decapping activity entirely. Optimal decapping may vary depending on the biological context. IMPORTANCE Modified vaccinia virus Ankara (MVA) is an attenuated virus that is approved as a smallpox vaccine and is in clinical trials as a vector for other pathogens. The safety of MVA is due in large part to its inability to replicate in mammalian cells. Although host range restriction is considered a stable feature of the virus, we describe the occurrence of spontaneous mutations in MVA that increase replication considerably in monkey BS-C-1 cells but only slightly in human cells. The mutants contain single nucleotide changes that lead to amino acid substitutions in one of the two decapping enzymes. Although the spontaneous mutations are distant from the decapping enzyme active site, engineered active-site mutations also increased virus replication in BS-C-1 cells. The effects of these mutations on the immunogenicity of MVA vectors remain to be determined.

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Mutations in modified virus Ankara protein 183 render it a non-functional counterpart of B14, an inhibitor of nuclear factor kappaB activation.

Publications

Mutations in modified virus Ankara protein 183 render it a non-functional counterpart of B14, an inhibitor of nuclear factor kappaB activation.

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