>95%, by SDS-PAGE visualized with Silver Staining and quantitative densitometry by Coomassie® Blue Staining.
<0.10 EU per 1 μg of the protein by the LAL method.
Measured by its ability to inhibit rhIFN-gamma mediated protection of HeLa human cervical epithelial carcinoma cells to viral lysis. Meager, A. (1987) in Lymphokines and Interferons, a Practical Approach. Clemens, M.J. et al. (eds): IRL Press. 129. Th ED50 for this effect is 0.5-3 ng/mL.
Chinese Hamster Ovary cell line, CHO-derived viral B8R protein Lys18-Ser272, with a C-terminal 6-His tag
Both Biotinylated Recombinant Viral B8R (Catalog # BT8225) and unlabeled Recombinant Viral B8R (Catalog # 8225-BR) inhibits IFN-gamma-mediated protection of HeLa human cervical epithelial carcinoma cells to viral lysis. The ED50 for this effect is 0.5-3 ng/mL. The similarity in activity highlights that the biotinylated protein is fully functional.
B8R is a secreted Interferon gamma (IFN-gamma ) binding protein encoded by the open reading frame of the Vaccina virus (smallpox) (1, 2). B8R is a 43 kDa protein and shares only 19% amino acid sequence identity with the extracellular region of the human IFN-gamma Receptor 1 (IFN-gamma R1). However, B8R binds IFN-gamma orthologs from multiple species including human, rat, rabbit, bovine, and chicken with high affinity, but it binds mouse IFN-gamma with low affinity (1, 3, 4). During infection, virally-induced B8R binds and sequesters endogenous IFN-gamma, thereby suppressing the host immune response and promoting viral immune evasion (5). While B8R is not required for viral replication, it contributes significantly to Vaccinia virus virulence and is frequently inactivated prior to Vaccinia use in vaccines (5-9). IFN-gamma peptide mimetics that activate IFN-gamma R1 but are not bound and sequestered by B8R have been developed for research and therapeutic use (10, 11).
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Goebel, S.J. et al. (1990) Virology 179:247.
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Mossman, K. et al. (1995) Virology 208:762.
Smith, G.L. et al. (2013) J. Gen. Virol. 94:2367.
Symons, J.A. et al. (2002) J. Gen. Virol. 83:1953.
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