ARS | Publication request: Mutations in the classical swine fever virus NS4B protein affects virulence in swine

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 30, 2009
Publication Date: December 6, 2009
Citation: Fernandez Sainz, I., Gladue, D.P., Holinka-Patterson, L.G., O'Donnell, V.K., Gudmundsdottir, I., Prarat, M.V., Patch, J.R., Golde, W.T., Zhiqiang, L., Risatti, G.R., Zhu, J.J., Borca, M.V. 2009. Mutations in the classical swine fever virus NS4B protein affects virulence in swine. Proceedings. P. 143.

Technical Abstract: NS4B is one of the non-structural proteins of Classical Swine Fever Virus (CSFV), the etiological agent of a severe, highly lethal disease of swine. Protein domain analysis of the predicted amino acid sequence of the NS4B protein of highly pathogenic CSFV strain Brescia (BICv) identified a Toll/Interleukin-1 receptor (TIR)-like domain. This TIR-like motif harbors two conserved domains, box 1 and box 2, also observed in other members of the TIR superfamily, including Toll-like receptors (TLRs). Mutations within the BICv NS4B box 2 domain (V2566A, G2567A, I2568A) produced recombinant virus NS4B.VGIv, with a phenotype displaying affected transcriptional activation of TLR-7 -induced genes in swine macrophages, including a significant sustained increase of IL-6 mRNA accumulation. Transfection of swine macrophages with wild-type NS4B protein partially blocked the TLR-7 activating effect of Imiquimod R837. In vivo, NS4B.VGIv was completely attenuated in swine, displaying a reduced replication in the oronasal cavity and limited spread from the inoculation site to secondary target organs. Furthermore, the level and duration of IL-6 production in the tonsils of pigs intranasally inoculated with NS4B.VGIv was significantly higher than in animals infected with BICv. The peak of IL-6 production in infected animals paralleled the ability of animals infected with NS4B.VGIv to resist challenge with virulent BICv. Interestingly, treatment of peripheral blood monocuclear cell cultures with recombinant porcine IL-6 results in a significant decrease of BICv replication.