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Amino acid residues in the non-structural protein 1 of porcine reproductive and respiratory syndrome virus involved in down-regulation of TNF-α expression in vitro and attenuation in vivo

School of Veterinary Medicine & Biomedical Sciences and Nebraska Center for Virology, University of Nebraska-Lincoln, NE 68583, USA.
Virology (Impact Factor: 3.28). 06/2012; 432(2):241-9. DOI: 10.1016/j.virol.2012.05.014
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ABSTRACT Porcine reproductive and respiratory syndrome virus (PRRSV) suppresses tumor necrosis factor-alpha (TNF-α) production at both transcriptional and post-transcriptional levels by its non-structural proteins 1α and 1β (Nsp1α and Nsp1β). To identify the amino acid residues responsible for this activity, we generated several alanine substitution mutants of Nsp1α and Nsp1β. Examination of the mutant proteins revealed that Nsp1α residues Gly90, Asn91, Arg97, Arg100 and Arg124 were necessary for TNF-α promoter suppression, whereas several amino acids spanning the entire Nsp1β were found to be required for this activity. Two mutant viruses, with mutations at Nsp1α Gly90 or Nsp1β residues 70-74, generated from infectious cDNA clones, exhibited attenuated viral replication in vitro and TNF-α was found to be up regulated in infected macrophages. In infected pigs, the Nsp1β mutant virus was attenuated in growth. These studies provide insights into how PRRSV evades the effector mechanisms of innate immunity during infection.

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Available from: Asit K Pattnaik, Jul 31, 2015
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    • "It has been recently shown that nsp1 of PRRSV modulates the expression of type I interferon (Beura et al, 2010; Beura et al, 2012; Chen et al, 2010; Wang et al, 2013; Kim et al, 2010) and TNF-α (Subramaniam et al, 2012), which leads to persistent infection (Lamontagne et al, 2003). In addition, PRRSV infects and destroys porcine alveolar macrophage (PAM), which is an active producer of cytokines and leukotrienes and has important roles in inducing pro-and anti-inflammatory responses in the alveolus (Gordon and Read, 2002) and innate immune response against respiratory infections (Pribul et al, 2008). "
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    • "Promoter and post-transcriptional downregulation of TNF-a has been associated with PRRSV non-structural proteins (NSPs) 1a, 1b and 2 (Chen et al., 2010; Subramaniam et al., 2010, 2012; Darwich et al., 2011). Specific amino acid residues of NSP1a and NSP1b have been identified that affect TNF-a promoter activity; substitution of specific NSP1b amino acids is potential tool for the generation of attenuated PRRSV vaccines (Subramaniam et al., 2012). The limited expression of TNF-a in experimental infections with some PRRSV strains may be a mechanism by which these strains impair the host immune response and prevent viral clearance (Table 1; Fig. 1). "
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