Porcine reproductive and respiratory syndrome virus non-structural protein 1 suppresses tumor necrosis factor-alpha promoter activation by inhibiting NF-κB and Sp1

Abstract

The objective of this study was to identify porcine reproductive and respiratory syndrome virus (PRRSV)-encoded proteins that are responsible for the inhibition of TNF-α expression and the mechanism(s) involved in this phenomenon. Using a TNF-α promoter reporter system, the non-structural protein 1 (Nsp1) was found to strongly suppress the TNF-α promoter activity. Such inhibition takes place especially at the promoter's proximal region. Both Nsp1α and Nsp1β, the two proteolytic fragments of Nsp1, were shown to be involved in TNF-α promoter suppression. Furthermore, using reporter plasmids specific for transcription factors (TFs) that bind to TNF-α promoter, Nsp1α and Nsp1β were demonstrated to inhibit the activity of the TFs that bind CRE-κB(3) and Sp1 elements respectively. Subsequent analyses showed that Nsp1α moderately inhibits NF-κB activation and that Nsp1β completely abrogates the Sp1 transactivation. These findings reveal one of the important mechanisms underlying the innate immune evasion by PRRSV during infection.

Dietary conjugated linoleic acid and its effect on immune response in pigs infected with the porcine reproductive and respiratory syndrome virus

“…Some reports indicate that TNF-α under PRRSV infection is practically non-existent (Chiou et al, 2000;López-Fuertes et al, 2000;Thanawongnuwech et al, 2001;Van Reeth et al, 1999), although some production can be detected at 28 days post infection (Thanawongnuwech et al, 2004). According to previous reports, CLA was able to modulate the expression of TNF-α more than other inflammatory cytokines (Akahoshi et al, 2002;Kim et al, 2011;Subramaniam et al, 2010), thus we expected changes mainly in TNF-α. Therefore a third time point was included at 4 weeks after infection as well as the study of its expression at mRNA level.…”

“…Furthermore, in infected pigs without CLA, no change was observed in this mediator. In the cells of pigs infected with PRRSV, the non-structural protein nsp1 strongly suppresses promoter activity of TNF-α by inhibiting the activation of NF-κB, revealing one of the mechanisms of innate immune evasion by PRRSV during infection (Subramaniam et al, 2010). However, our data showed that NF-κB expression was increased in infected pigs receiving the 1% CLA diet, a finding consistent with the enhanced production of TNF-α in the serum of pigs infected with PRRSV and receiving the same diet.…”

The N-N non-covalent domain of the nucleocapsid protein of type 2 porcine reproductive and respiratory syndrome virus enhances induction of IL-10 expression

“…For example, PRRSV infection was found to activate IL-10 production through the NF-kB (nuclear factor kappa-light-chain-enhancer of activated Bcells) and p38/mitogen-activated protein kinase (MAPK) pathways in porcine alveolar macrophages (Song et al, 2013) and the N protein was involved in NF-kB activation (Luo et al, 2011). Moreover, PRRSV Nsp1 was found to suppress activation of the TNF-a promoter by inhibition of NF-kB and Sp1 (Subramaniam et al, 2010). These studies confirmed that induction of inflammatory cytokines was involved in the activation of the NF-kB pathway.…”

Immune Evasion of Porcine Reproductive and Respiratory Syndrome Virus through Glycan Shielding Involves both Glycoprotein 5 as Well as Glycoprotein 3

“…MARC-145 cells (20) were used for viral RNA electroporation and virus propagation and titration. Swine monocyte-derived macrophages were prepared as previously described (40) and used for examination of viremia levels and for isolation of virus from serum samples. The porcine reproductive and respiratory syndrome virus (PRRSV) field isolate, designated PRRSV-01, was isolated at the Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL) in 2001 from a case of PRRSV infection associated with clinical disease.…”