Porcine Reproductive and Respiratory Syndrome Virus Nonstructural Protein 1 Modulates Host Innate Immune Response by Antagonizing IRF3 Activation

Nebraska Center for Virology and School of Veterinary and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska 68583, USA.
Journal of Virology (Impact Factor: 4.65). 11/2009; 84(3):1574-84. DOI: 10.1128/JVI.01326-09
Source: PubMed

ABSTRACT Porcine reproductive and respiratory syndrome virus (PRRSV) infection of swine leads to a serious disease characterized by a delayed and defective adaptive immune response. It is hypothesized that a suboptimal innate immune response is responsible for the disease pathogenesis. In the study presented here we tested this hypothesis and identified several nonstructural proteins (NSPs) with innate immune evasion properties encoded by the PRRS viral genome. Four of the total ten PRRSV NSPs tested were found to have strong to moderate inhibitory effects on beta interferon (IFN-beta) promoter activation. The strongest inhibitory effect was exhibited by NSP1 followed by, NSP2, NSP11, and NSP4. We focused on NSP1alpha and NSP1beta (self-cleavage products of NSP1 during virus infection) and NSP11, three NSPs with strong inhibitory activity. All of three proteins, when expressed stably in cell lines, strongly inhibited double-stranded RNA (dsRNA) signaling pathways. NSP1beta was found to inhibit both IFN regulatory factor 3 (IRF3)- and NF-kappaB-dependent gene induction by dsRNA and Sendai virus. Mechanistically, the dsRNA-induced phosphorylation and nuclear translocation of IRF3 were strongly inhibited by NSP1beta. Moreover, when tested in a porcine myelomonocytic cell line, NSP1beta inhibited Sendai virus-mediated activation of porcine IFN-beta promoter activity. We propose that this NSP1beta-mediated subversion of the host innate immune response plays an important role in PRRSV pathogenesis.

Download full-text


Available from: Asit K Pattnaik, Aug 21, 2015
  • Source
    • "Our results are not completely consistent with the previous report (Beura et al., 2010), in which NSP3, and NSP5 showed no inhibitory effect. The obvious disagreement might be due to the differences of PRRSV strains or method, in which performed CAT assays to evaluate IFN-␤ activation by co-transfected with IRF3 in HeLa cells (Beura et al., 2010). On the strength of previous reports and pertinent phenomena observed in this study, it is self-evident that NSP4 can strikingly influence the production of IFN-␤. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Type I interferons (IFNs), predominantly IFN-α and β, play important roles in both innate and adaptive immune responses against viral infections. Porcine reproductive and respiratory syndrome virus (PRRSV) has been recognized to be able to down-regulate the IFN response during in vivo and in vitro infection. In this study, we first analyzed inhibitory effect of each NSP of low pathogenic PRRSV HB-1/3.9 on IFN-β transcription in MARC-145 cells, and the results showed that the IFN-β promoter activation could be suppressed by NSP1α, NSP2, NSP1β, NSP3, NSP4, NSP5 and NSP11. We next confirmed that the inhibitory effect of NSP4 was mainly mediated through suppressing NF-κB activation, whereas not hindering NF-κB phosphorylation and nuclear translocation, and nuclear-localized NSP4 was responsible for inhibiting IFN-β activation. We further found that the NSP4 of different pathogenic PRRSV strains exhibited differential inhibitory effect on IFN-β, NF-κB, and IRF3 transcription, and the NSP4 of highly pathogenic (HP)-PRRSV could display more strong inhibitory effect. Finally, we determined that the amino acid at residue 155 in NSP4 contributed to its inhibitory effect for IFN-β transcription in vitro by altering its subcellular distribution. Our findings suggest that the nucleus-localized NSP4 of PRRSV participates in the modulation of the host type I IFNs system, and also provide novel insight for understanding the pathogenesis of the Chinese HP-PRRSV.
    Virus Research 06/2014; 189. DOI:10.1016/j.virusres.2014.05.027 · 2.83 Impact Factor
  • Source
    • "substitutions within epitope-M201 region was prepared by site-directed mutagenesis using synthesized mutagenic primers (Table 1). The resulting PCR products were cloned into the pIHA plasmid [31] at the XhoI and NotI restriction enzyme sites. The megaprimer PCR method [32] was used to prepare mutant pFL12 plasmids that contain mutations in the epitope-M201 region of the PRRSV strain FL12 [33] "
    [Show abstract] [Hide abstract]
    ABSTRACT: DIVA (differentiating infected from vaccinated animals) vaccines have proven extremely useful for control and eradication of infectious diseases in livestock. We describe here the characterization of a serologic marker epitope, so-called epitope-M201, which can be a potential target for development of a live-attenuated DIVA vaccine against porcine reproductive and respiratory syndrome virus (PRRSV). Epitope-M201 is located at the carboxyl terminus (residues 161-174) of the viral M protein. The epitope is highly immunodominant and well-conserved among type-II PRRSV isolates. Rabbit polyclonal antibodies prepared against this epitope are non-neutralizing; thus, the epitope does not seem to contribute to the protective immunity against PRRSV infection. Importantly, the immunogenicity of epitope-M201 can be disrupted through the introduction of a single amino acid mutation which does not adversely affect the viral replication. All together, our results provide an important starting point for the development of a live-attenuated DIVA vaccine against type-II PRRSV.
    Vaccine 07/2013; 31(40). DOI:10.1016/j.vaccine.2013.07.020 · 3.49 Impact Factor
  • Source
    • "The primers and probes for the NS1 gene of PPV were selected according to Song et al. (2010), and those for b-actin were selected according to Beura et al. (2010). In addition, a pair of primer sets and probes for quantitative RT-PCR of IFN-a and IFN-b were also designed using the program DNAStar. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Porcine parvovirus (PPV) is a major causative agent of reproductive failure in swine, which currently affects the swine industry worldwide. Although PPV was identified several years ago, little is known about how it overcomes host innate immunity. In this study, we used quantitative real-time PCR and a luciferase reporter assay to determine whether PPV infection induces type I interferon (IFN-α and IFN-β) and whether PPV infection blocks dsRNA-induced IFN-β promoter activation in cell cultures. The results indicate that PPV does not induce type I interferon and that the NS2 protein of PPV could blocks dsRNA-induced IFN-β promoter activation.
    Veterinary Microbiology 11/2012; 163(1-2). DOI:10.1016/j.vetmic.2012.11.032 · 2.73 Impact Factor
Show more