Immunodominant epitopes in nsp2 of porcine reproductive and respiratory syndrome virus are dispensable for replication, but play an important role in modulation of the host immune response

Chen, Zhenhai; Zhou, Xiaoxin; Lunney, Joan K.; Lawson, Steven R.; Sun, Zhoutong; Brown, Emily J.; Christopher‐Hennings, Jane; Knudsen, David; Nelson, Eric; Fāng, Yīng

doi:10.1099/vir.0.016212-0

Cited by 74 publications

(63 citation statements)

References 48 publications

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“…The highly conserved amino acids among OTU members are located at the putative Cys55-His124 catalytic motif of Nsp2. Moreover, it has been reported that immunodominant epitopes in Nsp2 play an important role in modulation of the host immune response (Chen et al, 2010b). In this study, we have provided evidence that PRRSV Nsp2 inhibits IFN induction by antagonizing the activation of IRF-3.…”

supporting

confidence: 56%

The cysteine protease domain of porcine reproductive and respiratory syndrome virus non-structural protein 2 antagonizes interferon regulatory factor 3 activation

Zheng

Zhou

et al. 2010

Journal of General Virology

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There is growing evidence that porcine reproductive and respiratory syndrome virus (PRRSV) has developed mechanisms to subvert the host innate immune response. PRRSV non-structural protein 2 (Nsp2) was suggested previously as a potential interferon (IFN) antagonist. This study focused on Nsp2 to investigate its inhibitory mechanism of IFN induction. It was demonstrated that Nsp2 strongly inhibited IFN-b production by antagonizing activation of the IFN regulatory factor 3 (IRF-3) pathway induced by the Sendai virus (SeV). Further studies revealed that the cysteine protease domain (PL2) of Nsp2 was necessary for IFN antagonism. Additionally, both full-length Nsp2 and the PL2 protease domain of Nsp2 were found to inhibit SeV-induced phosphorylation and nuclear translocation of IRF-3. These findings suggest that Nsp2 is likely to play an important role in subversion of IRF-3-dependent innate antiviral defences, providing a basis for elucidating the mechanisms underlying PRRSV pathogenesis. INTRODUCTIONThe production of type I interferons (IFN-a/b) plays a pivotal role in the host antiviral immune defence (Bonjardim, 2005). Cellular sensors capable of recognizing various viral determinants initiate IFN signal transduction. Positive-stranded RNA viruses can generate intermediate dsRNA during replication, which is an efficient inducer of type I IFNs. This intermediate dsRNA can trigger a cascade of cellular sensors, resulting in type I IFN production and secretion (Kawai & Akira, 2006a;Randall & Goodbourn, 2008). The induction of type I IFNs is initiated via recognition of a pathogen-associated molecule in dsRNA by cellular pattern recognition receptors, including Tolllike receptor 3 (TLR3), caspase recruitment domain (CARD)-containing proteins, retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 . TLR3 signals through the adaptor molecule Toll-interleukin-1-resistance domain-containing adaptor inducing IFN-b (TRIF), whilst MDA-5 and RIG-I signal through the adaptor molecule mitochondrial antiviral signal protein (MAVS; also known as IPS-1, Cardif and VISA) to activate a type I IFN response (Kawai & Akira, 2006b; Kawai et al., 2005; Yamamoto et al., 2003). Despite utilizing different adaptors, both pathways converge to activate two downstream kinases, TANK-binding kinase 1 (TBK-1) and inhibitor of kB kinase e (IKKe), subsequently leading to the activation of latent IFN transcription factors, including IFN regulatory factors (IRF-3 and/or IRF-7), nuclear factor-kB (NF-kB) and activating protein 1 (AP-1) (Fitzgerald et al., 2003;Randall & Goodbourn, 2008; Sharma et al., 2003). Activated IFN transcription factors translocate to the nucleus and activate IFN transcription (Biron, 2001). Secreted IFN binds to the IFN receptor and activates a JAK/STAT signalling pathway, upregulating the expression of a subset of genes that impede virus replication (Randall & Goodbourn, 2008). However, many viruses have evolved mechanisms to circumvent the IFN response (Blakqori et al., 2007;Jennings et al.,...

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confidence: 56%

The cysteine protease domain of porcine reproductive and respiratory syndrome virus non-structural protein 2 antagonizes interferon regulatory factor 3 activation

Zheng

Zhou

et al. 2010

Journal of General Virology

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“…The observation that a complete HVR deletion mutant is replication competent in vitro but noninfectious in vivo suggests a less critical role for the HVR in cells with innate immunity defects. Nonstructural viral genes that are dispensable for virus replication are known to play a role in modulating host immune responses such as deubiquitinating and interferon antagonism activities (7,36). It will be interesting to determine if the HVR of HEV also contains critical residues that may play a role in antagonizing or evading host immune responses in vivo.…”

Section: Discussionmentioning

confidence: 99%

Mutational Analysis of the Hypervariable Region of Hepatitis E Virus Reveals Its Involvement in the Efficiency of Viral RNA Replication

Pudupakam

Kenney

Córdoba

et al. 2011

J Virol

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The RNA genome of the hepatitis E virus (HEV) contains a hypervariable region (HVR) in ORF1 that tolerates small deletions with respect to infectivity. To further investigate the role of the HVR in HEV replication, we constructed a panel of mutants with overlapping deletions in the N-terminal, central, and C-terminal regions of the HVR by using a genotype 1 human HEV luciferase replicon and analyzed the effects of deletions on viral RNA replication in Huh7 cells. We found that the replication levels of the HVR deletion mutants were markedly reduced in Huh7 cells, suggesting a role of the HVR in viral replication efficiency. To further verify the results, we constructed HVR deletion mutants by using a genetically divergent, nonmammalian avian HEV, and similar effects on viral replication efficiency were observed when the avian HEV mutants were tested in LMH cells. Furthermore, the impact of complete HVR deletion on virus infectivity was tested in chickens, using an avian HEV mutant with a complete HVR deletion. Although the deletion mutant was still replication competent in LMH cells, the complete HVR deletion resulted in a loss of avian HEV infectivity in chickens. Since the HVR exhibits extensive variations in sequence and length among different HEV genotypes, we further examined the interchangeability of HVRs and demonstrated that HVR sequences are functionally exchangeable between HEV genotypes with regard to viral replication and infectivity in vitro, although genotype-specific HVR differences in replication efficiency were observed. The results showed that although the HVR tolerates small deletions with regard to infectivity, it may interact with viral and host factors to modulate the efficiency of HEV replication.Hepatitis E virus (HEV), the causative agent of hepatitis E, is classified in the genus Hepevirus of the family Hepeviridae (11,17). It is now known that hepatitis E is a zoonotic disease and that animal reservoirs exist for HEV (13, 26-29, 38, 40). The inefficient replication of HEV in cell cultures has hindered progress in understanding the biology of HEV. The problem has been overcome partially by either characterizing individually expressed proteins from expression vectors or transfecting cells and intrahepatically inoculating animals with capped RNA transcripts generated in vitro from infectious clones (16,17,32,33). More recently, efficient in vitro HEV replication systems have been reported (3,31,35,37), which may aid in future understanding of HEV replication.The 7.2-kb RNA genome of HEV contains three open reading frames (ORFs), namely, ORF1, ORF2, and ORF3, flanked by 5Ј-and 3Ј-nontranslated regions (2). The putative functional domains in the ORF1 protein include methyltransferase, protease, helicase, and RNA-dependent RNA polymerase (RdRp) domains (2). ORF2 encodes the major capsid protein, whereas ORF3 encodes a small multifunctional protein (2,6,18,30,39). The methyltransferase and guanylyltransferase activities in capping of the viral RNA (25), the role of RdRp in viral RNA synthesis...

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“…It is, therefore, one of the main targets used to monitor PRRSV evolution (25). Furthermore, the Nsp2-coding region is crucial for viral replication and modulation of host immunity because of its protease activity (2,8,13,42). Natural insertions and/or deletions are routinely observed in the hypervariable middle region of the Nsp2 protein in field strains, resulting in polymorphisms of considerable size (16,31).…”

Section: Discussionmentioning

confidence: 99%

Epidemiology and Evolutionary Characteristics of the Porcine Reproductive and Respiratory Syndrome Virus in China between 2006 and 2010

Fang

Guo

et al. 2011

J Clin Microbiol

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In 2006, an emerging highly pathogenic strain of porcine reproductive and respiratory syndrome virus (PRRSV), which causes continuous high fever and a high proportion of deaths in vaccinated pigs of all ages, broke out in mainland China and spread rapidly to neighboring countries. To examine the epidemiology and evolutionary characteristics of Chinese PRRSV after the 2006 outbreak, we tested 2,981 clinical samples collected from 2006 to 2010 in China, determined 153 Nsp2 sequences and 249 ORF5 sequences, and analyzed the epidemiology and genetic diversity of Chinese PRRSV. Our results showed that the percentage of PRRSV-positive specimens collected from sick pigs averaged 60.85% in the past 5 years and that the highly pathogenic PRRSV has become the dominant strain in China. Furthermore, a reemerging strain which apparently evolved from the highly pathogenic PRRSV strain in 2006 appeared to be widely prevalent in China from 2009 onwards. Sequence analyses revealed that the hypervariable region of Nsp2 in most of the isolates contained a discontinuous deletion equivalent to 30 amino acids, along with other types of deletions. Extensive amino acid substitutions in the GP5 sequence translated from ORF5 were found, particularly in the potential neutralization epitope and the N-glycosylation sites. Our results suggest that Chinese PRRSV has undergone rapid evolution and can circumvent immune responses induced by currently used vaccines. Information from this study will help in understanding the evolutionary characteristics of Chinese PRRSV and assist ongoing efforts to develop and use PRRSV vaccines in the future.

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Immunodominant epitopes in nsp2 of porcine reproductive and respiratory syndrome virus are dispensable for replication, but play an important role in modulation of the host immune response

Cited by 74 publications

References 48 publications

The cysteine protease domain of porcine reproductive and respiratory syndrome virus non-structural protein 2 antagonizes interferon regulatory factor 3 activation

The cysteine protease domain of porcine reproductive and respiratory syndrome virus non-structural protein 2 antagonizes interferon regulatory factor 3 activation

Mutational Analysis of the Hypervariable Region of Hepatitis E Virus Reveals Its Involvement in the Efficiency of Viral RNA Replication

Epidemiology and Evolutionary Characteristics of the Porcine Reproductive and Respiratory Syndrome Virus in China between 2006 and 2010

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