Porcine epidemic diarrhea virus nsp14 inhibits NF-κB pathway activation by targeting the IKK complex and p65

Coronaviruses(CoVs)are a group of related enveloped RNA viruses that have severe consequences in a wide variety of animals by causing respiratory,enteric or systemic diseases.Porcine epidemic diarrhea virus(PEDV)is an economically important CoV distributed worldwide that causes diarrhea in pigs.nsp14 is a nonstructural protein of PEDV that is involved in regulation of innate immunity and viral replication.However,the function and mechanism by which nsp14 modulates and manipulates host immune responses remain largely unknown.Here,we report that PEDV nsp14 is an NF-κB pathway antagonist.Overexpression PEDV nsp14 protein remarkably decreases SeV-,poly(I:C)-and TNF-α-induced NF-κB activation.Meanwhile,expression of proinflammatory cytokines is suppressed by nspl4.nsp14 inhibits the phosphorylation of IKKs by interacting with IKKs and p65.Furthermore,nsp14 suppresses TNF-α-induced phosphorylation and nuclear import of p65.Overexpression nsp14 considerably increases PEDV replication.These results suggest a novel mechanism employed by PEDV to suppress the host antiviral response,providing insights that can guide the development of antivirals against CoVs.

口蹄疫病毒等小RNA病毒可通过一种共性机制操纵细胞加速病毒复制

小RNA病毒是RNA病毒中最小的类群。这种病毒的颗粒为直径22~30 nm的正二十面体,无包膜,并且含有29%~32%的连续线型单链RNA。小RNA病毒科的主要成员包括口蹄疫病毒(FMDV)、脊髓灰质炎病毒(PV)、塞内卡病毒(SVA)、埃可病毒、柯萨奇病毒等,能引起多种人或动物传染性疾病,对人和动物的健康构成威胁。小RNA病毒的VP3蛋白是病毒结构中的关键组成部分,尤其在口蹄疫病毒、脊髓灰质炎病毒和塞内卡病毒等病毒中,VP3蛋白被视为病毒复制和致病过程中的关键毒力因子。

KIF5B-mediated internalization of FMDV promotes virus infection

Foot-and-mouth disease(FMD)is a highly contagious and economically important disease,which is caused by the FMD virus(FMDV).Although the cell receptor for FMDV has been identified,the specific mechanism of FMDV internalization after infection remains unknown.In this study,we found that kinesin family member 5B(KIF5B)plays a vital role during FMDV internalization.Moreover,we confirmed the interaction between KIF5B and FMDV structural protein VP1 by co-immunoprecipitation(Co-IP)and co-localization in FMDV-infected cells.In particular,the stalk[amino acids(aa)413–678]domain of KIF5B was indispensable for KIF5B-VP1 interaction.Moreover,overexpression of KIF5B dramatically enhanced FMDV replication;consistently,knockdown or knockout of KIF5B suppressed FMDV replication.Furthermore,we also demonstrated that KIF5B promotes the internalization of FMDV via regulating clathrin uncoating.KIF5B also promotes the transmission of viral particles to early and late endosomes during the early stages of infection.In conclusion,our results demonstrate that KIF5B promotes the internalization of FMDV via regulating clathrin uncoating and intracellular transport.This study may provide a new therapeutic target for developing FMDV antiviral drugs.

CRISPR/Cas9介导的RPSA基因敲除细胞系的建立及其应用

【目的】利用CRISPR/Cas9技术建立RPSA基因缺失的乳仓鼠肾细胞(baby hamster kidney cells,BHK21)细胞系,为开展RPSA调控病毒复制机制研究提供工具;同时,初步探究RPSA对塞内卡病毒复制的影响。【方法】根据GenBank中仓鼠的RPSA基因序列找到产生不同转录本的共同外显子段,设计并合成4对引导RNA(sgRNA),分别构建至PX330载体中;经过筛选选择打靶活性较高的PX330-RPSA-sgRNA2质粒用于后续敲除细胞系构建。将PX330-RPSA-sgRNA2质粒转染BHK21细胞后,通过有限稀释法筛选单克隆细胞,通过Western blot及序列测定检测RPSA基因的敲除。通过Western blot及qPCR分析比较塞内卡病毒在野生型及RPSA基因敲除BHK21细胞中的复制差异。【结果】Western blot检测及序列测序证实了RPSA基因敲除单克隆细胞构建成功。进一步研究发现,塞内卡病毒在RPSA基因敲除细胞中的复制水平明显低于其在野生型BHK21细胞中复制的水平。【结论】成功构建了RPSA基因敲除的BHK21细胞系,首次表明RPSA对塞内卡病毒的复制具有重要作用,为进一步开展RPSA在细胞内调控病毒复制机制研究奠定基础。

The Distribution of Different Clades of Seneca Valley Viruses in Guangdong Province,China

Seneca Valley virus (SVV), a newly determined etiological agent of vesicular disease in swine, causes porcine idiopathic disease and occasional acute death in piglets. Recently, an increased number of SVV infection cases have been reported in the United States (US) and China, resulting in significant economic losses to the swine industry. The first identification of SVV in China was reported in Guangdong Province, a major swine producing province. The cases of SVV were continuously reported in Guangdong in 2015 and 2016. However, the spread of SVV in Guangdong in 2017 remains unknown.In this study, we determined two new SVV strains, CH-GD-2017-1 and CH-GD-2017-2, from Guangdong. The genetic analysis suggested that the two Guangdong strains showed different characteristics to previous Guangdong strains. They showed lower nucleotide similarity with strains isolated in 2015 and 2016, and were more similar to the US strains.Phylogenetic analyses indicated that the new strains were clustered in a different clade with previous Guangdong strains.We found 28 mutated amino acids in the new strains, compared with the first Guangdong strain, SVV CH-01-2015. In the geographic analysis, we found that the US and China reported more SVV cases than other countries, and most of the SVV cases were reported in east and central China—of which, Guangdong Province is one of the major epidemic regions. In conclusion, our findings indicate that SVV continued to spread in Guangdong Province in 2017, and two different clades of SVVs have emerged in this region.

FoxJ1 inhibits African swine fever virus replication and viral S273R protein decreases the expression of FoxJ1 to impair its antiviral effect

African swine fever(ASF)is a highly pathogenic swine infectious disease that affects domestic pigs and wild boar,which is caused by the African swine fever virus(ASFV).ASF has caused huge economic losses to the pig industry and seriously threatens global food security and livestock health.To date,there is no safe and effective commercial vaccine against ASF.Unveiling the underlying mechanisms of ASFV-host interplay is critical for developing effective vaccines and drugs against ASFV.In the present study,RNA-sequencing,RT-qPCR and Western blotting analysis revealed that the transcriptional and protein levels of the host factor FoxJ1 were significantly down-regulated in primary porcine alveolar macrophages(PAMs)infected by ASFV.RT-qPCR analysis showed that overexpression of FoxJ1 upregulated the transcription of type I interferon and interferon stimulating genes(ISGs)induced by poly(dA:dT).FoxJ1 revealed a function to positively regulate innate immune response,therefore,suppressing the replication of ASFV.In addition,Western blotting analysis indicated that FoxJ1 degraded ASFV MGF505-2R and E165R proteins through autophagy pathway.Meanwhile,RT-qPCR and Western blotting analysis showed that ASFV S273R inhibited the expression of FoxJ1.Altogether,we determined that FoxJ1 plays an antiviral role against ASFV replication,and ASFV protein impairs FoxJ1-mediated antiviral effect by degradation of FoxJ1.Our findings provide new insights into the antiviral function of FoxJ1,which might help design antiviral drugs or vaccines against ASFV infection.

Foot-and-Mouth Disease Virus Inhibits RIP2 Protein Expression to Promote Viral Replication

Receptors interaction protein 2(RIP2)is a specific adaptor molecule in the downstream of NOD2.The role of RIP2 during foot-and-mouth disease virus(FMDV)infection remains unknown.Here,our results showed that RIP2 inhibited FMDV replication and played an important role in the activation of IFN-βand NF-κB signal pathways during FMDV infection.FMDV infection triggered RIP2 transcription,while it reduced the expression of RIP2 protein.Detailed analysis showed that FMDV 2B,2C,3C^(pro),and L^(pro) proteins were responsible for inducing the reduction of RIP2 protein.3C^(pro) and L^(pro) are viral proteinases that can induce the cleavage or reduction of many host proteins and block host protein synthesis.The carboxyl terminal 105-C114 and 135-C144 regions of 2B were essential for reduction of RIP2.Our results also showed that the N terminal 1-61 region of 2C were essential for the reduction of RIP2.The 2C-induced reduction of RIP2 was dependent on inducing the reduction of poly(A)-binding protein 1(PABPC1).The interaction between RIP2 and 2C was observed in the context of viral infection,and the residues 1-61 were required for the interaction.These data clarify novel mechanisms of reduction of RIP2 mediated by FMDV.

Porcine Picornavirus 3C Protease Degrades PRDX6 to Impair PRDX6-mediated Antiviral Function

Peroxiredoxin-6(PRDX6)is an antioxidant enzyme with both the activities of peroxidase and phospholipase A2(PLA2),which is involved in regulation of many cellular reactions.However,the function of PRDX6 during virus infection remains unknown.In this study,we found that the abundance of PRDX6 protein was dramatically decreased in foot-and-mouth disease virus(FMDV)infected cells.Overexpression of PRDX6 inhibited FMDV replication.In contrast,knockdown of PRDX6 expression promoted FMDV replication,suggesting an antiviral role of PRDX6.To explore whether the activity of peroxidase and PLA2 was associated with PRDX6-mediated antiviral function,a specific inhibitor of PLA2(MJ33)and a specific inhibitor of peroxidase activity(mercaptosuccinate)were used to treat the cells before FMDV infection.The results showed that incubation of MJ33 but not mercaptosuccinate promoted FMDV replication.Meanwhile,overexpression of PRDX6 slightly enhanced type I interferon signaling.We further determined that the viral 3Cprowas responsible for degradation of PRDX6,and 3Cpro-induced reduction of PRDX6 was independent of the proteasome,lysosome,and caspase pathways.The protease activity of 3Cprowas required for induction of PRDX6 reduction.Besides,PRDX6 suppressed the replication of another porcine picornavirus Senecavirus A(SVA),and the 3Cproof SVA induced the reduction of PRDX6 through its proteolytic activity as well.Together,our results suggested that PRDX6 plays an important antiviral role during porcine picornavirus infection,and the viral 3Cproinduces the degradation of PRDX6 to overcome PRDX6-mediated antiviral function.

Differential gene expression in porcine SK6 cells infected with wild-type and SAP domain-mutant foot-and-mouth disease virus

Foot-and-mouth disease virus(FMDV) is the causative agent of a highly contagious disease in livestock. The viral proteinaseL^(rop) of FMDV is involved in pathogenicity, and mutation of theL^(rop) SAP domain reduces FMDV pathogenicity in pigs. To determine the gene expression profiles associated with decreased pathogenicity in porcine cells, we performed transcriptome analysis using next-generation sequencing technology and compared differentially expressed genes in SK6 cells infected with FMDV containingL^(rop) with either a wild-type or mutated version of the SAP domain. This analysis yielded 1,853 genes that exhibited a ≥ 2-fold change in expression and was validated by real-time quantitative PCR detection of several differentially expressed genes. Many of the differentially expressed genes correlated with antiviral responses corresponded to genes associated with transcription factors, immune regulation, cytokine production, inflammatory response, and apoptosis. Alterations in gene expression profiles may be responsible for the variations in pathogenicity observed between the two FMDV variants. Our results provided genes of interest for the further study of antiviral pathways and pathogenic mechanisms related to FMDV L^(rop).

Correction to: Porcine Picornavirus 3C Protease Degrades PRDX6 to Impair PRDX6-mediated Antiviral Function

Correction to:Virologica Sinica(2021)36:948-957 https://doi.org/10.1007/s12250-021-00352-4 Due to our negligence,the original version of this article,published online on March 15,2021,contained a mistake in Figure 2E(The Knockdown band of Western blotting was provided incorrectly).The correct Fig.2E is given below.We apologize for this error and state that this does not change the scientific conclusions of the article in any way.