scholarly journals pMGF505-7R determines pathogenicity of African swine fever virus infection by inhibiting IL-1β and type I IFN production

2021 ◽  
Vol 17 (7) ◽  
pp. e1009733
Author(s):  
Jiangnan Li ◽  
Jie Song ◽  
Li Kang ◽  
Li Huang ◽  
Shijun Zhou ◽  
...  
Keyword(s):  
Immune Responses ◽  
Inflammatory Responses ◽  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Innate Immune ◽  
Fever Virus ◽  
Type I ◽  
Type I Ifn ◽  
Innate Immune Responses

Inflammatory factors and type I interferons (IFNs) are key components of host antiviral innate immune responses, which can be released from the pathogen-infected macrophages. African swine fever virus (ASFV) has developed various strategies to evade host antiviral innate immune responses, including alteration of inflammatory responses and IFNs production. However, the molecular mechanism underlying inhibition of inflammatory responses and IFNs production by ASFV-encoded proteins has not been fully understood. Here we report that ASFV infection only induced low levels of IL-1β and type I IFNs in porcine alveolar macrophages (PAMs), even in the presence of strong inducers such as LPS and poly(dA:dT). Through further exploration, we found that several members of the multigene family 360 (MGF360) and MGF505 strongly inhibited IL-1β maturation and IFN-β promoter activation. Among them, pMGF505-7R had the strongest inhibitory effect. To verify the function of pMGF505-7R in vivo, a recombinant ASFV with deletion of the MGF505-7R gene (ASFV-Δ7R) was constructed and assessed. As we expected, ASFV-Δ7R infection induced higher levels of IL-1β and IFN-β compared with its parental ASFV HLJ/18 strain. ASFV infection-induced IL-1β production was then found to be dependent on TLRs/NF-κB signaling pathway and NLRP3 inflammasome. Furthermore, we demonstrated that pMGF505-7R interacted with IKKα in the IKK complex to inhibit NF-κB activation and bound to NLRP3 to inhibit inflammasome formation, leading to decreased IL-1β production. Moreover, we found that pMGF505-7R interacted with and inhibited the nuclear translocation of IRF3 to block type I IFN production. Importantly, the virulence of ASFV-Δ7R is reduced in piglets compared with its parental ASFV HLJ/18 strain, which may due to induction of higher IL-1β and type I IFN production in vivo. Our findings provide a new clue to understand the functions of ASFV-encoded pMGF505-7R and its role in viral infection-induced pathogenesis, which might help design antiviral agents or live attenuated vaccines to control ASF.

scholarly journals The African swine fever virus protease pS273R inhibits DNA sensing cGAS-STING pathway by targeting IKKε

2021 ◽  
Author(s):  
Jia Luo ◽  
Jinghua Ni ◽  
Sen Jiang ◽  
Nengwen Xia ◽  
Yiwen Guo ◽  
...  
Keyword(s):  
Immune Responses ◽  
Immune Escape ◽  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Innate Immune ◽  
Fever Virus ◽  
Negative Regulator ◽  
Type I ◽  
Innate Immune Responses ◽  
Sting Pathway

African swine fever virus (ASFV), a large and complex cytoplasmic double-stranded DNA virus, has developed multiple strategies to evade the antiviral innate immune responses. Cytosolic DNA arising from invading ASFV is mainly detected by the cyclic GMP-AMP synthase (cGAS) and then triggers a series of innate immune responses to prevent virus invasion. However, the immune escape mechanism of ASFV remains to be fully clarified. The pS273R of ASFV is a member of the SUMO-1-specific protease family and is crucial for valid virus replication. In this study, we identified pS273R as a suppressor of cGAS-STING pathway mediated type I interferon (IFN) production by ASFV genomic open reading frame screening. The pS273R was further confirmed as an inhibitor of IFN production as well as its downstream antiviral genes in cGAS-STING pathway. Mechanistically, pS273R greatly decreased the cGAS-STING signaling by targeting IKKe but not TBK1 and pS273R was found to disturb the interaction between IKKe and STING through its interaction with IKKe. Further, mutational analyses revealed that pS273R antagonized the cGAS-STING pathway by enzyme catalytic activity, which may affect the IKKe sumoylation state required for the interaction with STING. In summary, our results revealed for the first time that pS273R acts as an obvious negative regulator of cGAS-STING pathway by targeting IKKϵ via its enzymatic activity, which shows a new immune evasion mechanism of ASFV.

African swine fever virus regulates host energy and amino acid metabolism to promote viral replication

2021 ◽  
Author(s):  
Qiao Xue ◽  
Huisheng Liu ◽  
Zixiang Zhu ◽  
Fan Yang ◽  
Yingying Song ◽  
...  
Keyword(s):  
Amino Acids ◽  
Immune Responses ◽  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Tca Cycle ◽  
Innate Immune ◽  
Fever Virus ◽  
Innate Immune Responses ◽  
First Time ◽  
Self Replication

African swine fever is one of the most serious viral diseases caused by African swine fever virus (ASFV). The metabolic changes induced by ASFV infection remain unknown. Here, PAMs infected with ASFV was analyzed by ultra-high-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS) in combination with multivariate statistical analysis. A total of 90 metabolites were significantly changed after ASFV infection, and most of them belong to amino acids and TCA cycle intermediates. ASFV infection induced increase of most of amino acids in host during the early stages of infection, and amino acids decreased in the late stages of infection. ASFV infection did not significantly affected glycolysis pathway, whereas it induced the increase of citrate, succinate, α-ketoglutarate, and oxaloacetate levels in the TCA cycle, suggesting that ASFV infection promoted TCA cycle. The activity of aspartate aminotransferase and glutamate production were significantly elevated in ASFV-infected cells and pigs, resulting in reversible transition between TCA cycle and amino acids synthesis. Aspartate, glutamate, and TCA cycle were essential for ASFV replication. In addition, ASFV infection induced an increase in lactate level using lactate dehydrogenase, which led to low expression of IFN-β and increased of ASFV replication. Our data, for the first time, indicated that ASFV infection controls IFN-β production through RIG-I-mediated signaling pathways. These data identified a novel mechanism evolved by ASFV to inhibit host innate immune responses, and will provide insights for development of new preventive or therapeutic strategies targeting the altered metabolic pathways. IMPORTANCE In order to promote viral replication, viruses often cause severe immunosuppression and seize organelles to synthesize a large number of metabolites required for self-replication. African swine fever virus (ASFV) has developed many strategies to evade host innate immune responses. However, the impact of ASFV infection on host cellular metabolism remains unknown. Here, for the first time, we analyzed the metabolomic profiles of ASFV-infected PAMs cells. ASFV infection increased host TCA cycle and amino acids metabolism. Aspartate, glutamate, and TCA cycle promoted ASFV replication. ASFV infection also induced the increase of lactate production to inhibit innate immune responses for self-replication. This study identified novel immune evasion mechanisms utilized by ASFV and provided viewpoints on ASFV-host interactions, which is critical for guiding the design of new prevention strategies against ASFV targeting the altered metabolic pathways.

scholarly journals How the Innate Immune DNA Sensing cGAS–STING Pathway Is Involved in Autophagy

2021 ◽  
Vol 22 (24) ◽  
pp. 13232
Author(s):  
Wanglong Zheng ◽  
Nengwen Xia ◽  
Jiajia Zhang ◽  
Nanhua Chen ◽  
François Meurens ◽  
...  
Keyword(s):  
Immune Responses ◽  
Inflammatory Responses ◽  
Complex Interaction ◽  
Innate Immune ◽  
Type I Interferons ◽  
Type I ◽  
Innate Immune Responses ◽  
Homeostatic Process ◽  
Sting Pathway ◽  
Dna Complex

The cGAS–STING pathway is a key component of the innate immune system and exerts crucial roles in the detection of cytosolic DNA and invading pathogens. Accumulating evidence suggests that the intrinsic cGAS–STING pathway not only facilitates the production of type I interferons (IFN-I) and inflammatory responses but also triggers autophagy. Autophagy is a homeostatic process that exerts multiple effects on innate immunity. However, systematic evidence linking the cGAS–STING pathway and autophagy is still lacking. Therefore, one goal of this review is to summarize the known mechanisms of autophagy induced by the cGAS–STING pathway and their consequences. The cGAS–STING pathway can trigger canonical autophagy through liquid-phase separation of the cGAS–DNA complex, interaction of cGAS and Beclin-1, and STING-triggered ER stress–mTOR signaling. Furthermore, both cGAS and STING can induce non-canonical autophagy via LC3-interacting regions and binding with LC3. Subsequently, autophagy induced by the cGAS–STING pathway plays crucial roles in balancing innate immune responses, maintaining intracellular environmental homeostasis, alleviating liver injury, and limiting tumor growth and transformation.

scholarly journals ASFV pD345L protein negatively regulates NF-kB signaling through inhibiting IKK kinase activity

2021 ◽  
Author(s):  
Yingjuan Qian ◽  
huan Chen ◽  
Xiaodong Wu ◽  
Zhenzhong Wang ◽  
Xiaoyu Gao ◽  
...  
Keyword(s):  
Immune Responses ◽  
Kinase Activity ◽  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Innate Immune ◽  
Innate Immune Responses ◽  
Great Capacity ◽  
Protein Protein Interaction ◽  
Signaling Process ◽  
Pro Inflammatory Cytokines

The NF-κB pathway is an essential signaling process against viral infection including African swine fever virus (ASFV). ASFV encodes for more than 151 proteins by its own transcription machinery and possesses a great capacity to evade or subvert antiviral innate immune responses. A couple of such viral proteins have been reported, but many remain unknown. Here, we showed that pD345L, an ASFV-encoded lambda-like exonuclease, is an inhibitor of cGAS/STING mediated NF-κB sig-naling by blocking IKKα/β kinase activity. Specifically, we showed that overexpression of pD345L suppresses cGAS/STING induced IFNβ and NF-κB activation, resulting in decreased transcription of IFNβ and several pro-inflammatory cytokines, including IL-1α, IL-6, IL-8, and TNFα. In addition, we showed that pD345L targeted at or downstream of IKK and upstream of p65. Importantly, we found that pD345L associates with KD and HLH domains of IKKα and LZ domain of IKKβ, and thus interrupts their kinase activity on downstream substrate IκBα. Finally, we showed that pD345L inhibition of NF-κB signaling was independent of its exonuclease activity. Taken together, we concluded that pD345L blocks IKKα/β kinase activity by protein-protein interaction and thus disrupts cGAS/STING mediated NF-κB signaling.

scholarly journals African Swine Fever Virus Multigene Family 360 and 530 Genes Affect Host Interferon Response

2004 ◽  
Vol 78 (4) ◽  
pp. 1858-1864 ◽  
Author(s):  
C. L. Afonso ◽  
M. E. Piccone ◽  
K. M. Zaffuto ◽  
J. Neilan ◽  
G. F. Kutish ◽  
...  
Keyword(s):  
Viral Infection ◽  
Multigene Family ◽  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Fever Virus ◽  
Cdna Clones ◽  
Type I ◽  
Mrna Levels ◽  
Type I Ifn ◽  
Transcriptional Responses

ABSTRACT African swine fever virus (ASFV) multigene family 360 and 530 (MGF360/530) genes affect viral growth in macrophage cell cultures and virulence in pigs (L. Zsak, Z. Lu, T. G. Burrage, J. G. Neilan, G. F. Kutish, D. M. Moore, and D. L. Rock, J. Virol. 75:3066-3076, 2001). The mechanism by which these novel genes affect virus-host interactions is unknown. To define MGF360/530 gene function, we compared macrophage transcriptional responses following infection with parental ASFV (Pr4) and an MGF360/530 deletion mutant (Pr4Δ35). A swine cDNA microarray containing 7,712 macrophage cDNA clones was used to compare the transcriptional profiles of swine macrophages infected with Pr4 and Pr4Δ35 at 3 and 6 h postinfection (hpi). While at 3 hpi most (7,564) of the genes had similar expression levels in cells infected with either virus, 38 genes had significantly increased (>2.0-fold, P < 0.05) mRNA levels in Pr4Δ35-infected macrophages. Similar up-regulation of these genes was observed at 6 hpi. Viral infection was required for this induced transcriptional response. Most Pr4Δ35 up-regulated genes were part of a type I interferon (IFN) response or were genes that are normally induced by double-stranded RNA and/or viral infection. These included monocyte chemoattractant protein, transmembrane protein 3, tetratricopeptide repeat protein 1, a ubiquitin-like 17-kDa protein, ubiquitin-specific protease ISG43, an RNA helicase DEAD box protein, GTP-binding MX protein, the cytokine IP-10, and the PKR activator PACT. Differential expression of IFN early-response genes in Pr4Δ35 relative to Pr4 was confirmed by Northern blot analysis and real-time PCR. Analysis of IFN-α mRNA and secreted IFN-α levels at 3, 8, and 24 hpi revealed undetectable IFN-α in mock- and Pr4-infected macrophages but significant IFN-α levels at 24 hpi in Pr4Δ35-infected macrophages. The absence of IFN-α in Pr4-infected macrophages suggests that MGF360/530 genes either directly or indirectly suppress a type I IFN response. An inability to suppress host type I IFN responses may account for the growth defect of Pr4Δ35 in macrophages and its attenuation in swine.

scholarly journals Disruption of MDA5-Mediated Innate Immune Responses by the 3C Proteins of Coxsackievirus A16, Coxsackievirus A6, and Enterovirus D68

2017 ◽  
Vol 91 (13) ◽  
Author(s):  
Yajuan Rui ◽  
Jiaming Su ◽  
Hong Wang ◽  
Junliang Chang ◽  
Shaohua Wang ◽  
...  
Keyword(s):  
Immune Responses ◽  
Respiratory Disease ◽  
Foot And Mouth Disease ◽  
Innate Immune ◽  
Type I ◽  
Type I Ifn ◽  
Innate Immune Responses ◽  
Key Factors ◽  
Coxsackievirus A16 ◽  
Enterovirus D68

ABSTRACT Coxsackievirus A16 (CV-A16), CV-A6, and enterovirus D68 (EV-D68) belong to the Picornaviridae family and are major causes of hand, foot, and mouth disease (HFMD) and pediatric respiratory disease worldwide. The biological characteristics of these viruses, especially their interplay with the host innate immune system, have not been well investigated. In this study, we discovered that the 3Cpro proteins from CV-A16, CV-A6, and EV-D68 bind melanoma differentiation-associated gene 5 (MDA5) and inhibit its interaction with MAVS. Consequently, MDA5-triggered type I interferon (IFN) signaling in the retinoic acid-inducible gene I-like receptor (RLR) pathway was blocked by the CV-A16, CV-A6, and EV-D68 3Cpro proteins. Furthermore, the CV-A16, CV-A6, and EV-D68 3Cpro proteins all cleave transforming growth factor β-activated kinase 1 (TAK1), resulting in the inhibition of NF-κB activation, a host response also critical for Toll-like receptor (TLR)-mediated signaling. Thus, our data demonstrate that circulating HFMD-associated CV-A16 and CV-A6, as well as severe respiratory disease-associated EV-D68, have developed novel mechanisms to subvert host innate immune responses by targeting key factors in the RLR and TLR pathways. Blocking the ability of 3Cpro proteins from diverse enteroviruses and coxsackieviruses to interfere with type I IFN induction should restore IFN antiviral function, offering a potential novel antiviral strategy. IMPORTANCE CV-A16, CV-A6, and EV-D68 are emerging pathogens associated with hand, foot, and mouth disease and pediatric respiratory disease worldwide. The pathogenic mechanisms of these viruses are largely unknown. Here we demonstrate that the CV-A16, CV-A6, and EV-D68 3Cpro proteins block MDA5-triggered type I IFN induction. The 3Cpro proteins of these viruses bind MDA5 and inhibit its interaction with MAVS. In addition, the CV-A16, CV-A6, and EV-D68 3Cpro proteins cleave TAK1 to inhibit the NF-κB response. Thus, our data demonstrate that circulating HFMD-associated CV-A16 and CV-A6, as well as severe respiratory disease-associated EV-D68, have developed a mechanism to subvert host innate immune responses by simultaneously targeting key factors in the RLR and TLR pathways. These findings indicate the potential merit of targeting the CV-A16, CV-A6, and EV-D68 3Cpro proteins as an antiviral strategy.

scholarly journals Innate immune responses elicited by Sin Nombre virus or type I IFN agonists protect hamsters from lethal Andes virus infections

2018 ◽  
Vol 99 (10) ◽  
pp. 1359-1366 ◽  
Author(s):  
Rebecca L. Brocato ◽  
Victoria Wahl ◽  
Christopher D. Hammerbeck ◽  
Matthew D. Josleyn ◽  
Anita K. McElroy ◽  
...  
Keyword(s):  
Immune Responses ◽  
Innate Immune ◽  
Sin Nombre Virus ◽  
Type I ◽  
Type I Ifn ◽  
Innate Immune Responses ◽  
Virus Infections ◽  
Andes Virus
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