DDX56 cooperates with FMDV 3A to enhance FMDV replication by inhibiting the phosphorylation of IRF3

Foot-and-Mouth Disease Virus Capsid Protein VP1 Antagonizes Type I Interferon Signaling via Degradation of Histone Deacetylase 5

Foot-and-mouth disease (FMD) is a highly contagious and economically important disease of cloven-hoofed animals that hampers trade and production. To ensure effective infection, the foot-and-mouth disease virus (FMDV) evades host antiviral pathways in different ways. Although the effect of histone deacetylase 5 (HDAC5) on the innate immune response has previously been documented, the precise molecular mechanism underlying HDAC5-mediated FMDV infection is not yet clearly understood. In this study, we found that silencing or knockout of HDAC5 promoted FMDV replication, whereas HDAC5 overexpression significantly inhibited FMDV propagation. IFN-β and IFN-stimulated response element (ISRE) activity was strongly activated through the overexpression of HDAC5. The silencing and knockout of HDAC5 led to an increase in viral replication, which was evident by decreased IFN-β, ISG15, and ISG56 production, as well as a noticeable reduction in IRF3 phosphorylation. Moreover, the results showed that the FMDV capsid protein VP1 targets HDAC5 and facilitates its degradation via the proteasomal pathway. In conclusion, this study highlights that HDAC5 acts as a positive modulator of IFN-β production during viral infection, while FMDV capsid protein VP1 antagonizes the HDAC5-mediated antiviral immune response by degrading HDAC5 to facilitate viral replication.

Foot-and-mouth disease virus downregulates vacuolar protein sorting 28 to promote viral replication

Vacuolar protein sorting 28 (Vps28), a component of the ESCRT-I (endosomal sorting complex required for transport I), plays an important role in the pathogen life cycle. Here, we investigated the reciprocal regulation between Vps28 and the foot-and-mouth disease virus (FMDV). Overexpression of Vps28 decreased FMDV replication. On the contrary, the knockdown of Vps28 increased viral replication. Subsequently, the mechanistic study showed that Vps28 destabilized the replication complex (RC) by associating with 3A rather than 2C protein. In addition, Vps28 targeted FMDV VP0, VP1, and VP3 for degradation to inhibit viral replication. To counteract this, FMDV utilized tactics to restrict Vps28 to promote viral replication. FMDV degraded Vps28 mainly through the ubiquitin-proteasome pathway. Additional data demonstrated that 2B and 3A proteins recruited E3 ubiquitin ligase tripartite motif-containing protein 21 to degrade Vps28 at Lys58 and Lys25, respectively, and FMDV 3Cpro degraded Vps28 through autophagy and its protease activity. Meantime, the 3Cpro-mediated Vps28 degradation principally alleviated the ability to inhibit viral propagation. Intriguingly, we also demonstrated that the N-terminal and C-terminal domains of Vps28 were responsible for the suppression of FMDV replication, which suggested the elaborated counteraction between FMDV and Vps28. Collectively, our results first investigate the role of ESCRTs in host defense against picornavirus and unveil underlying strategies utilized by FMDV to evade degradation machinery for triumphant propagation. IMPORTANCE ESCRT machinery plays positive roles in virus entry, replication, and budding. However, little has been reported on its negative regulation effects during viral infection. Here, we uncovered the novel roles of ESCRT-I subunit Vps28 on FMDV replication. The data indicated that Vps28 destabilized the RC and impaired viral structural proteins VP0, VP1, and VP3 to inhibit viral replication. To counteract this, FMDV hijacked intracellular protein degradation pathways to downregulate Vps28 expression and thus promoted viral replication. Our findings provide insights into how ESCRT regulates pathogen life cycles and elucidate additional information regarding FMDV counteraction of host antiviral activity.

Foot-and-mouth disease virus non-structural protein 2B downregulates the RLR signaling pathway via degradation of RIG-I and MDA5

Foot-and-mouth disease virus (FMDV) is a single-stranded, positive-sense RNA virus containing at least 13 proteins. Many of these proteins show immune modulation capabilities. As a non-structural protein of the FMDV, 2B is involved in the rearrangement of the host cell membranes and the disruption of the host secretory pathway as a viroporin. Previous studies have also shown that FMDV 2B plays a role in the modulation of host type-I interferon (IFN) responses through the inhibition of expression of RIG-I and MDA5, key cytosolic sensors of the type-I IFN signaling. However, the exact molecular mechanism is poorly understood. Here, we demonstrated that FMDV 2B modulates host IFN signal pathway by the degradation of RIG-I and MDA5. FMDV 2B targeted the RIG-I for ubiquitination and proteasomal degradation by recruiting E3 ubiquitin ligase ring finger protein 125 (RNF125) and also targeted MDA5 for apoptosis-induced caspase-3- and caspase-8-dependent degradation. Ultimately, FMDV 2B significantly inhibited RNA virus-induced IFN-β production. Importantly, we identified that the C-terminal amino acids 126-154 of FMDV 2B are essential for 2B-mediated degradation of the RIG-I and MDA5. Collectively, these results provide a clearer understanding of the specific molecular mechanisms used by FMDV 2B to inhibit the IFN responses and a rational approach to virus attenuation for future vaccine development.

Foot-and-Mouth Disease Virus: Molecular Interplays with IFN Response and the Importance of the Model

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals with a significant socioeconomic impact. One of the issues related to this disease is the ability of its etiological agent, foot-and-mouth disease virus (FMDV), to persist in the organism of its hosts via underlying mechanisms that remain to be elucidated. The establishment of a virus–host equilibrium via protein–protein interactions could contribute to explaining these phenomena. FMDV has indeed developed numerous strategies to evade the immune response, especially the type I interferon response. Viral proteins target this innate antiviral response at different levels, ranging from blocking the detection of viral RNAs to inhibiting the expression of ISGs. The large diversity of impacts of these interactions must be considered in the light of the in vitro models that have been used to demonstrate them, some being sometimes far from biological systems. In this review, we have therefore listed the interactions between FMDV and the interferon response as exhaustively as possible, focusing on both their biological effect and the study models used.

The DEAD-box helicase Hlc regulates basal transcription and chromatin opening of stress-responsive genes

Stress-responsive genes are lowly transcribed under normal conditions and robustly induced in response to stress. The significant difference between basal and induced transcription indicates that the general transcriptional machinery requires a mechanism to distinguish each transcription state. However, what factors specifically function in basal transcription remains poorly understood. Using a classic model stress-responsive gene (Drosophila MtnA), we found that knockdown of the DEAD-box helicase Hlc resulted in a significant transcription attenuation of MtnA under normal, but not stressed, conditions. Mechanistically, Hlc directly binds to the MtnA locus to maintain the accessibility of chromatin near the transcriptional start site, which allows the recruitment of RNA polymerase II and subsequent MtnA transcription. Using RNA-seq, we then identified plenty of additional stress-responsive genes whose basal transcription was reduced upon knockdown of Hlc. Taken together, these data suggest that Hlc-mediated basal transcription regulation is an essential and widespread mechanism for precise control of stress-responsive genes.

DDX56 inhibits PRV replication through regulation of IFN-β signaling pathway by targeting cGAS

Pseudorabies virus (PRV) is an agent of Aujeszky's disease, and causes great economic losses to pig farming. Re-outburst of pseudorabies implies that new control measures are urgently needed. We show here that DDX56 possesses the ability to inhibit PRV replication in vitro, which may be an important factor for PRV infection. Overexpression of DDX56 inhibited PRV genomic DNA transcription and lower titers of PRV infection in PK15 cells, whereas down-regulation of the DDX56 expression had a promotion role on virus replication. Further study demonstrated that DDX56 exerted its proliferation-inhibitory effects of PRV through up-regulating cGAS-STING-induced IFN-β expression. Moreover, we found that DDX56 could promote cGAS expression and direct interaction also existed between DDX56 and cGAS. Based on this, DDX56-regulated IFN-β pathway may be targeted at cGAS. To verify this, down-regulated cGAS expression in DDX56 over-expression cells was performed. Results indicated that knockdown of cGAS expression could abrogate the inhibition role of DDX56 on PRV proliferation and weaken the effect of DDX56 on IFN-β expression. In addition, DDX56 played a promotion role in IRF3 phosphorylation and nucleus translocation. Altogether, our results highlight DDX56's antiviral role in PRV infection, and our findings contribute to a better understanding of host factors controlling PRV replication.

DExH/D-box helicases at the frontline of intrinsic and innate immunity against viral infections

DExH/D-box helicases are essential nucleic acid and ribonucleoprotein remodelers involved in all aspects of nucleic acid metabolism including replication, gene expression and post-transcriptional modifications. In parallel to their importance in basic cellular functions, DExH/D-box helicases play multiple roles in viral life cycles, with some of them highjacked by viruses or negatively regulating innate immune activation. However, other DExH/D-box helicases have recurrently been highlighted as direct antiviral effectors or as positive regulators of innate immune activation. Innate immunity relies on the ability of Pathogen Recognition Receptors to recognize viral signatures and trigger the production of interferons (IFNs) and pro-inflammatory cytokines. Secreted IFNs interact with their receptors to establish antiviral cellular reprogramming via expression regulation of the interferon-stimulated genes (ISGs). Several DExH/D-box helicases have been reported to act as viral sensors (DDX3, DDX41, DHX9, DDX1/DDX21/DHX36 complex), and others to play roles in innate immune activation (DDX60, DDX60L, DDX23). In contrast, the DDX39A, DDX46, DDX5 and DDX24 helicases act as negative regulators and impede IFN production upon viral infection. Beyond their role in viral sensing, the ISGs DDX60 and DDX60L act as viral inhibitors. Interestingly, the constitutively expressed DEAD-box helicases DDX56, DDX17, DDX42 intrinsically restrict viral replication. Hence, DExH/D-box helicases appear to form a multilayer network of primary and secondary factors involved in both intrinsic and innate antiviral immunity. In this review, we highlight recent findings on the extent of antiviral defences played by helicases and emphasize the need to better understand their immune functions as well as their complex interplay.

Foot-and-Mouth Disease Virus 3A Hijacks Sar1 and Sec12 for ER Remodeling in a COPII-Independent Manner

Positive-stranded RNA viruses modify host organelles to form replication organelles (ROs) for their own replication. The enteroviral 3A protein has been demonstrated to be highly associated with the COPI pathway, in which factors operate on the ER-to-Golgi intermediate and the Golgi. However, Sar1, a COPII factor exerting coordinated action at endoplasmic reticulum (ER) exit sites rather than COPI factors, is required for the replication of foot-and-mouth disease virus (FMDV). Therefore, further understanding regarding FMDV 3A could be key to explaining the differences and to understanding FMDV’s RO formation. In this study, FMDV 3A was confirmed as a peripheral membrane protein capable of modifying the ER into vesicle-like structures, which were neither COPII vesicles nor autophagosomes. When the C-terminus of 3A was truncated, it was located at the ER without vesicular modification. This change was revealed using mGFP and APEX2 fusion constructs, and observed by fluorescence microscopy and electron tomography, respectively. For the other 3A truncation, the minimal region for modification was aa 42–92. Furthermore, we found that the remodeling was related to two COPII factors, Sar1 and Sec12; both interacted with 3A, but their binding domains on 3A were different. Finally, we hypothesized that the N-terminus of 3A would interact with Sar1, as its C-terminus simultaneously interacted with Sec12, which could possibly enhance Sar1 activation. On the ER membrane, active Sar1 interacted with regions of aa 42–59 and aa 76–92 from 3A for vesicle formation. This mechanism was distinct from the traditional COPII pathway and could be critical for FMDV RO formation.

African Swine Fever Virus MGF360-14L Negatively Regulates Type I Interferon Signaling by Targeting IRF3

African swine fever (ASF) is a devastating infectious disease caused by African swine fever virus (ASFV). The ASFV genome encodes multiple structural and non-structural proteins that contribute to evasion of host immunity. In this study, we determined that the viral non-structural protein MGF360-14L inhibits interferon-β (IFN-β) promoter activity induced by cGAS-STING signaling. MGF360-14L was also found to downregulate expression of the IRF3 protein and promote its degradation through ubiquitin-meditated proteolysis. Moreover, MGF360-14L was shown to interact with and destabilize IRF3 by facilitating E3 ligase TRIM21-mediated K63-linked ubiquitination of IRF3. Overall, our study revealed that MGF360-14L promotes degradation of IRF3 through TRIM21, thereby inhibiting type I interferon production. These findings provide new insights into the mechanisms underlying ASFV immune evasion.

Global Phosphoproteomics Analysis of IBRS-2 Cells Infected With Senecavirus A

Phosphorylation is a widespread posttranslational modification that regulates numerous biological processes. Viruses can alter the physiological activities of host cells to promote virus particle replication, and manipulating phosphorylation is one of the mechanisms. Senecavirus A (SVA) is the causative agent of porcine idiopathic vesicular disease. Although numerous studies on SVA have been performed, comprehensive phosphoproteomics analysis of SVA infection is lacking. The present study performed a quantitative mass spectrometry-based phosphoproteomics survey of SVA infection in Instituto Biologico-Rim Suino-2 (IBRS-2) cells. Three parallel experiments were performed, and 4,520 phosphosites were quantified on 2,084 proteins. Gene Ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses showed that many phosphorylated proteins were involved in apoptosis and spliceosome pathways, and subcellular structure localization analysis revealed that more than half were located in the nucleus. Motif analysis of proteins with differentially regulated phosphosites showed that proline, aspartic acid, and glutamic acid were the most abundant residues in the serine motif, while proline and arginine were the most abundant in the threonine motif. Forty phosphosites on 27 proteins were validated by parallel reaction monitoring (PRM) phosphoproteomics, and 30 phosphosites in 21 proteins were verified. Nine proteins with significantly altered phosphosites were further discussed, and eight [SRRM2, CDK13, DDX20, DDX21, BAD, ELAVL1, PDZ-binding kinase (PBK), and STAT3] may play a role in SVA infection. Finally, kinase activity prediction showed 10 kinases’ activity was reversed following SVA infection. It is the first phosphoproteomics analysis of SVA infection of IBRS-2 cells, and the results greatly expand our knowledge of SVA infection. The findings provide a basis for studying the interactions of other picornaviruses and their mammalian host cells.

DDX56 antagonizes IFN-β production to enhance EMCV replication by inhibiting IRF3 nuclear translocation

DEAD (Asp-Glu-Ala-Asp)-box RNA helicases (DDX) play important roles in viral infection, either as cytosolic viral nucleic acids sensors or as essential host factors for viral replication. In this study, we identified DDX56 as a positive regulator for encephalomyocarditis virus (EMCV) replication. EMCV infection promotes DDX56 expression via its viral proteins, VP3 and 3C. We showed that DDX56 overexpression promotes EMCV replication whereas its loss dampened EMCV replication. Consequently, knockdown of DDX56 increases type I interferon (IFN) expression during EMCV infection. We also showed that DDX56 interrupts IFN regulatory factor 3 (IRF3) phosphorylation and its nucleus translocation by directly targeting KPNA3 and KPNA4 in an EMCV-triggered MDA5 signaling activation cascade leading to the blockade of IFN-β production. Overall, we showed that DDX56 is a novel negative regulator of EMCV-mediated IFN-β responses and that DDX56 plays a critical role in EMCV replication. These findings reveal a novel strategy for EMCV to utilize a host factor to evade the host innate immune response and provide us new insight into the function of DDX56.

Regulation of antiviral innate immune signaling and viral evasion following viral genome sensing

A harmonized balance between positive and negative regulation of pattern recognition receptor (PRR)-initiated immune responses is required to achieve the most favorable outcome for the host. This balance is crucial because it must not only ensure activation of the first line of defense against viral infection but also prevent inappropriate immune activation, which results in autoimmune diseases. Recent studies have shown how signal transduction pathways initiated by PRRs are positively and negatively regulated by diverse modulators to maintain host immune homeostasis. However, viruses have developed strategies to subvert the host antiviral response and establish infection. Viruses have evolved numerous genes encoding immunomodulatory proteins that antagonize the host immune system. This review focuses on the current state of knowledge regarding key host factors that regulate innate immune signaling molecules upon viral infection and discusses evidence showing how specific viral proteins counteract antiviral responses via immunomodulatory strategies.

Inhibition of MAVS Aggregation-Mediated Type-I Interferon Signaling by Foot-and-Mouth Disease Virus VP3

As a structural protein of the Foot-and-mouth disease virus (FMDV), VP3 plays a vital role in virus assembly and inhibiting the interferon (IFN) signal transduction to promote FMDV replication. Previous studies demonstrated that FMDV VP3 blocks the type-I IFN response by inhibiting the mRNA expression of the mitochondrial antiviral-signaling protein (MAVS); however, the underlying mechanism is poorly understood. Here, we describe the specificity of FMDV VP3 interaction with the transmembrane (TM) domain of MAVS as FMDV driven type-I IFN inhibitory mechanism for its effective replication. The TM domain of MAVS governs the mitochondria localization of MAVS, and it is a key factor in type-I IFN signaling transduction via MAVS aggregation. Thereby, the interaction of FMDV VP3 with the TM domain of MAVS leads to the inhibition of MAVS mitochondria localization, self-association, and aggregation, resulting in the suppression of type-I IFN response. Collectively, these results provide a clear understanding of a key molecular mechanism used by the FMDV VP3 for the suppression of IFN responses via targeting MAVS.

DDX21, a Host Restriction Factor of FMDV IRES-Dependent Translation and Replication

In cells, the contributions of DEAD-box helicases (DDXs), without which cellular life is impossible, are of utmost importance. The extremely diverse roles of the nucleolar helicase DDX21, ranging from fundamental cellular processes such as cell growth, ribosome biogenesis, protein translation, protein–protein interaction, mediating and sensing transcription, and gene regulation to viral manipulation, drew our attention. We designed this project to study virus–host interactions and viral pathogenesis. A pulldown assay was used to investigate the association between foot-and-mouth disease virus (FMDV) and DDX21. Further insight into the DDX21–FMDV interaction was obtained through dual-luciferase, knockdown, overexpression, qPCR, and confocal microscopy assays. Our results highlight the antagonistic feature of DDX21 against FMDV, as it progressively inhibited FMDV internal ribosome entry site (IRES) -dependent translation through association with FMDV IRES domains 2, 3, and 4. To subvert this host helicase antagonism, FMDV degraded DDX21 through its non-structural proteins 2B, 2C, and 3C protease (3C^pro). Our results suggest that DDX21 is degraded during 2B and 2C overexpression and FMDV infection through the caspase pathway; however, DDX21 is degraded through the lysosomal pathway during 3C^pro overexpression. Further investigation showed that DDX21 enhanced interferon-beta and interleukin-8 production to restrict viral replication. Together, our results demonstrate that DDX21 is a novel FMDV IRES trans-acting factor, which negatively regulates FMDV IRES-dependent translation and replication.

Human DDX56 protein interacts with influenza A virus NS1 protein and stimulates the virus replication

Influenza A viruses (IAV) are enveloped viruses carrying a single-stranded negative-sense RNA genome. Detection of host proteins having a relationship with IAV and revealing of the role of these proteins in the viral replication are of great importance in keeping IAV infections under control. Consequently, the importance of human DDX56, which is determined to be associated with a viral NS1 with a yeast two-hybrid assay, was investigated for IAV replication. The viral replication in knocked down cells for the DDX56 gene was evaluated. The NS1 was co-precipitated with the DDX56 protein in lysates of cells transiently expressing DDX56 and NS1 or infected with the viruses, showing that NS1 and DDX56 interact in mammalian cells. Viral NS1 showed a tendency to co-localize with DDX56 in the cells, transiently expressing both of these proteins, which supports the IP and two-hybrid assays results. The data obtained with in silico predictions supported the in vitro protein interaction results. The viral replication was significantly reduced in the DDX56-knockdown cells comparing with that in the control cells. In conclusion, human DDX56 protein interacts with the IAV NS1 protein in both yeast and mammalian cells and has a positive regulatory effect on IAV replication. However, the mechanism of DDX56 on IAV replication requires further elucidation.

Picornaviruses: A View from 3A

Picornaviruses are comprised of a positive-sense RNA genome surrounded by a protein shell (or capsid). They are ubiquitous in vertebrates and cause a wide range of important human and animal diseases. The genome encodes a single large polyprotein that is processed to structural (capsid) and non-structural proteins. The non-structural proteins have key functions within the viral replication complex. Some, such as 3D^pol (the RNA dependent RNA polymerase) have conserved functions and participate directly in replicating the viral genome, whereas others, such as 3A, have accessory roles. The 3A proteins are highly divergent across the Picornaviridae and have specific roles both within and outside of the replication complex, which differ between the different genera. These roles include subverting host proteins to generate replication organelles and inhibition of cellular functions (such as protein secretion) to influence virus replication efficiency and the host response to infection. In addition, 3A proteins are associated with the determination of host range. However, recent observations have challenged some of the roles assigned to 3A and suggest that other viral proteins may carry them out. In this review, we revisit the roles of 3A in the picornavirus life cycle. The 3AB precursor and mature 3A have distinct functions during viral replication and, therefore, we have also included discussion of some of the roles assigned to 3AB.

Virus-Host Interactions in Foot-and-Mouth Disease Virus Infection

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals, which has been regarded as a persistent challenge for the livestock industry in many countries. Foot-and-mouth disease virus (FMDV) is the etiological agent of FMD that can spread rapidly by direct and indirect transmission. FMDV is internalized into host cell by the interaction between FMDV capsid proteins and cellular receptors. When the virus invades into the cells, the host antiviral system is quickly activated to suppress the replication of the virus and remove the virus. To retain fitness and host adaptation, various viruses have evolved multiple elegant strategies to manipulate host machine and circumvent the host antiviral responses. Therefore, identification of virus-host interactions is critical for understanding the host defense against virus infections and the pathogenesis of the viral infectious diseases. This review elaborates on the virus-host interactions during FMDV infection to summarize the pathogenic mechanisms of FMD, and we hope it can provide insights for designing effective vaccines or drugs to prevent and control the spread of FMD and other diseases caused by picornaviruses.

Foot-and-mouth disease virus VP1 target the MAVS to inhibit type-I interferon signaling and VP1 E83K mutation results in virus attenuation

VP1, a pivotal capsid protein encoded by the foot-and-mouth disease virus (FMDV), plays an important role in receptor-mediated attachment and humoral immune responses. Previous studies show that amino acid changes in the VP1 protein of cell culture-adapted strains of FMDV alter the properties of the virus. In addition, FMDV VP1 modulates host IFN signal transduction. Here, we examined the ability of cell culture-adapted FMDV VP1(83K) and wild-type FMDV VP1(83E) to evade host immunity by blocking mitochondrial antiviral signaling protein (MAVS)/TNF Receptor Associated Factor 3 (TRAF3) mediated cellular innate responses. Wild-type FMDV VP1(83E) interacted specifically with C-terminal TRAF3-binding site within MAVS and this interaction inhibited binding of TRAF3 to MAVS, thereby suppressing interferon-mediated responses. This was not observed for cell culture-adapted FMDV VP1(83K). Finally, chimeric FMDV harboring VP1(83K) showed very low pathogenicity in pigs. Collectively, these data highlight a critical role of VP1 with respect to suppression of type-I IFN pathway and attenuation of FMDV by the E83K mutation in VP1.

Foot-and-Mouth disease (FMD), a highly contagious viral disease of cloven-hoofed animals, causes huge economic losses. To generate a FMD vaccine, cell culture-adapted strains of FMDV that show improved growth properties and allow repeated passage are needed. Generally, adaptation of field-isolated FMDV is accompanied by changes in viral properties, including amino acid mutations. A VP1 E83K mutation in cell culture-adapted FMDV was identified previously; here, we examined the impact of VP1 E83K on virus pathogenicity and type-I IFN pathway. Cell culture-adapted FMDV O1 Manisa, and highly virulent strain of O/Andong/SKR/2010, acquired the E83K mutation in the VP1 protein, which attenuated the virus via disposing VP1 mediate negative regulation ability of host cellular IFN responses. The data suggest a rational approach to viral propagation in cell culture and virus attenuation, which could be utilized for future development of FMDV vaccines.

Advances in Foot-and-Mouth Disease Virus Proteins Regulating Host Innate Immunity

Foot-and-mouth disease (FMD) is a highly contagious disease that affects cloven-hoofed animals such as pigs, cattle, and sheep. The disease is caused by the foot-and-mouth disease virus (FMDV) which has a non-enveloped virion with icosahedral symmetry that encapsulates a positive-sense, single-stranded RNA genome of ∼8.4 kb. FMDV infection causes obvious immunosuppressive effects on the host. In recent years, studies on the immunosuppressive mechanism of FMDV have become a popular topic. In addition, studies have shown that many FMDV proteins are involved in the regulation of host innate immunity and have revealed mechanisms by which FMDV proteins mediate host innate immunity. In this review, advances in studies on the mechanisms of interaction between FMDV proteins and host innate immunity are summarized to provide a comprehensive understanding of FMDV pathogenesis and the theoretical basis for FMD prevention and control.

Molecular Mechanisms of Immune Escape for Foot-and-Mouth Disease Virus

Foot-and-mouth disease virus (FMDV) causes a highly contagious vesicular disease in cloven-hoofed livestock that results in severe consequences for international trade, posing a great economic threat to agriculture. The FMDV infection antagonizes the host immune responses via different signaling pathways to achieve immune escape. Strategies to escape the cell immune system are key to effective infection and pathogenesis. This review is focused on summarizing the recent advances to understand how the proteins encoded by FMDV antagonize the host innate and adaptive immune responses.