Xuexia Wen

Porcine Rotavirus ( PoRV ), a major pathogen causing diarrhea in piglets and significant economic losses, exhibits high genotypic diversity and poses a risk of cross-species transmission. PoRV infection is initiated by the interaction of its outer capsid proteins, VP4 and VP7, with multiple host cell receptors (e.g., sialic acids, integrins), triggering complex processes of endocytosis and membrane penetration that ultimately lead to enterocyte dysfunction and diarrhea. Diverse immune evasion strategies have been evolved by PoRV , among which the host interferon responses and cellular protein synthesis are both suppressed by nonstructural proteins including NSP1 and NSP3. Host defense relies on innate immunity (e.g., RIG-I/MDA-5 and TLR3 signaling pathways) and adaptive immunity centered on virus-specific T cells. Epidemiological surveillance indicates the dominance of RVA genotypes in swine populations worldwide. Furthermore, genetic reassortment events between porcine and human strains underscore a significant zoonotic transmission risk, which poses a significant challenge to public health and compromises the efficacy of existing vaccines. Current control measures rely on biosecurity management and vaccination to enhance maternal antibody transfer. However, given the high genetic variability of the virus, the development of novel broad-spectrum vaccine platforms, such as those based on virus-like particles (VLPs) or multi-epitope antigens, is urgently needed. In this review, current research progress is systematically integrated to advance the understanding of PoRV -host interactions and provide evidence-based guidance for the development of effective control strategies.

Senecavirus A (SVA) is a newly emerging picornavirus associated with porcine idiopathic vesicular disease and sudden death in newborn piglets. Currently, no specific vaccines or drugs are available against SVA, highlighting the importance of investigating the immunological characteristics of its key proteins. The VP1 protein of SVA exhibits strong immunogenicity and high sequence conservation, and it is indispensable to the viral life cycle. In the present study, a monoclonal antibody (mAb) against VP1 was generated. A series of truncated VP1 proteins was then expressed to precisely map the epitope recognized by this mAb. The minimal reactive unit was identified as ¹⁶DTDFSGELA²⁴. Homology analysis further revealed that this epitope is conserved among different SVA isolates deposited in GenBank. Moreover, AlphaFold prediction, along with PyMOL (Version 3.0.3) and GETAREA analyses, reveals that this epitope resides in the α-helix and loop regions of the three-dimensional structure of the VP1 protein and is surface-exposed. Collectively, these findings indicate that the mAb and its recognized epitope represent valuable tools for investigating SVA etiology and VP1 protein function.

Seneca Valley virus (SVV) infection gives rise to severe vesicular diseases in pigs, presenting a substantial threat to the global swine industry. The redox imbalance resulting from oxidative stress is an essential pathogenic mechanism during viral infections. Nevertheless, the regulatory mechanisms of oxidative stress by viral and host factors during SVV infection remain elusive. In this study, we discovered that SVV elicited cellular oxidative stress through the induction of reactive oxygen species production and the suppression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway. Our findings indicated that the overexpression of Nrf2/HO-1 exerted a remarkable anti-SVV effect. Conversely, the inhibition of Nrf2/HO-1 expression facilitated the proliferation of SVV. HO-1 metabolic products carbon monoxide and biliverdin inhibit SVV replication. HO-1 promotes type I interferon response and interferon-stimulated gene expressions, which contribute to its antiviral mechanism. Furthermore, our findings reveal that the SVV 3C proteinase targets the Nrf2/HO-1 axis for degradation via caspase pathway, thereby promoting viral replication. Collectively, these results clarify the convoluted molecular mechanisms by which SVV weakens the host’s antioxidant defense system and suggest potential targets for therapeutic interventions regarding SVV infections. IMPORTANCE: Nrf2 is a crucial redox regulator responsible for initiating the expression of downstream antioxidant genes, including HO-1 and superoxide dismutase. HO-1, an enzyme induced by stress, performs protective roles through the conversion of heme into carbon monoxide, biliverdin, and iron. Nevertheless, the function of Nrf2/HO-1 during Seneca Valley virus (SVV) infection is yet to be clearly defined. In this study, we showed that SVV infection led to a reduction in the expression of Nrf2/HO-1, and the overexpression of Nrf2/HO-1 induced a potent anti-SVV effect. SVV 3C proteinase promoted the caspase-dependent degradation of Nrf2/HO-1. As a result, it attenuated the cell's ability to resist oxidative stress and counteracted the antiviral function of Nrf2/HO-1. Our research further uncovered a novel mechanism through which SVV eludes the host's antiviral effects by disrupting cellular redox balance, offering important targets for preventing and controlling SVV infection.

The Seneca Valley virus (SVV) is an emerging novel etiological agent that triggers vesicular stomatitis in pigs. SVV leads to considerable financial detriment to the global swine industry. Availability of expeditious, simple, and precise detection techniques would aid in the diagnosis and control of Seneca Valley disease. In this study, we developed a novel SVV detection assay based on reverse transcription recombinase polymerase amplification (RT-RPA)/CRISPR-Cas13a. This technique can specifically identify SVV with no cross-reactivity with other viruses, such as the porcine reproductive and respiratory syndrome virus, pseudorabies virus, classical swine fever virus, and foot-and-mouth disease virus. It boasts a detection threshold as sensitive as 2.43 copies/μL, matching the proficiency of reverse transcriptase quantitative PCR in clinical diagnostics. The streamlined RT-RPA/CRISPR-Cas13a assay for SVV minimizes procedural complexity and the likelihood of contamination. Integrating this method with nucleic acid acquisition via nucleic acid releaser enables a turnaround time of only 40 min from sample acquisition to result determination, underscoring its suitability for on-site diagnostics and affirming its role as a robust instrument for the monitoring and detection of SVV.

Seneca Valley virus (SVV) is an emerging pathogen that causes severe vesicular diseases in swine, posing a significant threat to the global pork industry. DNA and RNA viruses manipulate the host DNA damage response (DDR) to modulate cellular machinery and facilitate their life cycles. However, the interaction between the host DDR and SVV infection remains unexplored. Here, we aimed to comprehensively investigate the DDR and DNA repair signaling pathways during SVV infection. We found that SVV infection causes DNA damage and triggers distinct DDR signaling pathways, including ataxia telangiectasia-mutated (ATM) kinase, ATM-Rad3-related kinase, and DNA-dependent protein kinase. However, it failed to induce the formation of γH2AX and 53BP1 foci, resulting in unrepaired DNA damage. Furthermore, we found that SVV 2B and 2C proteins can activate DDR signaling pathways and impair DNA repair. SVV-induced DDR triggered NF-κB signaling accompanied by upregulation of pro-inflammatory cytokines, as evidenced by the inhibition of ATM kinase, abolished SVV-induced NF-κB activation. Inhibition of the ATM pathway attenuated SVV replication. These findings expand our understanding of host DDR manipulation during viral infection and provide crucial insights into a novel mechanism exploited by SVV to regulate the inflammatory response for efficient replication. IMPORTANCE: DDR is a cellular machinery that senses and repairs host DNA lesions to maintain genome integrity. Viruses have evolved diverse strategies to manipulate host DDR for replicative efficiency. SVV is an emerging virus that causes vesicular diseases in pigs and severely threatens the swine industry. However, the interaction between SVV and DDR remains unclear. Here, we found that SVV modulates host DDR pathways to facilitate viral replication. Our results demonstrated that SVV infection causes DNA damage, activates ATM-mediated DNA double-strand break response, and impedes DNA repair. SVV 2B and 2C proteins induced DNA damage and activated the DDR pathway while impairing repair mechanisms. This study revealed a fine-tuned molecular mechanism of SVV-modulated DDR that contributes to viral replication, facilitating deeper insight into SVV replication.

Seneca Valley virus (SVV) is a newly identified pathogen that poses a notable threat to the global pig industry. SVV has evolved multiple strategies to evade host antiviral innate immune responses. However, the underlying molecular mechanisms have not yet been fully elucidated. Histone deacetylases (HDACs) have been shown to function as host antiviral innate immune factors. In this study, we examined the mechanisms underlying SVV evasion of host innate immunity and found that SVV infection induced degradation and cleavage of HDAC4. Ectopic expression of HDAC4 suppressed SVV replication, whereas siRNA-mediated knockdown of HDAC4 enhanced SVV replication. Further studies showed that the viral 3C protease (3C ^pro ) degraded HDAC4 in a protease activity- and caspase pathway-dependent manner. In addition, 3C ^pro cleaved HDAC4 at Q599, which blocked its ability to limit viral replication. We also found that HDAC4 interacted with the SVV viral RNA-dependent RNA polymerase 3D and induced its proteasomal degradation. The cleaved HDAC4 products did not block SVV replication or induce 3D degradation and did not induce type I interferon (IFN) activation and expression of IFN-stimulated genes (ISGs). Collectively, these findings identified HDAC4 as an antiviral factor with effects against SVV infection and provided mechanistic insights into how SVV 3C ^pro antagonizes its function, which has implications for viral evasion of innate immunity. IMPORTANCE: Seneca Valley virus (SVV) is an emerging pathogen that causes vesicular disease in pigs and poses a threat to the pork industry. Histone deacetylases (HDACs) are important in the regulation of innate immunity. However, little is known about their roles in SVV infection. Our results revealed HDAC4 as an anti-SVV infection factor that targets the viral RNA-dependent RNA polymerase, 3D, for degradation. The SVV proteinase 3Cpro targets HDAC4 for degradation and cleavage, and cleavage of HDAC4 abrogated its antiviral effect. HDAC4 promotes type I interferon (IFN) signaling, and SVV 3Cpro-mediated cleavage of HDAC4 antagonized induction of type I IFN and interferon-stimulated genes (ISGs). Our findings reveal a novel molecular mechanism by which SVV 3Cpro counteracts type I IFN signaling by targeting HDAC4.

Seneca Valley virus (SVV), a new member of Picornaviridae, causes idiopathic vesicular symptoms in pregnant sows and acute death in neonatal piglets, considerably damaging the swine industry. The viral protease 3C (3C^pro) cleaves host immune-related molecules to create a favorable environment for viral replication. In this study, we found that mRNA decapping enzyme 1A (DCP1A) is a novel antiviral effector against SVV infection that targets 3D viral RNA-dependent RNA polymerase for OPTN-mediated autophagic degradation. To counteract this effect, SVV 3C^pro targets DCP1A for cleavage at glutamine 343 (Q343), resulting in the cleaved products DCP1A (1–343) and DCP1A (344–580), which lose the ability to restrict SVV replication. In contrast, the 3C cleavage-resistant DCP1A-Q343A mutant exhibited stronger antiviral effects than the wild-type DCP1A. Additionally, the degradation of the viral 3D protein targeted by DCP1A was abolished after its cleavage by SVV 3C^pro. In conclusion, our study demonstrated that SVV 3C^pro is a pivotal ISG antagonist that cleaves DCP1A. These results offer novel insight into how viruses evade host immunity.

Avian influenza virus (AIV) causes huge losses to the global poultry industry and poses a threat to humans and other mammals. Fast, sensitive, and portable diagnostic methods are essential for efficient avian influenza control. Here, a clustered regularly interspaced short palindromic repeats (CRISPR)-Cas13a based platform was developed to detect AIV. This novel method was developed to specifically detect H1–H16 subtypes of AIV with fluorescence and lateral flow-based readouts and exhibited no cross-reactivity with Newcastle disease virus, avian infectious bronchitis virus, or infectious bursal disease virus. The limit of detection was determined to be 69 and 690 copies/μL using fluorescence and lateral flow as readouts, respectively. The developed assay exhibited 100% consistency with quantitative real-time polymerase chain reaction in detecting clinical samples. The heating of unextracted diagnostic samples to obliterate nuclease treatment was introduced to detect viral RNA without nucleic acid extraction. Single-step optimization was used to perform reverse transcription, recombinase polymerase amplification, and CRISPR-Cas13a detection in a tube. These advances resulted in an optimized assay that could specifically detect AIV with simplified procedures and reduced contamination risk, highlighting the potential to be used in point-of-care testing.

Porcine reproductive and respiratory syndrome virus (PRRSV), the causative agent of PRRS, has two distinct and highly diverse genotypes (genotype 1 and genotype 2) in the field. Accurate diagnosis and differentiation of the two genotypes of PRRSV are critical to the effective prevention and control of PRRS. The non-structural protein 10 (Nsp10) plays a vital role in viral replication and is one of the most conserved proteins of PRRSV, thus constituting a good candidate for PRRSV diagnosis. In this study, we generated a monoclonal antibody (mAb) 4D9 against Nsp10 by immunizing BALB/c mice with purified recombinant Nsp10 expressed by an Escherichia coli system. Through fine epitope mapping of mAb 4D9 using a panel of eukaryotic expressed polypeptides with GFP-tags, we identified the motif 286AIQPDYRDKL295 as the minimal unit of the linear B-cell epitope recognized by mAb 4D9. Protein sequence alignment indicated that 286AIQPDYRDKL295 was highly conserved in genotype 2 PRRSV strains, whereas genotype 1 PRRSV strains had variable amino acids in this motif. Furthermore, a mutant of the motif carrying two constant amino acids of genotype 1 PRRSV, Cys290 and Glu293, failed to react with mAb 4D9. More importantly, the mAb 4D9 could differentiate genotype 2 PRRSV strains from genotype 1 PRRSV strains using Western blotting and immunofluorescence analysis. Our findings suggest that Nsp10-specific mAb generated in this study could be a useful tool for basic research and may facilitate the establishment of diagnostic methods to discriminate between genotype 1 and genotype 2 PRRSV infection.