Whole-genome analysis of resilience based on the stability of reproduction performance during a porcine reproductive and respiratory syndrome virus outbreak in sows.

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is a very prevalent viral pathogen that can induce reproductive failure in infected sows. PRRSV infection can result in smaller litters, foetal death, late-term abortions and retarded growth of infected piglets. Not all sows respond equally to the infection partly due to genetic factors. In this study, we aimed to characterise the genetic variability of pig resilience to PRRSV infection by using a stability reproductive performance (SRP) index as a proxy of resilience. By comparing reproductive data from 183 sows, we selected 48 sows with extreme SRP values, measured as the difference in piglets lost at farrowings before and during a PRRSV outbreak. Short-read DNA fragments were sequenced from selected sows using an Illumina platform. The analysis of whole-genome sequencing information identified 16 genome regions associated with the SRP classification (cut-off P-value < 10-6). Functional evaluation of the positional candidates by gene-ontology identifiers and their participation in biological pathways were used to identify genes involved in virus entry and replication (vimentin, RAC1 and OAZ2) but also in immune responses from the host (IRF1, and IL4, IL5 and IL13). Importantly, genes related to chemokines, extracellular proteins and cell-to-cell junction integrity might contribute to placental microseparations, facilitating the trafficking of viral particles from sow to foetus that takes place during the pathogenesis of transplacental PRRSV infection. However, given the small number of animals in the study, these results shall need to be validated in larger populations.

Molecular mechanism of autophagy in porcine reproductive and respiratory syndrome virus infection.

Porcine reproductive and respiratory syndrome virus (PRRSV), a significant pathogen affecting the swine industry globally, has been shown to manipulate host cell processes, including autophagy, to facilitate its replication and survival within the host. Autophagy, an intracellular degradation process crucial for maintaining cellular homeostasis, can be hijacked by viruses for their own benefit. During PRRSV infection, autophagy plays a complex role, both as a defense mechanism of the host and as a tool exploited by the virus. This review explores the current understanding of the molecular mechanisms underlying autophagy induction under PRRSV infection, its impact on virus replication, and the potential implications for viral pathogenesis and antiviral strategies. By synthesizing the latest research findings, this article aims to enhance our understanding of the intricate relationship between autophagy and PRRSV, paving the way for novel therapeutic approaches against this swine pathogen.

Transcriptional kinetics of NADC34-like porcine reproductive and respiratory syndrome virus during cellular infection.

NADC34-like porcine reproductive and respiratory syndrome virus (PRRSV) employs complex strategies to synthesize subgenomic RNAs (sgRNAs); however, their plasticity and temporal dynamics remain largely unexplored. Using next-generation sequencing (NGS), we examined the high-resolution landscape of the PRRSV subgenome, highlighting considerable heterogeneity in temporal kinetics and transcriptional control and revealing extensive coordination between TRSL-dependent and TRSL-independent sgRNAs. In addition, a comprehensive re-annotation of transcription regulatory sequence (TRS) locations was conducted, clarifying that their usage involved canonical, alternative, and non-canonical splicing events for annotated genes. These insights emphasize that the coding of genetic material in PRRSV is far more intricate than previously anticipated. Collectively, the altered sgRNA phenotype offers distinctive insights into PRRSV transcription and gives additional impetus for mining the functional short- and long-range RNA-RNA interactome at active viral replication sites.

The first report of porcine parvovirus 8 (PPV8) on the American continent is associated with pigs in Colombia with porcine respiratory disease.

Seven novel porcine parvoviruses (PPV2 to PPV8) have been discovered in the last two decades. The last one reported was PPV8 in China in 2022, which was proposed to be a member of the genus Protoparvovirus. Here, we report the first detection of PPV8 outside China - in two provinces from Colombia. Six out of 146 (4.1%) pigs showing porcine respiratory disease (PRD) tested positive for PPV8. Sequencing and phylogenetic analysis of two Colombian PPV8 isolates (GenBank database accession numbers PP335559 and PP335560) showed them to be members of the genus Protoparvovirus. Furthermore, PPV8 was detected in coinfections with porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV), which are associated with PRD.

miR-451-targeted PSMB8 promotes PRRSV infection by degrading IRF3.

Porcine respiratory and reproductive syndrome (PRRS) is one of the most devastating infectious diseases of pigs, causing reproductive failures in sows and severe respiratory symptoms in piglets and growing pigs. MicroRNAs (miRNAs) are reported to play an essential role in virus-host interactions. In this study, we demonstrated that miR-451 enhanced type I interferon (IFN-I) production through targeting proteasome subunit ß8 (PSMB8), therefore restricting PRRS virus (PRRSV) replication. We showed that the expression of PSMB8 was upregulated by PRRSV infection, and knockdown of PSMB8 inhibited PRRSV replication by promoting IFN-I production. Moreover, we demonstrated that PSMB8 interacted with the regulatory domain of IRF3 to mediate K48-linked polyubiquitination and degradation of IRF3. Also, importantly, we showed that PSMB8, as a target gene of miR-451, negatively regulated IFN-I production by promoting IRF3 degradation, which is a previously unknown mechanism for PSMB8 to modulate innate immune responses. IMPORTANCE: Porcine respiratory and reproductive syndrome virus (PRRSV), as a huge threat to the swine industry, is a causative agent that urgently needs to be solved. The dissecting of PRRSV pathogenesis and understanding of the host-pathogen interaction will provide insights into developing effective anti-PRRSV strategies. In this study, we showed that miR-451 dramatically inhibited PRRSV replication by targeting proteasome subunit ß8 (PSMB8), a subunit of the immunoproteasome. Mutation of PSMB8 is often related to autoinflammatory diseases due to the elevated IFN production. We revealed that PSMB8 downregulated IFN production by promoting IRF3 degradation. In addition, we showed that PRRSV infection upregulated PSMB8 expression. Taken together, our findings reveal that miR-451 is a negative regulator of PRRSV replication, and PSMB8, a target gene of miR-451, negatively regulates IFN-I production by promoting IRF3 degradation, which is a previously unknown mechanism for PSMB8 to regulate innate immune responses.

The 5'UTR of porcine reproductive and respiratory syndrome virus strain JXwn06 harbors a uORF that regulates cellular inflammation.

The 5' untranslated region (5'UTR) of many positive-stranded RNA viruses contain functional regulatory sequences. Here, we show that the porcine reproductive and respiratory syndrome virus (PRRSV), a member of arteriviruses, harbors small upstream open reading frames (uORFs) in its 5'UTR. Bioinformatics analysis shows that this feature is relatively well conserved among PRRSV strains and Arteriviridae. We also identified a uORF, namely uORF2, in the PRRSV strain JXwn06, that possesses translational activity and exerts a suppressive effect on the expression of the primary ORF evidenced by in vitro reporter assays. We tested its importance via reverse genetics by introducing a point mutation into the PRRSV infectious cDNA clone to inactivate the start codon of uORF2. The recovered mutant virus Mut2 surprisingly replicated to the same level as the wild-type virus (WT), but induced a higher level of inflammatory cytokines (e.g., TNF-α, IL-1ß, and IL-6) both in vitro and in animal experiments, correlating well with more severe lung injury and higher death rate. In line with this, over-expression of uORF2 in transfected cells significantly inhibited poly(I:C)-induced expression of inflammatory cytokines. Together, our data support the idea that uORF2 encodes a novel, functional regulator of PRRSV virulence despite of its short size. IMPORTANCE: PRRSV has remained a major challenge to the world swine industry, but we still do not know much about its biology and pathogenesis. Here, we provide evidence to show that the 5'UTR of PRRSV strain JXwn06 harbors a functional uORF that has the coding capacity and regulates induction of inflammation as demonstrated by in vitro assays and animal experiment. The findings reveal a novel viral factor that regulates cellular inflammation and provide insight into the understanding of PRRSV pathogenesis.

Knock down of transforming growth factor beta improves expressions of co-stimulatory molecules, type I interferon-regulated genes, and pro-inflammatory cytokine in PRRSV-inoculated monocyte-derived macrophages.

Porcine reproductive and respiratory syndrome virus (PRRSV) induces a poor innate immune response following infection. This study evaluates the effects of transforming growth factor beta 1 (TGFß1) up-regulated by PRRSV on gene expressions of co-stimulatory molecules, type I interferon (IFN), type I IFN-regulated genes (IRGs), pattern recognition receptors, and pro-inflammatory cytokines in PRRSV-inoculated monocyte-derived macrophages (MDMs). Phosphorothioate-modified antisense oligodeoxynucleotides (AS ODNs) specific to various regions of porcine TGFß1 mRNA were synthesized, and those specific to the AUG region efficiently knockdown TGFß1 mRNA expression and protein translation. Transfection of TGFßAS ODNs in MDMs inoculated with either classical PRRSV-2 (cPRRSV-2) or highly pathogenic PRRSV-2 (HP-PRRSV-2) significantly reduced TGFß1 mRNA expression and significantly increased mRNA expressions of CD80, CD86, IFNß, IRGs (i.e. IFN regulatory factor 3 (IRF3), IRF7, myxovirus resistance 1, osteopontin, and stimulator of IFN genes), Toll-like receptor 3, and tumor necrosis factor-alpha. Transfection of TGFßAS ODNs in MDMs inoculated with HP-PRRSV-2 also significantly increased mRNA expressions of IFNα, IFNγ, and 2'-5'-oligoadenylate synthetase 1. The quantity of PRRSV-2 RNA copy numbers was significantly reduced in MDMs transfected with TGFßAS ODNs as compared to untransfected MDMs. Recombinant porcine TGFß1 (rTGFß1) and recombinant porcine IFNα (rIFNα) sustained and reduced the yields of PRRSV-2 RNA copy numbers in PRRSV-2 inoculated MDMs, respectively. These findings demonstrate a strategy of PRRSV for innate immune suppression via an induction of TGFß expression. These findings also suggest TGFß as a potential parameter that future PRRSV vaccine and vaccine adjuvant candidates should take into consideration.

Enhancing the understanding of coinfection outcomes: Impact of natural atypical porcine pestivirus infection on porcine reproductive and respiratory syndrome in pigs.

Atypical porcine pestivirus (APPV) is a novel member of the Pestivirus genus detected in association with congenital tremor (CT) type A-II outbreaks and from apparently healthy pigs, both as singular infection and as part of multi-pathogen infections. 'Classical' pestiviruses are known to cause immunosuppression of their host, which can increase susceptibility to secondary infections, severely impacting health, welfare, and production. To investigate APPV's effect on the host's immune system and characterise disease outcomes, 12 piglets from a natural APPV CT type A-II outbreak were experimentally infected with porcine reproductive and respiratory syndrome virus (PRRSV), a significant porcine pathogen. Rectal temperatures indicating febrile responses, viremia and viral-specific humoral and cellular responses were assessed throughout the study. Pathological assessment of the lungs and APPV-PRRSV co-localisation within the lungs was performed at necropsy. Viral co-localisation and pathological assessment of the lungs (Immunohistochemistry, BaseScope in situ hybridisation) were performed post-mortem. APPV status did not impact virological or immunological differences in PRRSV-infected groups. However, significantly higher rectal temperatures were observed in the APPV+ve/PRRSV+ve group over four days, indicating APPV increased the febrile response. Significant differences in the lung consolidation of the apical and intermediate lobes were also present, suggesting that APPV co-infection may augment lung pathology.

PRRSV hijacks DDX3X protein and induces ferroptosis to facilitate viral replication.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a severe disease with substantial economic consequences for the swine industry. The DEAD-box helicase 3 (DDX3X) is an RNA helicase that plays a crucial role in regulating RNA metabolism, immunological response, and even RNA virus infection. However, it is unclear whether it contributes to PRRSV infection. Recent studies have found that the expression of DDX3X considerably increases in Marc-145 cells when infected with live PRRSV strains Ch-1R and SD16; however, it was observed that inactivated viruses did not lead to any changes. By using the RK-33 inhibitor or DDX3X-specific siRNAs to reduce DDX3X expression, there was a significant decrease in the production of PRRSV progenies. In contrast, the overexpression of DDX3X in host cells substantially increased the proliferation of PRRSV. A combination of transcriptomics and metabolomics investigations revealed that in PRRSV-infected cells, DDX3X gene silencing severely affected biological processes such as ferroptosis, the FoxO signalling pathway, and glutathione metabolism. The subsequent transmission electron microscopy (TEM) imaging displayed the typical ferroptosis features in PRRSV-infected cells, such as mitochondrial shrinkage, reduction or disappearance of mitochondrial cristae, and cytoplasmic membrane rupture. Conversely, the mitochondrial morphology was unchanged in DDX3X-inhibited cells. Furthermore, silencing of the DDX3X gene changed the expression of ferroptosis-related genes and inhibited the virus proliferation, while the drug-induced ferroptosis inversely promoted PRRSV replication. In summary, these results present an updated perspective of how PRRSV infection uses DDX3X for self-replication, potentially leading to ferroptosis via various mechanisms that promote PRRSV replication.

Assessing the antiviral activity of antimicrobial peptides Caerin1.1 against PRRSV in Vitro and in Vivo.

The Porcine reproductive and respiratory syndrome (PRRS) causes severe financial losses to the global swine industry. Due to continuous virus evolution, the protection against the PRRS provided by current vaccines is limited. In order to find new antiviral strategies, this study investigated the antiviral potential of antimicrobial peptides (AMPs) against PRRSV. Given the diversity of PRRSV strains and the limited effectiveness of existing vaccines in controlling PRRSV, this study evaluated the inhibitory effects of KLAK, Cecropin B, Piscidin1, and Caerin1.1 on 3 strains of PRRSV (lineage 5 classical strain, lineage 8 highly pathogenic strain, and lineage 1 NADC30-like strain). Caerin1.1 exhibited significant dose-dependent antiviral activity, with an effective concentration (EC50) of 7.5 µM. Caerin1.1 effectively inhibited PRRSV replication when added before or in early infection but showed reduced effectiveness when added in late infection, indicating its potential involvement in targeting early transcription mechanisms of viral RNA polymerase and significantly upregulating cytokine gene expression. In the NADC30 strain-based animal infection model, Caerin1.1 treatment significantly reduced lung viral loads and inflammation in the lungs of PRRSV-infected pigs, with a mortality rate of 0 % (0/5) in the treated group compared to 66.67 % (4/6) in the untreated group, indicating a reduction in the mortality rate. Additionally, compared with the untreated group, the Caerin1.1-treated group showed significant improvements, such as lighter fever, more daily weight gain, less clinical symptoms, less viral load in blood, and less virus oral shedding (P < 0.05). These findings reveal the potential of antimicrobial peptides as PRRSV therapeutic agents and suggest that Caerin1.1 is a promising candidate for a novel anti-PRRSV drug.

Research progress on the pattern recognition receptors involved in porcine reproductive and respiratory syndrome virus infection.

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically devastating infectious diseases of pigs globally. The pathogen, porcine reproductive and respiratory syndrome virus (PRRSV), is an enveloped positive-stranded RNA virus, which is considered to be the key triggers for the activation of effective innate immunity through pattern recognition receptor (PRR)-dependent signaling pathways. Toll-like receptors (TLRs), RIG-I-like receptors (RLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs) and Cytoplasmic DNA receptors (CDRs) are used as PRRs to identify distinct but overlapping microbial components. The innate immune system has evolved to recognize RNA or DNA molecules from microbes through pattern recognition receptors (PRRs) and to induce defense response against infections, including the production of type I interferon (IFN-I) and inflammatory cytokines. However, PRRSV is capable of continuous evolution through gene mutation and recombination to evade host immune defenses and exploit host cell mechanisms to synthesize and transport its components, thereby facilitating successful infection and replication. This review presents the research progress made in recent years in the study of these PRRs and their associated adapters during PRRSV infection.

PRRSV infection facilitates the shedding of soluble CD163 to induce inflammatory responses.

Porcine reproductive and respiratory syndrome (PRRS), which poses substantial threats to the global pig industry, is primarily characterized by interstitial pneumonia. Cluster of differentiation 163 (CD163) is the essential receptor for PRRSV infection. Metalloproteinase-mediated cleavage of CD163 leads to the shedding of soluble CD163 (sCD163), thereby inhibiting PRRSV proliferation. However, the exact cleavage site in CD163 and the potential role of sCD163 in inflammatory responses during PRRSV infection remain unclear. Herein, we found that PRRSV infection increased sCD163 levels, as demonstrated in primary alveolar macrophages (PAMs), immortalized PAM (IPAM) cell lines, and sera from PRRSV-infected piglets. With LC-MS/MS, Arg-1041/Ser-1042 was identified as the cleavage site in porcine CD163, and an IPAM cell line with precise mutation at the cleavage site was constructed. Using the precisely mutated IPAM cells, we found that exogenous addition of sCD163 protein promoted inflammatory responses, while mutation at the CD163 cleavage site suppressed inflammatory responses. Consistently, inhibition of sCD163 using its neutralizing antibodies reduced PRRSV infection-triggered inflammatory responses. Importantly, sCD163 promoted cell polarization from M2 to M1 phenotype, which in turn facilitated inflammatory responses. Taken together, our findings identify sCD163 as a novel proinflammatory mediator and provide valuable insights into the mechanisms underlying the induction of inflammatory responses by PRRSV infection.

PRRSV NSP1α degrades TRIM25 through proteasome system to inhibit host antiviral immune response.

Porcine reproductive and respiratory syndrome (PRRS) is the most economically significant disease caused by porcine reproductive and respiratory syndrome virus (PRRSV). Type I interferon (IFN) induces a large number of interferon-stimulated genes (ISGs) expression to inhibit PRRSV infection. To survive in the host, PRRSV has evolved multiple strategies to antagonize host innate immune response. Previous studies have reported that PRRSV N protein decreases the expression of TRIM25 and TRIM25-mediated RIG-I ubiquitination to suppress IFN-ß production. However, whether other PRRSV proteins inhibit the antiviral function of TRIM25 is less well understood. In this study, we first found that PRRSV NSP1α decreased ISGylation of TRIM25. Meanwhile, NSP1α significantly suppressed TRIM25-mediated IFN-ß production to promote PRRSV replication. Further studies demonstrated that PRRSV NSP1α reduced the protein level of TRIM25 in proteasome system but did not regulate the transcription level of TRIM25. In addition, the function of NSP1α in TRIM25 degradation did not rely on its papain-like cysteine protease activity. Taken together, PRRSV NSP1α antagonizes the antiviral response of TRIM25 by mediating TRIM25 degradation to promote PRRSV replication. Our data identify TRIM25 as a natural target of PRRSV NSP1α and reveal a novel mechanism that PRRSV induces TRIM25 degradation and inhibits host antiviral immune response.

Quercetin alleviates inflammation induced by porcine reproductive and respiratory syndrome virus in MARC-145 cells through the regulation of arachidonic acid and glutamine metabolism.

BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) infection causes severe inflammatory response, respiratory disease and sow reproductive failure. Quercetin is among the widely occurring polypheno found abundantly in nature. Quercetin has anti-inflammatory, anti-oxidative and anti-viral properties. OBJECTIVES: This study aimed to explore the effect and mechanism of quercetin on PRRSV-induced inflammation in MARC-145 cells. METHODS: Observing the cytopathic effect and measurements of inflammatory markers in MARC-145 cells collectively demonstrate that quercetin elicits a curative effect on PRRSV-induced inflammation. Liquid chromatography-mass spectrometry was further used for a non-targeted metabolic analysis of the role of quercetin in the metabolic regulation of PRRSV inflammation in MARC-145 cells. RESULTS: It was shown that quercetin attenuated PRRSV-induced cytopathy in MARC-145 cells. Quercetin treatment inhibited PRRSV replication in MARC-145 cells in a dose-dependent manner. We also found that quercetin inhibited PRRSV-induced mRNA expression and secretion levels of tumour necrosis factor-α, interleukin 1ß and interleukin 6. Metabolomics analysis revealed that quercetin ameliorated PRRSV-induced inflammation. Pathway analysis results revealed that PRRSV-induced pathways including arachidonic acid metabolism, linoleic acid, glycerophospholipid and alanine, aspartate and glutamate metabolism were suppressed by quercetin. Moreover, we confirmed that quercetin inhibited the activation of NF-κB/p65 pathway, probably by attenuating PLA2, ALOX and COX mRNA expression. CONCLUSIONS: These results provide a crucial insight into the molecular mechanism of quercetin in alleviating PRRSV-induced inflammation.

The effect of matrine and glycyrrhizic acid on porcine reproductive and respiratory syndrome virus in Vitro and in vivo.

Porcine reproductive and respiratory syndrome (PRRS) is endemic worldwide, seriously affecting the development of the pig industry, but vaccines have limited protective effects against PRRSV transmission. The aim of this study was to identify potential anti-PRRSV drugs. We examined the cytotoxicity of seven compounds formulated based on the mass ratio of glycyrrhizic acid to matrine and calculated their inhibition rates against PRRSV in vitro. The results showed that the seven compounds all had direct killing and therapeutic effects on PRRSV, and the compounds inhibited PRRSV replication in a time- and dose-dependent manner. The compound with the strongest anti-PRRSV effect was selected for subsequent in vivo experiments. Pigs were divided into a control group and a medication group for the in vivo evaluation. The results showed that pigs treated with the 4:1 compound had 100% morbidity after PRRSV challenge, and the mortality rate reached 75% on the 8th day of the virus challenge. These results suggest that this compound has no practical anti-PRRSV effect in vivo and can actually accelerate the death of infected pigs. Next, we further analyzed the pigs that exhibited semiprotective effects following vaccination with the compound to determine whether the compound can synergize with the vaccine in vivo. The results indicated that pigs treated with the compound had higher mortality rates and more severe clinical reactions after PRRSV infection (p < 0.05). The levels of proinflammatory cytokines (IL-6, IL-8, IL-1ß, IFN-γ, and TNF-α) were significantly greater in the compound-treated pigs than in the positive control-treated pigs (p < 0.05), and there was no synergistic enhancement with the live attenuated PRRSV vaccine (p < 0.05). The compound enhanced the inflammatory response, prompted the body to produce excessive levels of inflammatory cytokines and caused body damage, preventing a therapeutic effect. In conclusion, the present study revealed that the in vitro effectiveness of these agents does not indicate that they are effective in vivo or useful for developing anti-PRRSV drugs. Our findings also showed that, to identify effective anti-PRRSV drugs, comprehensive drug screening is needed, for compounds with solid anti-inflammatory effects both in vitro and in vivo. Our study may aid in the development of new anti-PRRSV drugs.

The emergence, isolation, and phylogenetic analysis of a closely related human strain of parainfluenza virus 5 from a case of porcine reproductive and respiratory syndrome in China.

Reports of Parainfluenza virus 5 (PIV5) epidemics have been on a global upward trend, with an expanding host range across various animals. In 2020, we isolated a PIV5 strain from a PRRSV-positive serum sample. This strain was named GX2020. Genetic analysis revealed that GX2020 belongs to group A, represented by the AGS strain isolated from a human in the USA. Comparisons of amino acid identity in the coding regions showed that GX2020 had the highest amino acid identity (99.6%) with the AGS strain. The emergence of PIV5 strains genetically similar to human strains in pigs highlights its zoonotic potential and underscores the need for enhanced PIV5 surveillance in the future.

Host cells reprogram lipid droplet synthesis through YY1 to resist PRRSV infection.

Metabolism in host cells can be modulated after viral infection, favoring viral survival or clearance. Here, we report that lipid droplet (LD) synthesis in host cells can be modulated by yin yang 1 (YY1) after porcine reproductive and respiratory syndrome virus (PRRSV) infection, resulting in active antiviral activity. As a ubiquitously distributed transcription factor, there was increased expression of YY1 upon PRRSV infection both in vitro and in vivo. YY1 silencing promoted the replication of PRRSV, whereas YY1 overexpression inhibited PRRSV replication. PRRSV infection led to a marked increase in LDs, while YY1 knockout inhibited LD synthesis, and YY1 overexpression enhanced LD accumulation, indicating that YY1 reprograms PRRSV infection-induced intracellular LD synthesis. We also showed that the viral components do not colocalize with LDs during PRRSV infection, and the effect of exogenously induced LD synthesis on PRRSV replication is nearly lethal. Moreover, we demonstrated that YY1 affects the synthesis of LDs by regulating the expression of lipid metabolism genes. YY1 negatively regulates the expression of fatty acid synthase (FASN) to weaken the fatty acid synthesis pathway and positively regulates the expression of peroxisome proliferator-activated receptor gamma (PPARγ) to promote the synthesis of LDs, thus inhibiting PRRSV replication. These novel findings indicate that YY1 plays a crucial role in regulating PRRSV replication by reprogramming LD synthesis. Therefore, our study provides a novel mechanism of host resistance to PRRSV and suggests potential new antiviral strategies against PRRSV infection.IMPORTANCEPorcine reproductive and respiratory virus (PRRSV) has caused incalculable economic damage to the global pig industry since it was first discovered in the 1980s. However, conventional vaccines do not provide satisfactory protection. It is well known that viruses are parasitic pathogens, and the completion of their replication life cycle is highly dependent on host cells. A better understanding of host resistance to PRRSV infection is essential for developing safe and effective strategies to control PRRSV. Here, we report a crucial host antiviral molecule, yin yang 1 (YY1), which is induced to be expressed upon PRRSV infection and subsequently inhibits virus replication by reprogramming lipid droplet (LD) synthesis through transcriptional regulation. Our work provides a novel antiviral mechanism against PRRSV infection and suggests that targeting YY1 could be a new strategy for controlling PRRSV.

Porcine reproductive and respiratory syndrome virus infects the reproductive system of male piglets and impairs development of the blood-testis barrier.

Porcine reproductive and respiratory syndrome virus (PRRSV) causes a highly contagious disease that threatens the global swine industry. Recent studies have focused on the damage that PRRSV causes to the reproductive system of male pigs, although pathological research is lacking. Therefore, we examined the pathogenic mechanisms in male piglets infected with PRRSV. Gross and histopathological changes indicated that PRRSV affected the entire reproductive system, as confirmed via immunohistochemical analysis. PRRSV infected Sertoli cells and spermatogonia. To test the new hypothesis that PRRSV infection in piglets impairs blood - testis barrier (BTB) development, we investigated the pathology of PRRSV damage in the BTB. PRRSV infection significantly decreased the quantity and proliferative capacity of Sertoli cells constituting the BTB. Zonula occludens-1 and ß-catenin were downregulated in cell - cell junctions. Transcriptome analysis revealed that several crucial genes and signalling pathways involved in the growth and development of Leydig cells, Sertoli cells, and tight junctions in the testes were downregulated. Apoptosis, necroptosis, inflammatory, and oxidative stress-related pathways were activated, whereas hormone secretion-related pathways were inhibited. Many Sertoli cells and spermatogonia underwent apoptosis during early differentiation. Infected piglets exhibited disrupted androgen secretion, leading to significantly reduced testosterone and anti-Müllerian hormone levels. A cytokine storm occurred, notably upregulating cytokines such as tumour necrosis factor-α and interleukin-6. Markers of oxidative-stress damage (i.e. H2O2, malondialdehyde, and glutathione) were upregulated, whereas antioxidant-enzyme activities (i.e. superoxide dismutase, total antioxidant capacity, and catalase) were downregulated. Our results demonstrated that PRRSV infected multiple organs in the male reproductive system, which impaired growth in the BTB.

Mass Spectrometry-Based Proteomic Analysis of Potential Host Proteins Interacting with N in PRRSV-Infected PAMs.

One of the most significant diseases in the swine business, porcine reproductive and respiratory syndrome virus (PRRSV) causes respiratory problems in piglets and reproductive failure in sows. The PRRSV nucleocapsid (N) protein is essential for the virus' assembly, replication, and immune evasion. Stages in the viral replication cycle can be impacted by interactions between the PRRSV nucleocapsid protein and the host protein components. Therefore, it is of great significance to explore the interaction between the PRRSV nucleocapsid protein and the host. Nevertheless, no information has been published on the network of interactions between the nucleocapsid protein and the host proteins in primary porcine alveolar macrophages (PAMs). In this study, 349 host proteins interacting with nucleocapsid protein were screened in the PRRSV-infected PAMs through a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomics approach. Bioinformatics analysis, which included gene ontology annotation, Kyoto Encyclopedia of Genes and Genomes database enrichment, and a protein-protein interaction (PPI) network, revealed that the host proteins interacting with PRRSV-N may be involved in protein binding, DNA transcription, metabolism, and innate immune responses. This study confirmed the interaction between the nucleocapsid protein and the natural immune-related proteins. Ultimately, our findings suggest that the nucleocapsid protein plays a pivotal role in facilitating immune evasion during a PRRSV infection. This study contributes to enhancing our understanding of the role played by the nucleocapsid protein in viral pathogenesis and virus-host interaction, thereby offering novel insights for the prevention and control of PRRS as well as the development of vaccines.

Genetically modified pigs with CD163 point mutation are resistant to HP-PRRSV infection.

Porcine reproductive and respiratory syndrome (PRRS) is a globally prevalent contagious disease caused by the positive-strand RNA PRRS virus (PRRSV), resulting in substantial economic losses in the swine industry. Modifying the CD163 SRCR5 domain, either through deletion or substitution, can eff1ectively confer resistance to PRRSV infection in pigs. However, large fragment modifications in pigs inevitably raise concerns about potential adverse effects on growth performance. Reducing the impact of genetic modifications on normal physiological functions is a promising direction for developing PRRSV-resistant pigs. In the current study, we identified a specific functional amino acid in CD163 that influences PRRSV proliferation. Viral infection experiments conducted on Marc145 and PK-15 CD163 cells illustrated that the mE535G or corresponding pE529G mutations markedly inhibited highly pathogenic PRRSV (HP-PRRSV) proliferation by preventing viral binding and entry. Furthermore, individual viral challenge tests revealed that pigs with the E529G mutation had viral loads two orders of magnitude lower than wild-type (WT) pigs, confirming effective resistance to HP-PRRSV. Examination of the physiological indicators and scavenger function of CD163 verified no significant differences between the WT and E529G pigs. These findings suggest that E529G pigs can be used for breeding PRRSV-resistant pigs, providing novel insights into controlling future PRRSV outbreaks.