Activating FcγRI inhibits RIG-I-mediated host antiviral innate immunity by FGR during PRRSV-ADE infection.

Combination immunization with mRNAs encoding PRRSV antigens enhances immune responses and confers protective immunity against highly pathogenic PRRSV in piglets.

The porcine reproductive and respiratory syndrome virus (PRRSV) remains a significant threat to the global swine industry, underscoring the urgent need for innovative diagnostic methods to detect and manage outbreaks effectively. We developed a novel CRISPR-based fluorescence assay for the highly sensitive detection of PRRSV-2. By combining reverse transcription-recombinase polymerase amplification (RT-RPA) with multiple-crRNA CRISPR/Cas13a system and single-stranded RNA-fluorescently quenched reporters (RQ-5U), our assay achieved a significant 28-fold increase in sensitivity compared to existed CRISPR/Cas13a-based PRRSV-2 detection methods. This multiple crRNA strategy allows detecting as low as 6 copies/µL of PRRSV-2 RNA, significantly improving the detection limit. Moreover, our method's accuracy in detecting simulated PRRSV-2 clinical samples matches that of quantitative reverse transcription polymerase chain reaction (RT-qPCR). Our findings demonstrate that this visual, sensitive, and specific nucleic acid detection method holds great promise for enhancing the diagnosis and management of PRRS in the swine industry.

Experimental evaluation of Salmonella Choleraesuis pathogenicity and porcine reproductive and respiratory syndrome virus synergy in weaned pigs.

Equine arteritis virus (EAV) is a positive-stranded RNA virus of the Arteriviridae family. Its GP5/M dimer, the principal component of the viral envelope, mediates virus budding and serves as a key target for neutralizing antibodies. Using AlphaFold3, we predicted the 3D structure of the EAV GP5/M dimer and compared it to its homolog in porcine reproductive and respiratory syndrome virus (PRRSV). Both complexes share a conserved architecture comprising a short ectodomain, three helical transmembrane regions, and a β-sheet-rich endodomain. EAV GP5 features a longer ectodomain with four α-helices and a disulfide-linked β-sheet, which forms the most variable and surface-exposed region containing neutralizing epitopes. Adjacent conserved and variable N-glycosylation sites suggest immune evasion mechanisms involving antigenic drift and glycan shielding. Another epitope, located in a membrane-proximal helix, overlaps with known virulence and persistence determinants. The transmembrane domains are the most structurally conserved regions between EAV and PRRSV, characterized by tilted and kinked helices stabilized by hydrophilic interactions within the lipid bilayer. These findings provide molecular insights into the structural organization, immune targets, and virulence-associated features of the GP5/M dimer, offering a foundation for rational vaccine design against EAV.

PRRSV remains one of the most economically significant pathogens in the global swine industry. Current control strategies are largely hindered because PRRSV pathogenesis has not been fully elucidated. In this study, we identified EAP20, a core subunit of ESCRT-II, as a multifaceted proviral factor that participated in PRRSV entry and replication. These findings provide new insights into the interplay between PRRSV and the host ESCRT machinery, laying a foundation for the development of more effective strategies for PRRS control.

Porcine reproductive and respiratory syndrome (PRRS), which is caused by the porcine reproductive and respiratory syndrome virus (PRRSV), results in substantial economic losses for the global pig farming industry. A critical step in the infection process is the binding of PRRSV to the CD163 receptor on the surface of porcine alveolar macrophages. This study successfully generated CD163-/- Landrace pigs using CRISPR/Cas9 gene editing technology. Following an experimental challenge with two distinct Type II PRRSV strains, the edited pigs exhibited complete resistance to infection. Virological and pathological examinations confirmed the absence of viral replication and the presence of characteristic pulmonary lesions and other organ damage in CD163-/- pigs. In contrast, wild-type control pigs exhibited high viral loads and severe pulmonary lesions, as well as damage to other organs. Our findings provide direct evidence that CD163 is an essential receptor for PRRSV infection in vivo. The CD163-/- pig model offers an effective genetic strategy for breeding pigs with an inherent resistance to PRRSV.

Emergence of a novel porcine reproductive and respiratory syndrome virus strain inducing biphasic temperature fluctuations in Tianjin, northern China.

Natural sausage casings are derived from intestines of regularly slaughtered pigs, bovines and small ruminants. Although casings are derived only from healthy animals after mandatory veterinary inspection, some slaughtered animals may originate from areas where contagious animal viral diseases are endemic. A validated 3D collagen model was used to establish inactivation kinetics of bovine viral diarrhoea virus (BVDV), porcine epidemic diarrhoea virus (PEDV), porcine reproductive and respiratory syndrome virus (PRRSV), pseudorabies virus (PrV), swine vesicular disease virus (SVDV) and transmissible gastroenteritis virus (TGEV) following treatment with saturated sodium chloride (NaCl) brine in line with the common production process of natural casings and alternatively a phosphate supplemented sodium chloride (P-salt). Decimal reduction values (D-values), representing time needed to reduce the initial viral load by 1 log10 (or 90 %), were determined at 4°C, 12°C and 20°C. For PRRSV and PrV, NaCl treatment at 12°C and 20°C was effective in lowering D-values significantly, while opposite results were found for BVDV, PEDV, SVDV and TGEV. Compared to the non-treatment, P-salt significantly decreased D-values for each virus at all temperatures, except for PrV and SVDV at 4°C. Despite clear thermal inactivation, no consistent correlation was found between salt inactivation and virus characteristics, like enveloped versus non-enveloped, DNA versus RNA viruses, and virion sizes. However, for individual viruses, the presented D-values can be used for future quantitative microbial risk assessment (QMRA) and to support emergency protocols and precautionary measures for sourcing of natural casings in cases of an acute outbreak of viral disease in endemic areas.

Needle-free intradermal delivery of a recombinant PRRSV-vectored CSFV E2 vaccine enhances humoral immunity and growth performance in piglets.

Natural syndemic infection between African swine fever virus (ASFV) and porcine reproductive and respiratory syndrome virus (PRRSV) leads to shifting of ASFV tissue tropism to lungs with exacerbated presentation of the disease.

Porcine reproductive and respiratory syndrome (PRRS) is a highly infectious disease caused by the PRRS virus (PRRSV), its impact is second only to that of African swine fever (ASFV). Since the discovery of this disease, comprehensive studies have been conducted on its genome structure, protein function, pathogenicity, transmission route, and epidemiology as well as vaccines, prevention, and control. Despite the availability of numerous vaccines, complete immune protection in pigs is lacking. This limitation may be attributed to immune evasion, immunosuppression, or inherent characteristics of pigs. From the view of immunosuppression, the antigen escape, delayed neutralization antibody production, T cell immunity, antibody dependence enhancement, dendritic cell function inhibition, regulatory T cell induction and thymic destruction of PRRSV were discussed in this review to better understand PRRSV pathogenesis and inform vaccine development.

Porcine reproductive and respiratory syndrome virus (PRRSV) infection relies on glycolytic reprogramming to support replication, but the mechanisms driving this metabolic shift remain poorly understood. The stimulator of interferon genes (STING), an innate immune adaptor, recently emerged as a metabolic regulator by directly binding and inhibiting hexokinase-2 (HK2), a key rate-limiting enzyme in glycolysis. Whether PRRSV exploits the STING-HK2 axis to unleash glycolysis for its own replication is unknown. Here we demonstrate that PRRSV infection induced STING degradation and promoted HK2 suppression, activating glycolysis for viral replication. In PRRSV-infected Marc-145 cells, lactate production (a glycolysis marker) and HK2 expression increased time-dependently, peaking at 48 h post-infection (hpi). Conversely, STING protein levels decreased significantly at 36 hpi and further at 48 hpi, suggesting a correlation between STING downregulation and glycolytic activation. The HK2 inhibitor 2-deoxy-D-glucose reduced lactate production and viral load, while the glycolysis activator PS48 enhanced both. STING knockdown via siRNA increased HK2 expression, lactate secretion, and PRRSV nucleocapsid protein levels, whereas STING overexpression suppressed these phenotypes. Co-immunoprecipitation and confocal microscopy demonstrated direct STING-HK2 interaction and cytoplasmic co-localization, maintained during PRRSV infection. HK2 overexpression promoted viral replication without altering STING levels, confirming HK2 as a downstream effector. In conclusion, PRRSV-triggered degradation of STING enhances HK2 expression, promoting lactate accumulation and accelerating viral replication. These findings suggest that the STING-HK2 axis can act as a critical viral metabolic checkpoint and highlight targeting metabolic–immune crosstalk as a potential anti-viral strategy.

As an immunosuppressive virus, the occurrence of secondary bacterial infection following porcine reproductive and respiratory syndrome virus type 2 (PRRSV-2) infection is widely recognized. The immune escape capability of PRRSV-2 enables the virus to maintain efficient proliferation even within macrophages. In this study, we report that PRRSV-2 infection disrupts the intracellular F-actin, thereby causing the inability of macrophage lysosomes to transport to secondary infected bacteria promptly for bacterial clearance. RhoA is a crucial molecule in the polymerization of G-actin to F-actin within the cell. Silencing RhoA suppresses the production of F-actin in the cell, delays the targeted clearance of bacteria by lysosomes, and leads to an increase in the number of viable bacteria within the cell. Overexpression of RhoA promotes the production of F-actin, accelerates the targeted clearance of lysosomes to bacteria, and effectively reduces the number of viable bacteria. After PRRSV-2 infection, the expression of RhoA protein is down-regulated by nsp5 to inhibit the production of F-actin. Mechanistically, nsp5 interacts with the E3 ubiquitin ligase Smurf1 to mediate K63-linked ubiquitination of RhoA at lysine 187 (K187), which subsequently leads to its degradation via the autophagy-lysosome pathway under the guidance of the selective autophagy receptor TOLLIP. Therefore, our study presents a novel mechanism through which PRRSV-2 reprograms the cytoskeleton to facilitate the survival of bacteria in secondary infections, providing a theoretical foundation and target for the prevention and control of PRRSV-2 secondary bacterial infection.

Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious swine disease and poses a severe economic burden to the global swine industry. Owing to the inadequacy of current prevention and control measures, developing effective antiviral strategies for preventing PRRS epidemics is imperative. Honokiol (HNK) is a bioactive component of the dietary supplement magnolia extract. Here, we demonstrated that HNK exhibited potent antiviral effects against different PRRSV strains in vitro. Mechanistically, HNK was shown to interfere with PRRSV replication rather than attachment, internalization, or release. HNK was further determined to target PRRSV RNA-dependent RNA polymerase to impair viral genomic RNA synthesis. In addition, HNK was found to decrease PRRSV-triggered inflammatory responses. More importantly, HNK was revealed to reduce viral loads and alleviate lung damage in vivo. This study highlights the potential of HNK as an inhibitor of PRRSV and provides novel insights into its antiviral properties.

The detection rate of Porcine Reproductive and Respiratory Syndrome Virus type 1 (PRRSV-1) in China has been increasing, with its growing genetic diversity and evolving pathogenicity posing significant challenges to disease control. In this study, a novel PRRSV-1 strain, designated GD18-2, was identified from a pig farm in Guangdong Province that experienced an outbreak despite vaccination with a PRRSV-2 vaccine. Whole-genome sequencing indicated that the GD18-2 strain possesses a genome length of 14,932 bp and exhibits 81.4% to 83.9% nucleotide identity with classical PRRSV-1 strains. Phylogenetic analyses based on both the complete genome and the ORF5 gene indicated that GD18-2 belongs to a distinct, new lineage. A unique amino acid deletion (positions 306-357) was identified in the non-structural protein Nsp2, along with specific mutations within the hypervariable regions of the structural proteins GP3 and GP4. Pathogenicity assessment demonstrated that GD18-2 induced fever, respiratory symptoms, and mortality in piglets. In pregnant sows, it caused reproductive failure (abortion, stillbirth, weak piglets) and was capable of vertical transmission via the placenta. This study highlights the emergence of a PRRSV-1 strain with a unique genetic background and high pathogenicity in southern China, underscoring the necessity for enhanced molecular epidemiological surveillance and updated control strategies. Recombination analysis using RDP4 revealed no significant recombination events in GD18-2.

Abstract Porcine reproductive and respiratory syndrome virus 1 (PRRSV-1) has emerged as a critical pathogen that threatens swine herds across China. In this study, a novel PRRSV-1 strain, designated XJEU2308, was isolated from a PRRSV outbreak in a previously confirmed PRRSV-negative (both RNA and antibody negative) swine herd in Xinjiang, China. During the outbreak surveillance period, production records revealed a mean stillbirth rate of 12.19% and a suckling piglet mortality rate of 56.07%. Phylogenetic analysis on the basis of the ORF5 gene classified XJEU2308 as a BJEU06-1-like strain, whereas whole-genome analysis clustered it within the newly identified "New subgroup 1" of Chinese PRRSV-1. Notably, this strain carried a unique 3-amino acid deletion (at positions 693–695) in nonstructural protein 2 (NSP2). In challenge experiments, XJEU2308 induced typical clinical symptoms and exhibited moderate pathogenicity. Importantly, the implementation of the load-close-exposure (LCE) strategy combined with field virus (FLV) exposure successfully restored the herd to a provisional PRRSV-negative status. Overall, this study isolated a new subgroup 1-like PRRSV-1 strain from a swine farm that experienced a reproductive failure outbreak; the strain is characterized by a unique 3-amino-acid deletion in the NSP2 gene and moderate pathogenicity. Additionally, this study validated the effectiveness of the LCE-FLV strategy for containing PRRSV-1.

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a significant threat to swine health worldwide, primarily due to its extensive genetic diversity and ability to evade host immune responses, which reduces the effectiveness of vaccines. This field study investigated the immunomodulatory effects of the Saccharomyces cerevisiae strain MIIP as a dietary supplement to mitigate PRRSV infection in piglets under commercial farming conditions. Four trials were conducted across PRRSV-affected herds, with variations in PRRS vaccination practices and infection status. MIIP supplementation led to a significant reduction in the PRRSV antibody-positive rate, titers, and viremia in treated piglets compared to both non-concurrent and concurrent control groups. Enhanced mucosal immunity was also observed, as evidenced by higher total IgA concentrations in serum and milk in the MIIP groups. Although not all immune parameters reached statistical significance, trends consistently favored improved antiviral responses in MIIP-treated animals. These results suggest that dietary supplementation with MIIP yeast can enhance both systemic and mucosal immunity, potentially reducing PRRSV infection and transmission. Further research into its mechanisms, particularly its interaction with innate immune pathways and the gut microbiota, is warranted to optimize PRRSV control strategies.

Porcine Reproductive and Respiratory Syndrome (PRRS), caused by the PRRS virus (PRRSV), is a prevalent swine pathogen that results in reproductive and respiratory issues. The non-structural protein 4 (NSP4) of PRRSV is a 3C-like serine enzyme with a vital triad (His39-Asp64-Ser118), which is crucial for cleaving viral polyproteins pp1a and pp1ab to yield operational non-structural proteins (NSP3-NSP12). In addition to its role in viral replication, NSP4 suppresses interferon production and triggers host cellular apoptosis, thereby facilitating immune evasion and disease progression. This review provides insights into the structure and function of NSP4, which provide perspectives for enhancing PRRS management strategies and formulating more potent vaccines.

ABSTRACT Porcine reproductive and respiratory syndrome virus(PRRSV) is an economically important pathogen for global pork industry. As a positive-strand RNA virus, lacking exonuclease-mediated proofreading, its RNA-dependent RNA polymerase (RdRP) domain within the nonstructural protein 9(nsp9) plays a vital role in maintaining replication accuracy. To identify the residues of PRRSV that regulates replication fidelity, its RdRP structure was predicted by using Alpha Fold 2 and aligned with the solved structure of coxsackievirus B3 (CVB3) RdRP. This comparison identified conserved residues in PRRSV RdRP that are potentially involved in fidelity. Using site-directed mutagenesis, nucleoside analog sensitivity tests, and next-generation sequencing(NGS), it was found that the nsp9 K541R mutation enhances fidelity, as increasing viral resistance to mutagens like ribavirin, 5-Fluorouracil(5-FU), and 5-Azacytidine(5-AZC), as well as generating lower rate of non-contiguous junctions. In contrast, mutations at other positions, including A394G, L396S, and R401A, reduced fidelity and elevated frequency of recombination and mutation accumulation. Structural modeling revealed that the highly conserved residue K336 is spatially adjacent to the key fidelity site K541 but situated on the opposite side of the RNA channel. We found that K336R exhibits a dissociated “resistance-high recombination” phenotype. The findings reveal the importance of specific residues in PRRSV RdRP for replication fidelity and provide insights into the potential for improving the stability and safety of live attenuated vaccines through targeted modifications. Furthermore, the study emphasizes the structural conservation of fidelity determinants across RNA viruses, despite low sequence similarity, which can offer a framework for identifying fidelity key sites in other viral RdRPs.