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Simple Summary: The objective was to understand the improvement in clinical parameters in piglets where different modified live vaccines (MLVs) against porcine reproductive and respiratory syndrome (PRRS) were administered. We conducted the study in the field with a large group of piglets and three different MLVs, assessing both safety and efficacy parameters. We found that different MLVs can be used at different stages of production if needed without adverse impacts on production and that there are differences in safety and efficacy between MLVs. This study was conducted to evaluate the protective efficacy of modified live vaccines (MLVs) against porcine reproductive and respiratory syndrome (PRRS) in nursery pigs in a worst case scenario where MLV does not match the genetic profile of the field isolate, different MLVs are used for sows and piglets, and piglets are naturally exposed to genetically distinct heterologous PRRS virus (PRRSV) isolates. We divided 76,075, 2-week-old piglets from a seropositive sow herd vaccinated with US1-MLV into four groups. US1-MLV, US2-MLV, and US3-MLV groups were vaccinated with PRRSV-2 MLV including Ingelvac® PRRS MLV (Boehringer Ingelheim, Ingelheim am Rhein, Germany), HP-PRRSV-2 based MLV (Harbin Veterinary Research Institute, CAAS, Harbin, China), and Prime Pac® PRRS (MSD Animal Health, Rahway, NJ, USA), respectively. The NonVac group was left unvaccinated. At 0, 14, 28, and 56 days post-vaccination (DPV), sera were assayed for the presence of PRRSV-specific antibodies using ELISA and serum neutralization (SN), and PRRSV RNA using PCR. Average daily gain (ADG) and survival rates were compared between treatment groups. The results demonstrated vaccinated groups significantly improved in ADG compared to the non-vaccinated control group. Only US1-MLV and US3-MLV were able to significantly reduce mortality associated with field PRRSV infection in nursery pigs. Pigs vaccinated with US3-MLV displayed significantly lower mortality and higher ADG compared to all other groups. Field isolates were isolated and genetically compared to all three MLV vaccines at the start of the trial. The MLV with closest genetic similarity to the field isolate was US2-MLV by ORF5 gene comparison. This provided the lowest protection judging by ADG improvement and mortality reduction, as compared to US1-MLV and US3-MLV. Separately, strains of Thai PRRSV-2 isolates collected in 2017, 2019, and 2020 in the study area were investigated for evolutionary changes. Over time, we observed a shift in PRRSV-2 isolates from lineage 8.7 to lineage 1. The field isolates found shared 82.59–84.42%, 83.75–85.74%, and 84.25–85.90% nucleotide identity with the US1-MLV, US3-MLV and US2-MLV based vaccine, respectively. Our findings suggest genetic similarity between field viruses and vaccine strains should not be used as a predictor of field performance. We found that zootechnical performance of piglets was best in US3-MLV, despite sows being treated with a different vaccine The results also support that different MLVs can be used at different stages of production. Finally, we concluded that the shift from lineage 8.7 to lineage 1 was due to shifts in the worldwide prevalence of PRRSV isolates during that period of time and not due to vaccine recombination between isolates. Overall, MLV vaccine selection should be based on production performance and safety profile. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a major concern for swine health. Isolating PRRSV is essential for identifying infectious viruses and for vaccine formulation. This study evaluated the potential of using tongue fluid (TF) from perinatal piglet mortalities for PRRSV isolation. Four collection protocols were tested: extracting TF from fresh tissues using phosphate-buffered saline (PBS group), extracting TF from fresh tissues using virus transportation medium (VTM group), extracting TF from freeze-thawed tissue (freeze-thaw group), and using tissue homogenates (homogenate group). Two cell lines (ZMAC and MARC-145) and primary alveolar macrophages (PAM) were evaluated for their effect on successful PRRSV isolation. An eligible PRRSV-positive unstable breeding herd in Midwestern USA was chosen for the study. Tongues were collected in 20 batches (~30 mortalities per batch). Within each batch, each tongue tissue was cut into four quarters, with each quarter randomly assigned to one of the four collection protocols and RT-qPCR tested. Virus isolation (VI) was attempted on 10 batches. The mean RT-qPCR cycle threshold (Ct) values for the PBS, VTM, freeze-thaw, and homogenate groups were 21.9, 21.8, 22.6, and 24.8, respectively. The VI success rate was 22.6%, 12.1%, 2.8%, and 2.8% in the PBS, VTM, freeze-thaw, and homogenate groups, respectively. The probability of successful VI was 3.1% and 21.0% in the MARC-145 and ZMAC cell lines, respectively, and 4.8% in the PAM cells. TF from perinatal mortalities is an option for PRRS VI, aiding in PRRSV monitoring and control programs. [ABSTRACT FROM AUTHOR]

Simple Summary: Monitoring pathogens is essential to prevent, control and eliminate pathogens in the swine production systems. Postmortem tongue fluids collected from dead pigs are a practical method to assess the circulation of porcine reproductive and respiratory syndrome virus (PRRSV), a well-known pathogen to the swine industry that causes significant financial losses. However, there is limited information on optimal storage conditions to ensure correct test results. This study assessed PRRSV genetic material in tongue fluid samples stored under different practical field conditions (temperatures and time periods). Keeping the samples cold at fridge temperatures (4 °C) for up to 14 days was the best scenario to maintain optimal diagnostic quality. Storing samples at warmer temperatures, such as room temperature or higher (22 °C or 34 °C), negatively affected testing results. With these findings, producers, veterinarians, and diagnosticians can better handle the samples and correctly interpret the results. This will improve efforts to control and prevent diseases in swine, contributing to healthier herds. Population-based sampling has improved pathogen monitoring in the US swine industry by increasing sensitivity while reducing costs. Postmortem tongue fluids (TF) have emerged as a practical option for monitoring porcine reproductive and respiratory syndrome virus (PRRSV) in breeding herds, but limited data exist on optimal storage conditions. This study evaluated PRRSV RNA detection via RT-qPCR in TF samples under various storage times, temperatures, and viral loads. Additionally, the porcine endogenous reference gene (internal sample control, ISC) was assessed for monitoring sample quality. Three studies were conducted: Study 1 compared fresh TF samples to freeze–thaw TF samples, with significantly lower cycle threshold (Ct) values in fresh samples. Studies 2 and 3 evaluated PRRSV RNA stability across six time points (0 to 336 h) and four temperatures (−20 °C, 4 °C, 22 °C, and 34 °C). At 4 °C, Ct value variation was minimal (≤1.1) over 14 days (336 h), with no significant changes within 48 h. In contrast, storage at 22 °C and 34 °C resulted in increased Ct values. The ISC RNA showed similar stability patterns, maintaining quality at 4 °C but degrading at higher temperatures. In conclusion, storing TF at ≤4 °C for up to 14 days for PRRSV and ISC RNA detection is the best scenario, ensuring optimal diagnostic quality. [ABSTRACT FROM AUTHOR]

Simple Summary: The porcine reproductive and respiratory syndrome virus (PRRSV) is a major threat to pig farms globally, causing significant economic losses. The killed PRRSV vaccines with a high load of antigens might help induce humoral immune responses. In the present study, Marc-145 cell lines overexpressing viral Nsp4 or Nsp2 were constructed, and both engineered cell lines significantly enhanced virus production, particularly at the early stages of infection. Our results provide a promising strategy for developing safe and effective PRRSV vaccines by enabling the production of a large quantity of the virus economically. Porcine reproductive and respiratory syndrome (PRRS) causes significant economic losses to the swine industry. The killed PRRSV vaccine has been reported to be safe and could elicit humoral responses. The killed PRRSV vaccine with a high viral antigen load combined with robust adjuvants could provide good protection against the infection. However, the high virus titer of PRRSV on the successive production cell lines is the prerequisite for this strategy. In this study, we explored PRRSV production in two recombinant Marc-145 cell lines expressing Nsp2 or Nsp4 through a lentivirus system. The results demonstrated that either Nsp2 or Nsp4 expressing Marc-145 cells did not affect cell morphology and growth kinetics but significantly enhanced PRRSV replication. Overall, our exploration may enable the production of high-yield PRRSV and offer a potential tool for developing safer and more effective PRRSV vaccines. [ABSTRACT FROM AUTHOR]

Simple Summary: Porcine reproductive and respiratory syndrome (porcine blue ear disease), a highly contagious disease caused by the porcine reproductive and respiratory syndrome virus (PRRSV), is capable of causing reproductive disorders in sows and respiratory syndrome in pigs of all ages, which severely affects the global pig industry. In this study, a generalized rapid test for PRRSV was established based on a new fully pre-mixed RT-qPCR reaction mixture that specifically detects PRRSV without cross-reactivity with other porcine susceptible viruses, with a minimum limit of 3.12 × 100 copies/μL and 100 TCID50/μL for the detection of PRRSV genes. For the precision assay, the relative standard deviation CV values were less than 2.5% for repeatability and reproducibility. The method was successful for rapid detection of 247 real samples. The fully pre-mixed RT-qPCR assay system established in this study not only simplified the operation steps but also shortened the assay time. This new assay meets the need for early and rapid detection of PRRSV and can provide an efficient, rapid, and sensitive detection method for PRRSV infection, thus laying the foundation for better prevention and control of the occurrence and spread of PRRS. To establish a rapid and sensitive detection method for the porcine reproductive and respiratory syndrome virus (PRRSV), gene-specific primers and a TaqMan probe were designed based on the M gene of PRRSV, and a new stable fully pre-mixed reverse transcription real-time fluorescence quantitative PCR (RT-qPCR) reaction mixture was developed. A simple and rapid RT-qPCR detection method for PRRSV was developed by optimizing nucleic acid amplification conditions. The results showed that the method was able to specifically detect PRRSV without cross-reactivity with the other 11 porcine susceptible viruses. The sensitivities of the assay were 3.12 × 100 copies/μL and 100 TCID50/μL for M gene and virus, respectively, and the repeatability and reproducibility (relative standard deviation, CV) of the assay were less than 2.5%. Based on the new fullly pre-mixed RT-qPCR reaction mixture, the RT-qPCR detection method may provide a new, simple, and rapid method for accurately detecting PRRSV. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) is the pathogen that causes porcine reproductive and respiratory syndrome (PRRS), leading to abortion of sows and the manifestation of respiratory diseases in piglets. PRRSV strains are categorized into two distinct genotypes: PRRSV–1 and PRRSV–2. PRRSV–2 can be further classified into several lineages, including sub–lineage 1.8 (NADC30–like), sub–lineage 1.5 (NADC34–like), lineage 8 (HP–PRRSV–like), lineage 5 (VR–2332–like), and lineage 3 (QYYZ–like), all of which are prevalent in China. In order to identify PRRSV–1 and PRRSV–2, two primer–probe combinations were designed, targeting the M gene. In order to further differentiate the five lineages of PRRSV–2, another five primer–probe combinations were designed, targeting the Nsp2 gene. A TaqMan–based multiplex RT–qPCR assay was subsequently developed, integrating the aforementioned seven sets into two primer pools. Following the optimization of primer concentration and annealing temperature, a comprehensive evaluation was conducted to assess the assay's amplification efficiency, specificity, repeatability, and sensitivity. The developed multiplex RT–qPCR method exhibited excellent repeatability, with coefficients of variation (CVs) less than 2.12%. The detection limits for all seven targets were found to be less than 5 copies/μL. Ultimately, the method was utilized for the detection of a total of 1009 clinical samples, with a PRRSV–positive rate of 7.63% (77/1009). Specifically, the reference method was utilized to further confirm the status of the 77 PRRSV–positive samples and another 27 samples suspected of PRRSV infection. The sensitivity of the method was 97.40% (75/77), and the specificity was 96.30% (26/27), resulting in an overall coincidence rate of 97.12% (101/104). All the PRRSV–positive samples were typed as NADC30–like strains, and the accuracy of this typing was further confirmed by Sanger sequencing. In conclusion, A one–step multiplex RT–qPCR method was successfully constructed, evaluated, and applied to detect clinical samples. The assay provides an easy–to–operate, time–saving, and highly efficient way for the quick identification of PRRSV and simultaneous detection of five PRRSV–2 lineages prevalent in China. The method could offer guidance for PRRSV prevention and control measures. [ABSTRACT FROM AUTHOR]

Simple Summary: Porcine reproductive and respiratory syndrome virus (PRRSV) is among the most harmful pathogens affecting the swine industry. Traditional inactivated or attenuated vaccines have proven inadequate for effective control, highlighting the need for novel, safe, and effective vaccine strategies. In this study, bioinformatics and immunoinformatics methods were used to rationally design a universal multi-epitope vaccine, which demonstrated excellent performance based on physicochemical properties, structural stability, immune receptor binding affinity, and immunogenicity. These attributes suggest that the designed vaccine holds significant promise as a novel, universal subunit vaccine candidate for preventing PRRSV infection. Porcine reproductive and respiratory syndrome virus (PRRSV) causes reproductive disorders in sows and severe pneumonia in piglets, alongside immunosuppressive effects on the host. It poses a significant global threat to the swine industry, with no effective control measures currently available due to its complex pathogenesis and high variability. Conventional inactivated and attenuated vaccines provide inadequate protection and carry biosafety risks. In this study, we designed a universal multi-epitope peptide vaccine against PRRSV using bioinformatics and immunoinformatics approaches to address these limitations. By selecting sequences from seven representative PRRSV strains, we predicted highly conserved and immunogenic T cell (Th and CTL) epitopes across all encoded proteins. These were rationally concatenated with reported B cell neutralizing epitopes into a multi-epitope vaccine construct. We performed comprehensive assessments of the construct's physicochemical and biochemical properties, along with predictions and refinements of its secondary and tertiary structures. Molecular docking simulations with TLR2 and TLR4 revealed strong potential binding interactions. Immune simulations indicated that the multi-epitope vaccine could induce robust humoral and cellular immune responses. This study provides a scientific foundation for the development of safe and effective PRRSV subunit vaccines and offers new perspectives for designing vaccines against other viral diseases. [ABSTRACT FROM AUTHOR]

Simple Summary: In this retrospective and longitudinal field study, PRRSV was detected in fresh boar semen using PCR. The aim of the study was to reconstruct the duration and shedding profiles of PRRSV in semen using field data. The detection of PRRSV in semen proved to be difficult due to low virus concentrations and the presence of inhibitors that affect PCR accuracy. Shedding patterns were highly variable, with some boars shedding the virus intermittently, continuously, or not at all over a period of weeks to months. Regular monitoring of the boars included testing of serum and semen samples, with PRRSV often detected earlier in blood than in semen. The study demonstrates the importance of combining PCR and antibody testing to improve detection accuracy and timing. In addition, the results suggest that enhanced biosecurity measures such as air purification systems and strict hygiene protocols are crucial for controlling the spread of PRRSV in boar studs. Comprehensive surveillance and early detection are necessary to minimize PRRSV transmission, maintain boar health, and prevent further outbreaks. The porcine reproductive and respiratory syndrome virus (PRRSV) causes high economical costs due to reduced productivity and losses in pig production. The virus can infect sow herds through various routes. One possible risk factor is the transmission of PRRSV through artificial insemination with infected boar semen. For these reasons, conventional boar studs should be closely monitored to detect an outbreak of PRRSV at an early stage. In the presented retrospective study, 2184 fresh semen samples from 336 boars were investigated (RT-qPCR) after an accidental PRRSV introduction to the herd. Hence, the different shedding profiles of PRRSV via semen resulted in 42.2% where no virus was detected, 2.0% intermittent shedding, and 8.4% permanent shedding. The duration of viral shedding varies from 2 days to 83 days post outbreak (on average 33 days). A significant impact of breed on PRRSV shedding duration could not be shown. Also, the distribution of the shedding profile does not follow a consistent mode, indicating that not every boar is shedding the virus via semen. [ABSTRACT FROM AUTHOR]

Lung macrophage cells play a critical role in various lung diseases, and their state can change depending on the progression of the disease by inducing either an inflammatory or anti-inflammatory state. In this review, the potential therapeutic effects of treatment with antioxidant nanoparticles in air-borne diseases focusing on porcine reproductive and respiratory virus (PRRSV), considering reactive oxygen species (ROS) as one of the factors that regulate M1 and M2 macrophages in the inflammatory and anti-inflammatory states, respectively, was described. In addition, the author examines the status of protein structure research on CD163 (one of the markers of anti-inflammatory M2 macrophages) in human and veterinary lung diseases. [ABSTRACT FROM AUTHOR]

Simple Summary: Maintaining a sustainable supply of animal protein is the mission of the global swine production industry. The entry of infectious pathogens to swine populations can cause significant animal welfare issues, increase the use of antibiotics, challenge environmental stability, and interrupt/reduce the supply of pork; therefore, preventing pathogen entry is critical to achieve its mission using science-based biosecurity programs. Biosecurity is the application of science-based protocols to minimize the risk of pathogen entry. The objective of this review is to summarize basic biosecurity terms and concepts, review the transmission of porcine reproductive and respiratory syndrome virus (PRRSV) and the biosecurity protocols designed to mitigate these risk factors, and discuss how the swine industry is applying Next Generation Biosecurity to prevent PRRSV infection of the breeding herd. The prevention of disease introduction into swine herds requires the practice of science-based protocols of biosecurity that have been validated to reduce the risk of the entry of targeted pathogens. The fundamental pillars of biosecurity include bio-exclusion, biocontainment, and bio-management. Biosecurity protocols must be science-based, a way of life, continuously validated, cost-effective, and benchmarked over time. This paper will review these concepts, the direct and indirect routes of transmission of porcine reproductive and respiratory syndrome virus (PRRSV), and the interventions that have been designed and validated to prevent infection of the breeding herd. It will close with a review of Next Generation Biosecurity, describing how a science-based approach is being used to prevent PRRSV infection in breeding herds from a large commercial pork production system in the US. [ABSTRACT FROM AUTHOR]

The porcine reproductive and respiratory syndrome virus (PRRSV) belongs to the Arteriviridae family and is a single-stranded, positively stranded RNA virus. The currently available PRRSV vaccines are mainly inactivated and attenuated vaccines, yet none of the commercial vaccines can provide comprehensive, long-lasting, and effective protection against PRRSV. SR717 is a pyridazine-3-carboxamide compound, which is commonly used as a non-nucleoside STING agonist with antitumor and antiviral activities. Nevertheless, there is no evidence that SR717 has any antiviral effects against PRRSV. In this study, a dose-dependent inhibitory effect of SR717 was observed against numerous strains of PRRSV using qRT-PCR, IFA, and WB methods. Furthermore, SR717 was found to stimulate the production of anti-viral molecules and trigger the activation of the signaling cascade known as the stimulator of interferon genes (STING) pathway, which contributed to hindering the reproduction of viruses by a certain margin. Collectively, these results indicate that SR717 is capable of inhibiting PRRSV infection in vitro and may have potential as an antiviral drug against PRRSV. [ABSTRACT FROM AUTHOR]

Simple Summary: Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) leads to considerable economic losses for the global pig industry. Investigating PRRSV–host interactions is important for understanding PRRSV pathogenesis and developing antiviral strategies. This study focuses on the post-transcriptional regulation of let-7f-5p in response to PPRSV infection. Lipids play a key role in the replication cycle of PRRSV. We found that let-7f-5p directly targets the master lipid metabolism regulator SREBP2 and influences the expression of lipogenesis genes, which provide a novel target for PRRSV antiviral therapy. Porcine reproductive and respiratory syndrome (PRRS) has caused substantial damage to the pig industry. MicroRNAs (miRNAs) were found to play crucial roles in modulating the pathogenesis of PRRS virus (PRRSV). In the present study, we revealed that PRRSV induced let-7f-5p to influence lipid metabolism to regulate PRRSV pathogenesis. A transcriptome analysis of PRRSV-infected PK15CD163 cells transfected with let-7f-5p mimics or negative control (NC) generated 1718 differentially expressed genes, which were primarily associated with lipid metabolism processes. Furthermore, the master regulator of lipogenesis SREBP2 was found to be directly targeted by let-7f-5p using a dual-luciferase reporter system and Western blotting. The findings demonstrate that let-7f-5p modulates lipogenesis by targeting SREBP2, providing novel insights into miRNA-mediated PRRSV pathogenesis and offering a potential antiviral therapeutic target. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogens in pig production worldwide and responsible for enormous production and economic losses. PRRSV infection in gestating gilts and sows induces important reproductive failure. Additionally, respiratory distress is observed in infected piglets and fattening pigs, resulting in growth retardation and increased mortality. Importantly, PRRSV infection interferes with immunity in the respiratory tract, making PRRSV-infected pigs more susceptible to opportunistic secondary pathogens. Despite the availability of commercial PRRSV vaccines for more than three decades, control of the disease remains a frustrating and challenging task. This paper provides a comprehensive overview of PRRSV, covering its history, economic and scientific importance, and description of the viral structure and genetic diversity. It explores the virus's pathogenesis, including cell tropism, viral entry, replication, stages of infection and epidemiology. It reviews the porcine innate and adaptative immune responses to comprehend the modulation mechanisms employed by PRRS for immune evasion. [ABSTRACT FROM AUTHOR]

Simple Summary: The objective of this study was to investigate the impact of intradermal (ID) versus intramuscular (IM) vaccination with a porcine reproductive and respiratory syndrome virus (PRRSV)-modified live vaccine (MLV) in piglets on serum copeptin and hematological profile. The study included 104 suckling piglets (2 weeks of age) from a commercial farrow-to-finish PRRSV-positive pig farm. Blood samples were collected from piglets at 4, 7, and 10 weeks of age. Blood samples were used for the performance of the complete blood count and examination by PCR for PRRSV and by ELISA for copeptin. No significant differences in serum copeptin levels and the number of blood cell counts were noticed in the same group over time and among groups. In conclusion, it seems that the PRRSV vaccination does not affect the levels of the released copeptin. This study aimed to investigate the impact of intradermal (ID) and intramuscular (IM) vaccination with a porcine reproductive and respiratory syndrome virus (PRRSV)-modified live vaccine (MLV) in piglets on serum copeptin levels and hematological profile. This study included 104 suckling piglets (2 weeks of age) from a commercial farrow-to-finish pig farm suffering from positive unstable PRRSV status. Animals were assigned to four groups, with two replicates (13 piglets/group/replicate); group A: IM vaccination with a PRRSV MLV vaccine, group B: ID vaccination with the same vaccine, group C: ID of Diluvac Forte, and group D: IM of Diluvac Forte. Blood samples were collected from the same three pigs/group/replicate at 4, 7, and 10 weeks of age. Blood samples were used for the performance of the complete blood count, and they were also examined by PCR for PRRSV and by ELISA for copeptin. No significant differences in serum copeptin levels and the number of blood cell counts (packed cell volume—PCV, numbers of white blood cells—WBCs, and platelets number—PLTs) were noticed in the same group over time and among groups. In conclusion, it seems that the vaccination against PRRSV does not affect the levels of the released copeptin. Based on our results, the measurement of serum copeptin could not be proposed as a potential stress biomarker in pigs. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) presents a significant threat to the global swine industry. The development of highly effective subunit nanovaccines is a promising strategy for preventing PRRSV variant infections. In this study, two different types of ferritin (Ft) nanovaccines targeting the major glycoprotein GP5, named GP5m-Ft and (Bp-IVp)3-Ft, were constructed and evaluated as vaccine candidates for PRRSV. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) demonstrated that both purified GP5m-Ft and (Bp-IVp)3-Ft proteins could self-assemble into nanospheres. A comparison of the immunogenicity of GP5m-Ft and (Bp-IVp)3-Ft with an inactivated PRRSV vaccine in BALB/c mice revealed that mice immunized with GP5m-Ft exhibited the highest ELISA antibody levels, neutralizing antibody titers, the lymphocyte proliferation index, and IFN-γ levels. Furthermore, vaccination with the GP5m-Ft nanoparticle effectively protected piglets against a highly pathogenic PRRSV challenge. These findings suggest that GP5m-Ft is a promising vaccine candidate for controlling PRRS. [ABSTRACT FROM AUTHOR]

Since it was first reported in 2013, the NADC30-like PRRSV has been epidemic in China. Hubei Province is known as China's key hog-exporting region. To understand the prevalence and genetic variation of PRRSV, herein, we detected and analyzed 317 lung tissue samples from pigs with respiratory disease in Hubei Province, and demonstrated that the NADC30-like strain was the second-most predominant strain during 2017–2018, following the highly pathogenic PRRSV (HP-PRRSV). Additionally, we isolated a new NADC30-like PRRSV strain, named CHN-HB-2018, which could be stably passaged in Marc-145 cells. Genetic characterization analysis showed that compared with the NADC30 strain, the CHN-HB-2018 strain had several amino acid variations in glycoprotein (GP) 3, GP5, and nonstructural protein 2 (NSP2). Moreover, the CHN-HB-2018 strain showed a unique 5-amino acid (aa) deletion in NSP2, which has not previously been reported. Gene recombination analysis identified the CHN-HB-2018 strain as a potentially recombinant PRRSV of the NADC30-like strain and HP-PRRSV. Animal experiments indicated that the CHN-HB-2018 strain has a mild pathogenicity, with no mortality and only mild fever observed in piglets. This study contributes to defining the evolutionary characteristics of PRRSV and its molecular epidemiology in Hubei Province, and provides a potential candidate strain for PRRSV vaccine development. [ABSTRACT FROM AUTHOR]

Recombination is a pervasive phenomenon in RNA viruses and an important strategy for accelerating the evolution of RNA virus populations. Recombination in the porcine reproductive and respiratory syndrome virus (PRRSV) was first reported in 1999, and many case reports have been published in recent years. In this review, all the existing reports on PRRSV recombination events were collected, and the genotypes, parental strains, and locations of the recombination breakpoints have been summarized and analyzed. The results showed that the recombination pattern constantly changes; whether inter- or intra-lineage recombination, the recombination hotspots vary in different recombination patterns. The virulence of recombinant PRRSVs was higher than that of the parental strains, and the emergence of virulence reversion was caused by recombination after using MLV vaccines. This could be attributed to the enhanced adaptability of recombinant PRRSV for entry and replication, facilitating their rapid propagation. The aim of this paper was to identify common features of recombinant PRRSV strains, reduce the recombination risk, and provide a foundation for future research into the mechanism of PRRSV recombination. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome (PRRS) remains a formidable challenge for the global pig industry. Caused by PRRS virus (PRRSV), this disease primarily affects porcine reproductive and respiratory systems, undermining effective host interferon and other immune responses, resulting in vaccine ineffectiveness. In the absence of specific antiviral treatments for PRRSV, vaccines play a crucial role in managing the disease. The current market features a range of vaccine technologies, including live, inactivated, subunit, DNA, and vector vaccines, but only modified live virus (MLV) and killed virus (KV) vaccines are commercially available for PRRS control. Live vaccines are promoted for their enhanced protective effectiveness, although their ability to provide cross-protection is modest. On the other hand, inactivated vaccines are emphasized for their safety profile but are limited in their protective efficacy. This review updates the current knowledge on PRRS vaccines' interactions with the host interferon system, and other immunological aspects, to assess their current status and evaluate advents in PRRSV vaccine development. It presents the strengths and weaknesses of both live attenuated and inactivated vaccines in the prevention and management of PRRS, aiming to inspire the development of innovative strategies and technologies for the next generation of PRRS vaccines. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRVS) is a major swine viral pathogen that affects the pig industry worldwide. Control of early PRRSV infection is essential, and different types of PRRSV-positive samples can reflect the time point of PRRSV infection. This study aims to investigate the epidemiological characteristics of PRRSV in China from Q4 2021 to Q4 2022, which will be beneficial for porcine reproductive and respiratory syndrome virus (PRRSV)control in the swine production industry in the future. A total of 7518 samples (of processing fluid, weaning serum, and oral fluid) were collected from 100 intensive pig farms in 21 provinces, which covered all five pig production regions in China, on a quarterly basis starting from the fourth quarter of 2021 and ending on the fourth quarter of 2022. Independent of sample type, 32.1% (2416/7518) of the total samples were PCR-positive for PRRSV, including 73.6% (1780/2416) samples that were positive for wild PRRSV, and the remaining were positive for PRRSV vaccine strains. On the basis of the time of infection, 58.9% suckling piglets (processing fluid) and 30.8% weaning piglets (weaning serum) showed PRRSV infection at an early stage (approximately 90% of the farms). The sequencing analysis results indicate a wide range of diverse PRRSV wild strains in China, with lineage 1 as the dominant strain. Our study clearly demonstrates the prevalence, infection stage, and diversity of PRRSV in China. This study provides useful data for the epidemiological understanding of PRRSV, which can contribute to the strategic and systematic prevention and control of PRRSV in China. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogens in the pig industry. Marc-145 cells are widely used for PRRSV isolation, vaccine production, and investigations into virus biological characteristics. Despite their significance in PRRSV research, Marc-145 cells struggle to isolate specific strains of the North American virus genotype (PRRSV-2). The involvement of viral GP2a, GP2b, and GP3 in this phenomenon has been noted. However, the vital amino acids have not yet been identified. In this study, we increased the number of blind passages and successfully isolated two strains that were previously difficult to isolate with Marc-145 cells. Both strains carried an amino acid substitution in GP2a, specifically phenylalanine to leucine at the 98th amino acid position. Through a phylogenetic and epidemiologic analysis of 32 strains, those that were not amenable to isolation widely exhibited this mutation. Then, by using the PRRSV reverse genetics system, IFA, and Western blotting, we identified the mutation that could affect the tropism of PRRSV-2 for Marc-145 cells. Furthermore, an animal experiment was conducted. Through comparisons of clinical signs, mortality rates, and viral load in the organs and sera, we found that mutation did not affect the pathogenicity of PRRSV-2. In conclusion, our study firmly establishes the 98th amino acid in GP2a as a key determinant of PRRSV-2 tropism for Marc-145 cells. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV), a member of the Arteriviridae family, represents a persistent menace to the global pig industry, causing reproductive failure and respiratory disease in pigs. In this study, we delved into the role of histone deacetylases (HDAC2) during PRRSV infection. Our findings revealed that HDAC2 expression is downregulated upon PRRSV infection. Notably, suppressing HDAC2 activity through specific small interfering RNA led to an increase in virus production, whereas overexpressing HDAC2 effectively inhibited PRRSV replication by boosting the expression of IFN-regulated antiviral molecules. Furthermore, we identified the virus's nonstructural protein 11 (nsp11) as a key player in reducing HDAC2 levels. Mutagenic analyses of PRRSV nsp11 revealed that its antagonistic effect on the antiviral activity of HDAC2 is dependent on its endonuclease activity. In summary, our research uncovered a novel immune evasion mechanism employed by PRRSV, providing crucial insights into the pathogenesis of this virus and guiding the development of innovative prevention strategies against PRRSV infection. [ABSTRACT FROM AUTHOR]

Simple Summary: Different viral pathogens, some considered primary agents, affect the reproductive performance of gilts and sows, such as circoviruses 2 and 3, parvovirus 1, and the PRRS virus. Recently, new viruses have been discovered, such as novel parvoviruses (named 2 to 8), whose effects on reproductive performance are not evident. In this study, we evaluate the presence of these new parvoviruses together with the primary viruses in a particular group: the gilts. This group is essential since they are the ones that will replace the sows that leave the reproductive cycle in the herd. We found the presence of these new viruses (except parvovirus 8) simultaneously in the same gilt with primary viruses (in addition to sextuple coinfections). Furthermore, we found that some primary viruses may be associated with the presence of some parvoviruses, such as 6 and 5. Likewise, parvoviruses 4 and 6 could affect important reproductive variables, such as the farrowing rate. This observational field study attempts to draw attention to and be a starting point in the search for answers about the effect of these selected viruses in the group of gilts and their impact on reproductive performance. Seven novel porcine parvoviruses (nPPVs) (PPV2 through PPV8) have been described, although their pathogenicity and possible effects on porcine reproductive failure (PRF) are undefined. In this study, these nPPVs were assessed in gilts from Colombia; their coinfections with PPV1, PCV2, PCV3, PCV4, and PRRSV and an association between the nPPVs and the reproductive performance parameters (RPPs) in sows were determined. For this, 234 serum samples were collected from healthy gilts from 40 herds in five Colombian regions, and the viruses were detected via real-time PCR. The results confirmed the circulation of PPV2 through PPV7 in Colombia, with PPV3 (40%), PPV5 (20%), and PPV6 (17%) being the most frequent. Additionally, no PCV4 or PPV8 was detected. PPV2 to PPV7 were detected in concurrence with each other and with the primary PRF viruses, and these coinfections varied from double to sextuple coinfections. Additionally, the association between nPPVs and PRF primary viruses was statistically significant for the presence of PPV6 in PCV3-positive (p < 0.01) and PPV5 in PPRSV-positive (p < 0.05) gilts; conversely, there was a significant presence of PPV3 in both PCV2-negative (p < 0.01) and PRRSV-negative (p < 0.05) gilts. Regarding the RPPs, the crude association between virus detection (positive or negative) and a high or low RPP was only statistically significant for PCV3 and the farrowing rate (FR), indicating that the crude odds of a low FR were 94% lower in herds with PCV3-positive gilts. This finding means that the detection of PCV3 in gilts (PCV3-positive by PCR) is associated with a higher FR in the farm or that these farms (with positive gilts) have lower odds (OR 0.06, p-value 0.0043) of a low FR. Additionally, a low FR tended to be associated with the detection of PPV4 and PPV5 (p-value < 0.20). This study is important for establishing the possible participation of nPPVs in PRF. [ABSTRACT FROM AUTHOR]

PRRS is a viral disease that profoundly impacts the global swine industry, causing significant economic losses. The development of a novel and effective vaccine is crucial to halt the rapid transmission of this virus. There have been several vaccination attempts against PRRSV using both traditional and alternative vaccine design development approaches. Unfortunately, there is no currently available vaccine that can completely control this disease. Thus, our study aimed to develop an mRNA vaccine using the antigens expressed by single or fused PRRSV structural proteins. In this study, the nucleotide sequence of the immunogenic mRNA was determined by considering the antigenicity of structural proteins and the stability of spatial structure. Purified GP5 protein served as the detection antigen in the immunological evaluation. Furthermore, cellular mRNA expression was detected by immunofluorescence and western blotting. In a mice experiment, the Ab titer in serum and the activation of spleen lymphocytes triggered by the antigen were detected by ELISA and ICS, respectively. Our findings demonstrated that both mRNA vaccines can significantly stimulate cellular and humoral immune responses. More specifically, the GP5-mRNA exhibited an immunological response that was similar to that of the commercially available vaccine when administered in high doses. To conclude, our vaccine may show promising results against the wild-type virus in a natural host. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) is a typical immunosuppressive virus causing a large economic impact on the swine industry. The structural protein GP5 of PRRSV plays a pivotal role in its pathogenicity and immune evasion. Virus–host interactions play a crucial part in viral replication and immune escape. Therefore, understanding the interactions between GP5 and host proteins are significant for porcine reproductive and respiratory syndrome (PRRS) control. However, the interaction network between GP5 and host proteins in primary porcine alveolar macrophages (PAMs) has not been reported. In this study, 709 GP5-interacting host proteins were identified in primary PAMs by immunoprecipitation coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Bioinformatics analysis revealed that these proteins were involved in multiple cellular processes, such as translation, protein transport, and protein stabilization. Subsequently, immunoprecipitation and immunofluorescence assay confirmed that GP5 could interact with antigen processing and presentation pathways related proteins. Finally, we found that GP5 may be a key protein that inhibits the antigen processing and presentation pathway during PRRSV infection. The novel host proteins identified in this study will be the candidates for studying the biological functions of GP5, which will provide new insights into PRRS prevention and vaccine development. [ABSTRACT FROM AUTHOR]

African swine fever virus (ASFV) and porcine reproductive and respiratory syndrome virus (PRRSV) infections lead to severe respiratory diseases in pigs, resulting in significant economic losses for the global swine industry. While numerous studies have focused on specific gene functions or pathway activities during infection, an investigation of shared immune responses in porcine alveolar macrophages (PAMs) after ASFV and PRRSV infections was lacking. In this study, we conducted a comparison using two single-cell transcriptomic datasets generated from PAMs under ASFV and PRRSV infection. Pattern recognition receptors (PRRs) RIG-I (DDX58), MDA5 (IFIH1), and LGP2 (DHX58) were identified as particularly recognizing ASFV and PRRSV, triggering cellular defense responses, including the upregulation of four cytokine families (CCL, CXCL, IL, and TNF) and the induction of pyroptosis. Through weighted gene co-expression network analysis and protein–protein interaction analysis, we identified thirteen gene and protein interactions shared by both scRNA-seq analyses, suggesting the ability to inhibit both ASFV and PRRSV viral replication. We discovered six proteins (PARP12, PARP14, HERC5, DDX60, RSAD2, and MNDA) in PAMs as inhibitors of ASFV and PRRSV replication. Collectively, our findings showed detailed characterizations of the immune responses in PAMs during ASFV and PRRSV infections, which may facilitate the treatments of these viral diseases. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious and pathogenic infectious disease caused by the porcine reproductive and respiratory syndrome virus (PRRSV). It manifests as reproductive disorders in sows and respiratory disorders in piglets. PRRSV infects swine herds with symptoms such as abortions, stillbirths, and mummified fetuses in gestating sows. Piglets mainly experience abdominal respiration and respiratory symptoms. To date, the prevention of PRRS relies primarily on vaccination and the implementation of various preventive and control measures. Swine deaths caused by PRRS have resulted in significant economic losses to the pig industry worldwide. Non-structural protein 10 (NSP10) has helicase and adenosine triphosphatase (ATPase) activities that unwind DNA and RNA and play important roles in viral replication and transcription. Hence, it can be potentially used to develop novel reagents for the detection of PPRSV. This article reviews genetic variations, interaction with viral and host proteins, effects on PRRSV replication, immunomodulation, apoptosis, and viral virulence of NSP10, with the aim of providing a theoretical basis for the prevention and control of PRRS and drug development in the future. [ABSTRACT FROM AUTHOR]

Vaccination against the Porcine Reproductive and Respiratory Syndrome virus (PRRSV) is widely practiced in both sows and piglets. However, it has been shown that multivaccinated sows sometimes lack a detectable antibody response, testing seronegative in ELISA (non-responders). Moreover, PRRSV-vaccinated piglets can remain seronegative as well, which is mainly attributed to the interference of maternally derived antibodies (MDAs). The current study investigated the impact of the sow's immune status on the PRRSV vaccine effectiveness in the progeny. The experimental trial included forty-eight piglets (n = 48) originating from a commercial Belgian breeding herd, with twenty-four piglets born from PRRSV vaccinated responder sows (E+ piglets) and twenty-four piglets born from PRRSV vaccinated non-responder sows (E− piglets). Eight piglets in each group were either non-vaccinated (NoVac piglets; n = 8), intramuscularly vaccinated (IM piglets; n = 8), or intradermally vaccinated (ID piglets; n = 8), with the same PRRSV-1 vaccine as used in the sow population. Vaccination was performed at weaning at three weeks of age, and all study piglets were challenged with a high dose of the PRRSV-1 07V063 strain at 6 weeks of age. A clear interference of MDAs was observed in the E+ piglets: 66.7% of the vaccinated E+ piglets lacked an antibody response at 3 weeks post-vaccination (non-responders). Consequently, post-challenge, only the responding E+ piglets had a significantly reduced serum viremia compared to the E+ NoVac piglets. The observed viremia in the non-responding E+ piglets was similar to the viremia of the E+ NoVac piglets. In the vaccinated E− piglets, a lack of antibody response at 3 weeks post-vaccination was observed in 18.8% of the piglets. Interestingly, despite the lack of a vaccine antibody response, the non-responding E− piglets had a significantly reduced serum viremia compared to the NoVac E− piglets. In contrast, the viremia of the responding E− piglets was only numerically reduced compared to the NoVac E− piglets. Finally, some clear differences were observed in both the kinetics of infection and the immune responses post-challenge between the E+ and E− piglets. The results of this study confirm the consequences of the MDA interference on the induced partial protection of PRRSV vaccination in experimentally challenged piglets. More research is warranted to understand the immunological mechanisms behind MDA interference in PRRSV vaccination and to explain the observed differences between E+ and E− piglets. [ABSTRACT FROM AUTHOR]

Simple Summary: The extended storage of feed ingredients has been suggested as a method to mitigate the risk of viral transmission through contaminated ingredients. To validate the approach of extended storage of complete swine feed for inactivation of swine viruses, an experiment was conducted to evaluate the ability of extended storage to inactivate the porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and Senecavirus A (SVA) when stored for 58 d at 23.9 °C using a self-contained intermodal shipping container. Minimal detrimental impacts were observed when storing feed for 58 d on feed quality measurements including mycotoxin detection, identification and quantification of bacteria, and stability of vitamins and phytase. No infectivity was observed for PRRSV, PEDV, or SVA following 58 d storage at 23.9 °C with the exception of a documented biocontainment breach for PRRSV. The results indicate that the extended storage of complete swine feed can be a method to reduce risks associated with pathogen transmission through feed while having minimal effects on measures of nutritional quality. The extended storage of feed ingredients has been suggested as a method to mitigate the risk of pathogen transmission through contaminated ingredients. To validate the approach of extended storage of complete swine feed for the inactivation of swine viruses, an experiment was conducted wherein swine feed was inoculated with 10 mL of 1 × 105 TCID50/mL of porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and Senecavirus A (SVA) and stored for 58 d at 23.9 °C. Measures of feed quality were also evaluated at the initiation and conclusion of the storage period including screening for mycotoxins, characterization of select microbiological measures, and stability of phytase and dietary vitamins. Storing feed for 58 d under either ambient or anaerobic and temperature-controlled storage conditions did not result in substantial concerns related to microbiological profiles. Upon exposure to the feed following 58 d of storage in a swine bioassay, previously confirmed naïve pigs showed no signs of PEDV or SVA replication as detected by the PCR screening of oral fluids and serum antibody screening. Infection with SVA was documented in the positive control room through diagnostic testing through the State of Minnesota. For PRRSV, the positive control room demonstrated infection. For rooms consuming inoculated feed stored for 58 d, there was no evidence of PRRSV infection with the exception of unintentional aerosol transmission via a documented biocontainment breach. In summary, storing feed for 58 d at anaerobic and temperature-controlled environmental conditions of 23.9 °C validates that the extended storage of complete swine feed can be a method to reduce risks associated with pathogen transmission through feed while having minimal effects on measures of nutritional quality. [ABSTRACT FROM AUTHOR]

Successful reproductive performance is key to farm competitiveness in the global marketplace. Porcine parvovirus 1 (PPV1) has been identified as a major cause of reproductive failure, and since 2001 new species of porcine parvoviruses, namely PPV2–7, have been identified, although their role is not yet fully understood yet. The present study aimed to investigate PPVs' presence in reproductive failure outbreaks occurring in 124 farms of northern Italy. Fetuses were collected from 338 sows between 2019 and 2021 and tested for PPVs by real-time PCR-based assays and for other viruses responsible for reproductive disease. At least one PPV species was detected in 59.7% (74/124) of the tested farms. In order, PPV1, PPV5, PPV6, PPV7 and PPV4 were the most frequently detected species, whereas fewer detections were registered for PPV2 and PPV3. Overall, the new PPV2–7 species were detected in 26.6% (90/338) of the cases, both alone or in co-infections: PCV-2 (7.1%, 24/338), PCV-3 (8.2%, 28/338), and PRRSV-1 (6.2%, 21/338) were frequently identified in association with PPVs. Single PPVs detections or co-infections with other agents commonly responsible for reproductive failure should encourage future studies investigating their biological, clinical, and epidemiological role, for a better preparedness for potential emerging challenges in intensive pig production. [ABSTRACT FROM AUTHOR]

Simple Summary: This review summarizes the available information on the ex-vivo survival of the porcine reproductive and respiratory syndrome virus (PRRSV), the cause of porcine reproductive and respiratory syndrome in pigs. We highlight the possible role of different fomites and environmental sources in indirect transmission of this virus to susceptible hosts. The number of studies on this topic is limited but fomites (porous, non-porous, and liquid), insects, people, and pork meat have been studied, mostly under experimental conditions. Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important diseases of swine, with losses due to poor reproductive performance and high piglet and growing pig mortality. Transmission of porcine reproductive and respiratory syndrome virus (PRRSV) may occur by both direct and indirect routes; the latter includes exposure to PRRSV-contaminated fomites, aerosols, and arthropod vectors. This review has collected available data on the ex-vivo environmental stability and persistence of PRRSV in an effort to highlight important sources of the virus and to determine the role of environmental conditions on the stability of the virus, especially temperature. The ex-vivo settings include fomites (solid, porous, and liquid fomites), insects, people, and pork meat, as well as the role of environmental conditions on the stability of the virus, especially temperature. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) is globally prevalent and seriously harms the economic efficiency of pig farming. Because of its immunosuppression and high incidence of mutant recombination, PRRSV poses a great challenge for disease prevention and control. Nonstructural protein 2 (NSP2) is the most variable functional protein in the PRRSV genome and can generate NSP2N and NSP2TF variants due to programmed ribosomal frameshifts. These variants are broad and complex in function and play key roles in numerous aspects of viral protein maturation, viral particle assembly, regulation of immunity, autophagy, apoptosis, cell cycle and cell morphology. In this paper, we review the structural composition, programmed ribosomal frameshift and biological properties of NSP2 to facilitate basic research on PRRSV and to provide theoretical support for disease prevention and control and therapeutic drug development. [ABSTRACT FROM AUTHOR]

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) remains an infectious agent with high importance in the swine industry. In this study, the influence of maternally derived antibodies (MDAs) on an experimental PRRSV-1 challenge is investigated. Piglets included in the study (n = 36) originated from a Belgian farrow-to-finish herd in which the sow population was routinely vaccinated with a modified live vaccine against PRRSV. Eighteen piglets were born from three PRRSV-seropositive sows (responders to vaccination) and had a clear presence of PRRSV-specific MDAs (E+ piglets). The other eighteen piglets were born from three PRRSV-seronegative sows (non-responders to vaccination) and did not have PRRSV-specific MDAs (E− piglets). In each group, twelve piglets were intranasally challenged with a high dose of the heterologous PRRSV-1 07V063 strain, the remaining piglets were mock-challenged (PBS) and served as controls. During the first days after infection, higher serum viremia and nasal shedding were observed in the challenged E− piglets compared to the challenged E+ piglets. However, at 10 days post-infection, the peak serum viremia was significantly higher in the E+ piglets in comparison to the E− piglets and serum viremia remained slightly higher in this group until the end of the study. Additionally, the two challenged groups had a different immune response to the PRRSV infection. The E− challenged piglets showed an earlier and more intense seroconversion, leading to significantly higher antibody titers at 10 dpi compared to the E+ challenged piglets. Furthermore, a trend towards both higher induction of serum IFN-γ and higher induction of IFN-γ secreting cells was observed in the E− challenged piglets. In contrast, a significantly higher induction of serum TNF-α at 7 dpi was seen in the E+ challenged piglets compared to the E− challenged piglets. The results gathered in this study suggest that PRRSV-specific MDAs induce partial protection during the early stages of infection but are not sufficient to protect against a high challenge dose. The presence of piglets lacking PRRSV-specific MDAs might pose a risk for PRRSV infection and enhanced transmission in pig farms in young piglets. [ABSTRACT FROM AUTHOR]

The porcine reproductive and respiratory syndrome virus (PRRSV) has caused significant economic losses to the swine industry. The U.S., China, and Peru have reported NADC30-like or NADC34-like PRRSV-infected piglets, which have been identified as the cause of a significant number of abortions in clinics. Although the pathogenicity of NADC30-like PRRSV and NADC34-like PRRSV in piglets exhibits significant variability globally, studies on their pathogenicity in China are limited. In this study, the animal experiments showed that within 8–14 days post-infection, both piglets infected with NADC30-like PRRSV GXGG-8011 and those infected with NADC34-like PRRSV LNSY-GY exhibited significant weight loss compared to the control piglets. Additionally, the viremia of the LNSY-GY persisted for 28 days, while the viremia of piglets infected with the GXGG-8011 lasted for 17 days. Similarly, the duration of viral shedding through the fecal–oral route after the LNSY-GY infection was longer than that observed after the GXGG-8011 infection. Furthermore, post-infection, both the LNSY-GY and GXGG-8011 led to pronounced histopathological lesions in the lungs of piglets, including interstitial pneumonia and notable viral colonization. However, the antibody production in the LNSY-GY-infected group occurred earlier than that in the GXGG-8011-infected group. Our research findings indicate that LNSY-GY is a mildly pathogenic strain in piglets, whereas we speculate that the GXGG-8011 might be a highly pathogenic strain. [ABSTRACT FROM AUTHOR]

In this study, we developed and validated (1) singleplex real-time RT-PCR assays for specific detection of five PRRSV-2 MLV vaccine viruses (Ingelvac MLV, Ingelvac ATP, Fostera, Prime Pac, and Prevacent) and (2) a four-plex real-time RT-PCR assay (IngelvacMLV/Fostera/Prevacent/XIPC) including the internal positive control XIPC for detecting and distinguishing the three most commonly used vaccines in the USA (Prevacent, Ingelvac MLV, and Fostera). The singleplex and 4-plex vaccine-like PCRs and the reference PCR (VetMAXTM PRRSV NA&EU, Thermo Fisher Scientific, Waltham, MA, USA) did not cross-react with non-PRRSV swine viral and bacterial pathogens. The limits of detection of vaccine-like PCRs ranged from 25 to 50 genomic copies/reactions. The vaccine-like PCRs all had excellent intra-assay and inter-assay repeatability. Based on the testing of 531 clinical samples and in comparison to the reference PCR, the diagnostic sensitivity, specificity, and agreement were in the respective range of 94.67–100%, 100%, and 97.78–100% for singleplex PCRs and 94.94–100%, 100%, and 97.78–100% for the 4-plex PCR, with a CT cutoff of 37. In addition, 45 PRRSV-2 isolates representing different genetic lineages/sublineages were tested with the vaccine-like PCRs and the results were verified with sequencing. In summary, the vaccine-like PCRs specifically detect the respective vaccine-like viruses with comparable performances to the reference PCR, and the 4-plex PCR allows to simultaneously detect and differentiate the three most commonly used vaccine viruses in the same sample. PRRSV-2 vaccine-like PCRs provide an additional tool for detecting and characterizing PRRSV-2. [ABSTRACT FROM AUTHOR]

The recently emerged PRRSV 1-4-4 L1C variant (L1C.5) was in vivo and in vitro characterized in this study in comparison with three other contemporary 1-4-4 isolates (L1C.1, L1A, and L1H) and one 1-7-4 L1A isolate. Seventy-two 3-week-old PRRSV-naive pigs were divided into six groups with twelve pigs/group. Forty-eight pigs (eight/group) were for inoculation, and 24 pigs (four/group) served as contact pigs. Pigs in pen A of each room were inoculated with the corresponding virus or negative media. At two days post inoculation (DPI), contact pigs were added to pen B adjacent to pen A in each room. Pigs were necropsied at 10 and 28 DPI. Compared to other virus-inoculated groups, the L1C.5-inoculated pigs exhibited more severe anorexia and lethargy, higher mortality, a higher fraction of pigs with fever (>40 °C), higher average temperature at several DPIs, and higher viremia levels at 2 DPI. A higher percentage of the contact pigs in the L1C.5 group became viremic at two days post contact, implying the higher transmissibility of this virus strain. It was also found that some PRRSV isolates caused brain infection in inoculation pigs and/or contact pigs. The complete genome sequences and growth characteristics in ZMAC cells of five PRRSV-2 isolates were further compared. Collectively, this study confirms that the PRRSV 1-4-4 L1C variant (L1C.5) is highly virulent with potential higher transmissibility, but the genetic determinants of virulence remain to be elucidated. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome (PRRS) has been prevalent for nearly forty years since it was first reported. It has been one of the major diseases jeopardizing the healthy development of the world swine industry, as well as causing great economic losses to the industry's economic development. Furthermore, no way has been found to combat the disease due to the immunosuppressive properties of its pathogen porcine reproductive and respiratory syndrome virus (PRRSV) infection. We previously examined the mRNA expression of IFN-I in PRRSV-infected Marc-145 cells at different time periods using qRT-PCR, and found that the mRNA expression of IFN-I in the late stage of PRRSV infection showed suppression. Naringenin is a flavonoid found in citrus fruits and has a very wide range of pharmacological activities. Therefore, the aim of the present study was to investigate the modulatory effect of naringenin on the suppressed innate immune response after PRRSV infection. The expression of IFN-I, IL-10, and ISGs in the late stage of PRRSV infection was examined using qRT-PCR, and the results showed that naringenin improved the expression of antiviral cytokines suppressed by PRRSV infection. Further results showed that naringenin treatment significantly up-regulated the expression of proteins related to the RIG-I-MAV immune signaling pathway, and that naringenin could not significantly activate the RIG-I-MAVS signaling pathway after the addition of the RIG-I inhibitor Cyclo. Overall, these data demonstrated that naringenin could improve the innate immune response suppressed by PRRSV infection by modulating the RIG-I-MAVS signaling pathway. Therefore, our study will provide a theoretical basis for the development of naringenin as a drug against immunosuppressive viral infectious disease infections. [ABSTRACT FROM AUTHOR]

Simple Summary: In this review, we examine the application of different molecular diagnostic techniques in the pig industry; qPCR, isothermal methods, and novel techniques such as CRISPR-Cas and microfluidics platforms are discussed in detail. The main viruses affecting the health of pigs were identified, including the African swine fever virus, porcine reproductive and respiratory syndrome virus, porcine epidemic diarrhea virus, and porcine circovirus. Furthermore, the main challenges for the implementation of large-scale molecular diagnostic tests in the swine industry are discussed, which include lower costs, ease of operation for any type of user, portability for use on farms, and rapid response times. Molecular diagnostic tests have evolved very rapidly in the field of human health, especially with the arrival of the recent pandemic caused by the SARS-CoV-2 virus. However, the animal sector is constantly neglected, even though accurate detection by molecular tools could represent economic advantages by preventing the spread of viruses. In this regard, the swine industry is of great interest. The main viruses that affect the swine industry are described in this review, including African swine fever virus (ASFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and porcine circovirus (PCV), which have been effectively detected by different molecular tools in recent times. Here, we describe the rationale of molecular techniques such as multiplex PCR, isothermal methods (LAMP, NASBA, RPA, and PSR) and novel methods such as CRISPR-Cas and microfluidics platforms. Successful molecular diagnostic developments are presented by highlighting their most important findings. Finally, we describe the barriers that hinder the large-scale development of affordable, accessible, rapid, and easy-to-use molecular diagnostic tests. The evolution of diagnostic techniques is critical to prevent the spread of viruses and the development of viral reservoirs in the swine industry that impact the possible development of future pandemics and the world economy. [ABSTRACT FROM AUTHOR]

Simple Summary: Multiple viruses and bacteria can cause respiratory disease in pigs. We aimed to report how frequently certain viruses and bacteria were detected in samples from pigs with respiratory disease in the course of routine diagnostic procedures at the University of Veterinary Medicine in Vienna between 2016 and 2021. While Mycoplasma (M.) hyorhinis (55.1%) had the highest detection rate, influenza A virus had the lowest detection rate (6.1%) in the investigated samples. Lung samples tested positive for PRRSV RNA were also more likely to be positive for M. hyopneumoniae and Pasteurella (P.) multocida. Samples tested positive for M. hyopneumoniae were more likely to be positive for P. multocida and Streptococcus suis, but less likely to be positive for M. hyorhinis. In conclusion, lung samples that were positive for a primary pathogenic agent were more likely to be positive for a secondary pathogenic agent. The diagnostic workup of respiratory disease in pigs is complex due to coinfections and non-infectious causes. The detection of pathogens associated with respiratory disease is a pivotal part of the diagnostic workup for respiratory disease. We aimed to report how frequently certain viruses and bacteria were detected in samples from pigs with respiratory symptoms in the course of routine diagnostic procedures. Altogether, 1975 routine diagnostic samples from pigs in Austrian swine stocks between 2016 and 2021 were analysed. PCR was performed to detect various pathogens, including porcine reproductive and respiratory syndrome virus (PRRSV) (n = 921), influenza A virus (n = 479), porcine circovirus type 2 (PCV2) (n = 518), Mycoplasma (M.) hyopneumoniae (n = 713), Actinobacillus pleuropneumoniae (n = 198), Glaesserella (G.) parasuis (n = 165) and M. hyorhinis (n = 180). M. hyorhinis (55.1%) had the highest detection rate, followed by PCV2 (38.0%) and Streptococcus (S.) suis (30.6%). PRRSV was detected most frequently in a pool of lung, tonsil and tracheobronchial lymph node (36.2%). G. parasuis was isolated more frequently from samples taken after euthanasia compared to field samples. PRRSV-positive samples were more likely to be positive for PCV2 (p = 0.001), M. hyopneumoniae (p = 0.032) and Pasteurella multocida (p < 0.001). M. hyopneumoniae-positive samples were more likely to be positive for P. multocida (p < 0.001) and S. suis (p = 0.046), but less likely for M. hyorhinis (p = 0.004). In conclusion, our data provide evidence that lung samples that were positive for a primary pathogenic agent were more likely to be positive for a secondary pathogenic agent. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important pathogens in the global swine industry over the past three decades. There is no licensed antiviral medication that can effectively control this infection. In the present study, the structure of SP-1 isolated and purified from Sargassum weizhouense was analyzed, and its antioxidant capacity and antiviral effect in MARC-145 cells against PRRSV were investigated. The results showed that SP-1 is a novel polysaccharide which mainly is composed of →4)-β-D-ManpA-(1→, →4)-α-L-GulpA-(1→ and a small amount of →4)-β-D-GalpA-(1→. PRRSV adsorption, replication, and release were all suppressed by SP-1. SP-1 therapy down-regulated mRNA expression of the CD163 receptor while increasing the antioxidant gene expression of Nrf2, TXNIP, and HO-1; increasing the protein expression of NQO1 and HO-1; and drastically reducing the protein expression of p-p65. The findings indicated that SP-1 reduces PRRSV adsorption, replication, and release through blocking the expression of the crucial CD163 receptor during infection. Meanwhile, SP-1 exerts antioxidant effects in PRRSV-infected cells through the activation of the Nrf2-HO1 signaling pathway. [ABSTRACT FROM AUTHOR]

Background: Porcine reproductive and respiratory syndrome virus (PRRSV) causes porcine reproductive and respiratory syndrome (PRRS), leading to abortion in sows and respiratory distress in breeding pigs. In China, PRRSV1 and PRRSV2 are the two circulating genotypes in swine herds, with distinct virulence. PRRSV2 further consists of classical (C-PRRSV2), highly pathogenic (HP-PRRSV2), and NADC30-Like (N-PRRSV2) subtypes. The diversity of PRRSV poses challenges for control and eradication, necessitating reliable detection assays for differentiating PRRSV genotypes. Methods: A new TaqMan-based RT-qPCR assay with four sets of primers and probes targeting conserved regions of the ORF7 and NSP2 genes of PRRSV was developed, optimized, and evaluated by us. Reaction conditions such as annealing temperature, primer concentration, and probe concentration were optimized for the assay. Specificity, sensitivity, repeatability, stability, limit of detection (LOD), concordance with the reference method were evaluated for the assay. Results: The assay could detect and type PRRSV1, C-PRRSV2, HP-PRRSV2, and N-PRRSV2 simultaneously with 97.33% specificity, 96.00% sensitivity, 12 copies/μL LOD, 97.00% concordance with reference assays. We applied the assay to 321 clinical samples from swine farms in China. The assay successfully detected and typed 230 PRRSV-positive samples, with 24.78% (57/230) of them further confirmed by ORF5 gene sequencing. The prevalence of PRRSV subtypes among the positive samples was as follows: C-PRRSV2 (15.22%), HP-PRRSV2 (23.48%), and N-PRRSV2 (61.30%). Two samples showed coinfection with different PRRSV subtypes. Conclusion: The quadruple RT-qPCR assay is a powerful tool for detecting and typing the currently circulating PRRSV strains in Chinese swine populations. It can assist in the surveillance of PRRSV prevalence and the implementation of prevention and control strategies. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome (PRRS) has been a persistent challenge for the swine industry for over three decades due to the lack of effective treatments and vaccines. Reverse genetics systems have been extensively employed to build rapid drug screening platforms and develop genetically engineered vaccines. Herein, we rescued recombinant PRRS virus (rPRRSV) WUH3 using an infectious cDNA clone of PRRSV WUH3 acquired through a BstXI-based one-step-assembly approach. The rPRRSV WUH3 and its parental PRRSV WUH3 share similar plaque sizes and multiple-step growth curves. Previously, gene-editing of viral genomes depends on appropriate restrictive endonucleases, which are arduous to select in some specific viral genes. Thus, we developed a restrictive endonucleases-free method based on CRISPR/Cas9 to edit the PRRSV genome. Using this method, we successfully inserted the exogenous gene (EGFP gene as an example) into the interval between ORF1b and ORF2a of the PRRSV genome to generate rPRRSV WUH3-EGFP, or precisely mutated the lysine (K) at position 150 of PRRSV nsp1α to glutamine (Q) to acquire rPRRSV WUH3 nsp1α-K150Q. Taken together, our study provides a rapid and convenient method for the development of genetically engineered vaccines against PRRSV and the study on the functions of PRRSV genes. [ABSTRACT FROM AUTHOR]

Simple Summary: The aim of this study was to describe the rate of detection of PRRSV-1 by PCR in due-to-wean litters in an endemic infected herd using three different sample types (blood samples, family oral fluid and udder wipes). Rates of detection were compared after testing samples individually and after pooling. Blood samples gave the higher rate of detection even after pooling by five, confirming that, at this time, it seems to be the best sampling procedure. Knowing porcine reproductive and respiratory syndrome (PRRS) status is essential for designing herd management protocols. For this, weaning-age pigs are a key subpopulation. Recently, different alternatives to blood sampling have been introduced because they are easier, welfare-friendly and cost-saving tools. Moreover, most of them allow the testing of more animals and seem to be more sensitive in low-prevalence scenarios. However, these studies were implemented mainly in PRRSV-2-infected herds. The first objective of our study was to compare the rate of detection of PRRSV-1 by RT-qPCR in individual serum samples, family oral fluid samples (FOF) and udder wipes (UW) collected the day before weaning. The second objective was to evaluate the suitability of pooling. The study was performed on a 210-sow farrow-to-finish farm which was PRRSV-1 infected and unstable. A total of 119 litters were sampled. The rate of detection of PRRSV-1 in blood samples, FOF and UW was 10.9%, 7.6% and 0.8%, respectively. The agreement between sera and FOF was almost perfect even if the detection capacity of sera was numerically superior to FOF. The Ct values of positive sera were statistically lower than those of FOF. Two modalities of pooling (1:3 and 1:5) were tested for sera and FOF. For sera, both modalities did not impact the PRRSV-1 status either at the litter level or at the batch one. On the other hand, whatever the modality (pooled by 3 or 5), most of the pools of FOF gave negative results, misclassifying many litters and batches. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome (PRRS) seriously endangers the sustainable development of the pig industry. Our previous studies have shown that matrine can resist porcine reproductive and respiratory syndrome virus (PRRSV) infection. This study aimed to explore the anti-PRRSV targets of matrine in Marc-145 cells. Biotin-labeled matrine 1 and 2 were used as probes. MTT assay was used to determine the maximum non-cytotoxic concentration (MNTC) of each probe in Marc-145 cells. The anti-PRRSV activity of each probe was evaluated via MTT, qPCR and Western blot, and its anti-inflammatory activity was evaluated via qPCR and Western blot. The targets of matrine in Marc-145 cells were searched using activity-based protein profiling (ABPP), and compared with the targets predicted via network pharmacology for screening the potential targets of matrine against PRRSV. The protein–protein interaction networks (PPI) of potential targets were constructed using a network database and GO/KEGG enrichment analysis was performed. ACAT1, ALB, HMOX1, HSPA8, HSP90AB1, PARP1 and STAT1 were identified as potential targets of matrine, and their functions were related to antiviral capacity and immunity. Matrine may play an anti-PRRSV role by directly acting on ACAT1, ALB, HMOX1, HSPA8, HSP90AB1, PARP1 and STAT1. [ABSTRACT FROM AUTHOR]

Simple Summary: Research on the NSP7 protein is of great significance in the diagnosis, prevention, and control of porcine reproductive and respiratory syndrome virus (PRRSV). We summarize its genetic variation, recombination hotspots and breakpoints, replication, virulence, immune mechanisms, and interaction with viral proteins and host proteins, which provide theoretical support for its application in PRRS diagnosis, novel vaccine design, and therapeutic drug development. Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious and severe infectious disease caused by the PRRS virus (PRRSV). PRRS is characterized by reproductive disorders in sows and respiratory dysfunction in pigs. Non-structural protein 7 (NSP7) is one of the most conserved functional proteins in PRRSV, and it plays an important role in viral replication and humoral immune responses in infected hosts. This review discusses the biological characteristics of NSP7 to provide theoretical support for its application in PRRS diagnosis, novel vaccine design, and therapeutic drug development. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome (PRRS), caused by the PRRS virus (PRRSV), is a highly pathogenic porcine virus that brings tremendous economic losses to the global swine industry. PRRSVs have evolved multiple elegant strategies to manipulate the host proteins and circumvent against the antiviral responses to establish infection. Therefore, the identification of virus–host interactions is critical for understanding the pathogenesis of PRRSVs. Tripartite motif protein 28 (TRIM28) is a transcriptional co-repressor involved in the regulation of viral and cellular transcriptional programs; however, its precise role in regulating PRRSV infection remains unknown. In this study, we found that the mRNA and protein levels of TRIM28 were up-regulated in PRRSV-infected porcine alveolar macrophages (PAMs) and MARC-145 cells. Ectopic TRIM28 expression dramatically increased viral yields, whereas the siRNA-mediated knockdown of TRIM28 significantly inhibited PRRSV replication. Furthermore, we used a co-immunoprecipitation (co-IP) assay to demonstrate that TRIM28 interacted with envelope glycoprotein 4 (GP4) among PRRSV viral proteins. Intriguingly, TRIM28 inhibited the degradation of PRRSV GP4 by impeding its ubiquitination. Taken together, our work provides evidence that the host E3-ubiquitin ligase TRIM28 suppresses GP4 ubiquitination and is important for efficient virus replication. Therefore, our study identifies a new host factor, TRIM28, as a potential target in the development of anti-viral drugs against PRRSV. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) poses a global threat to pig health and results in significant economic losses. Impaired innate and adaptive immune responses are evident during PRRSV infection. Cyclic GMP-AMP synthase (cGAS), a classical pattern recognition receptor recognizing mainly intracytoplasmic DNA, induces type I IFN responses through the cGAS-STING signaling pathway. It has also been demonstrated that cGAS-STING is involved in PRRSV infection. This study utilized the qRT-PCR, ELISA, and WB methods to examine the effects of Astragaloside IV (AS-IV) on the regulation of innate immune function and cGAS-STING signaling pathway in porcine alveolar macrophages. The results showed that AS-IV attenuated the decreased innate immune function caused by PRRSV infection, restored the inhibited cGAS-STING signaling pathway, and increased the expression of interferon, ultimately exerting antiviral effects. Moreover, these results suggest that AS-IV may be a promising candidate for a new anti-PRRSV antiviral, and its mechanism of action may provide insights for developing novel antiviral agents. [ABSTRACT FROM AUTHOR]

Since its discovery, Porcine reproductive and respiratory syndrome (PRRS) has had a huge impact on the farming industry. The virus that causes PRRS is Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and because of its genetic diversity and the complexity of the immune response, the eradication of PRRS has been a challenge. To provide scientific references for PRRSV control and vaccine development, this study describes the processes of PRRSV-induced infection and escape, as well as the host adaptive immune response to PRRSV. It also discusses the relationship between PRRSV and the adaptive immune response. [ABSTRACT FROM AUTHOR]

Simple Summary: Processing fluids (PFs) are novel diagnostic specimens consisting of serosanguineous exudate obtained from tissues after piglets' castration. PFs can be used for some diagnostic tests that would otherwise require a blood sample. This has the advantage of not subjecting piglets to an additional stressful procedure and, at the same time, reducing sampling costs. In the present study, the efficacy and reliability of a monitoring plan for porcine reproductive and respiratory syndrome (PRRS), one of the main pig diseases, based on PF sampling has been assessed in the Italian swine production system. Twenty-five breeding herds were monitored for 4–5 months by RT-PCR performed on both PFs and blood serum (the standard specimen used for monitoring). Based on the results obtained from each method, the herds were classified following the standard PRRS status categories. The two methods fully agreed in discriminating between herds with stable and unstable PRRSV circulation. However, we observed a slight discrepancy in classifying high- and low-prevalence herds within unstable herds. We conclude that PFs are a reliable material for the PRRSV surveillance and classification of breeding herds, but in case of unstable circulation, a strategy combining blood and PF sampling is recommended. The porcine reproductive and respiratory syndrome (PRRS) control strategy within swine breeding farms is based on herd classification relative to PRRSV infection status. This study aims to assess the efficacy of a monitoring plan based on processing fluids (PFs) by comparing it with the classification of herds based on the analysis of blood serum. Twenty-five breeding herds were enrolled in the study, with at least five consecutive batches sampled from each herd. Each batch was tested for PRRSV by RT-PCR performed on (i) pre-weaning blood serum from 30 piglets and (ii) PFs from all the male piglets in the batch. PRRS categories following the Holtkamp classification were assigned based on the results of each testing protocol. The two protocols assigned the same category to 18 out of 25 herds: while they showed perfect agreement in identifying positive unstable and stable herds, we observed some discrepancy in discriminating between low- and high-prevalence classes within unstable herds. PFs are thus a reliable sample to assign PRRS categories in Italian breeding herds characterized by widespread PRRSV circulation. However, in case of an unstable epidemiological scenario, we recommend the adoption of an integrated monitoring strategy that combines blood sampling with PFs. [ABSTRACT FROM AUTHOR]

The porcine reproductive and respiratory syndrome virus (PRRSV) causes economic losses in the swine industry worldwide. However, current vaccines cannot provide effective protection against PRRSV, and PRRSV-specific treatments for infected herds are still unavailable. In this study, we found that bergamottin showed strong inhibitory effects against PRRSV replication. Bergamottin inhibited PRRSV at the stage of the replication cycle. Mechanically, bergamottin promoted the activation of IRF3 and NF-κB signaling, leading to the increased expression of proinflammatory cytokines and interferon, which inhibited viral replication to some extent. In addition, bergamottion could reduce the expression of the non-structural proteins (Nsps), leading to the interruption of replication and transcription complex (RTC) formation and viral dsRNA synthesis, ultimately restraining PRRSV replication. Our study identified that bergamottin possesses potential value as an antiviral agent against PRRSV in vitro. [ABSTRACT FROM AUTHOR]

It is well established that PRRSV elimination is an effective strategy for PRRS control, but published reports concerning successful PRRSV elimination cases in farrow-to-finishing herds are rare. Here, we have reported a successful PRRSV elimination case in a farrow-to-finish herd by employing a "herd closure and rollover" approach with some modifications. Briefly, the introduction of pigs to the herd was stopped and normal production processes were maintained until the herd reached a PRRSV provisional negative status. During the herd closure, strict biosecurity protocols were implemented to prevent transmission between nursery pigs and sows. In the current case, introducing gilts before herd closure and live PRRSV exposure were skipped. In the 23rd week post-outbreak, the pre-weaning piglets started to show 100% PRRSV negativity in qPCR tests. In the 27th week, nursery and fattening barns fully launched depopulation. In the 28th week, nursery and fattening houses reopened and sentinel gilts were introduced into gestation barns. Sixty days post-sentinel gilt introduction, the sentinel pigs maintained being PRRSV antibody negative, manifesting that the herd matched the standard of the provisional negative status. The production performance of the herd took 5 months to bounce back to normal. Overall, the current study provided additional information for PRRSV elimination in farrow-to-finish pig herds. [ABSTRACT FROM AUTHOR]