Porcine reproductive and respiratory syndrome virus: phylogenetic analysis of circulating strains in the Republic of Ireland from 2016 to 2017

Prevalence, Time of Infection, and Diversity of Porcine Reproductive and Respiratory Syndrome Virus in China

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.

Spatiotemporal Distribution of PRRSV-1 Clades in Hungary with a Focus on the Era of Disease Eradication

Porcine reproductive and respiratory syndrome (PRRS) is the cause of the most severe economic losses in the pig industry worldwide. PRRSV is extremely diverse in Europe, which poses a significant challenge to disease control within a country or any region. With the combination of phylogenetic reconstruction and network analysis, we aimed to uncover the major routes of the dispersal of PRRSV clades within Hungary. In brief, by analyzing >2600 ORF5 sequences, we identified at least 12 clades (including 6 clades within lineage 1 and 3 clades within lineage 3) common in parts of Western Europe (including Denmark, Germany and the Netherlands) and identified 2 novel clades (designated X1 and X2). Of interest, some genetic clades unique to other central European countries, such as the Czech Republic and Poland, were not identified. The pattern of PRRSV clade distribution is consistent with the route of the pig trade among countries, showing that most of the identified clades were introduced from Western Europe when fatteners were transported to Hungary. As a result of rigorous implementation of the national eradication program, the swine population was declared officially free from PRRSV. This map of viral diversity and clade distribution will serve as valuable baseline information for the maintenance of PRRSV-free status in the post-eradication era.

Genetic characterization of porcine reproductive and respiratory syndrome virus from Eastern China during 2017-2022

Porcine reproductive and respiratory syndrome (PRRS) is an immunosuppressive disease caused by PRSS virus (PRRSV). PRRSV mainly causes reproductive disorders in pregnant sows and respiratory diseases in piglets. Recently, it has emerged as one of the most important diseases of the pig industry across the globe. In this study, we have collected 231 samples from differently sized pig farms in Eastern China from 2017 to 2022 to investigate the epidemic characteristics of the disease. All samples were screened by RT-PCR and analyzed further using Nsp2 and ORF5 genes. The result showed that the positive rate of PRRSV was 24% (54/231). Phylogenetic analysis (13 positive samples) revealed that all isolates belonged to genotype 2, and they were mainly distributed in four lineages (i.e., lineage 1, 3, 5, and 8). Nsp2 is the most variable protein among all PRRSV NSPs, several isolates from this study had amino acid deletions within Nsp2 compared to that of strain VR-2332. The major structural protein glycoprotein (GP5) protein is encoded by ORF5. Epitope analysis of the 13 isolated strains and additional reference strains revealed that all 13 strains had some mutations on the decoy epitope, the primary neutralizing epitope, T cell epitopes, and B cell epitopes. This study showed that the prevalent PRRSV strain in Eastern China was still HP-PRRSV, while the proportion of NADC30-like and NADC34-like strains have increased. This study further enriches the epidemiological data of PRRS in Eastern China and provides a theoretical basis for vaccine development and prevention and control of the disease across the region.

Small molecule screening identified cepharanthine as an inhibitor of porcine reproductive and respiratory syndrome virus infection in vitro by suppressing integrins/ILK/RACK1/PKCα/NF-κB signalling axis

Porcine Reproductive and Respiratory Syndrome (PRRS) is a devastating disease among the most notorious threats to the swine industry worldwide and is characterized by respiratory distress and reproductive failure. Highly evolving porcine reproductive and respiratory syndrome virus (PRRSV) strains with complicated genetic diversity make the current vaccination strategy far from cost-effective and thus urge identification of potent lead candidates to provide prevention and treatment approaches. From an in vitro small molecule screening with the TargetMol Natural Compound Library comprising 623 small molecules, cytopathic effect (CPE) observations and RT-qPCR analysis of viral ORF7 gene expression identified cepharanthine (CEP) to be one of the most protent inhibitors of PRRSV infection in Marc-145 cells. When compared with tilmicosin, which is one of the most commonly used antibiotics in swine industry to inhibit infections, CEP more prominently inhibited PRRSV infection represented by both RNA and protein levels, further reduced the TCID₅₀ by 5.6 times, and thus more remarkably protected Marc-145 cells against PRRSV infection. Mechanistically, western blot analyses of the Marc-145 cells and the porcine alveolar macrophages (PAMs) with or without CEP treatment and PRRSV infection at various time points revealed that CEP can inhibit the expression of integrins β1 and β3, integrin-linked kinase (ILK), RACK1 and PKCα, leading to NF-κB suppression and consequent alleviation of PRRSV infection. Collectively, our small molecule screening identified cepharanthine as an inhibitor of PRRSV infection in vitro by suppressing Integrins/ILK/RACK1/PKCα/NF-κB signalling axis, which may enlighten the deeper understanding of the molecular pathogenesis of PRRSV infection and more importantly, suggested CEP as a potential promising drug for PRRS control in veterinary clinics.