Porcine Circovirus Type Research Articles

Coinfection of Mycoplasma suis and porcine circovirus type 3 is linked to reproductive failure in pig farms

Coinfection of Mycoplasma suis and porcine circovirus type 3 is linked to reproductive failure in pig farms

Well-Being and Performance of Nursery Pigs Subjected to Different Commercial Vaccines Against Porcine Circovirus Type 2, Mycoplasma hyopneumoniae and Lawsonia intracellularis

Background/Objectives: Vaccination is a strategy in pig farming for the control of several pathogens, but commercial vaccines may have detrimental side effects. This study aimed to evaluate the effects of commercial vaccines on the control of porcine circovirus type 2 (PCV2), Mycoplasma hyopneumoniae (Mhp), and Lawsonia intracellularis (L. intracellularis) and their potential side effects on welfare, behavior, acute inflammation biomarkers (C-reactive protein and haptoglobin), and the performance of piglets during the nursery phase. Methods: A total of 240 piglets, both female and castrated males, with an average weight of 6.3 ± 0.9 kg were subjected to four treatments: T1-FLEXcombo® (Ingelvac®CircoFLEX and Ingelvac®MycoFLEX) + Enterisol® Ileitis; T2-FLEXCombo® + Porcilis® Ileitis; T3-Porcilis® PCV M HYO + Porcilis® Ileitis; and T4-FLEXCombo® + 0.9% saline solution. This study measured therapeutic interventions, body condition score, behavioral changes, rectal temperature, and inflammation biomarkers post-vaccination. Results: The T3 group required more therapeutic interventions and exhibited a 23.1% higher incidence of thin body condition (p < 0.05) and 10 times more animals with depressed behavior than T1 (p < 0.05). The piglets vaccinated for L. intracellularis (T2 and T3) had rectal temperatures exceeding 39.7 °C post-vaccination, significantly higher than in T1 (p < 0.05). The T1 animals showed five times more positive behavior traits 24 h after vaccination (p < 0.05). Touch response was 29% lower in the T2 and T3 groups, and the lying down behavior was higher in these groups compared to T1. Additionally, 41.7% of the T3 animals exhibited a sitting posture 48 h after vaccination. Higher serum C-reactive protein and haptoglobin levels were observed in T3 (p < 0.05) at 24 and 48 h post-vaccination. Feed intake was higher in T1 compared to T3 between 29 and 35 days of age. It is important to note that this study did not measure immune responses to the pathogens and did not include challenge tests, and therefore, it does not assess which vaccine is superior in pathogen control. Conclusions: The vaccine programs resulted in similar zootechnical performance. However, T1, T2, and T4 showed better effects on piglet welfare and behavior compared to T3.

Prevalence and genetic evolution analysis of porcine epidemic diarrhea virus and porcine circovirus type 2 in Sichuan Province, China, from 2023 to 2024.

Porcine circovirus type 2 (PCV2) and Porcine epidemic diarrhea virus (PEDV) are highly prevalent in Sichuan, significantly affecting the swine industry's development. PCV2, known for its immunosuppressive effects, can compromise pigs' immune systems, while PEDV typically causes diarrhea in piglets, leading to high mortality rates. Despite their impact, recent studies on the epidemiology and genetic diversity of PCV2 and PEDV within Sichuan Province remain limited. This study examines clinical samples from 352 diarrheal piglets across 63 pig farms in 17 regions of Sichuan Province, revealing positivity rates of 42.33% (149/352) for PCV2 and 50.28% (177/352) for PEDV, with a co-infection rate of 27.56% (97/352). Notably, the highest positivity rates were observed in Ziyang for PCV2 at 61.90% (13/21), and in Meishan for PEDV at 73.81% (31/42), both regions also reported the highest co-infection rates of 47.62%. Seasonal analysis indicated that PEDV infections peaked during winter, whereas PCV2 showed no significant seasonal trends. Phylogenetic analysis identified 14 PCV2 strains, categorizing 2 as PCV2b (14.29%), 10 as PCV2d (71.43%), and 2 as PCV2e (14.29%). Among the 16 PEDV strains, 2 were classified as G1a (12.5%) and 14 as G2a (87.5%), with PCV2d and PEDV G2a identified as the predominant strains in the region. The study also highlights a high mutation rate at the antigenic sites of both viruses, potentially affecting vaccine efficacy. These findings underscore the need for ongoing surveillance and vaccine development tailored to the prevalent strains to improve control measures within the province.

Effect of yeast probiotics in lactation and yeast cell wall prebiotic and Bacillus subtilis probiotic in nursery on lifetime growth performance, immune response, and carcass characteristics.

Twenty-eight mixed-parity sows (Line 241; DNA) and their offspring were used to evaluate live yeast supplementation during lactation with or without a pre/probiotic combination during the nursery period on lactation performance, lifetime growth performance, and immune response. On day 110 of gestation, sows were allotted to a lactation diet with or without a live yeast probiotic (0.10% Actisaf Sc 47 HR+; Phileo by Lesaffre, Milwaukee, WI). At weaning, their offspring (350 pigs; initially 6.1 ± 0.02kg) were randomly assigned in a 2 × 2 factorial with main effects of sow treatment and nursery treatment consisting of a control diet or a diet with a yeast cell wall prebiotic and Bacillus subtilis probiotic (0.10% YB; Phileo by Lesaffre, Milwaukee, WI) fed for 42 d followed by common diets fed until marketing. Two nursery pens were combined into 1 finishing pen, such that there were 5 and 10 pigs per pen with 17 or 18 and 8 or 9 replications per treatment during the nursery and finishing periods, respectively. There were no significant effects of yeast supplementation on lactation performance (P ≥ 0.079). There was a sow × nursery diet interaction (P = 0.024) on nursery ADG. Pigs from yeast-fed sows had increased ADG when fed control nursery diets compared to pigs from control sows fed the control nursery diet with pigs fed pre/probiotic nursery diets intermediate, regardless of sow diet. Pigs from yeast-fed sows tended (P = 0.067) to have greater final body weight (BW) (day 165). A subset of pigs was sampled throughout their lifetime to determine serum porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae antibody sample-to-positive (S/P) ratios and percentage inhibition of Lawsonia intracellularis. There was a tendency for a PCV2 S/P ratio sow diet × day interaction (P = 0.097) where progeny from yeast-fed sows had higher PCV2 S/P ratios at 101 d of age compared to control sow progeny (P = 0.046). There was a PCV2 S/P ratio nursery diet × day interaction (P = 0.036) where pigs fed a pre/probiotic combination had reduced S/P ratios at 66, 78, and 162 d of age (P ≤ 0.022); however, at 22 d of age pigs fed a pre/probiotic combination tended to have an increased S/P ratio (P = 0.051). In conclusion, the effects of combining a yeast probiotic in lactation diets and a pre/probiotic in nursery diets were not additive. However, feeding a live yeast probiotic during lactation resulted in tendencies (P ≤ 0.10) for increased progeny final BW and hot carcass weight.

Molecular Positivity of Porcine Circovirus Type 2 Associated with Production Practices on Farms in Jalisco, Mexico

The modernization of pig production has led to increasingly larger populations of pigs. This dynamic allows for accelerated production and ensures a steady pork supply but also facilitates the spread of infections. PCV2 is a ubiquitous virus and can cause PCV2-associated diseases, depending on production practices. This study aimed to evaluate the conditions of pig production in the state of Jalisco, Mexico, and correlate them with PCV2. A total of 4207 serum samples from 80 farms were analyzed. Epidemiological data were collected and used to investigate factors associated with PCV2 detection. A relative frequency of approximately 30% was detected, primarily in grower pigs maintained on multisite farms. Several production practices, particularly biosecurity measures, were associated with PCV2 on the analyzed farms.

Synthesis and characterization of molecularly imprinted polymer nanoparticles against porcine circovirus type 2 viral-like particles.

PCV2 is a significant epidemic agricultural pathogen that causes a variety of swine diseases. PCV2 infections have significant economic impact on the swine industry, making effective strategies for rapid detection of PCV2 in pigs essential. Herein, we report on the synthesis of the so-called nano-MIPs which can be utilized for molecular recognition of PCV2. The morphology and structure of nano-MIPs were characterized using scanning electron microscopy (SEM). Nano-MIPs are spherical with sizes around 120-150nm. Binding experiments demonstrate that the fluorescence intensity of PCV2 samples decreases proportionally to increasing the concentration of nano-MIPs due to quenching, while non-imprinted polymer nanoparticles (nano-NIPs) do not affect the signal. The Stern-Volmer constant of nano-MIPs binding to PCV2 was 1.3 × 10-3mL/µg, whereas nano-NIPs led to 7 × 10-5mL/µg, i.e., 1.8 orders of magnitude lower. The detection limit for binding MIP particles to PCV2 by fluorescence measurements is 47µg/mL. This affinity test allows for designing both direct and competitive quartz crystal microbalance (QCM) assays for PCV2 leading to QCM measurements. The QCM results show nano-MIPs binding to PCV2 immobilized on the sensor surface with appreciable reproducibility. QCM sensor characteristics reveal signal saturation above around 200µg/mL at a response of - 354Hz and an LOD of approximately 35µg/mL. Nano-MIPs also show selectivity factors of 2-5 for CSFV and PRRSV probably because the three viruses have similar diameters around 50nm.

Modular Nano-Antigen Display Platform for Pigs Induces Potent Immune Responses.

Multivalent presentation of antigens using nanoparticles (NPs) as a platform is an effective strategy to enhance the immunogenicity of subunit vaccines and thus induce a high level of organismal immune response. Our previous results showed that pre-existing porcine circovirus type 2 (PCV2) antibodies could increase the antibody levels of nanoparticle vaccines carried in PCV2 VLPs. Here, we have established a generalized nanoantigen display platform, Cap-Cat virus-like particles (VLPs). By combining PCV2 VLPs with the modular linker element SpyTag003/SpyCatcher003 system, four porcine-derived viral protective antigens with different sizes and multimeric structures: the PRRSV B-cell epitope, the PEDV COE monomer, the CSFV E2 dimer, and the SIV HA trimer were efficiently demonstrated to elicit a strong immune response in mice. Crucially, the modification of antigens by the Cap-Cat VLPs platform enhanced the Th2 response and improved the Th1 response. The use of the platform demonstrates that HA antigen protects against lethal attacks by influenza viruses and reduces viral load in the lungs. We have demonstrated that the Cap-Cat VLPs platform demonstrates that antigens enhance the immune response by improving the processes of DC uptake, transport, lymph node (LN) localization, and immune cell activation. This "plug-and-display" assembly strategy facilitates the use of the Cap-Cat VLPs nanoantigen display platform for more applications and thus facilitates the development of more efficient, general-purpose porcine subunit vaccines.

Frequency and Genetic Analysis of Porcine Circovirus Type 2, Which Circulated between 2014 and 2021 in Jiangsu, China

Porcine circovirus-associated diseases, caused by porcine circovirus type 2 (PCV2), are widespread and result in significant economic losses to the global swine industry. PCV2 can currently be divided into nine genotypes (PCV2a to PCV2i), with the currently dominant one being the PCV2d genotype. In this study, 2675 samples from 804 pig farms in 13 cities in Jiangsu Province, China, were collected between 2014 and 2021 and subjected to polymerase chain reaction analysis to investigate the frequency and genetic diversity of PCV2. The results showed that 41.42% (1108/2675) of samples tested positive for PCV2. The researchers further analyzed the genetic characteristics of 251 PCV2 strains and found that they belonged to the following four genotypes: PCV2a, PCV2b, PCV2d, and PCV2i. The dominant genotype was PCV2d, with a frequency of 49.80% (125/251). The detection rate of PCV2b was significantly higher than those of PCV2a and PCV2i, at 35.46% (89/251), 7.57% (19/251), and 7.17% (18/251), respectively. The percentage of different genotypes of PCV2 varied irregularly over time. We have further revealed the fingerprint of PCV2i genomic nucleotides for the first time. In conclusion, this study illustrates the high frequency and evolutionary features of PCV2 in Jiangsu Province over the past few years.

Detection of Porcine Circovirus (PCV) Using CRISPR-Cas12a/13a Coupled with Isothermal Amplification.

The impact of porcine circovirus (PCV) on the worldwide pig industry is profound, leading to notable economic losses. Early and prompt identification of PCV is essential in managing and controlling this disease effectively. A range of detection techniques for PCV have been developed and primarily divided into two categories focusing on nucleic acid or serum antibody identification. The methodologies encompass conventional polymerase chain reaction (PCR), real-time fluorescence quantitative PCR (qPCR), fluorescence in situ hybridization (FISH), loop-mediated isothermal amplification (LAMP), immunofluorescence assay (IFA), immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA). Despite their efficacy, these techniques are often impeded by the necessity for substantial investment in equipment, specialized knowledge, and intricate procedural steps, which complicate their application in real-time field detections. To surmount these challenges, a sensitive, rapid, and specific PCV detection method using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas12a/13a coupled with isothermal amplification, such as enzymatic recombinase amplification (ERA), recombinase polymerase amplification (RPA), and loop-mediated isothermal amplification (LAMP), has been developed. This novel method has undergone meticulous optimization for detecting PCV types 2, 3, and 4, boasting a remarkable sensitivity to identify a single copy per microliter. The specificity of this technique is exemplary, with no observable interaction with other porcine viruses such as PEDV, PRRSV, PRV, and CSFV. Its reliability has been validated with clinical samples, where it produced a perfect alignment with qPCR findings, showcasing a 100% coincidence rate. The elegance of merging CRISPR-Cas technology with isothermal amplification assays lies in its on-site testing without the need for expensive tools or trained personnel, rendering it exceptionally suitable for on-site applications, especially in resource-constrained swine farming environments. This review assesses and compares the process and characteristics inherent in the utilization of ERA/LAMP/RPA-CRISPR-Cas12a/Cas13a methodologies for the detection of PCV, providing critical insights into their practicality and effectiveness.

Detection of PCV2d in Vaccinated Pigs in Colombia and Prediction of Vaccine T Cell Epitope Coverage against Circulating Strains Using EpiCC Analysis.

Porcine circovirus type 2 (PCV2) is strongly linked to a group of syndromes referred to as porcine-circovirus-associated diseases (PCVADs), which are controlled through vaccination; however, this does not induce sterilizing immunity but is instead involved in the evolution of the virus and is considered a factor in vaccine failure. This study sampled 84 herds (167 pigs) vaccinated against PCV2 and with clinical signs of PCVADs in five provinces across Colombia. PCV2 was identified and further characterized at the molecular level via genotyping and phylogenetic reconstructions. In addition, PCV2-associated lesions were examined via histopathology. Furthermore, the PCV2-Cap sequences retrieved were compared with three vaccines via the EpiCC tool and T cell epitope coverage. The prevalence of PCV2 was 82% in pigs and 92.9% in herds. The highest viral loads were identified in lymphoid tissue, and PCV2d emerged as the most predominant in pigs and herds (93.4% and 92.3%). Sequences for PCV2-ORF2 (n = 57; 55 PCV2d and 2 PCV2a) were determined, and PCV2d sequences were highly similar. The most common pneumonia pattern was suppurative bronchopneumonia, while the most common lung lesion was exudation in the airways; in lymphoid tissue, there was lymphoid depletion. The bivalent vaccine (PCV2a and PCVb) exhibited a higher EpiCC score (8.36) and T cell epitope coverage (80.6%) than monovalent PCV2a vaccines. In conclusion, PCV2d currently circulates widely in Colombia. Despite vaccination, there are clinical cases of PCV2, and immunoinformatic analyses demonstrate that bivalent vaccines improved the average coverage.

Epidemiological investigation and analysis of the infection of porcine circovirus in Xinjiang

Porcine circoviruses, particularly porcine circovirus type 2 (PCV2) and porcine circovirus type 3 (PCV3), significantly impact the global pig industry due to their high prevalence and pathogenicity. Conversely, porcine circovirus type 1 (PCV1) and porcine circovirus type 4 (PCV4) currently have low positivity rates. This study aimed to characterize the distribution and epidemiology of porcine circoviruses in Xinjiang, while also analyzing the genetic diversity and evolution of PCV2 and PCV3, which pose the greatest threats to the industry. In this study, we collected blood and tissue samples from 453 deceased pigs across eight regions in Xinjiang Province from 2022 to 2024. We utilized real-time PCR to detect the presence of PCV1, PCV2, PCV3, and PCV4. The positive rates were 15%, 71%, 25%, and 17%, respectively. Genetic analysis showed 9 PCV2 sequences and 12 PCV3 sequences. The capsid protein of PCV2 showed significant variability. In contrast, the amino acid sequences of capsid in PCV3 were relatively stable. Moreover, we predicted antigenic epitopes for PCV3 capsid using IEDB and ElliPro. The findings from this study provide valuable epidemiological data on PCV coinfection in the Xinjiang region and enhance the understanding of virus diversity nationwide. This research may serve as an important reference for the development of strategies to prevent and control porcine circovirus infections.

Retrospective Analyses of Porcine Circovirus Type 3 (PCV-3) in Switzerland.

Porcine circovirus 3 (PCV-3) has emerged as a significant pathogen affecting global swine populations, yet its epidemiology and clinical implications remain incompletely understood. This retrospective study aimed to investigate the prevalence and histopathological features of PCV-3 infection in pigs from Switzerland, focusing on archival cases of suckling and weaner piglets presenting with suggestive lesions. An in-house qPCR assay was developed for detecting PCV-3 in frozen and formalin-fixed paraffin-embedded tissues, enhancing the national diagnostic capabilities. Histopathological reassessment identified PCV-3 systemic disease (PCV-3-SD) compatible lesions in 19 (6%) of archival cases, with 47% testing positive by qPCR across various organs. Notably, vascular lesions predominated, particularly in mesenteric arteries, heart, and kidneys. The study confirms the presence of PCV-3 in Switzerland since at least 2020, marking the first documented cases within the Swiss swine population. Despite challenges in in situ hybridization validation due to prolonged formalin fixation, the findings indicate viral systemic dissemination. These results contribute to the understanding of PCV-3 epidemiology in Swiss pigs, emphasizing the need for continued surveillance and further research on its clinical implications and interaction with host factors. Our study underscores the utility and limitations of molecular techniques in confirming PCV-3 infections.

Glaesserella parasuis serotype 4 exploits fibronectin via RlpA for tracheal colonization following porcine circovirus type 2 infection.

Porcine circovirus type 2 (PCV2) often causes disease through coinfection with other bacterial pathogens, including Glaesserella parasuis (G. parasuis), which causes high morbidity and mortality, but the role played by PCV2 and bacterial and host factors contributing to this process have not been defined. Bacterial attachment is assumed to occur via specific receptor-ligand interactions between adhesins on the bacterial cell and host proteins adsorbed to the implant surface. Mass spectrometry (MS) analysis of PCV2-infected swine tracheal epithelial cells (STEC) revealed that the expression of Extracellular matrix protein (ECM) Fibronectin (Fn) increased significantly on the infected cells surface. Importantly, efficient G. parasuis serotype 4 (GPS4) adherence to STECs was imparted by interactions with Fn. Furthermore, abrogation of adherence was gained by genetic knockout of Fn, Fn and Integrin β1 antibody blocking. Fn is frequently exploited as a receptor for bacterial pathogens. To explore the GPS4 adhesin that interacts with Fn, recombinant Fn N-terminal type I and type II domains were incubated with GPS4, and the interacting proteins were pulled down for MS analysis. Here, we show that rare lipoprotein A (RlpA) directly interacts with host Fibronectin mediating GPS4 adhesion. Finally, we found that PCV2-induced Fibronectin expression and adherence of GPS4 were prevented significantly by TGF-β signaling pathway inhibitor SB431542. Our data suggest the RlpA-Fn interaction to be a potentially promising novel therapeutic target to combat PCV2 and GPS4 coinfection.

Recombinant Polymerase Amplification Coupled with CRISPR/Cas12a Detection System for Rapid Visual Detection of Porcine Circovirus 3.

The porcine circovirus type 3 (PCV3) infection is an emerging disease associated with clinical signs of porcine dermatitis and nephropathy syndrome (PDNS)-like clinical signs. Currently, there is a lack of effective vaccines and therapeutics against this disease. Therefore, rapid, effective, sensitive, and specific detection methods are crucial for the timely identification, prevention, and control of PCV3. In this study, we developed one- and two-pot visual detection methods for PCV3 using a clustered regularly interspaced short palindromic repeat (CRISPR)/Cas12a detection system combined with recombinase polymerase amplification (RPA). These two methods demonstrated no cross-reactivity with eight other swine viruses and exhibited minimum detection limits of five and two copies of viral DNA, respectively, revealing their high specificity and sensitivity. During a clinical sample detection within 30 min, the coincidence rates between the one- and two-pot detection methods and real-time quantitative polymerase chain reaction (qPCR) were 100%. In conclusion, both one- and two-pot RPA-CRISPR/Cas12a detection methods have significant potential for the rapid, sensitive, and specific visual detection of PCV3.

Quantitative proteomic analysis of PK-15 cells infected with porcine circovirus type 3 using 4D-DIA approach.

Porcine circovirus type 3 (PCV3) infection is clinically related to various diseases, including porcine dermatitis and nephrotic syndrome (PDNS)-like disease, respiratory disease, reproductive disorders, and gastrointestinal and neurological diseases. Since PCV3 infection was discovered in 2016, it has developed rapidly and has attracted much attention worldwide. However, specific preventive and therapeutic interventions are currently lacking. In this study, four-dimensional (4D) data-independent acquisition (DIA)-based quantitative proteomics detection combined with bioinformatics analysis were employed to quantitatively identify the differentially expressed proteins in PK-15 cells from the PCV3-infected group compared with those from the uninfected control group. A total of 194 cellular proteins were significantly altered in response to PCV3 infection, including 58 upregulated proteins and 136 downregulated proteins. In our Gene Ontology (GO) enrichment analysis, these differentially expressed proteins were mostly associated with cellular anatomical entities, binding, cellular processes, biological regulation, catalytic activity, metabolic processes, developmental processes, protein-containing complexes and responses to stimuli. Our Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the DEPs were predominantly involved in metabolic pathways, the cAMP signaling pathway, protein processing in the endoplasmic reticulum, the PI3K-Akt signaling pathway, and the calcium signaling pathway. For the experiments, Western blotting (WB) was used to confirm the changes in important molecules. The differentially expressed proteins identified should contribute to a greater understanding of the mechanism of PCV3 replication and pathogenesis, as well as the host response.

Molecular detection of emerging porcine circovirus in Taiwan

Porcine Circovirus type (PCV) 2 is an important pathogen that has been circulating worldwide and has cuased serious economic loss in pig industry. However, both PCV3 and PCV4 are newly emerging viruses. In Taiwan, PCV2 has been one of the critical pathogens in pig frams and PCV3 has been detected since 2016; however, the epidemiolog of PCV3 in Taiwan remains unclear and PCV4 has yet to be identified. Therefore, in order to detect the positive rate of PCV2, to investigate the epidemiolog of PCV3 in the pig farms, and to examine whether pigs were infected with PCV4 in Taiwan, a total of 128 samples from 46 clinical cases of pigs were collected from September 2020 to December 2021. The case detection rates were 54.3 % for PCV2, 43.5 % for PCV3, and 2.2 % for PCV4. The results suggested that the positivity rates for both PCV2 and PCV3 were still high in Taiwan. In addition, PCV3 was detected among cases from all 7 sampled counties and in 11 of the 16 sampling months, suggesting that PCV3 may lead to endemic pig disease in Taiwan. Surprisingly, the PCV4 was also detected, suggesting the first PCV4 case in Taiwan. The complete genomes derived from the identified PCV3 and PCV4 strains were subsequently sequenced followed by phylogenetic analysis. The results suggested that the 17 identified PCV3 strains could be divided into Taiwanese-like and Japanese-like strains. In addition, the amino acid residues at positions 27, 80, and 212 in the identified PCV4 cap protein were asparagine, isoleucine, and methionine, respectively, and thus the identified PCV4 was catalorized into clade PCV4b. Consequently, it is concluded that (i) the prevalence of PCV2 and PCV3 is still high in Taiwanese pigs, (ii) PCV3 has may be an endemic infection in Taiwan and can be classified into Japanese-like and Taiwanese-like strains, (iii) PCV4 was detected for the first time in Taiwanese pigs and can be classified into PCV4b. It remains unclear how PCV2, PCV3, and PCV4 were introduced to Taiwan, and thus continuous investigation of emerging pathogens in pigs is needed.

Identification of a conserved B-cell epitope on the capsid protein of porcine circovirus type 4.

Porcine circovirus type 4 (PCV4) is a novel circovirus. Although PCV4 has been identified in several countries, including China, Korea, Thailand, and Spain, no vaccine is available. Given the potential pathogenic effects of PCV4 on pigs, PCV4 could threaten the global pig farming industry, highlighting the urgency for further investigation. Thus, epitopes of PCV4 remain to be determined. Our finding of a conserved epitope significantly advances vaccine development and pathogen detection.

An in vitro self-ligation-based method for constructing infectious DNA clone of porcine circovirus type 2

The aim of this study was to establish a rapid method for constructing infectious clones of porcine circovirus type 2 (PCV2). In this study, we constructed circular infectious clones of PCV2 by seamless cloning technology, using the clinically isolated strain PCV2-LX as a template. Meanwhile, this method was compared with the conventional restriction-ligation approach, focusing on the in vitro circularization (self-ligation) process of the genome and the growth characteristics of rescued viruses. The results showed that this method eliminates the need to analyze and introduce restriction endonuclease sites, thus avoiding the complexities associated with traditional restriction enzyme-based cloning steps. It offers a simple and rapid operation, enabling more efficient editing of the PCV2 genome. The infectious clones constructed using this method could be successfully rescued through liposome transfection, resulting in the production of recombinant viruses that could be stably passaged. Moreover, the recombinant viruses rescued by this method exhibited enhanced proliferative capacity in PK-15 cells and 3D4/31 cells (immortalized porcine alveolar macrophages). In conclusion, this study has established a novel reverse genetics system for PCV2, providing a new strategy for the development of PCV2 genetic engineering vaccines. Additionally, it serves as a reference for the construction of infectious clones for other emerging circoviruses such as PCV3 and PCV4.

E3 ligase RNF2 inhibits porcine circovirus type 3 replication by targeting its capsid protein for ubiquitination-dependent degradation.

Porcine circovirus type 3 (PCV3) is closely associated with various diseases, such as the porcine dermatitis, nephropathy syndrome, and multisystemic clinicopathological diseases. PCV3-associated diseases are increasingly recognized as severe diseases in the global swine industry. Ring finger protein 2 (RNF2), an E3 ubiquitin ligase exclusively located in the nucleus, contributes to various biological processes. This ligase interacts with the PCV3 Cap. However, its role in PCV3 replication remains unclear. This study confirmed that the nuclear localization signal domain of the Cap and the RNF2 N-terminal RING domain facilitate the interaction between the Cap and RNF2. Furthermore, RNF2 promoted the binding of K48-linked polyubiquitination chains to lysine at positions 139 and 140 (K139 and K140) of the PCV3 Cap, thereby degrading the Cap. RNF2 knockdown and overexpression increased or decreased PCV3 replication, respectively. Moreover, the RING domain-deleted RNF2 mutant eliminated the RNF2-induced degradation of the PCV3 Cap and RNF2-mediated inhibition of viral replication. This indicates that both processes were associated with its E3 ligase activity. Our findings demonstrate that RNF2 can interact with and degrade the PCV3 Cap via its N-terminal RING domain in a ubiquitination-dependent manner, thereby inhibiting PCV3 replication.IMPORTANCEPorcine circovirus type 3 is a recently described pathogen that is prevalent worldwide, causing substantial economic losses to the swine industry. However, the mechanisms through which host proteins regulate its replication remain unclear. Here, we demonstrate that ring finger protein 2 inhibits porcine circovirus type 3 replication by interacting with and degrading the Cap of this pathogen in a ubiquitination-dependent manner, requiring its N-terminal RING domain. Ring finger protein 2-mediated degradation of the Cap relies on its E3 ligase activity and the simultaneous existence of K139 and K140 within the Cap. These findings reveal the mechanism by which this protein interacts with and degrades the Cap to inhibit porcine circovirus type 3 replication. This consequently provides novel insights into porcine circovirus type 3 pathogenesis and facilitates the development of preventative measures against this pathogen.

Immunometabolic features of the formation of post-vaccination immunity against porcine circovirus type 2 in sows

Immunometabolic features of the formation of post-vaccination immunity against porcine circovirus type 2 in sows