Search Results (282)

Porcine circovirus 2 (PCV2) is a DNA virus that is classified in the genus Circovirus of the Circoviridae family, which is a causative agent of Porcine Circovirus-Associated disease (PCVAD). PCVAD continues to cause substantial losses in global pig farming, with PCV2d being the prevalent genotype worldwide, including in Vietnam. In this study, we focused on generating a recombinant PCV2d Cap protein fused to the GCN4pII motif (Cap2d-pII) in a plant-based system and evaluating its immunogenicity. The Cap2d-pII gene was cloned into a plant expression vector and introduced into Agrobacterium tumefaciens for transient expression in Nicotiana benthamiana leaves. Western blot analysis confirmed the high accumulation of the Cap2d-pII protein, which was purified by Immobilized affinity chromatography and used for immunizing mice. ELISA and immunoperoxidase monolayer assay results demonstrated that immunization with the recombinant protein elicited robust humoral and cellular immune responses. At 56 days after immunization, mice vaccinated with the Cap2d-pII protein generated PCV2d-specific IgG titers and IFN-γ responses that were consistent with those in mice receiving the commercial inactivated vaccine. These observations confirm that the plant-expressed Cap2d-pII antigen effectively activates both antibody- and T cell-mediated immune pathways. Collectively, this study identifies the Cap2d-pII protein as a promising plant-derived vaccine candidate for the development of effective and affordable PCV2d subunit vaccines. Full article

Background: Porcine circovirus type 2 (PCV2) remains one of the most important pathogens that infects swine, causing considerable economic losses worldwide. PCV2 vaccines are commercially available, and the development of experimental vaccines that could confer better protection against emerging genotypes is underway. The expression of virus-like particles (VLPs) carrying different PCV2 capsid (Cap) peptides in E. coli was recently reported. These chimeric particles were adjuvated with an oil-in-water emulsion with polymer and induced different titers of serum IgG in BALB/c mice after a single subcutaneous injection. The aim of this study was to assess the immune response and protective efficacy elicited by VLPs carrying the PCV2b Cap carboxy-terminal peptide in the target species. Methods: Domestic pigs (Sus scrofa domesticus) were immunized intramuscularly with 25 μg of adjuvated chimeric VLPs on days 0 and 14 and challenged on day 28 with a PCV2b Mexican isolate. PCV2 peptide-specific IgG seroconversion, serum cytokines, viral load in nasal swabs and organs, and histopathological score were determined. Results: IgG levels peaked 28 days post-immunization. Interleukin-12 and -18 and interferon-gamma increased 21 days after immunization. In addition, genomic material of PCV2 was detected in nasal swabs from one specimen on day 7, two specimens on day 14, and two specimens on day 21 following viral challenge. Finally, histological lesions were not less severe in immunized specimens compared to non-vaccinated/challenged specimens. Conclusions: These results suggest that immunization with chimeric VLPs could contribute to controlling viral shedding in pig herds where a PCV2b genotype is most prevalent. Full article

Porcine circovirus type 2 (PCV2), a widely distributed immunosuppressive virus, causes substantial economic losses in the global swine industry. C1QTNF6 has emerged as a novel immunoregulatory factor attracting increasing research interest due to its dual roles in both pro-inflammatory and antiviral immune responses. However, the role of C1QTNF6 in regulating PCV2 replication remains poorly characterized. Here, we analyzed C1QTNF6 expression patterns and identified its highly specific expression in placental tissues in both humans and pigs. We then overexpressed C1QTNF6 and conducted RNA sequencing analysis. Remarkably, 68 upregulated genes were identified, and most of them were interferon-stimulated genes (ISGs), including MX2 and ISG15. Functional enrichment analysis revealed that these genes were primarily associated with defense response to viruses and antiviral innate immune response. Subsequently, experimental data show that PCV2 infection significantly suppressed inflammatory responses and markedly downregulated the expression of C1qtnf6, MX2, and IFIT2. Moreover, experimental data indicated that C1QTNF6 inhibits PCV2 replication by targeting ISGs, while restoring MX2 expression. To verify whether C1QTNF6-MX2 antiviral axis mediates this antiviral effect, we constructed an MX2 overexpression plasmid and demonstrated that MX2 overexpression indeed significantly suppressed PCV2 replication. Together, these results provide important insights into PCV2-host interactions and the development of novel antiviral strategies. Full article

Porcine circovirus types 2 (PCV2) and 3 (PCV3) are major pathogens affecting swine health and productivity, yet important gaps remain in understanding their evolution and circulation in Europe, particularly within wild boar populations that may serve as reservoirs. This study examined the genetic diversity and evolutionary dynamics of PCV2 and PCV3 in Portugal, drawing on viral genomes obtained from domestic pigs and wild boars to explore transmission patterns, spillover events and the contribution of recombination to viral emergence. We identified two PCV2 genotypes (PCV2a and PCV2d) and two PCV3 genotypes (PCV3-2a and PCV3-3g) circulating in Portuguese swine. Phylogeographic reconstruction revealed multiple introductions of both PCV2 and PCV3 from China into Europe, followed by regional diversification and subsequent spread within European wild boar populations. Evidence of bidirectional viral exchange between domestic pigs and wild boars was also observed. Recombination played a notable role in PCV2 evolution, with consistent signals detected among PCV2a sequences and indications that the PCV2h genotype likely originated from a recombinant event involving a Portuguese PCV2a strain and a Chinese PCV2d strain. By contrast, no recombination was detected in PCV3, suggesting that its evolution is primarily mutation-driven. Overall, these findings highlight the complex evolutionary history of swine circoviruses in Europe and underscore the importance of continuous genomic surveillance in both domestic and wild hosts. The study reinforces the value of a One Health approach for monitoring and controlling emerging circoviruses with implications for animal health and livestock production. Full article

Porcine circovirus type 2 (PCV2) represents a principal infectious agent causing considerable economic detriment to swine production. N-acetyltransferase 10 (NAT10), which catalyzes N⁴-acetylcytidine (ac⁴C) deposition, has been implicated in regulating immune responses, RNA stability, and viral replication. However, its role in PCV2 infection remains unclear. In this study, we established a PCV2-infected PK15 cell model and observed a marked downregulation of NAT10 expression following infection. Functional assays demonstrated that NAT10 knockdown significantly suppressed PCV2 replication in PK15 cells. Comparative transcriptomic analysis revealed that NAT10 silencing altered the expression of 81 genes, predominantly involved in immune-related signaling pathways. Notably, integrative omics analysis identified NR1H4 as a potential downstream target of NAT10. Collectively, these findings elucidate the regulatory mechanism of NAT10 in PCV2 replication and provide new insights for identifying NAT10 as a potential biomarker and therapeutic target for PCV2 infection in pigs. Full article

Background/Objectives: Porcine Circovirus Type 2 (PCV2) and Mycoplasma hyopneumoniae are primary pathogens causing respiratory disease in pigs. Recently, a Ready-to-Use bivalent PCV2 and M. hyopneumoniae vaccine has been registered in China. The aim of this randomized, side-by-side trial was to evaluate the efficacy and safety of this vaccine under field conditions in a Chinese commercial pig farm. Methods: In total, 938 piglets were allocated to three groups—A (tested vaccine), B, C—and vaccinated according to different schemes. Efficacy was assessed by Average Daily Gain (ADG), pneumonia lesions at slaughter and PCV2 viremia. Systemic reactions were recorded after vaccination to evaluate safety. Results: ADG was higher in group A compared with other vaccination schemes. The prevalence of pneumonia lesions was significantly lower in group A. PCV2 viremia was overall low in all groups, with no reported differences. No severe or moderate systemic reactions were observed after vaccination. Only four pigs showed mild reactions (A: 2/320, B: 2/309; C: 0/309). Conclusions: Under these conditions, the tested vaccine was proved to be efficacious in increasing ADG and reducing pneumonia at slaughter by protecting against both PCV2 and M. hyopneumoniae field infections. It can also be concluded that the Ready-To-Use bivalent vaccine was safe. Full article

Background/Objectives: Maternally derived antibody (MDA) levels of porcine circovirus 2 (PCV2) may eventually interfere with humoral response and vaccination efficacy. This study aimed to evaluate the efficacy of a ready-to-use PCV2d and Mycoplasma hyopneumoniae combined vaccine in piglets with different PCV2 MDA levels at vaccination in an experimental inoculation with a heterologous viral genotype. Methods: Forty-eight piglets were allocated into vaccinated (V) and non-vaccinated (NV) groups with high (H) and low (L) PCV2 MDA subgroups (H-V, H-NV, L-V, L-NV). At 3 weeks of age, the piglets received either one dose of vaccine or placebo. Five weeks later, all animals were intranasally challenged with a PCV2b inoculum. Body weight was registered at different time points. Blood samples, peripheral blood mononuclear cells and tracheobronchial lymph nodes (TBLN) were collected and used to assess viraemia, viral load, humoral and cellular responses and histological lesions. Results: The V group showed higher PCV2 antibody levels from challenge onwards, along with a lower percentage of viraemic pigs and reduced viral load in serum at 2 and 3 weeks post-challenge (wpc) and in TBLN tissues compared to the NV group. The H-V group had the highest antibody levels post-challenge, showed no detectable viraemia and had a lower overall amount of virus in tissues. The NV group (especially H-NV) exhibited increased levels of IFN-γ, IFN-α and TNF-α post-challenge. Conclusions: The tested vaccine elicited humoral and cellular immune responses and reduced viral presence in serum and tissues, demonstrating efficacy in a PCV2 subclinical infection model despite high MDA levels at the time of vaccination. Understanding both humoral and cellular immune responses according to different MDA levels can help design more effective vaccination strategies against PCV2. Full article

Background: Porcine circovirus type 2 (PCV2) is the primary pathogen responsible for postweaning multisystemic wasting syndrome (PMWS) and related diseases, leading to significant economic losses in the global pig industry. Methods: This study conducted a thorough epidemiological survey between 2022 and 2024, gathering 6600 samples from 24 large-scale pig farms in Hubei Province. On the basis of these findings, the immune response and economic benefits of two representative commercial PCV2 subunit vaccines, recombinant baculovirus CP08 and Ingelvac CircoFLEX^®, were assessed in a modern fattening farm in Xiangyang city. Results: The results indicated no detection of viral antigens in sows; however, weaned piglets and fattening pigs presented high positivity rates, with 8-week-old nursery pigs identified as the peak period for infection. Both vaccines significantly improved average weight gain and reduced antigen positivity, with Ingelvac CircoFLEX^® demonstrating superior viral control and economic returns. Conclusions: This study offers valuable scientific and practical guidance for PCV2 control strategies and vaccine selection in Hubei and comparable regions. Full article

Despite the widespread use of Porcine circovirus type 2 (PCV2) vaccination, subclinical infection persists and remains a concern due to its economic impact. Therefore, continuous herd-level monitoring is essential to assess the dynamics of this infection on farms and minimize its impact. This study evaluated the applicability of a loop-mediated isothermal amplification (LAMP) assay for PCV2 detection in serum, air, and surface samples collected under field conditions. In addition, a simplified Direct LAMP protocol, omitting DNA extraction, was compared with quantitative PCR (qPCR) as the reference method. A total of 360 samples from PCV2 vaccinated and unvaccinated fattening farms were analyzed. Diagnostic performance was assessed in terms of sensitivity, specificity, predictive values, and concordance with qPCR, using Cohen’s kappa coefficient (κ). LAMP showed higher agreement with qPCR (κ = 0.52) than Direct LAMP (κ = 0.16). Serum samples provided the most reliable results when DNA extraction was performed, reaching substantial agreement with qPCR (κ = 0.76). However, Direct LAMP applied directly to serum was negatively affected by inhibitory substances, resulting in a significant drop in sensitivity. In contrast both air and surface samples yielded comparable results between LAMP and Direct LAMP, without the need for DNA extraction. Notably, LAMP-based assays detected PCV2 circulation earlier than qPCR, particularly in environmental samples. These findings demonstrate the potential of LAMP as a practical alternative to qPCR for PCV2 monitoring. While DNA extraction remains essential for reliable detection in serum, Direct LAMP represents a promising strategy for environmental surveillance, enabling rapid, low-cost, and on-farm diagnostics. Full article

Porcine circovirus type 3 (PCV3), initially identified in the United States in 2016, is associated with multisystemic inflammation, myocarditis, reproductive failure in sows, and growth retardation in piglets, posing a significant economic threat to the swine industry. In this study, prokaryotic-expressed recombinant PCV3 Cap protein was used to immunize mice and rabbits. A monoclonal antibody (mAb 4G1) was generated through hybridoma technology, targeting a novel linear epitope (³⁷DYYDKK⁴²) within the first β-sheet of the Cap structure. This epitope exhibits high conservation (99.35%, 1239/1247) based on sequence alignment analysis, and residues 39 and 42 are critical residues affecting mAb binding. Subsequently, using rabbit polyclonal antibody (pAb) as the capture antibody and mAb 4G1 as the detection antibody, a double antibody sandwich ELISA (DAS-ELISA) method was developed. The assay demonstrates a cut-off value of 0.271, a detection limit for positive pig serum is 1:800, and shows no cross-reactivity with other swine pathogens. Intra- and inter-assay coefficients of variation were <10%, with a linear detection range for Cap protein down to 3.4 ng/mL. The coincidence rate between the DAS-ELISA and qPCR was 93.33% (70/75) for PCV3 detection in serum, with a kappa value of 0.837. This study establishes a simple, sensitive, and operationally efficient DAS-ELISA and provides a reference for monitoring PCV3 infection in swine herds. Full article

Porcine circovirus 2 (PCV2) is still infecting pigs after almost 20 years of massive vaccination all over the world. Vaccines are highly effective at counteracting the clinical signs of systemic disease caused by PCV2 and can significantly reduce the number of subclinically infected pigs. However, current vaccination programs based on one single dose in piglets are insufficient to prevent infection in a proportion of animals. Moreover, systematic vaccination of the herd changes viral epidemiology and, consequently, can cause modifications in infection timing. Such a scenario may prompt intrauterine and piglet early infections, thus facilitating viral circulation even before vaccination takes place. Considering the demonstrated high vaccine efficacy, it would be legitimate to explore the possibility of eliminating PCV2 from swine herds, but only one attempt to eliminate the virus from a herd has been published so far. The present speculative review evaluates the existing scientific literature regarding the feasibility of getting rid of this virus under commercial farm conditions. The use of PCV2 vaccination in all swine populations within a herd and the implementation of regional or national control programs are foreseen as compulsory for the eventual successful elimination of this endemic viral infection. Full article

Porcine circovirus 2 (PCV2) is one of the most widespread immunosuppressive viruses, impairing the protective efficacy of vaccines in pig herds. Previous studies have shown that PCV2 infection reduces the generation of immune memory and antibody secretion induced by vaccination in hosts. In this study, we used single-cell mRNA sequencing of mice splenic cells to show that PCV2 infection decelerates the differentiation of light zone germinal center (GC) B cells into memory B cells and plasma cells. We found that, although PCV2 infection led to lymphocyte depletion in the spleens of mice, the remaining splenic B cells were activated by the infection. The percentage of naïve B cells in PCV2-infected mice decreased mainly due to differentiation rather than death. Meanwhile, the percentages of memory B cells and plasma cells increased without significant enhancement of functional gene expression. Focusing on the GC B cells, we found that PCV2 infection activated the proliferation of dark zone GC B cells, but not the differentiation of light zone GC B cells. Furthermore, the transcriptional level of Prdm1 was not significantly altered by PCV2 infection, and the level of Bach2 was dramatically reduced. Further analysis showed that the interactions between light zone GC B cells and dendritic cells, macrophages, and follicular helper T cells were weakened in the spleens of PCV2-infected mice. In conclusion, this study found that PCV2 infection impairs the differentiation of B cells into functional memory B cells and plasma cells. This may be an important and previously unrecognized reason why PCV2 infection impairs vaccine efficiency. Full article

Background: The efficacy of a novel combined vaccine targeting porcine circovirus types 2a/d (PCV2a/d), Mycoplasma hyopneumoniae, and M. hyorhinis was evaluated in a controlled challenge study. Methods: A total of 45 pigs were randomly allocated into nine groups (five pigs per group). Vaccinated groups received a single 2 mL intramuscular dose of the combined vaccine and were subsequently challenged with PCV2a, PCV2d, M. hyopneumoniae, and M. hyorhinis. Unvaccinated groups received a single 2 mL intramuscular dose of phosphate-buffered saline (0.01 M, pH 7.4). Growth performance, systemic adaptive immune (humoral and cellular) responses, viremia, laryngeal and nasal mycoplasma loads, and histopathological lesions were assessed. Results: Vaccinated pigs exhibited enhanced growth performance and elicited systemic immune responses, including both humoral and cellular immunity, against all four pathogens. Vaccination also significantly reduced viremia, mycoplasmal loads in laryngeal and nasal swabs, and the severity of associated lesions compared with unvaccinated controls. Conclusions: These results indicated that the combined vaccine was efficacious and conferred protection against PCV2a, PCV2d, M. hyopneumoniae, and M. hyorhinis challenge under experimental conditions. This combined vaccine represented an effective strategy to enhance growth performance and control complex co-infection in swine populations. Full article

Respiratory infections are a major concern in pig farming as they negatively impact animal health and productivity. Coughing is a key symptom of respiratory disease and can be classified as productive or non-productive, but human assessment often leads to inconsistencies. This study aimed to use a machine learning model to classify pig coughs and investigate their association with respiratory infections. Cough sounds from 49 fattening pigs were recorded and analyzed using a Python-based machine learning system. The model’s accuracy in detecting coughs was 0.72, compared to 0.69 for farmers. For classification of non-productive coughs, the machine learning results showed strong agreement with infection status by Mycoplasma hyopneumoniae, with a Spearman’s correlation of 0.80 and a Cohen’s Kappa of 0.79. However, the association with Porcine Circovirus type 2 was weak, with correlation and Kappa values of 0.05 and 0.037, respectively. These findings indicate that machine learning can classify pig coughs more accurately than human evaluators and that non-productive coughs are strongly linked to Mycoplasma infection but not to PCV2. This suggests the potential use of machine learning for more reliable disease monitoring and early detection in swine production. Full article

Porcine circovirus type 2 (PCV2) is a globally prevalent swine pathogen that induces immunosuppression, predisposing pigs to subclinical infections. In intensive farming systems, PCV2 persistently impairs growth performance and vaccine efficacy, leading to substantial economic losses in the swine industry. Emerging evidence suggests that certain viruses exploit Suppressor of Cytokine Signaling 3 (SOCS3), a key immune checkpoint protein, to subvert host innate immunity by suppressing cytokine signaling. While SOCS3 has been implicated in various viral infections, its regulatory role in PCV2 replication remains undefined. This study aims to elucidate the mechanisms underlying the interplay between SOCS3 and PCV2 during viral pathogenesis. Porcine SOCS3 was amplified using RT-PCR and stably overexpressed in PK-15 cells through lentiviral delivery. Bioinformatics analysis facilitated the design of three siRNA candidates targeting SOCS3. We systematically investigated the effects of SOCS3 overexpression and knockdown on PCV2 replication kinetics and host antiviral responses by quantifying the viral DNA load and the mRNA levels of cytokines. PCV2 infection upregulated SOCS3 expression at both transcriptional and translational levels in PK-15 cells. Functional studies revealed that SOCS3 overexpression markedly enhanced viral replication, whereas its knockdown suppressed viral proliferation. Intriguingly, SOCS3-mediated immune modulation exhibited a divergent regulation of antiviral cytokines: PCV2-infected SOCS3-overexpressing cells showed elevated IFN-β but suppressed TNF-α expressions, whereas SOCS3 silencing conversely downregulated IFN-β while amplifying TNF-α responses. This study unveils a dual role of SOCS3 during subclinical porcine circovirus type 2 (PCV2) infection: it functions as a host-derived pro-viral factor that facilitates viral replication while simultaneously reshaping the cytokine milieu to suppress overt inflammatory responses. These findings provide novel insights into the mechanisms underlying PCV2 immune evasion and persistence and establish a theoretical framework for the development of host-targeted control strategies. Although our results identify SOCS3 as a key host determinant of PCV2 persistence, the precise molecular pathways involved require rigorous experimental validation. Full article