Porcine circovirus diseases

The stability of PCV2 virus-like particles from mammalian cells and challenges for biotechnological applications

Porcine circovirus type 2 (PCV2) is a highly damaging pathogen for pig farming, causing significant economic losses. Despite the availability of vaccines based on different technologies, the virus steadily infects the world's pig population. In this context, virus-like particles (VLPs) constitute appealing alternatives for vaccine development as they lack the viral genome but present intact external surfaces. Using PCV2 VLPs expressed and purified from Expi293F cells, we demonstrate the potential to generate high-purity VLPs with excellent antigenic properties through biochemical, biophysical, and immunological characterization. Using different techniques, we also determined the melting temperature of these VLPs at nearly 55 °C. Furthermore, we conducted multiscale simulations of whole VLPs combined with multiple sequence analyses to provide a new perspective into the stability determinants. Computational results support our findings and underscore the importance of protein-nucleic acid interactions in stabilizing the VLP structure. Moreover, we spotted an unforeseen correlation between amino acid conservation, solvent exposure, and flexibility, revealing a link to viral assembly and immune evasion. These novel insights are crucial to guide the development of stabilized VLP for new vaccine prototypes to respond to the emergence of new PCV2 genotypes.

A case report of porcine circovirus 3 (PCV3) reproductive disease in Iberian semi-outdoor reared sows

BACKGROUND

Porcine circovirus 3 (PCV3) is a recently discovered swine pathogen associated with reproductive disease. To date, clinical problems linked to PCV3 have been described in intensive rearing pig farms. The present case describes an Iberian semi-outdoors sow farm affected by PCV3 reproductive disease.

CASE PRESENTATION

The affected farm was composed of 420 self-replaced Iberian sows, working in 3-week batches (60 sows per batch). The farm was free from porcine reproductive and respiratory syndrome virus (PRRSV) and had been previously affected by porcine circovirus 2 (PCV2) reproductive disease, which was successfully managed through sow vaccination. In spring 2022, reproductive disease was noticed with a high increase in the number of mummified foetuses and stillborn piglets from gilts as the most remarkable finding; multiparous sows were not affected. A first analysis with pooled stillborn tissues ruled out most swine reproductive pathogens and revealed detection of PCV3. To further elucidate PCV3 implication in the reproductive disease, a complete post-mortem examination of stillborn and mummified foetuses from two affected litters was conducted. Pooled tissue samples yielded high PCV3 loads by quantitative PCR. Grossly, one (out of 5) stillborn had an enlarged, flaccid heart. Histopathological evaluation revealed PCV3 lesions consisting of lymphohistiocytic and systemic periarteritis (3/5). The grossly affected heart had lymphohistiocytic myocarditis with fibrosis and lymphohistiocytic endocarditis. By in situ hybridization, high amounts of PCV3 genome were observed within histological lesions. Moreover, immunohistochemistry against PRRSV and PCV2 resulted negative in the same tissues.

CONCLUSIONS

This is the first report of PCV3 reproductive disease in a semi-extensive production Iberian pig farm, affecting exclusively gilts. Moreover, this is the first description of grossly apparent myocarditis associated to PCV3 infection. Therefore, PCV3 should be considered within the differential diagnostic list of swine reproductive problems in non-intensive pig rearing production.

Retrospective investigation of porcine circoviruses in cases of porcine dermatitis and nephropathy syndrome

Porcine dermatitis and nephropathy syndrome (PDNS) is a severe condition that affects mainly growing pigs and is considered to be caused by a type III hypersensitivity reaction. Although porcine circovirus 2 (PCV-2) is the antigen linked to this condition, porcine circovirus 3 (PCV-3) has also been proposed to be causally associated with PDNS. Moreover, the initial description of porcine circovirus 4 (PCV-4) also related this novel agent to this clinicopathological entity. Therefore, this retrospective study included a large number of PDNS cases (n = 102) fulfilling specific histologic criteria in search of known porcine circoviruses (PCV-1 to PCV-4) by conventional and/or quantitative PCR (qPCR). All the samples were subjected to PCV-2 immunohistochemistry (IHC) or conventional in situ hybridization (C-ISH), and RNAscope® (R-ISH) was used to study PCV-2 and PCV-3 localization in a subset of the samples. All PDNS cases were PCV-2 positive by qPCR, while 30 of them (29.4%) yielded PCV-3 qPCR positivity; PCV-2 viral loads were significantly greater than PCV-3 viral loads. All animals were negative for PCV-1 and PCV-4. By C-ISH/IHC, 63 cases (61.8%) were positive for PCV-2, with low to moderate amounts of antigen. R-ISH demonstrated higher sensitivity, as all studied cases were positive; however, neither PCV-2 nor PCV-3 were consistently found within characteristic PDNS lesions. These results indicate that all PDNS-affected pigs were infected with PCV-2, emphasizing the likelihood that this viral antigen is causally linked to this condition. In contrast, no evidence of the association of PCV-1, PCV-3 or PCV-4 with PDNS was found.

Beak and feather disease virus (BFDV) persists in tissues of asymptomatic wild Crimson Rosellas

Infectious diseases can drive populations and species to extinction. Beak and feather disease virus (BFDV) is a circovirus of global conservation concern that can infect all Psittaciformes and some other species. Yet some parrot species, such as Crimson rosellas (Platycercus elegans), can live successfully with high BFDV prevalence (>40%) with no clinical signs reported in infected individuals. We assessed BFDV load in 10-12 tissues per bird, from n = 66 P. elegans, to reveal tissue tropism and BFDV persistence in tissues. Here we show that in 94% of individuals, BFDV was detected in one or more tissues. While BFDV replicated to high levels in subadults, in adults (some confirmed seropositive) the virus persisted in various tissues at much lower levels. Our findings reveal that BFDV is much more common in wild P. elegans than previously thought and suggest that current screening practices (mostly on blood) may substantially underestimate BFDV infection estimates, with implications for biosecurity and conservation programs globally.

Diversity of Molecular Functions of RNA-Binding Ubiquitin Ligases from the MKRN Protein Family

Makorin RING finger protein family includes four members (MKRN1, MKRN2, MKRN3, and MKRN4) that belong to E3 ubiquitin ligases and play a key role in various biological processes, such as cell survival, cell differentiation, and innate and adaptive immunity. MKRN1 contributes to the tumor growth suppression, energy metabolism, anti-pathogen defense, and apoptosis and has a broad variety of targets, including hTERT, APC, FADD, p21, and various viral proteins. MKRN2 regulates cell proliferation, inflammatory response; its targets are p65, PKM2, STAT1, and other proteins. MKRN3 is a master regulator of puberty timing; it controls the levels of gonadotropin-releasing hormone in the arcuate nucleus neurons. MKRN4 is the least studied member of the MKRN protein family, however, it is known to contribute to the T cell activation by ubiquitination of serine/threonine kinase MAP4K3. Proteins of the MKRN family are associated with the development of numerous diseases, for example, systemic lupus erythematosus, central precocious puberty, Prader-Willi syndrome, degenerative lumbar spinal stenosis, inflammation, and cancer. In this review, we discuss the functional roles of all members of the MKRN protein family and their involvement in the development of diseases.

A field evaluation of a new porcine circovirus type 2d and Mycoplasma hyopneumoniae bivalent vaccine in herds suffering from subclinical PCV2d infection and enzootic pneumonia

BACKGROUND

This field efficacy study was designed to determine the efficacy of a new bivalent vaccine containing porcine circovirus type 2d (PCV2d) and Mycoplasma hyopneumoniae at three independent pig farms.

METHODS

Three pig farms were selected based on their history of subclinical PCV2 infection and enzootic pneumonia. Each farm housed a total of 40, 18-day-old pigs that were randomly allocated to 1 of 2 treatment groups. Pigs were administered a 2.0 mL dose of the bivalent vaccine intramuscularly at 21 days of age in accordance with the manufacturer's recommendations, whereas unvaccinated pigs were administered a single dose of phosphate-buffered saline at the same age.

RESULTS

Clinically, the average daily weight gain of vaccinated groups was significantly higher (p < 0.05) than those of unvaccinated animals during the growing (70-112 days of age), finishing (112-175 days of age) and overall (3-175 days of age) stages of production. Vaccinated animals elicited neutralizing anti-PCV2 antibodies and PCV2d-specific interferon-γ secreting cells (IFN-γ-SC), which reduced the amount of PCV2d genomic copies in blood and reduced lymphoid lesions severity when compared with unvaccinated animals. Similarly, vaccinated animals elicited M. hyopneumoniae-specific IFN-γ-SC, which reduced the amount of M. hyopneumoniae in the larynx and reduced lung lesions severity.

CONCLUSIONS

The result of the field trial demonstrated that the bivalent vaccine was efficacious in the protection of swine herds suffering from subclinical PCV2d infection and enzootic pneumonia.

Porcine circovirus type 2 ORF5 induces an inflammatory response by up-regulating miR-21 levels through targeting nuclear ssc-miR-30d

Porcine circovirus type 2 (PCV2) infection leads to multi-system inflammation in pigs, and this effect can be achieved by upregulating host miR-21. The underlying mechanism of miR-21 regulates PCV2-induced inflammation is already known, however, how PCV2 regulates miR-21 levels and function using both autonomic and host factors remains to be further revealed. Here we present the first evidence that PCV2 ORF5 induces an inflammatory response by up-regulating miR-21 level through targeting nuclear miR-30d. In this study, we found that overexpression of ORF5 significantly increased miR-21 level and promoted the expression of inflammatory cytokines and activation of the NF-κB pathway, while ORF5 mutation had the opposite effect. Moreover, the differential expression of miR-21 could significantly change the pro-inflammatory effect of ORF5, indicating that ORF5 promotes inflammatory response by up-regulating miR-21. Bioinformatics analysis and clinical detection found that nuclear miR-30d was significantly down-regulated after ORF5 overexpression and PCV2 infection, and targeted pri-miR-21 and PCV2 ORF5. Functionally, we found that miR-30d inhibited the levels of miR-21 and inflammatory cytokines in cells. Mechanistically, we demonstrated that ORF5 inhibits miR-30d expression levels through direct binding but not via the circRNA pathway, and miR-30d inhibits miR-21 levels by targeting pri-miR-21. In summary, the present study revealed the molecular mechanism of ORF5 upregulation of miR-21, further refined the molecular chain of PCV2-induced inflammatory response and elucidated the role of miRNAs in it.

Analysis of the anti-PCV2 mechanism of Lactobacillus acidophilus based on non-target metabolomics and high-throughput molecular docking

Our previous studies have revealed that L. acidophilus possesses inhibitory effects on PCV2 proliferation in vivo, although the underlying mechanisms remain elusive. Probiotics like L. acidophilus are known to exert antiviral through their metabolites. Therefore, in this study, non-targeted metabolomics was used to detect the changes in metabolites of L. acidophilus after 24 h of proliferation. Subsequently, high-throughput molecular docking was utilized to analyze the docking scores of these metabolites with PCV2 Cap and Rep, aiming to identify compounds with potential anti-PCV2 effects. The results demonstrated that 128 compounds such as Dl-lactate were significantly increased. The results of high-throughput molecular docking indicated that compounds such as ergocristine, and telmisartan formed complexes with Cap and Rep, suggesting their potential anti-PCV2 properties. Furthermore, compounds like vitamin C, exhibit pharmacological effects consistent with L. acidophilus adding credence to the idea that L. acidophilus may exert pharmacological effects through its metabolites. These results will provide a foundation for the study of L. acidophilus.

Exudative glomerulonephritis associated with acute leptospirosis in dogs

In the past 20 years in Switzerland, dogs with suspect acute leptospirosis frequently showed severe glomerular changes that had not been previously reported. These features were characterized by abundant extravasated erythrocytes and fewer neutrophils accompanied by marked fibrin exudation into the urinary space that was interpreted as an exudative glomerulonephritis (GN). This retrospective study describes this significant glomerular pathological change and investigates the association with leptospirosis. Tissues from 50 dogs with exudative GN, retrieved from 2 pathology archives in Switzerland were reviewed using hematoxylin and eosin, periodic acid-Schiff, phosphotungstic acid-hematoxylin, and Warthin and Starry stains. Clinical and postmortem data were collected for each case. Immunohistochemistry (IHC) and/or polymerase chain reactions were used as confirmatory tests for leptospirosis. While all 50 cases had clinical and pathological features supporting a diagnosis of leptospirosis, 37 cases were confirmed for the disease. Using a LipL32 antibody in addition to the OMV2177 antibody raised against the lipopolysaccharide of Leptospira interrogans serovar Copenhageni increased the detection rate of Leptospira by IHC in exudative GN from 24% to 62%. Signalment, seasonality, clinical signs, blood results, and pathological changes in dogs with exudative GN were similar to those reported for dogs without GN and confirmed infection by Leptospira spp.. Exudative GN was common among Swiss dogs with leptospirosis where it caused acute severe disease. Leptospirosis should be considered as a cause of this new pathologic feature by the pathologist. The pathogenesis remains unclear, but involvement of a geographic-specific serovar with unique virulence factors is suspected and warrants further investigation.

Development of recombinant capsid protein-based single serum dilution ELISA for sero-detection of porcine circovirus type 2 infection in pigs

Porcine Circovirus 2 (PCV2) is the major causative agent of postweaning multisystemic wasting syndrome (PMWS) of swine and is one of the reasons for severe economic loss in swine industry. In India, there is a considerable prevalence rate of PCV2 infection in pig population, PCV2d being the most prominent genotype. Proper sero-diagnosis and sero-surveillance of the disease is formulated as an effective control measure. In this study, a recombinant capsid protein-based single serum dilution indirect ELISA was developed for determination of antibody titre of the infected pigs. The capsid protein (Cap) of PCV2d was produced in Saccharomyces cerevisiae cells and the capsid protein was purified by affinity chromatography. This recombinant protein was used as a coating antigen to develop a cost effective, highly sensitive and specific single serum dilution ELISA. The in-house developed ELISA was optimized to be used in a 1:200 single serum dilution. The developed ELISA along with a commercial ELISA kit were compared with a sensitive immuno-peroxidase assay (IPMA) by receiver-operating characteristics (ROC) test. Our results showed that the developed single serum dilution ELISA had a higher sensitivity and specificity in comparison to the commercial ELISA. The area under the ROC curve (AUC) also confirmed that the developed ELISA had a better overall diagnostic performance in comparison to the commercial ELISA kit.

Frequency of PCV-2 viremia in nursery piglets from a Spanish swine integration system in 2020 and 2022 considering PRRSV infection status

BACKGROUND

Porcine circovirus 2 (PCV-2) poses a significant economic threat for the swine industry, causing a range of diseases collectively referred to as porcine circovirus diseases (PCVDs). Despite PCV-2 vaccine effectiveness, the need for monitoring infectious pressure remains. PCV-2 coinfection with other pathogens like porcine reproductive and respiratory syndrome virus (PRRSV) can exacerbate disease severity and lead to PCV-2-systemic disease cases. Monitoring both PRRSV and PCV-2 in co-infected farms is crucial for an effective management and vaccination programs. The present cross-sectional study aimed to determine PCV-2 antibody levels in piglets at weaning and PCV-2 and PRRSV viremia in pooled serum samples at weaning (vaccination age) and at 6 and 9 weeks of age from a Spanish swine integration system in 2020 (48 farms) and in 2022 (28 out of the 48 analysed previously).

RESULTS

The frequency of PCV-2 detection in pools of piglet sera was 2.1% (2020) and 7.1% (2022) at vaccination age but increased at the end of the nursery period (10.4% in 2020 and 39.3% in 2022) in both years. Co-infections between PCV-2 and PRRSV were detected in a significant proportion of PRRSV positive farms (15% in 2020, and 60% in 2022). PCV-2 antibody levels (ELISA S/P ratios) at weaning were lower in PCV-2 qPCR positive farms at different sampling time-points (0.361 in 2020 and 0.378 in 2022) compared to PCV-2 qPCR negative ones (0.587 in 2020 and 0.541 in 2022). The 28 farms tested both years were classified in four different epidemiological scenarios depending on their PCV-2 virological status. Those PCV-2 qPCR negative farms in 2020 that turned to be positive in 2022 had a statistically significant increase of PRRSV RT-qPCR detection and a PCV-2 antibody levels reduction, facts that were not observed in the rest of the scenarios.

CONCLUSION

This epidemiological study in farms from the same integration system determined the occurrence, in 2020 and in 2022, of PCV-2 and PRRSV infections in piglets during the nursery period by using pooled serum samples.

Circular single-stranded DNA as switchable vector for gene expression in mammalian cells

Synthetic gene networks in mammalian cells are currently limited to either protein-based transcription factors or RNA-based regulators. Here, we demonstrate a regulatory approach based on circular single-stranded DNA (Css DNA), which can be used as an efficient expression vector with switchable activity, enabling gene regulation in mammalian cells. The Css DNA is transformed into its double-stranded form via DNA replication and used as vectors encoding a variety of different proteins in a wide range of cell lines as well as in mice. The rich repository of DNA nanotechnology allows to use sort single-stranded DNA effectors to fold Css DNA into DNA nanostructures of different complexity, leading the gene expression to programmable inhibition and subsequently re-activation via toehold-mediated strand displacement. The regulatory strategy from Css DNA can thus expand the molecular toolbox for the realization of synthetic regulatory networks with potential applications in genetic diagnosis and gene therapy.

Porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus alone or associated are frequent intralesional detected viruses in porcine respiratory disease complex cases in Northern Italy

Methods

This study aimed to examine the pathological impact of Porcine Circovirus type 2 (PCV2) and Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) through histological and immunohistochemical analysis of 79 cases of Porcine Respiratory Disease Complex (PRDC) collected from 22 farms in Northern Italy. Lung tissue and several lymphoid organ samples were deployed to associate PCV2-positive stain with Circovirus-associated Diseases (PCVD).

Results

The most common lung lesion observed was interstitial pneumonia, alone or combined with bronchopneumonia. By immunohistochemistry, 44 lungs (55.7%) tested positive for PCV2, 34 (43.0%) for PRRSV, 16 (20.3%) for both viruses and in 17 cases (21.5%) neither virus was detected. Twenty-eight out of 44 (63.6%) PCV2-positive cases had lymphoid depletion or granulomatous inflammation in at least one of the lymphoid tissues examined; thus, they were classified as PCV2 Systemic Diseases (PCV2-SD). In the remaining 16 out of 44 cases (36.4%), PCV2-positive lung lesions were associated with hyperplastic or normal lymphoid tissues, which showed PCV2-positive centrofollicular dendritic cells in at least one of the lymphoid tissues examined. Therefore, these cases were classified as PRDC/PCV2-positive. In the PCV2-positive animals, 42.9% of the PCV2-SD cases (12/28) showed immunohistochemistry (IHC) positivity for PRRSV in the lung tissue, while 25.0% of PRDC/PCV2-positive cases (4/16) showed double positivity for PCV2 and PRRSV.

Discussion

In light of the caseload presented in this study, characterized by the high proportion of PCV2-SD cases alongside the overall respiratory symptomatology, it is imperative to emphasize the crucial role of a comprehensive sampling protocol. This is critical to avoid underestimating the harm caused by PCV2 in farms, particularly with respect to the systemic form of the disease. PCV2 and PRRSV remain the primary infections associated with PRDC in Italy that can significantly impact farm health and co-infections in the field can worsen the pathology, thus the selection of appropriate preventive measures is critical.

Revisiting Porcine Circovirus Infection: Recent Insights and Its Significance in the Piggery Sector

Porcine circovirus (PCV), a member of the Circoviridae family within the genus Circovirus, poses a significant economic risk to the global swine industry. PCV2, which has nine identified genotypes (a-i), has emerged as the predominant genotype worldwide, particularly PCV2d. PCV2 has been commonly found in both domestic pigs and wild boars, and sporadically in non-porcine animals. The virus spreads among swine populations through horizontal and vertical transmission routes. Despite the availability of commercial vaccines for controlling porcine circovirus infections and associated diseases, the continuous genotypic shifts from a to b, and subsequently from b to d, have maintained PCV2 as a significant pathogen with substantial economic implications. This review aims to provide an updated understanding of the biology, genetic variation, distribution, and preventive strategies concerning porcine circoviruses and their associated diseases in swine.

Matrine Targets Intestinal Lactobacillus acidophilus to Inhibit Porcine Circovirus Type 2 Infection in Mice

Porcine circovirus type 2 (PCV2) has caused huge economic losses to the pig industry across the world. Matrine is a natural compound that has been shown to regulate intestinal flora and has anti-PCV2 activity in mouse models. PCV2 infection can lead to changes in intestinal flora. The intestinal flora has proved to be one of the important pharmacological targets of the active components of Traditional Chinese Medicine. This study aimed to determine whether matrine exerts anti-PCV2 effects by regulating intestinal flora. In this study, fecal microbiota transplantation (FMT) was used to evaluate the effect of matrine on the intestinal flora of PCV2-infected Kunming (KM) mice. The expression of the Cap gene in the liver and the ileum, the relative expression of IL-1β mRNA, and the Lactobacillus acidophilus (L. acidophilus) gene in the ileum of mice were determined by real-time quantitative polymerase chain reaction (qPCR). ELISA was used to analyze the content of secretory immunoglobulin A (SIgA) in small intestinal fluid. L. acidophilus was isolated and identified from the feces of KM mice in order to study its anti-PCV2 effect in vivo. The expression of the Cap gene in the liver and the ileum and the relative expression of L. acidophilus and IL-1β mRNA in the ileum were determined by qPCR. The results showed that matrine could reduce the relative expression of IL-1β mRNA by regulating intestinal flora, and that its pharmacological anti-PCV2 and effect may be related to L. acidophilus. L. acidophilus was successfully isolated and identified from the feces of KM mice. The in vivo experiment revealed that administration of L. acidophilus also reduced the relative expression of IL-1β mRNA, and that it had anti-PCV2 effects in PCV2-infected mice. It was found that matrine could regulate the abundance of L. acidophilus in the gut of mice to exert an anti-PCV2 effect and inhibit PCV2-induced inflammatory response.

Interaction between host cell proteins and open reading frames of porcine circovirus type 2

Postweaning multisystemic wasting syndrome (PMWS) is caused by a systemic inflammation after porcine circovirus type 2 (PCV2) infection. It was one of the most economically important pathogens affecting pig production worldwide before PCV2 vaccine was first introduced in 2006. After the development of a vaccine against PCV2a type, pig farms gradually restored enormous economic losses from PMWS. However, vaccine against PCV2a type could not be fully effective against several different PCV2 genotypes (PCV2b - PCV2h). In addition, PCV2a vaccine itself could generate antigenic drift of PCV2 capsid. Therefore, PCV2 infection still threats pig industry worldwide. PCV2 infection was initially found in local tissues including reproductive, respiratory, and digestive tracks. However, PCV2 infection often leads to a systemic inflammation which can cause severe immunosuppression by depleting peripheral lymphocytes in secondary lymphoid tissues. Subsequently, a secondary infection with other microorganisms can cause PMWS. Eleven putative open reading frames (ORFs) have been predicted to encode PCV2 genome. Among them, gene products of six ORFs from ORF1 to ORF6 have been identified and characterized to estimate its functional role during PCV2 infection. Acquiring knowledge about the specific interaction between each PCV2 ORF protein and host protein might be a key to develop preventive or therapeutic tools to control PCV2 infection. In this article, we reviewed current understanding of how each ORF of PCV2 manipulates host cell signaling related to immune suppression caused by PCV2.

Molecular characterization and phylogenetic analysis of porcine circovirus 2 from Kerala, India

Porcine circovirus type 2 (PCV2), the causative agent of porcine circovirus-associated diseases (PCVADs), has a worldwide distribution, and is considered as one of the most important emerging viral pathogens of economic importance. In Kerala, a total of 62 tissue samples were collected during post mortem from pigs suspected to have died of PCV2 infection. The animals exhibited symptoms like respiratory illness, gradual wasting, rough hair coat, polypnoea, dyspnoea, pallor, diarrhoea, icterus, etc. PCV2 was detected in 36 (58.06%) samples by PCR. Phylogenetic analyses of complete ORF2, and complete genome sequences were carried out and genotypes 2d, 2 h and 2b were detected. The genotype predominant in Kerala was 2d. It was observed that genotypes 2 h and 2b have been recently introduced into North Kerala as it was not detected in the region prior to 2016. Close relationship of Kerala sequences with sequences from Tamil Nadu, Uttar Pradesh and Mizoram were noticed in the phylogenetic tree and also at the amino acid level. A unique K243N mutation was observed in one of the samples. It was also noticed that the most variable amino acid position in ORF2 was 169 where the occurrence of three possible amino acids were observed. The results of the study indicate that multiple genotypes of PCV2 are prevalent in pigs in Kerala and that the percent positivity is higher than that recorded in the State previously.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-023-00814-1.

Into the backyard: Multiple detections of PCV-2e in rural pig farms of Northern Italy. An unexpected ecological niche?

Porcine circovirus type 2 (PCV-2) is among the most burdensome viruses of the swine industry globally. Several genotypes have been periodically emerging, but just three of them (PCV-2a, PCV-2b, and PCV-2d) seem to circulate worldwide and be associated with the disease. Conversely, the spatial-temporal distribution of minor genotypes appears limited and their clinical relevance is still unclear. Recently PCV-2e was incidentally detected for the first time in Europe in a breeding farm in Northeastern Italy, while no connection could be established with countries where this genotype had been previously detected. To investigate circulating genotypes in the neglected rural context and provide a comparison with the most explored industrial context, a molecular survey was performed on samples collected in rural (n = 72) and industrial farms (n = 110) located in the same geographic area. Phylogenetic analysis surprisingly evidenced PCV-2e circulation only in pigs reared in backyard farms (n = 5), while major genotypes (PCV-2a, -2b, -2d) circulate in both rearing contexts. However, the close genetic similarity between the herein detected PCV-2e strains and the previously reported one testify that, although unusual, such rural-to-industrial strains exchange affected also PCV-2e. The greater genetic and phenotypic diversity of PCV-2e genotype compared to other ones might threaten the protection granted by current vaccines. The present study suggests the rural context as an ecological niche for the circulation of PCV-2e, and even of other minor genotypes. PCV-2e detection in pigs with outdoor access further stresses the epidemiological role of backyard farms as interfaces for pathogen introduction, potentially ascribable to the different rearing approaches, lower managerial and biosecurity capabilities, and easier contacts with wildlife.

DNA virome composition of two sympatric wild felids, bobcat (Lynx rufus) and puma (Puma concolor) in Sonora, Mexico

With viruses often having devastating effects on wildlife population fitness and wild mammals serving as pathogen reservoirs for potentially zoonotic diseases, determining the viral diversity present in wild mammals is both a conservation and One Health priority. Additionally, transmission from more abundant hosts could increase the extinction risk of threatened sympatric species. We leveraged an existing circular DNA enriched metagenomic dataset generated from bobcat (Lynx rufus, n = 9) and puma (Puma concolor, n = 13) scat samples non-invasively collected from Sonora, Mexico, to characterize fecal DNA viromes of each species and determine the extent that viruses are shared between them. Using the metaWRAP pipeline to co-assemble viral genomes for comparative metagenomic analysis, we observed diverse circular DNA viruses in both species, including circoviruses, genomoviruses, and anelloviruses. We found that differences in DNA virome composition were partly attributed to host species, although there was overlap between viruses in bobcats and pumas. Pumas exhibited greater levels of alpha diversity, possibly due to bioaccumulation of pathogens in apex predators. Shared viral taxa may reflect dietary overlap, shared environmental resources, or transmission through host interactions, although we cannot rule out species-specific host-virus coevolution for the taxa detected through co-assembly. However, our detection of integrated feline foamy virus (FFV) suggests Sonoran pumas may interact with domestic cats. Our results contribute to the growing baseline knowledge of wild felid viral diversity. Future research including samples from additional sources (e.g., prey items, tissues) may help to clarify host associations and determine the pathogenicity of detected viruses.

A Sandwich ELISA for Quality Control of PCV2 Virus-like Particles Vaccine

Porcine circovirus type 2 (PCV2) is a highly prevalent virus in pig farms worldwide that causes significant economic losses in the swine industry. The PCV2 virus-like particles (VLPs) are potent subunit vaccines that are widely used. Currently, the adopted quality control of VLPs vaccines is mainly based in animal testing, the titration of neutralizing antibodies, or other biochemical/biophysical assays. In this study, we generated a monoclonal antibody that can distinguish assembled PCV2 VLPs from the capsid proteins. Subsequently, a convenient Sandwich ELISA was developed based on the monoclonal antibody (mAb) that recognizes the PCV2 VLPs specifically. This assay can be used for the quantity and quality control of PCV2 VLPs vaccines for both the intermediate or final products with high accuracy.

Presence of Porcine Circovirus Type 2 in the Environment of Farm Facilities without Pigs in Long Term-Vaccinated Farrow-to-Wean Farms

Vaccination against Porcine Circovirus Type 2 (PCV2) even over several years has proven as an insufficient measure to eradicate the infection from farms, possibly due to not producing sterilizing immunity. Viral persistence in the farm environment has been proposed as a possible cause of reinfection, and for that reason, the main objective of this study was to identify potential critical points where PCV2 could persist in farrow-to-wean farms which had been vaccinating piglets for years. Surface samples were collected from different farm facilities with and without animals and analyzed by qPCR to detect and quantify the viral load. Most of the samples taken in animal housing facilities tested negative (96.6%); however, PCV2 was more frequently detected in samples from the offices (37.5%), the farm staff (25%) and the perimeter (21%). These results indicate that PCV2 contamination is frequent in facilities despite the long-term use of vaccination programs. Therefore, PCV2 control programs should include more exhaustive cleaning and disinfection protocols in non-animal facilities, as well as the implementation of specific biosecurity measures in these areas to minimize the risk of PCV2 introduction from external sources.

Coinfections of African swine fever virus, porcine circovirus 2 and 3, and porcine parvovirus 1 in swine in Nigeria

As pig production increases in Africa, it is essential to identify the pathogens that are circulating in the swine population to assess pig welfare and implement targeted control measures. For this reason, DNA samples collected from pigs in Nigeria in the context of African swine fever monitoring were further screened by PCR for porcine circovirus 2 (PCV-2), porcine circovirus 3 (PCV-3), and porcine parvovirus 1 (PPV1). Forty-seven (45%) pigs were positive for two or more pathogens. Sequence analysis identified PCV-2 genotypes a, b, and d, while limited genetic heterogenicity was observed among PCV-3 strains. All except one of the PPV1 sequences were genetically distinct from those previously identified in other countries.

Visual and label-free ASFV and PCV2 detection by CRISPR-Cas12a combined with G-quadruplex

African swine fever (ASF) and postweaning multisystemic wasting syndrome (PMWS) are acute infectious diseases caused by the African swine fever virus (ASFV) and porcine circovirus type 2 (PCV2). At present, there are no effective vaccines for the prevention of ASFV. PMWS, which is harmful to the domestic and even the world pig industry, is difficult to cure and has a high mortality. So, developing simple, inexpensive, and accurate analytical methods to detect and effectively diagnose ASFV and PCV2 can be conducive to avoid ASFV and PCV2 infection. CRISPR has become a potentially rapid diagnostic tool due to recent discoveries of the trans-cleavage properties of CRISPR type V effectors. Herein, we report the visual detection based on CRISPR-Cas12a (cpf1), which is more convenient than fluorescence detection. Through in vitro cleavage target DNA activation, Cas12a can trans-cleavage ssDNA G-quadruplex. TMB/H2O2 and Hemin cannot be catalyzed by cleavaged G-DNA to produce green color products. This protocol is useful for the detection of ASFV and PCV2 with high sensitivity. This method can enable the development of visual and label-free ASFV and PCV2 detection and can be carried out in the field without relying on instruments or power. This method can complete nucleic acid detection at 37 °C without using other instruments or energy. Our research has expanded the application of Cas12a and laid the foundation for the field's rapid detection of viral nucleic acid in future.

Wild Boars (Sus scrofa, L. 1758) from Castile and Leon Region (Spain): A Histopathology Survey

Wild boars are wild ungulates with a wide distribution in Europe, with a relevant role in wildlife and public health. In Spain, high (and sometimes artificial) densities of wild boars are responsible for several health problems. Regular surveys, with hunters' collaboration, are crucial to monitor these diseases. Histological analyses were performed for lung, liver, and kidneys from 72 wild boars (58 from Zamora, 16 from Palencia). Lungs were the most affected organs, mainly revealing parasitic pneumonia (34.7%). Hydropic, vacuolar, and other cellular changes (33.3%) and congestion (16.7%) were found in the liver, and only 30.6% of the wild boars presented no alterations in this organ. Regarding the kidney, non-purulent nephritis (22.2%) was the most common lesion. This study gives an overview of the health status of wild boar populations in Castile and León. Other laboratory analyses are needed to obtain definitive diagnoses of these lesions, reach other conclusions, or apply any mitigation strategies to protect animals' or consumers' health.

Survey of porcine circovirus type 2 and parvovirus in swine breeding herds of Colombia

Background

One of the consequences of the presentation of reproductive failures in sows is the economic losses in production because it alters the estimated values of the volume of production, decreasing the productivity of the farm. Porcine circovirosis by porcine circovirus 2 (PCV2) has been associated with reproductive disorders, and porcine parvovirus (PVP) is one of the pathological agents most related to the presentation of reproductive failure in pigs. In Colombia, there are reports of the presence of PCV2 through molecular techniques, and PVP through serum tests; however, in the department of Tolima, the prevalence of these two viruses is unknown.

Objective

In this study, the aim was to establish a report of the prevalence of viruses in five municipalities of the department of Tolima‐Colombia.

Methods

Blood samples from 150 breeding sows of five municipalities in Tolima, Colombia, were obtained. Quantitative polymerase chain reaction (qPCR) was used to detect the PCV2 and PVP virus in the blood samples followed by PCR and sequencing of 16 PCR products of the amplification of the cap gene of PCV2. A phylogenetic tree was constructed to identify the genotype of the PCV2 virus.

Results

The presence of PCV2d in sows was detected in 135 samples (90%), as well as the identification of PVP in 2.6% of the samples. In addition, the phylogenetic analysis showed that 16 isolates were the PCV2d2 genotype.

Conclusion

PCV2d and PVP were found to coinfect the females, and the identification of variability in regions in the predicted amino acid sequence of the PCV2 capsid may be associated with virus pathogenicity.

Efficacy Studies of a Trivalent Vaccine Containing PCV-2a, PCV-2b Genotypes and Mycoplasma hyopneumoniae When Administered at 3 Days of Age and 3 Weeks Later against Porcine Circovirus 2 (PCV-2) Infection

Four studies under preclinical and clinical conditions were performed to evaluate the efficacy of a new trivalent vaccine against Porcine circovirus 2 (PCV-2) infection. The product contained inactivated PCV-1/PCV-2a (cPCV-2a) and PCV-1/PCV-2b (cPCV-2b) chimeras, plus M. hyopneumoniae inactivated cell-free antigens, which was administered to piglets in a two-dose regime at 3 days of age and 3 weeks later. The overall results of preclinical and clinical studies show a significant reduction in PCV-2 viraemia and faecal excretion, and lower histopathological lymphoid lesions and PCV-2 immunohistochemistry scores in vaccinated pigs when compared to non-vaccinated ones. Furthermore, in field trial A, a statistically significant reduction in the incidence of PCV-2-subclinical infection, an increase in body weight from 16 weeks of age to slaughterhouse and an average daily weight gain over the whole period (from 3 days of age to slaughterhouse) was detected in the vaccinated group when compared to the non-vaccinated one. Circulation of PCV-2a in field trial A, and PCV-2b plus PCV-2d in field trial B was confirmed by virus sequencing. In conclusion, a double immunization with a cPCV-2a/cPCV-2b/M. hyopneumoniae vaccine was efficacious against PCV-2 infection by reducing the number of histopathological lymphoid lesions and PCV-2 detection in tissues, serum, and faeces, as well as reducing losses in productive parameters.

Vimentin promotes porcine circovirus type 2 (PCV2) replication in pig alveolar macrophage

Porcine circovirus type 2 (PCV2) is a swine pathogen that causes postweaning multisystemic wasting syndrome, associated with a number of other disease symptoms in pigs. It has caused high economic losses for pig industries in China and worldwide. Vimentin is a cytoskeletal protein involved in the lifecycle of numerous viruses. In this study, the role of Vimentin in PCV2 replication in pig alveolar macrophage (3D4/21) cells was studied. A 3D4/21 cell line overexpressing Vimentin was established using a lentivirus expression system, in which PCV2 replication was significantly enhanced. Meanwhile, in the Vimentin silenced 3D4/21 cells, PCV2 replication was significantly reduced. Furthermore, we found that PCV2 infection in 3D4/21 cells promoted Vimentin phosphorylation and rearranged Vimentin distribution in cells. By inhibition of CaMKII pathway, Vimentin phosphorylation was significantly suppressed and PCV2 replication was significantly inhibited. The results in this study indicated that in 3D4/21 cells, PCV2 promoted CaMKIIγ-medicated Vimentin phosphorylation and altered its cellular distributions to accomplish its own replication.

Revisiting Porcine Circovirus Disease Diagnostic Criteria in the Current Porcine Circovirus 2 Epidemiological Context

Current knowledge on porcine circovirus diseases (PCVD) caused by Porcine circovirus 2 (PCV-2) includes the subclinical infection (PCV-2-SI), systemic (PCV-2-SD) and reproductive (PCV-2-RD) diseases, and porcine dermatitis and nephropathy syndrome (PDNS). Criteria to establish the diagnosis of these conditions have not changed over the years; thus, the triad composed by clinical signs, lesions and viral detection in lesions are still the hallmark for PCV-2-SD and PCV-2-RD. In contrast, PCV-2-SI diagnosis is not usually performed since this condition is perceived to be controlled by default through vaccination. PDNS is diagnosed by gross and histopathological findings, and PCV-2 detection is not recognized as a diagnostic criterion. Molecular biology methods as a proxy for PCVD diagnoses have been extensively used in the last decade, although these techniques should be mainly considered as monitoring tools rather than diagnostic ones. What has changed over the years is the epidemiological picture of PCV-2 through the massive use of vaccination, which allowed the decrease in infectious pressure paralleled with a decrease in overall herd immunity. Consequently, the need for establishing the diagnosis of PCVD has increased lately, especially in cases with a PCV-2-SD-like condition despite vaccination. Therefore, the objective of the present review is to update the current knowledge on diagnostic criteria for PCVDs and to contextualize the interest of using molecular biology methods in the overall picture of these diseases within variable epidemiological scenarios of PCV-2 infection.

Epidemiology of Porcine Circovirus Type 2 Circulating in Wild Boars of Portugal during the 2018–2020 Hunting Seasons Suggests the Emergence of Genotype 2d

Simple Summary

Porcine circovirus type 2 (PCV-2) is a swine disease associated with post-weaning multi-systemic wasting syndrome, which causes a high economic impact on animal production. Recently, new evidence has suggested the increasing circulation of the PCV-2d genotype. We screened wild boar stools collected from several districts across Portugal during the 2018–2020 hunting seasons, for PCV-2 and genetically characterized detected strains. From a total 76 stool samples of wild boar tested, two sequences were obtained, both of the PCV-2d genotype, showing the presence of this genotype in Portugal for the first time. Monitoring wild PCV-2 reservoirs is important for both veterinary public health and economic reasons.

Abstract

Porcine circovirus type 2 (PCV-2) is associated with several syndromes affecting swine, also known as porcine-circovirus-associated diseases, of which post-weaning multi-systemic wasting syndrome stands out due to its high economic impact on swine production. Recent data suggest the increasing circulation of the PCV-2d genotype in several countries worldwide. To provide updated data on PCV-2 genotypes currently circulating in swine in Portugal, we screened wild boar stools collected from several districts across Portugal, during the 2018–2020 hunting seasons, for PCV-2 and genetically characterized detected strains. From a total of 76 stool samples of wild boar tested by PCR for the partial PCV-2 ORF2 gene, two sequences were obtained (2/76; 2.6%, 95% confidence interval: 0.032–9.18). Bidirectional sequencing showed that the sequences were 100% identical and both of the PCV-2d genotype, showing for the first time the presence of this genotype in Portugal. Monitoring wild PCV-2 reservoirs is important for both veterinary public health and economic reasons, since PCV-2 infection has a strong economic impact on the swine industry.

Whole-Genome Sequence of a Porcine Circovirus Type 2 Strain Detected in Assam, India

Porcine circovirus-associated disease caused by porcine circovirus type 2 (PCV2) is a vital threat to the global pig industry. In this study, we have characterized the complete genome sequence of a PCV2 isolate, namely, Assam-01, belonging to the genotype PCV2d.

Minimal Dosage of Porcine Circovirus Type 2d Based Virus-like Particles to Induce Stable Protective Immunity against Infection

In recent years, porcine circovirus type 2d (PCV2d) has achieved a dominant position worldwide. Various PCV2d capsid-based vaccines have been used to alleviate concerns regarding the emergence of the variant. This study aimed to determine the dosage of recombinant PCV2d capsid protein to induce protective efficacy against experimental challenge with a virulent PCV2d strain. Conventional 3-week-old pigs were intramuscularly inoculated with different doses of the protein (60, 20, 10 and 2 µg). Four weeks after vaccination, all pigs were challenged with pathogenic PCV2d (SNU140003), which was isolated from a farm severely experiencing PCV2-associated disease in Korea. Vaccination with greater than 10 µg of the capsid protein caused a significant (p < 0.05) reduction in PCV2d viremia, lymphoid lesions and lymphoid PCV2 antigen levels in vaccinated challenged pigs compared to unvaccinated challenged pigs. The vaccination also resulted in significantly higher (p < 0.05) titers of neutralizing antibodies against PCV2d. However, the pigs vaccinated with 2 µg had significantly lower neutralizing antibody titers than the other vaccinated groups. They showed a similar level of challenged PCV2d in serum and lymphoid lesion score compared to unvaccinated challenged pigs. The difference in efficacy among the vaccinated groups indicates that there may be a baseline dosage to induce sufficient neutralizing antibodies to prevent viral replication in pigs. In conclusion, at least 10 µg dosage of capsid protein is essential for stable protective efficacy against PCV2d in a pig model.

Mitochondrial Localization Signal of Porcine Circovirus Type 2 Capsid Protein Plays a Critical Role in Cap-Induced Apoptosis

Porcine circovirus 2 (PCV2), considered one of the most globally important porcine pathogens, causes postweaning multisystemic wasting syndrome (PMWS). This virus is localized in the mitochondria in pigs with PMWS. Here, we identified, for the first time, a mitochondrial localization signal (MLS) in the PCV2 capsid protein (Cap) at the N-terminus. PK-15 cells showed colocalization of the MLS-EGFP fusion protein with mitochondria. Since the PCV2 Cap also contained a nuclear localization signal (NLS) that mediated entry into the nucleus, we inferred that the subcellular localization of the PCV2 Cap is inherently complex and dependent on the viral life cycle. Furthermore, we also determined that deletion of the MLS attenuated Cap-induced apoptosis. More importantly, the MLS was essential for PCV2 replication, as absence of the MLS resulted in failure of virus rescue from cells infected with infectious clone DNA. In conclusion, the MLS of the PCV2 Cap plays critical roles in Cap-induced apoptosis, and MLS deletion of Cap is lethal for virus rescue.

Integration of Microfluidics, Photonic Integrated Circuits and Data Acquisition and Analysis Methods in a Single Platform for the Detection of Swine Viral Diseases

Simple Summary

The control of several swine viral diseases relies mainly on evidence-based prevention protocols due to the lack of effective treatments or vaccines. To design these protocols, laboratory investigation of viral infections is critical to confirm their occurrence and determine their epizootiology. However, laboratory confirmation of certain swine viral diseases is a time-consuming and labor-intensive process, requiring scientific personnel with relevant expertise. Point-of-Care (POC) diagnostics are tests and devices that provide clinically relevant information on-site, facilitating decision-makers to swiftly take countermeasures for disease control. In the present study, novel photonic biosensors were integrated into a single, automated POC device that can record and analyze changes in the sensors’ refractive index, allowing the detection of Porcine Parvovirus (PPV) and Porcine Circovirus 2 (PCV-2) in oral fluids within 75 min. The objective of this work was to validate this device using reference and field samples (oral fluids). The system was able to detect PPV and PCV-2 in oral fluid samples satisfactorily. The device can be directly deployed in farms for the fast diagnosis of these diseases, contributing to farm biosecurity.

Abstract

Viral diseases challenge the health and welfare of pigs and undermine the sustainability of swine farms. Their efficient control requires early and reliable diagnosis, highlighting the importance of Point of Care (POC) diagnostics in veterinary practice. The objective of this study was to validate a novel POC system that utilizes Photonic Integrated Circuits (PICs) and microfluidics to detect swine viral pathogens using oral fluids and Porcine Parvovirus (PPV) and Porcine Circovirus 2 (PCV-2) as proofs of concept. The sensitivity and specificity of the device were calculated for both viruses, and Receiver Operating Characteristic (ROC) curves were drawn. PPV had an Area Under Curve (AUC) value of 0.820 (95% CI: 0.760 to 0.880, p < 0.0001), and its optimal efficiency threshold of detection shifts was equal to 4.5 pm (68.6% sensitivity, 77.1% specificity and Limit of Detection (LOD) value 10⁶ viral copies/mL). PCV-2 had an AUC value of 0.742 (95% CI: 0.670 to 0.815, p < 0.0001) and an optimal efficiency threshold of shifts equal to 6.5 pm (69.5% sensitivity, 70.3% specificity and LOD 3.3 × 10⁵ copies/mL). In this work, it was proven that PICs can be exploited for the detection of swine viral diseases. The novel device can be directly deployed on farms as a POC diagnostics tool.

Genetic association of polymorphisms in porcine RGS16 with porcine circovirus viral load in naturally infected Yorkshire pigs

Regulator of G protein signaling 16 (RGS16) is known to be associated with porcine circovirus type 2 (PCV2). PCV2 associated disease (PCVAD) is a serious problem in the swine industry. The representative symptoms of PCVAD are high viral titer proliferation and decreased average daily gain. In this study, we identified single nucleotide polymorphisms (SNPs) in the RGS16 region, including the upstream region. Of the 22 identified SNPs, rs332913874, rs326071195, and rs318298586 were genotyped in 142 Yorkshire pigs. These SNPs were significantly associated with the PCV2 viral load. Moreover, the haplotype combination was also related to the PCV2 viral load. The haplotype and diplotype analysis also had a significant difference with the PCV2 viral load. Taken together, our results suggest that RGS16 SNPs considerably affect the PCV2 viral load.

Balantidium coli in pig farms suspected of porcine circovirus type 2 (PCV2) associated enteritis

Introduction

Diarrhoea in growing-finishing pigs is a common problem of commercial pig farms. Among many causative factors, porcine circovirus type 2 (PCV2) is one considered an important pathogen in modern pig production. The aim of the study was to verify if PCV2 was responsible for antibiotic non-responsive diarrhoea and wasting in pigs.

Material and Methods

A total of 13 dead pigs aged between 12 and 15 weeks from three Polish farms with persistent herd symptoms suggestive of PCV2 infection were provided for evaluation. Sections of lymph nodes and intestines were analysed by in situ hybridization (ISH) for PCV2 and histopathological examination. Faeces and intestinal scrapings were tested for Lawsonia intracellularis and Brachyspira hyodysenteriae by real-time PCR and for parasitic infection by flotation and decantation.

Results

ISH and histopathological examination showed that all pigs were PCV2 systemic disease negative. Swine dysentery was confirmed by real-time PCR on two farms, and proliferative enteropathy on one farm. In histological examinations, erosions of the caecal and colonic mucosa were found, together with cysts and trophozoites of Balantidium coli. The protozoa were present in the intestinal lumen and mucosa. B. coli cysts were identified in faeces from all examined pigs.

Conclusion

These results suggest that monitoring of B. coli infections should be an additional measure of control and prevention of gastrointestinal tract disorders in modern swine husbandry.

Host immune response to infection with porcine circoviruses

Porcine circovirus type 2 (PCV2), which serves as a major causative agent of PCV2-associated diseases and causes severe loss to the pig industry worldwide, can dysregulate the immune response and induce immunosuppression in PCV2-infected pigs. Similar to PCV2, porcine circovirus type 3 (PCV3), a newly identified swine circovirus which might be closely associated with porcine dermatitis and nephropathy syndrome, reproductive disorder, and multisystemic inflammatory responses, also interferes with host immune defense. Interaction between host immune system and PCVs is considered to be a crucial determinant of pathogenicity in pigs. Here, we sought to briefly discuss the current knowledge regarding the interaction of porcine circovirus type 2 and/or 3 with host immune cells and immune responses to better depict the viral immunomodulatory capacity, pathogenic mechanisms, and the future research direction in host immune responses to infection with PCV2 and PCV3.

Selection and Characterization of a Single-Chain Variable Fragment against Porcine Circovirus Type 2 Capsid and Impedimetric Immunosensor Development

Porcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus-associated disease (PCVAD) that causes huge global economic losses for the swine industry. Effective strategies or rapid detection of PCV2 in pig are essential to control PCVAD. Here, single-chain variable fragments (scFvs) were selected and characterized against the PCV2 capsid using phage display technology. Phage scFv clones were selected from the human scFv phagemid library (Tomlinson I + J) for direct panning against the PCV2 capsid. Eighty-four monoclonal phage scFvs were individually tested for binding to the PCV2 capsid by ELISA. Eight scFv clones showed significant binding to the PCV2 capsid and only three clones (clone nos. 13, 37, and 81) contained both VHCDRs and VLCDRs in the sequence. Clone scFv no. 81 had the highest reactivity to the PCV2 capsid and was constructed in the pET22b (+) expression vector. The recombinant was transformed to Escherichia coli BL21(DE3) for expression and purification. The scFv showed appropriate affinity to the PCV2 capsid by western blot analysis. Kinetics of scFv and the PCV2 capsid were determined using surface plasmon resonance and showed binding affinity in the nanomolar range (K D = 57.2 nM). Our scFv was first applied in the development of an impedimetric immunosensor for PCV2 capsid detection, and results showed that impedance increased with increasing PCV2 capsid expression with limit of detection = 114 nM. Findings demonstrated that our scFv has potential for use as a receptor for biosensor devices.

Seasonal Variation in Prevalence of Mycoplasma hyopneumoniae and Other Respiratory Pathogens in Peri-Weaned, Post-Weaned, and Fattening Pigs with Clinical Signs of Respiratory Diseases in Belgian and Dutch Pig Herds, Using a Tracheobronchial Swab Sampling Technique, and Their Associations with Local Weather Conditions

Besides Mycoplasma hyopneumoniae (M. hyopneumoniae), many other viruses and bacteria can concurrently be present in pigs. These pathogens can provoke clinical signs, known as porcine respiratory disease complex (PRDC). A sampling technique on live animals, namely tracheobronchial swab (TBS) sampling, was applied to detect different PRDC pathogens in pigs using PCR. The objective was to determine prevalence of different PRDC pathogens and their variations during different seasons, including correlations with local weather conditions. A total of 974 pig farms and 22,266 pigs were sampled using TBS over a 5-year period. TBS samples were analyzed using mPCR and results were categorized and analyzed according to the season of sampling and local weather data. In samples of peri-weaned and post-weaned piglets, influenza A virus in swine (IAV-S), porcine reproductive and respiratory syndrome virus-European strain (PRRSV1), and M. hyopneumoniae were found as predominant pathogens. In fattening pigs, M. hyopneumoniae, porcine circovirus type 2 (PCV-2) and PRRSV1 were predominant pathogens. Pathogen prevalence in post-weaned and finishing pigs was highest during winter, except for IAV-S and A. pleuropneumoniae, which were more prevalent during autumn. Associations between prevalence of several PRDC pathogens, i.e., M. hyopneumoniae, PCV-2 and PRRSV, and specific weather conditions could be demonstrated. In conclusion, the present study showed that many respiratory pathogens are present during the peri-weaning, post-weaning, and fattening periods, which may complicate the clinical picture of respiratory diseases. Interactions between PRDC pathogens and local weather conditions over the 5-year study period were demonstrated.

Detection and molecular characterization of two canine circovirus genotypes co-circulating in Vietnam

Background

Canine circovirus is reported in dogs in many countries, including the USA, China and Thailand. It has been detected in healthy dogs and dogs with diarrhea, hemorrhagic gastroenteritis, and vasculitis. It comprises five genotypes and is frequently found as a coinfection with canine parvovirus-2 (CPV-2).

Aim

To characterize canine circovirus genotypes co-circulating with CPV-2 in Vietnam.

Method

PCR assessment of 81 CPV-2-positive fecal samples from Vietnamese diarrheic dogs up to seven months of age for other viral enteric pathogens, including canine bocavirus, canine adenovirus, paramyxovirus, canine coronavirus, porcine circovirus-3 and canine circovirus. In addition, eight selected full genome sequences of Vietnamese canine circovirus were analyzed and used for phylogeny.

Results

In total 19.8% of samples were found to be positive for canine circovirus. Phylogeny revealed that the Vietnamese canine circovirus strains were clustered in two different genotypes (genotype-1 and -3). The genetic diversity among Vietnamese canine circovirus was 86.0–87.2%. The nucleotide discrepancy among both genotypes altered the deduced amino acid sequence in 14 and ten residues of the replicase and capsid proteins, respectively. Genetic recombination analysis revealed that the Vietnamese canine circovirus-6 strain has the American and Chinese canine circovirus as its major and minor parents, respectively. Only a single dog revealed triple detections of CPV-2c, Canine circovirus and canine adenovirus (1.2%).

Conclusion

The co-circulation of two different genotypes of canine circovirus and CPV-2c in dogs in Vietnam has been illustrated.

Clinical relevance

The mortality rate with CPV-2 only (22%) doubled in dogs with canine circovirus and CPV-2 co-infection.

PCV3 in Thailand: Molecular epidemiology and relationship with PCV2

Porcine circovirus type 3 has been circulating throughout the world and since their first report, various clinical signs and disease developments have been documented. The virus is similar to the closely related PCV2 and is associated with several clinical signs called porcine circovirus-associated diseases (PCVAD). PCV2 or PCV3 is occasionally reported with clinical signs such as PDNS, respiratory signs and reproductive failure. Retrospective research conducted in Thailand revealed that both PCV2 and PCV3 have been circulation for decades. However, awareness about PCV3 infection has just arisen in recent years because of the similarities observed in disease circulation and clinical signs that have led to concerns. This study was conducted to find the relationship between the quantity of PCV2 and PCV3 in Thai pigs displaying the clinical signs related to PCVAD. A total of 479 serum samples with different production phases and clinical signs were sent to Kamphaeng Saen Veterinary Diagnostic Center (KVDC) for qPCR to detect the presence of PCV2 or PCV3. There was no relationship between the PCV3 and PCVAD-related clinical signs. Also, the relationship between PCV2 and PCV3 with no clinical signs suggested that both viruses might come from the same reservoir or have been circulating in Thailand for a long time, leading to common incidents in finding. The viral load of PCV2 was significantly different among the pig groups with and without clinical signs. The capsid sequence analysis of PCV3 revealed that 22 capsid sequences obtained from this study were found as clusters within PCV3a with a minor variation. Additional control measures are further needed to reduce the findings of the viruses. A future study with a control experiment may be needed to clarify the pathogenesis of PCV3.

Genotyping of Porcine Circovirus 2 (PCV-2) in Vaccinated Pigs Suffering from PCV-2-Systemic Disease between 2009 and 2020 in Spain

Vaccination against porcine circovirus 2 (PCV-2) is a common practice all over the world. Vaccines can prevent PCV-2-systemic disease (PCV-2-SD) outbreaks but not PCV-2 infection, which can be detectable in a percentage of vaccinated animals. Occasionally, PCV-2-SD is diagnosed in vaccinated farms. The objective of this study was to genotype the PCV-2 strains detected in vaccinated animals diagnosed with PCV-2-SD. Additionally, the evolution of the frequency of PCV-2 genotype detection at Spanish, European, and world levels was assessed. Fifty cases diagnosed as PCV-2-SD between 2009 and 2020 were included in this study. PCV-2 genotype was determined by sequencing the Cap gene region. Among them, only PCV-2b (23/50, 46%) and PCV-2d (27/50, 54%) genotypes were detected. Although the frequency of detection of these two genotypes was similar, their temporal distribution was different. Whereas most PCV-2b sequences (17/23, 74%) were detected between 2009 and 2012, PCV-2d sequences were obtained from 2013 to 2020. Indeed, a predominance of the PCV-2d genotype was observed from 2013 onwards, a trend also noticed at European and world levels. The results suggest that detection of particular genotypes in vaccinated animals probably reflects the general prevalence of the genotypes over time rather than genotype-specific vaccine-immunity escaping.

Oral Immunization with Lactobacillus casei Expressing the Porcine Circovirus Type 2 Cap and LTB Induces Mucosal and Systemic Antibody Responses in Mice

Porcine circovirus type 2 (PCV2) causes many diseases in weaned piglets, leading to serious economic losses to the pig industry. This study investigated the immune response following oral administration of Lactobacillus casei ATCC393 (L. casei 393) expressing PCV2 capsid protein (Cap) fusion with the Escherichia coli heat-labile toxin B subunit (LTB) in mice. Recombinant L. casei strains were constructed using plasmids pPG611.1 and pPG612.1. The expression and localization of proteins from recombinant pPG611.1-Cap-LTB (pPG-1-Cap-LTB)/L. casei 393 and pPG612.1-Cap-LTB (pPG-2-Cap-LTB)/L. casei 393 were detected. All recombinant strains were found to be immunogenic by oral administration in mice and developed mucosal and systemic immune responses against PCV2. The titers of specific antibodies in mice administered pPG-2-Cap-LTB/L. casei 393 were higher than those in mice administered pPG-1-Cap-LTB/L. casei 393 in serum and the mucosal samples. The mucosal immune response was not only limited to the gastrointestinal tract but was also generated in other mucosal parts. Thus, the application of recombinant L. casei could aid in vaccine development for PCV2.

Interaction of porcine circovirus-like virus P1 capsid protein with host proteins

Background

Porcine circovirus-like virus P1 is a relatively new kind of virus that is closely related to the post-weaning multisystemic wasting syndrome, congenital tremors, and abortions in swine. The molecular mechanisms of P1 virus infection and pathogenesis are fully unknown. To analyze P1 and its host interactions, we used a yeast two-hybrid (Y2H) assay to identify cellular proteins interacting with the Cap of the P1 virus. In this study, the Cap of the P1 virus exhibited no self-activation and toxicity to yeast cells and was used as bait to screen the Y2H library prepared from the pancreas tissue.

Results

Five cellular proteins (EEP, Ral GDS, Bcl-2-L-12, CPS1, and one not identified) were found to interact with P1 Cap. The interaction between Cap and Ral GDS was confirmed by co-immunoprecipitation.

Conclusions

Our data are likely to support the future investigation of the underlying mechanism of P1 infection and pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02926-6.

Efficacy of Two Commercial Ready-To-Use PCV2 and Mycoplasma hyopneumoniae Vaccines under Field Conditions

Porcine Circovirus Type 2 (PCV2) and Mycoplasma hyopneumoniae are economically important pathogens in swine farms. Vaccination is the main preventive measure for both infections. In order to test two ready-to-use bivalent vaccines, 646 piglets from a herd actively infected with both pathogens were stratified according to the sow parity number and randomly assigned to three groups: A and B were vaccinated with two different vaccines, respectively, while C remained as the unvaccinated control. Vaccine efficacy was assessed based on the weight, average daily weight gain (ADWG), degree of lung lesions, presence of PCV2 viremia by qPCR and presence of PCV2 and M. hyopneumoniae antibody levels by ELISA. Our data revealed that the sow parity did not influence the vaccine outcomes. Good results for most of the analyzed parameters were observed in both vaccinated groups. ADGW and final weight were higher and lung lesions were less evident in both vaccinated groups than in the control one, but only Group A showed a significant improvement. PCV2 viremia was not detected in Group A, but it did appear in Group B coinciding with its peak in Group C. Finally, both the PCV2 and M. hyopneumoniae serological patterns differed depending on the employed vaccine.

Efficient influence of ssDNA virus PCV2 replication by CRISPR/Cas9 targeting of the viral genome

Porcine circovirus type 2 (PCV2), a ubiquitous pathogen that primary cause of postweaning multisystemic wasting syndrome (PMWS), had caused significant morbidity and mortality in swine populations with huge economic losses in the worldwide swine industry. Currently, looking for effective antiviral drugs for PCV2 infection remains an important works. In our study, CRISPR/Cas9 system was used to further detected the key sites of PCV2 replication. We designed 8 single guide RNAs (sgRNA) by targeting essential genes across the genome of PCV2. Western-blot(WB), Cell counting kit-8 for high-throughput sgRNA screening were applied to detect PCV2 replication levels. The results showed that Oc8, O13, O134, NQT and NPS sgRNAs can edit the PCV2 genome efficiently and inhibit PCV2 replication in PK-15 cell; H3 sgRNA cannot edit the PCV2 genome successfully; NAT sgRNA can edit the PCV2 genome efficiently to improve the PCV2 replication in PK-15 cell; O26 sgRNA can edit the PCV2 genome successfully but it is not known yet of its effect on PCV2 replication, besides the Cas9 expression had no effect on cell viability. These data suggest that CRISPR/Cas9 system targeting PCV2 essential genes may serve as a novel therapeutic agent against PCV2 infection in the future.

Characterization and purification of pentameric chimeric protein particles using asymmetric flow field-flow fractionation coupled with multiple detectors

Porcine circovirus causes the post-weaning multi-systemic wasting syndrome. Despite the existence of commercial vaccines, the development of more effective and cheaper vaccines is expected. The usage of chimeric antigens allows serological differentiation between naturally infected and vaccinated animals. In this work, recombinant pentameric vaccination protein particles spontaneously assembled from identical subunits-chimeric fusion proteins derived from circovirus capsid antigen Cap and a multimerizing subunit of mouse polyomavirus capsid protein VP1 were purified and characterized using asymmetric flow field-flow fractionation (AF4) coupled with UV and MALS/DLS (multi-angle light scattering/dynamic light scattering) detectors. Various elution profiles were tested, including constant cross-flow and decreasing cross-flow (linearly and exponentially). The optimal sample retention, separation efficiency, and resolution were assessed by the comparison of the hydrodynamic radius (R_h) measured by online DLS with the R_h values calculated from the simplified retention equation according to the AF4 theory. The results show that the use of the combined elution profiles (exponential and constant cross-flow rates) reduces the time of the separation, prevents undesirable sample-membrane interaction, and yields better resolution. Besides, the results show no self-associations of the individual pentameric particles into larger clusters and no sample degradation during the AF4 separation. The R_g/R_h ratios for different fractions are in good correlation with morphological analyses performed by transmission electron microscopy (TEM). Additionally to the online analysis, the individual fractions were subjected to offline analysis, including batch DLS, TEM, and SDS-PAGE, followed by Western blot.

Review of the speculative role of co-infections in Streptococcus suis-associated diseases in pigs

Streptococcus suis is one of the most important bacterial swine pathogens affecting post-weaned piglets, causing mainly meningitis, arthritis and sudden death. It not only results in severe economic losses but also raises concerns over animal welfare and antimicrobial resistance and remains an important zoonotic agent in some countries. The definition and diagnosis of S. suis-associated diseases can be complex. Should S. suis be considered a primary or secondary pathogen? The situation is further complicated when referring to respiratory disease, since the pathogen has historically been considered as a secondary pathogen within the porcine respiratory disease complex (PRDC). Is S. suis a respiratory or strictly systemic pathogen? S. suis is a normal inhabitant of the upper respiratory tract, and the presence of potentially virulent strains alone does not guarantee the appearance of clinical signs. Within this unclear context, it has been largely proposed that co-infection with some viral and bacterial pathogens can significantly influence the severity of S. suis-associated diseases and may be the key to understanding how the infection behaves in the field. In this review, we critically addressed studies reporting an epidemiological link (mixed infections or presence of more than one pathogen at the same time), as well as in vitro and in vivo studies of co-infection of S. suis with other pathogens and discussed their limitations and possibilities for improvement and proposed recommendations for future studies.