PCV2 Uptake by Porcine Monocytes Is Strain-Dependent and Is Associated with Amino Acid Characteristics on the Capsid Surface.

Porcine circovirus type 2 (PCV2) is associated with several economically important diseases that are described as PCV2-associated diseases (PCVADs). PCV2 is replicating in lymphoblasts, and PCV2 particles are taken up by monocytes without effective replication or complete degradation. Glycosaminoglycans (GAGs) have been demonstrated to be important receptors for PCV2 binding and entry in T-lymphocytes and continuous cell lines. The objective of this study was to determine whether differences exist in viral uptake and outcome among six PCV2 strains from different disease outbreaks in primary porcine monocytes: Stoon-1010 (PCV2a; PMWS), 1121 (PCV2a; abortion), 1147 (PCV2b; PDNS), 09V448 (PCV2d-1; PCVAD with high viral load in lymphoid tissues [PCVADhigh]), DE222-13 (PCV2d-2; PCVADhigh), and 19V245 (PCV2d-2; PCVADhigh). The uptake of PCV2 in peripheral blood monocytes was different among the PCV2 strains. A large number of PCV2 particles were found in the monocytes for Stoon-1010, DE222-13, and 19V245, while a low number was found for 1121, 1147, and 09V448. Competition with, and removal of GAGs on the cell surface, demonstrated an important role of chondroitin sulfate (CS) and dermatan sulfate (DS) in PCV2 entry into monocytes. The mapping of positively/negatively charged amino acids exposed on the surface of PCV2 capsids revealed that their number and distribution could have an impact on the binding of the capsids to GAGs, and the internalization into monocytes. Based on the distribution of positively charged amino acids on PCV2 capsids, phosphacan was hypothesized, and further demonstrated, as an effective candidate to mediate virus attachment to, and internalization in, monocytes. IMPORTANCE PCV2 is present on almost every pig farm in the world and is associated with a high number of diseases (PCV2-associated diseases [PCVADs]). It causes severe economic losses. Although vaccination is successfully applied in the field, there are still a lot of unanswered questions on the pathogenesis of PCV2 infections. This article reports on the uptake difference of various PCV2 strains by peripheral blood monocytes, and reveals the mechanism of the strong viral uptake ability of monocytes of Piétrain pigs. We further demonstrated that: (i) GAGs mediate the uptake of PCV2 particles by monocytes, (ii) positively charged three-wings-windmill-like amino acid patterns on the capsid outer surface are activating PCV2 uptake, and (iii) phosphacan is one of the potential candidates for PCV2 internalization. These results provide new insights into the mechanisms involved in PCVAD and contribute to a better understanding of PCV2 evolution. This may lead to the development of resistant pigs.

Porcine circovirus-like virus P1 activates pancreatic secretion pathway by interacting with CHRM3 protein.

The porcine circovirus-like virus P1, a member of the circovirus family, causes post-weaning multisystemic wasting syndrome (PMWS) in weaned piglets with progressive wasting as the main clinical symptom. The pancreatic secretion pathway induces pancreatic acinar cells to secrete various digestive enzymes and as such is an important signaling pathway for the digestive system and somatic growth. This study examined the effects and mechanism of P1 virus infection on the pancreatic secretion pathway. The experiment was conducted by transfecting double-copy plasmid P1 into PK-15 and 3D4 cells and by infecting cells with the P1 virus. Samples were collected at various times after transfection or infection. The pathway's transcription and translation levels of CHRM3, Gq, PLC-ß2, PRKCA, Rab3D, RhoA, Rac1, and amyA proteins were detected by real-time PCR and Western blots; these analyses confirmed that the P1 virus infection could upregulate the expression level of key pancreatic secretion signaling molecules. Then, we confirmed that the VP1 protein of the P1 virus could interact with the pathway initiation protein CHRM3 using Co-IP, pull-downs, and confocal fluorescence microscopy. Finally, we demonstrated that the VP1 protein activates the pancreatic secretory pathway through the CHRM3 protein. In conclusion, this study demonstrated that the P1 virus can interact with the CHRM3 receptor protein to activate the pancreatic secretion pathway and promote the secretion of various digestive enzymes downstream of the pathway, thereby providing a basis for P1 virus pathogenesis.

Full-genome sequences of porcine circovirus 3 (PCV3) and high prevalence in mummified fetuses from commercial farms in Brazil.

The clinical implications of recently discovered porcine circovirus 3 (PCV3) infections are still unknown. The potential role of this emerging virus in reproductive loss in swine has been described. Herein, we report a high prevalence of PCV3 in mummified fetuses from sows maintained in modern farms in Rio Grande do Sul, Santa Catarina, Paraná, Goiás, and Mato Grosso do Sul states, Brazil. For this analysis, 276 mummified fetuses from 11 commercial swine farms were included. The presence of PCV3 DNA was confirmed using PCR, and the complete sequence of five different viral strains was obtained. Sequences of PCV3 genomes available on GenBank were then used for phylogenetic tree construction. Of the 276 mummified fetuses examined, 270 (nearly 97%) were positive for PCV3. In 93.1% of the fetuses, co-infections with at least one of the following agents were identified: porcine parvovirus (PPV), porcine circovirus 2 (PCV2) and Leptospira spp. Twelve fetuses were positive for PCV3 alone. The amino acid sequence of the capsid gene for the five viral strains shared 98-100% homology among them. Analysis of the DNA sequence indicates that the viruses identified in this study belong to the PCV3a1 subgroup. In summary, PCV3 DNA was detected in mummified fetuses at a surprisingly high rate. The role of PCV3 in porcine circovirus-associated disease (PCVAD) is still uncertain. However, considering that PCV3 has been detected in a variety of conditions, even in healthy animals, the present results confirm the need to investigate PCV3 as a causative agent of fetal mummification in swine.

A retrospective study of DNA prevalence of porcine parvoviruses in Mexico and its relationship with porcine circovirus associated disease.

Worldwide, many emerging porcine parvoviruses (PPVs) have been linked to porcine circovirus-2 (PCV2) associated disease (PCVAD), which includes post-weaning multi-systemic wasting syndrome (PMWS), PCV2-related reproductive failure (PCV2-RF), as well as other syndromes. To determine the DNA prevalence of PPVs and their relationship with PMWS and PCV2-RF in Mexico, 170 formalin-fixed paraffin-embedded tissues were selected from archival collections to detect PPVs using a nested polymerase chain reaction. The tissues were composed of 50 PMWS cases, 20 age-matched tissues from healthy pigs, 56 PCV2-related reproductive failure (PCV2+ -RF) cases, and 44 PCV2- -RF cases. Overall, PPV2 and PPV6 were the most prevalent species (90.0% and 74.7%, respectively). In 8-11 week old pigs, the highest prevalence was for PPV6 and PPV3. Concerning reproductive failure, the PCV2-affected farms had a significantly higher prevalence for PPV6 (61.6%) and PPV5 (36.4%) than the PCV2-unaffected farms (35.0% and 5.0%, respectively). The concurrent infection rate was high, being significant for PPV2/PPV4 and PPV1/PPV5 within the PMWS cases and for PPV6/PPV5 among the PCV2+ -RF tissues. PPV5 showed a significant relationship with PMWS, whereas PPV5 and PPV6 were significant for PCVAD. The prevalence and coinfection rate of PPVs in Mexico were markedly higher than that described in other countries, denoting that PPV5 and PPV6 might have a potential role in PCVAD in Mexico. It is concluded that it is likely that the density population of pigs in Mexico is contributing to high PPV inter-species and PCV2 coinfections which might lead to a different pathogenic outcome.

Dissecting clinical outcome of porcine circovirus type 2 with in vivo derived transcriptomic signatures of host tissue responses.

BACKGROUND: Porcine Circovirus Type 2 (PCV2) is a pathogen that has the ability to cause often devastating disease manifestations in pig populations with major economic implications. How PCV2 establishes subclinical persistence and why certain individuals progress to lethal lymphoid depletion remain to be elucidated. RESULTS: Here we present PorSignDB, a gene signature database describing in vivo porcine tissue physiology that we generated from a large compendium of in vivo transcriptional profiles and that we subsequently leveraged for deciphering the distinct physiological states underlying PCV2-affected lymph nodes. This systems genomics approach indicated that subclinical PCV2 infections suppress a myeloid leukocyte mediated immune response. However, in contrast an inflammatory myeloid cell activation is promoted in PCV2 patients with clinical manifestations. Functional genomics further uncovered STAT3 as a druggable PCV2 host factor candidate. Moreover, IL-2 supplementation of primary lymphocytes enabled ex vivo study of PCV2 replication in its target cell, the lymphoblast. CONCLUSION: Our systematic dissection of the mechanistic basis of PCV2 reveals that subclinical and clinical PCV2 display two diametrically opposed immunotranscriptomic recalibrations that represent distinct physiological states in vivo, which suggests a paradigm shift in this field. Finally, our PorSignDB signature database is publicly available as a community resource ( http://www.vetvirology.ugent.be/PorSignDB/ , included in Gene Sets from Community Contributors http://software.broadinstitute.org/gsea/msigdb/contributed_genesets.jsp ) and provides systems biologists with a valuable tool for catalyzing studies of human and veterinary disease. Finally, a primary porcine lymphoblast cell culture system paves the way for unraveling the impact of host genetics on PCV2 replication.

Identification and genotyping of porcine circovirus type II (PCV2) in Mexico.

Porcine circovirus type 2 (PCV2), family Circoviridae, genus Circovirus infection in domestic pig has been associated with several pathological conditions being the most important of them the postweaning multisystemic wasting syndrome. Many studies have demonstrated the existence of three PCV2 genotypes (a, b, and c) and recently PCV3. Until now, these genotypes or subgenotypes have not been described in Mexico. We found genetic changes in ORF2 from nine strains of PCV2 obtained from samples of Jalisco, Veracruz, Estado de México, Hidalgo and Sonora states of Mexico. Our results shown the presence of two genotypes (PCV2a and PCV2b) as well as, the presence and differences between the reported subgenotypes. The subgenotype PCV2b (1A/1B, 1A) has a higher prevalence (87.5%) in comparison with PCV2a (2C) (12.5%).

Porcine Circovirus-Like Virus P1 Inhibits Wnt Signaling Pathway in Vivo and in Vitro.

Porcine circovirus-like virus P1 is an important pathogen of the current pig industry, the infection mechanism is not entirely clear. Wnt signaling pathway plays an important role in the growth of young animals and infection of some viruses. This study was designed to demonstrate the effects of P1 infection on the Wnt signaling pathway. In vivo experiments, we demonstrated the down-regulatory effects of P1 infection in piglets and mice on the downstream components expression levels of Wnt signaling pathway, and the effects of Wnt signaling pathway activation on the pathogenesis of P1. In vitro studies, we found P1 infection down-regulated protein level of ß-catenin and mRNA level of mmp2, prevented the ß-catenin from entering into nucleus, abolished the TCF/LEF promoter activity, proved that P1 could inhibit the activation of Wnt signaling pathway in vitro. Finally, we found that VP1 of P1 virus also had the inhibitory effects on Wnt signaling pathway in vitro, elucidated the mechanism of P1's inhibitory effects on the Wnt signaling pathway and offered the possibility that the suppression of Wnt signaling pathway was involved in the post-weaning multisystemic wasting syndrome (PMWS), laying a foundation for elucidating the pathogenesis of P1.

Mental Health of the Prison Medical Workers (PMWs) and Influencing Factors in Jiangxi, China.

Prison medical workers (PMWs) are critically important, but they are also vulnerable to psychological problems. Currently, there is no study on examining PMWs' mental health conditions and possible influencing factors in China. Hence, we conducted this cross-sectional survey, aiming to understand the mental health status of the PMWs and related impact factors in Jiangxi province of China. We employed the Chinese version of the Symptom Checklist-90-R (SCL-90-R) to assess the mental disorders and psychological health conditions of PMWs in Jiangxi. The t tests were used to compare the differences for the average score of SCL-90-R between the Chinese general population and targeted PMWs of this study. Multivariable logistic regression analyses were conducted to identify the main factors associated with overall detection rate of PMWs' psychological health conditions. The scores of four dimensions (somatization, obsessive-compulsive symptoms, anxiety, and paranoid ideation) were significantly higher than the Chinese national norm, and the total positive rate was 49.09% among the PMWs. Gender, marital status, age, and length of employment are identified to be the most significant predictors to affect PMWs' mental health. Positive correlations between each of the nine dimensions of the SCL-90-R have been verified. This study demonstrated for the first time that PMWs are facing mental health risk and suffering serious psychological problems with psychopathology symptoms, which has become a growing concern in China. Our current findings suggest a need for more in-depth studies on this subject going forward to validate our conclusions and also to identify more impact factors, since such studies and knowledge of PMWs' mental health and influencing factors are very limited in China.

Coinfection with Haemophilus parasuis serovar 4 increases the virulence of porcine circovirus type 2 in piglets.

BACKGROUND: Postweaning multisystemic wasting syndrome (PMWS) is an emerging disease in swine. Pigs with PMWS are often infected with a variety of other pathogens, including bacteria, viruses and mycoplasm, in addition to porcine circovirus type 2 (PCV2). PCV2 and Haemophilus parasuis serovar 4 (HPS4) coinfection remain epidemic in China. METHODS: Here we report construction of a three-week-old naturally farrowed, colostrum-deprived (NFCD) piglet's infection model and demonstrate that PCV2-infected piglets with the HPS4 coinfection increased the virulence of PCV2 and these pathogens interact acquired PMWS. RESULTS: All the single infected piglets were transiently bacteremic or viremic. All the PCV2/HPS4 coinfected piglets developed PMWS, characterized by dyspnea, anorexia, prostration and lose weight severely. Co-infection with PCV2 and HPS4 resulted in an increased amount of virus in serum and tissues, presented a slower generation and lower levels of antibodies against PCV2. Co-infection with PCV2 and HPS4 resulted in further reductions in total and differential peripheral blood leukocyte counts. Meantime, PCV2/ HPS4 coinfection potentiated the severity of lung and lymphoid lesions by PCV2-associated, increased the virulence of PCV2-antigen and enhanced the incidence of PMWS in piglets. CONCLUSION: Co-infection with PCV2 and HPS4 induce the exacerbation of system injuries and enhance the pathogenicity of PCV2 in piglets.

Genetic analysis of porcine circovirus type 2 from pigs affected with PMWS in Chile reveals intergenotypic recombination.

BACKGROUND: Porcine circovirus type 2 (PCV2) is a very small, non-enveloped and icosahedral virus, with circular single stranded DNA genome. This virus is the most ubiquitous and persistent pathogen currently affecting the swine industry worldwide. PCV2 has been implicated as the major causative agent of postweaning multisystemic wasting syndrome (PMWS), a disease which is characterized by severe immunosuppressive effects in the porcine host. Worldwide PCV2 isolates have been classified into four different genotypes, PCV2a, PCV2b, PCV2c and PCVd. The goal of this work was to conduct the first phylogenetic analysis of PCV2 in Chile. METHODS: PCV2 partial ORF2 sequences (462 nt) obtained from 29 clinical cases of PMWS in 22 Chilean intensive swine farms, covering over the 90% of the local pork-production, were analyzed. RESULTS: 14% and 52% of sequences belonged to the genotypes PCV2a and PCV2b, respectively. Surprisingly, 34% of sequences were PCV2a/PCV2d recombinant viruses. CONCLUSIONS: Our findings suggested that a novel cluster of Chilean sequences emerged resulting from intergenotypic recombination between PCV2a and PCV2d.

Ten years of PCV2 vaccines and vaccination: Is eradication a possibility?

More than two decades after its emergence, porcine circovirus type 2 (PCV2) remains an economically important swine pathogen. Commercial vaccines which were first introduced to the U.S in 2006, have been highly effective in reducing clinical signs and improving production. Recent studies have indicated a declining level of PCV2 prevalence and viremia in the field. However, reports on the emergence of new viral variants have also continued to increase. This article reviews topics of current interest in the field of PCV2 vaccines; including the comparative efficacy of the available commercial products, efficacy of current vaccines against new and emerging strains, findings on the differences between immunity in natural infection versus vaccination, limitations of current experimental models for PCV2 vaccine studies, and new developments in novel experimental vaccines. The discussion is framed in the context of attempts for the possible eradication of PCV2 in the future.

Antigenic Determinants of Possible Vaccine Escape by Porcine Circovirus Subtype 2b Viruses.

Currently available commercial vaccines against porcine circovirus strain 2 (PCV2) solely target the PCV2a genotype. While PCV2 vaccines are highly effective in preventing clinical signs, PCV2b has dominated over the PCV2a genotype in prevalence, corresponding with the introduction of PCV2a vaccines. A recently emerged PCV2b recombinant with an additional amino acid in the capsid protein, designated the mutant PCV2b (mPCV2b), is cause for concern due to its increased virulence and rapid spread. The accumulation of recent evidence for the increased genetic diversity in PCV2 suggests that current vaccines against PCV2a may be inducing selection pressure and driving viral evolution. In this study, the hypothesis that differences in key immune epitopes between the PCV2a vaccine strains, a classical PCV2b strain called PCV2b 41513 obtained from a vaccine-failure case, and mPCV2b strains could promote vaccine escape was tested using immuno-informatic tools. In the major viral proteins, 9 of the 18 predicted swine leukocyte antigens (SLA) class-I epitopes, 8 of the 22 predicted SLA class-II epitopes, and 7 of the 25 predicted B cell epitopes varied between the vaccine and field strains. A majority of the substitutions in both the T- and B-cell epitopes were located in the capsid protein. Some B- and T-cell epitopes that were identified as immunogenic in the vaccine strain were not identified as epitopes in the field strains, indicating a subtle shift in the antigenic profile of the field strains. Several nonconserved epitopes had both predicted B- and T-cell functions. Therefore, substitutions in the dual epitopes could affect both arms of the immune response simultaneously, causing immune escape. Our findings support further rational design of PCV2 vaccines to increase the current threshold of protection.

Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2) viral loads in serum of postweaning multisystemic wasting syndrome (PMWS)-affected and healthy pigs in Brazil.

Associations between Torque teno sus viruses (TTSuVs) and the occurrence of postweaning multisystemic wasting syndrome (PMWS) have been reported with controversial results. Currently, no studies have been performed comparing simultaneously viral loads of TTSuVs and PCV2. To examine the role for TTSuVs in PMWS-affected animals, a SYBR Green-based quantitative PCR (qPCR) was designed to detect and quantify TTSuV1, TTSuV2 and PCV2 genomes in swine sera. TTSuV1 genome loads were significantly higher in healthy adults than in young and SPF animals (p<0.05) suggesting that the prevalence of TTSuV1 infection increases with age and bears no association with PMWS. Regarding TTSuV2, no significant variation was detected in viral loads within any of the groups. As expected, PCV2 genome loads were higher in PMWS-affected swine than in healthy or SPF animals (p<0.001). These findings provide clear evidence to indicate that neither TTSuV1 nor TTSuV2 viral loads have any correlation with the occurrence of PMWS.

Porcine cytomegalovirus infection is not associated to the occurrence of post-weaning multisystemic wasting syndrome.

Porcine cytomegalovirus (PCMV) is a Betaherpesvirus that causes lifelong latent infections in swine; occasionally, it may be associated with inclusion body rhinitis in piglets and reproductive disorders in pregnant sows. Post-weaning multisystemic wasting syndrome (PMWS) a condition where porcine circovirus type 2 (PCV2) infection is necessary - though not sufficient - to trigger disease, has become one of the major health problems to the porcine productive chain. Despite the high expected prevalence of both PCMV and PCV2 in swine-raising farms, no links between PCMV and PMWS have been investigated so far. In view of that, the present study was conducted to search for relations between PCMV infections and the occurrence of PMWS. Spleen and sera of PMWS-affected and non-PWMS-affected animals were examined. In PMWS-affected animals, PCMV DNA was detected in 88.4% of the spleen samples and 7.6% of the sera, whereas in non-PMWS-affected pigs, PCMV DNA was detected in 72.7% of the spleens and 10% of sera. Such differences were not statistically significant. These findings showed despite the high prevalence of PCMV infections in the swine population examined, no positive or negative association could be inferred from the presence of PCMV DNA and the occurrence of PMWS.

Secretory expression of Porcine Circovirus Type 2 capsid protein in Pichia pastoris.

Porcine circovirus type 2 (PCV2) is associated with postweaning multisystemic wasting syndrome (PMWS). The PCV2 capsid (Cap) protein is a leading antigen candidate for vaccine and serological diagnostic testing, due to its immunogenic properties. In this study, the codon-optimized PCV2 Cap gene was cloned into a pPICZαA vector for secretory expression in the methylotrophic yeast Pichia pastoris after methanol induction. The screening of recombinant yeasts was followed by detection of the recombinant Cap (rCap) protein by Western blot, using sera from pigs naturally infected with PCV2. The rCap secreted protein was used without prior purification as a coating antigen in the ELISA test, with high discrimination between PCV2-positive and negative sera. These results reveal a high confidence in the specific immunoreactivity of the secreted antigen and show the antigenicity of the recombinant protein. The feasibility of the P. pastoris expression system for the production of PCV2 Cap as secreted protein and its apparent bioactivity, suggests there are good prospects for the use of this antigen in the investigation of PCV2 infections and testing for vaccine purposes.

Unusual outcome of in utero infection and subsequent postnatal super-infection with different PCV2b strains / 中国病毒学·英文版

VC2002, isolated from postweaning multisystemic wasting syndrome (PMWS)-affected pig, is a mixture of two porcine circovirus genotype 2b (PCV2b) viruses, K2 and K39. Preliminary experiments disclosed short-term adverse effects of K39, but not K2, on porcine foetuses. These findings led to the hypothesis that infection of immuno-incompetent foetuses with K2 confers a status of immunotolerance, and postnatal super-infection with K39 triggers PMWS. To explore this hypothesis, nine 55-day-old foetuses were inoculated in utero (three with K2-104.3TCID50, three with K39-104.3TCID50 and three with medium), and foeto-pathogenicity examined. At 21 days post-inoculation (dpi), K2 did not induce pathology, whereas pathological effects of K39 were evident. Twenty-four 45-day-old foetuses were subsequently inoculated to examine the long-term effect of K2, including six with K2-high dose-104.3TCID50, six with K2-low dose-102.3TCID50 and 12 mock-inoculated controls. Both doses resulted in ifve mummiifed foetuses and one live-born piglet each (69dpi). K2 was recovered from all mummies. K2 and K2-speciifc antibodies were not detected in serum of the two live-born piglets at birth, indicating full control of K2 infection. The K2-low dose-infected piglet was immunostimulated at day 2, but not the K2-high dose-infected piglet. Both non-stimulated and stimulated K2-infected piglets were super-inoculated with K39 at day 6 or 8 (taken as 0 days post super-inoculation). Low viral replication was observed in the non-stimulated K2-K39 piglet (up to 103.3 TCID50/g;identiifed as K39). In contrast, viral replication was extremely high in the stimulated K2-K39 piglet (up to 105.6TCID50/g) and identiifed as K2, indicating that K2 infection is controlled during foetal life, but emerges after birth upon immunostimulation. However, none of the piglets showed any signs of PMWS.

Nonstructural proteins of Torque teno sus virus 2 from O2AUG: prediction to experimental validation.

The expression profiles of nonstructural proteins (NSPs) in Torque teno sus virus 2 (TTSuV2) have not yet been characterized. Here, we determined the coding sequences of the TTSuV2 NSPs ORF2, ORF2/2, and ORF2/2/3 by overlapping polymerase chain reaction (PCR) and subsequent expression in bacterial and mammalian cells. We generated two monoclonal antibodies (mAbs), 2E5 and 6F8, from mice immunized with mixed Escherichia coli expressing His-tagged ORF2 and ORF2/2. Enzyme-linked immunosorbent assay (ELISA) and western blot analysis revealed that, 2E5 mAbs bound to the consensus sequences of ORF2, ORF2/2, and ORF2/2/3, while 6F8 recognized the common sequences of ORF2/2 and ORF2/2/3. Immunofluorescence assay (IFA) revealed that ORF2 was localized in the cytoplasm, ORF2/2, in the nucleus but not the nucleolus, and ORF2/2/3, in the peri-nuclear region. To identify the expression profiles of TTSuV NSPs, a circular TTSuV2_ZJ (GenBank: KF660540) genomic DNA clone was constructed and transfected into HEK293T and HeLa cells. Splicing mRNAs and the expression and localization of ORF2/2 and ORF2/2/3 were identified by RT-PCR, western blot analysis, and IFA, respectively. However, ORF2 was not detected either at the RNA or protein level. Our study is the first to provide experimental evidence of the existence of ORF2/2 and ORF2/2/3 at the protein level. Moreover, the mAbs have potential applications in future research on TTSuV2 viral protein function and diagnosis of related diseases.

[Field trial on the simultaneous vaccination against porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae]. / Feldstudie zur simultanen Vakzination gegen das porzine Circovirus Typ 2 und Mycoplasma hyopneumoniae.

OBJECTIVE: The objective of the present study was to investigate whether a combined or concurrent application of two vaccines against Mycoplasma hyopneumoniae (M. hyo.) and porcine circovirus type 2 (PCV2) in suckling piglets can be as effective as the single use of both products. MATERIAL AND METHODS: A total of 598 piglets were allocated to five groups. In the 1st and 3rd weeks of life the placebo Porcilis® Diluvac forte and the two vaccines Porcilis® M HYO ("M HYO") and Porcilis® PCV ("PCV") were administered according to the following scheme: group A: placebo/PCV; group B: M HYO/M HYO; group C: placebo/placebo; group D: M HYO/M HYO + PCV (combined single dose); group E: placebo/M HYO + PCV (different injection sites). Lung lesions due to M. hyo. infection were recorded at slaughter, and average daily weight gain, morbidity, mortality, serum PCV2 load and specific humoral immune responses were compared between the groups. Local and systemic side effects were recorded. RESULTS: Sporadic impairment of the herd health status due to piglet diarrhoea (n = 111) from the 1st to 3rd weeks of life were not associated with M. hyo. or PCV2. A tendency towards a higher average daily weight gain was found in vaccinated pigs compared to the control group. Slight differences between groups in terms of lung lesions, morbidity and mortality were not significant. M. hyo. and PCV2 antibody-titers were significantly higher in vaccinated than in non-vaccinated pigs. One pig from both group A (PCV2) and group C (placebo) displayed local reactions at the vaccination site. CONCLUSION AND CLINICAL RELEVANCE: A positive effect on animal health can be achieved by vaccination against M. hyo. and PCV2 in herds with suboptimal health status. A simultaneous vaccination either by a combined or concurrent application has no negative effect on health status. Simultaneous vaccination yielded the same positive effect on average daily weight gain as single vaccinations. Therefore, a simultaneous vaccination against M. hyo. and PCV2, which reduces workload and is beneficial for animal welfare, can be recommended.

Detection of porcine circovirus type 2 and viral replication by in situ hybridization in primary lymphoid organs from naturally and experimentally infected pigs.

Porcine circovirus type 2 (PCV2) infection is the cause of postweaning multisystemic wasting syndrome (PMWS). It has been speculated whether cell types permissive of replication are found in the primary lymphoid organs and whether infection of these tissues has an important role in the pathogenesis of PMWS. The aim of this study was to determine if primary lymphoid organ cells support viral replication during PCV2 infection. This was done by histopathological examination of thymus and bone marrow from pigs experimentally inoculated with PCV2 (n = 24), mock-infected pigs (n = 12), pigs naturally affected by PMWS (n = 33), and age-matched healthy control animals (n = 29). In situ hybridization (ISH) techniques were used to detect PCV2 nucleic acid irrespective of replicative status (complementary probe, CP) or to detect only the replicative form of the virus (replicative form probe, RFP). PCV2 was not detected in the experimentally PCV2-inoculated pigs or the control animals. Among the PMWS-affected pigs, 19 of 20 (95%) thymuses were positive for PCV2 by CP ISH, and 7 of 19 (37%) of these also supported viral replication. By CP ISH, PCV2 was detected in 16 of 33 (48%) bone marrow samples, and 5 of 16 (31%) of these also supported replication. The 2 ISH probes labeled the same cell types, which were histiocytes in both organs and lymphocytes in thymus. The RFP labeled fewer cells than the CP. Thus, PCV2 nucleic acids and replication were found in bone marrow and thymus of PMWS-affected pigs, but there was no evidence that primary lymphoid organ cells are major supporters of PCV2 replication.

Dynamics of antibody response and viraemia following natural infection of porcine circovirus 2 (PCV-2) in a conventional pig herd.

Porcine circovirus 2 (PCV-2) is a primary agent of post-weaning multi-systemic wasting syndrome (PMWS), ubiquitous in pig herds. The course of viraemia and seroconversion in naturally infected pigs were investigated in piglets from the 2nd week of their life. Piglets were divided into seropositive (Ab(+)) and seronegative (Ab(-)) groups. Subsequently, after vaccination against PCV-2 (Ingelvac(®) CIRCOFLEX™, Böehringer Ingelheim), they were further divided into non-vaccinated seronegative (NVAC/Ab(-)) and seropositive (NVAC/Ab(+)), and vaccinated seronegative (VAC/Ab(-)) and seropositive (VAC/Ab(+)). PCV-2 colostral antibodies failed to prevent development of natural PCV-2 infection in conventional piglets; however, this occurred at a higher age in comparison with seronegative pigs. Neither colostral nor post-infection antibodies prevented development of viraemia, which persisted up to the end of the study (the 19th week), but without clinical signs of PMWS. Vaccination failed to prevent development of natural PCV-2 infection, but viraemia was limited to between the 8th and 10th week. The presence of colostral anti-PCV-2 antibodies did not show any untoward effect to vaccination; on the contrary, VAC/Ab(+) animals showed the lowest titre of viraemia.