Porcine Circovirus 2 Infection Research Articles

Епізоотологічний моніторинг цирковірусної, парвовірусної інфекцій і репродуктивно-респіраторного синдрому свиней на території Південно-Східного регіону України

Porcine circovirus infection (PCV), parvovirus infection of pigs (PVIS), porcine reproductive and respiratory syndrome (PRRS) at the present time, according to the productive serological monitoring in various countries, including the Russian Federation, are very widespread in pig breeding industrial enterprises. The aim of this study was to conduct serological monitoring for PCV, PVIS and PRRS in the Udmurt Republic taking into account a certain age factor when these diseases begin to appear and develop. Contamination of pig population aged from 28 to 120 days was determined above 50%, indicating that the virus is circulating widely in the study age group of animals. It was found that the level of PCV seropositivity was 49.1%, PRRS level - 47.5%, PVIS varied about 36.3%. During the study of different types of pathological materials in the polymerase chain reaction (PCR) viral antigens on PCV and PRRS were revealed, which indicates the associated form of the disease in group of weaning piglets. The most common epizootiological and economic problem in modern small-scale pig breeding is reproductive and neonatal infections of pigs (RNIP). RNIP are mixed viral-bacterial infectious diseases. The main feature of these infections is damage to genital organs of animals resulting in reproductive disorders in sows and buds, as well as reduction in viability of newborn piglets caused by immunodeficiency and depletion from various pneumoniae enteritis. Insufficient knowledge about the nature of zoonotic RNIP and underestimation of their significance for pig breeding have led to their unprecedented spread in the last decade. The zoonotic RNIP in pig farms of Ukraine currently have a viral-bacterial etiology. Traditional approaches to epizootic regulation of these polyetiological infections are ineffective and can not provide a sustainable disease-free status of the Ukrainian pig breeding for zoonotic RNIP. This gives a reason to consider these infectious diseases as emergent. The international experience in issues of elimination of the hotbeds of emergent diseases of polyetiological origin, shows that the development of a plan for antiepizootic measures individually for each farm proves effective. Our analysis of the latest scientific publications shows that reproductive respiratory syndrome, circovirus and parvovirus infection of pigs are considered to be among the viral diseases of economical significance for the industrial pig breeding along with the classical swine fever and Aujeszky's disease. According to the serological monitoring conducted in various countries, including Ukraine, the CVIP are widespread in pig farms of the industrial type. The circovirus infection manifests itself clinically in piglets 2-3 weeks after weaning. Rejection of food, shortness of breath, fever, exhaustion, lag in growth, increased mesenteric lymph nodes, pallor or yellowness of skin shave been observed in sick animals. Among piglets of 7-15 weeks of age, the circovirus infection is manifested as a syndrome of post weaning multiple systemic exhaustion. According to foreign researchers, the incidence in piglets is at the level of 5-10%, sometimes up to 50-70%, and the mortality level reaches 70-80%. The aim of our study was to carry out serological monitoring of CVIP, PVIP and PRRS on the territory of Kharkiv, Zaporizha and Poltava regions of Ukraine, taking into account the factor of age when these diseases begin to manifest itself and spread. A total of 1684 blood samples from pigs of all ages were investigated. Serological blood tests for CVIP and PRRS were conducted with the use of LIA method, for parvovirus infection by the, detection of HIT viral genetic material - by the PCR method of Narvak system. The virological examinations of the clinical and pathological material were carried out according to generally accepted methods using the transfilled lines of cell cultures PK-15, Mark-145. Manifestation of CPE with subsequent identification of the viruses in the immunofluorescence (RIF) reaction using the immunoperoxidase method on the cultural monosharm, HIT (AD, CSF, CVIP-2, PRRS) were also studied. The research was conducted in the P.I. Verbitsky scientific and educational laboratory of genetic-molecular research methods at the Department of Epizootology and Veterinary Management of the KhDZVA. We found that the level of seropositivity of pigs for CVIP was 51.4%, for PRRS 45.8%, while PVIP varies within 34.8%. In the study of various types of pathological materials in the polymerase chain reaction, the viral antigens of the CVIP and PRRS have been detected. This indicates the associated form of the disease in piglets in the growing group.

Efficacy of the Porcine circovirus 2 (PCV2) vaccination under field conditions.

The objective of this study was to determine the effect of the porcine circovirus type 2 (PCV2) vaccination on the levels of viremia, the number of viremic-positive pigs, and production performance [i.e. nursery mortality, post-weaning mortality, and average daily weight gain (ADWG)] under field conditions. There were 140 farrow-to-finish pig herds involved in this study. The vaccination of piglets was implemented in 82 of the 140 herds. In each herd blood samples were collected from sows and pigs in different age category. In addition, a questionnaire regarding the production performance was provided for each herd. Results demonstrate that the vaccination of piglets prevented the development of viremia in 23.2% of herds. Significant decreases in the levels of PCV2 DNA in serum and in the number of viremic pigs were also noted. These results indicate that the vaccination of piglets against PCV2 is a useful tool in controlling the PCV2 infection in herds with a high risk of a wide range of viral and bacterial agents, poor management strategies, and a low level of biosecurity practices.

Surveillance for respiratory and diarrheal pathogens at the human-pig interface in Sarawak, Malaysia.

BackgroundThe large livestock operations and dense human population of Southeast Asia are considered a hot-spot for emerging viruses.ObjectivesTo determine if the pathogens adenovirus (ADV), coronavirus (CoV), encephalomyocarditis virus (EMCV), enterovirus (EV), influenza A-D (IAV, IBV, ICV, and IDV), porcine circovirus 2 (PCV2), and porcine rotaviruses A and C (RVA and RVC), are aerosolized at the animal-interface, and if humans working in these environments are carrying these viruses in their nasal airways.StudyThis cross-sectional study took place in Sarawak, Malaysia among 11 pig farms, 2 abattoirs, and 3 animal markets in June and July of 2017. Pig feces, pig oral secretions, bioaerosols, and worker nasal wash samples were collected and analyzed via rPCR and rRT-PCR for respiratory and diarrheal viruses.ResultsIn all, 55 pig fecal, 49 pig oral or water, 45 bioaerosol, and 78 worker nasal wash samples were collected across 16 sites. PCV2 was detected in 21 pig fecal, 43 pig oral or water, 3 bioaerosol, and 4 worker nasal wash samples. In addition, one or more bioaerosol or pig samples were positive for EV, IAV, and RVC, and one or more worker samples were positive for ADV, CoV, IBV, and IDV.ConclusionsThis study demonstrates that nucleic acids from a number of targeted viruses were present in pig oral secretions and pig fecal samples, and that several viruses were detected in bioaerosol samples or in the nasal passages of humans with occupational exposure to pigs. These results demonstrate the need for future research in strengthening viral surveillance at the human-animal interface, specifically through expanded bioaerosol sampling efforts and a seroepidemiological study of individuals with exposure to pigs in this region for PCV2 infection.

Pathogen elimination and prevention within a regulated, Designated Pathogen Free, closed pig herd for long-term breeding and production of xenotransplantation materials.

BackgroundWe established a Source Animal (barrier) Facility (SAF) for generating designated pathogen‐free (DPF) pigs to serve as donors of viable organs, tissues, or cells for xenotransplantation into clinical patients. This facility was populated with caesarian derived, colostrum deprived (CDCD) piglets, from sows of conventional‐specific (or specified) pathogen‐free (SPF) health status in six cohorts over a 10‐month period. In all cases, CDCD piglets fulfilled DPF status including negativity for porcine circovirus (PCV), a particularly environmentally robust and difficult to inactivate virus which at the time of SAF population was epidemic in the US commercial swine production industry. Two outbreaks of PCV infection were subsequently detected during sentinel testing. The first occurred several weeks after PCV‐negative animals were moved under quarantine from the nursery into an animal holding room. The apparent origin of PCV was newly installed stainless steel penning, which was not sufficiently degreased thereby protecting viral particles from disinfection. The second outbreak was apparently transmitted via employee activities in the Caesarian‐section suite adjacent to the barrier facility. In both cases, PCV was contained in the animal holding room where it was diagnosed making a complete facility depopulation‐repopulation unnecessary.MethodInfectious PCV was eliminated during both outbreaks by the following: euthanizing infected animals, disposing of all removable items from the affected animal holding room, extensive cleaning with detergents and degreasing agents, sterilization of equipment and rooms with chlorine dioxide, vaporized hydrogen peroxide, and potassium peroxymonosulfate, and for the second outbreak also glutaraldehyde/quaternary ammonium. Impact on other barrier animals throughout the process was monitored by frequent PCV diagnostic testing.ResultAfter close monitoring for 6 months indicating PCV absence from all rooms and animals, herd animals were removed from quarantine status.ConclusionTen years after PCV clearance following the second outbreak, due to strict adherence to biosecurity protocols and based on ongoing sentinel diagnostic monitoring (currently monthly), the herd remains DPF including PCV negative.

Porcine circovirus 2 infection induces IFNβ expression through increased expression of genes involved in RIG-I and IRF7 signaling pathways

Porcine circovirus-associated disease (PCVAD), caused by porcine circovirus 2 (PCV2), is characterized by a highly variable pathogenesis that is manifested by various disease syndromes and includes immune evasion. Hence, even though PCVAD is effectively controlled by vaccination, pigs and farms remain infected so that continued vaccination is necessary to control disease. We investigated the molecular interactions of PCV2 and its permissive VR1BL host cell for gene expression signatures that could provide insight into mechanisms leading towards disease. Molecular pathways involved in the innate immune response to PCV2 infection were examined to identify changes in gene expression associated with productive infection of VR1BL cells. RNA profiling from infected and uninfected cells showed that 139 genes were induced by infection and 43 genes were down-regulated, using a p value <0.05 and an absolute fold-change difference>2. A strong type 1 interferon response, including an increase in genes involved in the RIG-I/MDA5 pathway and downstream interferon induced genes, was observed. Key regulators involved in PCV2 infection were identified as IFNβ, DDX58 (RIG-I), and IRF7. PCV2 infection induces a strong interferon response which unexpectedly facilitates viral gene expression, perhaps due to the presence of an interferon-sensitive response element in the viral promoter. The findings suggest that PCV2 interventions that attenuate type 1 interferon responses at the cellular level might enhance immunity and eliminate persistent infection.

Tween-20 transiently changes the surface morphology of PK-15 cells and improves PCV2 infection

BackgroundLow concentrations of nonionic surfactants can change the physical properties of cell membranes, and thus and in turn increase drug permeability. Porcine circovirus 2 (PCV2) is an extremely slow-growing virus, and PCV2 infection of PK-15 cells yields very low viral titers. The present study investigates the effect of various nonionic surfactants, namely, Tween-20, Tween-28, Tween-40, Tween-80, Brij-30, Brij-35, NP-40, and Triton X-100 on PCV2 infection and yield in PK-15 cells.ResultSignificantly increased PCV2 infection was observed in cells treated with Tween-20 compared to those treated with Tween-28, Tween-40, Brij-30, Brij-35, NP-40, and Triton X-100 (p < 0.01). Furthermore, 24 h incubation with 0.03% Tween-20 has shown to induce significant cellular morphologic changes (cell membrane underwent slight intumescence and bulged into a balloon, and the number of microvilli decreased), as well as to increase caspase-3 activity and to decrease cell viability in PCV2-infected PK-15 cells cmpared to control group; all these changes were restored to normal after Tween-20 has been washed out from the plate.ConclusionOur data demonstrate that Tween-20 transiently changes the surface morphology of PK-15 cells and improves PCV2 infection. The findings of the present study may be utilized in the development of a PCV2 vaccine.

Protective efficacy of a DNA vaccine encoding capsid protein of porcine circovirus-like virus P1 against porcine circovirus 2 in mice.

The capsid protein is the major immunogenic protein of porcine circovirus 2 (PCV2). The nucleotide sequence of porcine circovirus-like virus P1 shares high homology with open reading frame (ORF) 2 of PCV2, and ORF1 of P1 encodes its structural protein. Mice were vaccinated twice intramuscularly with a plasmid expressing the P1 ORF1 protein (pcDNA3.1(+)-ORF1) at 2-week intervals. All animals vaccinated with pcDNA3.1(+)-ORF1 developed higher specific anti-P1 antibody levels, and had less PCV2 viremia and milder histopathological changes than PCV2-challenged mice in the control group. Our results show that the P1 DNA vaccine elicited immune responses against PCV2 infection in a mouse model.

Field evaluation of piglet vaccination with a Mycoplasma hyopneumoniae bacterin as compared to a ready-to-use product including porcine circovirus 2 and M. hyopneumoniae in a conventional French farrow-to-finish farm

BackgroundA controlled randomized trial was performed on a well-managed conventional French 180-sow farm. The trial compared the growth performances of piglets vaccinated at weaning (single shot) either with a commercial monovalent Mycoplasma hyopneumoniae bacterin vaccine or with a commercial bivalent vaccine (Porcilis® PCV M Hyo) against M. hyopneumoniae and porcine circovirus 2 (PCV2). The farm’s porcine reproductive and respiratory syndrome status was stable, and most diseases (enzootic pneumonia, atrophic rhinitis, post-weaning multisystemic wasting syndrome) were controlled by routine vaccination.ResultsDuring the post-weaning phase, the growth performances of the piglets vaccinated with the bivalent vaccine were not significantly different from those vaccinated with the monovalent vaccine. However, during the fattening phase the group vaccinated with the bivalent vaccine had a significantly improved ADG (+34 g/d, p = 0. 047), resulting in a 5-day earlier shipment to slaughter. The group also had a shorter and lower PCV2 load in serum during the fattening period, and an improved lung lesions score. In both groups, three pigs died during the peak PCV2 viraemia (16–23 weeks of age). Immunohistochemistry of the lymph nodes showed that in the group vaccinated with the bivalent vaccine, none of these pigs had PCV2-like lesions, while 2 out of the 3 from the other group did. Results suggest that the added PCV2 valence in the vaccination protocol helps countering the negative impact of subclinical PCV2 infection on growth. The calculated return on investment of the added PCV2 vaccine valence was €1.7 extra revenue per slaughtered pig (€ 39 additional revenue per sow and per year), despite the fact that the cost of the bivalent vaccine was higher than the monovalent M. hyopneumoniae vaccine.ConclusionIn this healthy conventional sow farm, the combined M. hyopneumoniae and PCV2 vaccination was efficacious, convenient to administer and profitable.

СОВРЕМЕННАЯ ЭПИЗООТОЛОГИЧЕСКАЯ ХАРАКТЕРИСТИКА ЦИРКОВИРУСНОЙ БОЛЕЗНИ СВИНЕЙ

This article describes the historical-geographical and epizootological aspects of rising porcine circovirus infection, periods of study and spread of infection. The article contains the information about epizootic situation in the World and in Russian Federation. The methods of diagnosis, clinical and pathological manifestation are represented. In modern pig farming are important issues related to the comprehensive diagnosis of diseases of pigs, especially circovirus infection. The disease has various symptoms and mortality among piglets in the early period of rearing. Asymptomatic manifestation of the disease in the adult population deteriorating the epizootic situation not only within the herd, but also when moving the animals between different areas of the country. Discovered in 2015 PCV-3 is evidence of its evolutionary path of development that is particularly relevant for molecular biologic, immunological, epizootic and pathological and morphological studies.

Comparative enumeration of cytokine immune response in pbmc's of sows and piglets infected with porcine circovirus and classical swine fever virus

Cytokines are important in mucosal immune response and regulation of metabolism and growth. Maternal cytokines form constructive blocks in the development of neonatal immune system. We have studied the expression of pro-inflammatory (Interleukin6, Tumor Necrosis Factor-α), T-helper (Th)-1 (Interferon-γ, Interleukin-2, Interleukin-12, Tumor Necrosis Factor-β) and Th-2 (IL-10) cytokines in sow and weaned piglets based on the infection of porcine circovirus 2 (PCV2) and classical swine fever virus (CSFV). PCV2 infection being immunosuppressive and ubiquitous in farms, increase disease susceptibility. This study focused the detection and quantitation of PCV2 and CSFV in serum samples from an organised farm of Meghalaya and enumeration of the relative cytokine expression. TNF-a expression in piglets with combined infection (CI) is considerably very high. The expression of IL-12 was more in piglets with PCV2 infection compared with CI. Thus, this study indicates super expression of Th-1 and Th-2 type cytokine production by peripheral blood mononuclear cells in case of coinfection, indicating immunocompromise of cell-mediated and humoral immune responses resulting disease severity.

Antibody response between pigs of Piau and a commercial breed naturally infected with Porcine circovirus 2

ABSTRACT Brazilian pig population is made up of several naturalized breeds; among them the Piau breed is known for its rusticity and large fat stores. The naturalized breeds, in comparison with commercial ones, may have an increased resistance to diseases circulating in their territory. Thus, this study aimed to verify if there are differences between the serologic profile against Porcine circovirus 2 (PCV2) of Piau pigs and that of a commercial breed from a farm naturally infected by PCV2. The serum viral load was measured by qPCR, and levels of anti-PCV2 antibodies were measured by ELISA. The results showed that the serum viral load was similar across all animals. However, Piau piglets showed higher levels of antibodies compared to commercial piglets (P= 0.05), while sows of the commercial breed showed higher levels than the Piau breed (P&lt; 0.01). There was not a statistical difference between pigs of different production stages in the seroprevalence of PCV2 or the blood viral load. This work demonstrates that, with regard to a natural PCV2 infection, the Piau breed has a different humoral immune response compared to the response developed by the commercial pigs. The results support the importance of conservation of native breeds.

Hsp90 inhibitor reduces porcine circovirus 2 replication in the porcine monocytic line3D4/31.

Porcine circovirus 2 (PCV2) is an important pathogen of swine, which causes porcine circovirus disease and porcine circovirus-associated diseases (PCVD/PCVAD). However, no effective countermeasures exist to combat this virus infection so far. Recently, heat shock protein 90 (Hsp90) was found to be an important host factor for the replication of multiple viruses and the inhibition of Hsp90 showed significant antiviral effects. Inhibition of Hsp90 by treatment of porcine monocytic line 3D4/31 with geldanamycin (GA), a specific inhibitor of Hsp90, caused a 70% decrease in viral Cap protein expression. Further, individual knockdown targeting Hsp90α or Hsp90β with siRNAs resulted in down to 20-25% of decrease in viral replication, and inhibited the PCV2 titer by approximately 12- and 15-fold, respectively. In addition, we investigated alteration of several cytokine production in PCV2-infected cells following treatment with GA. Then, we found that GA could decrease IL-1β, IL-6, and IL-12p40 mRNA levels, respectively, by 30, 40, and 40% in PCV2-infected cells. Our results shed light on the possibility of developing potential therapeutics targeting Hsp90 against PCV2 infection.

Porcine circovirus 2 (PCV2) increases the expression of endothelial adhesion/junction molecules.

Porcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus disease, a complex multisystem syndrome in domestic pigs. Despite the significant economic losses caused by porcine circovirus disease, the mechanisms of pathogenesis underlying the clinical findings remain largely unclear. As various reports have highlighted the potential key role of vascular lesions in the pathogenesis of porcine circovirus disease, the aim of this work was to investigate effects of PCV2 infection on vascular endothelial cells, focusing on cell viability and expression of adhesion/junction molecules. PCV2 infection reduced endothelial cell viability, while viral infection did not affected the viability of several other classical cell lines. Also, PCV2 infection in endothelial cells displayed a dual/biphasic effect: initially, infection increased ICAM-1 expression, which can favor leukocyte recruitment and emigration to tissues and possibly inducing characteristic porcine circovirus disease inflammatory lesions; then, secondarily, infection caused an increase in zonula occludens 1 tight junction protein (ZO-1) expression, which in turn can result in difficulties for cell traffic across the endothelium and a potential impairment the immune response in peripheral tissues. These virus-induced endothelial changes could directly impact the inflammatory process of porcine circovirus disease and associated vascular/immune system disturbances. Data suggest that, among the wide range of effects induced by PCV2 on the host, endothelial modulation can be a pivotal process which can help to explain PCV2 pathogenesis in some porcine circovirus disease presentations.

Impact of porcine reproductive and respiratory syndrome virus and porcine circovirus-2 infection on the potency of the classical swine fever vaccine (LOM strain)

The classical swine fever (CSF) vaccine, which is derived from the LOM strain of the CSF virus (CSFV), induces protective immunity against CSFV infection. However, several factors influence vaccine efficacy. Evidence suggests that infection by porcine reproductive and respiratory syndrome virus (PRRSV) and/or porcine circovirus 2 (PCV2) reduces the efficacy of several vaccines. Here, we examined the effect of PRRSV or PCV2 alone or co-infection by PRRSV/PCV2 on the potency of the LOM vaccine in pigs. Neither CSFV antibody levels nor the period during which CSFV antigens were detectable in LOM-vaccinated pigs were negatively affected by infection by PRRSV or PCV2. However, co-infection with PRRSV/PCV2 may affect the replication or activity of the CSF vaccine virus in pigs vaccinated with the LOM strain, although CSFV antibody levels were not negatively affected. Nevertheless, the LOM vaccine afforded complete protection against a virulent strain of CSFV.

Lawsonia intracellularis and Porcine Circovirus type-2 infection in Estonia.

The present study describes the reasons of post-weaning distress in Estonian pig herds. Here we examined the natural cases of Lawsonia intracellularis and porcine circovirus 2 (PCV2) infection and co-infections. The presence of L. intracellularis in swine herds were tested by PCR and by histopathological methods, whereas PCV2 was detected by real-time-PCR and immunohistochemical stainings. Seven of the 11 investigated herds with signs of post-weaning wasting were infected with L. intracellularis and all 11 herds with PCV2. From the analysed samples 22.2% were infected with L. intracellularis and 25% with PCV2. The results of microbiological studies suggested that the piglets suffered from enteritis and pneumonia. Escherichia coli and Pasteurella multocida often aggravated the process of illness. The frequency of L. intracellularis was high in pigs 7-12 weeks old (18.5-42.7%) and PCV2 infection was too high in pigs 7-12 weeks old (24.8-32.7%). E. coli was often a co-factor with L. intracellularis and PCV2. The primary reasons of post weaning wasting were PCV2 and E. coli, later aggravated by L. intracellularis and other pathogens. Our results indicated that different pathogens have an important role in developing post-weaning wasting. Proliferative intestinal inflammation caused by L. intracellularis is mainly characterised by its localization and morphological findings. The main gross lesions were the enlargement of mesenteric lymph nodes and thickening of the wall of ileum. In post-weaning multi-systemic wasting syndrome there are characteristic histological lesions in lymphoid tissues. They consist of a variable degree of lymphocyte depletion, together with histiocytic and/or multinucleate giant cell infiltration. This basic lymphoid lesions is observable in almost all tissues of a single severely affected animal, including lymph nodes, Peyer's patches and spleen. Sporadically, multifocal coagulative necrosis may be observed.

Pig Diseases in Papua Province, Indonesia: Aetiology, Eco-epidemiology and Control Options

Pigs are an important commodity for Papuans, culturally and economically, but diseases and high pig mortality hamper production. The purpose of this review is to describe the ecology and epidemiology of pig diseases prevalent in Papua and to propose control options that may be suitable for the Papuan situation. The review was conducted using published papers on pig production and diseases in Papua, government documentation and published papers on related diseases from other locations. We determined that the major pig pathogens in Papua are Classical Swine fever (CSF), porcine circovirus 2 (PCV2), Trichuris suis, strongyle parasites and Streptococcus zooepidemicus. Farmers’ knowledge of pig diseases is low; hence the role of local government in control measures is pivotal. Control approaches should involve pig confinement as a prerequisite. Vaccination against CSF and parasite control, when indicated, should be part of routine control measures for confined pigs. Education of farmers is an important part of any control program and needs to focus on good farming practices such as the aforementioned confinement, appropriate feeds and feeding, sanitation, recognition of the clinical signs and major pathology of pig diseases, and the reporting of disease to local veterinary services. The ecology and epidemiology of pig diseases in Papua are still largely not understood. Future studies should be aimed at the evaluation of the proposed methods of disease control, an understanding of the impact of PCV2 infection on pig production in Papua and the role of the movement of pig products into and among regions in Papua in regard to CSF and PCV2 viral transmission as well as investigations of other underdiagnosed yet important pig diseases, such as PRRS, H1N1 influenza and toxoplasmosis.

Interactions of porcine circovirus 2 with its hosts.

Porcine circovirus 2 (PCV2) can cause porcine circovirus diseases and porcine circovirus-associated diseases (PCVD/PCVAD), which are widely presented in swine-producing countries. Since the discovery of this virus, considerable efforts have been devoted to understanding this pathogen and its interactions with its host. Here, we review the current state of knowledge on interactions between host cell factors and PCV2 with respect to viral proliferation, virus-induced cell apoptosis and autophagy, and host antiviral defenses during PCV2 infection. We also review mouse model systems for PCV2 infection.

Characterization of specific antigenic epitopes and the nuclear export signal of the Porcine circovirus 2 ORF3 protein

Porcine circovirus 2 (PCV2) is the etiological agent of postweaning multisystemic wasting syndrome. PCV2 ORF3 protein is a nonstructural protein known to induce apoptosis, but little is known about the biological function of ORF3 protein. Therefore, we undertook this study to map ORF3 protein epitopes recognized by a panel of monoclonal antibodies (mAbs) and to characterize putative nuclear localization (NLS) and nuclear export (NES) sequences in ORF3. The linear epitopes targeted by two previously published mAbs 3B1 and 1H3 and a novel mouse mAb 3C3 were defined using overlapping pools of peptides. Here, we find that ORF3 in PCV2 infected cells contains a conformational epitope targeted by the antibody 3C3, which is distinct from linear epitopes recognized by the antibodies 3B1 and 1H3 in recombinant ORF3 protein. These results suggest that the linear epitope recognized by 3B1 and 1H3 is masked in PCV2 infected cells, and that the conformational epitope is unique to PCV2 infection. Furthermore, we find that ORF3 protein expressed in cytoplasm in early stages of PCV2 infection and then accumulated in nucleus over time. Moreover, we localize a NES at the N-terminus (residues 1–35aa) of ORF3 which plays critical role in nuclear export activity. These findings provide a novel insight that deepens our understanding of the biological function of PCV2 ORF3.

Porcine circovirus 2 immunology and viral evolution.

Porcine circovirus 2 (PCV2) has and is still causing important economic losses to pig industry. This is due to PCV2-systemic disease (PCV2-SD), formerly known as postweaning multi-systemic wasting syndrome (PMWS), which increases mortality rates and slows down the growth of the animals, as well as other conditions collectively included within the so-called porcine circovirus diseases (PCVD). PCV2-SD affected pigs are considered to be immunosuppressed, with severe lymphocyte depletion and evidence of secondary infections. However, PCV2-infected pigs not developing the disease are able to mount humoral and cellular immune responses and clear the virus or limit the infection. On the contrary, insufficient amounts of neutralizing antibodies have been linked to increased PCV2 replication, severe lymphoid lesions and development of PCV2-SD. Central role in controlling PCV2 infection are played by the antigen specific memory T cells. These cells persist long term post-infection or vaccination and are able to expand rapidly after recall antigen recognition. Most farms in the main pig producing countries are applying vaccination against PCV2 to prevent the disease and improve the farm performance. Vaccines do not induce sterilizing immunity and PCV2 keeps on circulating even in farms applying vaccination. This, together with the high mutation rate of PCV2, world-wide fluctuations in the genotype dominance and emergence of novel genetic variants, warrant close molecular survey of the virus in the field.

TLR2/MyD88/NF-κB signalling pathway regulates IL-8 production in porcine alveolar macrophages infected with porcine circovirus 2.

Porcine circovirus 2 (PCV2) is the primary cause of post-weaning multisystemic wasting syndrome, in which it stimulates a strong IL-8 response that is associated with chronic inflammation as well as lesions in the lymphoid organs. However, the mechanism underlying PCV2-induced IL-8 production is still unclear. In the present study, we demonstrated that increased IL-8 expression during PCV2 infection depends on Toll-like receptor (TLR2), but not TLR4 or TLR9 signalling pathways in porcine alveolar macrophages. Moreover, we found that impairment of the MyD88/NF-κB signalling pathway by MyD88 knockdown or NF-κB inhibitors markedly decreased PCV2-induced IL-8 secretion. These results suggest that PCV2 induces IL-8 secretion via the TLR2/MyD88/NF-κB signalling pathway. Therefore, it is important to elucidate the molecular mechanisms of the PCV2-induced inflammatory response.