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Porcine circovirus type 2 (PCV2) has been a major problem for the pig production industry worldwide for decades. While the majority of commercially available vaccines are based on the original PCV2a genotype, the current dominant genotype is PCV2d. The notable differences between genotypes could lead to incomplete cross-protection. Moreover, most current subunit PCV2 vaccines are generated from expensive insect cell culture technology. In this work, we present a new workflow for production of an updated and relatively inexpensive PCV2d vaccine candidate. After expression in fed-batch Escherichia coli fermentation systems with a simple one-step ion-exchange chromatography purification protocol, the yield of purified PCV2d-based antigen reached over 1 g per litre bacterial culture. Using similar procedures, we also demonstrated even higher PCV2d-based antigen yields from a chimeric PCV2d-PCV3 capsid construct, which is cleaved during fermentation to release PCV2d- and PCV3-related polypeptides. Although the PCV2d-based recombinant protein from this protocol did not form viral-like particles as analysed by size-exclusion chromatography, it could effectively induce capsid-specific and PCV2d-neutralising antibodies in immunised animals, indicating significant potential as a new vaccine candidate that can be easily manufactured at commercial scale. Previous article in issue [ABSTRACT FROM AUTHOR]

A multiplex quantitative real-time polymerase chain reaction (mqPCR) assay was developed for the rapid and differential detection of porcine circovirus 2 (PCV2) and PCV3. Each of the capsid genes of PCV2 and PCV3 were amplified using specific primers and probe sets, while no other porcine pathogen genes were detected. Limit of detection of the assay was below 50 copies of the target genes of PCV2 and PCV3, and was comparable to that of previously described methods The assay showed high repeatability and reproducibility, with coefficients of intra-assay and inter-assay variation of less than 4.0%. Clinical evaluation using tissue samples from a domestic pig farm showed that PCV2 and PCV3 co-circulated at the farm. Moreover, singular infection rates of PCV2 or PCV3 were 21.7% (10/46) or 6.5% (3/46), respectively, while the co-infection rate of PCV3 with PCV2 was 28.3% (13/46). PCV3 DNA was detected by the mqPCR in respiratory diseased piglet tissue samples and aborted fetal tissue samples, suggesting that PCV3 infection is associated with porcine respiratory disease and reproductive failure in the pig farm. This mqPCR method is a rapid and reliable differential diagnostic tool for the monitoring and surveillance of PCV2 and PCV3 in the field. [ABSTRACT FROM AUTHOR]

Porcine circovirus type 2 (PCV2), a small, single-stranded circular DNA virus and the causative agent of porcine circovirus associated disease (PCVAD), was first observed in the mid-1990s in pigs with a post-weaning wasting disease. In 2006 the number of PCVAD cases greatly increased, marking it as an important viral pathogen for the United States (US) swine industry. PCV2 vaccines were introduced to the US in 2006 in response to widespread outbreaks of PCVAD. These vaccines were effective in preventing disease, but did not eliminate virus from the animals. In 2006, prior to vaccine use, a study of PCV2 prevalence in pig herds across the US was performed in conjunction with the US National Animal Health Monitoring System. In 2012, 6 years after widespread PCV2 vaccination, this study was repeated. Since the introduction of PCV2 vaccines in 2006, viral presence and viral loads have greatly decreased, and a genotypic shift dominated by PCV2b has occurred. Antibody levels have decreased in the pig population, but approximately 95% of sites continue to be antibody-positive. Widespread vaccination has controlled PCVAD and decreased PCV2 prevalence to the point that viremia is not detected on many sites. Thus, continued vaccination may lead to PCV2 elimination in the national herd over time. [ABSTRACT FROM AUTHOR]

Wild boar (Sus scrofa) is an exotic invasive species in Brazil and may be a reservoir for several pathogens, including those related to the porcine respiratory disease complex (PRDC), a critical infectious disease in pig production. The objective of this study was to investigate viral and bacterial pathogens related to PRDC in free-living wild boars from Brazil. Eighty animals were examined in search of genomes of porcine circovirus 2 (PCV2), Torque teno Sus virus 1a (TTSuV1a) and 1b (TTSuV1b), Influenza A virus (IAV), Actinobacillus pleuropneumoniae, Glaesserella parasuis, Pasteurella multocida , and Mycoplasma hyopneumoniae. The results demonstrated that 57.5% (46/80) of the animals had at least one detected pathogen, and 11.3% of them (9/80) were co-infected. TTSuV1a was the most prevalent genome, for which risk factors were associated with increased contact between wild boars and other animals. The other pathogens were detected at much lower frequencies or not detected (M. hyopneumoniae and IAV). An additional IAV serology search identified H1N1pdm09 antibodies in 35.5% (16/45) of the wild boars, bringing concern related to public health. In conclusion, wild boars are infected with pathogens that cause swine diseases, so their eventual contact with domestic pigs might risk animal production in Brazil. [ABSTRACT FROM AUTHOR]

Abstract: Capsid protein (Cap) of porcine circovirus 2 (PCV2) contained critical epitopes for inducing a protective immune response. Here, different fragments of PCV2 Cap protein were cloned, expressed, purified and used to raise polyclonal antibodies. The result showed the recombinant plasmids expressed efficiently in the prokaryotic system. Western blot and ELISA showed the recombinant protein had antigenicity and immunogenicity. Furthermore, efficiency of different constructs to produce antibody against PCV2 was compared. Reactivity and specificity of the polyclonal antibody were characterized by Western blot and indirect immunofluorescent assays. The results indicated that polyclonal antiserum prepared from protein ΔCap17-233 had better reactivity and specificity against PCV2 in comparison to that of protein ΔCap51-233 and the inactivated vaccine. These results will contribute to further studies focusing on the gene and vaccine development against PCV2. [Copyright &y& Elsevier]

Highlights: [•] ORF4-deficient viruses were constructed by inducing start codon mutation or in-frame termination mutation. [•] The ORF4 protein is not essential for viral replication but inhibits viral replication in the early stage of infection. [•] The ORF4 protein plays an important role in triggered apoptosis restriction by restricting ORF3 transcription. [ABSTRACT FROM AUTHOR]

Highlights: [•] We compared the shell vial technique with traditional adsorption for PCV2 isolation. [•] We used ST cells treated with 100mM d-glucosamine for PCV2 propagation. [•] The shell vial technique was more efficient for the isolation of PCV2 significantly. [•] qPCR/RT-qPCR were successfully used to monitor viral replication in infected cells. [•] PCV2 caused persistent infection in ST cells during the viral isolation period. [ABSTRACT FROM AUTHOR]

Abstract: Capsid protein (Cap), the only structural protein of porcine circovirus 2 (PCV2), is involved in the host protective response and is a target for vaccine development. To find a rapid and easy way to fully map the antigenic epitopes of Cap, purified Cap-specific polyclonal antibodies were used to screen a random heptapeptide phage display library. After three rounds of screening, twenty phage clones that had binding activity to Cap-specific antibodies (tested by phage ELISA) were sequenced. When the inserted amino acid sequences were aligned with the Cap protein sequence, eight core regions in Cap (50SRTFGYT56, 62VRTPSW67, 68AVDMMR73, 79FLPPGG84, 86SNPRSVPF93, 102KVEFWP107, 119GSSXXXLDDN128 and 229PPLNP233) were identified, three of which (50SRTFGYT56, 86SNPRSVPF93 and 102KVEFWP107) for the first time. Nine phagetopes representing the eight regions were chosen to immunize Kunming mice. All except minotopes 50SRTFGYT56 and 229PPLNP233 induced antibodies against PCV2 when injected into Kunming mice. [Copyright &y& Elsevier]

Investigations were performed to characterize porcine circovirus (PCV) 2 infection in 10 week old pigs from a case of apparent vaccine failure. Thirty serum samples were collected from affected or nonaffected pigs and tested for anti-PCV2 antibodies and PCV2 DNA. To address potential PCV2 vaccine compliance issues, samples were tested for antibodies against baculovirus and Mycoplasma hyopneumoniae antigens present in the PCV2 vaccine utilized in this herd. Both PCV2a and PCV2b DNA were detected in 76.6% (90% positive for PCV2a, 86.6% positive for PCV2b), anti-PCV2 IgG in 90%, anti-baculovirus IgG in 50%, and anti-M. hyopneumoniae IgG in 43.3% of the samples. Frequency of baculovirus and M. hyopneumoniae seropositive pigs was significantly lower in affected pigs. The finding that only 50% of the pigs developed a detectable immune response to vaccination suggests poor vaccine compliance or efficacy. Concurrent PCV2a and PCV2b infection was common and may have resulted in enhanced PCV2 replication. [ABSTRACT FROM AUTHOR]

Abstract: Two experiments were conducted to determine the association of porcine circovirus type 2 (PCV2) with embryos and the risk of viral transmission by embryo transfer. In the first experiment, 240 embryos from uninfected donors were exposed to PCV2a 104TCID50/mL in vitro before transfer to seronegative recipients; in the second experiment, 384 embryos recovered from infected donors, 10 days after donor inoculation with PCV2, were transferred to seronegative recipients. In total, 1120 embryos and/or ova were collected from 37 viral-free donors (experiment 1) and 1019 from 59 PCV2-infected donors (experiment 2) (P < 0.01). The washing and/or disinfection procedure recommended by the International Embryo Transfer Society was applied to embryos in both experiments. Transfer of embryos experimentally exposed in vitro to high titers of virus caused seroconversion of recipients (58%; N = 7/12) and their piglets (81%; N = 13/16). Postmortem, PCV2 DNA was detected in various organs of embryo transfer recipients and their embryo transfer-derived piglets. In contrast, the transfer of embryos recovered from infectious PCV2 donors did not result in the seroconversion of embryo recipients (N = 24) or their embryo transfer-derived piglets (N = 76). Neither PCV2 DNA nor infectious virus was detected in the tissues of either recipients or embryo transfer-derived piglets collected postmortem in the second experiment. The results obtained in this study indicate that the transmission of PCV2 from infected donors by embryo transfer is unlikely if the sanitary recommendations of the International Embryo Transfer Society are followed. In practical terms, this means that embryo transfer can be successfully used for the intentional elimination of PCV2 and to create virus-free offspring for the safe exchange of swine genetic materials. [Copyright &y& Elsevier]

Highlights: [•] A porcine cell line, VR1BL, was characterized for high titer growth of PCV2. [•] PCV2 grows to higher titers in VR1BL cells, than in PK-15 cells. [•] This cell line provides an in vitro model of acute versus persistent infection that replicates in vivo behavior of PCV2. [•] High MOI infection induces apoptosis-mediated cell death. [Copyright &y& Elsevier]

The porcine circovirus-2 (PCV2) is the main agent responsible for porcine circovirus associated diseases (PCVAD). Few studies have been done regarding PCV2 infection in other species. The purpose of this study was to investigate the occurrence of PCV2 infection in the peridomestic rodent species Mus musculus and Rattus rattus on commercial pig farms in Brazil. Immunohistochemistry assay demonstrated PCV2 in the spleen, lung and kidney. Viral DNA was detected in tissues by nested PCR assay. Partial sequences of PCV2 genomes detected in the rodents had strong identity with gene sequences of PCV2 isolates from pigs. These results show that the studied peridomestic rodent species can be naturally infected by PCV2. However, further studies are needed to confirm PCV2 transmission from rodents to pigs. [ABSTRACT FROM AUTHOR]

Abstract: Porcine circovirus 2 (PCV2) is an extremely slow-growing virus, and PCV2 infection and replication in cell culture yield very low viral titers. The effects of different methods of PCV2 cultivation in vitro were compared with the purpose of increasing viral yield. The results showed that treatment with IL-2, ConA, and d-glucosamine increased PCV2 yield more effectively than other treatments. Additionally, treatment with IL-2, ConA, d-glucosamine and MβCD consistently increased PCV2 infection in PK-15 cells during consecutive viral passages. A combinatorial treatment with ConA, MβCD and d-glucosamine increased PCV2 yield significantly in PK-15 cells, to 1.81×1010 genome copy numbers per mL of cell lysate at 72hpi, and the viral titer (−lgTCID50/100μL) was 8.6. The results of this study may be helpful for the investigation of PCV2 replication and the production of a PCV2 vaccine. [Copyright &y& Elsevier]

Abstract: The role of swine torque teno sus viruses (TTSuVs) as co-factors in disease syndromes involving porcine circovirus strain 2 (PCV2) and porcine reproductive and respiratory disease syndrome virus (PRRSV) has been a debatable subject. In this study, the prevalence of TTSuVs in Iowa, the leading pork producing state in the U.S., was estimated by a duplex PCR. The PCR is capable of simultaneously detecting both teno sus viruses 1 and 2 (TTSuV1 and 2). Based on an analysis of 300 random samples representing six major geographical regions of the state, the overall prevalence rates for TTSuV1 and 2 were 47.34% and 24.67% respectively while the combined prevalence rate was 52.33%. The epidemiological association of TTSuV1 and 2 with the common etiological agents of the porcine respiratory disease complex (PRDC) namely porcine PRRSV, PCV2, Mycoplasma hyopneumoniae and swine influenza virus (SIV) was estimated in lung tissue derived from 45 pigs showing clinical signs of PRDC. Notably, 86.67% of the PRDC-suspect samples were positive for TTSuV1 in comparison to the baseline population prevalence rate of 47.34%. However, the prevalence of TTSuV2 (26.67%) was not significantly different. TTSuV1 was detected in 80.00%, 81.81%, 75.00% and 77.78% of the PRRSV, SIV, M. hyopneumoniae and PCV2 positive PRDC-suspect samples respectively. Our results indicate that TTSuV1 is strongly associated with clinical PRDC and support the hypothesis that TTSuVs might function as co-factors in PRDC. Further studies to define their possible role in the pathogenesis of swine respiratory diseases are warranted. [Copyright &y& Elsevier]

Abstract: This review describes the characterization of porcine circovirus type 2 (PCV2), the field situation of porcine circovirus-associated disease (PCVAD) and the PCV2 vaccine in Korea. PCVAD has been considered the most devastating disease in Korean livestock history since its first outbreak in 1999. Postweaning multisystemic wasting syndrome (PMWS) and porcine respiratory disease complex (PRDC) are the most common clinical forms of PCVAD. Interestingly, only PCV2b strains have been isolated from pigs with PMWS since 2005, but only PCV2a strains were isolated from pigs with PMWS in 2000 to 2001. Clinically, PMWS is divided into two stages: early and late. Early PMWS primarily occurs in pigs between 4 and 8 weeks of age. This form is a typical presentation of PMWS and is characterized clinically by wasting, decreased weight gain, enlarged lymph nodes, and dyspnea. Late PMWS primarily occurs in pigs between 8 and 12 weeks of age. The main clinical manifestation is diarrhea, which is often accompanied by salmonellosis coinfection. In recent years, the PCVAD disease pattern has slightly changed. The occurrence of PMWS has decreased while PRDC cases are increasing in frequency. [Copyright &y& Elsevier]

Abstract: Porcine circovirus type 2 (PCV2) is the essential etiological infectious agent of postweaning multisystemic wasting syndrome (PMWS), which is considered one of the most economically important swine diseases worldwide. In this study, a comparison between methodologies based on classical phylogenetic trees and networks to infer the origin of PCV2 in Cuba was performed. In addition, the mechanisms supporting the genetic variability of Cuban PCV2 populations were investigated. A retrospective study, using pig sera collected in Cuba from 1993 to 2004, to evaluate the presence of PCV2 genome and PCV2-specific antibodies was also conducted and revealed a lack of evidence of PCV2 infection in Cuban swine from years 1993 to 2004. A total of 24 complete Cuban PCV2 sequences collected between 2005 and 2009 from different regions of the country were analyzed. Three classical methods of phylogenetic analysis, namely Neighbour-Joining, Maximum Parsimony and Bayesian Inference, as well as haplotype network construction, were used. Whereas the classical phylogenetic trees suggested different origins for the Cuban PCV2 strains, the haplotype network revealed a direct connection between all the Cuban sequences in agreement with the obtained epidemiological and viral sequence data. Moreover, the importation of pigs carried out in 2005 from the Quebec-Ontario region, Canada, seems to be the most likely origin of PCV2 in Cuba. Likewise, the genetic variability of Cuban PCV2 sequences was supported by geographic segregation and positive selection pressure with estimated rates of nucleotide substitution on the order of 3.12×10−3 and 6.57×10−3 substitutions/site/year, which are closer to those reported for RNA viruses. [Copyright &y& Elsevier]

Abstract: The efficacies of two commercial Mycoplasma hyopneumoniae bacterins and porcine circovirus 2 (PCV2) vaccines were compared in conventional pigs immunized at different ages based on humoral response, pathological observation, and growth performance from birth to finishing (175 days of age) using a M. hyopneumoniae and PCV2 co-infection challenge model. One-week-old pigs (n =110) were randomly assigned to five groups: three vaccinated and challenged (VC), and one each of non-vaccinated and challenged (NVC) and negative control. A significant difference was found in the number of genomic copies of M. hyopneumoniae in nasal swabs and PCV2 in serum samples, the average daily weight gain (gram/pig/day) between 63 and 133dpi, gross and histopathological lung lesion scores, histopathological lymph node lesion scores, and the immunohistochemical analysis of PCV2 among the three VC groups. The single dose schedule for M. hyopneumoniae bacterins and PCV2 vaccines have the advantages of (i) improving daily weight gain (122.4%) and slaughter weight (120.5%), and (ii) reducing the incidence of clinical signs and lung and lymph node lesions. [Copyright &y& Elsevier]

Abstract: Porcine circovirus type 2 (PCV2) is the essential infectious agent of postweaning multisystemic wasting syndrome (PMWS) considered as one of the most important swine diseases worldwide. One of the main risk factors reported for the development of PMWS is the PCV2 genotype. The presence of PCV2 in Cuban swine herds has been reported recently. However, genetic information about these viruses is not available yet. Hence, the objectives of this study were to classify the Cuban porcine circovirus type 2 sequences as well as to investigate the genetic diversity and the putative origins of the virus circulating in Cuban swine herds. PCV2 Cuban sequences appeared to be close related when an analysis of the entire viral genome sequences was performed. The main variations on amino acid sequences of the capsid protein were found within the immunoreactive areas. All the Cuban PCV2 sequences analyzed belonged to genotype 1 and were located within the same Cluster (1A). Interestingly, five of them were clustered with high confident values with those described as the PCV2 variants associated with severe porcine circovirus diseases reported in Canada from the late 2004 to 2006. Pigs imported from this source appeared to be the most probable origin of the viruses circulating in Cuban swine herds currently. The fact that one sequence was not clustered with any other group of PCV2 within genotype 1 might suggest that different introductions of the agent in the country from unknown sources have occurred. [ABSTRACT FROM AUTHOR]

Abstract: The bacteriophage lambda small capsid protein D forms trimers on the phage head. D-fusion polypeptides can be expressed from plasmids in E. coli and remain soluble without aggregation. We report a dual expression system for the display of four immunodominant regions of porcine Circovirus 2 (PCV2) capsid protein (CAP) as D-CAP fusions on lambda display particles (LDP). The LDP-D-CAP preparation proved an effective vaccine in pigs, eliciting both cellular and humoral immune responses and PCV2 neutralizing antibodies. In our dual system wild type D expression was encoded by a heteroimmune infecting phage. The D-fusion protein expression in the infected cells was from an inducible plasmid, enabling the deferral of D-fusion expression until needed. The effective vaccine preparation depended upon the gradient purification of very high concentration, essentially tail-less display particles, not previously described. [ABSTRACT FROM AUTHOR]

Abstract: Phage lambda particles displaying four immunodominant regions of porcine Circovirus 2 (PCV2) capsid protein (LDP–D–CAP) was shown to be immunogenic in pigs. The immunodominant regions were fused to the carboxyl-terminal of lambda head protein D. Expression of D–CAP on lambda display particles was demonstrated by ELISA and Western blots. Pigs receiving LDP–D–CAP, without incorporating adjuvant, showed significant anti-PCV2 immune response following the primary vaccination. The LDP–D–CAP preparation induced PCV2 neutralizing antibodies. Delayed type hypersensitivity (DTH) reaction scores revealed that the immunized pigs were hypersensitive to both lambda phage and PCV2 antigens. The LDP–D–CAP elicited both cellular and humoral immune responses. Neither LDP–D–CAP nor the lambda control elicited any untoward local or systemic reactions following immunization. These studies produced the first potential phage vaccine to porcine Circovirus 2. [Copyright &y& Elsevier]

Zoonotic hepatitis E virus (HEV) infection is an emerging global public health concern. It is usually transmitted to humans from domestic pigs (main host). Since virus-like particles (VLPs) exhibit unique structural and immunological characteristics that make them of momentous applications in vaccine development, the purpose of the present study was the production of immunogenic chimeric VLPs as vaccine candidates for the control of zoonotic HEV in its main host and the prevention of porcine circovirus associated disease, a multi-factorial disease with major economic repercussions on global pig industry. An immuno-informatics approach was applied for the design and screening of new chimeric antigens presenting the dominant immunogenic domains of both HEV and porcine circovirus 2 (PCV2). Then, using molecular cloning techniques, the chimeric proteins were expressed in Escherichia coli. After purification, full characterization of the physicochemical, morphological, and immunological properties of the target proteins has been conducted. The chimeric immunogens were successfully overexpressed and after the optimization of the expression conditions, 5 chimeric proteins were efficiently purified under native conditions. The purified HEV-PCV2 chimeric proteins were found thermo-stable and able to self-assemble into spherical virus-like particles. Four HEV-PCV2 chimeric proteins have displayed optimal antigenicity and immunogenicity properties, with the nPCV2cp-p166 chimeric immunogen slightly outranking the other designed proteins. In conclusion, this study reports the production of stable HEV-PCV2 chimeric VLPs that exhibited optimal antigenicity and immunogenicity and thus with potential applications in diagnostics and vaccine development. Besides, this study provides a reproducible approach for the design, assessment, and production of chimeric antigens. • A computational strategy for the design and analysis of HEV-PCV2 chimeric VLPs. • Efficient production of five HEV-PCV2 chimeric VLPs in E.coli. • The chimeric VLPs were thermostable and displayed optimal antigenicity/ immunogenicity. • nPCV2cp-p166 represents the best chimeric VLPs for diagnostics and/or vaccine development. [ABSTRACT FROM AUTHOR]

Summary: The aim of this study was to determine whether porcine circovirus 2 (PCV2) may infect the mammary gland of sows and be shed in the milk. Six pregnant sows were inoculated intranasally with PCV2 three weeks before their expected farrowing date and two further sows acted as uninfected controls. The animals remained clinically healthy and farrowed normally. Milk samples were collected from all sows on the first, second and third days of lactation. PCV2 DNA was detected in the milk of infected sows from day 1 of lactation but not in the milk of uninfected controls. PCV2 antigen and DNA were detected in the mammary gland and other tissues by immunohistochemistry and in-situ hybridization, respectively. Simultaneous detection of viral protein and DNA provided molecular evidence of PCV2 infection and replication within these tissues. [Copyright &y& Elsevier]

Summary: Six pregnant sows were inoculated intranasally at 3 weeks before the expected farrowing date with porcine circovirus 2 (PCV2). The PCV2-inoculated sows showed abortion and premature farrowing, whereas two uninfected negative control sows remained clinically healthy and farrowed normally. PCV2 antigen and DNA were detected by immunohistochemistry and in-situ hybridization, respectively, in lymph node, spleen, thymus, lung, tonsil and liver from both stillborn and liveborn piglets. Simultaneous detection of viral protein and DNA provided molecular evidence of PCV2 infection and replication. The experiment suggested that PCV2 is capable of crossing the placenta, replicating primarily in lymphoid tissues, and inducing reproductive failure. [Copyright &y& Elsevier]

• A SYBR Green I-based duplex qPCR assay was developed to detect PCV2 and PCV4 simultaneously. • Three PCV2 genotypes (PCV2a, PCV2b and PCV2d) existed in Henan province of China, and 6 PCV4 strains in this study belonged to PCV4a. • Eleven putative recombination events were found in newly emerging isolates of PCV2 in Henan province of China. • The functional regions of PCV4 strains were predicted by comparison with other circoviruses. Porcine circovirus 4 (PCV4) was identified as a novel porcine circovirus in China in 2019. To investigate the prevalence and genetic characteristics of PCV2 and PCV4, 133 clinical samples (103 tissue samples and 30 serum samples) were collected from 30 different pig farms in Henan province of China, and a SYBR Green I-based duplex quantitative real-time polymerase chain reaction assay was established to detect PCV2 and PCV4 genomes simultaneously. The complete genome sequences of 20 PCV2 and 6 PCV4 strains from 19 and 6 clinical samples respectively were sequenced and analyzed. The results showed the detection limits of this assay were 80.2 copies/μL for PCV2 and 58.6 copies/μL for PCV4. The detection results of clinical samples revealed the PCV2 positive rate was 63.16% (84/133), the PCV4 positive rate was 33.33% (45/133), and the PCV2 and PCV4 co-infection positive rate was 21.05% (28/133). Among 20 PCV2 strains, 6 belonged to PCV2a, 6 belonged to PCV2b and 8 belonged to PCV2d. Co-infection with JZ1 (PCV2b) and JZ2 (PCV2d) strains was identified in one sample (JZ-1). Eleven putative recombination events were found through the recombination analysis, suggesting that the new PCV2 variant strains had circulated in Henan province, which contributes to our understanding of evolutionary characteristics of PCV2 in China. The possible genotypes of PCV4 strains were determined based on genomic sequences of 6 PCV4 strains in this study and 29 PCV4 reference strains available at GenBank. According to three different phylogenetic trees (ORF1, ORF2 and complete genome), all 35 PCV4 strains were clustered into two major genotypes (PCV4a and PCV4b), and 6 PCV4 strains in this study belonged to PCV4a. Additionally, the functional regions of PCV4 strains were predicted by comparison with other circoviruses, which are conducive to the further study of the biological functions of PCV4 genome. [ABSTRACT FROM AUTHOR]

Serum antibodies and shedding of porcine circovirus type 2 (PCV2) into lacteal secretions were examined in naturally infected sows. Total (TA) and neutralising (NA) antibodies against PCV2 were evaluated in serum and colostrum from 20 vaccinated (Vac) and 21 unvaccinated (N-vac) sows. Anti-PC-V2 IgA titres and PCV2 infectious titres were determined in colostrum and milk. All sows had high TA and NA levels in serum and colostrum. Infectious PCV2 was detected in 22141 colostrum samples (7/20 Vac and 15/21 NVac sows) and 5/20 milk samples (1/5 Vac and 4[15 N-Vac sows). Anti-PCV2 IgA was found in high levels in colostrum and varying levels in milk. Infectious PCV2 may be present in milk and colostrum of naturally infected sows, even in the presence of NA. [ABSTRACT FROM AUTHOR]

• The PCV2-specific, IFN-gamma release assay is a valid tool for assessing the efficacy of whole virion PCV2b vaccines. • The PCV2b-specific, IFN-gamma response is stimulated by vaccination, and not by infection. • Mean antibody titers and T cell responses to PCV2b vaccines are proportional to antigen doses. Porcine Circovirus 2 (PCV2) vaccines are poorly standardized in terms of antigen payload and correlates of protection. Therefore, twenty, 45-day old piglets were divided into four groups of 5 animals each and vaccinated with 800 / 266 / 88 / 0 nanograms, respectively, of an inactivated PCV2b strain formulated in the same oil adjuvant. Twenty-six days later, all the pigs were challenged intranasally with the homologous PCV2b strain. No clinical signs were observed in the pigs under study. Viremia was observed after challenge in all the control pigs, as well as in 3 pigs of the 266 and 88-ng groups (one and two, respectively). No pigs of the 800-ng group developed viremia. On the basis of post challenge viremia, the PCV2b vaccine under study had a titer of 11 Protective Doses (PD) 50 %, and 1 PD 50 amounted to 74 ng of PCV2b Ag. Neutralizing and ELISA Ab titers showed no obvious correlation with protection in the single animals, even though the 800-ng group developed a significantly higher mean Ab response. All the pigs with a PCV2-specific, IFN-gamma response at 3 weeks after vaccination in whole blood samples were protected against viremia. In lymphoid tissues (mainly tonsils and ileum) the presence of sparse reactive histiocytes and multinucleated giant cells was the only PCV2-associated feature and, by immunohistochemistry, only 3 out of 20 subjects showed a low viral load. [ABSTRACT FROM AUTHOR]