Commercial Porcine Circovirus Type 2 Research Articles

Characterization of a gE/gI/TK gene-deleted pseudorabies virus variant expressing the Cap protein of porcine circovirus type 2d

Porcine circovirus type 2 (PCV2) plays a key role in the etiology of PCV2-associated disease (PCVAD), and its predominant strain is PCV2d which is not completely controlled by most commercially available vaccines against PCV2a strains. Pseudorabies (PR) caused by pseudorabies virus (PRV) variants re-emerged in Bartha-K61 vaccine-immunized swine herds in late 2011, which brought considerable losses to the global pig husbandry. Therefore, it is significantly important to develop a safe and effective vaccine against both PCV2d and PRV infection. In the present study, the PCV2d ORF2 gene was amplified by PCR, and cloned into the BamHI site of PRV transfer plasmid pG vector to obtain the recombinant transfer plasmid pG-PCV2dCap-EGFP. Subsequently, it was transfected into ST cells infected with the three gene deleted PRV variant strain NY-gE-/gI-/TK- to generate a recombinant virus rPRV NY-gE-/gI-/TK-/PCV2dCap+/EGFP+, and then the EGFP gene was knocked out to harvest the rPRV NY-gE-/gI-/TK-/PCV2dCap+ using gene-editing technology termed CRISPR/Cas9 system. The recombinant virus rPRV NY-gE-/gI-/TK-/PCV2dCap+ had similar genetic stability and proliferation characteristics to the parental PRV as indicated by PCR and one-step growth curve test, and the expression of Cap was validated by Western blot. In animal experiment, higher PCV2-specific ELISA antibodies and detectable PCV2-specific neutralizing antibodies could be elicited in mice immunized with rPRV NY-gE-/gI-/TK-/PCV2dCap+ compared to commercial PCV2 inactivated vaccine. Moreover, the recombinant virus rPRV NY-gE-/gI-/TK-/PCV2dCap+ significantly reduced the viral loads in the hearts, livers, spleens, lungs, and kidneys in mice following a virulent PCV2d challenge. Mice immunized with rPRV NY-gE-/gI-/TK-/PCV2dCap+ developed comparable PRV-specific humoral immune responses and provided complete protection against a lethal PRV challenge. Together, the rPRV NY-gE-/gI-/TK-/PCV2dCap+ recombinant strain has strong immunogenicity.

Evaluation of the protective efficacy of virus-like particles based on PCV 2b and 2d subtypes against mixed challenge in mice.

Porcine circovirus type 2 (PCV2) is an economically important swine pathogen and, although small, it has the highest evolution rate among DNA viruses. Commercial PCV2 commercial vaccines are inactivated PCV2 isolates or a subunit vaccine based on the Cap protein of PCV2. Currently, PCV2 VLPs of individual subtype vaccines are available. Although the main prevalent genotype worldwide is PCV2b, the emerging subtype PCV2d subtype is also increasingly associated with PCV disease. The aim of the study was to evaluate the protective efficacy of VLP based on the PCV2b and 2d subtypes against the mixed challenge of two hypotype PCV2 in mice. Thirty-six female SPV Kunming mice were immunized twice with PCV2b and 2d VLPs, then challenged with PCV2b and PCV2d, to assess the immunogenicity and effectiveness of the VLPs. Vaccination of the mice with PCV2b and 2d VLPs elicited a robust antibody response specific for the PCV2. The virus load detected in the 2b and 2d spleen vaccine group was the lowest compared to other groups. Furthermore, there was no pathological damage in the HE stained sections of the 2b and 2d spleen vaccine, and no virus was detected in the immunohistochemical sections. Our data suggest that the mixed PCV2b and 2d VLP vaccine could protect mice from challenge with the mixed infection of PCV2b and PCV2d..

Epidemiological Analysis From 2018 to 2020 in China and Prevention Strategy of Porcine Circovirus Type 2.

Porcine circovirus type 2 (PCV2) is one of the smallest known animal viruses and is the main pathogen of PCV-associated diseases (PCVAD). Epidemiological surveillance results have shown that the PCV2 infection rate is on the rise in China, thus, PCV2 disease prevention and control has become a huge challenge for the Chinese swine industry. We collected clinical samples from multiple different provinces in China from 2018 to 2020 and found that the positive rate of PCV2 was 53% (3619/6872), identity between the cloned 62 ORF2 genes was 84.4–100% and identity between the cloned 62 ORF2 sequences and reference sequence was 72.9–99.8%. Genetic evolution analysis found that PCV2d accounted for 79% (49/62 samples), PCV2a for 12.9% (8/62 samples), PCV2b for 8% (5/62 samples), and PCV2c and PCV2e genotypes were not found. However, most commercial PCV2 subunit vaccines are based on the PCV2a genotype, and there are very few vaccines based on PCV2b or PCV2d. Therefore, the homologous and heterologous protection ability of PCV2b and PCV2d Cap proteins based on the baculovirus against the PCV2b and PCV2d infections was evaluated, which is expected to design and develop excellent PCV2 protein vaccine candidates. This study found that both PCV2b and PCV2d Cap proteins can increase the level of humoral immunity and cellular immune response in mice. Importantly, both PCV2b and PCV2d cap proteins can provide homologous and heterologous protection against the PCV2b and PCV2d viruses. Overall, this study provides a reference for the prevention and control of PCVAD in mainland China and the development of PCV2 vaccines.

Comparative evaluation of ELPylated virus-like particle vaccine with two commercial PCV2 vaccines by experimental challenge

Porcine circovirus type 2 (PCV2) is an economically important swine pathogen and vaccination is the primary tool for the disease control. Previously, we developed a more cost-effective PCV2 virus-like particle (VLP) vaccine by using ELPylation technology. In the present study, we compared the ELPylated VLP (ELP-VLP) PCV2 vaccine efficacy with commercial inactivated Yuanlijia vaccine and VLP-based Circoflex vaccine by experimental challenge. After one dose of vaccination with the three different vaccines, ELP-VLP vaccine group showed significantly (p < 0.05) stronger virus neutralizing antibody and interferon-γ responses than the two commercial vaccine groups. All vaccinated pigs showed significant (p < 0.05) improvement in average daily weight gain (ADWG) before challenge. After challenge with PCV2, however, only ELP-VLP-vaccinated pigs showed significant (p < 0.05) improvement in ADWG. All vaccinated pigs showed significant (p < 0.05) reductions in PCV2 loads in the blood, nasal secretion and lymph nodes, ELP-VLP-vaccinated pigs in particular. In addition, vaccination with ELP-VLP vaccine provided stronger protection against pulmonary and lymphoid pathologies than that with the two commercial vaccines. Therefore, ELP-VLP vaccine is more effective to control PCV2 infection than the two commercial vaccines based on clinical, immunological, virological and pathological evaluations.

A Porcine circovirus type 2b (PCV2b)-based experimental vaccine is effective in the PCV2b-Mycoplasma hyopneumoniae coinfection pig model

Porcine circovirus type 2 (PCV2) is one of the major swine pathogens causing high economic losses due to PCV2-associated disease (PCVAD). PCV2 infection is not only immunosuppressive by damaging lymphoid tissues but is also exacerbated by co-infections with other pathogens including Mycoplasma hyopneumoniae. While PCV2 can be divided into several genotypes, currently only PCV2a, PCV2b and PCV2d are globally prevalent and considered of major importance. Most commercial PCV2 vaccines are based on PCV2a isolates; however, the high prevalence of PCV2b and PCV2d in the global pig population is raising concerns among pig veterinarians. The objective of this study was to evaluate the efficacy of an experimental PCV2b-based subunit vaccine in a combined PCV2b and M. hyopneumoniae coinfection model. Briefly, a total of 49 PCV2- and M. hyopneumoniae-free 3-week-old pigs were randomly divided into four groups: A non-vaccinated, non-infected NEG-CONTROL group, a non-vaccinated, PCV2b-infected, POS-CONTROL group, and two vaccinated and PCV2b-infected groups (SINGLE-VAC, DUAL-VAC). SINGLE-VAC and DUAL-VAC pigs were vaccinated at 3 weeks of age and DUAL-VAC pigs received a booster dose at 5 weeks of age. All pigs, except NEG-CONTROLs, were experimentally infected with M. hyopneumoniae 28 days after initial vaccination and challenged with PCV2b one week later. The pigs were necropsied 21 days after PCV2b challenge. Prior to PCV2b challenge, both vaccinated groups had detectable humoral and cell-medicated immune responses to PCV2. Vaccination significantly reduced PCV2b viremia and also reduced or eliminated PCV2-associated lymphoid lesions compared to the POS-CONTROL pigs. Under the study conditions, an experimental PCV2b vaccine protected conventional growing pigs against PCV2b viremia and associated lesions in a coinfection model with some advantages of the two-dose regimen versus the one dose regimen. Both protocols induced neutralizing antibodies against PCV2a and PCV2d prior to challenge.

Incorporation of ORF2 from Porcine Circovirus Type 2(PCV2) into genetically encoded nanoparticles as a novel vaccine using a self-aggregating peptide

Porcine Circovirus Type 2 (PCV2) is one of the most important pathogens in pigs around the world. PCV2 is a non-enveloped virus and its capsid is formed by a single protein known as open reading frame 2 (ORF2). The aim of this study was to evaluate the antigenicity and immunogenicity of genetically-encoded protein nanoparticles (NPs) containing ORF2 from PCV2 fused to the first 110 amino acids of the N-terminus of polyhedrin from the insect virus Autographa californica nucleopolyhedrovirus (PH(1 −1 1 0)). Our group has previously described that some polyhedrin fragments self-aggregate forming polyhedra-like particles. We identified a self-aggregating signal within the first 110 amino acids from polyhedrin (PH(1 −1 1 0)). Fusing the ORF2 from PCV2 to the carboxyl terminus from PH(1 −1 1 0) results in the formation of NPs which incorporate the antigen of interest. Using this system we synthesized NPs containing PH(1 −1 1 0) fused to ORF2 (PH(1 −1 1 0)PCV2) and purify them to immunize pigs and evaluate the humoral immune response generated by these NPs comparing them to a commercially available vaccine. Pigs immunized with PH(1 −1 1 0)PCV2 NPs produced antibodies against ORF2 from PCV2 as indicated by western blot and ELISA analysis. Antibodies obtained with PH(1 −1 1 0)PCV2 NPs were comparable to those obtained using a commercial PCV2 vaccine. These antibodies neutralized the infection of a recombinant PCV2 expressing the green fluorescent protein (GFP). These results together suggest that the self-aggregating peptide PH(1 −1 1 0) can be used for the synthesis of subunit vaccines against PCV2.

A pilot comparative study of recombinant protein and whole-virus inactivated vaccines against porcine circovirus type 2 in conventionally reared pigs

Porcine circovirus type 2 (PCV2) causes porcine circovirus-associated disease, which is characterized by systemic wasting syndrome, including respiratory problems worldwide. Most commercial PCV2 vaccines are derived from recombinant capsid protein or inactivated whole-virus. We compared average daily weight gain, interferon-γ, and neutralizing antibody levels of a recombinant protein vaccine and an inactivated whole-virus vaccine in a pilot study. Both PCV2 vaccines showed similar effect on immunity against PCV2 and a better average daily weight gain was found in both vaccinated groups compared to non-vaccinated animals.

Efficient production of porcine circovirus virus-like particles using the nonconventional yeast Kluyveromyces marxianus

Porcine circovirus type 2 (PCV2) is a ubiquitous virus with high pathogenicity closely associated with the postweaning multisystemic wasting syndrome (PMWS) and porcine circovirus diseases (PCVDs), which caused significant economic losses in the swine industry worldwide every year. The PCV2 virus-like particles (VLPs) are a powerful subunit vaccine that can elicit high immune response due to its native PCV2 virus morphology. The baculovirus expression system is the widely used platform for producing commercial PCV2 VLP vaccines, but its yield and cost limited the development of low-cost vaccines for veterinary applications. Here, we applied a nonconventional yeast Kluyveromyces marxianus to enhance the production of PCV2 VLPs. After codon optimization, the PCV2 Cap protein was expressed in K. marxianus and assemble spontaneously into VLPs. Using a chemically defined medium, we achieved approximately 1.91g/L of PCV2 VLP antigen in a 5-L bioreactor after high cell density fermentation for 72h. That yield greatly exceeded to recently reported PCV2 VLPs obtained by baculovirus-insect cell, Escherichia coli and Pichia pastoris. By the means of two-step chromatography, 652.8mg of PCV2 VLP antigen was obtained from 1L of the recombinant K. marxianus cell culture. The PCV2 VLPs induced high level of anti-PCV2 IgG antibody in mice serums and decreased the virus titers in both livers and spleens of the challenged mice. These results illustrated that K. marxianus is a powerful yeast for cost-effective production of PCV2 VLP vaccines.

Immunogenicity of adenovirus vaccines expressing the PCV2 capsid protein in pigs.

Porcine circovirus type 2 (PCV2) is the main pathogen of porcine circovirus associated disease (PCVAD), causing great economic losses in pig industry. In previous study, we constructed adenovirus vector vaccines expressing PCV2 Cap either modified with Intron A and WPRE, or CD40L and GMCSF, and evaluated all of these vaccines in mice and in pigs. Although Ad-A-C-W and Ad-CD40L-Cap-GMCSF could induce stronger immune responses than Ad-Cap, neither of them was better than commercial inactivated vaccine PCV2 SH-strain. In this study, secretory recombinant adenoviruses (Ad-A-spCap-W and Ad-A-spCD40L-spCap-spGMCSF-W) and non-secretory recombinant adenovirus Ad-A-CD40L-Cap-GMCSF-W were constructed, and identified by western blot and confocal laser microscope observation. The results of ELISA and VN showed that humoral immune responses induced by Ad-A-spCap-W and Ad-A-CD40L-Cap-GMCSF-W were not significantly different from SH-strain, but Ad-A-spCD40L-spCap-spGMCSF-W could induce significantly higher humoral immune response than SH-strain. Lymphocytes proliferative and cytokines releasing levels of Ad-A-spCap-W and Ad-A-CD40L-Cap-GMCSF-W were not significantly different from SH-strain, but Ad-A-spCD40L-spCap-spGMCSF-W was significantly higher than SH-strain. PCV2-challenge experiment showed that virus loads were significantly reduced in Ad-A-spCD40L-spCap-spGMCSF-W vaccinated group, and no obviously clinical and microscopic lesions were observed in Ad-A-spCD40L-spCap-spGMCSF-W vaccinated group. Altogether, these results demonstrate that recombinant adenovirus vaccine Ad-A-spCD40L-spCap-spGMCSF-W induces stronger immune responses and provides better protection than commercial inactivated vaccine PCV2 SH-strain, and suggest that Ad-A-spCD40L-spCap-spGMCSF-W could be a potential vaccine candidate against PCVAD.

Influence of four commercial porcine circovirus type 2 (PCV2) vaccines on the improvement of production parameters in pigs with maternally derived antibodies

Anti-PCV2 antibodies in serum, viremia and production parameters (average daily weight gain [ADWG] and mortality) were assessed in piglets immunized with four commercial PCV2 vaccines in the presence of high levels of maternally derived antibodies (MDA). A total of 217 sows were vaccinated (V) at 7 and 4 weeks before farrowing with an inactivated PCV2 vaccine. All piglets derived from these sows (n=2215) were divided into five groups and 3-week-old piglets were injected with one of four different vaccines (A-D): V sows-VA piglets (n=437), V sows-VB piglets (n=424), V sows-VC piglets (n=432) and V sows-VD piglets (n=417). A control group of non-vaccinated piglets (V-NV, n=426) received phosphate-buffered saline (PBS). Sows (n=39) received PBS (non-vaccinated group). The ADWG of vaccinated piglets (V-VA, V-VB, V-VC and V-VD) ranging from 661 to 669g/day were significantly higher than the control group (V-NV, 630g/day), but differences in ADWG between vaccinated groups were not statistically significant. An overall mortality ranging from 7.23% to 9.20% was observed in vaccinated piglets (V-VA, V-VB, V-VC and V-VD) compared with the control group (V-NV, 20.02%). The number of genomic copies of PCV2 in serum for the control group were significantly higher than those of the four vaccinated groups at 10, 15, and 22 weeks of age. Vaccination increased serum antibodies in sows 3- to 4-fold; PCV2-specific antibody titers in sera from piglets were very similar to those of their sows. The antibody titers in vaccinated piglets and V-NV group decreased gradually about 3-fold until the week 10. In the presence of high MDA levels, piglets immunized with four commercial PCV2 vaccines showed a significantly reduction of PCV2 infected pigs, viral load, number of PCV2-sero positive pigs and mortality rate as well as significantly higher ADWG than those of the V-NV group.

Production of Escherichia coli-based virus-like particle vaccine against porcine circovirus type 2 challenge in piglets: Structure characterization and protective efficacy validation

We report the strategies leading to the large-production of soluble non-tag full-length porcine circovirus type 2 (PCV2) Cap protein in Escherichia coli. Under neutral pH condition, the purified recombinant Cap protein derived from E. coli expression self-assembles into homogenous round virus-like particle at the similar size of that of the intact PCV2 virus, which is further characterized by Cryo-EM single particle structure determined at 4.5Å. The engineered PCV2 rCap VLP was tested as a subunit vaccine for the protective efficacy against PCV2 challenge on 3-week old piglets. Similar to commercial available PCV2 vaccine, the Cap VLP-immunized piglets developed specific antibody-mediated response and were protected from the virulent SH PCV2 strain challenge. Hence, the production of E. coli based PCV2Cap-VLP could be applied as a cost-friendly and effective subunit vaccine to control PCV2 spreading in developing countries.

Immunity Elicited by an Experimental Vaccine Based on Recombinant Flagellin-Porcine Circovirus Type 2 Cap Fusion Protein in Piglets.

In a recent study, we reported that a recombinant protein from fusion expression of flagellin to porcine circovirus type 2 (PCV2) Cap induced robust humoral and cell-mediated immunity that afforded full protection for PCV2 infection using BALB/c mice. Here, we further evaluated the immunogenicity and protection of the recombinant protein using specific pathogen free (SPF) pigs. Twenty-five 3-week-old piglets without passively acquired immunity were divided into 5 groups. All piglets except negative controls were challenged with a virulent PCV2 at 21 days after booster vaccination and necropsied at 21 days post-challenge. Vaccination of piglets with the recombinant protein without adjuvant induced strong humoral and cellular immune responses as observed by high levels of PCV2-specific IgG antibodies and neutralizing antibodies, as well as frequencies of PCV2-specific IFN-γ-secreting cells that conferred good protection against PCV2 challenge, with significant reduced PCV2 viremia, mild lesions, low PCV2 antigen-positive cells, as well as improved body weight gain, comparable to piglets vaccinated with a commercial PCV2 subunit vaccine. These results further demonstrated that the recombinant flagellin-Cap fusion protein is capable of inducing solid protective humoral and cellular immunity when administered to pigs, thereby becoming an effective PCV2 vaccine candidate for control of PCV2 infection.

Porcine circovirus type 2 in China: an update on and insights to its prevalence and control.

Currently, porcine circovirus type 2 (PCV2) is considered the major pathogen of porcine circovirus associated-diseases (PCVAD) that causes large economic losses for the swine industry in the world annually, including China. Since the first report of PCV2 in 1998, it has been drawing tremendous attention for the government, farming enterprises, farmers, and veterinary practitioners. Chinese researchers have conducted a number of molecular epidemiological work on PCV2 by molecular approaches in the past several years, which has resulted in the identification of novel PCV2 genotypes and PCV2-like agents as well as the description of new prevalence patterns. Since late 2009, commercial PCV2 vaccines, including the subunit vaccines and inactivated vaccines, have already been used in Chinese swine farms. The aim of this review is to update the insights into the prevalence and control of PCV2 in China, which would contribute to understanding the epidemiology, control measures and design of novel vaccines for PCV2.

Comparative analyses of humoral and cell-mediated immune responses upon vaccination with different commercially available single-dose porcine circovirus type 2 vaccines

The objective of this study was to compare the induction of humoral and cell-mediated immune responses by four commercially available single-dose porcine circovirus type 2 (PCV-2) vaccines. A total of 50 3-week-old piglets were assigned to five groups (10 pigs per group). Four commercial PCV-2 vaccines were administered according to the manufacturer's instructions and the piglets were observed for 154 days post vaccination (dpv). Inactivated chimeric PCV-1-2 vaccines induced higher levels of PCV-2-specific neutralizing antibodies (NA) and interferon-γ-secreting cells (IFN-γ-SC) in pigs than did the other three commercial PCV-2 vaccines. The proportions of CD4+ cells were significantly higher in animals vaccinated with inactivated chimeric PCV-1-2 and PCV-2 vaccines than in animals vaccinated with the two subunit vaccines. To our knowledge, this is the first comparison of humoral and cell-mediated immunity induced by four commercial single-dose PCV-2 vaccines under the same conditions. The results of this study demonstrated quantitative differences in the induction of humoral and cell-mediated immunity following vaccination.

A novel vaccine against Porcine circovirus type 2 (PCV2) and Streptococcus equi ssp. zooepidemicus (SEZ) co-infection

To develop a vaccine against Porcine circovirus type 2 (PCV2) and Streptococcus equi ssp. zooepidemicus (SEZ) co-infection, the genes of porcine IL-18, capsid protein (Cap) of PCV2 and M-like protein (SzP) of SEZ were inserted into the swinepox virus (SPV) genome by homologous recombination. The recombinant swinepox virus rSPV-ICS was verified by PCR and indirect immunofluorescence assays. To evaluate the immunogenicity of rSPV-ICS, 28 PCV2 and SEZ seronegative Bama minipigs were immunized with rSPV-ICS (n=8), commercial PCV2 vaccine and SEZ vaccine (n=8) or wild type SPV (n=8). The results showed that SzP-specific antibody and PCV2 neutralizing antibody of the rSPV-ICS immunized group increased significantly compared to the wild type SPV treated group after vaccination and increased continuously over time. The levels of IL-4 and IFN-γ in the rSPV-ICS immunized group were significantly higher than the other three groups, respectively. After been co-challenged with PCV2 and SEZ, 87.5% piglets in rSPV-ICS immunized group were survived. Significant reductions in gross lung lesion score, histopathological lung lesion score, and lymph node lesion score were noticed in the rSPV-ICS immunized group compared with the wtSPV treated group. The results suggested that the recombinant rSPV-ICS provided piglets with significant protection against PCV2-SEZ co-infection; thus, it offers proof-of-principle for the development of a vaccine for the prevention of these swine diseases.

Direct comparison of commercial porcine circovirus type 2 vaccines under field conditions

ABSTRACT Two experiments were done to directly compare the effects of commercially available porcine circovirus type 2 (PCV2) vaccines on growth mortality rate of pigs under field condition in a farm with a history of porcine circovirus disease. In Exp. 1 a total of 1470 pigs were used. Pigs (initially 8.8 kg of BW) within sex (barrow or gilt) were allotted to control or 1 of 2 commercial PCV2 vaccines (1DS; Suvaxyn PCV2 Fort Dodge Animal Health, Fort Dodge, IA, or 2DS; Circumvent PCV, Intervet/Schering-Plough Animal Health, Millsboro, DE). In Exp. 2 a total of 1,993 pigs (25.2 ± 1.24 d of age 7.4 ± 1.70 kg of BW) were allotted within litter and sex to 2 different commercial PCV2 vaccine treatments (BI; CircoFLEX, Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO, or IN; Circumvent PCV, Intervet/Schering-Plough Animal Health). On d 143, the one- 2-dose groups were 3.4 4.6 kg heavier (P

Comparison of Four Commercial One-Dose Porcine Circovirus Type 2 (PCV2) Vaccines Administered to Pigs Challenged with PCV2 and Porcine Reproductive and Respiratory Syndrome Virus at 17 Weeks Postvaccination To Control Porcine Respiratory Disease Complex under Korean Field Conditions

Under Korean field conditions, coinfection with porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) is most commonly observed in porcine respiratory disease complex (PRDC). Despite the wide use of PCV2 vaccination, PRDC remains a serious respiratory problem. Thus, the objective of this study was to determine and compare the efficacy of 4 one-dose PCV2 vaccines on 3-week-old pigs with an experimental PCV2-PRRSV challenge at 17 weeks postvaccination. Regardless of which commercial PCV2 vaccine was used, the vaccination of piglets at 3 weeks of age was efficacious against cochallenge of PCV2 and PRRSV, on the basis of growth performance and PCV2-associated lesions. However, the inactivated chimeric PCV1-2 and the PCV2 vaccines induced higher PCV2-specific neutralizing antibody (NA) titers and PCV2-specific gamma interferon-secreting cells and lower PCV2 viremia levels than the two PCV2 subunit vaccines. The vaccination of piglets against PCV2 at 3 weeks of age was effective in reducing PCV2 viremia and PCV2-associated lesions during the finishing period, which is an age at which pigs are frequently affected by PRDC caused by coinfection with PCV2 and PRRSV under Korean field conditions.

Comparison of three commercial one-dose porcine circovirus type 2 (PCV2) vaccines on PCV2 shedding in semen from experimentally infected boars

This study compared the effects of 3 different types of commercial PCV2 vaccines on PCV2 virus shedding in the semen from infected boars. Twenty-five non-PCV2 viremic and seronegative boars were randomly divided into five groups: three vaccinated and challenged groups, a non-vaccinated and challenged group, and a negative control group. The number of genomic copies of PCV2 in serum and semen samples was significantly decreased in vaccinated and challenged boars compared to non-vaccinated and challenged boars from 14 to 70 days post-inoculation (dpi). The number of PCV2 genomic copy in the semen correlated with the number of PCV2b genomic copy in the blood in vaccinated and challenged boars (r(2)=0.894-0.926, P<0.01), and non-vaccinated and challenged boars (r(2)=0.903, P<0.01). The vaccination protocol reduced the amount of PCV2 DNA shed in the semen. However, there was a significantly different amount of PCV2 DNA shed in semen among the 3 vaccinated and challenged boar groups.

Evaluation of cell-mediated immune responses against porcine circovirus type 2 (PCV2) Cap and Rep proteins after vaccination with a commercial PCV2 sub-unit vaccine

This study investigated the development of cellular immunity to Porcine circovirus type 2 (PCV2) Cap and Rep proteins in pigs vaccinated with a commercial PCV2 genotype a (PCV2a) based sub-unit vaccine, before and after a heterologous challenge with a PCV2b isolate. At three weeks of age, 20 pigs were inoculated intramuscularly with either the vaccine product (V group, n=9) or phosphate buffered saline solution (PBS) (NV group, n=11). Three weeks after vaccination, pigs were challenged intranasally with PCV2b (V-C and NV-C groups) or PBS (V-NC and NV-NC groups). None of the pigs developed clinical signs during the whole experiment, but all NV-C and 3/5 V-C pigs developed viraemia. Vaccination induced the development IFN-γ-secreting cells in response to the Cap protein of PCV2, which appeared three weeks post-vaccination and increased after challenge. By that time, no significant differences were detected on PCV2 antibody titres between vaccinated and non-vaccinated pigs, although there were significant differences on day 7 post-challenge. PCV2-inoculation induced a cellular response against the Rep protein. Such response was significantly reduced or even absent in PCV2-inoculated pigs that were previously vaccinated (V-C group), presumably as a result of a lower PCV2 replication in vaccinated animals compared to non-vaccinated ones.

Vaccination of sows reduces the prevalence of PCV-2 viraemia in their piglets under field conditions

The objectives of this study were to further understand vertical transmission of porcine circovirus type 2 (PCV-2) and the effect of dam vaccination on PCV-2 viraemia in newborn piglets. Randomly...