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A Virus-like Particle-Based F4 Enterotoxigenic Escherichia coli Vaccine Is Inhibited by Maternally Derived Antibodies in Piglets but Generates Robust Responses in Sows. Pathogens 2023; 12:1388. [PMID: 38133272 PMCID: PMC10745950 DOI: 10.3390/pathogens12121388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/14/2023] [Accepted: 11/23/2023] [Indexed: 12/23/2023] Open
Abstract
F4-positive enterotoxigenic Escherichia coli is associated with diarrhea and poor growth outcomes in neonatal and newly weaned piglets and is thus a major economic and welfare burden in the swine industry. Vaccination of sows with F4 fimbriae protects against the neonatal disease via passive transfer of maternal immunity. However, this strategy does not protect against infection post-weaning. Consequently, prevention and treatment methods in weaner pigs heavily rely on the use of antimicrobials. Therefore, in order to reduce antimicrobial consumption, more effective prophylactic alternatives are needed. In this study, we describe the development of a capsid virus-like particle (cVLP)-based vaccine targeting the major F4 fimbriae subunit and adhesion molecule, FaeG, and evaluate its immunogenicity in mice, piglets, and sows. cVLP-display significantly increased systemic and mucosal antibody responses towards the recombinant FaeG antigen in mice models. However, in piglets, the presence of anti-F4 maternally derived antibodies severely inhibited the induction of active humoral responses towards the FaeG antigen. This inhibition could not be overcome, even with the enhanced immunogenicity achieved via cVLP display. However, in sows, intramuscular vaccination with the FaeG.cVLP vaccine was able to generate robust IgG and IgA responses that were comparable with a commercial fimbriae-based vaccine, and which were effectively transferred to piglets via colostrum intake. These results demonstrate that cVLP display has the potential to improve the systemic humoral responses elicited against low-immunogenic antigens in pigs; however, this effect is dependent on the use of antigens, which are not the targets of pre-existing maternal immunity.
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Viral protein-based nanoparticles (part 2): Pharmaceutical applications. Eur J Pharm Sci 2023; 189:106558. [PMID: 37567394 DOI: 10.1016/j.ejps.2023.106558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 07/10/2023] [Accepted: 08/04/2023] [Indexed: 08/13/2023]
Abstract
Viral protein nanoparticles (ViP NPs) such as virus-like particles and virosomes are structures halfway between viruses and synthetic nanoparticles. The biological nature of ViP NPs endows them with the biocompatibility, biodegradability, and functional properties that many synthetic nanoparticles lack. At the same time, the absence of a viral genome avoids the safety concerns of viruses. Such characteristics of ViP NPs offer a myriad of opportunities for theirapplication at several points across disease development: from prophylaxis to diagnosis and treatment. ViP NPs present remarkable immunostimulant properties, and thus the vaccination field has benefited the most from these platforms capable of overcoming the limitations of both traditional and subunit vaccines. This was reflected in the marketing authorization of several VLP- and virosome-based vaccines. Besides, ViP NPs inherit the ability of viruses to deliver their cargo to target cells. Because of that, ViP NPs are promising candidates as vectors for drug and gene delivery, and for diagnostic applications. In this review, we analyze the pharmaceutical applications of ViP NPs, describing the products that are commercially available or under clinical evaluation, but also the advances that scientists are making toward the implementation of ViP NPs in other areas of major pharmaceutical interest.
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Carboxyl-Terminal Decoy Epitopes in the Capsid Protein of Porcine Circovirus Type 2 Are Immunogenicity-Enhancers That Elicit Predominantly Specific Antibodies in Non-Vaccinated Pigs. Viruses 2022; 14:v14112373. [PMID: 36366471 PMCID: PMC9693397 DOI: 10.3390/v14112373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/19/2022] [Accepted: 10/21/2022] [Indexed: 01/31/2023] Open
Abstract
In the context of the carboxyl-terminus (C-terminus) of the capsid protein of porcine circovirus type 2a (PCV2a) and PCV2a vaccines, this study aimed to explore its unrevealing cryptic epitope and its relation to PCV2-infected herd immunity. To discover the C-terminus of the capsid protein of PCV2a, monoclonal antibodies (mAbs) were generated in this work. Two mAbs bound the two minimal linear epitopes (229PPLKP233 and 228DPPLNP233 (or 229PPLNP233)), which were located at the C-terminus of the capsid proteins of PCV2a and PCV2b, respectively. One mAb bound to the minimal linear epitope (220QFREFNLK227, peptide P82), but it neither bound the virus-like particle (VLP) of PCV2a nor produced positive staining in PCV2a-infected cells by immunofluorescence assay. Further, the residues 220-227 were not accessible on the surface of the VLP on the three-dimensional model, but the residues 228-231 extend toward the VLP exterior. Immunoassays were conducted in this study to screen anti-viral peptide-specific IgGs, which could differentiate vaccinated pigs from non-vaccinated ones. The data show two 220QFREFNLKDPPLKP233-containing peptides had a significantly higher binding reactivity with sera from PCV2-infected pigs in the control group than with sera from the VLP-vaccine group, particularly seen in sera from swine aged 15 weeks to 24 weeks. However, the peptide P82 had not this phenomenon in that test. This study confirmed that C-terminal epitopes play an important role in PCV2-induced decoy of swine humoral immunity.
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Live attenuated Salmonella enterica serovar Choleraesuis vector delivering a virus-like particles induces a protective immune response against porcine circovirus type 2 in mice. Vaccine 2022; 40:4732-4741. [PMID: 35773121 DOI: 10.1016/j.vaccine.2022.06.046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/30/2022] [Accepted: 06/16/2022] [Indexed: 11/25/2022]
Abstract
The virus-like particles (VLPs) of porcine circovirus type 2 (PCV2) is an attractive vaccine candidate that retains the natural conformation of the virion but lacks the viral genome to replicate, thus balancing safety and immunogenicity. However, the assembly of VLPs requires cumbersome subsequent processes, hindering the development of related vaccines. In addition, as a subunit antigen, VLPs are defective in inducing cellular and mucosal immune responses. In this study, the capsid (Cap) protein of PCV2 was synthesized and self-assembled into VLPs in the recombinant attenuated S. Choleraesuis vector, rSC0016(pS-Cap). Furthermore, rSC0016(pS-Cap) induced a Cap-specific Th1-dominant immune response, mucosal immune responses, and neutralizing antibodies against PCV2. Finally, the virus genome copies in mice immunized with the rSC0016(pS-Cap) were significantly lower than those of the empty vector control group after challenge with PCV2. In conclusion, our study demonstrates the potential of using S. Choleraesuis vectors to delivery VLPs, providing new ideas for the development of PCV2 vaccines.
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A new strategy to develop pseudorabies virus-based bivalent vaccine with high immunogenicity of porcine circovirus type 2. Vet Microbiol 2021; 255:109022. [PMID: 33711567 DOI: 10.1016/j.vetmic.2021.109022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 02/22/2021] [Indexed: 12/28/2022]
Abstract
Herpesvirus based multivalent vaccines have been extensively studied, whereas few of them have been successfully used in clinic and animal husbandry industry due to the low expression of foreign immunogens in herpesvirus. In this study, we developed a new strategy to construct herpesvirus based bivalent vaccine with high-level expression of foreign immunogen, by which the ORF2 gene encoding the major antigen protein Cap of porcine circovirus type 2 (PCV2), was highly expressed in pseudorabies virus (PRV). To obtain the high expression of PCV2 immunogen, tandem repeats of PCV2 ORF2 gene were firstly linked by protein quantitation ratioing (PQR) linker to reach equal expression of each ORF2 gene. Then, the multiple copies of ORF2 gene were respectively inserted into the gE and gG sites of PRV using CRISPR/Cas9 system, in which the expression of ORF2 gene was driven by endogenous strong promoters of PRV. Through this way, the highest yield of Cap protein was achieved in two copies of quadruple ORF2 gene insertion. Finally, in mice and pigs immunized with the bivalent vaccine candidate, we detected high titer of specific antibodies for PRV and neutralized antibodies for PCV2, and observed protective effect of the bivalent vaccine candidate against PRV challenge in immunized pigs, suggesting a potential clinical application of the bivalent vaccine candidate we constructed. Together, our strategy could be extensively applied to the generation of other multivalent vaccines, and will pave the way to construct herpesvirus based multivalent vaccines to effectively reduce the cost of vaccine.
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The Monoclonal Antibody Recognized the Open Reading Frame Protein in Porcine Circovirus Type 2-Infected Peripheral Blood Mononuclear Cells. Viruses 2020; 12:v12090961. [PMID: 32872497 PMCID: PMC7551997 DOI: 10.3390/v12090961] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 08/25/2020] [Indexed: 12/17/2022] Open
Abstract
The purpose of this study in the context of the open reading frame 3 (ORF3) protein of porcine circovirus type 2 (PCV2) was especially its location and its relation to the capsid protein and the apoptosis protein in PCV2-infected porcine peripheral blood mononuclear cells (PBMCs). To detect the ORF3 protein, monoclonal antibodies (mAbs) were generated in this study. The mAb 7D3 binds to the ORF3 peptide (residues 35–66) and the native ORF3 protein in PCV2-infected PBMCs, as shown by immunofluorescence assay (IFA). The data show that 3–5% of PBMCs were positive for ORF3 protein or p53 protein. Further, 78–82% of PBMCs were positive for the capsid. This study confirmed the ORF3 protein not only colocalized with the capsid protein but also colocalized with the p53 protein in PBMCs. Immunoassays were conducted in this study to detect the capsid protein, the ORF3 protein, anti-capsid IgG, and anti-ORF3 IgG. The data show the correlation (r = 0.758) of the ORF3 protein and the capsid protein in the blood samples from the PCV2-infected herd. However, each anti-viral protein IgG had a different curve of the profile in the same herd after vaccination. Overall, this study provides a blueprint to explore the ORF3 protein in PCV2-infected PBMCs.
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Efficient application of a baculovirus-silkworm larvae expression system for obtaining porcine circovirus type 2 virus-like particles for a vaccine. Arch Virol 2020; 165:2301-2309. [PMID: 32757056 DOI: 10.1007/s00705-020-04754-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 06/24/2020] [Indexed: 12/11/2022]
Abstract
Porcine circovirus type 2 (PCV2) is a major pathogen associated with swine diseases. It is the smallest single-stranded DNA virus, and its genome contains four major open reading frames (ORFs). ORF2 encodes the major structural protein Cap, which can self-assemble into virus-like particles (VLPs) in vitro and contains the primary antigenic determinants. In this study, we developed a high-efficiency method for obtaining VLPs and optimized the purification conditions. In this method, we expressed the protein Cap with a 6× His tag using baculovirus-infected silkworm larvae as well as the E. coli BL21(DE3) prokaryotic expression system. The PCV2 Cap proteins produced by the silkworm larvae and E. coli BL21(DE3) were purified. Cap proteins purified from silkworm larvae self-assembled into VLPs in vitro, while the Cap proteins purified from bacteria were unable to self-assemble. Transmission electron microscopy confirmed the self-assembly of VLPs. The immunogenicity of the VLPs produced using the baculovirus system was demonstrated using an enzyme-linked immunosorbent assay (ELISA). Furthermore, the purification process was optimized. The results demonstrated that the expression system using baculovirus-infected silkworm larvae is a good choice for obtaining VLPs of PCV2 and has potential for the development of a low-cost and efficient vaccine.
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Incorporation of a truncated form of flagellin (TFlg) into porcine circovirus type 2 virus-like particles enhances immune responses in mice. BMC Vet Res 2020; 16:45. [PMID: 32028949 PMCID: PMC7006081 DOI: 10.1186/s12917-020-2253-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Accepted: 01/22/2020] [Indexed: 02/07/2023] Open
Abstract
Background Porcine circovirus type 2 (PCV2) is an economically important pathogen in the swine industry worldwide. Vaccination remains the principal tool to control PCV2-associated diseases (PCVADs). Current vaccines do not eliminate viral shedding in the environment. To enhance the efficacy of PCV2 vaccines, recombinant virus-like particles (VLPs) of PCV2 were generated by fusing a truncated form of flagellin FliC (TFlg: 85-111aa) with the PCV2 capsid protein (Cap). Results The recombinant proteins were expressed in Escherichia coli and detected using Western blotting. The abilities of the recombinant proteins to assemble into VLPs were observed under transmission electron microscopy (TEM). The protective immune responses of recombinant VLPs were further evaluated by immunization of mice. The results showed that insertion of TFlg into C terminal of the Cap protein did not affect the formation of VLPs and boosted both humoral and cellular immune responses in mice. After a challenge with PCV2, in the Cap-TFlg vaccinated group, viremia was milder and viral loads were lower as compared with those in the Cap vaccinated group. Conclusion These results suggest that recombinant VLPs of PCV2 containing a TFlg adjuvant can be used as a promising PCV2 vaccine candidate.
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Structural roles of PCV2 capsid protein N-terminus in PCV2 particle assembly and identification of PCV2 type-specific neutralizing epitope. PLoS Pathog 2019; 15:e1007562. [PMID: 30822338 PMCID: PMC6415871 DOI: 10.1371/journal.ppat.1007562] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 03/13/2019] [Accepted: 01/04/2019] [Indexed: 11/19/2022] Open
Abstract
Postweaning multisystemic wasting disease (PMWS) in piglets caused by porcine circovirus type 2 (PCV2) is one of the major threats to most pig farms worldwide. Among all the PCV types, PCV2 is the dominant genotype causing PMWS and associated diseases. Considerable efforts were made to study the virus-like-particle (VLP) assembly and the specific PCV2-associated epitope(s) in order to establish the solid foundation for engineered PCV2 vaccine development. Although the N-terminal fragment including Nuclear Localization Signal (NLS) sequence seems important for recombinant PCV2 capsid protein expression and VLP assembly, the detailed structural and functional information regarding this important fragment are largely unknown. In this study, we report crystal structure of PCV2 VLP assembled from N-terminal NLS truncated PCV2 capsid protein at 2.8 Å resolution and cryo-EM structure of PCV2 VLP assembled from full-length PCV2 capsid protein at 4.1Å resolution. Our in vitro PCV2 VLP assembly results show that NLS-truncated PCV2 capsid protein only forms instable VLPs which were easily disassembled in solution, whereas full-length PCV2 capsid protein forms stable VLPs due to interaction between 15PRSHLGQILRRRP27(α-helix) and 33RHRYRWRRKN42(NLS-B) in a repeated manner. In addition, our results also showed that N-terminal truncation of PCV2 capsid protein up to 27 residues still forms PCV2 particles in solution with similar size and immunogenicity, while N-terminal truncation of PCV2 capsid protein with more than 30 residues is not able to form stable PCV2 particles in solution, demonstrating the importance of interaction between the α-helix at N-terminal and NLS-B in PCV2 VLP formation. Moreover, we also report the cryo-EM structure of PCV2 VLP in complex with 3H11-Fab, a PCV2 type-specific neutralizing antibody, at 15 Å resolution. MAb-3H11 specifically recognizes one exposed epitope located on the VLP surface EF-loop (residues 128–143), which is further confirmed by PCV1-PCV2 epitope swapping assay. Hence, our results have revealed the structural roles of N-terminal fragment of PCV2 capsid protein in PCV2 particle assembly and pinpointed one PCV2 type-specific neutralizing epitope for the first time, which could provide clear clue for next generation PCV2 vaccine and diagnostic kits development. Porcine circovirus type 2 (PCV2) is considered as one of the most wide-spread pathogens threatening swine production by causing postweaning multisystemic wasting disease (PMWS) in piglets worldwide. Several VLP-based PCV2 vaccines are commercially available which significantly reduce the viral burden and virally induced lesions. However, prophylactic efficacy of VLP-based PCV2 vaccine largely relies on the correct VLP assembly from the individual PCV2 capsid protein. Notably, limited structural information of PCV2 N-terminal fragment containing arginine-rich patches significantly delays our understanding of PCV2 assembly at the molecular level, and the lack of solid evidence in identification of PCV2 type-specific epitope delays the development of PCV2 type-specific diagnosis kits. In this study, through the combination of structural and immunological approaches, we are able, for the first time, to disclose the structural details of the N-terminal Nuclear Localization Signal (NLS) region of PCV2 capsid protein. We show that the interaction between the α-helix from one capsid protein and the NLS-B from an adjacent capsid protein within the pentamer stabilizes the assembled PCV2 VLP in solution. Moreover, by the combination of structural determination and biochemical mapping, we have identified that a short linear sequence (134KATALT139) located within PCV2 EF-loop is a unique PCV2 type-specific neutralizing epitope. Therefore, our work has revealed the detailed structural information of PCV2 particle assembly and a PCV2 type-specific neutralizing epitope, which should provide insightful information for virus-host interaction studies and next-generation PCV2 vaccine and type-specific diagnostic kits development.
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Abstract
Classical molecular dynamics modeling of whole viruses or their capsids in explicit water is discussed, and known examples from the literature are analyzed. Only works on all-atom modeling in explicit water are included. Physical chemistry of the whole system is the focus, which includes the structure and dynamics of the biomolecules as well as water and ion behavior in and around the virus particle. It was demonstrated that in most investigations molecular phenomena that currently can not be studied experimentally are successfully reproduced and explained by the simulations. These include, for example, transport and distribution of ions inside viruses that ultimately connected to their stability, the hydrodynamic pressure in the capsid related to viruses' elastic properties, the role of metal ions in virus swelling, and others. Current and future tendencies in the development of all-atom virus simulations are outlined.
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Baculovirus-driven protein expression in insect cells: A benchmarking study. J Struct Biol 2018; 203:71-80. [DOI: 10.1016/j.jsb.2018.03.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 02/27/2018] [Accepted: 03/10/2018] [Indexed: 11/18/2022]
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Preparation of virus-like particles for porcine circovirus type 2 by YeastFab Assembly. Virus Genes 2018; 54:246-255. [PMID: 29417333 DOI: 10.1007/s11262-018-1537-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 01/30/2018] [Indexed: 12/13/2022]
Abstract
Porcine circovirus type 2 (PCV2) poses a genuine threat to pig industry. An effective vaccine production against the pandemic is desirable. The aim of this study was to construct recombination yeast strains with PCV2 Cap protein. We adopt to YeastFab Assembly method to synthesize transcriptional units in a single tube by piecing up promoter, open reading frame, and terminator in S. cerevisiae. Two yeast recombinants were successfully constructed using GPD and TEF2 promoters, respectively, to express PCV2 by secreting Cap protein in vitro. Electronic microscope observation demonstrated that the yeast-derived PCV2 Cap protein could self-assembles into 18-nm-diameter virus-like particles (VLPs). The yield of two different recombination yeasts containing GPD and TEF2 promoters were 12, 25 μg/ml, respectively. Our results showed that it is feasible to use S. cerevisiae as a safe and simple system to produce PCV2 virus-like particles. This indicated that there is possibility of obtaining PCV2 VLP vaccine by homologous recombination in yeast genome, and Cap protein was secreted into the cultural supernatant which can be used as a potential oral vaccine to protect pigs from PCV2-infection.
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The level of decoy epitope in PCV2 vaccine affects the neutralizing activity of sera in the immunized animals. Biochem Biophys Res Commun 2018; 496:846-851. [PMID: 29374509 PMCID: PMC7092900 DOI: 10.1016/j.bbrc.2018.01.141] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 01/23/2018] [Indexed: 02/08/2023]
Abstract
Viral pathogens have evolved a wide range of tactics to evade host immune responses and thus propagate effectively. One efficient tactic is to divert host immune responses toward an immunodominant decoy epitope and to induce non-neutralizing antibodies toward this epitope. Therefore, it is expected that the amount of decoy epitope in a subunit vaccine can affect the level of neutralizing antibody in an immunized animal. In this study, we tested this hypothesis by generating an antibody specific to the decoy epitope on the capsid protein of porcine circovirus type 2 (PCV2). Using this antibody, we found that two commercial vaccines contained statistically different amounts of the decoy epitope. The vaccine with lower levels of decoy epitope induced a significantly higher level of neutralizing antibody after immunization. This antibody can be used as an analytical tool to monitor the quality of a vaccine from batch to batch. We generated a novel antibody specific to an immunodominant decoy epitope of PCV2. Using this novel antibody, we measured levels of decoy epitope in PCV2 vaccine. Decoy epitope in PCV2 vaccine affected the neutralizing antibody titer induction.
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All-Atom Molecular Dynamics Simulations of Entire Virus Capsid Reveal the Role of Ion Distribution in Capsid's Stability. J Phys Chem Lett 2017; 8:779-784. [PMID: 28129688 PMCID: PMC5391438 DOI: 10.1021/acs.jpclett.6b02759] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Present experimental methods do not have sufficient resolution to investigate all processes in virus particles at atomistic details. We report the results of molecular dynamics simulations and analyze the connection between the number of ions inside an empty capsid of PCV2 virus and its stability. We compare the crystallographic structures of the capsids with unresolved N-termini and without them in realistic conditions (room temperature and aqueous solution) and show that the structure is preserved. We find that the chloride ions play a key role in the stability of the capsid. A low number of chloride ions results in loss of the native icosahedral symmetry, while an optimal number of chloride ions create a neutralizing layer next to the positively charged inner surface of the capsid. Understanding the dependence of the capsid stability on the distribution of the ions will help clarify the details of the viral life cycle that is ultimately connected to the role of packaged viral genome inside the capsid.
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Induction of a robust immunity response against novel duck reovirus in ducklings using a subunit vaccine of sigma C protein. Sci Rep 2016; 6:39092. [PMID: 27974824 PMCID: PMC5156932 DOI: 10.1038/srep39092] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 11/16/2016] [Indexed: 12/17/2022] Open
Abstract
Novel duck reovirus (NDRV) disease emerged in China in 2011 and continues to cause high morbidity and about 5.0 to 50% mortality in ducklings. Currently there are no approved vaccines for the virus. This study aimed to assess the efficacy of a new vaccine created from the baculovirus and sigma C gene against NDRV. In this study, a recombinant baculovirus containing the sigma C gene was constructed, and the purified protein was used as a vaccine candidate in ducklings. The efficacy of sigma C vaccine was estimated according to humoral immune responses, cellular immune response and protection against NDRV challenge. The results showed that sigma C was highly expressed in Sf9 cells. Robust humoral and cellular immune responses were induced in all ducklings immunized with the recombinant sigma C protein. Moreover, 100% protection against lethal challenge with NDRV TH11 strain was observed. Summary, the recombinant sigma C protein could be utilized as a good candidate against NDRV infection.
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Regulation of porcine circovirus type 2-like particles expressed in baculovirus expression system. BIORESOUR BIOPROCESS 2016. [DOI: 10.1186/s40643-016-0114-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Porcine circovirus type 2 protective epitope densely carried by chimeric papaya ringspot virus-like particles expressed in Escherichia coli as a cost-effective vaccine manufacture alternative. Biotechnol Appl Biochem 2016; 64:406-414. [PMID: 26970530 DOI: 10.1002/bab.1491] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 03/03/2016] [Indexed: 10/22/2022]
Abstract
Porcine circovirus type 2 (PCV2) still represents a major problem to the swine industry worldwide, causing high mortality rates in infected animals. Virus-like particles (VLPs) have gained attention for vaccine development, serving both as scaffolds for epitope expression and immune response enhancers. The commercial subunit vaccines against PCV2 consist of VLPs formed by the self-assembly of PCV2 capsid protein (CP) expressed in the baculovirus vector system. In this work, a PCV2 protective epitope was inserted into three different regions of papaya ringspot virus (PRSV) CP, namely, the N- and C-termini and a predicted antigenic region located near the N-terminus. Wild-type and chimeric CPs were modeled in silico, expressed in Escherichia coli, purified, and visualized by transmission electron microscopy. This is the first report that shows the formation of chimeric VLPs using PRSV as epitope-presentation scaffold. Moreover, it was found that PCV2 epitope localization strongly influences VLP length. Also, the estimated yields of the chimeric VLPs at a small-scale level ranged between 65 and 80 mg/L of culture medium. Finally, the three chimeric VLPs induced high levels of immunoglobulin G against the PCV2 epitope in immunized BALB/c mice, suggesting that these chimeric VLPs can be used for swine immunoprophylaxis against PCV2.
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Generation and immunogenicity of porcine circovirus type 2 chimeric virus-like particles displaying porcine reproductive and respiratory syndrome virus GP5 epitope B. Vaccine 2016; 34:1896-903. [DOI: 10.1016/j.vaccine.2016.02.047] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 02/15/2016] [Accepted: 02/17/2016] [Indexed: 10/22/2022]
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Production of Escherichia coli-based virus-like particle vaccine against porcine circovirus type 2 challenge in piglets: Structure characterization and protective efficacy validation. J Biotechnol 2016; 223:8-12. [DOI: 10.1016/j.jbiotec.2016.02.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 02/15/2016] [Accepted: 02/17/2016] [Indexed: 11/29/2022]
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Vaccination with virus-like particles containing H5 antigens from three H5N1 clades protects chickens from H5N1 and H5N8 influenza viruses. Vaccine 2016; 34:1575-1581. [PMID: 26868083 DOI: 10.1016/j.vaccine.2016.02.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 01/22/2016] [Accepted: 02/01/2016] [Indexed: 12/28/2022]
Abstract
Highly pathogenic avian influenza (HPAI) viruses, especially H5N1 strains, represent a public health threat and cause widespread morbidity and mortality in domestic poultry. Recombinant virus-like particles (VLPs) represent a promising novel vaccine approach to control avian influenza including HPAI strains. Influenza VLPs contain viral hemagglutinin (HA), which can be expressed in cell culture within highly immunogenic VLPs that morphologically and antigenically resemble influenza virions, except VLPs are non-infectious. Here we describe a recombinant VLP containing HA proteins derived from three distinct clades of H5N1 viruses as an experimental, broadly protective H5 avian influenza vaccine. A baculovirus vector was configured to co-express the H5 genes from recent H5N1 HPAI isolates A/chicken/Germany/2014 (clade 2.3.4.4), A/chicken/West Java/Subang/29/2007 (clade 2.1.3) and A/chicken/Egypt/121/2012 (clade 2.2.1). Co-expression of these genes in Sf9 cells along with influenza neuraminidase (NA) and retrovirus gag genes resulted in production of triple-clade H555 VLPs that exhibited hemagglutination activity and morphologically resembled influenza virions. Vaccination of chickens with these VLPs resulted in induction of serum antibody responses and efficient protection against experimental challenges with three different viruses including the recent U.S. H5N8 HPAI isolate. We conclude that these novel triple-clade VLPs represent a feasible strategy for simultaneously evoking protective antibodies against multiple variants of H5 influenza virus.
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Correlates of Protection Following Vaccination with Inactivated Porcine Circovirus 2 Vaccines. Viral Immunol 2015; 28:600-8. [DOI: 10.1089/vim.2015.0021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Improved Production Efficiency of Virus-Like Particles by the Baculovirus Expression Vector System. PLoS One 2015; 10:e0140039. [PMID: 26458221 PMCID: PMC4601761 DOI: 10.1371/journal.pone.0140039] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 09/21/2015] [Indexed: 12/29/2022] Open
Abstract
Vaccines based on virus-like particles (VLPs) have proven effective in humans and animals. In this regard, the baculovirus expression vector system (BEVS) is one of the technologies of choice to generate such highly immunogenic vaccines. The extended use of these vaccines for human and animal populations is constrained because of high production costs, therefore a significant improvement in productivity is crucial to ensure their commercial viability. Here we describe the use of the previously described baculovirus expression cassette, called TB, to model the production of two VLP-forming vaccine antigens in insect cells. Capsid proteins from porcine circovirus type 2 (PCV2 Cap) and from the calicivirus that causes rabbit hemorrhagic disease (RHDV VP60) were expressed in insect cells using baculoviruses genetically engineered with the TB expression cassette. Productivity was compared to that obtained using standard counterpart vectors expressing the same proteins under the control of the polyhedrin promoter. Our results demonstrate that the use of the TB expression cassette increased the production yields of these vaccine antigens by around 300% with respect to the standard vectors. The recombinant proteins produced by TB-modified vectors were fully functional, forming VLPs identical in size and shape to those generated by the standard baculoviruses, as determined by electron microscopy analysis. The use of the TB expression cassette implies a simple modification of the baculovirus vectors that significantly improves the cost efficiency of VLP-based vaccine production, thereby facilitating the commercial viability and broad application of these vaccines for human and animal health.
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Expression of porcine circovirus type 2 capsid protein fused with partial polyhedrin using baculovirus. ACTA ACUST UNITED AC 2015. [DOI: 10.7852/ijie.2015.30.2.50] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Enhanced production of porcine circovirus type 2 (PCV2) virus-like particles in Sf9 cells by translational enhancers. Biotechnol Lett 2015; 37:1765-71. [PMID: 25994579 DOI: 10.1007/s10529-015-1856-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Accepted: 04/30/2015] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To investigate the effect of three translational enhancers for enhancing transgene expression in baculovirus expression vector system using GFP as a reporter gene and selected translational enhancers to increase porcine circovirus type 2 (PCV2) VLPs production. RESULTS P10UTR (the 3'-untranslated region from the baculovirus p10 gene), Syn21 (a synthetic AT-rich 21-bp sequence) and P10UTR/Syn21 increased the GFP yield by 1.4-, 4- and 4.8-fold, respectively. While IVS (intron from Drosophila myosin heavy chain gene) decreased the GFP yield by 65%. Moreover, the synergy of P10UTR/Syn21 increased the yield of PCV2 VLPs by 4.1 fold (45 μg/10(6) cells) compared with standard baculovirus vector. CONCLUSION The synergy of P10UTR/Syn21 is a potential strategy to improve the recombinant vaccine production besides PCV2 VLPs in BEVS.
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Generation in yeast of recombinant virus-like particles of porcine circovirus type 2 capsid protein and their use for a serologic assay and development of monoclonal antibodies. BMC Biotechnol 2014; 14:100. [PMID: 25487652 PMCID: PMC4265424 DOI: 10.1186/s12896-014-0100-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 11/18/2014] [Indexed: 11/30/2022] Open
Abstract
Background Porcine circovirus type 2 (PCV2) is considered to be an important emerging pathogen associated with a number of different syndromes and diseases in pigs known as PCV2-associated diseases. It has been responsible for significant mortality among pigs and remains a serious economic problem to the swine industry worldwide leading to significant negative impacts on profitability of pork production. Results In this study we have demonstrated that PCV2 capsid (Cap) protein based virus-like particles (VLPs) were efficiently produced in yeast S. cerevisiae and induced production of monoclonal antibodies (MAbs) reactive with virus-infected cells. Moreover, PCV2 Cap VLPs served as a highly specific recombinant antigen for the development of an indirect IgG PCV2 Cap VLP-based ELISA for the detection of virus-specific IgG antibodies in swine sera. Four hundred-nine serum samples collected from pigs in Lithuania were tested for PCV2-specific IgG to determine the sensitivity and specificity of the newly developed ELISA in parallel using a commercial SERELISA test as a gold standard. From 409 tested serum samples, 297 samples were positive by both assays. Thirty-nine sera from 112 serum samples were determined as negative by SERELISA but were found to be positive both in the newly developed indirect IgG PCV2 Cap VLP-based ELISA and the PCR test. Conclusions We have demonstrated that S. cerevisiae expression system is an alternative to insect/baculovirus expression system for production of homogenous in size and shape PCV2 Cap protein-based VLPs similar to native virions. Yeast expression system tolerated native virus genes encoding PCV2 Cap protein variants as well as the codon-optimized gene. Moreover, yeast-derived PCV2 Cap VLPs were capable to induce the generation of PCV2-specific MAbs that did not show any cross-reactivity with PCV1-infected cells. The high sensitivity and specificity of the indirect IgG PCV2 Cap VLP-based ELISA clearly suggested that this assay is potentially useful diagnostic tool for screening PCV2–suspected samples.
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Secretory expression of Porcine Circovirus Type 2 capsid protein in Pichia pastoris. J Virol Methods 2014; 207:226-31. [DOI: 10.1016/j.jviromet.2014.07.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 04/23/2014] [Accepted: 07/15/2014] [Indexed: 01/17/2023]
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Insect cell technology is a versatile and robust vaccine manufacturing platform. Expert Rev Vaccines 2014; 10:1063-81. [DOI: 10.1586/erv.11.24] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Induction of robust immunity response in mice by dual-expression-system-based recombinant baculovirus expressing the capsid protein of porcine circovirus type 2. Virol J 2013; 10:316. [PMID: 24161107 PMCID: PMC4231451 DOI: 10.1186/1743-422x-10-316] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 10/22/2013] [Indexed: 01/14/2023] Open
Abstract
Background Porcine circovirus type 2 (PCV2) is associated with post-weaning multisystemic wasting syndrome (PMWS), an emerging swine disease that causes progressive weight loss, dyspnea, tachypnea, anemia, jaundice, and diarrhea in piglets. Although baculovirus is an enveloped virus that infects insects in nature, it has emerged as a vaccine vector, and we used it to develop a novel candidate vaccine for a preventive or therapeutic strategy to control PCV2 infections. Methods Immunoblotting analysis of recombinant baculovirus and immunofluorescent staining of baculovirus-infected cells were followed using anti-ORF2 monoclonal antibodies. The BALB/c mice were immunized intramuscularly with this baculovirus. The titers of antibodies were mensurated with a Cap-protein-specific enzyme-linked immunosorbent assay (ELISA) and a serum neutralization assay. The IFN-γ response in splenocytes harvested from immunized mice was measured by ELISA. Student's t-test was used to compare immune responses of different groups. Results In this study, we successfully constructed a dual-expression-system-based recombinant baculovirus BV-GD-ORF2, which can display the PCV2 capsid (Cap) protein and VSV-G protein on the viral envelope and also expressing Cap protein on transduced mammalian cells, thereby functioning as both a subunit and a DNA vaccine. After infection, the Cap protein was expressed and displayed on the viral surface, as demonstrated with an indirect fluorescence assay and immunoblotting. The vaccination of mice with recombinant baculovirus BV-GD-ORF2 successfully induced robust Cap-protein-specific humoral and cellular immune responses. Conclusions Our findings collectively demonstrate that the recombinant baculovirus BV-GD-ORF2 is a potential vaccine against PCV2 infections.
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Construction and immunogenicity of recombinant porcine circovirus-like particles displaying somatostatin. Vet Microbiol 2012; 163:23-32. [PMID: 23294858 DOI: 10.1016/j.vetmic.2012.11.045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Revised: 11/25/2012] [Accepted: 11/29/2012] [Indexed: 02/02/2023]
Abstract
In order to obtain a virus-like particles (VLPs) vaccine both for porcine circovirus type 2 (PCV2) prevention and growth-promotion, somatostatin (SS) gene was fused to the 3'-terminal of ORF2 gene of PCV2 with PCR, and a recombinant baculovirus (rAc-Cap-SS) was constructed. The expression of fusion protein Cap-SS (rCap-SS) with molecular weight of approximately 32kDa was identified by Western blot and indirect immunofluorescence assay in Sf9 cells. The self-assembled VLPs were observed under electron microscopy, which being morphologically similar to the recombinant Cap protein (rCap) expressed in the same baculovirus expressing system. Ninety four-week-old mice were immunized with the recombinant proteins twice. The results showed that mice immunized with rCap-SS protein developed antibody against Cap, which levels being similar to those immunized with rCap protein. The body weight gain and anti-SS antibody in rCap-SS group was higher than those of rCap and negative control groups during 28 and 42 days post inoculation (dpi). Furthermore, twenty 28-day-old piglets were vaccinated twice subcutaneously with the recombinant proteins. The results indicated that PCV2-specific antibody could be induced after vaccination with rCap-SS or rCap protein. Anti-SS antibody could be induced after rCap-SS vaccination and was higher than other groups at 14 and 28 dpi. The level of somatostatin concentration in the blood of pigs in rCap-SS group was significantly decreased at 14 dpi than other groups (P<0.05). The relative daily weight gain (RDWG) of pigs in rCap-SS group was obviously higher than that in other groups at 28 dpi. After challenge with PCV2, pigs in the vaccinated groups had no clearly clinical signs, and the RDWG was significantly higher than that in the challenge control group (CC) (P<0.05). The pathological lesions, viremia and viral load presented in the vaccinated groups were milder than those in challenge control group. It suggested that the recombinant porcine circovirus-like particles displaying somatostatin might be a novel subunit vaccine candidate for preventing PMWS and promoting pig growth.
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High-level expression and immunogenicity of a porcine circovirus type 2 capsid protein through codon optimization in Pichia pastoris. Appl Microbiol Biotechnol 2012; 97:2867-75. [DOI: 10.1007/s00253-012-4540-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 10/20/2012] [Accepted: 10/22/2012] [Indexed: 02/07/2023]
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Development and evaluation of single-tube nested PCR (STNPCR) for the detection of porcine circovirus type 2 (PCV2). Transbound Emerg Dis 2012; 61:233-8. [PMID: 23078249 DOI: 10.1111/tbed.12022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Indexed: 11/29/2022]
Abstract
Porcine circovirus 2 (PCV2) is a common virus in pig population and is associated with the postweaning multisystemic wasting disease (PMWS). In this study, it was developed and evaluated the single-tube nested PCR (STNPCR) method for the detection of PCV2 DNA. PCV2 reference controls and swine tissue samples were used, and primers were selected for targeting specific regions of the viral genome. In comparison of the methods, STNPCR was 10 times more sensitive than conventional PCR and showed the same sensitivity to nested PCR (NPCR), but with reduction in the risk of cross-contamination. In clinical application, 55 tissue samples were analysed by conventional PCR and resulted in 67% (37/55) of positive reactions, while the NPCR and STNPCR were able to identify the presence of viral DNA in 100% (55/55) of the samples. The high sensitivity combined with the elimination of cross-contamination makes the STNPCR method suitable for the epidemiological studies of PCV2 and can aid in the diagnosis of PMWS.
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Self-assembly of virus-like particles of porcine circovirus type 2 capsid protein expressed from Escherichia coli. Virol J 2010; 7:166. [PMID: 20646322 PMCID: PMC2919472 DOI: 10.1186/1743-422x-7-166] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2010] [Accepted: 07/21/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Porcine circovirus 2 (PCV2) is a serious problem to the swine industry and can lead to significant negative impacts on profitability of pork production. Syndrome associated with PCV2 is known as porcine circovirus closely associated with post-weaning multisystemic wasting syndrome (PMWS). The capsid (Cap) protein of PCV2 is a major candidate antigen for development of recombinant vaccine and serological diagnostic method. The recombinant Cap protein has the ability to self-assemble into virus-like particles (VLPs) in vitro, it is particularly opportunity to develop the PV2 VLPs vaccine in Escherichia coli,(E.coli ), because where the cost of the vaccine must be weighed against the value of the vaccinated pig, when it was to extend use the VLPs vaccine of PCV2. RESULTS In this report, a highly soluble Cap-tag protein expressed in E.coli was constructed with a p-SMK expression vector with a fusion tag of small ubiquitin-like modifiers (SUMO). The recombinant Cap was purified using Ni2+ affinity resins, whereas the tag was used to remove the SUMO protease. Simultaneously, the whole native Cap protein was able to self-assemble into VLPs in vitro when viewed under an electron microscope. The Cap-like particles had a size and shape that resembled the authentic Cap. The result could also be applied in the large-scale production of VLPs of PCV2 and could be used as a diagnostic antigen or a potential VLP vaccine against PCV2 infection in pigs. CONCLUSION we have, for the first time, utilized the SUMO fusion motif to successfully express the entire authentic Cap protein of PCV2 in E. coli. After the cleavage of the fusion motif, the nCap protein has the ability to self-assemble into VLPs, which can be used as as a potential vaccine to protect pigs from PCV2-infection.
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Enhanced expression of PCV2 capsid protein in Escherichia coli and Lactococcus lactis by codon optimization. World J Microbiol Biotechnol 2010. [DOI: 10.1007/s11274-010-0503-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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A genetically engineered chimeric vaccine against porcine circovirus type 2 (PCV2) improves clinical, pathological and virological outcomes in postweaning multisystemic wasting syndrome affected farms. Vaccine 2009; 27:7313-21. [DOI: 10.1016/j.vaccine.2009.09.084] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 09/17/2009] [Accepted: 09/18/2009] [Indexed: 10/20/2022]
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Bordetella bronchiseptica aroA mutant as a live vaccine vehicle for heterologous porcine circovirus type 2 major capsid protein expression. Vet Microbiol 2009; 138:318-24. [DOI: 10.1016/j.vetmic.2009.04.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 04/07/2009] [Accepted: 04/14/2009] [Indexed: 11/28/2022]
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The optimized capsid gene of porcine circovirus type 2 expressed in yeast forms virus-like particles and elicits antibody responses in mice fed with recombinant yeast extracts. Vaccine 2009; 27:5781-90. [PMID: 19664739 DOI: 10.1016/j.vaccine.2009.07.061] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 06/21/2009] [Accepted: 07/19/2009] [Indexed: 10/20/2022]
Abstract
Porcine circovirus type 2 (PCV2)-associated diseases are considered to be the biggest problem for the worldwide swine industry. The PCV2 capsid protein (Cap) is an important antigen for development of vaccines. At present, most anti-PCV2 vaccines are produced as injectable formulations. Although effective, these vaccines have certain drawbacks, including stress with concomitant immunosuppresion, and involve laborious and time-consuming procedures. In this study, Saccharomyces cerevisiae was used as a vehicle to deliver PCV2 antigen in a preliminary attempt to develop an oral vaccine, and its immunogenic potential in mice was tested after oral gavage-mediated delivery. The cap gene with a yeast-optimized codon usage sequence (opt-cap) was chemically synthesized and cloned into Escherichia coli/Saccharomyces cerevisiae shuttle vector, pYES2, under the control of the Gal1 promoter. Intracellular expression of the Cap protein was confirmed by Western blot analysis and its antigenic properties were compared with those of baculovirus/insect cell-produced Cap protein derived from the native PCV2 cap gene. It was further demonstrated by electron micrography that the yeast-derived PCV2 Cap protein self-assembles into virus-like particles (VLPs) that are morphologically and antigenically similar to insect cell-derived VLPs. Feeding raw yeast extract containing Cap protein to mice elicited both serum- and fecal-specific antibodies against the antigen. These results show that it is feasible to use S. cerevisiae as a safe and simple system to produce PCV2 virus-like particles, and that oral yeast-mediated antigen delivery is an alternative strategy to efficiently induce anti-PCV2 antibodies in a mouse model, which is worthy of further investigation in swine.
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Immunoprophylaxis against important virus disease of horses, farm animals and birds. Vaccine 2009; 27:1797-1810. [PMID: 19402200 PMCID: PMC7130586 DOI: 10.1016/j.vaccine.2008.12.063] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 11/24/2008] [Accepted: 12/18/2008] [Indexed: 01/31/2023]
Abstract
Since the refinement of tissue culture techniques for virus isolation and propagation from the mid 1960s onwards, veterinary virology has received much academic and industrial interest, and has now become a major global industry largely centred on vaccine development against economically important virus diseases of food animals. Bio-tech approaches have been widely used for improved vaccines development. While many viral diseases are controlled through vaccination, many still lack safe and efficacious vaccines. Additional challenges faced by academia, industry and governments are likely to come from viruses jumping species and also from the emergence of virulent variants of established viruses due to natural mutations. Also viral ecology is changing as the respective vectors adapt to new habitats as has been shown in the recent incursion by bluetongue virus into Europe. In this paper the current vaccines for livestock, horses and birds are described in a species by species order. The new promising bio-tech approaches using reverse genetics, non-replicating viral vectors, alpha virus vectors and genetic vaccines in conjunction with better adjuvants and better ways of vaccine delivery are discussed as well
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Abstract
Porcine circovirus type 2 (PCV2) is the primary causative agent for porcine circovirus-associated disease (PCVAD). PCVAD has been the cause of considerable economic losses to the pork industry worldwide. The disease is primarily characterized by wasting, enlarged lymph nodes, jaundice and weight loss in affected weanling pigs. Several other complex syndromes involving reproductive failure, enteritis, pneumonia and necrotizing dermatitis have also been associated with PCV2 infection. Lymphoid depletion, which is the hallmark lesion of PCVAD, predisposes the host to immunosuppression. Disease progression is further complicated by co-infections with other bacterial and viral pathogens. Despite the availability of effective vaccines for the last 2 years, newly emerging strains of the virus have been reported to cause more severe outbreaks in parts of the USA and Canada. While knowledge of the biology and pathogenesis of PCV2 has progressed considerably over the last 12 years since the disease was recognized, many questions still remain to be answered.
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Expression of the capsid protein of porcine circovirus type 2 in Lactococcus lactis for oral vaccination. J Virol Methods 2008; 150:1-6. [DOI: 10.1016/j.jviromet.2008.02.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 02/11/2008] [Accepted: 02/25/2008] [Indexed: 11/19/2022]
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Porcine circovirus type 2 (PCV2) viral components immunomodulate recall antigen responses. Vet Immunol Immunopathol 2008; 124:41-9. [PMID: 18304652 DOI: 10.1016/j.vetimm.2008.01.031] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Revised: 11/19/2007] [Accepted: 01/17/2008] [Indexed: 10/22/2022]
Abstract
Porcine circovirus type 2 (PCV2) is a single-stranded circular DNA virus infecting domestic pigs worldwide. Interaction of this virus with the immune system apparently modulates the immune response of the host. In the present study, the implication of different components of PCV2 in the modulation of the immune response of the host were investigated by using PCV2 viral-like particles (VLPs) and 16 novel oligodeoxyribonucleotides containing CpG motifs (CpG-ODNs) based on the PCV2 genomic sequence. The role of these viral components was studied by evaluating the cytokine profiles (IFN-alpha, IFN-gamma, IL-10, IL-2 and IL-12) on porcine peripheral mononuclear cell (PBMC) and bone marrow-derived dendritic cell (BMDC) cultures. Also, the effect of PCV2 and its elements were examined in recall antigen (pseudorabies virus, PRV) responses. While PCV2 was a potent inducer of IL-10 by PBMCs, such effect was not observed using CpG-ODNs or VLPs. However, IFN-gamma and IL-2 production by recall antigen was repressed in presence of PCV2 and most of the studied CpG-ODNs. VLPs did not have such repressive effect. In BMDC cultures, PCV2 and most of CpG-ODNs were able to inhibit IFN-alpha secretion induced by PRV. Interestingly, CpG-ODNs with inhibitory effect were located within the PCV2 Rep gene. Additionally, PCV2 virus was a very strong IL-12 inducer in BMDC cultures. Whereas, IFN-alpha modulation on BMDC after PCV2 VLP treatment was neglectable, PCV2 VLPs were potent IL-12 inducers. Our data shows that PCV2 viral elements can distinctly regulate cytokine production depending on the cell population studied. Thus, the final immune response upon PCV2 infection seems to depend on the fine balance between the regulatory elements present in viral DNA and structural protein within the host immune system.
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