Large-scale manufacture of VP2 VLP vaccine against porcine parvovirus in Escherichia coli with high-density fermentation

Lipid A-modified Escherichia coli can produce porcine parvovirus virus-like particles with high immunogenicity and minimal endotoxin activity

BACKGROUND

A cost-effective Escherichia coli expression system has gained popularity for producing virus-like particle (VLP) vaccines. However, the challenge lies in balancing the endotoxin residue and removal costs, as residual endotoxins can cause inflammatory reactions in the body.

RESULTS

In this study, porcine parvovirus virus-like particles (PPV-VLPs) were successfully assembled from Decreased Endotoxic BL21 (BL21-DeE), and the effect of structural changes in the lipid A of BL21 on endotoxin activity, immunogenicity, and safety was investigated. The lipopolysaccharide purified from BL21-DeE produced lower IL-6 and TNF-α than that from wild-type BL21 (BL21-W) in both RAW264.7 cells and BALB/c mice. Additionally, mice immunized with PPV-VLP derived form BL21-DeE (BL21-DeE-VLP) showed significantly lower production of inflammatory factors and a smaller increase in body temperature within 3 h than those immunized with VLP from BL21-W (BL21-W-VLP) and endotoxin-removed VLP (ReE-VLP). Moreover, mice in the BL21-DeE-VLP immunized group had similar levels of serum antibodies as those in the BL21-W-VLP group but significantly higher levels than those in the ReE-VLP group. Furthermore, the liver, lungs, and kidneys showed no pathological damage compared with the BL21-W-VLP group.

CONCLUSION

Overall, this study proposes a method for producing VLP with high immunogenicity and minimal endotoxin activity without chemical or physical endotoxin removal methods. This method could address the issue of endotoxin residues in the VLP and provide production benefits.

A comprehensive approach to developing a multi-epitope vaccine against Mycobacterium tuberculosis: from in silico design to in vitro immunization evaluation

Introduction

The Bacillus Calmette-Guérin (BCG) vaccine, currently used against tuberculosis (TB), exhibits inconsistent efficacy, highlighting the need for more potent TB vaccines.

Materials and methods

In this study, we employed reverse vaccinology techniques to develop a promising multi-epitope vaccine (MEV) candidate, called PP13138R, for TB prevention. PP13138R comprises 34 epitopes, including B-cell, cytotoxic T lymphocyte, and helper T lymphocyte epitopes. Using bioinformatics and immunoinformatics tools, we assessed the physicochemical properties, structural features, and immunological characteristics of PP13138R.

Results

The vaccine candidate demonstrated excellent antigenicity, immunogenicity, and solubility without any signs of toxicity or sensitization. In silico analyses revealed that PP13138R interacts strongly with Toll-like receptor 2 and 4, stimulating innate and adaptive immune cells to produce abundant antigen-specific antibodies and cytokines. In vitro experiments further supported the efficacy of PP13138R by significantly increasing the population of IFN-γ+ T lymphocytes and the production of IFN-γ, TNF-α, IL-6, and IL-10 cytokines in active tuberculosis patients, latent tuberculosis infection individuals, and healthy controls, revealing the immunological characteristics and compare the immune responses elicited by the PP13138R vaccine across different stages of Mycobacterium tuberculosis infection.

Conclusion

These findings highlight the potential of PP13138R as a promising MEV candidate, characterized by favorable antigenicity, immunogenicity, and solubility, without any toxicity or sensitization.

A Plant-Produced Porcine Parvovirus 1-82 VP2 Subunit Vaccine Protects Pregnant Sows against Challenge with a Genetically Heterologous PPV1 Strain

Porcine parvovirus (PPV) causes reproductive failure in sows, and vaccination remains the most effective means of preventing infection. The NADL-2 strain has been used as a vaccine for ~50 years; however, it does not protect animals against genetically heterologous PPV strains. Thus, new effective and safe vaccines are needed. In this study, we aimed to identify novel PPV1 strains, and to develop PPV1 subunit vaccines. We isolated and sequenced PPV1 VP2 genes from 926 pigs and identified ten PPV1 strains (belonging to Groups C, D and E). We selected the Group D PPV1-82 strain as a vaccine candidate because it was close to the highly pathogenic 27a strain. The PPV1-82 VP2 protein was produced in Nicotiana benthamiana. It formed virus-like particles and exhibited a 2¹¹ agglutination value. The PPV1-190313 strain (Group E), isolated from an aborted fetus, was used as the challenging strain because it was pathogenic. The unvaccinated sow miscarried at 8 days postchallenge, and mummified fetuses were all PPV1-positive. By contrast, pregnant sows vaccinated with PPV1-82 VP2 had 9-11 Log₂ antibody titers and produced normal fetuses after PPV1-190313 challenge. These results suggest the PPV1-82 VP2 subunit vaccine protects pregnant sows against a genetically heterologous PPV1 strain by inducing neutralizing antibodies.

Self-Assembly of Porcine Parvovirus Virus-like Particles and Their Application in Serological Assay

Porcine parvovirus (PPV) is widely prevalent in pig farms. PPV is closely related to porcine respiratory disease complex (PRDC) and porcine circovirus disease (PCVD), which seriously threatens the healthy development of the pig industry. Although commercial antibody detection kits are available, they are expensive and unsuitable for large-scale clinical practice. Here, a soluble VP2 protein of PPV is efficiently expressed in the E. coli expression system. The VP2 protein can be self-assembled into virus-like particles (VLPs) in vitro. After multiple steps of chromatography purification, PPV-VLPs with a purity of about 95% were obtained. An indirect, enzyme-linked immunosorbent assay (I-ELISA), comparable to a commercial PPV kit, was developed based on the purified PPV-VLPs and was used to detect 487 clinical pig serum samples. The results showed that the I-ELISA is a simple, cost-effective, and efficient method for the diagnosis of clinical pig serum and plasma samples. In summary, high-purity, tag-free PPV-VLPs were prepared, and the established VLP-based I-ELISA is of great significance for the sero-monitoring of antibodies against PPV.

Effects of three commercial vaccines against porcine parvovirus 1 in pregnant gilts

Porcine parvovirosis is a common and important cause of reproductive failure in naïve dams. Even though vaccination is generally effective at preventing disease occurrence, the homology between the vaccine and challenge strains has been recently suggested to play a role in protection. Therefore, the purpose of this study was to evaluate and compare the efficacy of three currently available commercial vaccines against porcine parvovirus genotype 1 (PPV1) in an experimental model using pregnant gilts. Seventy-seven PPV1-negative gilts were included in the trial and randomly allocated to four groups. In group 1, gilts received two doses, three weeks apart, of a PPV1 subunit vaccine (ReproCyc® ParvoFLEX). Following the same scheme, gilts from group 2 received two doses of a PPV1 bivalent vaccine (ERYSENG® PARVO). In group 3, gilts received two doses, four weeks apart, of a PPV1 octavalent vaccine (Porcilis® Ery + Parvo + Lepto). Lastly, gilts from group 4 were left untreated and were used as challenge controls. All gilts were artificially inseminated three weeks after completion of vaccination. Pregnant animals were subsequently challenged around 40 days of gestation with a heterologous PPV1 strain. Foetuses were harvested at around day 90 of gestation and evaluated for their macroscopic appearance (i.e., normal, mummified, or autolytic). Along the study, safety parameters after vaccination, antibody responses against PPV1 and viremia in gilts were also measured. All the foetuses in the challenge control group were mummified, which validated the challenge model, whereas the three evaluated vaccines protected the progeny against PPV1 by preventing the appearance of clinical manifestations associated to parvovirosis. Remarkably, the PPV1 subunit vaccine induced an earlier seroconversion of gilts and was the only vaccine that could prevent viremia after challenge. This vaccine also achieved the largest average litter size accompanied with a high average proportion of clinically healthy foetuses.

Field Application of a New CSF Vaccine Based on Plant-Produced Recombinant E2 Marker Proteins on Pigs in Areas with Two Different Control Strategies

A classical swine fever virus (CSFV)-modified live LOM (low-virulence strain of Miyagi) vaccine (MLV-LOM) to combat CSF has been used in places where the disease is prevalent around the world, including in Korea, except in Jeju Island. In general, modified live virus-based vaccines (MLV) are known to be highly effective in inducing immune responses. At the same time, MLVs also have potential dangers such as a circulation in the field. There is still a need for safer and more effective vaccines to control CSF in the field. In this study, we applied a new CSF vaccine based on plant-produced recombinant E2 marker proteins at two different locations, Jeju Island and a suburb of Pohang, using different CSF control strategies. The result suggested that vaccinated sows in Jeju Island highly developed immunogenicity and maintained stably until 102 days post-vaccination (dpv). Its piglets that received maternal antibodies were shown to carry high serological values and maintained them until 40 days of age, which was the end of the follow-up. Naïve piglets vaccinated at 40 days of age showed high serological values and these were maintained until 100 days of age (60 dpv), which was the end of the follow-up. The vaccine was also effective in inducing immune responses in newborn piglets that carried maternal antibodies received from MLV-LOM vaccine-immunized mother sows.

Self-assembled raccoon dog parvovirus VP2 protein confers immunity against RDPV disease in raccoon dogs: in vitro and in vivo studies

BACKGROUND

Raccoon dog parvovirus (RDPV) causes acute infectious diseases in raccoon dogs and may cause death in severe cases. The current treatment strategy relies on the extensive usage of classical inactivated vaccine which is marred by large doses, short immunization cycles and safety concerns.

METHODS

The present study aimed at optimization of RDPV VP2 gene, subcloning the gene into plasmid pET30a, and its subsequent transfer to Escherichia coli with trigger factor 16 for co-expression. The protein thus expressed was purified with ammonium sulfate precipitation, hydrophobic chromatography, and endotoxin extraction procedures. VLPs were examined by transmission electron microscopy, dynamic light scattering, and the efficacy of VLPs vaccine was tested in vivo.

RESULTS

Results indicated that RDPV VP2 protein could be expressed soluble. Transmission electron microscopy and dynamic light scattering results indicated that RDPV VP2 self-assembled into VLPs. Hemagglutination inhibition antibody titers elicited by Al(OH)3 adjuvanted RDPV VLPs were comparable with RDPV inactivated vaccines, and the viral loads in the blood of the struck raccoon dogs were greatly reduced. Hematoxylin and eosin and Immunohistochemical results indicated that RDPV VLPs vaccine could protect raccoon dogs against RDPV infections.

CONCLUSIONS

These results suggest that RDPV VLPs can become a potential vaccine candidate for RDPV therapy.

Capsid assembly is regulated by amino acid residues asparagine 47 and 48 in the VP2 protein of porcine parvovirus

Porcine parvovirus (PPV) is a major cause of reproductive failure in swine and has caused substantial losses throughout the world. Viral protein 2 (VP2) of PPV is a major structural protein that can self-assemble into virus-like particles (VLP) with hemagglutination (HA) activity. In order to identify the essential residues involved in the mechanism of capsid assembly and to further understand the function of HA, we analyzed a series of deletion mutants and site-directed mutations within the N-terminal of VP2 using the Escherichia coli system. Our results showed that deletion of the first 47 amino acids from the N-terminal of the VP2 protein did not affect capsid assembly, and further truncation to residue 48 Asparagine (Asn, N) caused detrimental effects. Site-directed mutagenesis experiments demonstrated that residue 47Asn reduced the assembly efficiency of PPV VLP, while residue 48Asn destroyed the stability, hemagglutination, and self-assembly characteristics of the PPV VP2 protein. Results from native PAGE inferred that macromolecular polymers were critical intermediates of the VP2 protein during the capsid assembly process. Site-directed mutation at 48Asn did not affect the ability of monomers to form into oligomers, but destroyed the ability of oligomers to assemble into macromolecular particles, influencing both capsid assembly and HA activity. Our findings provide valuable information on the mechanisms of PPV capsid assembly and the possibility of chimeric VLP vaccine development by replacing the first 47 amino acids at the N-terminal of the VP2 protein.

Identification of a dominant linear epitope on the VP2 capsid protein of porcine parvovirus and characterization of two monoclonal antibodies with neutralizing abilities

Porcine parvovirus (PPV) is a major cause of reproductive failure in swine, and has caused huge losses throughout the world. The structural viral protein VP2, which is able to self-assemble into empty capsids, known as virus-like particles (VLPs), is crucial to induce PPV-specific neutralizing antibodies and protective immunity. In this study, twelve monoclonal antibodies (mAbs) against PPV were generated. The mAbs were characterized by indirect enzyme-linked immunosorbent assay (ELISA), western blotting (WB) and virus neutralization (VN) assay. Two mAbs were defined to be able to neutralize the standard PPV 7909 strain. Subsequently, peptide scanning was applied to identify linear epitopes. The peptide, ⁸⁹ESGVAGQMV⁹⁷ was defined as a precise linear epitope. Results from structural analysis showed that the epitope was exposed on the virion surface. Multiple sequence alignment analysis indicated that peptide ⁸⁹ESGVAGQMV⁹⁷ was not completely conserved, with a higher amino acid mutation rate at ⁹¹G, ⁹²V and ⁹³A position. Alanine-scanning mutagenesis further revealed that residues ⁸⁹E, ⁹⁰S, ⁹¹G, ⁹²V and ⁹⁴G were the core sites involved in antibody recognition. These findings may facilitate further understanding the function of the VP2 protein and development of diagnostic tools.

The immunogenicity of the virus-like particles derived from the VP2 protein of porcine parvovirus

Porcine parvovirus (PPV) is a major cause of the syndrome of sow reproductive failure that can cause economic losses. In this study, we developed a subunit vaccine against porcine parvovirus (PPV), composed of virus-like particles (VLPs) derived from a prokaryotic system, and evaluated its potential against PPV infection. The soluble recombinant VP2 protein was expressed in E. coli Transetta(DE3) cells using a pCold II prokaryotic expression vector at a low temperature of 15 °C. After expression and purification, the recombinant VP2 protein was successfully assembled into VLPs with a similar shape of PPV viron and also hemagglutination activity. PPV VLPs formulated in a water-in-oil-in-water adjuvant evoked high hemagglutination inhibition antibody and neutralization antibody titres in both guinea pigs, used as reference model, and target species, pigs. Immunization with VLPs vaccine stimulated high hemagglutination inhibition antibody and neutralization antibody responses in guinea pigs, used as reference, and target species, weaned pigs, and primiparous gilts. PPV VLPs from E. coli yielded complete fetal protection against PPV infection in primiparous gilts immunized with a single-dose vaccine. PPV VLPs inhibited the replication and spread of PPV in primiparous gilts, which was confirmed by the detection of PPV DNA and infectious PPV in nasal and rectal swabs of challenged sows. These results suggest that VLPs-based PPV vaccine is a promising PPV vaccine candidate.