An immunoglobulin G based chimeric protein induced foot-and-mouth disease specific immune response in swine

A recombinant multi-epitope trivalent vaccine for foot-and-mouth disease virus serotype O in pigs

In order to develop a safe and effective broad-spectrum vaccine for foot-and-mouth disease (FMDV), here, we developed a recombinant FMD multiple-epitope trivalent vaccine based on three distinct topotypes of FMDV. Potency of the vaccine was evaluated by immune efficacy in pigs. The results showed that the vaccine with no less than 25 μg of antigen elicited FMDV serotype O specific antibodies and neutralization antibodies by primary-booster regime, and offered immune protection to pigs. More importantly, the vaccine elicited not only the same level of neutralization antibodies against the three distinct topotypes of FMDV, but also provided complete protection in pigs from the three corresponding virus challenge. None of the fully protected pigs were able to generate anti-3ABC antibodies throughout the experiment, which implied the vaccine can offer sterilizing immunity. The vaccine elicited lasting-long high-level antibodies and effectively protected pigs from virulent challenge within six months of immunization. Therefore, we consider that this vaccine may be used in the future for the prevention and control of FMD.

A meta-analysis on the potency of foot-and-mouth disease vaccines in different animal models

Whether mice can be used as a foot-and-mouth disease (FMD) model has been debated for a long time. However, the major histocompatibility complex between pigs and mice is very different. In this study, the protective effects of FMD vaccines in different animal models were analyzed by a meta-analysis. The databases PubMed, China Knowledge Infrastructure, EMBASE, and Baidu Academic were searched. For this purpose, we evaluated evidence from 14 studies that included 869 animals with FMD vaccines. A random effects model was used to combine effects using Review Manager 5.4 software. A forest plot showed that the protective effects in pigs were statistically non-significant from those in mice [MH = 0.56, 90% CI (0.20, 1.53), P = 0.26]. The protective effects in pigs were also statistically non-significant from those in guinea pigs [MH = 0.67, 95% CI (0.37, 1.21), P = 0.18] and suckling mice [MH = 1.70, 95% CI (0.10, 28.08), P = 0.71]. Non-inferiority test could provide a hypothesis that the models (mice, suckling mice and guinea pigs) could replace pigs as FMDV vaccine models to test the protective effect of the vaccine. Strict standard procedures should be established to promote the assumption that mice and guinea pigs should replace pigs in vaccine evaluation.

A meta-analysis: the efficacy and effectiveness of polypeptide vaccines protect pigs from foot and mouth disease

The protective effects of peptides on pigs are controversial. In this study, meta-analysis was used to analyze the protective immune response of peptides. The China National Knowledge Infrastructure, PubMed, Wanfang Data, Cochrane Library, Embase, and gray literature sources were searched for FMDV articles published from the inception of the databases to March 2022. Of the 1403 articles obtained, 14 were selected using inclusion criteria. The experimental data on polypeptide vaccines were analyzed using Microsoft Office Home and Student 2019 Software. From the results, polypeptide vaccine doses (PPVDs) ≤ 1 mg offered protection against FMDV in 69.41% pigs lower than World Organization for Animal Health (OIE) standard (75%, 12/16). PPVDs ≥ 2 mg provided protection against FMDV in 97.22% pigs. When the two groups were compared directly, PPVDs ≥ 2 mg (93.75%) was higher than PPVDs ≤ 1 mg (63.16%). PPVDs ≤ 1 mg provided protection 56% pigs and the inactivated vaccine was 93.33% in direct comparison. In conclusion, PPVDs has a dose-dependent protective effect on pigs and PPVDs ≤ 1 mg group was lower than the inactivated vaccines group.

Immunogenicity assessment of Clostridium perfringens type D epsilon toxin epitope-based chimeric construct in mice and rabbit

Epsilon toxin (Etx) belongs to family of pore-forming toxin and is produced by Clostridium perfringens type D. The Etx toxin is responsible for the pathogenesis of enterotoxaemia in sheep and goats, and occasionally in other livestock animals. The present study aimed to develop a Clostridium perfringens epsilon toxin-based chimeric epitope construct having immunodominant B-cell epitope and universal T-cell epitope and its immunogenicity was evaluated in mice and rabbit. An artificial chimeric epitope construct (CEC) was prepared by joining tandem repeats of a peptide containing amino acids (aa) 134–145 of epsilon toxin B-cell epitope and universal T-cell epitopes. The CEC was expressed in the Escherichia coli following codon optimization for efficient translational efficiency and purified by affinity chromatography. The antigenic reactivity of r-CEC proteins was confirmed by western blot with rabbit anti-r-Etox hyperimmune sera. The immunogenicity of the recombinant single CEC was examined in mice and rabbit by indirect ELISA. It was found that r-CEC yielded high titers of neutralizing antibodies (≥ 1.035 IU/ml) in immunized mice and rabbit. The potency of chimeric protein immunized serum was observed to be higher than the recommended level (0.1–0.3 IU/ml) for protection in sheep and goats. This indicated the potential ability of the chimeric protein as a vaccine candidate. This further requires studying the immune response in targeted host species (sheep and goat).

Challenges of Generating and Maintaining Protective Vaccine-Induced Immune Responses for Foot-and-Mouth Disease Virus in Pigs

Vaccination can play a central role in the control of outbreaks of foot-and-mouth disease (FMD) by reducing both the impact of clinical disease and the extent of virus transmission between susceptible animals. Recent incursions of exotic FMD virus lineages into several East Asian countries have highlighted the difficulties of generating and maintaining an adequate immune response in vaccinated pigs. Factors that impact vaccine performance include (i) the potency, antigenic payload, and formulation of a vaccine; (ii) the antigenic match between the vaccine and the heterologous circulating field strain; and (iii) the regime (timing, frequency, and herd-level coverage) used to administer the vaccine. This review collates data from studies that have evaluated the performance of foot-and-mouth disease virus vaccines at the individual and population level in pigs and identifies research priorities that could provide new insights to improve vaccination in the future.

Immune potential of a novel multiple-epitope vaccine to FMDV type Asia 1 in guinea pigs and sheep

To develop a safe and efficient recombinant subunit vaccine to foot-and-mouth disease virus (FMDV) type Asia 1 in sheep, a tandem repeated multiple-epitope gene consisting of residues 137-160 and 197-211 of the VP1 gene of FMDV was designed and artificially synthesized. The biologically functional molecule, the ovine IgG heavy constant region (oIgG) as a protein carrier was introduced for design of the multiple-epitope recombinant vaccine and recombinant expression plasmids pET-30a-RE and pET-30a-RE-oIgG were successfully constructed. The recombinant proteins, RE and RE-oIgG, were expressed as a formation of inclusion bodies in E. coli. The immune potential of this vaccine regime in guinea pigs and sheep was evaluated. The results showed that IgG could significantly enhance the immune potential of antigenic epitopes. The recombinant protein RE-oIgG could not only elicit the high levels of neutralizing antibodies and lymphocytes proliferation responses in the vaccinated guinea pigs, but confer complete protection in guinea pigs against virus challenge. Although the recombinant protein RE could not confer protection in the vaccinated animals, it could delay the appearance of the clinical signs and reduce the severity of disease. Inspiringly, the titers of anti-FMDV neutralizing antibodies elicited in sheep vaccinated with RE-oIgG was significantly higher than that for the RE vaccination. Therefore, we speculated that this vaccine formulation may be a promising strategy for designing a novel vaccine against FMDV in the future.

Promising multiple-epitope recombinant vaccine against foot-and-mouth disease virus type O in swine

In order to develop a completely safe immunogen to replace the traditional inactivated vaccine, a tandem-repeat multiple-epitope recombinant vaccine against foot-and-mouth disease (FMD) virus (FMDV) type O was developed. It contained three copies each of residues 141 to 160 and 200 to 213 of VP1 of the O/China/99 strain of FMDV coupled with a swine immunoglobulin G heavy-chain constant region (scIgG). The data showed that the multiple-epitope recombinant vaccine elicited high titers of anti-FMDV specific antibodies in swine at 30 days postvaccination (dpv) and conferred complete protection against a challenge with 10³ 50% swine infective doses of the O/China/99 strain. The anti-FMDV specific antibody titers were not significantly different between the multiple-epitope recombinant vaccine and the traditional vaccine (t test, P > 0.05). The number of 50% pig protective doses was 6.47, which is higher than the number recommended by the World Organization for Animal Health. The multiple-epitope recombinant vaccine resulted in a duration of immunity of at least 6 months. We speculate that the multiple-epitope recombinant vaccine is a promising vaccine that may replace the traditional inactivated vaccine for the prevention and control of FMD in swine in the future.

Immunization of DNA vaccine encoding C3d-VP1 fusion enhanced protective immune response against foot-and-mouth disease virus

Because foot-and-mouth disease virus (FMDV) remains a great problem to many livestock of agricultural importance, safe, effective vaccines are in great need. DNA vaccine would be a promising candidate but the design remains to be optimized. VP1 gene of FMDV strain O/ES/2001 was linked to three copies of either porcine or murine C3d or four copies of a 28-aa fragment of murine C3d containing the CR2 receptor binding domain (M28). The resultant plasmids encoding C3d/M28-VP1 fusion or only VP1 as control were immunized guinea pigs. Both cellular and humoral immune responses were evaluated and protection was observed after virus challenge. As a result, although the plasmid encoding only VP1 could elicit virus-binding antibody detected by ELISA, splenocyte proliferation, IL-4 and IFN-gamma production, the levels were significantly less than C3d/M28-VP1 fusion. Furthermore, VP1 failed to induce neutralization antibody and protect animals against virus challenge, while murine C3d-VP1 fusion efficiently induced neutralization antibody response and provided 87.50% of the animals with complete protection and 12.50% with partial protection. Among murine C3d, M28, and porcine C3d, the adjuvant effect of murine C3d is strongest, followed by porcine C3d, and last murine M28. In conclusion, the fact that C3d genes, when coupled to VP1 gene, are able to greatly enhance the protective immune response of VP1 DNA in guinea pigs suggests that C3d-VP1 DNA chimera has a significant potential for use as a novel DNA vaccine against FMDV.

Effects of Epitopes Combination and Adjuvants on Immune Responses to Anti-Alzheimer Disease DNA Vaccines in Mice

Alzheimer disease (AD) is a neurodegenerative disorder characterized by neuropathological hallmarks including deposits of the beta-amyloid peptide (AssP). Studies have shown that immunization with Abeta42 peptide reduces both the spatial memory impairments and Alzheimer disease-like neuropathologic changes in Alzheimer disease transgenic mice, but can cause side effect of a cell-mediated autoimmune meningoencephalitis. Recently, some studies showed that DNA vaccination could be used to generate an antibody response to Abeta without the adverse cell-mediated immune effect. In the current study, we generate four DNA vaccine plasmids (pV-GE1, pV-GE2, pV-GE3, and pV-GE4) against Alzheimer disease by separately fusing Abeta epitope sequences (coding for EFGH, DAEFGH, EFGH+EFGH, and EFGH+DAEFGH) with IgG heavy chain coding region of mouse. Meanwhile, the full-length gene Abeta encoding plasmid (pV-Abeta), empty vector (pVAX) and synthetic AssP were also included as control. The sera of BALB/c mice immunized via intramuscular with plasmids and peptide were tested by indirect ELISA for auto-AssP immunoreactivity. The results showed that all the DNA vaccine plasmids induced AssP-specific antibodies; moreover pV-GE2 and pV-Abeta constructs elicited higher antibody titers than other constructs (P < 0.05). To further enhance the immune response, GM-CSF encoding plasmid (pGM-CSF) and purified BCG-DNA were used as molecular adjuvants. BCG-DNA could enhance humoral and cellular immune responses simultaneously and did not alter the phenotype of the immune responses, whereas pGM-CSF showed no obvious effect on immune response. These results suggest that this immunization strategy of using Abeta epitope encoding plasmid plus BCG-DNA adjuvant may serve as the basis for developing anti-Alzheimer disease vaccines.

Human papillomavirus type 16 E7 peptide(38-61) linked with an immunoglobulin G fragment provides protective immunity in mice

OBJECTIVE

To explore whether the recombinant protein (Human papillomavirus (HPV) type16 E7 peptide(38-61) linked with an immunoglobulin G fragment) will generate protective immunity in mouse model.

METHODS

In our study, we combined the HPV16 E7 peptide(38-61) with a murine IgG heavy chain constant region to construct a chimeric protein compound, which was highly expressed as inclusion bodies in a bacterial expression system with Escherichia coli. The purified chimeric protein was injected into C57BL/6 mice and the efficiency of the chimeric vaccine candidate was evaluated by antibody response assay, T cell proliferation assay, CTL assay, tumor challenge assay and therapeutic experiment.

RESULTS

The chimeric vaccine candidate was able to induce anti-HPV antibodies as well as to elicit HPV16 E7-specific CTLs and T cell proliferation in a pre-clinical mouse model. It was also able to effectively protect mice against the challenge of HPV16-positive tumor cells, and to eradicate HPV16-expressing tumors in mice.

CONCLUSIONS

The chimeric protein vaccine can induce E7-specific immune responses and protect mice against challenge of HPV16-positive tumor, even eradicate developed tumor. The results indicated a possibility to use the chimeric protein vaccine to protect human against HPV infection.

Induction of immunity in swine by purified recombinant VP1 of foot-and-mouth disease virus

VP1, a capsid protein of foot-and-mouth disease virus (FMDV), contains neutralizing epitopes of the virus. Due to its poor water solubility, recombinant Escherichia coli derived VP1 (rVP1) has previously been used mainly in a denatured form and is not well characterized. Here, using SDS to assist protein refolding and then removing SDS with a detergent removing column, we have successfully purified rVP1 in two aqueous-soluble forms, i.e. monomer and dimer. Studies showed that dimerization occurs by an inter-molecular disulfide bond between two cysteine residues at position 187 of each monomer. Heat treatment revealed that rVP1 dimer exhibited a more thermal-stable conformation than the monomeric form. Both monomeric and dimeric rVP1 reacted with anti-FMDV antibodies. Immunization studies demonstrated that vaccination of swine with either forms of rVP1 was effective in generating immune responses and protecting them from viral challenge.

Porcine Ig isotypes: function and molecular characteristics

In pigs, protection against the toxigenic extra-cellular bacterium Actinobacillus pleuropneumoniae was correlated with an increased IgG(1):IgG(2) ratio of haemolytic toxin-specific antibodies. In all species so far studied, IgG isotype expression is controlled by Type 1 (IFN-gamma, IL-12) and Type 2 (IL-4, IL-10) cytokines which dictate immune response polarization to cell-mediated (CMI) or antibody-mediated immunity (AMI), respectively. Thus, immunoglobulin (Ig) isotypes reflect Type 1 or Type 2 immune responses. Immunoglobulin isotype production by porcine B-cells cultured in the presence of recombinant porcine (rp) cytokines varies by individual, however pigs tend to generate a high IgG(1):IgG(2) ratio in response to rp IL-10 and the inverse in response to rp IFN-gamma or rp IL-12. Differential Ig isotype production should favor an isotype with a functional advantage to control the inciting infection and disease. However, functions of porcine Ig isotypes have not been described. To compare function of porcine IgM, IgG(1) and IgG(2) of defined specificity for hen eggwhite lysozyme (HEWL), Ig isotypes were affinity purified from serum by HEWL specificity and by isotype-specific mouse monoclonal antibodies. Their ability to activate complement (C') and to opsonize was tested in vitro. Porcine IgG(2) had greater guinea pig C' activating ability than did IgG(1). Neither isotype opsonized HEWL-conjugated sheep erythrocytes in vitro. Amino acid sequence analysis of IgG isotypes revealed that all subclasses have putative C' binding sites but that IgG(2a), IgG(2b) and IgG(4) were more flexible in the middle hinge region than IgG(1) and IgG(3) and would likely activate C' more efficiently. Thus, porcine IgG isotypes associated with resistance and susceptibility to disease also differ in their actual and predicted biological functions.

A DNA vaccine against foot-and-mouth disease elicits an immune response in swine which is enhanced by co-administration with interleukin-2

A plasmid DNA vaccine candidate (pCEIS) encoding two foot-and-mouth disease virus (FMDV) VP1 epitopes (amino acid residues 141-160 and 200-213) has been demonstrated to have the ability to elicit both FMDV-specific T cell proliferation and neutralizing antibody against FMD in swine. In this study, the efficiency of the pCEIS DNA vaccine when administrated by intramuscularly injection in swine was confirmed, and the immunogenicity of the pCEIS vaccine candidate was found to be enhanced through co-administration with a newly constructed plasmid (pIL2S) encoding the swine interleukin-2 (IL-2) cDNA. The expression of the pIL2S plasmid was driven by a CMV promotor provided by a pcDNA3.1 vector. Swine IL-2 cDNA was cloned by RT-PCR from swine spleen cells. The pIL2S plasmid was expressed in COS-7 cells after 24 and 96h of transfection in vitro. In an animal trial, results from T cell proliferation assay indicated that the stimulation index (SI) in response to stimulation of FMDV proteins in the swine groups injected with pCEIS plus pIL2S (SI ranging from 9.9 to 15.5) were significantly higher than that with pCEIS alone (SI ranging from 3.3 to 6.6). However, there was no significant difference in FMDV-neutralizing antibody level detected in these two swine groups. Mouse protection tests (MPTs) showed that the blood sera from immunized swine injected with either pCEIS alone or pCEIS plus pIL2S were able to protect suckling mice from FMDV challenge, with protection levels ranging from 10(1) to 10(2) lethal dose 50 (LD(50)) M. In a direct FMDV challenge, all swines immunized with either pCEIS plus pIL2S or with pCEIS alone were challenged with 50LD(50)S (50 x lethal dosage in swine) of FMDV. The animals were fully protected (100%) from the FMD viral challenge. These results suggest that co-administration of the plasmids, pCEIS and pIL2S, enhances of the immunogenicity of the pCEIS DNA vaccine candidate, and both intramuscular injection of pCEIS alone and co-administration of the vaccine candidate with pIL2S can protect the swine from direct FMD challenge.