The role of zinc sulfate in enhancing cellular and humoral immune responses to foot-and-mouth disease vaccine

Foot-and-mouth disease (FMD) is a rapidly propagating infectious disease of cloven-hoofed animals, especially cattle and pigs, affecting the productivity and profitability of the livestock industry. Presently, FMD is controlled and prevented using vaccines; however, conventional FMD vaccines have several disadvantages, including short vaccine efficacy, low antibody titers, and safety issues in pigs, indicating the need for further studies. Here, we evaluated the efficacy of a novel bivalent vaccine containing zinc sulfate as an immunostimulant and FMD type O and A antigens (O PA2 and A YC, respectively) against FMD virus in mice and pigs. Zinc sulfate induced cellular immunity in murine peritoneal exudate cells (PECs) and porcine peripheral blood mononuclear cells (PBMCs) by increasing IFNγ secretion. Additionally, FMD vaccine containing O PA2 and A YC antigens and zinc sulfate induced early, mid-, and long-term immune responses in mice and pigs, and enhanced cellular and humoral immunity by regulating the expression of pathogen recognition receptors (PRRs), transcription factors, co-stimulatory molecules, and cytokines in porcine PBMCs from vaccinated pigs. Overall, these results indicated that the novel immunostimulant zinc sulfate induced potent cellular and humoral immune responses by stimulating antigen-presenting cells (APCs) and T and B cells, and enhanced long-term immunity by promoting the expression of co-stimulatory molecules. These outcomes suggest that zinc sulfate could be used as a novel vaccine immunostimulant for difficult-to-control viral diseases, such as African swine fever (ASF) or COVID-19.

B and T Cell Epitopes of the Incursionary Foot-and-Mouth Disease Virus Serotype SAT2 for Vaccine Development

Failure of cross-protection among interserotypes and intratypes of foot-and-mouth disease virus (FMDV) is a big threat to endemic countries and their prevention and control strategies. However, insights into practices relating to the development of a multi-epitope vaccine appear as a best alternative approach to alleviate the cross-protection-associated problems. In order to facilitate the development of such a vaccine design approach, identification and prediction of the antigenic B and T cell epitopes along with determining the level of immunogenicity are essential bioinformatics steps. These steps are well applied in Eurasian serotypes, but very rare in South African Territories (SAT) Types, particularly in serotype SAT2. For this reason, the available scattered immunogenic information on SAT2 epitopes needs to be organized and clearly understood. Therefore, in this review, we compiled relevant bioinformatic reports about B and T cell epitopes of the incursionary SAT2 FMDV and the promising experimental demonstrations of such designed and developed vaccines against this serotype.

Expression of FMD virus-like particles in yeast Hansenula polymorpha and immunogenicity of combine with CpG and aluminum adjuvant

BACKGROUND

Inactivated vaccines are limited in preventing foot-and-mouth disease (FMD) due to safety problems. Recombinant virus-like particles (VLPs) are an excellent candidate for a novel vaccine for preventing FMD, given that VLPs have similar immunogenicity as natural viruses and are replication- and infection-incompetent.

OBJECTIVES

The 3C protease and P1 polyprotein of type O FMD virus (FDMV) was expressed in yeast Hansenula polymorpha to generate self-resembling VLPs, and the potential of recombinant VLPs as an FMD vaccine was evaluated.

METHODS

BALB/c mice were immunized with recombinant purified VLPs using CpG oligodeoxynucleotide and aluminum hydroxide gel as an adjuvant. Cytokines and lymphocytes from serum and spleen were analyzed by enzyme-linked immunosorbent assay, enzyme-linked immunospot assay, and flow cytometry.

RESULTS

The VLPs of FMD were purified successfully from yeast protein with a diameter of approximately 25 nm. The immunization of mice showed that animals produced high levels of FMDV antibodies and a higher level of antibodies for a longer time. In addition, higher levels of interferon-γ and CD4⁺ T cells were observed in mice immunized with VLPs.

CONCLUSIONS

The expression of VLPs of FMD in H. polymorpha provides a novel strategy for the generation of the FMDV vaccine.

Assessment of the potency and effectiveness of a heptavalent oil-adjuvanted (ISA 206) foot-and-mouth disease vaccine in Egypt

Foot-and-mouth disease (FMD) is a serious highly contagious viral disease affecting all cloven-hoofed animals, and outbreaks can have a severe economic impact. An inactivated heptavalent oil-adjuvanted FMD vaccine (Aphtovac-7, MEVAC) was prepared from the foot-and-mouth disease virus (FMDV) strains A-Iran05, A-Africa-IV, O-PanAsia2, O-Manisa, O-EA3, SAT-2 Gharbia, and SAT-2 LIB-12. The vaccine potency and effectiveness were evaluated in three groups of 6- to 8-month-old calves and 200 adult dairy cattle under field conditions. All animals were vaccinated with the vaccine preparation, and the three groups of calves were challenged after 28 days by intradermolingual inoculation with 10⁴ 50% tissue culture infective dose (TCID₅₀) of FMDV serotype A, O, or SAT-2. Mock-vaccinated calves (two per group) served as unvaccinated controls during the challenge test. Adult dairy cattle were tested for seroconversion using a virus neutralization test at 30, 60, and 120 days post-vaccination. All calves displayed complete protection against challenge with the different serotypes of FMDV when compared to the control groups. Serum samples collected after the primary and booster immunizations at 30 days post-vaccination contained high titers of protective antibodies (≥ 1/32; i.e. 1.5 log₁₀). Antibodies persisted until the end of the study period (120 days), with a peak value around 60 days post-vaccination. The heptavalent FMD vaccine preparation was found to be potent and capable of providing a protective immune response under both experimental and field conditions.

Development and Efficacy Evaluation of a Novel Nano-Emulsion Adjuvant for a Foot-and-Mouth Disease Virus-like Particles Vaccine Based on Squalane

The successful development of foot-and-mouth disease virus-like particles (FMD-VLPs) has opened a new direction for researching a novel subunit vaccine for foot-and-mouth disease (FMD). Therefore, it is urgent to develop an adjuvant that is highly effective and safe to facilitate a better immune response to be pair with the FMD-VLP vaccine. In this research, we prepared a new nano-emulsion adjuvant based on squalane (SNA) containing CpG using the pseudo-ternary phase diagram method and the phase transformation method. The SNA consisted of Span85, Tween60, squalane, polyethene glycol-400 (PEG400) and CpG aqueous solution. The average particle diameter of the SNA was about 95 nm, and it exhibited good resistance to centrifugation, thermal stability, and biocompatibility. Then, SNA was emulsified as an adjuvant to prepare foot-and-mouth disease virus-like particles vaccine, BALB/c mice and guinea pigs were immunized, and we evaluated the immunization effect. The immunization results in mice showed that the SNA-VLPs vaccine significantly increased specific antibody levels in mice within 4 weeks, including higher levels of IgG1 and IgG2a. In addition, it increased the levels of IFN-γ and IL-1β in the immune serum of mice. Meanwhile, guinea pig-specific and neutralizing antibodies were considerably increased within 4 weeks when SNA was used as an adjuvant, thereby facilitating the proliferation of splenic lymphocytes. More importantly, in guinea pigs immunized with one dose of SNA-VLPs, challenged with FMDV 28 days after immunization, the protection rate can reach 83.3%, which is as high as in the ISA-206 control group. In conclusion, the novel squalane nano-emulsion adjuvant is an effective adjuvant for the FMD-VLPs vaccine, indicating a promising adjuvant for the future development of a novel FMD-VLPs vaccine.

Oil-in-ionic liquid nanoemulsion-based adjuvant simultaneously enhances the stability and immune responses of inactivated foot-and-mouth disease virus

Maintaining structural integrity and enhancing stability of inactivated foot-and-mouth disease virus (iFMDV) antigen in adjuvants is crucial to ensure the vaccine potency. Unfortunately, formulation with most reported adjuvants leads to the accelerated dissociation of iFMDV into inactive pentamers. Here, an ionic liquid, i.e., choline and niacin ([Cho][Nic]), which was found to stabilize iFMDV against the acid- and thermo- induced dissociation in buffer solution, was applied to construct a novel oil-in-ionic liquid (o/IL) nanoemulsion adjuvant composed of [Cho][Nic], squalene, and Tween 80. The o/IL nanoemulsion formulated with iFMDV has a monodisperse diameter of 135.8 ± 40.4 nm. The thermostability and long-term stability of iFMDV were remarkably enhanced in o/IL nanoemulsion compared with that in the o/w emulsion without [Cho][Nic] and in the commercial Montanide ISA 206 adjuvant. The o/IL nanoemulsion exerted its adjuvant effects by improving the humoral immune responses. Immunization of o/IL nanoemulsion adjuvanted iFMDV induced specific IgG titers similar to that adjuvanted by Montanide ISA 206 and about 4-fold higher than the un-adjuvanted iFMDV, also promoted the activation of B lymphocytes and the secretion of interleukin-4 in the mice model. This [Cho][Nic]-based o/IL nanoemulsion can serve as a promising adjuvant platform for the foot-and-mouth disease vaccine.

Pattern-Recognition Receptor Agonist-Containing Immunopotentiator CVC1302 Boosts High-Affinity Long-Lasting Humoral Immunity

Ideally, a vaccine should provide life-long protection following a single administered dose. In our previous study, the immunopotentiator CVC1302, which contains pattern- recognition receptor (PRR) agonists, was demonstrated to prolong the lifetime of the humoral immune response induced by killed foot-and-mouth disease virus (FMDV) vaccine. To elucidate the mechanism by which CVC1302 induces long-term humoral immunity, we used 4-hydroxy-3-nitrophenylacetyl (NP)-OVA as a pattern antigen and administered it to mice along with CVC1302, emulsified together with Marcol 52 mineral oil (NP-CVC1302). From the results of NP-specific antibody levels, we found that CVC1302 could induce not only higher levels of NP-specific antibodies but also high-affinity NP-specific antibody levels. To detect the resulting NP-specific immune cells, samples were taken from the injection sites, draining lymph nodes (LNs), and bone marrow of mice injected with NP-CVC1302. The results of these experiments show that, compared with mice injected with NP alone, those injected with NP-CVC1302 had higher percentages of NP+ antigen-presenting cells (APCs) at the injection sites and draining LNs, higher percentages of follicular helper T cells (TFH), germinal center (GC) B cells, and NP+ plasma-blasts in the draining LNs, as well as higher percentages of NP+ long-lived plasma cells (LLPCs) in the bone marrow. Additionally, we observed that the inclusion of CVC1302 in the immunization prolonged the lifetime of LLPCs in the bone marrow by improving the transcription expression of anti-apoptotic transcription factors such as Mcl-1, Bcl-2, BAFF, BCMA, Bax, and IRF-4. This research provides a blueprint for designing new generations of immunopotentiators.

The Potential Adjuvanticity of CAvant®SOE for Foot-and-Mouth Disease Vaccine

Foot-and-mouth disease (FMD) is a notifiable contagious disease of cloven-hoofed mammals. A high potency vaccine that stimulates the host immune response is the foremost strategy used to prevent disease persistence in endemic regions. FMD vaccines comprise inactivated virus antigens whose immunogenicity is potentiated by immunogenic adjuvants. Oil-based adjuvants have clear advantages over traditional adjuvant vaccines; however, there is potential to develop novel adjuvants to increase the potency of FMD vaccines. Thus, we aimed to evaluate the efficacy of a novel water-in-oil emulsion, called CAvant^®SOE, as a novel vaccine adjuvant for use with inactivated FMD vaccines. In this study, we found that inactivated A22 Iraq virus plus CAvant^®SOE (iA22 Iraq-CAvant^®SOE) induced effective antigen-specific humoral (IgG, IgG1, and IgG2a) and cell-mediated immune responses (IFN-γ and IL-4) in mice. Immunization of pigs with a single dose of iA22 Iraq-CAvant^®SOE also elicited effective protection, with no detectable clinical symptoms against challenge with heterologous A/SKR/GP/2018 FMDV. Levels of protection are strongly in line with vaccine-induced neutralizing antibody titers. Collectively, these results indicate that CAvant^®SOE-adjuvanted vaccine is a promising candidate for control of FMD in pigs.

Enhancing immune responses to inactivated foot-and-mouth virus vaccine by a polysaccharide adjuvant of aqueous extracts from Artemisia rupestris L

BACKGROUND

New-generation adjuvants for foot-and-mouth disease virus (FMDV) vaccines can improve the efficacy of existing vaccines. Chinese medicinal herb polysaccharide possesses better promoting effects.

OBJECTIVES

In this study, the aqueous extract from Artemisia rupestris L. (AEAR), an immunoregulatory crude polysaccharide, was utilized as the adjuvant of inactivated FMDV vaccine to explore their immune regulation roles.

METHODS

The mice in each group were subcutaneously injected with different vaccine formulations containing inactivated FMDV antigen adjuvanted with three doses (low, medium, and high) of AEAR or AEAR with ISA-206 adjuvant for 2 times respectively in 1 and 14 days. The variations of antibody level, lymphocyte count, and cytokine secretion in 14 to 42 days after first vaccination were monitored. Then cytotoxic T lymphocyte (CTL) response and antibody duration were measured after the second vaccination.

RESULTS

AEAR significantly induced FMDV-specific antibody titers and lymphocyte activation. AEAR at a medium dose stimulated Th1/Th2-type response through interleukin-4 and interferon-γ secreted by CD4⁺ T cells. Effective T lymphocyte counts were significantly elevated by AEAR. Importantly, the efficient CTL response was remarkably provoked by AEAR. Furthermore, AEAR at a low dose and ISA-206 adjuvant also synergistically promoted immune responses more significantly in immunized mice than those injected with only ISA-206 adjuvant and the stable antibody duration without body weight loss was 6 months.

CONCLUSIONS

These findings suggested that AEAR had potential utility as a polysaccharide adjuvant for FMDV vaccines.

Layered double hydroxide nanoparticles as an adjuvant for inactivated foot-and-mouth disease vaccine in pigs

Background

Foot-and-mouth disease (FMD) is a highly transmissible disease that leads to vast economic losses in many countries. Prevention using inactivated vaccines is one effective measure used to control FMD. Unfortunately, inactivated FMD vaccines provide only short-term protection and require a cold-chain system. In recent years, many studies have shown that layered double metal hydroxides (LDHs) carrying antigens can be used to strongly induce immune responses. In this study, LDH nanoparticles (NPs) were prepared by hydrothermal synthesis. LDH particle size, electric potential, and morphology were measured and observed. The adsorption capacity of LDH NPs to FMDV was tested. The effects of LDH as an adjuvant on inactivated FMDV vaccines were further evaluated and compared with commercial FMDV Montanide ISA-206 in BALB/C female mice and Yorkshire pigs.

Results

LDH NPs were successfully prepared with a uniform particle size of ~ 87.21 nm, regular edges, a loose hexagonal shape and positive zeta charge of 32 mV. The maximum absorption concentration was 0.16–0.31 μg FMDV/μg LDH. In the mouse experiment, antibody levels in group LDH + FMDV were significantly higher compared to group saline + FMDV (P < 0.01) from days 42–98 and were significantly higher to group ISA-206 + FMDV on day 56 post-immunization (P < 0.05). After day 14 post-immunization, IFN-γ content was significantly increased (P < 0.05). In the pig experiment, antibody levels in both the ISA-206 + FMDV and LDH + FMDV were positive and were significantly higher compared with the PBS group on day 7 (P < 0.005). Antibody levels in 90% pigs were positive on day 56 in the LDH group. The neutralizing antibody levels in the LDH and ISA-206 groups were significantly higher from days 7–28 compared to the PBS control group (P < 0.05). Thus, LDH NPs were effective at inducing an immune response against FMDV.

Conclusions

LDHs with a loose hexagonal shape and a positive charge were prepared and evaluated as adjuvant for FMD vaccine. It was demonstrated that LDHs can induce immune responses in mice and pigs. In addition, the LDHs produced antibodies continuously which may indicate a slow-release effect. The study shows that LDHs may act as a potentially useful FMDV adjuvant.

A Review on the Use of Antimicrobial Peptides to Combat Porcine Viruses

Viral infectious diseases pose a serious threat to animal husbandry, especially in the pig industry. With the rapid, continuous variation of viruses, a series of therapeutic measures, including vaccines, have quickly lost their efficacy, leading to great losses for animal husbandry. Therefore, it is urgent to find new drugs with more stable and effective antiviral activity. Recently, it has been reported that antimicrobial peptides (AMPs) have great potential for development and application in animal husbandry because of their significant antibacterial and antiviral activity, and the antiviral ability of AMPs has become a research hotspot. This article aims to review the research situation of AMPs used to combat viruses in swine production of animal husbandry, clarify the mechanism of action of AMPs on viruses and raise some questions, and explore the future potential of AMPs in animal husbandry.

Improved immune responses and safety of foot-and-mouth disease vaccine containing immunostimulating components in pigs

Background

The quality of a vaccine depends strongly on the effects of the adjuvants applied simultaneously with the antigen in the vaccine. The adjuvants enhance the protective effect of the vaccine against a viral challenge. Conversely, oil-type adjuvants leave oil residue inside the bodies of the injected animals that can produce a local reaction in the muscle. The long-term immunogenicity of mice after vaccination was examined. ISA206 or ISA15 oil adjuvants maintained the best immunity, protective capability, and safety among the oil adjuvants in the experimental group.

Objectives

This study screened the adjuvant composites aimed at enhancing foot-and-mouth disease (FMD) immunity. The C-type lectin or toll-like receptor (TLR) agonist showed the most improved protection rate.

Methods

Experimental vaccines were fabricated by mixing various known oil adjuvants and composites that can act as immunogenic adjuvants (gel, saponin, and other components) and examined the enhancement effect on the vaccine.

Results

The water in oil (W/O) and water in oil in water (W/O/W) adjuvants showed better immune effects than the oil in water (O/W) adjuvants, which have a small volume of oil component. The W/O type left the largest amount of oil residue, followed by W/O/W and O/W types. In the mouse model, intramuscular inoculation showed a better protection rate than subcutaneous inoculation. Moreover, the protective effect was particularly weak in the case of inoculation in fatty tissue. The initial immune reaction and persistence of long-term immunity were also confirmed in an immune reaction on pigs.

Conclusions

The new experimental vaccine with immunostimulants produces improved immune responses and safety in pigs than general oil-adjuvanted vaccines.

Green preparation of hydrogel particles-in-emulsions for simultaneous enhancement of humoral and cell-mediated immunity

Emulsions are one of the most often used vaccine adjuvant formulations. Although they promote high humoral immunity, the induced cellular immunity is often poor, which restrict their application. To enhance the cellular immunity, some researchers have prepared mixed formulations by adding particles into the aqueous phase of emulsions. However, the particle preparation process usually involves the addition and removal of organic reagents, which is environmentally unfriendly and cumbersome. Moreover, the obtained vaccine adjuvant only induces limited cell-mediated immunity and humoral immunity compared with emulsion-adjuvanted vaccines. Herein, we developed a green and simple method for fabricating a novel nanoparticles-in-emulsions (NPE) formulation. Firstly, a temperature-sensitive hydrogel was used to prepare particles by self-solidification without additional crosslinking reagents. Secondly, the white oil was used as organic phase to avoid the particle washing procedures and organic solvent residues. Moreover, the effect of NPE as vaccine adjuvant was evaluated by using two veterinary vaccines as model antigens. NPE showed advantages than the conventional vaccine formulations in inducing both humoral and cellular immunity. This work provides a facile and broadly applicable approach for preparing nanoparticles-in-emulsions formulation, and presents an effective adjuvant for enhancing immunity against infectious diseases.

Enhanced Immune Responses with Serum Proteomic Analysis of Hu Sheep to Foot-and-Mouth Disease Vaccine Emulsified in a Vegetable Oil Adjuvant

Our previous study demonstrated that a vegetable oil consisting of soybean oil, vitamin E, and ginseng saponins (SO-VE-GS) had an adjuvant effect on a foot-and-mouth disease (FMD) vaccine in a mouse model. The present study was to compare the adjuvant effects of SO-VE-GS and the conventional ISA 206 on an FMD vaccine in Hu sheep. Animals were intramuscularly (i.m.) immunized twice at a 3-week interval with 1 mL of an FMD vaccine adjuvanted with SO-VE-GS (n = 10) or ISA 206 (n = 9). Animals without immunization served as control (n = 10). Blood was sampled prior to vaccination and at 2, 4, 6, and 8 weeks post the booster immunization to detect FMD virus (FMDV)-specific IgG. Blood collected at 8 weeks after the booster was used for the analyses of IgG1 and IgG2, serum neutralizing (SN) antibody, IL-4 and IFN-γ production, and proteomic profiles. The results showed that IgG titers rose above the protection level (1:128) in SO-VE-GS and ISA 206 groups after 2 and 4 weeks post the booster immunization. At 6 weeks post the booster, the ISA 206 group had 1 animal with IgG titer less than 1:128 while all the animals in the SO-VE-GS group retained IgG titers of more than 1:128. At 8 weeks post the booster, 6 of 9 animals had IgG titers less than 1:128 with a protective rate of 33.3% in the ISA 206 group, while only 1 of 10 animals had IgG titer less than 1:128 with a protective rate of 90% in the SO-VE-GS group, with statistical significance. In addition, IgG1, IgG2, SN antibodies, IL-4, and IFN-γ in the SO-VE-GS group were significantly higher than those of the ISA 206 group. Different adjuvant effects of SO-VE-GS and ISA 206 may be explained by the different proteomic profiles in the two groups. There were 39 and 47 differentially expressed proteins (DEPs) identified in SO-VE-GS compared to the control or ISA 206 groups, respectively. In SO-VE-GS vs. control, 3 immune related gene ontology (GO) terms and 8 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were detected, while 2 immune related GO terms and 5 KEGG pathways were found in ISA 206 vs. control. GO and KEGG analyses indicated that 'positive regulation of cytokine secretion', 'Th1/Th2 cell differentiation', and 'Toll-like receptor signaling pathways', were obviously enriched in the SO-VE-GS group compared to the other groups. Coupled with protein-protein interaction (PPI) analysis, we found that B7TJ15 (MAPK14) was a key DEP for SO-VE-GS to activate the immune responses in Hu sheep. Therefore, SO-VE-GS might be a promising adjuvant for an FMD vaccine in Hu sheep.

Biocompatible cationic solid lipid nanoparticles as adjuvants effectively improve humoral and T cell immune response of foot and mouth disease vaccines

In this work, we explored the potential of cationic solid lipid nanoparticles (cSLN) as efficient adjuvants for inactivated foot and mouth disease virus (iFMDV) vaccine. The cSLN were prepared by O/W emulsion method with Compritol 888 ATO as lipid matrix, and were modified by cationic lipid Didodecyldimethylammonium bromide (DDAB). The content of cationic lipid was optimized to produce cSLN with appropriate particle size, surface morphology, zeta potential, and polydispersity. Loading iFMDV onto cSLN by electrostatic attraction did not destruct iFMDV particle structure as measured by high performance size exclusion chromatography (HPSEC). Differential scanning fluorimetry (DSF) showed the transition temperature, T_m, related to iFMDV dissociation increased for 1.2 °C after loading on cSLN, indicating an enhanced stability of this unstable antigen. The cSLN loaded iFMDV enhanced in vitro antigen uptake and activation of bone-marrow-derived dendritic cells (BMDCs) with augmented expression of CD86, CD40, and MHC I. In animal trials, BALB/c mice were immunized with free iFMDV, antigen adjuvanted with the cSLN, and antigen adjuvanted with Montanide ISA 206 emulsion. Specific antibody titers showed cSLN could stimulate similar FMDV-specific IgG and IgG subclasses antibody level compared with the widely used ISA 206. In addition, cSLN significantly enhanced memory immune response including effector-memory T cells and central-memory T cells compared to free iFMDV antigen and antigen adjuvanted with ISA 206. Taken together the enhanced humoral and T cell immune responses and the antigen structure friendly properties, cSLN can be a potential adjuvant for iFMDV vaccines.

Rapid test to detect cytotoxic activity in vaccines against foot-and-mouth disease

ABSTRACT Substances with cytotoxic activity present in vaccines against the foot-and-mouth disease may interfere with methods used to detect residual live virus in the product or cause undesirable postvaccination reactions. This study describes a rapid in vitro test to detect cytotoxic activity in water-in-oil vaccines against foot-and-mouth disease using a commercial saponin as a cytotoxic agent and a solution of sheep’s red blood cells as substrate. Hemolytic and cytotoxic activity was analyzed using experimental and commercial vaccines prepared with and without saponin. The hemolytic and cytotoxic potential of preparations containing saponin was evident. In contrast, hemolytic and cytotoxic activities were not observed in vaccines without saponin in their composition. The method described here allows to easily detect if the vaccine under study has cytotoxic activity, making it possible to select the most appropriate method to process the sample to be used for the innocuity test. Additionally, due to undesirable effects that may be observed in animals receiving vaccines containing saponin in their formulation, the use of the rapid test described here allows to identify those vaccines with cytotoxic activity and to verify the presence of saponin on them, through the mass spectrometry method.

Early IgG Response to Foot and Mouth Disease Vaccine Formulated with a Vegetable Oil Adjuvant

The present study evaluated soybean oil (SO) containing vitamin E (VE) and ginseng saponins (GS) (SO-VE-GS) for their adjuvant effect on foot-and-mouth disease (FMD) vaccine. Since mineral oil ISA 206 is a common adjuvant used in the FMD vaccine, it was used as a control adjuvant in this study. VE and GS were found to have a synergistic adjuvant effect. When mice were immunized with the FMD vaccine emulsified in SO with VE and GS, significantly higher serum IgG, IgG1, and IgG2a were found than VE and GS used alone. SO-VE-GS and ISA 206 behaved differently in adjuvant activities. When mice were immunized with the FMD vaccine adjuvanted with SO-VE-GS, significantly higher and earlier production of serum IgG was found than that adjuvanted with ISA 206. Although both adjuvants significantly increased the number of bone marrow plasma cells, a stimulation index of lymphocytes (SI) as well as the production of IL-4 and IL-6, SO-VE-GS promoted significantly higher SI and the ratio of CD4⁺/CD8⁺ T cells with production of increased IFN-γ and decreased TGF-β1 as compared with the ISA 206 group. The data suggested that SO-VE-GS activated Th1/Th2 immune responses. Transcriptome analysis of splenocytes showed that differentially expressed genes (DEGs), immune-related gene ontology (GO) terms, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were significantly enriched in the SO-VE-GS group. Therefore, the potent adjuvant effect of SO-VE-GS on the FMD vaccine may be attributed to the immune-related gene profile expressed in lymphocytes. Due to its plant origin and due to being much cheaper than imported mineral oil ISA 206, SO-VE-GS deserves further study in relation to vaccines used in food animals.

Antiviral effects of selected IMPDH and DHODH inhibitors against foot and mouth disease virus

Foot-and-mouth disease virus (FMDV) is an important pathogen that affects livestock breeding and causes huge economic losses worldwide. Currently, the development of antiviral agents to combat FMDV infection at the early stages is being explored. As viral replication critically depends on the host for nucleoside supply, host enzymes involved in nucleotides biosynthesis may represent potential targets for the development of antiviral agents. In the present study, the effects of IMP dehydrogenase (AVN-944 and mycophenolate mofetil) and dihydroorotate dehydrogenase (teriflunomide) inhibitors were evaluated both in vitro and in vivo. The results revealed that these compounds were effective in suppressing FMDV (O/MY98/BY/2010 and A/GD/MM/2013) infection. With regard to the antiviral mechanism, time-of-addition experiments revealed that these compounds were effective when added at the early stages of viral lifecycle (0-8 h post infection). However, exogenous guanosine/uridine eliminated the antiviral activity of these compounds. Importantly, treatment AVN-944 and teriflunomide significantly improved the survival of mice that were subcutaneously treated with FMDV. Together, the results of the present study indicate the broad-spectrum activities of anti-FMDV agents targeting IMP dehydrogenase or dihydroorotate dehydrogenase, which could be useful in developing strategies to prevent FMD.

Adjuvanticity of aqueous extracts of Artemisia rupestris L. for inactivated foot-and-mouth disease vaccine in mice

Several methods have been developed to improve the efficacy of foot-and-mouth disease virus (FMDV) vaccine. The study aims to determine whether aqueous extracts of Artemisia rupestris L. (AEAR) as an immunoactivator in combination with inactivated FMDV vaccine can promote immune responses in mice. Intramuscular co-immunization in ICR mice with different doses of AEAR plus FMDV vaccine could substantially improve the FMDV-specific antibody production (IgG, IgG₁, and IgG_2a) and lead to significant lymphocyte proliferative responses. Th1-type immune responses were also observed, including proliferative responses of CD8⁺, CD4⁺, CD4⁺CD44+, and CD8⁺CD44⁺ T cells and the killing efficacy of cytotoxic T lymphocyte (CTL) responses. AEAR also elicited the higher levels of IL-4 and IFN-γ in CD4⁺ T cells as well as the higher level of IFN-γ in CD8⁺ T cells. The medium dose of AEAR induced the significant adjuvant activity. Further tests in mice indicated that AEAR could activate DCs maturation by increasing the expression levels of co-stimulatory molecules (CD40, CD86, CD80, and MHC-II) on dendritic cells (DCs) from splenocytes and reduce the activity of regulatory T cells (Treg). Abnormal behaviors, side effects or death were not observed in immunized mice. AEAR could boost humoral and cell-mediated immunity elicited by FMDV vaccine, especially Th1-type immune responses.

Grouper (Epinephelus coioides) antimicrobial peptide epinecidin-1 exhibits antiviral activity against foot-and-mouth disease virus in vitro

Picornavirus is a highly contagious virus that usually infects cloven hoofed animals and causes foot-and-mouth disease. This disease is a major threat to livestock breeding worldwide and may lead to huge economic losses. Because effective vaccines or antiviral drugs remain unavailable, the search for new agents to combat FMDV infections is ongoing. Antimicrobial peptides are known to possess a broad range of biological activities, including antibacterial, antiviral, antitumor and immunomodulatory effects. In this work, we used a cell culture FMDV replication assay to evaluate several antimicrobial peptides for their ability to act as antiviral agents. We found that a synthesized form of the Epinephelus coioides antimicrobial peptide, epinecidin-1 (Epi-1), was effective at combatting FMDV. Epi-1 is known to have broad spectrum antimicrobial activity and low toxicity to normal eukaryotic cells, making it a good candidate for use as a therapeutic agent.The 50% cytotoxic concentration (CC₅₀) for BHK-21 cells was 19.5 μg/ml for synthesized Epi-1, and the 50% effective concentration (EC₅₀) for viral inhibition was 0.6 μg/ml. The selectivity index was 31.4, as calculated by the CC₅₀/EC₅₀ ratio. Furthermore, Epi-1 showed virucidal activity against FMDV at high concentrations. Interestingly, our data also showed that FMDV infection was most impaired when Epi-1 was treated at the time of viral adsorption. Taken together, our data show that Epi-1 may be a promising candidate for development as an anti-FMDV agent.

Use of ENABL® adjuvant to increase the potency of an adenovirus-vectored foot-and-mouth disease virus serotype A subunit vaccine

A foot-and-mouth disease (FMD) recombinant subunit vaccine formulated with a lipid/polymer adjuvant was evaluated in two vaccine efficacy challenge studies in steers. The vaccine active ingredient is a replication-deficient human adenovirus serotype 5 vector encoding the FMD virus (FMDV) A24/Cruzeiro/BRA/55 capsid (AdtA24). In the first study, AdtA24 formulated in ENABL® adjuvant was compared to a fourfold higher dose of AdtA24 without adjuvant. Steers vaccinated with AdtA24 + ENABL® adjuvant developed a significantly higher virus neutralizing test (VNT) antibody titer and an improved clinical response following FMDV A24/Cruzeiro/BRA/55 intradermal lingual challenge at 14 days post-vaccination (dpv) than steers vaccinated with the active ingredient alone. In the second study, vaccination with AdtA24 formulated in ENABL® at the same dose used in the first study, followed by FMDV A24/Cruzeiro/BRA/55 challenge on 7 or 14 dpv, prevented clinical FMD in all steers and conferred 90% protection against viremia. In addition, post-challenge FMDV titers in nasal samples from vaccinated steers compared to unvaccinated steers were significantly reduced. In both studies, none of the AdtA24 vaccinated steers developed antibodies to the FMDV non-structural proteins prior to challenge with FMDV, indicative of the capacity to differentiate infected from vaccinated animals (DIVA). These results demonstrate that administration of AdtA24 formulated in ENABL® adjuvant lowered the protective dose and prevented clinical FMD following exposure of vaccinated steers to virulent FMDV at 7 or 14 dpv.

Impact of antigens, adjuvants and strains on sexually dimorphic antibody response to vaccines in mice

Sexually dimorphic antibody response to vaccines has long been noticed. In addition to sex hormones, other factors such as antigens, adjuvants and strains of mice, as shown by indirect evidence, could also impact the sexual dimorphism. To clarify this, we immunized both gender mice of distinct strains with inactivated FMDV or HBsAg with or without adjuvants, and detected the specific antibody response of the mice. We found that in absence of adjuvants, the recombinant HBsAg but not the inactivated FMDV induced enhanced IgG antibody response in the female BALB/c mice. The o/w emulsion could facilitate the HBsAg to induce the comparable level of IgG antibodies in the male BALB/c mice as that in the females. The o/w emulsion rather than ISA206, a w/o/w emulsion, could assist the inactivated FMDV to induce higher levels of IgM antibodies in the female BALB/c mice. Moreover, the sexually dimorphic antibody response varied among the ICR, BALB/c and the F1 (BALB/c × C57BL/6) mice. Thus the data suggest that antigens, adjuvants and strains all impact the sexually dimorphic antibody response to vaccines and may provide insights for developing gender-based vaccines.

Global Foot-and-Mouth Disease Research Update and Gap Analysis: 3 - Vaccines

This study assessed research knowledge gaps in the field of FMDV (foot-and-mouth disease virus) vaccines. The study took the form of a literature review (2011-15) combined with research updates collected in 2014 from 33 institutes from across the world. Findings were used to identify priority areas for future FMD vaccine research. Vaccines play a vital role in FMD control, used both to limit the spread of the virus during epidemics in FMD-free countries and as the mainstay of disease management in endemic regions, particularly where sanitary controls are difficult to apply. Improvements in the performance or cost-effectiveness of FMD vaccines will allow more widespread and efficient disease control. FMD vaccines have changed little in recent decades, typically produced by inactivation of whole virus, the quantity and stability of the intact viral capsids in the final preparation being key for immunogenicity. However, these are exciting times and several promising novel FMD vaccine candidates have recently been developed. This includes the first FMD vaccine licensed for manufacture and use in the USA; this adenovirus-vectored FMD vaccine causes in vivo expression of viral capsids in vaccinated animals. Another promising vaccine candidate comprises stabilized empty FMDV capsids produced in vitro in a baculovirus expression system. Recombinant technologies are also being developed to improve otherwise conventionally produced inactivated vaccines, for example, by creating a chimeric vaccine virus to increase capsid stability and by inserting sequences into the vaccine virus for desired antigen expression. Other important areas of ongoing research include enhanced adjuvants, vaccine quality control procedures and predicting vaccine protection from immune correlates, thus reducing dependency on animal challenge studies. Globally, the degree of independent vaccine evaluation is highly variable, and this is essential for vaccine quality. Previously neglected, the importance of evaluating vaccination programme effectiveness and impact is increasingly being recognized.

Foot-and-mouth disease vaccines

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals. The disease affects many areas of the world, often causing extensive epizootics in livestock, mostly farmed cattle and swine, although sheep, goats and many wild species are also susceptible. In countries where food and farm animals are essential for subsistence agriculture, outbreaks of FMD seriously impact food security and development. In highly industrialized developed nations, FMD endemics cause economic and social devastation mainly due to observance of health measures adopted from the World Organization for Animal Health (OIE). High morbidity, complex host-range and broad genetic diversity make FMD prevention and control exceptionally challenging. In this article we review multiple vaccine approaches developed over the years ultimately aimed to successfully control and eradicate this feared disease.