Stabilization study of inactivated foot and mouth disease virus vaccine by size-exclusion HPLC and differential scanning calorimetry

Single-Domain Antibodies That Specifically Recognize Intact Capsids of Multiple Foot-and-Mouth Disease Serotype O Strains

BACKGROUND/OBJECTIVES

Intact (146S) foot-and-mouth disease virus (FMDV) particles easily dissociate into 12S particles with a concomitant decreased immunogenicity. Vaccine quality control with 146S-specific single-domain antibodies (VHHs) is hampered by the high strain specificity of most 146S-specific VHHs. This study aimed to isolate 146S-specific VHHs that recognize all serotype O strains.

METHODS

Biopanning was performed with the FMDV strain O/SKR/7/2010 146S, using a secondary library of mutagenized M170F VHH that did not recognize O/SKR/7/2010 or using phage-display libraries from llamas immunized with other serotype O strains. Novel VHHs were yeast-produced and their strain-, particle-, and antigenic-site specificities were determined by ELISA.

RESULTS

M170F mutagenesis did not improve the cross-reaction with O/SKR/7/2010. However, selection from immune libraries resulted in four VHHs that exhibited high 146S specificity for all five serotype O strains analyzed. These VHHs presumably recognize all serotype O strains since the five strains analyzed represent different phylogenetic clades. They bind the same antigenic site as M170F, which was previously shown to be a conserved site in serotypes A and O, and which has an altered 3D structure when 146S dissociates into 12S particles. M916F had the lowest limit of detection, which varied from 0.7 to 5.9 ng/mL 146S particles for three serotype O strains.

CONCLUSIONS

We identified four VHHs (M907F, M910F, M912F, and M916F) that specifically bind 146S particles of probably all serotype O strains. They enable further improved FMDV vaccine quality control.

Enhancing vaccine stability in transdermal microneedle platforms

Micron-scale needles, so-called microneedles (MNs) offer a minimally invasive, nearly painless, and user-friendly method for effective intradermal immunization. Maintaining the stability of antigens and therapeutics is the primary challenge in producing vaccine or drug-loaded MNs. The manufacturing of MNs patches involves processes at ambient or higher temperatures and various physio-mechanical stresses that can impact the therapeutic efficacy of sensitive biologics or vaccines. Therefore, it is crucial to develop techniques that safeguard vaccines and other biological payloads within MNs. Despite growing research interest in deploying MNs as an efficient tool for delivering vaccines, there is no comprehensive review that integrates the strategies and efforts to preserve the thermostability of vaccine payloads to ensure compatibility with MNs fabrication. The discussion delves into various physical and chemical approaches for stabilizing antigens in vaccine formulations, which are subsequently integrated into the MNs matrix. The primary focus is to comprehensively examine the challenges associated with the translation of thermostable vaccine MNs for clinical applications while considering a safe, cost-effective approach with a regulatory roadmap. The recent cutting-edge advances facilitating flexible and scalable manufacturing of stabilized MNs patches have been emphasized. In conclusion, the ability to stabilize vaccines and therapeutics for MNs applications could bolster the effectiveness, safety and user-compliance for various drugs and vaccines, potentially offering a substantial impact on global public health.

Development of a thermal stabilizer formulation optimized by response surface methodology for Senecavirus A antigen

Numerous members of the family Picornaviridae, such as the Senecavirus A (SVA) and foot-and-mouth disease virus (FMDV), exhibit thermal instability, resulting in the dissociation of viral particles, which affects the insufficient potency of the vaccine. Based on this characteristic, this study aimed to maintain the thermal stability of SVA by supplementing it with a stabilizer. Excipients, such as sucrose, mannitol, sorbitol, polyethylene glycol (PEG), L-arginine (L-Arg), glutamic acid (Glu), polyvinyl pyrrolidone (PVP), bovine serum albumin (BSA), and potassium chloride (KCl) dissolved in Tris-HCl buffer solution, retained the infectivity of SVA in the thermostability assay. Thermal stability formulations were developed by combining different excipients in disaccharide polyol systems and optimizing formulations using the Box-Behnken experimental design (BBD) combined with response surface methodology (RSM). Three significant factors were studied: sucrose 9.9%, sorbitol 9.9%, and L-Arg 0.06 mol/L against virus titer of thermal-resistance of SVA as a response. The formulation improved the stability of SVA, whose viral infectivity titer decreased by 101.0 TCID50/mL at 4°C, 25°C, and 37°C, respectively, until it decreased by 101.21 TCID50/mL at 7 d of incubation at 42°C. The combinational thermal stabilizer generated in this study enabled the stabilization of the SVA, which might contribute to storage and transportation when the cold chain is unavailable, especially in rural areas. Therefore, the thermal stabilizer is an efficient candidate stabilizer for picornavirus formulations, which keep picornavirus infectivity at various temperatures. Further optimization of this approach will provide new opportunities for the generation of stabilizer formulation from different stabilizers.

In situ bio-mineralized Mn nanoadjuvant enhances anti-influenza immunity of recombinant virus-like particle vaccines

Virus like particles (VLPs) have been well recognized as one of the most important vaccine platforms due to their structural similarity to natural viruses to induce effective humoral and cellular immune responses. Nevertheless, lack of viral nucleic acids in VLPs usually leads the vaccine candidates less efficient in provoking innate immune against viral infection. Here, we constructed a biomimetic dual antigen hybrid influenza nanovaccines THM-HA@Mn with robust immunogenicity via in situ synthesizing a stimulator of interferon genes (STING) agonist Mn3O4 inside the cavity of a recombinant Hepatitis B core antigen VLP (HBc VLP) having fused SpyTag and influenza M2e antigen peptides (Tag-HBc-M2e, THM for short), followed by conjugating a recombinant hemagglutinin (rHA) antigen on the surface of the nanoparticles through SpyTag/SpyCatcher ligating. Such inside Mn3O4 immunostimulator-outside rHA antigen design, together with the chimeric M2e antigen on the HBc skeleton, enabled the synthesized hybrid nanovaccines THM-HA@Mn to well imitate the spatial distribution of M2e/HA antigens and immunostimulant in natural influenza virus. In vitro cellular experiments indicated that compared with the THM-HA antigen without Mn3O4 and a mixture vaccine consisting of THM-HA + MnOx, the THM-HA@Mn hybrid nanovaccines showed the highest efficacies in dendritic cells uptake and in promoting BMDC maturation, as well as inducing expression of TNF-α and type I interferon IFN-β. The THM-HA@Mn also displayed the most sustained antigen release at the injection site, the highest efficacies in promoting the DC maturation in lymph nodes and germinal center B cells activation in the spleen of the immunized mice. The co-delivery of immunostimulant and antigens enabled the THM-HA@Mn nanovaccines to induce the highest systemic antigen-specific antibody responses and cellular immunogenicity in mice. Together with the excellent colloid dispersion stability, low cytotoxicity, as well as good biosafety, the synthetic hybrid nanovaccines presented in this study offers a promising strategy to design VLP-based vaccine with robust natural and adaptive immunogenicity against emerging viral pathogens.

Calcium Chloride as a Novel Stabilizer for Foot-and-Mouth Disease Virus and Its Application in the Vaccine Formulation

The thermal stability of the in-house-developed foot-and-mouth disease (FMD) type O and A viruses was evaluated, and the O Jincheon virus was found to exhibit the lowest thermal stability. To overcome this instability, we proposed a novel stabilizer, calcium chloride. The thermal stability of FMDVs increased up to a CaCl2 concentration of 10 mM, and it had a decreasing trend at >30 mM. The O Jincheon virus showed a significant decrease in the amount of antigen over time at 4 °C. In contrast, the samples treated with CaCl2 showed stable preservation of the virus without significant antigen loss. After the CaCl2-formulated vaccine was administered twice to pigs, the virus neutralization titer reached approximately 1:1000, suggesting that the vaccine could protect pigs against the FMDV challenge. In summary, the O Jincheon virus is difficult to utilize as a vaccine given its low stability during storage after antigen production. However, following its treatment with CaCl2, it can be easily utilized as a vaccine. This study evaluated CaCl2 as a novel stabilizer in FMD vaccines and may contribute to the development of stable vaccine formulations, especially for inherently unstable FMDV strains.

The SARS-CoV-2 Hydra, a tiny monster from the 21st century: Thermodynamics of the BA.5.2 and BF.7 variants

SARS-CoV-2 resembles the ancient mythical creature Hydra. Just like with the Hydra, when one head is cut, it is followed by appearance of two more heads, suppression of one SARS-CoV-2 variant causes appearance of newer variants. Unlike Hydra that grows identical heads, newer SARS-CoV-2 variants are usually more infective, which can be observed as time evolution of the virus at hand, which occurs through acquisition of mutations during time. The appearance of new variants is followed by appearance of new COVID-19 pandemic waves. With the appearance of new pandemic waves and determining of sequences, in the scientific community and general public the question is always raised of whether the new variant will be more virulent and more pathogenic. The two variants characterized in this paper, BA.5.2 and BF.7, have caused a pandemic wave during the late 2022. This paper gives full chemical and thermodynamic characterization of the BA.5.2 and BF.7 variants of SARS-CoV-2. Having in mind that Gibbs energy of binding and biosynthesis represent the driving forces for the viral life cycle, based on the calculated thermodynamic properties we can conclude that the newer variants are more infective than earlier ones, but that their pathogenicity has not changed.

Synthesis of a crystalline zeolitic imidazole framework-8 nano-coating on single environment-sensitive viral particles for enhanced immune responses

Encapsulating antigens with zeolitic imidazole framework-8 (ZIF-8) exhibits many advantages in vaccine development. However, most viral antigens with complex particulate structures are sensitive to pH or ionic strength, which cannot tolerate harsh synthesis conditions of ZIF-8. Balancing the viral integrity and the growth of ZIF-8 crystals is crucial for the successful encapsulation of these environment-sensitive antigens in ZIF-8. Here, we explored the synthesis of ZIF-8 on inactivated foot and mouth disease virus (known as 146S), which is easily disassociated into no immunogenic subunits under the existing ZIF-8 synthesis conditions. Our results showed that intact 146S could be encapsulated into ZIF-8 with high embedding efficiency by lowering the pH of the 2-MIM solution to 9.0. The size and morphology of 146S@ZIF-8 could be further optimized by increasing the amount of Zn2+ or adding cetyltrimethylammonium bromide (CTAB). 146S@ZIF-8 with a uniform diameter of about 49 nm could be synthesized by adding 0.01% CTAB, which was speculated to be composed of single 146S armored with nanometer-scale ZIF-8 crystal networks. Plenty of histidine on the 146S surface forms a unique His-Zn-MIM coordination in the near vicinity of 146S particles, which greatly increases the thermostability of 146S by about 5 °C, and the nano-scale ZIF-8 crystal coating exhibited extraordinary stability to resist EDTE-treatment. More importantly, the well-controlled size and morphology enabled 146S@ZIF-8(0.01% CTAB) to facilitate antigen uptake. The immunization of 146S@ZIF-8(4×Zn2+) or 146S@ZIF-8(0.01% CTAB) significantly enhanced the specific antibody titers and promoted the differentiation of memory T cells without adding another immunopotentiator. This study reported for the first time the strategy of the synthesis of crystalline ZIF-8 on an environment-sensitive antigen and demonstrated that the nano-size and appropriate morphology of ZIF-8 are crucial to exert adjuvant effects, thus expanding the application of MOFs in vaccine delivery.

Biothermodynamics of Viruses from Absolute Zero (1950) to Virothermodynamics (2022)

Biothermodynamics of viruses is among the youngest but most rapidly developing scientific disciplines. During the COVID-19 pandemic, it closely followed the results published by molecular biologists. Empirical formulas were published for 50 viruses and thermodynamic properties for multiple viruses and virus variants, including all variants of concern of SARS-CoV-2, SARS-CoV, MERS-CoV, Ebola virus, Vaccinia and Monkeypox virus. A review of the development of biothermodynamics of viruses during the last several decades and intense development during the last 3 years is described in this paper.

Enhanced stability of Foot-and-Mouth Disease Vaccine Antigens with a novel formulation

The structural instability of inactivated foot-and-mouth disease virus antigen hinders the development of vaccine industry. The use of an inexpensive, biocompatible formulation to slow down the degradation of antigen would address the problem. Here, PBS was showed to be effective in stabilizing 146S and hence determined as basic solution buffer. Excipients such as Trehalose, Sucrose, Arginine, Cysteine, Calcium chloride, BSA and Ascorbic acid were found to protect 146S from massive structural breakdown. Using orthogonal test, we confirmed the novel formulation as a combination of 5% (w/v) trehalose, 5% (w/v) sucrose, 0.05 M arginine, 0.01 M cysteine, 0.01 M calcium chloride, 1% (W/V) BSA and 0.001 M ascorbic acid in PBS. The formulation increased vaccine stabilization, with retention rate of 14% after storage at 4 °C for 14 months. Particle size for vaccine was at approximately 220 nm and physicochemical detecting findings were rarely abnormal in morphology and emulsion type. In summary, these results revealed that the novel formulation is beneficial to make FMD vaccine more stable and effective, reducing the dependence on cold storage and delivery.

Comparison of High-Performance Liquid Chromatography with Sucrose Density Gradient Ultracentrifugation for the Quantification of Foot-and-Mouth Disease Vaccine Antigens

Foot-and-mouth disease (FMD) causes substantial economic losses in the livestock industry. The protective immunizing component of the FMD virus (FMDV) is a ribonucleoprotein particle with a sedimentation coefficient of 146S. Size-exclusion high-performance liquid chromatography (SE-HPLC) was introduced to replace sucrose density gradient ultracentrifugation (SDG), which is the gold standard for the quantification of FMDV 146S particles. SE-HPLC showed a pattern similar to that of SDG; however, the two methods resulted in different quantities for the same amount of 146S particles. This study aimed to identify the reason for this disparity and adjust the difference between the two methods by employing a standard material. While SE-HPLC displayed all the virus particles in the peak fraction by SDS-PAGE and Western blotting, the virus particles were widely dispersed in multiple fractions, including peak fractions in the SDG. To adjust the difference between the two methods, a stable surrogate virus, bovine enterovirus, was devised to draw a standard curve, and the gap was reduced to <10%. To our knowledge, this is the first report to provide experimental evidence on the difference between SDG and SE-HPLC for the quantification of FMDV particles.

A Virus-Like Particle-Based Solid-Phase Competition Enzyme-Linked Immunosorbent Assay for Antibody Detection of Foot-and-Mouth Disease Virus Serotype O

Foot-and-mouth disease (FMD) is caused by FMD virus (FMDV) is a highly contagious disease of ruminants, which is primarily controlled by vaccination. The monitoring of antisera after vaccination is currently depending on liquid-phase blocking ELISA (LPBE). Recently, bacterium-original FMD virus-like particle (VLP) showed the potential as vaccine candidates. In this study, to minimize the risk of live virus involvement, the Escherichia coli original VLP of FMDV serotype O were used as the immunogen for monoclonal antibodies (Mabs) production and the capture antigen in the development of a solid-phase competition ELISA (SPCE). The samples with a percentage inhibition of >50% were considered positive in the SPCE assay. The concordance rate of the Mab-based SPCE compared with the LPBE for clinical serum samples test was 93.4%, and with a high agreement (kappa = 0.892) with LPBE in antibody duration monitoring. Results indicated that the VLP-based SPCE had high specificity and sensitivity, which provides an alternative method for postimmunization antibody evaluation of FMDV serotype O.

Development of a Potent Stabilizer for Long-Term Storage of Foot-and-Mouth Disease Vaccine Antigens

A local virus isolate, O/SKR/JC/2014 (O JC), has been considered as a candidate vaccine strain in the development of a domestic foot-and-mouth disease (FMD) vaccine in Korea. However, producing and preserving a sufficient quantity of intact vaccine antigens from the O JC strain was difficult owing to its distinctive structural instability compared to other candidate vaccine strains. Based on this feature, the O JC strain was adopted as a model virus for the stabilization study to determine the optimal stabilizer composition, which enables long-term storage of the FMD vaccine antigen in both aqueous and frozen phases. In contrast to O JC vaccine antigens stored in routinely used Tris-buffered or phosphate-buffered saline, those stored in Tris-KCl buffer showed extended shelf-life at both 4 °C and −70 °C. Additionally, the combined application of 10% sucrose and 5% lactalbumin hydrolysate could protect O JC 146S particles from massive structural breakdown in an aqueous state for up to one year. The stabilizer composition was also effective for other FMDV strains, including serotypes A and Asia 1. With this stabilizer composition, FMD vaccine antigens could be flexibly preserved during the general production process, pending status under refrigeration and banking under ultrafreezing.

On-line separation and quantification of virus antigens of different serotypes in multivalent vaccines by capillary zone electrophoresis: A case study for quality control of foot-and-mouth disease virus vaccines

Accurate quantification of effective antigens of different serotypes is crucial for quality control of multivalent vaccines but challenging. A simple and rapid capillary zone electrophoresis (CZE) method was developed for on-line separation and quantification of foot-and-mouth disease virus (FMDV) antigens in monovalent and bivalent FMDV vaccines. The FMDV peak identity in CZE was demonstrated by the study of FMDV dissociation combined with high performance size exclusion chromatography (HPSEC) analysis. After optimizing CZE conditions including UV detecting wavelength, injection volume, and separation voltage, both serotype A and O FMDV showed good reproducibility (RSD <5%) and linear responses (R²=0.999) between the peak area and FMDV content in the concentration range of 15-400 μg/mL. The two serotypes of FMDV with similar size had different migration time in CZE according to their different zeta potential, which allows them to be separated and quantified, with accuracy of <10% relative error. CZE was then successfully applied for antigen quantification of commercial O monovalent and A/O bivalent FMDV vaccines. Compared with HPSEC, CZE was not only able to quantify each serotype of FMDV, but also free from interference of nucleic acids impurities. In summary, the CZE can be a simple, rapid, and reliable tool for quality control of monovalent and bivalent FMDV vaccines. The CZE method can also be further extended to the quality control of other multivalent virus and virus like particle vaccines.

Characterization and stabilization in process development and product formulation for super large proteinaceous particles

Super large proteinaceous particles (SLPPs) such as virus, virus like particles, and extracellular vesicles have successful and promising applications in vaccination, gene therapy, and cancer treatment. The unstable nature, the complex particulate structure and composition are challenges for their manufacturing and applications. Rational design of the processing should be built on the basis of fully understanding the characteristics of these bio-particles. This review highlights useful analytical techniques for characterization and stabilization of SLPPs in the process development and product formulations, including high performance size exclusion chromatography, multi-angle laser light scattering, asymmetrical flow field-flow fractionation, nanoparticle tracking analysis, CZE, differential scanning calorimetry, differential scanning fluorescence, isothermal titration calorimetry , and dual polarization interferometry. These advanced analytical techniques will be helpful in obtaining deep insight into the mechanism related to denaturation of SLPPs, and more importantly, in seeking solutions to preserve their biological functions against deactivation or denaturation. Combination of different physicochemical techniques, and correlation with in vitro or in vivo biological activity analyses, are considered to be the future trend of development in order to guarantee a high quality, safety, and efficacy of SLPPs.

Study of Interactions between Antigens and Polymeric Adjuvants in Vaccines by Frontal Analysis Continuous Capillary Electrophoresis

Vaccine adjuvants are used to enhance the immune response induced by antigens that have insufficient immunostimulatory capabilities. The present work aims at developing a frontal analysis continuous capillary electrophoresis (FACCE) methodology for the study of antigen-adjuvant interactions in vaccine products. After method optimization using three cationic model proteins, namely lysozyme, cytochrome c, and ribonuclease A, FACCE was successfully implemented to quantify the free antigen and thus to determine the interaction parameters (stoichiometry and binding constant) between an anionic polymeric adjuvant (polyacrylic acid, SPA09) and a cationic vaccine antigen in development for the treatment for Staphylococcus aureus. The influence of the ionic strength of the medium on the interactions was investigated. A strong dependence of the binding parameters with the ionic strength was observed. The concentration of the polymeric adjuvant was also found to significantly modify the ionic strength of the formulation, the extent of which could be estimated and corrected.

Development and validation of a solid-phase competition ELISA based on virus-like particles of foot-and-mouth disease virus serotype A for antibody detection

Foot-and-mouth disease (FMD), caused by FMD virus (FMDV), is a highly contagious epidemic disease, which is controlled primarily by prophylactic vaccination and serological monitoring after vaccination. Here, we have developed a solid-phase competition ELISA (SPCE) method based on virus-like particles (VLPs) of FMDV serotype A. The use of VLPs in the SPCE assay as a replacement for inactivated FMDV provides a high level of biosafety. The SPCE showed high concordance rates when compared with the virus neutralization test and liquid-phase blocking ELISA for testing clinical serum samples and successive serological monitoring (kappa = 0.925). Thus, this SPCE is an alternative method for post-immunization detection of antibodies against FMDV serotype A, with high specificity and sensitivity.

The role of viral particle integrity in the serological assessment of foot-and-mouth disease virus vaccine-induced immunity in swine

The efficacy of foot-and-mouth disease virus (FMDV) inactivated vaccines is mainly dependent on the integrity of the whole (146S) viral particles. If the intact capsids disassemble to 12S subunits, antibodies against internal-not protective epitopes, may be induced. Serological correlates with protection may be hampered if antibodies against internal epitopes are measured. Here we compared the performance of different ELISAs with the virus-neutralization test (VNT) that measures antibodies against exposed epitopes. Sera from pigs immunized with one dose of an expired commercial FMDV vaccine were used. This vaccine contained about 50% of O1/Campos and over 90% of A24/Cruzeiro strains total antigen as whole 146S particles. Specific-total antibodies were measured with the standard liquid-phase blocking ELISA (LPBE). We also developed an indirect ELISA (IE) using sucrose gradient purified 146S particles as capture antigen to titrate total antibodies, IgM, IgG1 and IgG2. A good correlation was found between VNT titers and IgG-ELISAs for A24/Cruzeiro, with the lowest correlation coefficient estimated for IgG2 titers. For O1/Campos, however, the presence of antibodies against epitopes different from those of the whole capsid, elicited by the presence of 12S particles in the vaccine, hampered the correlation between LPBE and VNT, which was improved by using purified O1/Campos 146S-particles for the liquid-phase of the LPBE. Interestingly, 146S particles but not 12S were efficiently bound to the ELISA plates, confirming the efficiency of the IE to detect antibodies against exposed epitopes. Our results indicate that any serological test assessing total antibodies or IgG1 against epitopes exposed in intact 146S-particles correlate with the levels of serum neutralizing antibodies in vaccinated pigs, and might potentially replace the VNT, upon validation. We recommend that antigen used for serological assays aimed to measure protective antibodies against FMDV should be controlled to ensure the preservation of 146S viral particles.

Mechanism of bio-macromolecule denaturation on solid-liquid surface of ion-exchange chromatographic media - A case study for inactivated foot-and-mouth disease virus

Destruction of assembly structures has been identified as a major cause for activity loss of virus and virus-like particles during their chromatographic process. A deep insight into the denaturation process at the solid-liquid interfaces is important for rational design of purification. In this study, in-situ differential scanning calorimetry (DSC) was employed to study the dissociation process of inactivated foot-and-mouth disease virus (FMDV) during ion exchange chromatography (IEC) at different levels of pH. The intact FMDV known as 146S and the dissociation products were quantified by high performance size exclusion chromatography (HPSEC) and the thermo-stability of 146S on-column was monitored in-situ by DSC. Serious dissociation was found at pH 7.0 and pH 8.0, leading to low 146S recoveries of 12.3% and 43.7%, respectively. The elution profiles from IEC and HPSEC combined with the thermal transition temperatures of 146S dissociation (T_m1) from DSC suggested two denaturation mechanisms that the 146S dissociation occurred on-column after adsorption at pH 7.0 and during elution step at pH 8.0. By appending different excipients including sucrose, the improvement of 146S recovery and reduced dissociation was found highly correlated to increment of 146S stability on-column detected by DSC. The highest recovery of 99.9% and the highest T_m1 of 54.49 °C were obtained at pH 9.0 with 20% (w/v) sucrose. According to chromatographic behaviors and T_m1, three different dissociation processes in IEC were discussed. The study provides a perspective to understand the denaturation process of assemblies during chromatography, and also supplies a strategy to improve assembly recovery.

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.

Three-percent sucrose acts as a thermostabilizer for cell-adapted foot-and-mouth disease virus without any negative effect on viral growth

AIMS

As cell-adapted foot-and-mouth disease virus (FMDV) with H56R mutation in VP3 has reduced thermostability, this study aimed to investigate the effect of thermostabilizers on cell-adapted FMDV for vaccine production.

METHODS AND RESULTS

We examined the effect of 3% sucrose, 10% (or 25%) glycerol or 10% FBS on cell-adapted FMDV O/SKR/JC/2014, containing H56R mutation in VP3, as vaccine seed virus at -80, 4, 25 or 37°C for 2, 4 or 7 days. The stabilizing effect of 3% sucrose on O/SKR/JC/2014 was observed at 25, 37°C, and after repeated freeze-thaw cycles. Additionally, we tested the effect of 3% sucrose on the growth of FMDV or cells and did not observe any decrease in either viral growth or cell viability.

CONCLUSIONS

Our study showed the protective effect of 3% sucrose on FMDV infectivity at various temperatures; this virus stock in 3% sucrose could be used for infecting cells without the removal of sucrose.

SIGNIFICANCE AND IMPACT OF THE STUDY

We suggest that 3% sucrose-containing medium could be beneficial for the stable storage and transport of cell-adapted FMDV.

Unique stabilizing mechanism provided by biocompatible choline-based ionic liquids for inhibiting dissociation of inactivated foot-and-mouth disease virus particles

Choline-based ionic liquids provide a unique stabilizing mechanism for inhibiting the dissociation of inactivated foot-and-mouth disease virus particles.