Foot-and-mouth disease (FMD) is an acute, severe, and highly contagious infectious disease caused by foot-and-mouth disease virus (FMDV), which seriously endangers the development of animal husbandry. The inactivated FMD vaccine is the main product for the prevention and control of FMD, which has been successfully applied to control the pandemic and outbreak of FMD. However, the inactivated FMD vaccine also has problems, such as the instability of antigen, the risk of spread of the virus due to incomplete inactivation during vaccine production, and the high cost of production. Compared with traditional microbial and animal bioreactors, production of antigens in plants through transgenic technology has some advantages including low cost, safety, convenience, and easy storage and transportation. Moreover, since antigens produced from plants can be directly used as edible vaccines, no complex processes of protein extraction and purification are required. But, there are some problems for the production of antigens in plants, which include low expression level and poor controllability. Thus, expressing the antigens of FMDV in plants may be an alternative mean for production of FMD vaccine, which has certain advantages but still need to be continuously optimized. Here we review the main strategies for expressing active proteins in plants, as well as the research progress on the expression of FMDV antigens in plants. We also discuss the current problems and challenges encountered, with the aim to facilitate related research.
Animals ; Foot-and-Mouth Disease Virus/genetics* ; Foot-and-Mouth Disease/prevention & control* ; Antigens, Viral/genetics* ; Viral Vaccines

Hand, Foot and Mouth Disease ; epidemiology ; prevention & control ; Humans

Reverse-genetic engineering of foot and mouth disease virus (FMDV) can improve the productivity, antigen matching, antigen stability, immune response ability, and biological safety of vaccines, so vaccine candidates with anticipated biological characteristics can be promptly achieved. Negative influence in taming of virulent strains can also be decreased or avoided. Reverse genetics not only make up for deficiencies like limitation of viral nature, low success rate, and time and energy consuming, but also realize more active designing of vaccines. Therefore, reverse genetics is significant in improving integral quality and efficiency of vaccines. In this review, we use FMDV vaccines as an example to summarize improvement in biological characteristics of virulent strains and provide a reference for related researches.
Animals ; Antibodies, Viral ; immunology ; Foot-and-Mouth Disease ; immunology ; prevention & control ; virology ; Foot-and-Mouth Disease Virus ; genetics ; immunology ; Reverse Genetics ; Viral Vaccines ; genetics ; immunology

The stability of virus-like particles (VLPs) is currently the main factor affecting the quality of foot-and-mouth disease VLPs vaccines. In order to further improve the quality of the VLPs vaccine of foot-and-mouth disease (FMD), three amino acid modification sites were designed and screened through kinetic analysis software, based on the three-dimensional structure of FMDV. The three mutant recombinant plasmids were successfully prepared by the point mutation kit, transformed into Escherichia coli strain BL21 and expressed in vitro. After purification by Ni ion chromatography column, SDS-PAGE proved that the three amino acid mutations did not affect the expression of the target protein. The results of the stability study of three FMD mutant VLPs obtained by in vitro assembly show that the introduction of internal hydrophobic side chain amino acids made the morphology of VLPs more uniform (N4017W), and their stability was significantly improved compared to the other two VLPs. The internal hydrophobic force of the capsid contributes to the formation of VLPs and helps to maintain the stability of the capsid, providing new experimental ideas for improving the quality of VLPs vaccines, and helping to promote the development of VLPs vaccines.
Amino Acids ; Animals ; Capsid Proteins/genetics* ; Foot-and-Mouth Disease/prevention & control* ; Foot-and-Mouth Disease Virus/genetics* ; Kinetics ; Vaccines, Virus-Like Particle/genetics* ; Viral Vaccines/genetics*

Antigenic purity is important for quality control of the foot-and-mouth (FMD) whole virus inactivated vaccine. The recommended method for evaluation the antigenic purity of FMD vaccine is to check the serum conversion to non-structural protein (NSP) 3AB antibody after 2 to 3 times inoculation of animals with inactivated vaccine. In this study, we developed a quantitative ELISA to detect the amount of residual 3AB in vaccine antigen, to provide a reference to evaluate the antigenic purity of FMD vaccine. Monoclonal antibody (Mab) of NSP 3A and HRP-conjugated Mab of NSP 3B were used to establish a sandwich ELISA to quantify the NSP 3AB in vaccine antigen of FMD. Purified NSP 3AB expressed in Escherichia coli was serially diluted and detected to draw the standard curve. The detectable limit was determined to be the lowest concentration of standard where the ratio of its OD value to OD blank well was not less than 2.0. Results: The OD value was linearly corelated with the concentration of 3AB protein within the range between 4.7 and 600 ng/mL. The correlation coefficient R² is greater than 0.99, and the lowest detectable limit is 4.7 ng/mL. The amount of 3AB protein in non-purified inactivated virus antigen was detected between 9.3 and 200 ng/mL depending on the 12 different virus strains, whereas the amount of 3AB in purified virus antigen was below the lowest detectable limit. The amount of 3AB in 9 batches of commercial FMD vaccine antigens was between 9.0 and 74 ng/mL, whereas it was below the detectable limit in other 24 batches of commercial vaccine antigens. Conclusion: the sandwich ELISA established in this study is specific and sensitive to detect the content of 3AB protein in vaccine antigen of FMD, which will be a useful method for evaluation of the antigenic purity and quality control of FMD inactivated vaccine.
Animals ; Antibodies, Viral ; Enzyme-Linked Immunosorbent Assay ; Foot-and-Mouth Disease/prevention & control* ; Foot-and-Mouth Disease Virus ; Viral Nonstructural Proteins/genetics* ; Viral Vaccines

To further enhance the immune effect of the foot-and-mouth disease (FMD) virus-like particles (VLPs) vaccine, this study prepared FMDV VLPs-zeolitic imidazolate (framework-8, ZIF-8) complexes with different particle sizes. We used a biomimetic mineralization method with Zn²⁺ and 2-methylimidazole in different concentration ratios to investigate the effect of size on the immunization effect. The results showed that FMDV VLPs-ZIF-8 with three different sizes were successfully prepared, with an approximate size of 70 nm, 100 nm, and 1 000 nm, respectively. Cytotoxicity and animal toxicity tests showed that all three complexes exhibited excellent biological safety. Immunization tests in mice showed that all three complexes enhanced the titers of neutralizing and specific antibodies, and their immune effects improved as the size of the complexes decreased. This study showed that ZIF-8 encapsulation of FMDV VLPs significantly enhanced their immunogenic effect in a size-dependent manner.
Animals ; Mice ; Foot-and-Mouth Disease/prevention & control* ; Foot-and-Mouth Disease Virus ; Antibodies, Neutralizing ; Immunity, Humoral ; Immunization ; Vaccines, Virus-Like Particle ; Antibodies, Viral ; Viral Vaccines

Transient expression is the major method to express foot-and-mouth disease virus (FMDV) capsid proteins in mammalian cells. To achieve stable expression of FMDV capsid proteins and efficient assembly of virus like particles (VLPs) in cells, the plasmids of piggyBac (PB) transposon-constitutive expression and PB transposon-tetracycline (Tet) inducible expression vectors were constructed. The function of the plasmids was tested by fluorescent proteins. By adding antibiotics, the constitutive cell pools (C-WT, C-L127P) expressing P12A3C (WT/L127P) genes and the inducible cell pools (I-WT, I-L127P) expressing P12A3C (WT/L127P) genes were generated. The genes of green fluorescent protein, 3C protease and reverse tetracycline transactivator (rtTA) were integrated into chromosome, which was confirmed by fluorescence observation and PCR testing. The cell pool I-L127P has a stronger production capacity of capsid proteins and VLPs, which was confirmed by Western blotting and enzyme linked immunosorbent assay (ELISA), respectively. In conclusion, inducing the chromosomal expression of FMDV capsid proteins was firstly reported, which may facilitate the technical process of mammalian production of FMDV VLPs vaccine and the construction of mammalian inducible expression systems for other proteins.
Animals ; Foot-and-Mouth Disease Virus/genetics* ; Capsid Proteins ; Viral Proteins/metabolism* ; Foot-and-Mouth Disease/prevention & control* ; Tetracyclines/metabolism* ; Viral Vaccines ; Antibodies, Viral ; Mammals/metabolism*

Routine and emergency vaccination of small ruminants against foot-and-mouth disease (FMD) is mandatory in many endemic countries, yet data on the field effectiveness of the vaccines used is scarce. We conducted an investigation of a serotype O FMD outbreak that took place in a sheep and goat pen, and estimated the effectiveness of various routine vaccination statuses. We also evaluated the protection provided by colostrum administration and emergency vaccination. Animals which were routinely vaccinated twice were not clinically affected while disease incidence was observed among animals routinely vaccinated only once (p = 0.004 according to a two-sided Fisher's exact test). In groups vaccinated only once, there was a significant association between the average time that elapsed since last vaccination and the disease incidence (n = 5; Spearman correlation coefficient: r(s) = 1.0, p < 0.01). In addition, non-vaccinated lambs fed colostrum from dams vaccinated more than 2 months before parturition had a mortality rate of 33%. Administration of emergency vaccination 2 days after the occurrence of the index case was the probable reason for the rapid blocking of the FMD spread within 6 days from its onset in the pen.
Animals ; Colostrum ; Disease Outbreaks/veterinary ; Foot-and-Mouth Disease/*prevention & control ; Goat Diseases/*prevention & control ; Goats ; Immunization Schedule ; Sheep ; Sheep Diseases/*prevention & control ; Viral Vaccines/administration & dosage/*immunology

Objective: To understand the vaccination status of enterovirus type 71 (EV71) inactivated vaccines in China from 2017 to 2021 and provide evidence for making policy on immunization strategy against hand, foot and mouth disease (HFMD). Methods: Using the reported dose number of EV71 vaccination and birth cohort population data collected by the China immunizaiton program information system to estimate the cumulative coverage of EV71 vaccine by the end of 2021 among the birth cohorts since 2012 at national, provincial, and prefecture levels, and analyze the correlation between the vaccination coverage and the potential influencing factors. Results: As of 2021, the estimated cumulative vaccination coverage of the EV71 vaccine was 24.96% in birth cohorts since 2012. The cumulative vaccination coverage was between 3.09% and 56.59% in different provinces, between 0 and 88.17% in different prefectures. There was a statistically significant correlation between vaccination coverage in different regions and the region's previous HFMD prevalence and disposable income per capita. Conclusions: Since 2017, the EV71 vaccines have been widely used nationwide, but the coverage of EV71 vaccination varies greatly among regions. Vaccination coverage is higher in relatively developed regions, and the intensity of previous epidemic of HFMD may have a certain impact on the acceptance of the vaccine and the pattern of immunization service. The impact of EV71 vaccination on the epidemic of HFMD requires further studies.
Humans ; Enterovirus A, Human ; Hand, Foot and Mouth Disease/prevention & control* ; Vaccines, Inactivated ; Viral Vaccines ; Enterovirus ; Vaccination ; China/epidemiology*

A rapid detection of foot-and-mouth disease virus (FMDV) was established by using reverse transcription loop-mediated isothermal amplification (RT-LAMP) method, meanwhile its specificity and sensitivity were assessed. The results showed that the FMDV RNA could be amplified by incubation at 65degrees C for only 1h using six primers designed based on FMDV polyprotein gene and the amplification products could be detected easily by naked-eye. There is no cross reaction with other virus such as SVDV, SFV and PPV by detecting their RNA samples. The detection limit of this method was found to be 10(-5) dilution of RNA sample which was 100-fold higher than that of PCR and 10-fold higher than real-time PCR.
Animals ; DNA Primers ; Foot-and-Mouth Disease ; prevention & control ; virology ; Foot-and-Mouth Disease Virus ; genetics ; isolation & purification ; Genome, Viral ; genetics ; Nucleic Acid Amplification Techniques ; RNA, Viral ; Reverse Transcriptase Polymerase Chain Reaction ; methods ; Sensitivity and Specificity ; Swine Vesicular Disease ; virology