Foot-and-mouth Disease Virus Type Research Articles

Virus-like particle-based multipathogen vaccine of FMD and SVA elicits balanced and broad protective efficacy in mice and pigs

Inactivated vaccines lack the capability to serologically differentiate between infected and vaccinated animals, thereby impeding the effective eradication of pathogen. Conversely, vaccines based on virus-like particles (VLPs) emulate natural viruses in both size and antigenic structure, presenting a promising alternative to overcome these limitations. As the complexity of swine infectious diseases increases, the increase of vaccine types and doses may intensify the stress response. This exacerbation can lead to diminished productivity, failure of immunization, and elevated costs. Given the critical dynamics of co-infection and the clinically indistinguishable symptoms associated with foot-and-mouth disease virus (FMDV) and senecavirus A (SVA), there is a dire need for an efficacious intervention. To address these challenges, we developed a combined vaccine composed of three distinct VLPs, specifically designed to target SVA and FMDV serotypes O and A. Our research demonstrates that this trivalent VLP vaccine induces antigen-specific and robust serum antibody responses, comparable to those produced by the respective monovalent vaccines. Moreover, the immune sera from the combined VLP vaccine strongly neutralized FMDV type A and O, and SVA, with neutralization titers comparable to those of the individual vaccines, indicating a high level of immunogenic compatibility among the three VLP components. Importantly, the combined VLPs vaccines-immunized sera conferred efficient protection against single or mixed infections with FMDV type A and O, and SVA viruses in pigs. In contrast, individual vaccines could only protect pigs against homologous virus infections and not against heterologous challenges. This study presents a novel combined vaccines candidate against FMD and SVA, and provides new insights for the development of combination vaccines for other viral swine diseases.

Characterization of Foot-and-Mouth Disease Virus Serotype O-Specific Single Domain Antibody Expressed in the pET Expression System.

Foot and mouth disease (FMD) is an extremely contagious disease of cloven-hoofed domesticated and wild animals, resulting in significant economic losses in many parts of the world. FMD virus (FMDV) serotype O is responsible for approximately 70% of global outbreaks. For detection of FMDV antigen or antibody, ELISAs are used worldwide and have several limitations, such as batch-to-batch variation in generating immunobiologicals, high production cost and ethical concerns over animal sacrifice. The use of single domain antibody (sdAb) or variable N-terminal domain of the heavy chain of heavy chain antibody (VHH) found naturally in camels has proven their effectiveness in diagnostics and therapeutics. In the present study, the anti-FMDV serotype O-specific VHH-C1 gene sequence (Accession no. KJ751546) was retrieved from the NCBI database. The gene was synthesized commercially in the pBluescript KS+ cloning vector and expressed in E. coli BL21 (DE3) cells using the pET303/CT-His expression system with a C-terminal 6X-His tag. The expressed sdAb, verified by SDS‒PAGE and western blotting, was purified by Ni-chelate chromatography and used as a coating antibody in double antibody sandwich (DAS) ELISA for FMDV detection and typing. The sdAb exhibited a high binding affinity for FMDV serotype O, without any cross-reactivity toward serotypes A and Asia-1. It exhibited better thermostability up to 85°C than conventional rabbit polyclonal anti-FMDV sera. The potential of sdAbs thus produced without sacrificing lab animals could be explored for replacing polyclonal sera in DAS-ELISA as well as for developing biosensors or lateral flow devices for FMDV type O detection.

Preparation of purified vaccine from local isolate of foot and mouth disease virus and its immune response in bovine calves

Foot and Mouth Disease (FMD) is globally pandemic which badly affect the economics of livestock based countries like Pakistan. There are different types of Foot and Mouth Disease Virus (FMDV) among these types O is most prevalent in Pakistan. Recently Pakistan is producing approximately fifteen million doses of non-purified FMD vaccine against the demand of 160 million doses annually. More over the Pakistan is still striving for the development and optimization of concentration as well as purification of FMDV. The present project was designed to develop the technology for the purification of FMDV indigenously. The locally isolated and adapted FMDV type O virus was propagated on adherent culture of BHK-21cells to get final volume of virus one liter. This virus suspension was concentrated by peggylation as well as ultra-filtration method. The purification and quantification of concentrated virus was done by size exclusion chromatography. The results showed that peggylation is better method of concentration up to 603.75 µg/ml with 82.80 % recovery rate than ultra-filtration with 43.90 % followed by chromatography for purification. The PD50 was calculated in bovines at 24, 12, 6, 3 and 1.5 µg of FMDV Ag/dose and it revealed that antigen load of 1.98 µg is the dose, where the 50 % of inoculated animals showed the protective antibody level based upon percent inhibition through antibody detecting ELISA. According to the British pharmacopeia, the vaccine should contain 3PD50 which found equivalent to our findings about 6 µg/dose. The group of animal injected with 6/dose (3.23PD50) showed protective titer up to 20th week post priming.

Production and characterization of monoclonal antibodies against foot-and-mouth disease virus serotype O and development of a sandwich ELISA for virus antigen detection.

Foot-and-mouth disease (FMD) is endemic in India with a majority of outbreaks caused by FMD virus (FMDV) serotype O. In the present study a panel of eight (2F9, 2G10, 3B9, 3H5, 4C8, 4D6, 4G10 and 5B6) mouse monoclonal antibodies (MAbs) were developed against FMDV serotype O Indian vaccine strain, O/IND/R2/75 via hybridoma systems. The MAbs generated were FMDV/O specific without cross-reactivity against FMDV type A and Asia 1. All the MAbs were identified as IgG1/kappa type. Out of eight, three MAbs (3B9, 3H5 and 4G10) demonstrated virus neutralizing activity. The reactivity of all MAbs increased with heat treated (@560C) serotype O antigen compared to untreated antigen in sandwich ELISA indicating that their binding epitopes are linear. Six MAbs (except 2F9 and 4D6) reacted with recombinant P1 protein of homologous virus in an indirect ELISA among which only MAb 3B9 bound to VP1. MAb profiling of 37 serotype O field viruses isolated between the years 1962 and 2021 demonstrated antigenic similarity between field isolates and reference vaccine strain. MAbs 5B6 and 4C8 consistently reacted with all 37 isolates. In indirect immunofluorescence assay MAb 5B6 bound well with FMDV/O antigen. Finally, a sandwich ELISA was successfully developed using rabbit polyclonal anti-FMDV/O serum and MAb 5B6 for detection of FMDV/O antigen in clinical samples (n = 649). The new assay exhibited 100% and 98.89% diagnostic sensitivity and specificity respectively compared to traditional polyclonal antibody-based sandwich ELISA suggesting that the MAb-based ELISA developed here could be an effective method for detection of FMDV serotype O.

Molecular detection, genetic diversity, and phylogenetic analysis of foot-and-mouth disease virus (FMDV) type O in Iran during 2015-2016.

The major challenge of foot-and-mouth disease (FMD) control is attributed to the rapid mutations in the FMDV RNA genome, resulting in continuous antigenic changes of circulating strains. Despite widespread vaccination of livestock populations, the incidence of the FMDV serotype O outbreaks in Iran during 2015-2016 raised concerns about the emergence of new strains. The aim of this study is the genetic and antigenic evaluation of FMDV type O isolates from different outbreak areas including Alborz, Tehran, Isfahan, Markazi, Zahedan, and Qom provinces. For this purpose, 71 FMD-infected samples were collected from six provinces of Iran, of which 12 serotype O positive were selected for genetic analysis. All samples were in ME-SA topotypes/OPanAsia2 lineage, and the overall mean of genetic diversities at the 1D gene level was about 5% between the sequences. Blasting 1D gene sequences of isolated viruses showed more than 90% genetic identity with sequences registered from neighboring countries; therefore, it could be concluded that they had a common origin. Six isolates showed the highest genetic diversity (6% to 11%) with the OPanAsia2 vaccine strain (JN676146), which three of them (Qom, Alborz, and Zahedan isolates), had less than 30% antigenic homology with the OPanAsia2 virus (JN676146). Results of this study suggested OPanAsia2 vaccine had no enough coverage with some circulating strains in outbreak areas in Qom, Alborz, and Zahedan provinces, and the necessity of OPanAsia2 replacement with a new vaccine strain in Iran.

Characterization of the O/ME-SA/Ind-2001d foot-and-mouth disease virus epidemic recorded in the Maghreb during 2014-2015.

The O/ME-SA/Ind-2001d has been the main foot-and-mouth disease virus (FMDV) lineage responsible for FMD epidemics outside the Indian subcontinent from 2013 to 2017. In 2014, outbreaks caused by this FMDV lineage were reported in Maghreb, where it was initially detected in Algeria and Tunisia and later in Morocco. This was the first incursion of an FMDV type O of exotic origin in the Maghreb region after 14 years of absence. In this study, we report analyses of both VP1 and whole-genome sequences (WGSs) generated from 22 isolates collected in Algeria and Tunisia between 2014 and 2015. All the WGSs analysed showed a minimum pairwise identity of 98.9% at the nucleotide level and 99% at the amino acid level (FMDV coding region). All Tunisian sequences shared a single putative common ancestor closely related to FMDV strains circulating in Libya during 2013. Whereas sequences from Algeria suggest the country experienced two virus introductions. The first introduction is represented by strains circulating in 2014 which are closely related to those from Tunisia, the second one, of which the origin is more uncertain, includes strains collected in Algeria in 2015 that gave origin to the 2015 outbreak reported in Morocco. Overall, our results demonstrated that a unique introduction of O/Ind-2001d FMDV occurred in Maghreb through Tunisia presumably in 2014, and from then the virus spread into Algeria and later into Morocco.

Development of a competitive ELISA method based on VLPs detecting the antibodies of serotype A FMDV

Foot-and-mouth disease (FMD) is the highly contagious disease of cloven-hoofed animal that brings considerable economic losses to the animal husbandry. So FMD surveillance which relying on accurate diagnosis is important. Most producing the diagnostic antigen of inactivated FMD virus (FMDV) requires facilities with high biosafety. In our previous studies, virus-like particles(VLPs) resembled the structures of natural virus particles. Here, we established a competitive ELISA (cELISA) method for the detection of antibodies against serotype A FMDV based on serotype A FMDV-VLPs. Via detecting different positive serum and negative serum with different titers, and comparing with different commercial ELISA kits. The specificity and sensitivity of the assay were 100 % and 98 %, respectively. The coincidence rate using the PrioCHECK® FMDV Type A antibody ELISA kit and Liquid-phase blocking (LPB) ELISA were 95.30 % and 92.2 %. Repetitive experiments showed that variation coefficient of intra-batch and inter-batch were less than 9 % and 13 %. The result demonstrated that cELISA based on VLPs from prokaryotic system is highly specific, sensitive and reproducible. The cELISA could also be used to assess the immune responses of serotype A FMDV, especially in developing countries.

Immunogenicity of Foot-and-Mouth Disease Virus Dendrimer Peptides: Need for a T-Cell Epitope and Ability to Elicit Heterotypic Responses.

An approach based on a dendrimer display of B- and T-cell epitopes relevant for antibody induction has been shown to be effective as a foot-and-mouth disease (FMD) vaccine. B2T dendrimers combining two copies of the major FMD virus (FMDV) type O B-cell epitope (capsid proteinVP1 (140–158)) covalently linked to a heterotypic T-cell epitope from non-structural protein 3A (21–35), henceforth B2T-3A, has previously been shown to elicit high neutralizing antibody (nAb) titers and IFN-γ-producing cells in both mice and pigs. Here, we provide evidence that the B- and T-cell epitopes need to be tethered to a single molecular platform for successful T-cell help, leading to efficient nAb induction in mice. In addition, mice immunized with a non-covalent mixture of B2T-3A dendrimers containing the B-cell epitopes of FMDV types O and C induced similarly high nAb levels against both serotypes, opening the way for a multivalent vaccine platform against a variety of serologically different FMDVs. These findings are relevant for the design of vaccine strategies based on B- and T-cell epitope combinations.

Effective Diagnosis of Foot-And-Mouth Disease Virus (FMDV) Serotypes O and A Based on Optical and Electrochemical Dual-Modal Detection.

Foot-and-mouth disease virus (FMDV) is a highly contagious disease that affects cloven-hoofed animals. The traditional diagnostic methods for FMDV have several drawbacks such as cross-reactivity, low sensitivity, and low selectivity. To overcome these drawbacks, we present an optical and electrochemical dual-modal approach for the specific detection of FMDV serotypes O and A by utilizing a magnetic nanoparticle labeling technique with resorufin β-d-glucopyranoside (res-β-glc) and β-glucosidase (β-glc), without the use of typical lateral flow assay or polymerase chain reaction. FMDV serotypes O and A were reacted with pan-FMDV antibodies that recognize all seven FMDV serotypes (O, A, C, Asia 1, SAT 1, SAT 2, and SAT 3). The antigen–antibody complex was then immobilized on magnetic nanoparticles and reacted with β-glc-conjugated FMDV type O or type A antibodies. Subsequently, the addition of res-β-glc resulted in the release of fluorescent resorufin and glucose owing to catalytic hydrolysis by β-glc. The detection limit of fluorescent signals using a fluorescence spectrophotometer was estimated to be log(6.7) and log(5.9) copies/mL for FMDV type O and A, respectively, while that of electrochemical signals using a glucometer was estimated to be log(6.9) and log(6.1) copies/mL for FMDV type O and A, respectively. Compared with a commercially available lateral flow assay diagnostic kit for immunochromatographic detection of FMDV type O and A, this dual-modal detection platform offers approximately four-fold greater sensitivity. This highly sensitive and accurate dual-modal detection method can be used for effective disease diagnosis and treatment, and will find application in the early-stage diagnosis of viral diseases and next-generation diagnostic platforms.

The rescue and selection of thermally stable type O vaccine candidate strains of foot-and-mouth disease virus.

Inactivated foot-and-mouth disease virus (FMDV) vaccines have been used widely to control foot-and-mouth disease (FMD). However, the virions (146S) of this virus are easily dissociated into pentamer subunits (12S), which limits the immune protective efficacy of inactivated vaccines when the temperature is higher than 30 °C. A cold-chain system can maintain the quality of the vaccines, but such systems are usually not reliable in limited-resource settings. Thus, it is imperative to improve the thermostability of vaccine strains to guarantee the quality of the vaccines. In this study, four recombinant FMDV strains containing single or multiple amino acid substitutions in the structural proteins were rescued using a previously constructed FMDV type O full-length infectious clone (pO/DY-VP1). We found that single or multiple amino acid substitutions in the structural proteins affected viral replication to different degrees. Furthermore, the heat and acid stability of the recombinant viruses was significantly increased when compared with the parental virus. Three thermally stable recombinant viruses (rHN/DY-VP1Y2098F, rHN/DY-VP1V2090A-S2093H, and rHN/DY-VP1V2090A-S2093H-Y2098F) were prepared as inactivated vaccines to immunize pigs. Blood samples were collected every week to prepare sera, and a virus neutralization test showed that the substitutions S2093H and Y2098F, separately or in combination, did not affect the immunogenicity of the virus, but the Y2098F mutation increased the thermostability significantly (p < 0.05). Therefore, the rHN/DY-VP1Y2098F mutant should be considered for use in future vaccines.

Phage Display Screening of Bovine Antibodies to Foot-and-Mouth Disease Virus and Their Application in a Competitive ELISA for Serodiagnosis.

For serodiagnosis of foot-and-mouth disease virus (FMDV), monoclonal antibody (MAb)-based competitive ELISA (cELISA) is commonly used since it allows simple and reproducible detection of antibody response to FMDV. However, the use of mouse-origin MAb as a detection reagent is questionable, as antibody responses to FMDV in mice may differ in epitope structure and preference from those in natural hosts such as cattle and pigs. To take advantage of natural host-derived antibodies, a phage-displayed scFv library was constructed from FMDV-immune cattle and subjected to two separate pannings against inactivated FMDV type O and A. Subsequent ELISA screening revealed high-affinity scFv antibodies specific to a serotype (O or A) as well as those with pan-serotype specificity. When BvO17, an scFv antibody specific to FMDV type O, was tested as a detection reagent in cELISA, it successfully detected FMDV type O antibodies for both serum samples from vaccinated cattle and virus-challenged pigs with even higher sensitivity than a mouse MAb-based commercial FMDV type O antibody detection kit. These results demonstrate the feasibility of using natural host-derived antibodies such as bovine scFv instead of mouse MAb in cELISA for serological detection of antibody response to FMDV in the susceptible animals.

The HSP70-fused foot-and-mouth disease epitope elicits cellular and humoral immunity and drives broad-spectrum protective efficacy

Current foot-and-mouth disease (FMD) vaccines have significant limitations, including side effects due to oil emulsions at the vaccination site, a narrow spectrum of protective efficacy, and incomplete host defenses mediated by humoral immunity alone. To overcome these limitations, new FMD vaccines must ensure improved safety with non-oil-based adjuvants, a broad spectrum of host defenses within/between serotypes, and the simultaneous induction of cellular and humoral immunity. We designed a novel, immune-potent, recombinant protein rpHSP70-AD that induces robust cellular immunity and elicits a broad spectrum of host defenses against FMD virus (FMDV) infections. We demonstrated that an oil emulsion-free vaccine containing rpHSP70-AD mediates early, mid-term, and long-term immunity and drives potent host protection against FMDV type O and A, suggesting its potential as an FMD vaccine adjuvant in mice and pigs. These results suggest a key strategy for establishing next-generation FMD vaccines, including novel adjuvants.

Diagnosis Based on 1D Gene Analysis of the Foot-And-Mouth Disease Virus

A foot and mouth disease (FMD) is an acute, febrile and high contagious viral disease in many cloven hoofed domestic animals and more than 70 wild ones, resulting in severe finantial loss throughout the world. Choosing the correct seeds for foot-and-mouth disease (FMD) is an important issue in protecting this disease, and it is urgently necessary to establish a plan for vaccination in areas affected by FMD and to protect new foot-and-mouth disease. The genetic diversity and antigenic diversity of foot-and-mouth disease virus (FMDV) make eradication through vaccination difficult. Variable antigenic types exist in different geographic areas, and research projects on existing antigenic types are necessary to select vaccine in such an environment. From this, in this paper, oligonucleotide primers for detection and Selecting Serotype of FMDV were newly designed and synthesized. In addition, the nucleotide sequence of the 1D gene was aligned, the mutation region was determined, and the homology and phylogenetic relationship of the nucleotide sequence were analyzed. The antigenicity of the FMDV type O strains in the Democratic People's Republic of Korea and the correspondence between them were examined. The neutralization reaction was used to examine antigenicity between FMDV to select waxy seeds. To prevent FMD through this primer design and experimental method, the nucleic acid of FMDV was amplified by RT-PCR. Then, the nucleotide sequence of the 1D gene corresponding to the virus VP1 protein was analyzed and compared to select a seed vaccine strain.

Genetic and Antigenic Evaluation of Foot-and-mouth Disease Virus Type A in the Endemic Area of Iran within 2014-2015.

The foot-and-mouth disease virus (FMDV) with a wide variety of genomes and complicated biology is one of the infectious agents that put the lives of animals at risk. Therefore, to introduce suitable strains for vaccine production, it is essential to constantly evaluate genetic changes of circulating viruses in field. Within 2014-2015, a total of 126 clinical specimens consisting of epithelial tissue and vesicular fluid from tongue, dental pad, and hoofs suspected of FMD virus were submitted to the Reference Laboratory for FMD in Razi Vaccine and Serum Research Institute, and 86 of them were identified as FMD virus type A using sandwich Enzyme-Linked Immunosorbent Assay (ELISA). This virus was isolated from 42 samples from 16 provinces using cell culture. Firstly, the coding region that produces the main part of viral capsid was amplified by Polymerase chain reaction (PCR). This part of the genome by 800 bp length was related to the 1D gene that synthesizes the VP1 protein. The phylogenetic analysis of VP1 coding region determined two distinct genotypes with more than 15% nucleotide differences. The first cluster consisted of closely related viruses registered in the GeneBank of neighboring countries, including Afghanistan, Pakistan, and Turkey. All samples in Cluster1 were determined as relative viruses with genotype Iran-05. In-vitro serological examination indicated an antigenic relationship between Cluster 1 viruses and routine vaccine strain (A-IRN-2013). The second cluster with only two members was genetically far from earlier ones and could be considered a separate genotype. Furthermore, it was revealed that cluster 2 has not been previously reported in Iran. Genetic tracing indicated that these viruses might have been originated from circulating viruses from India. Antigenic evaluation exhibited that this group could not be cross-protected by the routine vaccinal strain (A-IRN-2013) used during the research period.

Development of Monoclonal Antibody Specific to Foot-and-Mouth Disease Virus Type A for Serodiagnosis.

Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease affecting cloven-hoofed livestock worldwide. FMD virus (FMDV) type A is one of the most common causes of FMD outbreaks among the seven FMDV serotypes, and its serological diagnosis is therefore important to confirm FMDV type A infection and to determine FMD vaccine efficacy. Here, we generated monoclonal antibodies (mAbs) specific to FMDV type A via hybridoma systems using an inactivated FMDV type A (A22/Iraq/1964) and found 4 monoclones (#29, #106, #108, and #109) with high binding reactivity to FMDV type A among 594 primary clones. In particular, the #106 mAb had a higher binding reactivity to the inactivated FMDV type A than the other mAbs and a commercial mAb. Moreover, the #106 mAb showed no cross-reactivity to inactivated FMDV type South African territories 1, 2, and 3, and low reactivity to inactivated FMDV type O (O1 Manisa). Importantly, the solid-phase competitive ELISA (SPCE) using horseradish peroxidase (HRP)-conjugated #106 mAb detected FMDV type A-specific Abs in sera from FMD type A-vaccinated cattle more effectively than a commercial SPCE. These results suggest that the newly developed FMDV type A-specific mAb might be useful for diagnostic approaches for detecting Abs against FMDV type A.

Artificially designed hepatitis B virus core particles composed of multiple epitopes of type A and O foot-and-mouth disease virus as a bivalent vaccine candidate.

Recently, many countries, including China, have experienced a series of type A and O foot-and-mouth disease virus (FMDV) epidemics, causing serious economic losses. Although concerns about the safety of inactivated FMD vaccines have been raised, the development of a safe and effective subunit vaccine is necessary. We constructed two chimeric virus-like particles (VLPs; rHBc/AO and rHBc/AOT VLPs) displaying tandem repeats of B cell epitopes (VP1 residue 134-161 and 200-213) derived from type A and O FMDV and one T cell epitope (3 A residue 21-35) using the truncated hepatitis B virus core (HBc) carrier. Our results indicate that the chimeric HBc can self-assemble into VLPs with these FMDV epitopes displayed on the surface. Immunization with the chimeric VLPs induced specific IgG and neutralization antibodies against type A and O FMDV in mice. Compared with the commercial type A/O FMDV bivalent inactivated vaccine, rHBc/AO and rHBc/AOT VLPs significantly stimulated the production of Th1 type cytokines (IFN-γ and IL-2), whereas Th2 cytokine production (IL-4 and IL-10) was decreased. Compared with rHBc/AO, rHBc/AOT induced increased Th2 cytokine and specific IgG production. These results demonstrate that the VLPs constructed in the current study induced both humoral and cellular immune responses and may represent potential bivalent VLP vaccines targeting both FMDV type A and O strains.

Оптимизация условий постановки ИФА для диагностики вируса ящура типа А

By concentration of PEG-6000 and purification with chloroform, strain "Talasskiy" of FMD virus type A is prepared with purified antigens, the activity of which was in CBR 1:32-1:64. For diagnostic sera antigens were subjected to additional purification after 30% sucrose cushion at 35,000 rpm for 2 hours. After purification, the antigen activity was 1:16-1: 32. Using purified antigen of FMD virus type A antiserums on sheep, pigs and rabbits with activity 1:8-1:64 were obtained. From antisera by Kohn isolated immunoglobulin, whose activity in the DPR was 1: 32, and the protein concentration ranging from 41.84 mg / ml to 60.2 mg / ml. Periodate using the method of M. B. Wilson, P. K. Nakane on the basis of specific porcine globulin conjugate prepared to optimize the conditions of production ELISA. The prepared diagnostic preparations are used to optimize the conditions for the formulation of ELISA for the diagnosis of FMD type A. The optimized version of ELISA proved to be sensitive and effective in the study of heterogeneous and homogeneous biomaterials. Key words: FMD type A, immunoassay, immunoglobulin, immunization, antigen

Development and validation of a competitive ELISA based on bacterium-original virus-like particles of serotype O foot-and-mouth disease virus for detecting serum antibodies.

Foot-and-mouth disease (FMD) is a highly contagious disease that affects all susceptible cloven-hoofed animals, resulting in considerable economic losses to animal industries worldwide. Numerous categories of enzyme-linked immunosorbent assays (ELISA) have been developed and widely used to evaluate herd immunity. Manufacturing inactivated FMD virus (FMDV) as a diagnostic antigen requires a facility with a high level of biosafety, but this requirement raises concern on viral leakage. In our previous study, bacterium-original FMD virus-like particles (VLPs) resemble the authentic FMDV and induce protective immunity against homologous viral challenges, thereby demonstrating that they are sufficiently safe without limitations on biosafety facilities and easily prepared. Herein, we developed a competitive ELISA (cELISA) based on FMDV-VLPs as a diagnostic antigen to evaluate herd immunity. The criterion of this cELISA was determined by detecting panels of positive sera with different antibody titers and negative sera. The working parameter of cELISA was optimized, and samples with a percentage inhibition of ≥ 50% were considered positive. The specificity of cELISA to test 277 serum samples with various antibody titers was 100%, and the sensitivity reached 96%. The coincidence rates of cELISA with a VDPro® FMDV and a PrioCHECK® FMDV type O antibody ELISA kit were 97.8% and 98.2%, respectively. Repeatability tests demonstrated that the coefficients of variation within and between runs were less than 7% and 14%, respectively. Our data demonstrated that cELISA based on bacterium-original VLPs had high specificity, sensitivity, and reproducibility. The cELISA could also be used for evaluating vaccination herd immunity effects, especially in developing countries.

A Study on effectiveness of a cocktail of protected feed additives in growing pigs

The objective of the study was to determine the effects of mixer of protected feed additives (MFA) on growth performance, blood metabolites, fecal microflora counts, and immune responses in growing pigs. A total of 150 pigs [(Landrace×Yorkshire)×Duroc] with an initial body weight (BW) of 25.61 ± 0.01 kg were used in a 4-week feeding trial. Pigs were allotted to one of five diet groups (basal diet supplemented with 0%, 0.35%, 0.75%, 1.50%, or 3.0% of MFA with 6 replicates per group and 5 pigs/replicate). Inclusion of MFA tended (P=0.085) to results in a linear increase in BW at week 4 and overall average daily gain (ADG, P=0.064). However, MFA inclusion had no effect on average daily feed intake or gain:feed ratio during the entire experiment period. When 3% MFA was added to the diet, reduction was observed for cortisol level (P=0.032) and low-density lipoprotein cholesterol (P=0.008) at 4 weeks after dietary treatments. The inclusion of MFA had positive effects on fecal score at week 3 and 4 (P=0.068, 0.023, respectively) and the count of Lactobacillus was increased at the end of week 1 and 4 (P=0.099, 0.014, respectively), whereas for E. coli decreased at the end of week 1 and 4 (P=0.043, 0.067, respectively). Type O antibody titres against foot-and-mouth disease virus (FMDV) in growing pigs fed diet supplemented with MFA (1.5%) was significantly (P=0.008) higher than other dietary treatment groups. In conclusion, inclusion of MFA in growing pigs diet may improve ADG, beneficial fecal microflora counts and FMDV type O antibody titre after vaccination and reduced cortisol level, LDL/C and incidences of diarrhoea.

SPREAD OF THE TYPE A FOOT-AND-MOUTH DISEASE VIRUS IN THE MIDDLE EAST

The article presents the official information on the epizootic situation of FMD type А in the Middle East: Saudi Arabia, Iran, Armenia and Turkey in the period 2005-2017. Analyzing the number of outbreaks of FMD in these countries, it was found that, despite strict preventive measures associated with regular vaccination of susceptible animals, the main cause of the disease - the appearance of new genetic lines of topotype Asia: A/Iran-05 and G-VII, antigenically different from the production of FMD virus strains used in the vaccine. In this region, phylogenetic drift among the population of FMD type a virus manifests itself not only in the appearance of new lines, but also new sublines within the same line. . This is due, first of all, to the tense political situation in the region, when, due to uncontrolled migration of people and animals, there is a close contact of FMD-susceptible domestic and wild animals of different species and the alternate transmission of the virus to them. Due to the existing danger of spreading the virus in the countries of Central Asia and the Caucasus it is necessary to conduct studies on the selection and training of new relevant in respect of production of epizootic strains of FMD virus type A for inclusion in the composition of foot and mouth disease vaccine.