FMD vaccines

Disease Investigations & Initial Response: Considerations from Policy to Farm

Transboundary animal disease (TAD) investigations are conducted routinely across the United States to rule out diseases of significant economic, trade, and/or food security importance. Established protocols exist for TAD investigations and disease response based on national and international policy; however, now more than ever, private practitioners may be called upon to assist in these investigations and response activities and may play an important role in communications, sample collection, and disease surveillance. Successful implementation of disease investigation and response, with or without vaccination, requires a collaborative effort between regulatory officials, industry groups, private practitioners, and producers.

Prophylactic treatment with PEGylated bovine IFNλ3 effectively bridges the gap in vaccine-induced immunity against FMD in cattle

Foot-and-mouth disease (FMD) is a vesicular disease of cloven-hoofed animals with devastating economic implications. The current FMD vaccine, routinely used in enzootic countries, requires at least 7 days to induce protection. However, FMD vaccination is typically not recommended for use in non-enzootic areas, underscoring the need to develop new fast-acting therapies for FMD control during outbreaks. Interferons (IFNs) are among the immune system's first line of defense against viral infections. Bovine type III IFN delivered by a replication defective adenovirus (Ad) vector has effectively blocked FMD in cattle. However, the limited duration of protection-usually only 1-3 days post-treatment (dpt)-diminishes its utility as a field therapeutic. Here, we test whether polyethylene glycosylation (PEGylation) of recombinant bovine IFNλ3 (PEGboIFNλ3) can extend the duration of IFN-induced prevention of FMDV infection in both vaccinated and unvaccinated cattle. We treated groups of heifers with PEGboIFNλ3 alone or in combination with an adenovirus-based FMD O1Manisa vaccine (Adt-O1M) at either 3 or 5 days prior to challenge with homologous wild type FMDV. We found that pre-treatment with PEGboIFNλ3 was highly effective at preventing clinical FMD when administered at either time point, with or without co-administration of Adt-O1M vaccine. PEGboIFNλ3 protein was detectable systemically for >10 days and antiviral activity for 4 days following administration. Furthermore, in combination with Adt-O1M vaccine, we observed a strong induction of FMDV-specific IFNγ+ T cell response, demonstrating its adjuvanticity when co-administered with a vaccine. Our results demonstrate the promise of this modified IFN as a pre-exposure prophylactic therapy for use in emergency outbreak scenarios.

Kinetics of foot-and-mouth disease vaccine-induced antibody responses in buffaloes (Bubalus bubalis): avidity ELISA as an alternative to the virus neutralization test

The role of water buffaloes in foot-and-mouth disease (FMD) epidemiology as one of the major hosts of the virus that can develop persistent asymptomatic infection highlights the importance of sustaining surveillance on the antibody response elicited by vaccination in these animals. There is gap in the knowledge on how serological assays that measure antibodies against capsid proteins perform with buffalo samples and which would be the most reliable test to substitute the virus neutralization test (VNT) a cumbersome and low-throughput tool for field surveillance. Alternatively, the liquid-phase blocking sandwich ELISA (LPBE) is commonly used. Previous data from our laboratory demonstrated that the vaccine-induced antibodies assessed by the LPBE yielded low specificity with buffaloes' samples. In contrast, a single-dilution avidity ELISA (AE) aimed to detect high-avidity antibodies against exposed epitopes, combined with an indirect ELISA (IE) to assess IgG levels, produced more reliable results. Here we analyzed for the first time the kinetics of the antibodies induced by vaccination in two different buffalo herds (n = 91) over 120 days using AE, IE, LPBE, and the VNT. Kinetics were similar in the different assays, with an increase of antibodies between 0- and 14-days post-vaccination (dpv) which were maintained thereafter. VNT and AE results were concordant (Kappa value = 0.76), and both assays revealed a decay in the antibody response in calves with maternal antibodies at 90 and 120 dpv, which was not evidenced by the LPBE. These results show that kinetics of antibody responses to FMD vaccination are similar in buffalo and cattle, and support the use of indirect ELISA assays, in particular Avidity ELISA, as alternatives to the VNT for vaccine-immunity monitoring irrespectively of the animal's passive or active immune status.

Broad immunogenic spectrum of monovalent and trivalent foot-and-mouth disease virus vaccines containing O1 campos, A24 cruzeiro and A Argentina 2001 strains against circulating viral lineages in cattle and pigs

FMD remains endemic in many Asian and African countries where multiple variants of serotypes O and A, among others, currently circulate. Due to lack of cross-protection between serotypes and incomplete protection between some strains even within a serotype, an important challenge for the application of effective vaccination programs is to select highly immunogenic and widely cross-reactive vaccine strains. Adaptation of a candidate field virus for use as a vaccine can be quite complex, so that whenever possible, the use of well-established vaccine viruses could have enormous advantages. FMD vaccine strains harmonized for use in South America have shown excellent results in FMD control, not only in the region, where it is still used systematically as a preventive measure, but also more recently in some Asian countries. To gain further insight into the immunogenic spectrum of these strains, VN tests (VNT) were performed with sera from cattle and/or pigs vaccinated with monovalent (type O) or trivalent (types O and A) formulations against 122 type O and 32 type A field viruses isolated from 35 countries in Asia and Africa, belonging to different lineages. Almost all VNT titers obtained were within the expected protective level, indicating the wide immunogenic spectrum of high potency FMD vaccines formulated with O1 Campos, A24 Cruzeiro and A Argentina 2001 South American vaccine strains belonging to EURO-SA topotypes against currently active viruses from other topotypes. These in vitro results are in line with previously reported in vivo challenge tests in pigs against three A/ASIA/Sea-97 isolates and two isolates belonging to type O lineages O/SEA/Mya-98 and O/ME-SA/Ind-2001e.

Production of Foot-and-Mouth Disease Type O and A Vaccine Antigens on a Pilot Scale and Determination of Optimal Amount of Antigen for Monovalent Vaccines

Foot-and-mouth disease (FMD) is a highly infectious disease affecting cloven-hoofed animals and causes significant economic losses to the livestock industry. The Type O PanAsia-2 (O PA-2) vaccine strain is protective against a wide range of serotype O FMD virus (FMDV) strains in East Asia, and A22 Iraq/24/64 (A22 IRQ) is the most widely used vaccine strain in FMD vaccine antigen banks. The aim of this study was to produce antigens from O PA-2 and A22 IRQ viruses using a 100 L bioreactor and evaluate the protective efficacy of varying antigen concentrations in pigs. More than 2 μg/mL of the antigen was recovered from the O PA-2 and A22 IRQ virus-infected supernatants. Further, inactivation of O PA-2 and A22 IRQ by binary ethyleneimine revealed that the viral titers decreased below 10^-7 TCID₅₀/mL within 13 h and 9 h, respectively. The O PA-2 and A22 IRQ vaccines, containing 10 μg and 5 μg of antigen, respectively, provided protection against homologous viruses in pigs. This is the first report demonstrating that the antigens obtained from the pilot-scale production of O PA-2 and A22 IRQ are viable candidate vaccines. These results will pave the way for industrial-scale FMD vaccine production in South Korea.

Comparison of vaccination schedules for foot-and-mouth disease among cattle and sheep in Mongolia

Vaccines are a critical tool for the control strategy for foot-and-mouth disease (FMD) in Mongolia where sporadic outbreaks regularly occur. A two-dose primary vaccination course is recommended for most commercial vaccines though this can be logistically challenging to deliver among nomadic pastoralist systems which predominate in the country. Although there is evidence that very high potency vaccines can provide prolonged duration of immunity, this has not been demonstrated under field conditions using commercially available vaccines. This study compared neutralizing titres to a O/ME-SA/Panasia strain over a 6-month period following either a two-dose primary course or a single double-dose vaccination among Mongolian sheep and cattle using a 6.0 PD50 vaccine. Titers were not significantly different between groups except in sheep at six-months post vaccination when the single double-dose group had significantly lower titers. These results indicate the single double-dose regimen may be a cost-effective approach for vaccination campaigns supporting FMD control in Mongolia.

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.

Molecular evolution, diversity, and adaptation of foot-and-mouth disease virus serotype O in Asia

Foot-and-mouth disease (FMD) is highly contagious and affects the economy of many countries worldwide. Serotype O is the most prevalent and is present in many regions of Asia. Lineages O/SEA/Mya-98, O/Middle East-South Asia (ME-SA)/PanAsia, O/Cathay and O/ME-SA/Ind-2001 have been circulating in Asian countries. Low antigenic matching between O/Cathay strains and current vaccine strains makes the disease difficult to control, therefore, analyzing the molecular evolution, diversity, and host tropisms of FMDV Serotype O in Asia may be helpful. Our results indicate that Cathay, ME-SA, and SEA are the predominant topotypes of FMDV serotype O circulating in Asia in recent years. Cathay topotype FMDV evolves at a higher rate compared with ME-SA and SEA topotypes. From 2011 onwards, the genetic diversity of the Cathay topotype has increased substantially, while large reductions were found in the genetic diversity of both ME-SA and SEA topotypes, suggesting a trend that infections sustained by the Cathay topotype were becoming a more severe epidemic in recent years. Analyzing the distributions of host species through time in the dataset, we found that the O/Cathay topotype was characterized by a highly swine-adapted tropism in contrast with a distinct host preference for O/ME-SA. The O/SEA topotype strains identified in Asia were isolated mainly from cattle until 2010. It is worth noting that there may be a fine-tuned tropism of the SEA topotype viruses for host species. To further explore the potential molecular mechanism of host tropism divergence, we analyzed the distribution of structure variations on the whole genome. Our findings suggest that deletions in the PK region may reflect a common pattern of altering the host range of serotype O FMDVs. In addition, the divergence of host tropism may be due to accumulated structural variations across the viral genome, rather than a single indel mutation.

Characterisation of capsid polypeptide P1 and capsid protein VP1 of the Malaysia foot and mouth disease virus (FMDV) serotype O and A isolates

Foot and mouth disease virus (FMDV) is the cause of foot and mouth disease (FMD) outbreaks in livestock worldwide, which affects domestic and international trade, resulting in significant economic losses and social consequences. For efficient monitoring and prevention of FMD outbreaks, the need for improved strategies to control FMDV and achieve FMD-free status with various control measures including vaccination can be established. In vaccinology, major advances and discoveries in vaccination variations including DNA and protein subunit vaccines proved to be more economical and sustainable. To develop a safe vaccine for animals, possible antigenic genes or antigens need to be identified and characterised. The FMDV is a single-stranded RNA virus consisting of a capsid precursor polypeptide, P1, which encodes for four structural proteins (VP4-1), leading to antigenic variation and VP1 potentially carrying the key epitope for vaccine development. This study aims to identify and characterise the capsid polypeptide, P1 and capsid protein, VP1 of the Malaysian FMDV serotype O and serotype A isolates. The nucleotide and protein sequences were identified based on the FMD outbreaks in Malaysia and the antigenicity of the P1 and VP1 was predicted by Kolaskar and Tongaonkar's semi-empirical method. Subsequently, the P1 and VP1 genes were inserted into pET-28a, respectively, and used for protein expression analysis. The P1 and VP1 were predicted to be antigenic via in silico analysis and successfully expressed and characterised through in vitro analysis. Hence, this study can be exploited as a tool to design a new novel vaccine for vaccine development against FMD in bovines.

Evaluation of Vaccine Strains Developed for Efficient, Broad-Range Protection against Foot-and-Mouth Disease Type O

Foot-and-mouth disease (FMD) type O includes 11 genetic topotypes. The Southeast Asia (SEA), Middle East-South Asia (ME-SA), and Cathay topotypes belong to FMD type O and occur frequently in Asia. Therefore, it is necessary to develop a potent vaccine strain with a broad antigenic coverage in order to provide complete protection against these three topotypes. In this study, an experimental vaccine was produced using chimeric vaccine strains (JC-VP1 or PA2-VP1) that contained VP4, VP2, and VP3 of the ME-SA topotype (O Manisa) and VP1 of the SEA topotype (Mya98 lineage; O/SKR/Jincheon/2014) or ME-SA topotype (PanAsia2 lineage; O/PAK/44). Mice were immunized with the experimental vaccines, and they were fully protected against the three topotypes. The neutralizing antibody titers of PA2-VP1 were significantly higher than those of JC-VP1 in the early vaccination phase in pigs. Here, we confirmed complete protection in pigs vaccinated with JC-VP1 or PA2-VP1, when challenged against the SEA (O/SKR/Jincheon/2014), ME-SA (O/SKR/Boeun/2017) and Cathay (O/Taiwan/97) topotype viruses, with moderately higher protection provided by PA2-VP1 than by JC-VP1.

The Parallel Presentation of Two Functional CTL Epitopes Derived from the O and Asia 1 Serotypes of Foot-and-Mouth Disease Virus and Swine SLA-2*HB01: Implications for Universal Vaccine Development

Foot-and-mouth disease virus (FMDV) poses a significant threat to the livestock industry. Through their recognition of the conserved epitopes presented by the swine leukocyte antigen (SLA), T cells play a pivotal role in the antiviral immunity of pigs. Herein, based on the peptide binding motif of SLA-2*HB01, from an original SLA-2 allele, a series of functional T-cell epitopes derived from the dominant antigen VP1 of FMDV with high binding capacity to SLA-2 were identified. Two parallel peptides, Hu64 and As64, from the O and Asia I serotypes, respectively, were both crystallized with SLA-2*HB01. Compared to SLA-1 and SLA-3, the SLA-2 structures showed the flexibility of residues in the P4, P6, and P8 positions and in their potential interface with TCR. Notably, the peptides Hu64 and As64 adopted quite similar overall conformation when bound to SLA-2*HB01. Hu64 has two different conformations, a more stable 'chair' conformation and an unstable 'boat' conformation observed in the two molecules of one asymmetric unit, whereas only a single 'chair' conformation was observed for As64. Both Hu64 and As64 could induce similar dominant T-cell activities. Our interdisciplinary study establishes a basis for the in-depth interpretation of the peptide presentation of SLA-I, which can be used toward the development of universal vaccines.

Mutation of FMDV Lpro H138 residue drives viral attenuation in cell culture and in vivo in swine

The foot-and-mouth disease virus (FMDV) leader proteinase (L^pro) is a papain like protease that cleaves the viral polyprotein and several host factors affecting host cell translation and induction of innate immunity. Introduction of L^pro mutations ablating catalytic activity is not tolerated by the virus, however, complete coding sequence deletion or introduction of targeted amino acid substitutions can render viable progeny. In proof-of-concept studies, we have previously identified and characterized FMDV L^pro mutants that are attenuated in cell culture and in animals, while retaining their capacity for inducing a strong adaptive immunity. By using molecular modeling, we have now identified a His residue (H138), that resides outside the substrate binding and catalytic domain, and is highly conserved across serotypes. Mutation of H138 renders possible FMDV variants of reduced virulence in vitro and in vivo. Kinetics studies showed that FMDV A12-L_H138L mutant replicates similarly to FMDV A12-wild type (WT) virus in cells that do not offer immune selective pressure, but attenuation is observed upon infection of primary or low passage porcine epithelial cells. Western blot analysis on protein extracts from these cells, revealed that while processing of translation initiation factor eIF-4G was slightly delayed, no degradation of innate sensors or effector molecules such as NF-κB or G3BP2 was observed, and higher levels of interferon (IFN) and IFN-stimulated genes (ISGs) were induced after infection with A12-L_H138L as compared to WT FMDV. Consistent with the results in porcine cells, inoculation of swine with this mutant resulted in a mild, or in some cases, no clinical disease but induction of a strong serological adaptive immune response. These results further support previous evidence that L^pro is a reliable target to derive numerous viable FMDV strains that alone or in combination could be exploited for the development of novel FMD vaccine platforms.

Epidemiologic and economic considerations regarding persistently infected cattle during vaccinate-to-live strategies for control of foot-and-mouth disease in FMD-free regions

Development of a foot-and-mouth disease (FMD) carrier state following FMD virus (FMDV) infection is a well-established phenomenon in cattle. However, the proportion of cattle likely to become carriers and the duration of the carrier state at a herd or population-level are incompletely understood. The objective of this study was to examine the epidemiologic and economic impacts of vaccination-to-live strategy in a disease-free region or country. We developed and simulated scenarios of FMD spread and control in the US livestock population, which included depopulation for a limited period, followed by a vaccinate-to-live strategy with strong biosecurity and movement restrictions. Six scenarios of FMD spread and control were simulated in the InterSpread Plus (ISP) modeling tool. Data on the number of infected and depopulated cattle (by operation types) from ISP model runs were used to estimate the monthly number of infected but not depopulated (potential carrier) cattle after the infection. Using available literature data on the FMD carrier state, we estimated the monthly proportion of carrier cattle (from infected but not depopulated cattle) over time following infection. Among the simulated scenarios, the median (25th, 75th percentile) number of infected cattle ranged from 43,217 (42,819, 55,274) head to 148,907 (75,819, 205,350) head, and the epidemic duration ranged from 20 (11, 30) to 76 (38, 136) days. In general, larger outbreaks occurred when depopulation was carried out through longer periods, and the onset of the vaccination was late (p > 0.05). The estimated proportion of surviving cattle, which were infected and not depopulated and had the potential to become persistently infected ranged from 14 to 35% of total infected cattle. Production losses in beef and dairy sectors were higher when outbreaks started in multiple states simultaneously, but production losses were small compared to trade losses and consumer avoidance losses. These results can be used to inform the consideration of a vaccinate-to-live strategy for FMD outbreaks and the development of appropriate post-outbreak management strategies. Furthermore, this output will enable a more detailed examination of the epidemiologic and economic implications of allowing convalescent cattle to survive and remain in production chains after FMD outbreaks in FMD-free regions.

Investigation of foot and mouth disease virus and other animal pathogens in cattle, buffaloes and goats at the interface with Akagera National Park 2017 – 2020

Background

Foot-and-Mouth Disease Virus (FMDV) is a positive-sense RNA virus of the family of the picornaviridæ that is responsible for one of the livestock diseases with the highest economic impact, the Foot-and-Mouth Disease (FMD). FMD is endemic in Rwanda but there are gaps in knowing its seroprevalence and molecular epidemiology. This study reports the FMD seroprevalence and molecular characterization of FMDV in Eastern Rwanda.

Results

The overall seroprevalence of FMD in the study area is at 9.36% in cattle and 2.65% in goats. We detected FMDV using molecular diagnostic tools such as RT-PCR and RT-LAMP and the phylogenetic analysis of the obtained sequences revealed the presence of FMDV serotype SAT 2, lineage II. Sequencing of the oropharyngeal fluid samples collected from African buffaloes revealed the presence of Prevotela ruminicola, Spathidium amphoriforme, Moraxella bovoculi Onchocerca flexuosa, Eudiplodinium moggii, Metadinium medium and Verrucomicrobia bacterium among other pathogens but no FMDV was detected in African buffaloes.

Conclusions

We recommend further studies to focus on sampling more African buffaloes since the number sampled was statistically insignificant to conclusively exclude the presence or absence of FMDV in Eastern Rwanda buffaloes. The use of RT-PCR alongside RT-LAMP demonstrates that the latter can be adopted in endemic areas such as Rwanda to fill in the gaps in terms of molecular diagnostics. The identification of lineage II of SAT 2 in Rwanda for the first time shows that the categorised FMDV pools as previously established are not static over time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03430-1.

A novel strategy for developing vaccine candidate against Jaagsiekte sheep retrovirus from the envelope and gag proteins: an in-silico approach

BACKGROUND

Sheep pulmonary adenocarcinoma (OPA) is a contagious lung cancer of sheep caused by the Jaagsiekte retrovirus (JSRV). OPA typically has a serious economic impact worldwide. A vaccine has yet to be developed, even though the disease has been globally spread, along with its complications. This study aimed to construct an effective multi-epitopes vaccine against JSRV eliciting B and T lymphocytes using immunoinformatics tools.

RESULTS

The designed vaccine was composed of 499 amino acids. Before the vaccine was computationally validated, all critical parameters were taken into consideration; including antigenicity, allergenicity, toxicity, and stability. The physiochemical properties of the vaccine displayed an isoelectric point of 9.88. According to the Instability Index (II), the vaccine was stable at 28.28. The vaccine scored 56.51 on the aliphatic index and -0.731 on the GRAVY, indicating that the vaccine was hydrophilic. The RaptorX server was used to predict the vaccine's tertiary structure, the GalaxyWEB server refined the structure, and the Ramachandran plot and the ProSA-web server validated the vaccine's tertiary structure. Protein-sol and the SOLPro servers showed the solubility of the vaccine. Moreover, the high mobile regions in the vaccine's structure were reduced and the vaccine's stability was improved by disulfide engineering. Also, the vaccine construct was docked with an ovine MHC-1 allele and showed efficient binding energy. Immune simulation remarkably showed high levels of immunoglobulins, T lymphocytes, and INF-γ secretions. The molecular dynamic simulation provided the stability of the constructed vaccine. Finally, the vaccine was back-transcribed into a DNA sequence and cloned into a pET-30a ( +) vector to affirm the potency of translation and microbial expression.

CONCLUSION

A novel multi-epitopes vaccine construct against JSRV, was formed from B and T lymphocytes epitopes, and was produced with potential protection. This study might help in controlling and eradicating OPA.

Assessment on Different Vaccine Formulation Parameters in the Protection against Heterologous Challenge with FMDV in Cattle

Foot-and-mouth disease (FMD) remains one of the major threats to animal health worldwide. Its causative agent, the FMD virus (FMDV), affects cloven-hoofed animals, including farm animals and wildlife species, inflicting severe damage to the international trade and livestock industry. FMDV antigenic variability remains one of the biggest challenges for vaccine-based control strategies. The current study analyzed the host’s adaptive immune responses in cattle immunized with different vaccine protocols and investigated its associations with the clinical outcome after infection with a heterologous strain of FMDV. The results showed that antigenic payload, multivalency, and revaccination may impact on the clinical outcome after heterologous challenge with FMDV. Protection from the experimental infection was related to qualitative traits of the elicited antibodies, such as avidity, IgG isotype composition, and specificity diversity, modulating and reflecting the vaccine-induced maturation of the humoral response. The correlation analyses of the serum avidity obtained per vaccinated individual might suggest that conventional vaccination can induce high-affinity immunoglobulins against conserved epitopes even within different FMDV serotypes. Cross-reaction among strains by these high-affinity antibodies may support further protection against a heterologous infection with FMDV.

BacMam Expressing Highly Glycosylated Porcine Interferon Alpha Induces Robust Antiviral and Adjuvant Effects against Foot-and-Mouth Disease Virus in Pigs

Foot-and-mouth disease (FMD) is an acute contagious disease that affects cloven-hoofed animals and has severe global economic consequences. FMD is most commonly controlled by vaccination. Currently available commercial FMD vaccines contain chemically inactivated whole viruses, which are thought to be slow acting as they are effective only 4 to 7 days following vaccination. Hence, the development of a novel rapid vaccine or alternative measures, such as antiviral agents or the combination of vaccines and antiviral agents for prompt FMD virus (FMDV) outbreak containment, is desirable. Here, we constructed a recombinant baculovirus (BacMam) expressing consensus porcine interferon alpha (IFN-α) that has three additional N-glycosylation sites driven by a cytomegalovirus immediate early (CMV-IE) promoter (Bac-Con3N IFN-α) for protein expression in mammalian cells. Bac-Con3N IFN-α expressing highly glycosylated porcine IFN-α protein increased the duration of antiviral effects. We evaluated the antiviral effects of Bac-Con3N IFN-α in swine cells and mice and observed sustained antiviral effects in pig serum; additionally, Bac-Con3N IFN-α exhibited sustained antiviral effects in vivo as well as adjuvant effects in combination with an inactivated FMD vaccine. Pigs injected with a combination of Bac-Con3N IFN-α and the inactivated FMD vaccine were protected against FMDV at 1, 3, and 7 days postvaccination. Furthermore, we observed that in combination with the inactivated FMD vaccine, Bac-Con3N IFN-α increased neutralizing antibody levels in mice and pigs. Therefore, we suggest that Bac-Con3N IFN-α is a strong potential antiviral and adjuvant candidate for use in combination with inactivated FMD vaccines to protect pigs against FMDV. IMPORTANCE Early inhibition of foot-and-mouth disease (FMD) virus (FMDV) replication in pigs is highly desirable as FMDV transmission and shedding rates are higher in pigs than in cattle. However, commercial FMD vaccines require at least 4 to 7 days postvaccination (dpv) for protection, and animals are vulnerable to heterologous viruses before acquiring high antibody levels after the second vaccination. Therefore, the development of antiviral agents for use in combination with FMD vaccines is essential. We developed a novel antiviral and immunostimulant, Bac-Con3N IFN-α, which is a modified porcine IFN-α-expressing recombinant baculovirus, to improve IFN stability and allow its direct delivery to animals. We present a promising candidate for use in combination with inactivated FMD vaccines as pigs applied to the strategy had early protection against FMDV at 1 to 7 dpv, and their neutralizing antibody levels were higher than those in pigs administered the vaccine only.

Evaluation of Immunoreactivity and Protection Efficacy of Seneca Valley Virus Inactivated Vaccine in Finishing Pigs Based on Screening of Inactivated Agents and Adjuvants

Seneca Valley virus (SVV), also known as Senecavirus A (SVA), is a non-enveloped and single-strand positive-sense RNA virus, which belongs to the genus of Senecavirus within the family Picornaviridae. Porcine idiopathic vesicular disease (PIVD) caused by SVV has frequently been prevalent in America and Southeast Asia (especially in China) since the end of 2014, and has caused continuing issues. In this study, an SVV strain isolated in China, named SVV LNSY01-2017 (MH064435), was used as the stock virus for the preparation of an SVV-inactivated vaccine. The SVV culture was directly inactivated using binary ethyleneimine (BEI) and β-propiolactone (BPL). BPL showed a better effect as an SVV inactivator, according to the results of pH variation, inactivation kinetics, and the detection of VP1 content during inactivation. Then, SVV inactivated by BPL was subsequently emulsified using different adjuvants, including MONTANIDE^TM ISA 201 VG (ISA 201) and MONTANIDE^TM IMG 1313 VG N (IMS 1313). The immunoreactivity and protection efficacy of the inactivated vaccines were then evaluated in finishing pigs. SVV-BPL-1313 showed a better humoral response post-immunization and further challenge tests post-immunization showed that both the SVV-BPL-201 and SVV-BPL-1313 combinations could resist challenge from a virulent SVV strain. The SVV LNSY01-2017-inactivated vaccine candidate developed here represents a promising alternative to prevent and control SVV infection in swine.

Susceptibility to foot and mouth disease virus infection in vaccinated cattle, and host BoLA A and BoLA DRB3 genes polymorphism

The vaccination of the susceptible animal population against FMDV remains the most important measure to control the virus and prevent economic loss. Occurrence of infection in vaccinated animals is well-known in some diseases and is termed as breakthrough infection. The reasons include host genetic factors which can play an important role resulting in differences in susceptibility of animals to virus infection even with vaccine induced protective immune response. The Major Histocompatibility Complex (MHC) of bovines i.e. Bovine Leukocyte Antigen (BoLA) is important for antigen presentation. The BoLA DRB3 allele, which codes for the beta chain in Class II antigen, has been extensively studied and numerous reports have previously shown association of polymorphism in the gene with resistance/ susceptibility to several bacterial and viral diseases. In addition, previous studies have shown relationship between BoLA Class I and resistance or susceptibility to different diseases in cattle. The present study investigated the polymorphism in BoLA DRB3 and BoLA gene sequences of host and their relation with breakthrough FMDV infection in vaccinated animals. The study has identified three polymorphic sites each in both the genes which correlate with evidence of recent infection indicating their role in determining susceptibility of vaccinated animals to FMDV infection. Our limited study was performed on a relatively small samples size collected from one region of country. Further validation would require more detailed investigations on larger sample size.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-021-00754-8.

Deciphering Molecular Dynamics of Foot and Mouth Disease Virus (FMDV): A Looming Threat to Pakistan’s Dairy Industry

Milk is seen as a chief source of protein and other biologically available nutrients for human beings. Pakistan, the fourth largest milk-producing country, is badly affected by the contagious transboundary apthoviral disease of ungulate animals; the foot and mouth disease (FMD) virus. FMD is endemic in Pakistan and has caused significant economic loss to the dairy industry in the form of a profound decrease in milk production and increased morbidity and deaths of dairy animals. Inclusively, the case fatality ratio of FMD was 15.11%. Of the seven FMDV serotypes, (O, A, C, Asia 1, SAT 1, SAT2, and SAT 3), three serotypes (O, A, and Asia-1) are endemic in Pakistan. Rapid and highly sensitive diagnostic tools are required for efficient control of this disease. Presently, FMD in the laboratory is diagnosed via ELISA and molecular approaches, i.e., RT-PCR. Serotype-specific RT-PCR analysis not only confirms ELISA serotyping results but can also be used for the screening of ELISA negative samples. Genotypically, FMDV serotype O has a topotype (Middle East–South Asia (ME–SA) and lineage PanAsia-2) that is reported frequently from different areas of Pakistan. Confirmed cases of serotype A and Asia-1 are also reported. The information gathered can be used for understanding the molecular epidemiology of FMD in Pakistan. Further studies on the molecular dynamics of FMD could be useful for ensuring the timely diagnosis of this deadly pathogen, which would ultimately be beneficial for the mass vaccination programs of FMD in Pakistan.

Development of a new serotyping ELISA for Toxoplasma gondii type II, type III and Africa 1 lineages using in silico peptide discovery methods, well categorized feline and human outbreak serum samples

BACKGROUND

Discovery of new Toxoplasma gondii serotyping epitopes is important due to reports showing the influence of genotype on the severity of toxoplasmosis. In Turkey, genotypes belonging to type II, type III and Africa 1 lineages were mainly detected. The present study focused on to find out epitopes with high discriminative capacity to serotype these genotypes using well characterized strains isolated from Turkey.

METHODS

To meet this objective, GRA6 and GRA7 genes were sequenced from strains belonging to the type II, III and Africa 1 lineages, and B cell epitopes inside these sequences were predicted by Bcepred and additional docking analysis was performed with B cell receptor. Based on these analyses, 22 peptides harboring lineage specific epitopes were synthesized. Then, the serotyping potency of these peptides was tested using peptide ELISA and well categorized serum samples collected from stray cats infected with genotypes of the different lineages type II (n:9), III (n:1) and Africa 1 (n:1). As a result of peptide-ELISA, a serotyping schema was constructed with peptides that show high discriminative capacity and this assay was validated by sera collected from humans after an outbreak (n:30) and mother/newborn pair sera (n:3). Later, the validated serotyping schema was used to serotype a larger group of human (n:38) and cat (n:24) sera.

RESULTS

Among 22 peptides, GRA6II/c, GRA7III/d, and GRA6 Africa 1/b epitopes have shown discriminative capacity. During the validation of peptide-ELISA, the serotype of toxoplasmosis outbreak and mother/newborn cases were detected to be serotype II. Moreover, the analyses in a larger group showed that serotype II was prevalent in humans and stray cats.

CONCLUSIONS

Overall, the results showed that the serotyping schema could be successfully used to serotype T. gondii infections caused by type II, III and Africa 1 genotype.

Booster administration can make a difference in the antibody response to intradermal foot-and-mouth disease vaccination in cattle

Foot-and-mouth disease (FMD) is a highly contagious and economically important viral disease of cloven-hoofed animals. Routine vaccination is one of the preferred methods of protection against this disease in endemic countries. For protective immunity against FMD, repeated immunizations with frequent administration are required. Intradermal immunization has many advantages over intramuscular administration of vaccines. In this study, a commercial tetravalent FMD vaccine adjuvanted with Montanide ISA 206 was administered to cattle via the intramuscular (2 mL [n = 10] and 0.5 mL [n = 9]) and intradermal (0.5 mL [n = 11]) routes. Booster doses were administered 28 days later using the same vaccine and routes. Serum samples were collected on days 0, 7, 14, and 28 post-vaccination (pv) and at 30 and 60 days post-booster. Homologous and heterologous virus neutralization tests and liquid-phase blocking and isotype ELISAs were used to measure the antibody response. The results showed that intradermal administration of quarter doses of the vaccine provides an equal or better virus neutralization antibody response than intramuscular administration of the same dose of vaccine after booster administration in cattle. This means that four times more cattle can be immunized with the same amount of vaccine using the intradermal route without compromising immunity.

Evaluation of Potency and Duration of Immunity Elicited by a Multivalent FMD Vaccine for Use in South Africa

South Africa (SA) experiences sporadic foot and mouth disease (FMD) outbreaks irrespective of routine prophylactic vaccinations of cattle using imported commercial vaccines. The problem could be mitigated by preparation of vaccines from local virus strains related to those circulating in the endemically infected buffalo populations in the Kruger National Park (KNP). This study demonstrates the individual number of protective doses (PD) of five vaccine candidate strains after homologous virus challenge, as well as the vaccines safety and onset of humoral immunity in naïve cattle. Furthermore, the duration of post-vaccination immunity over a 12-month period is shown, when a multivalent vaccine prepared from the five strains is administered as a primary dose with or without booster vaccinations. The five monovalent vaccines were shown to contain a 50% PD between 4 and 32, elicit humoral immunity with antibody titers ≥2.0 log10 from day 7 post-vaccination, and cause no adverse reactions. Meanwhile, the multivalent vaccine elicited antibody titers ≥2.0 log10 and clinical protection up to 12 months when one or two booster vaccinations were administered within 6 months of the primary vaccination. An insignificant difference between the application of one or two booster vaccinations was revealed. Owing to the number of PDs, we anticipate that the multivalent vaccine could be used successfully for prophylactic and emergency vaccinations without adjustment of the antigen payloads. Furthermore, a prophylactic vaccination regimen comprising primary vaccination of naïve cattle followed by two booster vaccinations 1.5 and 6 months later could potentially maintain herd immunity over a period of 12 months.

Generation of Replication Deficient Human Adenovirus 5 (Ad5) Vectored FMD Vaccines

Adenovirus vectors offer a convenient platform for the expression of antigens and have become an attractive system for vaccine development. Currently, the most successful approach to the development of new foot-and-mouth disease (FMD) vaccines has been the production of a replication-defective human serotype 5 adenovirus that delivers the capsid and capsid processing coding regions of FMD virus (FMDV) (Ad5-FMD). A specific construct for FMDV serotype A24 has been fully developed into a commercial product fulfilling the requirements of the Center of Veterinary Biologics (CVB) of the Animal and Plant Health Inspection Service (APHIS) of the U.S. Department of Agriculture (USDA), for commercialization in the USA. In this chapter, we describe a standard protocol for the generation and small-scale production of Ad5-FMDV serotype O1Manisa vaccines. We use directional cloning to introduce the FMDV O1Manisa capsid in the Ad5-Blue vector. This is followed by the linearization of the recombinant Ad5 with Pac I and transfection into HEK293 cells for rescue and propagation, and then by increased production and purification. Finally, purified recombinant virus is characterized by determining virus yield and expression of targeted antigen in specific cell type of interest.

A Five-Year Retrospective Study of Foot-and-Mouth Disease Outbreaks in Southern Africa, 2014 to 2018

Foot-and-mouth disease (FMD) virus (FMDv), like other ribonucleic acid (RNA) genome viruses, has a tendency to mutate rapidly. As such, available vaccines may not confer enough cross-protection against incursion of new lineages and sublineages. This paper is a retrospective study to determine the topotypes/lineages that caused previous FMD outbreaks in 6 southern African countries and the efficacy of the current vaccines to protect cattle against them. A total of 453 bovine epithelial tissue samples from 33 FMD outbreaks that occurred in these countries from 2014 to 2018 were investigated for the presence of FMDv. The genetic diversity of the identified Southern African Type (SAT)-FMD viruses was determined by comparing sequences from outbreaks and historical prototype sequences. Of the 453 samples investigated, 176 were positive for four FMDv serotypes. Out of the 176 FMD positive cases there were 105 SAT2 samples, 32 SAT1 samples, 21 SAT3 samples, and 18 serotype O samples. Phylogenetic analysis grouped the SATs VP1 gene sequences into previously observed topotypes in southern Africa. SAT1 viruses were from topotypes I and III, SAT2 viruses belonged to topotypes I, II, III, and IV, and SAT3 viruses were of topotypes I and II. Vaccine matching studies on the field FMDv isolates produced r 1-values greater than or equal to 0.3 for the three SAT serotypes. This suggests that there is no significant antigenic difference between current SAT FMD vaccine strains and the circulating SAT serotypes. Therefore, the vaccines are still fit-purpose for the control FMD in the region. The study did not identify incursion of any new lineages/topotypes of FMD into the sampled southern African countries.

A model exploration of carrier and movement transmission as potential explanatory causes for the persistence of foot-and-mouth disease in endemic regions

Foot-and-mouth disease (FMD) is a virulent and economically important disease of livestock, still endemic in many areas of Asia and sub-Saharan Africa. Transmission from persistently infected livestock, also known as carriers, has been proposed as a mechanism to support the persistence of FMD in endemic regions. However, whether carrier livestock can infect susceptible animals is controversial; recovered virus is infectious and there are claims of field transmission, but it remains undemonstrated experimentally. Alternate hypotheses for persistence include the movement of livestock within and between regions, and fomite contamination of the environment. Using a stochastic compartmental ordinary differential equation (ODE) model, we investigate the minimum rates of carrier transmission necessary to contribute to the maintenance of FMD in a region, and compare this to the alternate mechanism of persistence through cattle shipments. We find that carrier transmission can theoretically support persistence even at transmission rates much lower than the highest realistic rates previously proposed, and that the parameters with the most effect on the feasibility of carrier-mediated persistence are the average duration of both the carrier phase and natural immunity. However, shipment-mediated persistence remains a viable alternate mechanism for persistence without carrier transmission.

Effect of Foot-and-Mouth Disease Vaccine on Pregnancy Failure in Beef Cows

This study evaluates whether the foot-and-mouth disease (FMD) vaccination increases pregnancy failures in Bos taurus beef cows. A total of 3,379 cows were assigned to two experimental groups to receive (n = 1,722) or not receive (n = 1,657) a FMD vaccine (commercial preparation containing FMD virus, O1 Campos and A24 Cruzeiro) at different gestational age. Pregnancy diagnosis was performed by ultrasonography at vaccination time (Day 0), and the cows were classified by days of pregnancy as follows: (a) <29 days after mating (presumed pregnant cows, n = 778), (b) between 30 and 44 days of pregnancy (n = 1,100), (c) 45 and 59 days of pregnancy (n = 553), and (d) between 60 and 90 days of pregnancy (n = 948). Pregnancy failure was determined 30 days after vaccination by a second ultrasound examination. Cows that were vaccinated within 29 days after mating had a 7.8% greater pregnancy failure rate than non-vaccinated cows (44.1%, 163/370 vs. 36.3%, 148/408, respectively; P <0.05). Cows vaccinated between 30 and 44 days of gestation had a pregnancy failure rate greater than non-vaccinated cows (4.9%, 28/576 vs. 2.5%, 13/524, respectively; P <0.05). When cows received the vaccine between days 45 and 90 of gestation no differences in pregnancy failure were observed (0.8%, 6/776 vs. 1.2%, 9/725, respectively; P = NS). Body temperature and local adverse reactions to vaccine inoculation were recorded in a subset of 152 multiparous cows. Hyperthermia (>39.5°C) was detected on Day 1 or 2 in 28.0% (21/75) of vaccinated vs. 7.8% (6/77) of non-vaccinated cows (P <0.01). Local adverse reaction to the FMD vaccine inoculation increased from 0.0% (0/75) on Day 0, to 15.7% (11/75) on Day 4, and 38.7% (29/75) on Day 10 (P <0.01). On Day 30 local reaction was detected in 10.5% (34/323) and fell to 2.2% on Day 60 (7/323) post vaccination (P <0.01). In conclusion, FMD vaccine increases pregnancy failure when it is administered before 45 days of gestation, an effect that was associated with hyperthermia and local adverse reaction. No effect on pregnancy failure was found when vaccination was performed after 45 days of gestation.

Recent Development of Ruminant Vaccine Against Viral Diseases

Pathogens of viral origin produce a large variety of infectious diseases in livestock. It is essential to establish the best practices in animal care and an efficient way to stop and prevent infectious diseases that impact animal husbandry. So far, the greatest way to combat the disease is to adopt a vaccine policy. In the fight against infectious diseases, vaccines are very popular. Vaccination's fundamental concept is to utilize particular antigens, either endogenous or exogenous to induce immunity against the antigens or cells. In light of how past emerging and reemerging infectious diseases and pandemics were handled, examining the vaccination methods and technological platforms utilized for the animals may provide some useful insights. New vaccine manufacturing methods have evolved because of developments in technology and medicine and our broad knowledge of immunology, molecular biology, microbiology, and biochemistry, among other basic science disciplines. Genetic engineering, proteomics, and other advanced technologies have aided in implementing novel vaccine theories, resulting in the discovery of new ruminant vaccines and the improvement of existing ones. Subunit vaccines, recombinant vaccines, DNA vaccines, and vectored vaccines are increasingly gaining scientific and public attention as the next generation of vaccines and are being seen as viable replacements to conventional vaccines. The current review looks at the effects and implications of recent ruminant vaccine advances in terms of evolving microbiology, immunology, and molecular biology.

Foot and Mouth Disease Vaccine Development and Challenges in Inducing Long-Lasting Immunity: Trends and Current Perspectives

Foot and mouth disease (FMD) is an extremely contagious viral disease of livestock caused by foot and mouse disease virus genus: Aphthovirus, which causes a serious economic impact on both individual farmers and the national economy. Many attempts to advance a vaccine for FMD have failed to induce sterile immunity. The classical methods of vaccine production were due to selective accumulation of mutations around antigenic and binding sites. Reversion of the agent by positive selection and quasi-species swarm, use of this method is inapplicable for use in non-endemic areas. Chemical attenuation using binary ethyleneimine (BEI) protected the capsid integrity and produced a pronounced immunity against the challenge strain. Viral antigens which have been chemically synthesized or expressed in viruses, plasmid, or plants were tried in the vaccination of animals. DNA vaccines expressing either structural or nonstructural protein antigens have been tried to immunize animals. Using interleukins as a genetic adjuvant for DNA vaccines have a promising effect. While the challenges of inducing sterile immunity lies on non-structural (NS) proteins of FMDV which are responsible for apoptosis of dendritic cells and have negative effects on lympho-proliferative responses which lead to transient immunosuppression. Furthermore, destruction of host protein trafficking by nonstructural proteins suppressed CD₈⁺ T-cell proliferation. In this review, it tried to address multiple approaches for vaccine development trials and bottle necks of producing sterile immunity.

Efficacy of SAT2 Foot-and-Mouth Disease Vaccines Formulated with Montanide ISA 206B and Quil-A Saponin Adjuvants

The effective control of foot-and-mouth disease (FMD) relies strongly on the separation of susceptible and infected livestock or susceptible livestock and persistently infected wildlife, vaccination, and veterinary sanitary measures. Vaccines affording protection against multiple serotypes for longer than six months and that are less reliant on the cold chain during handling are urgently needed for the effective control of FMD in endemic regions. Although much effort has been devoted to improving the immune responses elicited through the use of modern adjuvants, their efficacy is dependent on the formulation recipe, target species and administration route. Here we compared and evaluated the efficacy of two adjuvant formulations in combination with a structurally stabilized SAT2 vaccine antigen, designed to have improved thermostability, antigen shelf-life and longevity of antibody response. Protection mediated by the Montanide ISA 206B-adjuvanted or Quil-A Saponin-adjuvanted SAT2 vaccines were comparable. The Montanide ISA 206B-adjuvanted vaccine elicited a higher SAT2 neutralizing antibody response and three times higher levels of systemic IFN-γ responses at 14- and 28-days post-vaccination (dpv) were observed compared to the Quil-A Saponin-adjuvanted vaccine group. Interestingly, serum antibodies from the immunized animals reacted similarly to the parental vaccine virus and viruses containing mutations in the VP2 protein that simulate antigenic drift in nature.

Post-vaccination Monitoring to Assess Foot-and-Mouth Disease Immunity at Population Level in Korea

In South Korea, domestic cattle, pigs, and goats were subjected to mandatory foot-and-mouth disease (FMD) vaccination and year-round serosurveillance since 2011. In 2020, approximately USD 95 million was spent solely for FMD vaccine purchase for 59 million livestock, and 1.25 million samples were tested to estimate the population immunity and demonstrate the absence of virus circulation. As the FMD vaccination program was revised in 2018, the post-vaccination monitoring (PVM) was designed to evaluate the effectiveness of the vaccine program of three vaccines approved for routine use. To this end, monitoring post-vaccination immunity has been conducted by collecting 35,626 serum samples at 28 days post-vaccination following regular national vaccinations, which were carried out in April and in October in 2020. The design of the serological test for PVM was specially targeted at particular livestock groups, including dairy cattle, goats, and beef cattle aged 6–12 months, which were generally estimated to have a low expected seroprevalence. The risk factors had also been identified, considering the increased likelihood of infection in a particular location, herd size, and husbandry system applied in a targeted sample collection. Serum sample collection and SP-O and NSP antibody tests were performed by local veterinary laboratories using commercially available ELISAs. The current FMD vaccination program, which was performed twice a year following the regimen of primary vaccination and boost, resulted in over 80% population immunity. The seroprevalence monitored after the vaccination in fall was higher than the one studied in spring except in pigs. It was demonstrated that the seroprevalence of risk-based targeted samples ranged from 93.8 to 100% in cattle, 63.2 to 100% in pigs, and 20.0 to 100% in goats. Of note is the area near the North Korean borders which showed a relatively low seroprevalence among the targeted regions, and no NSP sero-positive reactor was detected in this region. When subpopulation immunity at the individual level was assessed, the seroprevalence in young cattle stock was slightly lower (95.8%) than that of adults (98.4%). In conclusion, the FMD vaccination campaign has been successfully implemented in Korea, and the PVM can be a supplementary program for massive routine surveillance in terms of providing timely information needed both to estimate population immunity and to properly target “risk-based surveillance.”

Vaccine matching and antigenic variability of foot-and-mouth disease virus serotypes O and A from 2018 Ethiopian isolates

Foot-and-mouth disease (FMD) is highly infectious, limits live animal trade, and affects ranchers owing to the loss of animal yield. The present study was designed to perform vaccine matching for field FMD virus isolates from clinically diseased cattle and assess the antigenic properties of the field isolates against the current vaccine strains used for vaccine production at the National Veterinary Institute, Ethiopia. Both sequencing and reverse transcription-polymerase chain reactions were used for distinguishing between the viral strains. To evaluate the serological relationship of the vaccine strain with these field isolates (r1 value), in vitro cross-neutralization was performed using ETH/6/2000 and ETH/38/2005 antisera. Infectious field FMD viral samples represented serotypes A and O. Sequence analysis showed that serotype A VP1/1D possessed amino acid variability at positions 28 and 42 to 48, 138, 141, 142, 148, 156, 173, and 197 compared with the ETH/6/2000 vaccine strain, whereas serotype O possessed amino acid variability at positions 45, 48, 138, 139, 140, 141, and 197 compared with the ETH/38/2005 vaccine strain. Based on the one-dimensional virus neutralization test, serotypes A and O demonstrated antigenic matching of up to 13/17 (76.47%) with the vaccine strain, except for the isolates ETH/40/2018, ETH/48/2018, ETH/55/2018, and ETH/61/2018, which had r-values less than 0.3. Therefore, the currently used vaccine strains ETH/38/2005 for serotype O and ETH/6/2000 for serotype A protected against all and most field viruses characterized as serotypes O and A, respectively, and amino acid residue variation was observed in different FMD virus B-C loops, G-H loops, and C-termini of VP1 at sites 1 and 3 in both serotypes.

Knowledge, attitudes and practices of smallholder farmers on foot and mouth disease control in two Cambodian provinces

Food-and-mouth disease (FMD) is endemic in Cambodia. The control programme for FMD has relied on vaccination, with poor vaccination uptake by smallholder farmers becoming an increasing concern. A study to improve the understanding of farmer knowledge, attitudes and practices of FMD control and vaccination was conducted in two Cambodian provinces (Kampong Cham and Pursat). The aim was to identify opportunities to improve the livestock disease control programmes provided by both the government and private sectors. The survey comprised 300 smallholder farmers using a one-on-one interview technique and was completed between January to February 2014. Results identified that over two-thirds of the respondent farmers had not vaccinated their cattle over 2 years (2011-2013). Of those who did, most cattle were vaccinated either once a year or once every 3 years. A booster had never been administered. It was concluded that the FMD vaccine had only been administered through an unreliable and limited government vaccination programme, and private FMD vaccination services were not accessed in the study areas. FMD outbreaks occurred every year during the study period, with a morbidity rate of over 30%. Isolation of first infected cattle from the household herd was not practiced, with treatment identified as the first preference intervention. Farmers often assisted other farmers to restrain and treat infected cattle both before (57%) and after (43%) their own cattle were infected. This indicated that most farmers did not practice basic biosecurity measures and chose to report FMD outbreaks to the village animal health workers (VAHW), friends, neighbours and relatives in preference to government officials. It was concluded that poor knowledge of disease transmission and biosecurity, with low FMD vaccination coverage and a focus on treatment, contribute to regular FMD outbreaks in these communities. Improvement of FMD control requires the cooperation of villagers, VAHWs and village leaders in disease reporting, with either improved funding of government vaccination services or establishing a private FMD vaccination service. Training programmes for farmers on disease transmission, and the importance of biosecurity and vaccination, including information on the cost-benefits of treatment versus full fee bi-annual FMD vaccination, are required.

An adventitious agent-free clonal cell line that is highly susceptible to foot -and-mouth disease virus

Porcine LFBKαVβ6 cells have been successfully used for diagnostics and propagation of all FMDV serotypes/subtypes. Unfortunately, after initial characterization, these cells showed contamination with bovine viral diarrhea virus (BVDV), a non-cytopathic adventitious agent. Persistent infection with BVDV could interfere with diagnostic tests and, also prevent consideration for other uses, i.e., vaccine production. In this study, we developed a three-prong methodology to completely remove BVDV from LFBKαVβ6 cells. Combined treatment with siRNA against BVDV NS5A, porcine interferon alpha and ribavirin resulted in the elimination of BVDV, as determined by immunohistochemistry analysis, quantitative RT-PCR and RNA sequencing. Importantly, elimination of BVDV from LFBKαVβ6 did not affect FMDV growth and plaque phenotype from different serotypes isolated and propagated in the clean cell line, newly named MGPK αVβ6-C5. Additionally, isolation of FMDV from field oro-pharyngeal samples, was successful at the same sensitivity as in BVDV-contaminated LFBKαVβ6 cells. Our results identified a direct method to efficiently eliminate BVDV from porcine cells without altering FMDV permissiveness, diagnostic value, or potential for use in vaccine production. Furthermore, these cells may provide an improved platform for diagnostics and propagation of other viruses of interest in the veterinary field and the virology community at large.

Scale-Up Production of Type O and A Foot-and-Mouth Disease Bivalent Vaccine and Its Protective Efficacy in Pigs

South Korea has experienced FMD outbreaks almost every year since 2014. Therefore, a novel local vaccine that can cover various topotypes of viruses is required. Two virus strains, O/Boeun/SKR/2017 and A/Yeoncheon/SKR/2017, were cultured up to the pilot scale based on the optimized conditions set up on the flask scale. FMDV particles (146S) of 2 µg/mL or more were obtained from the virus culture supernatant using a 100 L bioreactor. The viruses were fully inactivated using binary ethylenimine within 16 h through two inactivation cycles and mixed with an adjuvant into a bivalent vaccine (types O and A) consisting of 15 µg viruses per strain. The experimental bivalent vaccine showed a broad spectrum of high neutralizing antibody titers against heterologous viruses, including type O Cathay strain and type A Asia topotypes, except for GVII. The 50% protective dose was determined as 12.5 for O/Boeun/SKR/2017 and 15.6 for A/Yeoncheon/SKR/2017. Collectively, we expect that the bivalent vaccine could protect against FMDV types O and A circulating in South Korea and neighboring countries. To our knowledge, this is the first report demonstrating that the vaccine strains could be successfully scaled-up to a 100 L bioreactor, with the determination of its protective efficacy in pigs.

An Engineered Maturation Cleavage Provides a Recombinant Mimic of Foot-and-Mouth Disease Virus Capsid Assembly-Disassembly

Picornavirus capsids are assembled from 60 copies of a capsid precursor via a pentameric assembly intermediate or ‘pentamer’. Upon completion of virion assembly, a maturation event induces a final cleavage of the capsid precursor to create the capsid protein VP4, which is essential for capsid stability and entry into new cells. For the picornavirus foot-and-mouth disease virus (FMDV), intact capsids are temperature and acid-labile and can disassemble into pentamers. During disassembly, capsid protein VP4 is lost, presumably altering the structure and properties of the resulting pentamers. The purpose of this study was to compare the characteristics of recombinant “assembly” and “disassembly” pentamers. We generated recombinant versions of these different pentamers containing an engineered cleavage site to mimic the maturation cleavage. We compared the sedimentation and antigenic characteristics of these pentamers using sucrose density gradients and reactivity with an antibody panel. Pentamers mimicking the assembly pathway sedimented faster than those on the disassembly pathway suggesting that for FMDV, in common with other picornaviruses, assembly pentamers sediment at 14S whereas only pentamers on the disassembly pathway sediment at 12S. The reactivity with anti-VP4 antibodies was reduced for the 12S pentamers, consistent with the predicted loss of VP4. Reactivity with other antibodies was similar for both pentamers suggesting that major antigenic features may be preserved between the VP4 containing assembly pentamers and the disassembly pentamers lacking VP4.

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-VP1^Y2098F, rHN/DY-VP1^{V2090A-S2093H}, and rHN/DY-VP1^{V2090A-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-VP1^Y2098F mutant should be considered for use in future vaccines.

Peptide-Based Vaccines: Foot-and-Mouth Disease Virus, a Paradigm in Animal Health

Vaccines are considered one of the greatest global health achievements, improving the welfare of society by saving lives and substantially reducing the burden of infectious diseases. However, few vaccines are fully effective, for reasons ranging from intrinsic limitations to more contingent shortcomings related, e.g., to cold chain transport, handling and storage. In this context, subunit vaccines where the essential antigenic traits (but not the entire pathogen) are presented in rationally designed fashion have emerged as an attractive alternative to conventional ones. In particular, this includes the option of fully synthetic peptide vaccines able to mimic well-defined B- and T-cell epitopes from the infectious agent and to induce protection against it. Although, in general, linear peptides have been associated to low immunogenicity and partial protection, there are several strategies to address such issues. In this review, we report the progress towards the development of peptide-based vaccines against foot-and-mouth disease (FMD) a highly transmissible, economically devastating animal disease. Starting from preliminary experiments using single linear B-cell epitopes, recent research has led to more complex and successful second-generation vaccines featuring peptide dendrimers containing multiple copies of B- and T-cell epitopes against FMD virus or classical swine fever virus (CSFV). The usefulness of this strategy to prevent other animal and human diseases is discussed.

Use of Protein Pegylation to Prolong the Antiviral Effect of IFN Against FMDV

Interferons (IFNs) are considered the first line of defense against viral diseases. Due to their ability to modulate immune responses, they have become an attractive therapeutic option to control virus infections. In fact, like many other viruses, foot-and-mouth disease virus (FMDV), the most contagious pathogen of cloven-hoofed animals, is highly sensitive to the action of IFNs. Previous studies demonstrated that type I, II, and III IFNs, expressed using a replication defective human adenovirus 5 (Ad5) vector, can effectively block FMDV replication in vitro and can protect animals when challenged 1 day after Ad5-IFN treatment, in some cases providing sterile immunity. Rapidly spreading foot-and-mouth disease (FMD) is currently controlled with vaccination, although development of a protective adaptive immune response takes 5–7 days. Therefore, an optimal strategy to control FMD outbreaks is to block virus replication and spread through sustained IFN activity while the vaccine-stimulated adaptive immune response is developed. Challenges with methods of delivery and/or with the relative short IFN protein half-life in vivo, have halted the development of such approach to effectively control FMD in the animal host. One strategy to chemically improve drug pharmacodynamics is the use of pegylation. In this proof-of-concept study, we demonstrate that pegylated recombinant porcine (po)IFNα displays strong and long-lasting antiviral activity against FMDV in vitro and in vivo, completely protecting swine against FMD for at least five days after a single dose. These results highlight the potential of this biotherapeutics to use in combination with vaccines to fully control FMD in the field.

Amber codon is genetically unstable in generation of premature termination codon (PTC)-harbouring Foot-and-mouth disease virus (FMDV) via genetic code expansion

The foot-and-mouth disease virus (FMDV) is the causative agent of FMD, a highly infectious and devastating viral disease of domestic and wild cloven-hoofed animals. FMD affects livestock and animal products' national and international trade, causing severe economic losses and social consequences. Currently, inactivated vaccines play a vital role in FMD control, but they have several limitations. The genetic code expansion technology provides powerful strategies for generating premature termination codon (PTC)-harbouring virus as a live but replication-incompetent viral vaccine. However, this technology has not been explored for the design and development of new FMD vaccines. In this study, we first expanded the genetic code of the FMDV genome via a transgenic cell line containing an orthogonal translation machinery. We demonstrated that the transgenic cells stably integrated the orthogonal pyltRNA/pylRS pair into the genome and enabled efficient, homogeneous incorporation of unnatural amino acids into target proteins in mammalian cells. Next, we constructed 129 single-PTC FMDV mutants and four dual-PTC FMDV mutants after considering the tolerance, location, and potential functions of those mutated sites. Amber stop codons individually substituted the selected amino acid codons in four viral proteins (3D, L, VP1, and VP4) of FMDV. We successfully rescued PTC-FMDV mutants, but the amber codon unexpectedly showed a highly degree of mutation rate during PTC-FMDV packaging and replication. Our findings highlight that the genetic code expansion technology for the generation of PTC-FMD vaccines needs to be further improved and that the genetic stability of amber codons during the packaging and replication of FMDV is a concern.

FMD empty capsids combined with the Immunostant Particle Adjuvant -ISPA or ISA206 induce protective immunity against foot and mouth disease virus

Foot and Mouth Disease Virus (FMDV) causes economy losses and is controlled by vaccination in many countries. Vaccine formulations based on empty capsids or Virus-Like Particles (VLPs) have the advantage of avoiding the biological hazard of using infectious FMDV, albeit are poorly immunogenic. Recently, we have described that ISPA a new Immune Stimulating Complex adjuvant, is useful to improve the response against FMD of vaccines that use inactivated virus. Now, the adjuvant effects of ISPA and ISA 206 (water/oil/water) on a VLPs-based FMD vaccine were evaluated. VLPs (strain A/Argentina/2001) were obtained in mammalian cell cultures and their elicitation of an immune response against FMDV with and without ISPA or ISA 206 was evaluated in mice as a first approach. Notably, VLPs-ISPA and VLPs-ISA 206 vaccines induced protection against viral challenge in 100 % of mice, while protection induced by VLPs alone was of 40 %. Total and neutralizing FMDV antibodies were higher in the VLPs-ISPA and VLPs-ISA 206 groups compared to the VLPs group. VLPs-ISPA induced significantly higher (p < 0.001) IgG1, IgG2a, IgG2b and IgG3 titers than the VLPs vaccine. Moreover, in comparison with non-adjuvanted VLPs, VLPs-ISPA and VLPs-ISA 206 elicited an increased virus-specific T response, including higher IFNγ+/CD8 + lymphocyte production in mice. When these vaccines were tested in calves, antibody titers reached an Expected Percentage of Protection (EPP) above 90 % in the case of the VLPs-ISPA and VLPs-ISA 206 vaccines, while, in the VLPs group, EPP reached 25 %. IFNγ levels secreted by mononuclear cells of VLP-ISPA-vaccinated cattle were significantly higher than in the VLPs group. Overall, the results demonstrate that VLPs-ISPA or VLPs-ISA 206 are promising formulations for the development of a novel FMD vaccine.

Foot-and-mouth disease seroprevalence and reporting behaviours in nine northern provinces in Lao PDR: The current situation and challenges for control

Foot-and-mouth disease (FMD), caused by the FMD virus (FMDV), is one of the most important of global livestock diseases, impacting even-toed ungulates and distributed mostly in less developed countries that are home to 75% of the human population. A progressive control pathway for FMD (PCP-FMD) was developed to assist countries to better manage FMD risks and progress towards control and eradication. This requires evidence of current FMD seroprevalence to enable the informed risk assessment and the disease control planning required to progress along the initial stages of the PCP-FMD. Despite Laos being an active member of the South East Asia and China FMD campaign, these data have been challenging to obtain. To address this gap, a cross-sectional seroprevalence study in nine northern Lao provinces was conducted in early 2019. The study sampled 602 large ruminants and 19 goats from 30 villages. Overall, the large ruminant seroprevalence was 43.7% (95% CI 39.7-47.8), and 90% of sampled villages had at least one seropositive animal. Large ruminants suspected of having had clinical FMD in their lifetime were found to have an increased risk of being seropositive (odds ratio 1.96, 95% CI 1.06-3.65, p = .03). An examination of current reporting behaviours of farmers, village veterinary workers and district and provincial officials found that individuals were using their discretion as to whether disease events required reporting along the chain of command. This, plus the lack of a computerized reporting system, contributed to a loss of historical data, potentially compromising progression on the PCP-FMD. Laos requires ongoing support from donor agencies to improve the current animal disease surveillance system and implement effective FMD control strategies that can enable progress on the PCP-FMD.

Challenges in foot-and-mouth disease virus strain selection as an input to attain broad vaccine intraserotype cross-protection

Introduction: Vaccination against foot-and-mouth disease virus is regarded as the most effective way to prevent disease. Selection of appropriate vaccine strains is challenging due to lack of cross-protection between serotypes and incomplete protection between some strains within a serotype. Vaccine effectiveness can be affected by vaccine formulation, vaccination approaches, and also by emerging field variants. Therefore, a precise evaluation of the protective capacity of the selected vaccine virus is essential.Areas covered: This article discusses the limitations of currently in use in vitro methods to assess the protective capacity of vaccine strains. It includes the assessment of well-established South American vaccine strains, O₁/Campos and A₂₄/Cruzeiro, against outbreaks/emergencies in the continent, as well as against recent isolates from East and Southeast Asia.Expert opinion: In vitro methods, and particularly r₁ values, used to evaluate the protective capacity of vaccine strains are not conclusive and do not cover the variety of field scenarios. At present, an option when facing emergencies could be to use well-established vaccine strains with broad antigenic/immunogenic coverage, including conditions that lead to increased coverage such as vaccine formulations and vaccination schemes.

Removal of 3C protease from the 3ABC improves expression, solubility, and purification of the recombinant 3AB of foot-and-mouth disease virus

During an ongoing outbreak of Foot-and-Mouth Disease Virus (FMDV), it is crucial to distinguish naturally infected from vaccinated seropositive animals. This would support clinical assessment and punctual vigilance. Assays based on 3ABC non-structural protein as an antigen are reliable for this intention. However, the insolubility and degradation of recombinant 3ABC during expression and purification are serious challenges. In this study, alternatively to expressing the recombinant 3ABC (r3ABC), we expressed the 3AB coding sequence (~672 bp) as a recombinant protein (r3AB) with a molecular mass of ~26 KDa. Analytical data from three-dimensional structure, hydrophilicity, and antigenic properties for 3ABC and 3AB exhibited the 3C protein as a hydrophobic, while 3AB as a hydrophilic and highly antigenic protein. The expressed r3AB was recovered as a completely soluble matter after merely native purification, unlike the full expressed r3ABC. Immunoreactivity of r3AB to anti-FMDV antibody in infected sera with different FMDV serotypes was confirmed by the western blot and indirect ELISA. Besides, the authentic antigenicity of purified r3AB was demonstrated through its ability to induce specific seroconversion in mice. Summarily, the removal of 3C: has influenced neither 3D structure nor antigenic properties of the purified r3AB, overcame insolubility and degradation of the r3ABC, and generated a potential superior antigen (r3AB) for herd screening of animals to any FMDV serotype.

Comparative evaluation of integrated purification pathways for bacterial modular polyomavirus major capsid protein VP1 to produce virus-like particles using high throughput process technologies

Modular virus-like particles and capsomeres are potential vaccine candidates that can induce strong immune responses. There are many described protocols for the purification of microbially-produced viral protein in the literature, however, they suffer from inherent limitations in efficiency, scalability and overall process costs. In this study, we investigated alternative purification pathways to identify and optimise a suitable purification pathway to overcome some of the current challenges. Among the methods, the optimised purification strategy consists of an anion exchange step in flow through mode followed by a multi modal cation exchange step in bind and elute mode. This approach allows an integrated process without any buffer adjustment between the purification steps. The major contaminants like host cell proteins, DNA and aggregates can be efficiently removed by the optimised strategy, without the need for a size exclusion polishing chromatography step, which otherwise could complicate the process scalability and increase overall cost. High throughput process technology studies were conducted to optimise binding and elution conditions for multi modal cation exchanger, Capto™ MMC and strong anion exchanger Capto™ Q. A dynamic binding capacity of 14 mg ml⁻¹ was achieved for Capto™ MMC resin. Samples derived from each purification process were thoroughly characterized by RP-HPLC, SEC-HPLC, SDS-PAGE and LC-ESI-MS/MS Mass Spectrometry analytical methods. Modular polyomavirus major capsid protein could be purified within hours using the optimised process achieving purities above 87% and above 96% with inclusion of an initial precipitation step. Purified capsid protein could be easily assembled in-vitro into well-defined virus-like particles by lowering pH with addition of calcium chloride to the eluate. High throughout studies allowed the screening of a vast design space within weeks, rather than months, and unveiled complicated binding behaviour for Capto^TM MMC.

Use of Synonymous Deoptimization to Derive Modified Live Attenuated Strains of Foot and Mouth Disease Virus

Foot-and-mouth disease (FMD) is one of the most economically important viral diseases that can affect livestock. In the last 70 years, use of an inactivated whole antigen vaccine has contributed to the eradication of disease from many developed nations. However, recent outbreaks in Europe and Eastern Asia demonstrated that infection can spread as wildfire causing economic and social devastation. Therefore, it is essential to develop new control strategies that could confer early protection and rapidly stop disease spread. Live attenuated vaccines (LAV) are one of the best choices to obtain a strong early and long-lasting protection against viral diseases. In proof of concept studies, we previously demonstrated that “synonymous codon deoptimization” could be applied to the P1 capsid coding region of the viral genome to derive attenuated FMDV serotype A12 strains. Here, we demonstrate that a similar approach can be extended to the highly conserved non-structural P2 and P3 coding regions, providing a backbone for multiple serotype FMDV LAV development. Engineered codon deoptimized P2, P3 or P2, and P3 combined regions were included into the A₂₄Cruzeiro infectious clone optimized for vaccine production, resulting in viable progeny that exhibited different degrees of attenuation in cell culture, in mice, and in the natural host (swine). Derived strains were thoroughly characterized in vitro and in vivo. Our work demonstrates that overall, the entire FMDV genome tolerates codon deoptimization, highlighting the potential of using this technology to derive novel improved LAV candidates.

Salmonella Vaccine Vector System for Foot-and-Mouth Disease Virus and Evaluation of Its Efficacy with Virus-Like Particles

Foot-and-mouth disease virus (FMDV) causes a highly contagious and devastating disease in livestock animals and has a great potential to cause severe economic loss worldwide. The major antigen of FMDV capsid protein, VP1, contains the major B-cell epitope responsible for effectively eliciting protective humoral immunity. In this study, irradiated Salmonella Typhimurium (KST0666) were used as transgenic vectors containing stress-inducible plasmid pRECN-VP1 to deliver the VP1 protein from FMDV-type A/WH/CHA/09. Mice were orally inoculated with ATOMASal-L3 harboring pRECN-VP1, and FMDV virus-like particles, where (VLP_FMDV)-specific humoral, mucosal, and cellular immune responses were evaluated. Mice vaccinated with attenuated Salmonella (KST0666) expressing VP1 (named KST0669) showed high levels of VLP-specific IgA in feces and IgG in serum, with high FMDV neutralization titer. Moreover, KST0669-vaccinated mice showed increased population of IFN-γ (type 1 T helper cells; Th1 cells)-, IL-5 (Th2 cells)-, and IL-17A (Th17 cells)-expressing CD4⁺ as well as activated CD8⁺ T cells (IFN-γ⁺CD8⁺ cells), detected by stimulating VLP_FMDV. All data indicate that our Salmonella vector system successfully delivered FMDV VP1 to immune cells and that the humoral and cellular efficacy of the vaccine can be easily evaluated using VLP_FMDV in a Biosafety Level I (BSL1) laboratory.