Control of type O foot-and-mouth disease by vaccination in Korea, 2014-2015

Foot-and-mouth disease virus strains isolated in Vietnam during 2010-2019: genetic characterization and antigenic relatedness to the Euro SA vaccine

Foot-and-mouth disease is a highly contagious disease that affects cloven-hoofed animals. It has an important socio-economic impact on the livestock industry because it produces a drastic decrease of productivity. The disease has been successfully eradicated from some regions, including North America and Western Europe, but it is still endemic in developing countries. Agriculture plays an important role in the national economy of Vietnam, to which animal production contributes a great proportion. The concurrent circulation of foot-and-mouth disease virus (FMDV) serotypes O, A, and Asia 1 has been detected in recent years, but serotype O remains the most prevalent and is responsible for the highest numbers of outbreaks. Appropriate vaccine strain selection is an important element in the control of FMD and is necessary for the application of vaccination programs in FMD-affected regions. Here, we present updated information about the genetic and antigenic characteristics of circulating strains, collected from endemic outbreaks involving types O and A, between 2010 and 2019. Neutralizing assays showed a good in vitro match between type O strains and the monovalent O1 Campos vaccine strain. High r1 values were obtained (above 0.7) when testing a swine serum pool collected 21 days after vaccination, but the O/VTN/2/2019 strain was an exception. An EPP estimation resulted in a median neutralizing titre of about 1.65 log10, indicating that good protection could be achieved. For type A Asia SEA 97 lineage strains, acceptable individual neutralizing titres were obtained with estimated EPP values over 80% for different combinations of vaccine strains. Taking into account that the r1 value is one tool of a battery of tests that should be considered for estimating the cross-protection of a field strain against a vaccine strain, an in vivo challenge experiment was also performed, yielding a PD50 value of 8.0. The results indicate that South American strains could be potentially used for controlling outbreaks involving these lineages. This study demonstrates the importance of considering strain characteristics when choosing vaccine strains and controls.

Effect of a Mismatched Vaccine against the Outbreak of a Novel FMD Strain in a Pig Population

In December 2014, a novel foot and mouth disease (FMD) virus was introduced to a pig farm in South Korea, despite the animals being vaccinated. A marginal antigenic matching between the novel and vaccine strains potentially led to the infection of the vaccinated animals. To understand the impact of using an FMD vaccine on the transmission dynamics of an unmatched field strain, simulation models were employed using daily reported data on clinical cases from the farm. The results of this study indicated that immunisation with the FMD vaccine reduced the shedding of the novel FMD virus in pigs. However, there was no evidence to suggest that the immunisation had a significant effect in reducing the development of clinical signs. These findings highlight that the use of an unmatched FMD vaccine can confound the outbreak by altering the disease dynamics of the novel virus. Based on this study, we emphasise the importance of continuous testing to ensure antigenic matching between the circulating strains and the vaccine pool.

Serological Conversion through a Second Exposure to Inactivated Foot-and-Mouth Disease Virus Expressing the JC Epitope on the Viral Surface

Foot-and-mouth disease (FMD) is a fatal contagious viral disease that affects cloven-hoofed animals and causes severe economic damage at the national level. There are seven serotypes of the causative foot-and-mouth disease virus (FMDV), and type O is responsible for serious outbreaks and shows a high incidence. Recently, the Cathay, Southeast Asia (SEA), and ME-SA (Middle East-South Asia) topotypes of type O have been found to frequently occur in Asia. Thus, it is necessary to develop candidate vaccines that afford protection against these three different topotypes. In this study, an experimental FMD vaccine was produced using a recombinant virus (TWN-JC) with the JC epitope (VP1 140-160 sequence of the O/SKR/Jincheon/2014) between amino acid 152 and 153 of VP1 in TWN-R. Immunization with this novel vaccine candidate was found to effectively protect mice against challenge with the three different topotype viruses. Neutralizing antibody titers were considerably higher after a second vaccination. The serological differences between the topotype strains were identified in guinea pigs and swine. In conclusion, a significant serological difference was observed at 56 days post-vaccination between animals that received the TWN-JC vaccine candidate and those that received the positive control virus (TWN-R). The TWN-JC vaccine candidate induced IFNγ and IL-12B.

Phylogenetic and genotypic characteristics of the foot-and-mouth disease virus from outbreaks in southern Vietnam, 2019

In 2019, multiple FMD outbreaks occurred in swine farms vaccinated against FMDV in southern Vietnam. This study investigated the genotypic characteristics of FMDV strains from these outbreaks. Seven samples were collected from pigs exhibiting FMD clinical signs. All FMDV-positive samples were amplified and sequenced for the gene encoding the VP1. Results were analyzed and compared with sequences of reference strains and vaccine strains on GenBank. Phylogenetic analysis showed that all seven field isolates belonged to serotype O, topotype SEA/Mya-98. These strains shared high homology with strains from Vietnam (2018), Korea, and China, but low homology with vaccine strains. Moreover, 21 amino acid substitutions were found in the VP1 protein of the FMDV field strains, many of which were crucial antigenic determinants involved in the neutralization of FMDV. These findings suggest that the current vaccine may not be effective against the emerging FMDV strains in southern Vietnam.

Heterologous Prime-Boost Vaccination with Commercial FMD Vaccines Elicits a Broader Immune Response than Homologous Prime-Boost Vaccination in Pigs

Three commercial vaccines are administered in domestic livestock farms for routine vaccination to aid for foot-and-mouth disease (FMD) control in Korea. Each vaccine contains distinct combinations of inactivated serotype O and A FMD virus (FMDV) antigens: O/Manisa + O/3039 + A/Iraq formulated in a double oil emulsion (DOE), O/Primorsky + A/Zabaikalsky formulated in a DOE, and O/Campos + A/Cruzeiro + A/2001 formulated in a single oil emulsion. Despite the recommendation for a prime-boost vaccination with the same vaccine in fattening pigs, occasional cross-inoculation is inevitable for many reasons, such as lack of compliance with vaccination guidelines, erroneous application, or change in vaccine types by suppliers. Therefore, there have been concerns that a poor immune response could be induced by cross-inoculation due to a failure to boost the immune response. In the present study, it was demonstrated by virus neutralization and ELISA tests that cross-inoculation of pigs with three commercial FMD vaccines does not hamper the immune response against the primary vaccine strains and enhances broader cross-reactivity against heterologous vaccine antigens whether they were applied or not. Therefore, it could be concluded that the cross-inoculation of FMD vaccines can be used as a regimen to strategically overcome the limitation of the antigenic spectrum induced by the original regimen.

Efficacy of a Novel Multiepitope Vaccine Candidate against Foot-and-Mouth Disease Virus Serotype O and A

Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease in cloven-hoofed animals. To prevent the spread of FMD virus (FMDV), traditional inactivated vaccines are used to immunize susceptible animals in disease-endemic countries. However, the inactivated FMD vaccine has several limitations, including safety concerns. To overcome these limitations, subunit proteins have been studied as alternative vaccine candidates. In this study, we designed two multiepitope recombinant proteins (OVM and AVM) containing antigenic sites (residue of VP1 132-162 and residue of VP1 192-212) of three topotypes of FMDV serotype O or three topotypes of FMDV serotype A. Each recombinant protein was efficiently expressed in Escherichia coli with high solubility, and the immunogenicity and protective efficacy of the proteins as FMD vaccine candidates were evaluated. The results showed that OVM and AVM emulsified with ISA201 adjuvant induced effective antigen-specific humoral and cell-mediated immune responses and successfully protected mice from O/Jincheon/SKR/2014, O/VET/2013, and A/Malaysia/97 viruses. In addition, intramuscular immunization of pigs with the OVM and AVM emulsified with ISA201 elicited effective levels of neutralizing antibodies to the viruses with homologous epitopes. Importantly, OVM-AVM emulsified with CAvant^®SOE-X adjuvant conferred 100% protection against the O/Jincheon/SKR/2014 virus with homologous residues and 75% protection against A/SKR/GP/2018 with heterologous residues. The results presented in this study suggest that the combination of OVM and AVM protein with an effective adjuvant could yield an effective and safe vaccine candidate for the prevention and control of foot-and-mouth disease. In addition, our results provide a vaccine platform that can safely, cost-efficiently, and rapidly generate protective vaccine candidates against diverse FMDVs.

Factors Involved in Removing the Non-Structural Protein of Foot-and-Mouth Disease Virus by Chloroform and Scale-Up Production of High-Purity Vaccine Antigens

Foot-and-mouth disease (FMD) is an economically important and highly infectious viral disease, predominantly controlled by vaccination. The removal of non-structural proteins (NSPs) is very important in the process of FMD vaccine production, because vaccinated and naturally infected animals can be distinguished by the presence of NSP antibodies in the FMD serological surveillance. A previous study reported that 3AB protein, a representative of NSPs, was removed by chloroform treatment. Therefore, in this study, the causes of 3AB removal and factors affecting the effect of chloroform were investigated. As a result, the effectiveness of chloroform differed depending on the virus production medium and was eliminated by detergents. In addition, it was found that 3AB protein removal by chloroform is due to the transmembrane domain of the N-terminal region (59–76 amino acid domain). Further, industrial applicability was verified by applying the chloroform treatment process to scale-up FMD vaccine antigen production. A novel downstream process using ultrafiltration instead of polyethylene glycol precipitation for high-purity FMD vaccine antigen production was established. This result will contribute toward simplifying the conventional process of manufacturing FMD vaccine antigens and ultimately reducing the time and cost of vaccine production.

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.”

The risk and mitigation of foot-and-mouth disease virus infection of pigs through consumption of contaminated feed

Transboundary movement of animal feed and feed ingredients has been identified as a route for pathogen incursions. While imports of animals and animal-derived products are highly regulated for the purpose of infectious disease prevention, there has been less consideration of the viability of infectious agents in inanimate products, such as feed. This study investigated the ability of foot-and-mouth disease virus (FMDV) to remain infectious as a contaminant of commercial whole pig feed and select pig feed ingredients, and to establish the minimum infectious dose (MID_F ) required to cause foot-and-mouth disease (FMD) in pigs that consumed contaminated feed. FMDV viability in vitro varied depending on virus strain, feed product, and storage temperature, with increased duration of infectivity in soybean meal compared to pelleted whole feed. Specifically, both strains of FMDV evaluated remained viable through to the end of the 37 day observation period in experimentally contaminated soybean meal stored at 4 or 20°C . The MID_F for pigs consuming contaminated feed varied across virus strains and exposure duration in the range of 10^6.2 to 10⁷ TCID₅₀ . The ability of FMDV to cause infection in exposed pigs was mitigated by pre-treatment of feed with two commercially available feed additives, based on either formaldehyde (SalCURB®) or lactic acid (Guardian™). Our findings demonstrate that FMDV may remain infectious in pig feed ingredients for durations compatible with transoceanic transport. Although the observed MID_F was relatively high, variations in feeding conditions and biophysical characteristics of different virus strains may alter the probability of infection. These findings may be used to parameterize modelling of the risk of FMDV incursions and to regulate feed importation to minimize the risk of inadvertent importation.

Production of a Foot-and-Mouth Disease Vaccine Antigen Using Suspension-Adapted BHK-21 Cells in a Bioreactor

The baby hamster kidney-21 (BHK-21) cell line is a continuous cell line used to propagate foot-and-mouth disease (FMD) virus for vaccine manufacturing. BHK-21 cells are anchorage-dependent, although suspension cultures would enable rapid growth in bioreactors, large-scale virus propagation, and cost-effective vaccine production with serum-free medium. Here, we report the successful adaptation of adherent BHK-21 cells to growth in suspension to a viable cell density of 7.65 × 10⁶ cells/mL on day 3 in serum-free culture medium. The suspension-adapted BHK-21 cells showed lower adhesion to five types of extracellular matrix proteins than adherent BHK-21 cells, which contributed to the suspension culture. In addition, a chemically defined medium (selected by screening various prototype media) led to increased FMD virus production yields in the batch culture, even at a cell density of only 3.5 × 10⁶ cells/mL. The suspension BHK-21 cell culture could be expanded to a 200 L bioreactor from a 20 mL flask, which resulted in a comparable FMD virus titer. This platform technology improved virus productivity, indicating its potential for enhancing FMD vaccine production.

Investigation of the optimal medium and application strategy for foot-and-mouth disease vaccine antigen production

AIMS

For the effective production of 146S particles, which determines foot-and-mouth disease (FMD) vaccine efficacy, we aimed to identify the optimal medium that is easy-to-use, productive and economically affordable for the large-scale production of FMD vaccine.

METHODS AND RESULTS

Nine combinations of cell growth media and replacement media were tested for virus propagation. Apart from the replacement strategy, we tested a simple addition strategy involving the addition of 30% v/v of fresh medium to the total spent medium using the Cellvento BHK-200 (Vento). Unlike other tested media that produced poor yields of 146S particles when the spent media were not eliminated, Vento exhibited high productivity with the 30% addition strategy.

CONCLUSIONS

Considering its lower price and media consumption compared to those of other media that require media replacement, the 30% addition strategy of Vento is highly effective. Furthermore, owing to its simple application strategy, it makes the scale-up process easy and helps in saving the time and labour involved in spent media removal.

SIGNIFICANCE AND IMPACT OF THE STUDY

Through the first comparative assessment of commercial media for the 146S particle recovery, this study suggests the best practical medium for the industrial-scale production of FMD vaccines.

Evaluation of swine protection with foot-and-mouth disease O1/Campos and O/Primorsky/2014 vaccines against the O Mya-98 lineage virus from East Asia

Two type O commercial vaccines, the O₁/Campos and O/Primorsky/2014 vaccines, were studied to evaluate the in vivo efficacy in pigs against heterologous virus challenge with the O/SKR/Jincheon/2014 virus (O/SEA/Mya-98 lineage) isolated in Korea in 2014. The in vivo challenge results indicated that both vaccines induced a high heterologous virus neutralization test (VNT) titer by a single injection and successfully protected specific pathogen-free (SPF) pigs from challenge infection. To determine the optimal vaccination age, a field trial with each vaccine was conducted with three one-shot-vaccinated groups that were injected at 8, 12, or 14 weeks of age and one two-shot-vaccinated group that was injected at 8 and 12 weeks of age in the pig farms. In these field trials, the improved serological performance at 20 and 24 weeks of age expected with vaccination at 12 or 14 weeks of age was not observed, although improved serological results were expected as the result of decreasing interference of maternally derived antibodies (MDAs), as MDAs waned with age. In addition, delayed vaccination resulted in MDA depletion at 14 weeks of age. Therefore, the optimal age for primary vaccination with two different formulated vaccines was 8 weeks old in pigs, considering that MDAs could provide a protective immunity against foot-and-mouth disease (FMD) infection. Prolonged significantly higher VNT titers of immunized pigs were demonstrated in the two-shot-vaccinated groups. In total, the effectiveness of the two vaccines was demonstrated through efficacy tests and field trials in pigs.

The Carrier Conundrum; A Review of Recent Advances and Persistent Gaps Regarding the Carrier State of Foot-and-Mouth Disease Virus

The existence of a prolonged, subclinical phase of foot-and-mouth disease virus (FMDV) infection in cattle was first recognized in the 1950s. Since then, the FMDV carrier state has been a subject of controversy amongst scientists and policymakers. A fundamental conundrum remains in the discordance between the detection of infectious FMDV in carriers and the apparent lack of contagiousness to in-contact animals. Although substantial progress has been made in elucidating the causal mechanisms of persistent FMDV infection, there are still critical knowledge gaps that need to be addressed in order to elucidate, predict, prevent, and model the risks associated with the carrier state. This is further complicated by the occurrence of a distinct form of neoteric subclinical infection, which is indistinguishable from the carrier state in field scenarios, but may have substantially different epidemiological properties. This review summarizes the current state of knowledge of the FMDV carrier state and identifies specific areas of research in need of further attention. Findings from experimental investigations of FMDV pathogenesis are discussed in relation to experience gained from field studies of foot-and-mouth disease.

Improved foot-and-mouth disease vaccine with O PanAsia-2 strain protect pigs against O/Jincheon/SKR/2014 originated from South Korea

Efforts are required to develop foot-and-mouth disease (FMD) vaccines in Asia that can respond to the type O outbreaks that have continued with the devastating damage since 2010. It is necessary to develop vaccine strains that can provide protection against the ME-SA topotype, which has tended to spread into neighboring areas, and the frequent SEA topotype outbreaks. To this end, this study aimed to develop a FMD vaccine utilizing O PanAsia-2 that is able to provide broad protection against ME-SA as the vaccine strain, with a focus on the O/Jincheon/SKR/2014 virus (SEA topotype), the outbreaks of which have persisted in spite of the enforcement of FMD vaccination. The virus neutralizing antibody (VN) titer to the ME-SA topotype (especially, Ind2001 lineage) virus in pigs was the highest, followed by SEA, while the VN titers to the Cathay and EURO-SA topotypes were similar. In the O/Jincheon/SKR/2014 virus challenge test, all pigs were protected against the virus, and almost no virus shedding was detected after the virus challenge. In the immunization test performed on cattle and pigs, antibodies with sufficient protective activity were produced in cattle two weeks after the first immunization, and pigs exhibited lower immunity compared to cattle. However, immunity was improved enough in pigs to provide protection against the virus challenge after the second immunization, with a significant increase in antibody production.

High-Resolution Composition Analysis of an Inactivated Polyvalent Foot-and-Mouth Disease Vaccine

Appropriate vaccine selection is crucial in the control of foot-and-mouth disease (FMD). Vaccination can prevent clinical disease and reduces viral shedding, but there is a lack of cross-protection between the seven serotypes and their sublineages, making the selection of an adequately protective vaccine difficult. Since the exact composition of their vaccines is not consistently disclosed by all manufacturers, incompatibility of the strains used for vaccination with regionally circulating strains can cause vaccination campaigns to fail. Here, we present a deep sequencing approach for polyvalent inactivated FMD vaccines that can identify all component strains by their genome sequences. The genomes of all strains of a commercial pentavalent FMD vaccine were de novo assembled and the vaccine composition determined semi-quantitatively. The genome assembly required high stringency parameters to prevent misassemblies caused by conserved regions of the genome shared by related strains. In contrast, reference-guided assembly is only recommended in cases where the number of strains is previously known and appropriate reference sequences are available. The presented approach can be applied not only to any inactivated whole-virus FMD vaccine but also to vaccine quality testing in general and allows for better decision-making for vaccines with an unknown composition.

Evaluation of novel inactivated vaccines for the SAT 1, SAT 2 and SAT 3 serotypes of foot-and-mouth disease in pigs

Background

The foot-and-mouth disease (FMD) virus is classified into seven serotypes, of which the South African types have South African Territories (SAT)1, SAT2, and SAT3 that are prevalent in Africa. Especially SAT2 have spread to Arabian Peninsula and the Palestinian Autonomous Territories. Of these viruses, the incidence of SAT2 is the highest. It is important to prepare for the spread of the virus to other continents, even though most FMD viruses are bovine-derived. In particular, due to the high breeding density of pigs in Asia, more attention is usually paid to the immunity and protection of pigs than cattle. For this reason, this study investigated the immunity and protection of pigs against the SAT viruses.

Methods

Specific vaccines were developed for SAT1, SAT2, and SAT3 serotypes. These vaccine viruses were designed to be distinguished from the wild-type strain. An immunogenicity test was conducted using these vaccines in both cattle (n = 5/group) and pigs (n = 20/group).

Results

High virus-neutralizing titer of antibodies (> 1:100) was induced in only 2 weeks after the immunization of cattle with the individual vaccine for SAT1, SAT2 or SAT3, and a clear immune response was induced after the second immunization in pigs. When the vaccinated pigs (n = 4–5/group) were challenged by the homologous wild-type virus strain 4 weeks after immunization, all the pigs were protected from the challenge.

Conclusions

This study confirmed that these vaccines can be used against SAT1, SAT2, and SAT3 viruses in cattle and pigs. The vaccine strains developed in this study are expected to be used as vaccines that can protect against FMD in the event of a future FMD outbreak in pigs in consideration of the situation in Asia.

New foot-and-mouth disease vaccine, O JC-R, induce complete protection to pigs against SEA topotype viruses occurred in South Korea, 2014-2015

Foot-and-mouth disease (FMD) is an acute epidemic that spreads rapidly among cattle and pigs. In 2014, in Korea, despite enforced vaccination, the type O Southeast Asia (SEA) topotype viruses (Mya-98 lineage) infected mainly cattle and pigs simultaneously, thereby causing enormous damage. If a vaccine that is completely protective against this FMD virus is developed and used, it can become a very important preventive measure in Asia, which is where this type of virus mainly circulates. The SEA topotype has been steadily evolving and transforming into new variations since it became epidemic in Asia. Therefore, it became necessary to develop a new vaccine that could provide protection against the FMD virus strain that was responsible for the 2014–2015 outbreak in Korea. This study aimed to develop a vaccine that would provide complete protection against the SEA topotype FMD virus to control sporadic FMD outbreaks, which occur despite the enforcement of vaccination, and to completely prevent virus shedding, thereby preventing the virus from spreading. The vaccine candidate virus developed in this study showed low pathogenicity and can be distinguished from the wild-type FMD virus strain. The developed vaccine was able to protect mice from SEA and Middle East–South Asia topotype virus strains and induced high titers of antibodies against both virus strains in pigs, thereby confirming the sufficiency of its protective function. In particular, the results of the SEA topotype virus challenge test in pigs revealed that perfect immunity was created in the vaccinated pigs, without virus shedding and viremia.

Needleless intradermal vaccination for foot-and-mouth disease induced granuloma-free effective protection in pigs

Vaccination is one of the most effective ways of controlling and preventing foot-and-mouth disease (FMD) outbreaks. The effective prevention of this disease requires the use of high-quality vaccines to meet the criteria that enable customers to use them simply. The administration of FMD vaccines containing oil-based adjuvants in pigs can induce the formation of granuloma in the muscle of the vaccinated, which makes these vaccines a less preferable option. Therefore, it is important to establish an FMD vaccine and vaccine delivery tool that offers better immunity and safer application. This study compared the immune responses of intramuscular and needleless intradermal vaccination in pigs. When the same amount of an FMD virus (FMDV) antigen was administered to pigs, both the intradermally and intramuscularly vaccinated groups were protected completely against a challenge of the homologous FMDV, but the intramuscularly vaccinated group showed an overall higher level of neutralizing antibodies. Importantly, the formation of granuloma in muscle could be excluded in the intradermally vaccinated group. Of the oil-based adjuvants selected in this study, ISA 207 was effective in eliciting immunogenicity in intradermal vaccination. In conclusion, a new vaccine formula can be chosen for the delivery of intradermal route to exclude the possibility of local reactions in the muscle and generate protective immunity against an FMDV challenge.

Validation of a high performance liquid chromatography method for quantitation of foot-and-mouth disease virus antigen in vaccines and vaccine manufacturing

Foot-and-mouth disease (FMD) is an infectious viral disease that affects the main meat and dairy production animals, including cattle, sheep, goats and swine. It is readily transmissible and countries where the disease is present suffer harsh international trade restrictions on livestock products and serious economic losses. Vaccines are important tools to contain outbreaks and maintain the status of free with or without vaccination, as defined by the World Organization for Animal Health (OIE). The efficacy of vaccines is reliant on the content and integrity of inactivated virus particles. The long-established method to quantify the viral content of vaccines along the manufacturing process and in the final product is the 140S sucrose density gradient analysis. This method has been a valuable tool for many decades. However, it requires gradient preparation for each sample, a lengthy ultracentrifugation and a manual UV reading of the gradient, rendering it highly operator dependent and almost impossible to automate. We present a method to quantify FMDV particles in vaccines and intermediate process samples that is based on separation of components by size exclusion high performance liquid chromatography (SE-HPLC) and measurement of virus by absorption at 254 nm. The method has been extensively validated; it is accurate, precise and linear. It is applicable to all FMDV strains and sample materials and has a good concordance with the 140S test. The proposed method uses off the shelf HPLC equipment and columns. It is easily automated for high throughput operation, affording a useful process analytical technology and a novel tool for control of final product by manufacturers and regulatory agencies.

Improved foot-and-mouth disease vaccine, O TWN-R, protects pigs against SEA topotype virus occurred in South Korea

Foot-and-mouth disease (FMD) is a highly contagious disease and causes economic damage at a national level. In particular, the type O FMD virus (FMDV) is a serotype that causes FMD outbreaks most frequently in the world. In recent years, Southeast Asia (SEA), Middle East-South Asia (ME-SA), and Cathay topotype-mediated FMD are prevalent in Asia, among which the SEA and ME-SA topotypes cause a majority of the outbreaks. The SEA topotype virus is more likely to infect both cattle and pigs simultaneously, thereby resulting in more severe damages; thus, it is necessary to study the protection ability of the candidate vaccines of this topotype after immunization. In this study, an experimental vaccine for pigs was produced using a vaccine strain that contains the structural protein of the O Taiwan97 strain, which was derived from the Cathay topotype, and its effect was evaluated. In the immunization test in pigs and cattle, the antibody titers were found to be elevated two weeks after immunization and very high titers of neutralizing antibodies were formed after four weeks. After the second inoculation, very high titers of neutralizing antibodies were produced in both species in the fourth week after immunization, and the antibodies maintained for up to six months and three months in cattle and pigs, respectively. No significant immunological difference in antibody production was observed in cattle and pigs. This study confirmed that complete protection from the challenge of the SEA topotype virus (O/Jincheon/SKR/2014), although the antibody titers against O/Jincheon/SKR/2014 strain were not that high, was achieved through immunization with the newly developed Cathay topotype vaccine in pigs.

Cross-protective efficacy of the O1 Manisa + O 3039 bivalent vaccine and the O 3039 monovalent vaccine against heterologous challenge with FMDV O/Jincheon/SKR/2014 in pig

After massive foot-and-mouth disease (FMD) outbreaks originated from Jincheon County from Dec. 2014 to Apr. 2015, the effectiveness of the previous FMD vaccine containing only the O1 Manisa as the O antigen, O1 Manisa + A Malaysia 97 + Asia 1 Sharmir trivalent vaccine, was questioned in South Korea, and a change in the O antigen in FMD vaccines was demanded to control the FMD caused by FMDV O/Jincheon/SKR/2014, the O Jincheon strain. Therefore, the efficacies of O1 Manisa + O 3039 bivalent vaccine and O 3039 monovalent vaccine were studied for cross-protection against heterologous challenge with the O Jincheon strain. In this study, the efficacy of the O1 Manisa + O 3039 bivalent vaccine was better than that of the O 3039 monovalent vaccine, even though the serological relationship (r₁ value) between O Jincheon and O 3039 was matched according to the OIE Terrestrial Manual. According to serological test results from vaccinated specific pathogen free pigs, virus neutralization test titers against Jincheon were good estimates for predicting protection against challenge. A field trial of the O1 Manisa + O 3039 bivalent vaccine was performed to estimate the possibility of field application in conventional pig farms, especially due to concerns about the effect of maternally derived antibodies (MDA) in field application of the FMD vaccine. According to the result of the field trial, the O1 Manisa + O 3039 bivalent vaccine was considered to overcome MDA. The results of the efficacy and field trials indicated that the O1 Manisa + O3039 vaccine could be suitable to replace previous FMD vaccines to control the FMD field situation caused by O Jincheon FMDV.

Chimeric vaccine strain of type O foot-and-mouth disease elicits a strong immune response in pigs against ME-SA and SEA topotypes

Foot-and-mouth disease (FMD) is an acute infectious disease occurring in cloven-hoofed animals. There are many variations of the virus, making it difficult to protect against the various strains with one virus vaccine. The immunogenicity has generally been evaluated in pigs using neutralizing antibodies to determine the protection level against foot-and-mouth disease virus type O. Therefore, the vaccine from the chimeric vaccine strain of ME-SA (VP4, VP2, and VP3) and SEA (VP1) topotypes developed in this study is expected to be able to protect with high neutralizing antibody titers against most of the eight FMD viruses of the four different topotypes (ME-SA, SEA, Cathay, and EURO-SA) of type O in pigs. This is a new technique for powerful vaccine development, with multiple preventive roles against various epidemic FMD strains.