Rapid Engineering of Foot-and-Mouth Disease Vaccine and Challenge Viruses.

There are seven antigenically distinct serotypes of foot-and-mouth disease virus (FMDV), each of which has intratypic variants. In the present study, we have developed methods to efficiently generate promising vaccines against seven serotypes or subtypes. The capsid-encoding gene (P1) of the vaccine strain O1/Manisa/Turkey/69 was replaced with the amplified or synthetic genes from the O, A, Asia1, C, SAT1, SAT2, and SAT3 serotypes. Viruses of the seven serotype were rescued successfully. Each chimeric FMDV with a replacement of P1 showed serotype-specific antigenicity and varied in terms of pathogenesis in pigs and mice. Vaccination of pigs with an experimental trivalent vaccine containing the inactivated recombinants based on the main serotypes O, A, and Asia1 effectively protected them from virus challenge. This technology could be a potential strategy for a customized vaccine with challenge tools to protect against epizootic disease caused by specific serotypes or subtypes of FMDV.IMPORTANCE Foot-and-mouth disease (FMD) virus (FMDV) causes significant economic losses. For vaccine preparation, the selection of vaccine strains was complicated by high antigenic variation. In the present study, we suggested an effective strategy to rapidly prepare and evaluate mass-produced customized vaccines against epidemic strains. The P1 gene encoding the structural proteins of the well-known vaccine virus was replaced by the synthetic or amplified genes of viruses of seven representative serotypes. These chimeric viruses generally replicated readily in cell culture and had a particle size similar to that of the original vaccine strain. Their antigenicity mirrored that of the original serotype from which their P1 gene was derived. Animal infection experiments revealed that the recombinants varied in terms of pathogenicity. This strategy will be a useful tool for rapidly generating customized FMD vaccines or challenge viruses for all serotypes, especially for FMD-free countries, which have prohibited the import of FMDVs.

Chemical stability of active ingredients in diluted veterinary disinfectant solutions under simulated storage conditions.

Introduction: The product labels of veterinary disinfectants specify their expiration dates to prevent the use of outdated products, as these may result in disinfection and biosecurity failures during outbreak situations. However, a clear standard for the storage conditions of diluted disinfectant solutions has not yet been established, and the effects of storage conditions have scarcely been investigated. To fill this research gap, our study examined the stability of the active ingredients of diluted veterinary disinfectants based on their change in concentrations when stored at various temperatures for various time periods. Methods: Twenty veterinary disinfectants effective against either foot-and-mouth disease or avian influenza viruses were selected. The disinfectants were diluted to effective concentrations following the manufacturer's instructions. Using selective analytical techniques, the concentrations of the active ingredients of the samples that had been stored for varying intervals at different temperatures (4, 20, 30, and 45°C) were determined. These samples included soaps and detergents, acids, oxidizing agents, aldehydes, and copper compounds. The active ingredient concentrations of two of the samples were determined following freezing/thawing cycle, to establish their stability when exposed to simulated winter conditions. Results: Our results showed that most of the active ingredients had concentrations of 90% or greater of their initial concentrations, indicating ≥90% stability over a 21-day period under the experimental storage conditions. However, there were some exceptions. Glutaraldehyde, formaldehyde, and malic acid are over 90% stable at ≤ 30°C for 21 days, but their concentrations decreased to below 90% of their initial concentrations at 45°C, indicating a decline in stability when stored at 45°C for 21 days. The concentrations of potassium peroxymonosulfate and peracetic acid rapidly declined with increasing time and temperature to less than 90% of their initial concentrations. Discussion: Based on our findings, we propose that diluted disinfectant solutions should preferably be prepared daily. However, if the daily preparation of a diluted disinfectant solution is not feasible, then our results can be used as a reference, providing basic scientific data on the chemical stability of diluted disinfectant solutions commonly used in the veterinary field, thus indicating suitable storage conditions.

The interference effect of maternally-derived antibodies on the serological performance of pigs immunized with a foot-and-mouth disease oil emulsion vaccine.

To control foot-and-mouth disease (FMD) outbreaks that originated in Jincheon County in South Korea between 2014 and 2015, several commercial vaccines were studied for their efficacy and serological performance in the field. In this study, the efficacy of the O SKR 7/10 vaccine was evaluated by challenge with the FMD virus (FMDV) O/Jincheon/SKR/2014 (O Jincheon), which has the same O/SEA/Mya-98 lineage as the O/SKR/7/10 strain that was isolated in 2010 in South Korea, in FMD-seronegative pigs. Full protection against the O Jincheon virus was demonstrated as early as 14 days postvaccination, which was explained by the strong serological relationship (r1 value: ≥ 0.92) between the O Jincheon and O SKR 2010 viruses. However, in the field trial, no satisfactory serological elevations against FMDV were observed, even in the double-vaccinated groups. Therefore, it can be concluded that the O SKR 7/10 vaccine may need to be improved to overcome the interference effects from the high levels of maternally-derived antibodies generated due to the mandatory nationwide vaccination of sows in South Korea.

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.

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

On December 3, 2014, a type O foot-and-mouth disease (FMD) outbreak began in Korea. Although vaccinations were administered, FMD cases increased steadily for five months, and reached 185 cases by April 2015. Most of the affected animals were pigs, which are vulnerable to vaccination. The FMD virus belonged to the South-East Asia (SEA) topotype that had been observed three times in Korea between April 2010 and July 2014. However, the FMD virus isolated in December 2014 had a unique feature; that is, partial deletion of the 5´ non-coding region, a deletion not seen in previous SEA topotype isolates identified in Korea. We conclude that this outbreak included the introduction of a new FMD strain to Korea, and that Korea was now affected by genetically similar FMD virus strains that are related to those from neighboring countries.

Coinjection of a vaccine and anti-viral agents can provide fast-acting protection from foot-and-mouth disease.

Foot-and-mouth disease (FMD) is the cause of an economically devastating animal disease. With commercial inactivated FMD vaccines, the protection against FMD virus (FMDV) begins a minimum of 4 days post vaccination (dpv). Therefore, antiviral agents could be proposed for rapid protection and to reduce the spread of FMDV during outbreaks until vaccine-induced protective immunity occurs. In previous studies, we have developed two recombinant adenoviruses that simultaneously express porcine interferon-α and interferon-γ (Ad-porcine IFN-αγ) and multiple siRNAs that target the non-structural protein-regions of FMDV (Ad-3siRNA), and we have shown that the combination of the two antiviral agents (referred to here as Ad combination) induced robust protection against FMDV in pigs. In an attempt to provide complete protection against FMDV, we co-administered Ad combination and the FMD vaccine to mice and pigs. In the C57BL/6 mice model, we observed rapid and continuous protection against homologous FMDV challenge from 1 to 3 dpv-the period in which vaccine-mediated immunity is absent. In the pig experiments, we found that most of the pigs (five out of six) that received vaccine + Ad combination and were challenged with FMDV at 1 or 2 dpv were clinically protected from FMDV. In addition, most of the pigs that received vaccine + Ad combination and all pigs inoculated with the vaccine only were clinically protected from an FMDV challenge at 7 dpv. We believe that the antiviral agent ensures early protection from FMDV, and the vaccine participates in protection after 7 dpv. Therefore, we can say that the combination of the FMD vaccine and effective antiviral agents may offer both fast-acting and continuous protection against FMDV. In further studies, we plan to design coadministration of Ad combination and novel vaccines.

Complete Genome Sequence of a Foot-and-Mouth Disease Virus of Serotype O, Isolated from Gochang, Republic of Korea, in 2016.

The complete genome sequence of a foot-and-mouth disease (FMD) serotype O virus isolated from Gochang, Republic of Korea, is reported here.

Complete Genome Sequence of a Foot-and-Mouth Disease Virus of Serotype O Isolated from Gimje, Republic of Korea, in 2016.

The complete genome sequence of a foot-and-mouth disease (FMD) serotype O virus isolated from Gimje, Republic of Korea, is reported here.

Antiviral activity of ovine interferon tau 4 against foot-and-mouth disease virus.

Foot-and-mouth disease (FMD) is an economically important disease in most parts of the world and new therapeutic agents are needed to protect the animals before vaccination can trigger the host immune response. Although several interferons have been used for their antiviral activities against Foot-and-mouth disease virus (FMDV), ovine interferon tau 4 (OvIFN-τ4), with a broad-spectrum of action, cross-species antiviral activity, and lower incidence of toxicity in comparison to other type І interferons, has not yet been evaluated for this indication. This is the first study to evaluate the antiviral activity of OvIFN-τ4 against various strains of FMDV. The effective anti-cytopathic concentration of OvIFN-τ4 and its effectiveness pre- and post-infection with FMDV were tested in vitro in LFBK cells. In vivo activity of OvIFN-τ4 was then confirmed in a mouse model of infection. OvIFN-τ4 at a concentration of 500 ng, protected mice until 5days post-FMDV challenge and provided 90% protection for 10 days following FMDV challenge. These results suggest that OvIFN-τ4 could be used as an alternative to other interferons or antiviral agents at the time of FMD outbreak.

Application of mouse model for effective evaluation of foot-and-mouth disease vaccine.

Efficacy evaluation of foot-and-mouth disease (FMD) vaccines has been conducted in target animals such as cows and pigs. In particular, handling FMD virus requires a high level of biosafety management and facilities to contain the virulent viruses. The lack of a laboratory animal model has resulted in inconvenience when it comes to using target animals for vaccine evaluation, bringing about increased cost, time and labor for the experiments. The FMD mouse model has been studied, but most FMD virus (FMDV) strains are not known to cause disease in adult mice. In the present study, we created a series of challenge viruses that are lethal to adult C57BL/6 mice. FMDV types O, A, and Asia1, which are related to frequent FMD outbreaks, were adapted for mice and the pathogenesis of each virus was evaluated in the mouse model. Challenge experiments after vaccination using in-house and commercial vaccines demonstrated vaccine-mediated protection in a dose-dependent manner. In conclusion, we propose that FMD vaccine evaluation should be carried out using mouse-adapted challenge viruses as a swift, effective efficacy test of experimental or commercial vaccines.

Novel foot-and-mouth disease virus in Korea, July-August 2014.

Despite nation-wide immunization with O, A, and Asia 1 type vaccines in Republic of Korea, foot-and-mouth disease type O occurred again in July 2014 after three years and three months. This virus was a Mya-98 strain of the Southeast Asian topotype and was most similar to the identified type that circulated in East Asia in 2014. This was new virus with the deletion of 23 amino acids in 3A/3B1 region and low pathogenic property.

Construction of stabilized and tagged foot-and-mouth disease virus.

Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease that affects cloven-hoofed animals worldwide. Construction and purification of stable antigen for vaccine are necessary but technically difficult and laborious. Here, we have tried to investigate an alternative method by inserting a hexa-histidine tag (6xHIS) in the VP1 C-terminal for easy purification and replacing two amino acids of VP1/VP2 to enhance the stability of the capsid of the FMD virus (FMDV) Asia1/MOG/05. In addition, infectious 6xHIS-tagged stable (S/T) FMDVs were maintained under acidic conditions (pH 6.0) and were readily purified from small-scale cultures using a commercial metal-affinity column. The groups vaccinated with the S/T FMDV antigen showed complete protection comparing to low survival rate in the group vaccinated with non-S/T FMDV against lethal challenge with Asia1 Shamir in mice. Therefore, the present findings indicate that the stabilized and tagged antigen offers an alternative to using the current methods for antigen purification and enhancement of stability and has potential for the development of a new FMD vaccine.

Meningoencephalitis caused by Halicephalobus gingivalis in a thoroughbred gelding.

A 6-year-old Thoroughbred gelding was euthanized after a 2-month period of abnormal neurological signs, such as circling left in his pen and hitting his head and body against the wall. After the horse was euthanized on the farm, a half of the brain and whole blood were submitted for diagnostic tests. Histopathological examination of the brain revealed granulomatous and eosinophilic meningoencephalitis with numerous intralesional nematodes, predominantly affecting the cerebrum. Multifocal malacic foci were scattered in the brain parenchyma. The intralesional parasites were identified as Halicephalobus gingivalis by morphological features and PCR testing. To the best of our knowledge, this is the first report of meningoencephalitis caused by H. gingivalis in the horse in Korea.