D-galacto-D-mannan-mediated Dectin-2 activation orchestrates potent cellular and humoral immunity as a viral vaccine adjuvant.

Introduction: Conventional foot-and-mouth disease (FMD) vaccines have been developed to enhance their effectiveness; however, several drawbacks remain, such as slow induction of antibody titers, short-lived immune response, and local side effects at the vaccination site. Therefore, we created a novel FMD vaccine that simultaneously induces cellular and humoral immune responses using the Dectin-2 agonist, D-galacto-D-mannan, as an adjuvant. Methods: We evaluated the innate and adaptive (cellular and humoral) immune responses elicited by the novel FMD vaccine and elucidated the signaling pathway involved both in vitro and in vivo using mice and pigs, as well as immune cells derived from these animals. Results: D-galacto-D-mannan elicited early, mid-, and long-term immunity via simultaneous induction of cellular and humoral immune responses by promoting the expression of immunoregulatory molecules. D-galacto-D-mannan also enhanced the immune response and coordinated vaccine-mediated immune response by suppressing genes associated with excessive inflammatory responses, such as nuclear factor kappa B, via Sirtuin 1 expression. Conclusion: Our findings elucidated the immunological mechanisms induced by D-galacto-D-mannan, suggesting a background for the robust cellular and humoral immune responses induced by FMD vaccines containing D-galacto-D-mannan. Our study will help to facilitate the improvement of conventional FMD vaccines and the design of next-generation FMD vaccines.

Isoprinosine as a foot-and-mouth disease vaccine adjuvant elicits robust host defense against viral infection through immunomodulation.

Background: Commercial foot-and-mouth disease (FMD) vaccines have limitations, such as local side effects, periodic vaccinations, and weak host defenses. To overcome these limitations, we developed a novel FMD vaccine by combining an inactivated FMD viral antigen with the small molecule isoprinosine, which served as an adjuvant (immunomodulator). Method: We evaluated the innate and adaptive immune responses elicited by the novel FMD vaccine involved both in vitro and in vivo using mice and pigs. Results: We demonstrated isoprinosine-mediated early, mid-term, and long-term immunity through in vitro and in vivo studies and complete host defense against FMD virus (FMDV) infection through challenge experiments in mice and pigs. We also elucidated that isoprinosine induces innate and adaptive (cellular and humoral) immunity via promoting the expression of immunoregulatory gene such as pattern recognition receptors [PRRs; retinoic acid-inducible gene (RIG)-I and toll like receptor (TLR)9], transcription factors [T-box transcription factor (TBX)21, eomesodermin (EOMES), and nuclear factor kappa B (NF-kB)], cytokines [interleukin (IL)-12p40, IL-23p19, IL-23R, and IL-17A)], and immune cell core receptors [cluster of differentiation (CD)80, CD86, CD28, CD19, CD21, and CD81] in pigs. Conclusion: These findings present an attractive strategy for constructing novel FMD vaccines and other difficult-to-control livestock virus vaccine formulations based on isoprinosine induced immunomodulatory functions.

Evaluation of a Vaccine Candidate Designed for Broad-Spectrum Protection against Type A Foot-and-Mouth Disease in Asia.

Foot-and-mouth disease (FMD) vaccines are currently the most powerful protective and preventive measures used to control FMD. In this study, the chimeric vaccine strain containing antigenic epitopes from the FMD virus serotype A, which belongs to the ASIA topotype, was produced and evaluated. The chimeric vaccine strains contain sea-97/G1 (VP4, VP2, VP3) and A22 Iraq (VP1) or G-VII (VP1) for use in FMD vaccines in Asia. The 50% protective dose was determined in mice. Vaccinated mice were challenged with three different type A viruses (Sea-97/G1, Sea-97/G2, G-VII clade) seven days post-vaccination (dpv), and mice that received the vaccine candidates were protected against the three viruses. The protective capability of one of the vaccine candidates was evaluated in pigs. Vaccinated pigs were challenged with three different type A viruses (Sea-97/G1, Sea-97/G2, G-VII clade) at 28 dpv, and pigs that received the vaccine candidate were protected against the three viruses. The results showed that this vaccine candidate, which was designed to provide protection against FMD in Asia, efficiently protected pigs against virus challenge and thus has potential as a broad-spectrum vaccine for various epidemic FMD viruses.

Bestatin, A Pluripotent Immunomodulatory Small Molecule, Drives Robust and Long-Lasting Immune Responses as an Adjuvant in Viral Vaccines.

An inactivated whole-virus vaccine is currently used to prevent foot-and-mouth disease (FMD). Although this vaccine is effective, it offers short-term immunity that requires regular booster immunizations and has several side effects, including local reactions at the vaccination site. To address these limitations, herein, we evaluated the efficacy of bestatin as a novel small molecule adjuvant for inactivated FMD vaccines. Our findings showed that the FMD vaccine formulated with bestatin enhanced early, intermediate-, and particularly long-term immunity in experimental animals (mice) and target animals (pigs). Furthermore, cytokines (interferon (IFN)α, IFNß, IFNγ, and interleukin (IL)-29), retinoic acid-inducible gene (RIG)-I, and T-cell and B-cell core receptors (cluster of differentiation (CD)28, CD19, CD21, and CD81) markedly increased in the group that received the FMD vaccine adjuvanted with bestatin in pigs compared with the control. These results indicate the significant potential of bestatin to improve the efficacy of inactivated FMD vaccines in terms of immunomodulatory function for the simultaneous induction of potent cellular and humoral immune response and a long-lasting memory response.

Inactivated vaccine with glycyrrhizic acid adjuvant elicits potent innate and adaptive immune responses against foot-and-mouth disease.

Background: Foot-and-mouth disease (FMD) is an extremely contagious viral disease that is fatal to young animals and is a major threat to the agricultural economy by reducing production and limiting the movement of livestock. The currently commercially-available FMD vaccine is prepared using an inactivated viral antigen in an oil emulsion, with aluminum hydroxide [Al(OH)3] as an adjuvant. However, oil emulsion-based options possess limitations including slow increases in antibody titers (up to levels adequate for defense against viral infection) and risks of local reactions at the vaccination site. Further, Al(OH)3 only induces a T helper 2 (Th2) cell response. Therefore, novel adjuvants that can address these limitations are urgently needed. Glycyrrhizic acid (extracted from licorice roots) is a triterpenoid saponin and has great advantages in terms of price and availability. Methods: To address the limitations of the currently used commercial FMD vaccine, we added glycyrrhizic acid as an adjuvant (immunostimulant) to the FMD bivalent (O PA2 + A YC) vaccine. We then evaluated its efficacy in promoting both innate and adaptive (cellular and humoral) immune reactions in vitro [using murine peritoneal exudate cells (PECs) and porcine peripheral blood mononuclear cells (PBMCs)] and in vivo (using mice and pigs). Results: Glycyrrhizic acid has been revealed to induce an innate immune response and enhance early, mid-, and long-term immunity. The studied bivalent vaccine with glycyrrhizic acid increased the expression of immunoregulatory genes such as pattern-recognition receptors (PRRs), cytokines, transcription factors, and co-stimulatory molecules. Conclusion: Collectively, glycyrrhizic acid could have utility as a novel vaccine adjuvant that can address the limitations of commercialized FMD vaccines by inducing potent innate and adaptive immune responses.

The role of zinc sulfate in enhancing cellular and humoral immune responses to foot-and-mouth disease vaccine.

Foot-and-mouth disease (FMD) is a rapidly propagating infectious disease of cloven-hoofed animals, especially cattle and pigs, affecting the productivity and profitability of the livestock industry. Presently, FMD is controlled and prevented using vaccines; however, conventional FMD vaccines have several disadvantages, including short vaccine efficacy, low antibody titers, and safety issues in pigs, indicating the need for further studies. Here, we evaluated the efficacy of a novel bivalent vaccine containing zinc sulfate as an immunostimulant and FMD type O and A antigens (O PA2 and A YC, respectively) against FMD virus in mice and pigs. Zinc sulfate induced cellular immunity in murine peritoneal exudate cells (PECs) and porcine peripheral blood mononuclear cells (PBMCs) by increasing IFNγ secretion. Additionally, FMD vaccine containing O PA2 and A YC antigens and zinc sulfate induced early, mid-, and long-term immune responses in mice and pigs, and enhanced cellular and humoral immunity by regulating the expression of pathogen recognition receptors (PRRs), transcription factors, co-stimulatory molecules, and cytokines in porcine PBMCs from vaccinated pigs. Overall, these results indicated that the novel immunostimulant zinc sulfate induced potent cellular and humoral immune responses by stimulating antigen-presenting cells (APCs) and T and B cells, and enhanced long-term immunity by promoting the expression of co-stimulatory molecules. These outcomes suggest that zinc sulfate could be used as a novel vaccine immunostimulant for difficult-to-control viral diseases, such as African swine fever (ASF) or COVID-19.

Dectin-1 signaling coordinates innate and adaptive immunity for potent host defense against viral infection.

Background: Most commercial foot-and-mouth disease (FMD) vaccines have various disadvantages, such as low antibody titers, short-lived effects, compromised host defense, and questionable safety. Objectives: To address these shortcomings, we present a novel FMD vaccine containing Dectin-1 agonist, ß-D-glucan, as an immunomodulatory adjuvant. The proposed vaccine was developed to effectively coordinate innate and adaptive immunity for potent host defense against viral infection. Methods: We demonstrated ß-D-glucan mediated innate and adaptive immune responses in mice and pigs in vitro and in vivo. The expressions of pattern recognition receptors, cytokines, transcription factors, and co-stimulatory molecules were promoted via FMD vaccine containing ß-D-glucan. Results: ß-D-glucan elicited a robust cellular immune response and early, mid-, and long-term immunity. Moreover, it exhibited potent host defense by modulating host's innate and adaptive immunity. Conclusion: Our study provides a promising approach to overcoming the limitations of conventional FMD vaccines. Based on the proposed vaccine's safety and efficacy, it represents a breakthrough among next-generation FMD vaccines.

Genetic diversity of porcine reproductive and respiratory syndrome virus and evaluation of three one-step real-time RT-PCR assays in Korea.

BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) has caused huge economic losses in the global swine industry. Frequent genetic variations in this virus cause difficulties in controlling and accurately diagnosing PRRSV. METHODS: In this study, we investigated the genetic characteristics of PRRSV-1 and PRRSV-2 circulating in Korea from January 2018 to September 2021 and evaluated three one-step real-time reverse transcription polymerase chain reaction (RT-PCR) assays. RESULTS: A total of 129 lung samples were collected, consisting of 47 samples for PRRSV-1, 62 samples for PRRSV-2, and 20 PRRSV-negative samples. Nucleotide sequence analysis of open reading frames (ORFs) 5, ORF6, and ORF7 genes from PRRSV samples showed that PRRSV-1 belonged to subgroup A (43/47, 91.49%) and subgroup C (4/47, 8.51%), whereas PRRSV-2 was classified as lineage 1 (25/62, 40.32%), Korean lineage (Kor) C (13/62, 20.97%), Kor B (10/62, 16.13%), lineage 5 (9/62, 14.52%), and Kor A (5/62, 8.06%). Amino acid sequence analysis showed that the neutralizing epitope and T cell epitope of PRRSV-1, and the decoy epitope region and hypervariable regions of PRRSV-2 had evolved under positive selection pressure. In particular, the key amino acid substitutions were found at positions 102 and 104 of glycoprotein 5 (GP5) in some PRRSV-2, and at positions 10 and 70 of membrane protein (M) in most PRRSV-2. In addition, one-step real-time RT-PCR assays, comprising two commercial tests and one test recommended by the World Organization for Animal Health (OIE), were evaluated. CONCLUSION: The results revealed that two of the real-time RT-PCR assays had high sensitivities and specificities, whereas the real-time RT-PCR assay of the OIE had low sensitivity due to mismatches between nucleotides of Korean PRRSVs and forward primers. In this study, we genetically characterized recent PRRSV occurrences and evaluated three one-step real-time RT-PCR assays used in Korea.

Whole-genome sequencing and genetic characteristics of representative porcine reproductive and respiratory syndrome virus (PRRSV) isolates in Korea.

BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) is a macrophage-tropic arterivirus with extremely high genetic and pathogenic heterogeneity that causes significant economic losses in the swine industry worldwide. PRRSV can be divided into two species [PRRSV1 (European) and PRRSV2 (North American)] and is usually diagnosed and genetically differentiated into several lineages based on the ORF5 gene, which constitutes only 5% of the whole genome. This study was conducted to achieve nonselective amplification and whole-genome sequencing (WGS) based on a simplified sequence-independent, single-primer amplification (SISPA) technique with next-generation sequencing (NGS), and to genetically characterize Korean PRRSV field isolates at the whole genome level. METHODS: The SISPA-NGS method coupled with a bioinformatics pipeline was utilized to retrieve full length PRRSV genomes of 19 representative Korean PRRSV strains by de novo assembly. Phylogenetic analysis, analysis of the insertion and deletion (INDEL) pattern of nonstructural protein 2 (NSP2), and recombination analysis were conducted. RESULTS: Nineteen complete PRRSV genomes were obtained with a high depth of coverage by the SISPA-NGS method. Korean PRRSV1 belonged to the Korean-specific subtype 1A and vaccine-related subtype 1C lineages, showing no evidence of recombination and divergent genetic heterogeneity with conserved NSP2 deletion patterns. Among Korean PRRSV2 isolates, modified live vaccine (MLV)-related lineage 5 viruses, lineage 1 viruses, and nation-specific Korean lineages (KOR A, B and C) could be identified. The NSP2 deletion pattern of the Korean lineages was consistent with that of the MN-184 strain (lineage 1), which indicates the common ancestor and independent evolution of Korean lineages. Multiple recombination signals were detected from Korean-lineage strains isolated in the 2010s, suggesting natural interlineage recombination between circulating KOR C and MLV strains. Interestingly, the Korean strain GGYC45 was identified as a recombinant KOR C and MLV strain harboring the KOR B ORF5 gene and might be the ancestor of currently circulating KOR B strains. Additionally, two novel lineage 1 recombinants of NADC30-like and NADC34-like viruses were detected. CONCLUSION: Genome-wide analysis of Korean PRRSV isolates retrieved by the SISPA-NGS method and de novo assembly, revealed complex evolution and recombination in the field. Therefore, continuous surveillance of PRRSV at the whole genome level should be conducted, and new vaccine strategies for more efficient control of the virus are needed.

Temporal lineage dynamics of the ORF5 gene of porcine reproductive and respiratory syndrome virus in Korea in 2014-2019.

Porcine reproductive and respiratory syndrome virus (PRRSV) is the most important pathogen in the Korean swine industry. Despite efforts including improved biosecurity and vaccination protocols, the virus continues to circulate and evolve. Based on phylogenetic analysis of open reading frame 5 (ORF5), Korean PRRSVs are known to form not only globally circulating lineages but also country-specific lineages (Lin Kor A, B, and C). To understand the recent epidemiological status of PRRSV in Korea, a total of 1349 ORF5 sequences of Korean PRRSV isolates from 2014 to 2019 were analyzed. Phylogenetic analysis was conducted using the maximum-likelihood method, and temporal changes in the relative prevalence of lineages were investigated. The analysis showed that PRRSV1 and PRRSV2 were both highly prevalent throughout the years examined. Among the PRRSV1 isolates, subgroup A (90.1%) and vaccine-like subgroup C (9.0%) composed most of the population. For PRRSV2 isolates, vaccine-like lineage 5 (36.3%) was dominant, followed by Lin Kor B (25.9%), Kor C (16.6%), lineage 1 (11.6%), and Kor A (9.1%). The PRRSV2 lineage 1 population increased from 2014 (1.8%) to 2019 (29.6%) in Korea due to the continual spread of sublineage 1.8 (NADC30-like) and introduction of sublineage 1.6 into the country. Additional genetic analysis, including analysis of non synonymous and synonymous mutations, revealed evidence of diversification and positive selection in immunologically important regions of the genome, suggesting that current vaccination is failing and promoting immune-mediated selection. Overall, these findings provide insights into the epidemiological and evolutionary dynamics of cocirculating viral lineages, and constant surveillance of PRRSV occurrence is needed.

Evaluation of the Variability of the ORF34, ORF68, and MLST Genes in EHV-1 from South Korea.

Equine herpesvirus-1 (EHV-1) is an important pathogen in horses. It affects horses worldwide and causes substantial economic losses. In this study, for the first time, we characterized EHV-1 isolates from South Korea at the molecular level. We then aimed to determine the genetic divergences of these isolates by comparing them to sequences in databases. In total, 338 horse samples were collected, and 12 EHV-1 were isolated. We performed ORF30, ORF33, ORF68, and ORF34 genetic analysis and carried out multi-locus sequence typing (MLST) of 12 isolated EHV-1. All isolated viruses were confirmed as non-neuropathogenic type, showing N752 of ORF30 and highly conserved ORF33 (99.7-100%). Isolates were unclassified using ORF68 analysis because of a 118 bp deletion in nucleotide sequence 701-818. Seven EHV-1 isolates (16Q4, 19R166-1, 19R166-6, 19/10/15-2, 19/10/15-4, 19/10/18-2, 19/10/22-1) belonged to group 1, clade 10, based on ORF34 and MLST analysis. The remaining 5 EHV-1 isolates (15Q25-1, 15D59, 16Q5, 16Q40, 18D99) belonged to group 7, clade 6, based on ORF34 and MLST analysis.

Efficient protection against Asia1 type foot-and-mouth disease using a chimeric vaccine strain suitable for East Asia.

The type Asia1 genetic group(G)-V lineage foot-and-mouth disease (FMD) virus was identified in the East-Asian region in 2009. To date, only Shamir has been used as a standard vaccine strain worldwide for type Asia1. To prevent type Asia1 FMD in eastern Asia, two vaccine strains (ASM-R: G-V and ASM-SM: G-V/Shamir fusion) were developed and tested against type Asia1 virus strains. After immunization with the two experimental vaccines, the ASM-SM strain showed a higher level of protection against Shamir virus in mice. Additional immunogenicity tests were carried out in cattle and pigs, revealing sufficient antibody production capable of protecting the animals against the viral challenge. In cattle, the immune response started just 2 weeks after vaccination. Immunogenicity was lower in pigs, but antibody production was greatly increased to a high level after a second vaccination round. In particular, herein, 60 % and 100 % of the vaccinated pigs challenged with the Asia1 Shamir virus were determined to be clinically protected after one and two vaccination rounds with ASM-R, respectively. Pigs vaccinated twice produced sufficient antibody titers with low virus shedding for short time. Moreover, ASM-SM single-vaccinated pigs showed 100 % protection when challenged with the Asia1 Shamir virus. In summary, the vaccine strain ASM-SM designed for the defense of the Asian region efficiently granted protection to pigs against the typical Asia1 virus, Shamir.

Improved immune responses and safety of foot-and-mouth disease vaccine containing immunostimulating components in pigs.

BACKGROUND: The quality of a vaccine depends strongly on the effects of the adjuvants applied simultaneously with the antigen in the vaccine. The adjuvants enhance the protective effect of the vaccine against a viral challenge. Conversely, oil-type adjuvants leave oil residue inside the bodies of the injected animals that can produce a local reaction in the muscle. The long-term immunogenicity of mice after vaccination was examined. ISA206 or ISA15 oil adjuvants maintained the best immunity, protective capability, and safety among the oil adjuvants in the experimental group. OBJECTIVES: This study screened the adjuvant composites aimed at enhancing foot-and-mouth disease (FMD) immunity. The C-type lectin or toll-like receptor (TLR) agonist showed the most improved protection rate. METHODS: Experimental vaccines were fabricated by mixing various known oil adjuvants and composites that can act as immunogenic adjuvants (gel, saponin, and other components) and examined the enhancement effect on the vaccine. RESULTS: The water in oil (W/O) and water in oil in water (W/O/W) adjuvants showed better immune effects than the oil in water (O/W) adjuvants, which have a small volume of oil component. The W/O type left the largest amount of oil residue, followed by W/O/W and O/W types. In the mouse model, intramuscular inoculation showed a better protection rate than subcutaneous inoculation. Moreover, the protective effect was particularly weak in the case of inoculation in fatty tissue. The initial immune reaction and persistence of long-term immunity were also confirmed in an immune reaction on pigs. CONCLUSIONS: The new experimental vaccine with immunostimulants produces improved immune responses and safety in pigs than general oil-adjuvanted vaccines.

Antigenic properties of a novel vaccine strain for type Asia1 foot-and-mouth disease in pigs.

Newly developed vaccine strains to prevent foot-and-mouth disease caused by the emerging serotype Asia1 virus were evaluated. To protect against the group (G)-VIII strain, which occurred recently, we produced an infectious cDNA clone of Asia1 Shamir cDNA (Asia1 Shamir-R). In addition, by adding a site 1 epitope of VP1 of the G-VIII lineage virus to this virus, we produced a new virus (Sham GVIII- EPI), and another virus(Sham GVIII-VP1) was replaced with that of G-VIII lineage in the VP1 region of Shamir. Test vaccines were produced using these three types of vaccine virus, and their immunogenicity and protection capabilities were evaluated in mice. Immunized mice were challenged with the Asia1 Shamir or G-VIII virus, and the results show that all the vaccines have similar protective effects. As they showed similar antigenicity, we chose the Shamir-R vaccine. Pigs maintained relatively high neutralizing antibody levels against homologous viruses of the Shamir and G-VII or G-VIII lineage three to four weeks after immunization. However, they formed relatively low levels of antibodies to G-IV and G-V viruses. In conclusion, we produced a vaccine candidate capable of protection against the G-VIII virus in the vaccine experiment for the type Asia1 serotype vaccine. This Shamir-R vaccine virus was found to protect against the viruses of the Asia1 genotype G-VII and G-VIII lineages, which occurred recently in Asia.

Advanced Foot-And-Mouth Disease Vaccine Platform for Stimulation of Simultaneous Cellular and Humoral Immune Responses.

Currently available commercial foot-and-mouth disease (FMD) vaccines have various limitations, such as the slow induction and short-term maintenance of antibody titers. Therefore, a novel FMD vaccine that can rapidly induce high neutralizing antibody titers to protect the host in early stages of an FMD virus infection, maintain high antibody titers for long periods after one vaccination dose, and confer full protection against clinical symptoms by simultaneously stimulating cellular and humoral immunity is needed. Here, we developed immunopotent FMD vaccine strains A-3A and A-HSP70, which elicit strong initial cellular immune response and induce humoral immune response, including long-lasting memory response. We purified the antigen (inactivated virus) derived from these immunopotent vaccine strains, and evaluated the immunogenicity and efficacy of the vaccines containing these antigens in mice and pigs. The immunopotent vaccine strains A-3A and A-HSP70 demonstrated superior immunogenicity compared with the A strain (backbone strain) in mice. The oil emulsion-free vaccine containing A-3A and A-HSP70 antigens effectively induced early, mid-term, and long-term immunity in mice and pigs by eliciting robust cellular and humoral immune responses through the activation of co-stimulatory molecules and the secretion of proinflammatory cytokines. We successfully derived an innovative FMD vaccine formulation to create more effective FMD vaccines.

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.

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.

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.

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.

Evaluation of novel inactivated vaccine for type C foot-and-mouth disease in cattle and pigs.

Foot-and-mouth disease virus (FMDV) is the cause of an economically devastating disease in major cloven-hoofed livestock. Although type C foot-and-mouth disease (FMD) has not occurred anywhere worldwide since 2004, the antigen bank should be preserved in preparation for an unexpected outbreak. We therefore conducted experiments to develop inactivated vaccines that are safer and exhibit improved characteristics over existing vaccines. Our previous study showed that the replacement of the capsid-encoding gene (P1) from the vaccine strain O1 Manisa could be rescued successfully from the vaccine strains. In addition, novel point mutation in the 3C region in the virus genome, for induction of properties with low pathogenesis to create a safe vaccine, and 3B1B2 replacement, for differential diagnosis with the wild type virus, were performed. The modified FMD vaccine strain, C3 Resende-R, was shown to provide lower pathogenesis in young mice than the wild-type virus. To identify the immune responses after vaccination with 146S antigen (15 µg/mL/dose), we conducted a virus neutralization test using serum from pigs and cattle vaccinated with the inactivated vaccine. The neutralizing titers in the cattle were higher than those in the pigs and maintained mean antibody titers of around 1:100 until the end of the experiment. The vaccine showed protection capability of 16 PD50 against C3 Resende virus in the pigs. The replacement of the structural protein-coding gene for the new FMDV was a useful tool in the development of an effective vaccine candidate strain. This inactivated vaccine will be used for the establishment of a safe vaccine strain for the antigen bank.