Foot-and-mouth disease 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.

Foot-and-Mouth Disease

Foot-and-mouth disease (FMD) is a viral infection of livestock that is an important determinant of global trade in animal products. The disease causes a highly contagious vesicular syndrome of cloven-hoofed animals. Successful control of FMD is dependent upon early detection and recognition of the clinical signs, followed by appropriate notification and response of responsible government entities. Awareness of the clinical signs of FMD amongst producers and veterinary practitioners is therefore the key in protecting US agriculture from the catastrophic impacts of an FMD outbreak. This review summarizes key clinical and epidemiologic features of FMD from a US perspective.

National Beef Quality Audit-2022 Phase 1: face-to-face and digital interviews

The National Beef Quality Audit (NBQA) has been conducted regularly since 1991 to assess and benchmark quality in the U.S. beef industry, with the most recent iteration conducted in 2022. The goal of NBQA Phase I is to evaluate what needs to be managed to improve beef quality and demand. Interviews (n = 130) of industry personnel were conducted with the aid of routing software. In total, packers (n = 24), retailers (n = 20), further processors (n = 26), foodservice (n = 18), and allied government agencies and trade organizations (n = 42) were interviewed. Interviews were routed in software based on interviewee involvement in either the fed steer and heifer market cow and bull sectors, or both. Interviews were structured to elicit random responses in the order of determining "must-have" criteria (quality factors that are required to make a purchase), best/worst ranking (of quality factors based on importance), how interviewees defined quality terms, a strength, weakness, opportunities, threats (SWOT) analysis, general beef industry questions, and sustainability goals (the latter four being open-ended). Quality factors were 1) visual characteristics, 2) cattle genetics, 3) food safety, 4) eating satisfaction, 5) animal well-being, 6) weight and size, and 7) lean, fat, and bone. Best/worst analysis revealed that "food safety" was the most (P < 0.05) important factor in beef purchasing decisions for all market sectors and frequently was described as "everything" and "a way of business." Culture surrounding food safety changed compared to previous NBQAs with interviewees no longer considering food safety as a purchasing criterion, but rather as a market expectation. The SWOT analysis indicated that "eating quality of U.S. beef" was the greatest strength, and cited that educating both consumers and producers on beef production would benefit the industry. Irrespective of whether companies' products were fed or market cow/bull beef, respondents said that they believed "environmental concerns" were among the major threats to the industry. Perceived image of the beef industry in the market sectors has improved since NBQA-2016 for both fed cattle and market cow/bull beef.

Intradermal Inoculation of Inactivated Foot-and-Mouth Disease Vaccine Induced Effective Immune Responses Comparable to Conventional Intramuscular Injection in Pigs

All pigs in the Republic of Korea are given the foot-and-mouth disease virus (FMDV) vaccine intramuscularly (IM) as part of the country's vaccination policy. However, the IM administration of the FMDV vaccine to pig results in residual vaccine components in the muscle and undesirable changes in muscle and soft tissues, causing economic losses in swine production. In this study, we evaluated whether intradermal (ID) vaccination could be proposed as an alternative to IM administration. ID vaccination (0.2 mL on each side of the neck muscle) and IM vaccination (2 mL on each side of the neck muscle) were performed twice, separated by 14 days, using a commercial FMD vaccine in specific-pathogen-free pigs. We observed growth performance, gross and microscopic lesions at the inoculation site, FMDV-specific antibodies, and neutralizing antibodies for 35 days after vaccination. Side effects on the skin grossly appeared following ID administration, but most were reduced within two weeks. All ID-vaccinated pigs showed inflammatory lesions limited to the dermis, but IM-vaccinated pigs had abnormal undesirable changes and pus in the muscle. ID-vaccinated pigs performed comparably to IM-vaccinated pigs in terms of growth, FMD virus-specific antibodies, protection capability against FMDV, and T-cell induction. This study demonstrated that the ID inoculation of the inactivated FMD vaccine induced immune responses comparable to an IM injection at 1/10 of the inoculation dose and that the inoculation lesion was limited to the dermis, effectively protecting against the formation of abnormal undesirable changes in muscle and soft tissues.

Recombinant bacteriophage T4 displaying key epitopes of the foot-and-mouth disease virus as a novel nanoparticle vaccine

Foot-and-mouth disease virus (FMDV) is a highly contagious pathogen that has caused significant economic losses in the livestock industry. Peptide vaccines engineered with the protective epitopes of FMDV have provided a safer alternative for disease prevention than the traditional inactivated vaccines. However, the immunogenicity of the peptide is usually poor and therefore an adjuvant is required. Here, we showed that recombinant T4 phages displaying the B-cell epitope of the FMDV VP1 protein (VP1130-158), without additional adjuvants, induced similar levels of antigen-specific IgG1 but higher levels of IgG2a compared to the peptide vaccine. Incorporation of a CD4+ T cell epitope, either 3A21-35 of FMDV 3A protein or P2830-844 of tetanus toxoid, further enhanced the immunogenicity of VP1-T4 phage nanoparticles. Interestingly, the extrinsic adjuvant cannot enhance the immunogenicity of the nanoparticles, indicating the intrinsic adjuvant activities of T4 phage. Furthermore, the recombinant T4 phage can be produced on a large scale within a short period of time at a relatively low-cost using Escherichia coli, heralding its potential in the development of a safe and effective FMDV vaccine.

Structure-based virtual screening and molecular dynamics studies to explore potential natural inhibitors against 3C protease of foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is a highly infectious animal disease caused by foot-and-mouth disease virus (FMDV) and primarily infects cloven-hoofed animals such as cattle, sheep, goats, and pigs. It has become a significant health concern in global livestock industries because of diverse serotypes, high mutation rates, and contagious nature. There is no specific antiviral treatment available for FMD. Hence, based on the importance of 3C protease in FMDV viral replication and pathogenesis, we have employed a structure-based virtual screening method by targeting 3C protease with a natural compounds dataset (n = 69,040) from the InterBioScreen database. Virtual screening results identified five potential compounds, STOCK1N-62634, STOCK1N-96109, STOCK1N-94672, STOCK1N-89819, and STOCK1N-80570, with a binding affinity of -9.576 kcal/mol, -8.1 kcal/mol, -7.744 kcal/mol, -7.647 kcal/mol, and - 7.778 kcal/mol, respectively. The compounds were further validated through physiochemical properties and density functional theory (DFT). Subsequently, the comparative 300-ns MD simulation of all five complexes exhibited overall structural stability from various MD analyses such as root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (Rg), solvent accessible surface area (SASA), H-bonds, principal component analysis (PCA), and free energy landscape (FEL). Furthermore, MM-PBSA calculation suggests that all five compounds, particularly STOCK1N-62634, STOCK1N-96109, and STOCK1N-94672, can be considered as potential inhibitors because of their strong binding affinity toward 3C protease. Thus, we hope that these identified compounds can be studied extensively to develop natural therapeutics for the better management of FMD.

Immuno-Enhancing Effect of Ginsenoside Rh2 Liposomes on Foot-and-Mouth Disease Vaccine

The adjuvant is essential for vaccines because it can enhance or directly induce a strong immune response associated with vaccine antigens. Ginsenoside Rh2 (Rh2) had immunomodulatory effects but was limited by poor solubility and hemolysis. In this study, Rh2 liposomes (Rh2-L) were prepared by ethanol injection methods. The Rh2-L effectively dispersed in a double emulsion adjuvant system to form a Water-in-Oil-in-Water (W/O/W) emulsion and had no hemolysis. The physicochemical properties of the adjuvants were tested, and the immune activity and auxiliary effects indicated by the Foot-and-Mouth disease (FMDV) antigen were evaluated. Compared with the mice vaccinated with the FMD vaccine prepared with the double emulsion adjuvant alone, those with the FMD vaccine prepared with the double emulsion adjuvant containing Rh2-L had significantly higher neutralizing antibody titer and splenocyte proliferation rates and showed higher cellular and humoral immune responses. The results demonstrated that Rh2-L could further enhance the immune effect of the double emulsion adjuvant against Foot-and-Mouth Disease.

EV-D68 virus-like particle vaccines elicit cross-clade neutralizing antibodies that inhibit infection and block dissemination

Enterovirus D68 (EV-D68) causes severe respiratory illness in children and can result in a debilitating paralytic disease known as acute flaccid myelitis. No treatment or vaccine for EV-D68 infection is available. Here, we demonstrate that virus-like particle (VLP) vaccines elicit a protective neutralizing antibody against homologous and heterologous EV-D68 subclades. VLP based on a B1 subclade 2014 outbreak strain elicited comparable B1 EV-D68 neutralizing activity as an inactivated viral particle vaccine in mice. Both immunogens elicited weaker cross-neutralization against heterologous viruses. A B3 VLP vaccine elicited more robust neutralization of B3 subclade viruses with improved cross-neutralization. A balanced CD4⁺ T helper response was achieved using a carbomer-based adjuvant, Adjuplex. Nonhuman primates immunized with this B3 VLP Adjuplex formulation generated robust neutralizing antibodies against homologous and heterologous subclade viruses. Our results suggest that both vaccine strain and adjuvant selection are critical elements for improving the breadth of protective immunity against EV-D68.

Synergetic interaction of capsid proteins for virus-like particles assembly of foot-and-mouth disease virus (serotype O) from the inclusion bodies

Recombinant virus-like particles (VLP) with single capsid protein have been successfully produced through prokaryotic system, but for those with multiple capsid proteins such as the foot-and-mouth disease virus (FMDV), this approach is more challenging. In this study, in vitro assembly of FMDV VLP was investigated with its capsids VP1, VP2 and VP3 separately expressed as inclusion bodies. After extraction and solubilization, three capsids were purified in denatured state through a flow-through model, increasing its purity to 90%. VLP assembly for FMDV was observed after diluting the mixture of denatured capsids in the ration of 1: 1: 1, while no VLP appeared if the separately diluted and refolded capsids were co-incubated. This result suggests certain synergetic interactions exist among the three capsids, which are crucial for FMDV VLP assembly. Sodium chloride and capsid protein concentration both greatly affect the assembling efficiency. After purification through size exclusion chromatography, VLP with similar diameter and morphology as inactivated FMDV were obtained, which elicited high IgG titers and B cell activation when vaccinated in mouse. It could also induce specific humoral and cellular immune responses in splenocytes proliferative experiments. Our study demonstrated the feasibility of in vitro assembling FMDV VLP from inclusion bodies of VP1, VP2 and VP3 for the first time.

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.

Near-Complete Genome Sequences of Three Foot-and-Mouth Disease Virus O/ME-SA/Ind-2001e Isolates Obtained from Cattle and Pigs in Thailand in 2016

Here, we report near-complete genome sequences of three foot-and-mouth disease viruses isolated in 2016 from bovine and porcine epithelial tissue samples collected in Nonthaburi, Songkhla, and Ratchaburi provinces, Thailand. These viruses were classified as serotype O, topotype ME-SA, and sublineage Ind-2001e.

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.

Mapping of foot-and-mouth disease virus antigenic sites recognized by single-domain antibodies reveals different 146S particle specific sites and particle flexibility

Vaccination with intact (146S) foot-and-mouth disease virus (FMDV) particles is used to control FMD. However, 146S particles easily dissociate into stable pentameric 12S particles which are less immunogenic. We earlier isolated several single-domain antibody fragments (VHHs) that specifically bind either 146S or 12S particles. These particle-specific VHHs are excellent tools for vaccine quality control. In this study we mapped the antigenic sites recognized by these VHHs by competition ELISAs, virus neutralization, and trypsin sensitivity of epitopes. We included two previously described monoclonal antibodies (mAbs) that are either 12S specific (mAb 13A6) or 146S specific (mAb 9). Although both are 12S specific, the VHH M3F and mAb 13A6 were found to bind independent antigenic sites. M3F recognized a non-neutralizing and trypsin insensitive site whereas mAb 13A6 recognized the trypsin sensitive VP2 N-terminus. The Asia1 146S-specific site was trypsin sensitive, neutralizing and also recognized by the VHH M8F, suggesting it involves the VP1 GH-loop. The type A 146S-specific VHHs recognized two independent antigenic sites that are both also neutralizing but trypsin insensitive. The major site was further mapped by cross-linking mass spectrometry (XL-MS) of two broadly strain reactive 146S-specific VHHs complexed to FMDV. The epitopes were located close to the 2-fold and 3-fold symmetry axes of the icosahedral virus 3D structure, mainly on VP2 and VP3, overlapping the earlier identified mAb 9 site. Since the epitopes were located on a single 12S pentamer, the 146S specificity cannot be explained by the epitope being split due to 12S pentamer dissociation. In an earlier study the cryo-EM structure of the 146S-specific VHH M170 complexed to type O FMDV was resolved. The 146S specificity was reported to be caused by an altered conformation of this epitope in 12S and 146S particles. This mechanism probably also explains the 146S-specific binding by the two type A VHHs mapped by XL-MS since their epitopes overlapped with the epitope recognized by M170. Surprisingly, residues internal in the 146S quaternary structure were also cross-linked to VHH. This probably reflects particle flexibility in solution. Molecular studies of virus-antibody interactions help to further optimize vaccines and improve their quality control.

Formulation enhanced the stability of Foot-and-mouth virus and prolonged vaccine storage

Foot-and-mouth disease (FMD) is a highly contagious viral disease that affects cloven-hoofed animals. Vaccination is the most effective measure to control FMD. However, FMDV particles are prone to dissociation, leading to insufficient potency of vaccine. Based on this characteristic, a combination of twenty percentage trehalose, 500 mM NaCl and 3 mM CuSO₄·5H₂O was developed to increase viral stability. Heating-resistance test showed that FMDV infectivity was maintained when formulated with formulation. Additionally, the half-life of FMDV inactivation was prolonged remarkably. Sequencing analysis demonstrated that viral genome could not be altered in serial passages. Vaccine stability was monitored for up to 1 year at 4 °C, with a higher level of 146S content remained. This study suggested that the formulation could protect FMDV against massive structural breakdown and extend the shelf life of vaccine. Our findings could provide strategy to develop more solutions for the stabilization of viral vaccine.

Enhancement of intestinal mucosal immunity and immune response to the foot-and-mouth disease vaccine by oral administration of danggui buxue decoction

This study investigated the effect of Danggui Buxue decoction (DBD) on the immunity of an O-type foot-and-mouth disease (FMD) vaccine and intestinal mucosal immunity. SPF KM mice were continuously and orally administered DBD for 5 d and then inoculated with an O-type FMD vaccine. The contents of a specific IgG antibody and its isotypes IgG1, IgG2a, IgG2b, and IgG3 in serum and SIgA in duodenal mucosa were determined by ELISA at 1 and 3 W after the 2^nd immunization. qRT-PCR was used to detect mRNA expression levels of IL-4, IL-10, IFN-γ, and IL-33 in the spleen, and mRNA expression levels of J-chain, pIgR, BAFF, APRIL, IL-10, IFN-γ and IL-33 in the duodenum. The results showed that compared with the control group, oral administration of DBD significantly increased levels of the anti-FMD virus (FMDV)-specific antibodies IgG, IgG1, and IgG2a in the serum of O-type FMD vaccine-immunized mice 1 W after the 2^nd immunization (P < 0.05), upregulated mRNA expression levels of spleen lymphocyte cytokines IL-4 and IL-33 (P < 0.05), promoted the secretion of SIgA in duodenal mucosa (P < 0.05). The mRNA expression levels of J-chain, pIgR, BAFF, APRIL, IL-10, and IL-33 in duodenal tissues were upregulated (P < 0.05). This study indicates that DBD has a good promotion effect on the O-type FMD vaccine and the potential to be an oral immune booster.

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.

Investigation into the protective ability of monovalent and bivalent A Malaysia 97 and A22 Iraq 64 vaccine strains against infection with an A/Asia/SEA-97 variant in pigs

Over the last 15 years, FMDV serotype A viruses in South-East Asia (A/ASIA/SEA-97 lineage) have diverged into several clusters. Variants from Thailand in 2011-2013 have caused vaccine failures and returned poor r₁-values (<0.30) to A₂₂ Iraq 64 (A22) and A Malaysia 97 (A May) vaccine strains. We investigated the protective ability of monovalent and bivalent A Malaysia 97 and A22 Iraq 64 vaccine strains against infection with an A/Asia/SEA-97 variant in pigs. Pigs were challenged with a variant of A/Asia/SEA-97 lineage either 21- or 7- days post-vaccination (V21 or V7) using the heal-bulb challenge. Only one in five pigs were protected in the V21 monovalent vaccine groups. Less severe clinical signs were observed in the A22 IRQ group compared to the A MAY 97 group. In the V21 combination group, 4 out of 5 pigs were protected and viraemia was significantly reduced compared to the monovalent V21 groups. V7 vaccine groups were not protected. The neutralising antibody response was below the detection limit in all groups on the challenge day, showing a poor correlation with protection. There was no evidence that the pigs protected from systemic disease had protective antibody responses sooner than other pigs in the study, implying other immune mechanisms might play a role in protecting these animals. FMDV was detected in the nasal and oral swab samples between 1 and 6 dpc. Viral loads were lower in the nasal swab samples from the V21 combination group than the other groups, but there was no difference in the oral swab samples. Since all unvaccinated controls were euthanised by 6-day post-challenge for ethical reasons, the ‘area under the curve (AUC)' method was used to compare the viraemia and virus excretion in different groups. We recommend that for the A/Asia/SEA97 variants, a combination vaccine with A Malaysia 97 and A22 Iraq 64 vaccine strains would be ideal compared to monovalent vaccines.

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

Adenoviral delivery of soluble ovine OX40L or CD70 costimulatory molecules improves adaptive immune responses to a model antigen in sheep

The tumour necrosis factor superfamily OX40L and CD70 and their receptors are costimulatory signalling axes critical for adequate T and B cell activation in humans and mice. In this work we inoculated groups of sheep with human recombinant adenovirus type 5 (Ad) expressing Ovis aries (Oa)OX40L or OaCD70 or a control adenoviral vector to determine whether they could improve the immune response to the model antigen OVA. PBMCs and serum samples were obtained for analysis of the adaptive immune response to OVA at days 0, 15, 30 and 90 post-inoculation (pi). Recall responses to OVA were assessed at day 7 and 30 after the second antigen inoculation (pb) at day 90. Administration of these immunomodulatory molecules did not induce unspecific PBMC stimulation. While OaOX40L administration mainly increased TNF-α and IL-4 in PBMC at day 15 pi concomitantly with a slight increase in antibody titer and the number of IFN-γ producing cells, we detected greater effects on adaptive immunity after OaCD70 administration. AdOaCD70 inoculation improved antibody titers to OVA at days 30 and 90 pi, and increased anti-OVA-specific IgG-secreting B cell counts when compared to control. Moreover, higher IFN-γ production was detected on days 7 pi, 7 pb and 30 pb in PBMCs from this group. Phenotypic analysis of T cell activation showed an increase in effector CD8+ T cells (CD8+ CD62L- CD27-) at day 15 pi in AdOaCD70 group, concurrent with a decrease in early activated cells (CD8+ CD62L- CD27+). Moreover, recall anti-OVA CD8+ T cell responses were increased at 7 pb in the AdOaCD70 group. AdOaCD70 administration could therefore promote CD8+ T cell effector differentiation and long-term activity. In this work we characterized the in vivo adjuvant potential on the humoral and cellular immune response of OaOX40L and OaCD70 delivered by non-replicative adenovirus vectors using the model antigen OVA. We present data highlighting the potency of these molecules as veterinary vaccine adjuvant.

Analysis of Foot and Mouth Disease Virus Polyprotein for Multi Peptides Vaccine Design: An In silico Strategy

Foot-and-mouth disease virus (FMDV) is small RNA virus from Picornaviridae family; genus Aphthovirus. FMDV causes maximum levels of infectivity in cattle and harmful socioeconomic effects. The present report attempted to design vaccine candidate from the polyprotein of FMDV to stimulate protective immune response. The IEDB server was used to predict B and T cells epitopes that were linked via GPGPG and YAA linkers, respectively. Mycobacterium tuberculosis 50S ribosomal protein was exploited as an adjuvant and a six histidine-tag sequence was linked to the carboxyl end of the vaccine for purification and identification. The predicted vaccine comprised 313aa and was antigenic and not allergic. Moreover, the vaccine was acidic and showed stability and hydrophilicity. Vaccine secondary and tertiary structures were predicted. The tertiary structure was refined to ameliorate the quality of the global and local structures of the vaccine. Vaccine model validation was performed and the final quality score of the structural model was computed. The validated model was used for molecular docking with bovine (N*01801-BoLA-A11) allele. Docking process in terms of binding free energy score was significant. Vaccine solubility was investigated based on the protein of E. coli and the stability was based on the disulfide bonding to lessen the entropic and mobile points in vaccine. Lastly, the in silico cloning ensured the proper cloning and best translation of the DNA of vaccine in molecular vectors.

B cell memory responses induced by foot-and-mouth disease virus-like particles in BALB/c mice

A challenging but critical question is that new foot-and-mouth disease (FMD) vaccines should be to induce B cell memory to provide antibodies for long-term protection. The maintenance of B cell memory is dependent on long-lived plasma cells (LLPCs) and memory B cells. We developed a chimeric FMDV virus-like particles (FMDV-VLPs), fusing VP1-VP4 into HBcAg. In our study, we investigated if or how long B cell memory was induced by FMDV-VLPs in mice. The data showed that FMDV-VLPs can induce memory humoral responses with a high level of total IgG1, IgG2a, IgA, and FMDV-specific IgG antibodies in serum. The persistence of antibody levels in serum could depend on LLPCs. The proportion of LLPCs in CD19+ cells in bone marrow exhibited a dynamic trend with two peaks at 28 days post-immunization (dpi) and 72 dpi, respectively. Additionally, the proportion of memory B cells in CD19+ cells in the spleen increased significantly both at 7 days post primary immunization and at 7 days post -boost immunization. Of note, LLPCs together with memory B cells contribute to the production of FMDV-specific IgG and IgG1. The changes of LLPCs and memory B cells may be related to TNF-α, IL-6 and, CXCL12. Taken together, FMDV-VLPs could induce B cells memory responses. A further understanding of the mechanisms that FMDV-VLPs how we can manipulate the induction and maintenance of memory B cells and LLPCs will promote vaccine design and likely address several challenges to develop FMDV new vaccines in the future.

Biodegradable Imiquimod-Loaded Mesoporous Organosilica as a Nanocarrier and Adjuvant for Enhanced and Prolonged Immunity against Foot-and-Mouth Disease Virus in Mice

Foot-and-mouth disease (FMD), a serious, fast-spreading, and virulent disease, has led to huge economic losses to people all over the world. Vaccines are the most effective way to control FMD. However, the weak immunogenicity of inactivated FMD virus (FMDV) requires the addition of adjuvants to enhance the immune effectiveness of the vaccines. Herein, we formulated and fabricated biodegradable dendritic mesoporous tetrasulfide-doped organosilica nanoparticles SOMSN with imiquimod complex (SOMSN-IMQ) and used it as a platform for FMD vaccine delivery and as an adjuvant. SOMSN-IMQ demonstrated excellent stability for 6 months when stored in PBS, while it could be completely degraded within 42 days in SBF at room temperature. Biosafety experiments such as cell toxicity, hemolysis, and histology indicated that the as-prepared SOMSN-IMQ showed nontoxicity and good biocompatibility. Furthermore, SOMSN-IMQ exhibited a maximum adsorption capacity of 1000 μg/mg for inactivated FMDV antigens. Our results showed that SOMSN-IMQ can be effectively engulfed by RAW264.7 cells in a dose-dependent manner. After immunization, SOMSN-IMQ@FMDV can elicit persistent higher antibody levels, higher IgG2a/IgG1 ratio, and cytokine expression, which indicated that SOMSN-IMQ@FMDV triggered superior humoral and cellular immune responses. Moreover, SOMSN-IMQ could provoke maturation and activation of dendritic cells in lymph nodes (LDCs) as well as the proliferation of lymphocytes in vivo. Thus, SOMSN-IMQ could promote effective and potent immunity and provide a promising adjuvant platform for FMDV vaccination with acceptable safety.

Assessment of the foot-and-mouth disease surveillance system in Brazil

In 2021, the 88th General Session of the World Assembly of National Delegates to the World Organisation for Animal Health (OIE) recognized the estates of Acre, Paraná, the Rio Grande do Sul, and Rondônia as being free of foot-and-mouth disease (FMD) without vaccination. The certification was also extended to some cities in Amazonas and Mato Grosso. The new national strategic plan for 2026, which focuses on creating and maintaining sustainable conditions to expand FMD-free zones without vaccination, imposes new challenges and requires continuous evaluation of the FMD surveillance system. The objective of this research was to evaluate the FMD surveillance system in Brazil using quantitative models through Bayesian network approaches. The research was conducted using the Continental Surveillance and Information System (SivCont) database for Official Veterinary Services in Brazil, which refers to notified vesicular syndromes. The data on states, reported diseases, source of notification, disease confirmation, and timeliness (TL in days) of the delay by owners in notifying (TL.1) after a suspected case of the disease, and the response of Brazilian Veterinary Services after being notified (TL.2), were analysed. The collected data were analysed using Bayesian networks. It was observed that diseases with symptoms identical to FMD are the most notified events. TL.1 was long (mean of 18.96, CI: 18.33-19.59), and a low number of notifications was observed throughout the study period, which increases the chances of disseminating FMD in the population. Meanwhile, TL.2 suggests appropriate effectiveness of the Veterinary Services responding to suspected cases of FMD with interventions in less than 24 h (mean of 1, CI: 0.68-1.31). This study evaluated the performance of Brazilian Veterinary Services facing the report of vesicular diseases in the period 2004-2018. The results can help the states improve the surveillance system and the transition to the vaccination stop. Furthermore, the analytical method presented in the paper could serve as a model for other countries to evaluate the effectiveness of FMD surveillance systems.

Design of live-attenuated animal vaccines based on pseudorabies virus platform

Pseudorabies virus (PRV) is a double-stranded DNA virus with a genome approximating 150 kb in size. PRV contains many non-essential genes that can be replaced with genes encoding heterogenous antigens without affecting viral propagation. With the ability to induce cellular, humoral and mucosal immune responses in the host, PRV is considered to be an ideal and potential live vector for generation of animal vaccines. In this review, we summarize the advances in attenuated recombinant PRVs and design of PRV-based live vaccines as well as the challenge of vaccine application.

An Emerging Duck Egg-Reducing Syndrome Caused by a Novel Picornavirus Containing Seven Putative 2A Peptides

Since 2016, frequent outbreaks of egg-reducing syndromes caused by an unknown virus in duck farms have resulted in huge economic losses in China. The causative virus was isolated and identified as a novel species in Avihepatovirus of the picornavirus family according to the current guidelines of the International Committee on Taxonomy of Viruses (ICVT), and was named the duck egg-reducing syndrome virus (DERSV). The DERSV was most closely related to wild duck avihepatovirus-like virus (WDALV) with 64.0%, 76.8%, 77.5%, and 70.7% of amino acid identities of P1, 2C, 3C, and 3D proteins, respectively. The DERSV had a typical picornavirus-like genomic structure, but with the longest 2A region in the reported picornaviruses so far. Importantly, the clinical symptoms were successfully observed by artificially infecting ducks with DERSV, even in the contact exposed ducks, which suggested that DERSV transmitted among ducks by direct contact. The antibody levels of DERSV were correlated with the emergence of the egg-reducing syndromes in ducks in field. These results indicate that DERSV is a novel emerging picornavirus causing egg-reducing syndrome in ducks.

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.

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.

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.

Screening of host genes regulated by ID1 and ID3 proteins during foot-and-mouth disease virus infection

Foot-and-mouth disease virus (FMDV) is an important pathogen that harms cloven-hoofed animals and has caused serious losses to livestock production since its discovery. Furthermore, inhibitor of DNA binding (ID) proteins have been thoroughly studied in tumorigenesis, differentiation and metastasis, but its role in viral infection is rarely known. In this study, three gene knockout cell lines ID1 KO, ID3 KO, ID1/3 KO were obtained based on BHK-21 cells. We found that ID1 and ID3 genes single or double knockout promote the replication of FMDV. Moreover, compared with negative control cells during virus infection, there were 551 up-regulated genes and 1222 down-regulated genes in the ID1 KO cell line; 916 up-regulated genes and 1845 down-regulated genes in the ID3 KO cell line; 810 up-regulated genes and 1566 down-regulated genes in ID1/3 KO cell line. Further genes expression patterns verification results also showed a good correlation between the data of RT-qRCR and RNA-seq. These findings provide a basis for studying the relevant mechanisms between host genes and ID genes during FMDV infection.

Porcine Picornavirus 3C Protease Degrades PRDX6 to Impair PRDX6-mediated Antiviral Function

Peroxiredoxin-6 (PRDX6) is an antioxidant enzyme with both the activities of peroxidase and phospholipase A2 (PLA2), which is involved in regulation of many cellular reactions. However, the function of PRDX6 during virus infection remains unknown. In this study, we found that the abundance of PRDX6 protein was dramatically decreased in foot-and-mouth disease virus (FMDV) infected cells. Overexpression of PRDX6 inhibited FMDV replication. In contrast, knockdown of PRDX6 expression promoted FMDV replication, suggesting an antiviral role of PRDX6. To explore whether the activity of peroxidase and PLA2 was associated with PRDX6-mediated antiviral function, a specific inhibitor of PLA2 (MJ33) and a specific inhibitor of peroxidase activity (mercaptosuccinate) were used to treat the cells before FMDV infection. The results showed that incubation of MJ33 but not mercaptosuccinate promoted FMDV replication. Meanwhile, overexpression of PRDX6 slightly enhanced type I interferon signaling. We further determined that the viral 3Cpro was responsible for degradation of PRDX6, and 3Cpro-induced reduction of PRDX6 was independent of the proteasome, lysosome, and caspase pathways. The protease activity of 3Cpro was required for induction of PRDX6 reduction. Besides, PRDX6 suppressed the replication of another porcine picornavirus Senecavirus A (SVA), and the 3Cpro of SVA induced the reduction of PRDX6 through its proteolytic activity as well. Together, our results suggested that PRDX6 plays an important antiviral role during porcine picornavirus infection, and the viral 3Cpro induces the degradation of PRDX6 to overcome PRDX6-mediated antiviral function.

Exosome-Based Vaccines: Pros and Cons in the World of Animal Health

Due to the emergence of antibiotic resistance and new and more complex diseases that affect livestock animal health and food security, the control of epidemics has become a top priority worldwide. Vaccination represents the most important and cost-effective measure to control infectious diseases in animal health, but it represents only 23% of the total global animal health market, highlighting the need to develop new vaccines. A recent strategy in animal health vaccination is the use of extracellular vesicles (EVs), lipid bilayer nanovesicles produced by almost all living cells, including both prokaryotes and eukaryotes. EVs have been evaluated as a prominent source of viral antigens to elicit specific immune responses and to develop new vaccination platforms as viruses and EVs share biogenesis pathways. Preliminary trials with lymphocytic choriomeningitis virus infection (LCMV), porcine reproductive and respiratory syndrome virus (PRRSV), and Marek's disease virus (MDV) have demonstrated that EVs have a role in the activation of cellular and antibody immune responses. Moreover, in parasitic diseases such as Eimeria (chickens) and Plasmodium yoelii (mice) protection has been achieved. Research into EVs is therefore opening an opportunity for new strategies to overcome old problems affecting food security, animal health, and emerging diseases. Here, we review different conventional approaches for vaccine design and compare them with examples of EV-based vaccines that have already been tested in relation to animal health.

Transboundary Animal Diseases, an Overview of 17 Diseases with Potential for Global Spread and Serious Consequences

Animals provide food and other critical resources to most of the global population. As such, diseases of animals can cause dire consequences, especially disease with high rates of morbidity or mortality. Transboundary animal diseases (TADs) are highly contagious or transmissible, epidemic diseases, with the potential to spread rapidly across the globe and the potential to cause substantial socioeconomic and public health consequences. Transboundary animal diseases can threaten the global food supply, reduce the availability of non-food animal products, or cause the loss of human productivity or life. Further, TADs result in socioeconomic consequences from costs of control or preventative measures, and from trade restrictions. A greater understanding of the transmission, spread, and pathogenesis of these diseases is required. Further work is also needed to improve the efficacy and cost of both diagnostics and vaccines. This review aims to give a broad overview of 17 TADs, providing researchers and veterinarians with a current, succinct resource of salient details regarding these significant diseases. For each disease, we provide a synopsis of the disease and its status, species and geographic areas affected, a summary of in vitro or in vivo research models, and when available, information regarding prevention or treatment.

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.

Immune response in dairy cattle against combined foot and mouth disease and haemorrhagic septicemia vaccine under field conditions

Background

Foot-and-mouth disease (FMD) and Haemorrhagic septicemia (HS) are two important diseases that are known to have caused significant economic losses to the cattle industry. Accordingly, vaccinations have been recognized as an efficient method to control and prevent both of the above-mentioned diseases. This study aimed to determine the immune response to FMD virus antigens and the recombinant outer membrane protein of HS (rOmpH) of Pasteurella multocida in cattle administered as a combination vaccine and compare antibody titers with the two vaccines given independently, under field conditions. Dairy cattle were divided into three groups. Each group was immunized with different vaccine types according to the vaccination program employed in this study. Antibody responses were determined by indirect ELISA, liquid phase blocking ELISA (LPB-ELISA) and viral neutralization test (VNT). Furthermore, the cellular immune responses were measured by lymphocyte proliferation assay (LPA).

Results

The overall antibody titers to HS and FMDV were above cut-off values for the combined FMD-HS vaccine in this study.The mean antibody titer against HS after the first immunization in the combined FMD-HS vaccine groups was higher than in the HS vaccine groups. However, no statistically significant differences (p > 0.05) were observed between groups. Likewise, the antibody titer to the FMDV serotypes O/TAI/189/87 and Asia 1/TAI/85 determined by LPB-ELISA in the combined vaccine were not statistically significantly different when compared to the FMD vaccine groups. However, the mean VNT antibody titer of combined vaccine against serotype O was significantly higher than the VN titer of FMD vaccine groups (p < 0.05). Moreover, the LPA results showed that all vaccinated groups displayed significantly higher than the negative control (p < 0.05). Nevertheless, no differences in the lymphocyte responses were observed in comparisons between the groups (p > 0.05).

Conclusions

The combined FMD-HS vaccine formulated in this study could result in high both antibody and cellular immune responses without antigenic competition. Therefore, the combined FMD-HS vaccine can serve as an alternative vaccine against both HS and FMD in dairy cattle under field conditions.

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.

Structures of Foot-and-mouth Disease Virus with neutralizing antibodies derived from recovered natural host reveal a mechanism for cross-serotype neutralization

The development of a universal vaccine against foot-and-mouth disease virus (FMDV) is hindered by cross-serotype antigenic diversity and by a lack of knowledge regarding neutralization of the virus in natural hosts. In this study, we isolated serotype O-specific neutralizing antibodies (NAbs) (F145 and B77) from recovered natural bovine hosts by using the single B cell antibody isolation technique. We also identified a serotype O/A cross-reacting NAb (R50) and determined virus-NAb complex structures by cryo-electron microscopy at near-atomic resolution. F145 and B77 were shown to engage the capsid of FMDV-O near the icosahedral threefold axis, binding to the BC/HI-loop of VP2. In contrast, R50 engages the capsids of both FMDV-O and FMDV-A between the 2- and 5-fold axes and binds to the BC/EF/GH-loop of VP1 and to the GH-loop of VP3 from two adjacent protomers, revealing a previously unknown antigenic site. The cross-serotype neutralizing epitope recognized by R50 is highly conserved among serotype O/A. These findings help to elucidate FMDV neutralization by natural hosts and provide epitope information for the development of a universal vaccine for cross-serotype protection against FMDV.

FMDV is the causative agent of foot-and-mouth disease, one of the most contagious and economically devastating diseases of cloven-hoofed animals. The antigenic diversities of the currently known epitopes throughout FMDV serotypes and the lack of understanding of FMDV neutralization in natural hosts limit the development of a vaccine that is able to provide cross-serotype protection. In this work, we isolated FMDV serotype O-specific neutralizing antibodies (NAbs) (F145 and B77) and a serotype O/A cross-reacting NAb (R50) from recovered natural bovine hosts and determined virus-NAb complex structures by cryo-electron microscopy at near-atomic resolution. Structures of virus-NAb complex reveal F145 and B77 engage the capsid of FMDV-O near the icosahedral threefold axis. In contrast, R50 engages the capsids of both FMDV-O and FMDV-A between the 2- and 5-fold axes, revealing a previously unknown antigenic site. This is the first time to present structure details of FMDV neutralization by natural hosts. And this work also provides epitope information for the development of a universal vaccine for cross-serotype protection against FMDV.

Enhancing immune responses to inactivated foot-and-mouth virus vaccine by a polysaccharide adjuvant of aqueous extracts from Artemisia rupestris L

BACKGROUND

New-generation adjuvants for foot-and-mouth disease virus (FMDV) vaccines can improve the efficacy of existing vaccines. Chinese medicinal herb polysaccharide possesses better promoting effects.

OBJECTIVES

In this study, the aqueous extract from Artemisia rupestris L. (AEAR), an immunoregulatory crude polysaccharide, was utilized as the adjuvant of inactivated FMDV vaccine to explore their immune regulation roles.

METHODS

The mice in each group were subcutaneously injected with different vaccine formulations containing inactivated FMDV antigen adjuvanted with three doses (low, medium, and high) of AEAR or AEAR with ISA-206 adjuvant for 2 times respectively in 1 and 14 days. The variations of antibody level, lymphocyte count, and cytokine secretion in 14 to 42 days after first vaccination were monitored. Then cytotoxic T lymphocyte (CTL) response and antibody duration were measured after the second vaccination.

RESULTS

AEAR significantly induced FMDV-specific antibody titers and lymphocyte activation. AEAR at a medium dose stimulated Th1/Th2-type response through interleukin-4 and interferon-γ secreted by CD4⁺ T cells. Effective T lymphocyte counts were significantly elevated by AEAR. Importantly, the efficient CTL response was remarkably provoked by AEAR. Furthermore, AEAR at a low dose and ISA-206 adjuvant also synergistically promoted immune responses more significantly in immunized mice than those injected with only ISA-206 adjuvant and the stable antibody duration without body weight loss was 6 months.

CONCLUSIONS

These findings suggested that AEAR had potential utility as a polysaccharide adjuvant for FMDV vaccines.

Chimeric VLPs Based on HIV-1 Gag and a Fusion Rabies Glycoprotein Induce Specific Antibodies against Rabies and Foot-and-Mouth Disease Virus

Foot and mouth disease is a livestock acute disease, causing economic losses in affected areas. Currently, control of this disease is performed by mandatory vaccination campaigns using inactivated viral vaccines. In this work, we describe the development of a chimeric VLP-based vaccine candidate for foot-and-mouth disease virus (FMDV), based on the co-expression of the HIV-1 Gag protein and a novel fusion rabies glycoprotein (RVG), which carries in its N-term the FMDV main antigen: the G-H loop. It is demonstrated by confocal microscopy that both Gag-GFP polyprotein and the G-H loop colocalize at the cell membrane and, that the Gag polyprotein of the HIV virus acts as a scaffold for enveloped VLPs that during the budding process acquires the proteins that are being expressed in the cell membrane. The obtained VLPs were spherical particles of 130 ± 40 nm in diameter (analyzed by TEM, Cryo-TEM and NTA) carrying an envelope membrane that efficiently display the GH-RVG on its surface (analyzed by gold immunolabeling). Immunostainings with a FMDV hyperimmune serum showed that the heterologous antigenic site, genetically fused to RVG, is recognized by specific G-H loop antibodies. Additionally, the cVLPs produced expose the G-H loop to the liquid surrounding (analyzed by specific ELISA). Finally, we confirmed that these FMD cVLPs are able to induce a specific humoral immune response, based on antibodies directed to the G-H loop in experimental animals.

Enhanced immunogenicity of foot and mouth disease DNA vaccine delivered by PLGA nanoparticles combined with cytokine adjuvants

Although the immunogenicity of DNA vaccines is nonideal, they are still considered as potential alternative vaccine candidates to conventional vaccines. Various DNA delivery systems, including nanoparticles, have been extensively explored and validated to further enhance the immunogenicity of DNA vaccines. DNA vaccines are considered as alternative vaccine candidates. Various DNA delivery systems, including nanoparticles, have been extensively explored to enhance the immunogenicity of DNA vaccines. In this study, positively charged Poly (D, l-lactide-co-glycolic acid) (PLGA) nanoparticles were generated and characterized as a delivery system for O-serotype foot-and-mouth DNA vaccine. A recombinant plasmid encoding swine interleukin (IL)-18, IL-2, or granulocyte-macrophage colony-stimulating factor (GM-CSF) gene was introduced into the DNA vaccine to further improve its immunogenicity, which was evaluated in a guinea pig model. PLGA-pVAX-VP013/IL-18 elicited significantly (P = 0.0149) higher FMDV-specific antibody levels than naked DNA before the challenge. The level of neutralizing antibodies induced by PLGA-pVAX-VP013/IL-18, PLGA-pVAX-VP013/IL-2, and PLGA-pVAX-VP013/GM-CSF significantly increased compared with that induced by naked DNA (P < 0.0001). The lymphocyte proliferation assay showed that cellular immunity induced by PLGA-pVAX-VP013/IL-18 and PLGA-pVAX-VP013/GM-CSF was dramatically enhanced compared with that induced by the inactivated vaccine. The protection by PLGA-pVAX-VP013/IL-18 was consistent with that by the inactivated vaccine post-challenge and was followed by PLGA-pVAX-VP013/GM-CSF. Therefore, cationic PLGA nanoparticles can deliver DNA vaccines and induce humoral and cellular immune responses. The co-administration of FMD DNA vaccine with IL-18 formulated with PLGA nanoparticles was the optimal strategy to improve the immunogenicity of FMD DNA vaccines.

New possibilities for egg white lysozyme: heat-denatured lysozyme partially inactivates select foot-and-mouth disease virus strains

Foot-and-mouth disease (FMD) is one of the most contagious diseases of cloven-hoofed animals. Disinfectants are used to inactivate FMD virus (FMDV) in Japan. Reports that heat-denatured lysozyme inactivates bacteria as well as viruses, such as norovirus and hepatitis A virus, led us to determine its effects on FMDV. We show here that heat-denatured lysozyme partially inhibited the infectivity of FMDV O/JPN/2010-1/14C but of FMDVs A/TAI/46-1/2015 and Asia1/Shamir (ISR/3/89). Further, heat-denatured lysozyme variably reduced RNA loads of FMDVs O/JPN/2010-1/14C, O/MOG/2/Ca/BU/2017, O/Taiwan/1997, Asia1/Shamir (ISR/3/89), Asia1/TUR/49/2011, SAT1/KEN/117/2009, SAT2/SAU/6/2000 and SAT3/ZIM/3/83 but could not those of O/JPN/2000, A/TAI/46-1/2015, A₂₂/IRQ/24/64, A₁₅/TAI/1/60 and C/PHI/7/84. These findings indicate that heat-denatured lysozyme may serve as a new disinfectant against FMDV.

A Comprehensive Review of the Immunological Response against Foot-and-Mouth Disease Virus Infection and Its Evasion Mechanisms

Foot-and-mouth disease (FMD) is a highly contagious viral disease, which has been reported for over 100 years, and against which the struggle has lasted for the same amount of time. It affects individuals from the order Artiodactyla, such as cattle, swine, sheep, wild animals from this order, and a few non-cloven hoofed species, such as mice and elephants. FMD causes large-scale economic losses for agricultural production systems; morbidity is almost 100% in an affected population, accompanied by a high mortality rate in young animals due to myocarditis or an inability to suckle if a mother is ill. The aetiological agent is an Aphthovirus from the family Picornaviridae, having seven serotypes: A, O, C, SAT1, SAT2, SAT3, and Asia 1. Serotype variability means that an immune response is serospecific and vaccines are thus designed to protect against each serotype independently. A host’s adaptive immune response is key in defence against pathogens; however, this virus uses successful strategies (along with most microorganisms) enabling it to evade a host’s immune system to rapidly and efficiently establish itself within such host, and thus remain there. This review has been aimed at an in-depth analysis of the immune response in cattle and swine regarding FMD virus, the possible evasion mechanisms used by the virus and describing some immunological differences regarding these species. Such aspects can provide pertinent knowledge for developing new FMD control and prevention strategies.

Layered double hydroxide nanoparticles as an adjuvant for inactivated foot-and-mouth disease vaccine in pigs

Background

Foot-and-mouth disease (FMD) is a highly transmissible disease that leads to vast economic losses in many countries. Prevention using inactivated vaccines is one effective measure used to control FMD. Unfortunately, inactivated FMD vaccines provide only short-term protection and require a cold-chain system. In recent years, many studies have shown that layered double metal hydroxides (LDHs) carrying antigens can be used to strongly induce immune responses. In this study, LDH nanoparticles (NPs) were prepared by hydrothermal synthesis. LDH particle size, electric potential, and morphology were measured and observed. The adsorption capacity of LDH NPs to FMDV was tested. The effects of LDH as an adjuvant on inactivated FMDV vaccines were further evaluated and compared with commercial FMDV Montanide ISA-206 in BALB/C female mice and Yorkshire pigs.

Results

LDH NPs were successfully prepared with a uniform particle size of ~ 87.21 nm, regular edges, a loose hexagonal shape and positive zeta charge of 32 mV. The maximum absorption concentration was 0.16–0.31 μg FMDV/μg LDH. In the mouse experiment, antibody levels in group LDH + FMDV were significantly higher compared to group saline + FMDV (P < 0.01) from days 42–98 and were significantly higher to group ISA-206 + FMDV on day 56 post-immunization (P < 0.05). After day 14 post-immunization, IFN-γ content was significantly increased (P < 0.05). In the pig experiment, antibody levels in both the ISA-206 + FMDV and LDH + FMDV were positive and were significantly higher compared with the PBS group on day 7 (P < 0.005). Antibody levels in 90% pigs were positive on day 56 in the LDH group. The neutralizing antibody levels in the LDH and ISA-206 groups were significantly higher from days 7–28 compared to the PBS control group (P < 0.05). Thus, LDH NPs were effective at inducing an immune response against FMDV.

Conclusions

LDHs with a loose hexagonal shape and a positive charge were prepared and evaluated as adjuvant for FMD vaccine. It was demonstrated that LDHs can induce immune responses in mice and pigs. In addition, the LDHs produced antibodies continuously which may indicate a slow-release effect. The study shows that LDHs may act as a potentially useful FMDV adjuvant.

Meta-analysis of Genetic Diversity of the VP1 Gene Among the Circulating O, A, and SAT2 Serotypes and Vaccine Strains of FMD Virus in Egypt

Introduction

Three strains of the FMD virus (A, O, and SAT 2) were recognised as causes of the FMD circulating in Egypt. The aims of this study were to trace the FMDV isolates from outbreaks in Egypt to understand their epidemiology and evolution and to understand the situation of the vaccine strains compared with the circulating serotypes.

Material and Methods

A meta-analysis was carried out by using the data available for FMD outbreaks in Egypt from GenBank and the World Reference Laboratory for Foot-and-Mouth Disease (WRLFMD); a comparison was done with both data sets for the three serotypes. MEGA-X was used for the evolution analysis, through constructions of phylogenetic trees for all sequences recorded in GenBank for each serotype in different Egyptian outbreaks in different years and also within the same year. Additionally, nucleotide substitution rate, molecular clock, and mean evolutionary rates were estimated for the three serotypes to understand and compare their evolution.

Results

Absence of some records of certain serotype outbreaks from the WRLFMD database was noted as were subsequent missing appropriate vaccine programmes. Genetic variation was recorded among the virus isolates within the same years and also the vaccine strain was associated with up to 26 amino acid substitutions. The evolution rate of the SAT2 strain was the highest of the circulating strains. SAT2 had high amino acid substitution per year at an important immunogenic site (130–170), serotype A had less, and serotype O the least.

Conclusion

The need for different strategies for vaccine serotype selection is indicated.

Evolution of antigenic and genetic characteristics of foot-and-mouth disease virus serotype A circulating in Thailand, 2007-2019

Foot-and-mouth disease (FMD) is a persistent, major economic concern for livestock productivity, which is highly exacerbated by outbreaks in Thailand. FMD virus (FMDV) serotype A is more highly antigenic and genetically diverse than other serotypes, which has important implications for vaccine development as well as selection. Therefore, it is essential to continuously monitor antigenic and genetic changes of field isolates of FMDV serotype A. Here we used antisera against three vaccine strains (A/118/87, A/Sakolnakorn/97, and A/Lopburi/2012) to analyze the antigenicity of 133 field isolates of FMDV serotypes A in Thailand from 2007 to 2019. The majority of the isolates from 2007 to 2008 reacted only with the antiserum against strain A/118/87. In contrast, antigenic analysis revealed broad cross-reactivity and antigenic variations of the isolates from 2009 through 2019 against strains A/Sakolnakorn/97 and A/Lopburi/2012. These results indicate periodic changes in the antigenicity of field isolates of FMDV serotype A. Phylogenetic analysis of the VP1 region revealed that all isolates were of the Sea-97 lineage within the ASIA topotype. Analysis of the L-fragment genome sequences of 30 FMDV isolates collected throughout Thailand revealed highly variable amino acid sequences of VP1 and 3A, with the lowest average identity (94.56 %) and invariant (78.43 %) rates, respectively. The present findings indicate the importance of an active routine surveillance system incorporating antigenic and genetic analysis designated to continually update information about field isolates of FMDV serotype A. Such a system is essential for establishing and improving measures to control FMDV infections in Thailand and in neighboring Asian countries.

Sequence Analysis of Egyptian Foot-and-Mouth Disease Virus Field and Vaccine Strains: Intertypic Recombination and Evidence for Accidental Release of Virulent Virus

In spite of annual mass vaccination programs with polyvalent inactivated vaccines, the incidence and economic impact of foot-and-mouth disease (FMD) in Egypt is high. Viruses of the A, O and SAT 2 serotypes are endemic and repeated incursions of new lineages from other countries lead to an unstable situation that makes the selection of appropriate vaccine antigens very difficult. In this study, whole genome sequencing of a 2016 serotype A isolate from Egypt revealed a recombination event with an African serotype O virus. Based on available vaccine matching data, none of the vaccines currently used in Egypt are expected to sufficiently protect against this virus or other viruses of this lineage (A/AFRICA/G-IV) circulating there since 2012. In addition to the risk of vaccine failure caused by strain mismatch, the production of inactivated FMD vaccines is dangerous if adequate biosafety cannot be maintained. Using a high-throughput sequencing protocol optimized for short nucleic acid fragments, the composition of a local inactivated vaccine was analyzed in depth. The serotype O strain identified in the vaccine was genetically identical to viruses found in recent FMD outbreaks in Egypt.