Robust Protection against Highly Virulent Foot-and-Mouth Disease Virus in Swine by Combination Treatment with Recombinant Adenoviruses Expressing Porcine Alpha and Gamma Interferons and Multiple Small Interfering RNAs

Porcine interferon-α linked to the porcine IgG-Fc induces prolonged and broad-spectrum antiviral effects against foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is an economically important disease, and the FMD virus (FMDV) can spread rapidly in susceptible animals. FMD is usually controlled through vaccination. However, commercial FMD vaccines are only effective 4-7 days after vaccination. Furthermore, FMDV comprises seven serotypes and various topotypes, and these aspects should be considered when selecting a vaccine. Antiviral agents could provide rapid and broad protection against FMDV. Therefore, this study aimed to develop a fusion protein of consensus porcine interferon-α and Fc portion of porcine antibody IgG (poIFN-α-Fc) using a baculovirus expression system to develop a novel antiviral agent against FMDV. We measured the antiviral effects of the poIFN-α-Fc protein against FMDV and the enhanced duration in vitro and in vivo. The broad-spectrum antiviral effects were tested against seven FMDV serotypes, porcine reproductive and respiratory syndrome virus (PRRSV), and bovine enterovirus (BEV). Furthermore, the early protective effects and neutralizing antibody levels were tested by co-injecting poIFN-α-Fc and an FMD-inactivated vaccine into mice or pigs. Sustained antiviral effects in pig sera and mice were observed, and pigs injected with a combination of the poIFN-α-Fc and an inactivated FMD vaccine were protected against FMDV in a dose-dependent manner at 2- and 4-days post-vaccination. In addition, combined with the inactivated FMD vaccine, poIFN-α-Fc increased the neutralizing antibody levels in mice. Therefore, poIFN-α-Fc is a potential broad-spectrum antiviral and adjuvant candidate that can be used with inactivated FMD vaccines to protect pigs against FMDV.

Interferon alpha and beta receptor 1 knockout in human embryonic kidney 293 cells enhances the production efficiency of proteins or adenoviral vectors related to type I interferons

Human embryonic kidney (HEK) 293 cells are widely used in protein and viral vector production owing to their high transfection efficiency, rapid growth, and suspension growth capability. Given their antiviral, anticancer, and immune-enhancing effects, type I interferons (IFNs) have been used to prevent and treat human and animal diseases. However, the binding of type I IFNs to the IFN-α and-β receptor (IFNAR) stimulates the expression of IFN-stimulated genes (ISGs). This phenomenon induces an antiviral state and promotes apoptosis in cells, thereby impeding protein or viral vector production. In this study, we generated an IFNAR subtype 1 knockout (KO) HEK 293 suspension (IFNAR-KO) cell line by using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) technology. Upon treatment with human IFN-α, the IFNAR-KO cells showed a constant expression of ISGs, including 2'-5'-oligoadenylate synthetase 1 (OAS1), myxovirus resistance 1 (Mx1), protein kinase RNA-activated (PKR), and IFN-induced transmembrane protein 1 (IFITM1), when compared with the wild-type HEK 293 (WT) cells, wherein the ISGs were significantly upregulated. As a result, the titer of recombinant adenovirus expressing porcine IFN-α was significantly higher in the IFNAR-KO cells than in the WT cells. Furthermore, the IFNAR-KO cells continuously produced higher amounts of IFN-α protein than the WT cells. Thus, the CRISPR-Cas9-mediated IFNAR1 KO cell line can improve the production efficiency of proteins or viral vectors related to IFNs. The novel cell line may be used for producing vaccines and elucidating the type I IFN signaling pathway in cells.

Perspective vaccines for emerging viral diseases in farm animals

The world has watched the emergence of numerous animal viruses that may threaten animal health which were added to the perpetual growing list of animal pathogens. This emergence drew the attention of the experts and animal health groups to the fact that it has become necessary to work on vaccine development. The current review aims to explore the perspective vaccines for emerging viral diseases in farm animals. This aim was fulfilled by focusing on modern technologies as well as next generation vaccines that have been introduced in the field of vaccines, either in clinical developments pending approval, or have already come to light and have been applied to animals with acceptable results such as viral-vectored vaccines, virus-like particles, and messenger RNA-based platforms. Besides, it shed the light on the importance of differentiation of infected from vaccinated animals technology in eradication programs of emerging viral diseases. The new science of nanomaterials was explored to elucidate its role in vaccinology. Finally, the role of Bioinformatics or Vaccinomics and its assist in vaccine designing and developments were discussed. The reviewing of the published manuscripts concluded that the use of conventional vaccines is considered an out-of-date approach in eliminating emerging diseases. However, these types of vaccines are considered the suitable plan especially in countries with few resources and capabilities. Piloted vaccines that rely on genetic-based technologies with continuous analyses of current viruses should be the aim of future vaccinology. Smart genomics of emerging viruses will be the gateway to choosing appropriate vaccines, regardless of the evolutionary rates of viruses.

Preventive effects of quercetin against foot-and-mouth disease virus in vitro and in vivo by inducing type I interferon

Foot-and-mouth disease (FMD) is an acute contagious infectious disease that affects cloven-hoofed animals. Although current emergency FMD vaccines only take effect 7 days after vaccination, antiviral agents, such as quercetin, which is a common flavonoid, could reduce the spread of FMD virus (FMDV) during outbreaks. We investigated the in vitro and in vivo antiviral effects of quercetin against FMDV. Analysis of viral copy numbers showed that quercetin had a dose-dependent inhibitory effect on FMDV at concentrations between 19.5 and 1,250 μM in porcine cells. In addition, we observed a quercetin-induced interferon (IFN)-α protein and interferon-stimulated gene (ISG) upregulation in swine cells. Enzyme-linked immunosorbent assay of sera revealed that quercetin induces the production of IFN-α, IFN-β, IFN-γ, interleukin (IL)-12, and IL-15 in mice. Inoculation of mice with quercetin or a combination of quercetin with an inactivated FMD vaccine enhanced both the survival rate and neutralizing antibody titer. Therefore, we suggest the use of quercetin as a novel and effective antiviral agent for controlling FMDV infection; however, further investigation of its application in livestock is required.

Epigenetics and the role of nutraceuticals in health and disease

In the post-genomic era, the data provided by complete genome sequencing could not answer several fundamental questions about the causes of many noninfectious diseases, diagnostic biomarkers, and novel therapeutic approaches. The rapidly expanding understanding of epigenetic mechanisms, as well as widespread acceptance of their hypothesized role in disease induction, facilitated the development of a number of novel diagnostic markers and therapeutic concepts. Epigenetic aberrations are reversible in nature, which enables the treatment of serious incurable diseases. Therefore, the interest in epigenetic modulatory effects has increased over the last decade, so about 60,000 publications discussing the expression of epigenetics could be detected in the PubMed database. Out of these, 58,442 were published alone in the last 10 years, including 17,672 reviews (69 historical articles), 314 clinical trials, 202 case reports, 197 meta-analyses, 156 letters to the editor, 108 randomized controlled trials, 87 observation studies, 40 book chapters, 22 published lectures, and 2 clinical trial protocols. The remaining publications are either miscellaneous or a mixture of the previously mentioned items. According to the species and gender, the publications included 44,589 human studies (17,106 females, 14,509 males, and the gender is not mentioned in the remaining papers) and 30,253 animal studies. In the present work, the role of epigenetic modulations in health and disease and the influencing factors in epigenetics are discussed.

Antiviral effect of vesatolimod (GS-9620) against foot-and-mouth disease virus both in vitro and invivo

Foot-and-mouth disease (FMD) is an acute contagious disease of cloven-hoofed animals such as cows, pigs, sheep, and deer. The current emergency FMD vaccines, to induce early protection, have limited use, as their protective effect in pigs does not begin until 7 days after vaccination. Therefore, the use of antiviral agents would be required for reducing the spread of foot-and-mouth disease virus (FMDV) during outbreaks. Vesatolimod (GS-9620), a toll-like receptor 7 agonist, is an antiviral agent against various human disease-causing viruses. However, its antiviral effect against FMDV has not been reported yet. The aim of this study was to investigate the antiviral effects of GS-9620 against FMDV both in vitro and in vivo. The inhibitory effect of GS-9620 on FMDV in swine cells involved the induction of porcine interferon (IFN)-α and upregulation of interferon-simulated genes. Protective effect in mice injected with GS-9620 against FMDV was maintained for 5 days after injection, and cytokines such as IFN-γ, interleukin (IL)-12, IL-6, and IFN-γ inducible protein-10 could be detected following the treatment with GS-9620. Furthermore, the combination of GS-9620 with an FMD-inactivated vaccine was found to be highly effective for early protection in mice. Overall, we suggest GS-9620 as a novel and effective antiviral agent for controlling FMDV infection.

Peste des Petits Ruminants Virus Exhibits Cell-Dependent Interferon Active Response

Peste des petits ruminants (PPR) is an acute and highly pathogenic infectious disease caused by peste des petits ruminants virus (PPRV), which can infect goats and sheep and poses a major threat to the small ruminants industry. The innate immune response plays an important role as a line of defense against the virus. The effect of PPRV on the active innate immune response has been described in several studies, with different conclusions. We infected three goat-derived cell lines with PPRV and tested their innate immune response. PPRV proliferated in caprine endometrial epithelial cells (EECs), caprine skin fibroblasts cells (GSFs), and goat fibroblast cells (GFs), and all cells expressed interferon (IFN) by poly (I: C) stimulation. PPRV infection stimulated expression of type I and type III IFN on EECs, and expression of the latter was significantly stronger, but IFN was not stimulated in fibroblasts (GSFs and GFs). Our results suggested that the effect of PPRV on IFN was cell-type specific. Nine IFN-stimulated genes (ISGs) were detected in EECs, but only ISG15 and RSAD2 were significantly upregulated. The effects of PPRV on IFN and IFN-induced ISGs were cell-type specific, which advances our understanding of the innate immune response induced by PPRV and creates new possibilities for the control of PPRV infection.

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

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

The Swine IFN System in Viral Infections: Major Advances and Translational Prospects

Interferons (IFNs) are a family of cytokines that play a pivotal role in orchestrating the innate immune response during viral infections, thus representing the first line of defense in the host. After binding to their respective receptors, they are able to elicit a plethora of biological activities, by initiating signaling cascades which lead to the transcription of genes involved in antiviral, anti-inflammatory, immunomodulatory and antitumoral effector mechanisms. In hindsight, it is not surprising that viruses have evolved multiple IFN escape strategies toward efficient replication in the host. Hence, in order to achieve insight into preventive and treatment strategies, it is essential to explore the mechanisms underlying the IFN response to viral infections and the constraints thereof. Accordingly, this review is focused on three RNA and three DNA viruses of major importance in the swine farming sector, aiming to provide essential data as to how the IFN system modulates the antiviral immune response, and is affected by diverse, virus-driven, immune escape mechanisms.

A Vaccine Strain of the A/ASIA/Sea-97 Lineage of Foot-and-Mouth Disease Virus with a Single Amino Acid Substitution in the P1 Region That Is Adapted to Suspension Culture Provides High Immunogenicity

There are seven viral serotypes of foot-and-mouth disease virus (FMDV): A, O, C, Asia 1, and Southern African Territories 1, 2, and 3 (SAT 1–3). Unlike serotype O FMDV vaccine strains, vaccine strains of serotype A FMDV do not provide broad-range cross-reactivity in serological matching tests with field isolates. Therefore, the topotype/lineage vaccine strain circulating in many countries and a highly immunogenic strain might be advantageous to control serotype A FMDV. We developed a new vaccine strain, A/SKR/Yeoncheon/2017 (A-1), which belongs to the A/ASIA/Sea-97 lineage that frequently occurs in Asian countries. Using virus plaque purification, we selected a vaccine virus with high antigen productivity and the lowest numbers of P1 mutations among cell-adapted virus populations. The A/SKR/Yeoncheon/2017 (A-1) vaccine strain has a single amino acid mutation, VP2 E82K, in the P1 region, and it is perfectly adapted to suspension culture. The A/SKR/Yeoncheon/2017 (A-1) experimental vaccine conferred high immunogenicity in pigs. The vaccine strain was serologically matched with various field isolates in two-dimensional virus neutralization tests using bovine serum. Vaccinated mice were protected against an A/MAY/97 virus that was serologically mismatched with the vaccine strain. Thus, A/SKR/Yeoncheon/2017 (A-1) might be a promising vaccine candidate for protection against the emerging FMDV serotype A in Asia.

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

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

Use of IFN-Based Biotherapeutics to Harness the Host Against Foot-And-Mouth Disease

Foot-and-mouth disease (FMD) is a highly contagious vesicular disease of cloven-hoofed animals that severely constrains international trade of livestock and animal products. Currently, disease control measures include broad surveillance, enforcement of sanitary policy, and use of an inactivated vaccine. While use of these measures has contributed to eliminating foot-and-mouth disease virus (FMDV) from a vast area of the world, the disease remains endemic in three continents, and outbreaks occasionally appear in previously declared FMD-free zones, causing economic and social devastation. Among others, a very fast rate of viral replication and the need for 7 days to achieve vaccine-induced protection are the main limitations in controlling the disease. New fast-acting antiviral strategies targeted to boost the innate immunity of the host to block viral replication are needed. Here we review the knowledge on the multiple strategies FMDV has evolved to block the host innate immunity, with particularly focus on the past and current research toward the development of interferon (IFN)-based biotherapeutics in relevant livestock species.

Foot-and-Mouth Disease Virus: Immunobiology, Advances in Vaccines and Vaccination Strategies Addressing Vaccine Failures-An Indian Perspective

A mass vaccination campaign in India seeks to control and eventually eradicate foot-and-mouth disease (FMD). Biosanitary measures along with FMD monitoring are being conducted along with vaccination. The implementation of the FMD control program has drastically reduced the incidence of FMD. However, cases are still reported, even in regions where vaccination is carried out regularly. Control of FMD outbreaks is difficult when the virus remains in circulation in the vaccinated population. Various FMD risk factors have been identified that are responsible for FMD in vaccinated areas. The factors are discussed along with strategies to address these challenges. The current chemically inactivated trivalent vaccine formulation containing strains of serotype O, A, and Asia 1 has limitations including thermolability and induction of only short-term immunity. Advantages and disadvantages of several new-generation alternate vaccine formulations are discussed. It is unfeasible to study every incidence of FMD in vaccinated animals/areas in such a big country as India with its huge livestock population. However, at the same time, it is absolutely necessary to identify the precise reason for vaccination failure. Failure to vaccinate is one reason for the occurrence of FMD in vaccinated areas. FMD epidemiology, emerging and re-emerging virus strains, and serological status over the past 10 years are discussed to understand the impact of vaccination and incidences of vaccination failure in India. Other factors that are important in vaccination failure that we discuss include disrupted herd immunity, health status of animals, FMD carrier status, and FMD prevalence in other species. Recommendations to boost the search of alternate vaccine formulation, strengthen the veterinary infrastructure, bolster the real-time monitoring of FMD, as well as a detailed investigation and documentation of every case of vaccination failure are provided with the goal of refining the control program.

Foot-and-mouth disease vaccines: recent updates and future perspectives

Foot-and-mouth disease (FMD) is a major worldwide viral disease in animals, affecting the national and international trade of livestock and animal products and leading to high economic losses and social consequences. Effective control measures of FMD involve prevention through vaccination with inactivated vaccines. These inactivated vaccines, unfortunately, require short-term protection and cold-chain and high-containment facilities. Major advances and pursuit of hot topics in vaccinology and vectorology are ongoing, involving peptide vaccines, DNA vaccines, live vector vaccines, and novel attenuated vaccines. DIVA capability and marker vaccines are very important in differentiating infected animals from vaccinated animals. This review focuses on updating the research progress of these novel vaccines, summarizing their merits and including ideas for improvement.

Synergistic effect of ribavirin and vaccine for protection during early infection stage of foot-and-mouth disease

In many countries, vaccines are used for the prevention of foot-and-mouth disease (FMD). However, because there is no protection against FMD immediately after vaccination, research and development on antiviral agents is being conducted to induce protection until immunological competence is produced. This study tested whether well-known chemicals used as RNA virus treatment agents had inhibitory effects on FMD viruses (FMDVs) and demonstrated that ribavirin showed antiviral effects against FMDV in vitro/in vivo. In addition, it was observed that combining the administration of the antiviral agents orally and complementary therapy with vaccines synergistically enhanced antiviral activity and preserved the survival rate and body weight in the experimental animals. Antiviral agents mixed with an adjuvant were inoculated intramuscularly along with the vaccines, thereby inhibiting virus replication after injection and verifying that it was possible to induce early protection against viral infection prior to immunity being achieved through the vaccine. Finally, pigs treated with antiviral agents and vaccines showed no clinical signs and had low virus excretion. Based on these results, it is expected that this combined approach could be a therapeutic and preventive treatment for early protection against FMD.

Recombinant adenovirus-delivered soluble CD163 and sialoadhesin receptors protected pigs from porcine reproductive and respiratory syndrome virus infection

Porcine reproductive and respiratory syndrome (PRRS) is one of the most important swine diseases affecting pig industry worldwide. Sialoadehesin (Sn) and CD163 are the two specific receptors for PRRSV infection of porcine alveolar macrophages. Our previous study showed that the soluble Sn receptor Sn4D-Fc and soluble CD163 receptor SRCR59-Fc expressed by the two recombinant adenoviral (rAd) vectors have an additive anti-PRRSV effect in vitro. In the present study, rAd-Sn4D-Fc and rAd-SRCR59-Fc were inoculated into pigs, and the efficient expression of Sn4D-Fc and SRCR59-Fc proteins was detected by ELISA. Then, PRRSV-naïve pigs were inoculated with rAd-Sn4D-Fc and/or rAd-SRCR59-Fc before contagious infection with different PRRSV strains. Among the three rAd inoculation groups, simultaneous inoculation with the two rAd vectors provided the best protection against highly pathogenic JXA1 strain PRRSV, followed by rAd-SRCR59-Fc inoculation and rAd-Sn4D-Fc inoculation. Clinical observation and quantitative RT-PCR analyses showed that all of the double rAd-inoculated pigs (n = 9) survived from the contagious infection with highly pathogenic JXA1, JS07 or SH1705 strain PRRSV with significantly alleviated clinical scores, viremia, fecal viral emission and tissue virus loads. These data suggest that rAd-Sn4D-Fc and rAd-SRCR59-Fc can be developed further as the universal therapeutic vaccine to facilitate PRRSV eradication.

Antivirals against animal viruses

Antivirals are compounds used since the 1960s that can interfere with viral development. Some of these antivirals can be isolated from a variety of sources, such as animals, plants, bacteria or fungi, while others must be obtained by chemical synthesis, either designed or random. Antivirals display a variety of mechanisms of action, and while some of them enhance the animal immune system, others block a specific enzyme or a particular step in the viral replication cycle. As viruses are mandatory intracellular parasites that use the host's cellular machinery to survive and multiply, it is essential that antivirals do not harm the host. In addition, viruses are continually developing new antiviral resistant strains, due to their high mutation rate, which makes it mandatory to continually search for, or develop, new antiviral compounds. This review describes natural and synthetic antivirals in chronological order, with an emphasis on natural compounds, even when their mechanisms of action are not completely understood, that could serve as the basis for future development of novel and/or complementary antiviral treatments.

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

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

Host microRNA-203a Is antagonistic to the progression of foot-and-mouth disease virus infection

Sam68 was previously shown to be a critical host factor for foot-and-mouth disease virus (FMDV) replication. MicroRNA (miR) miR-203a is reportedly a negative regulator of Sam68 expression both in vitro and in vivo. Here, transfection of miR-203a-3p and miR-203a-5p mimics separately and in combination in a porcine cell line followed by FMDV infection resulted in diminished viral protein synthesis and a 4 and 6log reduction in virus titers relative to negative controls, respectively. Unexpectedly, Sam68 expression was increased by miR-203a-5p transfection, but not miR-203a-3p. miR-203a-5p also down-regulated Survivin expression, which was predicted to play a role in FMDV infection. Moreover, miR-203a-5p but not miR-203a-3p affected a reduction in FMDV viral RNA. These effects were not replicated with a related Picornavirus, suggesting FMDV specificity. Importantly, miR-203a-3p and miR-203a-5p impaired FMDV infection across multiple FMDV serotypes. We concluded that miR-203a-3p and miR-203a-5p represent attractive potential naturally occurring bio-therapeutics against FMDV.

Challenges of Generating and Maintaining Protective Vaccine-Induced Immune Responses for Foot-and-Mouth Disease Virus in Pigs

Vaccination can play a central role in the control of outbreaks of foot-and-mouth disease (FMD) by reducing both the impact of clinical disease and the extent of virus transmission between susceptible animals. Recent incursions of exotic FMD virus lineages into several East Asian countries have highlighted the difficulties of generating and maintaining an adequate immune response in vaccinated pigs. Factors that impact vaccine performance include (i) the potency, antigenic payload, and formulation of a vaccine; (ii) the antigenic match between the vaccine and the heterologous circulating field strain; and (iii) the regime (timing, frequency, and herd-level coverage) used to administer the vaccine. This review collates data from studies that have evaluated the performance of foot-and-mouth disease virus vaccines at the individual and population level in pigs and identifies research priorities that could provide new insights to improve vaccination in the future.

Short Interfering RNA Inhibits Rift Valley Fever Virus Replication and Degradation of Protein Kinase R in Human Cells

Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen causing severe outbreaks in humans and livestock in sub-Saharan Africa and the Arabian Peninsula. Human infections are characterized by fever, sometimes leading to encephalitis, retinitis, hemorrhagic fever, and occasionally death. There are currently no fully licensed vaccines or effective therapies for human use. Gene silencing mediated by double-stranded short interfering RNA (siRNA) is a sequence-specific, highly conserved mechanism in eukaryotes, which serves as an antiviral defense mechanism. Here, we demonstrate that siRNA duplexes directed against the RVFV nucleoprotein can effectively inhibit RVFV replication in human (MRC5 cells) and African green monkey cells (Vero E6 cells). Using these cells, we demonstrate that individual or complex siRNAs, targeting the RVFV nucleoprotein gene completely abrogate viral protein expression and prevent degradation of the host innate antiviral factor, protein kinase R (PKR). Importantly, pre-treatment of cells with the nucleoprotein-specific siRNAs markedly reduces the virus titer. The antiviral effect of the siRNAs was not attributable to interferon or the interferon response effector molecule, PKR. Thus, the antiviral activity of RVFV nucleoprotein-specific siRNAs may provide novel therapeutic strategy against RVFV infections in animals and humans.

Constitutively Active IRF7/IRF3 Fusion Protein Completely Protects Swine against Foot-and-Mouth Disease

Foot-and-mouth disease (FMD) remains one of the most devastating livestock diseases around the world. Several serotype-specific vaccine formulations exist, but they require about 5 to 7 days to induce protective immunity. Our previous studies have shown that a constitutively active fusion protein of porcine interferon (IFN) regulatory factors (IRF) 7 and 3 [IRF7/3(5D)] strongly induced type I IFN and antiviral genes in vitro and prevented mortality in an FMD mouse model when delivered with a replication-defective adenoviral vector [Ad5-poIRF7/3(5D)]. Here, we demonstrate that pigs treated with 10(8), 10(9), or 10(10) PFU of Ad5-poIRF7/3(5D) 24 h before FMDV challenge were fully protected from FMD clinical signs and did not develop viremia, virus shedding or antibodies against FMDV nonstructural proteins. Pigs treated with Ad5-poIRF7/3(5D) had higher levels of IFN and antiviral activity in serum, and upregulated expression of several IFN-stimulated genes in peripheral blood mononuclear cells, compared to pigs treated with Ad5-Blue vector control. Importantly, treatment of porcine cultured cells with Ad5-poIRF7/3(5D) inhibited the replication of all 7 FMDV serotypes. In vitro experiments using cultured embryonic fibroblasts derived from IFN receptor knockout mice suggested that the antiviral response induced by Ad5-poIRF7/3(5D) was dependent on type I and III IFN pathways; however, experiments with mice demonstrated that a functional type I IFN pathway mediates Ad5-poIRF7/3(5D) protection conferred in vivo Our studies demonstrate that inoculation with Ad5-poIRF7/3(5D) completely protects swine against FMD by inducing a strong type I IFN response and highlights its potential application to rapidly and effectively prevent FMDV replication and dissemination.

IMPORTANCE

Foot-and-mouth disease virus (FMDV) causes a fast-spreading disease that affects farm animals, with economically and socially devastating consequences. Our study shows that inoculation with a constitutively active transcription factor, namely, a fusion protein of porcine interferon (IFN) regulatory factors (IRF) 7 and 3 delivered by an adenovirus vector [Ad5-poIRF7/3(5D)], is a new effective treatment to prevent FMD in swine. Animals pretreated with Ad5-poIRF7/3(5D) 1 day before being exposed to FMDV were completely protected from viral replication and clinical disease. It is noteworthy that the doses of Ad5-poIRF7/3(5D) required for protection are lower than those previously reported for similar approaches using Ad5 vectors delivering type I, II, or III IFN, suggesting that this novel strategy would be economically appealing to counteract FMD. Our results also indicate that a dynamic interplay among different components of pigs' innate immune defenses allows potent antiviral effects after Ad5-poIF7/3(5D) administration.

The Pathogenesis of Foot-and-Mouth Disease in Pigs

The greatest proportion of foot-and-mouth disease (FMD) clinical research has been dedicated to elucidating pathogenesis and enhancing vaccine protection in cattle with less efforts invested in studies specific to pigs. However, accumulated evidence from FMD outbreaks and experimental investigations suggest that critical components of FMD pathogenesis, immunology, and vaccinology cannot be extrapolated from investigations performed in cattle to explain or to predict outcomes of infection or vaccination in pigs. Furthermore, it has been shown that failure to account for these differences may have substantial consequences when FMD outbreaks occur in areas with dense pig populations. Recent experimental studies have confirmed some aspects of conventional wisdom by demonstrating that pigs are more susceptible to FMD virus (FMDV) infection via exposure of the upper gastrointestinal tract (oropharynx) than through inhalation of virus. The infection spreads rapidly within groups of pigs that are housed together, although efficiency of transmission may vary depending on virus strain and exposure intensity. Multiple investigations have demonstrated that physical separation of pigs is sufficient to prevent virus transmission under experimental conditions. Detailed pathogenesis studies have recently demonstrated that specialized epithelium within porcine oropharyngeal tonsils constitute the primary infection sites following simulated natural virus exposure. Furthermore, epithelium of the tonsil of the soft palate supports substantial virus replication during the clinical phase of infection, thus providing large amounts of virus that can be shed into the environment. Due to massive amplification and shedding of virus, acutely infected pigs constitute a considerable source of contagion. FMDV infection results in modulation of several components of the host immune response. The infection is ultimately cleared in association with a strong humoral response and, in contrast to ruminants, there is no subclinical persistence of FMDV in pigs. The aim of this review is to provide an overview of knowledge gained from experimental investigations of FMD pathogenesis, transmission, and host response in pigs. Details of the temporo-anatomic progression of infection are discussed in relation to specific pathogenesis events and the likelihood of transmission. Additionally, relevant aspects of the host immune response are discussed within contexts of conventional and novel intervention strategies of vaccination and immunomodulation.

Comparative transcriptome analyses indicate enhanced cellular protection against FMDV in PK15 cells pretreated with IFN-γ

Interferon gamma (IFN-γ) can induce a host antiviral response to foot and mouth disease virus (FMDV) in vivo and in vitro. To elucidate the mechanism of IFN-γ anti FMDV infection in host cells, high-throughput RNA sequencing was analyzed for systemic changes in gene expression profiles in PK15 cells infected by FMDV with or without IFN-γ pretreatment. More than 25 million reads, covering 1.2-1.5 Gb, were analyzed from each experiment panel. FMDV challenge altered the transcription of genes involved in positively and negatively regulating cell death or apoptosis; however, the expected immune suppression response was not obvious. IFN-γ pretreatment combined with FMDV infection normalized the increase in apoptosis. Furthermore, the transcription factors required for IFN-γ functioning, STAT1 and IRF1 were up-regulated by IFN-γ pretreatment and stimulated downstream IFN-stimulated genes (ISGs). These induced ISGs are mainly responsible for antigen processing, antigen presentation or antiviral defense. Interestingly, a synergistic effect on some ISGs, including OAS1, OAS2, MX1, MX2, RIG-I and IFIT1, was observed in the combined treatment compared to the IFN-γ treatment alone. The suggested effects identified by RNA sequencing were consistent with cellular morphology changes and confirmed by related protein markers. This is the first report exploring transcriptome alterations introduced by FMDV infection with or without IFN-γ pretreatment. The identified key host genes that control cell survival in vitro broaden our comprehensive understanding of how IFN-γ inhibits FMDV infection and may shed light on developing improved FMD control approaches.