An MHC-restricted CD8+ T-cell response is induced in cattle by foot-and-mouth disease virus (FMDV) infection and also following vaccination with inactivated FMDV

The ex vivo infection model of the peripheral bovine mononuclear cells (PBMCs) and the bovine spleen cells with the bovine coronavirus (BCoV) induced a differential expression of the host cytokine genes profiles and modulates the virus replication

The adaptive immune response during BCoV infection of peripheral blood mononuclear cells (PBMCs), the bovine spleen cells, and their isolated T lymphocytes was not studied well. Our study confirmed successful BCoV infection in PBMCs and spleen T cells. The BCoV replication was evidenced by measuring genome copy numbers using real-time PCR and expression levels of BCoV spike and nucleocapsid proteins via western blot and immunofluorescence assays. In infected PBMCs, CD4 T-cell levels were 1.45-fold higher, and CD8 T-cell levels were 1.6-fold lower compared to sham-infected cells. Conversely, infected splenocytes showed a 0.88-fold decrease in CD4 T-cells and a 1.88-fold increase in CD8 T-cells. The cytokine gene expression analysis revealed that BCoV infection activated type I interferon and upregulated IL-6 expression in PBMCs and splenocytes. These findings demonstrate that BCoV successfully infects immune cells from PBMCs and spleen, inducing differential host cytokine gene expression that favors virus replication.

Defining correlates of protection for mammalian livestock vaccines against high-priority viral diseases

Enhancing livestock biosecurity is critical to safeguard the livelihoods of farmers, global and local economies, and food security. Vaccination is fundamental to the control and prevention of exotic and endemic high-priority infectious livestock diseases. Successful implementation of vaccination in a biosecurity plan is underpinned by a strong understanding of correlates of protection-those elements of the immune response that can reliably predict the level of protection from viral challenge. While correlates of protection have been successfully characterized for many human viral vaccines, for many high-priority livestock viral diseases, including African swine fever and foot and mouth disease, they remain largely uncharacterized. Current literature provides insights into potential correlates of protection that should be assessed during vaccine development for these high-priority mammalian livestock viral diseases. Establishment of correlates of protection for biosecurity purposes enables immune surveillance, rationale for vaccine development, and successful implementation of livestock vaccines as part of a biosecurity strategy.

Enhanced antigen-specific CD8 T cells contribute to early protection against FMDV through swine DC vaccination

Foot-and-mouth disease virus (FMDV) remains a challenge for cloven-hooved animals. The currently licensed FMDV vaccines induce neutralizing antibody (NAb)-mediated protection but show defects in the early protection. Dendritic cell (DC) vaccines have shown great potency in inducing rapid T-cell immunity in humans and mice. Whether DC vaccination could enhance early protection against FMDV has not been elaborately explored in domestic pigs. In this study, we employed DC vaccination as an experimental approach to study the roles of cellular immunity in the early protection against FMDV in pigs. Autologous DCs were differentiated from the periphery blood mononuclear cells of each pig, pulsed with inactivated FMDV (iFMDV-DC) and treated with LPS, and then injected into the original pigs. The cellular immune responses and protective efficacy elicited by the iFMDV-DC were examined by multicolor flow cytometry and tested by FMDV challenge. The results showed that autologous iFMDV-DC immunization induced predominantly FMDV-specific IFN-γ-producing CD4+ T cells and cytotoxic CD8+ T cells (CTLs), high NAb titers, compared to the inactivated FMDV vaccine, and accelerated the development of memory CD4 and CD8 T cells, which was concomitantly associated with early protection against FMDV virulent strain in pigs. Such early protection was associated with the rapid proliferation of secondary T-cell response after challenge and significantly contributed by secondary CD8 effector memory T cells. These results demonstrated that rapid induction of cellular immunity through DC immunization is important for improving early protection against FMDV. Enhancing cytotoxic CD8+ T cells may facilitate the development of more effective FMDV vaccines.IMPORTANCEAlthough the currently licensed FMDV vaccines provide NAb-mediated protection, they have defects in early immune protection, especially in pigs. In this study, we demonstrated that autologous swine DC immunization augmented the cellular immune response and induced an early protective response against FMDV in pigs. This approach induced predominantly FMDV-specific IFN-γ-producing CD4+ T cells and cytotoxic CD8+ T cells, high NAb titers, and rapid development of memory CD4 and CD8 T cells. Importantly, the early protection conferred by this DC immunization is more associated with secondary CD8+ T response rather than NAbs. Our findings highlighted the importance of enhancing cytotoxic CD8+ T cells in early protection to FMDV in addition to Th1 response and identifying a strategy or adjuvant comparable to the DC vaccine might be a future direction for improving the current FMDV vaccines.

Expression of FMD virus-like particles in yeast Hansenula polymorpha and immunogenicity of combine with CpG and aluminum adjuvant

BACKGROUND

Inactivated vaccines are limited in preventing foot-and-mouth disease (FMD) due to safety problems. Recombinant virus-like particles (VLPs) are an excellent candidate for a novel vaccine for preventing FMD, given that VLPs have similar immunogenicity as natural viruses and are replication- and infection-incompetent.

OBJECTIVES

The 3C protease and P1 polyprotein of type O FMD virus (FDMV) was expressed in yeast Hansenula polymorpha to generate self-resembling VLPs, and the potential of recombinant VLPs as an FMD vaccine was evaluated.

METHODS

BALB/c mice were immunized with recombinant purified VLPs using CpG oligodeoxynucleotide and aluminum hydroxide gel as an adjuvant. Cytokines and lymphocytes from serum and spleen were analyzed by enzyme-linked immunosorbent assay, enzyme-linked immunospot assay, and flow cytometry.

RESULTS

The VLPs of FMD were purified successfully from yeast protein with a diameter of approximately 25 nm. The immunization of mice showed that animals produced high levels of FMDV antibodies and a higher level of antibodies for a longer time. In addition, higher levels of interferon-γ and CD4⁺ T cells were observed in mice immunized with VLPs.

CONCLUSIONS

The expression of VLPs of FMD in H. polymorpha provides a novel strategy for the generation of the FMDV vaccine.

Effect of cell density on the biological titer and yield of 146S fraction of foot-and-mouth disease virus O in cell suspension

Foot-and-mouth disease (FMD) is a highly infectious disease of cattle and other cloven-hoofed animals, causing huge economic losses annually worldwide. This disease is endemic in Pakistan where the serotypes of the foot-and-mouth disease virus (FMDV) are A, O and ASIA-1. At present, trivalent FMDV vaccines are being used to prevent FMD but the current production process is laborious and is unable to fulfill the needs of the meat and dairy industries. To meet the vaccine needs of Pakistan, the conventional method of using adherent cell lines to produce the vaccine could be replaced by suspension cell cultures which produce higher yields in less time and less volume. Therefore, the aim of this study was to investigate and optimize some of the factors that affect viable cell density and subsequent virus yield. The relationship between the yield of the 146S fraction and the TCID₅₀ of the virus preparations obtained was also evaluated as a mean to control and check the quality of the vaccine product. The results provided optimized conditions for vaccine production using cell suspensions and showed that there was a linear relationship between TCID₅₀ and 146S fraction yield. Either TCID₅₀ or the 146S fraction yield, or both could be used as parameters for quality monitoring during vaccine production. Using TCID₅₀ reduced the number of steps involved in virus production while measuring 146S fraction yield was useful for quality control. However, more studies are required to evaluate the relative effectiveness of vaccines produced by virus cultures using either TCID₅₀ or 146S fraction as quality monitoring tools.

An Adenovirus Vector Expressing FMDV RNA Polymerase Combined with a Chimeric VLP Harboring a Neutralizing Epitope as a Prime Boost Strategy to Induce FMDV-Specific Humoral and Cellular Responses

Foot and mouth disease is a highly contagious disease affecting cattle, sheep, and swine among other cloven-hoofed animals that imposes serious economic burden by its direct effects on farm productivity as well as on commerce of farmed produce. Vaccination using inactivated viral strains of the different serotypes is an effective protective measure, but has several drawbacks including a lack of cross protection and the perils associated with the large-scale growth of infectious virus. We have previously developed chimeric virus-like particles (VLPs) bearing an FMDV epitope which induced strong specific humoral responses in vaccinated pigs but conferred only partial protection against homologous challenge. While this and other FMD vaccines under development mostly rely on the induction of neutralizing responses, it is thought that induction of specific T-cell responses might improve both cross protective efficacy as well as duration of immunity. Therefore, we here describe the development of a recombinant adenovirus expressing the highly conserved nonstructural FMDV 3D protein as well as its capacity to induce specific T-cell responses in a murine model. We further describe the generation of an FMDV serotype C-specific chimeric VLP and analyze the immunogenicity of two different prime-boost strategies combining both elements in mice. This combination can effectively induce both humoral and cellular FMDV-specific responses eliciting high titers of ELISA and neutralizing antibodies anti-FMDV as well as a high frequency of IFNγ-secreting cells. These results provide the basis for further testing of this anti FMD vaccination strategy in cattle or pig, two of the most relevant natural host of this pathogen.

The detection of long-lasting memory foot-and-mouth disease (FMD) virus serotype O-specific CD4+ T cells from FMD-vaccinated cattle by bovine major histocompatibility complex class II tetramer

Foot‐and‐mouth disease (FMD) is a highly contagious, economically devastating disease of cloven‐hooved animals. The development of long‐lasting effective FMD vaccines would greatly benefit the global FMD control programme. Deep analysis of adaptive immunity in cattle vaccinated against FMD is technically challenging due to the lack of species‐specific tools. In this study, we aimed to identify CD4⁺ T‐cell epitopes in the FMD virus (FMDV) capsid and to phenotype the CD4⁺ T cells that recognize them using bovine major histocompatibility complex (BoLA) class II tetramer. A BoLA class II tetramer based on the DRA/DRB3*020:02 allele and FMDV antigen‐stimulated PBMCs from bovine vaccinates were used to successfully identify four epitopes in the FMDV capsid, three of which have not been previously reported; two epitopes were identified in the structural protein VP1, one in VP3 and one in VP4. Specificity of the three novel epitopes was confirmed by proliferation assay. All epitope‐expanded T‐cell populations produced IFN‐γ in vitro, indicating a long‐lasting Th1 cell phenotype after FMD vaccination. VP3‐specific CD4⁺ T cells exhibited the highest frequency amongst the identified epitopes, comprising >0·004% of the CD4⁺ T‐cell population. CD45RO⁺CCR7⁺ defined central memory CD4⁺ T‐cell subpopulations were present in higher frequency in FMDV‐specific CD4⁺ T‐cell populations from FMD‐vaccinated cattle ex vivo. This indicates an important role in maintaining cell adaptive immunity after FMD vaccination. Notably, FMDV epitope‐loaded tetramers detected the presence of FMDV‐specific CD4⁺ T cells in bovine PBMC more than four years after vaccination. This work contributes to our understanding of vaccine efficacy.

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.

Virus-Host Interactions in Foot-and-Mouth Disease Virus Infection

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals, which has been regarded as a persistent challenge for the livestock industry in many countries. Foot-and-mouth disease virus (FMDV) is the etiological agent of FMD that can spread rapidly by direct and indirect transmission. FMDV is internalized into host cell by the interaction between FMDV capsid proteins and cellular receptors. When the virus invades into the cells, the host antiviral system is quickly activated to suppress the replication of the virus and remove the virus. To retain fitness and host adaptation, various viruses have evolved multiple elegant strategies to manipulate host machine and circumvent the host antiviral responses. Therefore, identification of virus-host interactions is critical for understanding the host defense against virus infections and the pathogenesis of the viral infectious diseases. This review elaborates on the virus-host interactions during FMDV infection to summarize the pathogenic mechanisms of FMD, and we hope it can provide insights for designing effective vaccines or drugs to prevent and control the spread of FMD and other diseases caused by picornaviruses.

Swine T-Cells and Specific Antibodies Evoked by Peptide Dendrimers Displaying Different FMDV T-Cell Epitopes

Dendrimeric peptide constructs based on a lysine core that comprises both B- and T-cell epitopes of foot-and-mouth disease virus (FMDV) have proven a successful strategy for the development of FMD vaccines. Specifically, B₂T dendrimers displaying two copies of the major type O FMDV antigenic B-cell epitope located on the virus capsid [VP1 (140–158)], covalently linked to a heterotypic T-cell epitope from either non-structural protein 3A [3A (21–35)] or 3D [3D (56–70)], named B₂T-3A and B₂T-3D, respectively, elicit high levels of neutralizing antibodies (nAbs) and IFN-γ-producing cells in pigs. To assess whether the inclusion and orientation of T-3A and T-3D T-cell epitopes in a single molecule could modulate immunogenicity, dendrimers with T epitopes juxtaposed in both possible orientations, i.e., constructs B₂TT-3A3D and B₂TT-3D3A, were made and tested in pigs. Both dendrimers elicited high nAbs titers that broadly neutralized type O FMDVs, although B₂TT-3D3A did not respond to boosting, and induced lower IgGs titers, in particular IgG2, than B₂TT-3A3D. Pigs immunized with B_2, a control dendrimer displaying two B-cell epitope copies and no T-cell epitope, gave no nABs, confirming T-3A and T-3D as T helper epitopes. The T-3D peptide was found to be an immunodominant, as it produced more IFN-γ expressing cells than T-3A in the in vitro recall assay. Besides, in pigs immunized with the different dendrimeric peptides, CD4⁺ T-cells were the major subset contributing to IFN-γ expression upon in vitro recall, and depletion of CD4⁺ cells from PBMCs abolished the production of this cytokine. Most CD4⁺IFN-γ⁺ cells showed a memory (CD4⁺2E3⁻) and a multifunctional phenotype, as they expressed both IFN-γ and TNF-α, suggesting that the peptides induced a potent Th1 pro-inflammatory response. Furthermore, not only the presence, but also the orientation of T-cell epitopes influenced the T-cell response, as B₂TT-3D3A and B₂ groups had fewer cells expressing both cytokines. These results help understand how B₂T-type dendrimers triggers T-cell populations, highlighting their potential as next-generation FMD vaccines.

A New Cage-Like Particle Adjuvant Enhances Protection of Foot-and-Mouth Disease Vaccine

Foot-and-Mouth Disease (FMD) is an acute viral disease that causes important economy losses. Vaccines with new low-cost adjuvants that stimulate protective immune responses are needed and can be assayed in a mouse model to predict their effectiveness in cattle. Immunostimulant Particle Adjuvant (ISPA), also known as cage-like particle adjuvant, consisting of lipid boxes of dipalmitoyl-phosphatidylcholine, cholesterol, sterylamine, alpha-tocopherol, and QuilA saponin, was shown to enhance protection of a recombinant vaccine against Trypanosoma cruzi in a mouse model. Thus, in the present work, we studied the effects on the magnitude and type of immunity elicited in mice and cattle in response to a vaccine based on inactivated FMD virus (iFMDV) formulated with ISPA. It was demonstrated that iFMDV–ISPA induced protection in mice against challenge and elicited a specific antibody response in sera, characterized by a balanced Th1/Th2 profile. In cattle, the antibody titers reached corresponded to an expected percentage of protection (EPP) higher than 80%. EPP calculates the probability that livestock would be protected against a 10,000 bovine infectious doses challenge after vaccination. Moreover, in comparison with the non-adjuvanted iFMDV vaccine, iFMDV–ISPA elicited an increased specific T-cell response against the virus, including higher interferon gamma (IFNγ)+/CD8+ lymphocyte production in cattle. In this work, we report for first time that an inactivated FMDV serotype A vaccine adjuvanted with ISPA is capable of inducing protection against challenge in a murine model and of improving the specific immune responses against the virus in cattle.

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.

Adjuvanticity of aqueous extracts of Artemisia rupestris L. for inactivated foot-and-mouth disease vaccine in mice

Several methods have been developed to improve the efficacy of foot-and-mouth disease virus (FMDV) vaccine. The study aims to determine whether aqueous extracts of Artemisia rupestris L. (AEAR) as an immunoactivator in combination with inactivated FMDV vaccine can promote immune responses in mice. Intramuscular co-immunization in ICR mice with different doses of AEAR plus FMDV vaccine could substantially improve the FMDV-specific antibody production (IgG, IgG₁, and IgG_2a) and lead to significant lymphocyte proliferative responses. Th1-type immune responses were also observed, including proliferative responses of CD8⁺, CD4⁺, CD4⁺CD44+, and CD8⁺CD44⁺ T cells and the killing efficacy of cytotoxic T lymphocyte (CTL) responses. AEAR also elicited the higher levels of IL-4 and IFN-γ in CD4⁺ T cells as well as the higher level of IFN-γ in CD8⁺ T cells. The medium dose of AEAR induced the significant adjuvant activity. Further tests in mice indicated that AEAR could activate DCs maturation by increasing the expression levels of co-stimulatory molecules (CD40, CD86, CD80, and MHC-II) on dendritic cells (DCs) from splenocytes and reduce the activity of regulatory T cells (Treg). Abnormal behaviors, side effects or death were not observed in immunized mice. AEAR could boost humoral and cell-mediated immunity elicited by FMDV vaccine, especially Th1-type immune responses.

Expression of the VP1 protein of FMDV integrated chromosomally with mutant Listeria monocytogenes strain induced both humoral and cellular immune responses

Live vector-based vaccine is a modern approach to overcome the drawbacks of inactivated foot-and-mouth disease (FMD) vaccines such as improper inactivation during manufacture. Listeria monocytogenes (LM), an intracellular microorganism with immune-stimulatory properties, is appropriate to be utilized as a live bacterial vaccine vector. FMDV-VP1 protein has the capability to induce both cellular and humoral immune responses since it is considered the most immunogenic part of FMDV capsid and has the most of antigenic sites for viral neutralization. The codon-optimized vp1 gene was ligated to the integrative pCW702 plasmid to construct the target cassette. The antigen cassette was integrated successfully into the chromosome of mutant LM strain via homologous recombination for more stability to generate a candidate vaccine strain LM△actAplcB-vp1. Safety evaluation of recombinant LM△actAplcB-vp1 revealed it could be eliminated from the internal organs within 3 days as a safe candidate vaccine. Mice groups were immunized I.V. twice with the recombinant LM△actAplcB-vp1 at an interval of 2 weeks. Antigen-specific IgG antibodies and the level of CD4+- and CD8+-specific secreted cytokines were estimated to evaluate the immunogenicity of the candidate vaccine. The rapid onset immune response was detected, strong IgG humoral immune response within 14 days post immunization and augmented again after the booster dose. Cellular immunity data after 9 days post the prime dose indicated elevation in CD4+ and CD8+ secreted cytokine level with another elevation after the booster dose. This is the first report to explain the ability of attenuated mutant LM to be a promising live vector for FMDV vaccine.

Cellular response to persistent foot-and-mouth disease virus infection is linked to specific types of alterations in the host cell transcriptome

Food-and-mouth disease virus (FMDV) is a highly contagious virus that seriously threatens the development of animal husbandry. Although persistent FMDV infection can dramatically worsen the situation, the mechanisms involved in persistent FMDV infection remain unclear. In the present study, we identified the presence of evolved cells in the persistently FMDV-infected cell line. These cells exhibited resistance to the parent FMDV and re-established persistent infection when infected with FMDV-Op (virus supernatant of persistent infection cell lines), emphasizing the decisive role of evolved host cells in the establishment of persistent FMDV infection. Using RNA-seq, we identified the gene expression profiles of these evolved host cells. In total, 4,686 genes were differentially expressed in evolved cells compared with normal cells, with these genes being involved in metabolic processes, cell cycle, and cellular protein catabolic processes. In addition, 1,229 alternative splicing events, especially skipped exon events, were induced in evolved cells. Moreover, evolved cells exhibited a stronger immune defensive response and weaker MAPK signal response than normal cells. This comprehensive transcriptome analysis of evolved host cells lays the foundation for further investigations of the molecular mechanisms of persistent FMDV infection and screening for genes resistant to FMDV infection.

Interplay of foot and mouth disease virus with cell-mediated and humoral immunity of host

Foot and mouth disease virus (FMDV) causes a communicable disease of cloven hoofed animals, resulting in major economic losses during disease outbreaks. Like other members of the Picornaviridae FMDV has a relatively short infectious cycle; initiation of infection and dissemination, with production of infectious virions occurs in less than a week. The components of innate immunity as well as cell-mediated and humoral immunity play a crucial role in control of FMDV. However, it has been shown in vitro using a mouse model that FMDV has evolved certain mechanisms to counteract host immune responses ensuring its survival and spread. The viral leader proteinase, L pro, deters interferon beta (IFN-β) mRNA synthesis, thus, inhibiting host cell translation. Another viral proteinase, 3C pro, disrupts host cell transcription by cleaving histone H3. A transient lymphopenia in swine as a consequence of FMDV infection has also been observed, but the mechanism involved and viral protein(s) associated with this process are not clearly understood. In this review, we have covered the interaction of FMDV with different immune cells including lymphocytes and antigen presenting cells and their consequences.

Combination of Adt-O1Manisa and Ad5-boIFNλ3 induces early protective immunity against foot-and-mouth disease in cattle

Foot-and-mouth-disease (FMD) remains the most infectious livestock disease worldwide. Although commercially available inactivated or adenovirus-vectored-vaccines (Ad5-FMD) are effective, they require 5-7 days to induce protection. Therefore, new control strategies that stimulate rapid immune responses are needed. Expression of bovine interferon λ3 using the Ad5-vector platform (Ad5-boIFNλ3) is able to delay disease in cattle, but clinical signs appear at 9 days after challenge. We hypothesized that combination of Ad5-boIFNλ3 and Ad5-FMD could induce immediate and lasting protection against FMD. Cattle were vaccinated with an Ad5-FMD, Ad5-boIFNλ3, or the combination of both, followed by challenge at three days post-immunization. All animals treated with Ad5-FMD combined with Ad5-boIFNλ3 were fully protected against FMD, despite the absence of systemic neutralizing antibodies or antiviral activity at the time of challenge. Induction of a strong cell-mediated immune response suggested that Ad5-boIFNλ3 is able to act as an adjuvant of Ad5-FMD vaccine in cattle.

Transduction of skin-migrating dendritic cells by human adenovirus 5 occurs via an actin-dependent phagocytic pathway

Dendritic cells (DC) are central to the initiation of immune responses, and various approaches have been used to target vaccines to DC in order to improve immunogenicity. Cannulation of lymphatic vessels allows for the collection of DC that migrate from the skin. These migrating DC are involved in antigen uptake and presentation following vaccination. Human replication-deficient adenovirus (AdV) 5 is a promising vaccine vector for delivery of recombinant antigens. Although the mechanism of AdV attachment and penetration has been extensively studied in permissive cell lines, few studies have addressed the interaction of AdV with DC. In this study, we investigated the interaction of bovine skin-migrating DC and replication-deficient AdV-based vaccine vectors. We found that, despite lack of expression of Coxsackie B–Adenovirus Receptor and other known adenovirus receptors, AdV readily enters skin-draining DC via an actin-dependent endocytosis. Virus exit from endosomes was pH independent, and neutralizing antibodies did not prevent virus entry but did prevent virus translocation to the nucleus. We also show that combining adenovirus with adjuvant increases the absolute number of intracellular virus particles per DC but not the number of DC containing intracellular virus. This results in increased trans-gene expression and antigen presentation. We propose that, in the absence of Coxsackie B–Adenovirus Receptor and other known receptors, AdV5-based vectors enter skin-migrating DC using actin-dependent endocytosis which occurs in skin-migrating DC, and its relevance to vaccination strategies and vaccine vector targeting is discussed.

Rapid identification of bovine MHCI haplotypes in genetically divergent cattle populations using next-generation sequencing

The major histocompatibility complex (MHC) region contains many genes that are key regulators of both innate and adaptive immunity including the polymorphic MHCI and MHCII genes. Consequently, the characterisation of the repertoire of MHC genes is critical to understanding the variation that determines the nature of immune responses. Our current knowledge of the bovine MHCI repertoire is limited with only the Holstein-Friesian breed having been studied in any depth. Traditional methods of MHCI genotyping are of low resolution and laborious and this has been a major impediment to a more comprehensive analysis of the MHCI repertoire of other cattle breeds. Next-generation sequencing (NGS) technologies have been used to enable high throughput and much higher resolution MHCI typing in a number of species. In this study we have developed a MiSeq platform approach and requisite bioinformatics pipeline to facilitate typing of bovine MHCI repertoires. The method was validated initially on a cohort of Holstein-Friesian animals and then demonstrated to enable characterisation of MHCI repertoires in African cattle breeds, for which there was limited or no available data. During the course of these studies we identified >140 novel classical MHCI genes and defined 62 novel MHCI haplotypes, dramatically expanding the known bovine MHCI repertoire.

Expression of bovine non-classical major histocompatibility complex class I proteins in mouse P815 and human K562 cells

Major histocompatibility complex class I (MHC-I) proteins can be expressed as cell surface or secreted proteins. To investigate whether bovine non-classical MHC-I proteins are expressed as cell surface or secreted proteins, and to assess the reactivity pattern of monoclonal antibodies with non-classical MHC-I isoforms, we expressed the MHC proteins in murine P815 and human K562 (MHC-I deficient) cells. Following antibiotic selection, stably transfected cell lines were stained with H1A or W6/32 antibodies to detect expression of the MHC-I proteins by flow cytometry. Two non-classical proteins (BoLA-NC1*00501 and BoLA-NC3*00101) were expressed on the cell surface in both cell lines. Surprisingly, the BoLA-NC4*00201 protein was expressed on the cell membrane of human K562 but not mouse P815 cells. Two non-classical proteins (BoLA-NC1*00401, which lacks a transmembrane domain, and BoLA-NC2*00102) did not exhibit cell surface expression. Nevertheless, Western blot analyses demonstrated expression of the MHC-I heavy chain in all transfected cell lines. Ammonium-sulfate precipitation of proteins from culture supernatants showed that BoLA-NC1*00401 was secreted and that all surface expressed proteins where shed from the cell membrane by the transfected cells. Interestingly, the surface expressed MHC-I proteins were present in culture supernatants at a much higher concentration than BoLA-NC1*00401. This comprehensive study shows that bovine non-classical MHC-I proteins BoLA-NC1*00501, BoLA-NC3*00101, and BoLA-NC4*00201 are expressed as surface isoforms with the latter reaching the cell membrane only in K562 cells. Furthermore, it demonstrated that BoLA-NC1*00401 is a secreted isoform and that significant quantities of membrane associated MHC-I proteins can be shed from the cell membrane.

A Recombinant Adenovirus Expressing P12A and 3C Protein of the Type O Foot-and-Mouth Disease Virus Stimulates Systemic and Mucosal Immune Responses in Mice

Foot-and-mouth disease (FMD) is a highly contagious livestock disease of cloven-hoofed animals which causes severe economic losses. The replication-deficient, human adenovirus-vectored FMD vaccine has been proven effective against FMD. However, the role of T-cell-mediated antiviral responses and the mucosae-mediated antiviral responses induced by the adenovirus-vectored FMD vaccine was rarely examined. Here, the capsid protein precursor P1-2A and viral protease 3C of the type O FMDV were expressed in replicative-deficient human adenovirus type 5 vector. BALB/c mice immunized intramuscularly and intraperitoneally with recombinant adenovirus rAdv-P12A3C elicited higher FMDV-specific IgG antibodies, IFN-γ, and IL-4 cytokines than those in mice immunized with inactivated FMDV vaccine. Moreover, BALB/c mice immunized with recombinant adenovirus rAdv-P12A3C by oral and intraocular-nasal immunization induced high FMDV-specific IgA antibodies. These results show that the recombinant adenovirus rAdv-P12A3C could resist FMDV comprehensively. This study highlights the potential of rAdv-P12A3C to serve as a type O FMDV vaccine.

A modern approach for epitope prediction: identification of foot-and-mouth disease virus peptides binding bovine leukocyte antigen (BoLA) class I molecules

Major histocompatibility complex (MHC) class Imolecules regulate adaptive immune responses through the presentation of antigenic peptides to CD8+ T cells. Polymorphisms in the peptide binding region of class I molecules determine peptide binding affinity and stability during antigen presentation, and different antigen peptide motifs are associated with specific genetic sequences of class I molecules. Understanding bovine leukocyte antigen (BoLA), peptide-MHC class I binding specificities may facilitate development of vaccines or reagents for quantifying the adaptive immune response to intracellular pathogens, such as foot-and-mouth disease virus (FMDV). Six synthetic BoLA class I (BoLA-I) molecules were produced, and the peptide binding motif was generated for five of the six molecules using a combined approach of positional scanning combinatorial peptide libraries (PSCPLs) and neural network-based predictions (NetMHCpan). The updated NetMHCpan server was used to predict BoLA-I binding peptides within the P1 structural polyprotein sequence of FMDV (strain A24 Cruzeiro) for Bo-LA-1*01901, BoLA-2*00801, BoLA-2*01201, and BoLA-4*02401. Peptide binding affinity and stability were determined for these BoLA-I molecules using the luminescent oxygen channeling immunoassay (LOCI) and scintillation proximity assay (SPA). The functional diversity of known BoLA alleles was predicted using theMHCcluster tool, and functional predictions for peptide motifs were compared to observed data from this and prior studies. The results of these analyses showed that BoLA alleles cluster into three distinct groups with the potential to define BBoLA supertypes.^ This streamlined approach identifies potential T cell epitopes from pathogens, such as FMDV, and provides insight into T cell immunity following infection or vaccination.

Effect of different culture systems on the production of foot and mouth disease trivalent vaccine

Aim:

This study aims to determine the effect of the stationary rawx, roller, and the suspension cell culture systems on the total virus yield infectivity and antigenicity.

Materials and Methods:

Three serotypes of foot and mouth disease virus (FMDV) (serotype A, O and SAT-2) were inoculated separately into baby hamster kidney-21 cell line in rawx, roller, and suspension cultivation systems using multiplicity of infection (1:100). Samples were taken from the total virus yield from each system at 15, 18, 21, and 24 h post-inoculation. Testing the total virus yield infectivity through virus titration and antigenicity through estimation of complement fixing titer and 146S content and evaluation of the potency of the vaccine prepared from the different cultivation systems were done.

Results:

The results showed that the FMDV titer of serotype A, O, and SAT-2 obtained from the roller cultivation system showed the highest level followed by suspension cultivation system then the rawx cultivation system. The FMDV titer showed its highest level at 21 h post-inoculation in all the cultivation systems and then decline at 24 h post-inoculation. The antigenicity reached its highest value content at 18 h post-inoculation either by complement fixation test or by quantifying the 146S intact virion. Montanide ISA 206 oil inactivated trivalent vaccines were prepared from the tested serotypes (A Iran O5. O Panasia and SAT-2/EGY/2012) harvested at 18 h post-inoculation from the 3 culture systems. The results of tracing the antibody response showed that the mean antibody response from the roller cultivation system start its protective antibody titer earlier at 2 weeks post-vaccination (WPV) than the vaccine prepared from the other two cultivation system and the immune protection period lasts longer for 36 WPV for the roller cultivation system vaccine than the other two cultivation systems.

Conclusion:

The best cultivation system used for the production of FMD vaccine regarding its highest infectivity and antigenicity is the roller system.

The assembly and characterisation of two structurally distinct cattle MHC class I haplotypes point to the mechanisms driving diversity

In cattle, there are six classical MHC class I genes that are variably present between different haplotypes. Almost all known haplotypes contain between one and three genes, with an allele of Gene 2 present on the vast majority. However, very little is known about the sequence and therefore structure and evolutionary history of this genomic region. To address this, we have refined the MHC class I region in the Hereford cattle genome assembly and sequenced a complete A14 haplotype from a homozygous Holstein. Comparison of the two haplotypes revealed extensive variation within the MHC class Ia region, but not within the flanking regions, with each gene contained within a conserved 63- to 68-kb sequence block. This variable region appears to have undergone block gene duplication and likely deletion at regular breakpoints, suggestive of a site-specific mechanism. Phylogenetic analysis using complete gene sequences provided evidence of allelic diversification via gene conversion, with breakpoints between each of the extracellular domains that were associated with high guanine-cytosine (GC) content. Advancing our knowledge of cattle MHC class I evolution will help inform investigations of cattle genetic diversity and disease resistance.

Foot-and-mouth disease virus infection of dendritic cells triggers phosphorylation of ERK1/2 inducing class I presentation and apoptosis

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals. This pathology is caused by foot-and-mouth disease virus (FMDV). Over time, the development of vaccines to prevent the spread of this illness became essential. Vaccines currently used contain the inactivated form of the virus. However, vaccination generates an immune response different to that induced by the infection. We investigated whether these differences are related to intracellular mechanisms on dendritic cells (DCs). As a result, we demonstrated that the internalization of infective virus triggered the phosphorylation of ERK1/2, which was involved in the activation of caspase-9, the intrinsic pathway of apoptosis and the delivery of viral peptides on MHC class I molecules. While, inactivated virus (iFMDV) did not affect this pathway or any function mediated by its activation. As described, infectious virus in DCs was also associated to autophagy LC3 protein and was associated to lysosomal protein Lamp-2; contrary to observe for the iFMDV. Strikingly, the processing of viral antigens to accommodate in class I molecules does not appear to involve the proteasome. Finally, this increased presentation promotes a specific cytotoxic response against infectious virus.

Bovine Genome-wide Association Study for Genetic Elements to Resist the Infection of Foot-and-mouth Disease in the Field

Foot-and-mouth disease (FMD) is a highly contagious disease affecting cloven-hoofed animals and causes severe economic loss and devastating effect on international trade of animal or animal products. Since FMD outbreaks have recently occurred in some Asian countries, it is important to understand the relationship between diverse immunogenomic structures of host animals and the immunity to foot-and-mouth disease virus (FMDV). We performed genome wide association study based on high-density bovine single nucleotide polymorphism (SNP) chip for identifying FMD resistant loci in Holstein cattle. Among 624532 SNP after quality control, we found that 11 SNPs on 3 chromosomes (chr17, 22, and 15) were significantly associated with the trait at the p.adjust <0.05 after PERMORY test. Most significantly associated SNPs were located on chromosome 17, around the genes Myosin XVIIIB and Seizure related 6 homolog (mouse)-like, which were associated with lung cancer. Based on the known function of the genes nearby the significant SNPs, the FMD resistant animals might have ability to improve their innate immune response to FMDV infection.

Evolutionary Analysis and Prediction of Peptide Vaccine Candidates for Foot-and-Mouth-Disease Virus Types A and O in Bangladesh

Foot-and-mouth disease (FMD), an endemic disease of cloven-hoofed animals, causes an annual economic loss of US$60–150 million in Bangladesh. There is no cross-protection among the foot-and-mouth disease virus (FMDV) serotypes and vaccination escape mutation may happen. Peptide vaccine is a safer alternative. The aim of this study is to predict and map the B and T cell epitopes of VP1 proteins of FMDV serotypes O and A that were circulating in Bangladesh from 2011 to 2013. Using evolutionary and computational approach (BCPred, BepiPred, DiscoTope, ElliPro, and ProPred-I, IEDB analysis for MHC-I prediction), a total of 11 B and T cell epitopes were predicted. Also, the three-dimensional (3D) structure of VP1 protein showed that the predicted five epitopes residing on N- and C-termini can be considered as good vaccine candidates, and epitopes on the G–H loop can serve as receptor recognition sites for vaccine design. The scores of predicted epitopes of one method were cross-checked with other one for potential epitope mining. Within the VP1 antigenic sites, significant evidence of positive selection was present indicating evolution of VP1 under high immune surveillance.

Laboratory animal models to study foot-and-mouth disease: a review with emphasis on natural and vaccine-induced immunity

Laboratory animal models have provided valuable insight into foot-and-mouth disease virus (FMDV) pathogenesis in epidemiologically important target species. While not perfect, these models have delivered an accelerated time frame to characterize the immune responses in natural hosts and a platform to evaluate therapeutics and vaccine candidates at a reduced cost. Further expansion of these models in mice has allowed access to genetic mutations not available for target species, providing a powerful and versatile experimental system to interrogate the immune response to FMDV and to target more expensive studies in natural hosts. The purpose of this review is to describe commonly used FMDV infection models in laboratory animals and to cite examples of when these models have failed or successfully provided insight relevant for target species, with an emphasis on natural and vaccine-induced immunity.

Supplementation of dietary germanium biotite enhances induction of the immune responses by foot-and-mouth disease vaccine in cattle

Background

After the recent outbreak of foot-and-mouth disease (FMD) in Korea, a vaccination policy has been applied to control the disease. In addition, several non-specific immune stimulators have been used without any scientific evidence that they would enhance the immune response after FMD vaccination and/or protect against FMD. Based on the current situation, the aim of this study was to evaluate the effect of the non-specific immune stimulator germanium biotite on FMD vaccination and immune responses in cattle. To achieve our goal, immune responses to FMD vaccination, such as levels of IgG and IgA, antibody duration, and virus-neutralizing titers were investigated after germanium biotite feeding. The PBMC typing and proliferative response after stimulation with mitogens, the cytokines expression level of PBMC, and the lysozyme activity in the serum were measured to evaluate the immune enhancing effects of germanium biotite following its administration.

Results

Following the first vaccination, high level of IgG (at 4 weeks) and IgA (at 2 and 31 weeks) titers in serum and saliva were observed in the germanium biotite-feeding group (p < 0.05). The germanium biotite group also showed high and longstanding inhibition percentage value in ELISA assay at 31 weeks (p < 0.05). Generally, higher virus-neutralizing antibody titers were observed in the feeding group at 20 and 31 weeks after vaccination. Following the feeding germanium biotite, the germanium biotite group showed increased subpopulation of CD4⁺ lymphocytes and MHC I⁺II⁺ cells in PBMCs at 23 week, responding to stimulation of ConA. The levels of IFN-γ (at 3 and 8 weeks), IL-1α (at 3, 11, and 23 weeks), IL-1β (at 3, 8, and 11 weeks), and IL-4 (at 8 and 11 weeks) gene expression were also significantly increased in the feeding group (p < 0.01 and p < 0.05). Feeding with germanium biotite increased the lymphocytes’ proliferative response to the stimulation of ConA and LPS at 23 weeks and lysozyme activity at 9 weeks after feeding.

Conclusions

These results suggest that germanium biotite feeding could increase the protection against FMD virus infection via the induction of higher humoral and cellular immune responses in cattle.

A genome-wide association study of immune response traits in Canadian Holstein cattle

Background

Breeding for enhanced immune response (IR) has been suggested as a tool to improve inherent animal health. Dairy cows with superior antibody-mediated (AMIR) and cell-mediated immune responses (CMIR) have been demonstrated to have a lower occurrence of many diseases including mastitis. Adaptive immune response traits are heritable, and it is, therefore, possible to breed for improved IR, decreasing the occurrence of disease. The objective of this study was to perform genome-wide association studies to determine differences in genetic profiles among Holstein cows classified as High or Low for AMIR and CMIR. From a total of 680 cows with immune response phenotypes, 163 cows for AMIR (81 High and 82 Low) and 140 for CMIR (75 High and 65 Low) were selectively genotyped using the Illumina Bovine SNP50 BeadChip. Results were validated using an unrelated population of 164 Holstein bulls IR phenotyped for AMIR and 146 for CMIR.

Results

A generalized quasi likelihood score method was used to determine single nucleotide polymorphisms (SNP) and chromosomal regions associated with immune response. After applying a 5% chromosomal false discovery rate, 186 SNPs were significantly associated with AMIR. The majority (93%) of significant markers were on chromosome 23, with a similar peak found in the bull population. For CMIR, 21 SNP markers remained significant. Candidate genes within 250,000 base pairs of significant SNPs were identified to determine biological pathways associated with AMIR and CMIR. Various pathways were identified, including the antigen processing and presentation pathway, important in host defense. Candidate genes included those within the bovine Major Histocompatability Complex such as BoLA-DQ, BoLA-DR and the non-classical BoLA-NC1 for AMIR and BoLA-DQ for CMIR, the complement system including C2 and C4 for AMIR and C1q for CMIR, and cytokines including IL-17A, IL17F for AMIR and IL-17RA for CMIR and tumor necrosis factor for both AMIR and CMIR. Additional genes associated with CMIR included galectins 1, 2 and 3, BCL2 and β-defensin.

Conclusions

The significant genetic variation associated with AMIR and CMIR in this study may imply feasibility to include immune response in genomic breeding indices as an approach to improve inherent animal health.

Bovine γδ T cells are a major regulatory T cell subset

In humans and mice, γδ T cells represent <5% of the total circulating lymphocytes. In contrast, the γδ T cell compartment in ruminants accounts for 15–60% of the total circulating mononuclear lymphocytes. Despite the existence of CD4⁺CD25^high Foxp3⁺ T cells in the bovine system, these are neither anergic nor suppressive. We present evidence showing that bovine γδ T cells are the major regulatory T cell subset in peripheral blood. These γδ T cells spontaneously secrete IL-10 and proliferate in response to IL-10, TGF-β, and contact with APCs. IL-10–expressing γδ T cells inhibit Ag-specific and nonspecific proliferation of CD4⁺ and CD8⁺ T cells in vitro. APC subsets expressing IL-10 and TFG-β regulate proliferation of γδ T cells producing IL-10. We propose that γδ T cells are a major regulatory T cell population in the bovine system.

Immunity to bovine herpesvirus 1: II. Adaptive immunity and vaccinology

Bovine herpesvirus 1 (BHV-1) infection is widespread and causes a variety of diseases. Although similar in many respects to the human immune response to human herpesvirus 1, the differences in the bovine virus proteins, immune system components and strategies, physiology, and lifestyle mean the bovine immune response to BHV-1 is unique. The innate immune system initially responds to infection, and primes a balanced adaptive immune response. Cell-mediated immunity, including cytotoxic T lymphocyte killing of infected cells, is critical to recovery from infection. Humoral immunity, including neutralizing antibody and antibody-dependent cell-mediated cytotoxicity, is important to prevention or control of (re-)infection. BHV-1 immune evasion strategies include suppression of major histocompatibility complex presentation of viral antigen, helper T-cell killing, and latency. Immune suppression caused by the virus potentiates secondary infections and contributes to the costly bovine respiratory disease complex. Vaccination against BHV-1 is widely practiced. The many vaccines reported include replicating and non-replicating, conventional and genetically engineered, as well as marker and non-marker preparations. Current development focuses on delivery of major BHV-1 glycoproteins to elicit a balanced, protective immune response, while excluding serologic markers and virulence or other undesirable factors. In North America, vaccines are used to prevent or reduce clinical signs, whereas in some European Union countries marker vaccines have been employed in the eradication of BHV-1 disease.

The functional significance of cattle major histocompatibility complex class I genetic diversity

Current concerns about food security highlight the importance of maintaining productive and disease-resistant livestock populations. Major histocompatibility complex (MHC) class I genes have a central role in immunity. A high level of diversity in these genes allows populations to survive despite exposure to rapidly evolving pathogens. This review aims to describe the key features of MHC class I genetic diversity in cattle and to discuss their role in disease resistance. Discussion centers on data derived from the cattle genome sequence and studies addressing MHC class I gene expression and function. The impact of intensive selection on MHC diversity is also considered. A high level of complexity in MHC class I genes and functionally related gene families is revealed. This highlights the need for increased efforts to determine key genetic components that govern cattle immune responses to disease, which is increasingly important in the face of changing human and environmental demands.

Immunogenicity of two FMDV nonameric peptides encapsulated in liposomes in mice and the protective efficacy in guinea pigs

It has been predicted that nonameric peptides I (VP1_26–34, RRQHTDVSF), II (VP1_157–165, RTLPTSFNY) and III (VP1_45–53, KEQVNVLDL) from the VP1 capsid protein of the foot-and-mouth disease virus (FMDV) are T cell epitopes. To investigate whether these peptides have immunological activity, BALB/c mice were immunized with peptide I, II or III conjugated with immunostimulating complexes (ISCOMs). A cytotoxic T lymphocyte assay was used to evaluate the cytotoxic activity induced by peptides along with by measuring peptide-specific T-cell proliferation and CD8⁺ T lymphocyte numbers in whole blood and interferon (IFN)-γ production in peripheral blood mononuclear cells induced by peptides. To further identify the protective efficacy of peptides, an FMDV challenge assay was done in guinea pigs. Peptides I and II stimulated significant increases in T-cell proliferation, CD8⁺ T lymphocytes, and IFN-γ secretion and cytotoxic activity compared to controls. The FMDV challenge assay indicated peptides I and II can protect over 60% of animals from virus attack. The results demonstrate that peptides I and II encapsulated in liposomes should be CTL epitopes of FMDV and can protect animals from virus attack to some extent.

Characterization of cytotoxic T lymphocyte function after foot-and-mouth disease virus infection and vaccination

The induction of neutralizing antibodies specific for foot-and-mouth disease virus (FMDV) has been the central goal of vaccination efforts against this economically important disease of cloven-hoofed animals. Although these efforts have yielded much success, challenges remain, including little cross-serotype protection and inadequate duration of immunity. Commonly, viral infections are characterized by induction of cytotoxic T lymphocytes (CTL), yet the function of CTL in FMDV immunity is poorly defined. We developed an assay for detection of CTL specific for FMDV and reported that a modified adenovirus-vectored FMDV vaccine could induce CTL activity. This allowed us to determine whether FMDV-specific CTL responses are induced during infection and to test further whether vaccine-induced CTL could protect against challenge with FMDV. We now show the induction of antigen-specific CTL responses after infection of swine with FMDV strain A24 Cruizero. In addition, we developed a vaccination strategy that induces FMDV-specific CTL in the absence of significant neutralizing antibody. Animals vaccinated using this protocol showed delayed clinical disease and significantly suppressed viremia compared to control animals, suggesting a role for CTLs in the control of virus shedding. These results provide new insights showing induction of CTL responses to FMDV following infection or vaccination, and create the potential for improving vaccine performance by targeting cellular immunity.

Induction of partial protection against foot and mouth disease virus in guinea pigs by neutralization with the integrin β6-1 subunit

The mechanism by which the foot-and-mouth disease virus (FMDV) initiates infection of cells is thought to involve the attachment of the viral capsid to host integrins on the surface of target cells. However, the role of integrins in FMDV infection still needs to be fully understood, although it has been demonstrated that integrin αvβ6 interferes with FMDV in vitro and results in neutralization of its infectivity. In the present study, we describe the cloning and sequencing of suckling mouse integrin β6 and the subsequent expression of two segments of integrin β6 extracellular domains: β6-1 (which contains the ligand-binding domain) and β6-2. Sequencing of the mouse integrin β6 subunit revealed close homology (~90%) with its human counterpart. When recombinant integrin extracellular domains β6-1 and β6-2 formulated with adjuvant were inoculated into guinea pigs, anti-integrin antibody expression was high before FMDV challenge. Interestingly, guinea pigs (50%) inoculated with integrin β6-1 were protected from FMDV infection; in contrast, none of the animals inoculated with integrin β6-2 were protected. This result indicates that an integrin blockade may be able to interfere with FMDV infection in vivo, which raises the possibility that targeting integrin in vivo may be the basis for a new strategy to control FMDV infection.

An adenovirus vectored mucosal adjuvant augments protection of mice immunized intranasally with an adenovirus-vectored foot-and-mouth disease virus subunit vaccine

Foot-and-mouth disease virus (FMDV) is a highly contagious pathogen that causes severe morbidity and economic losses to the livestock industry in many countries. The oral and respiratory mucosae are the main ports of entry of FMDV, so the stimulation of local immunity in these tissues may help prevent initial infection and viral spread. E. coli heat-labile enterotoxin (LT) has been described as one of the few molecules that have adjuvant activity at mucosal surfaces. The objective of this study was to evaluate the efficacy of replication-defective adenovirus 5 (Ad5) vectors encoding either of two LT-based mucosal adjuvants, LTB or LTR72. These vectored adjuvants were delivered intranasally to mice concurrent with an Ad5-FMDV vaccine (Ad5-A24) to assess their ability to augment mucosal and systemic humoral immune responses to Ad5-A24 and protection against FMDV. Mice receiving Ad5-A24 plus Ad5-LTR72 had higher levels of mucosal and systemic neutralizing antibodies than those receiving Ad5-A24 alone or Ad5-A24 plus Ad5-LTB. The vaccine plus Ad5-LTR72 group also demonstrated 100% survival after intradermal challenge with a lethal dose of homologous FMDV serotype A24. These results suggest that Ad5-LTR72 could be used as an important tool to enhance mucosal and systemic immunity against FMDV and potentially other pathogens with a common route of entry.

CD4+ T-cell responses to foot-and-mouth disease virus in vaccinated cattle

We have performed a series of studies to investigate the role of CD4⁺ T-cells in the immune response to foot-and-mouth disease virus (FMDV) post-vaccination. Virus neutralizing antibody titres (VNT) in cattle vaccinated with killed FMD commercial vaccine were significantly reduced and class switching delayed as a consequence of rigorous in vivo CD4⁺ T-cell depletion. Further studies were performed to examine whether the magnitude of T-cell proliferative responses correlated with the antibody responses. FMD vaccination was found to induce T-cell proliferative responses, with CD4⁺ T-cells responding specifically to the FMDV antigen. In addition, gamma interferon (IFN-γ) was detected in the supernatant of FMDV antigen-stimulated PBMC and purified CD4⁺ T-cells from vaccinated cattle. Similarly, intracellular IFN-γ could be detected specifically in purified CD4⁺ T-cells after restimulation. It was not possible to correlate in vitro proliferative responses or IFN-γ production of PBMC with VNT, probably as a consequence of the induction of T-independent and T-dependent antibody responses and antigen non-specific T-cell responses. However, our studies demonstrate the importance of stimulating CD4⁺ T-cell responses for the induction of optimum antibody responses to FMD-killed vaccines.

Interferon-γ induced by in vitro re-stimulation of CD4+ T-cells correlates with in vivo FMD vaccine induced protection of cattle against disease and persistent infection

The immune defense against FMDV has been correlated to the antibody mediated component. However, there are occasions when some animals with high virus neutralising (VN) antibody are not protected following challenge and some with low neutralising antibody which do not succumb to disease. The importance of cell mediated immunity in clinical protection is less clear and so we investigated the source and production of interferon-gamma (IFN-γ) in re-stimulated whole blood of FMDV immunized cattle and its correlation to vaccine induced protection and FMDV persistence. We were able to show a positive correlation between IFN-γ response and vaccine induced protection as well as reduction of long term persistence of FMD virus. When combining this IFN-γ response in re-stimulated blood with virus neutralizing antibody titer in serum on the day of challenge, a better correlation of vaccine-induced protection with IFN-γ and VN antibody was predicted. Our investigations also showed that CD4+ T-cells are the major proliferating phenotype and IFN-γ producing cells.

Use of replication-defective adenoviruses to develop vaccines and biotherapeutics against foot-and-mouth disease

We have developed a replication-defective human adenovirus (Ad5) vectored foot-and-mouth disease (FMD) vaccine platform that protects both swine and cattle from subsequent challenge with homologous virus after a single immunization. This Ad5-FMD vaccine has undergone testing following the requirements of the Center for Veterinary Biologics of the Animal Plant and Health Inspection Service, US Department of Agriculture, and has recently been granted a conditional license for inclusion of the vaccine in the US National Veterinary Vaccine Stockpile. In this review, we will describe the approaches we have taken to improve the potency and efficacy of this vaccine platform. Furthermore, we will discuss the development of Ad5 vector-based biotherapeutics to generate rapid protection against FMD virus prior to vaccine-induced adaptive immunity and describe the use of a combination of these approaches to stimulate both fast and long-lasting immunity.

Immune markers and correlates of protection for vaccine induced immune responses

Vaccines have been a major innovation in the history of mankind and still have the potential to address the challenges posed by chronic intracellular infections including tuberculosis, HIV and malaria which are leading causes of high morbidity and mortality across the world. Markers of an appropriate humoral response currently remain the best validated correlates of protective immunity after vaccination. Despite advancements in the field of immunology over the past few decades currently there are, however, no sufficiently validated immune correlates of vaccine induced protection against chronic infections in neither human nor veterinary medicine. Technological and conceptual advancements within cell-mediated immunology have led to a number of new immunological read-outs with the potential to emerge as correlates of vaccine induced protection. For T(H)1 type responses, antigen-specific production of interferon-gamma (IFN-γ) has been promoted as a quantitative marker of protective cell-mediated immune responses over the past couple of decades. More recently, however, evidence from several infections has pointed towards the quality of the immune response, measured through increased levels of antigen-specific polyfunctional T cells capable of producing a triad of relevant cytokines, as a better correlate of sustained protective immunity against this type of infections. Also the possibilities to measure antigen-specific cytotoxic T cells (CTL) during infection or in response to vaccination, through recombinant major histocompatibility complex (MHC) class I tetramers loaded with relevant peptides, has opened a new vista to include CTL responses in the evaluation of protective immune responses. Here, we review different immune markers and new candidates for correlates of a protective vaccine induced immune response against chronic infections and how successful they have been in defining the protective immunity in human and veterinary medicine.

Cattle MHC nomenclature: is it possible to assign sequences to discrete class I genes?

The cattle major histocompatibility complex (MHC) region contains a variable number of classical class I genes encoding polymorphic molecules involved in antigen presentation. Six classical class I genes have been described, but assigning sequences to these genes has proved problematic. We propose a refinement of the existing nomenclature, which currently names the 97 known classical class I sequences in a single series. Phylogenetic analysis of the 3' portion of the coding region allows segregation of these into six groups; thus, we have prefixed existing names with the appropriate number. Although it is clear that some of these groups correspond to discrete genes, it is currently not possible to state definitively that all do. However, the main groupings are consistent, and in conjunction with other evidence, we feel it is now appropriate to rename the sequences accordingly. Segregation of sequences into groups in this way will facilitate ongoing research and future use of the cattle MHC section of the Immuno Polymorphism Database.

Theileria annulata-transformed cell lines are efficient antigen-presenting cells for in vitro analysis of CD8 T cell responses to bovine herpesvirus-1

Continuously growing cell lines infected with the protozoan parasite Theileria annulata can readily be established by in vitro infection of leukocytes with the sporozoite stage of the parasite. The aim of the current study was to determine whether such transformed cell lines could be used as antigen presenting cells to analyse the antigenic specificity of bovine CD8 T cell responses to viral infections. Bovine herpes virus 1 (BHV-1), which is known to induce CD8 T cell responses, was used as a model. T. annulata- transformed cells were shown to express high levels of CD40 and CD80 and were susceptible to infection with BHV-1, vaccinia and canarypox viruses. The capacity of the cells to generate antigen-specific CD8 T cell lines was initially validated using a recombinant canarypox virus expressing a defined immunodominant T. parva antigen (Tp1). Autologous T. annulata-transformed cells infected with BHV-1 were then used successfully to generate specific CD8 T cell lines and clones from memory T cell populations of BHV-1-immune animals. These lines were BHV-1-specific and class I MHC-restricted. In contrast to previous studies, which reported recognition of the glycoproteins gB and gD, the CD8 T cell lines generated in this study did not recognise these glycoproteins. Given the ease with which T. annulata-transformed cell lines can be established and maintained in vitro and their susceptibility to infection with poxvirus vectors, these cell lines offer a convenient and efficient in vitro system to analyse the fine specificity of virus-specific CD8 T cell responses in cattle.

Inoculation of swine with foot-and-mouth disease SAP-mutant virus induces early protection against disease

Foot-and-mouth disease virus (FMDV) leader proteinase (L(pro)) cleaves itself from the viral polyprotein and cleaves the translation initiation factor eIF4G. As a result, host cell translation is inhibited, affecting the host innate immune response. We have demonstrated that L(pro) is also associated with degradation of nuclear factor κB (NF-κB), a process that requires L(pro) nuclear localization. Additionally, we reported that disruption of a conserved protein domain within the L(pro) coding sequence, SAP mutation, prevented L(pro) nuclear retention and degradation of NF-κB, resulting in in vitro attenuation. Here we report that inoculation of swine with this SAP-mutant virus does not cause clinical signs of disease, viremia, or virus shedding even when inoculated at doses 100-fold higher than those required to cause disease with wild-type (WT) virus. Remarkably, SAP-mutant virus-inoculated animals developed a strong neutralizing antibody response and were completely protected against challenge with WT FMDV as early as 2 days postinoculation and for at least 21 days postinoculation. Early protection correlated with a distinct pattern in the serum levels of proinflammatory cytokines in comparison to the levels detected in animals inoculated with WT FMDV that developed disease. In addition, animals inoculated with the FMDV SAP mutant displayed a memory T cell response that resembled infection with WT virus. Our results suggest that L(pro) plays a pivotal role in modulating several pathways of the immune response. Furthermore, manipulation of the L(pro) coding region may serve as a viable strategy to derive live attenuated strains with potential for development as effective vaccines against foot-and-mouth disease.