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Rapid protection of cattle from direct challenge with foot-and-mouth disease virus (FMDV) by a single inoculation with an adenovirus-vectored FMDV subunit vaccine.

We have previously demonstrated that swine vaccinated with one dose of a replication-defective human adenovirus type 5 (Ad5) vector containing the capsid and 3C proteinase coding regions of foot-and-mouth disease virus (FMDV) were protected when challenged 7 days later with homologous virus. In the current study, we have extended this approach to cattle, the most economically important animals susceptible to FMD. Five cattle were vaccinated with the Ad5-FMDV subunit vaccine and these animals and 2 co-housed control animals were challenged intradermolingually 7 days later. Both control animals developed typical signs of FMD including fever and vesicular lesions on all 4 feet. All 5 vaccinated animals were protected against disseminated disease.

Adenoviridae↗

Molecular epidemiology of foot-and-mouth disease virus type O.

A phylogenetic tree based on the VPI sequences of type O foot-and-mouth disease virus (FMDV) has been derived. Direct sequencing of PCR products has been used to obtain the VP1 gene sequences of new isolates. The tree exhibits four main lineages that largely correlate with the geographical origin of isolates. The analysis supports a close relationship between European O1 field isolates and vaccine strains, with the exception of O Thalheim Aus/81 and O Wuppertal Ger/82 which were probably of non-European origin. Analysis of nucleotide substitutions indicates that synonymous mutations play a major role in FMDV evolution.

Amino Acid Sequence↗

Detection of foot-and-mouth disease virus from culture and clinical samples by reverse transcription-PCR coupled to restriction enzyme and sequence analysis.

A reverse transcription-PCR (RT-PCR) method is presented for the highly sensitive and specific detection of foot-and-mouth disease virus (FMDV). A primer pair flanking a region of the viral polymerase gene (3D) corresponding to the C-terminus of the protein was designed and a single step RT-PCR reaction was developed. The assay allowed the detection of viral RNA from a variety of animal samples and from a wide range of FMDV isolates of different origins and serotypes. The presence of an Ahd I restriction site within the amplicon in 96% of the isolates analyzed allowed an additional confirmation step of the positive reactions by a simple digestion yielding characteristic fragment sizes. The set of primers described here was suitable for direct sequencing of the PCR product (290 bp), and the nucleotide sequences corresponding to the SAT 1 and SAT 3 strains were determined. The segment amplified, when used in phylogenetic studies, allowed the clustering of SAT isolates and the rest of FMDV strains as two separate lineages.

Animals↗

RNA interference targeting VP1 inhibits foot-and-mouth disease virus replication in BHK-21 cells and suckling mice.

RNA interference (RNAi) is a powerful tool to silence gene expression posttranscriptionally. In this study, we evaluated the antiviral potential of small interfering RNA (siRNA) targeting VP1 of foot-and-mouth disease virus (FMDV), which is essential during the life cycle of the virus and plays a key role in virus attachment to susceptible cells. We investigated in vivo the inhibitory effect of VP1-specific siRNAs on FMDV replication in BHK-21 cells and suckling mice, a commonly used small animal model. The results showed that transfection of siRNA-expressing plasmids gave an 80 to 90% reduction in the expression of FMDV VP1 in BHK-21 cells. Moreover, BHK-21 cells transiently transfected with siRNA-expressing plasmids were specifically resistant to FMDV infection when exposed to 100 50% tissue culture infective doses of virus, and the antiviral effects extended to almost 48 h postinfection. Furthermore, subcutaneous injection of siRNA-expressing plasmids in the neck made suckling mice significantly less susceptible to FMDV. In conclusion, our data suggests that RNAi may provide a viable therapeutic approach to treat FMDV infection.

Animals↗

Recombinant adenovirus co-expressing capsid proteins of two serotypes of foot-and-mouth disease virus (FMDV): in vitro characterization and induction of neutralizing antibodies against FMDV in swine.

Human adenovirus type 5 (Ad5) has been evaluated as a novel gene delivery vector for the development of live-viral vaccines for foot-and-mouth disease (FMD). In this study, we constructed an Ad5 vector co-expressing the capsid precursor proteins, P1, of FMD virus (FMDV) field strains A24 Cruzeiro and O1 Campos and examined the neutralizing antibody responses in swine after inoculation with the vector. To construct the Ad5 vector, a bicistronic expression cassette containing a cytomegalovirus promoter, the P1 coding sequence of FMDV A24, the internal ribosomal entry site (IRES) of FMDV A12, the P1 coding sequence of FMDV O1 Campos and the coding region of A12 3C protease was inserted into the E1 region of an E1/E3-deleted Ad5. The recombinant adenovirus, Ad5A24+O1, was generated by transfection of 293 cells with full-length pAd5A24+O1 recombinant plasmid DNA. The recombinant Ad5 co-expressed P1 of both A24 and O1 in infected 293 cells and P1 of both serotypes was processed to produce VP0, VP3, and VP1. We further demonstrated the formation of capsid protein complexes by co-precipitation of VP0, VP3, and VP1 with monoclonal antibodies against viral capsid proteins. Swine inoculated with Ad5A24+O1 generated neutralizing antibodies against both A24 and O1. However, the overall neutralizing antibody response was considerably lower than that induced by a commercial FMD vaccine or a monovalent Ad5-A24 vaccine.

Adenoviruses, Human↗

Antigenic variants in a plaque-isolate of foot-and-mouth disease virus: implications for vaccine production.

The occurrence of many subtypes within a serotype of foot-and-mouth disease virus (FMDV) makes it difficult to control the disease by vaccination. Although inactivated vaccines are used successfully in many countries, the appearance in the field of antigenic variants against which the vaccines do not confer protection is a constant problem in vaccine manufacture. We had found previously a mixture of antigenic variants in a field isolate of serotype A12. In this report we demonstrate the presence of two variants in a plaque-isolate from this mixture. The second variant was detected only when the growth conditions were altered. Our observation points to the problems which may be encountered in the large scale growth of a virus for vaccine production.

Amino Acid Sequence↗

Detection of all seven serotypes of foot-and-mouth disease virus by real-time, fluorogenic reverse transcription polymerase chain reaction assay.

A fluorogenic RT-PCR (5'-nuclease probe-based) assay using a primer/probe set designed from the internal ribosomal entry site region of the virus genome was developed for the specific detection of all seven serotypes of foot-and-mouth disease (FMD) virus in epithelial suspensions and cell culture virus preparations. The reverse transcription polymerase chain reaction (RT-PCR) specifically detected FMD virus in sample submissions from the UK 2001 FMD outbreak with greater sensitivity than our conventional RT-PCR procedure and our routine diagnostic procedures of ELISA and virus isolation in cell culture. The fluorogenic RT-PCR provides relatively fast results, enables a quantitative assessment to be made of virus amounts and can handle more samples and/or replicates of samples in a single assay than the conventional RT-PCR procedure. Therefore it is seen as a valuable tool to complement the routine diagnostic procedures for FMD virus diagnosis.

Animals↗

The impact of live animal importation on the epizootiology of foot-and-mouth disease in Saudi Arabia.

Saudi Arabia imports annually more than 6 millions live ruminants for slaughter. The majority of these animals are imported from countries where foot-and-mouth disease (FMD) is enzootic. Serotypes of FMD virus not incorporated in the vaccine currently used in Saudi Arabia (e.g. SAT1 and SAT2) are prevalent in some of these exporting countries, and in others, the prevalent serotypes of FMD virus are not routinely typed. The previous exposure of imported animals to field FMD virus in the countries of origin has been confirmed by the detection of precipitating antibodies against virus infection associated (VIA) antigen and neutralizing antibodies against serotypes O, A, C and/or Asia1 of FMD virus in the sera of some imported animals. However, no isolation of FMD carrier virus could be made from 209 proband samples collected from sheep and goats imported from countries where FMD is enzootic. The significance of the obtained results is discussed. Particular emphasis has been placed on the possibility of importing either carrier animals which might act as potential source of infection or subclinically infected animals which might actively excrete FMD virus. In addition recommendations are made to reduce the risks of introducing exotic FMD virus strains to the Kingdom through live animal importation.

Animals↗

Low linkage disequilibrium indicative of recombination in foot-and-mouth disease virus gene sequence alignments.

We have applied tests for detecting recombination to genes of foot-and-mouth disease virus (FMDV). Our approach estimated summary statistics of linkage disequilibrium (LD), which are sensitive to recombination. Using the genealogical relationships, rate heterogeneity and mutation parameters estimated from individual sets of aligned gene sequences, we simulated matching RNA sequence datasets without recombination. These simulated datasets allowed for recurrent mutations at any site to mimic homoplasy in virus sequence data and allow construction of null distributions for LD parameters expected in the absence of recombination. We tested for recombination in two ways: by comparing LD in observed data with corresponding null distributions obtained from simulated data; and by testing for a negative relationship between observed LD between pairs of polymorphic nucleotide sites and inter-site distance. We applied these tests to six FMDV datasets from four serotypes and found some evidence for recombination in all of them.

Capsid Proteins↗

Foot and mouth disease in livestock and reduced cryptosporidiosis in humans, England and Wales.

During the 2001 epidemic of foot and mouth disease (FMD) in livestock in England and Wales, we discovered a corresponding decrease in laboratory reports of cryptosporidiosis in humans. Using a regression model of laboratory reports of cryptosporidiosis, we found an estimated 35% (95% confidence interval [CI] 20% to 47%) reduction in reports during the weeks spanning the period from the first and last cases of FMD. The largest reduction occurred in northwest England, where the estimated decrease was 63% (95% CI 31% to 80%). Genotyping a subgroup of human isolates suggested that the proportion of Cryptosporidium genotype 2 strain (animal and human) was lower during the weeks of the FMD epidemic in 2001 compared with the same weeks in 2000. Our observations are consistent with livestock making a substantial contribution to Cryptosporidium infection in humans in England and Wales; our findings have implications for agriculture, visitors to rural areas, water companies, and regulators.

Animals↗

Direct detection of enterovirus 71 (EV71) in clinical specimens from a hand, foot, and mouth disease outbreak in Singapore by reverse transcription-PCR with universal enterovirus and EV71-specific primers.

A recent outbreak of hand, foot, and mouth disease in Singapore in 2000 affected several thousand children and resulted in four deaths. The aim of this study was to determine the applicability of reverse transcription-PCR (RT-PCR) with universal pan-enterovirus primers and enterovirus 71 (EV71) type-specific primers for the direct detection of enteroviruses in clinical specimens derived from this outbreak. With the universal primers, EV71 RNA sequences were successfully detected by RT-PCR and direct sequencing in 71% of positive specimens. Three pairs of EV71 type-specific primers were evaluated for rapid detection of EV71 directly from clinical specimens and cell culture isolates. By using a seminested RT-PCR strategy, specific identification of EV71 sequences directly in clinical specimens was achieved, with a detection rate of 53%. In contrast, cell culture could isolate EV71 in only 20% of positive specimens. EV71 was detected directly from brain, heart, and lung specimens of two deceased siblings. Although more than one type of enterovirus was identified in clinical specimens from this outbreak, 90% of the enteroviruses were confirmed as EV71. The data demonstrate the clinical applicability of pan-enterovirus and seminested RT-PCR for the detection of EV71 RNA directly from clinical specimens in an outbreak situation.

Child↗

A qualitative assessment of the risk of introducing foot and mouth disease into Russia and Europe from Georgia, Armenia and Azerbaijan.

A qualitative risk assessment was performed to evaluate the risk of introducing foot and mouth disease (FMD) virus into Russia and the rest of Europe from the countries of Transcaucasia (Armenia, Azerbaijan and Georgia). The assessment was based on data collected during a three-week mission to these countries by the Food and Agriculture Organization, the European Union and the Office International des Epizooties in March 1999. Due to the strong involvement of the local veterinary services, much information was obtained. Although the data were not sufficient to allow a quantitative risk assessment to be performed, the investigation served as a useful initial approach, prior to undertaking a quantitative risk assessment. The risk of FMD virus infection is a function of two elements, namely: the probability of the hazard (virus infection) occurring, and the magnitude of the consequences. The probability of the hazard occurring is the product of the probability of entry of the virus and the probability of exposure to the virus. These elements were assessed using the following parameters: prevalence of infection; volume of trade; capacity of the virus to survive; and potential for infection. The magnitude of the consequences is derived from the probability of transmission and spread. Combining these parameters, the probability of occurrence of the hazard was rated as 'moderate'. Economic consequences of potential transmission and spread of FMD, in the local context, were rated as 'negligible'. As a result, the overall risk of introducing FMD virus into Russia and the rest of Europe from Trancaucasia was rated as 'low' at the time of evaluation. The method and results are presented to serve as a basis for further discussion.

Animals↗

Importation of beef from countries infected with foot and mouth disease: a review of risk mitigation measures.

Risk mitigation measures to reduce the risks associated with importing beef from countries affected by foot and mouth disease (FMD) consist of controls at the farm of origin, inspection of slaughterhouses and maturation and deboning of carcasses. This assessment evaluates the effect of these measures on the mitigation of the risks presented by meat from cattle with FMD, for each of the different stages of the disease. The four disease stages considered are the incubation period, the period of clinical signs, convalescence and the carrier stage. Efficient animal health systems, disease surveillance, and ante-mortem and post-mortem inspection of all cattle effectively reduce the risk of FMD transmission from cattle slaughtered during the period of clinical signs or convalescence. These measures fail if the cattle are slaughtered during the incubation period, because of the absence of clinical signs. Cattle in this stage of the infection are likely to be viraemic, with FMD virus present in the skeletal muscles. Maturation of the carcasses of viraemic cattle reduces the risk of virus presence in the beef. In addition, deboning and removal of the principal lymph nodes and large blood vessels eliminate a source of FMD contamination of the beef. However, the slaughter of viraemic cattle creates an additional hazard of gross environmental viral contamination of the slaughterhouse facilities. Therefore, the maturation process may create a false sense of security, and the emphasis should instead be placed on disease surveillance within the infected zone and on the farms of origin, to prevent the slaughter of herds that are incubating FMD. Cattle slaughtered during the carrier stage do not pose a risk for the international beef trade.

Animals↗

Phylogenetic analysis of foot-and-mouth disease viruses isolated in Argentina.

We have analysed complete or partial VPI sequences of 31 foot-and-mouth disease (FMD) viruses belonging to serotypes A, O and C to determine the genetic relatedness of field strains of FMD virus (FMDV) that have circulated in Argentina between 1961 and 1994. Phylogenetic analysis, which also included 15 previously published Argentinean sequences and six reference strains, revealed that (i) FMD type A strains showed the highest genetic heterogeneity and could be divided into five lineages with a sequence divergence of 0.9-18.5% between strains (ii) most of the FMD type O viruses grouped in two clusters (within cluster sequence divergence ranging from 0.2% to 6.0%) circulating in Argentina since the early 1960s, and (iii) FMD type C viruses were grouped in two clusters with a 13.4% nucleotide sequence divergence between each cluster. The availability of sequence data for many more field isolates from the region will enable us to understand the genetic relationships between FMDV strains and to rapidly trace the source of an FMD outbreak for epidemiological surveillance.

Argentina↗

Comparison between in vitro neutralization titres and in vivo protection against homologous and heterologous challenge induced by vaccines prepared from two serologically distinct variants of foot-and-mouth disease virus, serotype A22.

Guinea-pigs were challenged with homologous or heterologous strains of foot-and-mouth disease virus (FMDV) following vaccination with baby hamster kidney (BHK) monolayer cell-adapted or BHK suspension cell-adapted strains of FMDV serotype A22 Iraq 24/64. The protection afforded by these vaccines was analysed as a function of antigen dose and the in vitro serum virus neutralization titres achieved. The results show that the level of neutralizing antibody induced that afforded 50% protection was similar for both vaccines in homologous or heterologous challenge situations. However, although the dose of antigen required to achieve this titre against homologous virus was similar for the two vaccines, approximately 20-fold more of the suspension cell-adapted virus was required to elicit a protective titre against heterologous challenge compared to the dose of monolayer cell-adapted virus required. A synthetic peptide representing the amino acid sequence 135 to 167 of VP1, which is identical in the A22 Iraq 24/64 variant viruses, was shown to induce protection against both homologous and heterologous virus challenge.

Animals↗

RT-PCR in foot-and-mouth disease diagnosis.

A RT-PCR assay for the specific detection of RNA sequences from foot-and-mouth disease virus (FMDV) has been developed. The procedure permits also the detection of sequences that correlate with established FMDV serotypes. A computer program that allows selection of genotype-specific primers for RT-PCR amplification was used for the identification of FMDV specific sequences for PCR amplification on RNA replicase (3D) gene regions. Specific, rapid and highly sensitive detection was achieved for a wide collection of RNA samples from FMDV types C, A and O, either purified from tissue culture or extracted from lesions of infected animals. Similarly, serotype-specific primers were designed to amplify the carboxy-terminal end of the VP1 gene of FMDV types either C, A or O. The results of PCR amplification of different FMDV RNAs using type-specific primers are in agreement with the serological typing of the corresponding viruses. A combination of this approach with a simplified sample processing, carried out following direct adsorption of viral suspensions to microtiter plates, provides a rapid, reliable method of viral diagnosis.

Animals↗

Risks of introducing foot and mouth disease through the importation of beef from South America.

The safety of beef with respect to foot and mouth disease (FMD) is determined by the level of risk which the exporting region poses through disease prevalence, the reliability of the surveillance system of the region, the efficacy of the prevention and control measures, the efficiency of the Veterinary Services and the support of the private sector. The South American continent has been regionalised in accordance with these criteria. Today there are approximately 90 million cattle in a territory of over 5 million km2 comprising regions classified as having a very low to low level risk for FMD with regard to the export of animals and animal products. Another 50 million cattle live in regions classified as posing a moderate risk. These risk categories reflect varying levels of risk. The harvest of beef in the meat-exporting regions of South America includes a series of risk mitigation measures, from the origin of the source herd to the final packing of the beef. These measures reduce the unrestricted risk estimate by almost six orders of magnitude. Therefore, the final risk of FMD for the global trade of beef originating from the low risk regions in South America is extremely small.

Animals↗

Extract from Agaricus blazei Murill can enhance immune responses elicited by DNA vaccine against foot-and-mouth disease.

The fungus Agaricus blazei Murill (ABM) is particularly rich in polysaccharides, which have shown particularly strong results in treating and preventing cancers. The goal of this study was to investigate whether co-administration of the ABM extract with foot-and-mouth disease virus (FMDV) DNA vaccine could increase the immune responses. Compared with the control mice, which received FMDV DNA vaccine alone, significant increase in not only the FMDV-specific antibody response but also T cell proliferation was observed in mice which received FMDV DNA vaccine plus the ABM extract. Taken together, these results demonstrated that application of the ABM extract might provide a strategy to improve the efficacy of DNA vaccines.

Adjuvants, Immunologic↗