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Development and comparison of genome detection assays for the diagnosis of foot-and-mouth disease suspected clinical samples.

Detection of foot-and-mouth disease virus (FMDV) from clinical specimens by conventional sandwich enzyme-linked immunosorbent assay (ELISA) and virus isolation in cell culture is often compromised owing to limited sensitivity and inactivation during transit, respectively. A RT-PCR (oligoprobing) ELISA in both solid and aqueous phase hybridization formats targeting an across serotype conserved site at 3C-3D region was developed and its effectiveness was compared with that of the known targets at the IRES region. A non-isotopic RNA dot hybridization assay with colorimetric detection targeting both the IRES and the 3D region were also validated, which is capable of handling high throughput samples with ease. RT-PCR (oligoprobing) ELISA and dot hybridization assay showed 1000- and 10-fold greater sensitivity than the sandwich ELISA, respectively. Robustness of these diagnostic methods was explored by examining on sandwich ELISA-negative clinical samples. Both the assays developed in the present study were able to detect viral genomes in samples undetectable by conventional ELISA, thereby demonstrating 'proof of sensitivity'. Although the potential of these assays for providing definitive diagnosis in carrier hosts and in species where clinical disease is inapparent remains to be examined, nevertheless these assays can be adapted for comprehensive surveillance of foot-and-mouth disease in India.

3C Viral Proteases↗

Inhibition of foot-and-mouth disease virus replication by small interfering RNA.

Foot-and-mouth disease, caused by foot-and-mouth disease virus (FMDV), is one of the most dangerous diseases of cloven-hoofed animals and is a constant threat to the dairy and beef industries in the Middle East and other regions of the world, despite intensive vaccination programmes. In this work, the ability of specific small interfering (si)RNAs to inhibit virus replication in BHK-21 cells was examined. By using bioinformatic computer programs, all FMDV sequences in public-domain databases were analysed. The analysis revealed three regions of at least 22 bp with 100 % identity in all FMDV entries. From these sequences, three specific siRNA molecules were prepared and used to test the ability of siRNAs to inhibit virus replication. By using real-time quantitative PCR to measure the amount of viral RNA in infected cells, it was shown that virus replication was inhibited in cells that were transfected with siRNAs. When viral titres were examined, 100 % inhibition of growth could be demonstrated in cells transfected with a mixture of all three anti-FMDV siRNAs, compared with control cells transfected with anti-LacZ siRNA.

Animals↗

Hand-foot-and-mouth disease in Calicut.

OBJECTIVE: Hand-Foot-and-Mouth Disease (HFMD) is a mild exanthematous illness seen worldwide, affecting mainly children under ten years of age. The causative agents were initially Coxsackie virus type A 16 and related serotypes. The situation changed drastically about thirty years ago with the advent of a new aetiological agent, Enterovirus type 71 (EV 71), which has caused very large outbreaks with severe complications and many deaths. METHODS: The authors report an outbreak of papulovesicular lesions on the skin and oral mucosa compatible with the diagnosis of HFMD in children in and around Calicut in October 2003. Clinical and laboratory study in collaboration with the National Institute of Communicable Diseases, Delhi. Eighty one children with the syndrome were examined and followed up from October 2003 to February 2004, when the outbreak subsided. RESULT: The outbreak was mild and all children recovered within 1 to 2 weeks. CONCLUSION: Acute and convalescent paired serum samples collected from 19 patients were examined at the NICD for IgM antibody against EV 71 by microneutralisation test in cell culture. All the paired samples tested showed significant rise in titre of antibodies, confirming the diagnosis of EV 71 infection in each of them.

Child↗

Foot-and-mouth disease in camelids: a review.

Foot-and-mouth disease (FMD) in South American camelids, in dromedaries and Bactrians is reviewed. Recent well-executed experimental studies in New World camels indicate that, although the llama and alpaca can be infected with FMD virus (FMDV) by direct contact, they are not very susceptible and do not pose a risk in transmitting FMD to susceptible animal species. They do not become FMDV carriers. Reports on FMD in dromedaries are, however, conflicting. Serological investigations in Africa and the United Arab Emirates (UAE) on thousands of camel sera were negative and experimental infections have been conducted on only a few dromedaries with one serotype and in one country. The design and execution of most of these experiments were poor and therefore the conclusions are questionable. From these investigations, it seems that dromedaries can contract the disease after experimental infection and through close contact with FMD diseased livestock, but do not present a risk in transmitting FMD to susceptible animals. They do not become FMDV carriers. Recent reports from Mongolia describe similar FMD lesions in Bactrian camels. However, so far no samples have tested positive for FMD. To clarify the situation in Bactrians, samples from suspected clinical cases should be tested because other viral vesicular diseases cannot be distinguished from FMD. Thus, further research on the epidemiology of FMD in camelids is necessary. This would include large-scale serological investigations and experimental infections with different FMD serotypes in connection with susceptible contact animals. The Office International des Epizooties (OIE) Code chapter on FMD includes camelids as being susceptible species to FMD, giving the impression that they are similar to cattle, sheep, goats and pigs in their potential involvement in the epidemiology of FMD. This is clearly not the case, and this issue should be re-addressed by the relevant authorities.

Animals↗

The Northumberland epidemic of foot-and-mouth disease, 1966.

The spread of foot-and-mouth disease during an epidemic in Northumberland in July, August and September 1966 was analysed. Although strong emitters, for example pigs, were not involved, in 18 of the 32 outbreaks spread could be attributed to the airborne route and in another 4, spread by this route was the most likely. Airborne spread was in general between 1 and 8 km but on two occasions as much as 20 km. Other means of spread included movement by animals, people and vehicles and carriage of virus between animals in neighbouring fields. No spread by milk or milk lorries took place. Sheep were involved in 9 farms; on each, lesions older than 48 h were found and it is likely that the sheep were the source of virus for other animals, especially cattle, on the farm and on neighbouring farms. The analysis suggests that control measures such as slaughtering direct contacts, as used in this epidemic, or ring vaccination as well as movement control would be effective in limiting spread.

Animals↗

The impact of local heterogeneity on alternative control strategies for foot-and-mouth disease.

The 2001 epidemic of foot-and-mouth disease (FMD) in the UK resulted in the death of nearly 10 million livestock at a cost that was estimated to be up to 8 billion pounds. Owing to the controversy surrounding the epidemic, the question of whether or not alternative policies would have resulted in significantly better control of the epidemic remains of great interest. A hexagonal lattice simulation of FMD in Cumbria is used to address the central question of whether or not better use could have been made of expert knowledge of FMD transmission to target pre-emptive culling, by assuming that the premises at greatest risk of becoming infected can be targeted for culling. The 2000 UK census and the epidemiological database collected during the epidemic are used to describe key characteristics of disease transmission, and the model is fit to the epidemic time-series. Under the assumptions of the model, the parameters that best fit the epidemic in Cumbria indicate that a policy based on expert knowledge would have exacerbated the epidemic compared with the policy as implemented. However, targeting more distant, high-risk farms could be more valuable under different epidemic conditions, notably, if risk factors of sufficient magnitude could be identified to aid in prioritizing vaccination or culling of farms at high risk of becoming infected.

Animals↗

Hand, foot and mouth disease--1973.

Nine cases of hand, foot and mouth disease were found in a small area within a month. The condition is benign, commonest in small children, and the infectivity is low. It is suggested a fuller investigation be considered in 1976.

Child↗

Serological probes for some foot-and-mouth disease virus nonstructural proteins.

Foot-and-mouth disease virus (FMDV) O1 Kaufbeuren-specific cDNA fragments were subcloned into the E. coli expression vector pRIT.2T. Fusion proteins thus produced in bacteria were purified by affinity chromatography and inoculated into rabbits. Three sera thus obtained were found to be monospecific for FMDV proteins 3A, 3C, and 3D, respectively. Two others were prevalently directed against protein 2C, but in addition, either to protein 2B or to protein 3A. Five out of six mature nonstructural virus proteins can therefore be separately investigated in FMDV-infected cells, either by indirect immunofluorescence or by radioimmunoprecipitation. Immunofluorescence shows all investigated proteins to be located exclusively in the cytoplasm. One of them, protein 2C, transiently forms aggregates at the periphery of cells. Radioimmunoprecipitation confirmed current knowledge on maturation of FMDV proteins. It was further used to characterize postinfectional sera with regard to FMDV-specific antibodies. Cattle and guinea pig were found to have responded differently to FMDV nonstructural antigens. Furthermore, antigenicity of yet to be described FMDV polypeptides was observed in the guinea pig.

Animals↗

Serial passage in tissue culture of mixed foot-and-mouth disease virus serotypes.

The foot-and-mouth disease (FMD) virus field specimen SAU/8/88 was previously shown to consist of a mixture of O and Asia 1 serotypes [15]. In this study, plaques representing the O and Asia 1 components isolated from the original epithelial virus suspension were used to construct mixtures of known ratios, and these were serially passaged in tissue culture. After each passage, the ratio of O to Asia 1 virus was calculated. The two virus populations were shown to be cycling through time. This cycling phenomenon has not been described before for FMD virus in tissue culture, but is consistent with current population theory.

Animals↗

Function of minor polypeptides in foot-and-mouth disease virus and poliovirus.

Foot-and-mouth disease virus and poliovirus each contain several minor polypeptides, in addition to the four structural proteins. One of these, the viral RNA polymerase, can also act as a nuclease, hydrolysing the RNA and thus destroying viral infectivity. It is tightly bound to the RNA and may be the packaging signal for assembly of the particle.

Aphthovirus↗

Identification of amino acid and nucleotide sequence of the foot-and-mouth disease virus RNA polymerase.

Foot-and-mouth disease virus (FMDV) RNA polymerase was purified from the polyethylene glycol (PEG)-treated supernatant of infected cell media by a combination of ion-exchange chromatography, membrane molecular filtration, and affinity chromatography. The purified RNA polymerase which migrated as a single band of 56,000 molecular weight on a polyacrylamide gel was subjected to automated Edman degradation and the sequence of the first 30 amino acid residues established. On the basis of previous evidence, which indicated that the RNA polymerase was the most 3'-translated polypeptide, plasmids containing cDNA mapping at the 3' end of the genome were characterized by restriction enzyme analysis and nucleotide sequencing. These investigations definitively established the derived amino acid sequence by confirmation of 28 of the amino terminal residues determined by amino acid sequence analysis; the location of the FMDV RNA polymerase coding region at the extreme 3' end of the genome, 96 nucleotides from the poly(A) tail; and the N-terminal cleavage point of the RNA polymerase from its precursor P100 was found to be a glutamic acid-glycine bond.

Amino Acid Sequence↗

Structure of a major immunogenic site on foot-and-mouth disease virus.

Attachment of foot-and-mouth disease virus (FMDV) to its cellular receptor involves a long and highly antigenic loop containing the conserved sequence, Arg-Gly-Asp, a motif known to be a recognition element in many integrin-dependent cell adhesion processes. In our original crystal structure of FMDV the Arg-Gly-Asp-containing loop ('the loop'), located between beta-strands G and H of capsid protein VP1, was disordered and hence essentially invisible. We previously surmised that its disorder is enhanced by a disulphide bond linking the base of the loop (Cys 134) to Cys 130 of VP2 (ref. 8). We report here the crystal structure of the virus in which this disulphide is reduced. Reduced virus retains infectivity and serological experiments suggest that some of the loop's internal structure is conserved. But here its structure has become sufficiently ordered to allow us to describe an unambiguous conformation, which we relate to some key biological properties of the virus.

Aphthovirus↗

The location of the ploy(C) tract in the RNA of foot-and-mouth disease virus.

Fragments of foot-and-mouth disease virus RNA of decreasing size, containing the 3' poly(A) sequence have been prepared by alkali treatment and sucrose gradient centrifugation followed by oligo(dT)-cellulose affinity chromatography. Polyacrylamide gel electrophoresis of the ribonuclease T1 resistant oligonucleotides from these polyadenylated fragments has enabled us to locate the position of some of the longer oligonucleotides on the RNA. In particular the poly C tract has been shown to be near the 5' end of the RNA; The possible function of the poly(C) tract is discussed in the light of these findings.

Aphthovirus↗

An extended genetic recombination map for foot-and-mouth diseases virus.

The original foot-and-mouth diseases virus recombination map (Lake, Priston & Slade, 1975), which include 35 mutagen-induced ts mutants, has been extended both in detail and size by the mapping of a further 33 ts mutants (9 mutagen-induced and 24 spontaneous). The size increase from 0.57% to 3.27% maximum recombination fequency was principally due to the use of a new standardization technique for recombination fequencies but, in addition, the original map distance was increased by approx. 30% due to the mapping of new mutations. As in the original map, there was a marked concentration of mutations near the guanidine (gs) locus, i.e. 83% of the mutants had mutations in the third of the map adjacent to the gs locus.

Aphthovirus↗

Isolation and characterization of trypsin-resistant O1 variants of foot-and-mouth disease virus.

Strains of foot-and-mouth disease virus of types O1 and A10 were isolated which showed no significant loss of infectivity upon trypsinization. These 'trypsin-resistant' (TR) viruses were obtained by serial passage in BHK cells of virus that was trypsin-treated before inoculation of the cells. Three O1 isolates were cloned and studied further. Cell attachment of those TR O1 variants (OTR1) was not reduced by trypsinization, unlike that of parent virus. The polypeptide compositions of TR viruses as determined by SDS-polyacrylamide gel electrophoresis were identical with those of parent virus, with the exception of OTR1 which contained an additional polypeptide approx, 3000 daltons larger than VP1. After trypsinization, which normally cleaves VP1, the polypeptide composition of the three TR viruses (including OTR1) and of parent virus did not show any significant difference. In OTR1 both the additional virus protein and VP1 were cleaved into a P18 molecule and smaller fragments. The surface location of this additional polypeptide was confirmed by iodination experiments. It was shown by immunodiffusion experiments that only OTR1 differed from the parent virus. This antigenic change was present on the trypsin-sensitive part of the virus since trypsinized TR viruses (including OTR1) were antigenically identical to trypsinized parent virus. The electrophoretic mobilities of the three OTR viruses isolated, and of parent virus, differed somewhat before trypsinization. After trypsin-treatment, the mobilities of TR viruses were all increased to the same level; however, their rate of migration was lower than that of trypsin-treated parent virus. This lower mobility of trypsin-treated OTR viruses was the only difference which could be associated with retained infectivity.

Antigens, Viral↗

Modification of the leader protein (Lb) of foot-and-mouth disease virus.

Translation of foot-and-mouth disease virus RNA for extended periods in rabbit reticulocyte lysates results in the appearance of a previously undescribed protein. A protein with similar properties can also be detected in BHK cells at late times after virus infection. Specific immunoprecipitation has shown that this protein (Lb') is closely related to the smaller of the two leader proteins, Lb, although it migrates with an apparently higher Mr in SDS-polyacrylamide gels. The conversion of Lb to Lb' can be mimicked by treatment with carboxypeptidase B. It is suggested that C-terminal trimming of Lb to produce Lb' results in an increase in negative charge and is responsible for its slower migration in SDS-PAGE.

Aphthovirus↗