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Detection of Minimal Quantities of Foot-and-Mouth Disease Virus with Bovine Kidney Tissue Cultures.

Minute quantities of foot-and-mouth disease virus (FMDV) were suspended in 500-, 1,000- and 2,000-ml volumes of virus growth medium and inoculated into primary bovine kidney cell cultures grown as monolayers in 5-liter Povitsky bottles. After 48 hr of incubation, the low concentrations of FMDV, containing from 10 to 10 plaque-forming units (PFU) per milliliter of inoculum, multiplied to approximately 10 PFU per milliliter of fluid. The presence of extracellular virus after multiplication was verified by assaying the fluid in 4-oz prescription-bottle cultures. Minimal quantities of FMDV were able to infect the cells and replicate despite the large volume of the suspending fluid. This technique may be applicable for the detection of trace amounts of FMDV in clinical samples and vaccines. Skin samples of unknown infectivity in limited tests gave identical positive or negative results in both steers and Povitsky cultures, but were consistently negative when tested in suckling mice and in prescription-bottle tissue cultures.

Journal Article↗

Mouse Resistance Against Foot-and-Mouth Disease Virus Induced by Injections of Pyran.

Mouse resistance to foot-and-mouth disease virus (FMDV) was induced by intraperitoneal injections of pyran copolymer. A biphasic pattern of protection occurred with greatest resistance 4 and 48 hr after injection of this polyanion. Viremia was not detectable in pretreated mice challenge-exposed with FMDV. Incubation of virus with pyran did not alter viral infectivity in mice or tissue culture. Serum interferon was demonstrated 1 and 2 days after pyran administration.

Journal Article↗

Rapid selection in modified BHK-21 cells of a foot-and-mouth disease virus variant showing alterations in cell tropism.

With persistent foot-and-mouth disease virus (FMDV) in BHK-21 cells, there is coevolution of the cells and the resident virus; the virulence of the virus for the parental BHK-21 cells is gradually increased, and the cells become partially resistant to FMDV. Here we report that variants of FMDV C3Arg/85 were selected in a single infection of partially resistant BHK-21 cells (termed BHK-Rb cells). Indirect immunofluorescence showed that the BHK-Rb cell population was heterogeneous with regard to susceptibility to C3Arg/85 infection. Infection of BHK-Rb cells with C3Arg/85 resulted in an early phase of partial cytopathology which was followed at 6 to 10 days postinfection by the shedding of mutant FMDVs, termed C3-Rb. The selected C3-Rb variants showed increased virulence for BHK-21 cells, were able to overcome the resistance of modified BHK-21 cells to infection, and had acquired the ability to bind heparin and to infect wild-type Chinese hamster ovary (CHO) cells. A comparison of the genomic sequences of the parental and modified viruses revealed only two amino acid differences, located at the surface of the particle, at the fivefold axis of the viral capsid (Asp-9-->Ala in VP3 and either Gly-110-->Arg or His-108-->Arg in VP1). The same phenotypic and genotypic modifications occurred in a highly reproducible manner; they were seen in a number of independent infections of BHK-Rb cells with viral preparation C3Arg/85 or with clones derived from it. Neither amino acid substitutions in other structural or nonstructural proteins nor nucleotide substitutions in regulatory regions were found. These results prove that infection of partially permissive cells can promote the rapid selection of virus variants that show alterations in cell tropism and are highly virulent for the same cells.

Amino Acid Substitution↗

Comparison of a radioactive and non-radioactive method for sequencing foot and mouth disease virus isolates.

The authors compare the radioactive method of detecting foot and mouth disease virus sequence products with a non-radioactive, silver stain sequencing method. The latter was found to compare favourably to the radioactive technique for detecting such products. The silver stain sequencing method was simple and did not require expensive specialised equipment. This new approach will be particularly useful in developing countries, since the method does not depend on the availability of fresh radioactive isotopes and is also safer and considerably cheaper.

Animals↗

Pathologic studies of fatal cases in outbreak of hand, foot, and mouth disease, Taiwan.

In 1998, an outbreak of enterovirus 71-associated hand, foot, and mouth disease occurred in Taiwan. Pathologic studies of two fatal cases with similar clinical features revealed two different causative agents, emphasizing the need for postmortem examinations and modern pathologic techniques in an outbreak investigation.

Disease Outbreaks↗

C-terminal region of VP1 of selected foot-and-mouth disease virus serotypes: expression in E. coli and affinity purification.

Foot-and-mouth disease (FMD), one of the most contagious and economically important diseases of farm animals, is caused by a FMD virus (FMDV) which belongs to the family of Picornaviridae. The virus occurs as seven serotypes of which four (A, O, C and Asia 1) are prevalent in India. Immunoprophylaxis supported by precise diagnosis is the prime requirement for achieving the success in controlling the disease. Recently, recombinant DNA technology is gaining importance for the production of cost-effective and safer diagnostics and immunogens. Based on this approach, cDNA of a part of gene for major variable immunogenic region, VP1, of FMDV of four serotypes (A22, O, C and Asia 1) was amplified by PCR and cloned into expression vector. The expression of the 16 K protein gene from the clones was induced with IPTG and analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) and [35S]-methionine labeling. The immunoreactivity of the labeled proteins was assayed by immunoprecipitation with anti-FMDV type-specific sera. Since the proteins contain 6 His residues at the N-terminal end, their affinity purification was carried out using nickel nitrilo-tri-acetic acid (Ni-NTA) agarose matrix. The proteins were found to be immunoreactive and the useful in the FMD diagnosis.

Aphthovirus↗

Stimulation by heterotypic antigens of foot-and-mouth disease virus antibodies in vaccinated cattle.

Immunisation of cattle with foot-and-mouth disease virus failed to raise a level of antibody that provides protection against heterotypic challenge. Further the 12S substructure, produced from the 146S particle, was ineffective in providing protection against challenge by homotypic virus. These findings suggest considerable antigenic differences in the virus serotypes and between the virus and its substructure. Inoculation of homologous 12S and heterologous 1246S and 12S antigens into vaccinated cattle, however, revealed antigenic relationship between different serotypes, and between serotypes and their substructures.

Animals↗

Serological study of type A Indian foot-and-mouth disease virus isolates.

The antigenic relationship of sixty type A foot-and-mouth disease (FMD) viruses isolated between 1968 and 1993 has been determined with reference to a post-vaccinal bovine serum produced against type A IND 17/82. A micro-neutralization test and ELISA were used to compare isolates. Analysis of the results indicated that there was a positive correlation between the data from the two methods. The study indicated that type A IND 17/82 had a broad immunogenic spectrum and could be considered as a candidate vaccine strain for incorporation in FMD vaccines in India.

Animals↗

Experimental studies with foot-and-mouth disease virus, strain O, responsible for the 2001 epidemic in the United Kingdom.

In 2001, the United Kingdom experienced its worst epidemic of foot-and-mouth disease (FMD). To date approximately 3.9 million animals have been culled and direct and indirect revenue losses are probably in excess of pound 12 billion. This study was carried out to investigate the biological characteristics of the FMD virus strain O/UKG/2001 responsible for the epidemic. Animal transmission experiments indicated that this strain is not host restricted and will infect the three main susceptible livestock species (cattle, sheep and pigs). Immunisation with high potency emergency vaccine derived from O(1) Manisa strain of FMD virus protected all three species against clinical disease when challenged with FMD virus strain O/UKG/2001.

Animals↗

Role of apoptosis in the pathogenesis of Asian and South American foot-and-mouth disease viruses in swine.

In this study, we performed experiments to evaluate the extend of the process of apoptotic cell death by foot-and-mouth disease virus (FMDV). Apoptosis can also occur in some virus-infected cells, and ability of viruses to either inhibit or promote apoptosis may influence the pathologic outcome of infection. In this study, to determine if apoptosis plays a role in the outcome of FMDV infection in swine, we evaluated apoptosis in diseased tissues collected from pigs inoculated with two different stains of FMDV (O1 Campos and O Taiwan). And host cell DNA fragmentation in diseased tissue from animals which were infected with either virus was evaluated by occurrence of a laddering pattern characteristic of apoptosis. Infection of cultured keratinocytes from swine tongue failed to demonstrate apoptosis in the first few hours of infection, suggesting that cell-to-cell correlation between viral antigen and apoptotic changes, e.g. cytokine secretions by immune system cells, could be critical to initiating apoptosis. Consistent with this finding, we were able to detect the pro-inflammatory cytokine TNF-alpha in diseased tissues. A clear difference in the pathogenicity of the two different FMDV isolates to pigs was not demonstrated in our study.

Animals↗

Evaluation of genetically engineered derivatives of a Chinese strain of foot-and-mouth disease virus reveals a novel cell-binding site which functions in cell culture and in animals.

Adaptation of field isolates of foot-and-mouth disease virus (FMDV) to grow in cells in culture can result in changes in viral properties that include acquisition of the ability to bind to cell surface heparan sulfate (HS). After 13 passages on BHK cells to produce a vaccine, a Cathay topotype isolate of FMDV serotype O from China (O/CHA/90) extended its cell culture host range and bound to heparin-Sepharose, although it did not require cell surface HS as a receptor molecule. To understand these phenomena, we constructed chimeric viruses by using a type A(12) infectious cDNA and the capsid protein-coding regions of O/CHA/90 and its cell culture-adapted derivative (vac-O/CHA/90). Using a set of viruses derived from these chimeras by exchanging portions of the capsid-coding regions, we discovered that a group of amino acid residues that surround the fivefold axis of the icosahedral virion determine host range in cell culture and influence pathogenicity in pigs. These residues included aromatic amino acids at positions 108 and 174 and positively charged residues at positions 83 and 172 in protein 1D. To test if these residues participated in non-integrin-dependent cell binding, the integrin-binding RGD sequence in protein 1D was changed to KGE in two different chimeras. Evaluation of these KGE viruses indicated that growth in cell culture was not dependent on HS. One of these viruses was tested in pigs, where it produced a mild disease and maintained its KGE sequence. These results are discussed in terms of receptor utilization and pathogenesis of this important pathogen.

Amino Acid Sequence↗

Demonstration of bovine CD8+ T-cell responses to foot-and-mouth disease virus.

The aim of this study was to investigate the importance of cellular immunity in foot-and-mouth disease in cattle, in particular to determine whether a CD8+ T-cell response could be detected, as these cells may play a role in both immunity and virus persistence. As attempts to characterize classical cytotoxic T cells had yielded non-reproducible results, largely due to high backgrounds in control cultures, a proliferation assay was developed that was demonstrated to detect antigen-specific, MHC class I-restricted bovine CD8+ cells responding to foot-and-mouth disease virus (FMDV). Proliferative CD8+ T-cell responses were detected consistently from 10 to 14 days following infection with FMDV and typically lasted 3-4 weeks. The role of CD8+ T cells in control of the disease, in particular their relevance for the establishment of persistence, may now be investigated.

Animals↗

Differential significance of epizootiological factors in the control of foot-and-mouth disease. A brief review.

The discovery of respiratory tract involvement in the pathogenesis of foot-and-mouth disease (FMD) and the recognition of the role of inhalated aerosols in virus transfer opened new outlooks in the epizootology and prophylaxis of the disease. Nevertheless, FMD should be regarded for an infection transmitted by contaminated passive vectors including man and stable equipment. Transient persistence of FMD virus in the upper respiratory airways of cattle is of interest, but there is no reason to consider this for a significant hazard. Regular annual immunization with a vaccine containing the most isolated virus serotypes seems to be the best way how to prevent epizootics and panzootics.

Aerosols↗

Procedures for preventing the transmission of foot-and-mouth disease virus to pigs and sheep by personnel in contact with infected pigs.

The most effective method of containing an outbreak of foot-and-mouth disease (FMD) is by the culling of livestock. However, qualified people must diagnose the disease before the culling can begin, and they must avoid susceptible animals after having been in contact with infected premises, to prevent them from transmitting the virus. To test the effectiveness of biosecurity procedures in preventing the transmission of FMD virus (O/UK/35/2001) investigators contacted and sampled pigs inoculated with FMD virus for approximately 45 minutes and then contacted and sampled sentinel pigs and sheep after either using no biosecurity procedures, or washing their hands and donning clean outerwear, or showering and donning clean outerwear. The virus was detected in the nasal secretions of one investigator immediately after the postmortem investigation of the inoculated pigs but was not detected in samples collected between approximately 12 and 84 hours later. After the contaminated personnel had showered and changed into clean outerwear they did not transmit the strain of FMD virus to susceptible pigs and sheep.

Animal Husbandry↗

Presence of antibodies to non-structural proteins of foot-and-mouth disease virus in repeatedly vaccinated cattle.

For the purpose of removing infected animals by detecting humoral immune responses to non-structural proteins of the foot-and-mouth disease (FMD) virus, antibodies induced by contaminated residual non-structural proteins contained in less pure FMD vaccine can be problematic for serological screening. The aim of the present study was to measure the possible presence of antibodies against these non-structural proteins in repeatedly vaccinated calves and beef cattle. Five imported FMD vaccines were examined using two commercial ELISA kits, UBI FMDV NS EIA and Ceditest FMDV-NS, for serological testing. After five doses of vaccination, the serum of one calf tested positive, and two vaccines induced a significant increase in anti-3ABC antibodies in calves. This finding demonstrated that a positive reaction to non-structural proteins due to impurities in the FMD vaccine was detectable using commercial tests. A low percentage of field sera sampled from beef cattle in Kinmen also tested positive, but the key factor resulting in the positive reactions could not be positively identified based on our data.

Animals↗

Spatio-temporal epidemiology of foot-and-mouth disease in two counties of Great Britain in 2001.

The spatial, temporal, and spatio-temporal features of the 2001 British foot-and-mouth disease epidemic in selected areas within the counties of Cumbria and Devon, which experienced the greatest incidence of disease, are described using hazard functions, extraction mapping and the space-time K-function. In Cumbria, the hazard of foot-and-mouth disease infection peaked at 2.8% in the week commencing 8 March 2001 and farm holdings in this area continued to be identified with disease to 12 September 2001. In contrast, peak infection hazard in Devon was 0.7% in the week commencing 15 March 2001 and eradication of the disease was achieved in this area by 31 May 2001. Persistence of the disease in Cumbria was consistent with: (1) many cattle holdings infected early in the epidemic (creating a high environmental viral load), and (2) a relatively large amount of medium-to-long-distance spread of the virus associated with seasonal farming activities-compounded to some extent by the movement of people and vehicles between disaggregated farm land parcels. The interaction of disease risk in Cumbria showed that premises remained infectious for longer throughout May, June and July, consistent with delays in disease detection during this period.

Animals↗

Detection of foot-and-mouth disease virus RNA in clinical samples and cell culture isolates by amplification of the capsid coding region.

Foot-and-mouth disease is one of the most economically important virus diseases of livestock. Two important requirements for the control of this disease are rapid laboratory diagnosis and epidemiological investigation. The use of the polymerase chain reaction method (PCR) to amplify specific nucleic acid regions offers the unique possibility of combining swift viral detection with the production of genetic material suitable for sequencing and other methods of molecular epidemiological analysis. The sequencing of the region of foot-and-mouth disease virus (FMDV) genome encoding the capsid proteins of the virus (approximately 2260 bps), provides valuable information that adds to the molecular characterisation of an isolate. This paper describes the use of the PCR for the amplification of this region of the FMDV genome from bovine clinical samples and cell culture isolates. Suitable pairs of oligonucleotide primers were selected from the published sequence of FMDV type O1, Kaufbeuren. One primer set amplified 2091 bps of the capsid coding region of all seven serotypes of FMDV. The other primer set amplified 216 bp from this region of FMDV type O1, BFS 1860, in nucleic acid extracts from several clinical samples. Nucleic acid extracts from the picornaviruses, bovine enterovirus and swine vesicular disease virus, which affect the same animals, were not amplified. Direct sequencing was carried out on the amplified fragments and showed that the PCR products were > 98% homologous to published FMDV sequences.

Animals↗

Utility of recombinant integrin alpha v beta6 as a capture reagent in immunoassays for the diagnosis of foot-and-mouth disease.

Recombinant integrin alpha v beta6 was evaluated as a capture ligand in a sandwich ELISA for the detection and serotyping of foot-and-mouth disease (FMD) virus. Our routinely applied method employs seven serotype-specific rabbit polyclonal antibodies as capture ligands and seven serotype-specific guinea pig polyclonal antibodies as detecting reagents. The recombinant integrin bound FMD virus of all seven serotypes but not that of another vesicular disease, swine vesicular disease (SVD). Considerable heterotypic cross-reactions were evident when using the integrin capture ligand in combination with guinea pig detecting antibodies but totally type-specific reactions resulted when serotype-specific monoclonal antibodies (mabs) were used instead of the guinea pig reagents. The specificity of reaction of the integrin capture/mab detector combination was superior to that of our routinely employed rabbit/guinea pig ELISA and offers an improvement for test interpretation. As a universal trapping reagent for all FMD virus serotypes the alpha v beta6 recombinant protein also has the potential for application in other test procedures for viral identification (e.g. pen-side chromatographic strip-tests, biosensors, immunocapture RT-PCR, antigenic characterization procedures and monoclonal antibody profiling of emerging field virus strains) and in antibody detection assays employed for the diagnosis of FMD.

Animals↗