Antigenic analysis of serotype O foot-and-mouth disease virus isolates from the Middle East, 1981 to 1988.

During the period 1981-88 foot-and-mouth disease virus (FMDV) serotype O continued to be isolated from outbreaks in the Middle East. Field isolates submitted to the World Reference Laboratory have been examined in relation to reference strains by either complement fixation, virus neutralization or enzyme-linked immunosorbent assays. Most isolates were related to the European type O1 reference strains although strains emerging in late 1987 and 1988 were more closely related to O1/Manisa.

Serological prospects for peptide vaccines against foot-and-mouth disease virus.

Antibodies to a synthetic peptide corresponding to the 141 to 160 amino acid sequence of the protein VP1 of type O foot-and-mouth disease virus (FMDV) neutralize a wider range of type O isolates than anti-virion serum. Extending this peptide at the amino terminus reduced the number of strains neutralized by the antipeptide sera. Reactions with antisera to peptides representing non-contiguous native sequences showed that it was also possible to increase the number of strains effectively neutralized.

Neutralizing epitopes of type O foot-and-mouth disease virus. II. Mapping three conformational sites with synthetic peptide reagents.

Four neutralizing monoclonal antibodies (MAbs), recognizing three functionally independent, conformational sites on type O foot-and-mouth disease virus (FMDV) failed to react with immobilized structural proteins or synthetic peptides but bound to the isolated capsid protein VP1 and peptides in solution. Inhibition ELISA techniques were, therefore, applied using peptide antigens and anti-peptide sera to block MAb binding to virus particles, permitting the identification of those portions of the VP1 protein contributing to the epitopes. The binding site of one MAb, which neutralized a range of type O FMDV isolates, was shown to have components within regions 146 to 150 and 200 to 213 of VP1 with a critical involvement of the amino acids at positions 146 and 206 or 207.

Neutralizing epitopes of type O foot-and-mouth disease virus. I. Identification and characterization of three functionally independent, conformational sites.

Eleven neutralizing monoclonal antibodies (MAbs) were produced to the O1BFS 1860/67 strain of foot-and-mouth disease virus (FMDV), and were characterized for their ability to bind viral and subviral antigens in different ELISA tests and to neutralize heterologous type O isolates. Neutralization escape variants of the homologous virus, isolated under pressure from five of these MAbs, were used in cross-neutralization tests with all of the 11 antibodies. These studies identified three functionally independent, conformational, neutralizing sites.

Epitope mapping of foot-and-mouth disease virus with neutralizing monoclonal antibodies.

Epitopes of strain A22 Iraq 24/64 of foot-and-mouth disease virus have been mapped with monoclonal antibodies (MAbs). Three methods were used: (i) an indirect ELISA using an overlapping set of peptides, (ii) production of neutralization escape variants against each MAb and (iii) sequencing of neutralization escape variants. The study has shown that the virus has at least three overlapping liner neutralizing epitopes within a major antigenic site on VP1.

Host cell selection of antigenic variants of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) A22 Iraq 24/64 adapted to grow in BHK monolayer cells induced antibodies which neutralized many isolates belonging to the A serotype. Plaque-purified virus isolated from this stock also induced broadly reactive antibodies, showing that this property is not due to the combined response to a mixture of variants in the original stock virus. However, viruses obtained by passage in suspension BHK cells of either the monolayer cell-adapted virus or a virus cloned from this stock resulted in the selection of virus which induced antibodies with highly specific neutralizing activity.

The use of a logistic model for the quantitative interpretation of indirect sandwich enzyme labelled immunosorbent assays (ELISA) for antibodies and antigens in foot and mouth disease.

A three parameter logistic model is described for the analysis of profiles of optical density vs log dose for indirect sandwich ELISA tests in foot and mouth disease. The model describes the observed phenomenon of saturability with increasing dose, and its parameters can be interpreted in terms of molecular binding events. A computer program to fit the model is described.

The differentiation of foot and mouth disease virus strains using an indirect sandwich enzyme-linked immunosorbent assay saturation model.

Sigmoid saturation curves were fitted to the results of titrations of antiserum to foot and mouth disease virus against homologous and heterologous virus strains. Differentiation of strains was readily evident from the different levels of the homologous and heterologous curves. These differences could be quantified by comparison of the saturation curve parameters K and PRmax.

An indirect sandwich enzyme labelled immunosorbent assay for the detection of foot and mouth disease virus immunizing antigen in tissue culture harvests.

The optimum conditions for an indirect sandwich enzyme-linked immunosorbent assay for foot and mouth disease virus 140S antigen assay are described. Factors which could contribute to the variation in the test were investigated and a calibration coefficient for the conversion of ELISA values to antigen concentration in micrograms of 140S antigen per millilitre was calculated. Antigen mass in nine tissue culture harvests was estimated and these correlated well with estimates made by sucrose density gradients (r = 0.

The effect of antiserum quality on strain specificity assessment of foot and mouth disease virus by the neutralization reaction.

The factors affecting the virus strain specificity of antibody to foot an mouth disease virus prepared by a variety of protocols in several species were evaluated by neutralization tests. The time at which the serum was taken, the antigen dose given, whether or not revaccination had occurred and the animal species in which the sera were prepared, did not appear to affect the strain specificity of serum prepared to inactivated antigens when measured in neutralization tests, probably because of the restricted nature of the antigenic site involved. However, variation was observed with convalescent animal sera or sera from animals which had received trypsin cleaved virus were used.

Evaluation of the antigenic variation within type-A foot and mouth disease virus isolates from Asia.

The serological interrelationships among 17 type A FMD virus strains from eight Asian countries were studied by the two-dimensional microneutralization test. Complex direct and indirect relationships were observed. Overall, however, the virus strains studied could be classified as belonging to the A22 group on the basis of r value differentiation at P less than 0.

Demonstration of neutralizing and non-neutralizing epitopes on the trypsin-sensitive site of foot-and-mouth disease virus.

The isolation of monoclonal antibodies directed against the trypsin-sensitive site on the 140S particle of foot-and-mouth disease virus (FMDV) has enabled the demonstration of at least three distinct epitopes within this site. Reaction with two of these resulted in neutralization of virus infectivity. None of the epitopes appeared to be present on the 12S particles, and one of the neutralizing epitopes was sensitive to even milder configurational changes of the particle.

Computerization of foot and mouth disease virus strain relationship data.

Since 1976 the two dimensional microneutralization test has been adopted in our laboratory as the reference test for foot and mouth disease virus (FMDV) strain differentiation. Large numbers of homologous-heterologous comparisons have been performed and manual storage and retrieval of the data had become cumbersome. The objective of computerization was to provide a databank with fast easy access to enable accurate statistical calculations to be performed on the raw data entries and to simplify the evaluation of statistical and biological significance.

A serological evaluation of 1979-1982 Kenyan foot-and-mouth disease type SAT 2 viruses.

Serological evaluations of foot-and-mouth disease type SAT 2 viruses isolated in Kenya between 1979 and 1982 were performed using the two-dimensional microneutralization test. Nine field isolates of epizootiological significance were compared with four vaccine viruses. The results obtained identified Tan 5/68 as the most appropriate reference vaccine virus strain since it had the broadest serological spectrum.

Antibody response in bovine pharyngeal fluid following foot-and-mouth disease vaccination and, or, exposure to live virus.

Samples of pharyngeal fluid and serum were collected from cattle after exposure to live foot-and-mouth disease (FMD) virus (with or without prior vaccination) or after subcutaneous vaccination with inactivated virus. The pharyngeal fluid samples were examined for FMD neutralising activity and specific anti-FMD IgG, IgM and IgA antibodies. The neutralising activity of the serum was also monitored.

Antibody response of pigs to foot-and-mouth disease oil emulsion vaccine: the antibody classes involved.

Groups of three pigs were vaccinated with water-in-oil emulsion vaccine and revaccinated either 21 and 148 or 106 days later. Sera were taken periodically for six months and fractionated into heavy and light elements on sucrose density gradients. The heavier fraction contained IgM and the lighter fraction IgG and IgA.