ABSTRACT
An in situ hybridization technique has been optimised for use on paraffin-embedded sections of tissues collected from cattle infected experimentally with foot-and-mouth disease virus type O1BFS. Tissue was collected 5 days after infection by direct contact. In situ hybridization was carried out using an RNA probe corresponding to a region of the 3D gene which codes for the RNA polymerase, and labelled with digoxigenin. Consistent, reproducible signal was detected within the epithelial layers of the palatine tonsil, soft palate and pharyngeal tissue studied. This is the first time that a digoxigenin-based system has been used successfully for FMD virus RNA detection with bovine tissue samples.
Subject(s)
Aphthovirus/genetics , Aphthovirus/isolation & purification , In Situ Hybridization/veterinary , Animals , Aphthovirus/enzymology , Cattle , Cattle Diseases/virology , Digoxigenin , Evaluation Studies as Topic , Foot-and-Mouth Disease/virology , Genes, Viral , In Situ Hybridization/methods , Palate, Soft/virology , Palatine Tonsil/virology , Pharynx/virology , RNA Probes , RNA-Dependent RNA Polymerase/genetics , Virology/methodsABSTRACT
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.
Subject(s)
Aphthovirus/physiology , Virus Replication/physiology , Animals , Aphthovirus/immunology , Cattle , Cell Line , Serial Passage , Species Specificity , Viral Plaque AssayABSTRACT
Plaque purification of foot-and-mouth disease (FMD) type O viruses isolated from cattle in Saudi Arabia showed the presence of mixed serotype infections. Sixteen out of 31 samples collected between 1985 and 1991 also contained Asia 1 virus, a serotype which had previously only been isolated from a single outbreak in that country in 1980. Nucleotide sequences of the Asia 1 component of all these samples revealed little variation and showed that they were closely related to both a Russian lapinized vaccine virus strain (Asia 1/Tadzhikistan/64), and to a field isolate from Turkey (Asia 1/TUR/15/73). Although mixed FMD infections have been observed previously this is a first report of a serotype, considered to be exotic to a country, co-existing undetected for an extended period of time.
