E. coli expressed proteins as diagnostic reagents for typing of foot-and-mouth disease virus
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Truncated proteins corresponding to the C-terminal half of VP1 of four vaccine strains and two field variants of foot-and-mouth disease virus (FMDV) were expressed in E. coli. The expressed proteins were affinity purified and their type specific reactivity was confirmed by immunoprecipitation with anti-virus antibodies. Antibodies were raised against the purified proteins in guinea pigs and the type specificity of the anti peptide antibodies was confirmed by antigen capture reverse transcription polymerase chain reaction (Ag-RT/PCR) where the sera against a particular type captured the homologous virus. Antibodies were purified by immuno-affinity chromatography and tested for specificity by various serological tests. Using the purified proteins and the antibodies raised against them, tests like ELISA, Ag-RT/PCR, and latex agglutination test (LAT) were standardized. Application of the reagents in various tests was studied by screening a few field samples and by nucleotide sequencing. Specific reactivity of antibodies raised against expressed protein was seen with both vaccine virus and field samples. Thus E. coli expressed proteins and antibodies to them may form an alternative and cheap source of diagnostic reagents. The studies showed that antibodies against peptides were mono-specific and therefore may be used in LAT for rapid typing of FMDV and Ag-RT/PCR for typing ELISA negative field samples.
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