Development of a reverse-transcription polymerase chain reaction assay with fluorogenic probes to discriminate Korean wild-type and vaccine isolates of Classical swine fever virus.

A 1-step reverse-transcription polymerase chain reaction (RT-PCR) assay using TaqMan minor-groove-binding (MGB) probes was developed to distinguish between vaccine-type and wild-type strains of Classical swine fever virus (CSFV) in Korea. Because attenuated Korean LOM strains have been used in animal vaccination in Korea for some time but CSF remains a serious problem, there was a need for a practical approach to differentiating vaccine and field strains. We examined the fluorescence of 5 vaccine strains, 10 field strains, and 5 mixed samples. Three clusters of the samples could be distinguished: those with only fluorescence of the vaccine-type-specific probe, VIC; those with only fluorescence of the wild-type-specific probe, FAM; and those with both VIC and FAM fluorescence. The RT-PCR assay with fluorogenic probes is sensitive and accurate and is therefore useful for differentiating vaccine and field strains of CSFV in Korea.