The CSFV DNAChip: a novel diagnostic assay for classical swine fever virus

A novel assay, the CSFV DNAChip, was developed to clearly and rapidly discriminate three genotypes of classical swine fever virus (CSFV). Total RNA was extracted from clinical samples and then subjected to a one-step reverse-transcription polymerase chain reaction (RT-PCR) using Cy3-labeled primers from the 5' non-coding region (NCR) of CSFV. Amplicons were hybridized to the CSFV DNAChip and fluorescence scanning was performed for detection of CSFV. A cut-off fluorescence intensity value of 5000 was determined by two-graph receiver operating curve (TG-ROC) analysis. The limit of detection values for the developed DNA chip assay were 0.313ng/μL for amplicon concentration and 1TCID50/100μL for virus titer. Using the developed DNA chip, 157 field samples (91 CSFV-positive and 66 CSFV-negative) were investigated. The genotypes determined by the CSFV DNAChip agreed completely with those determined by nucleotide sequence analysis of the viral genome. The developed CSFV DNAChip will be helpful in implementing a CSFV eradication strategy, as it provides a rapid and accurate diagnostic assay that can discriminate easily among CSFV genotypes.