Development Of A Rapid Neutralization Assay For FMDV Using Quantitative RT-PCR-based Endpoint Assessment

Foot and mouth disease(FMD) is a highly contagious disease affecting cloven-hoofed animals.Virus neutralization test(VNT) is the most recommended method for vaccine matching test of FMD virus(FMDV) and to measure the serological response to FMDV infection and vaccination, but currently available VNT can be time-consuming and easily affected by man-made factors. In this study,a novel virus neutralization assay using qRT-PCR-based endpoint assessment was developed for the detection of neutralizing antibodies against FMDV serotype Asia 1(the qRT-PCR-VNT assay). In this assay, the endpoint assessment was assessed as early as 20 hours post-infection and the dynamic range of the reduction in FMDV replication resulting from neutralizing antibodies in sera was detected due to the high sensitivity of qRT-PCR in detection of virus replication. Nineteen of FMDV negative sera and four of positive sera were tested with q RT-PCR-VNT. Copy number of FMDV RNA in each well was quantified at 20 hpi, the cut off value was set up as 7 lg copy number per well for calculation of neutralizing antibody against FMDV Asia 1 in sera samples. The results showed that the q RT-PCR-VNT assay has good correlation with traditional VNT for detection of neutralizing antibodies in sera samples.In conclusion, the developed qRT-PCR-VNT assay is suitable for rapid detection of neutralizing antibodies in sera against FMDV Asia 1.