Rapid pathotyping of Newcastle disease virus (NDV) using fluorogenic probes in a PCR assay

Hybridisation of PCR fragments with fluorogenic probes specific for pathoty pe allowed an estimation of pathogenicity of Newcastle disease virus (NDV) isolates using a modified TaqMan (TM) procedure. Six probes were used, desi gned to recognise nucleotide sequences in the fusion protein gene sequence corresponding to the precursor protein FO cleavage site of both virulent an d avirulent viruses. Forty-three of the 45 isolates tested, including 18 ex amined in a blind study were pathotyped successfully and rapidly, with clos e correlation between cleavage site nucleotide sequences. TaqMan (TM) resul ts and intracerebral pathogenicity index (ICPI) values. One isolate, which could not be pathotyped by nucleotide sequencing, was shown using the TaqMa n (TM) system to be a mixture of virulent and avirulent NDV. The results of this study suggest that using this modified TaqMan (TM) protocol, the like ly virulence of most ND isolates can be determined rapidly and reproducibly . Crown Copyright (C) 2001 Published by Elsevier science B.V. All rights re served.