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

Hybridisation of PCR fragments with fluorogenic probes specific for pathotype allowed an estimation of pathogenicity of Newcastle disease virus (NDV) isolates using a modified TaqMan (TM) procedure. Six probes were used, designed to recognise nucleotide sequences in the fusion protein gene sequence corresponding to the precursor protein FO cleavage site of both virulent and avirulent viruses. Forty-three of the 45 isolates tested, including 18 examined in a blind study were pathotyped successfully and rapidly, with close correlation between cleavage site nucleotide sequences. TaqMan (TM) results and intracerebral pathogenicity index (ICPI) values. One isolate, which could not be pathotyped by nucleotide sequencing, was shown using the TaqMan (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 likely virulence of most ND isolates can be determined rapidly and reproducibly. Crown Copyright (C) 2001 Published by Elsevier science B.V. All rights reserved.