Newcastle disease virus: Detection and characterization by PCR of recent German isolates differing in pathogenicity.

The fusion (F) protein plays an important role in determining the virulence of Newcastle disease virus (NDV) strains. A reverse transcriptase-polymerase chain reaction (RT-PCR) is described which amplifies a 362 bp fragment encompassing the region of the F protein most important for pathogenicity. A specific PCR product was obtained independent of strain, pathogenicity and host of origin. Sequencing of the region specifying the F protein cleavage site confirmed the correlation between deduced amino acid sequence and pathogenicity. Oligonucleotides corresponding to the sequence of the pathospecific region were designed for recent German NDV isolates and labelled with digoxigenin. Hybridization of PCR fragments of different isolates with pathotype-specific oligonucleotides allowed an estimation of the pathogenicity of most isolates. Results were in good agreement with experimentally determined ICPI values.