Sequence analysis of the cleavage site-encoding region of the fusion protein gene of Newcastle disease viruses from India and Nepal.

Five field isolates of Newcastle disease virus, including one from a pigeon from the Indian subcontinent, along with three vaccine strains have been characterized by sequence analysis of the fusion protein (F) gene in the region encoding the F 2 -F 1 cleavage site. Based on the amino acid sequence present at the cleavage site and on the percent divergence at nucleotide and amino acid levels, three field isolates could be classified as velogenic and two were of lentogenic pathotypes. The velogenic pathotypes had the sequence RRQK/RRF at the cleavage site, while the lentogenic strains had GRQA/GRL at the corresponding position.