Genetic and antigenic analysis of Newcastle disease viruses from recent outbreaks in Taiwan.

Portions of the haemagglutinin-neuraminidase (HN) and fusion protein (F) genes of Newcastle disease virus (NDV) isolated from recent outbreaks in Taiwan were amplified and sequenced. These isolates were velogenic, based on the amino acid sequences of the F protein cleavage site and the mean death time in chicken embryos. All the recent viruses contained the amino acid sequences 112RRQKR116 for the C-terminus of the F2 protein. The serological relatedness of recent isolates was determined using a serum neutralization (SN) test. Relatedness values, determined by a cross-SN test, revealed that all belonged to a single serotype but could be classified into distinct subtypes, suggesting that antigenic variations occurred in these isolates. Phylogenetic trees based on the nucleotide sequences of the HN and F genes revealed that recent Taiwanese isolates had evolved into two groups. Antigenic analysis also suggested that there are at least two groups of NDVs involved in recent outbreaks and that these outbreaks in Taiwan might have been caused by co-circulation of multiple velogenic NDV strains.