Phylogenetic and pathogenic analysis of Indian isolates of Newcastle disease virus

In the present study, Indian Newcastle disease virus (NDV) isolates UP/3 and UP/4 collected from suspected field samples were characterized to be velogenic by pathogenic and phylogenetic analysis. Phylogenetic analysis based on the nucleotide sequences of the F gene indicated that UP/3 and UP/4 isolates belong to genotype VII and genotype IV, respectively. These isolates possessed the amino acid sequence R-112/K-R-Q-K/R-R-F-117 in the F-0 cleavage site, which is typical of velogenic NDV pathotype. All the NDV strains analyzed have shown to have non-synonymous to synonymous base substitution rate in the F gene ranging between 0.074-0.197, demonstrating the presence of purifying selection. HN gene of the isolates was found to have an open reading frame encoding 571 amino acids. The deduced amino acid sequences of the HN glycoprotein revealed that the cysteine residues essential for intra-molecular disulphide bonds to stabilize the HN molecules, antigenic sites and key residues for receptor binding were all conserved in Indian isolates.