Molecular Characterization of Thermostable Newcastle disease virus Isolated from Pigeon.

The HN and L gene sequences of an Indian isolate of Newcastle disease virus was analyzed prior to and after exposure to 56 °C at tenth passage and fifteenth passage to study the variations at molecular level. In the HN gene sequence of progenitor and thermostable strain, substitution of K373I, F374L, M516R, D517V were considered to contribute to the increase in the stability of the protein. In the L gene of the thermostable strain, variations were observed at many positions and among these the substitutions at position P675H K677R, K893D, R1132K, had charged amino acids, and at L656A, F657V, F869L, T886I, M899I, G1131V, V1675L, had hydrophobic amino acids that could be related to increased stability of L protein at high temperatures. The changes in amino acid sequence in HN and L gene of the thermostable strain might render structural variations that might have contributed to the stability of the strain at higher temperature.