Molecular characterization and phylogenetic study of the hemagglutinin-neuraminidase gene of newcastle disease virus isolated from peacock (Pavo cristatus) and Turkey (Meleagris) and its comparison with broiler isolates.

Abstract

Newcastle disease has been endemic within the Iranian poultry industry for decades. However, the genetic nature of the circulating Hemagglutinin-Neuraminidase (HN) gene among Iranian domesticated bird populations is broadly unexplored. The presented study was carried out to gain insights into the biological and molecular characterization of four complete HN genes isolated from turkey, peacock, and broiler isolates in Iran between 2018 and 2020. The phylogenetic analysis revealed that the isolates belong to the Newcastle disease virus (NDV) subgenotype VII.1.1, previously known as VIIL. Further analysis demonstrated the thermostable substitutions S315P and I369V within the isolates. Finding the N-glycosylation site (NIS) at positions 144-146 and the cysteine residue 123 might influence the fusogenicity abilities of the isolates, while identification of multiple amino acid substitutions in both antigenic sites, especially I514V and E347Q, and the binding sites of the HN protein, raised concern about the pathogenicity of the isolates. In addition, the annual rate of change based on the HN gene of Iranian NDV was calculated at about 1.8088E-3 between 2011 and 2020. In conclusion, a new NDV variant with multiple site mutagenesis is circulating not only among chickens but also in turkey and captive birds such as peafowls, and failure of routine vaccination programs could be attributed to the differences between circulating NDV strains and those used in vaccine manufacturing. Therefore, future legislation aimed at providing vaster vaccination cover and biosecurity plans will be needed to control the spread of circulating NDV strains.