M. H Kiani - Department of Poultry and Obstetrics, Science and Research Branch, Islamic Azad University, Tehran, Iran
M. H Bozorgmehrifard - Department of Poultry and Obstetrics, Science and Research Branch, Islamic Azad University, Tehran, Iran
H Hosseini - Department of Clinical Science, Faculty of Veterinary Medicine, Karaj Branch, Islamic Azad University, Alborz, Iran
S Charkhkar - Department of Poultry and Obstetrics, Science and Research Branch, Islamic Azad University, Tehran, Iran
A Ghalyanchilangeroudi - Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

Newcastle disease is a highly contagious viral infection affecting many species of birds that can spread fast between poultry houses and cause a heavy economic burden on the poultry industry all around the world. Fusion and hemagglutinin-neuraminidase (HN) protein are important in the pathogenesis of the Newcastle disease virus (NDV). The HN protein is a critical viral protein with multiple functions and plays a key role in the formation of the virulence of NDV. Head of HN protein is responsible for receptor binding, neuraminidase activity. This study aimed to investigate the sequence homology of hemagglutinin-neuraminidase of two NDV isolates sampled from infected farms in Iran. The samples were collected from flocks that had been vaccinated by both types of live and killed vaccines for NDV. After isolation of NDV, the viruses were subjected to the polymerase chain reaction (PCR) amplification using two pairs of specific primers designed for the HN gene to amplify the complete HN gene (۱۷۳۰bp). Afterward, the PCR products were sequenced and analyzed by phylogenetic tree construction software. Based on the analysis, substantial sequence homology among Iranian isolates is within the range of ۹۷.۱-۱۰۰%. Moreover, the sequence homology searching revealed a level of similarity between HN sequences of Iranian isolates and the HN sequences from other countries, particularly Asian ones. For instance, a high homology ratio (۹۵.۳۴%) was found between Iranian isolates and the sequences registered on online molecular databases from China. Based on phylogenetic analysis, the NDV isolates belong to the VIId genotype. Finally, it can be concluded that monitoring the circulation of NDVs among poultry and other birds can help to obtain an insight into the evolution of NDVs and control of panzootic viruses in the future.

Hemagglutinin-neuraminidase, Iran, Newcastle disease virus, Phylogenetic tree