Background and Aims: Newcastle disease (ND) is one of the most serious illnesses of chickens. Live vaccines are widely used to prevent chicken from the disease all over the world. Materials and Methods: To access the effective and potentiate ND vaccine, a homogenous subpopulation from LaSota strain was selected following cultivation of the virus on primary chicken embryofibroblast (CEF) cells. Pathogenicity indices and molecular characterization of a several plaques at 3rd passage were analyzed and then the selected clone was candidate for vaccine development. ND vaccine was prepared according to the standard protocols. Results: The immunogenicity of the live vaccine was examined in specific pathogen free (SPF) and commercial chickens. The geometric mean hemagglutination-inhibition (HI) titers induced in chickens vaccinated with the cloned vaccine were not significantly differ than those induced in chickens vaccinated with the similar ND clone vaccine. Conclusion: Efficacy of the ND vaccine was estimated against the virus challenge. The results indicate that the cloned vaccine could confer a complete protection against NDV.

Highly pathogenic avian influenza (HPAI) H5N1 virus is causing the death of a large number of wild birds and poultry. HPAI H5N1 was reported in the north of Iran in 2011. In this study, two A/Chicken/Iran/271/2011 and A/Duck/Iran/178/2011 viruses were genetically characterized by sequence analysis of Hemagglutinin (HA) and Neuraminidase (NA) genes. Phylogenetic analysis revealed that these viruses were different from previous Iranian isolates (Clade 2.2) and belonged to the subclade 2.3.2.1. The results showed that the detected viruses are almost identical to each other and closely related to HPAI H5N1 strains isolated in Mongolia in 2010. Based on the amino acid sequence analysis, these viruses at their HA cleavage sites contained the multibasic amino acid motif PQRERRRK-R/GLF lacking a lysine residue compared with the previous reports of the same motif. There is also a 20-amino acid deletion (resides 49-69) in the NA stalk similar to other viruses isolated after 2000. It seems that introduction of HPAI H5N1 to Iran might have happened by wild birds from Mongolian origin virus.