Phylogenetic Analysis of Newcastle Disease Virus and Its Potential in Vaccine Development

Despite the availability of Newcastle disease (ND)vaccines, outbreaks have continued to occur for more than six decades, with huge economic consequences for the global poultry industry. The variability of the Newcastle disease virus requires constant monitoring, detection of new cases and study of the origin of the pathogen. The aim of the study was to develop an inactivated ND vaccine using a topical strain with different adjuvants and to compare them for stability, harmlessness, immunogenicity and efficacy. As a result of the phylogenetic study of the F-gene of the ND strain isolated in Kazakhstan, selected to create a vaccine for the prevention of this disease, it was revealed that this pathogen belongs to the genotype VII class II and was uploaded to GenBank (NCBI). Two different adjuvants were used to create the vaccine – Montanide ISA 70 VG and Montanide ISA 78 VG. The birds were vaccinated intramuscularly. Evaluation of antibody titers in the vaccinated groups during the experiment shows that the vaccines were able to induce adequate levels of antibodies to provide protection against the virulent virus. Vaccination provided high antibody titers in the HAI in the vaccinated groups as early as 14 days after vaccination in 100% of birds. When studying the effectiveness of vaccines, the average antibody titer in both vaccinated groups was above 7 log2, which is more than enough to protect birds from clinical signs. None of the vaccinated birds showed clinical signs after control infection. In groups of unvaccinated birds, clinical manifestations were observed as early as 3 days after infection with increasing severity, and eventually they all died (100% mortality). The vaccine from the epizootic topical strain developed by us is stable, harmless, immunogenic and effective when infected with a virulent strain of the ND virus at a dose of 100,000 EID50/cm3.