Abstract

The selection of appropriate adjuvants is vital for boosting the efficacy of inactivated poultry vaccines. This study aimed to evaluate the immunological potential and safety of inactivated Newcastle Disease Virus (NDV) vaccine formulated with Calcium Phosphate (CaP) gel, comparing its performance as a substitute adjuvant to traditionally used aluminum hydroxide gel and oil- based adjuvant in chickens. The experiment was conducted on four groups of chicks. The first group was vaccinated with an inactivated NDV vaccine coupled with CaP adjuvant. The second group received the inactivated NDV vaccine formulated with the traditionally used Aluminum hydroxide adjuvant. The third group was inoculated with a commercially prepared oil-based inactivated NDV vaccine. Group 4 kept as a control unvaccinated group. Humoral immune response were monitored weekly using Hemagglutination inhibition (HI) test and the challenge trial was conducted 21 days post- vaccination using a virulent NDV strain to assess protective efficacy. Our finding demonstrated that while all vaccinated groups developed protective antibody levels, the CaP adjuvented group showed faster onset of immunity compared to oil adjuvented group. Specifically, HI titers in CaP and aluminum hydroxide groups reached their peak (4.8 log2) by the 2nd week after vaccination, outperforming the oil based formulation. Furthermore, the CaP vaccine provided a high protection rate of (93.3%) during the challenge trial, with no adverse clinical signs or injection site reactions observed, confirming its safety profile. In conclusion, CaP gel serves as an effective and safe alternative to traditional adjuvants for inactivated NDV vaccines. It capable of stimulating high and early immune response and provides high clinical protection, offering a promising natural and cost- effective tool for improving poultry vaccination strategies.

Key words: Newcastle Disease Virus, Calcium Phosphate, Adjuvant, Vaccine.