Evaluation of the Immunogenicity of an Inactivated Vaccine against the Adenovirus Egg Drop Syndrome 1976 in Poultry.

Egg Drop Syndrome 1976 (EDS-76) causes significant economic losses in Egyptian poultry. This study aimed to develop a safe and effective vaccine prepared from locally isolated and characterized EDS virus using mineral oil as adjuvants. The virus was propagated in duck embryos, achieving high hemagglutination unit (HAU) titers (15 log₂ HAU) and 50% embryo infectious (EID₅₀) titers (8.1 log₁₀ EID₅₀ /mL). The virus was successfully inactivated with 0.2% formalin. The virus antigen was formulated into oil-emulsion vaccines (250-2000 HAU per dose). In SPF chickens, the EDS hemagglutination inhibition (HI) and serum neutralization (SNT) tests were used to determine antibody levels. The results of HI and SNT showed that the vaccine induced rapid and robust immunity, with 100% seroconversion by week two. The highest dose (2000 HAU) elicited superior hemagglutination inhibition (HI; 13.5 ± 0.6 log₂) and virus neutralizing (12.0 ± 0.5 log₂) antibody titers by week four compared to a commercial vaccine. Furthermore, our results showed a strong correlation (R²=0.98) between HI and neutralization tests. These findings demonstrate that the local Egyptian EDS-76 virus is an ideal isolate for vaccine production, providing a promising and cost-effective tool for the effective control of EDS-76 in the Egyptian poultry.