The Immunogenic Potential of an Inactivated Vaccine Candidate against Ornithobacterium Rhinotracheale in SPF Chicken

Ornithobacterium Rhinotracheale (ORT) is a gram-negative bacterium that causes respiratory infection in chickens and turkeys. The Co-infection of ORT with other viral or bacterial pathogens results in the development of severe clinical symptoms and significant economic losses. The proportion of ORT strains resistant to the current antibiotics employed in poultry flocks has increased in successive years. Contingent on the source of the isolate. It is recommended that the inactivated whole-cell vaccine (bacterin) be administered against multi-drug resistant strains of ORT that are present on poultry farms. In the present study, a formalin-inactivated bacterin formulated with an oil adjuvant (Montanide ^TM ISA 70 VG) was developed based on a local ORT isolate. A prime-boost regimen was employed for the immunization of specific pathogen-free chicken (SPF) groups. Subsequently, the immunogenic potency of the vaccine candidate was evaluated via ELISA and compared with that of a Nobilis^® commercial inactivated ORT vaccine.The safety of the Vaccine was studied following the inoculation of a dose that was twice the recommended dose of the prepared bacterin. The commercial inactivated ORT vaccine and the prepared bacterin both elicited the production of induced specific antibodies after three weeks following the initial vaccination, with this response continuing until 16 weeks post-vaccination. The immunization of chickens with the commercial vaccine resulted in a higher level of antibody compared to the experimental vaccine. However, no significant difference (P<0.05) was observed between the treated groups overall. The safety test revealed the absence of any adverse local or systemic reactions were found in chickens throughout the post-vaccination period. The data indicate that the prepared ORT-inactivated vaccine is safe and capable of inducing adequate and long-lasting immune responses in experimental SPF chickens. It is imperative to conduct field trials to ensure the efficacy of this vaccine candidate in preventing ORT infection.