Virus shedding after H9N2 strain challenge of SPF Chickens immunized by an experimental Nano-Adjuvant and commercial oil emulsion avian influenza (H9N2) vaccines

Background and Aims: Vaccination of poultry has a major impact on the prevention and control of avian influenza viruses. Nanobiotechnology techniques provide a new approach for improvement of influenza vaccine efficacy. In this study, efficacy of an inactivated nanoadjuvant vaccine developed based on an endemic H9N2 virus was evaluated in SPF chickens. Materials and Methods: In each three trial 40 specific pathogen free (SPF) white Leghorn chickens were used in four groups. Chickens from treatment groups (n= 10) via subcutaneous route received a single dose of the nano-adjuvant or the oil emulsion Razi® H9N2 vaccines. Chickens in the control group C received antigen only. All the birds were challenged with H9N2 strain on day 21 post-vaccination. Cloacal and tracheal swabs were taken at 1-10 days post-challenge and viral shedding was examined using inoculation of SPF embryonated eggs. Results: Both vaccinated SPF chicken groups induced complete protection against clinical signs. Viral shedding in the nano-adjuvant H9N2 vaccinated chickens was completely blocked after challenge with a homologous H9N2 virus. Statistical analysis based on the protection effects of the chickens immunized with nano-adjuvant and the Razi® H9N2 vaccine showed no significant difference, but there was a significant difference to unvaccinated group. Conclusions: The results of this study indicated that the nano-adjuvant vaccine was efficacious in protection of SPF chickens over H9N2 infection. Further field experiments are needed to demonstrate the efficacy of the vaccines under field conditions.