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

Abstract 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 nano-adjuvant 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 un-vaccinated 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.