Comparative efficacy of different adjuvant containing inactivated vaccines against low-pathogenicity Avian Influenza H9N2 virus

摘要

Background: Outbreaks of low-pathogenic Avian Influenza virus H9N2 (AIV-H9N2) occurred in poultry industry in Pakistan in 1998 and caused serious economic losses. Since then, many of the AIV-H9N2 vaccines have been introduced to Pakistani market to control the virus, however, it is still circulating all over the country. Therefore, the purpose of the study was to prepare and evaluate different adjuvant containing vaccines using local isolate of AIV-H9N2 in broiler birds. Methods: Three vaccines; Alum precipitated (AP-AIV), Aluminum hydroxide gel (AH-AIV) and Oil based (OB-AIV) were prepared in the laboratory and injected into broiler birds at 7^th and 14^th day of age. There were four groups of birds including one control group. To evaluate the serological response of the birds to vaccines, serum antibody titers were measured using haemagglutination inhibition test (HI). Vaccinated and control birds were challenged with AIV-H9N2 and virus shedding was determined from trachea and cloacal swabs by HI. Results: Out of the three prepared OB-AIV with hydrophile lypophile balance (HLB) values 5.37, 8.01 and 9.01, the vaccine with HLB value of 8.01 was the most stable. Each of the adjuvant containing vaccine was effective in inducing high HI antibody titers. However, OB-AIV was found to be the most effective in inducing a significantly higher (P 0.05) HI titer as compared to that of AP-AIV and AH-AIV each. No significant difference was observed between the HI titers induced by AP-AIV and AH-AIV. All the vaccines also showed effective protection against AIV-H9N2 challenge in vaccinated birds. Conclusion : In conclusion, this study reports the successful preparation and evaluation of adjuvant containing inactivated AIV-H9N2 vaccines. OB-AIV formulation was found to be most effective to control the H9N2 virus infections in broiler birds.