Abstract
To investigate cross-protective efficacy of commercial inactivated H5 avian influenza vaccines against recent HPAI H5N8 virus in quails. We evaluate the efficacy of two inactivated commercial H5 AI vaccine (imported H5N1 vaccine containing (Re-6 strain) and local H5N1 vaccine), using susceptible quails at one week age. The selection of these bird back to its a specific nature which characterized by presence of two types of avian influenza receptors giving a great chance for recombination of the different types of AIV emerging new mutant viruses can threat human health and poultry industry. Susceptible quails used for potency assay inoculated by one field dose and booster dose at 3 week post vaccination from each vaccine. Blood samples are collected weekly from all vaccinated groups and AI, HI antibodies are measured individuals of the collected sera by HI test using homologous H5N1 and heterologous H5N8 AI antigens containing 4 HA units. Vaccinated quails by one dose and booster dose of vaccine were challenged by 100 LD50 HPAI subtype H5N8 intranasally after 2, 4 and 8 weeks post vaccination, and 4 weeks post boostering, respectively. It was found HI antibody titer in sera of quails vaccinated by one or two doses of imported H5N1 AI vaccine containing RE-6 strain elicited higher immune response than local commercial vaccine when examined against homologous H5N1AI antigen, but two vaccines exhibited antibody titer not optimal against heterologous H5N8AI antigens. A challenge test with local H5N8 highly pathogenic influenza virus indicated unsatisfactory protection% for all groups of vaccinated quails.

Key words: Quails, immune response; HPAI H5N8 strain; vaccines and challenge test