1a. Objectives (from AD-416)
1. Determine seroconversion against avian influenza following in ovo and day-of-age vaccination of specific pathogen free (SPF) and commercial chickens with recombinant herpesvirus of turkeys (HVT)-vectored avian influenza (AI) vaccine. 2 Determine vaccine efficacy following vaccination with recombinant HVT/AI vaccine against highly pathogenic avian influenza (HPAI) H5N1 challenge.
1b. Approach (from AD-416)
Avian influenza (AI) hemagglutinin (HA) gene from current H5 field viruses was cloned into a herpesvirus of turkeys (HVT) vaccine. The HVT-AI vaccines, expressing HA protein, will be injected in SPF and commercial poultry to determine immune response and protection against HPAI challenge. Efficacy will be determined using high pathogenicity AI chicken models with measurement of protection being prevention of morbidity and mortality, reduction in number of infected birds and a decrease in the AI-shed from respiratory and alimentary tracts.
3. Progress Report
The project is related to objective 1 of the in-house project: Characterize mucosal immunity induced by natural infection and vaccination with both high and low pathogenicity avian influenza virus (AIV) to identify innate and adaptive immune indicators of protection. Vaccines against avian influenza (AI) are valuable in the prevention and control of the disease and can be used in eradication strategies. A herpesvirus of turkeys (HVT) recombinant-vectored avian influenza vaccine with an AI H5 gene insert (rHVT/AI-H5) from either H5N1 high pathogenicity avian influenza(HPAI) (A/swan/Hungary/4999/2006) or H5N9 low pathogenicity avian influenza (LPAI) (A/turkey/Wisconsin/68) was tested in specific-pathogen-free chickens (SPF) against H5N2 HPAI (A/chicken/Queretaro/94) and LPAI (A/parrot/U.S./04) of Mexican lineage. The vaccine was given by subcutaneous route (in the neck). After challenge, efficacy was evaluated by the presence or absence of clinical signs or mortality due to AI, and shedding of the challenge virus. Following direct challenge, SPF Leghorn chicks immunized with either of the rHVT/AI-H5 vaccines displayed significant protection against direct challenge with H5N2 HPAI. No clinical signs of disease were observed in any vaccinated birds, and viral shedding was significantly reduced in the rHVT/AI-H5 vaccinated birds compared to sham vaccinated animals. In addition, all sham-vaccinated birds died. In contrast, following LPAI challenge, no differences were observed in viral shedding from oral swabs from either rHVT/AI-H5 or sham vaccinated birds. Taken together, these data suggest that these recombinant-vectored vaccines expressing the HA are effective at protecting chickens against HPAI, but not as effective against shedding of LPAI. Progress was monitored via email and telephone conversations.