2010 Annual Report
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.