Submitted to: China-Japan Avian Influenza Symposium
Publication Type: Abstract only
Publication Acceptance Date: 2/1/2006
Publication Date: 2/6/2006
Citation: Swayne, D.E. 2006. Science of vaccine efficacy against Asian H5N1 highly pathogenic Avian Influenza [abstract] In: Proceedings of 2nd China-Japan Avian Influenza Symposium, February 6-7, 2006, Tokyo, Japan. p.8. Interpretive Summary:
Technical Abstract: Since December 2003, H5N1 highly pathogenic avian influenza viruses has caused outbreaks of disease in multiple Asian and European countries and affected between 100-200 million birds. Vaccines can be used as a tool to prevent the disease and reduce field virus replication, but must be used in the context of other critical components such as biosecurity, education, surveillance and diagnostics, and elimination of infected poultry. Current experimental studies with inactivated H5 avian-influenza, recombinant fowlpox-H5-avian-influenza, adenovirus-vectored-H5-avian-influenza and Newcastle-disease-virus-vectored-H7-AI vaccines were conducted to determine their ability to protect chickens, geese and/or ducks from H5 or H7 highly pathogenic avian influenza. The H5 and H7 avian influenza virus vaccines prevented disease and mortality in chickens, and reduced the ability of the field virus to replicate in gastrointestinal and respiratory tracts following intranasal challenge with highly pathogenic avian influenza viruses of the respective hemagglutinin subtype. In ducks, the Asian H5N1 highly pathogenic avian influenza virus did not cause disease or mortality, but protection was measured for the inactivated vaccine by reduction in field virus replication in the respiratory and intestinal tracts. The inactivated avian influenza and recombinant fowl pox vaccines protected geese from morbidity and mortality following challenge with H5 highly pathogenic avian influenza virus. The ability to detect infected birds within a vaccinated population is achievable by several “DIVA” strategies which look for specific antibodies of the infecting strain or detection of the virus itself. For inactivated avian influenza viruses, unvaccinated sentinels can be examined for antibodies against avian influenza viral proteins such as the nucleoprotein/matrix protein (agar gel immunodiffusion – AGID test) or hemagglutinin (hemagglutination inhibition – HI test). In vaccinated birds, antibodies against the NS1 protein were identified in infected birds but were absent or of low titers in vaccinated birds. Alternatively, the recombinant virus vaccines with avian influenza hemagglutinin gene inserts were used in a DIVA strategy using existing serological tests. Vaccinated birds had HI antibodies but not AGID antibodies, while infected birds have both HI and AGID antibodies.