Author
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Swayne, David |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 9/24/2008 Publication Date: 9/28/2008 Citation: Swayne, D.E. 2008. Viral vectors for avian influenza vaccines [abstract]. Viral Vectors Vaccine Conference, September 28-30, 2008, Hinxton, United Kingdom. p. T25. Interpretive Summary: Technical Abstract: Prior to 2003, vaccines against avian influenza (AI) had limited, individual country or regional use in poultry. In late 2003, H5N1 high pathogenicity (HP) AI spread from China to multiple Southeast Asian countries, and to Europe during 2005 and Africa during 2006, challenging governments and all poultry production sectors to seek alternatives to stamping-out program to control and eradicate AI. Over the past 40 years, AI vaccines have been based primarily on field outbreak strains used in inactivated AI vaccines. However, inactivated AI vaccines present multiple disadvantages in control programs including the need for long lead times for production in embryonating chicken eggs, the requirement for expensive and laborious injection of individual birds, and difficulty in serological identification of infected birds in a vaccinated population (i.e. DIVA). Since 1997, recombinant fowlpox and avian paramyxovirus type 1 (Newcastle Disease, ND) vectored vaccines with AI-H5 gene inserts have been developed and licensed with deployment and use in Central America and Asia. Additional virus vector technologies hold promise for future use either through production of the protective influenza A virus hemagglutinin antigen in in vitro culture systems such as with baculoviruses or some adenoviruses, or the use of attenuated virus vectors that replicate in poultry such as Marek’s disease herpesvirus, infectious laryngotracheitis virus, some adenoviruses, attenuated influenza A viruses and AI-ND virus chimeras. Such virus vectors could overcome limitations of existing vaccines by allowing production in tissue culture systems for more rapid vaccine production cycle; provide closer genetic match to field AI viruses through reverse genetics and gene insertions in vector systems; offer mass application of vaccines by aerosol, drinking water or in ovo administration; and provide easier DIVA strategies. However, these new virus vectors will be licensed only after demonstration of purity, safety, efficacy and potency against AI viruses, and a limited capacity for horizontal transmission in naïve poultry. Adoption and use of such licensed vaccines will require the cost to purchase and administer to be economically competitive with inactivated AI vaccines. |
