Author
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Swayne, David |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 2/10/2009 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Use of vaccines against avian influenza (AI) have been sporadic in poultry until 2002 when the H5N1 high pathogenicity avian influenza (HPAI) spread from China to Hong Kong, and then multiple southeast Asian countries in 2003-2004, and to Europe in 2005, and Africa in 2006. Over the past 40 years, AI vaccines have been primarily based on field outbreak low pathogenicity (LPAI) strains that were grown in embryonating chicken eggs, chemically inactivated, emulsified in mineral oil adjuvant and injected into individual birds. The initial inactivated vaccines utilized were based on H5 LPAI virus outbreak strains. Recently, recombinant viral vectored vaccines have been developed and licensed including recombinant fowlpox and avian paramyxovirus type 1 (Newcastle disease (ND)) vaccines with AI H5 gene inserts. Additional vectored technologies hold promise for usage in the future possibly including baculoviruses, herpesvirus of turkeys, infectious laryngotracheitis virus, adenoviruses, attenuated influenza A viruses, AI-ND virus chimeras and bacterial vectors such as salmonella. Historically, the H5 subtype AI vaccines have demonstrated broad homosubtypic protection, primarily against H5 high pathogenicity (HP) AI viruses isolated in the early stages of outbreaks. However, as H5 viruses have become endemic and outbreaks prolonged, some drift variants with resistance to earlier H5 AI vaccines have emerged in Central America, China, Egypt and Indonesia. How widespread such drift variants are will remain unknown until more detailed genetic and antigenic analyses are conducted on field isolates. Implementation of advances in biotechnologies will overcome some existing limitations and result in vaccines that can be grown in tissue culture systems for more rapid vaccine production; provide optimized protection as the result of closer genetic relationship to field viruses through reverse genetics and gene insertions in vector systems; can be mass applied by aerosol, drinking water or in ovo administration; and provide easier strategies for identifying infected birds within vaccinated populations; i.e. DIVA. |
