Author
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Swayne, David |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 5/1/2008 Publication Date: 6/1/2008 Citation: Swayne, D.E. 2008. Avian influenza vaccine development: Application technology platforms, field use and predictors of protection [abstract]. In: Program of Vaccine Technology II Conference, June 1-6, 2008, Albufeira, Algarve, Portugal. p. 57. Interpretive Summary: Technical Abstract: Vaccines against avian influenza (AI) began over 100 years ago as experimentally produced products, but commercial application did not occur until: 1) a reliable method was developed to grow and titer the virus (i.e. embryonating chicken eggs), 2) an efficient and predictable method was developed to inactivate the virus without destroying antigenic epitopes (i.e. formalin inactivation), and 3) a method was developed to enhance the immune response (i.e. oil emulsion adjuvants). Commercial usage of vaccines began in 1979, with limited usage of inactivated oil-emulsion vaccines for low pathogenicity avian influenza (LPAI) in meat and breeder turkeys. AI vaccine usage increased in the mid-1990s with H9N2 LPAI in developing countries, and the first usage of AI vaccines against high pathogenicity (HP) AI occurred following large scale outbreaks of H5N1 HPAI in Mexico and H7N3 in Pakistan. For the latter two epizootics, over 4 billion doses have been used in 10 years. However, the greatest quantity of AI vaccine used has been in response to the emergence of the H5N1 HPAI epizootic in Asia, Africa and Europe. The actual quantity of vaccine used is unknown, but from conservative estimates the amount has exceeded 30 billion doses since 2002. Over the past 40 years, AI vaccines have been primarily based on LPAI and HPAI viruses used in inactivated, oil emulsified vaccines. Recently, fowl poxvirus and avian paramyxovirus type 1 vectored vaccines with AI H5 gene inserts have been developed and licensed in some countries. Advances in biotechnologies may 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 rapid changing of AI hemagglutinin gene insert through cassette concept; can be mass applied by aerosol, drinking water or in ovo administration; and provide easier strategies for identifying infected birds within vaccinated populations. These rising technologies include AI viruses with partial gene deletions, AI-ND virus chimeras and vectored vaccines using adenoviruses, Marek’s disease, or sub-unit vaccines. An additional benefit of some vectored technologies is a broad application in multiple animal species. For example, fowl poxvirus-vectored vaccines have shown efficacy in chickens, geese and cats. There potential use in the field will also be determined on the requirement for low cost vaccines to be economically competitive. |
