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Title: Differentiation of infected and vaccinated animals (DIVA) using the NS1 protein of avian influenza virus in chickens

item Avellaneda, Gloria
item Suarez, David

Submitted to: International Symposium on Avian Influenza
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2009
Publication Date: 4/5/2009
Citation: Avellaneda, G.E., Mundt, E., Lee, C., Jadhao, S., Suarez, D.L. 2009. Differentiation of infected and vaccinated animals (DIVA) using the NS1 protein of avian influenza virus in chickens [abstract]. 7th International Symposium on Avian Influenza, April 5-8, 2009, Athens, Georgia. p. 95.

Interpretive Summary:

Technical Abstract: The use of avian influenza (AI) vaccination in poultry would have greater world-wide acceptance if a reliable test that clearly discriminates naturally infected from vaccinated only animals (DIVA) was available. Because the non-structural protein (NS1) is expressed in infected cells, and is not packaged in the infectious virion, it has been considered as a target candidate for a DIVA differential diagnostic test. The aim of this work was to determine the onset of the antibody response to the NS1 protein in chickens infected with low pathogenic avian influenza (LPAI) virus, and to evaluate the diagnostic potential of a baculovirus expressed purified NS1 protein in an indirect ELISA-based DIVA strategy. An antibody response against NS1 was first detected three weeks after infection, but the antibody levels were decreasing rapidly by 5 weeks after infection. However, most chickens did not have detectable antibodies in spite of high hemagglutination inhibition (HI) antibody titers in one group. In birds vaccinated with inactivated oil emulsion vaccines, antibodies against NS1 were not detected before virulent challenge and only a small percentage of birds seroconverted after homologous LPAI virus challenge. Vaccinated birds challenged with highly pathogenic AI showed a higher NS1 antibody response, but at most only 40% of birds seroconverted by three weeks after challenge. Because of the variability of seroconversion and the duration of the antibody response in chickens, the NS1 protein DIVA strategy did not perform as well as expected, and would require sampling a higher number of birds to compensate for the lower seroconversion rate.