Survey on ELISA Based on anti Influenza A NS1 Antibodies to Differentiate the Infected and Vaccinated Poultries

Abstract

Background: The Vaccination programs to control avian influenza (AI) infection in poultry, have limitations due to the difficulty in differentiating the vaccinated and naturally infected birds AI vaccination would bring greater global acceptance if a reliable test, which could clearly distinguish the naturally infected and vaccinated-only animals (DIVA), was available. Since the nonstructural protein (NS1) is expressed in influenza infected cells, and it is not presented as a virion, it could be a proper candidate for DIVA differential diagnostic test. Objectives: Vaccination programs for the control of avian influenza (AI) in poultry have limitations due to the problem of differentiating between vaccinated and virus-infected birds. The use of AI vaccination in poultry would have greater worldwide acceptance if a reliable test were available that clearly discriminated between naturally infected and vaccinated-only animals (DIVA). Because the nonstructural protein (NS1) is expressed in influenza virus–infected cells, and it is not packaged in the virion, it is an attractive candidate for a DIVA differential diagnostic test. Materials and Methods: A total of 300 day-old broiler chicks (Ross 308) divided into three equal groups (1 to 3) .The chicks in group 1 were immunized with killed AIV H9N2. The chicks in group 2 were infected with AI virus subtype H9N2. The chicks in group 3 were kept as controls and did not receive any vaccined or lived virus. Chicks sera were collected at day 42 usingrNS1-ELISA and Commercial ELISA kit. Results: Designed ELISA test for detection of antibody against influenza NS1 could experimentally distinguish the chicks infected with AIV and chicks immunized with killed influenza viruswith93.3% sensitivity and 100 ℅ specificity. 3 weeks after infection or vaccination, sera from all two treated groups were positively tested using commercial ELISA kit (IDEXX). In contrast, by NS1-ELISA, only infected groups sera were tested and the result was positive, and all sera samples from the vaccinated group were NS1-antibody titer were evaluated and the result were negative. Conclusions:: It was concluded that antibodies against AIV NS1 protein was only detected in the sera of chickens experimentally infected with AIV, not in the sera of chickens immunized with inactivated vaccine.