Determination of efficacy in inactive Newcastle disease vaccines with an in-vitro method as an alternative to in-vivo methods

Objective: In this study, applicability of an in-vitr o ELISA method, which reduces or eliminates the need for animal trials in establishing the efficacy of inactive Newcastle disease vaccines was investigated. Methods: For this purpose, the efficacy of nine (9) inactivated Newcastle disease vaccines and two non-Newcastle related vaccines (negative controls) were evaluated by in-vivo and in-vitro methods. As in-vivo tests, vaccines were applied to the Spesific Pathogen Free (SPF) chicks and antibody response was determined via hemagglutination inhibiton test. As in-vitro , antigen amount in vaccines were calculated with a sandwich ELISA test based on the determination of hemagglutinin and neuraminidase levels developed for inactive Newcastle vaccines. Relative potency values of vaccines were calculated by using the parallel line analysis method with Combistats statistical analysis software program by using optical density results obtained from ELISA test. Results: Hemagglutination inhibition test results were found to be between 2 3,3 and 2 6,1 ; immunization/