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

In this thesis study, the applicability of an in-vitro ELISA method which reduces or eliminates the need for animal trials in establishing the efficacy of inactive Newcastle Disease Vaccines was investigated. For this purpose, a single or multi-component 9 inactivated Newcastle disease vaccines used in poultry and two vaccines without Newcastle disease virus were used to assess pseudo-reactions. The efficacy levels of vaccines 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 serologically (hemagglutination inhibiton test), and protection levels were determined with challenge trials. 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. Hemagglutination inhibiton test results were found to be in between 23,3 and 26,1; immunization/challenge results ranged between 56 and 136 PD50 and ELISA test results were between 6,02 and 98,23 antigen units. Meaningful correlation was found between the ELISA test and immunization/challenge test (r2=0,93) as well as hemagglutination inhibiton and immunization/challenge test (r2=0,95). Sensitivity and specificity were found to be %89, %100 respectively and in terms of reproducibility and repeatability they were within acceptable range. According to these results, the ELISA procedure's applicability, compatibility with standard procedure as well as its ability to provide similar results on the same samples were demonstrated.