RESUMO
To Prepare of a specific FITC conjugate antibody for differentiation of velogenic and vaccinal strains of Newcastle disease virus. Experimental study.27 rabbits.4 velogenic strains of Newcastle disease virus were obtained from collection of viruses in Virology Laboratory of Faculty of Veterinary Medicine and two vaccinal strains [Bl and Lasota] were propagated in embryonated eggs and purified by ultra centrifugation. Purified viruses used for immunization of 7 groups of rabbits, each consisting of 4 animals. Each group was immunized by one of the virulent or vaccinal strains and one group by mix of vaccinal strains. The immunization process took about 4 months. Sera samples fro immunized animals after absorption by each of the vaccine and velogenic strains were put in proximity to one another in Agar gel Immunodiffusion test. Specific antibodies conjugated with FITC. 28 velogenic isolates, 2 vaccinal strains and 14 negative samples were tested by using the conjugated specific antibody.Eventually only one precipitate line was observed. That was indicative of the fact that specific antibody against velogenic and vaccine strains was obtained. The produced specific antibody can detect unique viral antigen and respond against it. This specific FITC conjugated antibody can differentiate velogenic and vaccinal strains of NDV in shorter time than classic methods