[Inhibition of NDV reproduction with antibodies against its F protein]

Obtained were the JgG and Fab fragments from a monovalent serum against the F-protein of the Newcastle disease virus. Both the JgG and the Fab fragment inhibited the virus reproduction in cell cultures of chick embryo fibroblasts and BHK21 if they were added after the adsorption and virus penetration of the cells. The inhibitory action of the antibodies was due to their direct fixation by the newly synthesized F-protein in the cells infected with the virus. The rate of inhibition of the Newcastle disease virus as shown by the JgG and Fab fragments of the serum produced against a pure F-protein was the same with the use of chick embryo fibroblasts as with BHK21.