[Cytopathic effect of the Newcastle disease virus on the BHK-21 cell line]

The cytopathic effect (CPE) of the Newcastle disease virus (NDV) in the BNK-21 permenant cell line is studied in a series of experiments. The CPE is assessed as a percentage of hemadsorption and polykaryocytosis, and the dynamics of the viral replication is followed up with the aid of the immunofluorescent method. The effect of the cyclohexamide protein inhibitor of the replication of various NDV strains, on the CPE, respectively, is likewise studied. Five vellogenic, one mesogenic and one lentogenic strains are used in the experiments. It is found that through the immunofluorescent method the viral replication is delayed some three hrs in the case of the La Sota lentogenic strain in comparison with the other strains used. The direct relationship, already established, between the virulence of the NDV and the percentage of haemadsorption and polykaryocytosis is confirmed also in the BNC-21 heterologous cellular tissue. On the basis of this relationship, a rapid typing method of virulent from avirulent field NDV strains is suggested. The blocking effect of the cyclohexamide protein inhibitor on the CPE in NDV is demonstrated in the BNK-21 line, as a result of the blocking of the viral specific protein synthesis.