Studies on the cytopathogenicity of Newcastle disease virus: relation between virulence, polykaryocytosis and plaque size.

Abstract

Summary The cytopathic effects produced by seven strains of Newcastle disease virus grown in chick embryo cell culture were examined. The principal form of cytopathic effect involved the formation of multinucleate cells (polykaryocytes) by cell fusion. The capacity of the different Newcastle disease virus strains to induce cell fusion was related directly to their virulence for chicks and fertile eggs. The virulent (velogenic) strains herts, warwick and texas produced significantly greater polykaryocytosis than the mesogenic strain beaudette c which, in turn, produced greater polykaryocytosis than the avirulent (lentogenic) vaccine strain f. The lentogenic strains queensland and ulster failed to produce detectable cytopathic effects. Distinct morphological differences were noted in the polykaryocytes produced by the different strains. The ability to form plaques and plaque size in chick embryo monolayers was also related to the virulence of the virus strains.